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.