Orodromeus

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Orodromeus
Artistic living image of Orodromeus

Artistic living image of Orodromeus

Temporal occurrence
Upper Cretaceous (Middle to Upper Campanium )
80.6 to 72 million years
Locations
Systematics
Dinosauria
Ornithischia
Cerapoda
Ornithopoda
Orodromeus
Scientific name
Orodromeus
Horner & Weishampel , 1988
Art
  • Orodromeus blemish

Orodromeus is a genus of dinosaurs and an original representative of the ornithopods . It was a small, two-legged herbivore. So far, fossils of numerous individuals are known - among them are the remains of adult animals as well as of young animals of various ages. The fossils come in particular from the Two Medicine Formation from Montana (USA); however, the genus could alsobe detectedin Alberta ( Canada ). Orodromeus lived during the Upper Cretaceous (middle to late Campanium ).

This genus was the only way orodromeus makelai , 1988 by paleontologist Jack Horner and David Weishampel first described . The name Orodromeus ( gr. Oros - "mountain", gr. Dromeus - "runner") means something like "mountain runner". This name is intended on the one hand to refer to the location of the holotype specimen, the "Egg Mountain", and on the other hand to the American state of Montana.

features

Orodromeus reached a length of about 2.5 meters. The crowns of the teeth were wide and triangular shaped like a shield. There were 10 to 13 teeth on each side of the upper jaw, depending on the age of the individual. In the intermaxillary bone (premaxillary), a bone in front of the upper jaw, there were another five teeth on each side, as in some related genera.

As with the related genera Zephyrosaurus and Oryctodromeus, the remaining skeleton was characterized by a bone tip on the shoulder blade; a feature that some researchers interpret as a possible adaptation to a burrowing way of life. Three features of the skull, such as the excessive post-orbitals, suggest a close relationship between Orodromeus and Zephyrosaurus .

Systematics

Orodromeus is traditionally assigned to the Hypsilophodontidae family . However, recent research shows that the Hypsilophodontidae were paraphyletic , i.e. not a natural group. Consequently Orodromeus is considered to be the original representative of the Ornithopoda.

Most of the analyzes indicate that Orodromeus was most closely related to Zephyrosaurus . Oryctodromeus is also placed in the close relationship of both genera .

Paleobiology

Nest and newly hatched young of Orodromeus (reconstruction)

It is speculated that this genus may have inhabited burrows, as has been demonstrated in its relative Oryctodromeus . No structures were found in association with the Orodromeus bones; some anatomical peculiarities, which are also found in Oryctodromeus and Zephyrosaurus , could, however, be interpreted as an adaptation to the digging. In addition, the bones were found close together in at least two specimens, although they would have to be more scattered in normal situations, which shows that they could have been preserved within a building.

Bone histological examinations on the long bones of various Orodromeus specimens allow conclusions to be drawn about the growth rates, growth patterns and age of these animals. The growth of this small dinosaur was relatively slow compared to other dinosaurs. The animals grew faster than today's crocodiles, but slower than today's birds. The growth was greatest immediately after hatching, but declined sharply in the youth phase - faster than with the larger relatives Tenontosaurus and Dryosaurus . After reaching adulthood, growth was almost complete. Presumed growth rings on the bones suggest that Orodromeus was fully grown by 4 to 6 years of age.

Jack Horner discovered fossil eggs and nests near the remains of newly hatched Orodromeus in the “Egg Mountain” of the Two Medicine Formation . Consequently, Horner described the eggs and nests as Orodromeus . However, later analysis looked at embryonic remains inside the eggs and concluded that the eggs and nests actually belonged to Troodon , a small theropod .

Individual evidence

  1. ^ A b Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , pp. 276-277, online .
  2. ^ A b John R. Horner , Armand De Ricqlès, Kevin Padian , Rodney D. Scheetz: Comparative Long Bone Histology and Growth of the "Hypsilophodontid" Dinosaurs Orodromeus makelai, Dryosaurus altus, and Tenontosaurus tillettii (Ornythlschla: Euornithopoda). In: Journal of Vertebrate Paleontology. Vol. 29, No. 3, 2009, ISSN  0272-4634 , pp. 734-747, doi : 10.1671 / 039.029.0312 .
  3. ↑ a b c d e David J. Varricchio, Anthony J. Martin, Yoshihiro Katsura: First Trace and Body Fossil Evidence of a Burrowing, Denning Dinosaur. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 274, No. 1616, ISSN  0950-1193 , pp. 1361-1368, doi : 10.1098 / rspb . 2006.0443 .
  4. ^ A b c David B. Norman , Hans-Dieter Sues , Lawrence M. Witmer , Rodolfo A. Coria : Basal Ornithopoda. In: David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 393-412, digitized version (PDF; 2.66 MB) .
  5. ^ John R. Horner, David B. Weishampel: A Comparative Embryological study of Two Ornithischian Dinosaurs. In: Nature . 332, No. 6161, 1988, pp. 256-257, doi : 10.1038 / 332256a0 , (on this Correction. In: Nature. 383, No. 6595, 1996, p. 103, doi : 10.1038 / 383103b0 , digitized version (PDF; 171.55 kB) ).
  6. ↑ Ben Creisler: Dinosauria Translation and Pronunciation Guide. Archived from the original on July 20, 2011 ; Retrieved December 3, 2013 .
  7. ↑ Thomas R. Holtz Jr .: Supplementary Information. to: Thomas R. Holtz Jr .: Dinosaurs. The most complete, up-to-date Encyclopedia for Dinosaur Lovers of all ages. Random House, New York NY 2007, ISBN 978-0-375-82419-7 , online (PDF; 184.08 kB) .
  8. ↑ Rodney D. Scheetz: Phylogeny of basal ornithopod dinosaurs and the dissolution of the Hypsilophodontidae. In: Journal of Vertebrate Paleontology. Vol. 18, Supplement to No. 3 = Abstracts of Papers Fifty-Eighth Annual Meeting Society of Vertebrate Paleontology, Snowbird Ski and Summer Resort Snowbird, Utah, September 30 - October 3, 1998 , 1998, p. 75A.
  9. ↑ Clint A. Boyd, Caleb Marshall Brown, Rodney D. Scheetz, Julia A. Clarke: Taxonomic revision of the basal neornithischian taxa Thescelosaurus and Bugenasaura. In: Journal of Vertebrate Paleontology. Vol. 29, No. 3, 2009, pp. 758-770, doi : 10.1671 / 039.029.0328 .
  10. ^ Anthony J. Martin: Introduction to the Study of Dinosaurs. 2nd edition. Blackwell Publishing, Malden MA et al. 2006, ISBN 1-4051-3413-5 , p. 350.

Web links

Commons : Orodromeus  - collection of images, videos and audio files