open access

Vol 75, No 4 (2016)
ORIGINAL ARTICLES
Published online: 2016-04-08
Submitted: 2016-01-08
Accepted: 2016-03-06
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Rostro-dorsal and rostro-lateral skull morphologic variability in three age-groups of the Egyptian mongoose (Herpestes ichneumon) (Linnaeus, 1758): implications of certain orbital parameters — angular geometric approach

M. O. Samuel, N. Wanmi, L. Usende
DOI: 10.5603/FM.a2016.0022
·
Pubmed: 27830878
·
Folia Morphol 2016;75(4):527-535.

open access

Vol 75, No 4 (2016)
ORIGINAL ARTICLES
Published online: 2016-04-08
Submitted: 2016-01-08
Accepted: 2016-03-06

Abstract

This study evaluated 30 skulls of the grey mongoose divided into three age-groups (6 pups, 10 juveniles and 14 adults) for skull shape variability determination. Specific geometric shapes were drawn from defined points. Angular geometric measurements of shapes derived from rostro-dorsal and rostro-lateral parts of the skull included; orbital angles (with and without the mandible), comprising of viscero-cranium, skull and orbital index that was calculated to evaluate the correlations, if any, with angles measured. It was observed that orbital height and width became higher with age; there was stronger correlation in this regard between pups and juveniles compared with juveniles and adults. There is a reduction (narrowing) in BrEcEc, BrEcN, EcPEc, EcEnN and NwNNw angles with concomitant enlargement of BrEcP, BrEcN, EcNEc, EnNEn, EcNNw and EnNP with age. The decline in the skull index shows a decrease in rate of skull width growth relative to rostro-facial length and demonstrates non-proportionality to zygoma bowing. Significantly varied orbital parameters include the inter-canthii distance and implications of certain significant variables observed in some geometric orbital measurements of the tropical mongoose (Herpestes ichneumon). The survey hypothesizes the observations follow typical carnivoran phylogenic affinity, differentiates this species from similar herpestid versions and is an estimation of functional morphology with respect to bite size. It is further suggested to contribute to visual acuity in timing of bite delivery as well an adaptation in prey summarisation. This study will serve as baseline information in herpestid cranial investigations. Such facial features are useful in population studies, species identification, eco-migrant species surveillance and species ontogenic evolution.

Abstract

This study evaluated 30 skulls of the grey mongoose divided into three age-groups (6 pups, 10 juveniles and 14 adults) for skull shape variability determination. Specific geometric shapes were drawn from defined points. Angular geometric measurements of shapes derived from rostro-dorsal and rostro-lateral parts of the skull included; orbital angles (with and without the mandible), comprising of viscero-cranium, skull and orbital index that was calculated to evaluate the correlations, if any, with angles measured. It was observed that orbital height and width became higher with age; there was stronger correlation in this regard between pups and juveniles compared with juveniles and adults. There is a reduction (narrowing) in BrEcEc, BrEcN, EcPEc, EcEnN and NwNNw angles with concomitant enlargement of BrEcP, BrEcN, EcNEc, EnNEn, EcNNw and EnNP with age. The decline in the skull index shows a decrease in rate of skull width growth relative to rostro-facial length and demonstrates non-proportionality to zygoma bowing. Significantly varied orbital parameters include the inter-canthii distance and implications of certain significant variables observed in some geometric orbital measurements of the tropical mongoose (Herpestes ichneumon). The survey hypothesizes the observations follow typical carnivoran phylogenic affinity, differentiates this species from similar herpestid versions and is an estimation of functional morphology with respect to bite size. It is further suggested to contribute to visual acuity in timing of bite delivery as well an adaptation in prey summarisation. This study will serve as baseline information in herpestid cranial investigations. Such facial features are useful in population studies, species identification, eco-migrant species surveillance and species ontogenic evolution.

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Keywords

Egyptian mongoose, Herpestes ichneumon, skull allometry, skull angular geometry, orbital morphometry

About this article
Title

Rostro-dorsal and rostro-lateral skull morphologic variability in three age-groups of the Egyptian mongoose (Herpestes ichneumon) (Linnaeus, 1758): implications of certain orbital parameters — angular geometric approach

Journal

Folia Morphologica

Issue

Vol 75, No 4 (2016)

Pages

527-535

Published online

2016-04-08

DOI

10.5603/FM.a2016.0022

Pubmed

27830878

Bibliographic record

Folia Morphol 2016;75(4):527-535.

Keywords

Egyptian mongoose
Herpestes ichneumon
skull allometry
skull angular geometry
orbital morphometry

Authors

M. O. Samuel
N. Wanmi
L. Usende

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