Research Publication Title

Cranial Variation in a Sample of Gray Squirrels (Sciurus carolinensis) from Putnam County, Georgia

Major

Biology

Faculty Mentor(s)

Alfred Mead

Keywords

cranial variation, gray squirrels, sexual dimorphism

Abstract

Understanding the range of morphological variation in extant taxa is of vital importance for taxonomists and paleontologists. Variation in extant species is used to determine taxonomic relationships as well as understand the possible range of variation for extinct species. In a previous study, we explored the presence of skeletal sexual dimorphism within a local population of gray squirrels (Sciurus carolinensis) from Putnam County, Georgia. No statistically significant sexual dimorphism was found. Recent studies by other researchers on additional squirrel species indicate the presence of cranial dimorphism in some taxa. Therefore, in this current study, intersexual and intrasexual cranial variation is being analyzed in our sample of gray squirrels from Putnam County. Twelve standard measurements are being recorded on 55 skeletons (30 females, 25 males) housed in the Georgia College Recent Mammal Collection. Measurements include total skull length, condylobasal length, length of upper diastema, length of upper molar row in alveoli, length of lower molar row in alveoli, length of the os palatinum, mandible length, zygomatic breadth, brain-case width, interorbital width, brain-case height per bullae, and mandible height. The potential significance of this study is two-fold: first, which of the cranial measurements is accurately repeatable and useful in morphological studies; and second, does cranial sexual dimorphism exist in this species that does not show skeletal dimorphism.

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Cranial Variation in a Sample of Gray Squirrels (Sciurus carolinensis) from Putnam County, Georgia

Understanding the range of morphological variation in extant taxa is of vital importance for taxonomists and paleontologists. Variation in extant species is used to determine taxonomic relationships as well as understand the possible range of variation for extinct species. In a previous study, we explored the presence of skeletal sexual dimorphism within a local population of gray squirrels (Sciurus carolinensis) from Putnam County, Georgia. No statistically significant sexual dimorphism was found. Recent studies by other researchers on additional squirrel species indicate the presence of cranial dimorphism in some taxa. Therefore, in this current study, intersexual and intrasexual cranial variation is being analyzed in our sample of gray squirrels from Putnam County. Twelve standard measurements are being recorded on 55 skeletons (30 females, 25 males) housed in the Georgia College Recent Mammal Collection. Measurements include total skull length, condylobasal length, length of upper diastema, length of upper molar row in alveoli, length of lower molar row in alveoli, length of the os palatinum, mandible length, zygomatic breadth, brain-case width, interorbital width, brain-case height per bullae, and mandible height. The potential significance of this study is two-fold: first, which of the cranial measurements is accurately repeatable and useful in morphological studies; and second, does cranial sexual dimorphism exist in this species that does not show skeletal dimorphism.