Sclerosaurus armatus (Meyer 1859) Middle Triassic ~50 cm in length, was originally considered a procolophonid, then a pareiasaurid, then back and forth again and again, with a complete account in Sues and Reisz (2008) who considered it a procolophonid. After Procolophon, Sues and Reisz (2008) considered Tichvinskia, Hypsognathus, Leptopleuron and Scoloparia sister taxa to Sclerosaurus. These all nest with Diadectes in the large reptile tree, not with pareiasaurs.
Here, based on data from Sues and Reisz (2008), Sclerosaurus nests between pareiasaurs and basal softshell turtles like Arganaceras, Odontochelys and Trionyx. It is a sister to Elginia and Meiolania. This is when soft shell turles split from hard shell turtles.
Overall smaller than other pareiasaurs, Sclerosaurus had a wide, flat body, like the horned lizard, Phrynosoma. The backbone remained quite flexible, as shown by the fossil (below). Only a sparse sprinking of dermal bones lined the dorsal vertebrae. Note the hypoischium posterior to the ischium and the position of the pectoral girdle anterior to the dorsal ribs. |
