Parahesperornis

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Hargeria redirects here. This is also an (invalid) name of a genus of tanaidacean crustaceans in the family Leptocheliidae.

Parahesperornis
Fossil range: Late Cretaceous

Conservation status

Fossil

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Subclass:	Hesperornithes
Order:	Hesperornithiformes
Family:	Hesperornithidae
Genus:	Parahesperornis

Species

Parahesperornis alexi
Parahesperornis gracilis
and see text

Synonyms

Of Parahesperornis:

Hargeria
F.A. Lucas, 1903

Of P. gracilis:

Hargeria gracilis
Hesperornis gracilis

Parahesperornis is a prehistoric flightless bird genus from the Late Cretaceous. Its range in space and time may have been extensive, but its remains are rather few and far between, at least compared with its contemporary relatives in Hesperornis. Remains are known from central North America, namely the former shallows of the Western Interior Seaway. Found mainly in the upper Niobrara Chalk, these are from around the Coniacian-Santonian boundary, 85-82 million years ago (mya).

Parahesperornis alexi was long lumped with specimen YPM 1478, described initially as Hesperornis gracilis and later moved to the monotypic genus Hargeria. It then turned out that this genus' description actually referred to specimen KUVP 2287, which eventually became the holotype of P. alexi. Nonetheless, the taxon the description of Hargeria was about was "Hesperornis" gracilis exclusively, and thus despite the misidentification it applies to YPM 1478, the holotype of "H." gracilis. It is now believed, contrary to the initial reassessment, that YPM 1478 is also referable to Parahesperornis, resulting in Parahesperornis gracilis as the name now usually seen in scientific publications; though some doubts remain this seems to be correct ^[1].

Parahesperornis was a member of the Hesperornithes, flightless toothed seabirds of the Cretaceous and more specifically in the main lineage, close to Hesperornis^[1]. Possibly the genus extended into the Campanian, to less than 80 mya^{[verification needed]}. In any case, there are two very similar fossils from the Nemegt Formation (Maastrichtian or possibly late Campanian, around 76-65 mya, which were found at Tsagaan Kushu (Mongolia). Both are distal ends of tibiotarsi, and they seem certainly more similar to the bones of Hesperornithiformes and (due to the smallish size) to Parahesperornis specifically. However, they are not very diagnostic regardless, and the diversity of Parahesperornis remains enigmatic.