eupelycosauria

Weird Backs Month #03 – Ianthasaurus

The synapsids diversified rapidly following their first appearance in the geologic record, and two particular families developed large showy sailbacks completely independently of each other: the edaphosaurs and the sphenacodonts.

Ianthasaurus here was a basal edaphosaur, known from the the Late Carboniferous of Kansas, USA (~302 mya). It was smaller than many of its more famous relatives, only about 75cm long (2′5″), and seems to have been an insect-hunting predator.

Its sail featured “cross bars” sticking out from the main spines on the front two-thirds or so of its body. The purpose of these extra ornaments is unclear – but they must have been useful for something because later edaphosaurs sported them much more extensively.

Weird Backs Month #04 – Lupeosaurus

Lupeosaurus was another edaphosaur, known from the Early Permian of Texas, USA (~298-295 mya). Only a few fragmentary fossils have been found, but it was probably an insectivorous species, around 60cm long (2′), about 3m long (9′10″), and seems to have had unusually beefy limbs – suggesting it was a relatively powerful predator.

Unusually for an edaphosaur, its sail completely lacked the characteristic cross-bars, which led to confusion over its classification when it was first discovered. With so much of its skeleton still unknown, however, it could still turn out to be even more unusual if other fossils are ever found.

It was also originally named as Luperosaurus, but was later changed when the first specimen turned out to actually be the pelvis of the amphibian Eryops, making the original name an invalid synonym. It was re-described with new material with its current name, which was fortunate because the original name would have eventually had to be changed anyway due to it being preoccupied  – Luperosaurus was already assigned to a type of gecko.