Istiorachis

Istiorachis (meaning "sail spine") is an extinct genus of iguanodontian ornithopod dinosaur from the Early Cretaceous (Barremian age) Wessex Formation of the Isle of Wight, England. The genus contains a single species, Istiorachis macarthurae, known from a partial postcranial skeleton including several vertebrae, incomplete ribs, and part of the pelvis. Its vertebral are notably elongated, giving the animal a 'sail-backed' appearance.

== Discovery and naming == thumb|left|Holotype tail vertebrae with elongated neural spines The holotype specimen, MIWG 6643, was discovered by Nicholas Chase in a rock bed of plant debris representing outcrops of the Wessex Formation near Grange Chine on the Isle of Wight, England. It consists of several vertebrae (one cervical (neck), eight dorsals, part of the sacrum, and seven caudals (tail)), three dorsal rib heads, and part of the pelvic girdle (both and ). The excavation site was poached during collection, resulting in the loss of an undetermined amount of the skeleton. This rock layer has also yielded the remains of the early tyrannosauroid Eotyrannus.