Christy C. Visaggi

Phanerozoic trends in the global diversity of marine invertebrates.

It has previously been thought that there was a steep Cretaceous and Cenozoic radiation of marine invertebrates. This pattern can be replicated with a new data set of fossil occurrences representing 3.5 million specimens, but only when older analytical protocols are used. Moreover, analyses that employ sampling standardization and more robust counting methods show a modest rise in diversity with no clear trend after the mid-Cretaceous. Globally, locally, and at both high and low latitudes, diversity was less than twice as high in the Neogene as in the mid-Paleozoic. The ratio of global to local richness has changed little, and a latitudinal diversity gradient was present in the early Paleozoic.

Variation in Composition and Abundance of Miocene Shark Teeth from Calvert Cliffs, Maryland

ABSTRACT Shark teeth are the most common vertebrate fossils found along the western shore of Chesapeake Bay at Calvert Cliffs in Maryland. The stratigraphic distribution of teeth within the cliffs has not yet been documented. We utilized museum collections of in situ teeth to access their distribution within stratigraphic beds and a large selection of float teeth retrieved from Calvert County beaches as a proxy for the distribution of teeth within stratigraphic beds and across underlying beaches. Museum collections provide 1,866 teeth recorded in situ; float collections yield a total of 24,409 teeth. These data sets offer different, but complementary, results. Miocene sediments along Calvert Cliffs comprise the Calvert, Choptank, and St. Marys formations. Over 96% of all teeth in the in situ data set derive from the Calvert Formation, likely due to favorable paleoenvironmental conditions for sharks. The non-uniform stratigraphic distribution of teeth is further supported by an uneven distribution of teeth collected on beaches below the cliffs. Samples from northern localities contained more float specimens; cliffs in this area are composed almost entirely of the Calvert Formation. Fifteen genera are represented in the in situ and float collections. The main constituents are Carcharhinus spp., Hemipristis serra, Galeocerdo spp., Isurus spp., and Carcharias spp. Most of these genera exhibit significant unidirectional trends in the proportional abundance of teeth across Calvert Cliffs beaches. Factors influencing these variations remain unclear, but the overall dominance of carcharhiniforms over lamniform and other sharks observed for the Miocene persists in modern nearshore environments.

THE INFLUENCE OF DATA SELECTION AND TYPE OF ANALYSIS ON INTERPRETATIONS OF TEMPORAL STABILITY IN OLIGOCENE FAUNAS OF MISSISSIPPI

Abstract Fossiliferous shallowing-upward parasequences in the early Oligocene Byram Formation of Mississippi provide an ideal opportunity to explore the effects of differences in data preparation, format, and analysis in testing for faunal persistence. Ten replicate bulk samples collected from each of three lithologically similar horizons in successive parasequences yielded >13,000 molluscan individuals. Assemblages were first compared using more traditional descriptive statistics that examined aspects of taxonomy, abundance, and guild structure, and were then compared using multivariate techniques with similarity coefficients that employed both compositional and abundance data. Different procedures for identifying and excluding rare taxa prior to analysis were also investigated. Simple numerical methods emphasized similarities among assemblages; hierarchical clustering, nonmetric multi-dimensional scaling (NMDS), and analysis of similarities (ANOSIM) revealed differences among the faunal horizons. Multivariate tests indicated stasis only when using presence-absence data with a large number of rare taxa excluded. When abundance data are utilized, however, faunal change through time is suggested, regardless of how rare taxa are treated. The choice of data format, rare taxon exclusion policy, and analytical approach all affect the interpretation of results and the outcome of hypothesis tests for stability, suggesting that differences in methodology partly contribute to disagreement among studies examining faunal persistence. Furthermore, various properties related to ecosystem structure are ascribed different degrees of importance depending on the study. Thus, comparisons of patterns should be made on equal footing to ensure that differences in methodology are not contributing to differences in interpretation.

The Mismeasure of Behavior: A Natural History Revision of Prey Preference in the Banded Tulip Snail

ABSTRACT The banded tulip snail, Fasciolaria (Cinctura) lilium hunteria (Perry), is a predatory gastropod that is capable of subduing a wide range of prey items using multiple attack behaviors. However, the literature contains conflicting accounts of this predators prey preferences, which vary between the extremes of strong preferences for snails over bivalves to opportunistic behavior in which prey are incorporated into the diet based on their relative abundance in the environment. Here we reexamine the extent to which prey items in the diet of F. hunteria are distributed in preference hierarchies to update the natural history data on this molluscan predator. We tested F. hunterias preference between oysters, Crassostrea virginica (Gmelin), and snails, Urosalpinx cinerea (Say), two ecologically co-occurring prey items that require different attack behaviors to subdue. Based on cost-benefit analyses, U. cinerea is more energetically profitable than C. virginica, so we predicted that it should be favored by tulip snails. We offered both prey simultaneously to F. hunteria in a Y maze to test this hypothesis. Despite the vast differences between the prey items in terms of potential biomass reward, handling times, and risk to the predator, F. hunteria did not prefer either C. virginica or U. cinerea, live or crushed. Our results suggest F. hunteria has no strong preferences among prey items in its diet, and is an opportunistic predator. This study is an example of the necessity of revising natural history information at a time when accumulation of such data is declining. In light of our results, we discuss the importance of examining the sources of natural history information, and of considering the time period and theoretical framework in which natural history data were gathered and interpreted to prevent cascading error effects resulting from the use of flawed natural history observations.

Training Tomorrow’s Conservation Paleobiologists

Conservation paleobiology (CPB) is committed to the mission of applying geohistorical records to the conservation and restoration of biodiversity and ecosystem services. Fulfilling this mission remains challenging because most conservation paleobiologists have not been trained to translate their science into management practice and policy. Ongoing discussion among conservation biologists provides lessons applicable to training tomorrow’s conservation paleobiologists. We offer six recommendations for more effective training in conservation paleobiology: (1) integrate CPB into truly cross-disciplinary conservation curricula; (2) promote a problem-solving and policy-oriented approach to CPB education; (3) implement hands-on experience in real-world settings; (4) promote informal opportunities for cross-disciplinary interaction; (5) establish connections among stakeholders; and (6) modify faculty incentive systems to reward CPB activities. Institutional constraints make implementation of these recommendations challenging, and development of CPB programs will involve tradeoffs. Despite these challenges, the approach we propose will better prepare tomorrow’s conservation paleobiologists to function effectively in the conservation world.