Tyrannosaurs
3.1. Diversity Patterns of Tyrannosaurs and Apex Predators The first argument for recognizing Nanotyrannus as a distinct taxon is that tyrannosaurids achieved high diversity in the latest Cretaceous (Table 3) and that well-sampled dinosaurian assemblages typically had several large predator species....
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| Format: | Other/Unknown Material |
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Zenodo
2024
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| Online Access: | https://doi.org/10.5281/zenodo.10534257 http://treatment.plazi.org/id/201187CAFFCBFFA0FE21FAAEFD67F8A7 |
| Summary: | 3.1. Diversity Patterns of Tyrannosaurs and Apex Predators The first argument for recognizing Nanotyrannus as a distinct taxon is that tyrannosaurids achieved high diversity in the latest Cretaceous (Table 3) and that well-sampled dinosaurian assemblages typically had several large predator species. This point is far from conclusive, but it is an important starting point in considering the evidence. All else being equal, we should expect multiple tyrannosaurs to exist in the latest Maastrichtian of North America, and arguments for the existence of a distinct taxon should, therefore, be considered carefully. Tyrannosaurs were diverse in the Late Cretaceous of Laurasia [4, 39, 52, 56 – 62]. Small tyrannosaurs of the Cenomanian [63] and Turonian [64, 65] were replaced by large-bodied tyrannosaurs by the Campanian [52, 57]. Multiple lineages evolved, including the gracile Albertosaurinae [66] and robust Tyrannosaurinae [56]. Tyrannosaurs also show endemicity; distinct taxa occur up and down the Western Interior from Mexico [62] and the American Southwest [52, 56, 58, 59] north into the Northern Great Plains [61, 67] and the High Arctic [68], implying high speciation rates. Strikingly, several well-sampled assemblages supported two distinct tyrannosaurid taxa. The Dinosaur Park Formation assemblage of southern Canada included at least two species, the gracile Gorgosaurus libratus [66] and the larger and more robust Daspletosaurus [67]; similarly, Gorgosaurus and Daspletosaurus coexist in the Judith River Formation [69]. The Nemegt Formation of Mongolia was home to the small and gracile Alioramus [70] and the larger, more robust Tarbosaurus [53]. Although many formations contain just one species, these formations are generally poorly sampled, producing either a handful of diagnostic remains, or often, a single diagnostic specimen, so their low diversity may be due to sampling. The Horseshoe Canyon Formation is perhaps the only well-sampled formation in western North America to have a single tyrannosaur [71]. While our ... |
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