RECENT ADVANCES IN DECAPOD STUDIES: SHRIMP, LOBSTERS, AND ANOMURANS

Research on decapod Crustacea has exploded in the past three decades. The result has been a proliferation of data based and specimen based studies providing new and significant outcomes. Development of a database has now progressed to the point of having temporal and geographic records of every known species of fossil decapod. The bias in intensity of study of the fossils from the Northern Hemisphere has been mitigated to some extent by intense work in the Southern Hemisphere; nonetheless, the disparity continues to exist. The database makes it possible to examine patterns of diversity at all taxonomic levels within the order. Analysis of diversity patterns of astacoid and palinuroid lobsters show similar patterns, suggesting that the possession of claws was not necessarily the key factor in the Mesozoic expansion of the lobsters. Development of phylogenies based upon paleontological, adult morphological, and molecular data has resulted in several hypotheses within the last decade and a meta-analysis is currently in development. Specimen based studies conducted by workers primarily in Europe and North America have rapidly expanded the number of family-, genus-, and species-level taxa. Some of the new discoveries have yielded amazing results. Discovery of a dendrobranchiate shrimp from the Late Devonian of Oklahoma extended the range of that group from the Triassic back to the mid-Paleozoic. A new species of crayfish from the Eocene of British Columbia exhibits a spectrum of characters diagnostic of the southern Hemisphere Parastacidae. This discovery raises some perplexing questions of dispersal patterns or homology. Re-examination of what was previously thought to be the oldest brachyuran confirms that, in fact, it is an anomuran. The range of that group was extended into the Late Triassic based upon discovery of a new family of Anomura from the United Arab Emirates. Another group of anomurans, the galatheid squat lobsters, experienced an explosive radiation in reefal environments in the Late Jurassic. Phylogenetic, biogeographic, and morphologic studies on the shrimp, lobsters, and anomurans has shed new light on their evolution, systematic placement, and geographic distribution. Research supported by NSF EF 0531670 to Feldmann and Schweitzer.