Page 125 - Prehistoric Animals

Sea-More-Ea

Seymouria

Seymouria (from Seymour (USA)) is an extinct genus of
seymouriamorph*. It roamed the planet in the Early Permian
around 251 million to 299 million years ago. They were fairly
small, only about 60 cm in length. Fossils of Seymouria were first
found near the town of Seymour, Texas in 1882 and named by:
Ferdinand Broili, in 1904

Seymouria stout body was robustly-built but rather small.
It was rounded on top with a flat underside and it tapered off to a
longish broad tail; it looked almost reptilian. Its head was large
and triangular shaped with jaws lined with sharp teeth, typical of
a carnivorous animal who dieted on, insects, small reptiles, and
possibly small amphibians. It had large pineal eyes midway down
the length of its head. Its neck was short and its limbs muscular
with broad four-clawed feet. When on land it could raise itself
well off the ground; an elevated stance common in reptiles. How-
ever, Seymouria was not a reptile it was an amphibian.

For a long time after it was first discovered, Seymouria
was thought to be a primitive land based reptile. However, this
changed when juveniles of the species were found to use gills for
breathing, typical of amphibians. This meant that adult Sey-
mouria, once amphibians themselves, had to return to the water
to lay its eggs. In the hot arid conditions of the time, they may
have had to return to the water regularly just to cool down. This
was an important discovery and led many to believe Seymouria
must have been an early transitional species. Numerus studies
have confirmed this hypothesis and it’s now generally accepted
that Seymouria, if not the first, was one of the earliest transition-
al species; the transition from amphibians to primitive reptiles.

Seymouria disappearance is unclear. Some blame the Per-
mian-Triassic extinction event that killed off a large percentage
of terrestrial and marine species. However, the more popular
view is that it simply died out due to climatic change that slowly
eroded its environment.

*Seymouriamorpha… (Wikipedia)
were a small but widespread group of limbed vertebrates (tetrapods).
They have long been considered reptiliomorphs, and most paleontologists
may still accept this point of view, but some analyses suggest that seymour-
iamorphs are stem-tetrapods (not more closely related to Amniota than to
Lissamphibia). Many seymouriamorphs were terrestrial or semi-aquatic.
However, aquatic larvae bearing external gills and grooves from the lateral
line system have been found, making them unquestionably amphibians.
Seymouriamorphs form into three main groups, Kotlassiidae, Disco-
sauriscidae, and Seymouriidae, a group that includes the best known genus,
Seymouria.