Iberomeryx miaoi, Mennecart & Aiglstorfer & Li & Li & Wang, 2021

Mennecart, Bastien, Aiglstorfer, Manuela, Li, Yikun, Li, Chunxiao & Wang, ShiQi, 2021, Ruminants reveal Eocene Asiatic palaeobiogeographical provinces as the origin of diachronous mammalian Oligocene dispersals into Europe, Scientific Reports 1, pp. 1-12 : 7-8

Iberomeryx miaoi nov.sp.

Figure 1D and Figure S4.

v 1982 Lophiomeryx gracilis ?—Miao: 536, Fig. 820.

ZooBank LSID. urn:lsid:zoobank.org:act:EE3F88E9-0EAF-4EC6-A46F-8623241E614B.

Diagnosis. Iberomeryx with a very large paraconid, which is smaller in Iberomeryx minor and Iberomeryx parvus. Te metastylid is not strong but is more developed than in the other species. Te ectostylid is big on m1, smaller on m2 and absent on m3, while I. minor displays an ectostylid on all molars and I. parvus none at all. Iberomeryx miaoi nov. sp. is of similar size to I. minor and its m2 is smaller than the one of I. parvus. It differs from I. minor by a thin anterior cingulid. Moreover, its protoconid is positioned slightly more anterior than in I. parvus. Te molars appear to be more massive and bulkier in this species than in I. minor and I. parvus.

Holotype. IVPP V 6551 , lef mandible with m1–m3 (only specimen known). m1 5.1 × 3.5, m2 5.2 × 4.1, m3 8.0× 4.0.

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Etymology. We dedicate this species to Prof. Miao Desui who was the first to describe the Shinao fauna.

Locality and horizon. Shinao Basin , Panxian County, Southwestern Guizhou, China. Late Eocene .

Taxonomical attribution. Tis minute ruminant was referred to Lophiomeryx gracilis ? by Miao 20. However, he already noticed that the size of this individual was smaller than in the other specimens attributed to Lophiomeryx gracilis .Miao 20 excluded an attribution of IVPP V 6551 to " Lophiomeryx " gaudryi due to a closed posterior section of the posterior fossa on the m3. However, in both teeth, the posterior fossa is still open by the reduction of the postentocristid.

Te here-described specimen clearly differs from Lophiomeryx by the presence of an external postmetacristid forming a slight Dorcatherium fold, a developed external postprotocristid (clearly visible at least on m2), and a largeparaconid 36. Furthermore the external postprotocristid and prehypocristid are connected on their distal ends and the third basin of m3 forms a well-formed buckle, unlike the condition in Lophiomerycidae 14, 16, 33, 36, 37. Te combination of these characters is typical for Tragulidae 36.

Very few taxa are so far known in the early evolution of the Tragulidae . Only Archaeotragulus , Iberomeryx , and Nalameryx are recognized as potential Paleogene Tragulidae 17, 36, 46, of which Archaeotragulus is currently the oldest representative described 17, 47. Archaeotragulus possesses lower molars with a broadened talonid in comparison to the trigonid and displays an entoconidian groove 36. In the case of IVPP V 6551, the trigonid and talonid are of similar size and no specific entoconidian groove can be observed. Mennecart et al. 36 considered Nalameryx a Tragulidae notably based on the presence of the M structure (the external postmetacristid, the internal postmetacristid, the internal postprotocristid, and the external postprotocristid are interconnected forming a M in occlusal view), including the Tragulus fold and Dorcatherium fold, and the absence of a rounded mesolingual conid in the p 435. IVPP V 6551 differs from Nalameryx in having an m3 wider than m1 and similar m1 and m2 widths 17. In size proportions and molar morphology, IVPP V 6551 resembles the genus Iberomeryx . In IVPP V 6551, the relative size of the m2 is more similar to I. minor. In Iberomeryx minor, the anterior cingulid is big 36, 46, while in Iberomeryx parvus the cingulid is thin 48 like in IVPP V 6551. Te teeth of IVPP V 6551 appear to be more massive and bulkier than in I. minor and I. parvus 36, 48. Similarly to I. minor, the protoconid of IVPP V 6551 is a little more anterior than in I. parvus 36, 48. IVPP V 6551 clearly differs from I. parvus and I. minor by the presence of a very large paraconid, which is smaller in the two other species 36, 48. Moreover, the metastylid in IVPP V 6551 is slightly more developed than in I. minor and not present in I. parvus 43, 48. Iberomeryx minor displays an ectostylid on all molars 36, while this structure is absent from I. parvus 48. Te ectostylid in IVPP V 6551 is large on m1 to absent on m3. Based on these differences we decided to erect the new species Iberomeryx miaoi nov.sp.

Figures

Figure 1. Dentition of Krabimeryx gracilis nov. comb. (Miao, 1982)20 (A, B, G, H), Chiyoumeryx nov. gen. shinaoensis (Miao, 1982)20 (C, D), Chiyoumeryx nov. gen. flavimperatoris nov. sp. (E) and Iberomeryx miaoi nov. sp. (F–I). Krabimeryx gracilis nov. comb.(Miao, 1982)20: (A) IVPP V 6546-1 (holotype), partial skull with right and lef M1–M3; (B) IVPP V 6546-2 (holotype), right fragmented mandible with m2–m3. Chiyoumeryx nov.gen. shinaoensis (Miao, 1982)20: (C) IVPP V 6531 (holotype), right mandible with p2–m3 and tooth socket of p1; (D) IVPP V 6532 (paratype), right fragmented maxillary with P4-M3. Chiyoumeryx nov. gen. flavimperatoris nov. sp.: (E) IVPP V 6547 (holotype), right mandible with p4–m3; Iberomeryx miaoi nov. sp.: (F) IVPP V 6551 (holotype), lef mandible with m1–m3 (mirrored); (G) lower molar Lophiomerycidae dental nomenclature (based on the m3 of IVPP 6546-2): 1 internal postmetacristid, 2 metaconid, 3 external postmetacristid, 4 internal preentocristid, 5 entoconidian groove, 6 external preentocristid, 7 entoconid, 8 posthypoconulidcristid, 9 hypoconulid, 10 prehypoconuldicristid, 11 posthypocristid, 12 hypoconid, 13 prehypocristid, 14 ectostylid, 15 postprotocristid, 16 protoconid, 17 preprotocristid, 18 anterior cingulid; (H) upper molar Lophiomerycidae dental nomenclature (based on the M2 of IVPP 6546-1): 1 postmetacrista, 2 metacone, 3 premetacrista, 4 mesostyle, 5 postparacrista, 6 paracone, 7 paraconid labial groove, 8 preparacrista, 9 parastyle, 10 preprotocrista, 11 anterolingual cingulum, 12 protocone, 13 postprotocrista, 14 entostyle, 15 additional cone, 16 premetaconulecrista, 17 metaconule, 18 postmetaconulecrista; (I) lower molar Tragulidae dental nomenclature (based on the m2 of IVPP V 6551, reversed): 1 metaconid, 2 external postmetacristid, 3 Dorcatherium fold, 4 internal postmetacristid, 5 preentocristid, 6 entoconid, 7 postentocristid, 8 posterior cingulid, 9 posthypocristid, 10 hypoconid, 11 prehypocristid, 12 ectostylid, 13 external postprotocristid, 14 Tragulus fold, 15 internal postprotocristid, 16 protoconid, 17 preprotocristid, 18 paraconid, 19 preparacristid. (J) phylogenetic position and stratigraphie of the Shinao/ Yangjiachong/Xiaerhete ruminants (topology2). a stem Ruminantia, b Archaeomeryx, c Chiyoumeryx nov.gen. and Krabimeryx gracilis, d crown Ruminantia, e Iberomeryx miaoi nov. sp.; 1 lingual view, 2 occlusal view. Scale bare is 1 cm.