![]() Instead, other sites in the American West would come to provide many very complete specimens that would form the backbone of hadrosaur research. The Eastern states, too, would never yield particularly informative specimens. Research would continue in the Judith River area for years to come, but the formation never yielded much more than fragmentary remains, and Cope's species as well as Trachodon itself would in time be seen as of doubtful validity. As such, he supposed the animals must have fed largely on soft water plants he presented this idea to the Philadelphia Academy in 1883, and this idea would come to be very influential on future study. Cope had studied the jaws of hadrosaurs and come to the conclusion that the teeth were fragile and could have been dislodged incredibly easily. Upon the fragments discovered he named seven new species in two genera, as well as assigning material to Hadrosaurus. ![]() From the mid 19th century through much of the 20th century, hadrosaurs were considered aquatic animals which subsisted on soft water plantsįurther discoveries such as " Hadrosaurus minor" and " Ornithotarsus immanis" would come from the East, and Edward Drinker Cope led an expedition to the Judith River Formation where Trachodon was found. Among his 1858 work Leidy briefly suggested that the animal was likely amphibious in nature this school of thought about hadrosaurs would come to be dominant for over a century to come. Leidy provided additional description in a 1865 paper. They were described in the same year as Hadrosaurus foulkii, giving a slightly better picture of the form of a hadrosaur. ![]() Foulke obtained permission to investigate the now scattered fossils in 1858, and these specimens as well were given to Leidy. Around the same time in Philadelphia, on the other side of the continent, geologist William Parker Foulke was informed of numerous large bones accidentally uncovered by farmer John E. occidentalis would come to be recognized as the first recognized hadrosaur specimens. ![]() Although most of the Trachodon teeth turned out to belong to ceratopsids, the holotype and remains of T. The former was based on a collection of teeth whilst the later on two caudal centra and a phalanx. These specimens were obtained by Joseph Leidy, who described and named them in 1856 two of the several species named were Trachodon mirabilis of the Judith River Formation and Thespesius occidentalis of the " Great Lignite Formation". History of discovery Illustration of Trachodon mirabilis teethįerdinand Vandeveer Hayden, during expeditions near the Judith River in 1854 through 1856, discovered the very first dinosaur fossils recognized from North America. Hadrosaurids were facultative bipeds, with the young of some species walking mostly on two legs and the adults walking mostly on four. Lambeosaurines included the aralosaurins, tsintaosaurins, lambeosaurins and parasaurolophins, while saurolophines included the brachylophosaurins, kritosaurins, saurolophins and edmontosaurins. Saurolophines tended to be bulkier than lambeosaurines. Hadrosauridae is divided into two principal subfamilies: the lambeosaurines ( Lambeosaurinae), which had hollow cranial crests or tubes and the saurolophines ( Saurolophinae), identified as hadrosaurines (Hadrosaurinae) in most pre-2010 works, which lacked hollow cranial crests (solid crests were present in some forms). Unlike more primitive iguanodonts, the teeth of hadrosaurids are stacked into complex structures known as dental batteries, which acted as effective grinding surfaces. Like other ornithischians, hadrosaurids had a predentary bone and a pubic bone which was positioned backwards in the pelvis. Hadrosaurs were among the most dominant herbivores during the Late Cretaceous in Asia and North America, and during the close of the Cretaceous several lineages dispersed into Europe, Africa, and South America. Hadrosaurids are descendants of the Upper Jurassic/Lower Cretaceous iguanodontian dinosaurs and had a similar body layout. The ornithopod family, which includes genera such as Edmontosaurus and Parasaurolophus, was a common group of herbivores during the Late Cretaceous Period. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. Hadrosaurids (from Ancient Greek ἁδρός ( hadrós) 'stout, thick', and σαύρα ( saúra) 'lizard'), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae.
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