Crocodylomorphs - Blog Posts

Prehistoric Planet Croc Ideas

So this was a thing I did on Twitter in anticipation of Prehistoric Planet. Obviously crocs (in this case meaning crocodylomorphs) were a pretty massive part of earth's fauna during the late Cretaceous, and seeing as the first season featured NONE I came to speculate which taxa could hypothetically make an appearance. Now part of the challenge for myself was to come up with a new, interesting contender every day in anticipation of the show's release, each based around the confirmed episides we had and restricted purely to taxa from the Campanian and Maastrichtian. While it took a lot of energy, I did manage to do so. Hell, halfway through they dropped the reveal of Simosuchus, which I had saved for later.

Obviously we didn't get much still, but I'll regardless post my list of candidates and ideas here, perhaps third time's the charme for a lot of these (tho for convenience I'm still ordering them by S2s episode titles). I'll also try to break them apart roughly by biome, starting with islands. PS: I'd love to hear which crocs people would have loved to see themselves. Any on this list or stuff I didn't even mention? Let me know I'm curious.

We got a shit ton of island crocs from the Cretaceous actually, which you can broadly divide into two categories. The crocodiles of the European archipelago as seen in the top row. Featuring the small, possibly shellfish eating Acynodon (art by Adramelech89), the incredibly widespread Allodaposuchus which did have some possibly semi-terrestrial forms (art by Alejandro Blanco, Aina and Agnès Amblás) and Aprosuchus, a tiny terrestrial critter from Hateg (art by @knuppitalism-with-ue). They already give a nice diversity between tiny durophages with blunt snouts, large, more traditional crocs and lanky land species.

The other island category concerns Madagascar, which had a lot of attention in season 2. Discounting Simosuchus, we got Araripesuchus tsangatsangana (art by Scott Hartman) and Mahajangasuchus (art by Mark Hallet). Both are really cool. The former is yet another smaller terrestrial species that may not actually be part of Araripesuchus, while the later is a massive, 4 meter relative of the famous Kaprosuchus that took to the water independently from all other crocs and has been nicknamed "Hippo croc" for its weird skull. Really I'd have loved to seen an episode entirely dedicated to this place.

Next up we had the badlands episode, which oh boy has a lot of contenders from the clade Notosuchia. Brace yourself.

Here again I could split these in two categories. The first is just general badland taxa. There's Ogresuchus for example, from Spain's Tremp Formation (art by Aina and Agnès Amblás). A relatively small sebecid found in a sauropod nesting site. And we all know what PhP does with baby sauropods. Or the long-necked Gobiosuchus (art by @yoofilos) from Mongolia, which may look like its related to the other ones in this category but actually is a far more ancient type of croc.

The far bigger group concerns South America's Notosuchians. ALL OF THESE are from the Bauru Group, with some even from the same single formation. You got Stratiotosuchus (again by Joschua Knüppe), a large terrestrial baurusuchid that filled the nische of mid sized carnivore in an environment shared by sauropods and abelisaurs. There's Pissarrachampsa (by Felipe Alves Elias), another baurusuchid I decided to feature because we have evidence of a nesting site that shows they only had few eggs. A great opportunity to show their tender side. Uberabasuchus (justin_an74), part of the bizzarly proportioned peirosaurids. Adamantinasuchus (by Deverson da Silva), a small, lanky Notosuchian and of course the heavily armored omnivore Armadillosuchus (by the ever talented Júlia d'Oliveira). Hell you could do a full episode just on the foodweb of the Bauru Group (Godoy et al. 2014).

Then there's swamps, which I'll just use to dump all the crocs that don't fit into the other categories.

As you'd expect, freshwater would be ideal for crocs with a more traditional semi-aquatic lifestyle, here represented by three forms. Jiangxisuchus (image by Li et al. 2014) is a paralligatorid, which are tiny crocodilians from the Cretaceous and Paleogene of east Asia. We honestly don't know what they are, some say alligator relatives, others say they are closer to crocs. But its small and cute. Then there's Roxochampsa (artist of the model I couldn't find), which looks suspiciously crocodilian but is actually a relative of Uberabasuchus from the badlands, hell it appeared in the same formation. Still, I reasoned that I'd throw it into this category because I already proposed so much for badlands (none of which came true but hey). And then there's Denazinosuchus (art by Andrey Atuchin). Again it looks deceptively like a modern croc, but is actually the last remnant of the goniopholids, crocodyliforms that were prominent animals in the Jurassic and early Cretaceous. It could have brought both taxonomic diversity nad highlighted croc resilience till the end.

When it came to picking out crocs for Oceans, it got tricky. Obviously season 2 tried to differentiate itself by being set more in the open ocean, not the coast, and true pelagic crocodiles weren't around by the end of the Cretaceous. So I had to settle for coastal animals. There's Sabinosuchus (Schiller II et al. 2016), a cousin to Sarcosuchus and, like Denazinosuchus, one of the last of its lineage. Also its from Mexico which is rarely talked about for its fossils. Rhabdognathus (Ghedoghedo) is a distant cousin, a slender snouted dyrosaur. Unlike pholidosaurs, dyrosaurs actually did really well after the KPG impact and spread around a lot, living way into the Eocene. And finally Chenanisuchus (art by artbyjrc), which like Rhabdognathus was found both before and after the impact that killed the dinosaurs.

And the final two I shall talk about, both of which I thought/hoped would appear in the North America episode. Again, there's certainly overlap, both would have just as much fit into swamps, while many others would have also suited North America. Regardless, here's Brachychampsa (Tom Parker) and Borealosuchus (Chris Masna), both iconic animals from the Hell Creek Formation. One closely allied with alligators and caimans, the other more basal with a head-shape more similar to todays crocodiles.

Now obviously there'd have been a lot more. Part of the challenge to myself was to try and be as diverse as possible, rather than just listing 10 different baurusuchids I went with only two, tried to include as much of the world as possible, etc.... There's also the fact that some really awesome taxa, Titanochampsa, Brachiosuchus and Eurycephalosuchus, all incredibly unique or interesting, were published too late to have been considered for the show. And now, in hinsight, we obviously know that with the exception of Simosuchus none of them made it in. Which is a shame, but maybe next time.

Turnersuchus: First of the Sea Crocs

A big find for crocodile finds was revealed two days ago. Turnersuchus hingleyae (Hingley's and Turner's crocodile) is the oldest known and basalmost thalattosuchian described so far and is of great importance to slowly figuring out where thalattosuchians come from.

But lets start with a brief introduction to thalattosuchians. As the name already suggests, thalattosuchians are primarily known to have been marine animals (tho exceptions are known). thalattosuchians can broadly be split into two groups. The teleosauroids, which look somewhat similar to what one might call a normal crocodile, and the metriorhynchoids, which especially in the derived members could aptly be described as crocodile mermaids. Below an example of each, on the left Macrospondylus by Nikolay Zverkov and on the right a generalized metriorhynchid by Gabriel Ugueto.

Thalattosuchians such as these two groups, which are sister clades and not successive lineages (so they co-occured rather than one having evolved from the other), were incredibly successful during the Jurassic, evolving enormous forms such as Plesiosuchus, Dakosaurus and Machimosaurus. Their wild success held on throughout the Jurassic until they eventually went extinct in the early Cretaceous. But despite how common and whidespread they are, we don't actually have much of a clue where they come from. Thalattosuchians just kinda appear during the Toarcian and are already found across multiple continents with both groups established. To complicate matters, their position among crocodiles is also rather shaky. Three main hypothesis exist. One is that they are a sister group to crocodyliforms (Protosuchians, Notosuchians and Neosuchians), that they are basal mesoeucrocodylians or that they are Neosuchians related to Pholidosaurids (like Sarcosuchus) and Dyrosaurs.

This is where Turnersuchus comes in. Discovered in the  Charmouth Mudstone Formation of Dorset, England, this genus is known from the skeletal material belonging to the back of the head, mandible, parts of the forearms and shoulder girdle as well as neck, body and tail vertebrae all preserved in five blocks and a few isolated pieces of bone. From that we can already see general similarities to derived thalattosuchians and basic traits like narrow jaws and reduced forelimbs (tho not nearly as extreme as in metriorhynchids).

The first significant part about this discovery is its age. Turnersuchus is from the Pliensbachian stage of the Jurassic, so it predates any previously diagnostic thalattosuchians. Secondly is its position. As I said above, thalattosuchians are divided into teleosauroids and metriorhynchoids. But Turnersuchus is neither, with both phylogenetic analysis finding it to fall outside of these groups. Now in fairness this is not rock solid, as there is only a single trait excluding it from the derived groups in either analysis, so future works might shake things up. But as things are right now, it's the oldest named and basalmost member of the entire clade. On a sidenote at least the oldest part is bound to change, as the paper mentions a Moroccon teleosauroid currently in press that is even older.

All of this allows for two things. For one, by comparing Turnersuchus with the basal members of both teleosauroids and metriorhynchoids scientists were able to gather a list of traits that appear to be ancestral to the group. In addition, Turnersuchus also preserves some features that separate it from all other thalattosuchians that are also indicative of being an early member. Just as one example a specific part of the basioccipital thats associated with long skulls is poorly developed, which means that while slender the jaws weren't as long as in some later thalattosuchians. A Bayesian analysis was also conducted in an attempt to nail down when thalattosuchians evolved. Now depending on which phylogeny is used (one with thalattosuchians as non-crocodyliforms and another with them as mesoeucrocodylians) you get different times. The former would place their origin in the Norian stage of the Triassic, the later in the Sinemurian stage of the Jurassic. In light of the Moroccon material alluded to by the paper, it would appear that they likely split from other crocodylomorphs sometime in the late Triassic.

And finally to wrap this up let me share the press release artwork to finally give a face to all this information. Now if you've read my post about fossil crocs of 2022 you might already recognize the artist, as she's been on a real streak with illustrating fossil crocs. If you don't know her, I highly recommend checking out her work. I'm of course talking about Júlia d'Oliveira.

And yes, of course I got the Wikipedia page for it ready. Tho with work getting in the way when it was published I almost feared I'd be unable to get to it first.