TY - JOUR

T1 - Crocodylian assemblage from the middle Eocene Ikovo locality (Lugansk Province, Ukraine), with a discussion of the fossil record and geographic origins of crocodyliform fauna in the Paleogene of Europe

AU - Kuzmin, Ivan T.

AU - Zvonok, Evgeniy A.

N1 - Publisher Copyright: © 2021 Elsevier Masson SAS

PY - 2021/4/1

Y1 - 2021/4/1

N2 - The known fossil record of crocodyliforms in Europe during the Paleogene is significantly biased, in that the fauna of Western Europe is far better sampled and understood compared to that of Eastern Europe. We describe in detail all known crocodyliform remains from the middle Eocene (Lutetian) Ikovo locality in Ukraine. We conclude that at least two taxa were present: a moderate to large-sized Tomistominae indet. similar to the basalmost known tomistomines, and the small-sized basal alligatoroid cf. Diplocynodon sp. Despite its scarcity, this is the first basal alligatoroid material reported from Eastern Europe (as part of post-Soviet countries) and the easternmost record of diplocynodontines in Europe so far. An allegedly freshwater cf. Diplocynodon sp. contributes a rare faunal element to the vertebrate assemblage of the Ikovo locality, otherwise dominated by resident or facultative marine taxa. The fossil record and historical paleobiogeography of crocodyliforms from the Paleocene and Eocene of Europe are reviewed. As it has been already known, the middle Eocene fauna of crocodyliforms proves to be taxonomically diverse and complex. Its constituent lineages geographically originated in Asia or North America (Diplocynodontinae, Asiatosuchus-like crocodyloids, Planocraniidae), North America (derived alligatorines), Africa (Tomistominae), and Gondwana (ziphodont mesoeucrocodylians Iberosuchus and Bergisuchus), with possible subsequent speciation in Europe. We propose a novel hypothesis of Asian origins of European diplocynodontines, which will be explicitly tested in future studies. The revealed similarities between crocodylians and turtles from the Ikovo locality and those from Western Europe support the presence of a single Pan-European biogeographical zone during the middle Eocene, distinct from that of Asia.

AB - The known fossil record of crocodyliforms in Europe during the Paleogene is significantly biased, in that the fauna of Western Europe is far better sampled and understood compared to that of Eastern Europe. We describe in detail all known crocodyliform remains from the middle Eocene (Lutetian) Ikovo locality in Ukraine. We conclude that at least two taxa were present: a moderate to large-sized Tomistominae indet. similar to the basalmost known tomistomines, and the small-sized basal alligatoroid cf. Diplocynodon sp. Despite its scarcity, this is the first basal alligatoroid material reported from Eastern Europe (as part of post-Soviet countries) and the easternmost record of diplocynodontines in Europe so far. An allegedly freshwater cf. Diplocynodon sp. contributes a rare faunal element to the vertebrate assemblage of the Ikovo locality, otherwise dominated by resident or facultative marine taxa. The fossil record and historical paleobiogeography of crocodyliforms from the Paleocene and Eocene of Europe are reviewed. As it has been already known, the middle Eocene fauna of crocodyliforms proves to be taxonomically diverse and complex. Its constituent lineages geographically originated in Asia or North America (Diplocynodontinae, Asiatosuchus-like crocodyloids, Planocraniidae), North America (derived alligatorines), Africa (Tomistominae), and Gondwana (ziphodont mesoeucrocodylians Iberosuchus and Bergisuchus), with possible subsequent speciation in Europe. We propose a novel hypothesis of Asian origins of European diplocynodontines, which will be explicitly tested in future studies. The revealed similarities between crocodylians and turtles from the Ikovo locality and those from Western Europe support the presence of a single Pan-European biogeographical zone during the middle Eocene, distinct from that of Asia.

KW - Diplocynodon

KW - Eastern Europe

KW - Ikovo locality

KW - Lutetian

KW - Paleobiogeography

KW - Tomistominae

KW - ALLODAPOSUCHUS-PRECEDENS

KW - DIPLOCYNODON CROCODYLIA

KW - CRETACEOUS-EARLY PALEOGENE

KW - TOMISTOMINE CROCODYLIA

KW - SKULL

KW - PHYLOGENETIC-RELATIONSHIPS

KW - EARLY MIOCENE

KW - LATE PALEOCENE

KW - EUSUCHIA

KW - MORPHOLOGY

UR - http://www.scopus.com/inward/record.url?scp=85105745729&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/757a3505-e969-3d23-9723-6923b4c9d21d/

U2 - 10.1016/j.geobios.2021.02.002

DO - 10.1016/j.geobios.2021.02.002

M3 - Article

AN - SCOPUS:85105745729

VL - 65

SP - 7

EP - 27

JO - Geobios

JF - Geobios

SN - 0016-6995

ER -