Coelophysis rhodesiensis

Coelophysis rhodesiensis measured up to 3 meters (10 ft) long from nose to tail and weighed about 32 kilograms (70 lb). The bones of 30 C. rhodesiensis individuals were found together in a fossil bed in Zimbabwe, so paleontologists think it may have hunted in packs. The various fossils attributed to this species have been dated over a relatively large time span – the Hettangian, Sinemurian, and Pliensbachian stages of the Early Jurassic – meaning the fossils represent either a highly successful genus or a few closely related animals all currently assigned to Coelophysis.

C. rhodesiensis was a lean, elongated species of theropod dinosaur with an S shaped neck, long hind limbs that resembled the legs of large birds such as the secretarybird, shorter forelimbs with four digits on each hand unlike most later theropods, and a long tail. While still lean, it sported a more robust frame than other members of Coelophysoidea. Its lithe and superifically bird-like body lead to C. rhodesiensis being one of the first dinosaurs to be portrayed with feathers, though there is no direct evidence that it actually had feathers.[3]

Specimen UCMP V128659 was discovered in 1982 and referred to Megapnosaurus kayentakatae by Rowe (1989),[4] as a subadult gracile individual and later, Tykoski (2005)[5] agreed. Gay (2010) described the specimen as the new tetanurine taxon Kayentavenator elysiae,[6] but Mortimer (2010) pointed out that there was no published evidence that Kayentavenator is the same taxon as M. kayentakatae.[7]

"Syntarsus" rhodesiensis was first described by Raath (1969) and assigned to Podokesauridae.[1] The taxon "Podokesauridae", was abandoned since its type specimen was destroyed in a fire and can no longer be compared to new finds. Over the years paleontologists assigned this genus to Ceratosauridae (Welles, 1984), Procompsognathidae (Parrish and Carpenter, 1986) and Ceratosauria (Gauthier, 1986). Most recently, it has been assigned to Coelophysidae by Tykoski and Rowe (2004), Ezcurra and Novas (2007) and Ezcurra (2007), which is the current scientific consensus.[8]

According to Tykoski and Rowe (2004) Coelophysis rhodesiensis can be distinguished based on the following characteristics:[8] it differs from Coelophysis bauri in the pit at the base of the nasal process of the premaxilla; it differs from C.? kayentakatae because the promaxillary fenestra is absent and the nasal crests are absent; the frontal bones on the skull are not separated by a midline anterior extension of the parietal bones; the anterior astragalar surface is flat; metacarpal I has a reduced distal medial condyle (noted by Ezcurra, 2006); the anterior margin of antorbital fossa is blunt and squared (noted by Carrano et al., 2012); the base of lacrimal vertical ramus width is less than 30% its height (noted by Carrano et al., 2012); the maxillary and dentary tooth rows end posteriorly at the anterior rim of the lacrimal bone (noted by Carrano et al., 2012)

Marsh and Rowe (2020) retain the generic name Syntarsus for both QG 1 and MNA V2623, and the respective specimens assigned to these taxa, as opposed to Coelophysis or Megapnosaurus, due to systematic relationships within Coelophysoidea in flux. As such, congenericity or the need for Megapnosaurus would not be supported if Coelophysis bauri, Syntarsus rhodesiensis, and Syntarsus kayentakatae do not form respective clades, as evidenced by their phylogenetic analyses.[9]

Dinosaur footprints that were later attributed to C. rhodesiensis were discovered in Rhodesia in 1915. These tracks were discovered at the Nyamandhlovu Sandstones Formation, in eolian red sandstone that was deposited in the Late Triassic, approximately 235 to 201 million years ago.[18]