Abstract

This study investigated the vertebral carapace structure of some Australian chelids to compare the skeletal anatomy of taxa that do not routinely have neurals with those that do. It also provides a comprehensive review of the presence and condition of neurals across all known extinct and extant chelids and considers the evolution of variable possession of neurals in the Chelidae in relation to 2 phylogenetic hypotheses for the family. I found that neurals are completely absent from some taxa and that subsurface neurals are not ubiquitous in chelids that lack neurals on the carapace surface, as previously thought. The review indicates that reduction from the plesiomorphic series of 8 neurals has occurred widely but variably across the chelid radiation and it appears that reduction of the series is an ongoing evolutionary process in the family. Reduction and complete loss of a neural series appears to have occurred on a similar number of occasions when evaluated by either of 2 basic phylogenetic reconstructions and the condition of neurals is thus of limited utility in considerations of higher chelid turtle taxonomy.

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