Nomenclature: Share names for dinosaur divisions

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Matthew Baron and colleagues propose a radical revision of dinosaur relationships (Nature 543, 501506; 2017). I suggest that borrowing from the field's rich history could help to prevent unnecessary confusion.

Historically, Saurischia is one of the two basic divisions of dinosaurs, the other being the Ornithischia (H. G. Seeley Proc. R. Soc. Lond. 43, 165171; 1887). Saurischia comprises the mostly carnivorous Theropoda, which includes Tyrannosaurus rex (and birds as a subgroup), and the primarily herbivorous Sauropodomorpha, such as Diplodocus longus. The point of potential confusion in Baron and colleagues' proposal is that the authors retain the name Saurischia while removing the Theropoda.

A different scheme might be less confusing. For instance, Sauropodomorpha could be retained as the clade that comprises all species closer to Diplodocus than to theropod dinosaurs. In Baron and colleagues' analysis, this would differ only slightly from its use over the past several decades by including the limited group of late Triassic carnivorous Herrerasauridae.

Alternatively, the term Pachypodosauria, devised by Friedrich von Huene in 1914, could be revived. Initially used to unite larger theropods with the sauropodomorphs, the term could now be applied to a clade of dinosaurs that have four or more weight-bearing toes, as distinct from their lighter-footed ornithoscelidan sister taxon with three weight-bearing toes. Such a scheme would accommodate the two competing hypotheses: a conventional Saurischia–Ornithischia split versus the new Pachypodosauria–Ornithoscelida division.

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  1. University of Maryland, College Park, USA.

    • Thomas R. Holtz

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