Laelaps

Bringing phytosaurs back to life

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The reconstructions of Brachysuchus and Rhytiodon compared. From Case 1931.

In the winter of 1931, University of Michigan paleontologist E.C. Case commissioned artist Carleton W. Angell to bring two phytosaurs to life. Even though phytosaurs as a group were still poorly defined, Case recognized that there seemed to be at least two morphotypes represented by different skull reconstruction. According to Case’s summary, Rhytiodon (now called Rutiodon) represented a more lightly-built form that probably fed upon fish, while the more massive Brachysuchus (now often called Angistorhinus) appeared to have jaws better suited to taking down larger, armored prey. The reconstructions he commissioned from Angell (made 1/3 of the size of the actual fossils) were meant to reflect this difference, although he did suspect that other forms would represent intermediate stages between the gracile Rhytiodon and robus Brachysuchus.

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The skull and jaws of Brachysuchus. From Case 1930.

These reconstructions were made possible by the discovery of the lower jaw and skull of Brachysuchus during the previous two years. In 1930, Case described the lower jaw of Brachysuchus found not far from where the skull was recovered, and they fit well enough that there was little question that they were from the same species (if not the same individual).

For those of you not familiar with what a phytosaurs, they were a group of archosaurs that shared a common ancestor with crocodiles, but they developed a crocodile-like body form earlier than true crocodylians did (which did not appear until the Jurassic). The heyday of the phytosaurs was the Triassic, but ultimately they declined and disappeared by the end of the period. The easiest way to tell them apart from crocodylians if you see their remains in a museum, though, is to look where their nostrils are; rather than being on the tips of their snouts, their nostrils were further back, sometimes almost right over their eyes.

References;

Case, E.C. (1930) “On the Lower Jaw of Brachysuchus megalodon.” Contributions From the Museum of Paleontology, Vol. 3 (8), pp. 155-161

Case, E.C. (1931) “Life Model of the Heads of Two Types of Phytosaurs.” Contributions From the Museum of Paleontology, Vol. 3 (10), pp. 183-185

Comments

  1. #1 ScottE
    April 3, 2008

    Very interesting. By chance, do you have any plans for covering other archosaur groups like the Pholidosaurs &c.?