Saurolophus is a genus of large hadrosaurine duckbill that lived about 69.5-68.5 million years ago, in the Late Cretaceous of North America and Asia; it is one of the few genera of dinosaurs known from multiple continents. It is distinguished by a spike-like crest which projects up and back from the skull. At 40 feet (12 meters), Saurolophus was one of the larger of the hadrosaur family. Saurolophus was an herbivorous dinosaur which could move about either bipedally or quadrupedally. The type species, S. osborni, was described by Barnum Brown in 1912 from Canadian fossils. A second valid species, S. angustirostris, is represented by numerous specimens from Mongolia, and was described by Anatoly Konstantinovich Rozhdestvensky. A third species, S. "morrisi" from California, was made into the genus Augustynolophus, and a fourth species, S. kryschtofovici from China, is considered dubious.
Discovery and history[]
Photo from the excavation of S. osborni in 1911
Barnum Brown recovered the first remains of Saurolophus in 1911, including a nearly complete skeleton (AMNH 5220). Today displayed at the American Museum of Natural History, this was Canada's first nearly complete dinosaur skeleton. It was found in Maastrichtian sediments, in the Upper Cretaceous Horseshoe Canyon Formation, known at that time as the Edmonton Formation, near Tolman Ferry on the Red Deer River in Alberta. Brown wasted little time describing this animal, giving it its own subfamily of its own. Saurolophus is an important early reference for other hadrosaurids, as seen in the names Prosaurolophus ("pre- Saurolophus ") and Parasaurolophus ("close to Saurolophus "). However, little additional material has been recovered and described.
Instead, more abundant remains from Asia have provided more data. Initially the remains were not promising, a partial ischium from Heilongjiang, China that Riabinin named S. kryschtofovici . Better preserved remains were quickly found, although from the Nemegt Formation in the early Maastrichtian in Mongolia'. Between 1947 and 1949 the Polish-Mongolian paleontological expedition recovered the large skeleton that would be described as S. angustirostris by Anatoly Konstantinovich Rozhdestvensky. Other skeletons of a wide variety of growth stages have also been discovered, and S. angustirostris is today the most abundant hadrosaurid in Asia.
Description[]
Saurolophus is known from material including nearly complete skeletons, giving researchers a clear picture of its bony anatomy. S. osborni, the rarer Albertan species, was around 9.8 meters long, with its skull 1.0 meters long. S. angustirostris, the Mongolian species, was larger; the type skeleton is roughly 12 meters long, and larger remains are reported. Aside from size, the two species are virtually identical, with differentiation hindered by lack of study.
Diagram with labelled skulls of S. angustirostris (A) and S. osborni (B)
The most distinctive feature of Saurolophus is its cranial crest, which is present in young individuals, but is smaller. It is long and spike-like and projects upward and backward at about a 45° angle, starting from over the eyes. This crest is often described as solid, but appears to be solid only at the point, with internal chambers that may have had a respiratory and/or heat-regulation function.
The holotype of S. angustirostris is a skull and postcrania, so the cranium of the species is well-described. Bell et al. re-evaluated the entire species in a 2011 publication with Acta Palaeontologica Polonica. Their description found the skull to be generalized among hadrosaurines, and are much larger than any skulls of S. osborni. The most unusual feature for a hadrosaurine is the long, protruding, solid crest that extends upwards diagonally from the back of the skull roof. Unlike lambeosaurines, the crests are made up completely of the nasal bone. The premaxilla bones make up almost 50% of the entire skull length, and both sides are filled with small holes. Only in adult individuals has the front of the premaxillary contact been fused. Longer than the premaxilla, the nasal bones are the longest in the skull. They make up the entire length of the crest, and are never preserved as fused.
Classification[]
Skull of the holotype specimen of S. osborni
Barnum Brown, who described the first specimens, put it in its own subfamily in "Trachodontidae" (=Hadrosauridae), the Saurolophinae. At the time, this also featured Corythosaurus and Hypacrosaurus, the only well-known examples of what would become Lambeosaurinae.[1] Brown thought that Saurolophus had an enlarged tip to the ischium in the hip, as dinosaurs now seen as lambeosaurines had, but this seems to have been based on a wrongly associated lambeosaurine ischium. Also, he confused the crests of Saurolophus and lambeosaurines as being made of the same bones.[2]
Most publications before 2010 classified Saurolophus as a member of Hadrosaurinae, often known colloquially as the "flat-headed hadrosaurs". In 2010, the subfamily Saurolophinae was brought back to use since Hadrosaurus seem sto have branched off prior to the "hadrosaurine"–lambeosaurine split. As a result, Hadrosaurinae by definition can't include the traditional "hadrosaurines". Saurolophinae is the oldest available name for the former "hadrosaurine" clade.[3] Saurolophus, as the name suggests, is a saurolophine, as it has a saurolophine pelvis and a (largely) solid crest.
The following cladogram of hadrosaurid relationships was published in 2013 by Alberto Prieto-Márquez et al. in Acta Palaeontologica Polonica:
| Saurolophinae |
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Paleobiology[]
Like all hadrosaurids, Saurolophus could move bipedally and quadrupedally, being a herbivore, eating a wide variety of plants. The skull allowed movement analogous to chewing, and its teeth were continually replaced and packed into dental batteries containing hundreds of teeth, although only a handful of these were used at a time. The plant material was collected by a beak, and kept inside the mouth by an organ similar to the cheeks. It fed on vegetation that grew up to four meters high.
Skull of S. angustirostris
The common S. angustirostris must have been an important herbivore in the Nemegt Formation, but S. osborni was rare in the Horseshoe Canyon Formation competing with other hadrosaurids such as Edmontosaurus and Hypacrosaurus . The distinctive spike-like crest of Saurolophus has been interpreted in multiple ways. ways, and could have had multiple functions. Brown compared it to the crest of a chameleon, and suggested that it might provide an area for muscle insertion and an attachment point for a posterior sail like that seen in the Jesus Christ lizard. Peter Dodson interpreted similar shapes in other hadrosaurids as a form of sexual identification. Maryańska and Osmólska noted a hollow base, suggesting that the ridge expanded the respiratory area helping thermoregulation. James Hopson supported the function as a visual cue, and mentioned the remote possibility that there were inflatable flaps of skin over the nostrils that could have acted as resonators and additional visual cues. This idea has been taken up by authors of popular works on dinosaurs, for example David B. Norman who discussed the hadrosaurid display at length and included a restoration of such an adaptation in action.
Paleoecology[]
S. osborni was found in the Horseshoe Canyon Formation along with several other duck-billed dinosaurs Edmontosaurus and the crested Hypacrosaurus , hypsilophodontids such as Parksosaurus , ankylosaurids ( Euoplocephalus ), nodosaurids such as Edmontonia , the horned dinosaurs Montanoceratops , Anchiceratops , Arrhinoceratops and Pachyrhinosaurus , the pachycephalosaurid Stegoceras , ornithomimosaurians such as Ornithomimus and Struthiomimus , with a variety of poorly known small theropods including troodontids and dromaeosaurids, as well as the tyrannosaurids Albertosaurus and Daspletosaurus . The dinosaur fauna of this formation are sometimes known as Edmontonians, which should be differentiated from the Tertiary fauna of the same name, and are distinct from those of the Upper and Lower formations. The Horseshoe Canyon Formation is interpreted to have had a great marine influence, due to the ingression of the Western Interior Sea, an epicontinental sea that covered central North America during much of the Cretaceous. S. osborni may have preferred to remain on higher ground.
Restoration of a S. angustirostris herd in their native Nemegt Formation alongside a Homalocephale pair
S. angustirostris is one of the largest herbivores of the Nemegt Formation, in which ceratopsians are missing but sauropods and a more diverse theropod fauna are present. It coexisted with the crested hadrosaurid Barsboldia , the flat-headed pachycephalosaur Homalocephale and the dome-headed Prenocephale , the large ankylosaurid Tarchia and the saltosaurids Nemegtosaurus and Opisthocoelicaudia , the alvarezsaurid Mononykus , three types of troodontids including Saurornithoides , several oviraptorosaurs including Rinchenia and Nomingia , the ostrich mimics Gallimimus and Deinocheirus , the thericinosaurid Therizinosaurus , the tyrannosaurid relative Bagaraatan , and the tyrannosaurid proper Tarbosaurus . Unlike other well-known Mongolian formations such as the Djadochta Formation that include Velociraptor and Protoceratops , Nemegt is interpreted as an area of abundant moisture, like the Dinosaur Park Formation in Alberta.
JPInstitute.com Description[]
Saurolophus is a well-known member of the duck-bill family of dinosaurs. It had a small crest on the top of its head, highlighted by a fairly short and hollow tube. Like the other duck-billed dinosaurs, it had a large, flat beak (like a duck) at the front of its mouth and hundreds of teeth packed closely together to form what is called a dental battery. These were used to grind tough plant fiber into mushy pulp so that it could be digested more easily.
The Asian species of this genus, S. angustirostris, was considerably larger than the Saurolophus specimen found in Southwestern Canada. Discovered in 1911, this was the most complete Canadian dinosaur found up to that time. The Canadian species is about 7 feet (2 m) shorter than its Asian relative.
Appearance in other media[]
Jurassic Park[]
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Read more Saurolophus on Jurassic Park Wiki |
The Land Before Time[]
- Ducky from the Land Before Time franchise is a young Saurolophus.
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Read more Saurolophus on Land Before Time Wiki |
We're Back! A Dinosaur's Story[]
- Jorbi from the children's book We're Back! A Dinosaur's Story and its sequel, Going Hollywood! A Dinosaur's Dream is a purple Saurolophus.
Links[]
References[]
- ↑ Brown, Barnum (1914)."Corythosaurus casuarius, a new crested dinosaur from the Belly River Cretaceous, with provisional classification of the family Trachodontidae". Bulletin of the American Museum of Natural History 33 (55): 559–564. Retrieved 2007-04-29.
- ↑ Sternberg, Charles M. (1954). "Classification of American duckbilled dinosaurs". Journal of Paleontology 28 (3): 382–383.
- ↑ Template:Cite journal