''Paronychodon'' (meaning "beside claw tooth") was a

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

. It is a

tooth 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, tea ...

taxon In biology, a taxon (back-formation from ''taxonomy''; : 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 name and ...

, often considered dubious because of the fragmentary nature of the

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 preserve ...

s, which include "buckets" of teeth from many disparate times and places but no other remains, and should be considered a

form taxon Form classification is the classification of organisms based on their morphology (biology), morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncer ...

. The

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

, named by

Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontology, paleontologist, comparative anatomy, comparative anatomist, herpetology, herpetologist, and ichthyology, ichthyologist. Born to a wealthy Quaker fam ...

in 1876,Cope, E.D., 1876, "Descriptions of some vertebrate remains from the Fort Union Beds of Montana", ''Proceedings of the Academy of Natural Sciences of Philadelphia'', 28: 248-261 is ''Paronychodon lacustris'', from the

Judith River Formation The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Montana Group. It dates to the Late Cretaceous, between 79 and 75.3 million years ago, corresponding to the "Judithian" land vertebrate age. It was ...

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

, dating to 75 million years ago, during 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. Campa ...

stage. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

is specimen AMNH 3018. It is a tooth about one centimetre long, elongated, recurved, lacking serrations, possessing low vertical ridges and with a D-shaped cross-section, the inner side being flattened. Cope at first thought the tooth belonged to a

plesiosaur The Plesiosauria or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...

, but in the same year realised it represented a carnivorous dinosaur. A second species, ''Paronychodon caperatus'', is known from the

Hell Creek Formation The Hell Creek Formation is an intensively studied division of mostly Upper Cretaceous and some lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana. The Formation (stratigraphy), formation s ...

North Dakota North Dakota ( ) is a U.S. state in the Upper Midwest, named after the indigenous Dakota people, Dakota and Sioux peoples. It is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north and by the U.S. states of Minneso ...

, and

South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state, state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Dakota people, Dakota Sioux ...

and

Lance Formation The Lance (Creek) Formation is a division of Late Cretaceous (dating to about 69–66 Ma) rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the lates ...

Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...

(latest

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

stage, million years ago) and was originally referred to the mammal genus '' Tripriodon'' by

Othniel Charles Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of paleontology. A prolific fossil collector, Marsh was one of the preeminent paleontologists of the nineteenth century. Among his legacies are the discovery or ...

in 1889, but placed in ''Paronychodon'' by George Olshevsky in 1991. It is based on holotype YPM 10624, a tooth close in form to the holotype of ''P. lacustris'' but somewhat larger. In 1995 Olshevsky renamed '' Laelaps explanatus'' Cope 1876 into a ''Paronychodon explanatus''; today the taxon is seen as based on ''

Saurornitholestes ''Saurornitholestes'' ("lizard-bird thief") is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Canada (Alberta and Saskatchewan) and the United States (Montana, New Mexico, Alabama, and South Carolina). Two spe ...

'' teeth.

A very large number of other specimens matching these teeth in some or all aspects of their anatomy have been referred to ''Paronychodon''. Some of these included serrated teeth, low teeth and teeth without a flattened side. These teeth of the general "''Paronychodon''" type have been reported from a wide variety of times and places, including the Early Cretaceous Una Formation of

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

, dating to the late

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a ...

age 125 million years ago. ''Paronychodon'' has been considered a coelurid, an ornithomimosaur, a dromaeosaurid, an archaeopterygid, and a

troodontid Troodontidae is a clade of bird-like theropod dinosaurs from the Late Jurassic to Late Cretaceous. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinos ...

, though it could also be another kind of coelurosaurian theropod. While most researchers have therefore considered it simply represents indeterminate theropod teeth, a small consensus has found them to be

Deinonychosauria Deinonychosauria is a clade of paravian dinosaurs which lived from the Late Jurassic to the Late Cretaceous periods. Fossils have been found across the globe in North America, Europe, Africa, Asia, South America, and Antarctica,Case, J.A., Marti ...

. The teeth assigned to ''Paronychodon'' are all small, and may have come from various juvenile

deinonychosaur Deinonychosauria is a clade of paravian dinosaurs which lived from the Late Jurassic to the Late Cretaceous periods. Fossils have been found across the globe in North America, Europe, Africa, Asia, South America, and Antarctica,Case, J.A., Marti ...

s. Jaws from adult individuals bearing identical teeth have never been found. Marsh already suggested such teeth were pathological, having formed when the first teeth of the lower jaws by accident grew back-to-back to each other on the mandible suture. Philip J. Currie in 1990 also concluded to a malformation, thinking the flattened side resulted from the tooth remaining attached too long to the inner wall of the tooth-socket. Serrated specimens of the type would thus simply be deviant dromaeosaurid teeth; however, unserrated teeth might represent a separate taxon or taxa. One study, by Sunny Hwang, showed that the tooth enamel is identical to that found in ''

Byronosaurus ''Byronosaurus'' is a genus of Troodontidae, troodontid dinosaur from the Late Cretaceous Period (geology), Period of Mongolia. Discovery and naming In 1993, Michael Novacek, a member of an American Museum of Natural History expedition to the Go ...

'', a troodontid known from juveniles with serration-less teeth. Several taxa have on occasion been considered synonyms of ''Paronychodon'', though there is little consensus. ''Paronychodon'' was in 1876 by Cope described as being similar to '' Zapsalis'', another tooth taxon, itself often considered synonymous with '' Richardoestesia'', a possible

dromaeosaurid Dromaeosauridae () is a family (biology), family of feathered coelurosaurian Theropoda, theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous period (geology), Period. The name Drom ...

. ''Richardoestesia isosceles'' would, according to a study by Julia Sankey e.a., be synonymous with the elongated, so-called "Type A", teeth of ''Paronychodon'',Sankey, J.T., D.B. Brinkman, M. Guenther, and P.J. Currie, 2002, "Small theropod and bird teeth from the Judith River Group (late Campanian), Alberta", ''Journal of Paleontology'' 76(4): 751-763 to which also the ''Paronychodon'' holotype belongs. The Eurasian '' Euronychodon'' tooth genus is also sometimes considered a (junior) synonym of ''Paronychodon''.

References

{{Portal bar, Paleontology, Dinosaurs Troodontidae Dinosaur genera Campanian dinosaurs Maastrichtian dinosaurs Judith River Formation Hell Creek Formation Lance Formation Taxa named by Edward Drinker Cope Fossil taxa described in 1876 Dinosaurs of the United States

See also

References