Palaeosyops

Abstract: The northernmost records of early Eocene brontotheres, fossils of cf. Eotitanops and Brontotheriidae gen. et sp. indet., are described here from late Wasatchian-aged strata of upper parts of the Eureka Sound Group on central Ellesmere Island (∼79°N). Although the fossils were initially tentatively identified on faunal lists as Lambdotherium, their larger size and dental morphology ally them more closely to mid-latitude Eotitanops and Palaeosyops. The Ellesmere Island specimens are dentally most similar to mid-latitude Eotitanops, but can be distinguished from the latter by derived characters on their premolars that are shared with the younger (i.e., Bridgerian) Palaeosyops. The presence of brontotheres in early Eocene strata on Ellesmere Island implies that the group's evolution was well underway early in its history at northern high latitudes, and is consistent with either an Asian or North American origin and trans-Beringian dispersal. While cf. Eotitanops from Ellesmere Island appears dentally...

Abstract: Brontotheriids are common in Eocene faunas of North America and Asia but are poorly known from the Indian subcontinent. Here we describe three new late early Eocene brontotheriids from Pakistan, found in the upper part of the upper Ghazij Formation and representing the oldest Asian brontotheres. Eotitanops pakistanensis n. sp. is a small, primitive species, Balochititanops haqi n. gen. n. sp. is slightly larger and more derived, and fragmentary specimens identified as cf. Balochititanops sp. appear to represent a third, larger taxon. Improved knowledge of early brontotheres from North America permits better taxonomic resolution of some middle Eocene brontothere remains from Pakistan. ‘Eotitanops’ dayi from the Kuldana Formation is shown to be closer to Palaeosyops and is renamed Palaeosyops dayi n. comb. A new astragalus from the Baska Formation probably represents Pakotitanops latidentatus. A previously described humerus and a new calcaneum, both from the Subathu Formation, are tentatively refer...

Abstract: A systematic revision based on a morphological and statistical analysis recognizes the following Bridgerian and Uintan brontothere species as valid: Mesatirhinus megarhinus, Metarhinus fluviatilis, Metarhinus diploconus, Sphenocoelus uintensis, Sphenocoelus intermedius, Sphenocoelus hyognathus, Telmatherium validus, Protitanotherium emarginatum, Pseudodiplacodon progressum, Eotitanotherium osborni, Sthenodectes incisivum, and Metatelmatherium ultimum. The valid Bridgerian genus Palaeosyops is not discussed in the present paper. Mesatirhinus, Metarhinus, and Sphenocoelus are grouped within the subfamily Dolichorhininae; Telmatherium, Protitanotherium, Pseudodiplacodon, and Eotitanotherium are grouped within the subfamily Brontotheriinae; and Sthenodectes and Metatelmatherium are listed as Brontotheriidae incertae sedis. It is possible that Metatelmatherium may be a member of the subfamily Brontotheriinae or that it may be closely related to Sthenodectes, justifying the recognition of another North American brontothere subfamily, the Metatelmatheriinae.