[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Dryolestes (Jurassic mammal) molar function compared to Monodelphis



Ben Creisler
bcreisler@gmail.com

A new non-dino paper that may be of interest:

Julia A. Schultz & Thomas Martin (2014)
Function of pretribosphenic and tribosphenic mammalian molars inferred
from 3D animation.
Naturwissenschaften (advance online publication)
DOI: 10.1007/s00114-014-1214-y
http://link.springer.com/article/10.1007/s00114-014-1214-y

Appearance of the tribosphenic molar in the Late Jurassic (160 Ma) is
a crucial innovation for food processing in mammalian evolution. This
molar type is characterized by a protocone, a talonid basin and a
two-phased chewing cycle, all of which are apomorphic. In this
functional study on the teeth of Late Jurassic Dryolestes leiriensis
and the living marsupial Monodelphis domestica, we demonstrate that
pretribosphenic and tribosphenic molars show fundamental differences
of food reduction strategies, representing a shift in dental function
during the transition of tribosphenic mammals. By using the Occlusal
Fingerprint Analyser (OFA), we simulated the chewing motions of the
pretribosphenic Dryolestes that represents an evolutionary precursor
condition to such tribosphenic mammals as Monodelphis. Animation of
chewing path and detection of collisional contacts between virtual
models of teeth suggests that Dryolestes differs from the classical
two-phased chewing movement of tribosphenidans, due to the narrowing
of the interdental space in cervical (crown–root transition)
direction, the inclination angle of the hypoflexid groove, and the
unicuspid talonid. The pretribosphenic chewing cycle is equivalent to
phase I of the tribosphenic chewing cycle, but the former lacks phase
II of the tribosphenic chewing. The new approach can analyze the
chewing cycle of the jaw by using polygonal 3D models of tooth
surfaces, in a way that is complementary to the electromyography and
strain gauge studies of muscle function of living animals. The
technique allows alignment and scaling of isolated fossil teeth and
utilizes the wear facet orientation and striation of the teeth to
reconstruct the chewing path of extinct mammals.