Studies of ontogenetic processes are fundamentally dependent on hypotheses of phylogeny. The model of Alberch et al. (1979) is reformulated in terms of phylogenetics and used to describe how heterochronic ontogenetic processes can be detected in nature. Heterochronic processes producing paedomorphosis can result in morphologies which resemble primitive (retained ancestral) traits; the conditions under which paedomorphic and primitive features can and cannot be distinguished are described. The utility of ontogeny for determination of evolutionary character transformations and character polarity and for detection of convergence and parallelism are considered. The ontogenetic criterion for assessing polarity is independent of hypotheses of phylogeny and may be as effective as outgroup comparison. Ontogenetic analysis may aid in the detection of convergence but not in the detection of parallelism.

Shell form is not strictly linked to life habits in modern marine turritelliform gastropods. To test the usefulness of various morphological characters in determining life-mode, I present a set of predictions giving the expected distribution of characters occurring in turritelliform snails with three different life-modes. Burrowing species should lack sculpture, possess columellar folds and a flat whorl profile, and have an orthocline or prosocline aperture. Mobile epifaunal forms should have sculpture, a rounded whorl profile, a displaced tangential aperture and a smooth columella. Sedentary forms should resemble epifaunal forms but have non-tangential apertures. These predictions were tested with a sample of 105 Recent marine species. Each hypothesis was found to be a statistically valid generalization and in 92 of the species (88%) the life habits were correctly predicted. Accuracy may be further improved by considering additional features such as ratchet sculpture and disjunct or open coiling. These patterns of shell form can be used to interpret fossil species as burrowers, or as sedentary or active epifaunal forms. For example, the unusual Devonian murchisoniid gastropod Ptychocaulus verneuili is interpreted as an active burrower.

The relatively imperfect relationship between shell form and life-mode in turritelliform gastropods, as compared to the Bivalvia, apparently results in part from the behavioral complexity of the Gastropoda. Gastropods have a repertoire of activities which would place them in different life-modes at different times; snail morphology reflects this complexity.

The distribution of species abundance (number of individuals per species) is well documented. The distribution of species occurrence (number of localities per species), however, has received little attention. This study investigates the distribution of species occurrence for five large data sets. For modern benthic foraminifera, species occurrence is examined from the Atlantic continental margin of North America, where 875 species were recorded 10,017 times at 542 localities, the Gulf of Mexico, where 848 species were recorded 18,007 times at 426 localities, and the Caribbean, where 1149 species were recorded 6684 times at 268 localities. For Late Cretaceous molluscs, species occurrence is examined from the Gulf Coast where 716 species were recorded 6236 times at 166 localities and a subset of this data consisting of 643 species recorded 3851 times at 86 localities.

Logseries and lognormal distributions were fitted to these data sets. In most instances the logseries best predicts the distribution of species occurrence. The lognormal, however, also fits the data fairly well, and, in one instance, better. The use of these distributions allows the prediction of the number of species occurring once, twice, …, n times.

Species abundance data are also available for the molluscan data sets. They indicate that the most abundant species (greatest number of individuals) usually occur most frequently. In all data sets approximately half the species occur four or less times. The probability of noting the presence of rarely occurring species is small, and, consequently, such species must be used with extreme caution in studies requiring knowledge of the distribution of species in space and time.

Phyletic speciation arising from a shift between adaptive peaks in the selective surface is modeled. At a locus initially monomorphic, a new allele is introduced that triggers phenotypic evolution by making a new adaptive peak available. A phenotypic model is used to describe the evolution of a quantitative character that is important for fitness but not directly affected by the new allele. Recursion equations are derived for both the allele frequency and the mean of the quantitative character. It is shown that the dynamics of the quantitative trait fit a “punctuated equilibrium” pattern of evolution. Phyletic speciation is seen to occur over a time span so short as to make observation of the transition in the fossil record unlikely.

Growth rhythms are described in the accretionary skeletons of Rafinesquina alternata, a Late Ordovician brachiopod from southeastern Indiana. Contiguous growth increments widen and narrow in repeating series, giving the appearance of adjacent clusters of increments. Fourier analyses of growth increment widths and counts of the number of increments within individual clusters yield similar periodicities. Increments vary in width over a period of approximately 19 increments, modulated with a lower amplitude oscillation of 27 increments. The number of increments per cluster falls into two groups; clusters having between 8 and 17 increments outnumber those having between 18 and 30 increments.

All specimens were obtained from a Maysvillian facies of the Dillsboro Formation, previously inferred to represent a shallow subtidal environmental setting. The growth periodicities described here are consistent with this interpretation. The intensity of tidal parameters such as emersion-immersion cycles, substrate shifts, changes in nutrient supply or in oxygen tension declines with depth as would the number of growth increments added each month in response to these factors. Thus, for these specimens, the maximum number of increments per cluster probably approximates the true number of “tidal” days in the Late Ordovician synodic month (period between full moons).

The paleoecological model derived from these analyses can be used in future studies to predict the rate of the earth's rotation and the motion of the moon in the Late Ordovician and, equally importantly, to evaluate the limits of uncertainty of such studies.

The shape and arrangement of cusps and crests and the orientation of wear striations on the cheek teeth of fossil mammals can be used to reconstruct occlusal patterns. Occlusal patterns have been documented previously in a variety of therian mammals and also in triconodonts and docodonts among nontherians. This is the first detailed analysis of patterns of jaw movement and dental function in a member of the highly specialized nontherian order Multituberculata (Allotheria). Ptilodus, a Paleocene multituberculate, appears to have had two cycles of mastication that followed different paths of movement and utilized different sets of teeth. The first cycle, the slicing-crushing cycle, occurred as the large, laterally-compressed fourth lower premolar (P4) sliced orthally into food items held primarily against the fourth upper premolar (P4). Food items sliced in this manner passed down both the labial and lingual sides of P4, forming subparallel striations in valleys between the nearly vertical enamel ridges. The second cycle is the grinding cycle in which the mandible was retracted while the molars were in tight occlusion, thus producing longitudinal striations on the molars. Unlike the pattern in therians, triconodonts, and docodonts, there is no transversely triangular masticatory orbit in the grinding cycle of multituberculates. The generally accepted idea that the labial aspect of P4 in ptilodontoid multituberculates sheared orthally against the lingual aspect of P4 is not supported. Instead, predominantly horizontal striations developed on the posterolabial wear facet of P4, and on a conjoined facet posterolingually on P4 and anterolingually on the first upper molar (M1), indicate that relative movement between these surfaces was largely palinal (i.e., the jaw moved from front to back), rather than orthal and occurred during the grinding cycle of mastication.

In considering the dietary preferences of ptilodontoid multituberculates, it appears that most members were not folivorous. The small size of many species of Ptilodontoidea suggests that they could not have subsisted on a folivorous diet, which is rich in structural carbohydrates. The length of striations on the sides of P4 of Ptilodus, one of the largest of the Ptilodontoidea, indicates that large, hard food items were ingested. The presence of both smooth and highly-striated enamel on homologous dental wear facets in different individuals of Ptilodus mediaevus from a single quarry sample suggests a varied diet. The recent suggestion that ptilodontoids were omnivorous is supported.

Some ungulate species at Upper Pleistocene and Holocene archeological sites in South Africa exhibit catastrophic mortality profiles, while others exhibit attritional ones. The awareness by Stone Age people that some species are especially amenable to driving or snaring probably accounts for the catastrophic profiles. Natural catastrophic death immediately followed by human scavenging is a much less likely explanation because the species samples comprise material lumped from deposits that accumulated more or less continuously over hundreds or even thousands of years during which period there is no reason to suppose the repeated occurrence of natural catastrophes nearby.

The inability of Stone Age people to obtain prime-age adults in species that are not particularly amenable to driving or snaring presumably accounts for the attritional mortality profiles. Although the species that display attritional profiles conceivably were scavenged, the high proportion of very young individuals in the profiles suggests active hunting. Very young individuals are much less abundant in attritional profiles from local non-archeological sites, probably because their carcasses were removed from the record before burial, primarily by carnivore or scavenger feeding. Scavenging would account for the abundance of very young individuals in the archeological sites only in the unlikely event that people could regularly locate carcasses before other predators did.

In general, geomorphic/sedimentologic context is probably the best criterion for determining whether a species characterized by a catastrophic profile in an archeological site was hunted or scavenged. At the majority of known sites, active hunting is suggested. In the case of a species characterized by an attritional profile in an archeological site, the proportion of very young individuals in the sample probably provides the best criterion for distinguishing hunting from scavenging. A relatively high proportion of very young individuals suggests active hunting.

Substrata for numerous epizoans in the Silurian Waldron Shale were provided by the toppled and overturned calyces of camerate crinoids. These were inhabited by a skeletonized fauna consisting of at least 25 species; including several bryozoans, tabulates, inarticulate brachiopods, worms, and echinoderms.

Many of the encrusting bryozoans exhibit skeletal overgrowths which appear to reflect competitive interactions for space. Coexistence of certain of the bryozoans involved in such interactions is suggested by skeletal features such as inflated growth forms and upturned margins at junctions between colonies (both representing attempts to avoid being overgrown). In addition, the occurrence of overgrowth reversals within individual encounters indicates contemporaneity of that pair. Species may be ranked according to their relative overgrowth success; however, this ranking is far from rigid as lower ranked species may on occasion overgrow more highly ranked species. Such nontransitive patterns appear similar to those described from Recent cryptic bryozoan faunas.

The fossil stickleback, Gasterosteus doryssus, is highly variable for pelvic girdle structure and the number of dorsal spines. Six “sampling pits” were dug at known stratigraphic positions within a continuous section which contains abundant G. doryssus, and the stratigraphic position of each specimen within each pit was determined. The deposit apparently is composed of annual layers (varves), allowing relatively precise conversion of stratigraphic distance to years. The temporal distribution of phenotypes is heterogeneous but can be grouped into two temporally contiguous, nonheterogeneous sets. However, absence of heterogeneity for pelvic phenotypes within the two groups of pits could be an artifact of small sample size. The number of sample pits was insufficient to determine whether the observed phenotypic heterogeneity among pits represents temporal trends. Differences also occurred between mean temporal distributions of stickleback phenotypes within one of the pits located within a nonheterogeneous set of pits. Thus, there is within-pit temporal heterogeneity that is unresolved by between-pit comparisons, although the sampling pits are separated by an average of only about thirty thousand years. Larger time intervals usually used in paleontology may seriously underestimate evolutionary rates because fine scale reversals of evolutionary trajectory are undetected. Temporal variation in G. doryssus provides a system in which most limitations of other fossil systems for measuring the rate of evolution can be circumvented. As in virtually all paleontological studies, spatial variation cannot be entirely eliminated as a potential cause of stratigraphic variation.

A late Miocene population of Neohipparion cf. leptode from the Love Bone Bed of Florida was found to have 13 discrete annual age classes based on eruption sequences and tooth wear. The large sample size of individuals (minimum number = 229) allowed the estimation of standard population parameters, including age-specific mortality rates. The average age of death for a newborn was 3.5 years, but those individuals that survived the 64% juvenile mortality occurring during the first two years lived an average of 8.0 years. The potential longevity of this species of Neohipparion had not increased beyond that of known samples of Merychippus, despite increased crown height. The paleoenvironment of the collecting site was a wooded grassland savanna with annual wet and dry seasons. The Neohipparion population migrated into the area during the dry season but left in the wet season to give birth away from the collecting site.

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.

The siphuncular tube is a key component of the buoyancy control and mechanical strength systems in both Nautilus and fossil cephalopods. We measured the rate of hydrostatically induced fluid flow across the tube wall and tube rupture strength of Nautilus pompilius at hydrostatic pressures in the range of 10–85 bars. We found that in fresh, undecayed tubes, rupture occurs at pressures of about 80–85 bars. This is equivalent to the strength of the shell proper and to the depth limit of the live animal. The siphuncular tube is neither markedly stronger, nor weaker, than the shell. Siphuncle rupture strength is constant in the last 20 chambers of the shell despite a strong decrease in the siphuncle strength index (ratio of tube thickness to radius). The notion that strength index gives an accurate indication of tube strength is therefore in error. This suggests that the geometry of the siphuncular tube can not be straightforwardly used as an index of living depth in fossil cephalopods. Rupture occurs at the siphuncle-septum contact. The junction of the tube to its mechanical supports is thus weaker than the tube itself. Measured flow rates are in the range of 1–20 ml/h/chamber. Flow rates increase linearly with applied pressure and in successively larger chambers as a result of size-related variation in surface area and thickness of the tube wall. Rates of osmotic pumping in live animals are up to three orders of magnitude lower than hydrostatically induced flow rates across the siphuncular tubes of empty shells. Pumping capacity of live animals is apparently limited by functional constraints of the osmotic pump rather than by the fluid conductance properties of the tube wall. Living depth in evolving cephalopod lineages may be limited ultimately by physiologic or chemical restrictions of the osmotic pumping mechanism rather than by mechanical strength of the shell or siphuncle.

During the middle Cretaceous, exceptional ecologic conditions developed in the Tarfayan Basin (SW Morocco) marked by the deposition of marls and limestones, rich in organic matter. The ostracod fauna of the Cenomanian to Coniacian consisted of a few ornamentally stable species. Towards the close of the Turonian, Oertliella? tarfayaensis became dimorphic at the top of its range, the new morph with smooth lateral zones being the undoubted ancestor of Oertliella? chouberti. The multivariate morphometric evolutionary pattern for O.? tarfayaensis fluctuates about a stationary value in a manner which could reflect evolutionary stasis. The passage from the ancestral to the descendant species took between 1 × 105 and 2 × 105 yr. At the multivariate level, the transition could have taken place by random genetic drift with, or without, selective effects. At the univariate level, there is no clear evidence for either of these mechanisms. The phenotype is regionally stable which suggests that a non-genetic origin of the change is unlikely. An alternative model for the speciation event is allopatric speciation in a peripheral isolate and immigration. The Late Turonian morph may have resulted from environmentally cued polymorphism with elimination of the original morph due to a long term ecologic change, possibly connected with an increase in silica in the environment.

In a recent contribution, Rightmire (1981) claims that “No significant trends can be observed” in several characters measured in skulls of Homo erectus. While I sympathize with the frustrating problem of small sample size in hominid finds, one must ask the question: could you ever see a trend, given the quality of your information? If sample size is low, if trends are of relatively small magnitude, and if sample variance is high, one can always safely show that nothing (i.e., stasis) has happened. This form of inference falls into a classic statistical trap: attempting to prove statistical homogeneity. You cannot do it without a concomitant estimate of least significant difference, that is, estimating the magnitude of variation within which you cannot distinguish among estimates of a parameter.

Liquid removal rates in chambers of the living cephalopod Nautilus depend on two factors: the surface area of siphuncular epithelium exposed to liquid in the chambers and the buoyancy of the specimen. In Nautilus made artificially heavy, liquid removal rates are increased as much as five times above neutral buoyancy rates in surface aquaria. Although chamber volume increases faster than siphuncular surface area in successively larger chambers, the increase is small, especially in the last formed dozen chambers. Under conditions of constant liquid removal per unit area of siphuncular epithelium, this means that removal rates of liquid from any two or three successive chambers are nearly constant.

Nautilus shows ranges of chamber volume/siphuncular surface area ratios of .04 cc/mm2 (early, small chambers) to .12–.14 cc/mm2 in late, large chambers. These values are not characteristic of all chambered cephalopods. Comparison of extinct chambered cephalopod taxa with Nautilus indicate a variety of volume/area ratios for similarly sized chambers.