Troodontidae
Model of Troodon
- East Asia (Mongolia, China)
- Siberia ( Chukchi Autonomous District )
- North America (Alaska, Alberta, Montana, Wyoming, Baja California Norte )
The Troodontidae ( Syn: Saurornithoididae, bars Bold ) are a group of small to two -meter-long dinosaur from the group of Maniraptora. They have typical features of Deinonychosauria for example, the enlarged sickle-shaped claw second of the three toes. Among all non-avian dinosaurs they have, compared to body mass, the largest brain volume. The Troodontidae include those Deinonychosauria that are more closely related to Troodon than Velociraptor.
All Troodontidae, except for the North American genus Troodon occurred in East Asia.
- 4.1 Literature
- 4.2 Notes and references
- 4.3 External links
Features
The skull of the animals was slightly built and shallow, had a long muzzle, large eye sockets and was in most genera strongly pneumatized ( voided ). The eye sockets paid directly forward and enabled stereoscopic vision. The mouth of the lower jaw in the cross section was tubular, low-and seen from the side triangular. The bones of the skull were very strong grown together for adult forms. Troodontids had more teeth than most other theropods. Troodon and Saurornithoides had 35 on any dental, Saurornithoides 19-20 on the maxilla. On the premaxilla were usually four small teeth close together. The teeth were laterally flattened, slightly curved to the rear and front and rear or rear only sawed. Only Byronosaurus had unsawn teeth.
Fuselage skeleton and limbs
The spine of the Troodontidae is only incompletely known, as it is completely preserved in any copy. The cervical spine is pneumatized, the majority of the trunk vertebrae not. The cervical ribs are shorter than the eddy and grown together with them in adult Troodon. The ribs are little more than delivers. From Troodon and Saurornithoides belly ribs are known. Also, the shoulder girdle and pelvis are obtained only incomplete fossil. In the hind legs the shin bone (tibia) are always longer than the thigh bone ( femur). The metatarsals are greatly extended. At the base of the second toe ends in a curved sickle claw, which is not as pronounced as on the Dromaeosauridae.
Paleoecology
Troodontids lived predatory. Since its sickle claw but was delicate than that of Dromaeosauridae, it is believed that they hunted smaller prey and fed on insects, small mammals, dinosaur eggs and nestlings. Since its cusps were large and resembled those of iguanas, some scientists suspect a partial herbivore diet.
The large eye sockets and the large inner ear suggest that visual and auditory senses were well developed. The large brain, which corresponds to a rat, perhaps is a result of good sense-perception. The morphology of the hind legs showing that they were agile animals. Studies of different sized individuals of Troodon show that they reached their adult size in less than five years.
System
The Troodontidae form with its sister group, the Dromaeosauridae the taxon Deinonychosauria. These are the sister group of the Avialae from which the birds ( Aves) have emerged. Sinovenator is the most original Troodontidae, followed by Anchiornis and Mei.
The probable kinship does the following cladogram clearly:
Avialae
Dromaeosauridae
Sinovenator
Anchiornis
Mei
Byronosaurus
Borogovia
Tochisaurus
Troodon
Saurornithoides