Plutoniosaurus

{{Automatic taxobox

| fossil_range = Early Cretaceous,
~{{fossilrange|135|130}}

| taxon = Plutoniosaurus

| authority = Efimov, 1997

| type_species = {{extinct}}Plutoniosaurus bedengensis

| type_species_authority = Efimov, 1997

| synonyms = * Platypterygius bedengensis (Efimov, 1997)

}}

Plutoniosaurus is an extinct genus of ophthalmosaurid ichthyosaur of uncertain validity from the Early Cretaceous (late Hauterivian) of the vicinity of Ulyanovsk, European Russia.

Taxonomy

Plutoniosaurus was named by Vladimir Efimov in 1997 based on the holotype specimen UPM 2/740, a partial skeleton containing the skull, the shoulder girdle, forelimbs and vertebrae. The generic name is derived from the Ulyanovsk Regional Young Paleontologists Club that was nicknamed Plutonia. The specific name refers to the village of Novaya Beden’ga, the site of discovery on the right bank of the Volga.

In 1999, Maxim Arkhangel'skii synonymized the genus with Platypterygius,{{cite book|last1=Storrs|first1=G. W.|first2=M. S.|last2=Arkhangel'skii|first3=V. M.|last3=Efimov|year=2000|chapter=Mesozoic marine reptiles of Russia and other former Soviet republics|chapter-url=https://www.researchgate.net/publication/259842825|title=The Age of Dinosaurs in Russia and Mongolia|pages=187–210|editor-last1=Benton|editor-first1=M. J.|editor-last2=Shishkin|editor-first2=M. A.|editor-last3=Unwin|editor-first3=D. M.|editor-last4=Kurochkin|editor-first4=E. N.|publisher=Cambridge University Press|location=Cambridge}} as did Michael Maisch and Andreas Matzke in 2000.{{cite journal|last1=Maisch|first1=M. W.|last2=Matzke|first2=A. T.|year=2000|title=The Ichthyosauria|journal=Stuttgarter Beiträge zur Naturkunde, Serie B|volume=298|pages=1–159|url=https://www.biodiversitylibrary.org/item/278993#page/350/mode/2up|archive-date=2022-06-16|access-date=2023-05-06|archive-url=https://web.archive.org/web/20220616150140/https://www.biodiversitylibrary.org/item/278993#page/350/mode/2up|url-status=live}}{{Rp|82}} While agreeing with the synonymy, Christopher McGowan and Ryosuke Motani considered P. bedengensis to be a nomen dubium within the genus in 2003, too poorly known to identify as a distinct species.{{cite book|last1=McGowan|first1=C.|last2=Motani|first2=R.|year=2003|title=Handbook of Paleoherpetology Part 8: Ichthyopterygia|editor-last1=Sues|editor-first1=H.D.|publisher=Verlag Dr. Friedrich Pfeil|location=Munich|isbn=3899370074|url=http://beeld.teylersmuseum.nl/Digital_Library/Emags/Saur_028/page_76.html|archive-date=2022-12-13|access-date=2023-05-06|archive-url=https://web.archive.org/web/20221213165533/http://beeld.teylersmuseum.nl/Digital_Library/Emags/Saur_028/page_76.html|url-status=live}}{{rp|136}} In 2016, Valentin Fischer and colleagues considered the original description was too vague to confidently distinguish the genus and noted that the illustrations did not always match the written description. They thus regarded Plutoniosaurus bedengensis as a species inquirenda, while noting the possibility that it is the same species as the nearly coeval Simbirskiasaurus from the same region.{{cite journal|first1=V.|last1=Fischer|first2=N.|last2=Bardet|first3=R. B. J.|last3=Benson|first4=M. S.|last4=Arkhangelsky|first5=M.|last5=Friedman|year=2016|title=Extinction of fish-shaped marine reptiles associated with reduced evolutionary rates and global environmental volatility|journal=Nature Communications|volume=7|pages=10825|doi=10.1038/ncomms10825|pmid=26953824 |pmc=4786747|bibcode=2016NatCo...710825F }}

Phylogeny

Zverkov and Efimov (2019) recovered Plutoniosaurus in a polytomy with the type species of Platypterygius and Leninia.{{cite journal|first1=N. G.|last1=Zverkov|first2=V. M.|last2=Efimov|year=2019|title=Revision of Undorosaurus, a mysterious Late Jurassic ichthyosaur of the Boreal Realm|journal=Journal of Systematic Palaeontology|volume=17|issue=14|pages=963–993|doi=10.1080/14772019.2018.1515793|bibcode=2019JSPal..17.1183Z|url=https://undor-muz.ru/wp-content/uploads/2019/08/Zverkov_Efimov_2019_Undorosaurus_printed-1.pdf|archive-date=2023-05-06|access-date=2023-05-06|archive-url=https://web.archive.org/web/20230506195536/https://undor-muz.ru/wp-content/uploads/2019/08/Zverkov_Efimov_2019_Undorosaurus_printed-1.pdf|url-status=live}} The following cladogram shows a possible phylogenetic position of Plutoniosaurus in Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).{{cite journal |first1=N. G.|last1=Zverkov |first2=M. L.|last2=Jacobs |orig-year=2020 |title=Revision of Nannopterygius (Ichthyosauria: Ophthalmosauridae): reappraisal of the 'inaccessible' holotype resolves a taxonomic tangle and reveals an obscure ophthalmosaurid lineage with a wide distribution |journal=Zoological Journal of the Linnean Society |volume=191 |issue=1 |year=2021 |pages=228–275 |doi=10.1093/zoolinnean/zlaa028}}

{{clade

|label1=Ophthalmosauria

|1={{clade

|label1=Ophthalmosaurinae

|1={{clade

|1=Acamptonectes densus

|2={{clade

|1=Mollesaurus periallus

|2={{clade

|1=Ophthalmosaurus natans

|2=Ophthalmosaurus icenicus

}}