Today’s edition of Nature carries an article describing the most primitive tetrapod (four-legged creature) ever discovered. The creature, thought to have lived 365 million years ago, is ten years younger than the infamous Tiktaalik, but while Tiktaalik is thought to have more characteristics of fish than of tetrapods, the new discovery is thought to be a true tetrapod.
Some interesting notes:
The creature, named Ventastega curonica, is not the oldest tetrapod ever discovered, but it is the most primitive. This means that its features are more similar to fish (the ancestors of all land animals) than any other known tetrapod. This seems out of sequence with the usual trend in the fossil record, where more primitive animals are found in older rocks, and more complex creatures are found in newer ones. Because of this, the study’s lead author, Per Ahlberg, does not think that Ventastega is an ancestor of modern tetrapods, but rather an evolutionary branch that died out sometime in the past. That would have made it something of an evolutionary holdover in its time, somewhat like horseshoe crabs and egg-laying mammals today.
At the site in Latvia, no legs were found, but researchers were able to deduce that Ventastega had four legs through the shape of the pelvis and of other joints. Parts of the skull, shoulders and pelvis were all that was turned up.
Ventastega was probably three to four feet in length, and probably ate fish. It probably lived in shallow water, where its legs allowed it to move more efficiently than fins would have done. (Scientists say “probably” a lot.)
I love stories like this! Let’s hope paleontologists keep unearthing these key bits of the story of life.