Brontomerus
| Brontomerus | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Brontomerus fends off a predatory Utahraptor with its hind leg (live reconstruction). |
||||||||||||
| Temporal occurrence | ||||||||||||
| Lower Cretaceous ( Aptium to Albium ) | ||||||||||||
| 126.3 to 100.5 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Brontomerus | ||||||||||||
| Taylor , Wedel & Cifelli , 2011 | ||||||||||||
| Art | ||||||||||||
|
Brontomerus is a genus of sauropod dinosaur in the Macronaria group from the Lower Cretaceous North America. So far, only a few bone fragments are known that come from the Cedar Mountain Formation in eastern Utah (USA) and are dated to the Aptium to Albium (about 126.3 to 100.5 million years ago). The exact systematic position of the genus within the Macronaria is unclear - it is currently listed as a representative of the Camarasauromorpha thatcannot be classified further. From other sauropods, Brontomerus differed inthe unique morphology of the ilium , which provided attachment points for large and powerful adductors of the hind leg muscles . The only species is B. mcintoshi .
description
The holotype (copy number OMNH 66430) is a fragmentary left iliac bone. Other fossils attributed to this type include a fragmentary shoulder blade (scapula), two breast bones (sternum), three vertebrae (two caudal vertebrae and the broken fragment of a presacral vertebra (a vertebra from the region in front of the pelvis )), a rib and fragments of bones. Although all bones come from the same quarry, they belonged to at least two different individuals, as suggested by the very different sizes of the bones. The remnant of the shoulder blade is 98 centimeters long, with the original total length of this bone being estimated at 121 centimeters. While the shoulder blade and iliac bone of the titanosaur Rapetosaurus are about the same length, the found iliac bone of Brontomerus measured only a third of the length of the shoulder blade. The iliac bone, presacral vertebrae and sternum probably belonged to a young animal, while the shoulder blade and other bones came from a larger individual.
This genus can be explained by five unique features ( autapomorphies ) distinguished from other genera: So the präacetabulare blade of the ilium made (the front of the hip joint socket located (acetabulum) of this bone) 55 percent of the total length of the ilium, and is thus longer than any other sauropods. In addition, the pre-acetabular blade was displaced by 30 percent relative to the sagittal plane . The post-acetabular (located behind the acetabulum) blade, however, was largely reduced. Below this shovel the the closed ischial (ischium) facing style ( " ischiadic peduncle "), who was reduced to a very low hump. Furthermore, the iliac bone was higher than that of other sauropods.
Paleobiology
The enlarged presacral shovel of the iliac bone provided attachment points for very large muscles of the thigh, which allowed a powerful forward movement of the hind leg. One can only speculate about the function of these enlarged muscles. They may suggest that Brontomerus had unusually strong limbs for locomotion. They could also have made powerful kicks possible with the hind leg. Another possibility is that Brontomerus has developed an erection on the hind legs, for which muscles are required which allow the legs to be spread sideways; these muscles also attach to the iliac bone. On the other hand, the enlarged muscles could also indicate relatively long legs.
Systematics
Brontomerus is classified as a representative of the Camarasauromorpha , a group that includes the Camarasaurus , the Brachiosauridae and the Titanosauria . A cladistic analysis could not establish a stable systematic position within this group - but the most likely variant sees Brontomerus as a basal (original) representative of the Somphospondyli , as a relative of Euhelopus and the Titanosauria.
History of discovery and naming
The fossils come from the Mesa Quarry Hotel , a quarry in Grand County , eastern Utah. This quarry was first scientifically examined in 1994 by Richard Cifelli - further fossils were collected in 1995. The quarry has long been known to private fossil collectors, who have already taken a large part of the fossils with them - the researchers speak of a significant loss of information. Other fossils from this quarry include various fish, several species of crocodiles, and remains of theropod and ornithopod dinosaurs. The quarry is located in the upper portion of the Ruby Ranch Member, a stratum of the Cedar Mountain Formation , a significant fossil deposit .
Brontomerus was first scientifically described in 2011 by Michael P. Taylor , Mathew J. Wedel and Richard L. Cifelli . The name Brontomerus ( Gr. Bronto - "thunder", Gr. Merós - "thigh") means something like "thunder thigh", which indicates the very strong muscles of the thigh bone, which can be guessed at the morphology of the iliac bone. The second part of the species name, mcintoshi , honors the eminent paleontologist and sauropod expert John S. McIntosh .
Individual evidence
- ↑ a b c d e f g Michael P. Taylor, Mathew J. Wedel, Richard L. Cifelli: A new sauropod dinosaur from the Lower Cretaceous Cedar Mountain Formation, Utah, USA. In: Acta Palaeontologica Polonica. Vol. 56, No. 1, 2011, pp. 75-98, doi : 10.4202 / app.2010.0073 .
