02951nas a2200313 4500008004100000022001400041245014500055210006900200260000900269300001100278490000600289520193100295653001202226653001402238653001102252653001202263653004002275653003102315653001102346653001402357653001302371653001002384653002602394100001702420700002002437700002002457700002202477856013802499 2011 eng d a1932-620300aA new paleozoic Symmoriiformes (Chondrichthyes) from the late Carboniferous of Kansas (USA) and cladistic analysis of early chondrichthyans.0 anew paleozoic Symmoriiformes Chondrichthyes from the late Carbon c2011 ae249380 v63 a

BACKGROUND: The relationships of cartilaginous fishes are discussed in the light of well preserved three-dimensional Paleozoic specimens. There is no consensus to date on the interrelationship of Paleozoic chondrichthyans, although three main phylogenetic hypotheses exist in the current literature: 1. the Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are grouped along with the modern sharks (neoselachians) into a clade which is sister group of holocephalans; 2. the Symmoriiformes are related to holocephalans, whereas the other Paleozoic shark-like chondrichthyans are related to neoselachians; 3. many Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are stem chondrichthyans, whereas stem and crown holocephalans are sister group to the stem and crown neoselachians in a crown-chondrichthyan clade. This third hypothesis was proposed recently, based mainly on dental characters.

METHODOLOGY/PRINCIPAL FINDINGS: On the basis of two well preserved chondrichthyan neurocrania from the Late Carboniferous of Kansas, USA, we describe here a new species of Symmoriiformes, Kawichthys moodiei gen. et sp. nov., which was investigated by means of computerized X-ray synchrotron microtomography. We present a new phylogenetic analysis based on neurocranial characters, which supports the third hypothesis and corroborates the hypothesis that crown-group chondrichthyans (Holocephali+Neoselachii) form a tightly-knit group within the chondrichthyan total group, by providing additional, non dental characters.

CONCLUSIONS/SIGNIFICANCE: Our results highlight the importance of new well preserved Paleozoic fossils and new techniques of observation, and suggest that a new look at the synapomorphies of the crown-group chondrichthyans would be worthwhile in terms of understanding the adaptive significance of phylogenetically important characters.

10aAnimals10aCartilage10aFishes10aFossils10aImage Processing, Computer-Assisted10aImaging, Three-Dimensional10aKansas10aPhylogeny10aSkeleton10aSkull10aX-Ray Microtomography1 aPradel, Alan1 aTafforeau, Paul1 aMaisey, John, G1 aJanvier, Philippe uhttps://chondrichthyes.myspecies.info/content/new-paleozoic-symmoriiformes-chondrichthyes-late-carboniferous-kansas-usa-and-cladistic