View source for Earth:Triassic land vertebrate faunachrons

{{Short description|Subdivisions of geological time}}
'''Land vertebrate faunachrons''' (LVFs) are [[Physics:Biochronology|biochronological]] units used to correlate and date terrestrial sediments and fossils based on their [[Biology:Tetrapod|tetrapod]] faunas.<ref name=":0">{{Cite journal|last=Lucas|first=Spencer G|date=1998-11-01|title=Global Triassic tetrapod biostratigraphy and biochronology|url=http://www.sciencedirect.com/science/article/pii/S0031018298001175|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|language=en|volume=143|issue=4|pages=347–384|doi=10.1016/S0031-0182(98)00117-5|bibcode=1998PPP...143..347L |issn=0031-0182}}</ref> First formulated on a global scale by Spencer G. Lucas in 1998, LVFs are primarily used within the Triassic Period (252 - 201 [[Megaannum|Ma]]),<ref name=":0" /> though Lucas later designated LVFs for other periods as well.<ref name=":5">{{Cite journal|last=Lucas|first=Spencer G.|date=2005|title=Permian Tetrapod Faunachrons|url=https://books.google.com/books?id=7r75CQAAQBAJ&pg=PA197|journal=New Mexico Museum of Natural History and Science Bulletin|volume=30|pages=197–201|via=}}</ref> Eight worldwide LVFs are defined for the Triassic. The first two earliest Triassic LVFs, the '''Lootsbergian''' and '''Nonesian''', are based on {{wipe|South Africa}}n [[Biology:Synapsid|synapsid]]s and faunal assemblage zones estimated to correspond to the [[Earth:Early Triassic|Early Triassic]]. These are followed by the '''Perovkan''' and '''Berdyankian''', based on [[Biology:Temnospondyli|temnospondyl]] amphibians and {{wipe|Russia}}n assemblages estimated to be from the [[Earth:Middle Triassic|Middle Triassic]]. The youngest four Triassic LVFs, the '''Otischalkian''', '''Adamanian''', '''Revueltian''', and '''Apachean''', are based on [[Biology:Aetosaur|aetosaur]] and [[Biology:Phytosaur|phytosaur]] reptiles common in the [[Earth:Late Triassic|Late Triassic]] of the southwestern United States.<ref name=":0" /><ref name=":4" /><ref name=":7" />

The LVF system, though widely used, is also a controversial application of [[Earth:Biostratigraphy|biostratigraphy]], as many Triassic tetrapods are rife with complications which endanger their utility as index fossils. Limited occurrences, inaccurate age estimates, overlapping LVF faunas, or [[Taxonomy|taxonomic]] disagreement may jeopardize global correlations between Triassic tetrapods. This could render some LVFs as misleading assessments of Triassic faunal change through time.<ref name=":9" /><ref name=":10" /><ref name=":1">{{Cite journal |last1=Rayfield |first1=Emily J. |last2=Barrett |first2=Paul M. |last3=Milner |first3=Andrew R. |date=2009-03-12 |title=Utility and validity of Middle and Late Triassic 'land vertebrate faunachrons' |url=https://www.researchgate.net/publication/232684085 |journal=Journal of Vertebrate Paleontology |volume=29 |issue=1 |pages=80–87 |doi=10.1671/039.029.0132 |s2cid=86502146 |issn=0272-4634 |via=}}</ref><ref name=":2">{{Cite journal |last1=Irmis |first1=Randall B. |last2=Martz |first2=Jeffrey W. |last3=Parker |first3=William G. |last4=Nesbitt |first4=Sterling J. |date=March 2010 |title=Re-evaluating the correlation between Late Triassic terrestrial vertebrate biostratigraphy and the GSSP-defined marine stages |url=https://albertiana-sts.org/wp-content/uploads/2017/05/Albertiana_38.pdf#page=40 |journal=Albertiana |volume=38 |pages=40–53 |via=}}</ref> Regardless, Late Triassic phytosaurs are considered to have strong biostratigraphic utility even among detractors of Lucas's system.<ref name=":8" />

== Lucas's LVFs ==
Tetrapod biostratigraphy has been used for the Triassic of {{wipe|South Africa}} since 1906 and {{wipe|Argentina}} since 1966,<ref name=":10" /> but without much connection to global faunas.<ref name=":0" /> Starting in 1993, New Mexico Museum of Natural History and Science paleontologist Spencer G. Lucas and his colleagues began to define tetrapod biostratigraphy intervals in the Triassic of {{wipe|China}}<ref>{{Cite journal |last=Lucas |first=Spencer G. |date=1993 |title=Vertebrate biochronology of the Triassic of China |url=https://www.researchgate.net/publication/286048839 |journal=New Mexico Museum of Natural History & Science Bulletin |volume=3 |pages=301–306}}</ref> and eastern<ref>{{Cite journal |last1=Huber |first1=Phillip |last2=Lucas |first2=Spencer G. |last3=Hunt |first3=Adrian P. |date=1993 |title=Vertebrate biochronology of the Newark Supergroup Triassic, eastern North America |url=https://www.researchgate.net/publication/283271729 |journal=New Mexico Museum of Natural History & Science Bulletin |volume=3 |pages=179–186}}</ref> and western<ref name=":6" /> [[Earth:North America|North America]]. These named biostratigraphic intervals were inspired by the Land Mammal Age (LMA) system already in use for [[Earth:Cenozoic|Cenozoic]] faunal assemblages.

Triassic tetrapod biozones, under the term "land vertebrate faunachrons" (LVFs) were formalized on a global level by Lucas in 1998. They were diagnosed by a primary index fossil (a particular genus of widespread time-constrained tetrapod) and characterized by a faunal [[Biology:Type|type]] assemblage (distinguishing collection of taxa) from a fossiliferous [[Earth:Geological formation|geological formation]]. Together, the defining index fossil and assemblage could be used to correlate fossil assemblages worldwide.<ref name=":0" /> Updates to this system have been published continuously for Triassic LVFs, which remain a heavily-discussed topic in the study of Triassic chronology.<ref name="Letal07">{{cite book |last=Lucas |first=S.G. |title=The Global Triassic |author2=Hunt, A.P. |author3=Heckert, A.B. |author4=Spielmann, J.A. |year=2007 |editor=Lucas, S.G. |series=New Mexico Museum of Natural History and Science Bulletin |volume=41 |pages=229–240 |chapter=Global Triassic tetrapod biostratigraphy and biochronology: 2007 status |access-date=2010-07-17 |editor2=Spielmann, J.A. |chapter-url=http://paleo.cortland.edu/globaltriassic/Bull41/35-Lucas%20et%20al%20(LVF).pdf |archive-url=https://web.archive.org/web/20110927060257/http://paleo.cortland.edu/globaltriassic/Bull41/35-Lucas%20et%20al%20(LVF).pdf |archive-date=2011-09-27 |url-status=dead}}</ref><ref name=":4">{{Cite journal |last=Lucas |first=Spencer G. |date=2010-01-01 |title=The Triassic timescale based on nonmarine tetrapod biostratigraphy and biochronology |url=https://sp.lyellcollection.org/content/334/1/447 |journal=Geological Society, London, Special Publications |language=en |volume=334 |issue=1 |pages=447–500 |doi=10.1144/SP334.15 |bibcode=2010GSLSP.334..447L |s2cid=128911449 |issn=0305-8719}}</ref><ref>{{Cite journal |last1=Lucas |first1=Spencer G. |last2=Tanner |first2=Lawrence H. |date=2014 |editor-last=Rocha |editor-first=Rogério |editor2-last=Pais |editor2-first=João |editor3-last=Kullberg |editor3-first=José Carlos |editor4-last=Finney |editor4-first=Stanley |title=Triassic Timescale Based on Tetrapod Biostratigraphy and Biochronology |url=https://link.springer.com/chapter/10.1007/978-3-319-04364-7_192 |journal=Strati 2013 |series=Springer Geology |language=en |location=Cham |publisher=Springer International Publishing |pages=1013–1016 |doi=10.1007/978-3-319-04364-7_192 |isbn=978-3-319-04364-7}}</ref><ref name=":7">{{Citation |last=Lucas |first=Spencer G. |title=Late Triassic Terrestrial Tetrapods: Biostratigraphy, Biochronology and Biotic Events |date=2018 |url=https://doi.org/10.1007/978-3-319-68009-5_10 |work=The Late Triassic World: Earth in a Time of Transition |pages=351–405 |editor-last=Tanner |editor-first=Lawrence H. |series=Topics in Geobiology |volume=46 |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-319-68009-5_10 |isbn=978-3-319-68009-5 |access-date=2020-05-31}}</ref> Lucas has also defined LVFs for the [[Earth:Permian|Permian]],<ref name=":5" /><ref>{{Cite journal |last=Lucas |first=Spencer G. |date=2006 |title=Global Permian tetrapod biostratigraphy and biochronology |url=https://www.lyellcollection.org/doi/10.1144/GSL.SP.2006.265.01.04 |journal=Geological Society, London, Special Publications |language=en |volume=265 |issue=1 |pages=65–93 |doi=10.1144/GSL.SP.2006.265.01.04 |bibcode=2006GSLSP.265...65L |s2cid=129613959 |issn=0305-8719}}</ref><ref>{{Cite journal |last=Lucas |first=Spencer G. |date=2018 |title=Permian tetrapod biochronology, correlation and evolutionary events |url=https://www.lyellcollection.org/doi/10.1144/SP450.12 |journal=Geological Society, London, Special Publications |language=en |volume=450 |issue=1 |pages=405–444 |doi=10.1144/SP450.12 |bibcode=2018GSLSP.450..405L |s2cid=134768451 |issn=0305-8719}}</ref> [[Earth:Jurassic|Jurassic]],<ref>{{Cite journal |last=Lucas |first=S. |date=2008 |title=Global Jurassic tetrapod biochronology |url=https://yadda.icm.edu.pl/baztech/element/bwmeta1.element.baztech-article-BSL9-0067-0009 |journal=Volumina Jurassica |volume=6 |issue=1 |pages=99–108}}</ref> and [[Earth:Carboniferous|Carboniferous]],<ref>{{Cite journal |last=Lucas |first=Spencer G. |date=2022 |title=Carboniferous tetrapod biostratigraphy, biochronology and evolutionary events |url=https://www.lyellcollection.org/doi/10.1144/SP512-2021-5 |journal=Geological Society, London, Special Publications |language=en |volume=512 |issue=1 |pages=965–1001 |doi=10.1144/SP512-2021-5 |bibcode=2022GSLSP.512..965L |s2cid=235528136 |issn=0305-8719}}</ref> though these are not as widely used as his Triassic LVFs.

Later authors characterized Lucas's LVFs as "[[Earth:Biozone|interval]] eubiochrons". This means that they correspond to a segment of time (and strata) between two paleobiological events: the [[Earth:First appearance datum|first appearance datum]] (FAD) of one index taxon and the FAD of another.<ref name=":8">{{Citation |last1=Martz |first1=J. W. |title=Revised Formulation of the Late Triassic Land Vertebrate "Faunachrons" of Western North America: Recommendations for Codifying Nascent Systems of Vertebrate Biochronology |date=2017-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780128032435000029 |work=Terrestrial Depositional Systems |pages=39–125 |editor-last=Zeigler |editor-first=Kate E. |publisher=Elsevier |language=en |isbn=978-0-12-803243-5 |access-date=2022-08-28 |last2=Parker |first2=W. G. |editor2-last=Parker |editor2-first=William G.}}</ref> A first appearance datum is a point in the geological record with the earliest known fossil of a given animal, which can estimate when that animal [[Biology:Speciation|speciates]] or evolves into existence. As an example, the Lootsbergian LVF is defined as the period of time between the FAD (estimated speciation) of ''[[Biology:Lystrosaurus|Lystrosaurus]]'' and the FAD (estimated speciation) of ''[[Biology:Cynognathus|Cynognathus]]''. Some taxa which are index fossils for one stage may persist into a later stage.<ref name=":0" />

=== List of Triassic LVFs ===
LVFs of the Triassic Period from youngest to oldest:
{| class="wikitable"
|- style="text-align:center; background:gainsboro;"
| '''LVF name'''
| '''Namesake'''
| '''Primary index fossil'''
| '''Other index fossils'''
| '''Proposed age estimate<br><small>(but see below)</small>'''
| '''Type assemblage'''
| '''Other correlated assemblages'''
|-
|'''<u>Apachean</u>'''
|Apache Canyon, New Mexico, USA<ref name=":6" />
|[[File:Redondasaurus bermani at CMNH 04.jpg|140px|center]]{{br}}{{center|''[[Biology:Redondasaurus|Redondasaurus]]''}}
|''[[Biology:Redondasuchus|Redondasuchus]]'', ''[[Biology:Riojasaurus|Riojasaurus]]''
|late Norian to Rhaetian
|[[Earth:Redonda Formation|Redonda Formation]], New Mexico, USA
|Rock Point Formation (Chinle Group, New Mexico, USA), [[Earth:Wingate Sandstone|Wingate Sandstone]] (Utah, USA), upper "Cliftonian" strata of the [[Earth:Newark Supergroup|Newark Supergroup]] (eastern USA), [[Earth:Trossingen Formation|Trossingen Formation]] (Germany / Switzerland),<ref name=":4" /> upper Arnstadt Formation (Germany),<ref name=":4" /> [[Earth:Los Colorados Formation|Los Colorados Formation]]? (Argentina), [[Earth:Quebrada del Barro Formation|Quebrada del Barro Formation]]? (Argentina),<ref name=":4" /> Lower Elliot Formation? (South Africa), upper [[Earth:Mercia Mudstone Group|Mercia Mudstone Group]]? (UK), lower [[Earth:Penarth Group|Penarth Group]]? (UK), Rhaetian fissure fills? (UK)
|-
|'''<u>Revueltian</u>'''
|Revuelto Creek, New Mexico, USA<ref name=":6" />
|[[File:Typothorax coccinarum cropped.jpg|140px|center]]{{br}}{{center|''[[Biology:Typothorax|Typothorax coccinarum]]''<ref name=":4" />}}
|''[[Biology:Revueltosaurus|Revueltosaurus]],''<ref name=":4" /> ''[[Biology:Aetosaurus|Aetosaurus]], [[Biology:Rioarribasuchus|Rioarribasuchus]],''<ref name=":4" /> ''Pseudopalatus-''grade phytosaurs'', Eudimorphodon''<ref name=":4" />
|early to middle Norian
(but see below)
|Bull Canyon Formation, New Mexico, USA
|Painted Desert Member / Petrified Forest Formation (Chinle Group, Arizona / New Mexico, USA), Owl Rock Member (Chinle Formation, Arizona, USA),<ref name=":4" /> "Neshanician" and lower "Cliftonian" strata of the Newark Supergroup (eastern USA), [[Earth:Fleming Fjord Formation|Fleming Fjord Formation]] (Greenland), Stubensandstein (Germany), Lisowice (Poland),<ref>{{Cite journal |last=Lucas |first=Spencer |date=2015 |title=Age and correlation of Late Triassic tetrapods from southern Poland |url=https://geojournals.pgi.gov.pl/asgp/article/view/24878 |journal=Annales Societatis Geologorum Poloniae |doi=10.14241/asgp.2015.024|doi-access=free }}</ref><ref>{{Cite journal |last1=Racki |first1=Grzegorz |last2=Lucas |first2=Spencer G. |date=2020-04-20 |title=Timing of dicynodont extinction in light of an unusual Late Triassic Polish fauna and Cuvier's approach to extinction |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2018.1499734 |journal=Historical Biology |language=en |volume=32 |issue=4 |pages=452–461 |doi=10.1080/08912963.2018.1499734 |s2cid=91926999 |issn=0891-2963}}</ref> [[Earth:Calcare di Zorzino|Calcare di Zorzino]] (Italy), Dolomia di Forni (Italy), lower Dharmaran Formation (India), [[Earth:Los Colorados Formation|Los Colorados Formation]]? (Argentina),<ref name=":7" /> [[Earth:Quebrada del Barro Formation|Quebrada del Barro Formation]]? (Argentina),<ref name=":7" /> Lower Elliot Formation? (South Africa)<ref name=":7" />
|-
|'''<u>Adamanian</u>'''
|Adamana, Arizona, USA<ref name=":6" />
|[[File:Smilosuchus adamanensis flipped.jpg|140px|center]]{{br}}{{center|''Rutiodon''-grade phytosaurs (including ''Leptosuchus'' and ''[[Biology:Smilosuchus|Smilosuchus]]'')}}
|''[[Biology:Stagonolepis|Stagonolepis]],'' ''[[Biology:Spinosuchus|Spinosuchus]]'',<ref name=":4" /> ''Colognathus'',<ref name=":4" /> ''[[Biology:Tecovasaurus|Tecovasaurus]]'',<ref name=":4" /> ''[[Biology:Crosbysaurus|Crosbysaurus]]''<ref name=":4" />
|late Carnian
(but see below)
|[[Earth:Blue Mesa Member|Blue Mesa Member]], [[Earth:Chinle Formation|Chinle Formation]], Arizona, USA
|Bluewater Creek Formation (Chinle Group, New Mexico, USA), [[Earth:Santa Rosa Formation, New Mexico|Santa Rosa Formation]] (New Mexico, USA), Garita Creek Formation (New Mexico, USA), Tecovas Formation (Texas, USA), "Conewagian" strata of the [[Earth:Newark Supergroup|Newark Supergroup]] (eastern USA), [[Earth:Lossiemouth Sandstone|Lossiemouth Sandstone]] (Scotland, UK), Krasiejów (Poland),<ref name=":4" /> Lehrberg Schichten / [[Earth:Blasensandstein|Blasensandstein]] / Kieselsandstein (Germany),<ref name=":4" /> DeGeerdalen Formation (Svalbard),<ref name=":7" /> [[Earth:Ischigualasto Formation|Ischigualasto Formation]] (Argentina), upper Santa Maria Formation (Brazil), [[Earth:Caturrita Formation|Caturrita Formation]] (Brazil),<ref name=":4" /> upper Maleri Formation (India), [[Earth:Isalo II|Isalo II]] (Madagascar)<ref name=":4" />
|-
|'''<u>Otischalkian</u>'''
|Otis Chalk, Texas, USA<ref name=":6">{{Cite journal |last1=Lucas |first1=Spencer G. |last2=Hunt |first2=Adrian P. |date=1993 |title=Tetrapod biochronology of the Chinle Group (Upper Triassic), western United States |url=https://books.google.com/books?id=qbP9CQAAQBAJ&pg=PA327 |journal=New Mexico Museum of Natural History & Science Bulletin |volume=3 |pages=327–329}}</ref>
|[[File:Paleorhinus cropped.png|140px|center]]{{br}}{{center|''Paleorhinus / [[Biology:Parasuchus|Parasuchus]]''}}
|''[[Biology:Metoposaurus|Metoposaurus]], [[Biology:Placerias|Placerias]],''<ref name=":4" /> ''[[Biology:Hyperodapedon|Hyperodapedon]],''<ref name=":4" /> ''[[Biology:Doswellia|Doswellia]], [[Biology:Angistorhinus|Angistorhinus]], [[Biology:Longosuchus|Longosuchus]]''
|middle Carnian
|Colorado City Formation, Texas, USA
|Popo Agie Formation (Wyoming, USA), Salitral Formation (New Mexico, USA), "Sanfordian" strata of the [[Earth:Newark Supergroup|Newark Supergroup]] (eastern USA and Canada), [[Earth:Stuttgart Formation|Stuttgart Formation]] (Germany), Timezgadiouine Formation (Irohalene Member, Morocco), lower Maleri Formation (India), [[Earth:Tiki Formation|Tiki Formation]] (India),<ref name=":7" /> [[Earth:Madygen Formation|Madygen Formation]]? (Kyrgyzstan)
|-
|'''<u>Berdyankian</u>'''
|Berdyanka River, Russia
|[[File:Mastodonsaurus DB.jpg|140px|center]]{{br}}{{center|''Mastodonsaurus giganteus''<ref name=":4" />}}
|''[[Biology:Massetognathus|Massetognathus]], [[Biology:Dinodontosaurus|Dinodontosaurus]], [[Biology:Stahleckeria|Stahleckeria]]''
|late Anisian to early Carnian<ref name=":7" />
|Bukobay Formation, Russia
|Lower Keuper (Germany), [[Earth:Chañares Formation|Chañares Formation]] (Argentina), lower Santa Maria Formation (Brazil), upper [[Earth:Omingonde Formation|Omingonde Formation]] (Namibia)<ref name=":7" />
|-
|'''<u>Perovkan</u>'''
|Perovka, Russia
|[[File:Eocyclotosaurus wellesi1DB.jpg|140px|center]]{{br}}{{center|''[[Biology:Eocyclotosaurus|Eocyclotosaurus]]''<ref name=":4" />}}
|''[[Biology:Eryosuchus|Eryosuchus]]'', ''[[Biology:Paracyclotosaurus|Paracyclotosaurus]]'',<ref name=":4" /> ''[[Biology:Scalenodon|Scalenodon]]'', ''[[Biology:Shansiodon|Shansiodon]]'', ''[[Biology:Parakannemeyeria|Parakannemeyeria]]'', ''[[Biology:Sinokannemeyeria|Sinokannemeyeria]]'', "''Kannemeyeria cristarhynchus''",<ref name=":4" /> ''[[Biology:Arizonasaurus|Arizonasaurus]]''<ref name=":4" />
|Anisian
|[[Earth:Donguz Formation|Donguz Formation]], Russia
|[[Earth:Moenkopi Formation|Moenkopi Formation]] (Holbrook and Anton Chico members, USA), lower Wolfville Formation (Nova Scotia, Canada), [[Earth:Otter Sandstone Formation|Otter Sandstone]] (UK), Upper Buntsandstein (Germany / France), lower Kelamayi Formation (China), upper [[Earth:Ermaying Formation|Ermaying Formation]] (China), [[Earth:Yerrapalli Formation|Yerrapalli Formation]] (India),<ref name=":4" /> ''Cynognathus'' Assemblage Zone (Subzone C, South Africa),<ref name=":4" /> [[Earth:Omingonde Formation|Omingonde Formation]] (Namibia),<ref name=":4" /> Manda Beds (Tanzania)
|-
|'''<u>Nonesian</u>'''
|Nonesi's Nek Pass, South Africa
|[[File:Cynognathus NT small.jpg|140px|center]]{{br}}{{center|''[[Biology:Cynognathus|Cynognathus]]''}}
|''[[Biology:Parotosuchus|Parotosuchus]], [[Biology:Odenwaldia|Odenwaldia]],<ref name=":4" /> [[Biology:Trematosaurus|Trematosaurus]],<ref name=":4" /> [[Biology:Trematosuchus|Trematosuchus]], [[Biology:Diademodon|Diademodon]], [[Biology:Trirachodon|Trirachodon]], Kannemeyeria simocephalus, [[Biology:Erythrosuchus|Erythrosuchus]]''<ref name=":4" />
|Olenekian
|''Cynognathus'' Assemblage Zone (Subzones A-B), South Africa
|[[Earth:Moenkopi Formation|Moenkopi Formation]] (Torrey and Wupatki members, USA), Sticky Keep Formation (Svalbard), Middle Buntsandstein (Germany),<ref name=":4" /> Yarenskian Gorizont (Russia), lower [[Earth:Ermaying Formation|Ermaying Formation]] (China), Puesto Viejo Group (Argentina), Rio Mendoza Formation (Argentina), lower Zarzaïtine Formation (Algeria), lower [[Earth:Ntawere Formation|Ntawere Formation]] (Zambia), Kingori Sandstone (Tanzania), upper [[Earth:Fremouw Formation|Fremouw Formation]] (Antarctica)
|-
|'''<u>Lootsbergian</u>'''
|Lootsberg Pass, South Africa
|[[File:Lystr georg1DB.jpg|140px|center]]{{br}}{{center|''[[Biology:Lystrosaurus|Lystrosaurus]]''}}
|''[[Biology:Wetlugasaurus|Wetlugasaurus]]'', ''[[Biology:Tupilakosaurus|Tupilakosaurus]]'', ''[[Biology:Luzocephalus|Luzocephalus]]'', ''[[Biology:Lydekkerina|Lydekkerina]]'', ''[[Biology:Scaloposaurus|Scaloposaurus]]'', ''[[Biology:Thrinaxodon|Thrinaxodon]]'', ''[[Biology:Procolophon|Procolophon]]'', ''[[Biology:Prolacerta|Prolacerta]]'', ''[[Biology:Proterosuchus|Proterosuchus]]''
|latest [[Earth:Permian|Permian]] (Changxingian) to Induan
|''Lystrosaurus'' Assemblage Zone, South Africa
|upper Guodikeng Formation (China), lower Jiucaiyuan Formation (China), Heshanggou Formation (China), lower [[Earth:Fremouw Formation|Fremouw Formation]] (Antarctica), Panchet Formation (India), Wordie Creek Formation (Greenland), Vokhmian Gorizont (Russia),<ref name=":4" /> Sludkian Gorizont (Russia),<ref name=":4" /> Ustmylian Gorizont (Russia),<ref name=":4" /> [[Earth:Sanga do Cabral Formation|Sanga do Cabral Formation]] (Brazil),<ref name=":4" /> Rewan Formation (Australia),<ref name=":4" /> [[Earth:Arcadia Formation, Australia|Arcadia Formation]] (Australia)<ref name=":4" />
|}

== Criticism ==
Several paleontologists have independently questioned the validity of Lucas’s system, criticizing its inconsistent and often contradictory approach to taxonomy and faunal correlations.<ref name=":9">{{Cite journal|last1=Rayfield|first1=E. J.|last2=Barrett|first2=P. M.|last3=McDonnell|first3=R. A.|last4=Willis|first4=K. J.|date=2005-07-01|title=A Geographical Information System (GIS) study of Triassic vertebrate biochronology|url=https://core.ac.uk/download/pdf/51377075.pdf|journal=Geological Magazine|language=en|volume=142|issue=4|pages=327–354|doi=10.1017/S001675680500083X|bibcode=2005GeoM..142..327R |s2cid=129914103 |issn=0016-7568|via=}}</ref><ref name=":10">{{Cite journal |last=Langer |first=Max Cardoso |date=2005-06-01 |title=Studies on continental Late Triassic tetrapod biochronology. II. The Ischigualastian and a Carnian global correlation |url=https://www.sciencedirect.com/science/article/pii/S0895981105000581 |journal=Journal of South American Earth Sciences |language=en |volume=19 |issue=2 |pages=219–239 |doi=10.1016/j.jsames.2005.04.002 |bibcode=2005JSAES..19..219L |issn=0895-9811}}</ref><ref name=":1" /><ref name=":2" />

=== Endemic index taxa ===
Many index taxa are very rare or endemic to a single continent, and have no relevance to a global biostratigraphy system. These include ''[[Biology:Doswellia|Doswellia]]'', ''[[Biology:Longosuchus|Longosuchus]]'', ''[[Biology:Typothorax|Typothorax]]'', “''Pseudopalatus''” (''[[Biology:Machaeroprosopus|Machaeroprosopus]]''), ''[[Biology:Redondasaurus|Redondasaurus]]'', and ''[[Biology:Redondasuchus|Redondasuchus]]'', among others.<ref name=":9" /><ref name=":10" /><ref name=":1" /><ref name=":11">{{Cite journal |last1=Parker |first1=William G. |last2=Martz |first2=Jeffrey W. |date=2010 |title=The Late Triassic (Norian) Adamanian–Revueltian tetrapod faunal transition in the Chinle Formation of Petrified Forest National Park, Arizona |url=https://www.cambridge.org/core/product/identifier/S1755691011020020/type/journal_article |journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh |language=en |volume=101 |issue=3–4 |pages=231–260 |doi=10.1017/S1755691011020020 |s2cid=140536630 |issn=1755-6910}}</ref> For the Berdyankian LVF, very few species are shared between the index assemblage (the Bukobay Formation of Russia) and other correlated assemblages. Direct relationships between Russian, German, and South American [[Biology:Dicynodont|dicynodont]]s are conjectural and based on undiagnostic European fragments.<ref name=":9" /><ref name=":1" />

=== Imprecise or inaccurate time scales ===
Index taxa for a given LVF often range into the succeeding LVF, blurring the distinction between the two time periods. ''[[Biology:Angistorhinus|Angistorhinus]]'', ''[[Biology:Hyperodapedon|Hyperodapedon]]'', ''[[Biology:Paleorhinus|Paleorhinus]]''/''[[Biology:Parasuchus|Parasuchus]]'' (all Otischalkian index taxa) range into the Adamanian, fossils referred to ''[[Biology:Rutiodon|Rutiodon]]'' (an Adamanian index taxon) range into the Revueltian, and ''[[Biology:Metoposaurus|Metoposaurus]]'' can be found throughout the Otischalkian, Apachian, and Revueltian LVFs.<ref name=":9" /><ref name=":10" /><ref name=":1" /><ref name=":11" />

Lucas's approach to correlating LVFs with global marine stages has been met with criticism. The Triassic timescale is under constant revision from a series of age dating methods, including [[Earth:Magnetostratigraphy|magnetostratigraphy]], [[Earth:Cyclostratigraphy|cyclostratigraphy]], [[Physics:Radiometric dating|radiometric dating]], and biozones of marine invertebrates such as [[Biology:Conodont|conodont]]s and [[Biology:Ammonoidea|ammonoids]].<ref name=":2" /><ref name=":11" /> However, there are only a few areas where fossils of Triassic land tetrapods and marine organisms overlap, mostly restricted to coastal sediments in central Europe. Palynomorph and conchostracan biozones can help correlate terrestrial strata to an extent. One complication is that Lucas's view of the Late Triassic time scale contradicts the consensus established by other biostratigraphers. Most paleontologists estimate that the three stages of the Late Triassic (Carnian, Norian, and Revueltian) are strongly unequal in size, with the Norian far longer than the Carnian. Under this consensus "long-Norian" hypothesis, the Carnian-Norian boundary is close to 228 Ma. Lucas, on the other hand, prefers a "short-Norian" perspective, with a lengthier Carnian stage and a Carnian-Norian boundary at around 220 Ma.<ref name=":2" />

For example, Lucas has maintained that the lower part of the Chinle Formation (the [[Earth:Blue Mesa Member|Blue Mesa Member]] and equivalent units) is Carnian (>220 Ma) in age. This was justified by the assumption that fossils of ''[[Biology:Stagonolepis|Stagonolepis]]'', a European aetosaur, can be found in North and South America, allowing correlation between these regions. However, this proposed widespread occurrence of ''Stagonolepis'' is a debatable, as many species assigned to the genus may not be closely related (see below).<ref name=":0" /><ref name=":4" /><ref name=":10" /><ref name=":11" />

According to the "short-Norian" interpretation, these lower Chinle Formation, and other strata of the Adamanian LVF, would be firmly pre-Norian in age, suggesting that any taxonomic change between the Adamanian and Revueltian represents a Carnian-Norian extinction event. However, the consensus "long-Norian" interpretation firmly places Adamanian strata of North America into the Norian stage (<228 Ma). The Norian age of the lower Chinle Formation has been independently confirmed by U-Pb dating and magnetostratigraphic correlations to global time scales.<ref name=":2" /><ref name=":52">{{Cite journal |last1=Ramezani |first1=Jahandar |last2=Hoke |first2=Gregory D. |last3=Fastovsky |first3=David E. |last4=Bowring |first4=Samuel A. |last5=Therrien |first5=François |last6=Dworkin |first6=Steven I. |last7=Atchley |first7=Stacy C. |last8=Nordt |first8=Lee C. |date=2011-11-01 |title=High-precision U-Pb zircon geochronology of the Late Triassic Chinle Formation, Petrified Forest National Park (Arizona, USA): Temporal constraints on the early evolution of dinosaurs |url=https://doi.org/10.1130/B30433.1 |journal=GSA Bulletin |volume=123 |issue=11–12 |pages=2142–2159 |doi=10.1130/B30433.1 |bibcode=2011GSAB..123.2142R |issn=0016-7606}}</ref><ref name=":62">{{Cite journal |last1=Rasmussen |first1=Cornelia |last2=Mundil |first2=Roland |last3=Irmis |first3=Randall B. |last4=Geisler |first4=Dominique |last5=Gehrels |first5=George E. |last6=Olsen |first6=Paul E. |last7=Kent |first7=Dennis V. |last8=Lepre |first8=Christopher |last9=Kinney |first9=Sean T. |last10=Geissman |first10=John W. |last11=Parker |first11=William G. |date=2020-07-20 |title=U-Pb zircon geochronology and depositional age models for the Upper Triassic Chinle Formation (Petrified Forest National Park, Arizona, USA): Implications for Late Triassic paleoecological and paleoenvironmental change |url=https://doi.org/10.1130/B35485.1 |journal=GSA Bulletin |volume=133 |issue=3–4 |pages=539–558 |doi=10.1130/B35485.1 |issn=0016-7606}}</ref> Conversely, other "Adamanian" strata, such as fossiliferous layers in the lower [[Earth:Ischigualasto Formation|Ischigualasto Formation]] of Argentina, can be assigned to the late Carnian (~231 Ma).<ref name=":10" /><ref name="Ignotosaurus">{{Cite journal |last1=Martínez |first1=R. N. |last2=Apaldetti |first2=C. |last3=Alcober |first3=O. A. |last4=Colombi |first4=C. E. |last5=Sereno |first5=P. C. |last6=Fernandez |first6=E. |last7=Malnis |first7=P. S. |last8=Correa |first8=G. A. |last9=Abelin |first9=D. |year=2013 |title=Vertebrate succession in the Ischigualasto Formation |url=https://www.researchgate.net/publication/257448913 |journal=Journal of Vertebrate Paleontology |volume=32 |pages=10–30 |bibcode=2013JVPal..32S..10M |doi=10.1080/02724634.2013.818546 |s2cid=37918101|hdl=11336/7771 |hdl-access=free }}</ref> This supports the conclusion that LVFs such as the Adamanian are fraught with uncertain time estimates brought on by weak correlations on a global scale.<ref name=":10" /><ref name=":2" />

Some authors have elected to ignore LVFs in favor of older and more localized biostratigraphic units. Named tetrapod assemblages zones (AZs) were well-established for the Triassic of Gondwana prior to the LVF, and recent updates have helped to constrain these units with greater clarity and agreement than global correlations. In Argentina, Bonaparte (1966) established the Chanarian (named after the [[Earth:Chañares Formation|Chañares Formation]]) and the Ischigualastian (named after the Ischigualasto Formation). Equivalents faunas are easily traced across Brazil, Africa, and India. These two biostratigraphic zones correlate with Lucas's Berdyankian, Otischalkian, and Apachean LVFs, but do not precisely overlap in time with those LVFs. Moreover, aetosaurs and phytosaurs, which are common in the Northern Hemisphere, are rarer and more scattered in the Southern Hemisphere. As a result, Gondwanan assemblage zones are defined by more common Southern taxa. For example, the Ischigualastian zone is defined by the [[Biology:Rhynchosaur|rhynchosaur]] ''[[Biology:Hyperodapedon|Hyperodapedon]]'' and the [[Biology:Cynodont|cynodont]] ''[[Biology:Exaeretodon|Exaeretodon]],'' as well as the aetosaur ''[[Biology:Aetosauroides|Aetosauroides]]'' and [[Biology:Herrerasauridae|herrerasaurid]] [[Biology:Dinosaur|dinosaur]]s.<ref name=":10" />

=== Taxonomic uncertainty and dubious correlations ===
[[File:Mastodonsaurus giganteus.JPG|left|thumb|''Mastodonsaurus'', a purported index fossil of the Berdyankian LVF]]
Some correlations are based on connections between fragmentary or poorly-constrained taxa rather than direct correlations between type assemblages or LVF-defining index taxa. For example, the [[Earth:Ermaying Formation|Ermaying Formation]] of China is correlated with the [[Earth:Moenkopi Formation|Moenkopi Formation]] of the United States via a tenuous (and likely unjustifiable) comparison between proposed [[Biology:Erythrosuchidae|erythrosuchid]] fossils. The primary index fossil of the Perovkan LVF, ''[[Biology:Eocyclotosaurus|Eocyclotosaurus]]'', is absent from China.<ref name=":9" /><ref name=":1" />

One particularly contradictory index fossil is ''Mastodonsaurus'', the defining index fossil of the Berdyankian LVF. Fossils referable to this genus can be found across Ladinian-age Europe, but the proposed Russian species (''M. torvus'') may be unrelated to the endemic German [[Biology:Type species|type species]] (''M. giganteus''). Moreover, if one approaches ''Mastodonsaurus'' from a broader taxonomic perspective (as expected if ''M. torvus'' is included), they must also incorporate Anisian and Carnian material referred to the genus, including the small species ''“Heptasaurus” cappelensis''. This precludes any reason to use ''Mastodonsaurus'' as a time-constrained index taxon.<ref name=":9" /><ref name=":1" />

Some LVFs are based on [[Biology:Evolutionary grade|evolutionary grade]]s as index taxa. This ignores the potential for high diversity and long temporal ranges within a given grade, and may lead to arbitrary and subjective inclusion or exclusion of descendant taxa. “''[[Biology:Stagonolepis|Stagonolepis]]''”, in its broadest form, is a [[Wastebasket taxon|wastebasket taxon]] of [[Biology:Basal (phylogenetics)|basal]] aetosaurs ranging through the Otischalkian and Apachean. Lucas’s usage of ''Stagonolepis'' [[Lumpers and splitters|lumps]] in many genera separated by other authors, such as ''[[Biology:Aetosauroides|Aetosauroides]]'' and ''[[Biology:Calyptosuchus|Calyptosuchus]]''.<ref name=":10" /><ref name=":1" /> A similar situation occurs in ''Paleorhinus/Parasuchus'', which has historically been used as a persistent grade of early phytosaurs. On the other hand, the characteristic phytosaur (''Redondasaurus'') and aetosaur (''Redondasaurus'') genera of the Apachean LVF are very similar to, and perhaps synonymous with, index taxa of the underlying Revueltian LVF: “''Pseudopalatus''” (''Machaeroprosopus'') and ''Typothorax'', respectively.<ref name=":9" /><ref name=":1" />

== Martz & Parker (2017) revision ==
Although the utility of a global LVF system is questionable, LVF-derived biostratigraphy may be useful in limited circumstances. Phytosaurs in particular have played a large role in the tetrapod biostratigraphy of the [[Earth:Chinle Formation|Chinle]] and Dockum Group of the southwest United States. A revision of the LVF system in this narrow context was undertaken by Jeff Martz and Bill Parker (2017), retaining several names and concepts previously used by Lucas and colleagues.<ref name=":8" />

Martz and Parker argued that the term "faunachron" was misleading and redundant, as each "faunachron" is bound by a single taxon rather than an assemblage ([[Earth:Fauna|fauna]]) of multiple taxa. They preferred using a specific type of interval [[Earth:Biozone|biozone]] known as a [[Earth:Teilzone|teilzone]], referring to a local interval of strata equivalent to an interval of time.<ref name=":8" /><ref>{{Citation |last1=Parker |first1=W. G. |title=Building Local Biostratigraphic Models for the Upper Triassic of Western North America: Methods and Considerations |date=2017-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780128032435000017 |work=Terrestrial Depositional Systems |pages=1–38 |editor-last=Zeigler |editor-first=Kate E. |publisher=Elsevier |language=en |isbn=978-0-12-803243-5 |access-date=2022-08-28 |last2=Martz |first2=J. W. |editor2-last=Parker |editor2-first=William G.}}</ref> The base of each teilzone was marked by the Lowest known Occurrence (LOk) of a particular category of phytosaur, i.e. the oldest layer where fossils of that category are found in the study area. LOks are local points in time and stratigraphy, disregarding occurrences in other regions or the estimated time of [[Biology:Speciation|speciation]]. For the Otischalkian, Adamanian, and Revueltian, the top of each teilzone is marked by the LOk of a more exclusive subgroup of phytosaurs. The top of the Apachean is marked by the LOk of ''[[Biology:Protosuchus|Protosuchus]]'', an Early Jurassic [[Biology:Crocodylomorpha|crocodylomorph]], as with Lucas's system.<ref name=":8" />

"Faunachrons" could also be defined beyond the constraints of teilzones; other biozonation categories include holochronozones (a stratigraphic interval, involving multiple study areas) and holochrons (an estimated time interval, involving the time of speciation or immigration into the region). Each phytosaur-based "faunachron" could be considered a teilzone (in local biostratigraphy), an estimated holochronozone (in regional [[Earth:Chronostratigraphy|chronostratigraphy]]), or an estimated holochron (in regional [[Physics:Biochronology|biochronology]]).<ref name=":8" />

One complication in defining biozones based on phytosaurs is instability in phytosaur systematics. Many proposed phytosaur taxa are dubious, [[Biology:Paraphyly|paraphyletic]] (such as ''[[Biology:Leptosuchus|Leptosuchus]]'' and ''[[Biology:Machaeroprosopus|Machaeroprosopus]])'' or have unclear relationships to each other. Nevertheless, a series of nested [[Biology:Clade|clade]]s is apparent in most recent overviews. Rather than relying on a single index taxon per biozone, Martz and Parker allowed multiple representatives per a given stage of phytosaur evolution. These representatives were chosen based on their occurrence in the southwest United States, commonness, and relatively stable phylogenetic position despite paraphyly in some circumstances.<ref name=":8" />
{| class="wikitable"
!Name
!Base-defining event
!Representative phytosaurs
!Estimated age
!Included Chinle units
!Included Dockum units
|-
|'''<u>Apachean</u>'''
|LOk of "''[[Biology:Redondasaurus|Redondasaurus]]''"
|''"[[Biology:Redondasaurus|Redondasaurus]]"'' (subgenus of ''Machaeroprosopus''?)
|Rhaetian (207-202 Ma)
|
* Rock Point Member
* Church Rock Member
* "siltstone member”
* Owl Rock Member (in part)
|
* [[Earth:Redonda Formation|Redonda Formation]]
|-
|'''<u>Revueltian</u>'''
|LOk of Pseudopalatinae (= [[Biology:Mystriosuchini|Mystriosuchini]])
|''[[Biology:Machaeroprosopus|Machaeroprosopus]]'' (''sensu lato'')
|middle to late Norian (Alaunian to Sevatian, 215-207 Ma)
|
* lower Owl Rock Member?
* [[Earth:Petrified Forest Member|Petrified Forest (Painted Desert) Member]]
* lower Kane Springs beds?
* upper Sonsela Member
|
* lowermost [[Earth:Redonda Formation|Redonda Formation]]
* middle to upper Cooper Canyon Formation (including "Bull Canyon Formation")
* upper Trujillo Formation
|-
|'''<u>Adamanian</u>'''
|LOk of [[Biology:Leptosuchomorpha|Leptosuchomorpha]]
|''[[Biology:Smilosuchus|Smilosuchus]]'', ''[[Biology:Leptosuchus|Leptosuchus]]'', ''"Phytosaurus" doughtyi''
|early to middle Norian (Lacian to early Alaunian, 224-215 Ma)
|
* lower Sonsela Member
* [[Earth:Blue Mesa Member|Blue Mesa Member]]
* Cameron Member
|
* lower to middle Cooper Canyon Formation
* lower Trujillo Formation
* lower to middle Tecovas Formation
* Garita Creek Formation
|-
|'''<u>Otischalkian</u>'''
|LOk of [[Biology:Phytosaur|Phytosaur]]ia
|''[[Biology:Wannia|Wannia]]'', ''[[Biology:Paleorhinus|Parasuchus (Paleorhinus) bransoni]]''
|earliest Norian (earliest Lacian, 227-224 Ma)
|
* lowermost [[Earth:Blue Mesa Member|Blue Mesa Member]]
* lowermost Cameron Member
* Shinarump Member
* Mesa Redondo Member
|
* lowermost Cooper Canyon Formation
* lowermost Tecovas Formation
* lowermost Garita Creek Formation
* Colorado City Member
* Camp Springs Conglomerate
* [[Earth:Santa Rosa Formation, New Mexico|Santa Rosa Formation]]
|}

=== Adamanian-Revueltian turnover ===
Although most LVFs or equivalent concepts are not marked by major biotic changes, one exception is apparent in the southwest United States. The boundary between the Adamanian and Revueltian zones is marked by a faunal turnover, an event where several tetrapod species quickly disappear from the fossil record as others appear for the first time. At Petrified Forest National Park, the event occurs in the Jim Camp Wash beds. This sediment layer is positioned in the middle of the Chinle Formation's Sonsela Member, and would have been deposited around 215 million years ago. ''[[Biology:Trilophosaurus|Trilophosaurus]]'', ''[[Biology:Poposaurus|Poposaurus]]'', ''[[Biology:Desmatosuchus|Desmatosuchus]]'', [[Biology:Dicynodont|dicynodont]]s, and non-[[Biology:Mystriosuchini|mystriosuchin]] phytosaurs are extirpated from the area around this time, while [[Biology:Metoposauridae|metoposaurs]] and [[Biology:Allokotosauria|allokotosaurs]]<ref name=":12" /> as a whole decline in abundance. New species of aetosaurs and phytosaurs replaced losses across the purported boundary event. Palynomorph assemblages overturn to more dry adapted species, and a higher concentration of pedogenic [[Chemistry:Carbonate mineral|carbonate]] nodules may also support increasing aridity.<ref name=":11" /><ref name=":12">{{Cite journal |last1=Kligman |first1=Ben T. |last2=Marsh |first2=Adam D. |last3=Nesbitt |first3=Sterling J. |last4=Parker |first4=William G. |last5=Stocker |first5=Michelle R. |date=2020-03-26 |title=New trilophosaurid species demonstrates a decline in allokotosaur diversity across the Adamanian-Revueltian boundary in the Late Triassic of western North America |journal=Palaeodiversity |volume=13 |issue=1 |pages=25 |doi=10.18476/pale.v13.a3 |s2cid=216308379 |issn=1867-6294|doi-access=free }}</ref>

The cause and relevance of this turnover is debatable, as it may indicate only a small localized extinction. The Manicouagan Impact, the second-largest bolide impact of the Mesozoic Era (besides the Chicxulub Impact which caused the K-Pg Mass Extinction at 66 Ma), is dated to around 215.4 Ma.<ref>{{Cite journal |last1=Jaret |first1=Steven J. |last2=Hemming |first2=Sidney R. |last3=Rasbury |first3=E. Troy |last4=Thompson |first4=Lucy M. |last5=Glotch |first5=Timothy D. |last6=Ramezani |first6=Jahandar |last7=Spray |first7=John G. |date=2018-11-01 |title=Context matters – Ar–Ar results from in and around the Manicouagan Impact Structure, Canada: Implications for martian meteorite chronology |url=https://www.sciencedirect.com/science/article/pii/S0012821X18304758 |journal=Earth and Planetary Science Letters |language=en |volume=501 |pages=78–89 |doi=10.1016/j.epsl.2018.08.016 |bibcode=2018E&PSL.501...78J |s2cid=134725972 |issn=0012-821X}}</ref><ref>{{Cite journal |last1=Kent |first1=Dennis V. |last2=Olsen |first2=Paul E. |last3=Lepre |first3=Christopher |last4=Rasmussen |first4=Cornelia |last5=Mundil |first5=Roland |last6=Gehrels |first6=George E. |last7=Giesler |first7=Dominique |last8=Irmis |first8=Randall B. |last9=Geissman |first9=John W. |last10=Parker |first10=William G. |date=16 October 2019 |title=Magnetochronology of the entire Chinle Formation (Norian age) in a scientific drill core from Petrified Forest National Park (Arizona, USA) and implications for regional and global correlations in the Late Triassic |journal=Geochemistry, Geophysics, Geosystems |language=en |volume=20 |issue=11 |pages=4654–4664 |bibcode=2019GGG....20.4654K |doi=10.1029/2019GC008474 |issn=1525-2027 |hdl-access=free |hdl=10150/636323 |s2cid=207980627}}</ref> While certainly large enough to momentarily devastate areas near the impact point in Quebec, broader environmental effects of the Manicouagan impact are mostly conjectural.<ref name=":2" /> Besides the Adamanian-Revueltian turnover, the impact has also been linked to a minor marine extinction in eastern [[Earth:Panthalassa|Panthalassa]].<ref>{{Cite journal |last1=Onoue |first1=Tetsuji |last2=Sato |first2=Honami |last3=Yamashita |first3=Daisuke |last4=Ikehara |first4=Minoru |last5=Yasukawa |first5=Kazutaka |last6=Fujinaga |first6=Koichiro |last7=Kato |first7=Yasuhiro |last8=Matsuoka |first8=Atsushi |date=8 July 2016 |title=Bolide impact triggered the Late Triassic extinction event in equatorial Panthalassa |journal=Scientific Reports |volume=6 |pages=29609 |bibcode=2016NatSR...629609O |doi=10.1038/srep29609 |issn=2045-2322 |pmc=4937377 |pmid=27387863}}</ref>

Alternatively, the Adamanian-Revueltian turnover may be a consequence of the gradual aridification of western Pangea as it drifted north into arid latitudes.<ref name=":12" /> Comparative estimates of extinction rates and occurrences find little support for a synchronized Adamanian-Revueltian turnover, and instead support a model where extinctions are stretched out over several million years. For most species, extinction probabilities are "decoupled" in time from other species, as well as geological or climatological drivers. The only plausible correlation is between the Manicouagan Impact and palynomorph turnover, and even then the probability of synchronicity is only about 34%.<ref>{{Cite journal |last1=Hayes |first1=Reilly F. |last2=Puggioni |first2=Gavino |last3=Parker |first3=William G. |last4=Tiley |first4=Catherine S. |last5=Bednarick |first5=Amanda L. |last6=Fastovsky |first6=David E. |date=2020-04-01 |title=Modeling the dynamics of a Late Triassic vertebrate extinction: The Adamanian/Revueltian faunal turnover, Petrified Forest National Park, Arizona, USA |url=https://pubs.geoscienceworld.org/gsa/geology/article/48/4/318/579957/Modeling-the-dynamics-of-a-Late-Triassic |journal=Geology |language=en |volume=48 |issue=4 |pages=318–322 |doi=10.1130/G47037.1 |bibcode=2020Geo....48..318H |s2cid=213822986 |issn=0091-7613}}</ref>

== References ==
{{reflist}}

[[Category:Regional geologic time scales]]
[[Category:Triassic life]]

{{Sourceattribution|Triassic land vertebrate faunachrons}}