Parahesperornis

Parahesperornis was a genus of flightless birds belonging to the Hesperornithes, a group of toothed seabirds from the Late Cretaceous period. Its remains are relatively rare compared to those of its contemporary relatives, such as Hesperornis, and are primarily found in central North America, specifically in the upper Niobrara Chalk deposits near the Coniacian-Santonian boundary (approximately 85–82 million years ago). These deposits were part of the Western Interior Seaway in what is now Kansas.

The species Parahesperornis alexi was initially misclassified as Hesperornis gracilis and later assigned to the genus Hargeria. However, subsequent research clarified that the holotype of P. alexi (KUVP 2287) was distinct from YPM 1478, which retained its classification under Hesperornis. In 2017, Asiahesperornis was proposed as a potential synonym for Parahesperornis.

Fossils of Parahesperornis are also found in the Nemegt Formation of Mongolia, dating to the Maastrichtian or late Campanian periods (around 76–66 million years ago). These fossils include distal tibiotarsi that resemble those of Hesperornithiformes and may belong to Parahesperornis. However, their diagnostic features are limited, leaving the diversity of the genus uncertain.

Overall, Parahesperornis was closely related to Hesperornis and represented a lineage of flightless seabirds adapted to marine environments during the Cretaceous period.