Long-term persistence of patterns in geographic variation within species is an interesting and puzzling phenomenon. I present a well-defined natural experiment in the land snail Cerion agassizi from the islands of Great Bahama Bank. C. agassizi is the best-known fossil of the ca. 120,000 years BP dunes of New Providence, Cat and Eleuthera Islands; populations have survived on Cat and Eleuthera. During the Wisconsin glacial advance, all these islands joined together in an emergent bank. Presence of the same species on two islands at two times permits a test for both time signatures (does change occur in the same manner on both islands) and island signatures (do aspects of shell phenotypes remain constant on each island through time).

Factor and discriminant analyses establish morphological separations among fossil populations of the three islands. These differences occur along pathways specified by well-known covariance sets in the complex allometric ontogeny of Cerion. By these routes, small variations in the geometry of growth may be magnified to large differences in external appearance. I found a time signature, probably attributable to introgression of modern populations by Cerion glans on both Cat and Eleuthera. Despite the intermediate period of emergence and joining of all islands, I also found an island signature in the preservation through time, on both Cat and Eleuthera, of the differentia that separate fossil populations. The basic distinctions of the two islands, expressed as patterns of covariance in growth, have been stable for at least 120,000 years.

We propose that the kelps (Laminariales) radiated in the North Pacific following the onset of late Cenozoic polar cooling. The evidence is that (1) extant kelps occur exclusively in cold-water habitats; (2) all but one of 27 kelp genera occur in the North Pacific, 19 of these exclusively; and (3) limpets and herbivorous marine mammals obligately associated with kelps or other stipitate brown algae appeared late in the Cenozoic, even though more generalized forms of both groups are much older. We propose, further, that sea otters and perhaps other groups of benthic-feeding predatory mammals, whose late Cenozoic distributions all were limited to the North Pacific, created an environment for the evolution of kelps in which the intensity of herbivory was unusually low. We hypothesize that this interaction created predictable differences among habitats in the intensity of herbivory on several spatial scales, with resulting trade-offs between anti-herbivore defenses and plant competitive abilities in their respective floras. Sea otters incur time and energy costs for diving, resulting in depth-related reductions to foraging efficiency and thus increased sizes and densities of herbivorous sea urchins. Thus, the deep-water flora is well defended, but competitively subordinate, compared with the shallow-water flora. Similarly, we argue that during the same period of earth history, predation had less of a limiting influence on herbivorous invertebrates in the temperate southwestern Pacific. We hypothesize that (1) consequent biogeographical differences in the intensity of herbivory may have selected the phenolic-rich brown algal flora in temperate Australia/New Zealand; and (2) tightly coevolved plant/herbivore interactions may explain why Australian and New Zealand herbivores are undeterred by phenolics and why other classes of secondary compounds in the Australian/New Zealand flora significantly deter herbivores.

The Cretaceous–Tertiary (K–T) extinction reduced the gamma diversity of molluscs on the U.S. Gulf Coast from over 500 species in the late Maastrichtian to a little over 100 species in the early Danian. Gamma (total) diversity increased in a series of steps that generally tracked temperature, to a high of around 400 species in the late Middle Eocene, at which time diversity declined in the Late Eocene–Oligocene extinctions. The molluscan radiation occurred in at least two distinct phases: 1) an Initial Radiation Phase in which certain families underwent unusually high speciation, apparently filling ecological niches vacated by the extinction, followed by extinction of many of the species in these families in the late Danian; and, 2) a Secondary Radiation Phase where gamma diversity gradually increased and new genera gradually appeared. The fact that the gamma diversity of molluscs did not reach pre-extinction levels before the next extinction in the Late Eocene suggests that molluscan faunas may spend much of their evolutionary time recovering from these extinctions.

Lunules have evolved independently in several groups of clypeasteroids, including the Rotulidae, Astriclypeidae, Mellitidae and Scutasteridae. In this paper, only the monophyletic assemblage Monophorasteridae plus Mellitidae is considered. Lunules result from modifications of the growth patterns of test plates which bring about changes in relative growth in specific directions. It is unnecessary to postulate resorption of the test. Ambulacral lunules, which are known to have hydrodynamic functions, originated as part of a series of changes: 1) bifurcation of food grooves, 2) formation of pressure drainage channels, 3) lobulation of the ambitus (as in Monophoraster), 4) complete lunule formation. The anal lunule shares the hydrodynamic function but arose separately, as a developmental aberration. The position of the periproct is highly variable but it is most commonly located at the junction of suture lines, at plate corners. In Scutella it is located between the first and second post-basicoronal plates. In Monophoraster the periproct is located further forward, between the first post-basicoronal plates, and the small anal lunule occupies the junction point between first and second post-basicoronals. It is hypothesized that the anal lunule originated as an all-or-nothing event following the forward migration of the periproct and failure to resume normal plate growth at the sutural junction point between first and second post-basicoronal plates. Its walls were derived from paired interambulacral supports. The hypothesis is discussed in connection with the ontogenetic formation of the anal lunule in living mellitid sand dollars.

Because the paleontologic concept of Coccolithophoridae species is restricted and far removed from the biologic concept, which itself is not yet satisfactorily established, calcareous nannofossil taxonomy remains in an unsatisfactory state. This situation is clearly reflected by various authors' widely different interpretations of the phylogenetic relationships among species in a given genus and among genera. Examples taken from the extant genus Helicosphaera suggest that because of parallel evolution, delineation of phylogenetic relationships among coccolith morphospecies using morphologic data alone are hazardous, as is delineation of phylogenetic relationships among closely related genera.

Seven taxa of raptorial birds were experimentally fed a controlled sample of 50 house mice (Mus musculus). Bones recovered from the pellets were examined for interspecies variability in preservation to assess the potential contribution of specific raptors to patterning in fossil assemblages. Quantitative analyses demonstrate that patterns in bone fragmentation may assist in the identification of particular raptor species as depositional agents in small mammal assemblages.

The ability of paleobiologists to draw paleoecological inferences based on spatial faunal variability within a single stratigraphic interval depends ultimately on the spatial resolving power of the fossil record. This paper evaluates the potential spatial resolution of fossil assemblages by examining modern skeletal remains of molluscs on a benthic transect, along which there is a marked decrease in seagrass cover, in Smuggler's Cove, St. Croix, U.S. Virgin Islands. The sampling transect began in a Thalassia-covered area approximately three meters deep, extended into slightly deeper water with lighter seagrass cover, and ended on an open, bioturbated sandy tract at a depth of nearly six meters.

Two-way cluster analysis and polar ordination of 37 samples of molluscan remains, taken at 10-meter intervals along the 360-meter transect, reveal patterns of variation that are shown by correlation analyses and consideration of the autecologies of individual species to be related to measured changes in vegetation. There is a transition from dominance primarily by epifaunal gastropods living on seagrass blades to dominance by infaunal, burrowing bivalves as grass cover becomes lighter. Some non-systematic variability exists in faunal distributional patterns within areas where the environment does not vary systematically, but this does not mask the regular faunal transitions related to environmental changes. Correspondence between the dead and live faunas is difficult to ascertain because of the scarcity of live fauna in collected samples.

The results suggest that spatial faunal transitions in fossil remains at even the fine scale evaluated in this study are potentially preservable in the fossil record.