Saltopus

Saltopus ("hopping foot") is a genus of very small bipedal dinosauriform, roughly 80 to 100 centimeters (30-40 in) long,[1] from the late Triassic of Scotland.

A fossil of Saltopus was discovered by William Taylor in the Lossiemouth West & East Quarries. It was named and described by Friedrich von Huene in 1910 as the type species Saltopus elginensis. The generic name is derived from Latin saltare, "to jump" and Greek πούς, pous, "foot". The specific name refers to its provenance near Elgin. The holotype NHMUK R.3915, was excavated from the Lossiemouth Sandstone Formation dating from the Carnian-Norian stage. It consists of a partial skeleton lacking the skull but including parts of the vertebral column, the forelimbs, the pelvis and the hindlimbs. These have been mainly preserved as impressions or natural casts in the sandstone; very little bone material is present.[2] To date, Saltopus is known only from this very poor material.

Saltopus was a carnivore, about the size of a domestic cat, with hollow bones like those of a bird. It may have weighed in at around two pounds (one kilogram). Most of the length was accounted for by the tail. Based on related forms, it probably had a long head with dozens of sharp teeth. It had five-fingered hands, with the fourth and fifth finger reduced in size. Contrary to the original description, in 2011 it was established that the sacrum consisted of two vertebrae, the ancestral condition, not four.[1]

It has been variously identified as a saurischian (lizard-hipped) dinosaur, a more advanced theropod, and a close relative of the herrerasaurs, but its taxonomy has been in dispute because only fragmentary remains have been recovered. Some researchers, such as Gregory S. Paul,[3] have suggested it may represent a juvenile specimen of a coelophysid theropod such as Coelophysis or Procompsognathus. Rauhut and Hungerbühler in 2000 concluded it is a primitive dinosauriform, not a true dinosaur, closely related to Lagosuchus.[4] Michael Benton, continuing the studies of the late Alick Walker redescribing the fossil, in 2011 found it to be a dinosauriform more derived than Pseudolagosuchus and outside the smallest clade including Silesauridae and Dinosauria.