Abstract
The skull of an unusual new mammal-like reptile of the family Tritylodontidae, recently discovered in the Jurassic of northeastern Mexico, is described here as Bocatherium mexicanum. Tritylodontids are the last survivors of the great radiation of mammal-like reptiles that also gave rise to mammals at or near the Triassic-Jurassic boundary (∼200 Myr ago). These superficially rodent-like herbivores coexisted with early carnivorous mammals for some 50 Myr before becoming extinct in the late Jurassic. Although eight genera are recognized, their interrelationships have remained unclear because it has been impossible to determine the direction of morphological change within this morphologically stereotyped group. Unusual specializations of the Mexican skull now permit character polarities within the family to be determined and a cladogram to be constructed. Bocatherium shows a close relationship to Bienotheroides1 of China and Stereognathus2,3 of Great Britain. It is the first mammal-like reptile and probably the oldest terrestrial vertebrate from Mexico.
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Clark, J., Hopson, J. Distinctive mammal-like reptile from Mexico and its bearing on the phylogeny of the Tritylodontidae. Nature 315, 398–400 (1985). https://doi.org/10.1038/315398a0
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DOI: https://doi.org/10.1038/315398a0
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