Discriminant function analysis is used to examine the role of within-species differentiation in macroevolution of four Miocene bivalve genera. According to the punctuational model, macroevolution is decoupled from microevolution; within-species trends may be unrelated to between-species differences. The reductionist alternative suggests that intraspecific (primarily geographic) differentiation is the basis of macroevolution. If macroevolution depends on within-species differentiation, discriminant function analysis should separate interspecific and intraspecific populations of a genus using the same set of characters.

Chesapecten macroevolution apparently involved within-species differentiation. Shell length, height, and posterior auricle length differentiate geographic populations within species as well as interspecific populations. Results for Astarte, Anadara, and Eucrassatella are more consistent with the punctuational model. Characters which readily separate species of a genus are much less successful at differentiating intraspecific populations. Rank correlation techniques indicate that, for all three genera, the order of importance of characters in interspecific discrimination is not significantly related to their order in intraspecific discrimination. Decoupling of macroevolution from microevolution is implied for these taxa.

The effect of preservational quality on paleoecologic studies is evaluated quantitatively by using data from 83 fossil collections. These collections are from a restricted Cretaceous time interval (Haustator bilira Assemblage Zone) of Maestrichtian Age and are from the Eastern Gulf Coastal Plain Province. In all, 32,335 specimens were identified, resulting in recognition of 643 different taxa. Each collection was categorized into one of six preservational types, ranging from those in which both aragonite and calcite shells are well preserved to those having only calcite shells preserved.

Statistical comparisons reveal that preservation affects the faunal makeup of these collections. Specifically, collections in which both aragonite and calcite are well preserved have more taxa than collections of poorer preservational quality and contain faunal elements not found in other collections.

These two effects can confound paleoecologic studies of endemism, eurytopy vs. stenotopy, species longevity and other studies of the distribution of organisms in space and time. These effects are especially significant for studies based on presence/absence data, such as published faunal lists and selectively collected samples. In such studies, collections of good preservational quality may be interpreted to represent strata of high diversity, taxa having the more durable hard parts will appear to be widespread and long ranging, and taxa that are preserved only in collections of the best preservational quality will appear stenotopic, endemic, and rare.

One method of increasing the resolving power of paleontological inquiries is to assess the time distribution, or phenology, of perispeciational change. The rationale for this test is that, while concentration of morphologic change around the time of speciation is consistent with both known microevolutionary mechanisms and punctuated equilibria, punctuated equilibrium theory presupposes that most of the change occurs either before or during initial allopatry to produce morphologically static taxa. Considerable change in the initial phases of speciation could also result from known microevolutionary mechanisms, but if significant change occurs in the neosympatric phase, or at any time after the species have become differentiated, then that change is best explained by known microevolutionary mechanisms.

Amount and rate of morphologic change during each phase of the allopatric speciation process were determined for two cognate species of the radiolarian genus Eucyrtidium. In this case, morphologic change accruing to these species during the neosympatric phase was 2-3 times as great as that which occurred during the initial allopatric phase. Morphologic trends in both these species during the allopatric phase differed significantly from a random walk. The size differential that characterized this speciation event was not the product of a single large step early in the process but of a disproportionate number of small steps in one direction during neosympatry. Therefore, the hypothesis of no statistically significant change following the “first stage” of speciation, which is a major tenet of punctuated equilibrium theory, is falsified for this case.

Teeth and other dermal skeletal elements from three osteolepid and two eusthenopterid rhipidistians were examined with the scanning electron microscope to establish whether the hypermineralized outer layer was enameloid or enamel. Using Smith's (1978) morphological criteria to infer the developmental history of enamel and enameloid, enamel was found in the teeth and dermal bones of the osteolepids, whereas enameloid was identified in scales. Hyneria and Eusthenopteron teeth also had enamel. As enamel has also been found in teeth of living lungfishes and extant Latimeria, the presence of enamel in tetrapod teeth represents a primitive character retained from a lobe-finned ancestor and is not useful for phylogenetic studies within the lobe-finned/tetrapod group. Shellis and Miles' (1974) hypothesis that the transition from enameloid to enamel occurred via a fairly simple regulatory change is discussed.

Bases of attachment of Archimedes colonies are very rare, but many colonies show evidence of origination from a pre-existing set of branches. The evidence consists of spiralled supports (axial screws) originating from fragments of pre-existing sets of branches, proximal taper of colonies or axial screws to a diameter smaller than that of bases of attachment, early stages of new colonies originating from the whorl margins of older colonies, and sets of laterally fused colonies. In the most favorable environments Archimedes populations were dominated by a few genets that consisted of hundreds to perhaps thousands of genetically identical colonies.

The ability to reproduce by colony fragmentation was probably an important cause of Archimedes' abundance in the Chesterian seas of eastern North America, especially where it occurred in dense populations in the lee of submarine carbonate shoals. Colony fragmentation, the importance of which is becoming increasingly recognized in modern corals and bryozoans, was also of importance in Paleozoic seas.

Methods currently used to estimate taxonomic extinction probabilities from fossil data generally assume that the probability of encountering a specimen in a particular stratum, given that the taxon was extant in the time period and location represented by the stratum, either equals 1.0 or else is a constant for all strata. Methods used to estimate taxonomic diversity (number of taxa) and speciation rate generally assume that encounter probabilities equal 1.0. We suspect that these assumptions are often false. Capture-recapture models were historically developed for estimation in the face of variable and unknown sampling probabilities. These models can thus be used to estimate parameters of interest from paleobiological data when encounter probabilities are unknown and variable over time. These models also permit estimation of sampling variances, and goodness-of-fit tests are available for assessing the fit of data to most models. Here we describe capture-recapture models which should be useful in paleobiological analyses and discuss the assumptions which underlie them. We illustrate these models with examples and discuss aspects of study design. We conclude that these models should prove useful in paleobiological analyses.

Polycystine radiolarians axe the most widely distributed (geographically and geologically) of the well-preserved microzooplankton. To correctly interpret the tempo and mode of radiolarian microevolution, speciation and macroevolution, the zoogeography and ecological niches of extant, and paleozoogeography and paleoecological niches of extinct subspecies, species and higher taxa of the studied lineages should be carefully considered. Such studies of the Stichocorys and Lamprocyrtis lineages suggest that allopatric speciation as peripheral isolates is important. Sympatric speciation is also a possible mode of evolution in these lineages. Hybridization may play a role in the evolution of one subspecies and one species. Allopatrically evolved subspecies and species require some time to inhabit their maximum geographical range after evolving in an isolated and peripheral part of that “environment,” whereas the supposedly sympatrically evolved forms do not. Cooling trends and water mass reorganization may be related to the speciation events. Similar, but much less controlled, studies on a macroevolutionary scale (evolution above the species level, essentially the “family” level) suggest that there have been about half a dozen periods of major adaptive breakthroughs resulting in quantum, or macro, evolution. Global coolings and the initiations of “new” cold-water spheres and related water masses appear to have allowed these macroevolutionary steps during the Ordovician, Devonian-Carboniferous, Permian, and early Neogene. Ecological pressure from diatoms and planktonic foraminiferans appears to have been related to macroevolutionary events bounding the Cretaceous-Tertiary transition.

Observations on the morphology of the early whorls of Eutrephoceras dekayi (Morton), a widespread Cretaceous nautilid, are supplemented with oxygen and carbon isotopic analyses (δ18O and δ13C) of the early septa of five well-preserved specimens to help identify the point of hatching on the shell. Septa 4 and 5 are more closely spaced than preceding septa and probably correspond in time of formation with a constriction or first broken aperture on the outer shell one-third whorl forward of the fourth septum. In modern Nautilus, morphologic, isotopic, and observational data suggest that similar features mark hatching. Between the fourth and fifth septa in E. dekayi, δ18O values show a shift of variable magnitude from heavy to lighter values followed by a return to heavier values over the next one to three septa. This isotopic shift is compatible with a hatching interpretation and may be explained as the result of kinetic and equilibrium effects on emergence from an egg capsule.

Eutrephoceras dekayi hatched at about 9 mm in diameter, one-third the hatching size of modern Nautilus. Like Nautilus, E. dekayi probably produced few young, all of which were active swimmers at hatching. In contrast, Mesozoic ammonoids produced numerous offspring ranging from 0.5 to 1.5 mm in diameter which may have spent some time in the plankton. These differences in life history may correlate with differences in ecologic specialization, environmental tolerance, and habitat between ammonoids and nautilids and may have contributed to their disparate rates of evolution during the Mesozoic.

The warm-water planktonic foraminiferal Globorotalia tumida lineage has been studied in a 10-Myr-long stratigraphic sequence (Late Miocene through Recent) from the Indian Ocean to determine long-term evolutionary patterns through the lineage's history, and particularly to study in great detail the evolutionary transition from G. plesiotumida to G. tumida across the Miocene/Pliocene boundary. Sampling resolution was very good, between 5 × 103 and 15 × 103 yr across the Miocene/Pliocene boundary and about 2 × 105 yr otherwise. The test shape was analyzed in edge view, permitting determinations of variation in inflation and elongation of the test. Shape was analyzed quantitatively using eigenshape analysis. This method represents the greatest proportion of variation observed among a collection of shapes by the least number of different shapes. The Late Miocene (10.4-5.6 Myr B.P.) populations exhibited only minor fluctuations in shape that did not result in any net phyletic change. This period of stasis was followed by an 0.6-Myr-long period (between 5.6 and 5.0 Myr B.P.) of gradual transformation of the Late Miocene morphotype (G. plesiotumida) into the Early Pliocene morphotype (G. tumida). The populations were again more or less in stasis in the Pliocene and Pleistocene (5.0 Myr to the present day), so that no major modifications of the newly evolved Early Pliocene morphotype occurred during these 5 Myr. Thus it would appear that the G. tumida lineage, while remaining in relative stasis over a considerable part of its total duration underwent periodic, relatively rapid, morphologic change that did not lead to lineage branching. This pattern does not conform to the gradualistic model of evolution, because that would assume gradual changes throughout the history of the lineage. It also does not conform to the punctuational model, because (1) there was no speciation (lineage branching) in this lineage and (2) the transition was not rapid enough (<1% of the descendant species' duration according to definition). For this evolutionary modality we propose the term “punctuated gradualism” and suggest that this may be a common norm for evolution—at least within the planktonic foraminifera.

Large cats, canids, bears, and hyenas create distinctive types of damage when they gnaw bones. This paper describes the diagnostic characteristics of damage done by each taxon to femora and tibiae of herbivores whose body weights are 300 kg or more. Pleistocene and Recent fossil collections that include gnawed bones might provide data on the presence of carnivores whose own remains are not found in the collections. Information might also be gained about predator and scavenger utilization of prey carcasses, often a reflection of prey vulnerability or availability in past communities.

Capture-mark-recapture of Nautilus belauensis in Palau shows that (a) immature animals added an average of 0.1 mm of shell per day at the ventral circumference (projected mean annual increment of 37 mm), but this rate decreases rapidly as maturity is approached; (b) rate of growth line secretion is irregular, ranging from 4 to 8 days per growth line in immature animals; (c) overall weight is an imprecise measure of size and growth in Nautilus due to fluctuations in crop content and chamber liquid; (d) this species is shown to live for at least 4 yr beyond maturity. Age estimates based on the highest growth rate obtained (0.12 mm/day = 43.8 mm/yr) range from 14.5 to 17 yr for seven animals recaptured 45–355 days after release. Combined, these data indicate that the life span of Nautilus may exceed 20 yr.

Evolutionary changes in herbivore abundance, diversity, and ability to excavate calcareous substrata occurred independently in three major herbivore groups: mollusks, urchins, and fish. These changes in herbivory have escalated dramatically since the mid-Mesozoic Era to the extent that herbivory today is more intense than at any time in the past.

Today, calcareous red algal crusts (i.e., corallines) are a conspicuous and frequently dominant element of shallow marine communities. Corallines and their (assumed) parent taxon, solenopores, probably always required grazing to remain free of epiphytes. The large scale evolutionary trend toward increased grazing intensity may have given the corallines a distinct advantage over the more herbivore-susceptible solenopores. Four anatomical characters unique to corallines may have facilitated their rapid expansion into shallow reef environments and subsequently (more than 100 million years later) allowed them to withstand the more intense levels of grazing that evolved in those environments. Today corallines are the only algal form to thrive under, and often even require, intensive herbivory. The extinction of solenopores and the adaptive radiation of corallines parallel a gradient of escalating herbivory over time.

Herbivores capable of excavating calcareous substrate are also frequently capable of denuding, and preventing the establishment of, stands of large leathery (kelp-like) macrophytes. It is possible that large-scale increases in herbivory have caused large-scale reduction of algal biomass in benthic communities. The presence of algal forests especially in the Paleozoic and early Mesozoic Eras may be a new variable to consider in reconstructing paleoenvironments.

One testable hypothesis of the theory that dinosaurs were endothermic is the observation that sauropod dinosaurs were too large, their heads were too small, and their food was too indigestible for them to be warm-blooded. Calculations on the daily calorie requirements of the sauropod Brachiosaurus, adjusted for digestibility and the energetic cost of “free-living,” were compared with the caloric density of Late Jurassic food plants and the feeding rates of an elephant and a giraffe. Using Brachiosaurus as a model I concluded that endothermy in large sauropods (greater than 55 metric tons) was impossible. Depending on assumptions about feeding rates and the cost of free-living, endothermy in smaller sauropods ranges from improbable to impossible.

656 mandibles and isolated teeth of the bovid Pachytragus solignaci Robinson from two localities in the Miocene Beglia Formation, Gafsa, Tunisia, have been individually aged on the basis of ontogenetic development and state of dental wear. The sample probably represents normal but seasonally restricted mortality. Life table analysis indicates an annual mortality rate of 25–30%, increasing in old animals. Dental dimensions are affected by stabilizing selection which sets in as the tooth comes into function, earlier mortality being nonselective in that respect.

Small mammal bone assemblages from the scats of three families of mammalian carnivores are described here as a means of assessing paleontological bone assemblages. These are the Viverridae, Canidae, and Mustelidae. Marking behavior by the carnivores or their use of latrine areas can produce concentrations of bone comparable with those produced from owl pellets, but the nature of the bone assemblages is very different. Skeletal element preservation has a characteristic pattern related to the relative strength of the individual elements, so that the strongest elements are the ones that best survive the physical abrasion of the predator's teeth. Bone breakage is greatest in canids and least in some viverrids. Digestion of the bone occurs to a certain extent with all carnivores, with moderate rounding but little corrosion of either bones or teeth in viverrid-derived bone assemblages, very great rounding and severe corrosion of bone and tooth enamel (but little corrosion of tooth dentine) in canids, and moderate rounding and slight to moderate corrosion of bone and tooth dentine (but less of enamel) in mustelid-derived bone assemblages. Tooth marks are generally rare except in canid-derived bone assemblages. These patterns may enable the identification of predators responsible for the accumulation of fossil predator assemblages, and a consideration of the hunting and other behavior of that type of predator then permit the identification of possible biases in the fossil fauna. In the viverrids, for instance, the mongoose selected for large prey size and against cranial elements, while the genet took all prey sizes available to it and all body parts. Larger canids such as foxes and coyotes took both large and small species, but proportionally more of the most common prey species were present. Skulls were underrepresented. The small canid, the bat-eared fox, selected for the smallest prey species available to it but took all body parts. Mustelids took all sizes of prey, although not necessarily in proportion to their abundance in the habitat, and large species were underrepresented. If the predator type is known, therefore, for a fossil assemblage, these biases can be taken into account in assessing the paleoecological significance of the fauna. An example from the Olduvai Pleistocene deposits is given.

A preliminary report is presented documenting the evolution of the Globorotalia crassaformis (Galloway and Wissler) lineage from the Early Pliocene G. cibaoensis (Bermudez) in Hydraulic Piston Core 72/516 on the Rio Grande Rise (western South Atlantic). A new technique, eigenshape analysis, is used to describe the gross changes in morphology, and the use of “Raupian” analysis of expansion rates, angular displacement, position relative to coiling axis, and translation rates of chambers is suggested as a useful vehicle for inferring the geometric causes of observed evolutionary changes. These changes include size increase, decrease in the number of chambers per whorl, inflation, reduction of relative height of aperture, and increase in the peripheral angle. The sequence is judged to be an example of phyletic gradualism.

Changes in shape and in the pattern of the reticulate carapace ornament of 63 representative female ostracode specimens of the deep-sea genus Poseidonamicus from 28 Deep Sea Drilling Project Sites, extending over a geographic distance of 40,000 miles and a geologic age of 40 × 106 yr, have been analyzed by Resistant Fit Theta-Rho Analysis, conventional least-squares Theta-Rho Analysis, and by inspection of homologies in the fossae of the reticulum. Through comparison of the relative rates of morphological change on at least three levels of integrated complexity, it is possible to demonstrate that a sudden evolutionary change in the architectural framework of the carapace can be the product of mechanical accommodation under stress to more gradual and general changes in carapace shape. Certain geometric imperatives related to these mechanical needs determine morphologic stability and consequently rates of evolutionary change. In the western deep South Atlantic (near the Vema Channel on the Rio Grande Rise), an important evolutionary “punctuational event” seems to have taken place at about 14 Myr, whereas its concomitant, more gradual transformation is traceable in the shallower eastern South Atlantic (Walvis Ridge). This evolutionary event in Poseidonamicus probably reflects the relatively sudden invasion of deep Antarctic Bottom Water through the Vema Channel resulting from the formation of the East Antarctic Ice Cap, while the more gradual transition in shallower depths of Walvis Ridge represents a temporary transitory refuge. The problems of recognizing allopatric origins of species in the deep sea compared to in situ sudden transitions caused by biomechanical instability are considered.

Stage-level range data for 983 Jurassic and Cretaceous ammonite genera, distributed within 83 families, were analyzed by assigning absolute ages to stages or substages. We found ammonite genera to have a mean generic range of 7.3 Myr/ammonite genus. Using a similar methodology, mean generic range per family was also computed. The distribution of long-ranging genera (arbitrarily chosen as those ammonite genera ranging for 12 Myr or more) among families was found to be nonrandom. Instead, long-ranging genera were found to be concentrated in a few families, resulting in significant heterogeneity in the distribution of generic longevities within families (taxotely sensu Raup and Marshall 1980). Although some of the long-ranging genera were found to be morphologically simpler than shorter-ranging genera, others were equally or even more complex, indicating that longevity among ammonite genera is not merely a taxonomic artifact, dependent on degree of differentiable conch morphology. Those Cretaceous families composed of a large number of long-ranging genera were also among the leaders in mean species longevity per family, based on species-level range data for Cretaceous ammonites of the Great Valley Sequence of California. Many of the long-ranging genera and species possess a similar morphologic attribute: siphuncular tubes (connecting rings) of small diameter but high wall thickness.

The age (mortality) profiles of ungulate species in a fossil fauna are useful for reconstructing modes of death and of bone accumulation. Crown height measurements probably provide the most practical means of obtaining age profiles in most fossil samples. Reliable, interpretable profiles will result when individual age is estimated from crown height using a mathematical model first suggested by C. A. Spinage and when the individual ages are grouped into relatively broad age classes. One potential objection to the model is that it requires tedious calculation and there is a strong possibility of calculation error when many crown heights are involved. This problem may be circumvented by the use of an interactive BASIC program appended to this paper. The user supplies the raw crown heights in a fossil sample, together with estimates of initial unworn crown height, ages of dental shedding and eruption, and maximum possible individual age. The program then tabulates the number of individuals in successive 10%-of-potential-lifespan intervals.