[D] Ignavusaurus rachelis [sG] [T]
Describer
Knoll 2010
Time
Jurassic Early Hettangian
Classification
Saurischia Sauropodomorpha
Diet
Herbivore
Fossilsite
Elliot Formation [Upper], Lesotho, South Africa
Info
A well-preserved, articulated dinosaur skeleton from southern Africa is described. The specimen comes from the upper Elliot Formation (?Hettangian) of Ha Ralekoala (Lesotho) and represents a new species: Ignavusaurus rachelis genus et species nova. A cladistic analysis suggests that Ignavusaurus is more derived than Thecodontosaurus–Pantydraco, but more primitive than Efraasia. Ignavusaurus indeed shares a number of unambiguous synapomorphies with the taxa more derived than Thecodontosaurus–Pantydraco, such as a fully open acetabulum, but it is more plesiomorphic than Efraasia and more derived sauropodomorphs as shown by the evidence of, for instance, the distal extremity of its tibia that is is longer (cranio-caudally) than wide (latero-medially). The discovery of Ignavusaurus increases the known diversity of the early sauropodomorph fauna of the upper Elliot Formation, which stands as one of the richest horizons in the world in this respect.
Holotype
BM HR 20, a partial, articulated skeleton. The specimen is provisionally housed in the NationalMuseum of Natural History in Paris. It will eventually return to Lesotho as soon as the National Museum is built in Maseru.
Etymology
From Latin ignavus, coward, and ancient Greek σα ´υρoς (masc.), a lizard, because the type locality, Ha Ralekoala, literally means ‘The place of the father of the coward’. / In honour of the paleontologist Raquel L´opez-Anto˜nanzas from the National Museum of Natural Sciences in Madrid (CSIC). The name Raquel comes from the Hebrew (ewe); its most common Latin form (Rachel) is a noun of the third declension, hence the genitive ending in ‘-is’.
Type locality
The specimen was found at a remote site in southern Lesotho, whose coordinates are S: 30◦04; E: 28◦23. It lay close to the place named Ha Ralekoala (Qacha’s Nek district), not far from Sekake, at an elevation of approximately 1725 m.
Type horizon and age
The skeleton, which is largely articulated, was isolated in well-indurated reddish siltstone of the upper Elliot Formation. Apalynological study of the matrix has been carried out by R. Rauscher (Universit´e de Strasbourg 1, Strasbourg) and E. Masure (Universit´e Paris VI, Paris). It proved unsuccessful, but the upper Elliot Formation is most often thought to be Hettangian in age (Knoll, 2005 and references therein).
Diagnosis
A non-sauropod sauropodomorph dinosaur with the following unique combination of character-states: transversewidth of the ventral ramus of the postorbital greater than its rostrocaudal width at midshaft; height of the postorbital rim of the orbit raised so that it projects laterally to the caudal dorsal process; first dentary tooth adjacent to symphysis; teeth linearly placed within the jaws; orientation of the dentary tooth crowns slightly procumbent; distribution of the serrations along the mesial and distal carinae of the tooth restricted to the apical half of the crown; 14 vertebrae between cervicodorsal transition and primordial sacral vertebrae; transverse processes of the dorsal vertebrae dorsally directed; caudal margin of middle dorsal neural spines concave in lateral view with a projecting caudodorsal corner; first caudal centrumshorter than high; shape of the metacarpalVabout as wide as it is long with a strongly convex proximal articulation surface; caudal margin of the postacetabular process of the ilium bluntly pointed; lateral margins of the pubic apron concave in dorsal view; no longitudinal dorsolateral sulcus on proximal ischium; roughly hemispherical femoral head with no sharp medial distal corner; subrectangular astragalus in proximal view; pyramidal process on the craniolateral corner of the proximal surface of the astragalus; transverse width of the proximal end of the fifth metatarsal 50 % of the length of this bone. Although none of these features are proper to Ignavusaurus rachelis, they do not occur in this combination in any other taxon.