#thalattosuchia

[arminreindl]

Fossil Crocs of 2023

2023 has been a year with its ups and downs, but one consistent thing has been its fossil crocs at least, giving us another interesting variety of species and genera not known before. Like last year, I'll go down each of them (including phytosaurs) and give you some key notes. And since I've done my best to make individual posts for them I'll link those when available. I'll also try to give translations where possible, but do note that sometimes I might switch around a word due to it just sounding awkward otherwise.

Scolotosuchus

Starting us off is Scolotosuchus basileus ("royal scythian crocodile"), a basal, rauisuchian-like animal from the early stages of the Triassic. An animal roughly 3 meters long, it is primarily known from vertebrae and some other material, which however does have interesting implications. Based on the anatomy of the vertebrae, it has been speculated that Scolotosuchus performed a lot of rapid movement of the neck, presumably while hunting. Furthermore, it might be that Scolotosuchus lacked osteoderms, instead having developed a bracing system for its body much more like that of dinosaurs and mammals. Artwork by @knuppitalism-with-ue (he'll pop up quite a lot)

Colossosuchus

Fast forward to the Late Triassic, the hayday of early Pseudosuchians, and we find our first phytosaur of the list. Colossosuchus techniensis ("colossal crocodile of the Indian Institute of Technology") was an enormous animal from India's Tiki Formation. This one is known from undisputably better material, perhaps some of the best on this list as we have an entire bone bed of these guys, possibly representing a mass death site. Size estimates of the large specimens generally range from 6 to 9 meters in length, also making it the largest animal of this list, with the authors favoring an estimated 8 meters for the largest individual. Of course this is all subject to change, as we don't know the precise proportions (the downside of a bone bed is that all the bones are kinda jumbled together and god knows what belongs to what). Artwork by Joschua Knüppe again, a female being courted by an overconfident and confused Volcanosuchus (told you so)

Kryphioparma

Ok I won't bother you with this one too much. Kryphioparma caerula ("blue mysterious shield") is an aetosaur from the Late Triassic Chinle Formation of Arizona. Now aetosaurs are cool of course, but the thing is that Kryphioparma is known from exclusively osteoderms, their large armour plates. While thats valid, its also not really exciting (as you could have guessed from the absolute lack of artwork). Best I can say is that it coexisted with a bunch of other aetosaurs, which surely would have been a sight to see back in the day.

Venkatasuchus

Now Venkatasuchus armatum ("Venkata's armoured crocodile") is in a similar boat. This Indian aetosaur too is only known from osteoderms, tho at least a lot more of them that were found together, meaning we got a much better idea of its shape. There are some interesting implications it has on paleogeography and how different animal groups spread across Pangea, but that's probably beyond the scope of this post. There is at least some art of it tho, including one piece by Joschua featuring Jaklapallisaurus, an early sauropodomorph.

Mystriosuchus alleroq

Now we got our first new species of a preexisting genus. While I did my best to make posts on new genera, which typically went hand in hand with their respective wikipedia pages, species are a different matter since they'd require me to overhaul and research the whole genus. Which for Mystriosuchus would go all the way back to 1896.

Anyhow, Mystriosuchus alleroq ("jawbone spoon crocodile") is the newest in a long line of Mystriosuchus species and has been recovered from western Greenland of all places. Like Colossosuchus it is known from multiple individuals, at least four in fact, And like Venkatasuchus, it appears to have wideraning implications for the spread of archosaurs during the Triassic. Oh look its Josch's art again, neat.

Jupijkam

The final phytosaur and the final Triassic taxon of the year, Jupijkam paleofluvialis ("horned serpent of ancient rivers") was recovered from Nova Scotia Canada and represents one of the northernmost phytosaurs (alongside obviously our friend Mystriosuchus alleroq above). It is far less complete than the other phytosaurs I covered so far, but still nothing to scoff at. It's also one of the youngest known phytosaurs, possibly having lived during the last stage of the Triassic. There's no art but here's an image of its snout from the original paper.

Turnersuchus

And with this we have reached the Jurassic and somewhat of a double feature. Ordering these via chronology makes this almost like storytelling. Turnersuchus hingleyae ("Hingley's and Turner's crocodile") is the oldest and basalmost named thalattosuchian, a group of crocodylomorphs that took to the seas. As such it shows a mosaic of features, already having begun to reduce its limbs, having a moderately long snout and still bearing osteoderms, which some of its descendents would come to lose. Turnersuchus dates to the Pliensbachian, a stage of the early Jurassic, tho the paper mentions how its not likely to hold its title as oldest member of its group for long as even older material has been discovered and is awaiting publication. Artwork by Júlia d’Oliveira and Joschua Knüppe

Torvoneustes jurensis

While Turnersuchus gives us a glimpse at what the earliest thalattosuchians were like, Torvoneustes jurensis ("savage swimmer of the Jura Mountains") represents them at one of their most derived. At 4 meters long, it must have been an impressive creature, entirely smooth and lacking osteoderms, highly reduced arms and a tail fluke to boot. There are some interesting features, as unlike other species of Torvoneustes, this one does not appear to have been as durophagous, instead appearing to be more of a generalist. It's the last Jurassic croc of the year and practically lived at the opposite end of this time period relative to our previous thalattosuchian, during the Kimmeridgian. Artwork by Sophie De Sousa Oliveira, not to be confused with Jùlia who drew Turnersuchus.

Comahuesuchus bonapartei

From marine to terrestrial, Comahuesuchus bonapartei is a member of the Notosuchia, land-dwelling cousins to the Neosuchia. This new species is known from the Cretaceous of Argentina and was described on the basis of a lower jaw, which differs from the previously described species of Comahuesuchus by the fact that the teeth are situated in individual sockets. Its jaws were short and wide, being described as U-shaped, giving it a somewhat pug-nosed appearance. In case you're wondering why I don't have the translation of the name thats because I can't access Bonaparte's first paper, so all I can say is that the new species is named after famed Argentinian paleontologist Jóse Fernando Bonaparte. Artwork by I mean you probably guessed it, its Josch again.

Aphaurosuchus kaiju

I have some mixed feelings on Aphaurosuchus kaiju ("powerless kaiju crocodile"), not just because I have to rewrite its genus wikipedia page that I am no longer happy with. No, Aphaurosuchus is a great genus in my opinion, given the complete nature of the holotype. But I do think that the species name of this second form is a bit of an exaggeration, seeing as it is to my knowledge not that exceptionally big. So why name it kaiju other than to sound cool? I also think it just kinda becoms funny when you consider the meaning of the genus name. Anyhow, it does look pretty mean, but thats to be expected from a baurusuchid. It lived during the Late Cretaceous in Brazil and the phylogenetic analysis that accompanied its description had some interesting implications that I'm curious to see tackled in the future. Other than that it's just another baurusuchid from a place crawling with baurusuchids, which tbh is pretty cool itself but doesn't really help make it stand out. Arwork by Paula Zeinner

Dentaneosuchus

It is the middle Eocene. France is entirely occupied by mammals. Well, not entirely... One indomitable reptile still holds out against the invaders. Yes, I am of course talking about Dentaneosuchus ("frightfull crocodile"), the titan of the Eocene, the terror of the jungle. Easily among the most exciting finds, this animal was an enormous sebecid previously thought to be a member of the genus Iberosuchus, but recent research not only shows its distinct but enormous. With a lower jaw around 90 cm long, it rivals even the famed Barinasuchus of Miocene South America. The total body lenght is of course a matter of debate given how little we know about sebecid proportions, with the paper lowballing it at 3 to 4 meters and I personally recovering something more akin to 5 meters. Regardless of the specifics, this would make it easily one of the top predators of its time, tho sadly this was not meant to last. It was among the last non-mammalian apex predators of Europe, before climate change and competition from mammals eventually drove them to extinction. Arwork by Joschua Knüppe and @mariolanzas

Baru iylwenpeny

Our last three entries were all members of the Notosuchia, the terrestrial crocodiles that existed from the Jurassic to the Miocene, so lets jump to the other major group of the time, the Neosuchians, specifically their most recent branch, the Crocodilians. Yes finally we are getting to crocs in the stricter sense.

Baru iylwenpeny ("divine crocodile thats good at hunting") is an animal we also knew for a while under the informal name Alcoota Baru based on where it was found. This year I spent a lot of time writing in the Mekosuchinae, Australasian crocodiles of the Cenozoic and just when I had finished the page for Baru, this guy got published. It's the largest, most robust and most recent member of the genus. Good at hunting is a good choice for the species name, as this animal was over 4 meters long with a head commonly likened to a cleaver and a hunting style speculated to consist of inflicting a lot of trauma on its prey with its massive teeth. I could gush about Baru for ages, but thats the important parts. It lived in central Australia during the Miocene only 8 million years ago. Artwork by the incredible @manusuchus

Antecrocodylus

Now for the last crocodilian described this year and one I remised to make a dedicated post for due to time constraints (I had a busy few months). Antecrocodylus chiangmuanensis ("before Crocodylus from Chiang Muan") is a close relative of the modern dwarf and true crocodiles from the Miocene of Thailand. It is only known from the back of the skull and an associated lower jaw, but it serves to highlight how little we know about the crocodiless of eastern Asia during the Miocene, which is a shame given that this region is crucial to deciphering where true crocodiles originated.

Alligator munensis

And our final taxon is Alligator munensis ("Mun river alligator"), which, obviously, is a member of the modern genus Alligator and thus most closely related to the still extant Chinese and American Alligator. Likely having been split from its Chinese relatives when the Tibetan plateau was lifted up, this species lived during the middle Pleistocene in Thailand and may have survived until the Holocene. It's head was short and robust and its teeth globular, which could indicate that it fed on hard-shelled prey like clams and snails. It was also small, likely not much bigger than 1.5 meters. Artwork by Joschua Knüppe

And that should be all of them, all new species and genera of Pseudosuchians described this past year. It's once again been fun to look back and I hope that you find them just as interesting as I do. Lets hope that 2024 will bring equally fascinating discoveries.

[ildarotyrannus]

I apologize for such a long delay. I couldn't find the motivation to keep posting here. But, as I promised in my last post, here are three more drawings made for last year's scientific conference. :)

Front half of Dakosaurus andiniensis, massive metriorhynchid from Late Jurassic of Argentina. As with Cricosaurus, I based this reconstruction on metriorhynchid specimens with skin. Note the presence of speculative skin parasites, whose marks were founds in fossil skin. Also, there are salt glands in antorbital fenestra. This feature is based on this study: https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.24678 BTW, some recons portray Dakosaurus with crocodile-like facial integument and some recons even have "lips"! I decided to diversify from these both options and did it with smooth streamlined skin.

Prognathodon sp. reconstruction based on purportedly juvenile specimen with soft tissue outlines from Late Cretaceous of Jordan. This small individual was described in this paper: https://www.nature.com/articles/ncomms3423 Preserved skin impressions include silhouettes of the skin fringes of the flippers and the caudal fin. The caudal fin is quite small, but in adults it could be proportionally larger. This finding confirmed that mosasaurs converged with ichthyosaurs and metriorhynchids to develop a fish-like caudal fin.

And finally, Seeleyosaurus guilelmiimperatoris (formerly species of Plesiosaurus), a microcleidid plesiosaur from Early Jurassic of Germany. Holotype of this species is almost complete specimens with some skin impressions including rhomboidal skin flap. Perhaps all plesiosaurs had caudal fins of one form or another. However, their orientation is controversial: many paleontologists are of the opinion that the fin was vertical, but others think it was horizontal.The arguments in favor of the second point of view are the rigidity of the chest, the flat and wide shape of the tail in the proximal part and the absence of bending in the distal part of the tail: https://www.researchgate.net/publication/339423536_Peculiarities_of_the_Structure_and_Locomotor_Function_of_the_Tail_in_Sauropterygia I decided to choose this version for reconstruction. Which of the scientists is closer to the truth, new findings will show. All of these drawings were done with black gel ink pen and black colored pencil with small additions of white gouache.

[mesozoicmarket]

An indeterminate crocodylomorph tooth, possibly a thalattosuchian from the Isalo III Formation in Ambondromamy, Madagascar. These primarily Jurassic aged crocodylomorphs are sometimes known as marine crocodiles or sea crocodiles, though not particularly related to true crocodilians.

[northwyrm]

My second paper is out!

I'm second author rather than first on this one, but if you have any questions on it feel free to reach out! It's about the grooves we found on the palates of fossil crocodylomorph skulls! These palatal grooves (PG in the thumbnail image) are found in Thalattosuchians, crocodylomophs adapted for live at sea!

[northwyrm]

I uploaded the data onto morphosource for this paper hehe

This ancient crocodile looked kind of like a dolphin

Enalioetes schroederi’s ‘radically different’ body was scaleless, speedy, and lost to researchers for decades.

A set of 135 million-year-old fossils, once thought lost during World War II, are now accounted for and analyzed.  According to a study published July 18 in the Journal of Systematic Paleontology, a team of international researchers from Germany and the UK has determined the “well preserved” skull and first neck vertebrae are from what they now call Enalioetes schroederi. But while paleontologists now know they belong to a newly discovered species of ancient marine crocodile, these creatures likely looked more like dolphins than reptiles...

Read more:

https://www.popsci.com/science/ancient-crocodile-dolphin/

[saritapaleo]

Patreon request for @/rome.and.stuff (Instagram handle) - Turnersuchus hingleyae

Described just last year, the Early Jurassic Turnersuchus is the most basal known member of the thalattosuchians: sea-dwelling crocodylomorphs. It existed before the two major thalattosuchian groups, the paddle-limbed Metriorhynchoidea and the long-snouted Teleosauroidea, split, and it may be the ancestor of both. While only parts of the skull are known, its shape suggests a narrow snout that was not as long as that of later thalattosuchians. Only one osteoderm is known, and it is oval with a slight keel down the middle, believed to have been attached to the tail. As humble as this small pseudosuchian was, it helped us fill in the major gaps of our understanding of thalattosuchia, and finally gave us an idea of their origin. Previously, all we knew was that the highly-derived metriorhynchoids and the more crocodile-like teleosauroids were related, lived alongside each other, and seemingly appeared in the Jurassic. While not as well known as the icthyosaurs, plesiosaurs, and mosasaurs, thalattosuchians were very successful sea crocodylomorphs until around the Early Cretaceous, and they owe their success to this little pseudosuchian who decided to return to the sea.

Found in the Charmouth Mudstone Formation of England, Turnersuchus would have lived alongside a variety of ammonites like Phricodoceras and Gemmellaroceras, as well as icthyosaurs like Leptonectes. It likely fed on the small fish that lived here. As it was not as highly adapted for ocean life as its descendants, it may have spent some time basking on land, where it could have come across early dimorphodontid pterosaurs and the armored Scelidosaurus.

[greenfrog04]

Description and phylogenetic relationships of a new species of Torvoneustes (Crocodylomorpha, Thalattosuchia) from the Kimmeridgian of Switzerland

Published 19th July 2023

A new metriorhynchid from the Kimmeridgian of Porrentruyi Switzerland based on a relatively complete disarticulated skeleton, Torvoneustes jurensis.

Torvoneustes jurensis holotype

Artist illustration of jaw and mandible

Torvoneustes jurensis teeth

Artist reconstruction of Torvoneustes jurensis, by SDSO.

Source:

[cacatoto-2024]

Machimosaurus adalah salah satu genus Teleosauridae yang sudah punah. Hewan ini masih satu keluarga dengan buaya, dan berasal dari zaman Jura Akhir (Kimmeridgian dan Tithonian) dan Kapur Awal.[2][3] Tipe spesies Machimosaurus hugii ditemukan di Swiss. Fosil lainya juga ditemukan di Inggris, Prancis, Jerman, Portugal, dan Tunisia.[2][4][5] Machimosaurus bukan saja teleosaurid dan thalattosuchia terbesar, dengan panjang tubuh mencapai 9.6 meter (panjang tengkorak 155 cm), ia merupakan buaya terbesar dari zaman Jurasik.[2][3][4]

[arminreindl]

Two more croc-line archosaurs to dig into with this one and both are super fascinating.

Obviously the star of this piece is our friend in the foreground, Plesiosuchus manselii, the largest of the fully marine metriorhynchids (the skull of which being the first one shown in the image to the right, taken from Young et al. 2012)

More broadly speaking, metriorhynchids are a fascinating group of early croc-relatives that stand out for having returned completely back into the water, developing a fluked tail, tiny little reduced forelimps, flipper like hindlimbs and smooth skin entirely lacking in the osteoderm armour we so strongly associate with pseudosuchians.

Plesiosuchus specifically is the largest of them. Close to 7 meters in length, it's basically in the same range as Liopleurodon (although smaller than several of the pliosaurs we know from the Kimmeridge Clay like that very decorative skeleton). Plesiosuchus actually wasn't the only metriorhynchid from the formation either. We also know of the small Cricosaurus, the name-giving Metriorhynchus and most interestingly the large-bodied Dakosaurus and Torvoneustes, which were likely to reach lengths of 4.5 to 4.7 meters respectively. At least with metriorhynchids this diversity can be explained in the different animals having very different preferences. Torvoneustes is interpreted as a durophage, feeding on hard-shelled prey. Dakosaurus is characterized by slicing dentition, potentially able to cut apart large prey with tooth wear possibly suggesting sharks or suction feeding habits. Plesiosaurus meanwhile would be able to take on large prey simply due to its great size and large gape but may have been limited by the size of its own head.

The other marine "croc" in the image is Bathysuchus, which may be described as a cousin to the metriorhynchids.

Remember Machimosaurus from the Guimarota locality that Josch drew a few weeks back? Yeah its related to that one. A teleosauroid to be precise, which are the sister group to metriorhynchoids and appear much more croc-like in their appearance despite still being a long way off from crocodiles in the strict sense. Teleosauroids may appear like what you'd think of as basal to metriorhynchoids, but they simply did their own thing after diverging, thus retaining this more ancestral bauplan with more developed limbs, more croc-like skulls and maintaining their armour plating (keep that in mind).

Bathysuchus is kind of a weird one tho. Why? Because from what we can tell Bathysuchus seems to have tried to become more like its metriorhynchoid cousins. It's known from deeper waters, its osteoderms were much more reduced and if the closely related Aelodon is anything to go from then its quite likely that this guy also started reducing the size of its forelimbs. In short, adaptations to a more pelagic lifestyle that moves away from the coastal habitat other teleosauroids seem to have preferred. Who knows, maybe its possible that in some other timeline these guys might have become something akin to metriorhynchoids like what happened with mosasaurs.

Unlike metriorhynchoids, teleosauroids were way less common in the Kimmeridge Clay, hell, to my knowledge Bathysuchus is the only one of them, a pretender among the other pelagic pseudosuchians.

Result from the Kimmeridge Clay #paleostream!

We were only able to scratch the surface, but I think you get the idea ;)

[arminreindl]

Thalattosuchus and Leedsichthys

Quickly stopping by to report on a new paper describing stomach contents of a thalattosuchian (Jurassic marine crocodile).

The paper in brief describes a specimen of Metriorhynchus superciliosus (aka Thalattosuchus) with preserved stomach contents, which is already rare enough as is. What's even more interesting is that the stomach contents preserve both the gill rakes of the large fish Leedsichthys as well as various mollusc shells. Strange prey for what's a rather small piscivore. Although it was previously suggested that Metriorhynchus/Thalattosuchus attacked living Leedsichthys, this appears to have been based on missinterpreted evidence and given the enormous size difference its way more likely that the fish was simply scavenged, sorta like a kind of Jurassic whalefall. This actually finds support in the mollusc shells, which might have been ingested on accident alongside the fish remains.

Top left: The skeleton of this Thalattosuchus specimen Top right: The stomach contents in detail (G are gill rakes, S are shells) Bottom left: Live reconstriction of Thalattosuchus by Gabriel Ugueto Bottom right: Live reconstruction of Leedsichthys by @knuppitalism-with-ue

The paper itself: Fossil Studies | Free Full-Text | The Diet of Metriorhynchus (Thalattosuchia, Metriorhynchidae): Additional Discoveries and Paleoecological Implications (mdpi.com)

[alphynix]

It's been a while since I last showed off some of these, but here's some more commission work I've done for PBS Eons:

The metriorhynchid marine crocodilians Aggiosaurus and Cricosaurus, from "When Crocs Thrived in the Seas" https://www.youtube.com/watch?v=vgqs_9BBX10

And… what's this?

A familiar Scutellosaurus makes an appearance in a recently-published children's dinosaur book!

———

Nix Illustration | Tumblr | Twitter | Patreon

[mesozoicmarket]

A worn crocodylomorph tooth of a Dakosaurus maximus from the Kimmeridge Clay in the Wicklesham Pit in Faringdon, Oxfordshire, England. This species of marine croc was likely fully aquatic and hunted plesiosaurs and ichthyosaurs. The heavy wear seen in this tooth is due to these Jurassic fossils from the Kimmeridge Clay being reworked into the overlaying Lower Cretaceous aged Faringdon Sand.

[arminreindl]

Croc sweep. How can you not love them, metriorhynchids in particular. I mean just look at those baby hands, they are ADORABLE. @knuppitalism-with-ue for scale, photo by Sven Sachs

obviously I can't include everything. Rip to the various groups I was forced to leave out, including Mesosaurs, my beloveds.

[antiqueanimals]

From Dinosauriërs, written by Peter Klepsch and published in the 80s. Illustrated by Thomas Thiemeyer.

(via)

[typhlonectes]

A new early diverging thalattosuchian (Crocodylomorpha) from the Early Jurassic (Pliensbachian) of Dorset, U.K. and implications for the origin and evolution of the group

Eric W. Wilberg,Pedro L. Godoy,Elizabeth F. Griffiths,Alan H. Turner &Roger B. J. Benson

ABSTRACT

Among archosaurs, thalattosuchian crocodylomorphs experienced the most extensive adaptations to the marine realm. Despite significant attention, the phylogenetic position of the group remains uncertain. Thalattosuchians are either the sister-group to Crocodyliformes, basal mesoeucrocodylians, or nest among longirostrine neosuchians. 

The earliest definite thalattosuchians are Toarcian, and already possess many synapomorphies of the group. All phylogenetic hypotheses imply a ghost lineage extending at least to the Sinemurian, and a lack of older or more plesiomorphic forms may contribute to the uncertain phylogenetic placement of the group. 

Here we describe a new species, Turnersuchus hingleyae, gen. et sp. nov., from the early Pliensbachian Belemnite Marl Member of the Charmouth Mudstone Formation (Dorset, U.K.). The specimen includes partially articulated cranial, mandibular, axial, and appendicular elements. It can be attributed to Thalattosuchia based on the following features: distinct fossa on the posterolateral corner of the squamosal; broad ventrolateral process of the otoccipital covering the dorsal surface of the quadrate; large supratemporal fenestrae lacking a flattened skull table; broadly exposed prootic; orbital process of quadrate lacking bony attachment with the braincase. This specimen represents the earliest thalattosuchian currently known from diagnostic material. 

Phylogenetic analyses of two published datasets recover Turnersuchus as the earliest diverging thalattosuchian, and sister to Teleosauroidea + Metriorhynchoidea. Bayesian tip-dating analyses suggest a Rhaetian or Sinemurian divergence of Thalattosuchia from other crocodylomorphs, depending on topology, with confidence intervals spanning from the Norian to the Pliensbachian. 

The new specimen extends the fossil record of Thalattosuchia, but the time-scaling analyses demonstrate that a significant ghost lineage remains.

Read the paper here:

https://www.tandfonline.com/doi/abs/10.1080/02724634.2022.2161909

[joeled]