Kronosaurus

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Later discoveries and genus validity

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[[File:Kronosaurus in Kronosaurus Korner.jpg|thumb|Assigned specimen in ''Kronosaurus'' Korner museum, Queensland]]	[[File:Kronosaurus in Kronosaurus Korner.jpg|thumb|Assigned specimen in ''Kronosaurus'' Korner museum, Queensland]]
Given that the holotype specimen of ''K. queenslandicus'' (QM F1609) is fragmentary and does not present any unique characteristics that would qualify the genus as distinct from other pliosaurs, the validity of this taxon has therefore been questioned. As early as 1962, [[Samuel Paul Welles]] considered ''Kronosaurus'' as a ''[[nomen vanum]]'' and recommended the designation of a [[neotype]] specimen from [[Harvard University]] which would preserve the genus validity.{{sfn|Welles|1962|p=48}}{{efn|No details were given by Welles as to which Harvard specimen should be designated as a neotype, as several were discovered by the university's expedition. It is, however, very likely that Welles would have been referring to MCZ 1285, given that it is the most complete specimen discovered by the Harvard expedition.{{sfn|Poropat|Bell|Hart|Salisbury|2023|p=148}}}} From 1979,<ref name="Mather1986"/> a good number of fossils from large pliosaurs are discovered in various localities in Australia, mainly in the geological strata of the Toolebuc Formation, the formation from which the first fossils attributed to the genus were discovered.{{sfn|McHenry|2009|p=27-28}} In other formations, only one additional attributed specimen was discovered in the Doncaster Member of the Wallumbilla Formation,{{sfn|McHenry|2009|p=28}} while three specimens, including one attributed to the [[type species]], were discovered in the [[Allaru Formation]].<ref name="Kear2005">{{cite journal|author=Benjamin P. Kear|title=Marine reptiles from the Lower Cretaceous (Aptian) deposits of White Cliffs, southeastern Australia: implications of a high latitude, cold water assemblage|year=2005|journal=[[Cretaceous Research]]|volume=26|issue=5|pages=769-782|doi=10.1016/j.cretres.2005.04.006|s2cid=128735962|bibcode=2005CrRes..26..769K|url=https://doc.rero.ch/record/16191/files/PAL_E3400.pdf}}</ref><ref name="Kear2006">{{cite journal|author=Benjamin P. Kear|title=Plesiosaur remains from Cretaceous high-latitude non-marine deposits in southeastern Australia|year=2006|journal=[[Journal of Vertebrate Paleontology]]|volume=26|issue=1|pages=196-199|doi=10.1671/0272-4634(2006)26[196RFCHN]2.0.CO;2|s2cid=130794388|bibcode=2006JVPal..26..196K|jstor=4524550}}</ref><ref name="Kear2016">{{cite journal|author=Benjamin P. Kear|title=Cretaceous marine amniotes of Australia: perspectives on a decade of new research|year=2016|journal=[[Memoirs of Museum Victoria]]|volume=74|pages=17-28|doi=10.24199/j.mmv.2016.74.03|s2cid=58903086|doi-access=free}}</ref><ref name="Holland2018">{{cite journal|author=Timothy Holland|title=The mandible of ''Kronosaurus queenslandicus'' Longman, 1924 (Pliosauridae, Brachaucheniinae), from the Lower Cretaceous of northwest Queensland, Australia|journal=[[Journal of Vertebrate Paleontology]]|year=2018|volume=38|issue=5|page=e1511569|doi=10.1080/02724634.2018.1511569|jstor=26765770|s2cid=91599158|url=https://www.researchgate.net/publication/328540944}}</ref> In his 2009 thesis, McHenry describes in detail many fossils attributed to ''Kronosaurus'', including most of the new specimens that he judges to possibly belong to this genus.{{sfn|McHenry|2009}}{{efn|Some specimens like QM F18762, which consists of an almost complete skull, are not analyzed due to the fact that no preparation was made to allow a clear description.{{sfn|McHenry|2009|p=27}}}} Of the numerous fossil specimens that he analyzed, McHenry proposed that two partial skeletons, cataloged as QM F10113 and QM F18827, which both come from the Toolebuc Formation, could be candidate [[neotype]]s, because they present features that seem to fit with the holotype.{{sfn|McHenry|2009|p=448-449}} However, no formal [[International Code of Zoological Nomenclature|ICZN]] petition to designate a neotype was submitted. In 2021, Leslie Francis Noè and Marcela Gómez-Pérez published a study that revised most of the specimens historically attributed to ''Kronosaurus''. Both authors limit ''Kronosaurus'' only to the holotype and consider it a ''[[nomen dubium]]''. The holotype specimen does not possess any features allowing a diagnostic, the other attributed fossils are provisionally moved to a new taxon that the two authors name ''[[Eiectus|Eiectus longmani]]'', in homage to Longman, the paleontologist who named the original genus. The Harvard skeleton (MCZ 1285) is also designated a holotype of this same genus.<ref name=NG21>{{cite journal|author1=Leslie F. Noè|author2=Marcela Gómez-Pérez|year=2021|title=Giant pliosaurids (Sauropterygia; Plesiosauria) from the Lower Cretaceous peri-Gondwanan seas of Colombia and Australia|journal=[[Cretaceous Research]]|volume=132|page=105122|doi=10.1016/j.cretres.2021.105122|bibcode=2022CrRes.13205122N}}</ref>	Given that the holotype specimen of ''K. queenslandicus'' (QM F1609) is fragmentary and does not present any unique characteristics that would qualify the genus as distinct from other pliosaurs, the validity of this taxon has therefore been questioned. As early as 1962, [[Samuel Paul Welles]] considered ''Kronosaurus'' as a ''[[nomen vanum]]'' and recommended the designation of a [[neotype]] specimen from [[Harvard University]] which would preserve the genus validity.{{sfn|Welles|1962|p=48}}<ref name="Carpenter1996">{{efn|No details were given by Welles as to which Harvard specimen should be designated as a neotype, as several were discovered by the university's expedition. It is, however, very likely that Welles would have been referring to MCZ 1285, given that it is the most complete specimen discovered by the Harvard expedition.{{sfn|Poropat|Bell|Hart|Salisbury|2023|p=148}}}} From 1979,<ref name="Mather1986"/> a good number of fossils from large pliosaurs are discovered in various localities in Australia, mainly in the geological strata of the Toolebuc Formation, the formation from which the first fossils attributed to the genus were discovered.{{sfn|McHenry|2009|p=27-28}} In other formations, only one additional attributed specimen was discovered in the Doncaster Member of the Wallumbilla Formation,{{sfn|McHenry|2009|p=28}} while three specimens, including one attributed to the [[type species]], were discovered in the [[Allaru Formation]].<ref name="Kear2005">{{cite journal|author=Benjamin P. Kear|title=Marine reptiles from the Lower Cretaceous (Aptian) deposits of White Cliffs, southeastern Australia: implications of a high latitude, cold water assemblage|year=2005|journal=[[Cretaceous Research]]|volume=26|issue=5|pages=769-782|doi=10.1016/j.cretres.2005.04.006|s2cid=128735962|bibcode=2005CrRes..26..769K|url=https://doc.rero.ch/record/16191/files/PAL_E3400.pdf}}</ref><ref name="Kear2006">{{cite journal|author=Benjamin P. Kear|title=Plesiosaur remains from Cretaceous high-latitude non-marine deposits in southeastern Australia|year=2006|journal=[[Journal of Vertebrate Paleontology]]|volume=26|issue=1|pages=196-199|doi=10.1671/0272-4634(2006)26[196RFCHN]2.0.CO;2|s2cid=130794388|bibcode=2006JVPal..26..196K|jstor=4524550}}</ref><ref name="Kear2016">{{cite journal|author=Benjamin P. Kear|title=Cretaceous marine amniotes of Australia: perspectives on a decade of new research|year=2016|journal=[[Memoirs of Museum Victoria]]|volume=74|pages=17-28|doi=10.24199/j.mmv.2016.74.03|s2cid=58903086|doi-access=free}}</ref><ref name="Holland2018">{{cite journal|author=Timothy Holland|title=The mandible of ''Kronosaurus queenslandicus'' Longman, 1924 (Pliosauridae, Brachaucheniinae), from the Lower Cretaceous of northwest Queensland, Australia|journal=[[Journal of Vertebrate Paleontology]]|year=2018|volume=38|issue=5|page=e1511569|doi=10.1080/02724634.2018.1511569|jstor=26765770|s2cid=91599158|url=https://www.researchgate.net/publication/328540944}}</ref> In his 2009 thesis, McHenry describes in detail many fossils attributed to ''Kronosaurus'', including most of the new specimens that he judges to possibly belong to this genus.{{sfn|McHenry|2009}}{{efn|Some specimens like QM F18762, which consists of an almost complete skull, are not analyzed due to the fact that no preparation was made to allow a clear description.{{sfn|McHenry|2009|p=27}}}} Of the numerous fossil specimens that he analyzed, McHenry proposed that two partial skeletons, cataloged as QM F10113 and QM F18827, which both come from the Toolebuc Formation, could be candidate [[neotype]]s, because they present features that seem to fit with the holotype.{{sfn|McHenry|2009|p=448-449}} However, no formal [[International Code of Zoological Nomenclature|ICZN]] petition to designate a neotype was submitted. In 2021, Leslie Francis Noè and Marcela Gómez-Pérez published a study that revised most of the specimens historically attributed to ''Kronosaurus''. Both authors limit ''Kronosaurus'' only to the holotype and consider it a ''[[nomen dubium]]''. The holotype specimen does not possess any features allowing a diagnostic, the other attributed fossils are provisionally moved to a new taxon that the two authors name ''[[Eiectus|Eiectus longmani]]'', in homage to Longman, the paleontologist who named the original genus. The Harvard skeleton (MCZ 1285) is also designated a holotype of this same genus.<ref name=NG21>{{cite journal|author1=Leslie F. Noè|author2=Marcela Gómez-Pérez|year=2021|title=Giant pliosaurids (Sauropterygia; Plesiosauria) from the Lower Cretaceous peri-Gondwanan seas of Colombia and Australia|journal=[[Cretaceous Research]]|volume=132|page=105122|doi=10.1016/j.cretres.2021.105122|bibcode=2022CrRes.13205122N}}</ref>
In 2023, Valentin Fischer and colleagues criticized the reassignments even under these circumstances, predicting that they stand contrary to ICZN Articles 75.5 and 75.6 (which codifies preference for neotype designation for previously iconic taxa with non-diagnostic holotypes) and that the aforementioned multiple-species possibility cannot justify a tentative reassignment of all specimens to ''Eiectus''. The authors instead opted to refer to all relevant fossils as ''Kronosaurus-Eiectus''.<ref name=Fischeretal2023>{{cite journal|author1=Valentin Fischer|author2=Roger B. J. Benson|author3=Nikolay G. Zverkov|author4=Maxim S. Arkhangelsky|author5=Ilya M. Stenshin|author6=Gleb N. Uspensky|author7=Natalya E. Prilepskaya|title=Anatomy and relationships of the bizarre Early Cretaceous pliosaurid ''Luskhan itilensis''|journal=[[Zoological Journal of the Linnean Society]]|volume=198|issue=1|pages=220–256|year=2023|doi=10.1093/zoolinnean/zlac108|s2cid=257573659}}</ref> The same year, Stephen F. Poropat and colleagues maintained ''K. queenslandicus'' as a nominally valid taxon that includes all fossils from the Toolebuc and Allaru Formation pending an official ICZN petition, recommending specimen QM F18827 as neotype.{{sfn|Poropat|Bell|Hart|Salisbury|2023|p=148-151}} The authors also criticize the repurposing of Toolebuc specimens,{{sfn|Poropat|Bell|Hart|Salisbury|2023|p=150}} on the grounds that Noè and Gómez-Pérez presumably ignored the conclusion of McHenry's 2009 thesis that only one species of large pliosaur exists in the formation and that, therefore, all of its specimens can be reliably considered [[Biological specificity#Conspecific|conspecific]] to the holotype.{{sfn|McHenry|2009|p=257}} As for ''Eiectus'', Poropat and colleagues limit it only to MCZ 1285 and the referred specimen MCZ 1284, but their assignment without formal redescription also remains subject to debate, given that the holotype is so massively restored with [[plaster]] that all features apparent diagnostics are probably unreliable without comprehensive CT scans.{{sfn|Poropat|Bell|Hart|Salisbury|2023|p=150}}	In 2023, Valentin Fischer and colleagues criticized the reassignments even under these circumstances, predicting that they stand contrary to ICZN Articles 75.5 and 75.6 (which codifies preference for neotype designation for previously iconic taxa with non-diagnostic holotypes) and that the aforementioned multiple-species possibility cannot justify a tentative reassignment of all specimens to ''Eiectus''. The authors instead opted to refer to all relevant fossils as ''Kronosaurus-Eiectus''.<ref name=Fischeretal2023>{{cite journal|author1=Valentin Fischer|author2=Roger B. J. Benson|author3=Nikolay G. Zverkov|author4=Maxim S. Arkhangelsky|author5=Ilya M. Stenshin|author6=Gleb N. Uspensky|author7=Natalya E. Prilepskaya|title=Anatomy and relationships of the bizarre Early Cretaceous pliosaurid ''Luskhan itilensis''|journal=[[Zoological Journal of the Linnean Society]]|volume=198|issue=1|pages=220–256|year=2023|doi=10.1093/zoolinnean/zlac108|s2cid=257573659}}</ref> The same year, Stephen F. Poropat and colleagues maintained ''K. queenslandicus'' as a nominally valid taxon that includes all fossils from the Toolebuc and Allaru Formation pending an official ICZN petition, recommending specimen QM F18827 as neotype.{{sfn|Poropat|Bell|Hart|Salisbury|2023|p=148-151}} The authors also criticize the repurposing of Toolebuc specimens,{{sfn|Poropat|Bell|Hart|Salisbury|2023|p=150}} on the grounds that Noè and Gómez-Pérez presumably ignored the conclusion of McHenry's 2009 thesis that only one species of large pliosaur exists in the formation and that, therefore, all of its specimens can be reliably considered [[Biological specificity#Conspecific|conspecific]] to the holotype.{{sfn|McHenry|2009|p=257}} As for ''Eiectus'', Poropat and colleagues limit it only to MCZ 1285 and the referred specimen MCZ 1284, but their assignment without formal redescription also remains subject to debate, given that the holotype is so massively restored with [[plaster]] that all features apparent diagnostics are probably unreliable without comprehensive CT scans.{{sfn|Poropat|Bell|Hart|Salisbury|2023|p=150}}

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