Carr, R. K., 1995a. - Biological Sciences

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IG inferognathal plate, injerognathale;
MD median dorsal plate, plaque mediane dorsale;
Mk Meckel's cartilage, cartilage de Meckel;
PVL posterior ventrolateral plate, plaque ventrolaterale posterieure;
Qu quadrate ossification of the palatoquadrate, ossification carree du palatocarre;
SO suborbital plate, plaque suborbitaire;
scler sclerotic plate, anneaux sclerotiques.
MATERIAL AND METHODS
Appendix I provides a species level compilation of stratigraphic ranges for all placoderms
(DENISON, 1978; placoderm references from the Zoological Record, 1975-1991). It includes taxonomically
and temporally ambiguous taxa (e.g. indeterminate material, unresolved synonyms,
species based on fragmentary material, incerfae sedis). Indeterminate taxa are included whenever
they provide temporal range information or represent forms from distinct geographic regions.
Temporal resolution for taxa ranges from indeterminate to substage (50 species without stratigraphic
resolution to series are recorded in Appendix I, but are not included in diversity analyses).
A range through method is used for taxa with poor stratigraphic resolution (e.g. a Frasnian occurrence
is recorded as a Lower to Upper Frasnian presence at the substage level). Also included
is unpublished data from research in progress (indicated in Appendix I as "n. sp.", CARR &
HLAVIN, in press, Dunkleosteus n. sp. 1, D. n. sp. 2; CARR, MS, Stenosteus n. sp. -pers. comm.­
LELIEVRE, Maideriajalipoui, this volume). A total of 720 taxa are recorded with diversity patterns
(number of taxa per unit of time) analyzed at different levels of temporal and taxonomic resolution
(among the 720 taxa there are 267 recognized genera and 591 recognized species. Thirty-three
forms are indeterminate to a generic level with an additional 41 species having questionable
assignments to generic level. Seventy-five taxa assigned to a genus lack assignment of a species
name; recorded as "sp.". Eight taxa represent species provisionally assignable to other recognized
species; recorded as "cf.". One conferrable genus is recorded. Seven questionable species assignments
are recorded with one specific variety noted.). Extinction levels for the Frasnian­
Famennian boundary are recorded for both species- and genus-levels and at stage- and
substage-levels of analysis (table]).
It is important to consider the level and units of anillysis to be used in the study of diversity.
Placoderm data suggest substage-level analyses are necessary to clearly evaluate subclade patterns.
The resolution of the individual data is less critical; however, this may be due solely to
the relatively low level of indeterminate taxa (4.6% indeterminate to genus and 5.7% with
questionable generic assignments) and taxa with poor stratigraphic resolution (6.8% not resolved
to series (epoch) and 11.9% resolved to series). Stage names follow those of DENISON (1978)
which are used in his compendium. No effort has been made to convert DENISON'S Early Devonian
stage names (Gedinnian and Siegenian) to current formal names (Lochkovian and Pragian) since
exact stratigraphic data is not available for an accurate conversion (refer to HARLAND et aI.,
1989, for a discussion of the relationship between formal names and those used by DENISON,
1978). Stage names for the last appearance data taken from SEPKOSKI (1992) follow those of
HARLAND et al. (1989).