Calliostoma ligatum shells inhabited by hermit crabs were weaker than shells inhabited by snails collected at the same locality. When shells of C. ligatum were loaded repetitively to 80% of their predicted failure load, hermit crab-inhabited shells showed an immediate drop in shell strength followed by a progressive further loss of shell strength over the next 18 days. Snailinhabited C. ligatum shells exhibited a decrease in strength after 9 days, but returned to initial values within 18 days of loading.

Hermit crabs thus bear shells significantly weaker than they were when borne by the gastropods that produced them. Reported similarities in vulnerability of gastropods and hermit crabs to shell-crushing predators may be artifacts of the metric (critical size) used to compare vulnerabilities. Hermit crabs probably were a significant factor in the diversification of durophagous predators in the Mesozoic, supplying a prey base identical in size and shape to gastropods but with significantly lower resistance to crushing. The unpredictability of strength in hermit-crab inhabited shells may maintain the apparently inefficient indiscriminate attacks common among durophagous predators.

Dickinsonia is reconstructed as a benthic polypoid of generally cnidarian design. The oral surface was without tentacles but contained a median oral slit that probably led through a pharynx into an enteron, which was divided into digestive diverticulae by radiating mesenteries; feeding may have been via ciliary tracts. The mesenteries and body wall contained a stiff form of mesogloea. There seems to be no need to postulate a novel constructional grade for this organism, bringing the concept of the Vendozoa into question.

New evidence from fossil plants at the Middle Miocene fossil quarry near Fort Ternan, Kenya, together with that from paleosols, allow reconstruction of a mosaic of early successional woodland (on Dhero paleosols), grassy woodland (on Chogo clay eroded phase and ferruginized nodule variant paleosols) and wooded grassland (on type Chogo and Onuria clay paleosols). This grassy open vegetation was on a high plateau of phonolite at the foot of a carbonatite-nephelinite stratovolcano, which probably supported dry Afromontane forest, alpine meadows, and marsh. This earliest savanna-mosaic vegetation yet documented from Africa, was probably recruited from dry lateritic soils elsewhere in Africa during climatic drying and cooling some 15 Ma. These early grassland ecosystems were very different from Early Miocene forest ecosystems of East Africa, but not altogether like modern grasslands either. Already present were grasses with dense growth and rich in silica bodies, and abundant antelope with moderately high crowned teeth and cursorial limb structure. These mammalian adaptations to grasslands, however, were not nearly so pronounced as they are in modern African grassland faunas, which include zebra and other Asiatic immigrants, as well as antelope. Grasses of the subfamily Chloridoideae and supertribe Panicanae were common in tropical Africa by Middle Miocene time, if not much earlier, but there is not yet evidence so far back in time for the grass supertribe Andropogonae which is now dominant in seasonally arid, overgrazed, and burned African grasslands.

Ecologists attempt to explain species diversity within Recent seabird communities in terms of Recent oceanographic and ecological phenomena. However, many of the principal oceanographic processes that are thought to structure Recent seabird systems are functions of geological processes operating at many temporal and spatial scales. For example, major oceanic currents, such as the North Pacific Gyre, are functions of the relative positions of continents and Antarctic glaciation, whereas regional air masses, submarine topography, and coastline shape affect local processes such as upwelling. I hypothesize that the long-term development of these abiotic processes has influenced the relative diversity and community composition of North Pacific seabirds. To explore this hypothesis, I divided the history of North Pacific seabirds into seven intervals of time. Using published descriptions, I summarized the tectonic and oceanographic events that occurred during each of these time intervals, and related changes in species diversity to changes in the physical environment. Over the past 95 years, at least 94 species of fossil seabirds have been described from marine deposits of the North Pacific. Most of these species are from Middle Miocene through Pliocene (16.0-1.6 Ma) sediments of southern California, although species from Eocene to Early Miocene (52.0-22.0 Ma) deposits are from Japan, British Columbia, Washington, and Oregon. During the history of the North Pacific seabirds, thee were many widespread (global) and local (California Current) oceanographic events, but the underlying physical processes that affected the diversity of seabirds throughout the North Pacific were tectonic changes that led to sequential stages of thermal isolation and refrigeration of Antarctica. Besides these broad-scale phenomena, the uplift of the Isthmus of Panama and the initiation and intensification of coastal upwelling in the California Current directly affected the diversity of seabirds in southern California. For the most part, Middle to Late Miocene and Pliocene seabird faunas from California resembled Recent communities, but with several exceptions: (1) the extreme diversity and abundance, but subsequent extinction of gannets (Morus) and flightless alcids (mancallids); (2) the comparatively low abundance and diversity of cormorants and shags (Phalacrocoracidae) until the Late Pliocene; and (3) the absence of marine Laridae until the Late Pliocene. By affecting both the physical and biological environments, geological factors such as Antarctic glaciation, eustatic changes in sea levels, and local tectonic activities influenced and will continue to influence the structure of seabird systems in the North Pacific.

A phylogeny of Cretaceous Montastraea-like corals was constructed and used to evaluate the importance of differential speciation, selective extinction, and developmental constraints in the evolutionary history of the clade. Colonies assembled from localities across the central and western Tethyan region were subdivided into four stratigraphic levels: (1) Neocomian to lower Albian, (2) upper Albian to Cenomanian, (3) Turonian to Campanian, and (4) Maastrichtian. Ten corallite characters were measured on transverse thin sections of each colony, and analyzed following a three-step procedure: (1) species were recognized using all-inclusive average linkage cluster analyses (UPGMA) and a series of iterative canonical discriminant analyses; (2) species were separated by stratigraphic level and linked between levels by comparative analysis of the resulting discriminant scores; and (3) ancestor-descendant relationships were interpreted within and among adjacent levels using phenetic and cladistic approaches. A composite tree was then examined with respect to biogeography.

The results suggest that a total of 16 species existed during the Cretaceous, only 2 of which extended between stratigraphic levels. Speciation events between levels 1 and 2 were associated with the radiation of “small-corallite” forms from a “large-corallite” form, as its distribution expanded southward into the Tethyan realm. Limited speciation and stasis predominated among species within the clade between levels 2 and 3. Speciation events between levels 3 and 4 were associated with the radiation of predominantly “large-corallite” forms from a “small-corallite” form, as the clade became restricted to the Caribbean. Extinction initially focussed on “small-corallite” forms, but later shifted to “large-corallite” forms. Morphologic change was constrained between two extremes, the lower limit of which involved a minimum corallite diameter possibly set by developmental or ecological constraints, and the upper by limitations to increases in number of septa. The overall net result was that of nonprogressive evolution within the clade.

The mass, wingspan, and wing area of pterosaurs were reconstructed. Mass was estimated by determining volume and multiplying by avian density. This method was considered appropriate only for smaller pterosaur species because there is evidence for lower density in larger species. These reconstructions were used to compare the wing shapes of Triassic and Jurassic pterosaurs with those of birds. Pterosaurs had wings of below-average loading and above-average aspect compared to the avian mean. This wing design was compatible with relatively slow and highly efficient flight, with high maneuverability. Wing area depends on the reconstruction model adopted; wings attached to the hindlimb principally reduced aspect, and secondarily reduced loading, which would improve take-off performance at the expense of efficiency. The wing shape and cranial feeding adaptations of pterosaurs were most compatible with a marine or aerial predatory adaptive zone. The reconstructed pterosaurs show a limited range of wing shape compared to birds. This may partly reflect preservational bias favoring species living in marine or lagoonal environments, but this is not a complete explanation because there is a lack of pterosaurs with wings of high loading like the marine ducks and auks. Structural, physiological, or adaptive factors may have limited pterosaur wing shape.

A biomechanical study of archaeocyathan (phylum Archaeocyatha) skeletal construction was undertaken in order to compare its function with that of poriferans. Flume experiments were conducted on three cylindrical, brass models of regular archaeocyathans. Two of these, the porous-septate and aporous-septate models (i.e., possessing septa either with or without pores), represent an ontogenetic series; regular archaeocyathans (class Regulares) typically exhibit a reduction in septal porosity as they grow and many have aporous septa as adults. The third model is aseptate and represents a morphology that is not found in the fossil record. All models exhibit passive entrainment of flow during flume testing, a phenomenon on which modern sponges depend for suspension feeding. Flow direction through the models is consistent with predictions of the spongiomorph-affinity hypothesis. The three models behave quite differently, however. The aseptate model is least effective at passive entrainment. Although some fluid exits the top of the central cavity (or osculum), a great deal of fluid is entrained out the top of the intervallum and also leaks out the outer wall. Flow induction from the oscula of the septate models is augmented when compared to the aseptate model. The porous-septate model exhibits slight leakage from the outer wall, and a dye-rich plume exits the top of the intervallum. Alternatively, the aporous-septate model exhibits no outer-wall leakage and no entrainment from the intervallum. These differences in flow pattern between the porous- and aporous-septate models suggest a hitherto unknown function for septa. Imperforate septa prohibit the migration of fluid through the intervallum to the low-pressure, downstream side where leakage occurs. The ontogenetic shift in septal porosity, common to many archaeocyathan species, may be a mechanism by which outer-wall leakage is avoided later in life. Archaeocyathans would have encountered progressively higher ambient current velocities as their height increased through growth. Outer-wall leakage is not a problem at low velocities or small sizes, but leakage becomes serious at higher velocities when tall, adult morphologies are attained.