Body form and trackway pattern in Australian desert monitors (Squamata : Varanidae): Comparing zoological and ichnological diversity

To what en:tent does ichnological diversity (the number of distinctive trac e fossil morphologies) serve as a proxy for zoological diversity (species r ichness of trackmakers in the living fauna) in footprint assemblages made b y terrestrial lower vertebrates a This question was investigated in a study of body, form and trackway features of monitor lizards (varanids) from the Western Australian desert. Body-shape parameters deemed likely to affect t rackway pattern of seven varanid species were measured. These lizards diffe r in average adult size, but there is considerable size overlap between adu lts of small-bodied species and juveniles of large-bodied species. Although subtle species differences in body form were detected, these were largely swamped by intraspecific variability. Furthermore, the most distinctive fea tures in which trails of monitor species differ reflect interspecific diffe rences in foraging behavior rather than anatomical differences, and are fea tures that would be difficult or impossible to recognize without actually c apturing the trackmaker. These observations provide empirical support for t he widely held belief that trace fossil diversity commonly under-represents zoological diversity. The degree to which this is so is likely to be influ enced by trackmaker body size and metabolic physiology.