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. 109; Zelenkov and Kurochkin, 2015, p. 157.
Type species. Anas blanchardi Milne-Edwards, 1863.
Diagnosis (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 pneumotricipitalis 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 deltopectoralis is distinctly concave; the crista bicipitalis is elongated, steeply approaching the shaft; the sulcus transversus is short; the distance between the tuberculum supracondylare ventrale and condylus dorsalis is not less than the width of the tuberculum supracondylare ventrale; protruding tuberculum supracondylare dorsale is absent; the tuberculum supracondylare ventrale 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.
Comparison. An exhaustive comparison is given by B. Livezey and L. Martin (Livezey and Martin, 1988).
Remarks. 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 morphological
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 distinguish 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 Middle Miocene of Germany (Göhlich, 2002) differs morphologically 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 Miocene of the Sansan locality (France) into the genus
Mionetta, noting the similarity of this species to extant Dendrocygninae (Mlíkovský, 2002). Following Cheneval (2000), I exclude “
A.” r
obusta 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 observations). “
Anas”
integra from the Lower Miocene of the United States was preliminarily included in the genus
Dendrochen (Cheneval, 1987); however, it is morphologically 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 paleontological record (Mayr, 2017) is of considerable interest for understanding the evolution of the family. Cheneval (1983) assigned the species of this genus to the subfamily Dendrocygninae, the basal group of extant Anatidae (Sun et al., 2017). Livezey and Martin (1988) included
Mionetta in the separate subfamily Dendrocheninae, which they placed between Dendrocygninae 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 Dendrocygninae and Oxyurinae (“Erismaturinae” sensu Worthy et al., 2022), which better matches the morphology of
M. blanchardi (see Zelenkov and Kurochkin,
2015) and confirms the validity of Dendrocheninae.
The above revised diagnosis is based on the diagnosis 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
Dendrochen 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 allow confirmation of many of these differences (personal data), which calls into question the validity of the genus
Mionetta.
Here, a cranial fragment of the left coracoid (specimen 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 specimens of
M. blanchardi and is characterized by a very large rounded cotyla scapularis and medium-sized and pointed facies articularis humeralis. Extant
Dendrocygna are similar in morphology of the facies articularis humeralis but have a smaller cotyla scapularis. 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.
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 mediumsized 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.
Holotype. MB, no. Av 325-1, right coracoid; France, group of Saint-Gérand-le-Puy localities; Lower Miocene.
Description. 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 medially; the cotyla scapularis is very large, rounded, occupies most of the shaft in dorsal view; the facies articularis humeralis with a pointed cranial angle; the facies articularis clavicularis without a notch in the caudal margin, does not clearly overhang the sulcus m. supracoracoidei; the sulcus m. supracoracoidei is moderately concave.
Measurements in mm. Coracoid: medial length, 33.0 (holotype) and 34.2 (specimen MB, no. Av 325-5); length of cranial end from apex to caudal margin of cotyla scapularis, 12.0 (holotype, specimen 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) nd 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. Carpometacarpus (n = 5; type locality): total length, 36.2–38.2; craniocaudal width of the proximal end, 9.0–9.2; dorsoventral height of the trochlea carpalis, 3.6–4.1; dorsoventral height of the os metacarpale majus in the central part, 3.1–3.3.
Comparison. 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.
Remarks. 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 necessary 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 different from those of the more advanced
Caerulonettion, which show similarities to
Mioquerquedula. On
this basis, small humerus and ulna, as well as carpometacarpus, are assigned to
M. defossa, which are characterized by morphological and proportional similarity 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 preservation, 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 caudal margin of the caput humeri is more convex, and 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 specimen is characterized by a caudally protruding dorsal semiblock of the trochlea carpalis (noticeable in proximal 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 truncated. 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 (present in “
M.”
natator; Plate 10, p). The zone of the proximal symphysis between the os metacarpale minus and
os metacarpale majus is short, as in
Mionetta.
Material. In addition to the holotype, the following 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 bonebearing 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 Miocene (MN 1; see Lopatin, 2004); collected by A.A. Karkhu, 1993.
Fred
Explanation of Plate 1
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 proximal
(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.
