Saturday, January 12, 2008

Drawings of little-known lizards, or parts thereof. II.

"Hello there. I'm not a drawing. That is yet to come. I'm a male Broad-headed Skink, Plestiodon laticeps (formerly Eumeces laticeps), from the south-eastern United States."

Aerial view, complete with museum tag.

A remarkable thing about Broad-headed Skinks is that unusual broad head (in the males).

A more typical skink looks like this Bermuda Rock Lizard, Plestiodon longirostris (although to be fair this is a youngster, and a Broad-headed male of the same age would not yet be broad-headed.) Most Plestiodon (a genus found throughout North America, Bermuda, and eastern Asia) show head-broadening in males to some degree, but it is most conspicuous in some of the largest species. Another way of referring to the phenomenon is "sexual dimorphism," which in many ways makes the world go around. Here's what happens in these animals:

Here are drawings (as advertised) of P. laticeps skulls, viewed from behind (c & d). The top is a juvenile, the bottom an adult male. For those keeping score, the top skull was 15.9 mm long, the bottom 27.5 mm long. Things a and b are quadrate bones (front view), which are the ear-like bones on the bottom corners of the skulls in c and d. The scale bars = 5 mm. On these bones the muscles to the mandibles (the biting muscles) originate, and the more the merrier. In large males the quadrate bones expand impressively, creating formidable biters, all the better to fend of rivals during breeding season, or herpetologists. The heads of ardent males become bright red too, to warn you it's gonna hurt.

There is no sensible reason on this planet to become a herpetologist. It is all just heartbreak and pain. Really.

"Like we care. It was one of you guys who put us in that jar."

Male and female P. laticeps, showing sexual dimorphism in head shape. Unfortunate about the female's tail. Things tend to drop off.

For a slightly cheerier ending, back to Bermuda to see a live and frisky Plestiodon longirostris (not the Broad-headed skink) emerging from a crevice, unaware it is critically endangered.

It is all just heartbreak and pain. Really. And it will not pay your mortgage.

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