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Johan Lindgren

Johan Lindgren

Universitetslektor

Johan Lindgren

Landlubbers to leviathans: evolution of swimming in mosasaurine mosasaurs

Författare

  • Johan Lindgren
  • Michael J. Polcyn
  • Bruce A. Young

Summary, in English

Incremental stages of major evolutionary transitions within a single animal lineage are rarely observed in the fossil record. However, the extraordinarily complete sequence of well preserved material spanning the 27-Myr existence of the marine squamate subfamily Mosasaurinae provides a unique exception. By comparison with extant and extinct analogs, the tail morphology of four mosasaurine genera is examined, revealing a pattern of evolution that begins with the generalized varanoid anatomy and culminates in a high-aspect-ratio fin, similar to that of sharks. However, unlike the epicercal caudal fluke of selachians in which the tail bends dorsocaudally, derived mosasaurs develop a hypocercal tail with a ventrocaudal bend. Progressive caudal regionalization, reduced intervertebral mobility, increased tail depth due to a marked downturn of the posterior caudal segment, and the development of finlike paired appendages reveal a pattern of adaptation toward an optimized marine existence. This change in morphology reflects a transition from anguilliform or sub-carangiform locomotion to carangiform locomotion, and indicates a progressive shift from nearshore dwellers to pelagic cruisers-a change in foraging habitat independently corroborated by paleobiogeographic, stable isotope, osteohistological, and paleopathological data. Evolutionary patterns similar to those observed in mosasaurine mosasaurs are seen in other secondarily aquatically adapted ainniotes, notably metriorhynchid crocodyliforms, cetaceans, and ichthyosaurs, and may be explained by developmental modularity governing the observed phenotypic expression.

Avdelning/ar

  • Berggrundsgeologi

Publiceringsår

2011

Språk

Engelska

Sidor

445-469

Publikation/Tidskrift/Serie

Paleobiology

Volym

37

Issue

3

Dokumenttyp

Artikel i tidskrift

Förlag

Paleontological Soc Inc

Ämne

  • Geology

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1938-5331