Morphological and morphometric characterization of forelimb bones in the Hanuman langur (Semnopithecus entellus)

Abstract

Background: The Hanuman langur (Semnopithecus entellus) is a widely distributed non-human primate in South Asia; however, detailed anatomical and morphometric information on its appendicular skeleton remains limited. Baseline data on the forelimb osteology of this species are important for comparative anatomy, functional interpretation, radiology, and forensic investigations. The present study aimed to describe the gross morphology and morphometric characteristics of the forelimb bones of the Hanuman langur and to provide reference anatomical data with clinical and comparative relevance.

Methods: The forelimb bones (scapula, humerus, radius, and ulna) of an adult male Hanuman langur obtained from the Upazila Livestock Office and Veterinary Hospital, Barishal Sadar, Bangladesh, were examined. After standard gross anatomical processing in the Gross Anatomy Laboratory, the bones were prepared and cleaned for observation. Qualitative morphological features were documented photographically, and morphometric measurements were taken using standard anatomical landmarks and a calibrated measuring scale. Because the study involved a single specimen, the data were analyzed descriptively without inferential statistical testing.

Results: The scapula was quadrangular with a well-developed spine dividing the lateral surface into unequal supraspinous and infraspinous fossae, an oval glenoid cavity, and an acromion composed of hamate and suprahamate processes. The humerus was elongated with a spirally twisted cylindrical shaft, prominent greater tubercle, a small non-articulating tubercle beneath the head, distinct brachial groove, poorly developed deltoid tuberosity, tricipital line, caudally located nutrient foramen, and a medial supracondyloid foramen. The radius exhibited a well-defined head with a concave fovea capitis radii, prominent radial tuberosity, medial styloid process, and distal ulnar notch. The ulna was the longest forelimb bone, characterized by a triangular shaft, prominent olecranon tuberosity, large trochlear notch, coronoid processes, and a laterally placed styloid process.

Conclusions: The forelimb osteological features of the Hanuman langur reflect functional adaptations related to limb mobility and arboreal activity. These findings provide baseline anatomical reference data that may support comparative anatomical research, functional morphology, radiological interpretation, and forensic identification involving primates.