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A CENTRAL goal of paleontological research on the marine biota of tropical America is to recognize and interpret evolutionary patterns associated with closure of the Central American Isthmus, and more broadly with regional environmental changes caused by the developing barrier (Cronin, 1985; Vermeij, 1987; Jung, 1989; Jackson et al., 1993, 1996a; Collins and Coates, 1999). Much of the work to date has focussed on documenting large-scale trends in biodiversity over the past 25 million years (e.g., Budd and Johnson, 1999; Cheetham et al. 1999; Jackson and Johnson, 2000); however, the underlying systematics of most taxa used in this research has yet to be articulated, and much of the phylogenetic framework essential for interpreting the causes of patterns has yet to be formulated (Vermeij, 1997). The 16 papers in this special issue represent a first step in this direction. Most of the studies included herein have only just begun, and collectively, they cover only a minute fraction of the total biota. Many are based on collections that were made over the past 20 years by two large multidisciplinary team projects, the "Neogene Paleontology of the northern Dominican Republic" or "DR" project (Saunders et al., 1986, and subsequent monograph series in the Bulletins of American Paleontology; Cheetham, 1986) and the "Panama Paleontology Project" or "PPP" (Coates et al., 1992; Jackson et al., 1996a; Collins and Coates, 1999). Both projects use rigorous sampling methods (Jackson et al., 1993) and highresolution age-dating techniques (McNeill et al., 2000), but have yet to explore the effects of taxonomic practice on biodiversity estimates. In organizing this issue, we hope to stimulate interest in the systematics of taxa in the collections, and to encourage indepth analyses of their morphology and evolution.
The articles in this issue reflect the diversity and nature of current research on the systematics of the fossil marine taxa of tropical America. These taxa consist of a broad array of organisms, including foraminifers, corals, bryozoans, mollusks, echinoderms, and fish. All are examined at the species level; however, numbers of species per article vary from < 10 to > 100. Similarly, individual articles range in scope from species complexes (Budd and Klaus) and geminate species pairs (Marko and Jackson) to genera (Cheetham et al., Roopnarine, Tschudin) to families and superfamilies (Beu,...