Monday, 10 May 2010

Mothers Day Tale: Saving a seaturtle

This blog is inspired by a very special mother’s day tale. I was helping with a Seaturtle patrol on a Grenadine Island, witnessing my first ever leatherback: a massive creature relatively unchanged since the Cretaceous, among the dinosaurs. The poor creature was ensnarled in a fisher net, cutting into its own flesh as it struggled to bury its eggs. After a grueling half-hour of sawing, cutting and imploring her to stay, we managed to free her. What a great mother’s day, to let one mother live and give life another day.

It got me thinking about Reptiles. The very word is troubling to taxonomists, unlike the monophyletic mammals, it is not so neat and tidy. The Chelonia, the turtle/terrapin/tortoise clad, split off of from the Diapsids (the group containing all other lizards, dinosaurs, birds and crocodiles) some 200 million years ago, contained within the Sauropsids, the class generally thought of as reptiles.

The problem is that genetics and morphology show that Birds, once thought of as a grand class on equal rank as mammals, reptiles, etc., is nestled within the Reptile clad. In fact, a goose is more closely related to a crocodile than a turtle, i.e., they share a more recent common ancestor to crocodiles than they do with Turtles. They also share a more recent ancestor with geckos, monitor lizards, caymens, and most of other “reptiles” than the very reptilean-looking Turtles.

The confusion is that the Sauropsids are a very fragmented and persecuted group. Had it not been for the asteroid that whipped clean the dinosaurs, and could have had before us a continuous gradient of morphologies from a crocodile to a cormorant: big and small, scaled and feathered, beaked and toothed, all the extinct intermediates would be obvious to such a lucky taxonomist, who would easily classify all these things --all lizards and birds and dinosaurs -- as being related without batting an eye. Our laymen language would do away with a “reptile” word altogether, instead having something unique for the birds/lizards/dinosaurs (Diapsids) and the turtles (Chelonia).

Perhaps this uniqueness of the sea turtles is their alien allure. Staring into the snapping, jagged maw of the wounded mother, was like staring into an ancient earth.

No comments:

Post a Comment