The Crocodylia include all modern crocodiles, alligators, caimans and gharials, and their extinct relatives. They are an ancient lineage that originated around 70 million years ago. Recently, the field of crocodylian paleontology has experienced a rise in attention from researchers, however, much is still unknown about the early evolution of this group. Our research describes newly discovered fossil material comprised of a small crocodylian skull and associated partial lower jaw of early Paleocene age. It was discovered during a Belgian-Chinese expedition in Qianshan Basin, Anhui Province, China, as part of a bilateral cooperation project between the Royal Belgian Institute of Natural Sciences and the Institute of Botany of the Chinese Academy of Sciences. In the present study, the fossil material is formally described for the first time. Micro-CT scans are made to visualize internal anatomical structures, as well as characters hidden by the sediment. A comprehensive morphological study is executed, revealing that the specimen is a juvenile. It likely constitutes a new species and genus, as it differs from other crocodyloids by several autapomorphies. A phylogenetic analysis based on morphological characteristics reveal that this specimen is the most basal taxon among Crocodyloidea, a group that comprises all species more closely related to modern crocodiles than to modern alligators, caimans, or gharials. Although it is not the oldest crocodyloid ever reported, it is the earliest crocodyloid in Asia. Moreover, its basal phylogenetic position implies that it is part of an ancient ghost lineage of crocodyloids that had already been around in Asia for a longer time. The presence of crocodyloid remains in the Late Cretaceous of North America and the late Paleocene of Europe suggests that crocodyloids may have migrated there from Asia early on in their evolutionary history.
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RBINS Staff Publications 2021
Excavations during 2015 at a channel deposit in the early Eocene Cambay Shale Formation of the Tadkeshwar open cast lignite mine near Vastan in Gujarat Province, western India, have yielded terrestrial mammals, lizards, snakes, frogs, and birds as well as a few marine/brackish-water animals, predominantly teeth of the shark Physogaleus and Myliobatis rays. Among these is a jaw of an unusual teleost. This lower jaw of a gymnodont has fused dentaries, lacks a beak, and shows a remarkable series of teeth that are unique among all known fossil and living Tetraodontiformes. The teeth are molariform with raised “spokes” radiating inward from the emarginated peripheral edge of the crown. Tooth development is intraosseous, with new teeth developing in spongy bone before they erupt and attach to the dentary by pedicels. Although many of the 110 tooth loci in the fossil specimen have lost their teeth, in life the teeth would have grown to fit tightly together to form a broad and continuous crushing surface. The estimated age of the early Eocene Cambay Shale vertebrate fauna is ca. 54.5 Ma, making the jaw the second oldest confirmed gymnodont fossil. Comparisons to extant taxa of gymnodonts with fused dentaries (e.g., Diodon, Chilomycterus, and Mola) offer few clues about evolutionary relationships of the new fossil. Although the fused dentaries suggest affinities to diodontids and molids among living tetraodontiforms, it remains challenging to interpret phylogenetic relationships of the new Indian gymnodont because no living or fossil tetraodontoid has similar tooth morphology. We describe it as a new genus and species, and place it in its own new family of Gymnodontes. Grant Information: National Geographic Society, Leakey Foundation, Belgian Science Policy Office, Tontogany Creek Fund, National Science Foundation, Wadia Institute of Himalayan Geology.
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RBINS Staff Publications 2017
