Corythosaurus

The first specimen, AMNH 5240, was discovered in 1911 by Barnum Brown in Red Deer River of Alberta and secured by him in the Fall of 1912. The two best preserved specimens of Corythosaurus, found by Charles H. Sternberg in 1912, were lost on December 6, 1916, while being carried by the SS Mount Temple to the United Kingdom during World War I. They were being sent to Arthur Smith Woodward, a paleontologist of the British Museum of Natural History in England, when the ship transporting them was sunk by the German merchant raider in the middle of the ocean. There were formerly up to seven species described, including C. casuarius, C. bicristatus (Parks 1935), C. brevicristatus (Parks 1935), C. excavatus (Gilmore 1923), C. frontalis (Parks 1935), and C. intermedius (Parks 1923). In 1975, Peter Dodson studied the differences between the skulls and crests of different species of lambeosaurine dinosaurs. He found that the differences in size and shape may have actually been related to the sex and age of the animal. Only one species is currently recognized for certain, C. casuarius, The specific name of C. intermedius is derived from its apparent intermediate position according to Parks. C. intermedius lived at a slightly later time in the Campanian than C. casuarius and the two species are not identical, which supported the separation of them in a 2009 study. ==Description==

Size Benson et al. (2012) estimated that Corythosaurus has an average length of . The total length of Corythosaurus specimen AMNH 5240 was found to be long, with a weight close to . In 2016, Gregory S. Paul estimated that C. casuarius reached long and in weight and that C. intermedius reached in length and in weight. A "morphologically adult-sized specimen" of C. casuarius measured approximately long. Proportionally, the skull is much shorter and smaller than that of Edmontosaurus (formerly Trachodon), Kritosaurus, or Saurolophus. But, when including its crest, its superficial area is almost as large. 1984.121.0001 The mouth of the holotype of Corythosaurus is narrow. The praemaxillae each form two long folds that enclose air passages extending the narial passages to the front of the snout. There, they end in narrow openings, sometimes called "pseudonares", which are false bony nostrils. These were mistaken by Brown for the real nares or nostrils. These are actually situated inside the crest, above the eye sockets. As in Saurolophus, the expanded portion of the premaxillary in front of the pseudonaris' opening is elongate. By comparison, the bill of Kritosaurus is short and the pseudonares extend far forward. At the end of the Corythosaurus bill, the two pseudonares unite into one. Ossified tendons are present on all the vertebrae, except for those in the cervical region. On no vertebrae do the tendons extend below the transverse processes. Each tendon is flattened at its origin, transversely ovoid in the central rod, and ends at a rounded point. Aside from those found on Corythosaurus casuarius, extensive skin impressions have been found on Edmontosaurus annectens and notable integument has also been found on Brachylophosaurus canadensis, Gryposaurus notabilis, Parasaurolophus walkeri, Lambeosaurus magnicristatus, L. lambei, Saurolophus angustirsotris, and on unidentified ornithopods. Of these, L. lambei, C. casuarius, G. notabilis, P. walkeri, and S. angustirsotris have preserved polygonal scales. The scales on L. lambei, S. angustirostris, and C. casuarius are all similar. Corythosaurus is one of very few hadrosaurids which have preserved skin impressions on the hind limbs and feet. A study in 2013 showed that, amongst hadrosaurids, Saurolophus angustirostris preserved the best and most complete foot and limb integument, although other species like S. osborni, Edmontosaurus annectens, and Lambeosaurus lambei (= L. clavinitialis) share a fair amount of preserved tissue on those regions. It was once thought that this dinosaur lived mostly in the water, due to the appearance of webbed hands and feet. However, it was later discovered that the so-called "webs" were in fact deflated padding, much like that found on many modern mammals. Distinguishing characteristics A set of characters were indicated by Barnum Brown in 1914 to distinguish Corythosaurus from all other hadrosaurids from Alberta. These include a comparatively short skull with a high helmet-like crest formed by the nasals, prefrontals, and frontals; the nasals not being separated in front by the premaxillaries; a narrow beak with an expansion in front of an elongated naris; and a small narial opening. In 1916, Brown expanded the character set to include even more features. In the revised version, these extra features include a comparatively short skull with a high helmet-like crest formed by nasals, prefrontals, and frontals; the nasals not being separated in front by premaxillaries; a narrow beak; expanded section in front of the elongated nares; a small narial opening; a vertebral formula of 15 cervicals, 19 dorsals, 8 sacrals, and 61+ caudals; possession of dorsal spines of a medium height; high anterior caudal spines; long chevrons; long scapulae that possess a blade of medium width; a radius considerably longer than the humerus; comparatively short metacarpals, an anteriorly decurved ilium; a long ischium with a foot-like terminal expansion; a pubis with an anterior blade that is short and broadly expanded at the end; a femur that is longer than the tibia; the phalanges of pes are short; that the integument over the sides and tail composed of polygonal tuberculate scales without pattern, but graded in size in different parts of the body; and a belly with longitudinal rows of large conical limpet-like scales separated by uniformly large polygonal tubercles. Again, the presumed traits of the snout are incorrect because Brown confused the praemaxillae with the nasal bones and the nasal bones with the frontals. Most of the postcranial traits are today known to be shared with various other lambeosaurines. ==Classification==

Originally, Brown referred to Corythosaurus as a member of the family Trachodontidae However, even though the pelvic structure of Corythosaurus and other ornithischians does bear a greater superficial resemblance to birds than the saurischian pelvis does, birds are now known to be highly derived maniraptoran theropods. of Corythosaurus cf. intermedius cf. excavatus Parks 1935 at the Royal Ontario Museum }} ==Paleobiology==

Comparisons between the scleral rings of Corythosaurus and modern reptiles suggest that it may have been cathemeral, meaning it was most active throughout the day at short intervals. The presence of a thin stapes (an ear bone that is rod-like in reptiles), combined with a large eardrum, implies the existence of a sensitive middle ear. Growth Corythosaurus casuarius is one of a few lambeosaurines, along with Lambeosaurus lambei, Hypacrosaurus stebingeri, and H. altispinus, to have had surviving fossilized juveniles assigned to it. Juveniles are harder to assign to species because, at a young age, they lack the distinctive larger crests of adults. As they age, lambeosaurine crests tend to grow and become more prominent come maturity. In the Dinosaur Park Formation, over fifty articulated specimens have been found that come from many different genera. Among them, juveniles are hard to identify at the species level. Earlier, four genera and thirteen species were recognized from the formation's area when paleontologists used differences in size and crest shape to differentiate taxa. The smallest specimens were identified as Tetragonosaurus, now seen as a synonym of Procheneosaurus, and the largest skeletons were called either Corythosaurus or Lambeosaurus. An adult was even identified as Parasaurolophus. Work by Dodson (1975) recognized that there were many less taxa present in Alberta. Tetragonosaurus was found to be juveniles of Corythosaurus or Lambeosaurus. T. erectofrons was assigned to Corythosaurus based largely on biometric information. The only non-typic specimen of Tetragonosaurus, assigned to T. erectofrons, was later found to be referable to Hypacrosaurus, although the holotype of the species was still found to be assignable to Corythosaurus. Diet Corythosaurus was an ornithopod, therefore being a herbivore. Benson et al. (2012) realized that the beak of Corythosaurus was shallow and delicate, concluding that it must have been used to feed upon soft vegetation. Based on the climate of the Late Cretaceous, they guessed that Corythosaurus would have been a selective feeder, eating only the juiciest fruits and youngest leaves. A Corythosaurus specimen has been preserved with its last meal in its chest cavity. Inside the cavity were remains of conifer needles, seeds, twigs, and fruits, meaning that Corythosaurus probably fed on all of these, implying that it was a browser. ==Paleoecology==

Fossils have been found in the upper Oldman Formation and lower Dinosaur Park Formation of Canada. The Oldman Formation dates to the Campanian, about 77.5 to 76.5 million years ago, In it, Corythosaurus was found to be closely associated with the ceratopsid Centrosaurus apertus. Their associating was found in the Dinosaur Park, Judith River, and Mesaverde formations, as well as the Wind River Basin and the Wheatland County area. Corythosaurus lived alongside numerous other giant herbivores, such as the hadrosaurids Gryposaurus and Parasaurolophus, the ceratopsids Centrosaurus and Chasmosaurus, and the ankylosaurids Scolosaurus, Edmontonia, and Dyoplosaurus in the earliest stages of the formation, Dyoplosaurus, Panoplosaurus, and Euoplocephalus in the middle age, and Euoplocephalus alone in later stages of the formation. Studies of the jaw anatomy and mechanics of these dinosaurs suggests they probably all occupied slightly different ecological niches in order to avoid direct competition for food in such a crowded eco-space. The only large predators known from the same levels of the formation as Corythosaurus are the tyrannosaurids Gorgosaurus libratus and an unnamed species of Daspletosaurus. Thomas M. Lehman has observed that Corythosaurus hasn't been discovered outside of southern Alberta, even though it is one of the most abundant Judithian dinosaurs in the region. Large herbivores like the hadrosaurs living in North America during the Late Cretaceous had "remarkably small geographic ranges" despite their large body size and high mobility. This restricted distribution strongly contrasts with modern mammalian faunas whose large herbivores' ranges "typical[ly] ... span much of a continent." ==See also==