Tetrapod Zoology

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While googling for astrapothere images recently I came across the image used here: wow! This is a life-sized reconstruction of the gigantic Miocene alligatoroid Purussaurus, first named in 1892 for P. brasiliensis from the Upper Miocene Solimões Formation of Brazil. Most of the salient features that are diagnostic for Purussaurus can be seen in the reconstruction: the snout is incredibly deep, wide, rounded at its tip, and decorated with bumps and ridges, the dorsal surface of the snout is strongly concave, the external bony nostril opening was proportionally huge and anteroposteriorly elongate, and the nasal bones were shortened and reduced. And, of course, the animal was huge. Complete skeletons are unknown (purussaurs are known primarily from cranial material: vertebrae and ribs are also known), but – with a skull 1.5 m long – it’s estimated that P. brasiliensis reached 12 m (some sources say as much as 15 m, but that might be pushing it)…

Two species are known in addition to P. brasiliensis. P. neivensis – originally described as Dinosuchus neivensis (not to be confused with another giant alligatoroid, Deinosuchus) – is from the famous Middle Miocene La Venta fauna of Colombia. P. mirandai, from the Upper Miocene Urumaco Formation of Venezuela, was named in 2006. It has a particularly flattened skull compared to the other species and has a wider, bigger nostril opening. Why purussaurs had this immense bony nostril is unknown. In life it was surely roofed over by soft tissue, but it must have had some function. A large concave area that surrounds the nostrils is seen in some other, closely related alligatoroids.

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In his large and nicely illustrated monograph on the crocodilians of La Venta, Langston (1965) regarded Purussaurus as a species of Caiman and the name Purussaurus sort of fell out of favour after that. However, it’s been back in use since the late 1980s and new material has substantially increased our knowledge of these animals. Is Purussaurus really a ‘giant caiman’ as Langston thought? Recent phylogenetic analyses of Alligatoroidea indicate that yes, it is. Within Caimaninae, it appears to be particularly close to Orthogenysuchus from Lower Eocene Wyoming and Mourasuchus from La Venta, with the clade that includes extant Caiman and Melanosuchus also closely related (the dwarf caimans, Paleosuchus, are the sister-taxon to this Purussaurus + Caiman clade) (Brochu 1999, Aguilera et al. 2006).

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Unfortunately we essentially know nothing about the lifestyle and biology of Purussaurus. Its massive size and broad skull suggest that it was strongly aquatic, and its fossils occur in faunas where diverse aquatic, amphibious and terrestrial vertebrates occur. Purussaur teeth are subcircular at their bases but somewhat flattened at the crown, and those of P. neivensis have been described as curving backwards and slightly inwards (Langston 1965). These features all suggest that purassaurs were predators of vertebrates, perhaps grabbing large mammals, but also eating turtles, smaller crocodilians, fish and other prey. The closely related, even more bizarre ‘nettosuchid’ caimans (which include Mourasuchus) have been suggested to be part-time herbivores, and it’s even possible that Purussaurus might have eaten plants on occasion given that modern caimans will do this (Brito et al. 2002).

More astrapotheres next…

UPDATE (added 7-2-2008): I’ve since learnt that the model used at the top can be seen at the Museo de Historia Natural Javier Prado de la Universidad Mayor de San Marcos. The gentleman standing next to the model is Rodolfo Salas Gismondi. For more information go here… and among other things you’ll see a giant turtle shell apparently bearing bite marks made by a purussaur. Despite losing a leg, its tail, and a chunk of its shell, the turtle survived.

Refs – -

Aguilera, O. A., Riff, D. & Bocquentin-Villanueva, J. 2006. A new giant Purussaurus (Crocodyliformes, Alligatoridae) from the Upper Miocene Urumaco Formation, Venezuela. Journal of Systematic Palaeontology 4, 221-232.

Brito, S. P., Andrade, D. V. & Abe, A. S. 2002. Do caimans eat fruit? Herpetological Natural History 9, 95-96.

Brochu, C. A. 1999. Phylogenetics, taxonomy, and historical biogeography of Alligatoroidea. Journal of Vertebrate Paleontology 11, Supplement to Number 4, Memoir 6, 9-100.

Langston, W. 1965. Fossil crocodilians from Colombia and the Cenozoic history of the Crocodilia in South America. University of California Publications in Geological Sciences 52, 1-169.

Comments

  1. #1 John Conway
    February 6, 2008

    Hory carp, what a honker! It almost looks like a whale…

  2. #2 Cameron
    February 6, 2008

    What an amazing beast; it’s hard to believe that an Archosaur as large as the biggest theropods (~10 tons?) was alive so recently. Well, I guess the comparably sized Rhamphosuchus was alive even more recently, but information on it seems even more lacking.

  3. #3 Sordes
    February 6, 2008

    Finally a true monster again! Purussaurus is one of my absolute favorourites among crocodylians, but sadly there is nowhere much information about it. I searched in the whole net but could neither find much information nor much good fotos. My personal speculation is that Purussaurus showed a distinct specialization of break the carapaces of giant turtles like Stupendemys. It huge jaws and the massive anterior part of the snout, as well es the comparably blunt teeth could easily do this, especially if you keep in mind, how flat the carapaces of Stupendemys were. Somewhere I found even a photo of a fossil Stupendemys carapace, which seems to be crashed by a huge crocodylian (also Purussaurus). Manatis would also very well fit in this predators prey scheme, as they are very large but also very slow.
    The jaw morphology of Purussaurus is really interesting, because there seems to be nearly no other crocodylians (okay, you probably know such oddballs)with such a massive snout. Turtles are a common food for many crocs and alligators, but they can only deal with them up to a distinct size, as they normally crush the carapces with thier posterior teeth, where they can bite with most strength. Stupendemys was possibly even for a Purussaurus to big to do this, as the carapace was much bigger than its skull. But if it used its teeth in the strengthened anterior jaw part, it was probably able to crush even the carapaces of turtles, which would be ways too big for any other crocodylian. Perhaps Purussaurus crushed Spupedemys-carapaces from the edges like a monstrous nutcracker.
    Given the fact that crocodiles have in general extremely strong jaws, Purussaurus seems a very good candidate to surpass every other living or extinct carnivore which was at least part-time terrestrial.

  4. #4 Jerzy
    February 6, 2008

    Cool! I didn’t know such monster existed. :)

    I wonder if broad snout could be adaptation to mating/territorial fights? Might be useful if two crocs bite each other noses.

  5. #5 Sordes
    February 6, 2008

    All who think this guy was strange should look for the contemporary Mourasuchus Darren already mentioned…

  6. #6 The Ridger
    February 6, 2008

    Cool. I’m looking forward to the inevitable movie which features these guys being discovered somewhere…

  7. #7 Crazyharp81602
    February 6, 2008

    That skull looks as if it was drawn from a cartoon. That’s what I’m reminded of every time I looked at that skull.

  8. #8 Mike Keesey
    February 6, 2008

    Jeebus!

    I’d heard that Purussaurus was one of the largest suchians ever, but there’s a difference between knowing that little factoid and the visceral impact of seeing those images.

  9. #9 Nick Herold
    February 6, 2008

    Aww… he looks like he’s smiling!

  10. #10 Adam Pritchard
    February 6, 2008

    More obscure, litte-known Cenozoic goodness is always welcome! I’ve done brief internet searches for Purussaurus and Mourasuchus every once in a while with little success. These two (and the equally obscure Rhamphosuchus) have always held a special fascination for me.
    Does anyone know anything more about the formations that these giant Cenozoic crocodylians (not to mention Stupendemys) come from? It would be fascinating to know what kind of ecosystems could drive the evolution of huge, aquatic reptiles deep in the Cenozoic.

  11. #11 Hai~Ren
    February 6, 2008

    Holy shi-

    I remember a photo of Purrusaurus that was a composite of a swimsuit-clad Japanese girl superimposed next to the skull. =)

    Like Sordes, I was actually wondering whether the unique appearance of Purrusaurus jaws hints at a durophagous diet.

    I actually went to do a Google search for Mourasuchus. Er… wha-? I’m surprised at how similar it is to Stomatosuchus.

    We need a post (or bunch of posts) listing out all the giant crocodylomorphs, extant and extinct!

  12. #12 Laelaps
    February 6, 2008

    Like some other people have already said, I had never even heard of purussaurs prior to this post. I’m surprised they haven’t gotten more attention (especially given their size and how geologically recent they were).

  13. #13 Zach Miller
    February 6, 2008

    Geeze! I never new this beastie existed, but I’m going to suggest we throw it in (maybe as a side-sketch) in the Archosauria show that Scott and I are doing in August. What a whopper of a croc!

  14. #14 Alec T
    February 6, 2008

    I agree completely with Hai-Ren. All of these suchuses are messing with my brain.

  15. #15 Darren Naish
    February 6, 2008

    A couple of years ago I approached a few fossil croc workers with the idea of doing a ‘Fossil Crocodilians of the World’ book (think Greg Paul’s PDW, but with crocs!). It petered out… but I think you can all see how awesome it would have been. In frustration, I produced a short article that very briefly reviewed the crocodyliform fossil record. More recently, serious efforts were made by a colleague to get a TV company interested in a TV version of, essentially, the same project. Alas: because the word ‘dinosaur’ wasn’t in the title, this project sank into the morass that has claimed so many other victims, dammit.

  16. #16 Hai~Ren
    February 6, 2008

    I think one of the worst cliches in documentaries these days is to claim that crocodiles/turtles/sharks haven’t changed for hundreds of millions of years. But then again, I’ve lost count of the number of times I’ve heard the claim that rhinos are prehistoric survivors from 50 million years ago (or even from the Age of Dinosaurs).

    And I’d think that a documentary series charting the evolution of the crocodylomorphs a la The Velvet Claw would be totally kick-ass.

  17. #17 David Marjanovi?
    February 6, 2008

    This post is now the 5th most active ScienceBlogs post.

  18. #18 Arnie and the terminators
    February 6, 2008

    YEE-HA! :)

  19. #19 John Scanlon, FCD
    February 6, 2008

    I’m pretty sure I heard the guy in the top photo say, to a lamented compatriot of mine: “That’s not a croc… THIS is a caiman!”
    Actually this line must have been on my mind all day, because earlier (perhaps after looking at some old MAD magazine covers on the NYTimes site) I came up with a version for a poster advertising a fictional product called ‘CrocoDildoDee’.
    Crikey, I’d better get my meds checked.

  20. #20 Nathan Myers
    February 7, 2008

    I suspect that extending the term “dinosaur” to cover everything that lived prior to K-T, and to every extinct reptile, bird, and mammal over 100 kg since, would be a net win. (If Dick Cheney and Exxon can be dinosaurs, why can’t an innocent glyptodont?) Thus far the studios seem not to have discovered that pterosaurs and plesiosaurs aren’t proper dinosaurs, but it’s only a matter of time.

  21. #21 Matt Wedel
    February 7, 2008

    Incidentally, if you’d like to see a picture of Stupendemys, the ridiculously overnormous titanoturtle mentioned by Sordes, there’s one here with me for scale.

    [From Darren: dammit Wedel, that was going to be another 'picture of the day'! Oh well].

    Regarding the suggestion that we call all large cool things ‘dinosaurs’ so we can get idiot TV producers to make shows about them, may I also suggest the general term ‘hellasaur’ (first aired here, third comment down)?

    Nice work, Darren. Keep ‘em coming.

  22. #22 Matt Wedel
    February 7, 2008

    dammit Wedel, that was going to be another ‘picture of the day’!

    Oops. Well, hey, you’re the boss. Just delete that comment, and this one, and no one will be the wiser.

    Or just blog it right now, before it gets stale.

  23. #23 Jerzy
    February 7, 2008

    Just out of interest. In view of recent explosion of gory TV documentaries. Did anybody ever film non-staged croc attacking human, or any other predator attacking human?

  24. #24 Nemo Ramjet
    February 7, 2008

    Wow… its head shape, and your mention of potential herbivory reminds me of hippos for some reason…

  25. #25 Moro
    February 7, 2008

    Wow, that’s great.
    …Too bad it was so funny looking.

  26. #26 Roberto
    February 9, 2008

    The museum in Lima with the Purussaurus its called in spanish Museo de Historia Natural Javier Prado de la Universidad Mayor de San Marcos, not in french Musée d’Histoire Naturelle de Lima, like you named in the update. Sorry for the correction but can be confuse try to find it with a french name and not the original one in spanish.

  27. #27 Jorge
    February 14, 2008

    there is an abstract (the complete work soon) on the paleoecology of giant Tertiary crocodiles from south America in the SVP meeting abstracts, page 120A.

    SIZE AND PALAEOECOLOGY OF GIANT MIOCENE SOUTH AMERICAN CROCODILES (ARCHOSAURIA: CROCODYLIA)

    MORENO-BERNAL Jorge, Universidad Nacional de Colombia, Bogotá, Colombia.

    The free abstracts will be found in pdf format at:
    http://www.vertpaleo.org/documents/JVP07_supplement_to_3.pdf

  28. #28 Nick Gardner
    May 19, 2009

    “I actually went to do a Google search for Mourasuchus. Er… wha-? I’m surprised at how similar it is to Stomatosuchus.”

    Em, I am waiting to receive a PDF of Stromer’s description of _Stomatosuchus_, but not being sure how complete either specimen was, and given that the latter was blown to rubble in WWII, I am a bit curious on this statement!

  29. #30 David Garcia
    January 24, 2011

    they should have this monster on JP4