Assessment of dental ontogeny in late Miocene hipparionines from the Lamagou fauna of Fugu, Shaanxi Province, China

Abstract

A collection of 28 hipparionine skull and mandible fossils with a dated age of approximately 7.4 Ma from Fugu, Shaanxi, northwestern China (belonging to Hipparion chiai and Hipparion cf. coelophyes) shows an age distribution in a successive development sequence. By observing the dentitions in these fossil materials, knowledge of dental ontogeny has been gained, such as the opening time of the posterior wall of post-fossettes, the displacement of the plis hypostyle, the morphologic changes of the protocone and hypocone, etc. Additionally, 4 isolated maxillary cheek teeth and 2 mandibular cheek teeth were cut into slices in the traditional manner for authentication. These discoveries indicate that both of the hipparionine species in the Lamagou fauna are Hipparion cf. chiai exactly and offer further insight into the morphologic changes that occur during dental wear in hipparionines, which may greatly promote the morphological and taxonomic study of hipparionine species.

First Radiological Study of a Complete Dental Ontogeny Sequence of an Extinct Equid: Implications for Equidae Life History and Taphonomy

“…In any event, the dental ontogeny sequences remain unknown for most extinct mammals. Only paleontological sites with exceptionally rich and well-preserved fossil assemblages provide an adequate number of specimens (including juvenile individuals) to describe ontogenetic series 16 , 19 – 29 . This is the case of Cerro de los Batallones fossil sites, which are known for containing diverse and extremely rich mammalian fossil assemblages 30 , 31 .…”

“…Recently, Li et al . 29 used X-ray techniques to analyse the dental ontogeny of the late Miocene hipparionine horses from the Lamagou fauna of Fugu (China). Nevertheless, their X-ray sample belonged to adult horses exclusively, so they described wear patterns on permanent dentition but not the complete sequence of mineralization, eruption and replacement.…”

“…P. perditus Verdigre Quarry (USA) Early Pliocene m1, m2, (p2–p4) b , m3 Hypsodont Equini or Protohippini (Equinae) Catastrophic 19 Hipparion chiai and Hipparion cf. H. coelophyes Lamagou Fauna of Fugu (China) Late Miocene m1, m2, p2, p3, (p4, m3) Hypsodont Hipparionini (Equinae) Not reported 29 Hipparion sp. Batallones-10 (Spain) Late Miocene m1, m2, (p2, p3), p4, m 3 Hypsodont Hipparionini (Equinae) Attritional This study Merychippus primus Sheep Creek (USA) Middle Miocene m1, m2, (p2, p3), p4, m3 Mesodont Primitive Equinae Catastrophic 22 Parahippus leonensis Thomas Farm (USA) Early Miocene m1, m2, (p2–p4) c , m3 Brachydont Anchitheriinae Attritional (but taphonomic underrepresentation of juvenile remains) 24 Archaeohippus blackbergi Thomas Farm (USA) Early Miocene m1, m2, (p2–p4) c , m3 Brachydont Anchitheriinae Intermale combat 26 Propalaeotherium hassiacum Geiseltal (Germany) Middle Eocene m1, m2, m3, (p2–p4) Brachydont Palaeotheriidae (Equoidea) Not reported 28 Fossil species are listed from younger to older.…”

Hippotherium Datum implies Miocene palaeoecological pattern

“…S6 b). In more recent report, Lantian specimens and Fugu ones respectively attributed by Liu 10 and Li et al 18 into H. chiai also have subtriangular POFs.…”

“…In China, H . weihoense is mainly distributed in the Linxia Basin, Gansu 17 ; the Qaidam Basin, Qinghai 32 (9.9–7.5 Ma, biochronologic comparison by Wang et al 33 ); and Lantian 10 , 13 (8.21–7.26 Ma, magnetostratigraphic data of Zhang et al 34 ) and Fugu 17 , 18 (7.4 Ma, magnetostratigraphic data of Xue et al 35 ), Shaanxi. The former two are located respectively on the east and north margins of the Tibetan Plateau.…”