bluuebunny/crossref_metadata_2025 huggingface dataset:
Beginnings of biospheric evolution and their biogeochemical consequences
Authors: Cloud Preston
Published: July 2016

The beginnings of biospheric evolution had far-reaching biogeochemical consequences for the related evolutions of atmosphere, hydrosphere, and lithosphere. Feedback to the sedimentary record from these several simultaneously interacting aspects of crustal evolution provides the evidence from which historical biogeology is reconstructed. The interpretation of that evidence, however, is beset with pitfalls. Both biogenicity and a primary origin need to be demonstrated, or confidence limits established for each supposed morphological and biochemical fossil. Relevance to biospheric or related evolutions must be critically evaluated for every geochemical and sedimentological anomaly.

Indirect evidence suggests primitive, oxygen-generating autotrophy by ∼ 3.8 × 109 years ago (3.8 Gyr or gigayears), while free O2 first began to accumulate only ∼ 2 Gyr ago. Various reduced substances in the atmosphere and in solution functioned as oxygen sinks, keeping photolytic and biogenic O2 at levels tolerable by primitive anaerobic and microaerophilic procaryotes.

The oldest demonstrably biogenic and certainly primary microstructures are procaryotes from ∼ or > 2 Gyr old strata around Lake Superior. Improved biologic O2 mediation, continued carbon segregation, and filling of O2 sinks initiated atmospheric O2 buildup, leading to an ozone screen ∼ or < 2 Gyr ago. Consequences were essential termination of banded iron formation, onset of red beds, and O2 shielding of anaerobic intracellular processes, heralding the eucaryotic cell.

Probable eucaryotes appear in ∼ 1.3 Gyr old rocks in California as large unicells and large-diameter, branched, septate filaments. Likely consequences of eucaryotic evolution were increased atmospheric O2, increased carbonate and sulfate ion, and the rise of sexuality. Meiosis had definitely evolved > 0.7 Gyr ago and probably > 1.3 Gyr ago, perhaps simultaneously with the mitosing cell. Whatever the timing, it completed the evolution of the eucaryotic heredity mechanism and foreshadowed (given sufficient free O2) the differentiation of tissues, organs, and advanced forms of life—with all their potential for biogeochemical feedback to sedimentary, diagenetic, and metallogenic processes. The first Metazoa appeared ∼ 0.7 Gyr ago. Being dependent on simple diffusion for O2, they lacked exoskeletons. The latter appeared, perhaps 0.6 Gyr ago, when increasing O2 levels favored the emergence of more advanced respiratory systems.
Natural selection in a Cretaceous oyster
Authors: Sambol Melvin , Finks Robert M.
Published: July 2016

A population of shells of the Cretaceous oyster Agerostrea mesenterica was obtained from a single locality. The age at death for each shell could be determined, and the population was deemed to be essentially undisturbed and capable of providing a mortality record of the local population averaged over a span of time. We measured four morphometric characters which, on the basis of a functional morphologic model, could be expected to have adaptive value. The frequency distribution of each character was analyzed separately for the three year old and for the six year and older specimens in order to determine which individuals died young and which survived to old age. Ontogenetic effects were separated from those of differential mortality by independent means. The results indicated that there was (1) directed selection for maximum curvature, (2) centripetal selection for a plica number of about 8, and (3) a net centripetal effect on both arc length and plica height, composed of selection against largest values coupled with a possible selection against smaller values that cannot be separated from ontogenetic effects. Only the selection for maximum curvature and optimal plica number can be reconciled with the predictions of the model.
A test for evolutionary equilibria: Phanerozoic brachiopods and Cenozoic mammals
Authors: Mark Graham A. , Flessa Karl W.
Published: July 2016

The fossil record of Phanerozoic brachiopod genera and Late Cenozoic New World mammal genera is examined for evidence of evolutionary equilibria. One necessary (but insufficient) condition is met: within temporal intervals, numbers of originations correlate with numbers of extinctions. Eliminating temporally short-ranging brachiopods, however, reduces the correlation so that it explains only 16% of the variation. More decisive tests of the equilibrium hypothesis appear impossible with available data. Difficulties of temporal and geographic scale, taxonomic level, and ecological consistency must be resolved before equilibrium models can be applied in paleontology for other than inspiration.
The shape of evolution: a comparison of real and random clades
Authors: Gould Stephen Jay , Raup David M. , Sepkoski J. John , Schopf Thomas J. M. , Simberloff Daniel S.
Published: July 2016

The history of life is replete with apparent order. Much of this order may reflect the deterministic causes conventionally invoked, but we cannot be sure until we measure and subtract the order that arises in simple random systems. Consequently, we have constructed a random model that builds evolutionary trees by allowing lineages to branch and become extinct at equal probabilities. We proceed by dividing our simulated tree into clades and by comparing their sizes and shapes with the patterns exhibited by “real” clades as recorded by fossils.

We regard the similarity of real and random clades as the outstanding result of this comparison. In both real and random systems, extinct clades arising after an “ecological barrel” had been filled have their maximum diversity at the midpoint of their duration; clades arising during the initial “filling” reach an earlier climax during this preequilibrial period of rapid diversification. However, some potential differences also emerge. Clades still living are much larger than extinct clades. We may attribute this to the morphological superiority of survivors, but we can also simulate it in a model that chooses the originators of clades at random. Real clades undergo greater fluctuations in diversity than do random clades, but the effect is not marked.
Species richness in marine benthic habitats through the Phanerozoic
Authors: Bambach Richard K.
Published: July 2016

The distribution of numbers of species and the median number of species from 386 selected fossil communities are tabulated for high stress, variable nearshore, and open marine environments during the Lower, Middle, and Upper Paleozoic, the Mesozoic and the Cenozoic. The number of species always increases from high stress to variable nearshore to open marine environments. Within-habitat variation in number of species is small for long intervals of the Phanerozoic. The median number of species in communities from high stress environments remains fixed at about 8 from the Cambrian to the Pleistocene. In open marine environments, the median is near 30 for the Middle and Upper Paleozoic and almost the same for the Mesozoic. Increases of 50% in median number of species between the Lower and Middle Paleozoic and 2 times between the Mesozoic and Cenozoic occur in open marine environments with parallel, but less pronounced, increases in variable nearshore environments. Conditions controlling overall within-habitat species richness changed at those times. These changes do not correlate directly with evolution of new major taxa, change in physical conditions, predation, space availability or oxygen supply. They may be related to changes in resource availability influenced by factors such as the developing terrestrial flora, to lag-time inherent in the evolutionary process of diversification, or to as yet undetermined factors. Although provinciality determines total species richness for the biosphere, the within-habitat data suggest that the number of marine invertebrate species in the world has increased since the Middle Paleozoic, contrary to Raup's (1976b) contention, but possibly only by about 4 times, not the order of magnitude or more suggested by Valentine (1970).
Quantification of shape by use of Fourier analysis: the Mississippian blastoid genus Pentremites
Authors: Waters Johnny Arlton
Published: July 2016

Psychological evidence suggests that the visual outline of an object is the most important character for discriminating differences in external morphology. External morphology is an important taxonomic character in describing living and fossil species, for example, the blastoid Pentremites. Comparison of different views of the same specimen utilizing Fourier series suggests that the skeleton of Pentremites commonly is not rotationally symmetrical and that the asymmetry is not associated with any specific ray. Analysis of a growth series indicates that the amplitudes of the second and third harmonics are significantly correlated with growth, which is demonstrated to be anisometric. Definable changes in the lateral outline can be attributed to changes in harmonic amplitudes and a wide range of morphological forms comparable to known taxa can be generated by systematically varying the amplitudes of the first four harmonics. The population used in this study probably represents Pentremites robustus Lyon and is from Bangor Limestone in the abandoned Moulton Quarry, Lawrence County, Alabama.
Brains of early carnivores
Authors: Radinsky Leonard
Published: July 2016

It is commonly believed that the brains of the ancestors of modern carnivores (miacids) were superior to (e.g., larger than) those of other early carnivores (creodonts and mesonychids). Examination of the fossil record of brains of early carnivores reveals no evidence to support that belief. Moreover, evolutionary trends towards increasing relative brain size and an expansion of neocortex are seen in both miacids and creodonts. The neocortex expanded in a different way in miacids than in creodonts and mesonychids (evidenced by different sulcal patterns), but the biological significance of the observed differences is unknown.
Cohort analysis of generic survivorship
Authors: Raup David M.
Published: July 2016

Cohort analysis provides an effective method of analysing taxonomic survivorship in the fossil record where large data sets are available. An analysis of the stratigraphic ranges of about 8,500 fossil genera and subgenera shows that survivorship patterns are substantially the same throughout the Phanerozoic. These patterns are used to calculate an average value for mean species duration among fossil invertebrates (11.1 Myr.). Also, the extra extinctions near the Permo-Triassic boundary are shown to be equivalent to about 85 Myr of normal, background extinction.
How rare is phyletic gradualism and what is its evolutionary significance? Evidence from Jurassic bivalves
Authors: Hallam Anthony
Published: July 2016

Both intensive analysis of Gryphaea and an extensive survey of Jurassic bivalves in Europe supports the punctuated equilibria model of speciation, with the exception of phyletic size increase, which appears within the limits of the data to be gradualistic and affects at least a significant minority of species. The size increase takes place both within species and between successive species in a lineage. In Liassic Gryphaea, a combination of allometry in the ontogenetic development of the ancestral species and paedomorphosis led also to changes of shape up the sequence. The production of evolutionary trends by species selection is not supported.

The favoured interpretation of phyletic size increase is a gradual delay in maturation time consequent upon a change in the organisms' adaptive strategy from the r-selected to the K-selected mode and is backed up by evidence on changing population numbers and distribution. An extinction/speciation model is proposed for neritic organisms based on fluctuating sea levels. Times of low sea level or regression correspond with times of high stress and hence high extinction among stenotopic organisms and increased rates of allopatric speciation, with r-selection as the dominant mode. Times of high sea level or transgression correspond with low extinction and speciation rates and increased freedom of migration. K-selection is the dominant mode and often leads to phyletic size increase provided the environment remains stable for a sufficiently long period.
Variability, evolutionary rates, and allometry in dwarfing lineages
Authors: Marshall Larry G. , Corruccini Robert S.
Published: July 2016

Evolutionary “dwarfism” or “nanism” is the phenomenon in which a significant decrease in mean body size of a lineage (an ancestral-descendant sequence of populations) occurs through time. A detailed analysis of several Late Quaternary dwarfed marsupial lineages from Australia is given. Based on linear tooth dimensions of the dwarfed lineages, four points are considered: 1) percent dwarfing; 2) evolutionary rates of change of tooth dimensions; 3) variation within lineages before and after dwarfing; and 4) several aspects of multivariate dental allometry. [The lineages includeMacropus titan(fossil)—M. giganteus(Recent) andOsphranter cooperi(fossil)—O. robustus(Recent) in the family Macropodidae (kangaroos), andSarcophilus laniarius(fossil)—S. harrisii(Recent) in the family Dasyuridae (Tasmaniandevil).]

Dental measurements led to these conclusions: 1) Species with the largest body size show the greatest size reduction, and the species with the smallest body size change the least. 2) Evolutionary rates for this reduction in Australian lineages are similar to comparable Post-Pleistocene dwarfed lineages in Europe. 3) Tooth width, especially posterior width, changes more rapidly than length. The first molar changes relatively slowly, especially in length. 4) Variability is higher in the dwarfed forms than in the larger ancestors. 5) Multivariate allometric rates of dwarfing are consistent with results for rates of change calculated in darwins for the relation between change in length and maximum width (and less so for the relation between M1 and M4 reduction). This pattern of dwarfing allometry is broadly similar to within-species allometry, and is quite dissimilar to synchronous interspecific allometry.

Brief consideration is also given to taxonomy of dwarfing lineages and to problems of concurrent megafaunal extinctions. It is concluded that dwarfism is an adaptive process which is probably the result of a density-dependent factor(s) (i.e. a resource limited system).
The measurement of taxonomic evolution: preservational consequences
Authors: Lasker Howard R.
Published: July 2016

The accuracy of numerical summaries of data from the fossil record has been hotly contested in recent years. In this paper I present a computer simulation which mimics the process of preservation and the resultant loss of data in survivorship records. The simulation accepts as its input data a hypothetical “original” record and a time dependent model of preservational loss. These parameters are used to generate a “preserved” record, and the “original” and “preserved” data sets are then compared. Eleven hypothetical original records having different patterns of diversity and turnover were “preserved” in this manner. Indices of diversity, origination, extinction, turnover, and longevity were evaluated for each of five different models of preservational bias. All of the indices behaved in a single characteristic fashion. Taxonomic data that contained large fluctuations (of the order 100%) were preserved accurately. Similarly the large scale changes in preserved records matched original distributions. Records with small fluctuations (30%) were variably preserved and when such fluctuations were present in the preserved record they did not always correlate with events in the original record. Longevities were more accurately preserved than were other forms of taxonomic data. The results are believed to reflect the levels of accuracy obtainable from generic and familial data and suggest ways in which data sets warranting more detailed study may be singled out.
Initial diversification of macroboring ichnofossils and exploitation of the macroboring niche in the lower Paleozoic
Authors: Kobluk David R. , James Noel P. , Pemberton S. George
Published: July 2016

The traces of macroboring organisms are known throughout the Phanerozoic, with diversification and exploitation of the macroboring niche paralleling variations in the development of skeletal metazoa. The oldest macroboring biota is an abundant yet low diversity fauna in hardgrounds and reefs of Lower Cambrian age. Following the extinction of archaeocyathids at the end of the Lower Cambrian (and thus the demise of skeletal reefs until the Middle Ordovician), boring organisms appear to be restricted to submarine hardgrounds. With the development of skeletal reefs in the Middle Ordovician the macroboring fauna shows a rapid speciation and a dramatic increase in diversity. This same pattern occurs again in the Devonian. This record appears to represent refuge of the fauna in low stress, hardground environments when skeletal reefs were not present and radiation in the high stress environment of the reef when large skeletal metazoa were abundant and diverse.
Mammalian Faunal Dynamics of the Great American Interchange: Reply to an Alternative Interpretation
Authors: Webb S. David
Published: July 2016

In their “alternative interpretation” Marshall and Hecht raise two interesting questions:

I)

Is “Taxocene Analysis” a permissible approach to community evolution, and if so under what conditions?

II)

What really happened to the ten South American ungulate genera that vanished during the Early Pleistocene?

As these are fundamentally different questions, I shall consider each separately.
Bias in the published fossil record
Authors: Koch Carl F.
Published: July 2016

The published fossil record has significant bias in favor of common and biostratigraphically important taxa when compared with data obtained from a thorough examination of several hundred collections from the Western Interior of North America. Overall species diversity is underestimated by a factor of 3 to 4, and bivalve and gastropod diversity by a factor of 5. The proportion of bivalves increased from 40 to 56% of the fauna, and the proportion of ammonites decreased from 28 to 18%. Thirteen published reports listed 65 species from 203 reported occurrences. Data from all sources showed 170 species for 1050 occurrences. By using abundance data and assuming a log-normal distribution, as many as 200 fossilizable mollusc species may have inhabited the Western Interior during the uppermost biozone of the Cenomanian. The importance of this study is that it quantifies the bias in the published fossil record relative to the potential fossil record for an unusually well studied interval of geologic time. The bias would be greater for less well studied strata.
Mechanical properties of coral skeleton: compressive strength and its adaptive significance
Authors: Chamberlain John A.
Published: July 2016

Measurement of the compressive strength and elastic modulus of the skeletal material of three common Caribbean corals suggests that the mechanical properties of coral skeleton are an important factor in the adaptive repertoire of these animals. The strength (stress at fracture) of the specimens tested is 12–81 meganewtons/meter2, with material from branched colonies being generally stronger than material from massive colonies. These values are lower than the strength of most other carbonate skeletal materials, but higher than that of carbonate engineering materials like concrete and limestone. The comparatively low strength of coral skeleton may be the result of architectural properties produced by the requirements of competing adaptive factors, such as polyp phototropism, or it may reflect the low probability that a colony will be broken, and therefore need to be stronger, before it achieves reproductive parity. The skeleton of the three species tested here is strongest when stress is applied parallel to the growth direction of the polyps. Strength varies inversely with skeletal porosity. Decreasing porosity in highly stressed colonies represents a potentially valuable adaptation for enhancing strength. The adaptive value of porosity modification may explain differences in porosity and strength between highly stressed branched growth forms and more moderately stressed massive growth forms. Boring organisms reduce the strength of coral skeleton by increasing its porosity. Only minor amounts of boring can produce strength reductions of up to 50%. Specialized, stress-minimizing branch arrangements help maximize resistance of coral structures to mechanical degradation in situations where colony size is unusually large or hydraulic energy dangerously high.
Mastication in the hyrax and its relevance to ungulate dental evolution
Authors: Janis Christine M.
Published: July 2016

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.
Maximum likelihood estimation of fossil assemblage composition
Authors: Holtzman Richard C.
Published: July 2016

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.
Deep-sea foraging pathways: an analysis of randomness and resource exploitation
Authors: Kitchell Jennifer A.
Published: July 2016

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.
Taphonomic investigations of owl pellets
Authors: Dodson Peter , Wexlar Diane
Published: July 2016

Owls are important consumers of small vertebrates, and because they regurgitate pellets rich in bone, they may be important potential contributors of the concentrated remains of small vertebrates to the fossil record. Owls of three sizes, the large great horned owl (Bubo virginianus), the medium-sized barn owl (Tyto alba), and the small screech owl (Otus asio), were fed a common diet of mice. The bony contents of the pellets were analyzed to determine the amount of bone loss by digestion, bone completeness, and sites of bone breakage. For all three species, only about half the number of bones ingested were recovered in the pellets. Mandibles and femora were most abundant, and pelves and scapulae were the least abundant. Screech owls broke 80% of the cranial and limb elements, barn owls only 30%. Skulls fared poorly in great horned and screech owl pellets, while barn owls returned 80% of the skulls intact, with only the caudal portion of the cranium damaged; barn owls also returned articulated strings of vertebrae and complete paws. These results provide a baseline for the recognition of owls as agents of accumulation of small bones in the fossil record and suggest that the actions of ancient predators may be revealed by species-specific patterns of bone destruction of an assemblage of fossil prey species.
Evolving paleontological views on deterministic and stochastic approaches
Authors: Schopf Thomas J. M.
Published: July 2016

Experienced workers in a field are unlikely to change their assessment of basic philosophical issues. Einstein for example never accepted the indeterminacy required by the Heisenberg uncertainty principle, despite the urgings of Max Born and virtually all others. Similarly even earlier, some older workers had refused to accept the young Einstein's theories. Now if issues in physics are not open and shut, they are even less so in paleontology. Possibly it is useful to probe the underlying basic philosophical background to our discipline. The purpose of the present article is to indicate that the inductive, deterministic approaches which have been used almost exclusively in paleontology have stringent limitations. For some types of problems, deductive stochastic processes are more interesting. If we can make the distinction of ‘few’ versus ‘many,’ then it is quite easy to consider deterministic explanations for the individual cases (the movement of individual molecules) but to reserve stochastic explanations for the ensembles of events (the movement of molecules too numerous to count).
Function of cameral water inNautilus
Authors: Collins Desmond , Ward Peter D. , Westermann Gerd E. G.
Published: July 2016

Cameral water in the shell of the cephalopodNautilusphysically supports each septum while it is being formed; it also provides a reservoir of liquid ballast which is extracted to balance the increase in weight in seawater due to shell and tissue growth. It is not used as an aid to vertical movement. In adults, the sole function of cameral water is ballast in order to maintainNautilus'slight weight in seawater.
Annual cycle of shell growth increment formation in two continental shelf bivalves and its paleoecologic significance
Authors: Jones Douglas S.
Published: July 2016

The bivalvesSpisula solidissima, the Atlantic surf clam, andArctica islandica, the ocean quahog, from the continental shelf off New Jersey, contain repeating structures in their shells. By analyzing the growing shell margins in living specimens at bi-weekly (or sometimes monthly) intervals throughout two consecutive years, it was possible to define an annual cycle of shell growth increment formation in both species. The shell increments in each species are microstructurally distinct units that form over a period of several months at select seasons of the year. Each species has two alternating shell growth increments, GI I and GI II. GI I (the annual growth line of previous studies) is formed annually in the late summer-fall inS. solidissimaand in the fall-early winter inA. islandica.These periods correspond to the spawning phase of the reproductive cycle in both species. No winter rings were found. The annual increments were used to determine age and growth rate in both Recent and Pleistocene specimens. They may also be useful in determining season of death. Because shell growth increments are formed in synchrony among living populations in these species, mass mortalities may be distinguished in the fossil record. Accurate age and growth rate determinations in fossils are important in many paleobiologic contexts, such as deciding between increased longevity or growth rate in cases of phyletic size increase.
Predation in time and space: peeling and drilling in terebrid gastropods
Authors: Vermeij Geerat J. , Zipser Edith , Dudley Elizabeth C.
Published: July 2016

Two types of predation (shell breakage at the lip by calappid crabs and drilling by gastropods) were studied in more than 6000 Recent and 1500 fossil terebrid gastropods. The occurrence of lip-peeling was assessed by the frequency of shell repair, defined as the number of repaired injuries divided by the total number of shells in a sample. This frequency is interpreted as a measure of the demonstrated importance of the shell as a protective device against peeling. In the Recent fauna, frequencies of repair are highest in the tropical Indo-West-Pacific, intermediate in tropical America, and lowest in warm-temperate areas. When comparisons are restricted to particular size classes, these geographical differences become blurred, especially among smaller shells. Slender, many-whorled species have significantly lower frequencies of repair than do terebrids with more compact shells. Samples of Terebra affinis from atolls have fewer repairs than do those from high islands or continental shores. Among fossils, there is no difference in repair between Paleogene and Neogene samples. In the Miocene, warm-temperate terebrids had frequencies of repair similar to those of tropical species. The frequency of repair is loosely correlated with the number of species of shell-peeling calappid crabs. Frequencies of drilling have been at high modern levels since Eocene time. Incomplete drill-holes are common in large Recent species, and suggest that the terebrid shell is well adapted to withstand attacks by naticid gastropods. The results of this study are consistent with those of architectural analyses of soft-bottom gastropod assemblages and with other studies on predation of gastropods.
Computer simulations of early land plant branching morphologies: canalization of patterns during evolution?
Authors: Niklas Karl J.
Published: July 2016

Using computer simulations and a quantitative method for describing bifurcating structures, the morphology of branching patterns seen in early land plants is analyzed. Four types or models of random branching (regular, geometric, binomial, and poisson) are shown to adequately describe the range of observed branching in most early land plants. Approximately 57% of all randomly generated computer patterns show reiterative branching events (=three successive identical modes of branching). Artificial canalization of reiterative events results in branching patterns structurally analogous with that of ancient fossil plants. Simulated phylogenetic changes among early land plant lineages, based on parsimonious transitions in branching patterns, indicate that most observed trends can be related directly to those seen in randomly generating branching patterns in which “size” is increased. The trimerophyte to progymnosperm trend in changing branching patterns is an exception, since the binomial model describing the progymnosperms has not been simulated by random processes.

While the apparent phylogenetic changes among early land plant groups do not require deterministic explanations, the transition from regular to geometric branching and the “canalization” of reiterative branching patterns may represent a grade level response to selective pressures related to mechanical design and vegetative reproduction.
Roles for holes in sand dollars (Echinoidea): a review of lunule function and evolution
Authors: Smith Andrew B. , Ghiold Joe
Published: July 2016

The function of lunules in sand dollars is reviewed and it is argued that ambulacral lunules and the anal lunule evolved for quite different purposes. Whereas ambulacral lunules evolved to increase the perimeter of the test for food gathering, this was clearly not the original function of the anal lunule, although in some genera it has become secondarily adapted to this role. Many of the unique features of the anal lunule can be explained if it evolved as an outlet for ciliary feeding currents drawn centripetally into the mouth, without disrupting either oral or aboral currents. This allowed the entire margin of the test to be used for collecting the fine particles sieved through the aboral spine canopy. Anal lunules probably evolved only once, in the Miocene, and the Monophorasteridae and Mellitidae are probably sister groups.
A reappraisal of the systematics, biogeography, and evolution of fossil horses
Authors: Woodburne M. O. , MacFadden Bruce J.
Published: July 2016

The founders of North American vertebrate paleontology, F. V. Hayden, Joseph Leidy, E. D. Cope, O. C. Marsh, and their colleagues, collected and described the first suites of fossil mammals obtained from the rich Tertiary successions of the western United States. Among them were remains of fossil horses, and subsequent study of these resulted in an interpretation that supported the concept of Darwinian gradualism as the major mode of evolution. The fossil record of horses also contributed importantly to the demise of orthogenesis as an evolutionary pattern, and to the evaluation of evolutionary rates and long-term evolutionary trends in a major phyletic group of organisms.
On The Measurement of Morphology and its Change
Authors: Benson Richard H. , Chapman Ralph E. , Siegel Andrew F.
Published: July 2016

Few would argue with the assertion that within the practice of comparative morphology, the comparison of shapes is fundamental to any line of synthesis in paleontology. Yet the common act of such a comparison involves a great range of judgments concerning the homology, correspondence and divergence of form of various parts of any two related shapes. Considerations of similarity must include the scalar effects of size and material, the conversion of proportions as descriptive geometric dimensions to those useful numerical values that will be represented as ratios of measured distance (relative or compared against a standard), and, by no means insignificant, the judgment about the design or functional geometry implicit in the static as well as dynamic systems being measured. This review is concerned with these considerations and with quantitative comparisons of biological shape wherein some parts of specimens obviously have changed and others parts have not.
Resolution analysis: A new approach to the gaps in the fossil record
Authors: Schindel David E.
Published: July 2016

Fine-scale sampling and analysis of fossiliferous sequences have been used in the debate over gradual vs. punctuated evolutionary transitions between species. The time scale and completeness of these studied sequences can be evaluated using criteria based on compilations of sedimentation rates over different time spans. A set of procedures, herein termed “resolution analysis,” provides the means for estimating the time scale and quality of sequences from which evolutionary patterns are distilled. Seven such published studies are evaluated with these procedures. In general, most fossil sequences are too incomplete on fine time scales to show changes operating within a standing population. Short segments of some sequences have the potential to document nearly complete morphological histories on time scales approaching generation-to-generation processes. Resolution analysis is a necessary step in inferences regarding fossil evidence of evolutionary tempo and mode.

Stratigraphic incompleteness necessarily results from the episodic nature of sedimentation. Many stratigraphic gaps result from minor, temporary shifts in sediment distribution, though other, more profound gaps result from changes in habitat conditions that must have had an effect on local biotic distribution. Analyzing paleontological patterns involves not only the positive evidence provided by fossiliferous strata, but also the negative evidence left as gaps by shifting habitat conditions. Thus, incomplete sequences may not be “flawed” records of continuous populations. Incomplete sequences may be a faithful, literal record of separate populations separated in time by local extinctions and re-invasions.
Modes of larval development in Early Tertiary neogastropods
Authors: Hansen Thor A.
Published: July 2016

A survey was undertaken of the developmental types of the neogastropod families Volutidae, Fasciolariidae, Nassariidae, Mitridae, Buccinidae and Olividae in the Palaeocene and Eocene series of the Gulf of Mexico. Although the families were dominated by planktotrophic development in the Paleocene, most show a general increase in numbers of species with nonplanktotrophic development through the Eocene. Present day environmental correlations with larval development do not adequately explain the observed shift in developmental types in the Early Tertiary. It is proposed that higher speciation rates for nonplanktotrophs and a unidirectional trend in developmental change may account for the progressive increase of nonplanktotrophic development.
Rupture strength and flow rate of Nautilus siphuncular tube
Authors: Chamberlain John A. , Moore William A.
Published: July 2016

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.
Analysis of the preservation of community structure in assemblages of fossil mammals
Authors: Damuth John
Published: July 2016

The degree to which the relative abundances of the species in a fossil assemblage represent those in the living community from which it came is an indication of the fidelity of the assemblage in preserving most of the aspects of community structure that we may hope to find in the fossil record. I have developed a model for the formation of attritional fossil mammal assemblages that shows that the logarithm of the number of individuals of each species in an ideal unbiased assemblage, when regressed on the logarithm of body mass, will exhibit a slope of approximately −1.05 ± 0.25 (approximate 95% confidence interval). This value is based upon ubiquitous scaling relationships of population density and turnover rate with body mass among extant mammals. These relationships are the results of widespread energetic and metabolic regularities in community structure and physiology and can be expected to have been essentially the same in the remote past. The slope of −1.05 provides for the first time a reference standard for community structure of sufficient generality for use in the analysis of this aspect of fossil assemblages. We can use this value as a sort of “null hypothesis” of no bias against which we can compare actual fossil assemblages.

Analysis of some promising assemblages reveals that they exhibit badly biased relative abundances. However, it is likely that in these cases we can explain this bias as almost entirely the result of pre-burial differential destruction of the carcasses of different-sized species.

The combination of this new, biological approach with the largely physical approaches of taphonomy and sedimentology will allow us to ask more specific questions about bias in fossil assemblages, avoiding circular arguments. We can now distinguish, in a large number of situations, assemblages that preserve reliable community-structure information from those that do not.
Diachronic variation in insectivores from Cheek Bend Cave and environmental change in the Midsouth
Authors: Klippel Walter E. , Parmalee Paul W.
Published: July 2016

Diachronic variation in insectivore remains from a deeply stratified cave deposit in southeastern North America is described. The paleobotanical record for the region is congruent with variation in the soricid (shrew) and talpid (mole) faunal assemblages. Both faunal and floral records reflect considerable climatic change since the full Wisconsinan in this unglaciated portion of eastern North America. Variations in the insectivore assemblages indicate the presence of a more equable climate during the late Pleistocene. Continental climates ushered in at the end of the Pleistocene resulted in a marked decrease in insectivore diversity. Relative frequency changes in taxa throughout the Holocene reflect the mid-Holocene Climatic Optimum.
Centers of origin revisited
Authors: McCoy Earl D. , Heck Kenneth L.
Published: July 2016

Historical biogeographers are divided over the major process whereby extant species, or their ancestors, arrived in their present geographical locations. One faction promotes the idea of discrete “centers” of evolutionary radiation, from which species have been supplied to other areas by long-distance dispersal. A second faction advances the notion of widespread ancestral biotas, which have been fractionated into descendant biotas over time (vicariance). A seemingly endless polemic has elevated these rather simple alternatives to causes célèbres, and many workers have responded by dismissing virtually the entire vicariance literature (see Pielou 1981). We believe that the important distinction between vicariance and center-of-origin/long-distance-dispersal can be made clear to those interested in questions of paleobiogeography. In our opinion, the recent contribution by Briggs (1981) in this journal did not do so, and we now take the opportunity to try.
Time scales and taxonomic survivorship
Authors: Holman Eric W.
Published: July 2016

Stratigraphic range data are used to derive time scales on which taxonomic survivorship curves for genera and families are as nearly as possible independent of their times of origin. These time scales correct for temporal variations in overall extinction rates caused by major extinctions and the pull of the Recent. Survivorship curves for genera and families on their respective time scales are well fit by Pareto distributions differing only in their scale parameter.
The distribution and significance of enamel and enameloid in the dermal skeleton of osteolepiform rhipidistian fishes
Authors: Meinke Deborah K. , Thomson Keith Stewart
Published: July 2016

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.HyneriaandEusthenopteronteeth also had enamel. As enamel has also been found in teeth of living lungfishes and extantLatimeria, 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.
Estimating taxonomic diversity, extinction rates, and speciation rates from fossil data using capture-recapture models
Authors: Nichols James D. , Pollock Kenneth H.
Published: July 2016

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.
A functional analysis of flying and walking in pterosaurs
Authors: Padian Kevin
Published: July 2016

An analysis of the structure and kinematics of the forelimbs and hindlimbs of pterosaurs, and functional analogy with recent and fossil vertebrates, supports a reappraisal of the locomotory abilities of pterosaurs. A hypothesis of structural, aerodynamic, and evolutionary differences distinguishing vertebrate gliders from fliers is proposed; pterosaurs fit all the criteria of fliers but none pertaining to gliders. The kinematics of the reconstructed pterosaur flight stroke reveal a down-and-forward component found also in birds and bats; structural features of the shoulder girdle and sternum unique to pterosaurs may be explained in light of this motion. The recovery stroke of flight was accomplished, in birdlike fashion, by a functional reversal of the action of theM. supracoracoideusby the pronounced enlargement of the acrocoracoid process, which acted as a pulley. The wing membrane was supported and controlled through a system of stiffened, intercalated fibers, which were oriented like the main structural elements in the wings of birds and bats.

The hindlimbs of pterosaurs were independent of the wing membrane, and articulated like those of other advanced archosaurs and birds, not like those of bats. The gait was parasagittal and the stance digitigrade. Because of limitations on the motion of the forelimb at the shoulder, pterosaurs could not have walked quadrupedally. However, bipedal locomotion appears to have been normal and quite sufficient in all pterosaurs. There is nothing batlike about pterosaur anatomy; on the other hand, pterosaurs bear close structural resemblances to birds and dinosaurs, to which they are most closely related phylogenetically.