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.

Paleogene vertebrate communities in North and South America show dramatic changes in taxonomic composition and ecological organization. Worldwide, mammals diversified substantially following dinosaur extinction (Fig. 1). Most families of living vertebrates appear by the end of the Paleogene. In North America, placental omnivores, herbivores and carnivores dominate mammalian communities, but in South America marsupial carnivores and omnivores and placental herbivores dominate them. Immigration from Asia and Europe to North America of taxa from several placental orders (Perissodactyla, Primates, Artiodactyla, Rodentia, Carnivora, Mesonychia, Creodonta) occurred periodically during the Paleogene. South America, however, was completely isolated from the Paleocene to the Oligocene when Rodentia and perhaps Primates first appear. Despite the independent evolutionary histories of these continents, their constituent species show remarkable convergences in morphological adaptations including body size distributions, dental morphology, and other features. Low resolution chronostratigraphic data for the Paleogene of South America precludes correlation with North American faunas. In North America, patterns of diversification and extinction appear to be related to climatic events. Morphological convergences appear to be related to climate and concomitant habitat change, but may also be a function of coevolution via predator-prey interactions and diffuse competition among guild members.

During the past decade, phylogenetic analyses of Late Paleozoic tetrapods have consistently demonstrated that the Permo-Pennsylvanian tetrapod suborder Diadectomorpha is closely related to more traditionally defined amniotes. Recent analyses provide two competing hypotheses of relationship: 1) the Diadectomoropha is the sister group of all amniotes, or 2) the Diadectomorpha and Synapsida comprise the most primitive clade within the Amniota. Subsequently more derived groups within the Amniota are: the reptilian family Captorhinidae, and the Protorothyrididae plus the Diapsida. The availability of well preserved atlas-axis complexes for all of the better known genera of diadectomorphs now allow a determination of the primitive condition of the atlas-axis complex for the Amniota. Further, accepted hypotheses of phylogenetic relationships among Late Paleozoic tetrapods allow mapping of features of the atlas-axis complex onto predefined topologies so that the transformations of the complex may be analyzed.

The diadectomorph atlas-axis complex may be characterized in the following manner: paired, well developed proatlases and atlantal neural arches; lack of proatlantal and atlantal neural spines with only posteriorly directed epipophyses present; an extremely robust atlantal intercentrum; tight articulation of the atlantal pleurocentrum with the dorsal aspect of the axial intercentrum preventing exposure of the former on the ventral surface of the vertebral column; a large, anteriorly directed midline projection of the axial intercentrum; a tall and well-developed axial neural spine, presumably for attachment of strong occipital muscles and ligaments. Except for the anterior projection of the axial intercentrum (which is an autapomorphic feature of diadectomorphs), basal amniotes share all of these features with diadectomorphs. Shared, derived features of the atlas-axis complex of diadectomorphs plus other basal amniotes include: 1) fusion of the axial centrum and neural arch, 2) small epipophyses of the atlantal neural arch and, with the exception of Tseajaia, 3) fusion of the atlantal pleurocentrum to the dorsal surface of the axial intercentrum.

The morphology of the atlas-axis complex alone is not sufficient to generate hypotheses of relationship between diadectomorphs and other basal amniotes. However, the atlas-axis complexes of diadectomorphs and other basal amniotes are clearly more similar to one-another than to those of other taxa.

Edrioasteroids are an extinct group of primitive echinoderms whose geologic range is Early Cambrian to Late Pennsylvanian. Several authors have argued whether edrioasteroids could freely move about on the sea floor or were firmly attached to a hard substrate throughout post-larval life. Arguments that edrioasteroids were mobile are based primarily on orientation of individuals within a population and positioning of individuals on a host shell. We disagree with these arguments based on overwhelming evidence that edrioasteroids could not move and remained firmly attached throughout post-larval life.

Edrioasteroids have specialized attachment structures that are almost always found on hard substrates such as hardgrounds, fossil shells or fragments, and conglomerate pebbles. There are two types of edrioasteroid attachment structures, an aboral disk and a peripheral rim. Edrioasteroids with an aboral disk are typically found attached to hard substrates. Although some individuals have been found loose in muddy sediment, many of these individuals show signs of being torn loose from their attachment surface based on their inverted orientation, disrupted attachment structures, and shingling by currents. Edrioasteroids with a peripheral rim are almost never found free in the sediment, and the few known examples of this are either small juveniles indicating that soft substrates probably could not support adult edrioasteroids or else thick-rimmed adults apparently attached to soft algae.

In uncrowded conditions, edrioasteroids are circular in outline, but they become polygonal and abutting under crowded conditions. Other encrusters such as tube worms also affect their peripheral outline. Edrioasteroids occur in crowded clumps even though nearby skeletal grains are uncolonized. In these individuals, peripheral rims and oral surfaces are severely distorted which would make living conditions and continued growth difficult. Also, some individuals attach to objects much smaller than their eventual thecal diameter. In such conditions, the edrioasteroid gradually engulfs the object it is attached to, severely distorting the animal, with the peripheral rim migrating toward the bottom of the attachment object. Under either of these conditions, individuals would almost certainly have moved to nearby open spots or to larger, uncolonized clasts if they could.

In crowded conditions, individuals of the same species do not overgrow one another, but individuals of one species will overgrow living individuals of another species competing for the same attachment space. Two localities preserve large edrioasteroids partially overgrowing smaller articulated individuals of a different species. Because they are fully articulated, overgrown individuals must have been alive during the overgrowth, but were not able to move out of the way.

Disrupted edrioasteroids are often found with the oral surface completely disarticulated or missing, but with a completely articulated peripheral rim. Apparently, the peripheral rim was firmly attached to the substrate and more strongly constructed than the oral surface and therefore better able to withstand wave activity, death and decay, and subsequent disarticulation than the oral surface. This firm attachment to hard substrates also suggests lack of movement.

The edrioasteroid attachment grows from the periphery. New ossicles are added to distal plate circlets of the attachment while plates in more proximal circlets enlarge. Clearly some degree of movement is required for this type of growth but not active locomotion. Large edrioasteroids growing along the margin of a large skeletal fragment show an underdevelopment of the peripheral rim along this edge even though the rest of the animal is round and symmetrical.

Some authors have used living psolid holothurians as a good analog for extinct edrioasteroids with a peripheral rim. Psolids will move using tube feet under the theca in the ventrally positioned A, B, and E rays under extreme disturbance, but only at the rate of a few millimeters per day. Edrioasteroids have all the ambulacra dorsally oriented away from the substrate and therefore have no similar mechanism for locomotion. We suggest balanimorph barnacles as a better analog for the vast majority of edrioasteroids. They firmly attach to a hard substrate, become polygonal in crowded conditions, have feeding structures facing upward, grow from the periphery of the attachment surface, and do not move as adults.

The mesic broad-leaved and coniferous forests of the Middle Miocene of the northern Intermountain region of the United States contrast strongly with the semi-arid shrub/grassland steppe vegetation that comprises the extant vegetation. This contrast is a consequence of the progressive development of a regional rain shadow, beginning in the Late Miocene, coincident with the uplift of the Cascades to the west. It is generally assumed that the emergence of the extant vegetation was a consequence of a combination of in situ evolution of taxa in response to moisture and thermal stress and the immigration of taxa already adapted to such stressful environments. The study of stratigraphically sequential successional vegetation stages in a number of Middle Miocene floras in the northern Great Basin suggest that many elements of the extant vegetation of the region were already present as taxa adapted to the several characteristic environmental conditions of landscapes affected by volcanic disturbance.

The Middle Miocene “climax” vegetation of southeastern Oregon and southwestern and southcentral Idaho, documented by paleobotanical and palynological data from floras such as Stinking Water (Oregon), Succor Creek (Oregon-Idaho), and Trapper Creek (Idaho), was a complex mosaic of vegetation types comprised of broad-leaved evergreen, mixed mesophytic, and mixed coniferous forest elements. These floras are preserved in volcaniclastic sediments. Palynological analysis of sequential samples from overlying strata indicate that the bulk of the sedimentary record at each of these sites records vegetation in varying stages of recovery following destruction of forests by local volcanism. The earliest seral stages following such events are characterized by taxa, including Artemisia, Sarcobatus, and other Malvaceae, Chenopodiaceae, Amaranthaceae, Compositae, and Gramineae that represent important components of the extant vegetation of the region.

An ash-covered landscape, denuded of forest cover, is a highly stressful environment. Ash forms an edaphically dry and nutrient-poor substrate and such sites would be exposed to a significantly greater range of annual temperatures and much greater exposure than forested sites. Grasses, forbs, and shrubs that evolved in ways that permitted the colonization of such landscapes would be preadapted to the drier and less equable climates that would accompany the development of the Cascadian rain shadow. In addition, such successional areas also supported a mammalian fauna dominated by grazers in contrast to the browsing-dominated fauna of the climax forest mosaic. It would thus appear that the post-disturbance grass/forb/shrub communities provided an evolutionary proving ground for mammalian niches that now dominate the extant cold desert/steppe biome.

Oleanane is a triterpane that is commonly found in Late Cretaceous (Campanian) through Cenozoic marine and deltaic rocks and related oils. Based on its affinity to the β-Amyrin group of natural products and its abundance in Tertiary deltaic sediments and oils, such as in the Niger Delta, oleanane is thought to be a geochemical fossil of terrestrial flowering plants. The β-Amyrin group forms the basis of many angiosperm triterpenoids and triterpenoid saponins. These compounds appear in moderately advanced flowering plant lineages and are often used as a defense against herbivores. This group of compounds has not been reported from any other seed plant group, including conifers.

We examined a suite of middle to early Cretaceous terrestrial sediments and plant fossils for the presence of oleanane. The existence of oleanane was documented by Gas Chromatography - Mass Spectrometry (GC-MS) and confirmed with Metastable Reaction Monitoring (MRM) GC-MS.

Oleanane was identified from fossil bennettitaleans, an extinct group of seed plants. Cycadeoidea paynei and C. superba are permineralized fossil stems and are from the Early Cretaceous Inyan Kara Group of the Black Hills, SD. Oleanane was also found in carbonaceous compressed leaf fossils of Dioonites from the Barremian - early Aptian (Zone I) of the Potomac Group from Richmond, VA. This increases the number of seed plant groups known to have oleanane, and is of additional interest as the bennettitaleans are thought to be closely related to angiosperms.

Oleanane was not found in contemporaneous fossil conifers. Our sample consisted of fossil conifer wood collected from the Campanian Magothy Beds of Martha's Vineyard, MA; the Cenomanian Raritan Formation of Sayreville, NJ; and the Barremian - early Aptian Patuxent Formation of Greenbelt, MD.

Confirmed reports of oleanane have been from Late Cretaceous and younger marine sediments. We now report oleanane from Early Cretaceous terrestrial strata of the Inyan Kara Group. In addition we systematically sampled the sequence of Cretaceous terrestrial sediments of the coastal plain of the eastern U.S.A, and found oleanane in the Barremian - early Aptian (Zone I) Potomac Group. Preliminary data indicate variation in the occurrence of oleanane in contemporaneous Early Cretaceous sites from the Potomac Group. The localities accumulated in different depositional environments and the occurrence may be controlled by lithofacies.

Bioimmuration, broadly defined as fossilization by virtue of organic overgrowth, allows preservation of soft-bodied organisms and soft parts of organisms with mineralized skeletons. Sessile organisms attached to hard or firm substrates are routinely overgrown by other organisms competing for living space. If the overgrowing organism has a mineralized skeleton which is likely to be fossilized, then it may carry a high fidelity (sub-micron scale) impression of the overgrown organism on its underside. This is a mould bioimmuration, the simplest mode of preservation. A diagenetic infilling of the mould, commonly by calcite, produces a cast bioimmuration. In addition, the protected microenvironment between the overgrowing organism and the substratum favours early diagenetic permineralization of the soft tissues of the bioimmured organism and the development of more complex preservational styles.

In spite of its potential for soft part fossilization, very little research has been undertaken on bioimmuration, with the notable exception of the work of Ehrhard Voigt principally on Maastrichtian sea-grass communities. Research in progress is revealing a great abundance of bioimmured fossils in Mesozoic shallow marine deposits of NW Europe where oysters and serpulids overgrew a variety of other organisms.

Bioimmured soft-bodied bryozoans belonging to the Order Ctenostomata are very common and display a range of preservational styles. Minute spines and pores ornamenting the cuticular zooidal walls are sometimes present, as are permineralized pore chambers. The high diversity of stoloniferan and carnosan ctenostomes encrusting hard substrates in the Oxfordian and Kimmeridgian is striking and contrasts with the depauperate fauna of calcified cyclostome bryozoans.

Oyster shells in the Kimmeridge Clay are often encrusted by myriads of tiny individuals of the inarticulate brachiopod Discinisca, previously known from comparatively few specimens of this age. Emerging from the fragile commissures are setae several times the length of the delicate phosphatic shells. Setae of neighbouring individuals may be aligned in parallel facing away from the direction of approach of the overgrowing organism.

The hemichordate Rhabdopleura is common as a bioimmured fossil in the Oxford Clay. Overgrowth protects the periderm and the black stolons, and colonies are much more intact than previously described examples of this genus from the Jurassic.

The Phylum Entoprocta had no unequivocal fossil record before the recent discovery of bioimmured entoprocts in the Kimmeridge Clay. Colonies comprise stolons linking erect zooids which have been pushed flat against the substratum during overgrowth. The existence of thickened sockets at the base of the zooids permits assignment of the fossils to the extant genus Barentsia. Permineralization of the entoproct cuticle has occurred, leaving minute pores apparently once occupied by epithelial microvilli.

Pedunculate barnacles are commonly found bioimmured by oysters in the mid-Cretaceous Cambridge Greensand. Normally the cirri are retracted but in one exceptional example their outlines are clearly visible as moulds on the attachment area of an oyster.

During diving studies of comatulid crinoids at Lizard Island, Great Barrier Reef, detatched but intact crinoid arms and arm groups were sometimes encountered on the substratum. These arms are thought to originate through autotomy or breakage during attacks of predatory fish that remove the calyx and visceral mass but leave the arms intact. Detached arms remain in a vital condition for several days but soon lose pinnules and fragment as decay ensues.

Occurrence of intact, isolated arms and arm groups in the Banff Formation of western Alberta requires a catastrophic disturbance (not necessarily predation) followed closely, if not coincidently, with burial. The loose arms are preserved mostly as short, straight, distal arm segments (1–2 cm long) or sometimes as long, curved arm segments (2–4.5 cm). The arm groups range from complete arm rays to partial arm rays. If originally present, pinnules are still articulated to the arms and cover plates are preserved on most pinnules. Biserial arms with pinnules, uniserial arms and uniserial arms with pinnules occur in a 2:1 ratio to crinoids having that type of arm structure whereas cuneiform arms with pinnules have a 3:1 ratio of preserved loose arms and arm groups to calyces. Loose, single arms and arm groups account for 33% and 11%, respectively, of the identifiable crinoid remains for the western, deep-water Banff Formation crinoid fauna. Overall, this fauna shows an equitable range from complete articulated crinoid crowns with attached stems to loose isolated plates. The preservation of this fauna has both a time-averaged, accumulation component as well as an instantaneous storm deposited component as represented by both completely articulated crinoids and the high abundance (44%) of loose arms and arm groups. The comparatively anomalous abundance of loose arms and arm groups probably originated through breakage or autotomy coincident with the burial event.

In comparison, the Gilmore City crinoid fauna of Iowa represents an obrution deposit with over 75% of the crinoid specimens preserved as complete articulated crowns with attached stems whereas the eastern Banff Formation crinoid fauna is preserved as a shallow-water, time-averaged accumulation of mainly isolated crinoid calyx plates (54%) and partial calyces (20%). However, both of these faunas have few preserved loose arms or arm groups (<4% for either fauna).

The Wenlockian lichid trilobite Arctinurus boltoni has been regarded as a classic example of a “snow-shoe” type adaptation. That is, the broad flat doublure has been interpreted as a resting surface, with well-developed terrace ridges serving as either sensory or frictional devices. New data from the Rochester Shale of western New York State indicate that this interpretation is incorrect The discovery of the small, calcareous worm tube Cornulites on complete, articulated specimens of Arctinurus indicates that these trilobites seldom rested their doublure on the sediment surface. Apertures of all specimens of Cornulites are oriented posteriorly, suggesting a rheophilic response to persistent water circulation patterns beneath the trilobite. The presence of suspension feeding organisms on the doublure also indicates that the water currents beneath the trilobite were free of suspended mud, so that Arctinurus may not have processed sediment in search of food.

Large specimens of Arctinurus also have numerous epibionts on the dorsal shield, including cyclostome bryozoans, brachiopods (Stegerhynchus) and Cornulites. The presence of these suspension feeders indicates that Arctinurus did not burrow or even partially cover itself with mud. The large number of epibionts on adult specimens of Arctinurus, including several age classes for Stegerhynchus, indicates that molting stopped or at least slowed greatly once a certain size was attained, and that these trilobites may have had fairly long life spans.

Preliminary evidence supports a series of predictions and speculations that derive from the hypothesis of evolutionary escalation (Red Queen). If biotic interactions have intensified over geologic time, then:

(1) Energy budgets of individuals have increased. This involves both sides of the equation Consumption = Growth + Reproduction + Respiration (includes locomotion & feeding) + Feces + Excreta. Thus living representatives of formerly successful taxa have lower energy budgets than ecologically similar taxa that were successful later, e.g., reptiles vs. mammals, Sphenodon vs. other reptiles, brachiopods vs. bivalves, Nautilus vs. coeleoids, gymnosperms vs. angiosperms.

(2) The price of success (cals. per reproducing offspring) has increased. Thus Red Queen evolution leads to energetic inefficiency.

(3) Energetic escalation is fueled by increasing plant biomass and turnover, especially on land (angiosperms, including N-fixers such as legumes). The enlarged trophic base pemits diversification without reduction of niche size. Evolution of marine benthos (our primary record of evolution) may be fueled directly by fixed C or indirectly by fixed N (shelf waters are normally N-limited), both increasingly supplied from land as a result of steady state mortality (deciduousness, self-thinning, short life-cycles) or disturbance mortality (fire, wind) of bigger standing crops. The Mesozoic origin of new phytoplankton such as diatoms may be a consequence of terrestrial angiosperms. In turn, diatoms produce lipid, a more energy-dense food than the carbohydrate produced by other phytoplankton. Increased skeletonization of Mesozoic phytoplankton may have diluted the food of Paleozoic-style suspension-feeders, especially brachiopods. Brachiopods have blind guts, which they readily stuff with non-nutritive particles and tight (efficient) energy budgets that might not sustain increased feeding costs.

4) Archaic organisms survive in oligotrophic refugia that exclude more recent, high-energy enemies. Marine animals move to deeper water (explaining offshore migration over the Phanerozoic, e.g., Latimeria, Nautilus, Zoophycos.). Other refugia are high latitudes, caves, or dark fiords. Living articulate brachiopods flourish in all of these except the fluvial-influenced Arctic Ocean. Refugia for archaic flora restrict light, water, or N (high latitudes and elevations, forest floor, poor soil).

5) Survival in oligotrophic refugia selects for lower energy budgets, including reduction of respiring tissue, so Cope's Rule is reversed (thecideid brachiopods, lycopods, sphenopsids).

Organic design arises, on every scale, by the spontaneous self-organization of successively more complex structures from simpler subsidiary components. The resulting structures converge repeatedly on architectural designs that can be constructed by growing organisms, and that are viable but not necessarily optimal in relation to any one function. Empirical observations and theoretical models of developmental processes suggest that these recurrent elements of design are fixed point attractors which organic dissipative structures must necessarily approach. We characterize these structures as topological attractors, thereby emphasizing that they are determined by the properties of matter and the geometry of space-time.

We have derived a set of potential designs for the elements of animal skeletons, in terms of geometric rules, growth processes, and the properties of materials. Skeletons or components of the skeletons of actual living and extinct organisms are matched with the possibilities defined within this theoretical morphospace. The extent to which the skeletal components of individual organisms are differentiated, exploiting various parts of the skeleton space, provides a crude metric of structural complexity. The skeleton space serves as a common context, in which we can compare the extent and pattern of exploitation of this range of potential organic designs, from one taxon to another.

Our analyses show that the most evolutionarily advanced animals in a given class or phylum generally do not have the most complex skeletons; that molluscs and vertebrates are more morphologically diverse than arthropods; and that the physical constraints of life on land and in the air substantially limit the variety of skeletal structures suitable to be employed by animals living in these environments. Moreover, when the skeletons of all known animals, living and extinct, are considered together, we find that the total range of possible skeletal designs has been very fully exploited.

These results strongly support the hypothesis that the essential elements of organic design are inherent in and predictable from the material properties of the universe. Environmental and demographic circumstances, invariably involving a large element of chance, together with the constraints of phylogenetic history largely determine the course of evolution in individual lineages. In contrast, structural principles such as those delineated here determine the recurrent themes of organic design, over large numbers of taxa and long periods of time. Thus, it is no accident that two major groups of animals that have most successfully exploited jointed lever skeletons, vertebrates and arthropods, have achieved the most diversified adaptive radiations, in the sea, on land and in the air.

Among the structural paradigms defined within the skeleton space, stronger and weaker topological attractors may be identified empirically by the frequencies with which particular design elements have evolved independently, in unrelated taxa. Plausible functional or constructional rationales can readily be devised, ex post facto, to explain the repeated convergence of organic structures on some obvious strong topological attractors, such as branching networks, spiral cones, and bivalved shells. Unfortunately, it seems unlikely that an analytical method can be devised to predict these strong attractors a priori, as the variables involved cannot all be quantified in the same way.

Species populations commonly carry a great deal of genetic variation which is not expressed in individual phenotypes. Cryptic variation can be carried in recessive alleles, in cases of heterosis, or where modifier genes inhibit expression of the hidden trait. Other genetic and ecological factors also allow cryptic variation. Stabilizing selection prevents the expression of hidden traits; normalizing selection weeds out the deviants and canalizing selection suppresses their traits. Together the two keep the species near the top of the adaptive peak. Cryptic variation balances a species' need to be well-adapted to its environment and also for it to maintain a reserve of variation for potential environmental change. Expression of cryptic traits is rare and is usually associated with times of greatly reduced natural selection and rapid population growth, when the lower slopes of the adaptive peak are exposed.

A possible example of the manifestation of cryptic traits occurs within the lower Trentonian Rafinesquina lineage of New York State. The two most commonly reported species of the genus have been reappraised in terms of cryptic variation. Extensive collections of Rafinesquina “lennoxensis” reveal far more intergrading morphotypes than had hitherto been recognized. The form which Salmon (1942) described is broadly U-shaped with sulcate margins. It grades into very convex forms as well as sharply-defined or convexly geniculate types. Of great importance, all forms grade into the flat, U-shaped, alate R. trentonensis, which is, by far, the most common and widespread lower Trentonian member of the genus. The R. “lennoxensis” assemblage has a very narrow biostratigraphy, being confined to a few locations in the upper Napanee Limestone. This places it in a quiet, protected, low stress, lagoonal setting behind the barrier shoal facies of the Kings Falls Limestone.

The R. “lennoxensis” assemblage does not constitute a natural biologic species; it is reinterpreted as an assemblage of phenodeviants occupying a low stress, low natural selection lagoon facies. All such forms should be included within R. trentonensis. Given the evolutionary plasticity of this genus, extensive cryptic variation is not surprising.

The records of nuculid bivalves from the Surma Group sediments of Mizoram, India, are very rare. This paper describes 3 known and 4 new forms of bivalves of the family nuculidae which were collected in the course of field study from Upper Bhuban Formation of Bhuban Subgroup (Surma Group), Mizoram. They are : Nucula alcocki Noetling, Nucula warsarensis Eames, Nucula cf. pulchara Hinds, Nucula agrawali n.sp., Nucula sahnii n.sp., Nucula tewarii n.sp., and Acila (Truncacila) kachharai n.sp. The first three forms, though, known from the other areas of the Indian subcontinent, are reported for the first time from the study area and their synonymy is updated.

These forms, together with the other associated vivalves, gastropods and decapod crustacea, indicate a Lower Miocene (Aquitanian-Burdigalian) age and shallow marine enviroment of deposition for the Upper Bhuban Formation.

Shape identification of eurypterid prosomas currently uses the ratio of prosoma length to prosoma width and the lateral angle. Because many species of eurypterids have the same prosoma shape as determined by these criteria, the method is limited in its taxonomic applications. Thompson transformation grids are of little value due to the lack of sufficient topographic reference points, even though some limited success has been achieved in its application to allometry.

Fourier analysis is a more rigorous mathematical descriptor of two-dimensional shape than is simple ratios. Being independent of topographic reference points and ratios, Fourier analysis is well suited, theoretically, to the identification of prosoma shape and potential taxonomic identifications. Problems arise, though, in that Fourier analysis is sensitive to distorted specimens.

My study departs from previous methods of Fourier analysis in that the choice of the reference point from which to measure the radii is not the center of gravity, but instead is the midpoint between the eyes. My reasons for this unorthodox reference point are threefold: 1) this point is determinable on all specimens; 2) the position of the eyes is taxonomically significant (Kjellesvig-Waering, 1961) and 3) allows for the simultaneous identification of prosoma shape and the differentiation of taxa with similar outlines but different eye positions.

As defined by current methods, the taxa used in this study (Eurypterus remipes, E. lacustris, E. pittsfordensis, and E. dekayi) all have similar prosoma shapes. When specimens of the same stage of development were compared statistically, Fourier analysis was successful in the differentiation between E. remipes, E. pittsfordensis and E. dekayi, and between E. lacustris, E. pittsfordensis and E. dekayi, but not between E. remipes and E. lacustris.

The prosoma shapes as studied by Fourier analysis for both E. remipes and E. lacustris are also similar for all size classes examined. All size classes are dominated by the 4th harmonic. The contribution to the outline from other harmonics changes during ontogeny. The 3rd and 7th harmonics are the important components of the prosoma outline for the small size classes (classes 1-3 = maximum prosoma length of 17mm), while the 2nd and 7th harmonics are the important components for the larger size classes (classes 4-7). Further study involving other eurypterid taxa is in progress.

The Cretaceous rise of flowering plants marked an important transition in the modernization of terrestrial ecosystems. Well documented is the diversification of angiosperm pollen during the mid-Cretaceous and the migration of angiosperms from low latitudes to middle and high latitudes during the Barremian to Cenomanian. Global compilations of “species” diversity indicate a rapid rise in angiosperm diversity during the Albian to Cenomanian. This rise parallels a decline in the species diversity of archaic pteridophytes and the gymnosperm orders Cycadales, Bennettitales, Ginkgoales, Czekanowskiales, and Caytoniales. Late Cretaceous floras show more gradual trends in species diversity than mid-Cretaceous floras.

Megafloral reconstructions of vegetation and climate for North America and other continents indicate warm temperatures in coastal regions of middle to high latitudes. Cretaceous biomes, however, often cannot be compared closely with Recent biomes. During much of the Cretaceous, conifers and other gymnosperms shared dominance with angiosperms in tropical and subtropical vegetation, unlike the Recent. During the Late Cretaceous, tropical rainforest was areally restricted. The few known leaf megafloras from equatorial regions indicate subhumid, rather than rainforest, conditions. Desert and semi-desert were widespread at lower latitudes and are documented by the occurrence of evaporite minerals in China, Africa, Spain, Mexico, and South America. Mid-latitude vegetation consisted of open-canopy broadleaved and coniferous evergreen woodlands that existed under subhumid conditions and low seasonality. High-latitude vegetation of the Northern Hemisphere consisted of coniferous and broadleaved deciduous forest, rather than boreal forest and tundra. High-latitude vegetation from coastal regions of the Southern Hemisphere consisted of evergreen conifers and angiosperms. Rainforest conditions appear to have been largely restricted to polar latitudes.

Data on relative abundance, though often incomplete, indicate that angiosperms became ecologically important in tropical to warm subtropical broadleaved evergreen forests and woodlands by the Cenomanian. However, their rise to dominance took longer in other biomes. Conifers formed an important component of many Late Cretaceous biomes, and the persistence of archaic gymnosperms was strongly influenced by climate. Deciduous Ginkgoales, Czekanowskiales, Bennettitales, and Caytoniales are rare to absent in Late Cretaceous megafloras from warm subtropical to tropical climates, but they persist in megafloras from cooler climates. Archaic conifers such as Frenelopsis occur in megafloras representing low-latitude desert and semi-desert, but they are generally absent in more humid assemblages. Within mid-latitude broadleaved and coniferous evergreen woodland from North America, conifers show evidence for co-dominance with angiosperms into the early Maastrichtian. However, this co-dominance appears to have ended by latest Maastrichtian, which implies that vegetational reorganization occurred during the last few million years of the Cretaceous in North America.

The number of cell types present in a metazoan body is a reasonable metric of its complexity. If evolutionary progress is defined as increase in complexity, from “lower” to “higher” forms, then progress occurs as cell-type numbers are increased. Using a lumper's definition of cell type, living metazoans range from 4 (placozoans) to over 210 (higher mammals) somatic cell types. The earliest fossil traces may be 580 my old and require an organism of about 30 cell types, while the primitive members of higher invertebrate phyla, appearing near 525 my ago, require about 50 cell types, an increase of about 0.3 cell type/my. Average Phanerozoic cell-type increase was about 0.4 cell type/my. These estimates are indistinguishable considering their crudity, and imply an origin of metazoans between about 645 and 680 my ago. While it may have been episodic rather than gradual, evolutionary progress would seem to have continued throughout metazoan history.

The Cambrian “explosion” occurred chiefly among organisms of 50 or so cell types, but so far as one can judge represented no major leap in the complexity of body plans. Rather it was characterized by a radiation of a number of clades that were at about this same level of complexity, one that permitted the construction of a rich variety of body plans, within a few million years. The diversity of the daughter body types was thus spectacularly broad. Though it may have been only a locus on a sweeping trend of continuing progress, the Cambrian explosion was something special in the history of life.

Concomitant with the rise in cell type numbers during the late Precambrian, the genetic regulatory apparatus that characterizes most metazoans was assembled, involving a cascading, hierarchical system of genes with feedback mechanisms and with informational systems that are not directly encoded. This flexible and open-ended regulatory architecture underlies evolutionary progress in metazoans, and permitted the evolution of cell differentiation. It may prove possible to judge the steps in the assembly of this regulatory system from the early metazoan record of body types, and conversely, it may prove possible to reconstruct the pattern of divergence of clades and the rise of body types as comparative data on pattern-formation systems become available for a variety of major taxa.

Phylogenetic relationships among the cnidarian classes Anthozoa, Hydrozoa and Scyphozoa, and between Cnidaria and other metazoan phyla, continue to be subject to widely divergent interpretations. Also controversial are the affinities of numerous fossil groups, including Byronia Bischoff, Sphenothallus Hall and conulariids, that have been interpreted as extinct cnidarians. Currently favored interpretations of evolution within Cnidaria are generally consistent with one of two alternative hypotheses of phylogenetic relationships: scyphozoans and anthozoans are members of a monophylclic group that excludes hydrozoans; or scyphozoans and hydrozoans are members of a monophyletic group that excludes anthozoans. Putative anthozoan-scyphozoan synapomorphies include (1) gastric septa present; (2) cnidae present in both ectoderm and gastroderm; (3) sex cells gastrodermal; and (4) mesoglea contains amoeboid cells. Putative hydrozoan-scyphozoan synapomorphies include (1) medusa present; (2) tetraradial symmetry; (3) rhopaloid nematocysts; and (4) similarities in sperm structure.

Evaluation of alternative hypotheses of relationships within Cnidaria is complicated by uncertainty surrounding relationships between this and other metazoan phyla. While some investigators have interpreted Cnidaria and Ctenophora as members of a monophyletic group that excludes other phyla, others have argued that ctenophorans are more closely related to platyhelminths than they are to cnidarians. Putative cnidarian-ctenophoran synapomorphies include (1) production of cells modified for prey capture; and (2) presence of a medusa. Putative ctenophoran-platyhelminth synapomorphies include (1) presence of gonoducts; (2) ciliated cells with several to many cilia; (3) determinate cleavage; and (4) muscle cells developed from mesoderm. Comparisons of these and other phyla indicate that the strongest hypotheses of synapomorphy are those between cnidarians and ctenophorans. Ctenophorans do not have a mesoderm, and they lack complex reproductive structures that can be homologized with platyhelminth gonoducts. Similarities between ctenophorans and platyhelminths in ciliation and cleavage type are either non-homologous or shared primitive. The most recent common ancestor of ctenophorans and cnidarians was probably a medusa-like animal with circular and meridional muscle fibers and a non-septate digestive cavity having four radial canals. This cavity probably lacked cells specialized for prey capture, but glutinant prey-capture structures may have been present on tentacles. Sperm produced by this common ancestor were most similar to sperm of extant ctenophorans, hydrozoans and scyphozoans. Anatomical features unique to ctenophorans or cnidarians, regarded by some investigators as evidence against a close relationship between these two groups, are autapomorphies. These interpretations imply that putative hydrozoan-scyphozoan synapomorphies are actually shared primitive, and that the presence of gastric septa and cnidae-bearing gastric filaments in scyphozoans and anthozoans is shared derived. This would mean that the most parsimonious hypothesis of phylogenetic relationships within Cnidaria is that anthozoans and scyphozoans are members of a monophyletic group that excludes hydrozoans.

Debate over relationships among these extant taxa has heightened interest in the affinities of prominent groups of problematic fossil cnidarians. Byronia Bischoff, Sphenothallus Hall and conulariids, all characterized by an apatitic, multilamellar theca, show detailed anatomical similarities to hydrozoans and/or scyphozoans. Putative synapomorphies linking Byronia and coronatid scyphozoans include the presence of multiple whorls of thorn-like nodes projecting into the thecal cavity, with each whorl consisting of eight nodes arranged in two sets of four nodes each. Sphenothallus, characterized by a pair of tentacles and, in some species, multiple branching, is most similar to hydrozoan and scyphozoan polyps, many of which are colonial or exhibit a single pair of tentacles early in their development. Similarities in hard- and soft-part anatomy between scyphozoans and conulariids suggest that conulariids, like scyphozoans, possessed four gastric septa and produced medusae through polydisc strobilation. Although conulariids have been interpreted as ancestral to extant cnidarians, they are more likely either a sister group to Scyphozoa or members of this class.

Individual organisms compete for resources. Among competitive dominants, per-capita energy use has generally increased through time. This increase has had a ripple effect on all other species by increasing the number of competitive and predatory encounters among individuals. Species unable to cope with such biological rigors have become restricted to environments where resource supply is low and where encounters with enemies are few. Among species that hold their own in biologically rigorous habitats, construction materials that are cheap to produce and that enable individuals to grow and respond quickly have generally been favored over those that exact a high cost in energy and time. Extinction interrupts but does not reverse or fundamentally alter these long-term between-clade evolutionary trends. The availability of resources to organisms, as well as the opportunity for evolutionary change, depends on extrinsic events and factors as well as on the competitive abilities of organisms.

Those who have raised methodological and theoretical objections against this economic interpretation of the history of life deny the overriding importance of organisms as agents of natural selection, emphasize the random nature of extinction, deny the existence of long-term trends, favor a larger role for mutualistic as opposed to antagonistic interactions, or accord a larger role to species-level attributes in evolution that are not reducible to the properties of individual organisms. These arguments are either unpersuasive or incorrect. The long-term economics of life may have important lessons for our own use of resources.

Over the past two decades, extensive seismic mapping of the Baltimore Canyon Trough off New Jersey, Delaware and Virginia, has documented a succession of progradational Miocene stratigraphic sequences. Understanding the depositional timing of these sequences is critical in evaluating the role of eustasy in their development, but has until now been hampered by the lack of suitably high resolution biostratigraphic data. Attempts to produce an integrated Neogene basin history have previously been frustrated by an inability to directly correlate individual shelf-based seismic sequences, with regionally mapped onshore, unconformity-bound, stratigraphic units. This study addresses both problems using data comprising the stratigraphic distribution of dinoflagellate cysts in two composited outcrop and ten subsurface sections from the Salisbury Embayment and adjacent Baltimore Canyon Trough. The result is a detailed age model for the entire Miocene depositional history of the area. Onshore samples are from the type sections of the Chesapeake Group in Maryland and Virginia. Offshore COST B-2 & B-3, Exxon 684 & 902 and Mobil 500 wells are directly tied to the regional seismic grid.

According to our model, the magnitude and timing of mapped sequences in the Baltimore Canyon Trough compare well with Miocene third order cycles of the Exxon Cycle Chart. With the exception of the 22 Ma sequence (Cycle 1.5 of Haq et al., 1988), all of the other postulated eustatically controlled sequences are potentially present in the study area. In addition, on the basis of seismic mapping and integrated biostratigraphy, our model predicts one additional lower Serravalian sequence between 15.5 Ma and 13.8 Ma, and two additional lower Tortonian sequences between 10.5 Ma and 8.2 Ma. The onshore expression of these sequences are, respectively, the Calvert Beach Member of the Calvert Formation and parts of the Little Cove Point Beds of the Saint Marys Formation. An important implication of the age model is that the entire Fairhaven Member and “beds 4-9” of the Plum Point Marl Member, of the Calvert Formation, are lower Miocene strata.

These dinocyst data were not available when the Exxon model of Miocene eustatic cycles was developed and therefore represent a critical independent test of that model. This is particularly so because the tectonically quiescent, mature, divergent-margin setting of the basin limits the role of causative variables other than eustasy, in the development and architecture of third order depositional sequences. Our model should be further tested by detailed sedimentological and taphonomic field studies of the Chesapeake Group.

The Archaeogastropoda are one of the most abundant orders of the Paleozoic, but they have received surprizingly little systematic analysis. I have conducted a cladistic analysis of archaeogastropod species appearing during the initial radiation of the clade during the latest Cambrian through the Ordovician. The analysis included over 100 species. Most specimens were from North America, but some European and Asian material was included. The hypothesized phylogeny also includes an additional 40 Ordovician species from a previous cladistic work on a single family (the Lophospiridae), and only the stem members of this clade were included here.

The analysis used 54 meristic and 12 morphometric traits encompassing 154 character states. This seemingly large number of character states for a group considered character-poor can be attributed to: 1) the breadth of morphologic diversity produced during the initial phases of the clade's radiation, resulting in nearly all conceivable morphologies being included here; and 2) the high number of character states for “types” of selenizones and sinuses, morphologies absent on most extant gastropods.

The results of the analysis suggest the following:

1. There were two large clades present by the Early Ordovician that most closely correspond to present definitions of the Murchisonoidea and Euomphaloidea. The clades shared an anisostrophically coiled common ancestor and thus were not derived separately from bellerophonts. However, the Macluritidae appear to have been derived separately from bellerophonts, corroborating a widely held hypothesis.

2. Early Paleozoic species presently considered “pleurotomaroids” comprise a polyphyletic assemblage, with the major families independently derived from either the murchisonoid clade (the Eotomaridae, Lophospiridae and Phanerotrematidae) or from the euomphaloid clade (the Liospiridae, Luciellidae and post-Middle Ordovician members of the Raphistomatidae). It had been assumed previously that pleurotomaroids represent the least-derived anisostrophically coiled gastropods, as well-developed selenizones and sinuses were considered primitive traits. However, those features actually represent derived conditions of the Ordovician that appear to have been secondarily lost in later lineages; thus seemingly “modern” appearing early Paleozoic species often simply retained non-derived conditions. As the Mesozoic Pleurotomaria can not be linked with any Early Paleozoic clades, there is no basis for classifying early Paleozoic gastropods in the Pleurotomaroidea.

3. The Subulitoidea and Loxonematoidea (which may be ancestral to the Caenogastropoda) evolved separately from murchisonoids. The origins of the Trochoidea are not clear. If the Holopeidae represent the stem members of the Trochoidea, then trochoids evolved from euomphaloids. However, the Platyceratidae also have been linked with trochoids. The earliest known members of that group possess many unique homologies and no obvious synapomorphies with any other archaeogastropods. The taxon can not be linked reliably with holopeids or any other taxon included in this study, and I do not discount the possibility that platyceratids were evolved separately from bellerophonts.

4. Gross shell convergences abound, as turritelliform and planispiral-to-hyperstrophic shells both evolved at least four times. However, the combinations of character states used to achieve these gross morphologies differ among clades, allowing “homoplasies” of character complexes to be recognized.