| Brachysuchus | |
|---|---|
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| Skull ofBrachysuchus megalodon in theUniversity of Michigan Museum of Natural History | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauromorpha |
| Clade: | Archosauriformes |
| Order: | †Phytosauria |
| Family: | †Parasuchidae |
| Genus: | †Brachysuchus Case, 1929 |
| Type species | |
| †Brachysuchus megalodon Case, 1929 | |
Brachysuchus (meaning "wide crocodile") is anextinctgenus ofphytosaur known from the lateTriassicperiod (Carnian stage) ofDockum Group inTexas, United States. It is known from theholotypeUMMP 10336[1] is composed of askull, lowerjaws and partialpostcranium and from the associated paratype UMMP 14366, nearly complete skull, recovered from the 'Pre-Tecovas Horizon' in theDockum Group.[2][3] It was first named by Case in1929 and thetype species isBrachysuchus megalodon. Its closest relative wasAngistorhinus.[3] However, its rostral crest was much smaller than that ofAngistorhinus, and therostrum as a whole is shorter and thicker.
Thelower jaws ofBrachysuchus are expanded at the tip to form a large bulge, holding the creature's largesttusks. The surface of this part of thebone has a wrinkled look, with manyblood vessels running through it. In the lower jaw, there are three tusks in each side of this protuberance. Behind this part the jaws have fused together for a little under half their length before diverging after thirty-one of forty-six post-protuberanceteeth. While some of the tusks at the tip are missing, most of the rest of the teeth in the jaw are still present. There are new tusks forming in thesockets, indicating thatBrachysuchusregrew teeth all its life. There is a largeforamen between thedentary, theangular and the prearticular that passes right through the jaw (visible on the picture).[4]
The teeth themselves areasymmetrical incross-section, with the outer side moreconvex than the inner side. This asymmetry increases from front to back. They are long and conical, and those from the ninth to twenty-ninth haveflutings on the sides. From the thirtieth to the forty-ninth, they have no flutings but arecrenulated and broaden antero-posteriorly. This suggests that these teeth were better for slicingprey than the previous tusks and conical teeth, which would have impaled and injured it. In parts of the jaws the fused section in the middle rises so high that the teeth could only grip prey and could probably have done little damage.[4]
The prearticular is fused with thearticular.[4]
The skull is around 125 cm long, with a distinctive hooked tip. It is much shorter and broader than that of many phytosaurs such asLeptosuchus orAngistorhinus. Theeye sockets are narrow and long, and thefenestrae are smaller and less rounded thanAngistorhinus. It has a comparatively small rostral crest. There are several rough surfaces at the posterior end denoting probablemuscle attachments, which show that it had very powerful jaw muscles and a strong bite.[4][5]
OverallBrachysuchus was approximately eight metres long, much bigger than most contemporary phytosaurs. It had extremely heavy jaws and a relatively short fused region, giving it a wider bite. There is also evidence of heavily developed jaw muscles. This, as well as the cutting teeth mentioned earlier, indicates thatBrachysuchus preyed on different animals to its thinner-jawed relatives. Instead of using its jaws to catchfish, it was able to attack and feed off the heavilyarmouredstegocephalians that roamed the surrounding area, and would probably have eaten other phytosaurs if food was scarce. The slightly deformed tip of one specimen's lower jaw suggests that it used a lot of force to break through its prey's armour.[4]
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