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Phylogeny of the Ichthyopterygia



Ben Creisler
bcreisler@gmail.com

A recent paper:

Cheng Ji, Da-Yong Jiang, Ryosuke Motani, Olivier Rieppel, Wei-Cheng
Hao & Zuo-Yu Sun (2015)
Phylogeny of the Ichthyopterygia incorporating recent discoveries from
South China.
Journal of Vertebrate Paleontology (advance publication).
DOI: 10.1080/02724634.2015.1025956
http://www.tandfonline.com/doi/full/10.1080/02724634.2015.1025956

During the last decade, abundant ichthyopterygian material has been
found from the Triassic of South China as well as the Upper Jurassic
and Lower Cretaceous of Europe and South America, significantly
expanding our knowledge of ichthyopterygian diversity through the
Mesozoic. Previous phylogenetic hypotheses of the group no longer
account for these extensive additions, necessitating a new
phylogenetic framework for the entire Ichthyopterygia to enable
evolutionary studies of the group. We present here a comprehensive
phylogenetic hypothesis for Ichthyopterygia based on cladistic
analysis of 163 characters coded for 59 ingroup and five outgroup
taxa. The monophyly of Ichthyopterygia is strongly supported by a
Bremer index value of 7. Five major groups of Ichthyopterygia during
the Triassic, viz., Grippioidea, Cymbospondylidae, Mixosauridae,
Shastasauridae, and Toretocnemidae, are well supported by Bremer index
values between 3 and 5. Major clades that evolved in the Triassic,
including Merriamosauria, Euichthyosauria, and Parvipelvia, are also
robustly supported, whereas most post-Triassic clades are very weakly
supported with a Bremer index value of 1, with a few exceptions, such
as Thunnosauria and Ophthalmosauridae. The traditional Shastasauridae
is expanded to comprise six genera but excludes Callawayia, which is
more closely related to Parvipelvia than to Shastasauridae. ‘C.’
wolonggangensis is a shastasaurid but does not form a monophyletic
clade with Callawayia neoscapularis or Guizhouichthyosaurus tangae as
previously asserted. The new phylogenetic hypothesis is generally
consistent with the stratigraphic occurrences of each taxon especially
for the Triassic taxa.



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