Dead Things!

By Ray Hopkins

This is skeleton and skull of a Black Spiny-Tailed Iguana (Ctenosaura similis). I’m not sure if it was a male or female, but I found it while hitting softballs out into the soccer field and brought it back to the station for an ID. At first I thought it might be a snake, but the teeth are too flat and indicate a more vegetarian diet, which, combined with the size of the skeleton, points to a big lizard. Ctenosaura similis is the only iguanid species at the field station, so it was an easy deduction. What was really cool however wasn’t the species discovery itself but the teeth.

      There are two kinds of lizard teeth, pleurodont and acrodont. Acrodont teeth have no roots, and as a result are fused to the top of the alveolar ridge. If these teeth fall out, they cannot be replaced in adulthood. This kind of dentition is common in amphibians and reptiles. However, these are pleurodont teeth. Lizards can have acrodont teeth, but pleurodont teeth are lizard-specific. Pleurodont teeth are attached to the rim of a jaw. Fellow student Michael spotted this and noted that the teeth, as you can see in the second image, are pushing outwards rather than being straight up and down.

A drawing of reptile dentition, courtesy of Wyneken, J. “Anatomy and Physiology of the Reptile Mouth.” Pet Education, PetCo Wellness, www.peteducation.com/article.cfm?creference,

In addition to finding deceased Ctenosaurs, I also found a very large and very dead toad this morning, likely a deceased Cane Toad, Bufo marinus. I didn’t think much of it, other than that it was pretty neat because I had never seen the carcass of an amphibian that had fallen prey to a predator. All the dead amphibians I had previously seen had been hit by cars or were cooked on the side of the road or fell victim to a parasite. There was never much to see until now. It looked like something had just ripped it straight down the middle and scooped out its innards as if with an ice cream scooper. It was really neat, the skin was discarded like a used plastic bag and the bones picked clean. What it really reminded me of was the movie “Cocoon” when the aliens discarded their human skin to show the old people their true selves. Over the course of the rest of the week that we were at the Palo Verde station, I saw dozens more disemboweled Cane Toads, and it never ceased to be a strange sight. One night, a group I was not a part of went hiking just as the rain began and saw a Cane Toad dragging itself along by its two front legs because its back legs had had the flesh sucked from them by a predator and they were now useless. I imagine that something, likely an opossum, either finished it off or it crawled into the tall grass to die.

When I got back to the field station. I showed one of the professors the picture and he said that because the frogs here have such toxic skin, the animals have evolved to flip them onto their backs and remove the meat through the belly so as never to touch the skin. Indeed, even after this they still refuse to eat the skin and instead leave it to the snakes. I found that super interesting. Imagine if the Australian fauna evolved to turn Cane Toads inside out, I’m sure that’d solve most of Australia’s problems right there. Buuuuut, on the other hand if they did catch on to that strategy we might not have the “Cane Toads: An Unnatural History” video so I’ve got some mixed feelings.

Finding dead reptiles or amphibians is usually not a common occurrence for me, largely because I live in a heavily fragmented area and reptiles and amphibians are no longer nearly as common as they were when I was in elementary school. Walking outside and seeing the evidence of thriving predator-prey relationships was pretty neat; usually the only deceased amphibians I find are killed my cars and there aren’t any interesting observations to be made. In the ripped body of one of the Cane Toads I observed later in the week was the partially digested body of a snake. I can only imagine that it must have been one upsetti spaghetti.