Antetonitrus
- Orange Free State, South Africa ( Lower Elliot Formation)
- Antetonitrus ingenipes
Is a genus of sauropod dinosaur Antetonitrus from the Upper Triassic of South Africa. The only way is Antetonitrus ingenipes. As one of the earliest and most primitive known sauropods this genre sheds light on the little-known origin of this group. Unlike its still bipedal precursor forms Antetonitrus was already four-legged, like all other sauropods. The hand showed a flexible thumb; the forelimb was therefore not used exclusively for locomotion, as was the case with other sauropods, but also took probably a gripping function.
The name Antetonitrus ( "Before the Thunder ", the Latin ante - " before "; tonitrus - "Thunder " ) has the very early appearance of this sauropod long before " Brontosaurus " ( " thunder lizard" ) appeared on the scene. The name " Brontosaurus " is no longer used in favor of Apatosaurus; nonetheless, it is still the most famous in the public generic name of a sauropod. The second part of the species name, ingenipes (Latin ingens - "massive"; pes - "foot" ) has the robust hands and feet.
Features
This small, stocky built sauropod is estimated at a length of 8 to 10 feet and a hip height of 1.5 to 2 meters. In comparison with more primitive Sauropodomorpha as Plateosaurus the forelimb was greatly extended, while the metatarsal was shortened. This Antetonitrus already showed the typical appearance for all sauropods with approximately equal length front and rear extremities.
The obligate bipedal Plateosaurus could not turn with the palm down ( pronation ) hands; Instead, the palms faced each other, the hand was in this genus presumably as a gripping tool. In contrast Antetonitrus could pronate his hands, making an effective four-legged locomotion possible. In later sauropods pronation was enforced, the palms could not outwardly rotated ( supinated ) are. The rounded lower end of the spoke in Antetonitrus suggests, however, that the time required for the supination movement of the rolling radius at Antetonitrus possible. The thus moving the forearm could forelimb so that in addition to locomotion function a gripping function have enabled. This is also suggested by the flexible thumb and large, serving as muscle attachment points projections in the upper and lower arm (the great Deltopektoralkamm and the olecranon ).
As with later sauropods of the metatarsal was shortened. Hand and foot were robust, while the femur showed the typical oval cross section; both are adaptations to the increasing body size. The enlarged claw of the first toe was longer than metatarsal I, like other sauropods; but this claw has not yet taken sauropodentypische sickle shape. The femur was not, as in other sauropods, but from the side, slightly S-shaped bent. The vortex of Antetonitrus characterized by high spinous processes and pronounced Hyposphen - Hypantrum joints, additional spinal stability conferring fasteners.
System
Antetonitrus
Antetonitrus is one of the most primitive known sauropods. The relationships to other very primitive sauropod, as Blikanasaurus, Melanorosaurus and Isanosaurus, are due to the sparse fossil record, however, unclear. Presumably, these species were more primitive than Vulcanodon and Kotasaurus.
Finds
So far, two specimens have been described, in 1981 discovered James Kitching in the South African province of Orange Free State. They come from the Lower Elliot Formation, which is dated to the Norian. The Lower Elliot Formation is for their rich fossil fauna of great importance; from these layers also come the remains of two other very early sauropod, Melanorosaurus and Blikanasaurus.
The finds were of were originally used by Kitching and Raath (1984 ) a prosauropods ( Euskelosaurus sp.) Attributed. The holotype specimen includes mainly the front and rear limbs and a few vertebrae and a pubis with one, the second copy includes parts of the forelimbs. The holotype specimen is not yet a full-grown animal, what point are not yet fused with the vertebrae vertebral arches. The second copy was by 80 % smaller than the holotype. Both finds are archived in the Bernard Price Institute for Palaeontological Research, Johannesburg.