Taxon of the Week: Postosuchus

In this week’s TotW, Ryan takes us through the posto child of the ‘rauisuchians’, Postosuchus.

When someone mentions the Mesozoic, you instantly think about dinosaurs. Admit it, it’s fine, there’s no judgement on this blog. You also will predominately think about dinosaurs from the Jurassic and the Cretaceous, with good old T. rex and co. (allosaurs, carcharodontosaurs, spinosaurs etc.) ruling the roost at the top of the food chain, whilst sauropod behemoths (amongst other ridiculously sized herbivores) wandering about in herds etc. etc. However, the Triassic (seemingly the Cretaceous and Jurassic’s ugly sister) is often forgotten about. Yes, we don’t have things which are outrageously large or ridiculously bipedal (or do we..?), but in the Triassic, crurotarsans (crocodile-line archosaurs) were having a bit of a field day.


The image that immediately springs to mind as soon as you mention ‘Jurassic’ or ‘Cretaceous’. Clearly.

Here on TDS, we think the Triassic (as well as plenty other eras, not just the Jurassic and Cretaceous) is pretty awesome too. The Triassic was a time of recovery, the Permian-Triassic mass extinction event had been and gone (and almost taken all of life on Earth with it). Dinosaurs were just starting out, and sitting on top of the food chain was, you guessed it, Postosuchus. If you look at the skull of Postosuchus kirkpatricki below, look carefully. Back in the 1980s famous palaeontologists thought Postosuchus (along with Poposaurus) could be a tyrannosaur ancestor. You can see where they’re coming from. Postosuchus was first discovered in 1922, and for 60 odd years after that, people didn’t really know what to make of it. First reports penned it as a Coelophysis, 20 years later, other finds were thought to belong to a new phytosaur. It wasn’t up until 1985 that the holotype, a well preserved skull and some postcranial remains, of Postosuchus kirkpatricki was formally announced. 


Totally not a dinosaur. No seriously.

Weighing in at almost 300kg, at reaching almost 4m when fully grown, Postosuchus was one (if not the) largest predator in the Triassic. With good long distance vision, a decent sense of smell, and a possible Jacobson’s organ, and oh, not to mention, over 7cm dagger-like teeth, this killing machine well may have taken down a fair few aetosaurs in it’s time (not a small feat). So fairly fearsome, but not as impressive as the theropods that were to come later in the Mesozoic, surely? Well, again, no.


These coelophysoids clearly came to the wrong neighbourhood.

What makes Postosuchus (and many other ‘rauisuchians‘) so interesting are its hindlimbs. One of the major dinosaurian innovations was the erect hindlimb posture, enabling more efficient locomotion. In the Triassic, descendants of crocodiles (who now have the ‘sprawling’ hindlimb posture) such as Postosuchus had a go at this hindlimb arrangement (evolutionary speaking). Whilst debated, many palaeontologists view Postosuchus (amongst other Triassic crurotarsans) as being bipeds (or at the very least facultative bipeds). So that means Postosuchus could use it’s forelimbs to kill things as well as it’s terrifyingly huge mouth (like bears do). To summarise, Postosuchus is a nightmare-inducing, killer croc-bear from back in time. It also raises the question (to be investigated by a future blog post on TDS, hopefully) of why exactly did dinosaurs survive through to the Jurassic, and rauisuchians go extinct, and why did crurotarsans go back to being solely quadrupedal?


Killer croc-bear from back in time. (Thank you internet).

Told you the Triassic was awesome. (Also, more to come on the locomotory strategies of Triassic crurotarsans to come, right after I finish my final 4th year exams…).

Bonus picture (because it’s cool and reasonably accurate, although not as accurate as the previous picture):


There’s no escape from the Post(o) Man (not actually a man).


  • Case, E. C. (1922). “New reptiles and Stegocephalians from the Upper Triassic of western Texas”. Carnegie Institution of Washington Publication 321: 1–84.
  • Case, E. C. (1932). “On the caudal region of Coelophysis sp. and on some new or little known forms from the Upper Triassic of western Texas”. University of Michigan Museum of Paleontology Contributions 4 (3): 81–91.
  • Case, E. C. (1943). “A new form of Phytosaur pelvis”. American Journal of Science 241 (3): 201–203. doi:10.2475/ajs.241.3.201.
  • Chatterjee, S. (1985). “Postosuchus, a new Thecodontian reptile from the Triassic of Texas and the origin of Tyrannosaurs”. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 309 (1139): 395–460. doi:10.1098/rstb.1985.0092.
  • Drymala, S. & Bader, K. (2012). Assessing predator-prey interactions through the identification of bite marks on an aetosaur (Pseudosuchia) osteoderm from the Upper Triassic (Norian) Chinle Formation in Petrified Forest National Park (Arizona, USA). Journal of Vertebrate Palaeontology, Program and Abstracts 2012, p89.

FAQ: Ryan.

First and foremost, what’s your favourite dinosaur?

What a horrific question. It’s like asking a proud parent to choose their favourite child. In my younger days, it was all about the big theropods, tyrannosaurs and the like. But now, I can’t resist the enormous (heh…) charm of sauropods (I prefer the macronarians, Brachiosaurus and the other ‘tall’ sauropods).

Secondly, what’s you favourite (preferably extinct) animal?

A much nicer question question. Pakasuchus kapilimai. As the name suggests it’s a cat-like crocodile. What more could you want? However, honorary mention to Quetzacoatlus (the ‘evil, pin-headed, toothy nightmare monster that wants to eat your soul’, a quote from Darren Naish), because what other flying reptile with a 11m wingspan has a rap about it? Exactly.


Cute and scaly? Best combo ever. (Courtesy of Wikimedia Commons)

What’s your area of ‘expertise’?

I’m not huge expert in anything yet, but I have a passion for biomechanics in the archosaurs (birds, dinosaurs, crocodiles and their ancestors). I’m currently using a lot of computer software to digitally model fossils, so I guess some of my ‘expertise’ lie in digital palaeontology (the shiny-new future, more on that in a future post, probably).

How did you get into palaeontology?

Like most children of the 1990s, I grew up loving Jurassic Park. The scene where Dr. Grant (a personal hero of mine, even as I enter my twenties) first meets the Brachiosaurus is still up there as my favourite movie-moment ever. Even before that, I was an absolute dinosaur-nut. So much so, by the age of 5 I could spell palaeontologist. Since then I’ve never lost that desire to become a palaeontologist. So, after spending primary and secondary school, then college work my behind off I went to the University of Bristol to study on the Palaeontology and Evolution course. I’m now a masters student at the University of Bristol, currently looking for PhD positions to continue my career in ‘dinosaurs’.


To reiterate: this is the best film ever. Period.

What do you do in your spare time?

To be honest, I’m pretty much always reading about palaeontology. Here’s a tip for free: if you want to be an academic you have to be almost obsessed with your subject, if not, you’ll just learn to hate it. In the small amount of time I’m not holed up reading about palaeo (more likely: looking at awesome palaeo art), I’m usually performing/hanging out with Bristol Improv, reading other books, playing video games, or on Twitter (desperately attempting to get #notosuchia trending).

Favourite palaeontological paper?

Ah, I remember it well. It was the first paper I read (all the way back in the first year of my undergraduate degree) that I actually enjoyed reading. It was Rayfield (2004), and I only read it simply because it had Tyrannosaurus rex in the title. But it began my interest in biomechanics (even though I was scared by the maths behind FEA). It was one of the first papers (along with Rayfield et al. 2001) to show the importance of new computational methods in palaeontology. Essentially, I like papers with shiny pictures of fossils (and models of fossils). More recent favourites of mine include:


The future of how palaeontologists assess om-nom-nomming in dinosaurs.

You’re a palaeontologist, so you’re like Ross from ‘F.R.I.E.N.D.S’?

If I had a penny for every time someone asks me this, I’d have paid my student loan off years ago. For simplicity, yes, I’m like Ross from Friends.

And yes Jenniston, I am still awaiting your marriage proposal.

Any tips for any budding palaeontologists out there?

If you’re still in school/college/pre-university, work hard! If you’re in university, work even harder! But seriously, if you want to go into an academic career (not just palaeontology) you’re going to have to get used to hard graft. Also, if there’s any dig sites near you (I’m looking at you American readers), then volunteer! Not only is it great fun, but it looks great when you’re applying for uni/palaeo jobs. If you can’t visit dig sites, read around the subject a lot! We know accessing the primary literature is hard (both in terms of paywalls and understanding), but don’t fear! There’s plenty of really accessible blogs (like us!) giving you news and views on all things palaeo. Also, National Geographic magazine occasionally has some nice articles (palaeo related) inside.