Life history theory has undergone considerable scrutiny since Stearns (1976) pointed out that neither the deterministic nor the stochastic theories, then current, provided an adequate fit for much of the empirical data he reviewed. Today, opinions on the future of life history studies may vary according to one's view of the mode of operation of evolution itself, the gradualist recommending detailed intraspecific studies and selection experiments, and the punctuationist aiming toward models involving laboratory speciation experiments (Stearns 1980).

No one needs reminding that we are well into a revolutionary phase in the study of evolution, systematics, and the interrelationships of organisms. To belabor the metaphor a little, to the thesis of Darwinian evolution and Mayrian systematics has been added a new cladistic antithesis which says that the search for ancestors is a fool's errand, that all we can do is determine sister group relationships of monophyletic taxa based on the analysis of derived characters. Consequently, our attention should be focused upon patterns which can be delineated, discussed, and modified in the light of new data, rather than upon processes which may only be the subject of untestable hypotheses. It is a change in approach that is not easy to accept for, in a sense, it runs counter to what we have all been taught, and it is particularly difficult for the paleontologist to accept because a major feature of the approach is a concentration upon living rather than on fossil forms. In fact, fossils are, in general, either difficult to use or irrelevant, or both, in terms of new attempts to set out the relationships of the major groups of organisms. The subject of this brief notice is a critically important new addition to the literature on this growing, dare I say evolving, subject.

Writers as disparate in professional interest as those describing speciation in Drosophila, predicting weather, or supporting creationism have all recently focused on the “sudden” appearance of taxa in the geologic record. In the process, each has cited the punctuated equilibrium argument. Owing to the enormously wide attention which this issue has received since its introduction almost a decade ago, it seems worthwhile to try to place the paleontological and biological evidence in a 1981 perspective. The focus I have chosen is to try to analyze the issue, much as in recent columns in Current Happenings on competitive exclusion, and on larval dispersal and biogeography, in which are put forth alternative explanations for a set of data on a general problem.

Micropaleontology is a peculiar subject: it is not easily defined, it focuses on geologic problems, and it ignores fundamental paleontologic and evolutionary questions it could best attack. As a result of its historic development, micropaleontology is directed to the solution of stratigraphic, paleoceanographic and paleoclimatologic problems, but it has seldom addressed paleobiologic or evolutionary ideas. It is a tradition rather than a discipline. The term “micropaleontology” and all it signifies should be abandoned, for it obscures natural relationships, attracts people with geologic rather than biologic approaches, isolates its practitioners in a blanket of systematics, biostratigraphies, and terminologies, and, as a result, discourages outsiders with other viewpoints or contributions from utilizing its fine fossil record. The growth of the field has been exponential in people-power and literature but not in the development of fundamentally new ideas. Micropaleontology has therefore contributed little to recent paleobiologic or evolutionary hypotheses, in spite of the possession by the many organisms relegated to it of biological properties and fossil records which have much potential for the generation and testing of such hypotheses. Microfossil studies have served geology powerfully and they should continue in that role, but they should also be used to fulfill their promise in the interpretation of paleobiogeography, paleoecology, morphology, evolutionary processes and the origin of new groups and ground plans.

The classic biometrical study of phyletic evolution in Kosmoceras (Brinkmann 1929) is evaluated using unpublished raw data provided by Professor Brinkmann. Most morphological characters show statistically significant changes over time yet it is difficult to provide an unequivocal biological interpretation for these changes. In a few cases, runs tests indicate that evolution was nonrandom in the sense that fewer reversals in the direction of evolution occurred than would be predicted from a null hypothesis based on a random walk. These cases suggest persistence of natural selection regimes for fairly long periods of time. In other cases, and with other kinds of testing, the random walk model cannot be rejected although failure to reject the hypothesis does not justify its acceptance! Thus, the contribution of random factors (either genetic drift or selection in a randomly changing environment) cannot be assessed with confidence. It is problematical also whether the Kosmoceras series represent significant evolution by phyletic gradualism or just the natural temporal variation that characterizes stasis (sensu Eldredge and Gould 1972).

The history of diversity, origination and extinction of Cambro-Ordovician nautiloid cephalopods is explored to determine if differences in evolutionary rates between nautiloid orders are sufficient to document significantly high or low rates of evolutionary turnover (taxotely of Raup and Marshall 1980). The stratigraphic ranges of 425 nautiloid genera are analyzed for this purpose.

Evolutionary rates for five of the seven time intervals analyzed fall within frequency distributions of rates which are thought to be characteristic for a given time interval (horotelic distribution of Simpson 1944). Sufficient heterogeneity is present among extinction rates of Arenigian orders and origination rates of Caradocian orders to reject the null hypotheses of horotely in favor of taxotely. The orders Ellesmerocerida and Tarphycerida, each with a significantly high rate of extinction (P ≥ 0.99), and the Actinocerida, with a significantly low rate of extinction (P ≥ 0.99), were responsible for taxotely during the Arenigian. The Oncocerida and Discosorida, each with a significantly high rate of origination (P ≥ 0.99), were responsible for taxotely during the Caradocian. In each case, taxotely is attributable to the influence of North American endemics. This effect is believed to be more the result of real biological aspects of nautiloid evolution than an artifact of the fossil record.

Shape measurements have been made on planktonic foraminifera from a South Pacific Late Miocene to Recent temperate evolutionary lineage (Globorotalia conoidea through intermediate forms to G. inflata in DSDP Site 284). The sampling interval is about 0.1 Myr over nearly 8 Myr. Gradual evolution (phyletic gradualism) clearly occurs in all but one measured parameter. No clear evidence exists for abrupt evolutionary steps (punctuated equilibria) within the bioseries. If they occur, they are the exception rather than the rule. The number of chambers in the final whorl decreases almost linearly, despite known paleoceanographic oscillations within the temperate water mass. Mean size and apertural shape variations seem to correlate with paleoceanographic change. It is speculated that certain major morphological changes that took place within this evolutionary bioseries (i.e. loss of keel, rounding of periphery) developed in response to a major latest Miocene cooling, associated with instability in the water column and resulting adjustments of the test structure to water density changes. Changes exhibited in shape measurements may offer a precise method of stratigraphic correlation between temperate South Pacific Late Cenozoic sequences. Four species and two subspecies, long recognized to form the basis of this lineage, are redefined biometrically.

Skull and tooth dimensions of Homo erectus fossils from Africa, Europe and Asia appear to fluctuate rather than to change progressively during an interval of 1.3 Myr prior to the start of the Upper Pleistocene. No significant trends can be observed. This suggests a period of stasis in human evolution, after which Homo sapiens may have evolved rapidly from archaic mid-Pleistocene ancestors.

Fusion occurred between pairs of conspecific colonies of Permian fenestrate bryozoans that were of approximately equal radius at time of contact. In contrast, no fusion occurred in pairs of conspecific colonies that were of unequal radius at time of contact. It is suggested that histologically compatible colonies developed from larvae that settled essentially simultaneously and that the larvae were siblings, lecithotrophic with low mobility, and of the same genotype (i.e., polyembryonic). Thus polyembryony appears to have existed as a reproductive “strategy” for at least 275 Myr, and its scarcity in modern taxa cannot be due to recentness of evolution.

Lambeosaurine dinosaur crests are judged to have been conducive to resonation on the basis of an acoustic analysis of the structure of the nasal cavity. Size and shape of the nasal cavity suggest low vocal frequencies in adults, as does information on potential auditory acuity in these animals. Lateral diverticula (present in all but juvenile specimens) acted to suppress portions of the vocal spectrum. Juveniles vocalized at higher frequencies than adults and potential auditory sensitivity at high frequencies in adults suggests a high degree of parent-offspring vocal communication. Sexual variation and causes of selection for low frequency vocalization are also examined.

It has been suggested that certain fossil assemblages consisting of disarticulated and broken remains of small to medium-sized vertebrates (“microvertebrate concentrations”) may be accumulations of incompletely digested material defecated by crocodilians. Experiments on crocodilian digestion show, however, that these reptiles demineralize calcified tissues, frequently leaving intact organic matrices of dentine, cementum, and bones in their feces. Such matrices, even if preserved as fossils, would not resemble most specimens in microvertebrate concentrations. Therefore, crocodilian digestion does not appear to have been an important factor in the formation of these fossil assemblages. Teeth similar to those defecated by crocodilians nevertheless do occur in the fossil record. Such teeth, lacking enamel but often complete in other respects, are interpreted here as having been digested by crocodilians, defecated as demineralized organic matrices, and subsequently remineralized. Enamel, with its extremely low organic content, does not yield a demineralized matrix susceptible to remineralization. A number of recently recognized occurrences of enamel-less teeth attest to the significance of crocodilian digestion as a factor in the taphonomic history of many Mesozoic and Cenozoic fossil vertebrate assemblages.

The correlation between epidermal cells and cuticular reticulation was clearly shown by transmission and scanning electron microscopes with larval ostracods just before ecdysis. Comparison of the reticulation patterns of Recent and Pleistocene specimens revealed that the epidermal cell arrangement of the adult ostracods is both consistent in the Recent population and conservative in phylogeny. Ontogenetic changes of the reticulation pattern were studied with specimens cultivated separately. Some gene control over the mitosis of epidermal cells was assumed, based on the ontogenetic development of the reticulation pattern. The pattern of fossil specimens suggests that the control has been well maintained in ostracod phylogeny.