Antarctilamna has robust ctenacanthid-like spines which lack a deep insertion area, and are borne in front of the first dorsal fin; in addition to distinctive diplodont teeth with small intermediate cusps.

[6][7] The description of Antarctilamna prisca includes material derived from both Antarctic and New South Wales localities, the prior comprising the holotype, a partial decayed carcass with dermal denticles, a fin spine and teeth preserved.

[3] Antarctilamna ultima is one of two shark species diagnosed from the Waterloo Farm lagerstätte in South Africa.

[8] It is described from an assemblage of elements including a dorsal fin spine, jaws and diplodont teeth derived from an individual that was approximately 1m long.

[8] Studies suggests that large sharks frequently entered the Waterloo Farm estuary from the sea when the mouth was open, in order to forage, but it is also possible that they gave birth within the estuarine lake which acted as a nursery area for these species.