The study of fossil eggshell has prompted the development of an eggshell parataxonomy, or 'ootaxonomy'. Parataxonomic-nomenclatural approaches toward the naming of fossil eggshell taxa (ootaxa) were recently outlined by Mikhailov et al. (1996), Mikhailov (1997), and Hirsch et al. (1997) among others. These workers recognized that the fossil remains of eggs can rarely if ever be confidently identified with osteological remains of the animal that produced them, necessitating a separate nomenclatural classification for egg and skeletal remains. The parataxonomic approach suggests that fossil eggshell taxonomic ranks incorporate the prefix oo- (e.g., ootaxa, oogenus, oospecies) and that generic names end in the suffix -oolithus (Mikhailov et al. 1996; Hirsch et al. 1997). Under a parataxonomic framework, avian eggshell is described and discussed separately from avian osteological remains. Ichnotaxonomy provides an analogous case of nomenclatural parallelism, whereby the fossil traces described are rarely able to be associated with the animal species that created them. Ichnotaxa are widely recognized, and ichnotaxonomy (a form of parataxonomy) has become formalized (ICZN 2000: Article 42.2.1) and is well-developed (for a review, see Prothero 1998).

Recent work has demonstrated the applicability of cladistic phylogenetic analyses to ratite eggshell (Grellet-Tinner 2000; Zelenitsky and Modesto 2003), possibly doing away with any need for a parataxonomic approach. Grellet-Tinner (2000) conducted a cladistic analysis of eggshell that included fossil and recent palaeognath taxa. His end result included a monophyletic Paleognathae. Zelenitsky and Modesto (2003) found that analyses that included only eggshell characters, only skeletal characters, and both eggshell and skeletal characters produced very similar tree topologies. Although their work included only modern ratites, its implications extend to the fossil record, suggesting that analyses that include eggshells of both fossil ootaxa and recent ratites may provide a basis for the formulation and testing of evolutionary and biogeographic hypotheses. We agree with these workers that cladistic analyses are the best way to test phylogenetic statements regarding eggshell. Yet it is still the case that many taxa have been erected solely on the basis of fossil eggshell, with no association of these specimens to skeletal remains. We maintain that such taxa are more properly referred to as ootaxa and that unless they are either: 1) confidently associated with skeletal remains; or 2) demonstrated cladistically to share synapomorphies with eggs of a skeletally based taxon, their Latin binomials remain parataxonomic. Parataxonomic status does not exclude fossil eggshell from inclusion with skeletal taxa in cladistic phylogenetic analyses, and such analyses do have the capacity to illuminate phylogenetic and evolutionary trends.

In discussing the Namibian eggshell taxa, we employ the taxonomic nomenclature used by the original authors (Pickford and Dauphin 1993; Pickford et al. 1995) purely for simplicity's sake and with the aim of avoiding unnecessary confusion in the literature. These taxa are, however, understood to be ootaxa, and are referred to as such throughout. We elect to replace the commonly used term 'aepyornithoid' with the more meaningful 'aepyornithid-like' (or 'aepyornithid-type', as appropriate), which refers to the actual family-level taxon.