Polarornis gregorii was named by Chatterjee (2002) [It is diagnostically distinct from known species of Gaviidae and differs as follows: external naris small; frontals narrow across the orbit with narrow salt gland depressions; orbital process of the quadrate thick, shot and directed horizontally; pterygoid condyle of the quadrate is bordered by a dorsal groove; caudal tympanic recess in the same plane with the fenestra ovalis and the fenestra pseudorotunda, and not bounded caudally by an overhanging wall; lateral wall of the rostral tympanic recess is flat, not bulbous; vomers fused and rounded rostrally; femoral neck long; distal condyles of femur are subequal and project caudally, not twisted sidewise; intercnemial sulcus perforated by a nutrient foramen.]. Its type specimen is TTU P 9265, a partial skeleton, and it is a 3D body fossil. Its type locality is Polarornis type-locality, which is in a Maastrichtian marine sandstone in the López de Bertodano Formation of Antarctica. It is the type species of Polarornis.