Craniometrics Analysis for Ontogenetic Physiognomy and Sexual Dimorphism in Emin’s Silvery Mole-Rats (Heliophobius argenteocinereus emini: Bathyergidae) from Tanzania

Abstract

Emin’s silvery mole-rat, the Heliophobius argenteocinereus emini belongs to a family
Bathyergidae. The Heliophobius argenteocinereus emini (Noak, 1894) is among the least studied
sub-Saharan subterranean rodents. Among others, information on ontogenetic physiognomy and
status of sexual dimorphism in H. a. emini is missing. The present study intended to fill gaps on
ontogenetic characteristics and status of sexual dimorphism in these mole-rats by comprehensively
examining 55 skulls. Based on teeth eruption and wear, the dental formula of 1/1, 0/0, 1/1, 3/3 is
reported for the first time, and subsequently established eight relative age classes. This information
was key to the assessment of ontogenetic variations between sexes and age classes. The
multidisciplinary analyses of craniometrics between and within relative age classes showed a sharp
increase in sizes of cranial facets from relative age classes III to VIII, which signifies a divergence
in the investment of energy for growth between age classes. Within all relative age classes except
age classes I and II, females showed smaller craniometrics than males, indicating that sexual
dimorphism in H. a. emini is well noticeable from the relative age class III. Subsequent analyses of
craniometrics revealed that sexual dimorphism in H. a. emini is attributed by size.

Keywords: Ontogenetic; Heliophobius argenteocinereus emini; craniometrics; sexual dimorphism