Parahesperornis
Encyclopedia
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
in Kansas. Found only in the upper Niobrara Chalk, these are from around the Coniacian
-Santonian
boundary, 85-82 million years ago (mya).
Parahesperornis alexi (Martin, 1984) was long lumped with specimen YPM 1478, described initially as Hesperornis gracilis and later moved to the monotypic
genus Hargeria (Lucas, 1903). 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. This mistake was rectified by later authors, who sank Hargeria back into Hesperornis.
Parahesperornis was a member of the Hesperornithes
, flightless toothed seabirds of the Cretaceous
and more specifically in the main lineage, close to Hesperornis
. Possibly the genus extended into the Campanian
, to less than 80 mya. In any case, there are two very similar fossil
s 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.
Flightless bird
Flightless birds are birds which lack the ability to fly, relying instead on their ability to run or swim. They are thought to have evolved from flying ancestors. There are about forty species in existence today, the best known being the ostrich, emu, cassowary, rhea, kiwi, and penguin...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
from the Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
. 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
Hesperornis
Hesperornis is a genus of flightless aquatic birds that spanned the first half of the Campanian age of the Late Cretaceous period . One of the lesser-known discoveries of the paleontologist O. C. Marsh in the late 19th century Bone Wars, it was an important early find in the history of avian...
. Remains are known from central North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, namely the former shallows of the Western Interior Seaway
Western Interior Seaway
The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves, Laramidia and Appalachia, during most of the mid- and late-Cretaceous Period...
in Kansas. Found only in the upper Niobrara Chalk, these are from around the Coniacian
Coniacian
The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series and spans the time between 89.3 ± 1 Ma and 85.8 ± 0.7 Ma...
-Santonian
Santonian
The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 85.8 ± 0.7 mya and 83.5 ± 0.7 mya...
boundary, 85-82 million years ago (mya).
Parahesperornis alexi (Martin, 1984) was long lumped with specimen YPM 1478, described initially as Hesperornis gracilis and later moved to the monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
genus Hargeria (Lucas, 1903). It then turned out that this genus' description actually referred to specimen KUVP 2287, which eventually became the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
of P. alexi. Nonetheless, the taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
the description of Hargeria was about was "Hesperornis" gracilis exclusively, and thus despite the misidentification it applies to YPM 1478, the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
of "H." gracilis. This mistake was rectified by later authors, who sank Hargeria back into Hesperornis.
Parahesperornis was a member of the Hesperornithes
Hesperornithes
Hesperornithes is an extinct and highly specialized clade of Cretaceous toothed birds. Hesperornithine birds, apparently limited to former aquatic habitats in the Northern Hemisphere, include genera such as Hesperornis, Parahesperornis, Baptornis, Enaliornis, and probably Potamornis, all...
, flightless toothed seabirds of the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
and more specifically in the main lineage, close to Hesperornis
Hesperornis
Hesperornis is a genus of flightless aquatic birds that spanned the first half of the Campanian age of the Late Cretaceous period . One of the lesser-known discoveries of the paleontologist O. C. Marsh in the late 19th century Bone Wars, it was an important early find in the history of avian...
. Possibly the genus extended into the Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
, to less than 80 mya. In any case, there are two very similar fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s from the Nemegt Formation
Nemegt Formation
The Nemegt Formation is a geological formation dating from the Late Cretaceous sedimentary from the Gobi Desert of Mongolia. It overlies and sometimes forms folds with the Barun Goyot Formation. It consists of river channel sediments and contains fossils of fish, turtles, crocodilians, birds and a...
(Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
or possibly late Campanian, around 76-65 mya, which were found at Tsagaan Kushu (Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
). Both are distal ends of tibiotarsi
Tibiotarsus
The tibiotarsus is the large bone between the femur and the tarsometatarsus in the leg of a bird. It is the fusion of the proximal part of the tarsus with the tibia.A similar structure also occurred in the Mesozoic Heterodontosauridae...
, and they seem certainly more similar to the bones of Hesperornithiformes
Hesperornithiformes
Hesperornithes is an extinct and highly specialized clade of Cretaceous toothed birds. Hesperornithine birds, apparently limited to former aquatic habitats in the Northern Hemisphere, include genera such as Hesperornis, Parahesperornis, Baptornis, Enaliornis, and probably Potamornis, all...
and (due to the smallish size) to Parahesperornis specifically. However, they are not very diagnostic regardless, and the diversity of Parahesperornis remains enigmatic.
External links
- Kansas Geological SurveyKansas Geological SurveyThe Kansas Geological Survey, operated by The University of Kansas in connection with its research and service program, is to conduct geological studies and research and to collect, correlate, preserve, and disseminate information leading to a better understanding of the geology of Kansas, with...
: Parahesperornis alexi reconstruction. Retrieved 2007-NOV-04. - Oceans of Kansas PaleontologyOceans of Kansas PaleontologyOceans of Kansas Paleontology is a website founded in 1996 by Michael J. Everhart, a paleontologist specializing in Cretaceous marine reptiles, mosasaurs in particular, of western Kansas, and author of Oceans of Kansas- A Natural History of the Western Interior Sea...
: http://www.oceansofkansas.com/Hesperornis.html. Retrieved 209-JAN-15 - UC Davis: Moveable 3D rendering of P. alexi tibiotarsus. Digitized from KUVP 2287. Requires Java, IFC or 3DC plugin. Retrieved 2007-NOV-04.
