bluuebunny/crossref_metadata_2025 huggingface dataset:
Marine biotic interchange between the northern and southern hemispheres
Authors: Lindberg David R.
Published: July 2016

Patterns of bipolar or antitropical distributions occur in a diverse array of marine invertebrate, vertebrate, and plant groups in the eastern Pacific Ocean. Available geologic and paleontological evidence does not support vicariance as a process in the creation of these distributions but instead favors biotic interchange between hemispheres. Moreover, the timing of these events suggests several breaches (both northward and southward) of the tropics rather than a single event. The fossil record is extremely important in delimiting potential hypotheses and allowing correlation with vicariance events. The congruence of some interchanges with major regional tectonic activity and others with Pleistocene glaciations is not surprising and argues for a plurality of mechanisms. Extinction of endemic taxa following interchange among marine invertebrates is rare, and none of the antitropical distributions reviewed here suggests that the arrival of a taxon in the adjoining hemisphere resulted in the extinction of an endemic taxon. Instead, interchange and endemic taxa coexist. In contrast to the extinction patterns, the patterns of radiations are extremely diverse with some immigrant taxa undergoing remarkable radiations, whereas other taxa are represented by single species. Temperate nearshore rocky communities in both the northern and southern hemispheres appear to be mosaics of species that share common ancestry (because of interchange), are cosmopolitan, and have independent origins within the region. Although some communities appear to be organized around products of interchange (e.g., kelp forests of California and Chile), only the taxa have immigrated; linkages and interactions between species are independent and locally derived.
The biogeography of origin and radiation: dendrasterid sand dollars in the northeastern Pacific
Authors: Beadle Steven C.
Published: July 2016

Under favorable circumstances, biogeographic and biostratigraphic data can be combined to identify accurately the time and place of origin of a given taxon, and to reconstruct the pattern of its subsequent radiation. This study considers the dendrasterid sand dollars, which are abundant today along the Pacific Coast of North America. The Neogene sand dollar record in this region is particularly good; in fact, sand dollars have traditionally been used as provincial index fossils.

The dendrasterids originated in central California at the end of the Miocene; the oldest forms are dated at about 6.0–6.5 Ma. They spread south to Baja California during the Pliocene, and then north to Alaska during the Quaternary. This historical pattern is not an artifact of the record; it is consistent with independent paleogeographic evidence. The dendrasterids supplanted an older Mio-Pliocene sand dollar fauna; they are now completely dominant in the temperate coastal waters of the northeastern Pacific. They have reached this position in less than 7 m.y. since their first local appearance. The rapid rise of dendrasterids could be related to their aberrant morphology and behavior; these adaptations allow dendrasterids to suspension-feed, in a manner unique among living echinoids.

Dendrasterids are characterized by “eccentric” test morphologies. Even the oldest species are highly eccentric; transitional forms are unknown. The first dendrasterids appear suddenly in the provincial “Jacalitos Stage,” above an unconformity which represents no more than about 1 m.y. They do not occur in the underlying units, although other fossil sand dollars are abundant. The dendrasterids may have arisen rapidly, through a heterochronic change in the development of older, noneccentric forms. Recent ontogenetic studies have documented the feasibility of this process.
Intercontinental variation in mass extinction patterns: influence of biogeographic structure
Authors: Westrop Stephen R.
Published: July 2016

Studies of the fates of clades during mass extinctions at the end of the Cretaceous and near the Cambrian-Ordovician boundary have indicated that geographically widespread groups have a much higher probability of survival than narrowly distributed groups. If biogeographic distribution does play a significant role in influencing the outcome of extinction events, then geographic variability in extinction intensity should be mirrored by patterns of endemism. A comparison of data for the terminal Cambrian extinction indicates that survival of trilobite families in Kazakhstan was significantly greater than in North America. As predicted, the Kazakh sequence was characterized by a significantly larger number of pandemic families. The Baltic Province, which includes Scandinavia, England, and Wales, was composed entirely of pandemic groups and did not suffer any trilobite extinction at the family level. The results are consistent with the suggestion that latitudinal variation in extinction magnitude may be the result of differences in biogeographic structure.
Biased extinction and evolutionary trends
Authors: Norris Richard D.
Published: July 2016

The directionality of long-term trends can be strongly biased by forces intrinsic to a clade. Trends in body size and skeletal shape may be dictated more by variations in survivorship that reflect differences in ecology than by long-term directional changes in the environment. Hence, mass extinctions can help drive evolutionary trends by selectively eliminating some morphologies and permitting the survivors to found the next radiation.

Examples include repeated trends toward larger maximum body size and the evolution of keeled species from those with globose tests in planktonic foraminifera. Both the trends in size and shape develop because small species with globose tests are significantly more resistant to extinction than species that are large or have peripheral keels. Hence, the survivors of both the Cretaceous-Tertiary and Eocene-Oligocene extinction episodes are small, unkeeled taxa. Large species and species with keels evolved convergently after both mass extinctions as the founders radiated anew.

Comparison of three radiations of planktonic foraminifera suggest that the convergent evolution of similar test shapes and sizes is not due to synchronous changes in oceanography that track evolutionary trends. Instead, the reestablishment of habitat heterogeneity is needed to permit the ensuing radiation to unfold rather than to closely guide its progress. Similar evolutionary trends will develop in each radiation as long as the founders have similar morphology and the evolution of variants present in the previous radiation is not precluded by the environment.
Middle Miocene fossil plants from Fort Ternan (Kenya) and evolution of African grasslands
Authors: Retallack Gregory J.
Published: July 2016

New evidence from fossil plants at the Middle Miocene fossil quarry near Fort Ternan, Kenya, together with that from paleosols, allow reconstruction of a mosaic of early successional woodland (on Dhero paleosols), grassy woodland (on Chogo clay eroded phase and ferruginized nodule variant paleosols) and wooded grassland (on type Chogo and Onuria clay paleosols). This grassy open vegetation was on a high plateau of phonolite at the foot of a carbonatite-nephelinite stratovolcano, which probably supported dry Afromontane forest, alpine meadows, and marsh. This earliest savanna-mosaic vegetation yet documented from Africa, was probably recruited from dry lateritic soils elsewhere in Africa during climatic drying and cooling some 15 Ma. These early grassland ecosystems were very different from Early Miocene forest ecosystems of East Africa, but not altogether like modern grasslands either. Already present were grasses with dense growth and rich in silica bodies, and abundant antelope with moderately high crowned teeth and cursorial limb structure. These mammalian adaptations to grasslands, however, were not nearly so pronounced as they are in modern African grassland faunas, which include zebra and other Asiatic immigrants, as well as antelope. Grasses of the subfamily Chloridoideae and supertribe Panicanae were common in tropical Africa by Middle Miocene time, if not much earlier, but there is not yet evidence so far back in time for the grass supertribe Andropogonae which is now dominant in seasonally arid, overgrazed, and burned African grasslands.
A review of the fossil seabirds from the Tertiary of the North Pacific: plate tectonics, paleoceanography, and faunal change
Authors: Warheit Kenneth I.
Published: July 2016

Ecologists attempt to explain species diversity within Recent seabird communities in terms of Recent oceanographic and ecological phenomena. However, many of the principal oceanographic processes that are thought to structure Recent seabird systems are functions of geological processes operating at many temporal and spatial scales. For example, major oceanic currents, such as the North Pacific Gyre, are functions of the relative positions of continents and Antarctic glaciation, whereas regional air masses, submarine topography, and coastline shape affect local processes such as upwelling. I hypothesize that the long-term development of these abiotic processes has influenced the relative diversity and community composition of North Pacific seabirds. To explore this hypothesis, I divided the history of North Pacific seabirds into seven intervals of time. Using published descriptions, I summarized the tectonic and oceanographic events that occurred during each of these time intervals, and related changes in species diversity to changes in the physical environment. Over the past 95 years, at least 94 species of fossil seabirds have been described from marine deposits of the North Pacific. Most of these species are from Middle Miocene through Pliocene (16.0-1.6 Ma) sediments of southern California, although species from Eocene to Early Miocene (52.0-22.0 Ma) deposits are from Japan, British Columbia, Washington, and Oregon. During the history of the North Pacific seabirds, thee were many widespread (global) and local (California Current) oceanographic events, but the underlying physical processes that affected the diversity of seabirds throughout the North Pacific were tectonic changes that led to sequential stages of thermal isolation and refrigeration of Antarctica. Besides these broad-scale phenomena, the uplift of the Isthmus of Panama and the initiation and intensification of coastal upwelling in the California Current directly affected the diversity of seabirds in southern California. For the most part, Middle to Late Miocene and Pliocene seabird faunas from California resembled Recent communities, but with several exceptions: (1) the extreme diversity and abundance, but subsequent extinction of gannets (Morus) and flightless alcids (mancallids); (2) the comparatively low abundance and diversity of cormorants and shags (Phalacrocoracidae) until the Late Pliocene; and (3) the absence of marine Laridae until the Late Pliocene. By affecting both the physical and biological environments, geological factors such as Antarctic glaciation, eustatic changes in sea levels, and local tectonic activities influenced and will continue to influence the structure of seabird systems in the North Pacific.
Early life history ofNautilus: evidence from isotopic analyses of aquarium-reared specimens
Authors: Landman Neil H. , Cochran J. Kirk , Rye Danny M. , Tanabe Kazushige , Arnold John M.
Published: July 2016

Specimens ofNautilusspecies caught in the wild show a marked increase in oxygen isotopic composition between embryonic and postembryonic septa. The significance of this increase in terms of the early life history ofNautilushas been unclear. To help explain this pattern, we analyzed the isotopic composition of the septa of three specimens ofNautilus belauensisraised in aquariums under controlled temperature conditions. Our results indicate that both embryonic and postembryonic septa are secreted with the same temperature-dependent fractionation of aragonite relative to water as that of other aragonite-secreting molluscs (Grossman and Ku 1986). The δ18O values of the septa thus provide a reliable means of determining the water temperature in which the septa form. Calculated temperatures based on oxygen isotopic data from specimens caught in the wild reveal that embryonic development occurs at 22°-24° corresponding to a depth of 100-200 m depending on the location. The increase in δ18O in postembryonic septa reflects a migration into colder, deeper water after hatching. In Cretaceous nautilids, a systematic shift in δ18O is not present, indicating that these animals probably did not change their habitat after hatching. This is consistent with the likelihood that they lived in shallower environments than that of modernNautilus.
Allometric heterochrony in the Pliocene-Pleistocene planktic foraminiferal cladeGloboconella
Authors: Wei Kuo-Yen
Published: July 2016

Allometric analysis of the size-shape relationships in the Pliocene-Pleistocene planktic foraminiferalGloborotalia(Globoconella)puncticulata-inflataplexus reveals several heterochronic modes underlying the morphological evolution of the clade. The ancestral lineage,G. puncticulata,is a peramorphocline, showing a pre-displacement mode of heterochrony between 3.5 Ma and 3.0 Ma and an acceleration mode from 3.0 to 2.7 Ma. A different peramorphosis process, isometric giantism (hypermorphosis), in the ontogeny of the ancestral stocks ofGloboconellaoccurred at about 3.5 Ma and gave rise to theG. inflatalineage. The descendant lineage,G. inflata,appears to have adopted a paedomorphosis trend by delaying the onset of the neanic stage in ontogeny during the period of 3.5 to 2.35 Ma, resulting in a series of transposition allometries. During the interval of 2.4 to 1.73 Ma, the allometries shifted to the opposite direction, signifying a pre-displacement trend. Evolutionary stasis marks the evolution during 1.73 to 0.25 Ma. Neoteny concluded the final evolutionary stage of theG. inflatalineage during the latest Quaternary (0.26 to 0.05 Ma). The enormous plasticity and fluctuations in morphology ofG. inflataare attributed to the highly positive allometric growth during the ontogeny and the wide-range transposing allometries in the phyletic history. The major changes in heterochronic mode coincide with paleoceanographic events, suggesting that the morphological evolution in theGloboconellaclade has been modulated by changes in paleoceanographic conditions.
Mathematical models of cladogenesis
Authors: Raup David M.
Published: July 2016

The evolutionary pattern of speciation and extinction in any biologic group may be described by a variety of mathematical models. These models provide a framework for describing the history of taxonomic diversity (clade shape) and other aspects of larger evolutionary patterns. The simplest model assumes time homogeneity: that is, speciation and extinction probabilities are constant through time and within taxonomic groups. In some cases the homogeneous model provides a good fit to real world paleontological data, but in other cases the model serves only as a null hypothesis that must be rejected before more complex models can be applied. In cases where the homogeneous model does not fit the data, time-inhomogeneous models can be formulated that specify change, regular or episodic, in speciation and extinction probabilities. An appendix provides a list of the most useful equations based on the homogeneous model.
Systematics and paleobiology
Authors: Eldredge Niles , Novacek Michael J.
Published: July 2016

Systematics, ostensibly the “old” paleontology, actually plays a central and crucial role in modern paleobiology. We argue that a revised ontology has recently clarified the nature of species and has expressly added monophyletic groups to the roster of spatiotemporally bounded entities—“individuals”—that are now seen as participants in the evolutionary process. Systematics is the study of species and monophyletic taxa, and fossils alone provide the data on the temporal boundedness of such taxa.

Cladistics (phylogenetic systematics) is explicitly geared to the recognition of monophyletic taxa. We review aspects of the core problem of character analysis in systematics, particularly addressing the still contended issue of the seemingly competitive claims of three methodologies: out-group comparison, comparative ontogeny, and the “paleontological method.” We find that these methods overlap in their basic assumptions to a significant extent, yet each retains a characteristic and distinctive flavor. They are not all “the same,” nor are they always “complementary”—and no one method is superior to the others in all circumstances.

Far from being the Victorian symbol of a moribund science, systematics lies at the very heart of modern paleobiological research, providing the central data for paleobiology's truly unique contribution, both real and potential, to evolutionary biology in general.
Evolutionary paleoecology: recent contributions to evolutionary theory
Authors: Kitchell Jennifer A.
Published: July 2016

In the past decade, evolutionary paleoecology has shifted away from corroborative research of the “me-too-ecology” type toward its proper domain—the evolutionary consequences of ecological properties, roles, and strategies at the individual, population, community, and species levels. The science of evolutionary paleoecology tests for linkage between a species' ecology and its macroevolutionary history. Do the ecological characters of species within clades influence differential rate dynamics, particularly rates of faunal turnover and diversification? Intellectual coequality, once hampered by the misunderstanding that the role of paleoecology is to find examples of past ecology imperfectly entombed in the fossil record, is strengthened by the increasing number of evolutionary ecologists who have called for explicit paleontological contributions to resolve theoretical issues. The fossil record provides a necessary perspective to an understanding of process.
Evolutionary implications of predation on Recent comatulid crinoids from the Great Barrier Reef
Authors: Meyer David L.
Published: July 2016

Diving investigations of Recent comatulid crinoids at Lizard Island, Great Barrier Reef, indicate that, contrary to long-held notions, crinoids are subject to predation, principally by fishes of several families. Predation usually occurs as sublethal damage to the visceral mass and arms, from which the crinoids usually recover by regeneration. Aspects of the life habits, morphology, biochemistry, and physiology of comatulids are postulated to be adaptations that enable comatulid crinoids to resist predation. Comatulid versatility in coping with predation may account in large measure for their evolutionary success in the face of the late Mesozoic teleost radiation. Frequency of damage and repair in fossil crinoids can be used as a measure of predation pressure in order to assess the impact of predation during the Phanerozoic evolution of crinoids. Paleozoic stalked crinoids made a heavy investment in skeletal armor, while in contrast, comatulids reduced the calyx and became mobile. The relationship between these phyletic trends and predation pressure can now be critically examined.
Phenotypic evolution in a lineage of the Eocene ostracod Echinocythereis
Authors: Reyment Richard A.
Published: July 2016

Two speciation events occurred in the Eocene lineage beginning with Echinocythereis isabenana Oertli (Aragon, Spain). After a long period of stasis in ornament and shape/size, this species underwent a relatively rapid decrease in size, accompanied by ornamental changes. The transition required about 30,000 yr. The new species E. aragonensis Oertli is significantly smaller (20% decrease in size). The lateral papillation is denser and less regular, the papillae being significantly smaller than in the ancestral form. This ornament gradually yields to increasing frequencies of individuals with reduced papillae superimposed on a progressively better developed network of filaments. This change, which is regionally valid, is ultimately replaced by fully expressed reticulations, on which minute pustules may occur; this development typifies the third species, E. posterior Oertli. Some ornamental characteristics of E. aragonensis are anticipated in rare individuals of E. isabenana. Ornamental features of E. posterior appear in late larvae of E. isabenana. Generally, E. aragonensis and E. posterior do not differ significantly in size. A trend toward smaller carapaces in the upper samples of E. posterior could be related to ecophenotypic effects.

All species are highly polymorphic for both shape and ornament; the morphs are not sharply bounded and are mostly of uncertain evolutionary status. The transition from isabenana to aragonensis is heralded by a sharp rise in the coefficient of variation for length measures of the carapace. There is a pronounced multivariate morphometric discontinuity between isabenana and the descendant forms, which are largely multivariately homogeneous. The isabenana-aragonensis transition could have occurred by selection or by random genetic drift. Both models can be accommodated by the data; however, the weight of evidence favors the former hypothesis. Evolution in the Echinocythereis lineage seems to have occurred by two different mechanisms. The first transition was rather rapid, with many disjunct features. The second was slow, the changes being more of degree than of kind.
The enigmatic Ediacaran (late Precambrian) genusRangeaand related forms
Authors: Jenkins Richard J. F.
Published: July 2016

The late Precambrian genusRangeaGürich, 1929, a frond-like fossil composed of repeated foliate elements, is one of the first discovered forms belonging to the now widely known soft-bodied assemblages characterizing the Ediacaran Period.Rangeaoccurs together with the generaPteridiniumGürich, 1933, andErniettaPflug, 1966, in the lower parts of the Nama Group, Namibia (South West Africa).

Investigation of the preservation and structure ofRangea, utilizing a methodology similar to that established by Wade (1968, 1971), indicates that it was probably a colonial octocoral consisting of a large tapering primary polyp, or oozoid, and a number of leaf-shaped, conjoined fronds which bore the feeding polyps; it is suggested to belong to a group of early Ediacaran anthozoans which provide a fossil link between the still living Telestacea and Pennatulacea. Similar investigations ofPteridiniumandErniettadisclose that their structure is different fromRangeaand does not support ideas that they are related to it.
Proboscidean origins of mastodon and woolly mammoth demonstrated immunologically
Authors: Shoshani Jeheskel , Lowenstein Jerold M. , Walz Daniel A. , Goodman Morris
Published: July 2016

Immunologically reactive protein substances were extracted from bone samples of an American mastodon (Mammut americanum), 10,200 yr old by radiocarbon dating, and from muscle samples of three woolly mammoths (Mammuthus primigenius), 10,000, 40,000 and 53,000 yr old, respectively. The mastodon samples contained significant quantities of the amino acids hydroxylysine and hydroxyproline, both of which are usually found in collagens and not in albumins. Using these products and other comparable extracts, as well as sera and purified collagens from modern elephants and other living mammals, as test antigens, immunological comparisons were carried out with the following antisera: rabbit anti-mastodon bone; chicken anti-mammoth muscle; chicken anti-elephant muscle; rabbit anti-elephant albumin and rabbit anti-elephant collagen, as well as with rabbit antisera to purified albumins and collagens of other mammals. For the first time, mastodon bone was found to have elephant-like proteins, which elicited antibodies that reacted strongly with collagen and serum proteins of extant elephants. Mammoth muscle strongly reacted with anti-elephant collagen and anti-elephant albumin, but the concentrations of the recoverable mammoth collagen and albumin decreased with increasing chronological age of the mammoth specimens. Nevertheless, in the immunological comparisons, the mammoth was closer to Asian (Elephas maximus) and African (Loxodonta africana) elephants than to the mastodon; in turn, the mastodon was closer to these elephantid species than to mammals outside the order Proboscidea.
Prolonged stability in local populations of Cerion agassizi (Pleistocene-Recent) on Great Bahama Bank
Authors: Gould Stephen Jay
Published: July 2016

Long-term persistence of patterns in geographic variation within species is an interesting and puzzling phenomenon. I present a well-defined natural experiment in the land snail Cerion agassizi from the islands of Great Bahama Bank. C. agassizi is the best-known fossil of the ca. 120,000 years BP dunes of New Providence, Cat and Eleuthera Islands; populations have survived on Cat and Eleuthera. During the Wisconsin glacial advance, all these islands joined together in an emergent bank. Presence of the same species on two islands at two times permits a test for both time signatures (does change occur in the same manner on both islands) and island signatures (do aspects of shell phenotypes remain constant on each island through time).

Factor and discriminant analyses establish morphological separations among fossil populations of the three islands. These differences occur along pathways specified by well-known covariance sets in the complex allometric ontogeny of Cerion. By these routes, small variations in the geometry of growth may be magnified to large differences in external appearance. I found a time signature, probably attributable to introgression of modern populations by Cerion glans on both Cat and Eleuthera. Despite the intermediate period of emergence and joining of all islands, I also found an island signature in the preservation through time, on both Cat and Eleuthera, of the differentia that separate fossil populations. The basic distinctions of the two islands, expressed as patterns of covariance in growth, have been stable for at least 120,000 years.
Predation, herbivory, and kelp evolution
Authors: Estes James A. , Steinberg Peter D.
Published: July 2016

We propose that the kelps (Laminariales) radiated in the North Pacific following the onset of late Cenozoic polar cooling. The evidence is that (1) extant kelps occur exclusively in cold-water habitats; (2) all but one of 27 kelp genera occur in the North Pacific, 19 of these exclusively; and (3) limpets and herbivorous marine mammals obligately associated with kelps or other stipitate brown algae appeared late in the Cenozoic, even though more generalized forms of both groups are much older. We propose, further, that sea otters and perhaps other groups of benthic-feeding predatory mammals, whose late Cenozoic distributions all were limited to the North Pacific, created an environment for the evolution of kelps in which the intensity of herbivory was unusually low. We hypothesize that this interaction created predictable differences among habitats in the intensity of herbivory on several spatial scales, with resulting trade-offs between anti-herbivore defenses and plant competitive abilities in their respective floras. Sea otters incur time and energy costs for diving, resulting in depth-related reductions to foraging efficiency and thus increased sizes and densities of herbivorous sea urchins. Thus, the deep-water flora is well defended, but competitively subordinate, compared with the shallow-water flora. Similarly, we argue that during the same period of earth history, predation had less of a limiting influence on herbivorous invertebrates in the temperate southwestern Pacific. We hypothesize that (1) consequent biogeographical differences in the intensity of herbivory may have selected the phenolic-rich brown algal flora in temperate Australia/New Zealand; and (2) tightly coevolved plant/herbivore interactions may explain why Australian and New Zealand herbivores are undeterred by phenolics and why other classes of secondary compounds in the Australian/New Zealand flora significantly deter herbivores.
The contribution of raptorial birds to patterning in small mammal assemblages
Authors: Hoffman Rob
Published: July 2016

Seven taxa of raptorial birds were experimentally fed a controlled sample of 50 house mice (Mus musculus). Bones recovered from the pellets were examined for interspecies variability in preservation to assess the potential contribution of specific raptors to patterning in fossil assemblages. Quantitative analyses demonstrate that patterns in bone fragmentation may assist in the identification of particular raptor species as depositional agents in small mammal assemblages.
The role of anoxia in the decay and mineralization of proteinaceous macro-fossils
Authors: Allison Peter A.
Published: July 2016

Actualistic experiments have quantified rate of anaerobic decay and associated mineralization around proteinaceous macro-organisms. Carcasses of the polychaete wormNereisand the eumalacostracansNephropsandPalaemonwere buried in airtight glass jars filled with sediment and water from marine, brackish, and lacustrine environments. Over a period of 25 weeks the contents were examined to determine the state of decay and were chemically analyzed to monitor early diagenetic mineralization (two methods for such analysis are reviewed). Decay processes were active in the experimental conditions despite anoxia and had virtually destroyed the carcasses within 25 weeks. However, decay-rate in the sulfate-reducing marine system was greater than in the methanogenic freshwater environments. Petrological and geochemical analyses of the organic remains identified discrete layers of authigenic iron monosulfide (a pyrite precursor) on the surface of the decayingNephropscuticle within weeks of initiating the experiment. Chemical analysis of decomposing flesh showed a marked increase in pore-water calcium content with time.

The results clearly show that anoxia is ineffective as a long-term conservation medium in the preservation of soft-bodied fossils. However, decay-induced mineralization can be very rapid so that even a slight reduction in decay rate can lead to improved levels of fossil preservation. Traditionally, stagnation and rapid burial are considered to be the main prerequisites for the preservation of soft-bodied fossils and the formation ofKonservat-Lagerstätten. Clearly these factors are only important in that they promote early diagenetic mineralization. This is the only way to halt information loss through decay.
Swimming capabilities of Mesozoic marine reptiles: implications for method of predation
Authors: Massare Judy A.
Published: July 2016

Body shape and mode of swimming were major factors that affected the swimming capabilities of Mesozoic marine reptiles. By estimating the total drag and the amount of energy available through metabolism, the maximum sustained swimming speed was calculated for 115 marine reptile specimens. Calculated sustained swimming speeds range from 1.8 to 2.7 m/sec, but are probably too high by as much as a factor of two. Mesozoic marine reptiles were probably much slower than modern toothed whales. The diversification of fast, agile teleost fish in the Cretaceous may have therefore contributed to the decline of the marine reptiles.

Long-bodied reptiles appear to have had slower sustained swimming speeds than deep-bodied forms of the same length. For a given length, ichthyosaurs were probably faster sustained swimmers than plesiosaurs, and plesiosaurs were probably faster sustained swimmers than crocodiles and mosasaurs. This suggests that the long-bodied forms probably used an ambush technique to capture prey, to maximize the range of possible prey and to minimize competition with the faster pursuit predators.
Macroevolutionary differences between the two major clades of Neogene planktonic foraminifera
Authors: Stanley Steven M. , Wetmore Karen L. , Kennett James P.
Published: July 2016

Being of especially high quality, the Neogene fossil record of planktonic foraminifera offers special opportunities for assessing patterns of extinction and speciation. A variety of metrics indicates that within this group the mean duration of lineages has been much shorter (rate of extinction has been higher) for the globorotaliid clade than for the globigerinid clade. Furthermore, in the globorotaliid clade rates of extinction and speciation have not been closely linked to changes in diversity, but rather have been relatively high even at times when diversity has undergone little change. Thus, the globorotaliid clade has undergone more rapid evolutionary turnover than the globigerinid clade. Data for living species reveal that neither geographic range nor temperature tolerance is the primary factor controlling lineage duration. On the other hand, there is evidence that lineages marked by low abundance (small population size) are relatively short-lived. The reason that globorotaliid lineages have generally survived for shorter intervals, on the average, may be that their populations have been less abundant and less stable. Usually they live deeper in the water column, where food is often sparse, and many flourish only in areas of upwelling. Furthermore, the globorotaliids lack symbiotic algae for nutritional support. The same ecological factors may have accelerated speciation in the globorotaliid clade, by causing species to be patchily distributed. Thus, population size and structure have been more important than geographic range in determining rates of extinction and speciation. This parallels the situation for Neogene marine bivalves.

For planktonic foraminifera, as for Western Atlantic Bivalvia, the normal pattern of extinction was reversed in late Pliocene time, apparently in response to climatic cooling. The globigerinids suffered a sudden pulse of extinction. The deeper dwelling globorotaliids fared better; probably many of their species benefited from elevation of the seasonal thermocline into the photic zone. At the same time, rate of speciation declined in the globorotaliid clade, which supports the idea, inferred from the evolutionary history of marine bivalves, that an increase in the size and stability of populations should depress both rate of extinction and rate of speciation.
Interpreting the diet of extinct ruminants: the case of a non-browsing giraffid
Authors: Solounias Nikos , Teaford Mark , Walker Alan
Published: July 2016

Modern ruminant species have traditionally been placed in three broad dietary categories (browsers, grazers and intermediates) based on their observed feeding habits. Shape analysis of premaxillary outlines of 31 species of ruminants shows that their premaxillae differ according to their dietary category. Browsers have pointed premaxillae and grazers square ones. Intermediate feeders have intermediate outlines.

The Miocene giraffidSamotherium boissierihas always been viewed as a specialized browser similar to the modern okapi,Okapia johnstoni. However, the premaxillary shape ofS. boissierifalls very close to the mean of the grazers and is most similar to that of the African buffalo (Syncerus caffer), a committed grazer.

Quantitative analyses of the microscopic wear patterns on the molars reveal significant differences between three modern species from the three dietary groups.S. boissierihas more microscopic scratches on its teeth than either the modern giraffeGiraffa camelopardalis(a browser) or Grant's gazelleGazella granti(an intermediate feeder). In this respect, it is indistinguishable from the wildebeestConnochaetes taurinuswhich is a committed grazer.

Both of these analyses suggest that this extinct giraffid was a grazer, although we cannot rule out the possibility that it was an intermediate feeder. It was definitely not a specialized browser as are both living members of the Giraffidae.
Real and random patterns associated with molluscan spatial and temporal distributions
Authors: Russell Michael P. , Lindberg David R.
Published: July 2016

The species-level properties of geographic range and geologic duration are often used as variables in evolutionary studies. However, estimates of species duration are not independent of estimates of geographic range. Before these properties are used in macroevolutionary hypotheses, error associated with these estimates must be quantified. This error may lead to spurious inferences of evolutionary processes. To assess the error associated with estimates of geographic range and geologic duration, we modeled various sampling regimes and calculated the bias associated with these estimates.

We present three analyses which document the bias associated with estimates of geographic range and geologic duration. First, we find a positive correlation between local abundance and geographic range for a sample of 180 species of Recent prosobranch gastropods from the northeastern temperate Pacific Ocean. Therefore, geographically short-ranging species are less likely to be represented in the fossil record than geographically long-ranging species because of their local rarity. Second, we demonstrate that the chance of underestimating the geographic range of a species is acute for species with restricted spatial distributions, further compounding the problem of documenting their distribution in space and time. Third, we present a simulation which quantifies the degree of autocorrelation between geographic range and geologic duration for different levels of sampling resolution and spatial distributions of fossil localities.
Phyletic gradualism and punctuated equilibrium in the late Neogene planktonic foraminiferal clade Globoconella
Authors: Wei Kuo-Yen , Kennett James P.
Published: July 2016

Substantial geographic coverage in paleontological study is essential in testing evolutionary models of phyletic gradualism and punctuated equilibrium. We present a multivariate morphometric study of the late Neogene planktonic foraminiferal clade Globoconella using specimens from four Deep Sea Drilling Project sites (DSDP 284, 207A, 208, and 588) along a latitudinal traverse in the southwest Pacific.

During the Late Miocene (7 Ma to 5 Ma), populations of the ancestral species Globorotalia (Globoconella) conomiozea formed a geographic cline showing continuous morphological variation from the temperate sites (DSDP 284 and 207A) to the warm subtropical sites (DSDP 208 and 588). Populations living to the south had higher conical angle and fewer chambers in the final whorl compared to the northern populations. Nevertheless, populations across the entire cline exhibited a coherent, directional trend towards having larger conical angle and fewer chambers through time. At the Miocene/Pliocene boundary, the intensification of the Tasman Front (Subtropical Divergence) possibly isolated the peripheral populations in the warm subtropics from the central stocks of the temperate water masses. The evolutionary trends became decoupled: the central populations gradually lost their keel and transformed into G. (G.) sphericomiozea, while the peripheral populations in the warm subtropical areas retained their keel and evolved into a flattened species, G. (G.) pliozea.

The gradual transformation of G. (G.) conomiozea terminalis (a form retaining a keel) into G. (G.) sphericomiozea (a form lacking a keel) occurred during an interval of about 0.2 m.y., with all measured morphologic variables showing continuous and steady changes. The evolution of the central populations follows the model of phyletic gradualism. In peripheral populations, the origin of the descendant species G. (G.) pliozea from the ancestor G. (G.) conomiozea terminalis occurred very rapidly within an interval of less than 0.01 m.y. The population size of G. (G.) pliozea was small at the incipient stage at about 5.05 Ma, but increased rapidly to become dominant during the next 0.2 m.y. when the ancestral species G. (G.) conomiozea terminalis became locally extinct. Following speciation, G. (G.) pliozea exhibited morphological stasis for about 0.6 m.y., until the central stock form G. (G.) puncticulata migrated back to the warm subtropics; during the next 0.5 m.y. of their sympatry, there is no sign of hybridization between these two sister species. The evolution of G. (G.) pliozea follows the model of punctuated equilibrium.

The evolution of the Globoconella clade shows both phyletic gradualism and punctuated equilibrium. These two “alternative” evolutionary models complement each other rather than being mutually exclusive. Both models are indispensable towards providing a complete picture of the evolution of Globoconella.
The evolution of nasal turbinates and mammalian endothermy
Authors: Hillenius Willem J.
Published: July 2016

Complex nasal turbinal bones are associated with reduction of respiratory water loss in desert mammals and have previously been described as an adaptation to xeric conditions. However, complex turbinates are found in virtually all mammals. Experimental data presented here indicate that turbinates also substantially reduce respiratory water loss in five species of small mammals from relatively mesic environments. The data support the conclusion that turbinates did not evolve primarily as an adaptation to particular environmental conditions, but in relation to high ventilation rates, typical of all mammals. Complex turbinates appear to be an ancient attribute of mammals and may have originated among the therapsid ancestors of mammals, in relation to elevated ventilation rates and the evolution of endothermy.
The reflection of deciduous forest communities in leaf litter: implications for autochthonous litter assemblages from the fossil record
Authors: Burnham Robyn J. , Wing Scott L. , Parker Geoffrey G.
Published: July 2016

To assess the degree to which forest litter reflects the source forest, three 1-ha plots of temperate deciduous forest were mapped and litter accumulating in these forests was sampled. Identity, position, and diameter of all stems 2 cm or larger diameter at breast height are known for each forest. Composition of the leaf litter is governed by two key factors: (1) abscised leaves are deposited primarily on the forest floor directly underneath the canopy that produced them, and (2) the leaf mass of a species is highly correlated with its stem cross-sectional area. These factors produce autochthonous litter samples that correspond closely in composition to the forest within a circle of canopy-height radius or less. Even relatively small litter samples (350 leaves) consistently contained all the common species in the local area. However, the rarer tree species were seldom recovered in the litter samples. Correlation coefficients for litter mass and basal area by species are typically over .80.

These observations have three important implications for interpreting autochthonous compression-fossil assemblages. First, approximate relative abundances of locally dominant and subdominant forest taxa can be obtained from relatively small samples of autochthonous compression-fossil assemblages. Second, representation of rare forest species, even in large fossil samples, will be fortuitous. For this reason, complete species lists and consistent estimates of richness cannot be derived directly from most existing samples of autochthonous compression-fossil assemblages. Third, the strong tendency for leaves to fall beneath the canopy of the tree that sheds them suggests that properly sampled autochthonous fossil leaf assemblages may yield information on crown size of individual trees and the spatial distribution of individuals and species, aspects of vegetational structure that have been thought accessible only in well-preserved “fossil forests” with standing trunks.
Large-body impact and extinction in the Phanerozoic
Authors: Raup David M.
Published: July 2016

The kill curve for Phanerozoic marine species is used to investigate large-body impact as a cause of species extinction. Current estimates of Phanerozoic impact rates are combined with the kill curve to produce an impact-kill curve, which predicts extinction levels from crater diameter, on the working assumption that impacts are responsible for all “pulsed” extinctions. By definition, pulsed extinction includes the approximately 60% of Phanerozoic extinctions that occurred in short-lived events having extinction rates greater than 5%. The resulting impact-kill curve is credible, thus justifying more thorough testing of the impact-extinction hypothesis. Such testing is possible but requires an exhaustive analysis of radiometric dating of Phanerozoic impact events.
On the declining extinction and origination rates of fossil taxa
Authors: Pease Craig M.
Published: July 2016

The per-stage extinction rate is the product of the per-taxon extinction rate and stage length, and the per-stage origination rate is defined similarly. These rates decline from ancient to recent times because of the pull of the Recent, because there is more young than old fossiliferous rock, and because average stage length increases from the recent to the past. More specifically, the present model assumes that the graphs of ln(per-stage extinction rate) and ln(per-stage origination rate) versus geologic time have slope zero in the absence of sampling biases, and shows how sampling biases cause both these graphs to appear to have slope min(h,q) + s in the distant past, where h and q are the fossil loss and actual per-taxon extinction rates, and the stratigraphic constant, s, quantifies how stage length changes through time.

Although the per-stage rates of bivalve families and marine invertebrate genera decline toward the recent, the magnitudes of these declines are entirely consistent with what the present model predicts sampling biases will produce. Hence there is no need to postulate a biological explanation for these patterns.
The importance of phylogenetic analysis for the assessment of species turnover: a case history of Paleocene mammals in North America
Authors: Archibald J. David
Published: July 2016

During the latest Cretaceous and the Paleocene in western North America, disappearance rates for mammalian genera track appearance rates, both reaching their peak in the early Paleocene (Puercan) following the extinction of non-avian dinosaurs. Some of the disappearances during this time were pseudoextinctions that resulted when ancestral species disappeared during speciation.

Species-level cladistic analyses and a well-constrained biostratigraphic framework are required to study this form of pseudoextinction. Cladistic analyses show that monophyly cannot be established or rejected for some species because these species lack autapomorphies (uniquely derived character states) that unite their constituent members. Such taxa, termed metaspecies, are potential ancestors to species and higher clades with which they share a node in the cladogram.

A hypothetical species-level cladistic analysis coupled with three different hypothetical biostratigraphies shows how different models of speciation (bifurcation, budding, or anagenesis) result in very different patterns of true versus pseudoextinction. Depending on the speciation model, true extinction can be overestimated by as much as a factor of four, raising the specter of mass extinction. Species-level studies for three early Tertiary mammalian taxa—taeniodont eutherians, taeniolabidid multituberculates, and periptychid ungulates—use the same procedures. They show that almost 25% of disappearances during the early Paleocene (Puercan) for species in the analysis were pseudoextinctions of metaspecies. Budding and anagenetic-like peripatric speciation, but not bifurcation, are seen in the three examples.

Equating disappearance to true extinction can profoundly affect interpretations of faunal turnover, especially during mass extinctions or major faunal reorganizations. Some authors use pseudoextinction to describe the taxonomic rather than evolutionary disappearance of nonmonophyletic groups. Pseudoextinction, as used here refers only to the evolutionary disappearance of metaspecies via speciation. Both usages seem appropriate but should not be confounded.