Your Daily Fossil

Metoposaurus

Mounted specimen from the Krasiejów Museum in Poland.

When: Mid Triassic (~228 - 216 Million Years Ago)

Where: Europe and North America

What: Metoposaurus is an amphibian that lived on the northern continents during the mid Triassic. It was very large compared to modern amphibians, at 10 feet (3 meters) long and weighing an estimated 1000 lbs (450 kg), but these large amphibians were typical of this time, and for tens of millions of years previously. Its limbs are fairy small and weak for its body size, leading researchers to conclude it spend much of its time in the water. Its head was very well adapted for catching fish, with its dozens upon dozens of needle like teeth. Its head was extremely flat, again typical for these amphibians. A flat head like this would have allowed it to breath and look over the surface of the water with out causing disturbances which would have scared away fish. The flat head of Metoposaurus would also allow it to wait at the surface with out easily being seen by predators on the shore. Large groups of Metoposaurus have been found in some areas, in what appear to be pools that were drying out. These animals clustered together in the last remaining water there was during droughts, but alas, the rains didn’t return again in time.

Metoposaurus fairy typical member of the Temnospondyli. This group is known from most of the continents from the Carboniferous to the Triassic, with some species making it all the way to the Cretaceous. Temnospondyls include the largest amphibians ever known, some of them easily dwarfing Metoposaurus. All of these large forms still spend a lot of time in the water, shown by a variety of skeletal features, such as the weak limbs seen in Metoposaurus. It is uncertain how the temnospondyls are related to the rest of Tetrapoda. They are farther down the tetrapod line than Pederpes, but past this there is a lot of controversy. Some researchers place them as outside of crown tetrapods (modern amphibians + amniotes), while others place them on the line leading to the modern amphibians (frogs, salamanders, and caecilians). It is also very likely that Temnospondyli is not even a natural group, and that some species are closer to amphibians than others.

Did I mention they have really really flat heads?