METRIORHYNCHOIDEA, Fitzinger, 1843

Young, Mark T., Brusatte, Stephen L., Ruta, Marcello & Andrade, Marco Brandalise De, 2010, The evolution of Metriorhynchoidea (mesoeucrocodylia, thalattosuchia): an integrated approach using geometric morphometrics, analysis of disparity, and biomechanics, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 158 (4), pp. 801-859 : 803

METRIORHYNCHOIDEA

The evolutionary relationships of the Metriorhynchidae were elucidated by Young & Andrade (2009), with a comprehensive cladistic analysis that considered all currently known valid taxa in the Metriorhynchoidea ( Metriorhynchidae s.s. and their closest relatives). Young & Andrade’s (2009) analysis included 38 metriorhynchids, five species of Teleosauridae (the sister taxon to Metriorhynchidae ), representatives from numerous metasuchian clades, as well as more basal crocodylomorphs ( Protosuchus , three species of sphenosuchians), and with Erpetosuchus as an out-group. The resultant strict consensus, here simplified to show only the interrelationships of Metriorhynchoidea ( Fig. 2 ), is well resolved.

Young & Andrade (2009) proposed a phylogenetic definition for both Metriorhynchidae and related family groups. Their terminology, which is used throughout, defines the superfamily Metriorhynchoidea as all species more closely related to Metriorhynchus geoffroyii von Meyer, 1830 than to Teleosaurus cadomensis ( Lamouroux, 1820) (i.e. the teleosaurids). They restricted the family Metriorhynchidae to the least inclusive clade consisting of M. geoffroyii and Ge. giganteus , and regarded the two clades into which Metriorhynchidae are split as subfamilies ( Figs 2 and 3 ). The first subfamily, Metriorhynchinae , is defined as all metriorhynchids closer to M. geoffroyii than to Ge. giganteus ; whereas the second, Geosaurinae , consists of all metriorhynchids closer to Ge. giganteus than to M. geoffroyii . In addition, the genera considered valid in this study follow the recent taxonomic changes introduced by Young (2006, 2007) and Young & Andrade (2009), and we herewith erect two new genera ( Eoneustes gen. nov. and Gracilineustes gen. nov.; see Appendix). Note that we use Crocodylia Gmelin, 1789 as defined by Martin & Benton (2008), i.e. the least-inclusive clade containing Protosuchus richardsoni (Brown, 1933) and Crocodylus niloticus Laurenti, 1768 . This clade has at times been referred to as Crocodyliformes Hay, 1930 (sensu Benton & Clark, 1988).

Figures

Figure 2. Strict consensus of Metriorhynchoidea from Young & Andrade (2009), calibrated by Tethys ammonite zones. See the Appendix for further details regarding genera and taxonomy.

Figure 3. Metriorhynchoidea phylogeny, with character complexes relating to marine adaptation mapped by shading. The light-grey shading indicates taxa demonstrating the ‘typical’ adaptations of metriorhynchids, i.e. hypocercal tails, no osteoderms, and no external mandibular fenestrae. The mid-grey shading refers to taxa with dorsally inclined paroccipital processes and verticalized squamosals; whereas the dark-grey shading highlights taxa with streamlined crania (lateral processes of the frontal reoriented caudally, creating an acute angle between the medial and lateral processes of the frontal) and more flattened humeri.