Organismal metabolic rates reflect the interaction of environmental and physiological factors. Thus, calcifying organisms that record growth history can provide insight into both the ancient environments in which they lived and their own physiology and life history. However, interpreting them requires understanding which environmental factors have the greatest influence on growth rate and the extent to which evolutionary history constrains growth rates across lineages. We integrated satellite measurements of sea-surface temperature and chlorophyll-a concentration with a database of growth coefficients, body sizes, and life spans for 692 populations of living marine bivalves in 195 species, set within the context of a new maximum-likelihood phylogeny of bivalves. We find that environmental predictors overall explain only a small proportion of variation in growth coefficient across all species; temperature is a better predictor of growth coefficient than food supply, and growth coefficient is somewhat more variable at higher summer temperatures. Growth coefficients exhibit moderate phylogenetic signal, and taxonomic membership is a stronger predictor of growth coefficient than any environmental predictor, but phylogenetic inertia cannot fully explain the disjunction between our findings and the extensive body of work demonstrating strong environmental control on growth rates within taxa. Accounting for evolutionary history is critical when considering shells as historical archives. The weak relationship between variation in food supply and variation in growth coefficient in our data set is inconsistent with the hypothesis that the increase in mean body size through the Phanerozoic was driven by increasing productivity enabling faster growth rates.

Cellana ampla n. sp. from late Eocene rocks in Oregon is the first New World record of a genus and family heretofore considered to have radiated in Australia and the mid-Pacific. Re-examination of some other Eocene limpets from the Pacific Northwest reveals that species previously assigned to Acmaea belong in Patelloida and Siphonaria. Thus, all three major components of the modern Australian limpet guild were present in the late Eocene of western North America along a coastline occupied today by acmaeid limpet guilds. Re-examination of a large Pliocene ‘Patella’ from South America shows the shell structure of a Cellana and constitutes a second documentation of a large nacellid limpet in the New World Tertiary.

Although the taxonomy of modern limpets is founded on anatomical characters, shell structure characters are sufficient to identify genera and families directly in the fossil record. Re-evaluation and reclassification of fossil limpets using shell structure contributes not only to a better understanding of the phylogeny of major limpet groups but also provides a powerful tool for elucidating the evolutionary, biogeographic, and ecologic development of the complexly structured limpet guilds of differing taxonomic composition that dominate rocky intertidal habitats throughout the world.

Associations of bathymetrically anomalous fossils, a phenomenon particularly common in shallow-water, marine, Neogene faunas of the northeastern Pacific, have yet to be explained adequately. No known physical transport processes can selectively move species upslope from deep water into diverse nearshore, shallow-water habitats. Previously proposed biological explanations are based on undocumented phenomena. We document bathymetric anomalies in Recent mollusc accumulations on Southeast Farallon Island, California, that are created by the activities of diving marine birds. Application of these observations to patterns in the Neogene fossil record is direct, involving the same genera and often the same species. We argue that the process has occurred since at least the Miocene when diving marine birds radiated rapidly, probably in response to trophic resources created by intensive upwelling (Lipps and Mitchell 1976) and that they could have transported specimens upslope in sufficient quantity to have contributed anomalous species to the Neogene fossil record. Specific examples from the literature are discussed.

Kelps and other fleshy macroalgae—dominant reef-inhabiting organisms in cool seas—may have radiated extensively following late Cenozoic polar cooling, thus triggering a chain of evolutionary change in the trophic ecology of nearshore temperate ecosystems. We explore this hypothesis through an analysis of body size in the abalones (Gastropoda; Haliotidae), a widely distributed group in modern oceans that displays a broad range of body sizes and contains fossil representatives from the late Cretaceous (60–75 Ma). Geographic analysis of maximum shell length in living abalones showed that small-bodied species, while most common in the Tropics, have a cosmopolitan distribution, whereas large-bodied species occur exclusively in cold-water ecosystems dominated by kelps and other macroalgae. The phylogeography of body size evolution in extant abalones was assessed by constructing a molecular phylogeny in a mix of large and small species obtained from different regions of the world. This analysis demonstrates that small body size is the plesiomorphic state and largeness has likely arisen at least twice. Finally, we compiled data on shell length from the fossil record to determine how (slowly or suddenly) and when large body size arose in the abalones. These data indicate that large body size appears suddenly at the Miocene/Pliocene boundary. Our findings support the view that fleshy-algal dominated ecosystems radiated rapidly in the coastal oceans with the onset of the most recent glacial age. We conclude with a discussion of the broader implications of this change.

The species-level properties of geographic range and geologic duration are often used as variables in evolutionary studies. However, estimates of species duration are not independent of estimates of geographic range. Before these properties are used in macroevolutionary hypotheses, error associated with these estimates must be quantified. This error may lead to spurious inferences of evolutionary processes. To assess the error associated with estimates of geographic range and geologic duration, we modeled various sampling regimes and calculated the bias associated with these estimates.

We present three analyses which document the bias associated with estimates of geographic range and geologic duration. First, we find a positive correlation between local abundance and geographic range for a sample of 180 species of Recent prosobranch gastropods from the northeastern temperate Pacific Ocean. Therefore, geographically short-ranging species are less likely to be represented in the fossil record than geographically long-ranging species because of their local rarity. Second, we demonstrate that the chance of underestimating the geographic range of a species is acute for species with restricted spatial distributions, further compounding the problem of documenting their distribution in space and time. Third, we present a simulation which quantifies the degree of autocorrelation between geographic range and geologic duration for different levels of sampling resolution and spatial distributions of fossil localities.

Phylogenetic analysis of the metazoan evolutionary tree as a whole, and of trees of component major clades, indicates that marine herbivores, defined here as macrophagous consumers of living multicellular attached marine plants, always occupy terminal positions at several scales of analysis. Nearly all living benthic marine herbivores are derived from microphages, detritivores, or predators, and most have post-Paleozoic origins. The derived nature of herbivory in the sea parallels the evolutionary situation among land animals. Pre-Mesozoic marine benthic ecosystems, characterized by relatively low rates of flow of energy and nutrients, may have relied even more heavily on decomposers for the transfer of carbon from primary producers to animals than do living marine ecosystems in the photic zone.

Collections from the basal part of the marine Eocene Tejon Formation, Tehachapi Mountains, southern California, reveal new stratigraphic occurrences of patellogastropod limpets. Reports of these gastropods from California Paleogene strata are uncommon. The Tejon limpets are all members of the tropical genus Patelloida. Four taxa are represented in 33 specimens from five localities. These taxa include: mature specimens of P. tejonensis (Gabb, 1869), the first occurrence of the Eocene P. vokesi (Hickman, 1980) outside of Oregon, and P. triquetrus n. sp., described herein. Our study shows that a hypotype referred to P. tejonensis by Anderson and Hanna in 1925 is actually a fissurelloidean species, and we tentatively reallocate it to the genus Megathura Pilsbry, 1890. Analysis of depositional settings indicates that nearshore, shallow-subtidal depositional environments have higher patellogastropod abundance and diversity than intertidal or offshore-subtidal depositional environments. Morphological convergence between Tejon and Recent patellogastropod taxa is documented. Resemblance of the Eocene P. triquetrus n. sp. and an indeterminate Patelloidea sp. to the Quaternary “Collisella” scabra (Gould, 1846) and Lottia digitalis (Rathke, 1833), respectively, is remarkable.

Patterns of bipolar or antitropical distributions occur in a diverse array of marine invertebrate, vertebrate, and plant groups in the eastern Pacific Ocean. Available geologic and paleontological evidence does not support vicariance as a process in the creation of these distributions but instead favors biotic interchange between hemispheres. Moreover, the timing of these events suggests several breaches (both northward and southward) of the tropics rather than a single event. The fossil record is extremely important in delimiting potential hypotheses and allowing correlation with vicariance events. The congruence of some interchanges with major regional tectonic activity and others with Pleistocene glaciations is not surprising and argues for a plurality of mechanisms. Extinction of endemic taxa following interchange among marine invertebrates is rare, and none of the antitropical distributions reviewed here suggests that the arrival of a taxon in the adjoining hemisphere resulted in the extinction of an endemic taxon. Instead, interchange and endemic taxa coexist. In contrast to the extinction patterns, the patterns of radiations are extremely diverse with some immigrant taxa undergoing remarkable radiations, whereas other taxa are represented by single species. Temperate nearshore rocky communities in both the northern and southern hemispheres appear to be mosaics of species that share common ancestry (because of interchange), are cosmopolitan, and have independent origins within the region. Although some communities appear to be organized around products of interchange (e.g., kelp forests of California and Chile), only the taxa have immigrated; linkages and interactions between species are independent and locally derived.

Protandric hermaphroditism, the sequential change from male to female, has been reported in several superfamilies of prosobranch gastropods including the Fissurellacea, Patellacea, Calyptraeacea, and Eulimacea (Webber, 1977). It is most common in members of the Calyptraeacea and the Patellacea. In the Calyptraeacea changes in sex are readily followed by observing copulative structures (Coe, 1944). Because patellacean limpets are predominantly broadcast spawners with external fertilization, external characters that can be used to determine the sex of individuals are rare. Hence, previous to this report the occurrence of protandry in most patellacean limpets has been based primarily on sexual dimorphism in size; the smaller size classes being made up of male individuals and the larger size classes of female individuals (Willcox, 1898; Orton, 1920, 1928; Orton, Southward & Dodd, 1956; Dodd, 1956; Branch, 1974). However, given this type of data it is often difficult to assess whether the observed sexual dimorphism is indicative of protandry or merely a result of differential growth and/or survival. The presence of simultaneous hermaphrodites in the intermediate size classes, as evidence of protandry is of limited value because simultaneous hermaphrodites occur sporadically in patellaceans that do not show a sexual dimorphism in size (Dodd, 1956; Branch, 1974). The only unambiguous way of proving the existance of protandry in patellacean limpets is the direct monitoring of gonadal changes in individuals through time. We report here the first direct observations of protandric hermaphroditism in a patellacean limpet.

Lottia gigantea Sowerby, 1834 is a large (100 + mm), territorial, intertidal limpet that ranges from northern California to central Baja California, Mexico (Stimson, 1970).

Achieving consensus on the definition of the Mollusca is fortunately not prerequisite to the exercise of taxonomic classification and phylogenetic analysis. Definitions emerge from analysis, and it is therefore germane to consider the ways in which analytic procedures and underlying assumptions may affect growth of knowledge of the Mollusca.

The “primitive,” “minor” or “lesser” classes of the Mollusca comprise four groups that are typically recognized at the class level in most classification schemes. These classes are: (1) the Aplacophora, (2) the Monoplacophora, (3) the Polyplacophora, and (4) the Scaphopoda. Members of these classes are bilaterally symmetrical and typically possess a ventral muscular foot and a dorsal epidermal tissue (the mantle) that secretes a calcareous covering. Between these two structures lie the viscera. The space that develops between the mantle and the foot of the mollusc is referred to as the mantle cavity. Into this cavity open the ducts from the excretory, alimentary, and reproductive systems; gills are also typically located in this space. The anterior end of these molluscs is marked by a muscular head in which most of the ganglia are concentrated. The mouth is situated ventrally and opens internally into the pharynx which contains, at its anterior end, the radula and its associated musculature and support structures. The intestinal tract is typically arranged in complex loops.