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Landlubbers to leviathans: evolution of swimming in mosasaurine mosasaurs

Lindgren, Johan LU ; Polcyn, Michael J. and Young, Bruce A. (2011) In Paleobiology 37(3). p.445-469
Abstract
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Paleobiology
volume
37
issue
3
pages
445 - 469
publisher
Paleontological Soc Inc
external identifiers
  • wos:000292342200008
  • scopus:79958727807
ISSN
1938-5331
DOI
10.1666/09023.1
language
English
LU publication?
yes
id
245d3975-7603-42f1-8726-127228599721 (old id 2032226)
date added to LUP
2011-07-26 14:24:35
date last changed
2017-11-12 03:04:15
@article{245d3975-7603-42f1-8726-127228599721,
  abstract     = {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.},
  author       = {Lindgren, Johan and Polcyn, Michael J. and Young, Bruce A.},
  issn         = {1938-5331},
  language     = {eng},
  number       = {3},
  pages        = {445--469},
  publisher    = {Paleontological Soc Inc},
  series       = {Paleobiology},
  title        = {Landlubbers to leviathans: evolution of swimming in mosasaurine mosasaurs},
  url          = {http://dx.doi.org/10.1666/09023.1},
  volume       = {37},
  year         = {2011},
}