Climactichnites Logan, 1860, is known only from its large trail up to 20 cm in width, a trace superficially resembling a rope ladder. Prominent lateral ridges are parallel throughout the length of the trail; they may be smooth and hemispherical in cross-section or crenulated, much like a pie crust. Between these ridges is a series of raised dune-like bars and furrows dug into the substrate. The bars and furrows show considerable individual variation between trails and also variation along a trail. Ovoid impressions are known which occur at the start of trails. The posterior of these impressions is well rounded; the anterior is triangular, and for a short distance from the impression, the trail is developed on only one side. One exceptionally preserved impression shows curved, closely spaced, fine lines parallel to the posterior.

The trails are found only in sandstone, and where they are present, they are abundant. Slightly equivocable evidence indicates a Dresbachian (early Late Cambrian) age for the occurrences in New York, Missouri, and Wisconsin; trails in Ontario and Quebec are less certainly dated. Desiccation cracks and air escape hole suggest that the trail was fully exposed to the atmosphere.

From this data, a large number of sketches were made to reconstruct an animal able to make such a trail. Each attempt produced new speculation on the morphology. In the final rendition, the animal is bilaterally symmetrical, broad and low. The integument is tough, and the sole bears a subcentral mouth anteriorward. Lateral flaps scraped and compressed damp sand to make the parallel ridges. The anterior was strongly musculated and thin. This anterior flap grasped the sediment, alternating on either side of the animal to pull the form forward when the lateral flaps were relaxed. Curved rows of cilia on the posterior moved loose sand into dunes between the furrows formed by the anterior flaps.

This reconstruction is like that of no other animal known in the Vendian or the Phanerozoic.

Five distinctive vertebrate faunas characterised by endemic taxa can be recognised for the Early Devonian (Euramerica, Siberia, Tuva, China, and East Gondwana). By Late Devonian time these faunal provinces are obscured by widespread taxa which also inhabited nonmarine aquatic environments, but indicate faunal communication between Gondwana, Euramerica and China. This marked change in pattern between the Early and Late Devonian may be attributed to intrinsic (evolutionary) or extrinsic causal factors. Dispersal capabilities of aquatic vertebrates may have increased during the initial gnathostome radiation of the Devonian, but a predominantly extrinsic cause (e.g. global change in geography or climate) is suggested by the similar pattern for marine invertebrate faunas of Early Devonian endemism and Late Devonian cosmopolitanism. Outstanding problems of Devonian vertebrate biogeography include faunal differentiation on the largest landmass of the time (Gondwana), and the nature of barriers and connections between East and West Gondwana, East Gondwana and South and North China, and West Gondwana and Euramerica. A vertebrate equivalent of the cool-water Malvinokaffric invertebrate faunal realm of the Siluro-Devonian is not clearly identified, but vertebrate data from southern Africa and south America are sparse.

Wide latitudinal distributions for some Late Devonian vertebrate taxa appear anomalous, and could indicate either reduced global climatic gradients, or erroneous paleogeographic base maps. There are difficulties in formulating a hypothesis of global warming and/or major paleogeographic change in a way which clearly distinguishes basic from interpreted data. Three major subdisciplines (paleomagnetism, paleoclimatology, paleobiogeography) contribute to Paleozoic paleogeographic reconstructions. Their data tend to be organised and represented in different ways, but each relies on the same principle of concordance with a general pattern (Young 1990). Degree of consilience of a hypothesis based on one data set (the extent to which it explains patterns within an unrelated set of data) is a primary criterion for accepting or rejecting the hypothesis. Apparent polar wander path representation facilitates testing of paleomagnetic data against those paleoclimatic or paleobiogeographic data which provide evidence of paleolatitude. However, as well as the simple indication of paleolatitude, biogeographic and some other qualitative data sets provide more complex evidence concerning connections or barriers between regions, for which APWP representation is not appropriate. Cladistic analysis of hierarchically organised data sets (Young, 1986, 1987) provides a means of integrating qualitative paleobiogeographic, paleoclimatic, and paleogeographic data such that inconsistencies in the evidence are emphasised, and the hypothesis is exposed to falsification. These ideas are illustrated using Devonian examples.

Growth form in Paleozoic colonial corals is commonly used as an indicator of paleoenvironmental conditions. However, this character was also influenced by genetic factors, and it must be recognized that aspects of internal morphology were significant in the development of external form. In favositids a primary control on growth form was exerted by rates of corallite divergence, offsetting, and vertical growth, since the shape of the corallum base and growth surface resulted largely from these factors. This relationship worked in both directions; modifications of external shape that were apparently related to environmental conditions are reflected by measurable changes in internal morphology. In any favositid the most efficient packing of corallites is hexagonal, but this arrangement was thrown out of equilibrium by corallite offsetting. Rate of offsetting was largely controlled by internal packing stress and thus by the degree of corallite divergence. Periodic offsetting is reflected by a bimodal corallite size distribution (dimetrism). The distribution of corallite shapes and sizes in different parts of a corallum is therefore a key indicator of mode of growth; growth form can be seen to have had an influence on characters that are commonly used as species discriminators.

This study is based on analysis of serial sections of Paleofavosites subelongus (Savage) from the uppermost Ordovician to lowermost Silurian of the east-central United States. This species is highly variable in internal characters and the size range and type of corallite packing can differ substantially between coralla. The early part of each colony's astogeny played a major role in the development of growth form; specimens at either end of the variation continuum show contrasting modes of growth which generated different growth forms. In one mode, colonies produced broad bases through early axial offsetting and developed patterns of growth in which corallites expanded rapidly to mature sizes. Subsequent rates of offsetting were sufficiently high that dimetrism is common; such specimens most commonly have domical growth forms. In a second mode, colonies with lower rates of early axial offsetting have conical bases, a lower degree of dimetrism, and commonly bulbous forms.

Patterns of subsequent growth of all coralla demonstrate the connection between internal and external characters. Periods of increased axial offsetting and higher rates of corallite expansion occurred in conjunction with phases of lateral colony expansion. Elsewhere in the colony, offsetting was also periodic but occurred predominantly at the edges of the axis and in colony margins; this pattern allowed the axial polyps to continue upward growth while shorter-lived polyps were generated to maintain lateral parts of the growth surface. Bursts of offsetting commonly occurred in bands with close-spaced tabulae and thickened corallite walls, and were sometimes associated with intervals of increased corallite mortality. Paleofavosites subelongus was apparently unable to produce offsets at the outermost colony margins and was thus confined to upwardly expanding growth forms with outcurved corallites. Serial sectioning of other species of Paleofavosites in which tabular forms predominate indicates that coralla with such shapes were able to generate abundant offsets along colony margins and could maintain axial regions with predominantly hexagonal corallites and low rates of offsetting.

Although internal characters apparent early in astogeny set the basic mode of growth of each Paleofavosites subelongus colony, the subsequent growth form was influenced by numerous other factors, including reorientation during life, partial mortality of the growth surface, and probable changes in environmental conditions. In most populations one of the two modes of basal growth predominates, but populations with overlapping characters also occur. The growth pattern set down near the base of each corallum may be related to the environmental regime prevailing at and following the time of colony initiation, but may also reflect genetic differences within and between populations.

In northeastern Chihuahua and Trans-Pecos Texas, in the early Late Albian zone of Hysteroceras varicosum occurs the Boeseites romeri (Haas) fauna with B. romeri (Hass), B. perarmata (Hass), B. aff. barbouri (Haas), B. cf. howelli (Haas), B.proteus (Haas), Prohysteroceras cf. P. hanhaense Haas, Elobiceras sp., and Dipoloceras (?) sp. B. perarmata has also been collected at Cerro Mercado, near Monclova, Coahuila. Haas originally described this fauna from Angola. Now, from rocks in the same zone in the Sierra Mojada, Coahuila, Mexico, there is a form related to if not identical with Hysteroceras famelicum Van Hoepen, also originally described from Angola and also from the zone of Hysteroceras varicosum.

These fossils are known only from southern North America and Angola; they have not been described from the European Tethys. In 1984 I suggested that during the highstand of sea level of the early Late Albian (Hysteroceras varicosum zone) these ammonites migrated from Angola to Mexico and Trans-Pecos Texas via an epeiric seaway extending across the sag between South America and Africa proposed by Kennedy and Cooper. This would be twelve to fifteen million years prior to an oceanic connection between the North and South Atlantic.

I would now ask, can similar epeiric seas and highstands of sea level explain the migration of successive European, Tethyan, Jurassic ammonite faunas down the Mozambique Channel and around the horn of Africa into the Neuquen Basin of Argentina before Africa and Antarctica separated, as proposed by Spath.

The earliest known skeletal metazoan, Cloudina, was widespread in the late Neoproterozoic. We report here on phosphatized specimens of Cloudina sp. from dolomites of the Dengying Formation, 30 m below the first Cambrian skeletal fauna, in the Lijiagou section, Shaanxi Province, China. The specimens exhibit new details of shell morphology and fine structure that offer insights concerning the mechanism of shell accretion and the selective pressures influencing skeletogenesis in metazaons.

Cloudina formed curved to sinous tubular shells 0.2-8 mm in diameter and up to 4 cm in length. They consist of numerous thin (5-10 μm) calcareous layers, each in the form of a slightly flaring tube. New layers were deposited above and to one side of the previous layer, giving rise to a series of eccentrically nested shell laminae. Some of the phosphatized layers exhibit tight folding or wrinkling that may have been primary (imparting additional strength) or secondary (related to plastic deformation of organic-rich shell material). Pore space existed between terminal thin flanges, but concentric ridges may have served to strengthen the free standing portions of shell layers. SEM and cathodoluminescence of polished thin sections also reveal that each shell layer may itself have been constructed of an organized layering of organic matrix and carbonate, suggesting a fairly sophisticated biologic control over shell formation. The presence of circular holes, the size of which correlates positively with tube diameter, moreover, strongly suggests that one function of the shell was to protect the Cloudina organism from predatorial and/or parasitic attack.

The taxonomic status of Cloudina remains problematic. Rare specimens of the Lijiagou Cloudina which show two younger tubes growing within an older single tube suggest that the organism was capable of asexual reproduction by longitudinal fission. Such a latent tendency is not compatible with previously proposed affinities with polychaete worms.

Chitinozoa is an organic world group, the nature of which is not yet known. However, Chitinozoa is a uniform natural group of the organic world with a definite stratigraphical position (O-D). I suggest to use solely peridermal structures to specify evolutional trends of Chitinozoa.

1. The change of carinae that forms the morphological succession Cyathochitina calix-C. campanulaeformis-C. kuckersiana. This succession of species encompasses the early-middle Ordovician interval.

2. The change in the structure of longitudinal ridges that features the evolutionary succession Hercochitina repsinata-H. lindsaensis-H. crickmay at the middle-late Ordovician interval of the south part of Ontario.

3. The change in the ultrastructure of peridermal tissue. It shows well through the structure of appendices in the succession Ancyrochitina ancyrea-A. alveolata-A. siberica, llandovery-wenlock of the Siberian platform and ludlowpridoli of Europe and North America.

The points of peridermal appendix structure might be used for facial analysis. So, basal appendices change from simple branchwise up to complex anastomosis and loop-like during the change of the surrounding from shallow-water shelf up to a deep-water one, forming the morphology succession Ancyrochitina-Clathrochitina. Thus, evolutional trends of Chitinozoa and facial analysis might be based on a detailed study of peridermal structure morphology.

Historically, six Early Ordovician fossil-bearing facies have been recognized in North America, based on both their lithology and the most abundant types of fossils: the cryptalgal facies, cherty-carbonate - molluscan facies, thrombolite mound facies, sponge-algal mound facies, limestone-brachiopod facies, and graptolitic shale facies. However, complete or representative fossil assemblages characterizing these facies have not yet been defined. Paleogeographic controls on the distribution of these facies are primarily water depth and circulation; much of the North American continent exhibits a progression from dolomite to limestone to shale as one goes from shoreline out across the shelf to deep sea deposits.

Current study shows that the cherty-carbonate - molluscan facies as developed in the Nittany Dolomite of central Pennsylvania contains diverse assemblages consisting of, in decreasing order of abundance, gastropods, cephalopods, pelmatozoans, brachiopods, trilobites, sponges, polyplacophorans, rostroconchs, conodonts, encrusting and burrowing worms, and several types of algal structures. Within the mollusc dominated facies, different assemblages can be recognized which vary in the types of gastropods which predominate and in the abundance of cephalopods. These different assemblages appear limited enough that they approach the concept of fossil communities, although some might prefer to regard them as local biofacies. The assemblages are inferred to be related to current energy, water depth, salinity, and substrate texture. Intriguingly, diversity of the Nittany molluscs is highest where sponges and algal structures occur; comparison with the published literature also suggests a greater-than-expected faunal similarity and geographic proximity between the mollusc dominated facies and the sponge-algal mound facies.

A large amount of pteriomorphs of bivalve have been found in the Zlichovian–Givetian black mudstone-siltpelite in the trough in basin facies-zone of Luofu, Nandan, northwest Guangxi, South China. This fauna consists of 20 species, placed in 11 genera and 6 families, of which 1 family, 2 genera and 8 species are new. It has a very low diversity while compared with the contemperaneous fauna of Xiangzhou facies. This fauna is characterized by: a. Only 2 subclasses, the Pteriomorphia and Cryptodonta of 6 subclasses of Bivalvia were presented in the Nandan facies fauna; b. Among the occurred 6 families: Praecardiidae, Antipleuridae, Lunulacardiidae, Pterineidae, Posidoniidae, and Guangxiconchiidae, the Guangxiconchiidae (fam. nov.) is the most falourishing one. About 80% of individuals of bivalves belong to it. In contrast, the Pterineidae which was very flourish in the Xiangzhou facies, is represented by a small amount of specimens. In the generic level, the Guangxiconcha is mostly developed and distributed from Zlichovian to Givetian; c. This is a basically cosmopolitan fauna, and may compare with the contemperaneous bivalve fauna of the same facies of western Europe and North America. Among 11 genera of this fauna, 7 genera: Ptychopteria(Actinopteria), Cheiopteria, Pterochaenia, Posidonia, Lunulacardium and Buchiola are the cosmopolitan or basically cosmopolitan taxa, while Guangxiconcha, Nandannia and Opisthonia are the endemics to South China. 62% of the species are the endemics; d. This fauna is dominated by the small-sized, thin-shalled and fragile taxa. Except for Buchiola and Ptychopteria, most taxa are ornamented by fine concentrical line, or acrossed by very weakly radial line; e. About 54% of taxa and 90% of total individuals of this fauna may be the byssal attached epifauna, most of them may be the pseudoplanktonic bivalves.

Seven bivalve zones of Zlichovian–Givetian of Nandan, Guangxi have been recognized, and compared with the associated tentaculitid zones.

A greater number of floral provinces have been defined for the Permian than for any other Phanerozoic period, and this is presumably the reflection of a well differentiated set of climate zones. These floras have been assigned to an idealized set of ten “biomes” as defined on the basis of the equator-to-pole spectrum of present day climates (Ziegler, 1990). The biomes reflect temperature and precipitation, and in particular the way in which these parameters change through the annual cycle. The purpose of the present paper is (1) to expand the taxonomic database of Permian floras and climatically sensitive sediments, (2) to use ordination analyses and other multivariate techniques to relate taxonomic data to climate, geographic distance and other factors that controlled the global distribution of plants, and (3) to relate these results to the recognition of biomes during the Permian.

This approach reveals that the phytogeographic provinces, as recognized by paleobotanists, are objectively valid entities, but significant gradations can be detected, supporting the idea that the floras were controlled by climate rather than by geographic separation. In fact, there are no examples in the Permian world of strictly geographic barriers, which is not surprising in view of the fact that the continents were basically together through this time.

Biomes are defined by climatic parameters, but the taxonomic characteristics of biomes have evolved with time. The Permian floral provinces can be related to precipitation balance by their associations with such climatically sensitive sediments as coals, paleosols and evaporites, and this is critical for assigning each to an appropriate biome. At least at the generic level, taxonomic lists have significant limitations for identification of biomes in the geologic past. In particular, northern and southern hemisphere temperate biomes evolved radically different floras by the Permian. Ecomorphic characters and taxonomic diversity within critical groups may provide a more general scheme for phytologic recognition of biomes through geologic time.

Finally, detailed comparisons will be made to General Circulation Model and Energy Balance studies on the Permian. The numerical studies seem to overemphasize the seasonal extremes of temperature in the middle to high latitudes.