Trilophosaurus
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Trilophosaurus Temporal range: Late Triassic, Carnian–Norian |
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| Skeleton of Trilophosaurus buettneri | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | †Allokotosauria |
| Order: | †Trilophosauria |
| Family: | †Trilophosauridae |
| Genus: |
†Trilophosaurus Case, 1928 |
| Species | |
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| Synonyms | |
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Synonyms of T. buettneri:
Synonyms of T. jacobsi:
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Trilophosaurus (Greek for "lizard with three ridges") is a lizard-like trilophosaurid allokotosaur known from the Late Triassic of North America. It was a herbivore up to 2.5 m long. It had a short, unusually heavily built skull, equipped with massive, broad flattened cheek teeth with sharp shearing surfaces for cutting up tough plant material. Teeth are absent from the premaxilla and front of the lower jaw, which in life were probably equipped with a horny beak.
The skull is also unusual in that the lower temporal opening is missing, giving the appearance of a euryapsid skull. Because of this, the trilophosaurs were once classified with placodonts within Sauropterygia. Carroll (1988) suggested that the lower opening may have been lost to strengthen the skull.
Trilophosaurus is traditionally thought to include two valid species: the typical T. buettneri and the more robust T. jacobsi. In 1993, paleontologists Hans-Dieter Sues and Paul E. Olsen reassigned T. jacobsi, as well as two additional trilophosaurids (Tricuspisaurus and Variodens), to Procolophonidae based on similarities between its tricuspid teeth and those of the newly described procolophonid Xenodiphyodon. This view persisted in subsequent publications until the cranial material of T. jacobsi was described by Heckert et al. (2006). The new material confirmed the originally classification that T. jacobsi, as well as Tricuspisaurus and Variodens based on similarities to it, are indeed trilophosaurids. Meanwhile, a third species of Trilophosaurus, T. dornorum, was named by Mueller & Parker (2006) based on teeth of a robust individual. However, Spielmann et al. (2009) argued that the robustness of the new species is not sufficient to differentiate it from other Trilophosaurus species, especially in light of new robust specimens of T. jacobsi. Therefore, they considered T. dornorum to be a junior synonym of T. jacobsi, a view that was maintained since in other publications. Spielmann et al. (2006) redescribed the type material of Malerisaurus langstoni and concluded that it's indistinguishable from T. buettneri, and thus M. langstoni represents its synonym.
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