• Tag Archives filter feeding
  • Bad-ass shield crocs, or: Another weird Mesozoic crocodyliform

    Aegisuchus witmeri goes to town on a Mesozoic lungfish. Illustration by the talented Henry Tsai

    Oh hey look, the blog has come to life again, if just for a bit. As has been typical these few years, things IRL have taken up much of my time and the website has suffered because of it. I still have a few posts that I have been sitting on as I try to find the time to finish them. Until then small updates like this will have to do.

    Just announced today in the journal PLoS ONE:

    Holliday, C.M. and Gardner, N.M. 2012. A New Eusuchian Crocodyliform with Novel Cranial Integument and Its Significance for the Origin and Evolution of Crocodylia. PLoS ONE 7(1): e30471. doi:10.1371/journal.pone.0030471

    Congratulations to the internet’s own Nick Gardnerfor helping get this guy published.

    Stomatosuchus was the quintessential "duck faced" croc. Illustration by Dmitry Bogdanov

    The croc in question — Aegisuchus witmeri— was a member of the Aegyptosuchids. They were a strange group of eusuchians that are known mostly for their weird, flat “duck faces.” As there are no living crocodylians that even come close to these guys in skull shape, it is difficult to imagine what these guys were doing with these flattened rostra. One hypothesis was that, given their numerous small teeth, these guys were filter feeders.

    Holliday and Gardner describe a preserved braincase and compare it to other published data on Aegyptosuchids. Results suggest that this guy was huge by modern croc standards (~9 meters) and no slouch for a Mesozoic croc. Muscle scars indicate the presence of strong jaw opening abilities in this taxa, which would go well for a possible filter, or suction feeder.

    Probably the most interesting feature of this guy, and the one likely to spark the most controversy, was the presence of an enlarged boss on the top of the skull. Inferred vasculature to this region suggest that Aegisuchus witmeri was using this part of its skull for something. That thing might have been a display structure such as an “eyespot” or just a particularly bright patch of skin. Though speculative, there are reasons to consider this possibility, including the fact that extant crocodylians use their heads in all manner of displays.

    All in all this was a pretty cool critter. The species epithet was named in honour of professor Lawrence Witmer, PhD, prolific paleontologist, comparative anatomist and even blogger. He is my mentor and was Dr. Holliday’s back in his PhD days. It might not be Archaeopteryx, but getting named after a bad-ass ancient crocodile isn’t half bad.

    ~Jura

     


  • New paper on the strangest pterosaur ever.

    Ooh, I’m coming in under the wire this time (see the time stamp).

    So when someone talks about pterosaurs, or flying reptiles, you probably think of something like one of these:

    PteranodonRhamphorhynchus

    Pteranodon and Rhamphorhynchus. The two archetypes of pop culture pterosaurs.
    Former image from here. Latter image by Charlie McGrady.

     

    Few folks would normally think of this as a normal pterosaur:

    Pterodaustro

    Pterodaustro guinazui (pic culled from Wikipedian artist: Arthur Weasley).

     

    Its name was Pterodaustro guinazui, and unlike other pterosaurs, which fed on fish, insects, or other types of meat, P. guinazui was a filter feeder. It has commonly been compared to a Mesozoic flamingo (thus resulting in more than a fair share of flamingo like drawings). It sifted microorganisms from the waters that it lived near. Unlike today’s modern flamingo (Phoenicopterus), Pterodaustro could filter feed without dipping its head upside down. As far as pterosaurs go, it was certainly one of (if not) the strangest species to have come from this group.As is typical with the weird ones, though they are celebrated for their uniqueness; that is about all that is known about them.

    Well, no more:

    Chinsamy, A., Codorni?, L., Chiappe, L. 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters. DOI: 10.1098/rsbl.2008.0004 (online: first cite)

    Abstract
    Life-history parameters of pterosaurs such as growth and ontogenetic development represent an enigma. This aspect of pterosaur biology has remained perplexing because few pterosaur taxa are represented by complete ontogenetic series. Of these, Pterodaustro is unique in that besides being represented by hundreds of individuals with wing spans ranging from 0.3 to 2.5m, it includes an embryo within an egg. Here we present a comprehensive osteohistological assessment of multiple skeletal elements of a range of ontogenetic sizes of Pterodaustro, and we provide unparalleled insight into its growth dynamics. We show that, upon hatching, Pterodaustro juveniles grew rapidly for approximately 2 years until they reached approximately 53% of their mature body size, whereupon they attained sexual maturity. Thereafter, growth continued for at least another 3–4 years at comparatively slower rates until larger adult body sizes were attained. Our analysis further provides definitive evidence that Pterodaustro had a determinate growth strategy.

    Pterodaustro skull

    Pterodaustro guinazui skull (photo from: http://www.pterosaurier.de)

     

    I have yet to read the full paper, but from what it says here, it would appear that the filter feeding lifestyle took its toll on P. guinazui, as its growth rate was remarkably slow. As this is the first time a growth series has been done on a pterosaur, it probably shouldn’t be assumed that this growth was typical of all pterosaurs (which would have had diets that were much higher in protein, thus aiding growth). Still the results are definitely interesting. Plus any new bits of info on the world’s strangest pterosaur, is a good thing in my book.

    ~Jura