Sciurus vulgaris & carolinensis
1. Red & Grey compared
2. Red, lateral view 
3. Grey, lateral view
4. Details of specimens illustrated.
The skull of the Red Squirrel has a rounded, foreshortened appearance compared withthe Grey, and more elongated post-orbital processes. The species can be reliably separated by measurement. (see details section)

Dental Formula : / (both species) The first upper premolar is rudimentary, and is absent in some squirrel species.

1. Red (L) and Grey (R) Squirrels compared.
2. Red Squirrel, Sciurus vulgaris, lateral view
3. Grey Squirrel, Sciurus carolinensis, lateral view

Details of Specimens Illustrated

Image 2
Red Squirrel Sciurus vulgaris
Sex - Female
Stage - immature
Collection ref. 96.019
Date collected - October 1996
Area collected - Northumberland
Source - Road casualty
Condylobasal length46mm Zygomatic width31mm
Jaw length25mm Interorbital width16.5mm
Postorbital constriction18mm Nasal length15mm

Image 3
Grey Squirrel Sciurus carolinensis
Stage - adult
Collection ref. 91.010
Date collected - August 1991
Area collected - Llandrindod Wells, Powys
Source - Road casualty
Condylobasal length53mm Zygomatic width34mm
Jaw length30mm Interorbital width17mm
Postorbital constriction19mm Nasal length19mm

Separating Red and Grey Squirrels by measurement :

                                   Red         Grey     Condylobasal length         < 50mm      > 50mm     Nasal length                < 17mm      > 17mm     Ratio Nasal length /     Post-orbital constriction   ~ 0.85      ~ 1.0

Latin Names : Sciurus "a squirrel", but derived from the Greek wordsskia "shade" and oura "the tail".
vulgaris"common", carolinensis "of Carolina", referring to its American origins.

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