Troodontidae
| Troodontidae | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Upper Jurassic to Upper Cretaceous ( Oxfordian to Maastrichtian ) | ||||||||||||
| 163.5 to 66 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Troodontidae | ||||||||||||
| Gilmore , 1924 |
The Troodontidae ( Synonym .: Saurornithoididae, Barsbold, 1974 ) were a group of small, up to two meters long dinosaurs from the group of Maniraptora . They have typical characteristics of the Deinonychosauria , for example the enlarged sickle-shaped second claw of the four toes. Among all non-avian dinosaurs, they have the largest brain volume in relation to body mass. The Troodontidae include those Deinonychosauria, which are more closely related to Troodon than to Velociraptor .
All Troodontidae, with the exception of the North American genera Troodon , Geminiraptor and Pecticodon , as well as Euronychodon and Urbacodon , occurred mainly in East Asia.
features
skull
The skull of the animals was lightly built and flat, had a long snout, large eye sockets and in most genera was heavily pneumatized (provided with cavities). The eye sockets pointed straight forward and enabled stereoscopic vision . The mouth was tubular in cross-section, the lower jaw low and triangular when viewed from the side. The bones of the brain skull had grown together very strongly in adult specimens. Troodontids had more teeth than most other theropods. Troodon and Saurornithoides had 35 on each dental, Saurornithoides 19 to 20 on the maxillary. On the premaxillary there were usually four small teeth sitting close together. The teeth were flattened on the sides, slightly curved back, and sawed front and back or only back. Only Byronosaurus had unsawed teeth.
Trunk skeleton and limbs
The spine of the Troodontidae is only incompletely known, as it is not completely preserved in any specimen. The cervical spine is pneumatized, the majority of the trunk vertebrae are not. The cervical ribs are shorter than the vertebrae and have grown together with them in the adult Troodon . Little is known about the ribs either. Of Troodon and Saurornithoides are belly fins known. The shoulder girdle and pelvis are also only incompletely preserved in fossil form. In the hind legs, the shinbones (tibia) are always longer than the thighbones (femur). The metatarsals are greatly elongated. At the foot the second toe ends in a curved sickle claw, which is not as pronounced as in the Dromaeosauridae .
Paleoecology
Troodontids lived predatory. Since their sickle claws were more delicate than those of the Dromaeosauridae, it is believed that they hunted smaller prey and ate insects, small mammals, dinosaur nests and eggs. Because their tooth bumps were large and resembled those of iguanas, some scientists suspect a partially herbivorous diet.
The large eye sockets and the large inner ear suggest that sight and hearing were well developed. The large brain, like that of a rat, may be a result of good sensory perception. The morphology of the hind legs shows that they were agile animals. Research on troodon individuals of various sizes shows that they reached adult size in less than five years.
Systematics
The Troodontidae and their sister group , the Dromaeosauridae, form the taxon of the Deinonychosauria. These are the sister group of the Avialae , from which the birds (Aves) emerged. Sinovenator is the most primitive Troodontidae, followed by Anchiornis and Mei .
The likely family relationships are made clear by the following cladogram :
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literature
- Peter J. Makovicky , Mark A. Norell : Troodontidae. 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. 184-195.
Individual evidence
- ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , pp. 139-144, online .
- ↑ Dongyu Hu, Lianhai Hou, Lijun Zhang, Xing Xu : A pre-Archeopteryx troodontid theropod from China with long feathers on the metatarsus. In: Nature . Vol. 461, No. 7264, 2009, pp. 640-643, doi : 10.1038 / nature08322 .
- ^ Xing Xu, Mark A. Norell: A new troodontid dinosaur from China with avian-like sleeping posture. In: Nature. Vol. 431, No. 7010, 2004, pp. 838-841, doi : 10.1038 / nature02898 .
- ↑ Qiang Ji, Shu-An Ji, Jun-Chang Lü, Hai-Lu You, Wen Chen, Yong-Qing Liu, Yan-Xue Liu: First avialan bird from China (Jinfengopteryx elegans gen. Et sp. Nov.). In: Geological Bulletin of China. Vol. 24, No. 3, 2005, ISSN 1671-2552 , pp. 197-205, online .
