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ISSN 0031-0301, Paleontological Journal, 2023, Vol. 57, No. 6, pp. 659–670. © Pleiades Publishing, Ltd., 2023.
Russian Text © The Author(s), 2023, published in Paleontologicheskii Zhurnal, 2023, No. 6, pp. 62–75.
Small Ducks (Aves: Anatidae) from the Early–Middle Miocene
of Eurasia. 3. A Revision of Mionetta natator (Milne-Edwards, 1867)
N. V. Zelenkov*
Borissiak Paleontological Institute of Russian Academy of Sciences, Moscow, 117647 Russia
*e-mail: nzelen@paleo.ru
Received March 2, 2023; revised March 22, 2023; accepted March 22, 2023
Abstract—The results of a taxonomic and morphological revision of Mionetta natator (Milne-Edwards, 1867)
from the lower Miocene of Western and Central Europe are presented. It is shown that the collections of small
ducks from the Saint-Gérand-le-Puy localities (France) do indeed contain a small species of the genus Mio-
netta, which is here described as Mionetta defossa sp. nov. However, Mionetta natator represents a separate
taxon, and is here assigned to the genus Caerulonettion gen. nov., showing morphological similarities with
extant Malacorhynchus and fossil Mioquerquedula spp. The first small ducks from the lower Miocene of
Kazakhstan are also described (Aral Formation, the Agyspe and Altynshokysu localities; Akzhar Formation,
the Golubye Peski locality), tentatively attributed to Mionetta defossa and Mionetta sp. The diversity and rela-
tionships of small ducks of the Early and Middle Miocene of Eurasia are discussed.
Keywords: fossil birds, Anseriformes, taxonomy, evolution, Neogene, Lower Miocene, Kazakhstan, France
DOI: 10.1134/S0031030123060114
This paper completes a series of publications on
small ducks from the Early and Middle Miocene of
Eurasia (Zelenkov, 2023a, 2023b). This article pres-
ents a taxonomic revision of “Anas” (Mionetta) natator
Milne-Edwards, 1867, a small (teal-sized) duck
known from the Upper Oligocene–Middle Miocene
of Western and Central Europe. Until now, the sys-
tematic position of A. natator has remained unclear
(Howard, 1964; Livezey and Martin, 1988; Mlíkovský,
2002). This species was conventionally combined in
the same genus as the larger Anas blanchardi Milne-
Edwards, 1863 from the same Aquitanian deposits of
Saint-Gérand-le-Puy: first in the genus Anas in the
broadest taxonomic interpretation (Howard, 1964),
later in the genus Dendrochen (Cheneval, 1983), and
then in the genus Mionetta (Livezey and Martin,
1988). Only Brodkorb (1964) treated A. natator in a
separate genus from A. blanchardi, and placed the for-
mer in the extant genus Querquedula Stephens, 1824
(=Spatula Boie, 1822); however, this interpretation
was not generally accepted. In recent decades, both
species have conventionally been assigned to the genus
Mionetta Livezey et Martin, 1988.
The author has previously noted the unusual mor-
phology of some materials attributed to “Anas” natator
and their distinction from those of Mionetta blanchardi
(Zelenkov, 2012). Bone remains of M. blanchardi are
very numerous in collections from Saint-Gérand-le-
Puy (thousands of specimens), whereas small ducks
from these localities are known from a very small (sev-
eral dozens) number of bones. This article presents the
results of a revision of these materials, which showed
that the collections of small ducks from Saint-
Gérand-le-Puy actually contain the remains of two
similar-sized species: one is a small Mionetta species
(described here as Mionetta defossa sp. nov.), charac-
terized by proportions and morphology similar to
Dendrocygninae, whereas the other is an evolution-
arily more advanced member of Anatidae, partly sim-
ilar to Malacorhynchus and Mioquerquedula and
assigned here to the new genus Caerulonettion gen.
nov. The lectotype of Anas natator, which is consid-
ered in this work as Caerulonettion natator (Milne-
Edwards, 1867) comb. nov., belongs to this taxon.
The following abbreviations are used in this article:
PIN RAS, Borissiak Paleontological Institute of the
Russian Academy of Sciences; BSP, Bavarian State
Collection of Paleontology and Geology (Munich);
MB, Natural History Museum of Berlin (Germany);
MNHN, National Museum of Natural History (Paris,
France).
SYSTEMATIC PALEONTOLOGY
CLASS AVES
Order Anseriformes
Family Anatidae Leach, 1820
Genus Mionetta Livezey et Martin, 1988
Mionetta: Livezey and Martin, 1988, p. 208; Mlíkovský, 2002,
p. 10 9 ; Z elenkov and Ku rochki n, 2 015, p . 157.
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PALEONTOLOGICAL JOURNAL Vol. 57 No. 6 2023
ZELENKOV
Type s p ecies. Anas blanchardi Milne-
Edwards, 1863.
D i a g n o s i s (emended). In the humerus, the
caudal shaft ridge is oriented towards the tuberculum
dorsale; the tuberculum dorsale is subtriangular and
protrudes markedly from the caudal surface of the
bone; the caput humeri overhangs the dorsal part of
the fossa pneumotricipitalis; the fossa pneumotricipi-
talis is not pneumatized; the incisura capitis hardly
forms notch in the proximal bone profile (in caudal or
cranial views); the dorsal surface of the crista delto-
pectoralis is distinctly concave; the crista bicipitalis is
elongated, steeply approaching the shaft; the sulcus
transversus is short; the distance between the tubercu-
lum supracondylare ventrale and condylus dorsalis is
not less than the width of the tuberculum supracondy-
lare ventrale; protruding tuberculum supracondylare
dorsale is absent; the tuberculum supracondylare ven-
trale protrudes slightly cranially; the proximal apex of
the condylus dorsalis curves slightly ventrally.
Species composition. M. blanchardi
(Milne-Edwards, 1863), Late Oligocene and Early
Miocene of France, Early and Middle Miocene of
Germany and the Czech Republic (Zelenkov, 2012);
M. consobrina (Milne-Edwards, 1868), Early and
Middle Miocene of France, Germany, and the Czech
Republic; M. defossa sp. nov., Early Miocene of
France and Kazakhstan.
C o m p a r i s o n. An exhaustive comparison is
given by B. Livezey and L. Martin (Livezey and Mar-
tin, 1988).
R e m a r k s. The genus Mionetta was erected by
Livezey and Martin (1988) for the Early Miocene
anatid “Anas” blanchardi, which had previously been
included in the genus Dendrochen, originally
described from the Lower Miocene of the United
States (Cheneval, 1983). Two more species, small Anas
natator and large A. consobrina, had preliminary been
included in the genus Mionetta. Since then, the
generic position of these species has not been revised.
Here, the assignment of A. natator to a separate anatid
genus (see below) is confirmed. However, the fairly
small (large teal-sized) species of Mionetta, described
below as M. defossa sp. nov., is still present in the Early
Miocene of France. M. consobrina (Milne-Edwards,
1868) is sometimes considered to be large specimens of
M. blanchardi (Livezey and Martin, 1988; Mlíkovský,
2002). Nevertheless, M. consobrina has certain mor-
phological differences (Cheneval, 1983; Mourer-
Chauviré, 2008), which, along with the large size,
allow this species to be considered valid. It should be
taken into account that it may be impossible to distin-
guish between large specimens of M. blanchardi and
small specimens of M. consobrina; however, this does
not affect the validity of the two species. The most
recent representative of M. blanchardi from the Mid-
dle Miocene of Germany (Göhlich, 2002) differs mor-
phologically from the Early Miocene forms and, in my
opinion, represents a separate unnamed species.
Mlíkovský (2002) also included the large anatid Anas
robusta (Milne-Edwards, 1868) from the Middle Mio-
cene of the Sansan locality (France) into the genus
Mionetta, noting the similarity of this species to extant
Dendrocygninae (Mlíkovský, 2002). Following Chen-
eval (2000), I exclude “A.” robusta from the genus
Mionetta (in particular, on the basis of the distinctive
morphology of the femur). However, the inclusion of
this species in the genus Anserobranta (see Cheneval,
2000) cannot be confirmed either (personal observa-
tions). “Anas” integra from the Lower Miocene of the
United States was preliminarily included in the genus
Dendrochen (Cheneval, 1987); however, it is morpho-
logically similar to Mioquerquedula and in this study
(Zelenkov, 2023b) is considered in this fossil genus.
The phylogenetic position of Mionetta as one of the
most ancient and best-known anatids in the paleonto-
logical record (Mayr, 2017) is of considerable interest
for understanding the evolution of the family. Chene-
val (1983) assigned the species of this genus to the sub-
family Dendrocygninae, the basal group of extant
Anatidae (Sun et al., 2017). Livezey and Martin (1988)
included Mionetta in the separate subfamily Dendro-
cheninae, which they placed between Dendrocygn-
inae and Thalassornithidae (the latter including only
the genus Thalassornis, which is now also classified
with Dendrocygninae). Later, on the basis of the
results of phylogenetic analysis, Worthy and Lee
(2008) transferred Mionetta to the extant subfamily
Oxyurinae as a basal member. A new phylogenetic
analysis (Worthy et al., 2022) places Mionetta in an
intermediate position between the subfamilies Den-
drocygninae and Oxyurinae (“Erismaturinae” sensu
Worthy et al., 2022), which better matches the morphol-
ogy of M. blanchardi (see Zelenkov and Kurochkin,
2015) and confirms the validity of Dendrocheninae.
The above revised diagnosis is based on the diagno-
sis of the genus proposed by Livezey and Martin
(1988), with addition of our data, as well as data of
Worthy et al. (Worthy et al., 2007; Worthy and Lee,
2008). Here, only the diagnosis by the humerus is
given, as the most studied and diagnostically valuable
element of the skeleton. Differences in the structure of
other elements, in particular, carpometacarpus
(Livezey and Martin, 1988), require confirmation.
The taxonomic relationships of the genera Dendro-
chen and Mionetta require clarification. The general
morphological similarity of the type species Mionetta
blanchardi and Dendrochen robusta Miller, 1944 from
the Lower Miocene of the United States was obvious
to previous authors (Cheneval, 1983; Livezey and
Martin, 1988; Mlíkovský, 2002), but the separate
generic status of M. blanchardi was substantiated by a
number of morphological differences of this species in
the structure of the humerus (Livezey and Martin,
1988; see also Mlíkovský, 2002). The involvement of
broad comparative material on M. blanchardi does not
PALEONTOLOGICAL JOURNAL Vol. 57 No. 6 2023
SMALL DUCKS (AVES: ANATIDAE) FROM THE EARLY–MIDDLE MIOCENE 661
allow confirmation of many of these differences (per-
sonal data), which calls into question the validity of
the genus Mionetta.
Here, a cranial fragment of the left coracoid (spec-
imen PIN, no. 2976/1149) from the Golubye Peski
locality in the Zaisan basin of Kazakhstan, Akzhar
Formation, Lower Miocene (MN 4; Zazhigin and
Lopatin, 2000) is assigned to the genus Mionetta. This
specimen corresponds in size to medium-sized speci-
mens of M. blanchardi and is characterized by a very
large rounded cotyla scapularis and medium-sized
and pointed facies articularis humeralis. Extant Den-
drocygna are similar in morphology of the facies
articularis humeralis but have a smaller cotyla scapu-
laris. Although the poor preservation of the specimen
does not allow confirmation of its species status, it
presumably belongs to M. blanchardi.
Mionetta defossa Zelenkov, sp. nov.
Plate 10, figs. 2, 3, 9, 12, 15
Dendrochen natator (part.): Cheneval, 1983, p. 93.
Mionetta natator (part.): Livezey and Martin, 1988, p. 208,
Mlíkovský, 2002, p. 111.
Etymology. From Latin defossa (buried). The
name is found on 19th century labels for medium-
sized ducks from Saint-Gérand-le-Puy in the MNHN
collection. Presumably, this name was intended for
one of the small anatid species from the locality, but
was never published.
H o l o t y p e. MB, no. Av 325-1, right coracoid;
France, group of Saint-Gérand-le-Puy localities;
Lower Miocene.
D e s c r i p t i o n. The coracoid is morphologically
identical to that of M. blanchardi, but is noticeably
smaller. The processus acrocoracoideus is subparallel
to the long axis of the shaft and hardly deviates medi-
ally; the cotyla scapularis is very large, rounded, occu-
pies most of the shaft in dorsal view; the facies articu-
laris humeralis with a pointed cranial angle; the facies
articularis clavicularis without a notch in the caudal
margin, does not clearly overhang the sulcus m. supra-
coracoidei; the sulcus m. supracoracoidei is moder-
ately concave.
M e a s u r e m e n t s in mm. Coracoid: medial
length, 33.0 (holotype) and 34.2 (specimen MB,
no. Av 325-5); length of cranial end from apex to cau-
dal margin of cotyla scapularis, 12.0 (holotype, speci-
men MB, no. Av 325-5); minimum width of the shaft
is 3.4 (holotype) and 3.6 (specimen MB, no. Av 325-5).
Humerus: total length, 67.3 (specimen MB, no. Av
326-1), 65.6 (specimen MB, no. Av 327-2), and 67.4
(specimen MB, no. Av 327-3); width of the proximal
end, 15.1 (specimen MB, no. Av 326-1) and 15.6
(specimen MB, no. Av 327-3); minimum dorsoventral
width of the shaft, 4.8 (specimen MB, nos. Av 326-1,
Av327-3) and 4.5 (specimen MB, no. Av 327-2); width
of the distal end, 10.4 (specimen MB, no. Av 326-1),
9.3 (specimen MB, no. Av 327-2), and 10.1 (specimen
MB, no. Av 327-3); craniocaudal height of condylus
dorsalis, 6.3 (specimen MB, nos. Av 326-1, Av 327-2)
and 6.1 (specimen MB, no. Av 327-3). Ulna: total
length, 55.5; dorsoventral width of the proximal end,
6.5; minimum height of the shaft is 3.2; maximum
(oblique) width of the distal end, 7.1. Carpometacar-
pus (n = 5; type locality): total length, 36.2–38.2;
craniocaudal width of the proximal end, 9.0–9.2; dor-
soventral height of the trochlea carpalis, 3.6–4.1; dor-
soventral height of the os metacarpale majus in the
central part, 3.1–3.3.
C o m p a r i s o n. Noticeably smaller than
M. blanchardi; corresponds in size to large specimens
of Caerulonettion natator and extant Anas querquedula.
This comparison constitutes the diagnosis of the new
species.
R e m a r k s. Among the materials of anatids from
Saint-Gérand-le-Puy, there are remains of a small
duck that is morphologically very similar to
M. blanchardi but noticeably smaller. Previously
(Cheneval, 1983; Mlíkovský, 2022), all materials of
small ducks from the Early Miocene of Western
Europe were assigned to “Mionetta” natator, which, as
is shown below, represents a more advanced lineage of
Anatidae and is distinguished here as a separate genus.
Discrimination between large specimens of M. defossa
sp. nov. and small specimens of M. blanchardi may be
difficult or even impossible. However, it seems neces-
sary to indicate the very fact of the presence of another
small form in the fauna of the Early Miocene anatids
of Western Europe, which is more primitive than
“Mionetta” natator. The similarity with Mionetta (and
Dendrocygninae) in the structure of the coracoid
indicates that other elements of the skeleton of
M. defossa must have been similar in structure and dif-
ferent from those of the more advanced Caerulonet-
tion, which show similarities to Mioquerquedula. On
this basis, small humerus and ulna, as well as carpo-
metacarpus, are assigned to M. defossa, which are
characterized by morphological and proportional sim-
ilarity with those of M. blanchardi. The wing elements
of M. defossa are somewhat longer than those of
“M.” natator.
A fragment of the proximal end of the right
humerus (specimen PIN, no. 210/761) from the
Agyspe locality (Lower Miocene of the Aral Sea
region, Kazakhstan) corresponds in size to M. defossa
from Saint-Gérand-le-Puy and is provisionally
assigned to this species here. Despite partial preserva-
tion, it can be seen that the tuberculum dorsale was
very large (its proximal edge dorsally lags far behind
the caput humeri); the caput humeri is moderately
wide in caudal view; the dorsal tricipital fossa slightly
does not reach the caudal margin of the caput humeri;
the incisura capitis forms a poorly pronounced notch
in the proximal bone profile. In “M.” natator, the cau-
dal margin of the caput humeri is more convex, and
662
PALEONTOLOGICAL JOURNAL Vol. 57 No. 6 2023
ZELENKOV
Plate 10
1
23a 4a 5a 6a 7a
7b
6b
5b
4b
3b
11а
11b
11c
13b
13а
12b
dtc
pppi
itc
10
14
15
16
9
12а
8
pp
am
ib
ch
dtf
iic td
pa
cs
fah
17
816
PALEONTOLOGICAL JOURNAL Vol. 57 No. 6 2023
SMALL DUCKS (AVES: ANATIDAE) FROM THE EARLY–MIDDLE MIOCENE 663
the caput itself clearly overhangs the dorsal tricipital
fossa.
The carpometacarpus from Altynshokysu (Lower
Miocene of the Aral Sea region, Kazakhstan) is similar
in size and morphology to the materials from Saint-
Gérand-le-Puy assigned to this species. This speci-
men is characterized by a caudally protruding dorsal
semiblock of the trochlea carpalis (noticeable in prox-
imal view; Pl. X, dtc), as in M. defossa. In extant
anatids (including Oxyurinae), this semiblock is
greatly reduced. In dorsal view, this semiblock has the
shape of a caudally oriented subtriangular protrusion,
as in M. defossa from Saint-Gérand-le-Puy (specimen
MNHN, no. SG 10069). In materials attributed to
M. blanchardi, the degree of expression of this angle
varies (it may be rounded). In extant Malacorhynchus
and Nettapus, as well as in the fossil Mioquerquedula
and “Mionetta” natator, this angle is distinctly trun-
cated. The notch in the caudal margin of the dorsal
part of the trochlea carpalis (Plate 10, itc) is poorly
developed. There is no pronounced ventrally oriented
process on the base of the os metacarpale minor (pres-
ent in “M.” natator; Plate 10, p). The zone of the prox-
imal symphysis between the os metacarpale minus and
os metacarpale majus is short, as in Mionetta.
M a t e r i a l. In addition to the holotype, the follow-
ing remains from the Saint-Gérand-le-Puy localities:
specimen MB, no. Av 325-5, left coracoid; no. Av 326-1,
right humerus; no. Av 327-2, Av 327-3, left humerus;
nos. Av 328-1 and Av 328-3, right carpometacarpus;
no. Av 328-2, left carpometacarpus; specimen
MNHN, no. Av 6433, left ulna; no. SG 10069, right
carpometacarpus; no. SG 9096, left carpometacarpus.
Specimen PIN, no. 2614/604, proximal half of the
left carpometacarpus from the Altynshokysu locality,
Western Kazakhstan; Aral Formation, upper bone-
bearing horizon; Lower Miocene (MN 1; see Lopatin,
2004). Specimen PIN, no. 210/761, fragment of the
proximal epiphysis of the right humerus from the
Agyspe locality (Akespe), Kazakhstan; Lower Mio-
cene (MN 1; see Lopatin, 2004); collected by
A.A. Karkhu, 1993.
Genus Caerulonettion Zelenkov, gen. nov.
Etymology. From Latin caeruleus (azure,
“teal"-coloured) and Nettion, an obsolete generic
name for small extant teals.
Type sp ecies. Anas natator Milne-Edwards,
1867.
D i a g n o s i s. In the coracoid, the apex of proces-
sus acrocoracoideus is shifted distinctly medially, as a
result of which the impressio bicipitalis is located
noticeably medially to the medial edge of the shaft; the
cotyla scapularis is very large, its width somewhat
exceeds the smallest width of the bone shaft; the apex
of the processus procoracoideus protrudes slightly
cranially relative to the cranial margin of the process;
the coracoid itself is moderately shortened and notice-
ably widened in the sternal part.
In the humerus, the caput humeri is wide and has a
convex distal margin (in caudal view) and clearly over-
hangs the proximal part of the dorsal tricipital fossa;
the dorsal tricipital fossa is shallow, poorly concave;
the tuberculum dorsale with a distal angle lowered to
the level of the bone shaft, subtriangular; the caudal
shaft ridge is poorly pronounced and is oriented to the
ventral edge of the tuberculum dorsale; the tubercu-
lum ventrale is oriented largely caudally and overlaps
approximately half of the fossa pneumotricipitalis in
caudal view; the incisura capitis forms a poorly
expressed notch in the proximal bone profile; the shaft
is thickened, the general proportions of the bone are
somewhat shortened.
Explanation of Plate 10
Coracoids (figs. 1–7), humeri (figs. 8–10), carpometacarpus (figs. 11–13), and ulna (figs. 14–16) of Early Middle Miocene and
Recent Anatidae in dorsal (figs. 1a–7a, 11b), ventral (figs. 3b–7b, 11a, 12a, 13a, 14–16), caudal (figs. 8–10, 12b, 13b), and prox-
imal (fig. 11c) views.
Figs. 1, 16. Mionetta blanchardi (Milne-Edwards, 1863): (1) specimen MNHN, no. Av 6888; (16) specimen MNHN,
no. SG 6867 (reflected); France, Saint-Gérand-le-Puy locality; Lower Miocene.
Fig. 2. Mionetta sp., specimen PIN, no. 2976/1149; Kazakhstan, Zaisan basin, Golubye Peski locality; Lower Miocene.
Figs. 3, 8, 9, 11, 12, 15. Mionetta defossa sp. nov., Lower Miocene: (3) holotype MB, no. 325-1 (reflected); (8) specimen PIN,
no. 210/761; (9) specimen MB, no. 326-1 (reflected); (11) specimen PIN, no. 2614/604 (reflected); (12) specimen MNHN,
no. SG 10069; (15) specimen MNHN, no. Av 6433. Fig. 3, 9, 12, 15—France, Saint-Geran-le-Puy locality; 8—Kazakhstan, Aral
Sea region, Agyspe (Akespe) locality; 11—Western Kazakhstan, Altynshokysu locality.
Figs. 4, 5, 10, 13, 14. Caerulonettion natator (Milne-Edwards, 1867): (4) specimen. MNHN, no. SG 10071; (5) specimen.
MNHN, no. Av 6853; (10) specimen MNHN, no. 10066; (13) specimen MNHN, no. 10062; (14) lectotype MNHN, no. Av 6428;
France, Saint-Gérand-le-Puy locality; Lower Miocene.
Fig. 6. Malacorhynchus membranaceus (Latham, 1801), sp. osteological collection PIN RAS, no. 40-53-1, extant.
Fig. 7. Mioquerquedula soporata (Kurochkin, 1976), sp. MNHN, no. SA 10283; France, Sansan locality; middle Miocene.
Designations: ch, caput humeri; cs, cotyla scapularis; dtc, protruding dorsal semiblock of trochlea carpalis; dtf, dorsal tricipital
fossa; fah, facies articularis humeralis; ib, impressio bicipitalis; iic, notch of incisura capitis in the ventroproximal profile of the
humerus; p, ventrally oriented process on os metacarpale minus; pa, processus acrocoracoideus; pp, processus procoracoideus;
ppi, processus pisiformis; td, tuberculum dorsale.
Scale bar is 10 mm. Fig. 11c is out of scale.
664
PALEONTOLOGICAL JOURNAL Vol. 57 No. 6 2023
ZELENKOV
Species composition. Type species.
Comparison. It differs from Mionetta in a
somewhat shorter coracoid with medially protruding
processus acrocoracoideus (as a result of which the
impressio bicipitalis is located noticeably medially to
the adjacent edge of the bone shaft), the ventral plane
of which is flat (oriented parallel to the plane of the
sternal extremity), in a craniocaudally compressed
(less rounded) cotyla scapularis, as well as in the pres-
ence of a pronounced ventrocaudal angle of the facies
articularis humeralis. The facies articularis clavicularis
in Caerulonettion overhangs the sulcus m. supracora-
coidei. In all these characters, the coracoids of Caeru-
lonettion are more similar to those of Mioquerquedula.
The humerus differs from that of Mionetta in a wide
caput humeri with a convex caudal margin clearly
overhanging the dorsal tricipital fossa, a less protrud-
ing tuberculum dorsale with slightly elongated and
“lowered” (close to the surface of the shaft) distal
angle, as well as a less pronounced caudal shaft ridge
and a shallower dorsal tricipital fossa. In addition, the
tuberculum dorsale in Caerulonettion protrudes less
proximally (its proximal edge forms a smaller kink
with the adjoining caput humeri) than in Mionetta. In
the distal end, the fossa m. brachialis tends to form a
concavity with a more distinct dorsoproximal margin
in Mionetta, whereas in Caerulonettion this imprint
wanes dorsoproximally. The humerus of Mioquerque-
dula soporata from Sharga has a similar morphology
and proportions (Zelenkov, 2023a).
The carpometacarpus differs from that of Mionetta
in its relative shortening and more pronounced mus-
cular and tendon impressions on the ventral surface of
the proximal end, as well as in a pronounced ventrally
oriented process at the base of os metacarpale minus (as
in extant Malacorhynchus and Nettapus; Plate 10, p).
The coracoid differs from that of Mioquerquedula
in the very large cotyla scapularis, whose width
exceeds the minimum width of the shaft, as well as in
a more noticeable expansion of the sternal extremity
relative to the shaft. The humerus differs from that of
Mioquerquedula in a less pronounced incisura capitis
notch in the proximal bone profile, as well as a deeper
dorsal tricipital fossa.
The coracoid differs from Pinpanetta (exemplified
by the type species P. tedfordi Worthy, 2009) in its
noticeable gracile and elongated proportions, as well
as in a more elongated processus acrocoracoideus and
a narrower base of the processus procoracoideus. The
humerus differs from that of Pinpanetta in the absence
of distal narrowing and the presence of the incisura
capitis notch in the proximal bone profile, as well as in
a less protruding tuberculum dorsale with a distal
angle “lowered” to the level of the shaft.
Remarks. “Anas” natator from the Lower Mio-
cene of France is transferred here to a separate genus
primarily on the basis of the structure of the coracoid,
which in this species differs significantly from that of
Mionetta blanchardi (as well as M. defossa sp. nov.).
The general structure of the coracoid of Mionetta is
similar to that of Dendrocygninae, whereas the cora-
coid of Caerulonettion is similar to that of Malacorhyn-
chus and is characterized by a medially set aside pro-
cessus acrocoracoideus, a wide and craniocaudally
somewhat flattened cotyla scapularis, and an extended
extremitas sternalis. However, the possible close rela-
tionship between Caerulonettion and Malacorhynchus
is not supported by other known skeletal elements. For
example, the humerus of Caerulonettion differs from
that of Malacorhynchus in its shortness, massive shaft,
and unexpanded distal end. In Malacorhynchus, with a
generally similar size of the coracoid, the humerus (as
well as the ulna) is noticeably longer, has a thin shaft
and an extended distal end. The small humeri from
Saint-Gérand-le-Puy attributed to C. natator are sim-
ilar in proportions to Nettapus and the Miocene Mio-
querquedula. In this regard, the similarity of coracoids
of Caerulonettion and Malacorhynchus (shortened pro-
portions with the medially protruding processus acro-
coracoideus) can be considered as plesiomorphic for
Anatidae, more advanced than Dendrocygninae.
According to the structure of the coracoids, Caeru-
lonettion is also generally similar to the fossil Pinpa-
netta tedfordi from the Upper Oligocene of Australia,
one of the oldest members of Anatidae (Worthy,
2009). The humerus of Pinpanetta has a plesiomor-
phic morphology compared to Caerulonettion, which
corresponds to the basal position of Pinpanetta relative
to Mionetta on the phylogenetic tree of Anatidae
(Worthy et al., 2022). Caerulonettion, on the other
hand, is considered a more advanced taxon of Anati-
dae than Mionetta. However, the coracoid of P. t ed fo rd i
depicted by Worthy (200 9) (if it is correctly assigned to
this species) differs significantly from that of Dendro-
cygninae and Mionetta and, thus, does not fully corre-
spond to the evolutionary level of P. te df ord i, as follows
from the structure of humeri, which are a reliable phy-
logenetic marker in anatids (Zelenkov, 2012).
The general similarity in the structure of the cora-
coid and the humerus, as well as the temporal and geo-
graphical distribution, allow Caerulonettion natator to
be considered a possible ancestor of small Middle
Miocene anatids of the genus Mioquerquedula
(M. integra is considered as the basal species of this
genus). The transition from Caerulonettion to Mio-
querquedula is marked by a reduction of the large ple-
siomorphic cotyla scapularis, a consistent feature of
the basal taxa of anatids (from Dendrocygninae to
Malacorhynchus), and transformation of the proximal
humerus (an increase in the incisura capitis notch;
some reduction in the dorsal tricipital fossa). The
noted differences are obviously associated with the
rearrangement of the flying apparatus during the for-
mation of phylogenetically progressive Anatidae.
PALEONTOLOGICAL JOURNAL Vol. 57 No. 6 2023
SMALL DUCKS (AVES: ANATIDAE) FROM THE EARLY–MIDDLE MIOCENE 665
Caerulonettion natator (Milne-Edwards, 1867), comb. nov.
Plate 10, f igs. 4, 5, 10, 13, 14
Anas natator: Milne-Edwards, 1867, p. 148, Pate 25, figs. 19–22;
Lydekker, 1891, p. 120; Lambrecht, 1933, p. 357, Fig. 122 (part.);
Howard, 1964, p. 292.
Querquedula natator: Brodkorb, 1964, p. 223; Švec, 1981,
Plate I, fig. 1.
Dendrochen natator: Cheneval, 1983, p. 93, Plate 1, fig. 3.
Mionetta natator (part.): Livezey and Martin, 1988, p. 208;
Bocheński, 1997, p. 304; Mlíkovský, 2002, p. 111; Gohlich, 2002,
p. 172, Plate 1, fig. 5; 2017, p. 335.
L e c t o t y p e. MNHN Av-6428, left ulna;
France, Saint-Gérand-le-Puy locality; Lower Mio-
cene (selected: Storer, 1956).
D e s c r i p t i o n. See genus diagnosis.
Measurements in mm (materials from type
locality). Coracoid (n = 3): medial length, 30.7–32.8;
length of cranial end from apex to caudal margin of the
cotyla scapularis, 10.7–11.4; minimum width of the
shaft, 3.2–4.0. Humerus: total length, 56.6 (specimen
MNHN, no. SG 10064), 56.9 (specimen MNHN,
no. SG 10066); proximal end width, 13.7 (specimen
MNHN, no. SG 10066); minimum dorsoventral
width of the shaft, 4.3 (specimen MNHN, no. SG
10064) and 4.4 (specimen MNHN, no. SG 10066);
width of the distal end, 9.0 (specimen MNHN,
no. SG 10064) and 9.2 (specimen MNHN, no. SG
10066); craniocaudal height of the condylus dorsalis,
5.0 (specimen MNHN, no. SG 10064) and 5.3 (spec-
imen MNHN, no. SG 10066). Ulna: total length, 50.7
(lectotype), 52.2 (specimen MNHN, no. Av 6429),
and 52.1 (specimen MNHN, no. Av 6430); dorsoven-
tral width of the proximal end, 6.3 (lectotype), 6.4
(specimen MNHN, no. Av 6429), and 6.5 (specimen
MNHN, no. Av 6430); minimum height of the shaft,
3.4 (lectotype), 3.2 (specimen MNHN, no. Av 6429),
and 3.3 (specimen MNHN, no. Av 6430); maximum
(oblique) width of the distal end, 6.6 (lectotype and
specimen MNHN, no. Av 6429). Carpometacarpus
(n= 3): total length, 31.2–33.7; craniocaudal width of
the proximal end, 8.2–8.9; dorsoventral height of the
trochlea carpalis, 3.7–3.9; dorsoventral height of the
os metacarpale majus in the central part, 2.7–3.1.
V a r i a b i l i t y. Several coracoids from Saint-
Gérand-le-Puy, assigned here to C. natator, show vari-
ability in the structure of angulus medialis, which is
interpreted as individual (intraspecific). For example,
specimen MNHN, no. SG 10071, has a pointed angulus
medialis, whereas in specimen MNHN, no. Av 6953
the angulus medialis is blunt. Somewhat blunt angulus
medialis is found in Mioquerquedula and Anatini and,
therefore, can be regarded as an apomorphic condi-
tion. There is no information on the stratigraphic ref-
erence of the discussed specimens, but it cannot be
ruled out that this variability may reflect the morpho-
logical evolution of C. natator over time.
Comparison. Genus Caerulonettion includes
one species.
Remarks. The lectotype of “Anas” natator is the
ulna, which has a noticeably smaller size as compared
to that of Mionetta blanchardi. However, the fauna of
Saint-Gérand-le-Puy, in addition to “Anas” natator,
includes another small duck of a similar size, morpho-
logically similar to Mionetta blanchardi and described
here as M. defossa sp. nov. In th is regard, it is neces sary
to confirm the generic affiliation of the type specimen
of “Anas” natator. Indeed, the lectotype of “A.” natator
differs from the ulna of M. blanchardi not only in its
small size, but also in the noticeable shortening and
robustness of the shaft (Plate 10, figs. 14–16). This
makes it possible to distinguish specimen MNHN Av-
6428 from M. defossa and indicates that “Anas” natator
belongs to a separate anatid genus (other than Mio-
netta). The ulna of M. blanchardi and M. defossa is
more elongated, has a more stretched, straight, and
gracile shaft, in which it shows considerable similarity
to Oxyura and Dendrocygninae. The lectotype of
“Anas” natator is characterized by more apomorphic
proportions, similar to Anatini.
The femur (specimen MNHN, no. SG 8642), in
addition to its small size, has a straightened shaft
(without bends in lateral or medial views) and a nar-
row distal end, in which it differs from the femurs of
M. blanchardi. On this basis, this specimen is tenta-
tively assigned here to C. natator. The distal fragment
of the tibiotarsus (specimen MNHN, no. 6436; see
Cheneval, 1983, pl. 1, fig. 3; but not specimen
MNHN, no. 6622, see Mlíkovský, 2002) is character-
ized by a very small size and an oblique orientation of
the distal articular part; in larger Mionetta species, the
distal margin of the tibiotarsus is subperpendicular to
the long axis of the bone (Cheneval, 1983, pl. 1;
Livezey and Martin, 1988, text-fig. 7). Cheneval
(1983) erroneously noted that specimen MNHN,
no. 6436 is similar to the tibiotarsus depicted by
A. Milne-Edwards in the original description of Anas
natator, which does not really belong to Anatidae
(Storer, 1956; Howard, 1964). Specimen MNHN,
no. 6436 undoubtedly belongs to Anatidae and cannot
belong to the type series of A. natator. Tarsometatarsi
of small ducks from Saint-Gérand-le-Puy are not
known (Cheneval, 1983); the specimen assigned to
this species (Lambrecht, 1933) has a larger size (How-
ard, 1964).
“Anas” natator was originally known from the
Lower Miocene of France (Milne-Edwards, 1867–
1871). Later, materials from a number of localities of
the Upper Oligocene–Lower Middle Miocene of
Western and Central Europe were assigned to this spe-
cies (Lambrecht, 1933; Švec, 1981; Göhlich, 2002;
Mlíkovský, 2002; Mourer-Chauviré et al., 2004;
Zelenkov, 2012). The oldest record from the Upper
Oligocene of France (Mourer-Chauvire et al., 2004)
was assigned to Mionetta natator on the basis of its size
and is represented by a very poorly diagnostic proxi-
mal tibiotarsus. The taxonomy of this record requires
revision given the presence of at least two small ducks
666
PALEONTOLOGICAL JOURNAL Vol. 57 No. 6 2023
ZELENKOV
in the Early Miocene of France. The affiliation of a
poorly preserved carpometacarpus from the Lower
Miocene to Skyrice in the Czech Republic (see
Mlíkovský, 2000) remains unclear. A record from the
Lower Miocene of the Chisinau locality in Moldova
(Kessler, 1992) was not accepted due to its young age
(Mlíkovský, 2002; Zelenkov, 2012). The small duck
from Chisinau was assigned to Mionetta natator on the
basis of its dimensional similarity and was not
depicted; it probably represents the genus Mioquerq-
uedula, which was common at the turn of the Middle
and Late Miocene of Eurasia (Zelenkov, 2019, 2023a,
2023b). At the same time, coracoids of M. natator from
the Lower Middle Miocene of the Sandelshausen
locality (Göhlich, 2002) are very similar in morphol-
ogy to those from Saint-Gérand-le-Puy and Dolniche
(Lower Miocene of the Czech Republic; Švec, 1981),
which are assigned here to this species. However, the
humerus (specimen BSP, no. 1959 II 8272; Göhlich,
2002, Plate 1, fig. 4) differs markedly from those from
Saint-Gérand-le-Puy (both from C. natator and
M. defossa): it is characterized by a craniocaudally
narrow caput humeri with a smooth caudal edge, as in
Protomelanitta (Zelenkov, 2011; Stidham and Zelen-
kov, 2017), a deeper dorsal tricipital fossa, and a more
pronounced shaft triangular in cross section (in the
proximal part) due to the well-expressed caudal shaft
ridge. All these features, as well as the previously noted
small fossa pneumotricipitalis (Göhlich, 2002), char-
acterize diving ducks. On this basis, specimen BSP,
no. 1959 II 8272 is tentatively excluded here from
C. natator. Presumably, it may represent Protome-
lanitta velox or another small diving duck (it differs
from P. g r ac il is in the short crista bicipitalis). The
assignment of the distal part of the ulna and the tibio-
tarsus from Sandelshausen (Göhlich, 2002) to a par-
ticular taxon is not clear.
D i s t r i b u t i o n. Early Miocene of France and
the Czech Republic, early Middle Miocene of South-
ern Germany.
M a t e r i a l. In addition to the lectotype, all spec-
imens MNHN, nos. SG 10071, Av 6853, almost com-
plete right coracoids; SG 10064, right humerus;
SG 10066, complete left humerus; Av 6429, right
ulna; Av 6430, left ulna; SG 9099, SG 10061, left car-
pometacarpus; SG 10062, complete right carpometa-
carpus; SG 8642, left femur; Av 6436, distal half of the
right tibiotarsus; and specimen MB, no. Av 325-7,
right coracoid came from a series of localities of Saint-
Gérand-le-Puy, France, Lower Miocene. Specimens
BSP, nos. 1959 II 8269 and 1959 II 8982, cranial parts
of left coracoids are from the Sandelshausen locality,
Germany; lower Middle Miocene. Fragmentary cora-
coids from the Lower Miocene of the Dolniche local-
ity (Czech Republic; Švec, 1981, Plate 1, fig. 1) can
also be assigned to this species.
DISCUSSION
The revision of small ducks (similar in size to extant
Anas crecca or smaller), performed using new materi-
als from Mongolia and the Baikal region (Zelenkov,
2023a, 2023b, this work), indicates a noticeable taxo-
nomic diversity of Anatidae of this size class in the
Early and Middle Miocene of Eurasia (Table 1). The
main representative faunas of this interval (Saint-
Gérand-le-Puy and Sansan in France, Sharga in
Mongolia, and Tagay in Eastern Siberia) contain two
or three taxa of small ducks, most of which were pre-
viously combined into one species on the basis of small
sizes. The interpretations of previous authors were
Table 1. Stratigraphic distribution of small ducks of the Early and Middle Miocene of Eurasia
Locality
Taxa
Mionetta defossa
Caerulonettion
natator
Mioquerquedula
palaeotagaica
Mioquerquedula
soporata
Mioquerquedula
minutissima
Tagayanetta
palaeobaikalensis
Selenonetta
lacustrina
Protomelanitta
velox
Sharga (MN 7+8); Mongolia + +
Sansan (MN 6); France + ? +
Tagay (MN 5); Eastern Siberia,
Russia
+++
Sandelshausen (MN 5); Germany +
Dolniche (MN 4); Czechia +
Saint-Gérand-le-Puy (MN 2a);
France
++
Altynshokysu, Agyspe (MN 1);
Kazakhstan
+
PALEONTOLOGICAL JOURNAL Vol. 57 No. 6 2023
SMALL DUCKS (AVES: ANATIDAE) FROM THE EARLY–MIDDLE MIOCENE 667
probably partly based on the composition of the extant
Eurasian faunas of Anatidae, which usually contain
only one very small form (Anas crecca) from the evolu-
tionarily advanced group Anatini; very small members
of other phylogenetic lineages characteristic of the
faunas of the first half of the Miocene (e.g., tiny
Mergini or basal Anatinae) are absent. At the same
time, the presence of two or three species of small
ducks of various genera is characteristic of extant fau-
nas of other regions, in particular, tropical Africa and
Northern Australia, with which the Miocene faunas of
the temperate zone of Eurasia show significant eco-
logical and partly taxonomic similarity (Mayr, 2011,
2017; Zelenkov, 2016a). In general, the increased tax-
onomic diversity of birds that is currently characteris-
tic of tropical regions is a geologically relatively recent
phenomenon (Saupe et al., 2019). A series of extinc-
tions, including the Middle Miocene one, had a sig-
nificant impact on the modern composition of the avi-
fauna of the Northern Hemisphere. In the Early and
Middle Miocene, a number of groups of birds that
have tropical distribution today was still present in
Europe (Mayr, 2011, 2017).
The archaic evolutionary appearance of the Euro-
pean avifaunas in the Early and Middle Miocene was
initially established for forest birds, representatives of
families that are exotic for the modern European fauna
(parrots, mousebirds, trogons, suboscine passerines,
etc.; Cheneval, 2000; Manegold et al., 2004; Pavia,
2014). Recently, the first data on the Early and Middle
Miocene avifaunas of Central Asia and Siberia have
also appeared, which confirmed the commonality of
the evolutionary level of forest avifaunas of this
chronological interval for the entire proto-Palearctic
region of Eurasia (Zelenkov, 2016a, 2016b; Volkova
and Zelenkov, 2018; Zelenkov et al., 2018; Volkova,
2020a, 2020b, 2022). Semiaquatic birds of the Early
and Middle Miocene of Eurasia, on the contrary, were
for a long time assigned to extant or closely related
Palearctic genera (e.g., Anas for dabbling ducks and
Larus or Laricola for gulls) and, thus, were considered
as more advanced than the members of forest faunas
(an exception is the unconfirmed assignment of the
Early Miocene Anatidae to the extant tropical group
Dendrocygninae (Cheneval, 1983)). However, recent
studies on the Charadriiformes, Rallidae, and
Ciconiiformes (De Pietri et al., 2011; De Pietri, 2012;
De Pietri and Mayr, 2012, 2014a) have shown that the
Early Miocene European taxa of these groups actually
represent the basal stages of the divergence of the cor-
responding phylogenetic lineages, belong to fossil gen-
era and even families (e.g., Laricolidae), and have no
close relatives in extant faunas of the Palearctic (see
also De Pietri and Mayr, 2014b). The current revision
of small ducks also indicates the archaic appearence of
the Early and Middle Miocene Eurasian faunal
assemblages of Anatidae.
Small Anatidae appear in the fossil record of Eur-
asia in the Lower Miocene. Even the oldest faunas for
the studied interval from the series of Saint-Gérand-
le-Puy localities already include two forms—a small
member of the genus Mionetta, described as
M. defossa, and the evolutionarily more advanced
form Caerulonettion natator, partly similar to extant
Malacorhynchus. Remains of M. defossa are also
described from the Lower Miocene of Kazakhstan.
The taxonomic affinities of the Upper Oligocene
French record attributed to “Mionetta” natator on the
basis of its size (Mourer-Chauviré et al., 2004) is still
unclear.
The evolutionarily more advanced genus Mioquer-
quedula, morphologically somewhat similar to extant
Nettapus and characteristic of the end of the Early, the
Middle and, apparently, the beginning of the Late
Miocene of Eurasia, may originate from the Early
Miocene Caerulonettion or related taxa. The transi-
tional form between the two genera is Mioquerquedula
integra from the Lower Miocene of the United States
(19–18 Ma; Miller, 1944; Tedford et al., 2004), which
is similar in general structure of the coracoid to
C. natator but has a reduced cotyla scapularis
(advanced feature), which brings this species closer to
other members of Mioquerquedula. The oldest Eur-
asian Mioquerquedula are represented by somewhat
younger M. palaeotagaica from the Early Miocene (no
older than 16.5 Ma; Daxner-Höck et al., 2022; Kazan-
sky et al., 2022) of Eastern Siberia. In Europe, the
genus Caerulonettion persists until the beginning of the
Middle Miocene (Sandelshausen locality; ~15 Ma)
and is replaced by members of Mioquerquedula only in
the Sansan fauna (approximately 14 Ma), enriched, as
shown earlier, by Asian migrants (Mirzaie Ataabadi
et al., 2013). Thus, the formation of the genus Mio-
querquedula could have taken place in North America
in the Early Miocene, from where these small ducks
then (during the Miocene Climatic Optimum) dis-
persed through the North Pacific into Eurasia, where
they became widespread and existed until the begin-
ning of the Late Miocene. A lineage of these small
anatids from North America may have survived to the
Pliocene, where it is known as the poorly studied
genus Helonetta, which is also similar to Nettapus
(Emslie, 1992). The absence of the tropical genus Net-
tapus in America indicates its late origin (not earlier
than the end of the Middle Miocene), when subtropi-
cal conditions in Northern Asia, suitable for intercon-
tinental dispersal of these anatids, no longer existed.
The shortened coracoid and humerus of Mioquerq-
uedula compared to those of Anatini (Zelenkov,
2023b) indicate the limited flying (and, consequently,
dispersal) abilities of these Miocene ducks, in which
they are similar to extant Nettapus. The paleontology-
based shifting-home model, which explains the emer-
gence of migratory taxa of Palearctic birds (Louchart,
2008; but see Winger et al., 2019), suggests the per-
sistence of biotopic confinement in non-migratory
tropical ancestors in parallel with the emergence of
high-latitude migrations in their descendants as cli-
668
PALEONTOLOGICAL JOURNAL Vol. 57 No. 6 2023
ZELENKOV
mate changed (in particular, in the Late Miocene).
According to this model, extant Nettapus can be con-
sidered as fairly close relatives of Miocene Mioquerq-
uedula, which retained the original biotopic prefer-
ences of this evolutionary lineage of Anatidae.
In the more advanced group Anatini, the evolu-
tionary development of flying abilities was apparently
stimulated by the cooling and aridization of the cli-
mate in the Late Miocene (see Dufour et al., 2020),
which created the preconditions for the appearance of
large-scale migrations, which, during subsequent
cooling, led to the formation of expressed migrations.
According to molecular data, the divergence of Ana-
tini is estimated to be the end of the Middle Miocene
(Sun et al., 2017), which corresponds to the end of the
Miocene Climatic Optimum, as well as the epoch of
large-scale transformations of the natural environ-
ment and continental biomes in Eurasia. The oldest
known form close to the phylogenetic lineage of Ana-
tini (sensu Dickinson, Remsen, 2013) is Tagayanetta
palaeobaikalensis from the upper Lower Miocene of
Eastern Siberia, which is considered here as a possible
stem member of this tribe. This suggests the origin of
Anatini in the Northern Hemisphere. The genus
Matanas from the Early Miocene of New Zealand was
originally assigned to Anatini. However, it is morpho-
logically similar to extant Chenonetta (Worthy et al.,
2007) and, hence, apparently represents more primi-
tive Anatinae (may be close to Palearctic Chenoanas;
Zelenkov, 2012; Zelenkov et al., 2018). The initial
assignment of Matanas to Anatini is explained by the
broad taxonomic interpretation of this tribe by Worthy
et al. (2007).
The pronounced proportional and structural simi-
larity in the structure of the coracoid in the Early Mio-
cene European anatid Caerulonettion and extant Aus-
tralian Malacorhynchus is worth noting. However,
other materials on Caerulonettion do not yet confirm
the phylogenetic proximity of these two genera, and
the noted similarity in the structure of the coracoid is
interpreted as plesiomorphic. A generally similar cora-
coid is also found in the Oligocene Pinpanetta from
Australia (Worthy, 2009). However, the elongated
humerus of Malacorhynchus corresponds to the phylo-
genetic proximity of this genus to Anserinae (Burleigh
et al., 2015; Sun et al., 2017), which also have an elon-
gated forelimb. Thus, Malacorhynchus and the Mio-
cene Caerulonettion/Mioquerquedula apparently illus-
trate alternative evolutionary pathways implemented
in two groups of anatids (Anserinae and Anatinae) on
a common basis of the structure of the shoulder girdle
(and, in particular, the coracoid) but aimed at differ-
ent flight specializations, the characterization of
which requires special studies. Shortening of the wing
in the group Anatinae may be associated with an
increase in the hindlimb locomotor module (Shteg-
man, 1950), which corresponds to the repeated emer-
gence of diving forms in the evolution of this group
(Mergini and Aythyini; Buckner et al., 2018).
The divergence of the tribe Mergini, undoubtedly
the most primitive of the diving Anatinae, is estimated
at the beginning of the Middle Miocene (~15 Ma; Sun
et al., 2017). This dating is quite consistent with the
appearance and wide distribution of the group in the
fossil record of the Northern Hemisphere in the Mid-
dle Miocene (for review, see Zelenkov, 2012, 2019).
Protomelanitta velox from the Middle Miocene of San-
san is, apparently, the oldest undoubted member of
this group, still belonging to the stem radiation of
Mergini (Zelenkov, 2011, 2023a). Selenonetta lacus-
trina from the upper Lower Miocene of Baikalian
Siberia may be an even more basal member of this lin-
eage; however, the exact phylogenetic position of this
form is still unclear. The small size of these ancient
Mergini-like ducks is worth mentioning. In older
Early Miocene and preceding avifaunas, Mergini are
absent. Somateria sp. from the Lower Oligocene of
Kazakhstan (Kurochkin, 1968; Zelenkov and Kuroch-
kin, 2015) cannot unambiguously be assigned to this
genus and tribe Mergini (our data; contra Zelenkov
and Kurochkin, 2015). The systematic position of this
fairly large form remains unclear; it cannot be ruled
out that it belongs to Romainvilliidae, Paranyrocidae,
or Dendrocheninae from Anatidae.
ACKNOWLEDGMENTS
The author is grateful to N.V. Volkova (PIN RAS) for
photographs of the skeletons of extant and fossil birds, as
well as to R. Allain (Paris) and O. Rauhut (Munich) for
access to the collections, and G. Mayr (Frankfurt-am-
Main) for the skeleton of Malacorhynchus membranaceus.
FUNDING
The study was supported by the Russian Science Foun-
dation, project no. 18-74-10081, https://rscf.ru/project/18-
74-10081/.
CONFLICT OF INTEREST
The author declares that he has no conflicts of interest.
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Translated by M. Batrukova
