If you dug up a fossil that looked like a circular saw blade made of teeth, you’d be forgiven for being a little confused. Was it some sort of toothy nautilus? A relic of a dinosaur’s carpentry shop?
When Helicoprion (meaning “spiral saw”) was first discovered in 1899, its whorl of teeth was one of the few things identified. Even though there were few skeletal clues, it was quickly decided that these teeth were from a cartilaginous fish. But where did these “teeth” fit in? On the body? Some freaky mouth appendage?
Over a century of confusion followed, but recent work using X-ray analysis of fossil specimens has all but confirmed that this fish used a spiral-fed whorl of teeth, constantly regrowing as today’s sharks do, to catch soft prey like squid, 270 million years ago. It’s actually not a shark at all, but a ratfish, a branch of cartilage-skeletoned fish that branched from sharks in prehistoric times.
Check out more great analysis by Brian Switek at Laelaps. He also features even more great art by Ray Troll, a Helicoprion aficionado who did the image at top.
Fossils of Enigmatic Sea Creatures Surface
by Sid Perkins
New fossil finds reveal that an enigmatic seafloor dweller first described more than a decade ago was armored and much larger than its modern-day kin. Cotyledion tylodes had a goblet-shaped body that surrounded a U-shaped gut (dark feature in fossil at left; arrows denote flow of food), and the animal spent its life anchored to the seafloor or to hard objects that had settled there, such as the molted exoskeletons of trilobites (artist’s representation at right). C. tylodes was first described in 1999 based on a couple of fragmentary fossils unearthed from 520-million-year-old rocks in southern China.
Previously, some scientists have proposed that the tentacled creatures were related to cnidarians, a group that contains jellyfish. But analyses of the new fossils—hundreds of well-preserved specimens extracted from the same ancient rocks—reveal that the animals belong to a group called entoprocts, aquatic creatures that attach to surfaces and filter their food from passing currents, the researchers report online today in Scientific Reports…
(read more: Science NOW)
(images: Zhifei Zhang et al., Scientific Reports)
The sketch I’m going to be taking to final to submit with the book proposal going to Johns Hopkins University Press! Gotta make a few tweaks here and there, but I’m really excited to finish this in the next few days. Then I’ll get back to the cranes. :)
The Turrilitacaeae is a diverse superfamily of Cretaceous ammonites generally considered as heteromorphic… Shells of this diverse group did not coil planospirally, as typical for most ammonites, but rather took on a variety of unique forms. As with other ammonites, the last of the Turrilitaceae had perished by the end of the Cretaceous during the Cretaceous–Tertiary extinction event… (read more: Wikipedia)
(image: Hamites sp. by Neale Monks)