We here report on iguanians (both new and the previous record) from the earliest Eocene (MP 7) of the Dormaal locality in Belgium, from the time of the warmest global climates of the past 66 million years. Today iguanians are distributed mainly in the New World (Pleurodonta) and Old World (Acrodonta), having complicated biogeographic histories. Both lineages co-existed in Dormaal 56 Ma. Iguanians here document the presence of thermophilic faunas during greenhouse conditions in the northern mid-latitudes (above 50° north, the latitude of southern England). The complete maxilla of the agamid Tinosaurus europeocaenus is described and figured for the first time, being distinctive and furnishing a number of diagnostic characters. The dentary coronoid process of this species is also observed for the first time. Our morphological analysis supports the previous observation that Tinosaurus is similar to Leiolepis, but also differs from it by several distinguishing features. Some jaw character states present in T. europeocaenus are shared with the Indian T. indicus, Chinese T. doumuensis, and American Tinosaurus sp., but several differences among them are observed. Besides the wellknown Geiseltaliellus, we here erect and describe a new pleurodontan taxon. The new taxon is represented by a maxilla with a unique and peculiar tooth crown morphology: the central cusp is bifurcated, markedly split into two distinct and wellseparated “prongs.” This morphology likely indicates a high specialization on feeding sources. This might cause a higher extinction risk relative to generalists, because terrestrial ecosystems in Europe changed substantially during the Paleogene.
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RBINS Staff Publications 2023
The mammal fauna of Hainin is particularly interesting as the oldest in the Cenozoic of Europe, and the earliest reference level (MP1–5) of the mammalian biochronological scale for the European Palaeogene. This paper summarizes the mammal taxa discovered in the fauna, presents an analysis of the fauna as a whole (relative abundance and species richness), and describes four new eutherians: Belgoryctes thaleri gen. et sp. nov., Eurolestes dupuisi gen. et sp. nov., Quadratodon sigei gen. et sp. nov. and Cingulodon magioncaldai gen. et sp. nov. The assemblage is relatively small (about 400 dental specimens), characterized by a high diversity and abundance of small insectivorous species and very low abundance of ‘plesiadapiforms’ and ‘condylarths’. By comparison with younger European Paleocene faunas, ‘condylarths’ and ‘plesiadapiforms’ became more and more abundant and diverse through the Paleocene but collapsed at the Paleocene–Eocene Boundary. ‘Proteutherians’ declined steadily, while multituberculates remained diverse, although the early Paleocene was populated mainly by Kogaionidae whereas the late Paleocene was dominated by Neoplagiaulacidae. The palaeoecology of Hainin is deduced from the mammal assemblage: the local environment was likely a forested area. Stratigraphically, the Hainin deposits are most likely of late Danian age, and biochronologically its fauna represents a partial equivalent of the North American Torrejonian Land Mammal Age. When compared to younger Paleocene faunas of Europe, the composition of the Hainin fauna reveals that a relatively important intercontinental dispersal of mammals occurred around the Danian–Selandian boundary, roughly corresponding to the Torrejonian–Tiffanian boundary. This dispersal is marked by the arrival in Europe of typically North American taxa such as arctocyonids, plesiadapids and neoplagiaulacid multituberculates. Additional exchanges of lesser magnitude probably also occurred around the Selandian–Thanetian boundary (i.e. during the Tiffanian), although the evidence is less compelling and mainly concerns the plesiadapids Chiromyoides and Plesiadapis.
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RBINS Staff Publications 2016
