Isanosaurus
Femurs of Isanosaurus
- Chaiyaphum, Thailand ( Nam Phong Formation)
- Isanosaurus attavipachi Buffetaut et al., 2000
Is a genus of sauropod dinosaur Isanosaurus from the Upper Triassic of Thailand. The only way is Isanosaurus attavipachi. It is one of the oldest and most primitive known members of the sauropods, so is the genus for the understanding of the origin of this group is of great importance. The relationships to other very early sauropods, such as Antetonitrus, Blikanasaurus or Gongxianosaurus, are unclear.
Isanosaurus was described in 2000 by researchers led by Eric Buffetaut. The genus name ( Isan - Isaan, designation for northeast Thailand; gr sauros - " lizard" ) includes the Fund field, while the second part of the species name ( attavipachi ) a long-time supporter of the Thai paleontological research honors, the former chief of the Thai Ministry of Natural Resources P. Attavipach.
Features
The only skeleton consists of fragmentary remains of neck, back, and tail vertebrae, ribs, chevron bones, sternum, a scapula and a femur. This specimen is estimated to have a length of about 6.5 meters, the femur measures a length of 76 cm. Vertebral bodies and vertebral arches, however, were found separated from each other, indicating that these elements were not yet fused together - it was therefore probably a not yet full-grown animal.
The precursor forms of sauropods ( traditionally referred to as " prosauropods " ) were originally bipedal. As one of the oldest known sauropod but Isanosaurus danced the later sauropods typical for all, adapted to a four-footed locomotion physique. The legs were like a column under the body: For example, the femur was robust and straight, while he ( Antetonitrus ) was still slightly S-shaped bent on " prosauropods " and in another very primitive sauropod. As a result of the columnar legs also bone combs were reduced, which served at " prosauropods " as muscle attachment points - so, for example lacking the small trochanter.
Other important features can be found on the vertebrae. The cervical vertebrae were significantly opisthocoel, ie with a convex front that fits into a concave rear of the adjacent vertebra and thus formed a ball joint. The caudal vertebrae were against amphicoel (both sides concave). The spinous processes of the vertebrae were very high, as in some later sauropods, and stood in contrast to the low spinous processes of the " prosauropods ". The vertebrae were laterally concave; deep lateral cavities ( Pleurocoele ), as they showed later sauropods were missing however.
Discovery
The skeleton was discovered in 1998 near the village of Ban Non Thaworn in the Thai province of Chaiyaphum. Bone a long time had already been exposed to the ground surface, and therefore most part of the skeleton has already been destroyed by erosion of the discovery. The site closes at dark red sandstones of the Nam- Phong Formation, which are dated to the Upper Norian to Rhaetian. The vertebrate fauna of this formation is not well known; in 2000 alongside Isanosaurus only one finding from two seat legs was known. Whether this finding could belong to Isanosaurus is unclear, as no seat legs are preserved in Isanosaurus skeleton.