The parareptilian group Procolophonoidea has been increasingly studied in recent years, and a high survival rate during the P/Tr extinction event has been estimated tor the ciade. Procolophonoid interrelationships, however, remain poorly known. Here, descriptions of the procolophonids Anomoiodon liliensterni and Leptopleuron lacertinum, and the possible Permian Russian procolophonoids, are provided. Anomoiodon and the genus Kapes were found to be closely related but there is not enough evidence to support the synonymy of the two genera. Leptopleuron is described in great detail, making it one of the most completely knovm procolophonoids. Of the possible Permian Russian procolophonoids, Suchonosaurus minimus was found to be a member of the more inclusive Procolophonidae, whereas Microphon exiguus and Kinelia broomi fall outside of Procolophonoidea. Nyctiphruretus acudens might be the sister taxon of Procolophonoidea but an alternative hypothesis of Nyctiphruretus being more closely related to pareiasaurs and nycteroleterids also received support, A phylogenetic study. including 39 procolophonoid taxa, was conducted. The results suggest novel compositions of the procolophonid clades Leptopleuroninae and Procolopphoninae; the monophyly of the genus Kapes was questioned; the phylogenetic position of Suchonosaurus, Pintosaurus and Phaantosaurus among the other basal procolophonids remains unresolved; and the results cast doubt on Procolophonoidea being divided into the clades Owenettidae and Procolophonidae. The topology with the best stratigraphic fit indicates that only 57% of procolophonoid lineages might have survived through the P/Tr boundary. However, it is also possible that up to 80% lineages crossed the boundary but this requires a scenario that maximizes the number of ghost lineages. A stratigraphical analysis supports separate Owenettidae and Procolophonidae.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:492478 |
| Date | January 2008 |
| Creators | Saila, Laura K. |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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