A hand-specimen, bedding-plane sample of limestone (wackestone) from the Upper Ordovician Waynesville Formation has numerous brachiopod specimens (at least 60) exposed on its surface (Figure 1). The brachiopods have been identified as members of the atrypid species Zygospira modesta (Say in Hall) 1847 (the type species of the genus Zygospira Hall, 1862) and are concentrated in an area measuring approximately 9 cm x 2 cm. A wide range of specimen sizes from juvenile to adult are present and are believed to represent a brachiopod life-assemblage (Figure 2).

In 1994 an extensive collection of mainly Carboniferous conodonts was transferred from the Department of Geology, University of Southampton, England, to The Natural History Museum, London, on the retirement of R. L. Austin. The collection consists of approximately 2,000 slides of type/figured specimens and picked residue slides, which complement material previously deposited at The Natural History Museum, London. The following is a very brief resumé of figured material in the collection.

Phylogenetic taxonomy, that component of phylogenetic systematics concerned with the verbal representation (rather than the reconstruction or estimation) of phylogenetic relationships, was developed by de Queiroz and Gauthier (1990, 1992, 1994). Under phylogenetic taxonomy, all taxon names are names of clades (i.e., an ancestor and all of that ancestor's descendants). De Queiroz and Gauthier (1990, 1992, 1994) described three possible ways of denning clade names within the phylogenetic taxonomic system: 1) node-based definitions (Figure 1.1), of the form “the most recent common ancestor of Taxon A and Taxon B, and all of that ancestor's descendants”; 2) stem-based definitions (Figure 1.2), of the form “Taxon A and all taxa sharing a more recent common ancestor with Taxon A than with Taxon B”; and 3) apomorphy-based definitions (Figure 1.3), of the form “the first taxon with derived character X and all of that ancestor's descendants.” Bryant (1994) noted that, while the first two definition types will always be stable, apomorphy-based definitions are potentially confusing if that derived character is found to occur in more than one lineage (i.e., is homoplastic). Under the phylogenetic system of taxonomy, definitions of taxon names are independent with respect to previous diagnosis (as particular character states may be found to occur in other lineages or in more inclusive clades) and composition (as particular member taxa may subsequently be found to lie outside the defined clade boundary). This paper is the initial work in an ongoing study by Holtz and Padian (1995, in preparation) to clarify the phylogenetic taxonomy of major clades of theropods and related taxa.