Phytosaur portraits
5:36 pm
As I’ve hinted at in previous posts, I’m thinking a lot about phytosaurs lately. These Late Triassic predators are (literally) looming large in a project I’m involved with for the day job, and I’ve had the sketchbook out in an attempt to wrap my head around the overall proportions and life appearances of these ancient archosaurs.
The first thing you tend to notice about phytosaurs is how much they look like modern crocodiles. Technically, crocs are the closest living relatives of phytosaurs, but there are so many animals between the two groups that are distinctly un-crocodile-like in overall form that their similarities are likely due to convergence more than kinship.
Still, the overall resemblance between the two groups is striking, and oftentimes crocodilians become the go-to substitutes for reconstructing phytosaurs. Some restorations are more clearly crocodile-based than others, but nearly all (mine included) show some degree of crocodilian influence. I suppose this could be considered artistic laziness (or, more charitably, artistic tradition), but I think that a distant but demonstrable relationship coupled with convergent forms and habits make a certain degree of crocodile-emulation justifiable. However, if any phytosaur-workers out there have other ideas about how these animals should look, I’d be thrilled to incorporate any comments into future restorations.
The main way that you can tell if an artist has drawn a phytosaur or crocodile is by looking for the nostrils. The nostrils of crocodiles are situated at the tip of the snout, while in phytosaurs, the nostrils are farther back, in some cases just in front of their eyes. The phytosaur at the top left of this post is Parasuchus (“near crocodile”), one of the earliest and most primitive (or, to be phylogenetically correct, least derived) forms. The nostrils of Parasuchus, while further back than any crocodile, lie further forward than they do in more advanced phytosaurs, like Angistorhinus, pictured below.
Angistorhinus (“narrow snout”) was a contemporary of Parasuchus, but was more advanced in at least two obvious respects. First, the nostrils of Angistorhinus are situated much further back on the snout, raised in a little hump just in front of its eyes. Secondly, the teeth of Angistorhinus are differentiated depending on their location in the mouth. At the front of the jaws, the teeth are large and stout, built for grabbing and crushing prey. Teeth along the main length of the jaw are small, slender cones, excellent for catching small, slippery prey and working it toward the back of the throat. At the back of the jaw (and difficult to see in this closed-mouthed view), the teeth are flattened triangular wedges, well-suited to shearing off chunks of flesh from animals too large to swallow whole. This heterodont (“different-toothed”) condition presumably helped Angistorhinus tackle a wider variety of prey than than the simpler-toothed Parasuchus.
This second sketch is the first study for a series of portraits, restoring the faces of phytosaurs known from New Mexico and the U.S. Southwest. Focusing on the heads of these animals is probably the most accurate way they can be portrayed, as North American phytosaurs are known from an abundance of well-preserved skulls but, sadly, very few examples of reconstruction-ready, articulated postcrania. These sketches will end up becoming full color paintings for an interpretive display at the day job. Throughout the process, however, I hope to share more of my preliminary drawings and sketches with readers here.
Love your Angistorhinus head drawing – excellent!
Beautiful sketches! A few phytosaur queries:
1) I assume the recessed nostrils were for the same kind of smell & see above water, like modern crocs–only better. However, if the goal was the same, why don’t we see modern crocodilians with the extremely recessed nostrils that phytosaurs had? Or, to put it another way, why didn’t phytosaurs “stop” their nostrils where they lie in crocs? Crocs seem to be successful enough without moving their noses up to their eyeballs. Have any alternative theories for phytosaurian recessed nostrils been put forth?
2) Do phytosaurs have the bony armor that is so characteristic of modern crocs?
3) How big (and small) did phytosaurs get? Are their any deinosuchus-sized phytosaurs?
Thanks, Darren & Zach — should be more drawings to come!
As far as your questions, Zach:
1) Common thought seems to be that the nostrils are high up and back on the snout to allow phytosaurs to breathe while almost totally submerged, but I haven’t come across an explanation for why they hit on such a different solution from modern crocs. From what I’ve read, crocs have a bony palate that phytosaurs lacked, so perhaps it is part of an alternate solution to the problem of breathing through the nose while the mouth is submerged. But I’m totally spitballing here, maybe someone more knowledgeable about archosaur anatomy will have an answer.
2) Phytosaurs definitely have bony armor. Exactly how it was arranged isn’t entirely known, but it would sure be great if someone discovered a “phytosaur mummy” that preserved all or even most of its scutes intact. I’ve come across descriptions or figures of specimens showing a) one or two rows of lightly-keeled scutes down the midline of the back, b) a “net” of armor scutes in a pattern reminiscent of chicken-wire or fish scales underneath the throat, and c) subrectangular scutes at least partially covering the forelimb. Presumably they could have armor along the sides and hindlimb, as well, and perhaps on the belly and tail, but I don’t know of any clear evidence for or against this.
3) Figuring out exactly how large phytosaurs got is tricky, again due to the lack of complete skeletons. The biggest skull I’m aware of is from Smilosuchus gregorii, 1.4 meters long. There are estimates on the internet pegging it at 12 meters in total length, which would probably put it in Deinosuchus territory. But I’m skeptical about that ratio of skull length to total length, and would be more inclined to believe something in the 8-10 meter range. According to Palaeos, the smaller species of Parasuchus, Rutiodon, and Mystriosuchus top out at 2-3 meters, but there are smaller juvenile specimens of other species known.
Why “better”? It looks like a different solution to the same problem (and one that apparently doesn’t require a secondary palate). Crocs have lengthened the whole snout (the maxillae and nasals) — phytosaurs have lengthened the very tip of the snout (the premaxillae) and left the nostrils behind instead.
Yes, they are both two solutions to the same environment. There’s no reason for it, it just happened that way. I can’t understand why Phytosaurs became extinct since they were as well adapted to the amphibious ambush slot as crocs, and crocs have survived many serious extinction events, including the one that kissed off the phytosaurs.
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