The functional significance of morphological changes in the dentitions of early mammals.
The Mesozoic marked a time of experimentation in the tooth morphology of early mammals. One particular experiment involved the movement of three points, or cusps, on the surface of a molar tooth from a line into a triangle. This transition is exemplified by two extinct insectivorous mammals,Morganucodon(cusps in a line) andKuehneotherium(cusps in a triangle). Here we test whether this difference in cusp arrangement, alongside cusp heights and angles between cusps, is associated with differences in the ability of the teeth to fracture proxy-insect prey. We gathered measurements from molar teeth of both species and used them to create physical models. We then measured the force, time and energy at fracture and peak force, and the amount of damage inflicted by the models on hard and soft gels encased in a tough film that mimicked the material properties of insects. TheMorganucodonmodel required less force and energy to fracture hard gels and reach peak force compared withKuehneotheriumKuehneotheriumrequired a similar time, force and energy to fracture soft gels but reduced the time, force and energy to reach peak force. More importantly,Kuehneotheriumalso inflicted more damage to both the hard and the soft gels. These results suggest that changes in dental morphology in some early mammals was driven primarily by selection for maximizing damage, and secondarily for maximizing biomechanical efficiency for a given food material property.
Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA ajsmith@bio.umass.edu.
Andrew J
0000-0001-9357-6620
AJ
Conith
Polymer Science and Engineering Department, University of Massachusetts Amherst, Amherst, MA 01003, USA.
Michael J
MJ
Imburgia
Polymer Science and Engineering Department, University of Massachusetts Amherst, Amherst, MA 01003, USA.
Alfred J
AJ
Crosby
Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA.
Elizabeth R
ER
Dumont
D000818:Animals; D005075:Biological Evolution; D008322:Mammals / Q000033:anatomy & histology* / Q000502:physiology*
arthropod; dentition; feeding; mammal; physical testing