Tapuiasaurus

Skull of the type specimen. Photography and drawing from Zaher et al., 2011.

• Brazil, Minas Gerais ( Quirico Formation)

• Tapuiasaurus macedoi

Tapuiasaurus is a genus of sauropod dinosaur from the group of Titanosauria who lived in the Lower Cretaceous of Brazil. So far, a single fragmentary skeleton is known, which consists of a nearly complete skull, some vertebrae and bones of the limbs and the Aptian (before 126.3 to 112.9 million years) is dated. Tapuiasaurus 2011 was described with the only kind Tapuiasaurus macedoi scientifically.

Characteristics and importance

So far, only a few skull finds have been found of titanosaurs - nearly complete skulls are known only from the late Cretaceous, very derived ( advanced ) classes Nemegtosaurus and Rapetosaurus. The rather complete skull of Tapuiasaurus fills an important gap in the fossil record, and shows that the typical late Cretaceous Titanosauria skull shape was already common in the early Cretaceous. It is the only known Titanosauria skull from South America.

As with other derived Titanosauria as Nemegtosaurus and Rapetosaurus the skull is characterized by an elongated snout and through nostrils, which were located at the level of the orbits. The teeth were thin and cylindrical - the row of teeth handed back to the front edge of the Antorbitalfensters. A similar skull morphology is found in the Diplodocoideen - these similarities are probably due to convergent evolution.

From other Titanosauria can the genre with unique features ( autapomorphies ) limitations on the skull: So the posteroventrale ( abdominal side rear facing ) extension of the Quadratojugale was hook-shaped. The anterior (front ) projection of the zygomatic bone ( Jugale ) was tapered and forms a large part of the lower edge of the Antorbitalfensters. The anterolateral ( front side ) tip of the wing bone ( pterygoid ) is in contact with the medial ( middle ) area of ​​the wing leg extension, the Ectopterygoid.

System

Tapuiasaurus belongs to the derived ( advanced ) Titanosauria how front, for example to the procoelous ( concave on the front) and middle caudal vertebrae shows. Thereby Tapuiasaurus is probably most closely related to Rapetosaurus and forms the sister taxon in the genus, such as a phylogenetic analysis shows. Rapetosaurus and Tapuiasaurus show various anatomical similarities, which are not found in the also closely related Nemegtosaurus - so for instance, with two genera Antorbitalfenster the same size or larger than the eye sockets. The grouping Tapuiasaurus, Rapetosaurus and Nemegtosaurus is summarized under the name Nemegtosauridae.

Although Tapuiasaurus was a relatively derived Titanosauria, its fossils are about 30 million years older than the other derived Titanosauria. This discovery shows that there must be in the development of derived Titanosauria various "ghost lineages " that are not in the fossil record.

Fund and naming

The only skeleton comes from the northern Minas Gerais within the city of Coração de Jesus. This skeleton was discovered along with the skeleton of a theropod abelisauroiden and excavated. The rocks of the discovery site belong to Quirico formation, a formation within the Sanfranciscan Basin. This approximately 1100 km long basin is interpreted as a grave breach and is caused by the same tensile forces that led to the opening of the Atlantic Ocean.

The skeleton ( copy number MZSP - PV 807 ) consists of a nearly complete skull with jaw and hyoid ( hyoid ), different vertebrae ( the atlas, axis, another five cervical vertebrae, and five vertebrae with ribs), breastbone ( sternum), coracoid ( coracoid ) parts of the front legs (thigh bone (humerus ), radius ( radius), Elle ( ulna ), metacarpal bones ( metacarpals ) ), as well as parts of the hind legs (thigh bone (femur), fibula ( fibula ) and an almost complete foot skeleton ). The bones were found mostly in its original anatomical position.

This genus was described in February 2011 by researchers at Hussam Zaher first time scientifically. The name derives from Tapuiasaurus Tapuia, a word from the busi - languages ​​, which is used for Indian tribes that are located in the countryside of Brazil. The second part of the species name, macedoi honors Ubirajara Alves Macedo, who discovered the fossil- bearing strata near Coração de Jesus.