Hypselorhachis

Hypselorhachis is a genus of extinct reptile, possibly a ctenosauriscid archosaur related to Ctenosauriscus. It lived during the Triassic Period. It is currently known only from a single vertebra found from the Middle Triassic Manda Beds in Tanzania. The vertebra is preserved in reasonably good condition, as although the tall neural spine is chipped in several places it is not broken despite being quite slender, only around 20 mm thick transversely.

The type species is H. mirabilis, mentioned but never fully described by English paleontologist Alan J. Charig. Hypselorhachis was assigned to the Ctenosauriscidae, a group of sail-backed archosaurs, in 1988. It was formally described by Richard J. Butler and co-workers in 2009. The name means 'wonderful high spine', from the Latin 'mirabilis' 'wonderful' and the Greek 'ὑπσελος', 'high' and 'ῥαχις' 'spine' or 'backbone'. Hypselorhachis was probably at least 3 metres long, maybe up to 4 or 5 metres, as the vertebra is certainly from quite a large animal.