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Memoirs of Museum Victoria 74: 107–116 (2016) Published 2016
ISSN 1447-2546 (Print) 1447-2554 (On-line)
http://museumvictoria.com.au/about/books-and-journals/journals/memoirs-of-museum-victoria/
Mysticetes baring their teeth: a new fossil whale, Mammalodon hakataramea,
from the Southwest Pacic
R. Ewan FoRdycE1,2,* (http://zoobank.org/ur n:lsid:zoobank.org:author:311048BF-4642-412E-B5DA-E01B8C03B802) and
FElix G. MaRx1,3 (http://zoobank.org/urn:lsid:zoobank.org:author:1791C478-33A7-4C75-8104-4C98C7B22125)
1 Department of Geology, University of Otago, PO Box 56, Dunedin 9054, New Zealand (ewan.fordyce@otago.ac.nz)
2 Departments of Vertebrate Zoology and Paleobiology, National Museum of Natural History, Smithsonian Institution,
Washington DC 20560, USA
3 Department of Geology and Palaeontology, National Museum of Nature and Science, Tsukuba, Japan (feli x.marx@
otago.ac.nz)
* To whom correspondence should be addressed. E-mail: ewan.fordyce@otago.ac.n z
http://zoobank.org/urn:lsid:zoobank.org:pub:7A2CAF55-70DC-4561-AA3D-86FA72C721E6
Abstract Fordyce, R.E. and Marx, F.G. 2016. Mysticetes baring their teeth: a new fossil whale, Mammalodon hakataramea, from
the Southwest Pacic. Memoirs of Museum Victoria 74: 10 7–116.
A small, toothed fossil cetacean from Hakataramea Valley (South Canterbury, New Zealand) represents a new Late
Oligocene species, Mammalodon hakataramea. The new material is from the Kokoamu Greensand (Duntroonian Stage,
about 27 Ma, early to middle Chattian) of the Canterbury Basin, and thus about 2 Ma older than the only other species
included in this genus, Mammalodon colliveri (Late Oligocene, Victoria, Australia). The anterior pedicle of the tympanic
bulla is not fused to the periotic and resembles that of Delphinidae in basic structure. The teeth show extreme attritional
and/or abrasive wear, which has obliterated the crowns. Like Mammalodon colliveri, M. hakataramea was probably
raptorial or a benthic suction feeder.
Keywords systematics, evolution, stratigraphy, anatomy, New Zealand, Osedax.
Introduction
New Zealand is a notable source of fossil cetaceans (whales,
dolphins) in the Southwest Pacic, with specimens ranging
in age from late Middle Eocene to Pleistocene. Rocks of the
southern Canterbury Basin (Field et al., 1989), in particular,
have produced rare Eocene and more common Late Oligocene
to earliest Miocene cetaceans. These mid-Cenozoic fossils
include representatives of the archaeocete family
Basilosauridae, putative stem neocetes (Kekenodontidae)
and diverse odontocetes, such as kentriodontids and other
putative delphinoids, waipatiids (e.g. Otekaikea Tanaka and
Fordyce, 2014, 2015), squalodontids and Squalodelphis-like
taxa. Mysticetes are represented by a diverse assemblage
comprising Eomysticetidae (e.g. Tohoraat a Boessenecker
and Fordyce, 2014a), basal Balaenopteroidea, and enigmatica
(e.g. Horopeta Tsai and Fordyce, 2015). The key cetacean-
bearing units – the Kokoamu Greensand (see below) and the
Otekaike Limestone – and the localities in and around the
Waitaki Valley that expose them were reviewed in the
aforementioned ar ticles.
Here, we name and describe a new species of the toothed
mysticete Mammalodon, based on specimen OU 22026 from
the southern Canterbury Basin. The fossil is distinct from the
hitherto monotypic Mammalodon colliveri (Late Oligocene,
~23.9-25.7 Ma) of Victoria, Australia (Fitzgerald, 2010), and is
probably close to 27 Ma. Of note, the fossil includes a tympanic
bulla with a well-preserved anterior pedicle, otherwise poorly
described for archaeocetes and archaic Neoceti.
Specimen OU 22026 was listed by Fordyce (1991: 1312) as
Mammalodon sp. and was later mentioned, but not named, in
an abstract (Fordyce and Marx, 2011). Recently, we included
OU 22026 in a total-evidence phylogenetic analysis of extant
and fossil Mysticeti (Marx and Fordyce 2015: g. 2; see g. 4
here), which identied it as sister to Mammalodon colliveri,
with Janjucetus hunderi immediately adjacent (basal).
Together, these three species form an expanded
Mammalodontidae, which in turn are closely related to a
diverse range of aetiocetids described only from the North
Pacic. OU 22026 was also sampled for isotopes by Clementz
et al. (2014), who reported δ13C and δ18O values for structural
bone carbonate from the bulla that are inconsistent with
(lter-)feeding low in the food chain.
R.E. Fordyce & F.G. Marx
108
Denitions and terminology
Anatomical terminology follows Mead and Fordyce (2009),
unless indicated.
Methods
All elements were uncovered by hand scraping from soft
matrix. The bulla was recovered fractured but still naturally
associated; it was cleaned and consolidated with cyanoacrylate
region by region. For photography, the bulla, teeth and skull
roof of M. hakataramea and the bulla of Mammalodon colliveri
were coated with sublimed ammonium chloride. Images of the
bulla of M. hakataramea are composites, stacked (using Adobe
Photoshop) from multiple shots at varying foci. Photography
used a Nikon 105 mm micro lens with a D700 or D800 (M.
hakataramea) or D70 (M. colliveri) camera body.
Institutional abbreviations
NMV P, Museum Victoria Palaeontology Collection,
Melbourne, Australia. OU, fossil collection in Geology
Museum, University of Otago, Dunedin, New Zealand.
Systematic Palaeontology
Cetacea Brisson, 1762
Neoceti Fordyce and Muizon, 2001
Mysticeti Gray, 1864
Mammalodontidae Mitchell, 1989
Mammalodon Pritchard, 1939
Emended diagnosis of Mammalodon. Small-sized mysticetes
differing from chaeomysticetes in having teeth. Differ from all
toothed mysticetes except Janjucetus in having a foreshortened,
dorsoventrally tall rostrum, a linguiform anterior border of the
supraorbital process, a tr iangular wedge of the frontal separati ng
the ascending process of maxilla from the posterolateral margin
of the nasal, a roughly horizontal dorsal prole of the braincase
(relative to the lateral edge of the rostrum) and posteriorly
reclined mandibular cheek teeth; further differ from all other
toothed mysticetes except Janjucetus and Chonecetus in having
a distinctly V-shaped fronto-parietal suture in dorsal view; from
Llanocetus and two previously coded, undescribed archaic
mysticetes (ChM PV4745; OU GS10897) in having both
relatively and absolutely smaller posterior cheek teeth with
proximally fused roots, and an inner posterior prominence of
the tympanic bulla that is subequal to the outer prominence in
posterior view; from all aetiocetids in having a more elongate
intertemporal region and an anteroposteriorly broader coronoid
process of the mandible; from Aetiocetus and Fucaia in lacking
a medially expanded lacrimal and a dorsoventrally constricted
mandible, and in having more robust cheek teeth with distally
separate roots; from Chonecetus in having a broader, less
anteriorly-thrust supraoccipital bearing a well-developed
external occipital crest, and in lacking a parasagittal cleft on the
dorsal surface of the parietal; from Aetiocetus in having a
clearly heterodont dentition and closely-spaced posterior cheek
teeth with well-developed enamel ridges on both the labial and
lingual sides of the crown; from Morawanocetus in having a
much more robust postorbital process of the frontal; from
Ashorocetus in having a less steeply inclined supraoccipital
shield and a somewhat more anteromedially oriented
basioccipital crest; and from the enigmatic Willungacetus in
having a clearly marked orbitotemporal crest extending
posteriorly on to the intertemporal constriction and a rounded
(rather than triangular), less anteriorly-thrust supraoccipital
bearing a well-developed external occipital crest. Finally,
Mammalodon differs from the only other described
mammalodontid, Janjucetus, in having a rostrum with a bluntly
rounded apex and a gently convex lateral prole in dorsal view,
Fig. 1, Locality map and stratigraphy of the Sisters Creek-Homestead Creek area of Hakataramea Valley. The stratigraphic column, right, is
modied from that of Tsai and Fordyce (2015) for “Haughs’ Quarry”, which provides the nearest detailed column to Sisters Creek. Mammalodon
hakataramea came from about the horizon identied as the diffuse shellbed with Lentipecten hochstetteri and brachiopods.
Mysticetes baring their teeth: a new fossil whale, Mammalodon hakataramea, from the Southwest Pacic 109
coalesced alveoli for the upper incisors, a gracile, foreshortened
and dorsoventrally attened premaxilla, an anteriorly expanded
nasal, a transversely narrow, linguiform ascending process of
the maxilla extending posteriorly as far as the nasal, a more
anteriorly directed orbit, a more laterally oriented postorbital
process, a transversely convex dorsal prole of the parietals
with no salient sagittal crest, a more laterally oriented nuchal
crest, a broadly rounded apex of the supraoccipital shield in
dorsal view, an anterior portion of the tympanic bulla that is
squared (rather than obliquely truncated) in ventral view, an
inner posterior prominence of the tympanic bulla that is
subequal to the outer prominence in posterior view, a straight
and comparatively gracile mandible bearing large mental
foramina, and three upper and four lower molars, all of which
(at least in adult specimens) are affected by heavy occlusal wear.
Remarks. Comparisons of Mammalodon with Ashorocetus
eguchii, Willungacetus aldingensis and Chonecetus sookensis
are currently hampered by the poor state of preservation of the
available material; none of the latter, for example, includes the
tympanic bulla or teeth. Ashorocetus is currently known only
from the posterior portion of a braincase preserving little
surface detail (Barnes et al. 1995). Willungacetus and
Chonecetus sookensis are based on somewhat more complete,
but still highly fragmentary crania having lost their rostra, most
or all of the ear bones and much of the (basicranial) surface
detail (Pledge, 2005; Russell, 1968). Until the discovery of
better material, the comparisons made here are necessarily
provisional. The use of occlusal wear as a potential diagnostic
character may be queried, as this feature may primari ly correlate
with age or the foraging environment. Nevertheless, the extreme
wear present in the two species of Mammalodon is unusual
amongst fossil cetaceans as a whole, and highly so in the context
of toothed mysticetes in par ticular. If tooth wear in Mammalodon
is primarily linked to the manner of occlusion and/or food
preferences, it may record a valid character that can be used for
diagnostic and cladistic purposes. Without evidence to the
contrary, we therefore retain it here as part of the diagnosis.
Mammalodon hakataramea Fordyce and Marx sp. nov.
Zoobank LSID. http://zoobank.org/urn:lsid:zoobank.org:act:
6D9 60 230 -379 9- 4597-BAA D-2537772B99A6
Figs. 2, 3
Holotype. OU 22026 – dorsal part of braincase, comprising
much of the supraoccipital and parts of the parietals and
squamosals, preserved with the original dorsal surface down,
and the bioeroded ventral surface upwards; left tympanic bulla
lacking the posterior process; ve teeth with little or no
remnants of the crown. All elements were closely associated,
with no other fossil cetacean remains nearby.
Type locality. Open at bed of Sisters Creek, 70-80 m
downstream from a prominent limestone bank directly north of
Riverside farmhouse, McHenrys Road, Hakataramea Valley,
South Canterbury (Fig. 1). Field number REF 13-10-87-2. Grid
reference: latitude 44 deg 38 min 30.5 sec, longitude 170 deg 38
min 45.0 sec, or NZMS260 map I40: 232 158. The Geoscience
Society of New Zealand fossil record number is I40/f400. The
locality is 2 km NNW of the informally-named “Haughs’
Quarry,” as shown by Tanaka and Fordyce (2015).
Horizon and age. OU 22026 is from a massive, bioturbated,
calcareous section of the Kokoamu Greensand, where it was
associated with sparse macrofossils including scattered
pectinids (Lentipecten hochstetteri) and terebratulid
brachiopods. Lentipecten hochstetteri and the benthic
foraminiferan Notorotalia spinosa indicate the Duntroonian
Stage. Judging from a comparable section in the Greensand at
Haughs’ Quarry, about 2 km to the SSE (g. 1, right; also, see
Tsai and Fordyce, 2015), the diffuse shellbed of pectinids and
brachiopods is low in the Duntroonian, probably near the base.
The Duntroonian is dated as 25.2–27.3 Ma (Raine et al. 2015)
and OU 22026 is presumed close to 27 Ma, or early Chattian
(Vandenberghe et al., 2012).
Diagnosis. Differs from M. colliveri in having smaller teeth,
an anteroposteriorly longer supraoccipital and a parabolic
nuchal crest that lacks an abrupt anterolateral curve in dorsal
view, as well as in having a tympanic bulla with a more
distinct interprominential notch, a straight medial margin, an
anterolaterally more inated outer lip, and a deeper
involucrum bearing less developed oblique sulci (without
adjacent nodules).
Etymology. Hakataramea, a Maori name for the valley where
the holotype was collected. Haka, a dance; taramea, a sharp-
spined herb, “spear-grass” (Apiaceae: Aciphylla squarrosa),
with sweet-smelling gum from the ower stalks. The
name may commemorate a specic incident (Reed and
Dowling, 2010).
Description
Ontogenetic stage. The specimen is probably a mature adult
because of the extreme wear that has mostly obliterated the
tooth crowns (g. 1A–E). The parieto-occipital suture is open
along parts of the nuchal crest, but this condition is also seen in
adult modern baleen whales (e.g. Balaenoptera acutorostrata,
Miller, 1924: plate 4; Balaenoptera borealis, Andrews, 1916:
plate 41; Megaptera novaeangliae, True 1904: plates 29, 32).
Skull roof. The dorsal roof of the skull (g. 2 F, G; table 1) is
represented by the ventrally eroded, thin parietals, the
supraoccipital and, at the posterolateral margins, probably the
dorsalmost portions of both squamosals. There is no distinct
Table 1. Measurements of the skull roof of OU 22026, +/- 0.5 mm.
Skull roof, anteriormost parietal to posteriormost
supraoccipital, midline
+13 4.5
Length of parietals on vertex +45.0
Length of supraoccipital, midline +94.0
Width, outer margins of nuchal crest,
posteriormost preserved points
(= posterolateral extremities of skull roof)
+15 4.5
R.E. Fordyce & F.G. Marx
110
Fig. 2. A-G, I, holotype of Mammalodon hakataramea, OU 22026; all mater ial coated with sublimed ammonium chloride and lit from upper
left. A-E, individual isolated teeth in labial or lingual view. F, G, I, holotype skull roof of Mammalodon hakataramea. F, I, dorsal view, anterior
towards the top; G, oblique dorsolateral view from the left, anterior towards the lower left. H, holotype skull of Mammalodon colliveri Pritchard,
NMV P199986, dorsal view, not coated with sublimed ammonium chloride. H and I are shown at the same scale to compare the differences in
size and prole between the two Mammalodon species. The two dashed lines show the position of the apex of the nuchal crest and the dorsal lip
of the foramen magnum in M. colliveri; M. hakataramea is aligned with the upper line.
Mysticetes baring their teeth: a new fossil whale, Mammalodon hakataramea, from the Southwest Pacic 111
Fig. 3. A-F, L, M, holotype left tympanic bulla of Mammalodon hakataramea, OU 22026; all views show the bulla coated with sublimed
ammonium chloride and lit from upper left. A, dorsal. B, ventral. C, posterior. D, anterior. E, lateral. F, medial. G-K, holotype right tympanic
bulla of Mammalodon colliveri Pr itchard, NMV P199986, with views mirrored for ease of comparison with M. hakataramea; bulla is coated
with sublimed ammonium chloride and mir rored views show lighting from upper right. G, dorsal. H, ventral. I, medial. J, lateral. K, posterior.
L, M, enlarged views of left tympanic bulla of Mammalodon hakataramea to show anterior pedicle. L, slightly dorsomedial posterior view. M,
slightly posterior dorsomedial view.
R.E. Fordyce & F.G. Marx
112
interparietal. The dorsal periosteal surfaces are damaged by
patchy bioerosion, which in two places has also led to the
perforation of the supraoccipital. Enough remains to see that
the supraoccipital is longer, from its apex to the margin of
foramen magnum, than in M. colliveri (g. 2H, I). The gently
concave supraoccipital is raised little (~ 3 mm) above the
parietals, and forms a thin-edged nuchal crest with a parabolic
prole and a smoothly rounded apex in dorsal view (g. 2F, G).
By contrast, the crest in M. colliveri is more robust, with
abruptly curved anterolateral corners that markedly overhang
the parietals (g. 2H). A lateral or oblique view (g. 2G) shows
the nuchal crest gently convex anteriorly but markedly
steepening posteriorly, as if descending toward the posterior
margin of the temporal fossa. Anteriorly, the supraoccipital has
a small, attened dorsal apex, passing backwards into a short
but well-developed external occipital crest. Posteriorly, the
supraoccipital is raised and thickened in the midline, with the
adjacent surfaces steepening bilaterally; in M. colliveri, such
features are developed near the foramen magnum.
What remains of the parietals suggests that the fused bones
form a wide and smoothly rounded intertemporal region
without any salient sagittal or parasagittal crests, contrasting
with the narrower, dorsally tabular, condition in M. colliveri.
Irregular parasagittal grooves could result from bioerosion, but
are more likely to be sulci associated with parietal foramina.
Poorly-preserved irregularities in the bone surface posteriorly
(g. 2G) may represent the parieto-squamosal sutures.
Tympanic bulla (g. 3A–F, L–M; table 2). The left bulla is
slightly crushed, with the outer lip a little compressed ventrally.
The anterior pedicle has been distorted post-mortem and
rotated ventromedially, so that the suture for the anterior bullar
facet of the periotic is steeply dipping, rather than sub-
horizontal. The posterior process, conical process and the
anterolateral crest of the outer lip are lost.
In dorsal view (g. 3A), the bulla has a straight medial
pr ol e, a blunt ly ro und e d, sl igh tly squa r e d ape x and an in at e d
outer lip, with the bone attaining its greatest width at the level
of the sigmoid process. The two posterior prominences or
lobes are separated by the conspicuous, near-perpendicular
interprominential notch (g. 3A, B). In dorsal or ventral view,
the outer prominence is sharp, passing dorsally into a marked
prominential ridge (sensu Tsai and Fordyce, 2015). The inner
prominence is more smoothly rounded and does not extend as
far posteriorly, which may indicate an anteromedial in situ
orientation of the long axis of the bulla as seen, for example, in
Janjucetus hunderi. In posterior view (g. 3C, L) a strong,
slightly oblique ridge crosses the inner prominence to reach
the interprominential notch; there is no ridge on the outer
prominence. Ventrally (g. 3B), the interprominential notch
passes into a median furrow 22–23 mm long, about half the
length of the bulla.
The Eustachian outlet forms a shallow, anteromedially
oriented notch (g. 3A, M). The adjacent portion of the
involucrum is obliquely at medially and excavated laterally.
Posteriorly, the involucrum rises and widens via an abrupt,
obliquely oriented step at mid-length. Oblique striae that cross
the involucrum are ner than in M. colliveri (g. 3F) and not
separated by tubercles laterally. The otherwise smooth dorsal
surface anteriorly on the involucrum was probably covered by a
lobe of the peribullary sinus; this smooth bone extends posteriorly
20+ mm, at least to the oblique “step” in the dorsal prole, and
possibly to the level of the prominent sub-vertical postmortem
crack (g. 3M). Further posteriorly, the elevated involucral
surface is considerably rougher, suggesting that the peribullary
sinus may not have extended over the involucrum here. In medial
view, the involucrum has a horizontal zone of irregular ne
creases, probably marking tendinous connections to the
basioccipital crest (g. 3F, M). A large irregular depression on
the posteriormost portion of the involucrum (g. 3M) is probably
a collapsed cluster of galleries formed by the osteophagous
siboglinid worm Osedax (see Boessenecker and Fordyce, 2014b
for similar occurrences in other New Zealand Oligocene
Cetacea). In posterior view, the involucrum is more prolonged in
a dorsolateral-ventromedial plane than the sub-cylindrical
involucrum of M. colliveri (compare gs. 3C, D and 3K). An
oblique (slightly lateral) dorsal view, not gured here, shows a
slight concavity in the medial prole of the involucrum – much
less than in M. colliveri, in which this concavity is pronounced.
The outer lip preserves a sharp crest at the Eustachian
outlet and becomes anterolaterally inated as it passes back
towards the anterior pedicle. The anterolateral corner of the
tympanic bulla formed by this inated portion is more rounded
than in M. colliveri (compare g. 3B, H). The cre st of the outer
lip is broken to reveal the tympanic cavity in dorsal view. The
oor of the latter is smooth and has a marked transverse saddle
about level with the anterior pedicle, behind which the
tympanic cavity deepens markedly, and narrows. The cavity
both undercuts the involucrum and, at its posterior limit, rises
dorsally to excavate it below the inner posterior pedicle.
The anterior pedicle has a narrow, anteroposteriorly long
ju ncti on wi th the oute r lip (g . 3A, M). The jun ction is cr a ck e d,
and it is uncertain if a groove for the chorda tympani nerve
was present. In dorsal or dorsomedial view (g. 3A, M), the
anterior pedicle has three elongate faces roughly perpendicular
to each other. The original structure and orientations are
interpreted thus: a lateral plate that descends to the outer lip;
an elongate sub-oval dorsal face with a shallow grooved suture
for the periotic; and a descending medial crest, with a groove
that presumably contributes to the origin of the tensor tympani
Table 2. Measurements of left bulla of OU 22026, +/- 0.5 mm
Length, apex adjacent to Eustachian outlet
to apex of outer posterior prominence
56.5
Length, parallel with medial face 55.5
Width, maximum, immediately below sigmoid cleft 38.0
Depth of involucrum, maximum, at anterior margin
of broken base of inner posterior pedicle
25.5
Depth, tip of sigmoid process to ventral surface with
bulla sitting in stable position
38.0
Length, apex adjacent to Eustachian outlet to apex of
sigmoid process
38.5
Mysticetes baring their teeth: a new fossil whale, Mammalodon hakataramea, from the Southwest Pacic 11 3
muscle (following Tsai and Fordyce 2015). A posterior view
(g. 3L) shows the silhouetted cross section of the pedicle,
with the three surfaces bounding an elongate V- to U-shaped
ventral groove. On the dorsal face, the suture for the anterior
bullar facet of the periotic is a long, shallow groove (g. 3L,
M); accordingly, the fovea epitubaria was probably shallow
and at, rather than saddle-shaped. The dorsal face of the
pedicle does not show any clear region of fusion with the
anterior margin of the mallear fossa, although the lateral edge
of the posterior apex has lost a sub-mm area of surface bone
which might indicate fusion.
Adjacent to the anterior pedicle, the outer lip bears a shallow
vertical groove, but no obvious lateral furrow (g. 3E). The
mallear ridge is prominent, oriented obliquely and most raised
at its mid-length. Posteriorly, at the inner margin of the sigmoid
process, the ridge passes into a tiny projection representing the
broken anterior process of the malleus (g. 3M). In anterior or
posterior view (g. 3D, L), the dorsal prole of the sigmoid
process has three indistinctly separate faces: a medial one,
probably marking the proximity of the malleus; a dorsal one,
possibly apposing the sigmoid fossa of the squamosal; and a
lateral one. The enrolled posterior lip of the sigmoid process
overhangs a sigmoidal cavity (sensu Tsai and Fordyce, 2015)
delimited by a low oblique ridge presumably for the tympanic
sulcus (g. 3L). In lateral view (g. 3E), the sigmoid process is
bounded ventrally by a damaged, anteroventrally oblique
sigmoid cleft. The conical process is lost. A strong prominential
ridge (sensu Tsai and Fordyce, 2015) lateral to the elliptical
foramen is matched by a thickened ridge within the tympanic
cavity. Judging from well-preserved thin anges, the elliptical
foramen was patent as a narrow opening about 5 mm deep.
Tee t h (g. 2A–E; table 3). Five teeth are represented by roots,
with one tooth (g. 2B) retaining a tiny possible dentine
remnant of the crown. The other four teeth are worn, exposing
sections through the inlled pulp cavity. The worn, sub-ovate
surfaces curve down both labiolingually and mesiodistally.
Wear exposes lines of arrested growth (growth-layer groups, as
commonly used for Cetacea), marked by alternating lighter and
darker coloured bands in the outer biomineral, which is
presumed to be cementum. Occlusal surfaces were examined
under high magnication, but no wear patterns (grooves,
striations) were apparent. Tooth A of Figure 2 is laterally
compressed and conical. Tooth B is conical, with a double
distal tip, perhaps representing two fused roots. Tooth C is
laterally compressed. Tooth D is grooved on the labial and
lingual faces, perhaps representing two fused roots. Tooth E
has two closely approximated large roots that taper and
converge distally, with a small third root between the two
larger adjacent to the occlusal surface. Tooth E is the only one
that can reasonably be identied to position, as a posterior
premolar or molar.
Discussion
Mammalodon hakataramea is one of relatively few toothed
mysticetes to be formally described, and only the third member
of the highly unusual and seemingly rather localised
mammalodontids (g. 4). Bianucci et al. (2011), however,
mentioned a potential record of this family from the
Mediterranean. Mammalodon hakataramea is also the rst
new species of archaic toothed mysticete from the New Zealand
region to be formally named as such. Other New Zealand
Oligocene Cetacea likely also represent archaic Mysticeti, but
have either been misidentied or remain undescribed. One
example of such mater ial is “Squalodon” serratus Davis, 1888,
an isolated cheek tooth that may have belonged to an aetiocetid
(Fordyce, 2008). Another is an Early Oligocene specimen
described by Keyes (1973) as a “proto-squalodont”, but
identied as a basal mysticete by Marx and Fordyce (2015)
based on as-yet undescribed portions of the skull (OU
GS10897). Nevertheless, toothed mysticetes from New Zealand
are rare, and only a handful of potential candidates have been
recovered during Fordyce’s eld programme of 30 years.
The holotype of Mammalodon hakataramea shows two
features that are noteworthy in terms of structure and/or
function. First, the anterior pedicle of the bulla reveals details
rarely preserved in basal mysticetes: the long, thin lateral plate
merging with the outer lip, the dorsal face with the suture for
the anterior bullar facet of the periotic and the medial crest, all
of which bound a ventral groove. These structures are readily
homologised with the anterior pedicle, or accessory ossicle, in
extant Delphinidae, e.g. Tursiops truncatus and Globicephala
melas. In the delphinids, the lateral plate descends to the
groove for the chorda tympani. The dorsal face (with a faintly
grooved suture for the periotic) is short and arched
anteroposteriorly to match the saddle-shaped fovea epitubaria.
The medial plate is inated and nodular (thus partly closing
the ventral groove), and contributes to the origin for the tensor
tympani (see Mead and Fordyce, 2009: g. 25W). A ventrally-
grooved anterior pedicle and unfused bulla/periotic contact
also occur in at least one kekenodontid and one eomysticetid at
OU, albeit in pedicles broken from the bulla. In the putative
gulp-feeding Late Oligocene mysticetes Mauicetus parki and
Horopeta um arere (both Chaeomysticeti), the dorsal face of
the anterior pedicle is partly fused posteriorly to the periotic.
In addition, the medial ridge is not developed in these taxa, but
extends dorsally up the medial fac e of the periotic. Accordi ngly,
there is no ventral groove.
Table 3. Measurements of teeth of OU 22026, +/- 0.5 mm
Tooth of Fig. 2A, maximum length of root 9.5
Tooth of Fig. 2A, maximum diameter 4.0
Tooth of Fig. 2B, maximum length of root 21.0
Tooth of Fig. 2B, maximum diameter 5.5
Tooth of Fig. 2C, maximum length of root 16.5
Tooth of Fig. 2C, maximum diameter 7.0
Tooth of Fig. 2D, maximum length of root 26.0
Tooth of Fig. 2D, maximum diameter 7.0
Tooth of Fig. 2E, maximum length of root 23.5
Tooth of Fig. 2E, maximum diameter, mesiodistal 11.0
R.E. Fordyce & F.G. Marx
114
Secondly, the worn occlusal surfaces of the teeth curve
down on to the mesiodistal and labiolingual faces of the roots.
The similar shape and surface detail amongst the teeth suggest
that the wear is not post-mortem bioerosion, but was likely
caused by abrasion. Phylogenetic bracketing (g. 4) implies
that M. hakataramea actually had functional tooth crowns on
robust teeth in a short rostrum, like its sister taxon M. colliveri.
The rounded worn surfaces in M. hakataramea contrast with
the more clearly planar wear characterising the cheek tooth
crowns in the holotype of M. colliveri (see Fitzgerald, 2010).
Nevertheless, planar attrition cannot be ruled out as a factor
earlier in the ontogeny of OU 22026, and it is possible that the
rounded wear surfaces reect old age. Extensive attritional
wear might have removed much of the tooth crown, as in M.
colliveri, until proper occlusion, and thus further attrition,
became impossible. Abrasive wear, conversely, could have
continued through on-going contact of the teeth with food or
ingested sediment.
That OU 22026 survived despite having lost functional
tooth crowns argues against tooth-assisted lter feeding, as
was also argued by Fitzgerald (2010). This conclusion is
consistent with the isotopic values reported by Clementz et al.
(2014), which indicate that M. hakataramea fed higher in the
food chain than typical lter feeding mysticetes. We agree
with Fitzgerald (2010) that the extensive wear in Mammalodon
is more easily reconciled with suction feeding than with
raptorial feeding, which depends on functional teeth for
grasping and/or processing large prey; nevertheless, facultative
durophagy or raptorial sarcophagy cannot be ruled out.
Cetacean ecology during the Oligocene was rather
different from today. Modern seas are dominated by one
clade of mysticetes – the gulp-feeding rorquals
(Balaenopteridae) – and two clades of echolocating
odontocetes: the deep-diving, suction-feeding beaked whales
(Ziphiidae) and the ecologically rather plastic dolphins
(Delphinidae). Like the modern species, some of New
Zealand’s Late Oligocene baleen whales (e.g. Mauicetus
parki, Horopeta umarere), probably lter-fed by skimming or
gulping. The long- and narrow-jawed eomysticetids, with no
modern equivalents, could have been skimmers or suction
feeders, but probably not gulp feeders. The small-toothed
mysticetes from the wider Australasian region were rather
disparate, and probably included both raptorial and (benthic)
suction feeders, such as Mammalodon colliveri. Given their
overall similarity and shared extreme tooth wear, M. colliveri
and M. hakataramea were perhaps suction feeders. Late
Oligocene odontocetes were all echolocators, with
assemblages dominated by platanistoid dolphins in contrast
to the domina nt delphinids of modern s eas. These platanistoids
included both clearly heterodont taxa, such as shark-toothed
dolphins with a robust dentition suitable for crushing food,
and near-homodont forms that – like modern dolphins –
probably swallowed with minimal processing. Remarkably,
kekenodontid archaeocetes coexisted, until about 26 Ma, with
cetaceans of “modern” feeding habit, presumably snap-
feeding raptorially and without the benet of echolocation.
Acknowledgements
This work has its origins in a chance meeting between Thomas
H. Rich and R. Ewan Fordyce in 1974, in the ofce of GA
Tunnicliffe at Canterbury Museum. Fordyce was then a
Fig. 4. Relevant detail of phylogeny from Marx and Fordyce (2015: Fig. 2), showing relationships of Mammalodon hakataramea and other
Mysticeti basal to the crown group. Pli., Pliocene; Pls., Pleistocene.
Mysticetes baring their teeth: a new fossil whale, Mammalodon hakataramea, from the Southwest Pacic 11 5
student, considering New Zealand-based postgraduate studies
in some mix of zoology and geology; Rich was assessing the
potential to nd fossil terrestrial mammals in New Zealand.
Unsurprisingly, Rich raised the topic of vertebrate
palaeontology and, further, he persisted by letter to encourage
Fordyce. In turn, Fordyce started doctoral studies on New
Zealand fossil Cetacea, and ultimately took a job at University
of Otago where he developed a vertebrate palaeontology
research programme, leading to nds such as that reported
here. Thank you, Tom Rich. We also thank the following for
their help in this project: Michael Brosnan, landowner, for
allowing excavation; the McKenzie family for eld
accommodation; Andrew Grebneff and Craig Jones for eld
work; Andrew Grebneff for preparing the specimen; O.P.
Singleton and Neil Archbold for access to Mammalodon
colliveri; Erich Fitzgerald for discussions on Mammalodon.
We thank the reviewers, Travis Park and Erich Fitzgerald, for
their constructive critiques. Research was supported by a
University of Otago PhD scholarship and a Japan Society for
the Promotion of Science postdoctoral scholarship to FG
Marx, by National Geographic Society eld grants 3542-87
and 3657-87 to RE Fordyce, and by a Monash University
Postdoctoral Fellowship which supported Fordyce’s early
study on Mammalodon colliveri.
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