Laosaurus

{{Short description|Extinct genus of dinosaurs}} {{Automatic taxobox | fossil_range = Kimmeridgian, {{fossilrange|154|152|latest=70}} | image = Laosaurus celer pubis.png | image_caption = Pubis of ''Laosaurus'' (unknown species; possibly ''L. celer'') in 1896 | taxon = Laosaurus | authority = Marsh, 1878 | type_species = {{extinct}}'''''Laosaurus celer''''' | type_species_authority = Marsh, 1878 | subdivision_ranks = Species | subdivision = * †''L. celer'' Marsh, 1878 (type) (''nomen dubium'') * †''L. gracilis'' Marsh, 1878 (''nomen dubium'') * †''L. minimus'' Gilmore, 1924 (''nomen dubium'') }}

'''''Laosaurus''''' (meaning "stone or fossil lizard") is a genus of neornithischian dinosaur. The type species, '''''Laosaurus celer''''', was first described by O.C. Marsh in 1878 from remains discovered in the Upper Jurassic (Kimmeridgian) Morrison Formation of Wyoming. The validity of this genus is doubtful because it is based on fragmentary fossils. A second species also from the Morrison Formation, ''L. gracilis'', and a species from the Upper Cretaceous Allison Formation of Alberta, Canada, ''L. minimus'', are also considered dubious.

==History and taxonomy== Marsh (1878a) named his new genus from vertebrae (YPM 1874) found by Samuel Wendell Williston at Como Bluff, Wyoming, from rocks of the Morrison Formation. The type material includes nine partial and two complete tail vertebral centra, which he concluded came from a "fox-sized" animal.<ref name=OCM78a>{{cite journal |last=Marsh |first=Othniel Charles |authorlink=Othniel Charles Marsh |year=1878 |title=Notice of new dinosaurian reptiles |journal=American Journal of Science and Arts |volume=15 |issue=87 |pages=241–244|doi=10.2475/ajs.s3-15.87.241 |bibcode=1878AmJS...15..241M |s2cid=131371457 |url=https://zenodo.org/record/1450042 }}</ref> In the same year, he named two other species: ''L. gracilis'', originally based on a back vertebral centrum, a tail vertebral centrum, and part of an ulna;<ref name=OCM78a/><ref name=TEW73>{{cite journal |last=White |first=T.E. |year=1973 |title=Catalogue of the genera of dinosaurs |journal=Annals of Carnegie Museum |volume=44 |pages=117–155|doi=10.5962/p.243870 |doi-access=free |bibcode=1973AnCM...44..117W }}</ref> and ''L. altus'', originally based on a pelvis, hindlimb, and tooth (YPM 1876).<ref name=OCM78b>{{cite journal |last=Marsh |first=Othniel Charles |year=1878 |title=Principal characters of American Jurassic dinosaurs. Part I |journal=American Journal of Science and Arts |volume=16 |issue=95 |pages=411–416|doi=10.2475/ajs.s3-16.95.411 |bibcode=1878AmJS...16..411M |hdl=2027/hvd.32044107172876 |s2cid=219245525 |hdl-access=free }}</ref> A review by Peter Galton in 1983 found the type of ''L. gracilis'' to consist of thirteen back and eight tail centra, and portions of both hindlimbs.<ref name=PMG83>{{cite journal |last=Galton |first=Peter M. |authorlink=Peter Galton |year=1983 |title=The cranial anatomy of ''Dryosaurus'', a hypsilophodontid dinosaur from the Upper Jurassic of North America and East Africa, with a review of hypsilophodontids from the Upper Jurassic of North America |journal=Geologica et Palaeontologica |volume=17 |pages=207–243}}</ref> Charles Gilmore had assigned additional remains, including a partial skeleton (CM 11340), to ''L. gracilis'' based on size,<ref name=CWG09>{{cite journal |last=Gilmore |first=Charles W. |authorlink=Charles W. Gilmore |year=1909 |title=A new rhynchocephalian reptile from the Jurassic of Wyoming, with notes on the fauna of "Quarry 9" |journal=Proceedings of the U.S. National Museum |volume=37 |pages=35–42 |doi=10.5479/si.00963801.37-1698.35 |issue=1698|hdl=2027/njp.32101042899474 |url=https://www.biodiversitylibrary.org/part/51125 |hdl-access=free }}</ref><ref name=CWG25>{{cite journal |last=Gilmore |first=Charles W. |year=1925 |title=Osteology of ornithopodous dinosaurs from the Dinosaur National Monument, Utah |journal=Memoir of the Carnegie Museum |volume=10 |pages=385–409|doi=10.5962/p.234845 |s2cid=134260227 |doi-access=free }}</ref> but Galton transferred the remains to other taxa, assigning the skeleton to ''Dryosaurus''.<ref name=PMG83/> Marsh returned to the genus in 1894, when additional remains convinced him that ''L. altus'' deserved its own genus (''Dryosaurus''), and that there was another species present: ''L. consors'', based on YPM 1882, a partial skeleton also from Como Bluff.<ref name=OCM94>{{cite journal |last=Marsh |first=Othniel Charles |year=1894 |title=The typical Ornithopoda of the American Jurassic |journal=American Journal of Science |series=Series 3 |volume=48 |issue=283 |pages=85–90|doi=10.2475/ajs.s3-48.283.85 |bibcode=1894AmJS...48...85M |s2cid=130777820 |url=https://zenodo.org/record/2161731 }}</ref> In 1895, he coined the family Laosauridae for his genus, but this was eventually considered synonymous with Hypsilophodontidae.<ref name=OCM95>{{cite journal |last=Marsh |first=Othniel Charles |year=1895 |title=On the affinities and classification of the dinosaurian reptiles |journal=American Journal of Science |volume=50 |issue=300 |pages=483–498 |doi=10.2475/ajs.s4-7.42.403|url=https://zenodo.org/record/1450210 }}</ref> [[File:Marsh_laosaurus.jpg|left|thumb|250px|Othniel Charles Marsh's 1896 skeletal restoration of "''Laosaurus''" ''consors'' (now ''Nanosaurus'').]] Charles Gilmore in 1909 assigned a juvenile femur (USNM 5808) to ''L. gracilis'',<ref name="CWG09"/> and in 1925 added partial skeleton CM 11340 to ''L. gracilis'', based on size,<ref name="CWG25"/> but Galton transferred the femur to ''Othnielia'' (now ''Nanosaurus'') and the skeleton to ''Dryosaurus'' in 1983. Gilmore also described the fifth and final species, ''L. minimus'' (species name for its small size), based on NMC 9438, a partial left hindlimb and vertebral bits from the Late Cretaceous (late Campanian) Allison Formation of Alberta, Canada.<ref name=CWG24>{{cite journal |last=Gilmore |first=Charles W. |year=1924 |title=A new species of ''Laosaurus'', an ornithischian dinosaur from the Cretaceous of Alberta |journal=Transactions of the Royal Society of Canada, Section 4 |series=Series 3 |volume=18 |pages=1–6}}</ref> At the time, though, the discovery locality was thought to be in the Early Cretaceous Blairmore Group, but fieldwork at the ''L. minimus'' type locality in the early 1930s showed it to be within the Belly River Group, and Loris Russell published a paper in 1949 recognizing this new geologic information, while finding it generically distinct from ''Laosaurus'' proper.<ref name=LR49>{{cite journal |last=Russell |first=Loris S. |year=1949 |title=The relationships of the Alberta Cretaceous dinosaur "Laosaurus" ''minimus'' Gilmore |journal=Journal of Paleontology |volume=23 |issue=5 |pages=518–520}}</ref> Russell found this taxon to be most like ''Hypsilophodon'', from the Early Cretaceous Wessex Formation of southern England.<ref name=LR49/>

The next major publications which mentioned ''Laosaurus'' prominently were by Galton. In 1977, he assigned ''L. consors'' and ''L. gracilis'' to his new taxon ''Othnielia rex'';<ref name=PMG77>{{cite journal |last=Galton |first=Peter M. |year=1977 |title=The ornithopod dinosaur ''Dryosaurus'' and a Laurasia-Gondwanaland connection in the Upper Jurassic |journal=Nature |volume=268 |pages=230–232 |doi=10.1038/268230a0 |issue=5617 |bibcode=1977Natur.268..230G|s2cid=30721851 }}</ref> and in 1983 he redescribed most of the material and reassigned some of it, as described above.<ref name=PMG83/> Galton (1983) is also one of the sources for the "''Troodon'' as carnivorous ornithopod" hypothesis of the early 1980s, because it assigns ''L. minimus'' to ''Troodon'', based on unpublished evidence.<ref name=PMG83/> This would tie in with the ''Orodromeus''/''Troodon'' egg confusion of a few years later, which was eventually settled as ''Troodon'' individuals eating ''Orodromeus'' individuals at their nesting site (the troodontid embryoes were confused with hypsilophodont embryoes).<ref name=VJBH97>{{cite journal |last=Varricchio |first=D.J. |author2=Jackson, F. |author3=Borkowski, J.J. |author4= Horner, J.R. |year=1997 |title=Nest and egg clutches of the dinosaur ''Troodon formosus'' and the evolution of the avian reproductive system |journal=Nature |volume=385 |pages=247–250 |doi=10.1038/385247a0 |issue=6613 |bibcode=1997Natur.385..247V|s2cid=4313286 }}</ref> ''L. celer'' was assessed as dubious by Galton, a status it has kept through the last major reviews.<ref name=SN90>{{cite book |last=Sues |first=Hans-Dieter |author2=Norman, David B. |editor= Weishampel, David B. |editor2=Dodson, Peter |editor3=Osmólska Halszka|title=The Dinosauria |edition=1st |year=1990 |publisher=University of California Press |location=Berkeley |isbn=978-0-520-06727-1 |pages=498–509 |chapter=Hypsilophodontidae, ''Tenontosaurus'', Dryosauridae}}</ref><ref name=NSWC04>{{cite book |last=Norman |first=David B. |authorlink=David B. Norman |author2=Sues, Hans-Dieter |author3=Witmer, Larry M. |author4= Coria, Rodolfo A. |editor=Weishampel, David B. |editor2=Dodson, Peter |editor3=Osmólska Halszka|title=The Dinosauria |edition=2nd |year= 2004|publisher=University of California Press |location=Berkeley |isbn=978-0-520-24209-8 |pages=393–412 |chapter=Basal Ornithopoda}}</ref>

Two further developments have occurred. First, ''L. minimus'' is seen as a possible second species or specimen of ''Orodromeus'' (Sues and Norman, 1990),{{verification needed|date=December 2021}} although the remains are too meager to be certain.<ref name=SN90/> Second, Galton, in a 2007 review, declared ''Othnielia rex'' to be based on undiagnostic remains, and shifted diagnostic referred remains to new taxon ''Othnielosaurus consors'', a new combination based on the original ''L. consors'' partial skeleton.<ref name=PMG07>{{cite book |last=Galton |first=Peter M. |year=2007 |chapter=Teeth of ornithischian dinosaurs (mostly Ornithopoda) from the Morrison Formation (Upper Jurassic) of the western United States |editor=Carpenter K.|title=Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs |publisher=Indiana University Press |location=Bloomington and Indianapolis |pages=17–47 |isbn=978-0-253-34817-3}}</ref>

===Taxonomic summary=== *''L. celer'' (type species) = dubious ornithischian<ref name=NSWC04/> *''L. altus'' = ''Dryosaurus altus''<ref name=OCM94/> *''L. consors'' = ''Othnielosaurus consors'', now considered a junior synonym of ''Nanosaurus agilis''<ref name=PMG07/> *''L. gracilis'' = dubious ornithishian<ref name=NSWC04/> *''L. minimus'' = dubious ornithischian, possibly orodromine

==References== {{Reflist}}

==External links== *[http://dml.cmnh.org/1995Aug/msg00194.html More on the taxonomy of ''Nanosaurus'', ''Othnielia'', and ''Laosaurus''] {{Webarchive|url=https://web.archive.org/web/20210304200027/http://dml.cmnh.org/1995Aug/msg00194.html |date=2021-03-04 }}, from the Dinosaur Mailing List *[https://www.jstor.org/stable/1299481 First page and abstract of Russell, 1949]

Category:Neornithischia Category:Dinosaur genera Category:Kimmeridgian dinosaurs Category:Morrison Formation Category:Taxa named by Othniel Charles Marsh Category:Fossil taxa described in 1878 Category:Dinosaurs of the United States