Compsognathus longipes is a small theropod, coelurosaurian dinosaur from Solnhofen. The type specimen (below) has in its gut region the remains of a small long-tailed lizard. There are no signs of scale or feather impressions. If a specimen such as this were to have impressions of its integument, there would be some basis for knowing if small dinosaurs has an insulatory coating of feathers.
On the right is a lithograph of Compsognathus longipes from Solnhofen. This lithograph was made on the lithographic limestone from Solnhofen itself. Such lithographic plates are the reason the quarries were opened in the first place. If you click on the image, you will go to a web site in which Compsognathus is described in more detail.
|1. three-toed foot
2. digits IV and V lost on hand
3. long arms
4. semilunate carpal
5. fused pelvis
6. large hole in lacrimal bone in skull
7. ?no unique derived characters?
8. giant, hook-like claw on digit II of pes
9. flight feathers
10. ?no unique derived characters?
Cladogram of the Theropoda
Below is the Berlin specimen of Archaeopteryx from the Solnhofen Limestone. It was the third specimen found, and unquestionably the most spectacular specimen found to date. Particularly noteworthy are the very fine feather impressions, including the flight feathers of the wings. Despite its' obvious avian nature, Archaeopteryx has a hand virtually identical to other maniraptoran dinosaurs such as Velociraptor.
Bird and Dinosaur Features
||Comparison of reconstructed skeleton of Archaeopteryx (left) and a pigeon (right). Key to homologous bones follows: yellow, sternum (breastbone); orange, furcula = fused clavicles (wishbone); yellow, coracoids; red, semilunate carpal; yellow-green, digit I of manus; green, digit II of manus; blue, digit III of manus. This drawing is modified from Gerhard Heilmanns classic monograph "The Origin of Birds".
Note the long tail, separate fingures of the manus, and small sternum of Archaeopteryx, all primitive features inhereted virtually without modification of non-bird maniraptorans.
||Reconstruction of Archaeopteryx (based on Paul, 1988). Note the amazing similarity to the sketon of another. larger maniraptoran, Deinonychus from the Early Cretaceous Cloverly Formation of Montana.|
||Reconstruction of the skeleton of Deinonychus (modified from Paul, 1987)|
Some of the strongest and most convincing evidence of the maniraptoran origin of birds is in the comparision between the manus of various non-bird dinosaurs and a modern bird, the Hoatzin, from South America.
It is unique in a number of ways among birds. First, the young (see below) have claws of well developed fingers. They jump from their nests to escap predators (mostly snakes) and then return to the nest by clibing back up using their manus. In addition the Hoatzin is the only bird that has developed a foregut in which cellulose digestion takes place, aided by bacterial fermentation. It is a true folivore - it eats leaves (see www.knowledge.co.uk/frontiers/sf066/sf066b06.htm).
On the left is a comparison of the left manus of a variety of theropod dinosaurs all drawn so that digit II is of the same length.
The semilunate carpal and its homologues are shaded red.
A. Herrerasaurus (based on Sereno, 1993). Note that all five digits are present, which of course is primitive for the Amniota. Digit V is shaded yellow and would be hidden on the other side of the manus from this view.
B. Coelophysis (based on Colbert, 1989). Note that digit V is gone.
C. Deinonychus (based on Ostrom, 1969). Note loss of both digits IV and IV - the tetanurine condition.
D. Archaeopteryx (based on Heilmann, 1927). Note very close correspondence in proportions and relative lengths of bones to Deinonychus.
E. Hoatzin embryo Opisthocomus (based on Heilmann, 1927). Note reduction of number of bones in digit III.
F. Hoatzin adult Opisthocomus (based on Heilmann, 1927). Most of the bones of the manus fuse up in the adult, including the emilunate carpal to the metacarpals.
Colbert, E. H., 1989, The Triassic dinosaur Coelophysis. Museum of Norther Arizona Bull. 57, p. 1-160.
Heilman, G., 1927, The Origin of Birds. D. Appleton and Company, 21 pp.
Ostrom, J. H.., 1969, Osteology of Deinonychus antirrhopus, and unusual theropod from the Lower Cretaceous of Montana. Peabody Musuem of Natural Histroy, Bull. 30, p. 1-165.
Paul, G. S., 1987, The science and art of restoring the life appearance of dinosaurs and their relatives:a rigorous how-to-guide. in Czerkas, S. J. and Olseon, E. C. (eds.) Dinosaurs Past and Present, Volume II, p. 6-49.
Paul, G. S., 1988, Predatory Dinosaurs of the World. Simon and Schuster, New York, 464 pp.
Sereno, P. C., 1993, The pectoral girdle and forelimb of the basal theropod Herrerasaurus ischigulastensis. Jour. Vert. Paleo., v. 13, no. 4, p. 425-450.
25-10-2008 om 00:56
geschreven door Tsjok45