Modern biological principles and mathematical techniques applied to fossil data may contribute to a rigorous theoretical framework for the analysis of macroevolutionary trends. Such cross-fertilization may also serve to correct interpretative biases common in paleontological literature.

The most common methods of estimating the relative abundance of species in a fossil assemblage are all maximum likelihood estimates. They differ from one another in their inherent assumptions made about the effects of fragmentation and differential preservation in the assemblage. For many fossil assemblages, relative abundance is best estimated by the relative frequency of specimens or relative frequency of elements. Monte Carlo simulations suggest, however, that in most other circumstances estimates based on frequency of elements divided by the number of elements in a complete individual provide greater accuracy than estimates based on minimum number of individuals. This relation results from an interaction between random sampling error and a variety of biases inherent in the two estimates.

Fibrous ligament and aragonitic shell material have been found preserved in two specimens of radiolitid rudists [cf. Radiolites angeoides (De Lapeirouse)] from the Lower to Middle Coniacian of Tirol, Austria. The invaginated ligament apparently comprised two torn and overgrown non-functional strings, one in each valve, connected medially by a thin strip of active ligament. The original dimensions of the active ligament have been estimated, for shells of 4 to 5 cm commissural diameter, at 0.58 mm2 cross-sectional area and 1.3 mm length, with the shell closed. Using data on the adductor muscle of Recent oysters and the results of compression tests carried out on samples of oyster fibrous ligament, it is estimated that these radiolitid shells opened less than 1 mm in life; their gaping was highly restricted. This is taken to support the proposal that the expanded mantle margins (principally that of the right, attached valve) were responsible for food particle entrapment, rather than the gills as in most other bivalves. It is suggested that a tentaculate mantle flange was extruded through the narrow gap between the valves during feeding. The pair of pronounced radial bands on the posterior flanks of the shell are interpreted as marking pseudofaecal and faecal ejection sites. Finally, it is speculated that slime (possibly poisonous or foul-tasting) on the mantle tentacles inhibited predators.

The foraging paradigm of trace fossil theory has historically accorded random behavior to non-food-limited deposit-feeders and non-random behavior to food-limited feeders. A series of randomness measures derived from empirical modeling, simulation modeling, stochastic modeling and probability theory applied to foraging patterns observed in deep-sea bottom photographs from the Arctic and Antarctic yielded a behavioral continuum of increasing non-randomness. A linear regression of trace positions along the continuum to bathymetric data did not substantiate the optimal foraging efficiency-depth dependence model of trace fossil theory, except that all traces exhibited a greater optimization than that of simulated random foraging. It is hypothesized that optimization as evidenced by non-random foraging strategies represents maximization of the cost/benefit ratio of resource exploitation to risk of predation and that individual foraging patterns reflect an exploration response to the morphometry of a patchily distributed food resource. Differential predation and competition may account for the co-occurrence of random and non-random strategies within the same bathymetric zone.

A model for the paleobiogeographic history of South American cricetine rodents is proposed based on new and/or recently published fossil, geological, paleobotanical and radioisotope data. Cricetine rodents of the tribe Sigmodontini evolved in North America before 7.0 Myr BP. They got to South America by waif dispersal across the Bolivar Trough marine barrier from Central America during a world wide drop in sea level (the “Messinian Low”) between 7.0 and 5.0 Myr BP. The basal stock was probably a sylvan (forest) form, from which evolved pastoral (grazing) forms in the savanna-grassland area of Venezuela, Colombia and the Guianas. The pastoral forms in the northern savanna-grassland area were restricted there until about 3.5 Myr BP. At that time there occurred the first glaciation in South America and consonant with glacial advance was a retraction of forest habitats and an expansion of savanna-grassland habitats. At that time the pastoral forms were able to disperse southward through a savanna-grassland corridor along the eastern foothills of the Andes and spread throughout the previously disjunct savanna-grasslands of Bolivia and Argentina. Cricetines are first recorded as fossil in the Monte Hermoso Fm. of Argentina which is about 3.5 Myr BP in age. The Panamanian land bridge came into existence about 3.0 Myr BP as indicated by the beginning of a major interchange of terrestrial faunas between the Americas, which was well underway by 2.7 Myr BP.

The data on the longevity of genera of articulate brachiopods for the Upper Ordovician-Devonian interval (Boucot 1975) are averaged for the taxa of each order. The generic longevity-frequency distributions form three significantly different clusters. The orthids have the highest mean generic longevity value and display a semi-log survivorship profile that is more convex than the other orders. The spiriferid and strophomenid orders have mean generic longevity values higher than and slopes in the survivorship curves less steep than the pentamerids, rhynchonellids and terebratulids. The appreciable differences in the inferred generic extinction rates for the clusters are attributed to the heterogeneity of the ecologies of the orders. The pentamerids had a proportionately higher number of genera concentrated in narrow-niched reefs wherein higher extinction rates depressed the mean generic longevity of this order relative to the orthids, strophomenids and spiriferids. Enhanced longevity of many offshore (non-reef) genera possibly explains the greater mean generic longevity of the orthids, spiriferids and strophomenids relative to the rhynchonellids and terebratulids which included a proportionately higher number of genera concentrated in nearshore habitats. Alternatively, the depressed mean generic longevity values for the rhynchonellids and terebratulids may reflect systematic oversplitting and temporal bias, i.e., origination and initial diversification of order.

The organic matrix components of a fossil ammonoid shell from the Upper Cretaceous, can be separated into sub-fractions which are generally comparable to those found in extant Nautilus, using ion exchange chromatography. This suggests that at least portions of these components are sufficiently well preserved to interact characteristically with the ion exchange resin. Amino acid compositions of these sub-fractions, however, do not resemble Nautilus organic matrix sub-fractions, indicating that considerable diagenetic alteration of this material has taken place.

The EDTA-soluble fractions extracted from rostra of two late Cretaceous belemnites (Cephalopoda), Gonioteuthis and Belemnitella, were divided into an humic acid and a fulvic acid fraction (the latter was absent in Belemnitella). The extracts are compared with preparations from shells of two recent cephalopods, Nautilus pompilius and Sepia officinalis. Use was made of immunology, amino acid analysis, pyrolysis mass spectrometry and some other techniques.

The fulvic acid fraction of Gonioteuthis, a mixed peptide-like saccharide-like substance, produced confluent immunodiffusion patterns with an EDTA-soluble Nautilus extract against anti-Nautilus rabbit serum. The humic acid of Gonioteuthis did not contain D-alloisoleucine and its amino acid composition was very similar to that of the EDTA-insoluble fraction of Nautilus. This humic acid was enriched in polyphenol, which may be due to chemical reaction of peptides and carbohydrates during diagenesis. It is concluded that both fractions of Gonioteuthis are original belemnite materials that have undergone only minor alterations during diagenesis.

This is an exploratory study of biochemical compounds derived from fossils, with particular emphasis on immunological methods.

A paradoxical relationship exists between the genetic and morphologic adaptive strategies of benthic marine invertebrates; morphologically variable species from unstable environments have been shown to possess less genetic variability than species with more constant phenotypes from stable habitats. The mode of growth of Ordovician bryozoans provides an insight into this paradox. These bryozoans exhibit morphologic gradients within zooidal subcolonies that change throughout colony development. Entire clusters of zooids begin and cease growth as a function of their spatial position with respect to neighboring clusters. A comparison of the within-colony and among-colony components of developmental and morphologic variability was made from populations inhabiting Ordovician environments of differing stability. In four stratigraphically persistent species, the level of developmental variability is homogeneous within species, but varies significantly across taxa. The two species with the highest levels of developmental variability (less canalized development) fit the concept of r-selected opportunistic species and are most abundant in communities of lowest diversity. The other two species have much lower levels of variability (more canalized development), fit the concept of K-selected equilibrium species, and are most abundant in the communities of highest diversity. Within-colony morphologic variability is also higher in the opportunistic rather than the equilibrium species, indicating that the higher morphologic variability observed in unstable environments is the product of within-genotype deregulation, and not the result of higher genetic polymorphism. The equilibrium species in stable environments have lower levels of morphologic deregulation and correspondingly greater variation among genotypes than within genotypes in fossil populations.