Tapiroidea Gray, 1825

Tsubamoto, Takehisa, Egi, Naoko, Takai, Masanaru, Sein, Chit & Maung, Maung, 2005, Middle Eocene ungulate mammals from Myanmar: A review with description of new specimens, Acta Palaeontologica Polonica 50 (1), pp. 117-138 : 123

Superfamily Tapiroidea Gray, 1825 Family Deperetellidae Radinsky, 1965

Type genus: Deperetella Matthew and Granger, 1925a (including Cristidentinus Zdansky, 1930 and Diplolophodon Zdansky, 1930 ).

Included genera: Teleolophus Matthew and Granger, 1925b (including Pachylophus Tong and Lei, 1984 ) and Bahinolophus gen. nov. Tsubamoto.

Revised diagnosis.—Tapiroids with full placental dentition and strongly bilophodont and relatively high−crowned molars. Upper molars with developed protoloph and metaloph joined by U−shaped and buccally convex ectoloph, weak postmetacrista, metaloph not interrupted by postmetacrista, no distinct molar metacone, no or very weak buccal ridge on paracone, and no distinct posthypocrista. Lower molars with developed protolophid and hypolophid and no or extremely reduced paralophid and cristid obliqua. Hypoconulid of m3 reduced to a cingular bulge. Molar protoloph/protolophid and metaloph/hypolophid are parallel to each other, respectively.

Discussion of taxon content and synonymy.—Seven genera ( Deperetella , Teleolophus , Cristidentinus , Diplolophodon , Haagella , Pachylophus , and Irdinolophus ) of the Deperetellidae have been reported to date ( McKenna and Bell 1997; Dashzeveg and Hooker 1997). However, only two genera ( Deperetella and Teleolophus ) among these seven are now recognized as belonging in the Deperetellidae .

Three of the remaining five genera ( Cristidentinus , Diplolophodon , and Pachylophus ) have been synonymized with other deperetellid genera by previous researchers. Cristidentinus and Diplolophodon , which were discovered from the middle Eocene Heti Formation of central China and described by Zdansky (1930), were synonymized with Deperetella by Radinsky (1965) and Tsubamoto, Holroyd, et al. (2000). Diplolophodon was also reported from the middle Eocene Dongjun and Lumeiyi Formations from southern China ( Ding et al. 1977; Russell and Zhai 1987). Pachylophus , which was discovered from the middle Eocene Hetaoyuan Formation of central China and described by Tong and Lei (1984), was synonymized with Teleolophus by Dashzeveg and Hooker (1997).

Haagella , which was discovered from the lower Oligocene of Germany and described by Heissig (1978) as belonging in the Deperetellidae , was excluded from the Deperetellidae by Dashzeveg and Hooker (1997). This genus is more likely to be related to Colodon , a helaletid tapiroid ( Dashzeveg and Hooker 1997).

In this paper, Irdinolophus is excluded from the Deperetellidae . Irdinolophus was established for Desmatotherium mongoliense Osborn, 1923 (= Helaletes mongoliensis ) and was assigned to the Deperetellidae by Dashzeveg and Hooker (1997). However, Irdinolophus lacks deperetellid characteristics such as a high crown and very weak molar postmetacrista. It is distinct from deperetellids in having a slight posthypocrista, much stronger molar postmetacrista, less lophodont lower premolars, and much lower dental crown. Also, the molar metaloph of Irdinolophus is interrupted by a strong postmetacrista, making the upper molar lophs incompletely U−shaped. These characteristics of Irdinolophus are more similar to those of the Helaletidae than to those of the Deperetellidae .