Fossil Record 20(2): 279-290, doi: 10.5194/fr-20-279-2017
Foramina in plesiosaur cervical centra indicate a specialized vascular system
expand article infoTanja Wintrich, Martin Scaal§, P. Martin Sander
‡ Bereich Paläontologie, Steinmann-Institut für Geologie, Mineralogie und Paläontologie, Universität Bonn, 53115 Bonn, Germany§ Institut für Anatomie II, Universität zu Köln, Joseph-Stelzmann-Str. 9, 50937 Cologne, Germany
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The sauropterygian clade Plesiosauria arose in the Late Triassic and survivedto the very end of the Cretaceous. A long, flexible neck with over 35cervicals (the highest number of cervicals in any tetrapod clade) is asynapomorphy of Pistosauroidea, the clade that contains Plesiosauria. Basalplesiosaurians retain this very long neck but greatly reduce neck flexibility.In addition, plesiosaurian cervicals have large, paired, and highlysymmetrical foramina on the ventral side of the centrum, traditionally termedsubcentral foramina, and on the floor of the neural canal. We found thatthese dorsal and the ventral foramina are connected by a canal that extendsacross the center of ossification of the vertebral centrum. We posit thatthese foramina are not for nutrient transfer to the vertebral centrum butthat they are the osteological correlates of a highly paedomorphic vascularsystem in the neck of plesiosaurs. This is the retention of intersegmentalarteries within the vertebral centrum that are usually obliterated duringsclerotome re-segmentation in early embryonic development. The foramina andcanals are a rare osteological correlate of the non-cranial vascular(arterial) system in fossil reptiles. The adaptive value of the retention ofthe intersegmental arteries may be improved oxygen transport during deepdiving and thermoregulation. These features may have been important in theglobal dispersal of plesiosaurians.