Sunday, November 30, 2014

Intramandibular joint

Basal paraves and pterosaurs do not have a intramandibular joint. 
Dinosaurs do have a intramandibular joint.


PTEROSAURS

http://dml.cmnh.org/2002Sep/msg00187.html
The unusual intra-mandibular joint described above is found only in herrerasaurids and theropods among dinosaurs. Dinosaurian outgroups (pterosaurs, crurotarsal archosaurs) also lack an intra-mandibular joint.

BASAL PARAVES

Page 21:
http://books.google.ca/books?id=kZqJAAAAQBAJ&pg=PA21&lpg=PA21&dq=Archaeopteryx+intramandibular+joint&source=bl&ots=RKECg3KMdM&sig=0b_OE2jWhNOIFTxjXSdvNt4E-dU&hl=en&sa=X&ei=ocV7VKDBBfSZsQSk6YGwCw&ved=0CCYQ6AEwAg#v=onepage&q=Archaeopteryx%20intramandibular%20joint&f=false
[Archaeopteryx] does not appear to have had an intramandibular joint

http://en.wikipedia.org/wiki/Odontognathae
.....intramandibular articulation something that is actually absent in Archaeopteryx, but found in many of its theropod relatives.[2]

DINOSAURS 

 Feduccia:
It would not tax the imagination to engender a long list of obstacles for the now dominant model of a theropod origin of birds, including....the sliding lower jaw joint [sliding intramandibular joint] of theropods (absent in birds)

http://www.geol.umd.edu/~tholtz/G104/lectures/104therop.html
The traits uniting Theropoda seem to include:
.........
An intramandibular joint between the dentary and post-dentary bones: this may have served as a shock absorber while feeding on live prey. (Herrerasaurs have a slightly different configuration of the intramandibular joint, and thus may be convergent.)

http://www.bio.fsu.edu/James/Ornithological%20Monographs%202009.pdf
the analysis of Benton (2004) demonstrated that the only unequivocal synapomorphy diagnosing Theropoda is the presence of an intramandibular joint.
http://palaeos.com/vertebrates/coelurosauria/oviraptorosauria.html
Oviraptorosauria:
intramandibular joint absent

http://palaeos.com/vertebrates/coelurosauria/tyrannosauroidea.html



















3 comments:

  1. For future reference:
    Page 135
    http://books.google.ca/books?id=OUwXzD3iihAC&pg=PA43&redir_esc=y#v=onepage&q&f=false
    Symmetric feathers twist.

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  2. https://www.app.pan.pl/archive/published/app44/app44-189.pdf
    In the mid-length, the mandible is divided by the intramandibular joint. The articular, angular, surangular and coronoid are incorporated into the caudal structural unit, while the splenial and dentary form the rostral one.

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  3. https://books.google.ca/books?id=OUwXzD3iihAC&pg=PA43&redir_esc=y#v=onepage&q&f=false
    In theropods and Archaeopteryx (both mandibles of JM2257) the long, slender but strong anterior process of the angular lies in a long, subhorizontal groove of the splenial. The action of this joint has not been analyzed in detail, but vertical rotation of the dentary-splenial unit upon the posterior mandible appears to be favored.

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