Unknown at the time of this writing!: Gerrothorax - amphibian

I'm beginning this blog by going through the book Dinosaurs: Discover the World of These Amazing Prehistoric Creatures, published by Igloo. (Authors unnamed, but it's a teen's book). They started with Eryops, then moved on to Gerrothorax. This book doesn't mention the first time that bones of any amphibian, dinosaur or so on were found, so I conduct research, starting first with Wikipedia. That worked with Eryops, but was useless for Gerrorthorax. But I can't find out anything on the web about when this creature was first discovered. There were some news articles about it in 2008, but it's listed in Palmer, D., ed 1999 book: The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions

Gerrothorax ("Wicker Chest") is an extinct genus of temnospondyl amphibian from the Triassic period, found in Greenland.

"Gerrothorax is one of a group of odd amphibians called plagiosaurs with no modern descendants that vanished along with numerous other species 200 million years ago in a mass extinction at the end of the Triassic Period. Its fossils were found in the Fleming Fjord Formation of east Greenland." (Reuters, Ancient armored amphibian had world's oddest bite)

Gerrothorax was about 1 metre (3.3 ft) long, and had a remarkably flattened body. It probably hid under sand or mud on river and lake bottoms, scanning for prey with its large, upward-facing eyes. Gerrothorax had an unusually shaped skull with angular protrusions on the sides. This looked vaguely similar to the skull of the earlier, unrelated, amphibian Diplocaulus, but was not so developed.

Fossils have shown that Gerrothorax was pedomorphic, retaining its larval gills as an adult. This is also seen in some modern-day salamanders, such as the mudpuppy, the axolotl, and the olm. Gerrothorax had three pairs of external gills allowing it to breathe under water.

A 2008 study showed that Gerrothorax lifted its head rather than dropping its jaw when catching prey, which has been compared to how a toilet seat opens.