Bulletin of geosciences | |
Sibling echinoderm taxa on isolated Ordovician continents: Problem of center of origin | |
Rozhnov SV1  | |
关键词: Ordovician; echinoderms; sibling taxa; biogeography; Baltica; Laurentia; Gondwana; | |
DOI : | |
来源: Czech Geological Survey | |
【 摘 要 】
MorphologicallysimilarechinodermgeneraaremostlyknownfromtheOrdovicianoftwoisolatedcontinents,BalticaandLaurentia,althoughtheselandmasseswerestrictlyisolatedbiogeographicallybytheIapetusOceanandhaddifferentclimatesduringtheEarlyandMiddleOrdovician.ThemorphologicalcharactersofmostoftheseechinodermgeneraexcludethepossibilitythatBalticgeneraevolvedfromLaurentianformsorviceversaandsuggestthattheircommonancestralgroupwasfromadifferentregion.Iproposedtonamesuchgenera‘siblinggenera’,ortwingenerabyanalogywithsiblingspecies.Eocrinoidsiblinggeneraarerepresentativesofthecryptocrinitid-rhipidocystidclade.BalticParacryptocrinitesandCryptocrinitesaresiblinggeneraofLaurentianColumbocystis,SpringerocystisandFoerstecystis,BalticRhipidocystisisasiblinggenusofLaurentianMandalacystisandBalticNeorhipidocystisissiblinggenusofLaurentianBatherocystis.ItisassumedthatNorthAmericanplaticystidparacrinoids,cryptocrinidandrhipidocystideocrinoidsevolvedfromacommonancestraleocrinoid,similartoParacryptocrinites.SiblinggeneraarealsoknownamongotherOrdovicianechinoderms,forexample,crinoids(hybocrinids),edrioasteroids(edrioblastoids)andrhombiferans.SomegeneramigratedfromBalticatoLaurentiaandviceversa.ThetemperatewarmwaterseasofeasternGondwanainthenorthernChina-Australianregionwereapossiblebiogeographicalcenteroforigin,diversificationordistributionofLaurentianandBalticsiblinggenera.BiogeographicalanalysisofBalticechinodermsshowsthattheBalticRegioncouldbeviewedasa‘museum’or‘storehouse’formanyofthem,theyimmigratedandsurvivedthereforsomeconsiderabletime,ratherthena‘cradle’,wheretheyaroseandfromwheretheymigratedtoothercontinents.
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