Early artiodactyls from the middle Eocene of the Erlian basin, Inner mongolia, China

1. Bin Bai
Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences,
IVPP, Chinese Academy of Sciences, Beijing, China
Cas Center for Excellence in Life and Paleoenvironment, Beijing, China
baibin@ivpp.ac.cn

2. New artiodactyls from localities:
2. Irdin Manha
8. Huheboerhe
21. Ula Usu
Fossil localities in the Erlian Basin, Inner Mongolia, China
Bai et al., 2018

3. Taxon 1 and 2
Taxon 3
Wang et al., 2019
China
Indian-subcontinent
Distributions of early artiodactyls from Asia
Theodor et al., 2007
Luccisano et al., 2020

4. Homacodontidae Marsh, 1894
Taxon 1: Gen. et sp. nov.
Horizon and locality: Irdin Manha F. Irdin Manha
Field no. 130623LQi01
Character: M1/2 with a quadrilateral outline, selenodont paracone, metacone, and metaconule,
, a rudimentary mesostyle, a relatively small paraconule, a conical hypocone joining the protocone by
a prehypocrista, and a strong lingual cingulum.
Occlusal Labial Lingual

5. Homacodontidae
Taxon 1: Gen. et sp. nov.
Horizon and locality:
Irdin Manha F. Irdin Manha
Field no. 110627CB02
Homacodontidae
Taxon 1: Gen. et sp. nov.
Horizon and locality:
Irdin Manha F. Irdin Manha
Field no. 110627CB02
Horizon and locality:
Irdin Manha F. Irdin Manha
Field no. 110609LSJ01

6. Homacodontidae
Taxon 1: Gen. et sp. nov.
Horizon and locality:
Irdin Manha F. Huheboerhe
Field no. 130625LiQ02
Character: m1/2 with a talonid wider than a trigonid, an mesiodistally compressed trigonid, a
relatively more mesially placed entoconid related to the hypoconid, an endohypocristid and
postentocristid forming a rudimentary hypolophid, and a hypoconulid joining an endohypocristid
slightly labial to the midpoint of the hypolophid.
Comments: the specimen (Field no. 130625LiQ02) from Huheboerhe is different from other three
specimens from Irdin Manha in having a relatively longer trigonid with a more distinct and
separated paraconid. However, they are very similar in other characters. The differences in
trigonid are attributed to the intraspecific variation.

7. Homacodontidae
Taxon 1: Gen. et sp. nov.
Horizon and locality:
Irdin Manha F. Irdin Manha
Field no. 110627CB02
Homacodontidae
Taxon 1: Gen. et sp. nov.
Horizon and locality:
Irdin Manha F. Irdin Manha
Field no. 110612DGB03
Homacodontidae
Taxon 1: Gen. et sp. nov.
Horizon and locality:
Irdin Manha F. Huheboerhe
Field no. 130624WYF01

8. Homacodontidae
Taxon 1: Gen. et sp. nov.
Horizon and locality:
Irdin Manha F. Huheboerhe
Field no. 060722WYQ01
Character of m3: an mesiodistally compressed trigonid, an entoconid slightly mesially placed
related to the hypoconid, and a large hypoconulid lobe with a prehypocristulid mesially extended
and joining the posthypocristid.
Comments: Two specimens from Huheboerhe are different from those from Irdin Manha in having
smaller hypoconulid lobes and more lophodont hypolophids. These differences are attributed to
the intraspecific variation.

9. Characters Taxon 1 Elaschitotherium Hylomeryx Bunomeryx Mytonomeryx
M1/2 mesostyle distinct absent weak distinct distinct
M1/2 hypocone strong strong strong M1 distinct
M2 absent
distinct
M1/2 paraconule small large, crescentic small large,
crescentic
large,
crescentic
m1/2 paraconid present present absent absent absent
m1/2 talonid compared to
trigonid
wider wider equal equal equal
entoconid compared to
hypoconid
mesial mesial lingual lingual lingual
postentocristid present absent absent absent absent
posthypocristid direction lingual lingual distolingual distolingual ?
Table 1: Comparison among Taxa 1 and other related genera

10. Dichobunidae Turner, 1849
Lantianiinae Métais, Guo, et Beard,
2004
Taxon 2: Gen. et sp. nov.
Horizon and locality:
Irdin Manha F. Huheboerhe
Field no. 060716MJ01
Character: Upper molar with conical, widely
separated paracone and metacone, a distinct
paraconule close to the protocone, twinned
metaconules with a labial one crescentic, and a
weak hypocone rising from the distolingual
cingulum;
Lower molar with a mesiodistally compressed
trigonid, twinned entoconid with a mesiolingual
one more mesially placed related to the
hypoconid, and a small, isolated hypoconulid lobe.

11. Taxon 2 Elaschitotherium Lantianius Eolantianius Aksyria
M1/2 hypocone weak distinct weak weak absent
M1/2 paraconule conical crescentic conical conical crescentic
M1/2 metaconule
twinned
present absent absent preliminary present
lower molar paraconid high high ? low ?
lower molar trigonid
mesiodistally compressed
present present ? absent ?
Table 1: Comparison among Taxa 2 and other related genera

12. Homacodontidae Marsh, 1894
Taxon 3: Gen. et sp. nov.
Horizon and locality:
Base of the Shara Murun F.
Ula Usu
Field no. 100628LQi01
Character: Lower molars with a taloind wider than a trigonid, a strong
mesiodistally compressed trigonid, an entoconid slightly mesially
placed related to the hypoconid, a complete hypolophid with a
shallow notch, m3 with a cuspid hypoconulid lobe and a
prehypocristulid extending to the base of the talonid below the
midpoint of the hypolophid; Lower molars lacking the paraconid and
the cristid obliqua.
Comments: Taxon 3 probably derived from Taxon 1 from the Irdin
Manha Formation. In addition, Taxon 3 is also similar to European
Tapirulus , which is known from the middle Eocene through the early
Oligocene, in having a bilophiodont teeth.

13. l Three new genera and species of small artiodactyls are reported from the Irdin
Manha and Shara Murun formations in the Erlian Basin, increasing the diversity of
artiodactyls from the region.
l Taxon 1 from the Irdin Manha Formation shows some similarities with North Amercian
homacodontids, such as Hylomeryx, Bunomeryx, and Mytonomeryx. Taxon 2 from
the Irdin Manha Formation represents a new Lantianiine group.
l Taxon 3 from the Shara Murun Formation probably derived from Taxon 1, and shows
similarities with European Tapirulus. These new material will shed new light on the
origin of enigmatic Tapirulus.
l Besides bunodont and selenodont teeth in artiodactyls, bilophodont teeth in
Tapirulus and new material from the Erlian Basin represent a different adaption in
artiodactyl evolution.
Conclusions

14. • IVPP : YUAN-QING WANG, QIAN LI, ZHAO-QUN ZHANG, JING LU, XUN JIN, FANG-YUAN
MAO, HAI-BING WANG, WEI ZHOU, SHI-JIE LI ET AL.
• AMNH : J. MENG, J. FLYNN, R. O’LEARY, M. O’LEARY.
• KU: C. BEARD; NIU: D. GEBO
• FUNDING: