Gomphos

Abstract: Dental and postcranial specimens of Gomphos elkema, including lower and upper dentition and pedal elements, from the Huheboerhe locality, Erlian Basin, Nei-Mongol (Inner Mongolia), are described. Postcranial elements of Gomphos are similar to those of Mimolagus, suggesting affinity with lagomorphs. Gomphos elkema is a typical Bumbanian taxon, previously known only from Mongolia. Gomphos elkemaspecimens at Huheboerhe indicate occurrence of Bumbanian-equivalent beds and fauna in the region and suggest potential presence of the Paleocene‐Eocene boundary in the Huheboerhe section.

Abstract: Wulanhuxiu, a middle Eocene locality in the Erlian Basin, Nei Mongol (China) has been commonly regarded as belonging to the Ulan Shireh Formation, equated with the Irdin Manha Formation. We recognized two separate mammalian faunas of different age from the beds exposed at Wulanhuxiu. The lower fossiliferous horizon contains an anagalid, uncommon duplicidentate representatives (Gomphos progressus sp. nov., Mimolagus, Erenlagus, and Strenulagus), and diverse perissodactyls. This combination of taxa points to an Irdinmanhan age, but one element of the fauna (Schlosseria) may represent an Arshantan relic. Overall, the assemblage comprises “paleoplacental” mammals mixed with “neoplacentals”. The upper horizon is less species-rich and the only paleoplacentals present are scarce creodonts. However, this horizon is marked by abundant remains (including postcranial material) of the lagomorph Gobiolagus and by the presence of an advanced form of Gobiomys (Rodentia), and is most probably Sharamurunian in age. Thus, ...

Abstract: Mimotonids share their closest affinity with lagomorphs and were a rare and endemic faunal element of Paleogene mammal assemblages of central Asia. Here we describe a new species, Mimolagus aurorae from the Middle Eocene of Nei Mongol (China). This species belongs to one of the most enigmatic genera of fossil Glires, previously known only from the type and only specimen from the early Oligocene of Gansu (China). Our finding extends the earliest occurrence of the genus by at least 10 million years in the Paleogene of Asia, which closes the gap between Mimolagus and other mimotonids that are known thus far from middle Eocene or older deposits. The new species is one of the largest known pre-Oligocene Glires. As regards duplicidentates, Mimolagus is comparable with the largest Neogene continental leporids, namely hares of the genus Lepus. Our results suggest that ecomorphology of this species was convergent on that of small perissodactyls that dominated faunas of the Mongolian Plateau in the Eocene, and probably a result of competitive pressure from other Glires, including a co-occurring mimotonid, Gomphos.

Abstract: Mimotonids have recently been recognized as the likely ancestors to Lagomorpha (rabbits, hares, and pikas). Here a new species of mimotonid, Gomphos ellae, from Tsagaan Khutel locality, Valley of Lakes, Mongolia is described. This new material shows typical mimotonid features while also exhibiting important derived lagomorph features and helps to bridge the morphological and temporal gap between mimotonids and lagomorphs. The fossils comprise a right dentary, including cheek teeth and incisor, and a partial maxilla with two teeth. The dental features of G. ellae are similar to the mimotonid G. elkema, but G. ellae is distinguished from G. elkema and all other mimotonids by its long diastema. The diastema length of G. ellae is intermediate between all other mimotonids and all living and extinct lagomorphs. This feature distinguishes mimotonids from lagomorphs and the intermediate diastemal length of G. ellae further supports a strong pattern of lengthening of the diastema throughout Duplicidentata...