découverte

Diagram made to illustrate the debate over the hands of theropod dinosaurs and their alleged descendants, the birds ( Aves ). In the last years, the difference between the hands of theropods and birds have been an important thing when it comes question the theory that birds evolved from dinosaurs, even though some scientists may could refute it. In the diagram, a Neotheropoda ( 1 ), basal tetanurae ( 2 ), a coelurosaurian ( 3 ), the bird (?)Archaeopteryx ( 4 ) and modern bird ( 5 ). In 1997, birdexpert Alan Feduccia at University of North Carolina discovered that birds develop hands with the digits II, III and IV ( see The Cincinnati Enquirer, 25 - 10 - 1997 ). This is in contrast with the hands of tetanurae, which seems to have the digits I, II and III. This make it almost impossible for dinosaurs and birds to be closely related, according to Feduccia. Since the discovery by Feduccia, scientific research have came up with a possible explanation to the mystery of the dinosaur - bird hand difference, called The frame shift hypothesis ( see http://scienceblogs.com/tetrapodzoology/2009/06/limusaurus_is_awesome.php ). This hypothesis is based on a discovery which shows that although bird embryos develop the fingers II, III and IV, the genes which is coding for the external appearance of the digits seems to be from the fingers I, II and III. Based on this, scientists belive this: when neotheropods evolved into tetanurae, the losed digit I ( not digit IV, as earlier suggested ). During this process, the genes which coded for how the digits should looks like ( the number of phalanges, for example ) became refurnished ( see the color spots in th upper section in the diagram to understan ). The discovery of Limusaurus has been said to support this theory ( see https://www.livescience.com/animals/090617-dinosaur-hands.html ). One thing is that may can be used to refute that Limusaurus should support the Frame shift hypothesis is that Limusaurus was a ceratosaurian, and is dated to be much younger than the oldest tetanurae's. Also, some tetanure´s may had 4 digits' like the Archaeornithomimus ( see number 4 in the diagram ) ( see also http://dml.cmnh.org/1998Oct/msg00443.html and the Allosaurus hand in the image here: http://upload.wikimedia.org/wikipedia/commons/6/69/Allosaurus-mounted.jpg ). If this is the digits I, II, III and IV. If so, it shows that tetanurae had the digits I, II and III, and not II, II and IV, like birds. For more in this debate, see text section to my picture Raptor-Archaeopteryx-bird hands differens.JPG at http://commons.wikimedia.org/wiki/File:Raptor-Archaeopteryx-bird_hands_differens.JPG.

The Canadian Fossil Discovery Centre in Morden boasts the largest collection of marine invertebrate fossils in Canada. Visitors to the museum not only get to see this collection, but can join a dig in search for more fossils at a 109-acre escarpment property. Photo credit: Robyn Hanson

Tawa is an early theropod from the Late Triassic. The genus is named after the Hopi word for the Puebloan sun god. It was a bipedal carnivore, estimated around 2.5 m in length, and weighing about 15 kg. A basal theropod, Tawa shares physical characteristics with coelophysoids and herrerasaurids, and its discovery supports the theory that dinosaurs originated in the southern supercontinent of Gondwanna, before diversifying as Pangea split apart.

Tyrannosaurus rex, Palais de la Découverte, Paris

Reconstruceted skull of Dubreuillosaurus illustrating known (white) and unknown (grey) material. Scale bar is 10cm. Based of figures and description of Allain (2002) "Discovery of megalosaur (Dinosauria, Theropoda) in the middle Bathonian of Normandy (France) and its implications for the phylogeny of basal Tetanurae"

Malefica is a hadrosaurid dinosaur from the Late Cretaceous of Texas in the United States. Like other hadrosaurs, Malefica was herbivorous, processing plant matter with their broad beaks and battery of teeth in the back of the mouth. It could grow to around 6 m in length, and weighed about 1 t. The discovery of Malefica helped to understand the distribution of hadrosaurs in Cretaceous North America, as well as evolutionary lineages between basal hadrosaurs and the more derived saurolophids.

Jiangxititan a titanosaurian sauropod from the Late Cretaceous of China. Typical for a sauropod, it had a long neck and stood on four pillar-like legs to support its massive body. Jiangxititan is a member of the Lognkosauria, which include some of the largest dinosaurs known, and is one of the few from mainland Asia. The discovery of Jiangxititan demonstrates the presence of both early-diverging and late-diverging titanosauriform sauropods in that area during the Late Cretaceous.

Qunkasaura is a titanosaurian sauropod dinosaur that lived approximately 75 million years ago in the Late Cretaceous of what is now Spain. Specifically, it is a saltasaurid titanosaur, and its discovery marks the first instance of two distinct lineages of this group present in the same locality. In the Late Cretaceous, Europe was a large archipelago, and the coexistence of these differing lineages indicates that saltasaurids arrived in the Iberian Peninsula much later than other groups of dinosaurs.

In 2000 a virtually complete Scelidosaurus skeleton was discovered in England. This fossil's hundreds of armor plates and spikes are preserved in their life positions, providing extraordinary details about how this dinosaur looked. St. George is the only place anywhere in the Western Hemisphere that the 11-foot long Scelidosaurus replica has been on display. The St. George Dinosaur Discovery Site at Johnson Farm (St. George, Utah) is home to exceptionally well-preserved dinosaur tracks, some displaying skin impressions. These tracks, along with hundreds of fossil fish, plants, rare dinosaur remains, invertebrates traces and important sedimentary structures, show evidence that this site was produced along the western edge of a large, Early Jurassic (age between 195-198 million years ago) freshwater lake named Lake Dixie. Source: www.sgcity.org/dinotrax/

In 2000 a virtually complete Scelidosaurus skeleton was discovered in England. This fossil's hundreds of armor plates and spikes are preserved in their life positions, providing extraordinary details about how this dinosaur looked. St. George is the only place anywhere in the Western Hemisphere that the 11-foot long Scelidosaurus replica has been on display. The St. George Dinosaur Discovery Site at Johnson Farm (St. George, Utah) is home to exceptionally well-preserved dinosaur tracks, some displaying skin impressions. These tracks, along with hundreds of fossil fish, plants, rare dinosaur remains, invertebrates traces and important sedimentary structures, show evidence that this site was produced along the western edge of a large, Early Jurassic (age between 195-198 million years ago) freshwater lake named Lake Dixie. Source: www.sgcity.org/dinotrax/