Ceratosaurus
Skeleton cast of a young animal in the Dinosaur Discovery Museum in Wisconsin
- Ceratosaurus nasicornis
- Ceratosaurus dentisuclatus (?)
- Ceratosaurus magnicornis (?)
Ceratosaurus ( " horn lizard" ) is a genus theropod dinosaur from the Upper Jurassic of North America and Europe. Characteristic of this two-legged carnivores were three prominent horns on the skull as well as a number of small osteoderms ( dermal bones plates), which ran on neck, back and tail. Ceratosaurus is known primarily through five fragmentary skeletons with skulls, derived from the Morrison Formation of the western United States. He is the eponymous representative of Ceratosauria, a group of basal (original ) theropods. The only currently recognized species is generally Ceratosaurus nasicornis. Two other species have been described, but Ceratosaurus dentisulcatus and C. magnicornis whose validity is disputed today. Ceratosaurus is one of the dinosaurs known to the public and regularly appears in popular books about dinosaurs.
- 3.1 Types
- 3.2 External systematics
- 4.1 habitat and ecological niches
- 4.2 Function of the head horns
- 4.3 palaeopathology
- 6.1 Literature
- 6.2 External links
- 6.3 Notes and references
Features
The holotype specimen of Ceratosaurus nasicornis is estimated at a body length of 5.3 meters, which is not clear whether this individual was fully grown. The largest specimen found is from the Cleveland -Lloyd Quarry and is estimated to have a length of 8.8 meters; this copy is considered by some researchers to run as an independent type, Ceratosaurus dentisulcatus. Estimates of body weight vary depending on the author, as to amount different weight estimates of the holotype specimen of 418.4 kg, 524 kg and 670 kg.
The skull was like other Ceratosauria relatively large. Unique is a striking horn, which is located on the center line of the skull behind the nostrils. The fossil record is only the bony horn base that was covered in the living animal with keratin. The horn base is round and narrow. In the holotype specimen, it measures at its base a length of 13 centimeters and a width of 2 inches; immediately above the base, however, the width from 1.2 centimeters. Their height is 7 centimeters, relative to the top of the nasal bone. The horn base is formed by the fused right and left halves of the paired nasal bone ( nasal ). In young animals, the two halves of the horn base are not yet fused. In addition to the nose horn possessed Ceratosaurus a pair of horns, which is located on the top of the skull in front of the eye openings and the paired lacrimal bone ( lacrimal ) is formed. All three horns were larger than in juveniles in adult animals in proportion. The horns were probably only the display.
In each half of the upper jaw were 12-15 blade-shaped teeth. The paired premaxillary bone ( premaxilla ), a bone from the upper jaw, pointed to each half to just three teeth, less than in most other theropods. In the lower jaw were sitting on either side of 11 to 15 teeth, the little straighter and less vigorous than were the teeth of the upper jaw. The tooth crowns of the upper jaw were exceptionally long and measure the largest known Ceratosaurus specimen up to 9.3 cm long, corresponding to the lowest height of the mandible. When smaller holotype specimen, the length of the tooth crowns (7 cm) even exceeds the minimum height of the mandible (6.3 cm) - this feature can be found in other theropods only at the possibly closely related Genyodectes. In contrast, some representatives of related also with Ceratosaurus Abelisauridae experienced very low crowns.
The number of vertebrae can not be determined precisely because the spine of the holotype specimen has several gaps. The sacrum consists of 6 sacral vertebrae ( sacral vertebrae ); front of the sacrum were at least 20 Präsakralwirbel ( cervical and dorsal vertebrae), while behind the sacrum followed about 50 caudal vertebrae. The spinous processes of the vertebrae of the tail were just like the Chevronknochen extended, the tail was a deep profile viewed from the side. Unique among theropods is a series of small, elongated and irregularly shaped osteoderms ( dermal bones plates), which ran on the midline of the body above the bed on the neck, back, and the majority of the tail. Away from the midline of the body pointed Ceratosaurus to other osteoderms, followed by about 6 times 7 centimeter plate indicates that, together with the holotype specimen found, their location on the body of the animal, however, is unclear.
The arms were relatively short as in other representatives of Ceratosauria and ended in four fingers. So far, an incomplete skeleton of the hand is only found, so the exact number of phalanges is unclear. The first and fourth metacarpal were reduced in size, while the second metacarpal bone was a little longer than the third.
History of research and findings
The first specimen ( holotype, specimen number USNM 4737 ) consists of a relatively complete skeleton with skull and was discovered by the farmer Marshall P. Felch in the years 1883-1884. It dates from the Felch Quarry 1, one of the richest quarries of the Morrison Formation, in the Garden Park area north of Canyon City, Colorado. The Fund was exposed from hard sandstone, skull and spine have been found strongly crushed. From the same quarry was - in addition to many other dinosaur fossils - previously salvaged the holotype specimen of Allosaurus. 1884 Othniel Charles Marsh described based on this skeleton, a new genus and species, Ceratosaurus nasicornis. Thanks to the relatively complete remains of Ceratosaurus was at this time the best-known Jurassic theropod America. The name Ceratosaurus ( gr keras - " Horn ", sauros - " lizard" ) means something like " horn lizard" and is intended to indicate the prominent nose horn. Charles Gilmore in 1920 published an extensive redescription of the skeleton.
A first skeletal reconstruction Marsh published in 1892. As Gilmore (1920 ) noted, the dorsal spine of this reconstruction shows at least six supernumerary vertebrae, resulting in a significantly long fuselage. This error has been adopted in various publications of the following period, so, however, published in the first live reconstruction, Frank Bond anfertigte 1899 under the guidance of Charles Knight in 1920. A more correct live reconstruction was created by JM Gleeson, also under the guidance of Charles Knight, and published in 1901. The holotype skeleton was mounted in 1910 and 1911 by Gilmore and since then at the National Museum of Natural History in Washington, DC to see. Since the skeleton is strongly laterally crushed, mounted Gilmore the skeleton as bas-relief ( low relief ). Early reconstructions show Ceratosaurus usually in an upright position and resting on the floor with a tail. Gilmore assembly, however, was ahead of its time - inspired by the found in heavily angled position femur Gilmore presented the assembly as an ongoing animal is, with a horizontal posture and not touching the ground tail.
After the discovery of the holotype specimen initially only very fragmentary remains of Ceratosaurus were found. Only in the early 1960s, a fragmentary skeleton with skull ( copy number UMNH VP 5278 ) was recovered at the Cleveland -Lloyd Quarry in Utah under the direction of James Madsen - it involves the largest known Ceratosaurus specimen. Unlike the holotype specimen of this skeleton has been found not to be articulated; the bones no longer were in the discovery in its original anatomical position. Another articulated skeleton with skull ( copy number MWC 1) discovered Thor Erikson, the son of paleontologist Lance Erikson, 1976 near the city of Fruita, Colorado. This copy is relatively complete, important missing skeletal elements include the mandible, forearms and belly ribs ( Gastralia ) with a. It was a great individual who was not fully grown, after which point numerous open Schädelsuturen. Both skeletons were of Madsen and Welles ( 2000) in their revision of the genus, with the skeleton discovered in Utah of the new species Ceratosaurus magnicornis forms the holotype of the new species Ceratosaurus dentisuclatus and discovered in the Colorado. 1992 a further fragmentary skeleton ( copy number BYUVP 12893 ) was discovered in the Agate Basin Quarry, Utah; the description is currently being prepared. This copy includes a full face skull, seven fragmentary vertebrae and fragmentary pelvic bone with a. It is one of the largest known skeletons of Ceratosaurus. 1999 Brooks Britt reported about the discovery of the so far only Ceratosaurus skeleton that belonged to a young animal. This skeleton is from the Bone Cabin Quarry in Wyoming. It is about 34% smaller than the holotype instance, consisting of a complete skull, and the obtained Postkranium to 30% including a full tank.
In addition to the five skeletal remains more fragmentary finds from several major localities are known. Thus comes from the Dinosaur National Monument in Utah comes up found an isolated, right premaxillary bone ( premaxilla, copy number DNM 972). From Como Bluff in Wyoming the discovery of a large scapula with coracoid was reported. Also comes from the Dry Mesa Quarry in Colorado a still undescribed, of a left scapula with coracoid and fragments of vertebrae and limbs of current fund. In the Mygatt -Moore Quarry in Colorado, the genus is represented by teeth.
Evidence outside of North America
In the years 1909-1913 expeditions brought the Berlin Museum of Natural History, the diverse dinosaur fauna of the Tendaguru formation in present-day Tanzania days. The Tendaguru formation is regarded today as the most important location for dinosaur fossils in Africa, although large theropods are only narrated by few and very fragmentary remains. 1920 wrote Werner Janensch some vertebrae from the quarry TL of the genus Ceratosaurus, without assign it to a specific type ( Ceratosaurus sp.). 1925 described Janensch a new Ceratosaurus - kind, Ceratosaurus roechlingi based on fragmentary remains from the quarry Mw, comprising a square leg, a fibula, remains of caudal vertebrae and more fragments. This discovery was part of a beast that was significantly larger than the holotype specimen of Ceratosaurus. Madsen and Welles (2000) confirm the association of the two discoveries to Ceratosaurus and write some teeth of Janensch 1920 as Labrosaurus (?) Were described stechowi also to Ceratosaurus. However, other authors disagree and state that none of the findings derived from Tendaguru shows diagnostic features that would justify an assignment to Ceratosaurus. Rowe and Gauthier (1990 ) mention a second Ceratosaurus species from Tendaguru, Ceratosaurus ingens, which was set up supposedly from Janensch (1920 ) and is based on 25 isolated encountered and with up to 15 cm in length very big teeth. In fact, however Janensch has this type of the genus Megalosaurus attributed, so it may constitute a transcription errors in this name.
Octavio Mateus and colleagues ( 2000, 2006 ) Ceratosaurus Write a bone Fund, consisting of a femur and a tibia, as well as various isolated corpus of teeth, which emanate from the Lourinhã lineup in Portugal. These researchers come to the conclusion that the Portuguese Theropodenfauna similarly composed as those of the North American Morrison Formation. So were also detected in Portugal next Ceratosaurus two more typical of the Morrison Formation genus Allosaurus and Torvosaurus. Europe was divided at the time of the Upper Jurassic through the only young and narrow Atlantic Ocean from North America, the Iberian Peninsula was separated from other parts of Europe. The similarity of the Theropodenfaunen Portugal and North America suggest, however temporarily on the existing land bridges that allowed a faunal exchange. These authors attribute the bones found in the type Ceratosaurus dentisuclatus. While Carrano and Sampson (2008) confirm the assignment of these fossils to Ceratosaurus, but come to the conclusion that the Fund no particular type can be assigned.
From Moutier ( Switzerland ) where a single tooth, originally from Janensch (1920 ) described as meriani Labrosaurus, but by Madsen and Welles (2000) as Ceratosaurus sp. was designated. Soto and Perea ( 2008) describe teeth from the Tacuarembó formation of Uruguay, the show features that are diagnostic for the genus Ceratosaurus. However, an assignment of these teeth to Ceratosaurus is excluded because of only sparse fossil material according to these researchers. The assignments of fossils from Europe and Africa to the genus Ceratosaurus had to be considered, according to these researchers because of the sparse fossil material with caution.
System
Species
The type species and currently the only widely recognized species is Ceratosaurus nasicornis. Madsen and Welles (2000) presented two new species: Ceratosaurus Ceratosaurus dentisulcatus magnicornis from Colorado and Utah. While Ceratosaurus magnicornis a slightly rounder horn shows as Ceratosaurus nasicornis, the horn is in the fossil record at Ceratosaurus dentisulcatus. Both species were significantly larger than Ceratosaurus nasicornis. The validity of this species is controversial: Britt and colleagues ( 2000) suggest that it was indeed a juvenile in the holotype specimen of Ceratosaurus nasicornis, and that the two larger species actually represent adult stages of Ceratosaurus nasicornis. Rauhut (2003) and Carrano and Sampson (2008) hold the two new species are also identical with Ceratosaurus nasicornis and indicate that it is probably caused by ontogenetic ( development-specific ) or individual variations in the differences described by Madsen and Welles.
Outer systematics
Spinostropheus
Ceratosaurus
Abelisauroidea
The group includes the group Ceratosauria Abelisauroidea, which comprises all derived ( advanced ) representatives such as Carnotaurus and Noasaurus, as well as a number of basal ( original ) representatives, including Ceratosaurus, Elaphrosaurus, Spinostropheus and Deltadromeus. See Most studies Ceratosaurus than the abgeleitetste these basal genera and as a sister taxon of Abelisauroidea. Oliver Rauhut (2004 ) suggests, however, that the well-known only by the jaw bone Genyodectes is the sister taxon of Ceratosaurus; both classes he summarizes as Ceratosauridae. The group Ceratosauridae was erected in 1884 by Othniel Charles Marsh, but contained Ceratosaurus as the sole representative of why it was regarded by later authors as redundant and not used.
A native of the Middle Jurassic England's skull has a similar nose horn like that of Ceratosaurus. Friedrich von Huene (1926 ) described the skull as Proceratosaurus ( "pre- Ceratosaurus " ) because he assumed that it was a precursor of the late Jurassic Ceratosaurus. Today Proceratosaurus is regarded as a representative of the Tetanurae; Oliver Rauhut and colleagues ( 2010) classify this genus as the oldest known representative of the Tyrannosauroidea. The characteristic nose horn has at Proceratosaurus Ceratosaurus and thus convergent developed ( independently).
Paleobiology and paleoecology
Habitat and ecological niches
All the fossils of Ceratosaurus found in North America date from the Kimmeridgian and Tithonian of the Morrison Formation, one of the most important finds layers for dinosaur fossils. Ceratosaurus shared the habitat with other theropods, such as the Megalosauriden Torvosaurus and the Allosauriden Allosaurus. So contained the archaeological site Garden Park in Colorado, next to the remains of Ceratosaurus, the remains of Allosaurus. The Cleveland -Lloyd Quarry in Utah, the Dry Mesa Quarry in Colorado and Dinosaur National Monument on the border of Colorado and Utah each had the remains of at least three Großtheropoden on: Ceratosaurus, Allosaurus and Torvosaurus. Also Como Bluff and adjacent localities in Wyoming retrieved the remains of Ceratosaurus, Allosaurus and a large Megalosauriden.
Several studies try to clarify what mechanisms could have limited the direct competition of these species. Henderson (1998 ) examined Ceratosaurus and two morphotypes of Allosaurus - a form with a shortened snout, a high and broad skull and short, teeth turned backwards and a shape with a longer snout, a lower skull and long, more vertical teeth. The competition among sympatric living species is the greater, the more similar the species in their morphology, physiology and behavior are in general. Henderson comes to the conclusion that the short-snouted Allosaurus morphs another ecological niche occupied as Ceratosaurus and langschnäuzige Allosaurus morphs: So led the shorter skull of Allosaurus morphs to a reduction of the bending moments, which is exposed in a bite of the skull, resulting in a overall stronger bite, similar to a cat. The langschnäuzige skull of Ceratosaurus and the other Allosaurus morphs, however, might be compared with that of a dog: So the longer teeth may have had the function of fangs for adding slot wounds, the bite force was focused because of the narrower skull on a smaller area.
Henderson's comparison of the long-snouted Allosaurus Ceratosaurus morphs with contrast showed great similarities, from which he concludes that these two forms were in direct competition with each other. Henderson believed that Allosaurus Ceratosaurus has pushed further and further. So the Cleveland -Lloyd Quarry shows the remains of the long-snouted Allosaurus morphs and of Ceratosaurus, which seemed Ceratosaurus been very rare. In the Dry Mesa Quarry, however, that fossils of Ceratosaurus and Allosaurus kurzschnäuzigen morphs barg, Ceratosaurus is discovered far more common.
The evolution of the extremely elongated teeth in Ceratosaurus Henderson interpreted as a direct result of the pressure of competition with the long-snouted Allosaurus morphs. To escape into a different ecological niche, Ceratosaurus could have other prey preferred; as scavengers could Ceratosaurus have eaten other parts of carcasses. The elongated teeth could have served as a visual signal for recognition of conspecifics or possessed other social functions. The evolution of large body size of these theropods (6-8 m), according to Henderson contributes to the reduction of competition in, since with increasing body size, the prey spectrum is increased.
In a recent study suggest Robert Bakker and Gary Bir (2004) that Ceratosaurus was mainly specialized in living in water prey such as lung fish, crocodiles and turtles. A statistical analysis of the distribution of dental findings in 50 sites found in and around Como Bluff that teeth of Ceratosaurus and Megalosauriden be found mainly in aquatic -dominated sites, where Ceratosaurus occasionally also appears in sites with references to dry conditions. Allosauriden were found, however, in sites with references to dry conditions and in aquatic -dominated sites alike.
These researchers conclude that Ceratosaurus and Megalosauriden especially in and around the water chased, with Ceratosaurus occasionally ate at carcasses of large dinosaurs. Next, the researchers point to the unusually deep and thus crocodile-like tail of Ceratosaurus, in which it may have been an adaptation to swimming. Moreover, the body of Ceratosaurus and Megalosauriden was relatively long, low and flexible, while Allosauriden showed a short, high and rigid body - thus Ceratosaurus would have been a better swimmer than a Allosauride. Allosauriden other hand, are designed for fast running in open areas and on the capture of large herbivorous dinosaurs like sauropods and Stegosaurus, but are seasonal dodged on aquatic prey when these herbivores were not available.
Function of head horns
Othniel Charles Marsh (1884 ) and Charles Gilmore (1920 ) suggest that the seated on the base bony nose horn was big and sharp and was actively used for both defense and attack. Rowe and Gauthier (1990 ) counter that the nasal horn and brow horns were not stable enough to be used in combat can. Instead, these horns have probably served only the display. Also, the number of osteoderms on the midline of the body could have served according to these researchers the display.
Paleopathology
The foot of the holotype specimen is distinguished by the fused metatarsals 2 and 4. Although some authors assumed that this was a characteristic feature of the genus, it was a pathological feature, possibly due to a healed fracture.
In popular culture
Ceratosaurus is one with his characteristic head horns, his four - fingered hand and in a row over the body extending bone plates to the dinosaurs widely known among the public and, as such, to find regularly in popular books about dinosaurs. Ceratosaurus appears in numerous films about dinosaurs; it plays a major role, for example in the first dinosaur action movie Brute Force by David Wark Griffith ( 1913), where he attacks cavemen.