Acrocanthosaurus
Acrocanthosaurus, live reconstruction
- Antlers and Paluxy River Formation, Oklahoma, United States
- Twin Mountain Formation, Texas, USA
- Cedar Mountain Formation, Utah, USA
- Acrocanthosaurus atokensis
Acrocanthosaurus is a dinosaur that is the Carnosauria, a group that counted within the theropods. His remains, including several partial skeletons and a nearly complete skeleton found were recovered from layers of the Early Cretaceous ( Aptian to middle Albian ) in the USA. The only way is A. atokensis.
Acrocanthosaurus was a very tall, bipeder carnivores. A key feature of renewed spinous processes, perhaps formed a low sails.
Originally called this dinosaur " Acrocanthus " ( Langston, 1947), but the name was changed. Thus Acrocanthosaurus is the only correct term.
General
Acrocanthosaurus is named after its vertebrate spines, the name is from the Greek acro "high", akantha " sting " and sauros " lizard" together. The Artepitheth atokensis is named after Atoka Country where the holotype material was found.
Acrocanthosaurus was described in 1950 based on two partial skeletons of paleontologists Willis Stovall and Langston When. These findings ( holotype OMNH 10146 and para-type OMNH 10147 ), which also contain some skull material alongside other skeletal remains were previously recovered from the layers of the Antlers Formation in Oklahoma.
Since then, two more complete skeletons have been described. The first comes from the Twin Mountain Formation of Texas. It bears the number 74646 and SMU is obtained approximately 70%, including is an incomplete skull. This skeleton was rediscovered in 1990, although it has already been excavated more than 40 years earlier. The second skeleton ( OMNH 10168 ) bears the nickname " Fran" and comes, like the first two skeletons from the Antlers Formation of Oklahoma. It is the most complete Acrocanthosaurus skeleton, even the skull is completely preserved. Many other individual bones and bone fragments were recovered in Texas and Oklahoma, but also in Utah ( Cedar Mountain Formation).
The finds date from the Aptian and middle Albian, thus Acrocanthosaurus lived before 126-108 million years ago. In the same area at the same time lived as Deinonychus, Tenontosaurus and Sauroposeidon. This is one of the richest known Dinosaurierfaunen the Early Cretaceous, and Acrocanthosaurus was the top predators.
Three vertebrae bones from England who still had higher spikes were initially called Acrocanthosaurus altispinax. Later, however, a separate genus was described for this Fund: Becklespinax.
In America, many fossil footprints Acrocanthosaurus are traditionally attributed, especially the famous Glen Rose tracks in Dinosaur Valley State Park in northern Texas. While it is impossible to say whether these tracks are actually from Acrocanthosaurus. However, they are about the same age as the bone finds, and have the appropriate size, which is why one belonging to Acrocanthosaurus is quite possible.
Some of the tracks were found on the tracks of a Sauropodenherde, and it pointing in the same direction as that of herbivores. It is therefore assumed that the predators followed the great Sauropodenherden their walks and watching for sick and weak animals. Evidence can not be this, however.
Description
The nearly complete skeleton of " Fran" has a length of 11.5 m. Of this total, 129 cm on the skull, which thus is significantly longer than in the relatives of Allosaurus. His weight is therefore estimated to 2-3 tons. This Acrocanthosaurus is one of the largest known theropods, although he was slightly smaller than the relative Giganotosaurus with up to 13 m.
Important anatomical features of the skull are two additional small skull openings in the upper jaw, which are additional to the usual five. In addition, the antorbitale window, a skull opening which is located in front of the eye opening, with 42 cm unusually large. No skull horns are In Acrocanthosaurus, unlike many of his relatives are formed.
The neck, back and anterior caudal vertebrae have formed elongated extensions which may be higher than the respective vertebrae more than 2.5 times. These vertebrae spines also occur in other dinosaurs, the record is held by Egyptian Spinosaurus with a spiked length of 1.5 m. Perhaps the vertebral spines in Acrocanthosaurus have formed a low sails. Or were they, like the bison of today, surrounded by muscles, which formed a large hump on the back.
System
About the systematic classification within the Allosauroidea to which Acrocanthosaurus is counted, there is still disagreement. The Allosauroidea consist of three families who Allosauridae (eg Allosaurus ), the Carcharodontosauridae (eg, Carcharodontosaurus, Giganotosaurus, Tyrannotitan ) and the Sinraptoridae (eg Sinraptor ).
It was originally classified as Allosauride. Today, he is considered by many researchers for a more Carcharodontosauriden, although this was provided by recent studies in question. Coria and Currie (2003), for example, according to my investigations of the skull boxes that Acrocanthosaurus has none of the typical Carcharodontosauriermerkmale and therefore can not be made to the Carcharodontosauriden. Fanzoza (2002), has established clear similarities of Acrocanthosaurus skull boxes with those of Allosaurus and Carcharodontosaurus.
There was even a new family, " Acrodontosauridae " proposed ( Molnar, 2001), in which Acrocanthosaurus should be classified along with Carcharodontosaurus. This theory is rejected by most researchers.
Brain structure
In 2005, scientists have digitized the holotype skull of Acrocanthosaurus material using computer tomography to reconstruct as the brain and the nerves transitions can. The following observations were able to be made:
- The olfactory bulbs were large and thick, indicating a well-trained sense of smell.
- The reconstruction of the semicircular canals of the ear, the " balance organ " has shown that the head was held at an angle of 25 degrees below the horizontal.
- The brain is slightly S-shaped and is more like a crocodile than a bird.
- The brain is more similar to that of Carcharodontosaurus and Giganotosaurus than that of the Sinraptor or Allosaurus, which should strengthen the classification as Carcharodontosauride.
Computed tomography is a relatively new method in paleontology, with the brain imprints of other large theropods ( Tyrannosaurus, Ceratosaurus, Allosaurus and Carcharodontosaurus ) were reconstructed.