[dinosaur] Morganucodon and Megazostrodon (mammaliaforms) occlusion and dental function

Ben Creisler
[email protected]

A new paper:


Kai R. K. Jäger, Pam G. Gill, Ian Corfe &Thomas Martin (2019)
Occlusion and dental function of Morganucodon and Megazostrodon.
Journal of Vertebrate Paleontology Article: e1635135
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1080_02724634.2019.1635135&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=hDJTfy5WwtKHzvGjf8IejY7eW9FDj82BCBajRUbZmE8&s=hWXgwDzwS0JfJ0Rveyc4TZfxyyBl6yZ4CfCrwx8xMd0&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.tandfonline.com_doi_full_10.1080_02724634.2019.1635135&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=hDJTfy5WwtKHzvGjf8IejY7eW9FDj82BCBajRUbZmE8&s=yYElU2yLAJhr49eFqxnsqTnZizPZwAb9dwx2Nm0XsEk&e= 


A functional analysis of a well-preserved snout of the early-diverging
mammaliaform Morganucodon watsoni, with matching upper and lower
dentitions, and of the holotype of Megazostrodon rudnerae, showed that both
taxa had a primarily orthal occlusal path. In Morganucodon, the direction
was individually variable and either strictly orthal or slightly distally
or mesially inclined. An analysis with the Occlusal Fingerprint Analyser
(OFA) software confirmed an earlier hypothesis that the main cusp A of the
upper molars occluded between cusps b and a of the lower antagonists.
According to the OFA analysis, there was more extensive contact between
cusp a and the preceding anterior upper molar than previously assumed,
showing some similarities to the two-on-one pattern described for
Megazostrodon. According to our analyses, the molars of Morganucodon and
Megazostrodon had an adaptation to piercing, as well as shear-cutting.
‘Shearing flanks,’ which were the focus of previous studies, seem to be a
result of attrition, rather than functional areas in themselves. The
posterior upper molars in Morganucodon were rotated along their
longitudinal axis and lingually inclined within the tooth row, resulting in
a triangle between M1 and M2 into which the large m2 can occlude. Together,
this suggests a predetermined tooth placement and that contrary to previous
hypothesis Morganucodon did not rely on extensive wear in order to form a
precise occlusion.

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