The Little Placoderm Who Could

Bothriolepis

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When one considers the placoderms, the image of Dunkleosteus terrelli probably comes to mind. However, the class is much more diverse than the arthrodires, with a myriad of body forms arising over the group’s fifty million year run. Bothriolepis is a good example of this. Though they share armor plating, the similarities between these general seem to end there. Size, for instance, provides a stark contrast. Dunkleosteus grew to between twenty and thirty feet long, with a head up to four feet wide, whereas the diminutive Bothriolepis had a head only four inches wide (Waggoner, 2000).

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Bothriolepis lacks the craniovertebral joint of the arthrodires that allowed its chondrocranium to rise as its splanchnocranium drops. However, this may have allowed for a larger braincase in this benthic creature (Young, 1984). This genus, along with the rest of the placoderms, went extinct in the Mississippian Period with no modern relatives. The reason for placoderm extinction, especially when members of Class Chondrichthyes survive today, is mysterious.
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Young, G.C. (1984). “Reconstruction of the Jaws and Braincase in the Devonian Placoderm Fish, Bothriolepis .” Palaeontology, Vol. 27 (3), 635-661.
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Waggoner, B. (2000). “Introduction to the Placodermi.” Retrieved 29 Mar 2008 from http://www.ucmp.berkeley.edu/vertebrates/basalfish/placodermi.html.

To Be or Not to Be ... an Acanthodian

Groenlandaspis disjectus

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Found in the Upper Devonian (~365 million years ago) of Scotland, Cosmacanthus malcolmsoni caused a bit of confusion when it was unearthed in the mid-1800's. It had a peculiar spine that seemed to place it with the members of Class Acanthodia, which all sported a spine structure on their dorsum and venter that had membranous connections to the body mass. However, upon further comparison, the difference between C. malcolmsoni and acanthodians widened, and it was placed in Class Placodermi. Newman (2004) reviewed this taxonomic revision and found it to be better, seeing as it is similar spinal plates to, and was nearby, the known placoderm Groenlandaspis disjectus.

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Newman, M.J. (2004). “A Systematic Review of the Placoderm Genus Cosmacanthus and a Description of Acanthodian Remains from the Upper Devonian of Scotland.” Paleontology, Vol. 48 (5), 1111-1116.

Was It Ever Safe to Go in the Water?

Guarinisuchus munizi

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In what I'm sure will be a long line of blogging on ScienceBlogs posts as well as on peer reviewed research - and sometimes both - here is a summary of a post from Laelaps on a new crocodilian, G. munizi. After the K-T extinction that finished off the non-avian dinosaurs, especially the monstrous aquatic mosasaurs, the three-meter long archosauromorph fluorished. These sauropsids have a Gondwanan distribution, most likely moving from North Africa to the (then nearby) South America. G. munizi would certainly have made a snack out of the other major group filling the space left by the absent dinosaurs - mammals.

What Big Teeth You Have

Smilodon populator

An interesting piece of research published recently describes what it perceives to be the point of such long canine teeth in Smilodon and members of Nimravidae. Initially conceived to rend wounds into their prey, it has been shown that such force would snap those teeth right off. New tests propose a stabbing motion. Whether mainly for slicing or stabbing, the awe at this spectacularly singular dentition remains.

Introductions

The point of this blog, at its inception, is to chronicle experiences while partaking in a research internship with the Calvert Marine Museum's paleontology department. However, that is not to say other material will not appear here, or that were will be regular upkeep of this space. Expecting greatness from this piece of the interwebs is certainly setting oneself up for disappointment. For a random diversion, story, photo, or link, this page might be something of a useful timekiller. Hey, one might even learn a thing or two. No promises.