The conductance of water vapor and respiratory gases by diffusion through the eggshells of Upper Cretaceous dinosaurs has been estimated from measurements of shell and pore geometry in fossil specimens. When compared to recent reptile and bird eggs for which nest environments are known, the highly porous eggshells of three dinosaur species indicate that the dinosaur nests were high in humidity and probably low in oxygen and high in carbon dioxide. Such conditions most likely occurred underground or within an incubation mound.

By isolating the eggs from the atmosphere, however, some large sauropods may have been forced to limit their clutch size to numbers small enough to prevent depletion of oxygen and elevation of carbon dioxide to intolerable levels in the nest. Fossil evidence supports this and suggests that one sauropod actually divided her large eggs into several clutches. Each small clutch probably had a metabolic rate similar to those of clutches produced by recent reptiles and mound nesting birds.

Interpretations of vertebrate paleoecology depend on knowledge of taphonomical processes which alter the composition of the preserved fossil assemblage from that of the original community. Study of the potential fossil record of a recent mammal community in Amboseli National Park, Kenya, shows the effects of some of these biasing processes and demonstrates how a bone assemblage on a modern land surface can be a source of past and present ecological information. In the bone assemblage, species presence or absence and relative abundance differ from recorded living species occurrences and population sizes: only 74% of the extant species in the basin are identified in the bone sample, and carcass abundances vary significantly from known population sizes of the major herbivore species. Both biases appear to be strongly correlated to body size, and this results from greater destruction of bones of smaller animals within the weight range from about 1-1000 kg. This size-biasing against small species appears to be due primarily to the greater susceptibility of small bones to destruction by carnivore mastication, breakage through bioturbation (trampling), and physical and chemical processes of weathering. Size-biasing resulting from such primary processes can thus be inherited by buried bone assemblages whatever their final mode of deposition. The bone assemblage also provides information on the spatial distributions of the major herbivore species over six major habitats. Patterns of strong habitat specificity are accurately represented in the bone assemblage. However, the record for certain species is affected by their seasonal and diurnal habitat shifts so that their bone distributions do not match live census data. The Amboseli bone assemblage provides a modern analogue for taphonomical processes which may have affected fossil assemblages derived from paleo-land surfaces prior to fluvial transport. It also helps to define limits of resolution in interpreting paleoecological information from such fossil assemblages.

The faunas of three fossil sites in Africa that contain time successive groups of fossil Hominoidea have been analyzed to determine their paleoenvironments. The basis for the analysis is an assessment of the ecological diversity of the fauna, which is expressed in terms of four categories: taxonomic composition, body size, feeding habits and locomotor zonal adaptation. This method has shown that the community structures of the three fossil faunas are significantly different, and comparisons with the community structure of modern habitats suggest that the environment of the early Miocene fauna of Songhor, and the primitive apes associated with it, was probably a type of lowland forest; the habitat of Ramapithecus and the Fort Ternan middle Miocene fauna compares best with modern woodland-bushland habitats; and the habitat of Homo habilis at Olduvai appears to have been intermediate between grassland and woodland-bushland. If man evolved from one of the early forest living apes, as seems likely on present evidence, an adaptive shift from forest to non-forest habitats must have occurred at some stage in his evolution. The evidence from Fort Ternan shows that in Africa Ramapithecus made this adaptive shift, and it is also now becoming clear that several genera of Eurasian apes, including Ramapithecus, made a similar environmental change at the same time.

An unusual isolated specimen representing an immature rhabdosome of Dicellograptus sp. from the Middle Ordovician Athens Shale of Alabama has a flattened sphere attached to the distal end of the nema. The flattened sphere can be interpreted as a float that probably conferred buoyancy on the rhabdosome. Such floats, which became detached in mature rhabdosomes, may be common in the fossil record. The presence of nematophorous siculae in all planktonic graptolites suggests that for immature rhabdosomes a passive, buoyant mode of life, attained by means of a float, might have been widespread taxonomically. This mode of life is compatible with the theory of passive response for the mode of life of mature rhabdosomes, but it is difficult to reconcile with the theory of automobility.

Recent Nautilus pompilius from the Fiji Islands and N. macromaphalus from New Caledonia show decreasing cameral liquid volumes relative to total phragmocone volume during ontogeny. A maximal value of 32% of the phragmocone filled with cameral liquid was measured from a 190 g N. pompilius. No specimens of over 500 g total weight of either species exceeded 12%. These figures are in contrast to values derived for seven ammonoid species by Heptonstall (1970), who found values ranging between 19 and 52%.

The relationship between cameral liquid volume and salinity within single chambers engaged in the emptying process are examined in N. pompilius and N. macromphalus. Both species start with newly formed chambers filled with cameral liquid isotonic to seawater. Ionic removal by the siphuncular epithelium rapidly reduces the cameral liquid osmolarity, producing osmotic movement of the cameral liquid into the blood spaces of the siphuncle. In both species the lowest cameral liquid salinities occur when the chamber is slightly over half emptied. After this point, which coincides with decoupling of the cameral liquid from the siphuncle, cameral liquid volume continues to decrease, but cameral liquid salinity increases, indicating that the rate of ionic removal slows relative to liquid removal. In N. macromphalus decoupled cameral liquid salinity rises until it is nearly isotonic to seawater when the chamber is nearly emptied. In N. pompilius, however, the rate of ion removal in decoupled cameral liquid is not slowed as much as in N. macromphalus, since it rarely exceeds 40% seawater osmolarity even when the chamber is nearly emptied. The differences in emptying methods demonstrated in these two species are probably related to their different habitat depths: N. pompilius from Fiji is found in much deeper water and must employ more physiologic work to empty chambers at greater depth.

The hyrax, a living primitive subungulate, makes an ideal model in terms of its molar morphology for early lophodont ungulates. Cine fluoroscopic studies of mastication show that the proposed Phase II in jaw movement, experimentally demonstrated in primates, but surmised in ungulates only from molar wear facets, does in fact exist in this animal, but does not appear to be an important component of the masticatory cycle. Comparison of tooth wear in early Tertiary ungulates with contemporaneous primates shows that, whereas primates enlarge the Phase II wear facets on the molars as they move into more herbivorous niches, the same is not true for ungulates, and in fact Phase II may be lost altogether in grazing forms. It is concluded that “grinding” in herbivorous ungulates is a process fundamentally different from that described for herbivorous primates.

The mathematical relationship between species survivorship and duration curves is derived using standard demographic arguments. The result, when applied to the late Cenozoic mammals, suggests that there was an inhomogeneity in the mammalian radiation just before the Wurm, or that the mammalian speciation process has not yet attained the stable-age distribution.