bluuebunny/crossref_metadata_2025 huggingface dataset:
Ordovician Life on Land and Early Paleozoic Global Change
Authors: Retallack Gregory J.
Published: January 2018

Many Paleontologists share the opinion of McGhee (1996), who wrote “Prior to the Devonian, there was no terrestrial ecosystem to speak of. Some primitive plants precariously establishing a beachhead in protected coastal areas was about it. The interiors of the continents of the planet Earth were as barren as the rocky landscapes of Mars.” Thus, it was with trepidation that I reported paleosols containing trace fossils of early land animals in the late Ordovician, Juniata Formation, of Pennsylvania (Retallack and Feakes, 1987; Retallack, 1992a, 1992b, 1993). My late colleague, Jane Gray, engendered considerable debate by reporting Ordovician and Early Silurian spores like those of liverworts (Gray and Boucot, 1977; Gray, 1985). This spore, trace fossil and paleosol evidence for life on land in the Ordovician has remained controversial (Buatois et al., 1998; Shear, 1998), but evidence for Ordovician life on land has continued to accumulate. Especially important was discovery of myriapod trackways from mid-Ordovician (Llandeilian-Caradocian) Borrowdale Volcanics of the Lake District, England (Johnson et al., 1994). Abundant arthropod burrows and tracks, and a single body fossil of an euthycarcinoid in the fluvial-eolian Tumblagooda Sandstone of Western Australia (White 1990; McNamara and Trewin, 1993; Trewin and McNamara, 1995) are now thought to be late Ordovician in age (Iaksy et al., 1998). An enigmatic assemblage of arthropods and plants from a mid-Ordovician paleokarst in Tennessee (Caster and Brooks, 1956) is now thought to have been lacustrine (Gray, 1988a). The fossil record of Ordovician land plants also has improved with the discovery of possible megafossil mosses (Snigirevskaya et al. 1992), and possible late Ordovician trilete spores (Nøhr-Hansen and Koppelhus, 1998; Richardson 1988; Strother, 1991; Strother et al., 1996). But the most abundant evidence for Ordovician life on land remains fossil soils, now exploited by increasingly thorough and sophisticated studies (Retallack, 1985, 1992a, 1992b, 1993; Feakes et al., 1989; Driese and Foreman 1991, 1992a, 1992b; Driese et al., 1992, 1997; Mora et al., 1991, 1996; Mora and Driese, 1993; Yapp and Poths, 1992, 1994, 1996; Yapp, 1993, 1996). Mounting evidence from fossils and paleosols now presents an increasingly detailed view of Ordovician ecosystems on land.
Ecological Stability during the Late Paleozoic Cold Interval
Authors: Pfefferkorn Hermann W. , Gastaldo Robert A. , DiMichele William A.
Published: January 2018

Ecosystem Stability and taxonomic stasis are the opposite aspect in the history of life from ecosystem perturbation and reorganization, or extinction and origination. Naturally, change is more exciting than stasis, and change also is more useful in many ways as, for instance, in the development of biostratigraphic frameworks. Paleontological preference for geologically rapid change has gone so far that a fast evolving group of organisms has been used to create an orthostratigraphy (Orthochronologie of Schindewolf, 1950), which is claimed to be the “real” biostratigraphy. By implication, all other taxonomic groups are relegated to a secondary status of merely delivering “parastratigraphies,” which may be useful (locally or regionally), but are not the “real thing.” Ammonites, conodonts, foraminifera, and a few other taxa hold the distinction of being the “chosen” taxa, and it should be self-evident that only marine organisms qualify for this role. On the other hand, organisms on land always have been known to demonstrate coarser stratigraphic resolution. By implication, they might be more prone to ecosystem and taxonomic stasis over the long run. This, in itself, is an important observation.
The Invertebrate Invasion and Evolution of Mesozoic Soil Ecosystems: The Ichnofossil Record of Ecological Innovations
Authors: Hasiotis Stephen T.
Published: January 2018

Mesozoic soil ecosystems are intriguing because they are the products of many unique factors and events in geologic history. One of the most notable events that likely shaped Mesozoic soil ecosystems was the Permo-Triassic extinction. At that time, estimates of 20% of plant species, 50% of tetrapod genera, roughly 60% of insect families, and approximately 91 to 97% of shallow marine life became extinct (e.g., Padian and Clemens, 1985; Raup, 1986; Niklas et al., 1980; Wing and Sues, 1992; Labandeira and Sepkoski, 1993; and references therein). Over the span of the next 180 million years the supercontinent Pangea disassembled and the continents moved toward the configuration we see today (Scotese and Golonka, 1992); the Pangean mega-monsoonal climate pattern deteriorated into more zonal climates through to the Cretaceous (e.g., Parrish et al., 1982; Dubiel et al., 1991; Parrish, 1993); sea-level rose and flooded continental interiors, reaching its second greatest maximum since the Ordovician (e.g., Haq et al., 1987, 1988); and several major evolutionary episodes occurred, including the evolution and diversification of the angiosperms, mammals, birds, and many of the neopteran insects (Lillegraven et al., 1979; Carpenter and Burham, 1985; Friis et al., 1987; Wing and Sues, 1992; Labandeira and Sepkoski, 1993).
Dinosaur Architectural Adaptations for a Gymnosperm-Dominated World
Authors: Fastovsky David E.
Published: January 2018

The middle jurassic through Cretaceous was the heyday of gymnosperms. Gymnosperms—a paraphyletic group of seed-bearing, non-flowering vascular plants including conifers, ginkgos, seed ferns, cycads, and cycadeoids—comprised as much as 80% of global floras throughout this time interval. Even the much-heralded rise of angiosperms in the mid- to Late Cretaceous did little to shake the Mesozoic dominance among terrestrial floras of gymnosperms (in particular, conifers; see Tiffney, 1997). By the end of the Cretaceous, angiosperms comprised—depending upon whose estimate is being used—somewhere between 40 and 60% of the world's floras (Lidgard and Crane, 1988; Tiffney, 1997), leaving plenty of ecospace available for gymnosperms. The lower part of Figure 1, redrawn from Tiffney (1997), documents the flux of the major groups of plants throughout the Late Triassic-through-latest Cretaceous interval. The figure reaffirms that in the Mesozoic, gymnosperms were the floral force to be reckoned with.
Out of the Garden and into the Cooler? A Quaternary Perspective on Deep-Time Paleoecology
Authors: Jackson Stephen T.
Published: January 2018

Most of what we know about ecology inevitably comes from Late Quaternary ecosystems, particularly those of the past few decades. 20th Century ecosystems are the only ones for which we have direct observational and experimental studies. We can obtain detailed records of ecological dynamics at decade- to century-scales over the past few centuries using historical, permanent-plot, demographic, and paleoecological techniques, but only for a select few ecosystems. Radiocarbon-dated fossil assemblages provide records of ecological changes over the past 25,000 years. Because 14C-dating allows independent dating of the assemblages with precision of 50–500 years, detailed spatiotemporal patterns of change can be outlined, but these are limited to certain kinds of organisms and to regions with a high density of fossil sites. When we go beyond the radiocarbon barrier 30–40,000 years ago, the density of datable terrestrial assemblages decreases sharply, and our views of past ecosystems become murkier.
Meeting the challenge of funding and allocating resources to mental health across Europe: developing the Mental Health Economics European Network
Authors: McDaid David , Knapp Martin , Curran Claire ,   THE MHEEN GROUP
Published: January 2018

Aims – There is growing demand for economic analysis to support strategic decision-making for mental health but the availability of economic evidence, in particular on system performance remains limited. The Mental Health Economics European Network (MHEEN) was set up in 2002 with the broad objective of developing a base for mental health economics information and subsequent work in 17 countries. Methods – Data on financing, expenditure and costs, provision of services, workforce, employment and capacity for economic evaluation were collected through bespoke questionnaires developed iteratively by the Network. This was augmented by a literature review and analysis of international databases. Results – Findings on financing alone suggest that in many European countries mental health appears to be neglected while mechanisms for resource allocation are rarely linked to objective measure of population mental health needs. Numerous economic barriers and potential solutions were identified. Economic incentives may be one way of promoting change, although there is no one size fits all solution. Conclusions – There are significant benefits and synergies to be gained from the continuing development of networks such as MHEEN. In particular the analysis can be used to inform developments in Central and Eastern Europe. For instance there is much that can be learnt on both how the balance of care between institutional and non-institutional care has changed and on the role played by economic incentives in ensuring that resources were used to develop alternative community-based systems.

Declaration of Interest: none of the authors have received any financial support that presents a conflict of interest.
Trophic level & evolution in Paleozoic gastropods
Authors: Allmon Warren D. , Erwin Douglas H. , Linsley Robert M. , Morris Paul J.
Published: January 2018

Although trophic position or level is one of the most basic aspects of a benthic marine species' ecology, its evolutionary significance remains obscure. Gastropods offer a suitable model for examining the relationship between trophic level and evolution since they exhibit a wide variety of trophic strategies and their mode of life is often reflected in their shell form. We examined 196 genera of Paleozoic gastropods (≈ 1/3 of known genera) for which first appearance and last appearance could be specified to stage level and for which trophic strategy could be inferred with a reasonable degree of confidence. We classified these genera into four trophic categories on the basis of shell characters relating to locomotion and clamping. These trophic categories are: Suspension feeders, Grazers on firm substrata, Soft substrate Grazers/Detritivores, and Carnivores. Suspension feeders are the most unambiguously recognizable category, marked by clear indicators of a sessile mode of life such as a radial apertures and planispiral shell forms. Our central observation from these data is that suspension feeders have shorter generic longevities than the other three trophic groups. This pattern is robust to a variety of methods of analysis. The mean generic longevity of the suspension feeders is 15 MY less than the other trophic categories. Cumulative frequency of genera within trophic categories versus log duration shows suspension feeders to be statisticaly significantly shorter lived than the other three trophic categories. The other three categories are not distinguishable. This pattern is unchanged by the removal of taxa dying out at mass extinctions. Suspension feeders have lower origination rates and higher extinction rates than the other trophic classes. This is not a taxonomic artifact produced by ornamentation and the number of characters available. This background pattern is also present in the end Ordovician and Late Devonian mass extinctions. Suspension feeders loose about half their genera in these extinctions, the two classes of grazers loose about 1/3 of their genera, and the carnivores suffer almost no extinctions. Suspension feeding appears to carry a significant evolutionary detriment in both mass extinctions and background times. This may be reflected in the change in trophic distribution of gastropods from the Ordovician to the Recent. The end Permian extinction shows a different pattern of selectivity; detritivores suffer the least.
Micropaleontological studies on the Thebes Formation of the Red Sea Coast and the Nile Valley, Egypt
Authors: Aref Mahmoud M. , Kenawy Abbas I.
Published: January 2018

Thirty-eight species of larger foraminifera belonging to Nummulites, Operculina and Assilina are recorded, identified and systematically described from 5 stratigraphic sections of the Thebes Formation in the Red Sea Coast and the Nile Valley, Egypt.

According to these species the age assigned to the Thebes Formation is Lower Eocene (Ypresian).

The Nummulites species are subdivided here into 6 groups based on their evolutionary lineage following Schaub (1981). Moreover, spiral diagrams for the different species showing the relation between the number of whorls and the corresponding radius in median sections are drawn.
Macro- and microevolutionary aspects of the early Paleogene recovery of the planktonic foraminifera
Authors: Arnold Anthony J. , Kelly Daniel C. , Parker William C.
Published: January 2018

To date, most macroevolutionary studies have focused on taxonomic data; there are very few data sets that provide a large enough statistical population for extensive macroevolutionary studies involving direct morphometric data. The Cenozoic planktonic foraminifera are exceptional in this regard. Digitally captured shape descriptions of 342 species of Cenozoic planktonic foraminifera have been combined with the available data on their phylogenetic relationships to examine the interplay between speciation rates, size change, and various geometric characters. The results tend, at least for the planktonic foraminifera, to support Stanley's (1973) hypothesis regarding the causal mechanisms behind Cope's Rule. The tendency toward size increase may result from the disadvantages of large size during times of mass extinction rather than from the (conventionally assumed) advantages of larger size.

Additional results derived from morphotypic longevities and morphotypic turnover rates suggest an enhanced probability of speciation early in the Cenozoic, and enhanced longevity in the later Cenozoic.

Microevolutionary studies of patterns of changing variance within the Paleocene and Eocene genus Morozovella suggest that conventional foraminiferal taxonomic practice may not accurately reflect biological realities within the group, thus implying that our macroevolutionary results might be interpreted in other ways.

Paedomorphosis has now been seen in several foraminiferal lineages, including Morozovella angulata, a focus of the present study. Isotopic data (Shackleton, Corfield, and Hall, 1985) suggests that evolution of this group is accompanied by the invasion of a stratified water column. These observations suggest that one might look for systematic macroevolutionary morphologic tendencies in chamber expansion rate and size as a guide to understanding paleoecological conditions. It also seems reasonable to suggest that the complex morphological changes seen in the morozovellids may not represent morphological adaptation, but resource-related heterochronic shifts with ancillary morphological consequences.
Replacement events among tetrapods: expansion or competition?
Authors: Benton Michael J. , Storrs Glenn W.
Published: January 2018

Many macroevolutionary patterns have been explained in the past on the basis of expectations and prejudice rather than quantitative testing. Large-scale ecological replacements have been a prime example, where expectations of progress and competitive advantage have coloured interpretations. Equally, no doubt, others have looked for, and found, evidence for entirely noncompetitive processes to explain major replacements (reviewed, Benton 1987).

A partially quantitative approach is presented, based on a study of tetrapod families, marine and nonmarine, through the interval from Devonian to the present day. New data bases of the history of tetrapod diversification have the advantage over older attempts of (1) a fully cladistic phylogeny, and hence monophyletic families; (2) a detailed overview of stratigraphy and improved range data; (3) palaeobiogeographic control; and, (4) definition of ecological categories in terms of mean body size categories, diet, main habitat types (fully marine; partially marine/ coastal; freshwater; aquatic/terrestrial; lowland; upland; arboreal, aerial).

The bulk of the diversification of tetrapods is correlated with increases in the ranges both of habitats occupied and of diets (Benton 1990). However, tetrapod families came and went, and a large proportion of the diversification could have been driven by competition and progressive replacement of archaic families by competitively superior ones in ecological relays. In order to test this, the ranges of all tetrapod families were plotted against time and sorted into a variety of habitat, dietary, and palaeogeographic categories.

The results do not support a generalised view of competitive ecological relays. The majority of families appear to have arisen within new cells of the matrix, and did not apparently overlap in time with, or follow closely after, any potential competitors. This would be the minimum requirement for a postulate of competition. Only some 5% of cases could be open to a competitive explanation, and these include certain well known examples, such as multituberculates/ rodents, plesiadapiforms/ rodents, ichthyosaurs/ mosasaurs. The present study has narrowed the odds againt large-scale competition as a significant motor of large-scale biotic replacements. Most new taxa of tetrapods appear to have arisen in response to the availability of empty adaptive space.

Environmental shifts may also be detected during the course of tetrapod evolution, with expansions offshore to ever more fully aquatic lifestyles among marine tetrapods (because they all arose from terrestrial ancestors!), and with expansions from lowland tropical zones to temperate belts, uplands, and marginal lifestyles (burrowing, climbing, flying) among nonmarine tetrapods.
Biogeographic and evolutionary patterns of change in the terrestrial biota across the Cretaceous\Tertiary boundary
Authors: Clemens William A.
Published: January 2018

The currently available fossil record suggests, 1) biogeographic differentiation of the Late Cretaceous terrestrial biota and, 2) distinctly different patterns of evolution of terrestrial faunas and floras across the Cretaceous\Tertiary boundary.

Discovery in Alaska of dinosaurs and mammals that lived at Late Cretaceous northern high latitudes provides evidence that many groups of terrestrial vertebrates had extensive geographic ranges and faunas were biogeographically differentiated. The Alaskan dinosaurs, represented by individuals that range in size from hatchlings to adults, might have been migratory forms living at high latitudes only during the summer months. In contrast, the small mammals probably were not migratory.

Although recent discoveries are expanding our knowledge of the evolution of the terrestrial biota, the fossil record of terrestrial vertebrates during the Cretaceous\Tertiary transition is still heavily biased in favor of the northern Western Interior of North America. Here evolutionary change of the terrestrial fauna did not just involve extinction of lineages, some already decreasing in taxonomic diversity, and survival of many others. Shifts in biogeographic range and immigration of new groups played a significant role in remodeling the terrestrial fauna. The paleobotanical record is more extensive but also is biased with the most detailed record coming from the Western Interior where floral change is characterized as “massive” or “catastrophic” in scope.

These conflicting evolutionary patterns are well founded being based on analysis of substantial fossil records. A new program of research directed toward resolution of the apparent paradox tests the hypothesis that at the end of the Cretaceous the terrestrial biota was biogeographically heterogeneous and evolutionary patterns of faunal and floral change in the Western Interior cannot be taken as globally representative.
Environmental patterns in the origin and diversification of deep-water scleractinian and rugose corals
Authors: Droser Mary L. , Hampt Gretchen , Clements Steven
Published: January 2018

Scleractinian and rugose corals demonstrate a broad environmental distribution and have been documented in strata reflecting deposition from high-energy, nearshore reefal to low-energy basinal settings. Both clades have a relatively high diversity of representatives which live(d) at great depths. While deep-water scleractinian coral banks are well-documented, commonly the deep-water representatives of both clades are the small, solitary, and often delicate forms. In order to determine the nature of diversification of these deep-water forms the paleoenvironments of the earliest Rugosa and representatives of extant deep-water scleractinian families were determined. Environmental patterns of the subsequentdiversification of the Rugosa and scleractinian sub-order Caryophylliina were also documented. Environmental information was determined from independent sedimentological data.

The earliest reported Rugosa is Lambeophyllum from the Chazyan Crown Point Limestone (VT, U.S.A.), which was deposited in an nearshore/inner shelf setting. Subsequentto this occurrence, rugosans appear nearly simultaneously in North America, Australia, Europe and China. However, common Lambeophyllum, within the Blackriverian Orwell Limestone (NY, U.S.A), appearsto be the earliest of these occurrences. The Orwell is, likewise interpreted to be shallow water in origin. After their initial appearance in an onshore environment, the Rugosa rapidly expand offshore. While Middle Ordovician Rugosaare of low diversity (1 genus at a given locality), by the end of the Blackriverian they are found in middle and outer shelf settings.

Nearly all representatives of families of extant scleractinians now living in deep-water (>200’) also first occur in an onshore environment - primarily the inner shelf. The caryophylliids, the most speciousdeep-water coral clade, first appear in Toarcian age inner shelf strata and soon after occur in outer shelf deposits. However, occurrences of high diversities of caryophylliids (generic diversity greater than 4 at a given locality) are confined to inner shelf settings until the Cretaceous when generic diversities of 2 or more are common in the outer shelf. In the Tertiary, high diversities of caryophylliids are generally restricted to slope and deep basin settings, a pattern which characterises their modern distribution.

Both rugose and scleractinian corals expand offshore at low diversities within 5 million years of their first appearance and thus, demonstrate environmental diversification before taxonomic diversification.
Dinosaur behavior and growth
Authors: Horner John R.
Published: January 2018

Geological and paleontological data derived from the Upper Cretaceous Two Medicine Formation of Montana indicates that at least some dinosaur species exhibited complex social behaviors comparable to many living birds. Two species of duck-billed dinosaurs, a hypsilophodontid and a troodontid, nested in colonies and attended their respective young. Duckbilled dinosaurs had altricial young, whereas the hypsilophodontid and troodontid had precocial young. Morphological evidence indicates that several of the cranial elements of the nestling duckbills experienced retarded development, and a retention of juvenile features. Following their respective nesting periods duck-billed and horned dinosaurs aggregated into large herds, and apparently migrated seasonally. Cranial ornamentations possessed by duck-billed and horned dinosaurs were most likely used for sexual display and mate recognition.

Osteohistological data indicates that the duck-billed dinosaurs hatched from their eggs at .50 to .75 meters in length, and exited their nests at 1.5 to 2 meters in length, at an age of about one month. These dinosaurs reached 3 to 4 meters in length their first year, and 7 to 8 meters in length after about 5 years. Growth and metabolic rates decreased substantially upon reaching adult size.
Cretaceous Caribbean paleobiogeography: a comparison of the generic and species distributions of rudist bivalves in light of dispersal versus vicariance biogeography
Authors: Johnson Claudia C.
Published: January 2018

A dynamic interplay of tectonics and eustasy controlled the development and distribution of Cretaceous carbonate platforms, and subsequently influenced patterns of gene flow among tropical reef-forming rudist bivalves of the Caribbean Province. Mediterranean faunas first entered the Caribbean during the Valanginian, via trans-Atlantic larval drift. Larval drift distance was exceeded during the mid-Cretaceous opening of the Atlantic, and resulted in isolation of rudist gene pools and an Albian burst of endemism, the first of two for the Cretaceous. Following a Cenomanian, Turonian and Coniacian diversity drop, Caribbean endemism climbed again during the Santonian, Campanian and Maastrichtian. This second explosion of endemism is attributed, in part, to vicariance biogeography as Caribbean terranes split and became isolated, and in part to biotic factors (competition, niche partitioning) as terranes collided when the Caribbean plate moved eastward from its Pacific Ocean origin. Paleobiogeographic maps were compiled per stage of the Cretaceous, with substage resolution for the critical Albian, Campanian and Maastrichtian. Data utilized were 58 genera and 214 species of rudist bivalves plotted on Recent mercator projections and on 119, 100, 95, and 80 million year plate tectonic reconstructions. Diversity trends and indices of similarity were analyzed in drawing paleobiogeographic divisions. Generic plots delineated regions of tropical carbonate sedimentation, the northern and southern limits of reef building, and fluctuations of this reef line through time. Generic plots also identified areas with the greatest generic diversity per stage, and defined the timing and regional extent of the postulated Supertethyan climate zone. Paleobiogeographic plots revealed that Tropical reef-building in the Caribbean Province was wholly north of the paleoequator - a major paleoclimatic dilemna. Species plots mimicked those of genera for the Valanginian, Barremian, Turonian, Coniacian, and Santonian, but provided important new details of the movements of terranes, dispersal pathways, and isolation of rudist gene pools for the Aptian, Albian, Cenomanian, Campanian and Maastrichtian. These detailed data, the first to combine Cretaceous Tropical paleontology with Caribbean tectonic reconstructions, provide a framework for testing rates, patterns, and causes of evolution among Tropical bivalves.
Spine function in the odontopleurid trilobites

Leonaspis

and

Dicranurus

from the Devonian of Oklahoma
Authors: Kloc Gerald J.
Published: January 2018

The Lower Devonian Haragan Formation of Oklahoma has well preserved odontopleurid trilobites found in repeated calcarous mudstones. These layers (5–9cm. thick) represent distal tempestites that rapidly buried and preserved completely articulated odontopleurids which provide important paleobiological information. The genal and pleural spines of Leonaspis williamsi and Dicranurus hamatus elegantus of the Haragan Formation are examined and compared.

In Leonaspis the ventrally directed genal and pleural spines are straight and lay flat. The first pleural spine is the longest followed by progressively shorter pleural spines. Several collected and prepared enrolled specimens have the spines radiating outward. In an enrolled position the spines would protect Leonaspis from a large predator.

The pleural spines of Dicranurus have a very different pattern from Leonaspis. The first three spines are short and laterally directed, the fourth, sixth and seventh are very long, curved and directed ventrally, the eighth, ninth and pygidial spines are short and decrease in length toward the pygidium. There is no pleural spine on the fifth thoracic segment and the genal spine is very long and curved. On these spines at many growth stages there is direct and indirect evidence of being encrusted based on the following: (1) Epibionts such as bryozoans, brachiopods and a crinoid; 2) Endoliths (25–150 microns in diameter) of unknown origin are found all over Dicranurus but are predominantly on the spines; 3) Pyrite (now limonite) coating the spines apparently formed from the decay of organic matter. If the source of the organic matter came from the trilobite, then pyrite would be found all over Dicranurus. However, it is only found randomly on the spines. This pattern is like some of the encrusting bryozoans suggesting that the source of the organic matter may be from an encrusting organism.

It is doubtful that the pleural spines of Dicranurus would be adapted for resting on the bottom when bryozoans are found encrusting the entire surface of the spine. However, the very long pleural and genal spines with attched organisms would break up the outline of Dicraurus making it less conspicuous to a predator.
Competitive overgrowth and post-Paleozoic macroevolution of marine bryozoa
Authors: McKinney Frank K. , Lidgard Scott
Published: January 2018

The Lower Ordovician through Upper Jurassic record of the phylum Bryozoa consists almost entirely of the class Stenolaemata, excepting a very few Gymnolaemata (ichnofossils of the order Ctenostomata and, in the uppermost Upper Jurassic, Pyriporopsis, which is the oldest known Cheilostomata). Along with the decline to eventual extinction of most Paleozoic stenolaemates beginning with the end-Permian crisis, the stenolaemate order Cyclostomata radiated in Late Triassic and Jurassic to include the diversity of growth forms and locally the abundance common for Paleozoic bryozoan faunas. By late Cretaceous, however, cheilostomes had diversified and had come to dominate in bryozoan faunas; they have continued to dominate to the present.

In the abundant and diverse bryozoan fauna of the northern Adriatic Sea, cheilostomes are four to five times as diverse and are orders of magnitude more abundant than are cyclostomes. Within this fauna, encrusting sheet-like cheilostomes consistently overgrow adjacent encrusting cyclostomes. Different ontogenetic patterns of skeleton and organs, as well as larger zooid sizes at colony margins, produce patterns of feeding currents that allow cheilostomes to deliver their filtered water to and to overtop competing cyclostomes at interacting margins. These Bauplan differences apparently constitute a key evolutionary innovation characterizing the Cheilostomata. Along with higher growth rates in most cheilostomes, this key evolutionary innovation should have given cheilostomes a competitive edge since the origin of multiserial colonies within the clade in Early Cretaceous. It is hypothesized that superior overgrowth capability of cheilostomes has been an important factor in their success and the relative decline of cyclostomes.
Vendian body fossils (?) and isotope stratigraphy from the Caborca area, Sonora, Mexico
Authors: McMenamin Mark A.S. , Rowland Stephen M. , Corsetti Frank , Dix Anne M. , Nance Ronald P.
Published: January 2018

In the Proterozoic Clemente Formation at Cerro Rajon, south of Caborca, Sonora, we have collected sandstone beds that contain many small, sediment-filled structures. Each structure is a thin-walled, elongate sack, about 1.5 cm tall, oriented perpendicular to bedding. The sacklike structures are laterally flattened and roughly elliptical in transverse section, with the major axis of the ellipse measuring several mm and the minor axis 2-3 mm. The walls are not mineralized and consist of a thin layer of cryptocrystalline clay. One or both walls of each specimen is undulatory with a wavelength of 3-4 mm. The sacks are closed at the bottom, but appear to be open at the top, like an uninflated toy balloon. On the bottom surface of the sandstone bed, beneath each vertical sack structure, is a prolate ellipsoid-shaped sole mark. The long axis of each ellipsoid sole mark is parallel to the long axis of the associated sack structure, and the sole marks are oriented sub-parallel to one another on the surface of the bed. We tentatively interpret these structures to be the holdfasts of gregarious, attached, benthic organisms oriented sub-parallel to one another on the sea floor.

A preliminary study of carbon and oxygen isotope stratigraphy was carried out on the 2 km-thick Proterozoic through Lower Cambrian section at Cerro Rajon. Samples were collected every 50 m, and analyses were done in the laboratory of J.M. Hayes at Indiana University, whose assistance is gratefully acknowledged. The isotope record shows a primary signature for most of the section. Although the wide spacing of sample collection does not permit an unequivocal intercontinental correlation, a prominent negative δ13C excursion near the base of the Papalote Formation may correlate with similar excursions at the Vendian-Cambrian boundary on several continents. This would place the base of the Cambrian of the Caborca area several hundred meters lower than previously thought, but still several hundred meters above the possible body fossils of the Clemente Formation.
From environmental fluctuations and energy availability to evolutionary change and speciation
Authors: Parsons Peter A.
Published: January 2018

Evolutionary patterns can be considered in terms of two interacting continuums (a) the magnitude of environmental fluctuations of physical variables especially climatic, and (b) the availability of metabolic energy beyond basic needs for maintenance and survival (Parsons, 1991) so giving four extreme combinations:

(1) widely fluctuating environments, low metabolic energy availability. This situation is a feature of species borders where the energetic costs of environmental perturbations restrict normal physiological processes so that ecological range expansions are precluded. Provided extinctions do not occur, species would alter their ranges to track longer term climatic changes as described in the historical and fossil records.

(2) widely fluctuating environments, high metabolic energy availability. This combination favors opportunists and colonists. Furthermore, following a relaxation of stress intensity after a mass extinction there could be a burst of speciation in such generalist species.

(3) stable environments, low metabolic energy availabilty. This combination represents deep sea and cave environments where low metabolic rate is an adaptation to accomodate stresses such as anoxia and low resource availability. Consequently the capacity for evolutionary change is low in these habitats which tend to contain relict species.

(4) stable environments, high metabolic energy availability. On energetic grounds speciation is theoretically possible, but high vulnerability to any stressful perturbation would be restrictive in practice since some stress is the norm in natural populations.

The potential for evolutionary change and speciation is low in these four extremes, however in intermediate habitats the potential is higher as implied in (2) when stress intensity is relaxed. The intermediate habitats would be characterized by moderately fluctuating environments where the metabolic cost of stress would not preclude adaptive change. Furthermore, the stress levels in such habitats should lead to sufficient underlying genetic variability to be permissive of adaptive responses to environmental change (Parsons, 1991). This paradigm may apply to speciation in tropical rain forests. A fossil analogy would be marine invertebrates in frequently disturbed onshore habitats.
Apparatus architecture and allometry: the keys to conodont element function?
Authors: Purnell Mark A.
Published: January 2018

Much effort has been expended in determining the geological utility of conodont elements; little has been spent on determining their usefulness to the conodont animal. Most conodonts had an apparatus made up of a number of morphologically distinct, complex elements. Such apparatuses were borne by members of the Ozarkodinida, Prioniodinida, and Prioniodontida, together accommodating ~75 percent of known conodont genera.

The ozarkodinid apparatus consisted of an anterior battery of S and M elements behind which lay opposed pairs of Pb and Pa elements. Debate over its function has centered on two main hypotheses. These have considered the apparatus either as a filter feeding system, or as teeth. Ontogenetic analysis reveals that ozarkodinid apparatus growth was incompatible with a filtering function. The rate of increase in size of the S and M elements (the postulated filtering system) was insufficient to have met the increasing food requirements of the growing animal.

Like the apparatus of ozarkodinids, that of prioniodinids was differentiated into an anterior S and M element series and posterior, paired Pa and Pb elements. Despite these similarities in element arrangement, the prioniodinid apparatus does not exhibit the same degree of morphological differentiation as that of ozarkodinids. The Pa and Pb elements were probably involved in swallowing rather than cutting and grinding food.

The prioniodontid apparatus is poorly known but it is clear that although the morphology of elements is comparable to ozarkodinids, their arrangement in the apparatus was markedly different. Until the architecture of the apparatus has been determined, it's mode of function can only be guessed at. Preliminary knowledge of the apparatus, however, suggests that it operated differently to those of ozarkodinids and prioniodinids.

Understanding of the function of conodont elements requires that their morphology is studied within the context of an integrated multielement apparatus. There is substantial variation in apparatus composition and differentiation, and element morphology between clades. This variation undoubtedly reflects, to a large extent, differences in apparatus adaptability and versatility, functional flexibility, and food specificity; all factors that in other groups have had a major influence on evolutionary patterns.
Taphonomic features of benthic foraminifera in a temperate setting: experimental and field observations on the role of abrasion, solution and microboring in the destruction of foraminiferal tests
Authors: Shroba Cynthia S.
Published: January 2018

Benthic foraminifera recovered from sediments in the waters surrounding San Juan Island, Washington, were examined to assess taphonomic damage and to compare magnitude of the taphonomic agents of abrasion, solution and microboring to studies done in tropical environments. Abrasion experiments of 24, 72, 120 and 240 hour duration were run on Elphidiella and Islandiella, two benthic foraminifera common in the Puget Sound region. Results show that styles of taphonomic damage observed in field sediment samples, including impact pitting, scratching, caving and exfoliation, were produced on experimentally manipulated groups in as few as 24 hours. Elphidiella appears slightly more resistant to abrasive reduction compared to Islandiella, which produced a wide range of abrasive features within 3 days.

A control group of Elphidiella and Islandiella was placed in a mesh bag for 240 hours to assess taphonomic alteration by solution, boring and encrustation, removed from the effects of abrasion. These specimens showed no significant solution reduction, but within 3 days were covered with algal filaments and diatoms. Taphonomic damage observed in field specimens can be divided into destructive and constructive agents. Destructive features include breakage, pitting, boring, scratching, and exfoliation. Constructive features include pyritization and encrustation by diatoms and other algae. Although several naturally occurring abrasion features were produced in the experimental abrasion runs, the magnitude of taphonomic damage seen in field specimens was not achieved experimentally. Features of extreme taphonomic damage include complete removal of the outer chamber walls, as well as removal of all but the umbilical regions of planispiral forms. Solution and predation are largely responsible for such severely damaged tests.
Rudists as successful sediment-dwellers, not reef-builders, on Cretaceous carbonate platforms
Authors: Skelton Peter W. , Gili Eulàlia , Masse Jean-Pierre
Published: January 2018

The claim that rudist bivalves competitively displaced corals from reef frameworks in the Cretaceous combines two assertions: (1) that rudist formations commonly developed as reefs; and (2) that the autecology of rudists was convergent with that of hermatypic corals. We dispute both assertions, and thus reject the hypothesis of competitive displacement. We argue instead that mobile sediments, rather than frameworks, dominated the margins of most of the extensive carbonate platforms of the period, and that it was on these non-reefal biotopes that the rudists flourished.

Definitions of reefs tend to combine two major elements: (1) a robust biogenic framework (with accompanying sedimentary and diagenetic components); and (2) topographical relief. Such definitions are clearly rooted in Recent coral reefs, in which endosymbiotic zooxanthellae permit the extensive growth of colonial coral frameworks in shallow but relatively nutrient-poor waters and topography is largely the legacy of Pleistocene changes in sea-level. In rudist formations, in contrast, individual rudist aggregations are volumetrically limited, relative to sediment, often loosely constructed, and evidently showed little relief. Tabular and small lenticular units predominate.

Differences in structure and palaeoenvironmental situation between rudist and coralgal associations are the effect of the different autecologies of the constituent organisms. While the clonal growth of corals predisposed them to framework development, the aclonal development of rudists was better suited to the opportunistic occupation of a variety of temporarily available substrata. Moreover, the tolerances and growth responses of rudists to such factors as water turbidity, nutrients and current regime were quite different from those of hermatypic corals. Despite repeated assertions in the literature that rudists possessed zooxanthellae, only a few species show any evidence for such a symbiosis and other evidence suggests that most lacked them.

Rudist/coral competition is therefore doubtful, even though members of both groups co-occur in many areas. The relative demise and migration into deeper water of coral frameworks in the Cretaceous was thus probably independently caused.
Hierarchical factor analysis and the derivation of phylogenetic skull shape characters in canids
Authors: Stevens William P.
Published: January 2018

Character independence is an important assumption in parsimony-based phylogenetic analysis. For taxa with extant representatives, the analysis of within-species covariation of quantitative characters provides a basis for assessing character independence. One promising approach is to use mean species scores on factors of within-species covariation as phylogenetic characters, but the use of common morphometric factor models leads to problems with either the independence or the interpretability of such characters. Principal components and principal factors, whether rotated or not, may be constrained to be orthogonal but may be difficult to interpret since the effects of each factor are spread over all variables. In Wright-style factor analysis the restriction of secondary factors to subsets of variables facilitates their interpretation, but the factors may be highly correlated.

An alternative approach is to adopt a hierarchical factor model in which correlated first-order factors are restricted to subsets of the variables. Size is modelled as a second-order factor inducing correlation of the primary factors, in contrast to the common morphometric procedure of attempting to partial out size in the first stage of analysis. The size-independent components of the primary factors provide shape characters which are interpretable as the deviations of regional growth from their predictions based on size. Hierarchical factor models have been widely used in psychometric studies since their introduction by Thurstone in the 1930's, but have been little used in morphometric analyses.

The hierarchical model is applied to the covariances of interlandmark trusses measured on skulls of extant canids using a video-based stereophotogrammetric system. Preliminary results indicate that the canid skull may be partitioned into discrete regions of relatively independent local growth.
Eurasian and North American phylogeny of Turolian hipparionine horses (Perissodactyla, Mammalia) in China
Authors: Watabe Mahito
Published: January 2018

The late Miocene Chinese hipparions are morphologically diversified showing similarity to both western Old World's and North American forms. Two Chinese taxa that are phylogenetically related to western Old World's forms are Hipparion fossatum (= H. forstende) from Baode (Shanxi) and H. hippidiodus from Qingyang (Gansu) and Baode. The former is related to H. mediterraneum and the latter to H. urmiense - platygenys from the Turolian localities in the western Old World. H. fossatum and H. hippidiodus are associated with the “dorcadoides” (open-land) and “mixed” faunas in northern China. Hipparion fossatum that is characterized by POF located close to the orbit co-occurs with large and morphologically specialized form, H. dermatorhinum in Baode (Loc.30). H. hippidiodus with reduced POF is discovered with smaller H. coelophyes in Loc. 43, 44 (Baode) and Loc. 115 (Gansu).

The hipparions associated with the “gaudryi” (forest) fauna are characterized by well defined and small POF located far from the orbit. Those forms are: H. platyodus from Loc. 70; H. ptychodus from Loc. 73; H. tylodus from Hsi-Liang in Yushe - Wuxiang basins; and H. sefvei from Loc. 12 at Xin-an in Henan province. H. coelophyes from Baode (Loc.43 & 44) and Qingyang (Loc. 115) also show similar facial morphology to the these forms, although it has small size and shallow POF. Those forms are similar in facial and dental morphology to Hipparion sensu stricto and some species of Cormohipparion in North America.

The assemblages of Chinese hipparions are composed of two groups whose members are phylogenetically similar to the forms from both western part of Eurasia and North America. The “gaudryi” fauna is considered younger than the other two on the basis of faunal analyses. The similarity in hipparionine taxonomy between northern China and North America in the latest Miocene is an evidences for possible faunal interchange(s) occurred during that period, as suggested by taxonomic analyses on carnivores and proboscideans in eastern half of Eurasia and North America.