Abstract

Olorunfunmi Tobi

The pectoral limb of the African giant rat (Cricetomys gambianus) was studied using 12 adult rats of both sexes. Characteristics of the bones were studied by gross observation after preparation. Measurements of manus and pectoral limb (articulated) were also taken. The bones of the pectoral limb were found to be generally similar in both structure and number to other rodent species. Variation came only in the size of the bones. The scapula presented a metacromion process in addition to the acromion process. Like in all burrowing mammals, the pectoral girdle presented a rodlike clavicle and coracoids process with tuberous end. The humerus midshaft presented a prominent deltoid tuberosity, while the distal extremity has both the supratrochlear and supracondylar fossae. The radio-ulna bones are fused except at two points (proximal and distal interosseous spaces). Both the radius and ulna ended with styloid processes distally. There are 9 carpal bones with four on the proximal and five on the distal rows, respectively. Each limb presented five digits with three phalanges on each with the exception of the first digit which has two phalanges. The number of bones on each of the pectoral limb was found to be 33 plus 16 sessamoid bones making the total number of 98 bones on the pectoral limb of this rat.