POST NATAL CRANIAL AREAS OF EVOLUTION IN THE SMALL AFRICAN PANGOLIN
(PHATAGINUS TRICUSPIS) ONTOGENY FROM THREE GEO-ECOLOGIES – A FIRST
REPORT: ASYMMETRY, ELLIPTICAL FOURIER ANALYSES AND MODULARITY
Background; We here present a first intraspecific eco-variant post natal
attempt at evaluation of skull signaling in the small African pangolin
(Boreoeutheria) family, sub-family phatagininae emphasizing evolutionary
trend in ontogeny. Forty; digitally processed skulls and foramen magnum
outlines of this species from different geo-locations were assessed for
asymmetry, foramen magnum shape variations and modularity hypotheses on
skull areas using geometric and Elliptical Fourier analyses methods.
Results; Regression of log transformed centroid size and asymmetric
components suggested significant expression of asymmetry through
ontogeny (p˂0.03) with size accounting for 81.34% of asymmetric shape
changes. Multivariate analysis of regression confirmed directional but
low (p˂0.5) fluctuating asymmetry (F1539=3.4045, F882= 3.2665, for
dorsal and ventral views respectively). Intraspecific ontogenetic
allometric trajectories followed rostro-caudal and caudo-lateral
directions; intercepts for shape/size predictions were parallel.
Mahalanobis distances between centroids (2.42) of specimens were
significant (p˂ 0.01). Variance-covariance matrix in ontogeny lies
between 0.0017 and 0.56 suggestive of shape overlaps and variations.
Foramen magnum outline descriptors by incremental harmonics explained
morphologic details; the first 4 effective principal components defined
96.98% of shape properties, while (3.02%) constituted finer details.
74.1% accuracy decline after size factor elimination. Modulation PCA:
of Covariance Matrix and Asymmetry component was 88.38% and 7.48% (PC1
and 2) variance % predicted 10.08%. Conclusions; The study confirmed
directional ‘handedness’ and fluctuating asymmetries among skull samples
studied, an attenuated ability to maintain paired symmetric bilaterality
irrespective of geo-location. Foramen magnum shape assumed priority over
size in ontogeny with profound asymmetry (from the 5th harmonic); an
indication of precocity and early presumptive form for arboreal
adaptation this observation in conjunction with modularity inference
suggested instability and global weakness of cranial integration
processes and modules. These findings will be of value for species
conservation and may be vital in pangolin evolutionary systematics.