STL Science Center

STL Science Center

12 March 2016

Not a Dragon

(C) Dmitry Bogdanov
The general appearance of Prestosuchus can be argued based on the type of scientific illustration that one deems appropriate. In the past, and we have discussed this here, the typical images that were produced were images in which the skin appeared to conform and mold almost directly to the skeleton of the fossil animal. This approach is not always realistic (some aspects of some animals can appear as though skin is stretched tautly over the skeleton) and leads to the appearance of animals that look as though they have been starved and lost much of their muscle mass. When this type of technique is applied to Prestosuchus the stunning similarity, through the interpretation of the artist, to a tyrannosaurid skull is very evident. Our knowledge of the skulls and heads of tyrannosaurids allows us to safely assert that their skulls are not covered by tautly stretched skin-on-skeleton as they have massive muscles under the surface of the skin. The similarity between the two skulls is not perfect and here appears somewhat exaggerated, but the resemblance does exist. The neck, abdomen, and tail of this Prestosuchus do not appear to be wanting in terms of nutrition as the head does, which leads us to think that the artist pulled the skin tightly on the head to accentuate the tyrannosaurid features of the skull.

(C) Nobu Tamura
An alternative approach to taut skin or well muscled head is to have a little of both. This approach presents us with a lesser look of emaciation. The overall look of the body in this depiction is much more crocodilian than the previous illustration, which appears much more lizard-like. Despite basal muscular evidence that places Prestosuchus in an early position, the likelihood of crocodilian scuting along the back is not necessarily difficult to accept. The somewhat crocodilian interpretation of the skin on the skull may also not be difficult to accept. The caveat in interpreting a distant ancestor as possessing many phenotypically similar character attributes as extant animals is that there are a large number of changes that will still take place between Prestosuchus and modern crocodiles and alligators. Many of these are obviously not present in either image, including the flattened tail for swimming and high placed nostrils for breathing while submerged. Most telling, of course, is the posture of Prestosuchus in comparison to modern crocodiles. The hips of Prestosuchus are constructed such that the legs are erect under the body forming a "pillar-erect" stance. Crocodiles on the other hand have a sprawling posture. The hips of Prestosuchus are rotated to accommodate this orientation in a way that is different from the hip joints of crocodiles.

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