In all hominoids the piriformis originates from the anterior surface of the sacrum, as well as from its lateral aspect, and inserts onto the greater trochanter of the femur [
7]. In
Babirusas, also called deer-pigs, this muscle has fused completely with the M. gluteus medius [
10]. The piriformis of human anatomy differs in origin from that of the elephant, where it arises dorso-laterally from the sacral vertebrae close to the tuber sacrale of the ilium, and blends both with the superficial and middle glutei [
6]. Based on the literature, the piriformis muscle is absent in several vertebrates, such as solipeds, ruminants, porks, macaques, spider monkeys, coati, bats, etc. [
16]. The deep gluteal anlage, i.e., the gluteus medius, gluteus minimus and piriformis, is clearly homologous to the lizard iliofemoralis because in both groups this anlage has an acetabular bony origin, a proximal insertion, and a position posterior to the fibular nerve trunk [
4].