Troodontidae

From EvoWiki

Troodontidae Gilmore, 1924 sensu Currie, 1987

Autapomorphies of Troodontidae include (after Osmolska & Barsbold 1990):

a)Endocranial cavity expanded.

b)External naris bounded caudoventrally by the maxilla.

c)Basioccipital and periotic sinus systems present.

d)Parasphenoid capsule bulbous.

e)A lateral excavation of the caudoventral wall of the braincase, formed by the prootic, exoccipital, opisthotic, basioccipital, and basisphenoid is present. The rostral portion contained an enlarged middle ear.

f)Basipterygoid process enlarged and subhorizontal.

g)Quadrate in contact with the braincase.

h)Dentary tapers rostrally, with a well developed series of lateral foramina.

i)Teeth distinct from those of all other theropods (but similar in part to those of Archaeopteryx) by virtue of the constriction of the root and crown, and the presence of apically hooked denticles on the distal edge of each tooth.

j)Calcaneum thin and fused with the astragalus.

See Currie (1985, 1987) and Dodson et al (1990) and Currie & Zhao (1993) for comprehensive reviews of Troodontidae. It is worth nothing that troodonts are among the most exceptionally birdlike of all theropods, particulary in the features of the braincase and the lateral otic depression.

JGK