''Halimornis'' was an

enantiornithean The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and cla ...

bird. It lived during the Late Cretaceous about 80 mya and is known from

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s found in the

Mooreville Chalk Formation The Mooreville Chalk is a geological formation in North America, within the U.S. states of Alabama and Mississippi, which were part of the subcontinent of Appalachia. The strata date back to the early Santonian to the early Campanian stage of t ...

Greene County, Alabama Greene County is a county located in the west central portion of the U.S. state of Alabama. As of the 2020 census, the population was 7,730, the least populous county in Alabama. Its county seat is Eutaw. It was named in honor of Revolutionar ...

. It is known from a single fossil individual, including preserved vertebrae, leg bones and part of the humerus (upper arm bone). At the time, the area where the Mooreville Chalk was deposited was situated on the southern coast of the

Western Interior Seaway The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, and the Western Interior Sea) was a large inland sea that split the continent of North America into two landmasses. The ancient sea ...

, and may have been the site of a large delta where several major rivers flowed into the shallow sea. The fossil bird was found at a location that would have been about 50 km off shore, indicating that it was an ocean-going species. The name ''Halimornis'' means "bird of the sea". It would have lived alongside the more advanced seabird ''

Ichthyornis dispar ''Ichthyornis'' (meaning "fish bird", after its fish-like vertebrae) is an extinct genus of toothy seabird-like ornithuran from the late Cretaceous period of North America. Its fossil remains are known from the chalks of Alberta, Alabama, Kans ...

''. It is one of the few known enantiornithine birds to have lived in a marine environment, along with the Australian '' Nanantius eos'', the slightly younger ''

Martinavis ''Martinavis'' is a genus of enantiornithine birds which existed in what is now southern France, North America and Salta Province, Argentina during the late Cretaceous period. It was named by Cyril A. Walker, Eric Buffetaut and Gareth J. Dyke ...

'' and "Ichthyornis" ''minusculus'', which was originally misidentified as ''Ichthyornis'' based on its presence in marine deposits.

References

Avisaurids Bird genera Fossil taxa described in 2002 Late Cretaceous birds of North America Mooreville Chalk {{paleo-bird-stub