Nanosaurus

File:Nanosaurus.jpg

Nanosaurus has had a long and complicated taxonomic history. In 1877, Marsh named two species of Nanosaurus in separate publications, based on partial remains from the Morrison Formation of Garden Park, Colorado. One paper described N. agilis, based on YPM 1913, with remains including impressions of a dentary, and postcranial bits including an ilium, thigh bones, shin bones, and a fibula.{{cite journal |last=Marsh |first=Othniel Charles |author-link=Othniel Charles Marsh |year=1877 |title=Notice of some new vertebrate fossils |journal=American Journal of Science and Arts |volume=14 |issue=81 |pages=249–256|doi=10.2475/ajs.s3-14.81.249 |bibcode=1877AmJS...14..249M |s2cid=131230859 |url=https://zenodo.org/record/2429857 }} The other paper named N. rex, a second species which Marsh based on YPM 1915 (also called 1925 in Galton, 2007), a complete thigh bone.{{cite journal |last=Marsh |first=Othniel Charles |author-link=Othniel Charles Marsh |year=1877 |title=Notice of new dinosaurian reptiles from the Jurassic formations |journal=American Journal of Science and Arts |volume=14 |issue=84 |pages=514–516|doi=10.2475/ajs.s3-14.84.514 |bibcode=1877AmJS...14..514M |s2cid=130488291 |url=https://zenodo.org/record/1450040 }} He regarded both species as small ("fox-sized") animals. A third species, N. victor, was named, which he soon recognized to be something completely different, and is now known as the small, bipedal crocodylomorph Hallopus.{{Cite journal | last1 = Marsh | first1 = O.C. | year = 1881 | title = Principal characters of American Jurassic dinosaurs. Part V. | journal = American Journal of Science | volume = 21 | issue = 125 | pages = 418–423 | doi = 10.2475/ajs.s3-21.125.417 | bibcode = 1881AmJS...21..417M | s2cid = 219234316 }}

The next year, he named the new genus Laosaurus on material collected by Samuel Wendell Williston from Como Bluff, Wyoming. Two species were named: the type species L. celer, based on parts of eleven vertebrae (YPM 1875);{{cite journal |last=Marsh |first=Othniel Charles |author-link=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 |url=https://zenodo.org/record/1450042 |bibcode=1878AmJS...15..241M |s2cid=131371457 }} and the "smaller" L. gracilis, originally based on a back vertebra's centrum, a caudal centrum, and part of an ulna (review by Peter Galton in 1983 finds the specimen to now consist of thirteen back and eight caudal centra, and portions of both hindlimbs).{{cite journal |last=Galton |first=Peter M. |author-link=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}} A third species, L. consors, was established by Marsh in 1894 for YPM 1882, which consists of most of one articulated skeleton and part of at least one other individual.{{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|bibcode=1894AmJS...48...85M |doi=10.2475/ajs.s3-48.283.85 |s2cid=130777820 |url=https://zenodo.org/record/2161731 }} The skull was only partially preserved, and the fact that the vertebrae were represented only by centra suggests a partially grown individual. Galton (1983) notes that much of the current mounted skeleton was restored in plaster, or had paint applied.

File:Nano type.jpg

These animals attracted little professional attention until the 1970s and 1980s, when Peter Galton reviewed many of the "hypsilophodonts" in a series of papers. In 1973, he and Jim Jensen described a partial skeleton (BYU ESM 163 as of Galton, 2007) missing the head, hands, and tail as Nanosaurus? rex, which had been damaged by other collectors prior to description.{{cite journal |last=Galton |first=Peter M. |author2=Jensen, James A. |year=1973 |title=Skeleton of a hypsilophodontid dinosaur (Nanosaurus (?) rex) from the Upper Jurassic of Utah |journal=Brigham Young University Geology Series |volume=20 |pages=137–157}} By 1977, he had concluded that Nanosaurus agilis was quite different from N. rex and the new skeleton, and coined Othnielia for the latter species. The paper (primarily concerning the transcontinental nature of Dryosaurus) considered Laosaurus consors and L. gracilis synonyms of O. rex without elaboration, and considered L. celer an invalid nomen nudum.{{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 }}

File:Marsh laosaurus.jpg's 1896 skeletal restoration of "Laosaurus" consors (now Nanosaurus).]]

In 1990, Robert Bakker, Peter Galton, James Siegwarth, and James Filla described remains of a dinosaur they named Drinker nisti. The name is somewhat ironic; Drinker, named for renowned palaeontologist Edward Drinker Cope whose infamous "bone wars" with rival Othniel Charles Marsh produced many dinosaur fossils which are world-famous today, was described as a probable close relative of Othnielia, named for Marsh. The species name refers to the National Institute of Standards and Technology (NIST). Discovered by Siegwarth and Filla in upper Morrison Formation beds at Como Bluff, Wyoming, it was based on a partial subadult skeleton (listed as CPS 106 originally, then as Tate 4001 by Bakker 1996) including partial jaws, vertebrae, and partial limbs. Several other specimens found in the same area were assigned to it, mostly consisting of vertebral and hindlimb remains, and teeth.{{cite journal | last1 = Bakker | first1 = R.T. | last2 = Galton | first2 = P.M. | last3 = Siegwarth | first3 = J. | last4 = Filla | first4 = J. | year = 1990 | title = A new latest Jurassic vertebrate fauna, from the highest levels of the Morrison Formation at Como Bluff, Wyoming. Part IV. The dinosaurs: A new Othnielia-like hypsilophodontoid | journal = Hunteria | volume = 2 | issue = 6| pages = 8–14 }} The holotype specimen's current location is unknown; according to Carpenter and Galton (2018), the previous two institutions reported to have had it did not ever curate the specimen, and the collection it was originally said to be in never existed at all.

Several decades later, in his 2007 study of the teeth of Morrison ornithischians, Galton concluded that the holotype femur of Othnielia rex is not diagnostic, and reassigned the BYU skeleton to Laosaurus consors, which is based on better material. As the genus Laosaurus is also based on nondiagnostic material, he gave the species L. consors its own genus, Othnielosaurus. As a result, in practical terms, what had been thought of as Othnielia is now known as Othnielosaurus consors. Regarding Nanosaurus agilis, Galton considered it a potentially valid basal ornithopod, and noted similarities to heterodontosaurids in the thigh bone. He tentatively assigned to it some teeth that had been referred to Drinker.

File:Othnielosaurus dinosaur national monument.jpg]]

Another decade later, in 2018, Galton, alongside Kenneth Carpenter, described a new ornithischian specimen. They found it very similar to the fragmentary holotype of Nanosaurus, but more clear in its anatomical features. Their new specimen was also found to display extreme similarity with the specimens of Othnielosaurus and Drinker. Due to the new data, they concluded that all three species, alongside Othnielia, represented the same animal, united under the name Nanosaurus agilis. This painted a new picture of a singular, very common small dinosaur known from a large amount of material.{{cite journal | title=A photo documentation of bipedal ornithischian dinosaurs from the Upper Jurassic Morrison Formation, USA | last1=Carpenter | first1=Kenneth | last2=Galton | first2=Peter M. | journal=Geology of the Intermountain West | year=2018 | volume=5 | pages=167–207 | doi=10.31711/giw.v5.pp167-207| s2cid=73691452 | doi-access=free }} This conclusion has been recognized by papers since, some of which incorporating the new, all-encompassing taxon into their phylogenetic analyses.{{cite journal | title=New small-bodied ornithopods (Dinosauria, Neornithischia) from the Early Cretaceous Wonthaggi Formation (Strzelecki Group) of the Australian-Antarctic rift system, with revision of Qantassaurus intrepidus Rich and Vickers-Rich, 1999 | last1=Herne | first1=Matthew C. | last2=Nair | first2=Jay P. | last3=Evans | first3=Alistair R. | last4=Tait | first4=Alan M. | journal=Journal of Paleontology | volume=93 | issue=3 | pages=543–584 | year=2019 | doi=10.1017/jpa.2018.95| doi-access=free | bibcode=2019JPal...93..543H }}{{cite journal | title= A neornithischian dinosaur from the Middle Jurassic Xintiangou Formation of Yunyang, Chongqing, China: the earliest record in Asia | last1=Li | first1=Ning | last2=Dai | first2=Hui | last3=Tan | first3=Chao | last4=Hu | first4=Xufeng | last5=Wei | first5=Zhaoying | last6=Lin | first6=Yu | last7=Wei | first7=Guangbiao | last8=Li | first8=Deliang | last9=Meng | first9=Li | last10=Hao | first10=Baoqiao | last11=You | first11=Hailu | last12=Peng | first12= Guangzhou | journal=Historical Biology |pages = 1–14| year=2019 | volume=33 | issue=7 | doi=10.1080/08912963.2019.1679129| s2cid=209583081 }}{{cite journal | title=Photogrammetry of the Oryctodromeus cubicularis type locality burrow and the utility of preexisting, standard field photographs for three dimensional digital reconstruction | last1=Wilson | first1=John P. | last2=Varricchio | first2=David J. | journal=Historical Biology |pages = 1054–1061| year=2019 | volume=32 | issue=8 | doi=10.1080/08912963.2018.1563783| s2cid=91500384 }}

A 2025 study by Paul Barrett and Susannah Maidment failed to recognize autapomorphies (unique derived traits) or unique combinations of characters in the fragmentary or poorly preserved type specimens of Nanosaurus, Laosaurus, Othnielia, Othnielosaurus, and Drinker. As such, they opted to recognize the genera as nomina dubia that could not be conclusively synonymized with each other. They ultimately concluded that studies of the more complete specimens referred to these taxa may clarify the true relationships and diversity of small Morrison Formation ornithischians.{{Cite journal|last1=Barrett |first1=P. M. |last2=Maidment |first2=S. C. R. |year=2025 |title=A Review of Nanosaurus agilis Marsh and Other Small-Bodied Morrison Formation "Ornithopods" |journal=Bulletin of the Peabody Museum of Natural History |volume=66 |issue=1 |pages=25–50 |doi=10.3374/014.066.0102 }}

Barrett and Maidment observed that the teeth denticles (serrations) of Drinker are surprisingly similar to those of pachycephalosaurs such as Dracorex. Furthermore, the jugal bears ornamentation otherwise only seen in pachycephalosaurs. While this identification is highly tentative, it would make Drinker the only known Jurassic pachycephalosaur, and as such, the oldest member of the clade, filling a ghost lineage implied by the existence of Late Jurassic ceratopsians.

File:Othnielosaurus_Size_Comparison_by_PaleoGeek.svg

File:Othnielosaurus transparent.png]]

Nanosaurus is known from material from all parts of the body, including two good skeletons, although the skull is still poorly known.{{cite book |last=Norman |first=David B. |author-link=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 |url=https://archive.org/details/dinosauriandedit00weis |url-access=limited |edition=2nd |year= 2004|publisher=University of California Press |location=Berkeley |isbn=0-520-24209-2 |pages=[https://archive.org/details/dinosauriandedit00weis/page/n411 393]–412 |chapter=Basal Ornithopoda}} It was a small animal, with specimens previously assigned to Drinker and Othnielosaurus measuring {{convert|2|-|2.2|m|ft}} long and weighing {{convert|20|-|30|kg|lb}}.{{Cite book|last=Paul|first=Gregory S.|url=http://worldcat.org/oclc/985402380|title=The Princeton Field Guide to Dinosaurs|year=2016|publisher=Princeton University Press|isbn=978-1-78684-190-2|oclc=985402380|pages=306}}

It was a bipedal dinosaur with short forelimbs and long hindlimbs with large processes for muscle attachments.{{cite web |author=Scott Hartman|title=othnielia| url=http://skeletaldrawing.com/psgallery/pages/othnielia.html | access-date = 2007-01-25 }} The hands were short and broad with short fingers. The head was small. It had small leaf-shaped cheek teeth (triangular and with small ridges and denticles lining the front and back edges), and premaxillary teeth with less ornamentation.{{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, Kenneth |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}}

Like several other neornithischian dinosaurs, such as Hypsilophodon, Thescelosaurus, and Talenkauen, Nanosaurus had thin plates lying along the ribs. Called intercostal plates, these structures were cartilaginous in origin.{{cite journal |last=Butler |first=Richard J. |author2=Galton, Peter M. |year=2008 |title=The 'dermal armour' of the ornithopod dinosaur Hypsilophodon from the Wealden (Early Cretaceous: Barremian) of the Isle of Wight: a reappraisal |journal=Cretaceous Research |volume=29 |issue=4 |pages=636–642 |doi=10.1016/j.cretres.2008.02.002|bibcode=2008CrRes..29..636B }}

File:Nanosaurus BYU 163.tif

The cladogram below results from analysis by Herne et al., 2019.

{{clade| style=font-size:85%; line-height:85%

|label1=Ornithischia

|1={{clade

|1=Heterodontosauridae

|2={{clade

|1=Eocursor

|2={{clade

|1=Thyreophora

|label2=Neornithischia

|2={{clade

|1=Lesothosaurus

|2={{clade

|1=Agilisaurus

|2={{clade

|1={{clade

|1=Hexinlusaurus

|2=Yandusaurus }}

|2={{clade

|1={{clade

|1=Nanosaurus

|2={{clade

|label1=Jeholosauridae

|1={{clade

|1=Haya

|2={{clade

|1=Jeholosaurus

|2=Changchunsaurus }} }}

|label2=Thescelosauridae

|2={{clade

|1={{clade

|1=Orodromeus

|2=Koreanosaurus }}

|2={{clade

|1=Zephyrosaurus

|2={{clade

|1=Yueosaurus

|2=Thescelosaurus }} }} }} }} }}

|label2=Cerapoda

|2={{clade

|1=Marginocephalia

|2=Ornithopoda}} }} }} }} }} }} }} }} }}

File:Museum AL dinosaur.jpg mounted as if chasing Nanosaurus, Museum of Ancient Life]]

Nanosaurus was one of the smaller members of the diverse Morrison Formation dinosaur fauna, diminutive in comparison to the giant sauropods.{{cite journal|last=Foster|first=John R.|year=2003|title=Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A.|journal=New Mexico Museum of Natural History and Science Bulletin|volume=23|page=29}} The Morrison Formation is interpreted as a semiarid environment with distinct wet and dry seasons, and flat floodplains.{{cite book|last=Russell|first=Dale A.|title=An Odyssey in Time: Dinosaurs of North America|publisher=NorthWord Press|year=1989|isbn=1-55971-038-1|location=Minocqua, Wisconsin|pages=64–70|author-link=Dale Russell}} Vegetation varied from river-lining gallery forests of conifers, tree ferns, and ferns, to fern savannas with rare trees.{{cite book|last=Carpenter|first=Kenneth|title=Paleontology and Geology of the Upper Jurassic Morrison Formation|publisher=New Mexico Museum of Natural History and Science|year=2006|series=New Mexico Museum of Natural History and Science Bulletin, 36|location=Albuquerque, New Mexico|pages=131–138|chapter=Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus|author-link=Kenneth Carpenter |editor=Foster, John R. |editor2=Lucas, Spencer G.}} It has been a rich fossil hunting ground, holding fossils of green algae, fungi, mosses, horsetails, ferns, cycads, ginkgoes, and several families of conifers. Other fossils discovered include bivalves, snails, ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphs, several species of pterosaur, numerous dinosaur species, and early mammals such as docodonts, multituberculates, symmetrodonts, and triconodonts. Such dinosaurs as the theropods Ceratosaurus, Allosaurus, Ornitholestes, and Torvosaurus, the sauropods Apatosaurus, Brachiosaurus, Camarasaurus, and Diplodocus, and the ornithischians Camptosaurus, Dryosaurus, and Stegosaurus are known from the Morrison.{{cite book|last=Chure|first=Daniel J.|title=Paleontology and Geology of the Upper Jurassic Morrison Formation|author2=Litwin, Ron|author3=Hasiotis, Stephen T.|author4=Evanoff, Emmett|author5=Carpenter, Kenneth|publisher=New Mexico Museum of Natural History and Science|year=2006|editor=Foster, John R.|series=New Mexico Museum of Natural History and Science Bulletin, 36|location=Albuquerque, New Mexico|pages=233–248|chapter=The fauna and flora of the Morrison Formation: 2006|editor2=Lucas, Spencer G.}} Nanosaurus is present in stratigraphic zones 2-5.Foster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327-329.

Typically, Nanosaurus has been interpreted like other hypsilophodonts as a small, swift herbivore,{{cite book|last=Norman|first=David B.|title=The Dinosauria|author2=Sues, Hans-Dieter|author3=Witmer, Larry M.|author4=Coria, Rodolfo A.|publisher=University of California Press|year=2004|isbn=0-520-24209-2|editor=Weishampel, David B.|edition=2nd|location=Berkeley|pages=393–412|chapter=Basal Ornithopoda|editor2=Dodson, Peter|editor3=Osmólska, Halszka|author-link=David B. Norman}} although Bakker (1986) interpreted Nanosaurus as an omnivore.{{cite book|last=Bakker|first=Robert T.|title=The Dinosaur Heresies|publisher=William Morrow|year=1986|isbn=0-14-010055-5|location=New York|page=180|author-link=Robert T. Bakker}}

{{Reflist}}

{{Portal bar|Dinosaurs|United States}}

{{Ornithischia|O.}}

{{Taxonbar|from=Q1827215}}

Category:Neornithischia

Category:Dinosaur genera

Category:Tithonian dinosaurs

Category:Morrison Formation

Category:Taxa named by Othniel Charles Marsh

Category:Fossil taxa described in 1877

Category:Dinosaurs of the United States