Excerpts from Jim Conrad's
from the July 10, 2005 Newsletter issued from the Sierra Nevada foothills
somewhat east of Placerville, California, USA
SOUTHERN ALLIGATOR LIZARD
Back at the house Daniel welcomed me with a present: A Southern Alligator Lizard, GERRHONOTUS MULTICARINATUS. I'd been looking for one of these because it's a bit unusual, despite the fact that it's abundant and frequently seen here, and it looks a lot like the normal fence lizard, which we also have.
In fact, at first I had a hard time distinguishing alligator lizards from fence lizards. It must be a case of convergent evolution because the two species are very unrelated, being in entirely different families and even suborders. You can see the taxonomic relationships among different kinds of lizards on my Lizard Classification Page at www.backyardnature.net/lizclass.htm.There you'll observe that alligator lizards are about as unrelated to average lizards (iguanid lizards) such as fence lizards and anoles, as are Gila Monsters.
One difference between alligator lizards and "regular lizards" is that their have bony scales (osteoderms) encasing them so effectively that their bodies are fairly stiff. So stiff, in fact, that the critters would have a problem breathing were it not for a lengthwise flexible groove of soft granular scales along each of their sides.
That groove of soft granular scales is the reason I'd been looking for an alligator lizard, because I wanted to photograph it. As I held the lizard Daniel took a picture and it came out terrific. You can clearly see that band as well as the external ear opening below: