Dental variation in a collection of Lemmiscus curtatus from the northern plains of southern Saskatchewan: implications for morphological evolution

Authors

Christopher J. Bell, Jackson School of Geosciences, The University of Texas at Austin; Jackson Museum of Earth History, The University of Texas at AustinFollow
Christopher N. Jass, Royal Alberta Museum, Edmonton, Alberta, Cananda; Jackson Museum of Earth History, The University of Texas at AustinFollow
Robert W. Burroughs, Committee on Evolutionary Biology, The University of Chicago; Integrative Research Center, Field Museum of Natural History, Chicago, ILFollow

Abstract

We provide the first documentation of morphological variation in the lower first molar (m1) of Lemmiscus curtatus from southern Canada. A total of 370 specimens were obtained from owl pellets taken from 4 localities in southern Saskatchewan. The 4 most common morphotypes are, in order of descending relative abundance, molars with 5 closed triangles and a well-developed but widely open sixth triangle, molars with 5 closed triangles and a sixth triangle that is pinched at the confluence of the anterior cap, molars with 5 closed triangles and incipient closure of the sixth triangle from the anterior cap, and specimens with 6 closed triangles. As is true of other modern populations of L. curtatus, the samples from Saskatchewan include no morphotypes with only 4 closed triangles. This collection is notable for the relatively high proportion of specimens with pinched, incipient, or full closure of a sixth triangle on the m1, and it also highlights the complex dynamics of dental evolution in arvicoline rodents.


Documentamos por primera vez la variación morfológica del primer molar inferior (m1) de Lemmiscus curtatus procedente del sur de Canadá. Un total de 370 ejemplares fueron obtenidos de egagrópilas de búho procedentes de cuatro localidades del sur de Saskatchewan. Los cuatro morfotipos más comunes en las muestras son, en orden descendente de abundancia relativa, molares con cinco triángulos cerrados y un sexto triangulo bien desarrollado, pero ampliamente abierto, molares con cinco triángulos cerrados y un sexto triangulo que presenta una constricción a medida que se acerca a la confluencia con la porción anterior del diente, molares con cinco triángulos cerrados y un sexto triangulo incipientemente cerrado, y molares con seis triángulos cerrados. Al igual que otras poblaciones actuales de L. curtatus, las muestras de Saskatchewan no incluyen morfotipos que solamente tienen cuatro triángulos cerrados. Esta colección de molares destaca por la proporción relativamente alta de ejemplares m1 que presentan un sexto triangulo constreñido, incipientemente cerrado y cerrado y denota la dinámica compleja de la evolución dental en los roedores arvicolinos.

Recommended Citation

Bell, Christopher J.; Jass, Christopher N.; and Burroughs, Robert W. (2019) "Dental variation in a collection of Lemmiscus curtatus from the northern plains of southern Saskatchewan: implications for morphological evolution," Western North American Naturalist: Vol. 79: No. 2, Article 8.
Available at: https://scholarsarchive.byu.edu/wnan/vol79/iss2/8