ODD CREATURES HAVE BEEN ON EARTH FOR MILLIONS OF YEARS

by Whit Gibbons

February 1, 2009

A recent article by Farish A. Jenkins Jr. of Harvard University and colleagues was published in the Journal of Vertebrate Paleontology, a scientific journal that reports research findings based on fossil material. This particular article would be of interest to paleontologists and evolutionary biologists because of the comparisons of skeletal features among fossil vertebrates in general and amphibians in particular. It was of interest to me because it discussed an ancient extinct amphibian that opened its mouth in an unusual manner. Although the creature was bizarre and deserves odd-creature recognition, we should remind ourselves that we have equally strange and remarkable creatures alive on earth with us today.

The fossil amphibian, known by the genus name Gerrothorax, lived about 200 million years ago in the Late Triassic and reached a length of about three feet. It had a wide head and big jaws; its signature trait was that it opened its mouth by lifting the upper jaw rather than dropping the lower jaw like most animals. Presumably the monster sat on the bottom of an aquatic habitat, possibly buried in the sand with only its eyes visible. When a small animal such as a fish or baby turtle swam by, Gerrothorax would lift its jaw rapidly and suck the unwitting prey in as a meal. Cool stuff, to be sure, but before we marvel too much about the capabilities of predators of the past, consider what we still have here with us today.

A dramatic example of mouth movement and feeding mechanisms is that of the matamata, a South American turtle. The matamata has a black and brown shell and body, and crinkly skin on the neck--ideal camouflage as the turtle sits motionless in dark and muddy water. And why would it want to go unseen? Because live fish and other aquatic animals are its prey, which it captures by opening its mouth, quickly expanding its throat, and sucking in the unsuspecting animal. After the powerful suction brings a fish into the matamata's mouth, the predator expels excess water and debris, and then swallows the animal whole.

Another example of an unusual use of mouthparts is the alligator snapping turtle of southern rivers and swamps. These so-called sit-and-wait predators patiently remain in one spot and let their food find them. Fish literally swim into the turtle's mouth as it lies still on the bottom, mouth wide open. The reason fish make such a foolish mistake is because the turtle's tongue is a worm-like appendage that functions as a lure when the turtle wiggles it. The fish sees what looks like a free meal and swims right beneath the hooked beak and into the powerful jaws that snap shut.

To most people, the most impressive feature of the fossil amphibian Gerrothorax would not be its peculiar manner of opening its mouth but instead its large size, approaching that of a basset hound. Typical amphibians of today are tree frogs, stream salamanders, and garden toads, none of which reach more than a few inches in length or weigh more than a pound. Nonetheless a few big amphibians are still with us. A full-grown bullfrog is an impressive sight, but the world's biggest frog, the goliath frog of West Africa, could eat one if given the opportunity. A goliath frog with its legs outstretched is about two feet long. They can weigh around eight pounds.

Some modern salamanders are also large. The secretive amphiuma of southeastern wetlands can reach lengths over three feet. Hellbenders of clear, rocky streams are slightly shorter but because of their more robust body shape can weigh up to five pounds. The largest salamanders in the world are in Japan and China. They are related to hellbenders, some reaching lengths of more than five feet.

Animals that lived on earth millions of years ago have a certain fascination for most of us, and we are intrigued with what paleontologists can tell us about the behavior of these long-extinct creatures. But an eight-pound frog, a five-foot salamander, and a snapping turtle with a worm-like tongue are intriguing in their own right. And those are only three of the many natural wonders still with us today.

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