{{Short description|Genus of ornithischian dinosaurs}} {{speciesbox | fossil_range = Late Jurassic, {{fossil range|155|148}} | image = Skeletal and life reconstruction of Enigmacursor.jpg | image_caption = Skeletal and life reconstructions | genus = Enigmacursor | parent_authority = Maidment & Barrett, 2025 | species = mollyborthwickae | authority = Maidment & Barrett, 2025 | display_parents = 2 }} '''''Enigmacursor''''' (meaning "puzzle runner") is an extinct genus of neornithischian dinosaur from the Late Jurassic Morrison Formation of Colorado, United States. The type species is '''''Enigmacursor mollyborthwickae'''''.
== Discovery and naming == The holotype specimen, NHMUK PV R 39000, was discovered between 2021 and 2022 in Moffat County, Colorado by private company Dinosaurs of America, LLC. and acquired by the Natural History Museum, London (NHM) in 2024. It represents a three-dimensionally preserved partial postcranial skeleton with associated teeth.<ref name=Enigmacursor /> [[File:Enigmacursor mollyborthwickae.png|left|thumb|Speculative life restoration]] It was described as a new genus and species by Susannah Maidment & Paul Barrett in 2025. The generic name, ''Enigmacursor'', comes from the word ''enigma'', referring to the taxonomic confusion of Morrison Formation neornithischians such as ''Nanosaurus'',<ref name="Barrett&Maidment25">{{Cite journal |last1=Barrett |first1=P. M. |author1-link=Paul Barrett (palaeobiologist) |last2=Maidment |first2=S. C. R. |author2-link=Susannah Maidment |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}}</ref> and the Latin word ''cursor'', meaning "runner", after its cursorial hindlimbs. The specific name, ''mollyborthwickae'', honors Molly Borthwick, who donated the funds for the acquisition of the specimen by the NHM.<ref name="Enigmacursor">{{Cite journal |last1=Maidment |first1=S. C. R. |author1-link=Susannah Maidment |last2=Barrett |first2=P. M. |author2-link=Paul Barrett (palaeobiologist) |year=2025 |title=''Enigmacursor mollyborthwickae'', a neornithischian dinosaur from the Upper Jurassic Morrison Formation of the western USA |journal=Royal Society Open Science |volume=12 |issue=6 |at=242195 |doi=10.1098/rsos.242195 |pmc=12188093 |doi-access=free}}</ref>
The fossil that led to the scientific discovery was sold by natural history gallery David Aaron to the Natural History Museum, London, where it is now on display.<ref>{{Cite news |date=2025-06-24 |title=Natural History Museum to display rare dog-sized dinosaur |url=https://www.bbc.com/news/articles/cglzy4zndp0o |access-date=2026-02-27 |website=www.bbc.com |language=en-GB}}</ref><ref>{{Cite press release |title=Never-before-seen new dinosaur species to be displayed at the Natural History Museum, London |date=25 June 2025 |publisher=Natural History Museum |url=https://www.nhm.ac.uk/press-office/press-releases/never-before-seen-new-dinosaur-species-to-be-displayed-at-the-na.html |language=en |access-date=2026-02-27 |website=www.nhm.ac.uk}}</ref>
== Classification == Maidment & Barrett (2025) entered ''Enigmacursor'' into a phylogenetic analysis and placed as the sister taxon to the Chinese ''Yandusaurus''. A cladogram adapted from their analysis is shown below:<ref name=Enigmacursor />
{{clade |label1=Neornithischia |1={{clade sequential |1=''Agilisaurus'' |2=''Hexinlusaurus'' |3={{clade |1=''Yandusaurus'' |2='''''Enigmacursor''''' }} |4=Cerapoda }} }}
== Paleoecology == [[File:Museum AL dinosaur.jpg|thumb|''Torvosaurus'' skeleton mounted as if chasing small neornithischians]] ''Enigmacursor'' was one of the smaller members of the diverse Morrison Formation dinosaur fauna, diminutive in comparison to the giant sauropods.<ref name="JRF03a2">{{cite journal |last=Foster |first=John R. |author-link=John R. Foster |year=2003 |title=Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A. |url={{google books|plainurl=yes|id=tWQfCgAAQBAJ}} |journal=New Mexico Museum of Natural History and Science Bulletin |volume=23 |page=29}}</ref> The Morrison Formation is interpreted as a semiarid environment with distinct wet and dry seasons, and flat floodplains.<ref name="DAR89">{{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}}</ref> Vegetation varied from river-lining gallery forests of conifers, tree ferns, and ferns, to fern savannas with rare trees.<ref name="KC06">{{cite book |last=Carpenter |first=Kenneth |author-link=Kenneth Carpenter |title=Paleontology and Geology of the Upper Jurassic Morrison Formation |publisher=New Mexico Museum of Natural History and Science |year=2006 |editor1-last=Foster |editor-first=John R. |editor1-link=John R. Foster |series=New Mexico Museum of Natural History and Science Bulletin |volume=36 |location=Albuquerque, New Mexico |pages=131–138 |chapter=Biggest of the big: a critical re-evaluation of the mega-sauropod ''Amphicoelias fragillimus'' |editor2-last=Lucas |editor-first2=Spencer G. |editor2-link=Spencer G. Lucas |chapter-url={{google books|plainurl=yes|id=qKjECQAAQBAJ|page=131}}}}</ref> 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.<ref name="DJCetal06">{{cite book |last=Chure |first=Daniel J. |title=Paleontology and Geology of the Upper Jurassic Morrison Formation |author2=Litwin |first2=Ron |author3=Hasiotis |first3=Stephen T. |author4=Evanoff |first4=Emmett |author5=Carpenter |first5=Kenneth |author-link5=Kenneth Carpenter |publisher=New Mexico Museum of Natural History and Science |year=2006 |editor1-last=Foster |editor1-first=John R. |editor1-link=John R. Foster |series=New Mexico Museum of Natural History and Science Bulletin |volume=36 |location=Albuquerque, New Mexico |pages=233–248 |chapter=The fauna and flora of the Morrison Formation: 2006 |editor2-last=Lucas |editor-first2=Spencer G. |editor2-link=Spencer G. Lucas |chapter-url={{google books|plainurl=yes|id=qKjECQAAQBAJ|page=233}}}}</ref>
== References == {{Reflist}}
{{Ornithischia|O.}} {{Taxonbar|from=Q135092049}}
Category:Neornithischia Category:Dinosaur genera Category:Tithonian dinosaurs Category:Morrison Formation Category:Fossil taxa described in 2025 Category:Taxa named by Susannah Maidment Category:Dinosaurs of the United States