Bythaelurus bachi n. sp., a new deep-water catshark (Carcharhiniformes, Scyliorhinidae) from the southwestern Indian Ocean, with a review of Bythaelurus species and a key to their identification

Abstract

A new deep-water catshark, Bythaelurus bachi, is described based on 44 specimens caught on the southern Madagascar Ridge in the southwestern Indian Ocean. The new species is the only stout-bodied Bythaelurus with oral papillae in the region and is distinguished from all congeners by the plain beige to light gray-brown coloration, high diversity in dermal denticle morphology, and presence of composite oral papillae. Despite resemblance in body shape, Bythaelurus bachi n. sp. is distinguished from its closest congener, B. naylori Ebert & Clerkin, 2015, by the presence of numerous large, par- tially composite papillae on the tongue and roof of the mouth (vs. papillae lacking), plain light coloration (vs. medium to dark brown ground color, light fin edges and a distinctly dark dusky-colored snout), only slightly enlarged dermal denti- cles on the anterior upper caudal-fin margin (vs. dermal denticles distinctly enlarged), a higher diversity in dermal denticle morphology in general, and smaller maximum size and size at maturity. The distinction of both species is also supported by molecular results. The new species differs from all other congeners in the western Indian Ocean in the stout body shape of large specimens, coloration, larger size, as well as several morphometrics, including larger claspers, longer eyes and dorsal fins, and shorter pelvic—anal and pelvic—caudal spaces. The genus is reviewed, a key to its species given.

Full text

Accepted by M.R. de Carvalho: 26 Oct. 2016; published: 20 Dec. 2016
ZOOTAXA
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Copyright © 2016 Magnolia Press
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http://doi.org/10.11646/zootaxa.4208.5.1
http://zoobank.org/urn:lsid:zoobank.org:pub:74C3929D-570C-4555-9B7C-15A17CF511DF
Bythaelurus bachi n. sp., a new deep-water catshark (Carcharhiniformes,
Scyliorhinidae) from the southwestern Indian Ocean, with a review of
Bythaelurus species and a key to their identification
SIMON WEIGMANN
1,7
, DAVID A. EBERT
2,3,4
, PAUL J. CLERKIN
2
, MATTHIAS F.W. STEHMANN
5
& GAVIN J.P. NAYLOR
6
1
Elasmo-Lab, Elasmobranch Research Laboratory, Schlägertwiete 5b, 21335 Lüneburg, Germany
2
Pacific Shark Research Center, Moss Landing Marine Laboratories, Moss Landing, CA 95039, USA
3
Research Associate, South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown, 6140, South Africa
4
Research Associate, Department of Ichthyology, California Academy of Sciences, 55 Music Concourse Drive, San Francisco, CA.
94118, USA
5
ICHTHYS, Ichthyological Research Laboratory and Consultant, Hildesheimer Weg 13, 22459 Hamburg, Germany
6
Hollings Marine Laboratory, College of Charleston, Charleston, SC 29412
7
Corresponding author. E-mail: simon.weigmann@elasmo-lab.de
Abstract
A new deep-water catshark, Bythaelurus bachi, is described based on 44 specimens caught on the southern Madagascar
Ridge in the southwestern Indian Ocean. The new species is the only stout-bodied Bythaelurus with oral papillae in the
region and is distinguished from all congeners by the plain beige to light gray-brown coloration, high diversity in dermal
denticle morphology, and presence of composite oral papillae. Despite resemblance in body shape, Bythaelurus bachi n.
sp. is distinguished from its closest congener, B. naylori Ebert & Clerkin, 2015, by the presence of numerous large, par-
tially composite papillae on the tongue and roof of the mouth (vs. papillae lacking), plain light coloration (vs. medium to
dark brown ground color, light fin edges and a distinctly dark dusky-colored snout), only slightly enlarged dermal denti-
cles on the anterior upper caudal-fin margin (vs. dermal denticles distinctly enlarged), a higher diversity in dermal denticle
morphology in general, and smaller maximum size and size at maturity. The distinction of both species is also supported
by molecular results. The new species differs from all other congeners in the western Indian Ocean in the stout body shape
of large specimens, coloration, larger size, as well as several morphometrics, including larger claspers, longer eyes and
dorsal fins, and shorter pelvic—anal and pelvic—caudal spaces. The genus is reviewed, a key to its species given.
Key words: Chondrichthyes, Elasmobranchii, taxonomy, new species, morphology, DNA analysis, molecular phylogeny,
NADH2, western Indian Ocean
Introduction
Members of the genus Bythaelurus, originally erected as a subgenus of Halaelurus Gill, 1862 by Compagno
(1988), are deep-water catsharks with bluntly rounded snouts and soft bodies. In contrast, species of Halaelurus
live in shallow to moderately deep waters, have pointed snouts, firm bodies, and dorsal eyes and gill openings
(Compagno 1988). There was continuing disagreement about who elevated the subgenus Bythaelurus to generic
rank and when, but this issue has recently been resolved when Kaschner et al. (2015) attributed the formal
elevation to Hovestadt & Hovestadt-Euler (1995) on the basis of results by Herman et al. (1990).
One of the largest collections of deep-water chondrichthyans from the western Indian Ocean was sampled
during cruise 17 of the Russian RV ‘Vityaz’ in 1988/89. Together with a large number of other new taxa of deep-
water sharks, batoids and chimaeras, many specimens of different species of Bythaelurus were caught. These
include one specimen of B. clevai (Séret, 1987), 523 specimens of B. hispidus (Alcock, 1891), of which 100
specimens were preserved, 180 specimens of an undescribed species, of which 121 were preserved, one specimen

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of another species that was recently described as B. tenuicephalus Kaschner, Weigmann & Thiel, 2015, and 32
specimens of a second undescribed species. During a series of surveys conducted in 2012 and 2014 in the
southwestern Indian Ocean, one of the current authors (PJC) collected further specimens and fresh tissue samples
of the second undescribed species of Bythaelurus, together with another species of the genus that was described as
B. naylori Ebert & Clerkin, 2015. The second undescribed species of Bythaelurus is formally described herein
based on the 32 specimens collected by RV ‘Vityaz’ in 1988 and 12 specimens from the surveys in 2012 and 2014.
The description represents contribution no. 19 to the series “Deep-water chondrichthyan fishes of RV ‘Vityaz’
cruise 17 and other Soviet cruises in the Indian Ocean”, initiated with the description of Rhinochimaera africana
(Compagno et al. 1990). A review of and a key to the species of Bythaelurus are given.
Material and methods
Institutional acronyms follow Sabaj Pérez (2014). Specimens were fixed with formalin and stored in 70% ethanol.
External morphometric measurements were taken between perpendicular lines where relevant by vernier caliper to
one tenth of a millimeter and largely follow Compagno (1984a), with total length = TL instead of TOT. Additional
measurements after Nakaya et al. (2008): precaudal length from snout tip to ventral origin of caudal fin (PRCV),
pre-outer nostril length (PONL) from snout tip to a line connecting anterior ends of right and left outer nostrils
(equal to Compagno’s [1984a] prenarial length), pre-inner nostril length (PINL) from snout tip to a line connecting
inner ends of right and left inner nostrils, head width at mouth corners (HMCW), interorbital space (INO) between
anterior ends of orbits, caudal fin length (CL) from ventral caudal-fin origin to the tip, caudal fin height (CH) as
greatest height from caudal-fin dorsal margin perpendicularly to apex of the ventral lobe, caudal fin postventral
margin (CPoV) from apex of caudal-fin ventral lobe to subterminal notch, and caudal fin terminal lobe height
(CTH) at subterminal notch. Additional measurements according to Kaschner et al. (2015): head width at level of
lateral indention of head (slightly before anterior margin of nostrils) (HLIW), head width at level of maximum
outer extent of nostrils (HONW) and head width at posterior edge of nostrils (HPNW). Stage of maturity was
determined following Stehmann (2002). Terminology of glans clasper components is after Séret (1987), Compagno
(1988) and Kaschner et al. (2015). Measurements and terminology of egg cases follow Concha et al. (2010) and
Ishihara et al. (2012), vertebral counts and terminology Springer & Garrick (1964). Vertebrae and tooth rows were
counted from radiographs. The catch locations of the 44 type specimens are shown in the map in Figure 1, which
was generated based on the Global Relief Model ETOPO1 by the NOAA, the National Oceanic and Atmospheric
Administration (Amante & Eakins 2009). For a map with all stations of cruise 17 of R.V. ‘Vityaz’ see Weigmann et
al. (2013) or Weigmann et al. (2015).
The holotype and 31 paratypes were deposited in the Zoological Museum Hamburg (ZMH), eight paratypes in
the California Academy of Sciences (CAS), and two paratypes each in the South African Institute for Aquatic
Biodiversity (SAIAB) and in the United States National Museum of Natural History, Smithsonian Institution,
Washington DC (USNM).
Molecular data
Tissue samples collected in the field by PJC were stored in 95% alcohol and sent to GJPN for processing. DNA
was extracted from the alcohol preserved samples using the E.Z.N.A Tissue DNA Kit (Omega Bio-Tek, Inc
Norcross, GA). Extracted total DNA was then subjected to PCR amplification targetting the mitochondrial
NADH2 gene which is routinely used for species identification in GJPN’s laboratory (Naylor et al. 2005).
Resulting DNA sequences were edited using Geneious® Pro v. 6.1.7 (Biomatters Ltd Auckland, New Zealand.
Available at http://www.geneious.com). The edited sequences were translated to amino acids and aligned with
corresponding NADH2 sequences from representatives of closely related Bythaelurus species using the MAFFT
module within the Geneious Package (Biomatters Ltd Auckland, New Zealand). The aligned amino acid sequences
were translated back, in frame, to their original nucleotide sequences, to yield a nucleotide alignment. The full
protein-coding alignment was 1044 nucleotides long. The alignment was subjected to a maximum likelihood
analysis using the General Time Reversible model modified to accommodate rate heterogeneity among sites and a

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proportion of invariant sites estimated from the data set (GTR+I+G). Phylogenetic analyses were conducted using
the software package PAUP*4.0 version a148.
FIGURE 1. Map of the southwestern Indian Ocean depicting the catch locations of the holotype (black circle) and paratypes
(black and white circles) of Bythaelurus bachi n. sp. on Madagascar Ridge.
Systematic account
Bythaelurus bachi n. sp.
Bach’s Catshark
Figures 2–18; Tables 1–2
Holotype ZMH 26160, adult male, 422 mm TL fresh, 390.5 mm TL 70% ethanol preserved, RV ‘Vityaz’, cruise
17, station 2707, Walters Shoals, 33°01.8’ S, 44°23.6’ E – 32°59.8’ S, 44°24.4’ E, 910–925 m depth, 19.4 m
shrimp trawl, trawl # 60, on the bottom for 60 minutes, 15 Dec 1988.
Paratypes (43) ZMH 26161, adult female with one egg case in each uterus, 405 mm TL fresh, 395 mm TL
70% ethanol preserved, RV ‘Vityaz’, cruise 17, station 2668, Walters Shoals, 33°01.2’ S, 44°36.8’ E – 33°05.2’ S,
44°39.2’ E, 1010 m depth, 19.4 m shrimp trawl, trawl # 48, on the bottom for 61 minutes, 08 Dec 1988; ZMH
26162, female post-embryo, 122 mm TL fresh, 120 mm TL 70% ethanol preserved, data the same as ZMH 26161;
ZMH 26163, juvenile female, 227 mm TL fresh, 220 mm TL 70% ethanol preserved, data the same as ZMH
26161; ZMH 26164, juvenile female, 361 mm TL fresh, 355 mm TL 70% ethanol preserved, data the same as
ZMH 26161; ZMH 26165, juvenile male, 210 mm TL fresh, 205 mm TL 70% ethanol preserved, data the same as
ZMH 26161; ZMH 26166, juvenile male, 248 mm TL fresh, 240 mm TL 70% ethanol preserved, data the same as
ZMH 26161; ZMH 26167, juvenile male, 253 mm TL fresh, 246 mm TL 70% ethanol preserved, data the same as
ZMH 26161; ZMH 26168, juvenile male, 323 mm TL fresh, 317 mm TL 70% ethanol preserved, data the same as
ZMH 26161; ZMH 26169, juvenile female, 290 mm TL fresh, 284 mm TL 70% ethanol preserved, RV ‘Vityaz’,

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cruise 17, station 2670, Walters Shoals, 33°01.6’ S, 44°49.2’ E – 33°04’ S, 44°49.1’ E, 1090–1100 m depth, 19.4 m
shrimp trawl, trawl # 49, on the bottom for 60 minutes, 09 Dec 1988; ZMH 26170, juvenile female 292 mm TL
fresh, 289 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26171, juvenile female 295 mm TL
fresh, 290 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26172, juvenile female 314 mm TL
fresh, 309 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26173, juvenile female 320 mm TL
fresh, 312 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26174, juvenile female 339 mm TL
fresh, 331 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26175, juvenile female 346 mm TL
fresh, 339 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26176, juvenile female 350 mm TL
fresh, 347 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26177, juvenile male 254 mm TL
fresh, 248 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26178, juvenile male 305 mm TL
fresh, 297 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26179, juvenile male 314 mm TL
fresh, 309 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26180, juvenile male 322 mm TL
fresh, 313 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26181, juvenile male 328 mm TL
fresh, 322 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26182, juvenile male 354 mm TL
fresh, 346 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26183, juvenile male 359 mm TL
fresh, 349 mm TL 70% ethanol preserved, data the same as ZMH 26169; ZMH 26184, juvenile female, 312 mm
TL fresh, 297 mm TL 70% ethanol preserved, RV ‘Vityaz’, cruise 17, station 2671, Walters Shoals, 32°56’ S,
45°01’ E – 32°59’ S, 45°03’ E, 1175–1200 m depth, 19.4 m shrimp trawl, trawl # 50, on the bottom for 60 minutes,
09 Dec 1988; ZMH 26185, female post-embryo, 144 mm TL fresh, 132 mm TL 70% ethanol preserved, RV
‘Vityaz’, cruise 17, station 2706, Walters Shoals, 33°01’ S, 44°30’ E – 33°05’ S, 44°32’ E, 970–980 m depth, 19.4
m shrimp trawl, trawl # 59, on the bottom for 40 minutes, 15 Dec 1988; ZMH 26186, juvenile male, 376 mm TL
fresh, 350 mm TL 70% ethanol preserved, data the same as holotype ZMH 26160; ZMH 26187, adult male 410
mm TL fresh, 378 mm TL 70% ethanol preserved, data the same as holotype ZMH 26160; ZMH 26188, adult
female, 404 mm TL fresh, 393 mm TL 70% ethanol preserved, RV ‘Vityaz’, cruise 17, station 2735, Walters
Shoals, 33°36’ S, 44°32’ E – 33°38’ S, 44°34’ E, 930–950 m depth, 29 m shrimp trawl, trawl # 68, on the bottom
for 75 minutes, 19 Dec 1988; ZMH 26189, adult female 407 mm TL fresh, 400 mm TL 70% ethanol preserved,
data the same as ZMH 26188; ZMH 26190, female post-embryo, 132 mm TL fresh, 125 mm TL 70% ethanol
preserved, data the same as ZMH 26188; ZMH 26191, juvenile female, 265 mm TL fresh, 245 mm TL 70%
ethanol preserved, RV ‘Vityaz’, cruise 17, station 2736, Walters Shoals, 33°58.1’ S, 45°01’ E – 33°57’ S, 45°02.5’
E, 1030–1050 m depth, 29 m shrimp trawl, trawl # 69, on the bottom for 47 minutes, 19 Dec 1988; CAS 241442, 3
specimens: adult male, 400 mm TL (tissue accession GN 15514), adult females, 422 and 423 mm TL, Walters
Shoals, 34°01’ S, 45°36’ E, 950–1340 m depth, bottom trawl, 16 May 2014; CAS 241443, pregnant female, 405
mm TL, Walters Shoals, 34°01’ S, 45°36’ E, 950–1345 m depth, bottom trawl, 14 Apr 2014; CAS 241444, 2
specimens: adult female, 392 mm TL (tissue accession GN 15516), adult female, 445 mm TL (tissue accession GN
15517), Walters Shoals, 34°01’ S, 45°36’ E, 960–1210 m depth, bottom trawl, 14 Apr 2014; CAS 241445 (tissue
accession GN 12074), adult female, 404 mm TL, Walters Shoals, 34°24’ S, 45°06’ E, 1123–1294 m depth, bottom
trawl, 4 May 2012; CAS 241478 (tissue accession GN 15515), pregnant female, 408 mm TL, Walters Shoals,
34°01’ S, 45°36’ E, 950–1365 m depth, bottom trawl, 16 May 2014; SAIAB 202736, adult female, 403 mm TL,
data the same as CAS 241443; SAIAB 202737, adult female, 415 mm TL, data the same as CAS 241444; USNM
438923, adult female, 409 mm TL, data the same as CAS 241442; USNM 438924, adult female, 412 mm TL, data
the same as CAS 241442.
Type specimens at ZMH were collected by M.F.W. Stehmann, those at CAS, SAIAB and USNM by P.J.
Clerkin.
Diagnosis. A small scyliorhinid and a medium-sized Bythaelurus species with the following characteristics:
body firm and stout (slender in juveniles); snout long (preorbital length 4.7–7.6% TL) and broad, bell-shaped in
dorsoventral view with distinct lateral indention; pre-outer nostril length 1.1–1.9 times internarial space; preorbital
snout length 0.7–1.0 times interorbital space; preoral snout length 1.0–1.9 times in mouth width; eye length 9.0–
13.0 times in predorsal distance, 3.6–5.4 times in head length and 1.4–4.1 times eye height; head length 1.8–2.7
times width at level of maximum outer extent of anterior nostrils; head width at level of maximum outer extent of
anterior nostrils 1.1–1.5 times width at level of lateral indention of head, 1.1–1.8 times preorbital length, and 7.2–
10.0% TL; tongue and roof of mouth densely set with oral papillae of distinct size, which are partially very large
and conglomerated from several single papillae; pelvic anterior margin 1.1–2.1 times in pectoral-fin anterior

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margin; first dorsal-fin base 1.0–1.8 times in interdorsal space; length of second dorsal-fin inner margin 0.5–1.9
times in second dorsal-fin height; second dorsal-fin base length 6.7–9.7% TL; anal-fin base 0.7–1.3 times
interdorsal space. Coloration: body and fins plain beige to light grayish-brown, slightly brighter on ventral side.
Upper jaw with 70–84 and lower jaw with 60–76 rows of small tri- to pentacuspidate teeth with outer surface of
crown furrowed by strong longitudinal ridges and structured by reticulations in basal areas; monospondylous trunk
vertebrae centra 38–43, diplospondylous precaudal centra 33–43, total centra 124–132. Dermal denticle
morphology highly diverse in different body areas and post-embryonic specimens with very characteristic double
row each of about 20 distinctly enlarged, blunt, spatulate, cross-based dermal denticles along dorsal trunk. Claspers
rather long and very thick, inner margin length 10.6–11.3% TL, base width 2.3–3.1% TL; no clasper hooks, cover
rhipidion and pseudosiphon very large, envelope elongated. The new species is easily distinguished from all
congeners by the plain beige to light gray-brown coloration, high diversity in dermal denticle morphology, and
presence of composite oral papillae. In the western Indian Ocean, it is the only stout-bodied species of Bythaelurus
with oral papillae.
Description of the holotype (Figures 2–18). Values of the paratypes in parentheses. Morphometric
measurements and meristics are given in Table 1.
FIGURE 2. Bythaelurus bachi n. sp., female in lateral view illustrating its natural body shape. Drawing by SciGraphics.
External morphology. Body firm and stout (slender in juveniles), subcircular in cross section at mid-trunk,
laterally compressed and tapering posterior to cloaca; head region broad, long abdominal and caudal sections
(Figures 2–4). No predorsal, interdorsal, or postdorsal ridges; no postanal ridge; no lateral ridges on caudal
peduncle. Trunk about as long as tail, distance from tip of snout to anterior cloaca 51.6% TL (42.0–53.2% TL,
small values in post-embryos and small juveniles only, details can be found under Remarks); pre-first dorsal-fin
length 50.1% TL (41.1–51.9% TL, small values in post-embryos and small juveniles only), pre-second dorsal-fin
length 65.5% TL (56.4–66.7% TL, small values in post-embryos and small juveniles only), ventral precaudal
length 71.7% TL (61.7–72.8% TL, small values in post-embryos and small juveniles only). Head broad and
dorsoventrally flattened, with a broadly rounded snout; laterally slightly compressed in gill region (Figure 5); no
supraorbital crests on chondrocranium; head length 2.6 (1.8–2.7) times width at level of maximum extent of
anterior nostrils and 1.0 (0.6–1.3) times pectoral—pelvic space; head width at level of maximum outer extent of
anterior nostrils 1.3 (1.1–1.5) times width at level of lateral indention of head, 1.3 (1.1–1.8) times preorbital length,
and 8.8% (7.2–10.0%) TL; head width at posterior edge of nostrils 1.6 (1.2–1.7) and at mouth corners 2.0 (1.5–2.2)
times width at level of lateral indention of head; head width at middle gill slits 1.8 (1.2–2.1) times width at level of
lateral indention of head. Snout long and broad, its tip broadly rounded, strongly bell-shaped in dorsoventral view
with distinct lateral indention; pre-outer nostril length 1.5 (1.1–1.9) times internarial width and 0.5 (0.4–0.8) times
interorbital width; preoral length 0.8 (0.5–1.1) times mouth width and 1.1 (0.8–1.5) times preorbital length;
preorbital length 3.5 (2.4–4.1) times in head length and 0.8 (0.7–1.0) times interorbital space. Eyes rather large and
elongated, dorsolaterally on head, eye length 4.7 (3.6–5.4) times in head length, 10.3 (9.0–13.0) times in predorsal
distance, and 2.1 (1.4–4.1) times eye height; nictitating lower eyelids, anterior and posterior eye notches, and
suborbital grooves present. Spiracles very small and slit-like, close behind but well separated from eyes,
dorsolaterally on head and somewhat lower than level of eye notches, spiracle length 9.0 (6.2–14.5) times in eye
length and 14.7 (10.2–25.2) times in interorbital width. Gill slits moderately long, well separated, their upper ends
clearly below level of lower edge of eye; gill area fully scaled, gill filaments not visible externally; gill openings
decreasing in size from first to fifth, the latter above pectoral-fin origin. Nostrils oblique, expanding diagonally

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inwards from snout edge, clearly not reaching level of mouth, with triangular anterior nasal flaps; pre-outer nostril
length 1.0 (0.7–2.1) times nostril width and 0.5 (0.5–0.9) times preoral snout length, nostril width 1.6 (0.8–1.9)
times internarial width and 0.8 (0.5–1.0) times eye length. Mouth broad, width 1.3 (1.0–1.9) times preoral length,
0.6 (0.5–0.8) times head width at mouth corners, 2.6 (2.0–3.4) times in head length, and 2.8 (1.6–3.6) times mouth
length. Upper and lower labial furrows well developed, upper ones not reaching midpoint between mouth corner
and posterior margin of nostril, lower furrows 1.4 (1.1–2.8) times as long as upper ones. Tongue moderately long,
flat and rounded, light-colored, densely set with oral papillae of distinct size (Figure 6A–B). Entire roof of mouth
also densely set with papillae of distinct size, which are partially very large and conglomerated from several single
papillae (Figure 6C–F; Figure 7). Fleshy buccal curtain along inner margin of upper and lower jaws densely set
with large and globose papillae (Figure 7).
FIGURE 3. Bythaelurus bachi n. sp., holotype, ZMH 26160, adult male, 390.5 mm TL, in (A) lateral, (B) dorsal, and (C)
ventral views.
FIGURE 4. Bythaelurus bachi n. sp., paratype, ZMH 26161, adult female, 395 mm TL, in lateral view.

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TABLE 1. Bythaelurus bachi n. sp., morphometrics and meristics. Individual values for the adult male holotype (ZMH
26160) and one adult female paratype (ZMH 26161), ranges for all other paratypes (n=42), as well as means and
standard deviations (SD) for all 44 type specimens. Proportional values are expressed as percentages of total length (TL)
70% ethanol preserved except for minimum, maximum, and mean of TL in mm.
B. bachi n. sp. adult
male holotype
ZMH 26160
B. bachi n. sp. adult
female paratype
ZMH 26161
Minimum Maximmum Mean SD
mm % TL mm % TL % TL % TL % TL
TL, total length 390.5 100.0 395.0 100.0 120.0 445.0 328.0
PRC, precaudal length dorsally
(Compagno 1984a)
293.7 75.2 288.4 73.0 66.5 76.4 73.1 2.4
PRVC, precaudal length ventrally
(Nakaya et al. 2008)
279.8 71.7 277.0 70.1 61.7 72.8 69.1 3.0
PD2, pre-D2-length 255.7 65.5 256.7 65.0 56.4 66.7 63.8 2.6
PD1, pre-D1-length 195.6 50.1 195.9 49.6 41.1 51.9 48.2 2.5
HDL_1, head length (to middle end of
fifth gill slit)
89.3 22.9 79.3 20.1 17.8 22.4 20.2 1.2
HDL_2, head length (to level upper end
of fifth gill slit)
90.8 23.3 80.5 20.4 17.6 22.9 20.2 1.3
PG1, prebranchial length 72.2 18.5 68.6 17.4 12.9 18.1 16.6 1.2
PSP, prespiracular length 49.3 12.6 48.4 12.3 10.5 13.8 12.1 0.7
POB, preorbital length 25.5 6.5 26.2 6.6 4.7 7.6 6.4 0.7
PP1, prepectoral length 84.3 21.6 72.4 18.3 15.2 20.0 18.4 1.2
PP2, prepelvic length 190.2 48.7 189.7 48.0 37.9 51.1 46.3 3.1
SVL, snout—anterior vent length 201.7 51.6 203.4 51.5 42.0 53.2 50.0 2.8
PAL, pre-anal fin length 237.7 60.9 231.6 58.6 50.4 62.6 59.0 2.8
IDS, interdorsal space 34.8 8.9 42.1 10.6 7.9 12.0 9.5 1.0
DCS, dorsal (D2)—caudal space 3.3 0.8 1.0 0.3 0.0 4.1 1.6 1.2
PPS, pectoral—pelvic space 87.0 22.3 102.6 26.0 14.8 31.6 23.2 4.2
PAS, pelvic—anal space 26.1 6.7 17.2 4.3 3.0 8.6 6.0 1.2
ACS, anal—caudal space 0.0 0.0 5.0 1.3 0.0 1.6 0.3 0.4
PCA, pelvic—caudal space 67.6 17.3 60.1 15.2 13.9 22.0 16.4 1.7
VCL, anterior vent—caudal tip length 192.9 49.4 189.2 47.9 46.4 57.1 50.3 2.6
PONL, pre-outer nostril length 14.1 3.6 14.9 3.8 3.0 5.2 3.8 0.5
PINL, pre-inner nostril length 22.9 5.9 20.7 5.2 4.0 6.3 5.2 0.6
POR, preoral length 26.9 6.9 23.0 5.8 4.7 7.1 6.2 0.6
EYL, eye length 19.0 4.9 16.8 4.3 3.8 5.3 4.6 0.4
EYH, eye height 9.1 2.3 7.8 2.0 1.3 3.0 2.2 0.5
ING, intergill length 1st to last slit (upper
end to upper end)
18.1 4.6 15.9 4.0 2.5 5.3 4.0 0.6
GS1, 1st gill slit height (unspread) 7.3 1.9 9.7 2.5 1.2 3.3 2.3 0.5
GS2, 2nd gill slit height 5.0 1.3 8.3 2.1 1.1 3.1 2.0 0.5
GS3, 3rd gill slit height 4.6 1.2 7.7 2.0 0.7 2.5 1.6 0.5
GS4, 4th gill slit height 3.9 1.0 5.7 1.4 0.6 1.9 1.3 0.4
GS5, 5th gill slit height 2.9 0.8 2.4 0.6 0.4 1.6 0.9 0.3
P1A, pectoral anterior margin length 41.9 10.7 40.9 10.4 9.3 13.4 11.3 1.1
P1B, pectoral base length 21.6 5.5 27.0 6.8 5.2 7.6 6.5 0.6
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TABLE 1. (Continued)
B. bachi n. sp. adult
male holotype
ZMH 26160
B. bachi n. sp. adult
female paratype
ZMH 26161
Minimum Maximmum Mean SD
mm % TL mm % TL % TL % TL % TL
P1I, pectoral inner margin length 24.9 6.4 21.4 5.4 4.1 7.5 6.0 0.7
P1P, pectoral posterior margin length 38.3 9.8 37.1 9.4 4.9 10.9 8.8 1.3
P1H, pectoral height (base end to tip) 42.8 11.0 40.4 10.2 8.3 11.9 10.1 0.9
P1L, P length (ant. base to post. tip) 45.3 11.6 42.3 10.7 9.1 12.7 11.0 1.0
D1L, D1 total length 45.8 11.7 41.7 10.5 9.2 12.1 10.5 0.6
D1A, D1 anterior margin length 44.8 11.5 42.3 10.7 8.3 12.1 10.3 0.8
D1B, D1 base length 31.4 8.0 28.3 7.2 5.5 9.8 7.1 0.8
D1H, D1 vertical height 16.1 4.1 18.5 4.7 2.1 5.5 4.3 0.6
D1I, D1 inner margin length 12.1 3.1 11.2 2.8 1.9 3.8 3.1 0.4
D1P, D1 posterior margin length 12.2 3.1 14.4 3.7 1.8 4.1 3.4 0.5
D2L, D2 total length 47.3 12.1 46.8 11.9 10.0 13.9 11.5 0.7
D2A, D2 anterior margin length 48.8 12.5 45.1 11.4 9.0 13.5 11.5 0.9
D2B, D2 base length 32.4 8.3 31.2 7.9 6.7 9.7 7.9 0.7
D2H, D2 vertical height 19.0 4.9 19.0 4.8 2.3 5.3 4.4 0.6
D2I, D2 inner margin length 12.2 3.1 13.4 3.4 2.4 4.7 3.2 0.5
D2P, D2 posterior margin length 14.9 3.8 14.7 3.7 2.1 4.6 3.8 0.5
P2L, pelvic total length 47.2 12.1 45.7 11.6 9.3 13.1 11.2 0.8
P2A, pelvic anterior margin length 34.0 8.7 27.6 7.0 5.7 9.1 7.4 0.8
P2B, pelvic base length 26.3 6.7 28.2 7.1 4.3 9.3 7.6 1.0
P2H, pelvic height = max. width (excl.
clasper)
19.8 5.1 22.5 5.7 3.0 7.8 5.5 0.9
P2I, pelvic inner margin length 22.3 5.7 20.9 5.3 2.8 5.6 4.4 0.6
P2P, pelvic posterior margin length 22.0 5.6 28.2 7.1 4.2 8.7 6.8 1.0
ANL, anal fin total length 48.2 12.3 52.0 13.2 10.3 15.9 12.1 0.9
ANA, anal fin anterior margin length 37.6 9.6 38.7 9.8 7.0 13.6 9.4 1.2
ANB, anal fin base length 40.2 10.3 42.7 10.8 7.5 12.2 9.9 0.8
ANH, anal fin vertical height 22.0 5.6 23.3 5.9 3.3 6.2 5.1 0.6
ANI, anal fin inner margin length 8.8 2.2 8.6 2.2 1.6 3.3 2.2 0.4
ANP, anal fin posterior margin length 25.5 6.5 27.3 6.9 3.1 8.7 6.0 1.1
CL, caudal fin length 114.0 29.2 107.5 27.2 25.5 37.4 30.4 2.9
CH, caudal fin height 26.5 6.8 26.7 6.8 5.8 8.1 6.8 0.4
CPrV, caudal fin preventral margin 49.3 12.6 50.9 12.9 11.8 18.3 14.3 1.6
CPoV, caudal fin postventral margin 41.7 10.7 40.5 10.2 9.5 14.1 11.7 1.2
CTH, caudal fin terminal lobe height 19.9 5.1 18.3 4.6 3.3 5.4 4.6 0.5
CTL, caudal fin terminal lobe length 23.0 5.9 21.0 5.3 5.3 7.0 6.0 0.5
HDH, head height at P origin 38.9 10.0 41.3 10.4 5.4 12.0 9.1 1.4
TRH, trunk height at P base end 47.9 12.3 47.2 12.0 5.5 15.2 10.8 2.1
ABH, abdomen height at D1 base end 20.7 5.3 23.7 6.0 4.6 6.9 5.9 0.6
TAH, tail height at pelvic base end 21.7 5.5 24.6 6.2 4.9 7.2 6.0 0.5
CPH, caudal peduncle height at C origin 13.9 3.6 14.2 3.6 3.4 4.3 3.8 0.3
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TABLE 1. (Continued)
B. bachi n. sp. adult
male holotype
ZMH 26160
B. bachi n. sp. adult
female paratype
ZMH 26161
Minimum Maximmum Mean SD
mm % TL mm % TL % TL % TL % TL
MOL, mouth length (arc radius) 12.2 3.1 14.3 3.6 2.3 5.1 3.6 0.5
MOW, mouth width 34.5 8.8 31.1 7.9 6.0 9.7 8.3 0.8
ULA, upper labial furrow length 4.9 1.3 3.4 0.9 0.6 1.3 1.0 0.2
LLA, lower labial furrow length 7.0 1.8 5.5 1.4 1.0 2.3 1.6 0.2
NOW, nostril width 14.7 3.8 12.7 3.2 2.2 4.2 3.1 0.6
INW, internarial width 9.3 2.4 8.7 2.2 1.8 3.1 2.5 0.3
ANF, anterior nasal flap length 5.1 1.3 6.1 1.5 0.8 1.6 1.1 0.2
INO, interorbital space at ant. orbits 31.0 7.9 29.3 7.4 5.9 8.8 7.3 0.8
SPL, spiracle length 2.1 0.5 1.2 0.3 0.4 0.6 0.5 0.1
ESL, eye—spiracle length 5.0 1.3 5.0 1.3 0.5 1.6 0.9 0.3
HLIW, head width at level of lateral
indention
26.5 6.8 24.5 6.2 5.8 7.5 6.6 0.4
HONW, head width at max. outer extent
of nostrils
34.4 8.8 32.6 8.3 7.2 10.0 8.7 0.6
HPNW, head width at posterior edge of
nostrils
41.9 10.7 39.2 9.9 7.8 11.3 10.2 0.7
HMCW, head width at mouth corners 53.1 13.6 49.1 12.4 10.4 13.9 12.6 1.0
HDW, head width at 3rd gill slits 47.4 12.1 49.2 12.4 8.5 13.9 11.6 1.2
TRW, trunk width at P base ends 45.5 11.6 53.5 13.5 7.0 13.6 11.2 1.6
ABW, abdomen width at D1 base end 16.8 4.3 17.0 4.3 3.1 4.5 3.8 0.4
TAW, tail width at pelvic base ends 18.3 4.7 17.6 4.5 2.8 5.8 4.3 0.7
CPW, C peduncle width at C origin 9.1 2.3 9.2 2.3 1.8 4.0 2.3 0.4
CLO, clasper outer margin length 26.4 6.8 - - 1.4 6.7 3.6 2.5
CLI, clasper inner margin length 43.0 11.0 - - 3.6 11.3 5.8 2.7
CLB, clasper base width 9.7 2.5 - - 0.6 3.1 1.2 0.8
trunk vertebral centra (n=28) 40 40 38 43 40.0 1.1
diplospondylous precaudal centra
(n=28)
38 43 33 40 37.6 2.1
total precaudal centra (n=28) 78 83 73 81 77.6 2.3
caudal centra (n=28) 54 48 48 56 51.3 2.3
total centra (n=28) 132 131 124 132 128.9 2.2
tooth rows in upper jaw (approximately)
(n=14)
84 80 70 84 78.9 3.6
tooth rows in lower jaw (approximately)
(n=14)
74 70 60 76 70.2 4.9

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FIGURE 5. Bythaelurus bachi n. sp., holotype, ZMH 26160, adult male, 390.5 mm TL, head in (A) lateral, (B) dorsal, and (C)
ventral views.

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FIGURE 6. Bythaelurus bachi n. sp., paratype, ZMH 26180, juvenile male, 313 mm TL, SEM images of oral papillae. (A, B):
oral papillae on tongue; overview (A) and close-up (B). (C–F): oral papillae on roof of mouth; (C) overview of simple and
composite papillae, (D) close-up of simple papillae, (E, F) close-ups of composite papillae. Scale bars: (A–B, D–E) 100 µm,
(C) 300 µm, (F) 10 µm.
Upper jaw with approximately 84 (70–84) and lower jaw with about 74 (60–76) diagonal rows of small teeth
(n = 14; Figure 7). Anterolateral teeth in upper jaw tricuspidate (partially with minute additional cusplets) with
median cusp much longer than lateral cusps (Figure 8A–B); posterolateral teeth in upper jaw tetra- to
pentacuspidate and with median cusp only slightly longer than lateral cusps (Figure 8C–D). Anterolateral (Figure
8E–F) and posterolateral (Figure 8G–H) teeth in lower jaw similar to posterolateral teeth in upper jaw. Outer
surface of crown furrowed by strong longitudinal ridges from base of cusps to tip and structured by reticulations in
basal areas. Cutting edges of cusps without serrations.
Dermal denticles densely set and strongly overlapping. Dermal denticles on dorsal snout tip leaf-like, surface
almost completely structured by reticulations, median ridge very narrow and reaching denticle tip (Figure 9A–B).

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Dermal denticles on ventral snout tip subrhombic, surface structured by reticulations only in basal two thirds,
median ridge very narrow and not reaching denticle tip (Figure 9C–D). Branchial dermal denticles tricuspidate
with long, pointed and broad median cusp and tiny lateral cusps at lower level, surface structured by reticulations in
basal two thirds, one or two median ridges that do not fuse and do not reach the tip of the median cusp (Figure 9E–
F). Lateral trunk denticles tricuspidate with long, pointed and slender median cusp and small lateral cusps at lower
level, surface almost completely structured by reticulations, two median ridges that fuse near the tip of the median
cusp and reach the tip (Figure 10A–B). Dermal denticles on lateral caudal fin similar, tricuspidate with long,
pointed and slender median cusp and tiny lateral cusps at lower level, surface almost completely structured by fine
reticulations, two median ridges that fuse near the tip of the median cusp and reach its tip (Figure 10C–D). Dermal
denticles on anterior dorsal caudal-fin margin slightly enlarged, with short median cusp and slightly shorter lateral
cusps, surface structured by reticulations in basal half, one or two median and two to four lateral ridges, the median
ridges rarely fuse near the tip of the median cusp and only one median ridge reaches the tip, the lateral ridges do not
fuse and only one reaches the tip of each lateral cusp (Figure 10E–F). Post-embryonic paratypes (ZMH 26162,
ZMH 26185, and ZMH 26190) with very characteristic double row of each about 20 distinctly enlarged, blunt,
spatulate, cross-based dermal denticles along dorsal trunk from about level origin of pectoral fins to slightly
posterior to origin of first dorsal fin (Figure 11; Figure 12A–C). The body is otherwise loosely set with non-
overlapping, small, needle-shaped dermal denticles (Figure 12B–D).
Pectoral fins subtriangular, non-falcate, anterior margin weakly convex, its length 1.9 (1.4–2.2) times pectoral
base length and 1.1 (1.0–2.1) times length of the weakly convex posterior margin, apex rounded, inner margin
convex and 1.2 (0.6–1.3) times pectoral base length, inner pectoral corner broadly rounded (Figure 5). Pectoral -
pelvic space 2.1 (1.3–3.0) times length of pectoral-fin anterior margin and 2.5 (1.5–3.2) times interdorsal space.
FIGURE 7. Bythaelurus bachi n. sp., paratype, ZMH 26179, juvenile male, 309 mm TL, nostrils and open mouth. Note simple
and composite oral papillae on roof of mouth, as well as fleshy buccal curtain along inner margins of jaws, which is densely set
with large and globose papillae. Focus-stacked image.

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FIGURE 8. Bythaelurus bachi n. sp., paratype, ZMH 26180, juvenile male, 313 mm TL, SEM images of tooth rows and single
teeth. (A, B) Anterolateral teeth in upper jaw, (C, D) posterolateral lateral teeth in upper jaw, (E, F) anterolateral teeth in lower
jaw, (G, H) posterolateral teeth in lower jaw. Scale bars: 100 µm.

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FIGURE 9. Bythaelurus bachi n. sp., paratype, ZMH 26180, juvenile male, 313 mm TL, SEM images of dermal denticles on
dorsal (A–B) and ventral (C–D) snout tip, and branchial region (E–F). Scale bars: 100 µm.
Pelvic fins narrowly triangular with long, straight anterior and posterior margins and shorter straight inner
margin, anterior margin 0.8 (0.5–0.9) times pectoral-fin anterior margin, apex very bluntly rounded; pelvic-fin
origin clearly anterior to first dorsal-fin origin, pelvic posterior tips behind level of insertion of first dorsal fin
(Figure 13A). Pelvic—anal space very short, 6.7% (3.0–8.6%) TL and 0.3 (0.1–0.4) times pectoral—pelvic space.
First dorsal fin 0.8 (0.8–1.2) times as high and 1.0 (0.8–1.0) times as long as second dorsal fin, anterior margin
convex, apex rounded, posterior and inner margins straight, free rear tip rounded; base length 1.9 (1.2–2.8) times
fin height and 0.9 (0.5–1.0) times interdorsal space; first dorsal-fin origin anterior to level of pelvic-fin midbase
(Figure 13A).
Second dorsal fin slightly higher (slightly higher to slightly lower) than first dorsal fin, anterior margin slightly
convex, apex rounded, posterior and inner margins straight, free rear tip rounded, base length 1.7 (1.3–3.9: 3.0–3.9

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in post-embryos ZMH 26162 and ZMH 26185, 1.3–2.2 in all other paratypes) times fin height and 0.9 (0.6–1.2)
times interdorsal space; second dorsal-fin origin over anal-fin midbase (Figure 13A).
FIGURE 10. Bythaelurus bachi n. sp., paratype, ZMH 26180, juvenile male, 313 mm TL, SEM images of dermal denticles on
lateral trunk (A–B), lateral caudal fin (C–D), and anterior dorsal caudal-fin margin (E–F). Scale bars: 100 µm.
Anal fin a long and high, uneven triangle, with long straight anterior margin, slightly shorter and straight
posterior margin, and short inner margin, apex rounded, free rear tip pointed angular; base length 1.8 (1.4–2.9)
times fin height, 1.2 (0.7–1.3) times interdorsal space, and 1.5 (1.0–3.1) times pelvic—anal space; base 1.2 (1.0–
1.5) times longer than second dorsal-fin base. Anal—caudal space absent (absent to 1.6% TL) (Figure 13A). Anal-
fin origin distinctly anterior to second dorsal-fin origin.
Caudal fin slender, moderately long and strongly asymmetrical, its length 4.3 (3.7–6.5) times fin height and 3.3
(2.4–4.3) times interdorsal space; dorsal caudal margin weakly convex, no lateral undulations; upper caudal lobe
very low, lower caudal lobe much deeper, with straight pre- and postventral margins. Ventral caudal-fin origin far
anterior of dorsal caudal-fin origin due to very long preventral margin, which is slightly longer than the postventral

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margin and forms a strongly elongated fleshy ridge in about anterior two-thirds of its length. Ventral corner bluntly
angled; subterminal notch distinct; terminal lobe 5.0 (4.1–6.5) times in caudal fin length; terminal caudal margin
nearly straight with mesial indention (Figure 13B).
FIGURE 11. Bythaelurus bachi n. sp., paratype, ZMH 26162, female post-embryo, 120 mm TL, dorsal views of whole
specimen (A) and close-up of anterior trunk (B) showing characteristic double row of enlarged, blunt, spatulate, cross-based
dermal denticles.
Claspers (Figure 14) rather long, overlapping anal-fin origin, and very broad, lateral margins nearly straight,
not undulated, extending to about one third of their inner margin length beyond pelvic-fin free rear tips; inner
margin length 11.0% (10.6–11.3%) TL, base width 2.5% (2.3–3.1%) TL. Glans somewhat elongated, length about
half clasper inner margin; only slightly tapering to tip in distal half but terminally abruptly narrowing to bluntly
pointed tip without knob-like apex. Ventral and outer lateral surfaces of clasper covered with small tricuspidate
clasper denticles (CD), similar to those on trunk; dorsal and inner lateral surfaces largely naked. The narrow slit-
like apopyle opens the clasper groove proximally; the hypopyle ends the concealed clasper groove distally and is
detectable as a small cavity next to the rhipidion, but both are concealed by the cover rhipidion and exorhipidion
and thus not visible in Figure 14. The proximally concealed clasper groove (CG) opens widely in the distal glans.
An elongated, fleshy flap, the envelope (EN), on outer lobe of glans, does not overlap part of CG; outer lobe also
with a large, subtriangular exorhipidion (ER), which consists of a proximal convex blade and a distal fleshy wall;
no enlarged clasper denticles (clasper hooks) along inner edge of ER. Inner lobe with a fan-shaped flap, the
rhipidion, that partially covers the concealed part of CG and itself is concealed by a movable blade, the large cover
rhipidion (CR); inner lobe also with two blind cavities: the large and deep pseudopera (PP), that is partially
concealed by EN and RH, and – on the inner margin – the large, longitudinally slit-like pseudosiphon (PS).
Egg cases (Figure 15): the reproductive mode was determined to be oviparous based on egg cases found in
adult female paratypes ZMH 26161, CAS 241443 and CAS 241478. Each female had a single fully developed egg
case per uterus. The egg cases are small, 62.6–69 mm long, excluding horns, relatively broad, and thick, maximum
anterior case width about 28.3–31.7% of case length, maximum posterior case width about 32.6–40.2% of case
length, and minimum case width (through indention) about 24.6–30.9% of case length; greatest case height about
16.8–18.1% of case length and about 44.1–55.6% of posterior case width. Egg case surface with very fine
striations, relatively smooth to the touch. Lateral keels of case narrow, about 1 mm wide, flat, and without T-shaped
lateral surface, extending along entire capsule length and continuous with horns at both ends. The anterior border
of case is narrow and concave, with horns narrow, very short, and curved inwards, overlapping slightly, and
without any evidence of tendrils being present. The posterior border of case is slightly concave, broad, and with
horns relatively long, also without any evidence of tendrils being present. Posterior apron short, length about 15%
of case length, and wide, with weakly concave transverse edge, and attached to horns over about 3/4 of horn length,

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the tips of which are only free and curving inward. Anterior horns somewhat longer than posterior ones, curved
inward over their entire length and with their tips nearing to each other much closer than tips of posterior horns.
Anterior apron short, length about 10% of case length, and appearing strongly folded longitudinally, with folds
almost ridge-like, and extending to tips of horns. The egg cases removed from the preserved females were light
brown with a greenish tinge.
FIGURE 12. Bythaelurus bachi n. sp., (A) paratype, ZMH 26162, female post-embryo, 120 mm TL, radiograph in total dorsal
view depicting double row of enlarged dermal denticles on dorsal anterior trunk. (B–D) Paratype, ZMH 26190, female post-
embryo, 125 mm TL, SEM images of dermal denticles on dorsal anterior trunk showing overview of enlarged, blunt, spatulate,
cross-based and small, needle-shaped dermal denticles (B) and close-ups of an enlarged, spatulate (C) and a small, needle-
shaped (D) dermal denticle. Scale bars: (A) 10 mm, (B–D) 100 µm.

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FIGURE 13. Bythaelurus bachi n. sp., holotype, ZMH 26160, adult male, 390.5 mm TL, lateral views of (A) dorsal fins,
pelvic fin and anal fin, (B) caudal fin.
Skeletal meristics (from radiographs, n = 28, Table 1): monospondylous trunk vertebral centra: 40 (38–43);
diplospondylous precaudal centra: 38 (33–43); total precaudal centra: 78 (73–83); caudal centra: 54 (48–56); total
centra: 132 (124–132). Spiral valve turns (counted in three partially dissected paratypes): 6–8.
Coloration. Fresh, prior to preservation: nearly plain colored without pattern; back, upper flanks and fins light
grayish-brown, becoming lighter to creamy white or light grayish on body and ventral body creamy; prenasal area
and caudal peduncle brownish; all fins with very narrow dusky edging of anterior margins; dorsal fins with very
narrow pale posterior edge (Figure 16). Post-embryonic specimens have a distinctly dark edge along margins of
dorsal, pelvic, anal, and especially caudal fins (Figure 17). Color in preservative: body and fins plain beige to light
grayish-brown, slightly brighter on ventral side (Figures 3–4). Dark fin edges of post-embryonic specimens are still
prominent in specimen ZMH 26162 (Figure 11) but specimens ZMH 26185 and ZMH 26190 have almost

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completely faded. All specimens from station 2670 (ZMH 26169–26183) have almost completely faded as well.
Furthermore, the latter specimens have become very fragile and partially damaged.
FIGURE 14. Bythaelurus bachi n. sp., holotype, ZMH 26160, adult male, 390.5 mm TL, left clasper in dorsal view. CD =
clasper denticles; CG = clasper groove; CR = cover rhipidion; EN = envelope; ER = exorhipidion; PP = pseudopera; PS =
pseudosiphon; PV = pelvic fin.
FIGURE 15. Bythaelurus bachi n. sp., left egg case removed from paratype, CAS 241443, adult female, 405 mm TL.
Molecular analyses (Figure 18). The maximum likelihood analysis of the aligned NADH2 sequence data
clearly shows that Bythaelurus bachi is a monophyletic lineage that is distinct from, but closely related to, B.
naylori. These two species fall as sister to B. dawsoni (Springer, 1971) from New Zealand. Representatives of B.
canescens (Günther, 1878) and B. hispidus were included in the analysis for comparitive purposes. Both fall
outside the clade containing B. bachi, B. naylori and B. dawsoni. It is important that not too much stock be placed

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in the phylogenetic arrangements presented as the inference is based on a single mitochondrial gene and because
the sampling of taxa is sparse. Several described species of Bythaelurus and closely related genera were not
included in the present analysis because fresh tissue samples were not available. We anticipate a more
comprehensive analysis of the group at a later date as and when tissues become available.
FIGURE 16. Fresh image of Bythaelurus bachi n. sp., (A) holotype, ZMH 26160, adult male, 422 mm TL fresh in dorsal view
and (B) paratype, ZMH 26187, adult male, 410 mm TL fresh in ventral view.
FIGURE 17. Fresh image of Bythaelurus bachi n. sp., paratype, ZMH 26185, female post-embryo, 144 mm TL fresh in lateral
view.
Size (based on total length measurements prior to preservation). A small catshark and a medium-sized species
of Bythaelurus reaching a maximum total length of about 445 mm for females and 422 mm for males. Females are
mature at 392 mm and immature at 361 mm, males are mature at 400 mm and immature at 376 mm. Size at
hatching based on the three post-embryonic specimens is estimated at around 120 mm TL.
Distribution. Known only from the southern end of the Madagascar Ridge at Walters Shoals in 910–1365 m
depth (Figure 1).
Etymology. The new species is named in honor of Johann Sebastian Bach (1685–1750), a musical genius and
one of the greatest composers of all time.
Remarks. There are several morphometric differences between the post-embryonic, small immature, and large
immature plus adult specimens of Bythaelurus bachi, which might be of ontogenetic nature. These differences are
demonstrated in Table 2.

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TABLE 2. Morphometric differences between post-embryonic, small immature, and large immature plus adult type
specimens of Bythaelurus bachi. Proportional values are expressed as percentages of total length (TL) 70% ethanol
preserved.
As indicated in Table 2, there is strong variation in the measurements of pectoral—pelvic space among
specimens > 250 mm TL, which ranges from 20.2 to 26.0% TL in the holotype and 22 paratypes of 284–400 mm
TL in the ZMH collection and from 26.6 to 31.6% TL in the 12 other paratypes of 392–445 mm TL. Due to the
geographic proximity of catch locations and individual differences in taking the measurement having been
excluded, the large pectoral—pelvic space might be a characteristic of very large specimens. Nevertheless, this
difference might also be influenced by the condition of the specimens.
Discussion
Bythaelurus bachi n. sp. is easily distinguished from all congeners by the plain beige to light gray-brown
coloration, high diversity in dermal denticle morphology, and presence of composite oral papillae. In the western
Indian Ocean, the new species is the only stout-bodied species of Bythaelurus with oral papillae. The new species
can also be distinguished from three geographically close congeners by its reproductive mode; B. bachi is
oviparous, like B. naylori, while B. clevai, B. lutarius (Springer & D’Aubrey, 1972) and B. hispidus are yolk-sac
viviparous species (Springer & D’Aubrey 1972; Bass et al. 1975; Springer 1979; Séret 1987; Compagno 1988;
Akhilesh et al. 2013). Geographically, B. clevai is only known from off Madagascar and B. lutarius from off
Mozambique, whereas B. bachi and B. naylori both occur on seamounts in the southwestern Indian Ocean (Ebert &
Clerkin 2015).
The morphologically and genetically closest congener of Bythaelurus bachi is B. naylori, which resembles B.
bachi in the largely plain coloration and stout body shape. However, B. bachi has tongue and roof of mouth densely
set with—partially composite—oral papillae of distinct size (vs. oral papillae lacking in B. naylori), a lighter
ground color (beige to light grayish-brown vs. medium to dark brown), fins not light-edged (vs. fins with light
edges), and a snout that is colored like the body (vs. distinctly dark, dusky-colored snout). Furthermore, B. bachi
has only slightly enlarged dermal denticles on the anterior upper caudal-fin margin (vs. dermal denticles distinctly
enlarged), a higher diversity in dermal denticle morphology in general, and a smaller maturity and maximum size
(maturity size 36–40 cm and maximum size 45 cm vs. maturity size 38–48 cm and maximum size 55 cm according
to Ebert & Clerkin [2015] and Weigmann [2016]). Additionally, B. bachi has a smaller pre-outer nostril length
(2.2–2.9 vs. 3.0–5.2% TL), usually a longer head (17.8–22.4 vs. 13.6–18.7% TL), a shorter anal—caudal space (0–
1.6 vs. 6.0–8.6% TL), higher eyes (1.3–3.0 vs. 0.8–1.3% TL; albeit difference possibly due to condition of
specimens), smaller spiracles (length 0.3–0.6 vs. 0.7–1.5% TL), and a longer preventral caudal margin (11.8–18.3
vs. 6.1–7.3% TL).
Post-embryos
(< 150 mm TL;
n = 3)
Small immatures
(> 150 and < 250
mm TL; n = 6)
Large immatures and
adults (> 250 mm TL;
n = 35)
TL, total length (mm) 120–132 205–248 284–445
PRC, precaudal length dorsally (Compagno 1984a) 66.5–67.5 69.1–72.2 71.0–76.4
PRVC, precaudal length ventrally (Nakaya et al. 2008) 61.7–64.3 63.6–68.1 68.6–72.8
PD2, pre-D2-length 56.4–57.0 59.9–62.7 62.2–66.7
PD1, pre-D1-length 41.1–41.9 44.8–46.5 46.3–51.9
PP2, prepelvic length 37.9–39.7 40.7–43.7 43.0–51.1
SVL, snout—anterior vent length 42.0–43.1 44.6–47.3 48.5–53.2
PAL, pre-anal fin length 50.4–52.5 53.3–58.1 57.2–62.6
PPS, pectoral—pelvic space 14.8–15.8 16.2–18.5 20.2–31.6
VCL, anterior vent—caudal tip length 56.0–57.1 52.9–55.7 46.4–52.2
CL, caudal fin length 34.8–37.4 31.6–35.2 25.5–30.7
TRH, trunk height at P base end 5.6–7.7 5.5–11.2 9.5–15.2

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FIGURE 18. Maximum Likelihood tree estimated from 1044 aligned sites of the mitochondrial NADH2 gene using a General
Time Reversible model and an accommodation for among site rate variation and Invariant sites (GTR+I+G model).
The new species differs from all other congeners in the western Indian Ocean (B. clevai, B. hispidus, B.
lutarius, and B. tenuicephalus) in the stout body shape in adult specimens, plain beige to light grayish-brown
coloration, larger size, broader and longer claspers in adults (base width 2.3–3.1 vs. 1.5–2.1% TL, inner margin
length 10.6–11.3 vs. 7.4–9.6% TL), an eye length 9.0–13.0 times in predorsal distance (vs. 13.8–16.7), an anal-fin
base length equal to or less than 1.5 times second dorsal-fin base length (vs. 1.5–2.0), a caudal fin length 1.9–2.3
times preventral length (vs. 2.5–2.8), a shorter pelvic—anal space (3.0–8.6 vs. 10.2–13.6% TL), a shorter pelvic—
caudal space (13.9–22.0 vs. 22.2–28.5% TL), longer eyes (length 3.8–5.3 vs. 2.8–3.4% TL), a longer first dorsal fin
(total length 9.2–12.1 vs. 7.5–9.2% TL), a longer second dorsal fin (total length 10.0–13.9 vs. 6.8–9.0% TL,
anterior margin length 9.0–13.5 vs. 6.8–8.7% TL, inner margin 2.4–4.7 vs. 1.7–2.1% TL), a higher tail at pelvic-fin
base ends (4.9–7.2 vs. 4.3–4.9% TL), shorter upper labial furrows (length 0.6–1.3 vs. 1.4–1.8% TL), and—except
for post-embryos—a pectoral—pelvic space 1.8–3.2 times interdorsal space (vs. 1.2–1.7). Furthermore, large
specimens (> 250 mm TL) of B. bachi also differ from adult specimens of those congeners in a greater prepelvic
length (43.0–51.1 vs. 40.2–43.0% TL), a larger snout—anterior vent length (48.5–53.2 vs. 42.9–46.2% TL), a
larger pectoral—pelvic space (20.2–31.6 vs. 15.8–19.7% TL), a shorter anterior vent—caudal tip length (46.4–52.2
vs. 52.5–56.5% TL), and a higher anal fin (height 4.3–6.2 vs. 2.8–3.3% TL).
The only other largely plain-colored species of Bythaelurus, besides B. naylori, in the western Indian Ocean is
B. lutarius, which differs from B. bachi in the dusky markings near the bases of the dorsal fins. Furthermore, B.
bachi has a stout body in adults (vs. slender in B. lutarius), tongue and roof of mouth densely set with—partially
composite—oral papillae of distinct size (vs. no or virtually no oral papillae), a higher diversity in dermal denticle
morphology in general, and a larger maturity and maximum size (maturity size 36–40 cm and maximum size 45 cm

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A NEW SPECIES AND REVIEW OF BYTHAELURUS
vs. maturity size 28–31 cm and maximum size 39 cm according to Bass et al. [1975] and Weigmann [2016]).
Additionally, B. bachi has larger adult claspers (inner margin length 10.6–11.3 vs. 9.6% TL, base width 2.3–3.1 vs.
1.5% TL), a preorbital snout length 0.7–1.0 times interorbital space (vs. 1.1), an eye length 9.0–13.0 times in
predorsal distance (vs. 14) and 3.6–5.4 times in head length (vs. 6.2), an anal-fin base length equal to or less than
1.5 times second dorsal-fin base length (vs. twice), a caudal fin length 1.9–2.3 times preventral length (vs. 2.5), a
shorter pelvic—anal space (3.0–8.6 vs. 13.6% TL), a shorter anal—caudal space (0–1.6 vs. 2.4% TL), a shorter
pelvic—caudal space (13.9–22.0 vs. 28.5% TL), a greater pre-outer nostril length (3.0–5.2 vs. 2.3% TL), longer
eyes (length 3.8–5.3 vs. 3.4% TL), broader pectoral fins (height 8.3–11.9 vs. 5.8% TL), a longer first dorsal fin
(total length 9.2–12.1 vs. 7.5% TL, anterior margin length 8.3–12.1 vs. 7.6% TL, base length 5.5–9.8 vs. 5.3% TL),
a longer second dorsal fin (total length 10.0–13.9 vs. 6.8% TL, anterior margin length 9.0–13.5 vs. 6.8% TL, base
length 6.7–9.7 vs. 5.3% TL, inner margin 2.4–4.7 vs. 1.7% TL), broader pelvic fins (height 3.0–7.8 vs. 1.9% TL), a
longer anal-fin anterior (7.0–13.6 vs. 6.2% TL) and inner (1.6–3.3 vs. 1.5% TL) margin, a higher caudal fin (5.8–
8.1 vs. 5.0% TL), a longer caudal-fin preventral margin (11.8–18.3 vs. 10.6% TL), a longer caudal-fin terminal
lobe (5.3–7.0 vs. 4.9% TL), a higher (height 4.9–7.2 vs. 4.5% TL) and wider (width 1.8–4.0 vs. 1.5% TL) caudal
peduncle, shorter upper labial furrows (length 0.6–1.3 vs. 1.5% TL), a wider head at mouth corners (width 10.4–
13.9 vs. 9.4% TL), and—except for post-embryos—a pectoral—pelvic space 1.8–3.2 times interdorsal space (vs.
1.2). Large specimens (> 250 mm TL) of B. bachi also differ from adult B. lutarius in a greater prepelvic length
(43.0–51.1 vs. 41.8% TL), a larger snout—anterior vent length (48.5–53.2 vs. 45.2% TL), a larger pectoral—pelvic
space (20.2–31.6 vs. 15.8% TL), a shorter anterior vent—caudal tip length (46.4–52.2 vs. 54.8% TL), and a higher
anal fin (height 4.3–6.2 vs. 2.8% TL). Additionally, B. bachi has a lower spiral valve turn count (6–8 vs. 10).
Bythaelurus clevai, like B. bachi, has oral papillae, but lacks composite papillae and strongly differs in
coloration with numerous small and large dark blotches. Furthermore, B. bachi has a stout body in adults (vs.
slender), a higher diversity in dermal denticle morphology in general, and a larger maturity and maximum size
(maturity size 36–40 cm and maximum size 45 cm vs. maturity size 28–36 cm following Séret [1987] and
maximum size 40 cm based on specimen ZMH 26071 and following Weigmann [2016]). Additionally, B. bachi has
larger claspers in adults (inner margin length 10.6–11.3 vs. 8.9% TL, base width 2.3–3.1 vs. 1.8% TL), a preorbital
snout length 0.7–1.0 times interorbital space (vs. 1.2), an eye length 9.0–13.0 times in predorsal distance (vs. 16.7)
and 3.6–5.4 times in head length (vs. 7.3), an anal-fin base length equal to or less than 1.5 times second dorsal-fin
base length (vs. 1.5), a caudal fin length 1.9–2.3 times preventral length (vs. 2.5), a shorter preorbital length (4.7–
7.6 vs. 8.3% TL), a shorter dorsal—caudal space (0–4.1 vs. 4.9% TL), a shorter pelvic—anal space (3.0–8.6 vs.
10.6% TL), a shorter anal—caudal space (0–1.6 vs. 2.8% TL), a shorter pelvic—caudal space (13.9–22.0 vs. 22.8%
TL), longer eyes (length 3.8–5.3 vs. 2.8% TL), a longer first dorsal fin (total length 9.2–12.1 vs. 8.2% TL), a longer
second dorsal fin (total length 10.0–13.9 vs. 8.9% TL, anterior margin length 9.0–13.5 vs. 8.3% TL, inner margin
2.4–4.7 vs. 2.0% TL), longer pelvic fins (total length 9.3–13.1 vs. 8.6% TL, anterior margin length 5.7–9.1 vs.
5.1% TL), a longer anal-fin inner margin (1.6–3.3 vs. 1.3% TL), a higher caudal-fin terminal lobe (height 3.3–5.4
vs. 2.7% TL), a higher caudal peduncle (height 4.9–7.2 vs. 4.8% TL), shorter upper labial furrows (length 0.6–1.3
vs. 1.8% TL), a narrower head at level of lateral indention (width 5.8–7.5 vs. 7.6% TL), and—except for post-
embryos—a pectoral—pelvic space 1.8–3.2 times interdorsal space (vs. 1.7). Large specimens (> 250 mm TL) of
B. bachi also differ from adult B. clevai in a greater prepelvic length (43.0–51.1 vs. 43.0% TL), a larger snout—
anterior vent length (48.5–53.2 vs. 46.2% TL), a larger pectoral—pelvic space (20.2–31.6 vs. 19.7% TL), a shorter
anterior vent—caudal tip length (46.4–52.2 vs. 53.1% TL), and a higher anal fin (height 4.3–6.2 vs. 3.3% TL).
Bythaelurus hispidus, like B. bachi, has oral papillae, but lacks composite papillae and differs in coloration
with several indistinct dark blotches on dorsolateral surface at gill slits and between pectoral and pelvic fin, below
dorsal fins and laterally on caudal peduncle and fin. Furthermore, B. bachi has a stout body in adults (vs. slender),
a higher diversity in dermal denticle morphology in general, and a larger maturity and maximum size (maturity size
36–40 cm and maximum size 45 cm vs. maturity size 22–24 cm according to Weigmann [2016] and maximum size
32 cm based on specimen SAIAB 13741). Additionally, B. bachi has larger adult claspers (inner margin length
10.6–11.3 vs. 7.4% TL, base width 2.3–3.1 vs. 1.5% TL), an eye length 9.0–13.0 times in predorsal distance (vs.
13.8) and 3.6–5.4 times in head length (vs. 6.4), an anal-fin base length equal to or less than 1.5 times second
dorsal-fin base length (vs. 1.6), a caudal fin length 1.9–2.3 times preventral length (vs. 2.6), a shorter pelvic—anal
space (3.0–8.6 vs. 11.5% TL), a shorter pelvic—caudal space (13.9–22.0 vs. 23.5% TL), a greater pre-outer nostril
length (3.0–5.2 vs. 2.3% TL), longer eyes (length 3.8–5.3 vs. 3.3% TL), a longer first dorsal fin (total length 9.2–

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12.1 vs. 9.2% TL), a longer second dorsal fin (total length 10.0–13.9 vs. 9.0% TL, anterior margin length 9.0–13.5
vs. 8.7% TL, inner margin 2.4–4.7 vs. 1.9% TL), larger pelvic fins (anterior margin length 5.7–9.1 vs. 5.5% TL,
height 3.0–7.8 vs. 2.6% TL), a higher caudal fin (5.8–8.1 vs. 5.5% TL), a longer caudal-fin preventral margin
(11.8–18.3 vs. 11.4% TL), a higher caudal-fin terminal lobe (height 3.3–5.4 vs. 2.7% TL), a higher tail (4.9–7.2 vs.
4.3% TL), shorter upper labial furrows (length 0.6–1.3 vs. 1.4% TL), and—except for post-embryos—a pectoral—
pelvic space 1.8–3.2 times interdorsal space (vs. 1.6). Furthermore, large specimens (> 250 mm TL) of B. bachi
also differ from adult B. hispidus in a greater prepelvic length (43.0–51.1 vs. 41.6% TL), a larger snout—anterior
vent length (48.5–53.2 vs. 44.1% TL), a larger pectoral—pelvic space (20.2–31.6 vs. 16.4% TL), a shorter anterior
vent—caudal tip length (46.4–52.2 vs. 56.2% TL), and a higher anal fin (height 4.3–6.2 vs. 3.0% TL).
Bythaelurus tenuicephalus, like B. bachi, has oral papillae, but lacks composite papillae and differs in
coloration with a lateral demarcation of medium brown dorsal and whitish or beige ventral color and 5–6 indistinct
dark blotches on dorsolateral surface at gill slits, partially between pectoral and pelvic fin, below dorsal fins and at
middle and posterior caudal fin. Furthermore, B. bachi has a stout body in adults (vs. slender), a higher diversity in
dermal denticle morphology in general, a larger maturity and maximum size (maturity size 36–40 cm and
maximum size 45 cm vs. maturity size 28 cm and maximum size 30 cm according to Kaschner et al. [2015] and
Weigmann [2016]), pelvic posterior tips behind level of insertion of first dorsal fin (vs. below), dorsal fins of
subequal height (vs. first dorsal fin clearly higher than second) and differing shape, first dorsal-fin origin anterior to
level of pelvic-fin midbase (vs. over), and caudal-fin margins of differing shape. Additionally, B. bachi has larger
adult claspers (outer margin length 6.4–6.8 vs. 5.8% TL, inner margin length 10.6–11.3 vs. 9.1% TL, base width
2.3–3.1 vs. 2.1% TL), a preorbital snout length 0.7–1.0 times interorbital space (vs. 1.0–1.4), an eye length 9.0–
13.0 times in predorsal distance (vs. 14.0–15.3) and 3.6–5.4 times in head length (vs. 6.0–7.0), a head length 1.8–
2.7 times width at level of maximum outer extent of anterior nostrils (vs. 2.7–3.1), an anal-fin base length equal to
or less than 1.5 times second dorsal-fin base length (vs. 1.7), a caudal fin length 1.9–2.3 times preventral length (vs.
2.6–2.8), a shorter pelvic—anal space (3.0–8.6 vs. 10.2–11.8% TL), a shorter pelvic—caudal space (13.9–22.0 vs.
22.2–22.8% TL), longer eyes (length 3.8–5.3 vs. 3.2–3.3% TL), a longer first dorsal fin (total length 9.2–12.1 vs.
8.0–8.4% TL, anterior margin length 8.3–12.1 vs. 7.7–8.2% TL), a longer second dorsal fin (total length 10.0–13.9
vs. 8.1–8.8% TL, anterior margin length 9.0–13.5 vs. 7.7–8.7% TL, inner margin 2.4–4.7 vs. 2.1% TL), a longer
pelvic-fin anterior margin (5.7–9.1 vs. 4.8–5.1% TL), a higher caudal fin (5.8–8.1 vs. 5.6–5.7% TL), a longer
caudal-fin preventral margin (11.8–18.3 vs. 10.6–10.8% TL), a higher caudal-fin terminal lobe (height 3.3–5.4 vs.
2.7–2.8% TL), a higher caudal peduncle (height 4.9–7.2 vs. 4.5–4.9% TL), shorter upper labial furrows (length
0.6–1.3 vs. 1.4–1.5% TL), and—except for post-embryos—a pectoral—pelvic space 1.8–3.2 times interdorsal
space (vs. 1.5–1.6). Large specimens (> 250 mm TL) of B. bachi also differ from B. tenuicephalus in a greater
prepelvic length (43.0–51.1 vs. 40.2–42.6% TL), a larger snout—anterior vent length (48.5–53.2 vs. 42.9–46.2%
TL), a larger pectoral—pelvic space (20.2–31.6 vs. 16.4–16.6% TL), a shorter anterior vent—caudal tip length
(46.4–52.2 vs. 52.5–56.5% TL), and a higher anal fin (height 4.3–6.2 vs. 3.0–3.1% TL). Additionally, B. bachi has
lower diplospondylous precaudal (33–43 vs. 43–50) and total (124–132 vs. 133–138) vertebral counts.
A detailed comparison of Bythaelurus bachi with B. alcockii (Garman, 1913) is not possible due to the lack of
specimens or detailed descriptions. Following Alcock’s (1899) description of the lost holotype of B. alcockii, B.
bachi has a strongly different coloration (plain beige to light grayish-brown vs. blackish with hoary gray surface
and some fins white-tipped posteriorly) and tooth morphology (anterolateral teeth in upper jaw with median cusp
much longer than lateral cusps vs. teeth with cusps and lateral cusps of subequal length). Furthermore, B. bachi is
known only from the Madagascar Ridge in the southwestern Indian Ocean, whereas B. alcockii was described from
the Arabian Sea. Compagno (1984b) assumed that B. alcockii might even belong to Apristurus Garman, 1913
instead of Bythaelurus. For the time being, B. alcockii remains a species of uncertain validity and generic
assignment.
Review of Bythaelurus species
The 12 (including B. bachi n. sp.) currently valid species of Bythaelurus are found in water deeper than 200 m in
the Indian and Pacific Oceans (Weigmann 2016). Geographically, the western Indian Ocean appears to be a hotspot
of Bythaelurus species diversity with seven of the 12 currently valid species occurring in this area. Six of the seven
species, i.e. B. alcockii, B. bachi n. sp., B. clevai, B. lutarius, B. naylori and B. tenuicephalus, are found

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exclusively in this area, whereas the seventh species, B. hispidus, is also known from the eastern Indian Ocean
(Weigmann 2016).
The type species of Bythaelurus is B. canescens, which is known from the southeastern Pacific Ocean from off
Peru and Chile to the Straits of Magellan (Ebert et al. 2013). It is a common bycatch in demersal trawl and longline
fisheries in central and southern Chile (Concha et al. 2010). The species is plain dark brown or blackish above and
below, has distinct labial furrows, with lowers noticeably longer than uppers, an anal-fin base length less than 1.5
times second dorsal-fin base length, matures at 52–59 cm TL and reaches a maximum size of 73 cm TL. The
second species reported from the southeastern Pacific Ocean is B. giddingsi McCosker, Long & Baldwin, 2012,
which may be endemic to the Galapagos Islands (McCosker et al. 2012). It is distinguishable from all congeners by
having very few tooth rows per jaw (20–26 vs. 53–111) and its striking coloration: chocolate brown dorsally with
pale spots, the largest being about equal in size to eye diameter above midline, smaller below; posterior margin of
dorsal, pectoral, and pelvic fins pale; ventral surface pale. Additionally, it has a dorsal caudal-fin margin with
prominent crest of comb-like dermal denticles. From the western Pacific Ocean, two species have been recorded,
B. dawsoni and B. immaculatus (Chu & Meng, 1982). Bythaelurus dawsoni is apparently endemic to the waters
around New Zealand (Francis 2006). It is light brown to gray on dorsal and lateral surfaces with a line of white
spots on sides of small individuals and whitish ventrally, has fin tips with broad white areas and dark bands on the
caudal fin. The labial furrows are distinct, with lowers noticeably longer than uppers, the anal-fin base length is
less than 1.5 times second dorsal-fin base length, the size at maturity is 32–38 cm TL and the maximum size is 42
cm TL. Bythaelurus immaculatus is known only from the three type specimens, caught in the South China Sea
(White & Last 2013). This species has a plain dark yellowish brown coloration, reduced labial furrows, with uppers
and lowers about equal in length, an anal-fin base length less than 1.5 times second dorsal-fin base length, a pre-
vent length 1.3 times in tail length, a preorbital snout length subequal to eye length, a length of lateral trunk
denticles less than twice their width and reaches a maximum size of 76 cm TL (White & Last 2013), representing
the largest known species of Bythaelurus (Weigmann 2016). For the eastern Indian Ocean, two species have been
reported: B. incanus Last & Stevens, 2008 and B. hispidus. Bythaelurus incanus is known only from the holotype,
a juvenile male collected off the Ashmore Terrace, western Australia. This species has a mostly plain grayish
brown coloration with a few white blotches on belly, reduced labial furrows, with uppers and lowers about equal in
length, an anal-fin base length less than 1.5 times second dorsal-fin base length, a pre-vent length exceeding tail
length, a preorbital snout length 1.3 times eye length and a length of lateral trunk denticles more than twice their
width (Last & Stevens 2008). Bythaelurus hispidus is known from the eastern and western Indian Ocean with
records from off Kenya (three SAIAB specimens listed under Comparative material), Socotra Islands
(uncatalogued specimens at ZMH), Yemen (al Sakaff & Esseen 1999), Oman (L. Jawad, pers. comm., 2013),
southern India (Nair & Appukuttan 1973; Nair & Lal Mohan 1973; Appukuttan & Nair 1988; Raje et al. 2002;
Akhilesh et al. 2013), Andaman Islands (Alcock 1891; Springer & D’Aubrey 1972; Springer 1979; Séret 1987;
Kaschner et al. 2015), and off Myanmar (T. Krajangdara & P.N. Psomadakis, pers. comm., 2015). This species has
5–6 indistinct, dark blotches on trunk and tail, an anal-fin base more than 1.5 times second dorsal-fin base length,
rather slender (base width ~1.5% TL) adult claspers with knob-like apex, a maturity size of 22–24 cm TL and a
maximum size of 32 cm TL. In addition to B. hispidus, six further species of Bythaelurus are described from the
western Indian Ocean, i.e. B. alcockii, B. bachi n. sp., B. clevai, B. lutarius, B. naylori and B. tenuicephalus.
Bythaelurus alcockii was described from the Arabian Sea without exact locality data and is known only from the
holotype, which has been lost (Compagno 1984b; K.V. Akhilesh, pers. comm., 2014). For B. alcockii, a blackish
coloration with hoary gray surface and some fins white-tipped posteriorly, as well as teeth with cusps and lateral
cusps of subequal length were described (Alcock 1899). However, its validity is questionable (e.g. Springer 1979;
Compagno 1984b, 1988, 1999, 2005; Compagno et al. 2005; Last & Stevens 2008; Ebert et al. 2013; Kaschner et
al. 2015; Weigmann 2016). It was originally described as Halaelurus alcockii and preliminarily placed in the
subgenus Bythaelurus by Compagno (1988) but earlier Compagno (1984b) had also stated that the species might
instead belong to the genus Apristurus. As the only known specimen has been lost, it is currently impossible to
resolve this issue. Bythaelurus bachi n. sp. is known only from the southern Madagascar Ridge. The new species is
distinguished from all congeners by the plain beige to light gray-brown coloration, high diversity in dermal denticle
morphology and presence of composite oral papillae. It has a maturity size of 36–40 cm TL and reaches a
maximum size of 45 cm TL. Bythaelurus clevai is apparently endemic to the waters around Madagascar (Séret

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TABLE 3. Maximum sizes, geographic and depth distributions, reproductive modes, as well as vertebral, tooth row and spiral valve counts of Bythaelurus species.
Spiral valve
counts
7–8
5
8–10
3
10
2
7–8
6
6–8
3
Footer: Superscript numbers in meristics indicate numbers of specimens on which the values are based. * In Table 2 of McCosker et al. (2012), individual values for diplospondylous precaudal count indicate a maximum of 44, but range indicates 43 as maximum
count. Data sources: data of Bythaelurus bachi from the present study, sources for all other species: maximum total length and geographic distribution from Weigmann (2016) except for maximum total length of B. hispidus based on comparative specimen SAIAB
13741; depth data from Weigmann (2016) except for maximum depth of B. canescens from Meléndez & Meneses (1989); reproductive modes from Francis (2006), Concha et al. (2010), Akhilesh et al. (2013) and Ebert & Clerkin (2015); counts from Springer (1971),
Springer & D'Aubrey (1972), Bass et al. (1975), Springer (1979), Séret (1987), Compagno (1988), Last & Stevens (2008), McCosker et al. (2012), Ebert & Clerkin (2015) and Kaschner et al. (2015), as well as unpublished counts of comparative specimens of B.
canescens and B. dawsoni. Abbreviations: EIO = eastern Indian Ocean, NWP = northwestern Pacific Ocean, SEP = southeastern Pacific Ocean, SWP = southwestern Pacific Ocean, WIO = western Indian Ocean.
Vertebral counts
total
117–132
24
127–142
14
~124–~129
10
~121–~134
7
122–131
14
~142
1
129–142
46
~114–~128
10
133–138
2
124–132
28
caudal
40
1
50
1
~55–~62
10
~40–~51
7
48
2
~49
1
49
1
~44–~54
10
50
2
48–56
28
total
precaudal
82
1
88
1
67–73
11
81–85
7
74–78
2
~93
1
82–89
18
64–78
10
83–88
2
73–83
28
diplospondylous
precaudal
43
1
46–54
15
31–36
3
40–44
7
*
37–41
2
~47
1
44–50
12
25–38
10
43–50
2
33–43
28
monospondylous
39–43
>20
39–45
16
36–38
11
39–42
7
35–38
14
46
1
38–42
29
36–41
10
38–40
2
38–43
28
Tooth row counts
lower jaw
~60–111
2
53–70
16
~62–~70
2
23–26
7
61–83
2
~101
1
78–86
2
>70
10
62–64
2
60–76
14
upper jaw
80–101
2
62–80
16
~64–~66
2
20–23
7
67–70
2
~99
1
74–76
2
>70
10
67–76
2
70–84
14
Reproductive
mode
unknown
single
oviparity
yolk-sac
viviparity
single
oviparity
unknown
yolk-sac
viviparity
unknown
unknown
yolk-sac
viviparity
single
oviparity
unknown
single
oviparity
Depth
distribution
1134–1262 m
237–1260 m
400–500 m
240–992 m
428–562 m
200–800 m
534–1020 m
900–1000 m
338–766 m
752–1443 m
463–550 m
910–1365 m
Geographic
distribution
WIO
SEP
WIO
SWP
SEP
WIO, EIO
NWP
EIO
WIO
WIO
WIO
WIO
Maximum
total length
small
specimen
73 cm
40 cm
42 cm
>45 cm
32 cm
76 cm
>45 cm
39 cm
55 cm
30 cm
45 cm
Species
Bythaelurus alcockii (Garman, 1913)
Bythaelurus canescens (Günther, 1878 )
Bythaelurus clevai (Séret, 1987)
Bythaelurus dawsoni (Springer, 1971)
Bythaelurus giddingsi McCosker, Long & Baldwin, 2012
Bythaelurus hispidus (Alcock, 1891)
Bythaelurus immaculatus (Chu & Meng, 1982)
Bythaelurus incanus Last & Stevens, 2008
Bythaelurus lutarius (Springer & D’Aubrey, 1972)
Bythaelurus naylori Ebert & Clerkin, 2015
Bythaelurus tenuicephalus Kaschner, Weigmann & Thiel, 2015
Bythaelurus bachi n. sp.


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A NEW SPECIES AND REVIEW OF BYTHAELURUS
1987). This species has a grayish coloration with a pattern of dark brown saddle-like markings on back and tail,
with variegated dark brown blotches on flanks, is grayish with brown speckles inside of the mouth, has a whitish
ventral surface, matures at 28–36 cm TL and reaches a maximum size of 40 cm TL. Bythaelurus lutarius so far has
been confirmed only from off Mozambique. The records of B. lutarius from off Somalia (Springer & D’Aubrey
1972; Bass et al. 1975; Springer 1979) are based on B. tenuicephalus and an undescribed Bythaelurus species in the
ZMB collection. Bythaelurus lutarius has a largely plain coloration with dusky areas near the fins, an anal-fin base
more than 1.5 times second dorsal-fin base length, a maturity size of 28–31 cm TL and reaches a maximum size of
39 cm TL. Bythaelurus naylori is known only from the Southwest Indian Ridge. It has a medium to dark brown
coloration with light fin edges and a distinct dark dusky-colored snout, a dorsal caudal-fin margin with prominent
crest of comb-like dermal denticles, distinct labial furrows, with lowers noticeably longer than uppers, an anal-fin
base length equal to or less than 1.5 times second dorsal-fin base length, matures at 38–48 cm TL and reaches a
maximum size of 55 cm TL. Bythaelurus tenuicephalus is known only from off Tanzania and Mozambique. This
species differs from all congeners in the narrow head without distinct lateral indention anterior to outer nostrils.
Furthermore, the adult claspers are rather broad (base width ~2% TL) without knob-like apex, the species matures
at ~28 cm TL and reaches a maximum size of ~30 cm TL.
The 12 currently valid species can be grouped into two general morphotypes: one consists of species with
slender bodies, i.e. Bythaelurus clevai, B. hispidus, B. lutarius and B. tenuicephalus, the other includes species with
stocky bodies, at least in large specimens, i.e. B. bachi, B. canescens, B. dawsoni, B. giddingsi, B. immaculatus, B.
incanus and B. naylori. The body shape of Bythaelurus alcockii is unknown.
Another possible grouping arises from the presence or absence of oral papillae: species with numerous oral
papillae are B. bachi, B. canescens, B. clevai, B. dawsoni, B. giddingsi, B. hispidus, ?B. immaculatus, B. incanus
and B. tenuicephalus, species without (or with rudimentary) oral papillae are B. lutarius and B. naylori. The
presence of oral papillae in B. immaculatus is unknown but it is assumed that the species has oral papillae based on
its apparently close morphological relationship to B. canescens and B. incanus. White & Last (2013) did not
examine the holotype of B. immaculatus for the presence of oral papillae (W.T. White, pers. comm., 2015).
Furthermore, none of the type specimens could be found upon recent requests (H.-C. Ho & X.-Y. Kong, pers.
comm., 2015 & 2016) so the whereabouts of the type specimens and the presence of oral papillae remain unclear.
The presence of oral papillae in Bythaelurus alcockii is unknown.
A third possible grouping arises from the reproductive modes of Bythaelurus species that was reviewed by
Francis (2006). He noted that some species, e.g. B. canescens and B. dawsoni, are oviparous, whereas others are
viviparous. A detailed comparison of reproductive modes, as well as maximum sizes, geographic and depth
distributions, vertebral, tooth row and spiral valve counts of the 12 species of Bythaelurus can be found in Table 3.
Generally, the taxonomy and biology of Bythaelurus species are poorly known. So far, studies on the biology
and distribution are restricted to few species, i.e. B. canescens, B. dawsoni, B. hispidus and B. lutarius, and
partially based only on a small number of specimens examined (Nair & Appukuttan 1973; Bass et al. 1975;
Springer 1979; Meléndez & Meneses 1989; Francis 2006; Valenzuela et al. 2008; Acuña & Villarroel 2010;
Concha et al. 2010; Akhilesh et al. 2013; Lopez et al. 2013). Therefore, more specimens are needed of several
species, especially of those from the Indian Ocean and B. immaculatus. In order to further improve the knowledge
of Bythaelurus species in this area, a comprehensive study on the taxonomy and distribution of B. hispidus and
descriptions of two further undescribed species of the genus from the western Indian Ocean are currently in
preparation.
Key to the valid species of Bythaelurus:
1a. Coloration variegated, with irregularly distributed spots and blotches; markings not symmetrical . . . . . . . . . . . . . . . . . . . . . 2.
1b. Coloration pale, dusky, or with line of pale spots; usually without conspicuous blotches . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.
2a. Grayish with a pattern of dark brown saddle-like markings on back and tail, and with variegated dark brown blotches on
flanks; inside of mouth grayish with brown speckles; ventral surface whitish. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B. clevai [southwestern Indian Ocean: Madagascar]
2b. Chocolate brown dorsally with pale spots, the largest being about equal in size to eye diameter above midline, smaller below;
posterior margin of dorsal, pectoral, and pelvic fins pale; ventral surface pale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. giddingsi [southeastern Pacific Ocean: Galapagos Islands]
3a. Coloration blackish with hoary gray surface and some fins white-tipped posteriorly; teeth with cusps and lateral cusps of sub-

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equal length; validity and generic assignment uncertain . . . . . . . . . . . . . B. alcockii [northwestern Indian Ocean: Arabian Sea]
3b. Coloration lighter; at least anterolateral teeth in upper jaw with median cusp much longer than lateral cusps . . . . . . . . . . . . 4.
4a. Anal-fin base more than 1.5 times second dorsal-fin base length; color light to medium brown above with dusky areas near the
fins or indistinct dark blotches, whitish to light brown below; maturity size 22–31 cm TL; maximum size 30–39 cm TL . . 5.
4b. Anal-fin base equal to or less than 1.5 times second dorsal-fin base length; coloration variable but without dusky areas near
fins or indistinct dark blotches; maturity size 32–59 cm TL; maximum size 42–76 cm TL . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.
5a. Tongue and roof of mouth without (or with rudimentary) papillae; coloration largely plain with dusky areas near fins . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. lutarius [western Indian Ocean: Mozambique]
5b. Tongue and roof of mouth with numerous papillae; trunk and tail with 5–6 indistinct, dark blotches . . . . . . . . . . . . . . . . . . . 6.
6a. Head with distinct lateral indention anterior to outer nostrils; adult claspers rather slender (base width ~1.5% TL) and with
knob-like apex. . . . . . . . . . B. hispidus [western and eastern Indian Ocean: Kenya to Oman, southern India and Andaman Sea]
6b. Head narrow and without distinct lateral indention anterior to outer nostrils; adult claspers broader (base width ~2% TL) and
without knob-like apex . . . . . . . . . . . . . . . . . . . . . . . . . . .B. tenuicephalus [western Indian Ocean: Tanzania and Mozambique]
7a. Labial furrows reduced, with uppers and lowers about equal in length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.
7b. Labial furrows distinct, with lowers noticeably longer than uppers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.
8a. Pre-vent length 1.3 times in tail length; preorbital snout length subequal to eye length; length of lateral trunk denticles less than
twice their width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. immaculatus [western central Pacific Ocean: South China Sea]
8b. Pre-vent length exceeds tail length; preorbital snout length 1.3 times eye length; length of lateral trunk denticles more than
twice their width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. incanus [southeastern Indian Ocean: northwestern Australia]
9a. Light brown to gray on dorsal and lateral surfaces with a line of white spots on sides of small individuals, whitish ventrally, fin
tips with broad white areas, caudal fin also with dark bands . . . . . . . . . . . . B. dawsoni [western Pacific Ocean: New Zealand]
9b. Flanks of body lack a line of white spots, ventrally darker, fin tips without broad white areas, caudal fin without dark bands . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.
10a. Color plain dark brown or blackish above and below; maturity size 52–59 cm TL, maximum size 73 cm TL . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. canescens [southeastern Pacific Ocean: Peru and Chile, to Straits of Magellan]
10b. Coloration lighter; maturity size 36–48 cm TL, maximum size 45–55 cm TL; known only from the southwestern Indian Ocean
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.
11a. Coloration medium to dark brown with light fin edges and a distinct dark dusky-colored snout; dorsal caudal-fin margin with
prominent crest of comb-like dermal denticles; tongue and roof of mouth without papillae . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. naylori [southwestern Indian Ocean: Southwest Indian Ridge]
11b. Coloration plain beige to light grayish-brown; dorsal caudal-fin margin lacks prominent crest of comb-like dermal denticles;
tongue and roof of mouth with numerous, partially composite papillae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. bachi n. sp. [southwestern Indian Ocean: Madagascar Ridge]
Comparative material
Bythaelurus canescens
BMNH 1887.12.7.1 (holotype), juvenile female, 282 mm TL, RV ‘Challenger’, station 310, off Chile, 400 fms
(732 m) depth. According to Tizard et al. (1885), station details are as follows: date 10 Jan 1876, 51°27'30" S,
74°03' W, bottom: blue mud, temperature of the seawater: 46.5° F (8.1° C) at bottom, 50.5° F (10.3° C) at surface,
specific gravity of seawater at 60° F (15.6° C), distilled water at 39° (3.9°) = 1: 1.02451 at bottom, 1.01910 at
surface, trawled.
Bythaelurus clevai
ZMH 26071, adult male, 400 mm TL fresh, 385 mm TL 70% ethanol preserved, RV ‘Vityaz’, cruise 17, station
2645, off SW-Madagascar, 22°20'5" S, 43°03'6" E – 22°18'5" S, 43°03'1" E, 450–500 m depth, 19.4 m shrimp
trawl, trawl # 40, on the bottom for 43 minutes, 2 Dec 1988.
Bythaelurus dawsoni
ZMH 119617 (ex ISH 5215-1979), 2 juvenile males, 275 mm TL and 182 mm TL, fishing trawler
‘Wesermünde’, station 590, off western New Zealand, 41°10' S, 170°40' E, 540–560 m depth, 250'-BT (120 mm
mesh size), 17 Jul 1979.
Bythaelurus hispidus
BMNH 1898.7.13.21, adult male, 258.5 mm TL, off Andaman Islands, 338 m depth, from the Indian Museum,
Calcutta; SAIAB 13741 (field no. 80-20) adult male, 318 mm TL, off Kenya, 03°26’ S, 40°23’ E, 484 m depth, 11
Dec 1980 (photographs and radiographs); SAIAB 14057 (field no. PCH 80-19), female, 252 mm TL, off Kenya,

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A NEW SPECIES AND REVIEW OF BYTHAELURUS
03°49’ S, 40° E, 11 Dec 1980 (photographs and radiographs); SAIAB 14103 (field no. PCH 80-24), adult male,
310 mm TL, off Kenya, 03°11’ S, 40°38’ E, 12 Dec 1980 (photographs and radiographs); USNM 221384, female,
285 mm TL, adult male, 260 mm TL, and juvenile male, 194 mm TL, RV ‘Anton Bruun’, cruise 1, station 23, off
Andaman Islands, 10°39’ N, 96°35’ E, 367–375 m depth, 40 ft shrimp trawl, 24 Mar 1963 (photographs only); ZSI
13120 (holotype), juvenile male, 222 mm TL, station 115, off Andaman Islands, 11°31'40" N, 92°46'40 "E, 344–
402 m depth, Dec 1890 (photographs only).
Bythaelurus lutarius
USNM 205135 (holotype), adult male, 323 mm TL, RV ‘Anton Bruun’, cruise 8, station 396B, 25°32' S,
33°24' E, 450–455 m depth, shrimp trawl, 28 Sep 1964 (photographs and morphometrics plus meristics); USNM
221660 (paratype, field no. 182), female, 323 mm TL, data the same as holotype (photographs only); SAIAB 6141,
three adult females, 340–370 mm TL, caught off southern Mozambique, 10 Nov 2000 (photographs and
radiographs).
Bythaelurus naylori
CAS 237869 (holotype), adult male, 452 mm TL, Southwest Indian Ridge, 35°10’ S, 53°40’ E, 800–1300 m
depth, bottom trawl, collected by P.J. Clerkin, 21 May 2014. (Paratypes, n = 15): CAS 237870 (GN 123330), adult
male, 455 mm TL, Southwest Indian Ridge, 33°55’ S, 55°16’ E, 1008–1190 m depth, midwater trawl, collected by
P.J. Clerkin, 28 Apr 2014; CAS 237872, female, 506 mm TL, Southwest Indian Ridge, 34°53’ S, 54°23’ E, 811–
1150 m depth, bottom trawl, collected by P.J. Clerkin, 28 Apr 2014; CAS 237873, female, 505 mm TL, Southwest
Indian Ridge, 36°49’ S, 52°05’ E, 1438–1443 m depth, bottom trawl, collected by P.J. Clerkin, 21 May 2014; CAS
237941, adult male, 511 mm TL, Southwest Indian Ridge, 35°08’ S, 53°42’ E, 861–1160 m depth, bottom trawl,
collected by Ryan Downie, 11 Mar 2014; CAS 237942 (GN 11840), female, 548 mm TL, Southwest Indian Ridge,
39°00’ S, 46°30’ E, 800–1200 m depth, bottom trawl, collected by P.J. Clerkin, 17 Mar 2012; CAS 237943 (GN
11841), female, 450 mm TL, Southwest Indian Ridge, 39°00’ S, 46°30’ E, 800–1200 m depth, bottom trawl,
collected by P.J. Clerkin, 17 Mar 2012; CAS 237944 (GN 11857), adult male, 491 mm TL, Southwest Indian
Ridge, 35°10’ S, 53°40’ E, 800–1300 m depth, bottom trawl, collected by P.J. Clerkin, 8 Apr 2012; CAS 238013
(GN 11866), adult male, 502 mm TL, Southwest Indian Ridge, 35°10’ S, 53°40’ E, 800–1300 m depth, bottom
trawl, collected by P.J. Clerkin, 8 Apr 2012; CAS 238070 (GN 12399), immature male, 341 mm TL, Southwest
Indian Ridge, 33°55’ S, 55°16’ E, 1040–1250 m depth, bottom trawl, collected by P.J. Clerkin, 29 Apr 2014; CAS
238071 (GN 12378), female, 527 mm TL, Southwest Indian Ridge, 33°55’ S, 55°16’ E, 1008–1185 m depth,
bottom trawl, collected by P.J. Clerkin, 29 Apr 2014; SAIAB 200728, adult male, 482 mm TL, Southwest Indian
Ridge, 35°08’ S, 53°42’ E, 861–1160 m depth, bottom trawl, collected by Ryan Downie, 11 Mar 2014; SAIAB
200729, female, 464 mm TL, Southwest Indian Ridge, 33°55’ S, 55°16’ E, 1008–1190 m depth, midwater trawl,
collected by P.J. Clerkin, 28 Apr 2014; iSAM MB-F041239 (GN 12347), female, 453 mm TL, Southwest Indian
Ridge, 35°08’ S, 53°42’ E, 89–1240 m depth, bottom trawl, collected by P.J. Clerkin, 30 Apr 2014; USNM 432400
(GN 12371), adult male, 465 mm TL, Southwest Indian Ridge, 35°08’ S, 53°42’ E, 752–780 m depth, bottom
trawl, collected by P.J. Clerkin, 23 Apr 2014; USNM 432401, female, 466 mm TL, Southwest Indian Ridge, 35°08’
S, 53°42’ E, 861–1160 m depth, bottom trawl, collected by Ryan Downie, 11 Mar 2014.
Bythaelurus tenuicephalus
ZMH 10163 (holotype), adult male, 279 mm TL, RV ‘Valdivia’, station 245, off North Tanzania, 5°27'9" S,
39°18'8" E, 463 m depth, 22 March 1899; ZMH 26070 (paratype), juvenile male, 291 mm TL fresh, 285 mm TL
70% ethanol preserved, RV ‘Vityaz’, cruise 17, station 2622, off South Mozambique, 21°12'8" S, 35°41'8" E –
21°16'6" S, 35°41'3" E, 490–550 m depth, 29 m shrimp trawl, trawl # 25, on the bottom for 63 minutes, 21 Nov
1988.
Bythaelurus sp.
ZMB 17410, female, 325 mm TL, RV ‘Valdivia’, station 265, off Somalia, 6°24'1" N, 49°31'6" E, 628 m depth,
30 Mar 1899; ZMB 22423, female, 273 mm TL, data the same as specimen ZMB 17410.

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Acknowledgements
The authors are very grateful to SciGraphics (http://www.scigraphics.de) for making the drawing of Bythaelurus
bachi n. sp. in natural body shape (Figure 2) and to Carina J. Kaschner (ZMH), who provided wide-ranging
support with respect to measuring specimens and taking SEM images of dermal denticles and teeth. The first author
would also like to thank Ralf Thiel (ZMH) for granting access to the specimens in the ZMH collection for
examinations and to photo- and radiography facilities at ZMH and for permission for taking of samples for SEM
imaging, Irina Eidus (ZMH) for her help with the radiography and collection database, Renate Walter, Björn
Kullmann, and Dietmar Keyser (ZMH) for help with the SEM, Peter Bartsch and Corinna Enderes (ZMB) for loan
of the two Bythaelurus sp. specimens from the ‘Valdivia’ cruise, Tracy Heath and James Maclaine (BMNH) for
loan of the comparative specimen of B. hispidus, Bernard Séret (ICHTYO CONSULT) and Diego F.B. Vaz (VIMS)
for providing morphometrics and meristics of the holotype of B. lutarius, Roger Bills, Ofer Gon, Mark Lisher, and
Nkostinathi Mazungula (SAIAB) for many photographs and radiographs of three specimens each of B. hispidus
and B. lutarius, Sandra Raredon (USNM) for many photographs of the holotype and one paratype of B. lutarius, as
well as three specimens of B. hispidus, K.V. Akhilesh and K.K. Bineesh (CMFRI) and S.S. Mishra (ZSI) for
photographs of the holotype of B. hispidus and K.V. Akhilesh also for comments on the whereabouts of the
holotype of B. alcockii, Laith Jawad (AIM) for photographs of two specimens of B. hispidus caught off Oman,
Tassapon Krajangdara (AFRDEC) and Peter N. Psomadakis (FAO) for information on four specimens of B.
hispidus caught off Myanmar, and Hsuan-Ching Ho (NMMBA), Xiao-Yu Kong (SCSIO) and William T. White
(CSIRO) for comments on B. immaculatus. DAE and PJC would like to acknowledge Sealords Corporation, the
Captain and the crew of the F/V Will Watch for making possible the collection of specimens, the Mauritius Ministry
of Fisheries and Albion Fisheries provided facilities for us to process specimens, and we are grateful to D. Mauree,
D. Norungee, Y. Basant Rai, S. Beeharry-Panray, B. Ramcharrun, D. Degambur, D. Bolaky, R. Bacorisen, A.
Morrarby, N. Toofany, and the Albion Fisheries Research Centre staff whose assistance was invaluable. The
following individuals are sincerely thanked for their assistance and support: R. Downie (CSIRO Oceans and
Atmosphere Flagship, Hobart, Tasmania, Australia), D. Catania and J. Fong (California Academy of Sciences), D.
Clarke and M. Bougaardt (South African Museum), R. Leslie (Branch Fisheries Management, Department of
Agriculture, Forestry and Fisheries, South Africa), R. Bills (South African Institute for Aquatic Biodiversity), and
J. Cordova (Pacific Shark Research Center, Moss Landing Marine Laboratories) for support on various aspects of
this project. Partial funding was provided by the Save Our Seas Foundation. MFWS thanks Nigel Merrett and Jim
Chambers (BMNH) for loan in June 1992 of the Scyliorhinus canescens Günther, 1878 holotype female (BMNH
1887.12.7.1). MFWS remembers gratefully the comradeship and great assistance by the RV ‘Vityaz’ crew, all
Russian and western guest scientists; special thanks to the late chief scientist N.V. Parin. GJPN would like to thank
Peter N. Psommadakis, The Museum of New Zealand, K.K. Bineesh and K.V. Akhilesh for sending tissue samples
from vouchered reference material. The molecular component of this project was supported by NSF grant entitled
“Jaws and Backbone: Chondrichthyan Phylogeny and a Spine for the Vertebrate Tree of Life” (DEB 1132229) to
GJPN.
References
Akhilesh, K.V., White, W.T., Bineesh, K.K., Ganga, U. & Pillai, N.G.K. (2013) Biological observations on the bristly catshark
Bythaelurus hispidus from deep waters off the south-west coast of India. Journal of Fish Biology, 82 (5), 1582–1591.
http://dx.doi.org/10.1111/jfb.12087
Alcock, A. (1891) Class Pisces. In: II.–Natural history notes from H.M. Indian marine survey steamer ‘Investigator’,
Commander R.F. Hoskyn, R.N. commanding.–Series II., No. 1. On the results of deep-sea dredging during the season
1890–91. The Annals and Magazine of Natural History, 8 (6), 16–34.
http://dx.doi.org/10.1080/00222939109460385
Alcock, A. (1899) A descriptive catalogue of the Indian deep-sea fishes in the Indian Museum. Being a revised account of the
deep-sea fishes collected by the Royal Indian Marine Survey Ship Investigator. Indian Museum, Calcutta, 211 pp.
http://dx.doi.org/10.5962/bhl.title.4684
Amante, C. & Eakins, B.W. (2009) ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis.
NOAA Technical Memorandum NEDIS NGDC-24, 19 pp.
Appukuttan, K.K. & Nair, K.P. (1988) Shark Resources of India, with Notes on Biology of a Few Species. In: Joseph, M.M.

Zootaxa 4208 (5) © 2016 Magnolia Press
·
431
A NEW SPECIES AND REVIEW OF BYTHAELURUS
(Ed.) The First Indian Fisheries Forum, Proceedings. Asian Fisheries Society, Indian Branch, Mangalore, pp. 173–183.
Bass, A.J., D’Aubrey, J.D. & Kistnasamy, N. (1975) Sharks of the east coast of southern Africa. II. The families Scyliorhinidae
and Pseudotriakidae. Investigational Report, Oceanographic Research Institute, 37, 1–64.
Chu, Y.-T. & Meng, Q.-W. (1982) Halaelurus immaculatus sp. nov. Pp. 301–302, 309. In: Chu, Y.-T., Meng, Q.-W., Hu, A. &
Li, S. (Aut.) Five new species of elasmobranchiate fishes from the deep waters of South China Sea. Oceanologica et
Limnologica Sinica, 13 (4), 301–311. [in Chinese with English summary]
Compagno, L.J.V. (1984a) FAO species catalogue. Vol. 4, Sharks of the World. An annotated and illustrated catalogue of shark
species known to date (Part 1, Hexanchiformes to Lamniformes). FAO Fisheries Synopsis, 125, 4 (1). FAO, Rome, 249 pp.
Compagno, L.J.V. (1984b) FAO species catalogue. Vol. 4, Sharks of the World. An annotated and illustrated catalogue of shark
species known to date (Part 2, Carcharhiniformes). FAO Fisheries Synopsis, 125, 4 (2). FAO, Rome, pp. 251–655.
Compagno, L.J.V. (1988) Sharks of the order Carcharhiniformes. Princeton University Press, New Jersey, 486 pp.
Compagno, L.J.V. (1999) Checklist of Living Elasmobranchs. In: Hamlett, W.C. (Ed.), Sharks, Skates, and Rays – The Biology
of Elasmobranch Fishes. The Johns Hopkins University Press, Baltimore, pp. 471–498.
Compagno, L.J.V. (2005) Checklist of Living Chondrichthyes. In: Hamlett, W.C. (Ed.), Reproductive Biology and Phylogeny of
Chondrichthyes – Sharks, Batoids and Chimaeras. Science Publishers, Inc., Enfield, pp. 503–548.
Compagno, L.J.V., Stehmann, M. & Ebert, D.A. (1990) Rhinochimaera africana, a new longnose chimaera from southern
Africa, with comments on the systematics and distribution of the genus Rhinochimaera Garman, 1901 (Chondrichthyes,
Chimaeriformes, Rhinochimaeridae). South African Journal of Marine Science, 9 (1), 201–222.
Compagno, L.J.V., Dando, M. & Fowler, S. (2005) A field guide to the Sharks of the World. Harper Collins Publishing Ltd.,
London, 368 pp.
Concha, F., Bustamante, C., Oddone, M.C., Hernández, S. & Lamilla, J. (2010) Egg capsules of the dusky catshark Bythaelurus
canescens (Carcharhiniformes, Scyliorhinidae) from the south-eastern Pacific Ocean. Journal of Fish Biology, 77 (4),
963–971.
http://dx.doi.org/10.1111/j.1095-8649.2010.02736.x
Ebert, D.A. & Clerkin, P.J. (2015) A new species of deep-sea catshark (Scyliorhinidae: Bythaelurus) from the southwestern
Indian Ocean. Journal of the Ocean Science Foundation, 15, 53–63.
Ebert, D.A., Fowler, S. & Compagno, L.J.V. (2013) Sharks of the world: a fully illustrated guide to the sharks of the world.
Wild Nature Press, Devon, 528 pp.
Francis, M.P. (2006) Distribution and biology of the New Zealand endemic catshark, Halaelurus dawsoni. Environmental
Biology of Fishes, 75 (3), 295–306.
http://dx.doi.org/10.1007/s10641-006-0026-0
Garman, S. (1913) The Plagiostomia (Sharks, Skates, and Rays). Memoirs of the Museum of Comparative Zoology at Harvard
College, XXXVI, 1–528.
http://dx.doi.org/10.5962/bhl.title.43732
Gill, T. (1862) Squalorum Generum Novum Descriptiones Diagnosticae. Annals of the Lyceum of Natural History of New York,
7 (1), 409–413.
http://dx.doi.org/10.1111/j.1749-6632.1862.tb00167.x
Günther, A. (1878) Preliminary Notices of Deep-Sea Fishes collected during the Voyage of H.M.S. ‘Challenger.’ Annals and
Magazine of Natural History, 2 (5), 17–28.
http://dx.doi.org/10.1080/00222937808682376
Herman, J., Hovestadt-Euler, M. & Hovestadt, D.C. (1990) Part A: Selachii. No. 2b: Order : Carcharhiniformes—Family :
Scyliorhinidae. Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites in
living supraspecific taxa of Chondrichthyan fishes. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique,
Biologie, 60, 181–230.
Hovestadt, D.C. & Hovestadt-Euler, M. (1995) Additions to the fauna of the Boom Clay Formation of Beglium (Rupelian,
Oligocene). Taxonomic adjustments on the Scyliorhinidae and Rajoidei, discovery of a dasyatid species (Pisces,
Chondrichthyes) and of a curculionid species (Insecta, Coleoptera). Belgian Geological Survey Professional Paper, 278,
261–282.
Ishihara, H., Treloar, M., Bor, P.H.F., Senou, H. & Jeong, C.H. (2012) The Comparative Morphology of Skate Egg Capsules
(Chondrichthyes: Elasmobranchii: Rajiformes). Bulletin of the Kanagawa Prefectural Museum (Natural Science), 41, 9–
25.
Kaschner, C.J., Weigmann, S. & Thiel, R. (2015) Bythaelurus tenuicephalus n. sp., a new deep-water catshark
(Carcharhiniformes, Scyliorhinidae) from the western Indian Ocean. Zootaxa, 4013 (1), 120–138.
http://dx.doi.org/10.11646/zootaxa.4013.1.9
Last, P.R. & Stevens, J.D. (2008) Bythaelurus incanus sp. nov., a new deepwater catshark (Carcharhiniformes: Scyliorhinidae)
from northwestern Australia. In: Last, P.R., White, W.T. & Pogonoski, J.J. (Eds.) Descriptions of New Australian
Chondrichthyans. CSIRO Marine & Atmospheric Research Paper No. 022, pp. 123–128.
Lopez, S., Zapata-Hernández, G., Bustamante, C., Sellanes, J. & Meléndez, R. (2013) Trophic ecology of the dusky catshark
Bythaelurus canescens (Günther, 1878) (Chondrychthyes: Scyliorhinidae) in the southeast Pacific Ocean. Journal of
Applied Ichthyology, 29 (4), 751–756.
http://dx.doi.org/10.1111/jai.12151

WEIGMANN ET AL.
432
·
Zootaxa 4208 (5) © 2016 Magnolia Press
McCosker, J.E., Long, D.J. & Baldwin, C.C. (2012) Description of a new species of deepwater catshark, Bythaelurus giddingsi
sp. nov., from the Galápagos Islands (Chondrichthyes: Carcharhiniformes: Scylorhinidae). Zootaxa, 3221, 48–59.
Meléndez, R. & Meneses, D. (1989) Tiburones del talud continental recolectados entre Arica (18º19'S) e Isla Mocha (38º30'S),
Chile. Investigaciones Marinas, Valparaíso, 17, 3–73.
Nair, R.V. & Appukuttan, K.K. (1973) Observation on the food of deep sea sharks Halaelurus hispidus (Alcock), Eridacnis
radcliffei Smith and Iago omanensis Compagno and Springer. Indian Journal of Fisheries, 20 (2), 575–583.
Nair, R.V. & Lal Mohan, R.S. (1973) On a new deep sea skate, Rhinobatos variegatus, with notes on the deep sea sharks
Halaelurus hispidus, Eridacnis radcliffei and Eugaleus omanensis from the Gulf of Mannar. Senckenbergiana biologica,
54 (1/3), 71–80.
Nakaya, K., Sato, K., Iglésias, S.P. & White, W.T. (2008) Methodology for the taxonomic description of members of the genus
Apristurus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae). In: Last, P.R., White, W.T. & Pogonoski, J.J. (Eds.)
Descriptions of new Australian chondrichthyans. CSIRO Marine & Atmospheric Research Paper No. 022, pp. 49–60.
Naylor, G.J.P., Ry burn, J.A., Ferigo, O. & Lopez, A. (2005) Phylogenetic relationships among the major lineages of modern
elasmobranchs. In: Hamlett, W.C. (Ed.) Reproductive Biology and Phylogeny of Chondrichthyes – Sharks, Batoids and
Chimaeras. Science Publishers, Inc., Enfield, pp. 1–25.
Raje, S.G., Mathew, G., Joshi, K.K., Nair, R.J., Mohanraj, G., Srinath, M., Gomathy, S. & Rudramurthy, N. (2002)
Elasmobranch Fisheries of India – An Appraisal. CMFRI special publication 71. CMFRI, Cochin, pp. 1–76.
Sabaj Pérez, M.H. (Ed.) (2014) Standard Symbolic Codes for Institutional Resource Collections in Herpetology and
Ichthyology: an Online Reference, Version 5.0 (22 September 2014). Available from http://www.asih.org/ (accessed 13
December 2014)
Sakaff, H. & Esseen, M. (1999) Occurrence and Distribution of Fish Species off Yemen (Gulf of Aden and Arabian Sea). Naga
ICLARM Quaterly, 22 (1), 43–47.
Séret, B. (1987) Halaelurus clevai, sp. n., a new species of catshark (Scyliorhinidae) from off Madagascar, with remarks on the
taxonomic status of the genera Halaelurus Gill & Galeus Rafinesque. J.L.B. Smith Institute of Ichthyology Special
Publication, 44, 1–27.
Springer, S. (1971) A new cat shark (Scyliorhinidae) from New Zealand. Records of the Dominion Museum, 7 (18), 235–241.
Springer, S. (1979) A revision of the catsharks, family Scyliorhinidae. NOAA Technical Report NMFS Circular, 422, 1–152.
Springer, S. & D’Aubrey, J.D. (1972) Two New Scyliorhinid Sharks from the East Coast of Africa with Notes on Related
Species. Oceanographic Research Institute, Investigational Report, 29, 1–19.
Springer, V.G. & Garrick, J.A.F. (1964) A survey of vertebral numbers in sharks. Proceedings of the United States National
Museum, 116, 73–96.
http://dx.doi.org/10.5479/si.00963801.116-3496.73
Stehmann, M.F.W. (2002) Proposal of a maturity stages scale for oviparous and viviparous cartilaginous fishes (Pisces,
Chondrichthyes). Archive of Fishery and Marine Research, 50 (1), 23–48.
Tizard, T.H., Moseley, H.N., Buchanan, J.Y. & Murray, J. (1885) Narrative of the cruise of H.M.S. Challenger with a general
account of the scientific results of the expedition. Report on the scientific results of the voyage of H.M.S. Challenger
during the years 1873–76. Narrative 1 (2), 511–1110.
Valenzuela, A., Bustamante, C. & Lamilla, J. (2008) Morphological characteristics of five bycatch sharks caught by southern
Chilean demersal longline fisheries. Scientia Marina, 72 (2), 231–237.
Weigmann, S. (2016) Annotated checklist of the living sharks, batoids and chimaeras (Chondrichthyes) of the world, with a
focus on biogeographical diversity. Journal of Fish Biology, 88 (3), 837–1037.
http://dx.doi.org/10.1111/jfb.12874
Weigmann, S., Stehmann, M.F.W. & Thiel, R. (2013) Planonasus parini n. g. and n. sp., a new genus and species of false cat
sharks (Carchariniformes, Pseudotriakidae) from the deep northwestern Indian Ocean off Socotra Islands. Zootaxa, 3609
(2), 163–181.
http://dx.doi.org/10.11646/zootaxa.3609.2.3
Weigmann, S., Stehmann, M.F.W. & Thiel, R. (2015) Okamejei ornata n. sp., a new deep-water skate (Elasmobranchii,
Rajidae) from the northwestern Indian Ocean off Socotra Islands. Deep-Sea Research II, 115, 18–29.
http://dx.doi.org/10.1016/j.dsr2.2013.09.005
White, W.T. & Last, P.R. (2013) Notes on shark and ray types at the South China Sea Fisheries Research Institute (SCSFRI) in
Guangzhou, China. Zootaxa, 3752 (1), 228–248.
http://dx.doi.org/10.11646/zootaxa.3752.1.14