The hadrosaurs are known as the duck-billed dinosaurs due to the similarity of their head to that of modern ducks. In some genera, most notably Anatotitan, the whole front of the skull was flat and broadened out to form a beak, ideal for clipping leaves and twigs from the forests of Asia, Europe and North America. However, the back of the mouth contained literally thousands of teeth suitable for grinding food before it was swallowed. This has been hypothesized to have been a crucial factor in the success of this group in the Cretaceous, compared to the sauropods which were still largely dependent on gastroliths for grinding their food.
In 2009, paleontologist Mark Purnell conducted a study into the chewing methods and diet of hadrosaurids, a herbivore species of duck-billed dinosaurs from the Late Cretaceous period. By analyzing hundreds of microscopic scratches on the teeth of a fossilized Edmontosaurus jaw, the team determined hadrosaurs had a unique way of eating unlike any creature living today. In contrast to a flexible lower jaw joint prevalent in today's mammals, hadrosaurs had a unique hinge between the upper jaws and the rest of its skull. The team found the dinosaur's upper jaws pushed outwards and sideways while chewing, as the lower jaw slid against the upper teeth.
Discoveries
Hadrosaurids were the first dinosaur family to be identified in North America, the first traces being found in 1855-1856 with the discovery of fossil teeth. Joseph Leidy examined the teeth, and erected the genera Trachodon and Thespesius (others included Troodon, Deinodon and Palaeoscincus). One species was named Trachodon mirabilis. Now it seems that the teeth genus Trachodon is a mixture of all sorts of cerapod dinosaurs, including ceratopsids. In 1858 the teeth were associated with Leidy's eponymous Hadrosaurus foulkii, named after the fossil hobbyist William Parker Foulke. More and more teeth were found, resulting in even more (now obsolete) genera.
A second duck-bill skeleton was unearthed, and was named Diclonius mirabilis in 1883 by Edward Drinker Cope, which he incorrectly used in favor of Trachodon mirabilis. But Trachodon, together with other poorly typed genera, was used more widely and, when Cope's famous "Diclonius mirabilis" skeleton was mounted at the American Museum of Natural History, it was labeled as "Trachodont dinosaur". The duck-billed dinosaur family was then named Trachodontidae.
Fossil Displays
Seas and Shores of the Big Bend of Texas
From Mosasaurs to Dinosaurs
Ken Barnes
Founder & Curator
Hadrosaur video
Mosasaurs
A very well-preserved complete hadrosaurid specimen (Edmontosaurus annectens) was recovered in 1908 by the fossil collector Charles Hazelius Sternberg and his three sons, in Converse County, Wyoming. Analyzed by Henry Osborn in 1912, it has come to be known as the "Trachodon mummy". This specimen's skin was almost completely preserved in the form of impressions.
One of the most complete fossilized specimens was found in 1999 in Hell Creek Formation of North Dakota and now is nicknamed "Dakota". The hadrosaur fossil is so well preserved that scientists have been able to calculate its muscle mass and learn that it was more muscular than thought, probably giving it the ability to outrun predators such as Tyrannosaurus rex. Unlike the collections of bones found in museums, this mummified hadrosaur fossil comes complete with skin (not merely skin impressions), ligaments, tendons and possibly some internal organs. They also found a gap of about a centimeter between each vertebra, indicating there may have been a disk or other material between them, allowing more flexibility and meaning the animal was actually longer than what is shown in a museum.
Mosasaurs (from Latin Mosa meaning the 'Meuse river' in the Netherlands, and Greek sauros meaning 'lizard') were serpentine marine reptiles. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764.
These ferocious marine predators are now considered to be the closest relatives of snakes, due to cladistic analysis of symptomatic similarities in jaw and skull anatomies. Mosasaurs were not dinosaurs but lepidosaurs, reptiles with overlapping scales. These predators evolved from semi-aquatic squamates known as the aigialosaurs, close relatives of modern day monitor lizards, in the Early Cretaceous Period.
During the last 20 million years of the Cretaceous Period (Turonian-Maastrichtian), with the extinction of the ichthyosaurs and pliosaurs, mosasaurs became the dominant marine predators.
Ptychodus is a genus of extinct hybodontiform shark which lived from the Cretaceous to the Paleogene.
Mosasaur
Ranch
.gif){kind=small}
This page was last updated: October 10, 2010
Champosaurus
KB-M-16 Mosasaur
Tylosaur nepaeolicus
Ptychodus Shark pavement of teeth
This is a single middle row tooth of the upper pavement of teeth of a Ptychodus mortoni. Down is the front of the tooth
 | ||||||
I have a very large Tylosaurus nepaeolicus, (1300mm skull), that died trying to swallow a Toxochelys turtle. There is also a fish fin, tooth, and vertebra, (Pachyrhizodus ), in the throat area, probably upchuck. See two pics. below.
Toxochelys turtle
Mosasaur, T. nepaeolicus
Mosasaur video
Below is part of the stomach contents of a Tylosaurus nepaeolicus mosasaur. It ate three small Platecarpus planifrons mosasaur's and a ptychodus shark. There are +/- 270 fossils.
The closest Champsosaur fossils that have been found, that I am aware of, were in N.W. New Mexico about 900 kilometers away. Tom Lehman, TTU, and myself have a manuscript in review on this guy. PUBLISHED MARCH, 2010, JOURNAL OF PALEONTOLOGY!!!!!
Champsosaurus
Artist, Lagina Fairbetter
