Cimolopteryx is a prehistoric bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

 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...

 Period. Remains attributed to Cimolopteryx have been found in the Frenchman Formation

Frenchman Formation

The Frenchman Formation is a division of Upper Cretaceous rocks found in Saskatchewan, Canada. More accurately described as Late Maastrichtian, these rocks contain the youngest of dinosaur genera, much like the Hell Creek Formation in the United States....

 of Saskatchewan

Saskatchewan

Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....

, the Lance Formation

Lance Formation

The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas...

 of Wyoming

Wyoming

Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...

, and possibly the Hell Creek Formation

Hell Creek Formation

The Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana...

 of Montana

Montana

Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

. All date to the end of the 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...

 age, about 65.5 million years ago. An additional specimen from the much earlier Dinosaur Park Formation

Dinosaur Park Formation

The Dinosaur Park Formation is the uppermost member of the Judith River Group, a major geologic unit in southern Alberta. It was laid down over a period of time between about 76.5 and 75 million years ago. The formation is made up of deposits of a high-sinuosity fluvial system, and is capped...

 of Alberta

Alberta

Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...

 (mid 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 ...

 age, about 75 million years ago) may belong to a new species of Cimolopteryx.

Description and history

Cimolopteryx was a fairly small bird, with a maximum size about equal to that of a small gull

Gull

Gulls are birds in the family Laridae. They are most closely related to the terns and only distantly related to auks, skimmers, and more distantly to the waders...

. It is known almost exclusively from a number of coracoids (a bone in the shoulder girdle). These have a distinct enough anatomy, however, to allow it to be distinguished from other birds, and even for distinct species to be recognized. The first such coracoid to be found (specimen number YMP 1845, in the collections of the Peabody Museum of Natural History) was first mentioned and informally named by paleontologist Othniel Charles Marsh

Othniel Charles Marsh

Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...

 in the footnote of an 1889 paper, but it was not validly described by him until 1892. Marsh also described a second species in the same paper, which he named Cimolopteryx retusa, but this has since been recognized as a different kind of bird and reclassified as Palintropus retusus.

Classification and species

The classification of various species assigned to the genus Cimolopteryx is uncertain. As of a re-evaluation of the fossil remains in 2002 by Sylvia Hope, at most five species were recognized: Cimolopteryx rara, C. petra, C. maxima, C. minima, and one yet-unnamed species. C. rara and C. petra are almost identical, and were found in the same environments (the Lance and Frenchman formations), but differ in size, with C. petra smaller than C. rara. In a 2009 review, Nicholas Longrich synonymized them as the same species, dismissing the size difference as possibly based on gender or growth stage. However, Longrich reversed his position following a 2011 analysis of Lancian birds, in which he and co-authors considered all four named species to be distinct. An additional, unnamed species is known from the much earlier Dinosaur Park Formation of Alberta. Also known only from a partial coracoid, its exact identity is uncertain. C. maxima was about twice the size of C. rara, but not enough of its anatomy is known to determine if it belongs to Cimolopteryx or a different genus. As its name suggests, C. minima is one of the smallest species in the genus, about the same size as specimens referred to C. petra. It may group together in the same "species group" as several indeterminate fossils possibly belonging to Cimolopteryx. Several collections of material that is similar to Cimolopteryx were referred to by Hope as undetermined species, which lack enough unique characteristics to be properly identified, and these may or may not belong to Cimolopteryx.

Hope regarded Cimolopteryx as a likely member of the modern bird group Charadriiformes

Charadriiformes

Charadriiformes is a diverse order of small to medium-large birds. It includes about 350 species and has members in all parts of the world. Most Charadriiformes live near water and eat invertebrates or other small animals; however, some are pelagic , some occupy deserts and a few are found in thick...

, which includes a diverse array of shorebirds. However, since all species are known only from parts of the shoulder girdle and wing bone fragments, this classification is tentative.