Crocodiles, alligators

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  • The Phytosauria have the shared derived character of an elongated snout with nostrils that have moved posteriorly (like in a whale) (7). They were very common semiaquatic forms extremely convergent on modern crocodiles in their overall habitus. They can at once be distinguished from crocodiles by the nostrils, which are located towards the rear of the snout, often just in front of the eyes. Rutiodon is a common example from the Newark and the Chinle. They became extinct at the end of the Triassic.

    Discovery of a phytosaur skull in the Chinle Group, Petrified Forest National Park. Kevin Padian, leader of the expedition is on right. The phytosaur skull is the black rubble they are staring at.

    Manus and pes impression of a phytosaur (the track is called Apatopus), from the Newark Supergroup, Newark basin, Oaks, PA.

  • The Ornithosuchia were fairly robust carnivores with a large head. They have the shared derived condition of a large diastema (gap in the tooth row) between the premaxilla and the maxilla (6, above; d in figure below). They are known from only a few skeletons, mostly from England, such as Ornithosuchus. They had a tendency to develop small forelegs and probably some degree of bipedalism.

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