Differentiating between various species in the fossil record is one of the most vital tasks in paleontology. As such, evaluating the morphological features that we use to make these taxonomic distinctions is critical. Without any confirmation from molecular lines of evidence, morphological analyses are the only option for such studies. Determining the validity and independence of character changes is a major part of that evaluation. Compounding this limitation to morphological analyses is the fact that assembling a significant sample size of fossil specimens for a single taxon is frequently very difficult, if not impossible. Often, paleontologists compare a single fossil specimen with a single specimen of a closely related extant taxon or representatives of several such taxa. Analyses of this nature, while valuable first glimpses, do not account for variation within populations (of either the fossil or the extant groups), and therefore may result in inaccurate conclusions regarding the relationships of the organisms in question. In this chapter, I present an example of a species–status conflict within the pantherine felids and use allometric analyses to evaluate some of the morphological characteristics that have been used as evidence to support arguments in this conflict.
Since its first official use by Pocock (1930), the generic designation of Panthera for the clade consisting of the lion (P. leo), tiger (P. tigris), leopard (P. pardus), jaguar (P. onca), and now the snow leopard (P. uncia) has reached standard usage. However, the attribution of species or subspecies status below the rank of genus has not been so readily settled, especially for fossil groups that seem to show a relationship to one of the extant pantherine cats. One of these fossil groups is the ‘American lion’ (Panthera leo cf. atrox). There has been some argument regarding the nature of the relationship of P. atrox and P. spelea (the ‘cave lion’) within Panthera, and several authors have maintained a P. tigris or P. onca affinity for P. atrox (e.g. Simpson, 1941; Groiss, 1996).