Mandible shape and dwarfism in squirrels (Mammalia, Rodentia): interaction of allometry and adaptation.
Squirrels include several independent lineages of dwarf forms distributed into two ecological groups: the dwarf tree and flying squirrels. The mandible of dwarf tree squirrels share a highly reduced coronoid process and a condylar process drawn backwards. Dwarf flying squirrels on the other hand, have an elongated coronoid process and a well-differentiated condylar process. To interpret such a difference, Elliptic Fourier Transform was used to evaluate how mandible shape varies with dwarfism in sciurids. The results obtained show that this clear-cut difference cannot be explained by a simple allometric relationship in relation with size decrease. We concluded that the retention of anteriorly positioned eye sockets, in relation with distance estimation, allowed the conservation of a well-differentiated coronoid process in all flying species, despite the trend towards its reduction observed among sciurids as their size decreases.
Hautier
Lionel
L
Laboratoire de Paléontologie, Institut des Sciences de l'Evolution de Montpellier, UMR-CNRS 5554, Cc 064, Université de Montpellier 2, 2, place Eugène Bataillon, 34095 Montpellier Cedex 5, France. Lionel.Hautier@univ-montp2.fr
Fabre
Pierre-Henri
PH
Michaux
Jacques
J
D000220:Adaptation, Biological; D000818:Animals; D004392:Dwarfism / Q000662:veterinary*; D005145:Face / Q000033:anatomy & histology; D008334:Mandible / Q000033:anatomy & histology; D008335:Mandibular Condyle / Q000033:anatomy & histology; D009043:Motor Activity; D015999:Multivariate Analysis; D009144:Museums; D010802:Phylogeny; D012589:Sciuridae / Q000033:anatomy & histology* / Q000145:classification