Pareiasaur

Description

Pareiasaurs ranged in size from 60 to 300 centimetres (2.0 to 9.8 ft) long, with the largest pareiasaurs like Scutosaurus and Bradysaurus estimated to exceed 1,000 kilograms (2,200 lb) in body mass. The limbs of many parieasaurs were extremely robust, likely to account for the increased stress on their limbs caused by their typically sprawling posture. The cow-sized Bunostegos differed from other pareiasaurs by having a more upright limb posture, being amongst the first amniotes to develop this trait. Pareiasaurs were protected by bony scutes called osteoderms that were set into the skin. Their skulls were heavily ornamented with bosses, rugose ridges, and bumps. Their leaf-shaped multi-cusped teeth resemble those of iguanas, indicating a herbivorous diet. The body probably housed an extensive digestive tract. Most authors have assumed a terrestrial lifestyle for pareiasaurs. A 2008 bone microanatomy study suggested a more aquatic, plausibly amphibious lifestyle, but a later 2019 study found that the bone histology provided no direct evidence of this lifestyle, a conclusion also supported by a 2014 isotopic study, which found support for a terrestrial ecology.