Bambiraptor

Skeletal reconstruction of Bambiraptor feinbergorum in the Oxford University Museum of Natural History

• Montana, USA ( Two Medicine Formation)

• Bambiraptor feinbergorum

Bambi Raptor is a genus of carnivorous dinosaur from the group of Dromaeosauridae. The only known species is Bambiraptor feinbergorum.

So far, a nearly complete skeleton is known that a student discovered in 1994 in the U.S. state of Montana and the Upper Cretaceous (late Campanian ) has been allocated. Because of its many bird -like features Bambiraptor was referred to as a very important fossil for understanding the origin of birds.

Features

The skeleton found belonged to an animal that was less than a meter long and about 2 kg. These were but a young animal that has probably reached only 75 % of the size of an adult animal: Then let scattered bones of larger animals include, which were discovered along with the skeleton. It is speculated that there may have been a male animal, as the chevron bones of the tail analogies to show that today's male crocodiles. The researchers, who Bambiraptor first described scientifically, saw in him the most convincing evolutionary link between dinosaurs and birds. So is this discovery that many fundamental features of modern birds were already present in dromaeosauriden dinosaurs. Very bird-like features can be found in the shoulder girdle, such as the acromion ( shoulder height ) was free. A crescent-shaped ( semilunate ) finger bone, which was also detected in some theropods including Bambi Raptor, is the prerequisite for the lateral folds of the wrist for today's birds. In addition, the arms of Bambiraptor were proportionally longer than in any other theropod; only Archaeopteryx and other early birds showed similar long arms.

The skull was slightly built and showed a narrow snout, and a large, upward ( dorsal) inflated braincase. On each half of the upper jaw (maxilla ) were 12 teeth with strongly curved, up to 6 mm long tooth crowns. The premaxillary bone ( premaxilla ), one in front of the upper jaw bone befindlicher, depending on has four teeth. The lower jaw ( dentary ) finally showed on each side 13 teeth whose crowns almost reached 7 mm in length. Overall Bambiraptor thus contributed 58 teeth. The skull of the skeleton contains two bones, which have been handed rarely fossil in theropods: first, the hyoid bone ( hyoid ) - a 3 cm long, almost straight, thin rod; on the other hand the fragile right stirrup ( stapes ). The mandible shows an important autapomorphy - a feature by which the genre of other genres can distinguish: How to find especially in the front area of the dentary on the outer surface numerous small openings ( Foramia ).

Prior to the sacrum ( sacrum ) there were 22 vertebrae, the large cavities ( Pleurocoele ) showed. The sacrum itself was formed by 5 fused vertebrae. From the tail vertebrae 23 are known, with the rearmost section is missing. As with most Dromaeosauriden the tail pointed strongly elongated spinous processes on ( postal and prezygapophyses and chevron bones). The shoulder girdle is completely preserved in three dimensions and shows further autapomorphies: So the seam between coracoid is ( coracoid ) and shoulder blade (scapula ) is shorter than in other theropods. As a consequence of this is that the acromion ( shoulder height ) in the middle ( medial) is located and with the wishbone ( furcula ), but not related to the coracoid in contact. The coracoid also missing the opening ( foramen ), which is found in other theropods. The pubic bone ( pubis ) is directed backwards, his boots like end ( pubic boot) was turned backwards and upwards. The thigh bone (femur) was severely bent.

As a biomechanical study showed Bambiraptor was the first and third fingers facing each other fingers and thus grasp objects with only one hand - such opposable fingers are no other known theropods.

System

Bambi Raptor is one of the Dromaeosauridae, one with the birds closely related group of feathered theropods. Together with the Troodontidae form the Dromaeosauridae the group Deinonychosauria, which is regarded as a sister group of birds. Burnham (2004) arranges the Bambiraptor Velociraptorinae to a group langschnäuziger Dromaeosauriden because the denticles ( tooth ) on the front cutting face of the teeth was significantly smaller than that on the trailing edge surface. Recently, however, presented Long Rich and Currie (2009), a new group within the Dromaeosauridae on which Saurornitholestinae that will contain Bambiraptor, Saurornitholestes and Atrociraptor. These genera have, among other pneumatized ( laced with air-filled chambers ) sacral vertebrae together.

History of discovery and naming

The only previous Fund saw the 14- year-old boy Wes Linster in September 1994 on the site of the family farm near the Glacier National Park. Within days, he and his family put an entire skeleton free and began with the preparation of the bones. Because of the small size of the bones they gave the fossil nicknamed Bambi, the researchers also found wide use in the subsequent period. In November 1995, the family turned to the paleontologists David Burnham, which prompted the further preparation and scientific investigation of the find. Until then, the family had a lot of the bones from the rock matrix isolated so that only remaining three blocks with bones in the original rock matrix. Therefore, the taphonomy of the discovery may only be reconstructed limited. According to a sketch, which has made ​​the family, the bones were originally displaced slightly from their anatomical network. Nevertheless, it was the scientific investigation of the find some important features, such as no longer find the exact position of some bones such as hand and foot bones, leg and front of the neck vertebrae. For complete preparation of small and fragile bones, researchers have invested thousands of hours of work. Together with the skeleton almost 40 more Bambiraptor - bones were found, belonging to at least two different, larger individuals.

In 2000, the discovery of David Burnham and colleagues described scientifically. The designation of the researchers attacked the contracts awarded by the family nickname Bambi on, a small deer out of children's literature, while raptor comes from the Latin and means something like " predator " means. The species name honors feinbergorum Michael and Ann Feinberg, who recognized the importance of the skeleton and dedicated for his scientific investigation. Originally the species was named feinbergi. The International Rules for Zoological Nomenclature ( ICZN ) require, however, that the Latin genitive plural ending - orum must be used, since feinbergi refers to more than one person.

The skeleton found ( holotype, specimen number 001 FIP ) is now displayed in the Graves Museum of Archaeology and Natural History in Dania Beach ( Florida). Found with the skeleton isolated bones ( copy numbers FIP 002-036 ) are located in the archives of this museum. The site is located 19 km west of the city Bynum. The skeleton is from a 60 cm thick layer of siltstone; stratigraphically the reference is part of the Two Medicine Formation. Other fossils found in the reference close thousands of bones and a few partial skeletons of Hadrosauriden with one, probably from Maiasaurus. Furthermore, were discovered at least three findings of tyrannosaurid bone and two types of shells, and carbonized wood residues. These sediments were probably transported and deposited by a slowly flowing river.

Another find - an isolated, nearly complete left upper jaw ( specimen number MOR 553S - 7.30.91.274 ) - might also belong to Bambiraptor. This finding comes from the South Quarry at Jack 's Birthday Site near Cutbank, Montana, which is also a member of the Two Medicine Formation. Currie and Varicchio described this discovery as feinbergi cf Bambi Raptor, because it shows a similar morphology to Bambiraptor and comes from the same formation; Nevertheless the researchers note that this assignment is uncertain.