''Hesperornis'' (meaning "western bird") is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of cormorant-like bird that spanned the first half of the
Campanian
The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...
age of the
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...
period (83.5–78
mya). One of the lesser-known discoveries of the paleontologist
O. C. Marsh
Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among h ...
in the late 19th century
Bone Wars
The Bone Wars, also known as the Great Dinosaur Rush, was a period of intense and ruthlessly competitive fossil hunting and discovery during the Gilded Age of American history, marked by a heated rivalry between Edward Drinker Cope (of the Acade ...
, it was an early find in the history of avian paleontology. Locations for ''Hesperornis'' fossils include the Late Cretaceous marine
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
s from
Kansas
Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...
and the marine shales from
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
. Nine species are recognised, eight of which have been recovered from rocks in North America and one from Russia.
Description
''Hesperornis'' was a large bird, reaching up to in length.
[ It had virtually no wings, and swam with its powerful hind legs. Studies on the feet initially indicated that ''Hesperornis'' and kin had lobed toes similar to modern-day ]grebe
Grebes () are aquatic diving birds in the order Podicipediformes . Grebes are widely distributed freshwater birds, with some species also found in marine habitats during migration and winter. Some flightless species exist as well, most notably ...
s, as opposed to webbed toes as seen in most aquatic birds such as loon
Loons (North American English) or divers (British / Irish English) are a group of aquatic birds found in much of North America and northern Eurasia. All living species of loons are members of the genus ''Gavia'', family Gaviidae and order Gavi ...
s. More recent work looking at the morphometrics of the feet in hesperornithiformes and modern sea birds has thrown this interpretation into question, making webbed toes equally as likely as lobed toes for this group.
Like many other Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...
birds such as ''Ichthyornis
''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, Kansa ...
'', ''Hesperornis'' had teeth
A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...
as well as a beak
The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for food ...
. In the hesperornithiform lineage they were of a different arrangement than in any other known bird (or in non-avian theropod
Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...
dinosaurs), with the teeth sitting in a longitudinal groove rather than in individual sockets, in a notable case of convergent evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
with mosasaur
Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on th ...
s.[ The teeth of ''Hesperornis'' were present along nearly the entire lower jaw (dentary) and the back of the upper jaw (]maxilla
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
). The front portion of the upper jaw (premaxilla
The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...
) and tip of the lower jaw (predentary) lacked teeth and were probably covered in a beak. Studies of the bone surface show that at least the tips of the jaws supported a hard, keratin
Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
ous beak similar to that found in modern birds.[ The palate (mouth roof) contained small pits that allowed the lower teeth to lock into place when the jaws were closed.][ They also retained a dinosaur-like joint between the lower jaw bones. It is believed that this allowed them to rotate the back portion of the mandible independently of the front, thus allowing the lower teeth to disengage.][
]
History
The first ''Hesperornis'' specimen was discovered in 1871 by Othniel Charles Marsh
Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among h ...
. Marsh was undertaking his second western expedition, accompanied by ten students. The team headed to Kansas where Marsh had dug before. Aside from finding more bones belonging to the flying reptile ''Pteranodon
''Pteranodon'' (); from Ancient Greek (''pteron'', "wing") and (''anodon'', "toothless") is a genus of pterosaur that included some of the largest known flying reptiles, with ''P. longiceps'' having a wingspan of . They lived during the late Cr ...
'', Marsh discovered the skeleton of a "large fossil bird, at least five feet in height". The specimen was large, wingless, and had strong legs—Marsh considered it a diving species. Unfortunately, the specimen lacked a head. Marsh named the find ''Hesperornis regalis'', or "regal western bird".[Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,']
Winter 2010 Appendix.
/ref>
Marsh headed back west with a smaller party the following year. In western Kansas, one of Marsh's four students, Thomas H. Russell, discovered a "nearly perfect skeleton" of ''Hesperornis.'' This specimen had enough of its head intact that Marsh could see that the creature's jaws had been lined with teeth.[Wallace, 86.] Marsh saw important evolutionary implications of this find, along with Benjamin Mudge
Benjamin Franklin Mudge (August 11, 1817 – November 21, 1879) was an American lawyer, geologist and teacher. Briefly the mayor of Lynn, Massachusetts, he later moved to Kansas where he was appointed the first State Geologist. He led the fi ...
's find of the toothed bird ''Ichthyornis
''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, Kansa ...
''. In an 1873 paper Marsh declared that "the fortunate discovery of these interesting fossils does much to break down the old distinction between Birds and Reptiles". Meanwhile, Marsh's relationship with his rival Edward Drinker Cope
Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontologist, comparative anatomist, herpetologist, and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested ...
soured further after Cope accidentally received boxes of fossils, including the toothed birds, that were meant for Marsh. Cope called the birds "simply delightful", but Marsh replied with accusations Cope had stolen the bones. By 1873 their friendship dissolved into open hostility, helping to spark the Bone Wars
The Bone Wars, also known as the Great Dinosaur Rush, was a period of intense and ruthlessly competitive fossil hunting and discovery during the Gilded Age of American history, marked by a heated rivalry between Edward Drinker Cope (of the Acade ...
. While Marsh would rarely go into the field after 1873, the collectors he paid continued to send him a stream of fossils. He eventually received parts of 50 specimens of ''Hesperornis'', which allowed him to make a much stronger demonstration of an evolutionary link between reptiles and birds than had been possible before.
Classification and Species
Many species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
have been described in this genus, though some are known from very few bones or even a single bone and cannot be properly compared with the more plentiful (but also incomplete) remains of other similar-sized taxa
In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...
. In many cases, species have been separated by provenance, having been found in strata of different ages or in different locations, or by differences in size.
The first species to be described, the type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
, is ''Hesperornis regalis''. ''H. regalis'' is also the best known species, and dozens of specimens (from fragments to more complete skeletons) have been recovered, all from the Smoky Hill Chalk Member of the Niobrara Formation
The Niobrara Formation , also called the Niobrara Chalk, is a geologic formation in North America that was deposited between 87 and 82 million years ago during the Coniacian, Santonian, and Campanian stages of the Late Cretaceous. It is compose ...
(dating to the early Campanian
The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...
age, between 90 and 60 million years ago).[ It is the only species of ''Hesperornis'' for which a nearly complete skull is known.
''Hesperornis crassipes'' was named in 1876 by Marsh, who initially classified it in a different genus as ''Lestornis crassipes''. ''H. crassipes'' was larger than ''H. regalis'', had five ribs as opposed to four in the first species, and differed in aspects of the bone sculpturing on the breastbone and lower leg. ''H. crassipes'' is known from the same time and place as ''H. regalis''. One incomplete skeleton is known, including teeth and parts of the skull.][
]
Marsh explicitly named his second species of ''Hesperornis'' in 1876 for an incomplete metatarsus
The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the med ...
recovered from the same layers of the Niobrara chalk as ''H. regalis''. He named this smaller species ''H. gracilis'', and it was subsequently involved in the rather confused taxonomy of a specimen which would eventually form the basis of the new genus and species '' Parahesperornis alexi''. The type specimen of ''P. alexi'' was assumed to belong to the same specimen as that of ''H. gracilis'', so when Lucas (1903) decided that the former specimen represented a distinct genus, he mistakenly used the later specimen to anchor it, creating the name ''Hargeria gracilis''. This mistake was rectified by later authors, who sank ''Hargeria'' back into ''Hesperornis'' and renamed the more distinctive specimen ''Parahesperornis''.[
upType specimen (a partial right tibia) of ''H. altus'' in several views
The first species recognized from outside the Niobrara chalk, ''Hesperornis altus'', lived about 78 million years ago in ]Montana
Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...
, and is known from a partial lower leg from the base of the freshwater Judith River Formation
The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the Late Cretaceous, between 79 and 75.3 million years ago, corresponding to the "Judithian" land vertebrate age. It ...
(or, possibly, the top of the underlying, marine Claggett Shale formation). While initially placed in the new genus ''Coniornis'' by Marsh, this was due mostly to his belief that ''Hesperornis'' existed only in Kansas, so any species from Montana should be placed in a different genus. Most later researchers disagreed with this, and have placed ''Coniornis altus'' in the same genus as ''Hesperornis'' as ''H. altus''.[ A second species from Montana has also been described from the Claggett Shale. ''H. montana'' was named by Shufeldt in 1915, and while its known material (a single dorsal ]vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
) cannot be directly compared to ''H. altus'', Shufeldt and others have considered it distinct due to its apparently smaller size.[
In 1993, the first ''Hesperornis'' remains from outside of North America were recognized as a new species by Nessov and Yarkov. They named ''Hesperornis rossicus'' for a fragmentary skeleton from the early Campanian of ]Russia
Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
near Volgograd
Volgograd ( rus, Волгогра́д, a=ru-Volgograd.ogg, p=vəɫɡɐˈɡrat), geographical renaming, formerly Tsaritsyn (russian: Цари́цын, Tsarítsyn, label=none; ) (1589–1925), and Stalingrad (russian: Сталингра́д, Stal ...
. Several other specimens from contemporary deposits have since been referred to this species. At about long, ''H. rossicus'' was the largest species of ''Hesperornis'' and among the largest hesperornithines, slightly smaller than the large Canadian genus ''Canadaga
''Canadaga'' (meaning "Canadian bird") is a flightless bird genus from the Late Cretaceous. The single known species is ''Canadaga arctica''. It lived in the shallow seas around what today is Bylot Island in Nunavut, Canada. Its fossils were fou ...
''. Aside from its large size and different geographic location, ''H. rossicus'' differs from other ''Hesperornis'' in several features of the lower leg and foot, including a highly flattened metatarsus.[ Kurochkin, (2000). "Mesozoic birds of Mongolia and the former USSR." Pp. 533–559 in Benton, Shishkin, Unwin and Kurochkin (eds.). ''The Age of Dinosaurs in Russia and Mongolia.'']
In 2002, Martin and Lim formally recognized several new species for remains that had previously been unstudied or referred without consideration to previously named North American hesperornithines. These include the very small ''H. mengeli'' and ''H. macdonaldi'', the slightly larger ''H. bairdi'', and the very large ''H. chowi'', all from the Sharon Springs member of the Pierre Shale
The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico.
The Pierre Shale was described by Meek and Hayden in 1862 in th ...
Formation in South Dakota and Alberta, 80.5 million years ago.[
In addition, there are some unassigned remains, such as SGU 3442 Ve02 and LO 9067t and bones of an undetermined species from Tzimlyanskoe Reservoir near ]Rostov
Rostov ( rus, Росто́в, p=rɐˈstof) is a town in Yaroslavl Oblast, Russia, one of the oldest in the country and a tourist center of the Golden Ring. It is located on the shores of Lake Nero, northeast of Moscow. Population:
While t ...
. The former two bones are probably ''H. rossicus''; some remains assigned to that species in turn seem to belong to the latter undetermined taxon.
Paleobiology
''Hesperornis'' was primarily marine, and lived in the waters of such contemporary shallow shelf sea
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...
s as 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, ...
, the Turgai Strait, and the North Sea
The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...
, which then were subtropical
The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...
to tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
waters, much warmer than today. However, some of the youngest known specimens of ''Hesperornis'' have been found in inland freshwater deposits of the Foremost Formation
The Foremost Formation is a stratigraphic unit of Late Cretaceous (Campanian) age that underlies much of southern Alberta, Canada. It was named for outcrops in Chin Coulee near the town of ForemostGlass, D.J. (editor) 1997. Lexicon of Canadian S ...
, suggesting that some species of ''Hesperornis'' may have eventually moved, at least partially, away from a primarily marine habitat. Additionally, the species ''H. altus'' comes from the freshwater deposits at the base of the Judith River Formation
The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the Late Cretaceous, between 79 and 75.3 million years ago, corresponding to the "Judithian" land vertebrate age. It ...
.[
Traditionally, ''Hesperornis'' is depicted with a mode of locomotion similar to modern loons or grebes, and study of their limb proportions and hip structure has borne out this comparison. In terms of limb length, shape of the hip bones, and position of the hip socket, ''Hesperornis'' is particularly similar to the ]common loon
The common loon or great northern diver (''Gavia immer'') is a large member of the loon, or diver, family of birds. Breeding adults have a plumage that includes a broad black head and neck with a greenish, purplish, or bluish sheen, blackish o ...
(''Gavia immer''), probably exhibiting a very similar manner of locomotion on land and in water. Like loons, ''Hesperornis'' were probably excellent foot-propelled divers, but might have been ungainly on land. Like loons, the legs were probably encased inside the body wall up to the ankle, causing the feet to jut out to the sides near the tail. This would have prevented them from bringing the legs underneath the body to stand, or under the center of gravity to walk. Instead, they likely moved on land by pushing themselves along on their bellies, like modern seals.[ However, more recent studies on hesperornithean hindlimbs suggest they were more functionally similar to those of the still upright walking ]cormorant
Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the IOC adopted a consensus taxonomy of seven ge ...
s.
Young ''Hesperornis'' grew fairly quickly and continuously to adulthood, as is the case in modern birds, but not Enantiornithes
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 ...
.
Pathology
A ''Hesperornis'' leg bone uncovered in the 1960s was examined by David Burnham, Bruce Rothschild et al. and was found to bear bite marks from a young polycotylid plesiosaur (possibly a ''Dolichorhynchops
''Dolichorhynchops'' is an extinct genus of polycotylid plesiosaur from the Late Cretaceous (early Turonian to late Campanian stage) of North America, containing three species, ''D. osborni'', ''D. bonneri'' and ''D. tropicensis'', as well as a ...
'' or something similar). The ''Hesperornis's'' bone, specifically the condyle, shows signs of infection, indicating the bird survived the initial attack and escaped the predator. The discovery was published in the journal ''Cretaceous Research'' in 2016.
References
Sources
*
*
Further reading
* Everhart, M.J. (2012): Oceans of Kansas
''Hesperornis regalis'' Marsh 1872 – Toothed marine birds of the Late Cretaceous seas
Version of 2012-September-19.
* Everhart, M.J. 2011. Rediscovery of the ''Hesperornis regalis'' Marsh 1871 holotype locality indicates an earlier stratigraphic occurrence. Kansas Academy of Science, Transactions 114(1-2):59-68.
External links
* Eastern Kentucky University
Eastern Kentucky University (Eastern or EKU) is a public university in Richmond, Kentucky. As a regional comprehensive institution, EKU also maintains branch campuses in Corbin, Hazard, Lancaster, and Manchester and offers over 40 online un ...
Closeup of ''Hesperornis'' skull
Retrieved 2007-NOV-04.
* savageancientseas.com
Forward view of ''H. regalis'' skeleton in diving pose
Note realistic position of legs and toe rotation. Retrieved 2007-NOV-04.
* UC Davis
The University of California, Davis (UC Davis, UCD, or Davis) is a public land-grant research university near Davis, California. Named a Public Ivy, it is the northernmost of the ten campuses of the University of California system. The institut ...
Moveable 3D rendering of patella (kneecap) of ''Hesperornis'' sp.
Digitized from KUVP PU17193. Requires Java, IFC or 3DC plugin. Retrieved 2007-NOV-04.
{{Taxonbar, from=Q733644
Bird genera
Hesperornitheans
Extinct flightless birds
Late Cretaceous birds of North America
Taxa named by Othniel Charles Marsh