Archive for the ‘Two-Dog-Night Tetrapods’ Category

Party time! Let the media onslaught begin! We’ve published a paper in Nature on the limb motions of Ichthyostega (and by implication, some other stem tetrapods). Since we did use some crocodile specimens from Freezersaurus (see below) in this study, I figured WIJF could cover it to help celebrate this auspicious event. Briefly. Particularly since we already did a quasi-blog on it, which is here:


and some juicy fossily images at:


However I want to feature our rockin’ cool animations we did for the paper, to squeeze every last possible drop of science communicationy goodness out of them. So here they are in all their digital glory. Huge credit to Dr. Stephanie Pierce, the brilliant, hardworking postdoc who spearheaded the work including these videos! Dr. Jenny Clack is our coauthor on this study and the sage of Ichthyostega and its relatives- her website is here. Also, a big hurrah for our goddess of artsy science, Julia Molnar, who helped with the videos and other images. Enjoy!

The computer model

The forelimb model

The hindlimb model

We used some of my Nile crocodile collection to do a validation analysis of our joint range of motion (ROM) methods, detailed in the Supplementary info of the paper, which I encourage anyone interested to read since it has loads more interesting stuff and cool pics. We found that a bone-based ROM will always give you a greater ROM than an intact fleshy limb-based ROM. In other words, muscles and ligaments (and articular cartilage, etc.). have a net effect of reducing how far a joint can move. This is not shocking but few studies have ever truly quantitatively checked this with empirical data from whole animals. It is an important consideration for all vert paleo types. Here is a pic of one of the crocodiles from the study, with (A) and without muscles (B; ligaments only):

I’ll close with Julia Molnar’s jaw-droppingly awesome flesh reconstruction from our model. Why Nature wouldn’t use this as a cover pic, I’ll never understand, but I LOVE it! When I first saw it enter my email inbox and then opened it to behold its glory, my squeal of geeky joy was deafening.

(edit: Aha! Fellow Berkeley alum Nick Pyenson’s group made the Nature cover, for their kickass study of rorqual whale anatomy, including a “new” organ! Well, we don’t feel so bad then. Great science– and a win for anatomy!!!)

Read Full Post »

I’m gearing up for a major post with lots of striking pictures from The Freezers, but to tide you over, here’s a simple movie from one of my CT scans of a Hellbender salamander (Cryptobranchus alleganiensis; with a supportive rod down its GI tract; this was a museum specimen that apparently needed the rod to keep its body straight). We’ve scanned loads of salamanders and other cool critters for our NERC-funded project on the evolution of terrestrial locomotion in the earliest tetrapods (more about that coming up in a future post, as we have some Big News from that study!); this is just one of them.

The huge gaps between limb joints indicate extensive articular cartilage (typical of many aquatic animals, especially some amphibians) and would make a sauropod jealous. The relatively homogenous vertebral column, without much differentiation from head to tail, is also striking, contrasting even with that observed in animals with vaguely similar locomotor styles such as lizards; not to mention mammals, which take that regionalization to an extreme. Also, like most (all?) salamanders, this one has almost no ribs — this is a secondary reduction during their evolution; early fossil tetrapods had nice big ribs. But those ribs aren’t useless (they play a role in moving and breathing), and at least one caudate (member of the broader salamander group) has evolved a very cool use for them!

Read Full Post »

« Newer Posts