Bambiraptor

Bambiraptor
	Skeletal reconstruction of Bambiraptor feinbergorum in the Oxford University Museum of Natural History
Temporal occurrence
	Upper Cretaceous (late Campanium )
	76.4 to 72 million years
Locations
	Montana , USA ( Two Medicine Formation );
Systematics
	Lizard dinosaur (Saurischia)
	Theropoda
	Maniraptora
	Deinonychosauria
	Dromaeosauridae
	Bambiraptor
Scientific name
	Bambiraptor
	Burnham et al. , 2000
Art
	Bambiraptor feinbergorum;

Live reconstruction of Bambiraptor feinbergorum

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

So far, an almost complete skeleton is known, which a student discovered in 1994 in the US state of Montana and which is assigned to the Upper Cretaceous (late Campanium ). Because of its many bird-like features, Bambiraptor has been identified as a very important fossil in understanding the origins of birds.

features

The skeleton found belonged to an animal that was less than a meter long and about 2 kg. However, it was a young animal that has probably only reached 75% the size of an adult animal: This is suggested by the isolated bones of larger animals that were discovered together with the skeleton. It is speculated that it could have been a male animal, as the chevron bones of the tail show analogies to those of today's male crocodiles. The researchers who first scientifically described Bambiraptor saw it as the most convincing evolutionary connection between dinosaurs and birds to date . This finding shows that many of the fundamental features of today's birds were already present in dromaeosaurid dinosaurs. Very bird-like features can be found on the shoulder girdle, for example the acromion (shoulder height) was free. A crescent-shaped (semilunate) finger bone, which was also discovered in some theropods including Bambiraptor , is the prerequisite for the lateral folding of the wrist for today's birds. In addition, Bambiraptor's arms were proportionally longer than any other theropod; only Archeopteryx and other early birds had arms of similar length.

The skull was lightly built and showed a narrow snout and a large, upward (dorsally) inflated skull . On each half of the upper jaw (maxilla) there were 12 teeth with strongly curved tooth crowns up to 6 mm long. The intermaxillary bone (premaxillary), a bone located in front of the upper jaw, has four teeth each. The lower jaw (dental) finally showed 13 teeth on each side, the crowns of which reached almost 7 mm in length. In total, Bambiraptor had 58 teeth. The skull of the skeleton contains two bones that are rarely found in fossils in theropods: On the one hand, the hyoid bone - a 3 cm long, almost straight, thin rod; on the other hand the fragile right stirrup (stapes). The lower jaw shows an important autapomorphism - a feature by means of which the genus can be distinguished from other genera: There are numerous small openings (foramia) on the outer surface, especially in the front area of the dentary.

In front of the sacrum, there were 22 vertebrae that showed large cavities (pleurocoels). The sacrum itself was formed by 5 fused vertebrae. 23 vertebrae of the tail are known, the rearmost section being missing. As with most dromaeosaurids, the tail had strongly elongated vertebral processes (post- and prezygapophyses and chevron bones ). The shoulder belt is obtained complete three-dimensional and shows further autapomorphies Thus the seam between is coracoid (coracoid) and the shoulder blade (scapula) shorter than in other Theropoden. The consequence of this is that the acromion (shoulder height) is located in the middle (medial) and was in contact with the fork bone (furcula) but not with the raven bone. The raven bone also lacks the opening (foramen) that is found in other theropods. The pubis is directed backwards, its boot-like end ( pubic boot ) was turned backwards and upwards. The thigh bone (femur) was severely curved.

As a biomechanical study showed, Bambiraptor was able to place the first and third fingers opposite every other finger and thus grasp objects with only one hand - such opposable fingers are not known from any other theropod.

Systematics

Bambiraptor belongs to the Dromaeosauridae, a group of pinnate theropods closely related to birds. Together with the Troodontidae , the Dromaeosauridae form the group Deinonychosauria , which is considered to be the sister group of birds. Burnham (2004) assigns Bambiraptor to the Velociraptorinae, a group of long-snouted dromaeosaurids, because the denticles (teeth) on the front incisal surface of the teeth were significantly smaller than those on the rear incisal surface. Recently, however, Longrich and Currie (2009) established a new group within the Dromaeosauridae, the Saurornitholestinae, which is said to contain Bambiraptor , Saurornitholestes and Atrociraptor . These genera have, among other things, pneumatized sacral vertebrae (with air-filled chambers running through them).

History of discovery and naming

Skeleton cast of Bambiraptor feinbergorum in the Royal Ontario Museum , Toronto

The 14-year-old boy Wes Linster discovered the only find so far in September 1994 on the grounds of his family's farm near Glacier National Park . Within a few days, he and his family exposed an entire skeleton and began dissecting the bones. Because of the small size of the bones, they gave the fossil the nickname Bambi, which was also widely used by researchers in the period that followed. In November 1995, the family turned to the paleontologist David Burnham , who arranged for the further preparation and scientific investigation of the find. By then, the family had already isolated a large part of the bones from the rock matrix, so that only three blocks of bones remained in the original rock matrix. The taphonomy of the find can therefore only be reconstructed to a limited extent. According to a sketch made by the family, the bones were originally slightly displaced from their anatomical structure. However, the scientific investigation of the find could no longer determine some important features, such as the exact position of some bones such as the hand and foot bones, forkbone and anterior cervical vertebrae. The researchers invested thousands of hours of work in the complete preparation of the small and fragile bones. Along with the skeleton, almost 40 other Bambiraptor bones were found that belonged to at least two different, larger individuals.

In 2000 the find was scientifically described by David Burnham and colleagues . For the naming, the researchers took up the family nickname Bambi , a little deer from children's literature, while raptor comes from Latin and means something like “robber”. The species name feinbergorum honors Michael and Ann Feinberg, who recognized the importance of the skeleton and committed themselves to its scientific investigation. Originally the species was called feinbergi . However, the International Rules for Zoological Nomenclature (ICZN) stipulate that the Latin genitive plural ending -orum must be used, as feinbergi refers to more than one person.

The skeleton found ( holotype , copy number FIP 001) is exhibited today in the Graves Museum of Archeology and Natural History in Dania Beach ( Florida ). The isolated bones found with the skeleton (specimen numbers FIP 002-036) are in the archives of this museum. The site is 19 km west of the city of Bynum . The skeleton comes from a 60 cm thick layer of siltstone ; Stratigraphically , the site belongs to the Two Medicine Formation . Other fossils from this site include thousands of bones and some partial skeletons of hadrosaurids , probably from Maiasaurus . Furthermore, at least three finds of tyrannosaurid bones and two types of eggshells as well as carbonized wood residues were discovered. These sediments were believed to have been transported and deposited by a slow flowing river.

Another find - an isolated, almost complete left upper jaw (copy number MOR 553S-7.30.91.274) - could also belong to Bambiraptor . This find comes from the South Quarry at Jack's Birthday Site near Cutbank , Montana, which also belongs to the Two Medicine Formation. Currie and Varicchio described this find as cf. Bambiraptor feinbergi , since it shows a similar morphology to Bambiraptor and comes from the same formation; however, the researchers note that this assignment is uncertain.

literature

David A. Burnham, Kraig L. Derstler, Philip J. Currie , Robert T. Bakker , Zhonghe Zhou , John H. Ostrom : Remarkable New Birdlike Dinosaur (Theropoda: Maniraptora) from the Upper Cretaceous of Montana (= University of Kansas Paleontological Contributions . no. 13, ISSN 0889-0420 ). The University of Kansas, Lawrence KS 2000, digital version (PDF; 1.73 MB) .

Individual evidence

^ ^A ^b ^c Philip J. Currie, David J. Varicchio: A new dromaeosaurid from the Horseshoe Canyon Formation (Upper Cretaceous) of Alberta, Canada. In: Philip J. Currie, Eva B. Koppelhus, Martin A. Shugar, Joanna L. Wright (Eds.): Feathered Dragons. Studies on the Transition from Dinosaurs to Birds. Indiana University Press, Bloomington IN 2004, ISBN 0-253-34373-9 , pp. 112-132, digitized version (PDF; 1.67 MB) .

^ ^A ^b David A. Burnham: New Information on Bambiraptor feinbergi from the Late Cretaceous of Montana. In: Philip J. Currie, Eva B. Koppelhus, Martin A. Shugar, Joanna L. Wright (Eds.): Feathered Dragons. Studies on the Transition from Dinosaurs to Birds. Indiana University Press, Bloomington IN 2004, ISBN 0-253-34373-9 , pp. 67-111.

↑ Phil Senter: Comparison of forelimb function between Deinonychus and Bambiraptor (Theropoda: Dromaeosauridae). In: Journal of Vertebrate Paleontology. Vol. 26, No. 4, 2006, ISSN 0272-4634 , pp. 897-906, doi : 10.1671 / 0272-4634 (2006) 26 [897: COFFBD] 2.0.CO; 2 .

↑ Nicholas R. Longrich, Philip J. Currie: A microraptorine (Dinosauria – Dromaeosauridae) from the Late Cretaceous of North America. In: Proceedings of the National Academy of Sciences of the United States of America . Vol. 106, No. 13, 2009, pp. 5002-5007, doi : 10.1073 / pnas.0811664106 .

↑ ^a ^b Ben Creisler: Dinosauria Translation and Pronunciation Guide. Archived from the original on November 6, 2011 ; accessed on July 31, 2014 .

Web links

Commons : Bambiraptor - album with pictures, videos and audio files

[currie_04-1] A ^b ^c Philip J. Currie, David J. Varicchio: A new dromaeosaurid from the Horseshoe Canyon Formation (Upper Cretaceous) of Alberta, Canada. In: Philip J. Currie, Eva B. Koppelhus, Martin A. Shugar, Joanna L. Wright (Eds.): Feathered Dragons. Studies on the Transition from Dinosaurs to Birds. Indiana University Press, Bloomington IN 2004, ISBN 0-253-34373-9 , pp. 112-132, digitized version (PDF; 1.67 MB) .

[burnham_04-2] A ^b David A. Burnham: New Information on Bambiraptor feinbergi from the Late Cretaceous of Montana. In: Philip J. Currie, Eva B. Koppelhus, Martin A. Shugar, Joanna L. Wright (Eds.): Feathered Dragons. Studies on the Transition from Dinosaurs to Birds. Indiana University Press, Bloomington IN 2004, ISBN 0-253-34373-9 , pp. 67-111.

[senter_06-3] Phil Senter: Comparison of forelimb function between Deinonychus and Bambiraptor (Theropoda: Dromaeosauridae). In: Journal of Vertebrate Paleontology. Vol. 26, No. 4, 2006, ISSN 0272-4634 , pp. 897-906, doi : 10.1671 / 0272-4634 (2006) 26 [897: COFFBD] 2.0.CO; 2 .

[currie_09-4] Nicholas R. Longrich, Philip J. Currie: A microraptorine (Dinosauria – Dromaeosauridae) from the Late Cretaceous of North America. In: Proceedings of the National Academy of Sciences of the United States of America . Vol. 106, No. 13, 2009, pp. 5002-5007, doi : 10.1073 / pnas.0811664106 .

[creisler-5] Ben Creisler: Dinosauria Translation and Pronunciation Guide. Archived from the original on November 6, 2011 ; accessed on July 31, 2014 .