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 rich earliest Eocene mammal assemblage of Dormaal in northeast Belgium has yielded most of the earliest modern mammals of Europe and is the the reference-level for MP7 in the Mammalian Biochronological Scale of the European Paleogene. Despite the fact that several other localities in Europe, such as Silveirinha in Portugal, Le Quesnoy, Pourcy, Sotteville-sur-Mer, Rians, Palette, and Fordones in France, and the Suffolk Pebble Beds in England, contain faunas that have been correlated to Dormaal, none of them preserve the same fauna as Dormaal with the exception of Erquelinnes in southwest Belgium. Here we describe the new vertebrate site of Clairoix, located only 13 km from Le Quesnoy in the Paris Basin, France, but 225 km southwest of Dormaal. About 150 kilograms of sandy matrix has produced a collection of about 400 vertebrate specimens including 118 isolated mammal teeth. The fauna is composed of the following typical MP7 species: the herpetotheriid marsupial Peratherium constans, the amphilemurid erinaceomorph Macrocranion vandebroeki, the hyaenodonts Arfia gingerichi and Prototomus minimus, the carnivoraforms Dormaalocyon latouri and Gracilocyon solei, and the omomyid primate Teilhardina belgica. Besides these index taxa, the arctocyonid Landenodon woutersi, the louisinid “condylarths” Paschatherium dolloi and Paschatherium yvetteae, a perissodactyl, and several rodents also are present at Clairoix. As in Dormaal, the relative abundance analysis of the species from Clairoix indicates that P. dolloi and P. yvetteae are the most abundant species, followed by M. vandebroeki and T. belgica, respectively. In term of number of specimens, Paschatherium represents more than 50% of the fauna, which corresponds to the acme of Paschatherium defined across the Paleocene–Eocene boundary in continental Europe. The composition and relative abundance of the mammal fauna of Clairoix are very similar to those of Dormaal and Erquelinnes and suggest a similar or very close age. The results of this work also suggest that the mammal assemblage of these three localities does not only correspond to a different paleoenvironment than that of other MP7 correlated faunas but also to an older age closer to the Paleocene–Eocene Thermal Maximum. Fish, frog, lizard, crocodilomorph, and snake remains were also collected and support a fluvial paleoenvironment at Clairoix. Grant Information This research was supported by the BRGM ‘Régolithe’ Scientific Program and the Belgian Science Policy Office (project BR/121/A3/PalEurAfrica).
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RBINS Staff Publications 2016
