Painted turtles, Chrysemys picta, are perhaps the most-eye-catching creatures on my pond. They’re not rare: this spring there were eight on a log, basking:
One got wedged in a rotted tree stump. I was all ready to rescue it next day, but it managed to extricate itself.
There were three on a fallen tree some weeks later.
Two dived off when they saw my kayak but the smallest and youngest (and thus the most rash and least intimidated) let me get very close, so I can show you some details.
They have beautiful eyes,
with top and bottom eyelids, both closed in the next photo:
They don’t have teeth, but they do have ‘tomiodonts’ (my word of the week). Look at the center of the upper lip in the next two photos:
There are two bicuspid tooth-like things, with a notch in between.
Despite appearances, these are not teeth. Turtles have horny beaks made of keratin (think fingernails) that they use to grasp and crush food, and many species have a notch in the upper beak, flanked by two or even three tooth like tomiodonts. Their function is rather mysterious. Three explanations have been advanced. First, and most obviously, they may be useful in feeding, especially in immobilizing prey. Second, the fact that they are typically somewhat larger in males supports the idea that they may be used to immobilize the hapless females during mating. And third, they may be hangovers from some much much earlier ancestral species, and were perhaps just “spandrels”, in the sense of Stephen Jay Gould, by-products of some other evolutionarily-favored development.
And a parting wave goodbye!
PS If you’d like to know more, read Moldowan et al 2015. He was bitten by one, and it drew blood, so they are effective tools/weapons.