Dinosauria

Ареал карнозавров

Reconstruction of the theropod dinosaur Tachiraptor admirabilis. Artwork created with graphite and colored pencils. Author: Edwin Chávez "Disfrasaurio".

Ceratosaurus nasicornis reconstruction. Matches proportions shown in Gregory S. Paul (The Princeton Field Guide to Dinosaurs, 2010, p. 84)

Sketch-drawing of the vertebrate faunal assemblage of the Lisowice site (modified from Niedźwiedzki)10. (a) Large, theropod-like predatory archosaur (Smok wawelski); (b) large temnospondyl amphibian (Cyclotosaurus sp.); (c) small predatory dinosaurs (Neotheropoda indet.); (d) temnospondyl amphibian (Gerrothorax sp.); (e) small basal crocodylomorph (Crocodylomorpha indet.); (f) small diapsid (Choristodere-like animal); (g) hybodont sharks (Polyacrodus and Hybodus); (h) coelacanth fish; (i) dipnoan fish (Ptychoceratodus sp.); (j) actinopterygian fish; (k) gigantic dicynodont; (l) dinosauriforms or early dinosaurs (Dinosauriformes indet. or Dinosauria indet.); (m) small lepidosauromorphs (Sphenodontia indet.); (n) pterosaurs (Pterosauria indet.); (o) early mammaliaform (Hallautherium sp.).

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.

Cladogram of amniotes. Based on File:Cladogram Amniota A.jpg

Cladogram of the former "Reptilia" (red)

Dinosaur art by me!

The Chicago specimen of Archaeopteryx (PA 830), a well-preserved fossil highlighting the transitional features between non-avian dinosaurs and birds, housed at the Field Museum of Natural History.

Life representation of Bicharracosaurus dionidei

A badly drew sketch of Brontoholus (a placeholder for when an actual paleoart of Brontotholus is made.

Archeology center interior Svilajnac

Apex Stegosaurus Reconstruction drawn Jan, 7, 2025 by Adam Treviño

Anteavis

Dinosaur art by me!

A scientifically accurate reconstruction of the dinosaur Spinosaurus aegyptiacus.