An almost complete plastron, as well as several peripherals and a costal plate of a turtle from the middle Eocene of Saint-Gilles, is presented here. Although this turtle specimen was donated to the Institut royal des Sciences naturelles de Belgique (Brussels, Belgium) more than a century ago, it remained undescribed. Its study allows us to recognize the second pleurodiran in the Belgian fossil record, where, until now, the Eocene Neochelys was the only one known. The Belgian material of Neochelys is known in lower Eocene (early Ypresian) levels, but the new pleurodiran specimen comes from the middle Eocene (early Lutetian). It is the first partial articulate shell of a pleurodiran turtle recognized in Belgium, and the only member of this clade recognized in this country at specific level. The new specimen is a representative of the so-called Erymnochelys group, this lineage being known in Africa from the Upper Cretaceous to the present but in Europe only during the Eocene. It represents the first specimen of Eocenochelus eremberti identified outside its type locality, the French region of Saint-Germain-en-Laye (Yvelines, Île-de-France), where only one specimen was found. The plastron of the Belgian individual corresponds to the most complete for this species. Its analysis allows us not only to broaden the range of paleobiogeographical distribution of Eocenochelus eremberti but also to improve the knowledge about the anatomy and variability of this taxon.
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The bat genus Myotis is represented by 120+ living species and 40+ extinct species and is found on every continent except Antarctica. The time of divergence of Myotis has been contentious as has the time and place of origin of its encompassing group the Vespertilionidae, the most diverse (450+ species) and widely distributed extant bat family. Fossil Myotis species are common, especially in Europe, beginning in the Miocene but earlier records are poor. Recent study of new specimens from the Belgian early Oligocene locality of Boutersem reveals the presence of a relatively large vespertilionid. Morphological comparison and phylogenetic analysis confirms that the new, large form can be confidently assigned to the genus Myotis, making this record the earliest known for that taxon and extending the temporal range of this extant genus to over 33 million years. This suggests that previously published molecular divergence dates for crown myotines (Myotis) are too young by at least 7 million years. Additionally, examination of first fossil appearance data of 1,011 extant placental mammal genera indicates that only 13 first occurred in the middle to late Paleogene (48 to 33 million years ago) and of these, six represent bats, including Myotis. Paleogene members of both major suborders of Chiroptera (Yangochiroptera and Yinpterochiroptera) include extant genera indicating early establishment of successful and long-term adaptive strategies as bats underwent an explosive radiation near the beginning of the Early Eocene Climatic Optimum in the Old World. A second bat adaptive radiation in the New World began coincident with the Mid-Miocene Climatic Optimum.
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