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 : 823

DISPARITY OF METRIORHYNCHOIDEA : DISCRETE CHARACTER APPROACH

Geometric morphometrics enables the construction of a morphospace, but the above analysis only takes into account the shape of the skull in dorsal aspect, and only in the sample currently available. Although these shape differences have long been used to define metriorhynchoid taxa, and appear to be closely tied to different dietary and ecological strategies, they are a limited source of data for examining the larger macroevolutionary patterns in the group. An alternative data set for investigating such patterns is the set of discrete characters used in the phylogenetic analysis, as these have the advantage of sampling the entire skeleton, and include important variation that is difficult to quantify in geometric morphometrics (which is a largely phenetic form of comparison). Discrete cladistic characters can be used to define a morphospace and calculate metrics of disparity, which quantify morphological diversity, and the overall range of body plan variability ( Foote, 1994; Wills, Briggs & Fortey, 1994; Erwin, 2007). These metrics, which can be tracked over time or compared between different taxonomic groups, can reveal and describe macroevolutionary changes such as the evolution of new body plans and shifts in ecological structure ( Foote, 1993, 1996, 1997; Wesley- Hunt, 2005; Adamowicz, Purvis & Wills, 2008; Brusatte et al., 2008a, b).