Crocodiles, alligators

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The Suchia

  • The Suchia have the shared derived character of a reduced and triangular lower temporal opening (2). Three groups comprise the Suchia: 1) the Rauisuchia; 2) the Aetosauria; and 3) the Crocodylomorpha. The Rauisuchia were the largest and fiercest of the carnivores of the Triassic. Some species became gigantic with some forms having skulls more than a meter long. Their shared derived character is a slit between the premaxilla and maxilla (5). For the most part they remained quadrupedal. Postosuchus from the Chinle Group and the Newark Supergroup of North Carolina is an example.

    Skeleton of Postosuchus, after Long and Muray (1996).

    Skull of Postosuchus; after Long and Muray (1996).

    The skull of Postosuchus clearly shows the triangular lower temporal fenestra that is the shared derived character of the Suchia, as well as the slit between the maxilla and premaxilla that is the shared derived character of the Rauisuchia. Abbreviations are - a, antorbital fenestra; lt, lower temporal opening; o, orbit.

    • The foot of Postosuchus clearly has a crurotarsal ankle that can be seen on the photograph to the right. Abbreviations are: c, calcaneum; f, fibula; t, tibia. In this particular individual, the calcaneum and astragalus have fused together because of arthritis. There are also several bony outgrowths on the phalanges that were probably quite painful in life.

      Foot of Postosuchus from North Carolina

    • The
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