Species: gregorii CHATTERJEE, 2002
Etymology: In honor of Professor Joseph T. Gregory for his contributions to vertebrate Paleontology.

Holotype: TTU P 9265

Locality: Central valley of Seymour Island, near the cost of Lopez de Bertodano Bay, below James Ross Island, Northeast Peninsula, West Antarctica, Antarctica.

Horizon: Sandwich Bluff Member, Lopez de Bartodano Formation.

Biostratigraphy: Unit 9.

Age: Maastrichtian Stage, Upper Senonian Subepoch, Upper Gulf Epoch, Late Cretaceous.

Material: Fragmentary skull, 4 cervical vertebrae, complete left femur, proximal half of a left tibiotarsus, proximal part of a right femur and a sternal fragment.

Note: Polarornis has a pathology on the tibial shaft. Macroscopic and radiological research whowed the tibial shaft has lesions both interally and externally. There is no evidence of healing but periosteal reaction. This is similar to hypertrophic osteoarthropathy as seen in extant avian viral disease.

Referred material:

= cf. Polaornis gregorii ROBERTS, LAMANNA, CLARKE, MENG, GORSCAK, SERTICH, O'CONNOR, CLAESON, & MacPHEE, 2014

Locality: Vega Island, Western Antarctica.

Horizon: 8, Sandwich Bluff Member, Lopez de Bertodano Formation.

Biostratigraphy:

Age: Maastrichtian Stage, uppermost Senonian subepoch, Upper Gulf Epoch, Late Cretaceous.

Material:

Number: Not given:

= cf. Polarornis gregorii de SOUZA, BULAK, SOARES, SAYAO, WEINSCHUTZ, BATEZELLI & KELLNER, 2023

Locality: Sandwich Bluff, Cape Lamb, Vega Island, West Antarctica.

Horizon: Sandwich Bluv Member, Lopez de Bertodano Formation (40m above the level of cf. Vegavis iaai specimens).

Biostratigraphy:

Age: Upper Maastrichtian Stage, Upper Senonian Subepoch, Upper Gulf Epoch, Late Cretaceous.

Material:

MN 7832-V: 3 fused synsacral vertebrae lacking the corpus vertebrae.