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