Ignavusaurus

''Ignavusaurus'' is a genus of basal sauropodomorph dinosaur that lived during the Early Jurassic in what is now Lesotho. Its fossils were found in the Upper Elliot Formation which is probably Hettangian in age (around 200 million years ago). It was described on the basis of a partial, well preserved articulated skeleton. The type species, ''I. rachelis'', was described in 2010 by Spanish palaeontologist F. Knoll.

Discovery

The holotype was discovered in southern Lesotho near Ha Ralekoala. The fossils were discovered in a mostly articulated state, although the skull was badly damaged, having broken into more than 120 fragments. An unpublished 2002 Ph.D. dissertation referred to the remains, but they were not formally described for several years, and the find remained unpublished.

In 2010, the fossils were described by F. Knoll of the Museo Nacional de Ciencias Naturales-CSIC in Madrid as a new taxon, ''Ignavusaurus rachelis''. The fossils were brought to the National Museum of Natural History in Paris, where they were provisionally catalogued as BM HR 20; the plan was to return the fossils to Lesotho upon the opening of the Lesotho National Museum.

Etymology

The generic name ''Ignavusaurus'' is derived from the Latin word ''ignavus'' ("coward") and Ancient Greek ''sauros'' ("lizard"). It refers to the type locality – Ha Ralekoala, that literally means "The place of the father of the coward". The specific name of the type species, ''rachelis'', honours Spanish palaeontologist Raquel López-Antoñanzas.

Description

The holotype had a body length of about and weighed about . Histological analysis of the humerus and femur indicates that BM HR 20 was fast-growing individual, maybe less than one year old, based on age determination studies.

Like other early sauropodomorphs, ''Ignavusaurus'' had a long, slender neck and tail. It generally resembled ''Massospondylus'' and ''Melanorosaurus'', two other sauropodomorphs from southern Africa, although the shape and position of the teeth, among other factors, led Knoll to conclude that the remains belong to a previously unknown genus.

Classification

''Ignavusaurus'' is a basal sauropodomorph, a member of the long-necked, herbivorous, saurischian dinosaurs. Although originally recovered as more primitive than Plateosauria by Knoll (2010), Yates et al. (2011) noted that some characters used to place ''Ignavusaurus'' outside Massopoda are reflective of juvenile status and instead are more similar to juvenile ''Massospondylus'', considering ''Ignavusaurus'' probably synonymous with ''Massospondylus''. Meanwhile, a cladistic analysis presented by Apaldetti et al. (2011) found ''Ignavusaurus'' to be a valid genus which is most closely related to ''Sarahsaurus'' within Massopoda, somewhat agreeing with Yates et al. that ''Ignavusaurus'' is not as primitive as originally thought. A cladistic analysis conducted by Chapelle and Choiniere (2018) in their paper updating knowledge of the skull of ''Massospondylus'' recovered ''Ignavusaurus'' along with ''Sarahsaurus'' in Massospondylidae, as did the cladistic analysis of Chapelle et al. (2019).Chapelle KEJ, Barrett PM, Botha J, Choiniere JN. 2019. ''Ngwevu intloko'': a new early sauropodomorph dinosaur from the Lower Jurassic Elliot Formation of South Africa and comments on cranial ontogeny in Massospondylus carinatus. PeerJ 7:e7240 https://doi.org/10.7717/peerj.7240

References

{{Taxonbar, from=Q93603

Massopoda
Early Jurassic dinosaurs of Africa
Fossil taxa described in 2010
Paleontology in Lesotho