The extent to which origination and selective extinction influenced the structure and dynamics of Caribbean coral reef communities is evaluated by comparing the diversity and distributional patterns of coral species in two Dominican Republic reef sequences prior to and following late Cenozoic Caribbean faunal turnover. The two sequences consist of the late Miocene Arroyo Bellaco reef of the Cibao Valley, northern Dominican Republic, and the late Pleistocene 125-ka reef terrace of the southern Dominican Republic. Samples were collected along 20-meter transects (10 Miocene, 10 Pleistocene); species identifications were made using standard sets of characters and morphometrics. In particular, species of Montastraea annularis-like corals were distinguished within each sequence using a 2-dimensional landmark technique involving average linkage cluster analysis, discriminant analyses, and non-parametric tests. Four Miocene and four Pleistocene species were recognized. Subsequent community analysis was two-fold: (1) whole coral community, and 2) distribution of the Montastraea “annularis” complex.

For the whole coral community, occurrence matrices of transect samples, assembled separately for Miocene (35 species) and Pleistocene (20 species) reef sequences, were analyzed using average linkage cluster analysis, multidimensional scaling, similarity percentages, one-way analysis of similarity, and non-parametric tests for independent samples (Mann-Whitney U, Kruskal-Wallis H). Three assemblages were recognized within each sequence, which correspond with back-reef, reef-crest, and reef-front facies defined independently on the basis of sedimentological criteria. Comparisons between the two sequences suggest that widespread species (ecological generalists) are more common within the Pleistocene sequence than within the Miocene sequence. Fifteen of thirty-five (43%) Miocene species occur in single reef facies compared to five of twenty (25%) Pleistocene species. Of the five species found within both reef sequences, four occur in all three of the identified Miocene reef facies; one was found in two of these three facies.

For the distribution of the Montastraea “annularis” complex, samples of M. annularis-like corals were examined to determine if distributional patterns of species within the complex were similar before and after faunal turnover. The four M. annularis-like corals identified within each reef sequence had markedly different distributional patterns. During the late Miocene, cohabitation within reef facies was low. Following faunal turnover, cohabitation within facies increased. This result further suggests that niche partitioning may have been reduced on post-turnover reefs.

The results support the hypothesis of selective extinction of ecologically restricted species during Plio-Pleistocene turnover. Despite the prolonged and continuous nature of faunal turnover, reef community change involved more than species replacement–the underlying structure of reef communities and their biological interactions were fundamentally altered.

Estimates of species abundance used to quantitatively describe paleocommunities are more precise and more reliable when sampling effort is distributed among many small replicate samples, rather than concentrated in the collecting of one or a few large samples. This is because sampling error is introduced by the patchy distribution of individuals within a fossil deposit. This study applies a dispersed sampling protocol to compare the fossil assemblages preserved within a marine shell bed at two different localities of the Upper Cretaceous Navesink Formation in east-central New Jersey. A spatial hierarchy of small bulk samples (replicate samples collected along an outcrop, samples from different outcrops within a locality, and samples collected from two different localities) reveals the magnitude and scale of patchiness in the distribution of macrofauna in the Navesink shell bed. Species abundance is highly variable between replicate samples and moderately variable between outcrops due to small scale patchiness. Nevertheless, estimates of species abundance generated by collecting across the patches at each locality reveal that the overall species abundance distribution for the Navesink shell bed is nearly identical between the two localities. When collecting effort is dispersed among many widely distributed samples, different patches of fossil remains are sampled and contribute to the overall estimate of average composition obtained for a locality. Comparisons of fossil assemblages between localities or horizons are rendered more reliable by decreasing the probability that compositionally different patches have been sampled within otherwise identical paleocommunities. The significance of differences detected between local paleocommunities can be assessed more confidently when replicate samples provide a measure of local variability arising from patchiness. Paleontologists sampling to describe the species abundance composition of a discrete region of a stratigraphic horizon (e.g., outcrop, locality) should define the spatial scale of the region they are describing and disperse their sampling effort within that region.

Based on study of modern foraminifera, changes in test porosity of ancient planktic foraminiferal specimens may be interpreted to reflect primarily changes in water temperature. To test this hypothesis, planktic foraminiferal porosity data (percent pore space per unit area) of Hedbergella delrioensis from three localities in the Cretaceous Western Interior basin were analyzed in the context of basin history (e.g., relative sea-level). These data record spatial and temporal changes in water masses at the average living depth of H. delrioensis. A significant increase in porosity between the upper Cenomanian M. mosbyense biozone and lower S. gracile biozone suggests an increase in water mass temperature, reflecting northward advection of a central core of warmer (less dense) water into the central seaway. The spread of this water mass toward the north, and laterally east and west, correlates with an independent record of rising sea-level. In addition to this secular porosity trend, higher frequency fluctuations may reflect transient oceanographic events related to changes in sea-level or circulation. In this study, porosity measurement was improved utilizing a scanning electron microscope and image analysis software. The work confirms prior results that as few as five foraminifera are required to produce a statistical assessment of average sample porosity. Use of pore concentration (number of pores per unit area), previously suggested as a temperature proxy, was not supported. The major interpretative contribution is a temporally precise record of spatial changes in Western Interior water masses.

The benthic ecosystem off the northeastern Adriatic coast is composed largely of clades characteristic of Sepkoski's Modern Fauna. However, across broad expanses of fine-sediment substrate, attached epibenthic suspension feeders strongly dominate in some areas and are co-dominant with mobile epibenthic deposit feeders in other areas. Preservation of skeletal residues in these areas would be composed largely of remains of attached suspension feeders. Therefore, although composed largely of Modern Fauna clades, the benthic ecosystem and its potential fossil remains reflect Paleozoic rather than post-Paleozoic ecology. This Paleozoic-style benthic ecology corresponds with low-nutrient water, low intensity of grazing predation, and relatively few endobenthic bioturbators, all of which were more characteristic of Paleozoic than post-Paleozoic seas. The thriving epibenthic attached suspension-feeding benthos in the northeastern Adriatic apparently results from the interaction of all or a subset of these three conditions.

Twelve peat clasts were recovered from a paleochannel deposit on Skidaway Island, Chatham County, Georgia. An AMS radiocarbon date from a plant stem in one of these clasts indicates original peat deposition 36,830 ± 340 ¹⁴C years B.P., and the stratigraphic position of the clasts supports this age assignment. Fossil Pinus needles, pollen, and testate amoebae provide a snapshot of the environment and biota at a time when most other sites in coastal Georgia were not accumulating sediment. Pollen from the peat clasts is dominated by Pinus and other genera common on the coastal plain today (e.g., Quercus, Carya). Morphological and anatomical analyses of the fossil Pinus needles indicate they are either Pinus taeda or Pinus serotina, which both currently inhabit the Coastal Plain of Georgia. Seven testate amoeba taxa, all characteristic of relatively dry peatland conditions, were encountered in the clasts. Testate amoeba assemblages are dominated by Hyalosphenia subflava, a taxon that is not typically dominant in modern assemblages. More investigations describing the occurrence and distribution of Quaternary testate amoebae, as well as modern ecology and biogeography of testate amoebae, are necessary before the significance of these assemblages can be assessed fully. Deposition of the peat clasts occurred at a time when pollen evidence from Florida indicates warm and wet climatic conditions, and the paleoecology of the peat clasts indicates that a relatively warm climate also existed in coastal Georgia.

An ichthyosaur discovered in the Ultima Esperanza Province, southern Chile, is the southernmost specimen of this group yet discovered in South America. The incomplete fossil consists of 17 vertebrae and associated neural arches and ribs. Occurring within a large block in glacio-fluvial sediments adjacent to the Campo de Hielo Patagónico Sur, the remains cannot be given a species designation nor be dated with precision or tied to one specific formation at this time. However, the rock type, geologic occurrence of the block, and glaciology of the sector enable the material to be placed within the upper part of the Middle to Upper Jurassic Tobifera Formation or the Lower Cretaceous Zapata Formation. Although the fairly broad stratigraphic range and limited fossil material hamper careful stage-level paleobiogeographic analysis, this occurrence documents the existence of ichthyosaurs in the now closed Rocas Verdes back-arc basin. This occurrence extends the distribution of ichthyosaurs in South America some 1500 km south of previously reported fossil material. The fossil provides support for the existence of a possible migration seaway between southern South America and western Africa during the Late Jurassic associated with the breakup of the southern sector of Gondwana. This seaway would be the southern counterpart to the Hispanic Corridor that connected the Pacific to the west Tethys around the northern end of South America.

The meter-grid system, using spikes hammered into the quarry floor as grid nodes, is a common way to map paleontological and archaeological excavations. This method is invasive to the fossil-bearing horizon and can damage or even destroy buried specimens. This potential is greatest when the site is characterized by high bone concentrations, and/or specimen/matrix friability. A new portable mapping system based on a floating-grid was developed to circumvent these problems. This system also is well suited for excavations with uneven quarry floors. The floating-grid system extends over a quarry using retractable wires and mobile posts. It employs a mapping square that hangs from wires extended from a back wall or rebar posts.