[2][3] The species is named after anthropologist and primate researcher Elwyn L. Simons who discovered the type specimen in 1985.

In the wrist, the carpal bones are small like in Zygorhiza, but, unlike in this other basilosaurid, the magnum is fused with the trapezoid in Ancalecetus.

The roughened vertebral border suggests the presence of a cartilaginous extension that extends the surface of the scapula like in modern cetaceans.

The distal end has flat, textured surfaces for the articulation of the radius and ulna; these bones are fused on the left limb and tightly fitting and the right side, and neither permitted motion at the elbow joint.

Tooth wear show that Ancalecetus, like other basilosaurids, fed on larger prey, probably fish, that required mastication before swallowing and that the type specimen survived into adulthood.