Two new species of worm tubes referable to the genus Onuphionella occur in Lower Cambrian strata in eastern California and western Nevada. Onuphionella durhami n. sp. is found in the Campito Formation (in pre-trilobite strata, in the Fallotaspis and, possibly, the Nevadella Zones) and O. claytonensis n. sp. occurs in the Middle Member of the Poleta Formation (Nevadella Zone). The unusual tubes are armored with an imbricated coat of mica flakes, reminiscent of the modern genus Owenia. The lowest occurrence of Onuphionella in western North America corresponds closely with the lowest occurrence of the genus in the Baltic region, indicating that correlations between the two regions are not greatly in error.

Assessment of ontogenetic and geographic variation can have substantial influence on species delimitation and thereby on perceived patterns of species-level morphological variation and diversity in space and time. Here we describe the ontogeny and intraspecific variation of the early Cambrian trilobite, Zacanthopsis palmeri n. sp., based on silicified material from east-central Nevada, USA. Zacanthopsis palmeri is the oldest documented Cambrian corynexochine to shift from possessing a fused rostal-hypostomal plate to a functional hypostomal suture in mature specimens during ontogeny. Six geographically distinct samples of mature Z. palmeri from a single silicified limestone bed traceable over tens of kilometers in east-central Nevada permit exploration of geographic variation within this species using geometric morphometric methods. No one sample encompasses all of the shape variation expressed by Z. palmeri and several geographically segregated samples show some degree of morphological separation in pairwise comparison. Nonetheless, these samples are not qualitatively or quantitatively different from one another when all samples are taken into account. The degree of variation within Z. palmeri is similar in magnitude to the differences between other species in the genus known from much less material.

Three types of alimentary canals (=midgut) occur in the Annelida and non-trilobite Arthropoda: 1) a sagittal tube with metamerically paired diverticula related to the number of somites; 2) a tube that is constricted slightly between somites; and 3) a simple tubular gut that may taper slightly backwards to the anus. At least two of these three types (1 and 3) occur in the Trilobita. Pterocephalia and Olenoides share the first type with the probable sister taxon to the Trilobita, Naraoia (Nectaspida), and this is probably the plesiomorphic condition for the class. Varying feeding habits may well have made this character homoplastic within each of these groups. The preservation of parts of the alimentary tract in specimens of Upper Cambrian Pterocephalia n. sp. (McKay Group, British Columbia) was probably a function of taphonomic and/or very early diagenetic changes that resulted from the type of food preferred by that trilobite. Other trilobites from the same beds do not have their soft parts preserved. The alimentary structures are preserved in a different fashion from, apparently unattached to, and an order of magnitude larger than genal caeca that occur in this taxon. Thus, genal caeca are regarded as imprints of circulatory rather than alimentary structures.

Energy dispersive analysis of a fragment of preserved alimentary tract of Pterocephalia n. sp. showed the presence of Ca, Si, Al, Fe, P, K, Na, and Cl. These alimentary tracts are composed of a complex mixture of minerals that probably includes clays, detrital quartz, carbonates, phosphates, and oxides or hydroxides. The structure of these dark fillings is microcrystalline. The presence of detrital minerals as part of this mixture would suggest that this trilobite was a deposit feeder.

Holometabolan insects, including beetles (Coleoptera), represent about half of all living organisms. Their development cycle, allowing larvae and adults to exploit distinct ecological niches, is traditionally advocated as a critical adaptation resulting in this extraordinary diversity. Herein I report the occurrence of a beetle from the Pennsylvanian deposit of Mazon Creek (IL, USA). It predates the diversification of Coleoptera by at least 65 million years. This identification supports the view that, early in their history, hyper-diverse extant holometabolan lineages were dominated by Palaeozoic lineages, mostly extinct. End-Permian environmental perturbations might have played an important role in the Triassic radiation of holometabolans. However, it is hypothesized that ecological preferences of holometabolans might have resulted in an earlier diversification of moderate importance, correlating to that of seed plants, their putative host plants. The evolutionary success of ‘holometaboly’ might be the result of a sequence of favorable events.

The fossils described here were collected from the Lower Triassic (Olenekian) at two Majiashan sections in Chaohu City, Anhui Province, East China. Nine species belonging to five genera are introduced, including a new genus, Chaohuichthys, and some undetermined or unnamed fish specimens are discussed. The fish assemblage from Majiashan covers most of the Lower Triassic marine bony fish taxa known from China.

A new microconchid tentaculitoid, Microconchus utahensis new species, is described from the Lower Triassic (Spathian) Virgin Formation of two localities (Hurricane Cliffs and Beaver Dam Mountains) near St George, Utah. This small encrusting tubeworm, previously referred to erroneously as Spirorbis, has a laminated shell microstructure containing minute pores (punctae). The population from deeper water facies of the Beaver Dam Mountains is more abundant than that from Hurricane Cliffs and the tubes are significantly larger in size. Although represented by only one species (M. utahensis), microconchids are by far the most dominant component of the otherwise impoverished sclerobiont assemblage of the Virgin Formation, which also includes rare cemented bivalves and probable foraminifers. Whereas the remainder of the Virgin fauna is quite diverse, the low diversity of encrusters suggests a slow recovery from end-Permian mass extinctions. Indeed, more typically Mesozoic sclerobiont assemblages dominated by cyclostome bryozoans and serpulid polychaetes did not appear until the Late Triassic, probably Rhaetian.

We describe the integumentary anatomy of titanosaur sauropod embryos from the Auca Mahuevo nesting site. Natural (calcitic) casts of the skin show the non-imbricating, tuberculate scales (i.e., tubercles) typical of other non-avian dinosaurs. However, a variety of scale patterns previously unknown for the skin of these animals is reported. The observed integumentary patterns include ground tubercles, large and elongated tubercles, parallel rows of large tubercles, tubercles in rosette-like and flower-like arrangements, and in striate-like rows. Ground tubercles and rosette-like patterns resemble the few examples of skin known for adult sauropods. The former pattern also resembles the arrangement of osteoderms of the armored titanosaur Saltasaurus. Although the embryonic skin does not show definitive evidence of armor, the posthatching development of osteoderms cannot be ruled out. This material, the only available evidence of the embryonic skin of non-avian dinosaurs, contributes significantly to our knowledge of the integumentary morphology of these animals.

Sponges have an unrealized potential importance in biogeographic analysis. Biogeographic patterns determined from our analysis of all published data on distribution of Ordovician genera indicate Early Ordovician sponge faunas have relatively low diversity and are completely dominated by demosponges. Early Ordovician (Ibexian) faunas are characterized by the widespread co-occurrence of Archaeoscyphia and the problematic Calathium. This association is commonly found in biohermal structures. Middle Ordovician faunas show an increase in diversity, and two broad associations are differentiated: Appalachian faunas (including Southern China and the Argentine Precordillera) and Great Basin faunas.

Late Ordovician faunas show important changes in diversity and provincialism. Hexactinellid and calcareous sponges became important and new demosponge families appeared. Four Mohawkian-Cincinnatian associations are recognized here, including: 1) Midcontinent faunas; 2) Baltic faunas; 3) New South Wales faunas; and 4) Western North American (California and Alaska) faunas. However, two separate biogeographic associations are differentiated based on faunal differences. These are a Pacific association (western North American and New South Wales) and an Atlantic association (Midcontinent Laurentia and Baltica).

Distribution of sponge genera and migration patterns are utilized to consider paleogeographic dispositions of the different continental plates, climatic features, and oceanic currents. Such an analysis points to close paleogeographic affinities between the Argentine Precordillera and Laurentian Appalachian faunas. However, significant endemicity and the occurrence of extra-Laurentian genera suggest a relative isolation of the Precordillera terrane during the Late Ibexian-Whiterockian. The study also shows a faunal migration from the Appalachian region to South China during the Middle Ordovician and the migration of faunas from Baltica to Laurentia in the Late Ordovician. The occurrence of Laurentian migrants in New South Wales during the Late Ordovician could be related to inferred oceanic current circulation between these two areas, although other paleogeographic features may be involved.

Very few macroscopic soft-bodied Ediacaran fossils are hosted in carbonates; most of them are preserved as casts and molds in siliciclastic rocks or as carbonaceous compressions in black shales. This taphonomic bias limits our capability to fully understand the diversity and paleoecology of macroscopic Ediacaran life forms. Previous reports have shown that the upper Ediacaran Dengying Formation in South China and Khatyspyt Formation in Siberia contain macroscopic soft-bodied fossils preserved in bituminous limestone; thus they have the potential to expand our knowledge about the Ediacaran biosphere. However, the biogenecity of the Dengying fossils described in Xiao et al. (2005) has been questioned. In this paper, we provide additional material and arguments in support of the biogenecity of these fossils, which are formally described as Yangtziramulus zhangi new genus and species. Yangtziramulus zhangi consists of a branching system with a central axis and tubes on both sides. The tubes appear to be distally open. Yangtziramulus zhangi is interpreted as a flat-lying benthic organism, as indicated by the mutual avoidance relationship among densely clustered individuals. Yangtziramulus zhangi finds few morphological analogs among modern organisms, but it is broadly similar to several macroscopic Ediacaran forms. Its morphological and ecological complexity is inconsistent with a microbial interpretation. Yangtziramulus zhangi is typically covered by a thin veneer of fine-grained silts, suggesting that it was probably smothered and killed by an episodic flux of silty sediments (event deposits). Its tube walls are replaced with early diagenetic calcspars.

Thirty localities in the Upper Paleozoic (Mississippian–Permian) of North America have yielded more than 1,000 cephalopod mandibles preserved as carbon films, pyrite/limonite internal molds, and as nuclei in phosphate, carbonate, and ironstone concretions. With occasional exceptions, cephalopod mandibles, as part of either the microfauna or macrofauna, are rare despite the fact that co-occurring cephalopods may be extremely abundant. Without exception, the mandibles recovered co-occur with ammonoids and very frequently with bactritoids. Localities containing only nautiloids, either coiled or orthoconic, have not yet yielded cephalopod mandibles. Also, nekroplanktic accumulations of cephalopods have not yielded mandibles. Except for Lagerstätten deposits (two occurrences), the cephalopod mandibles were always recovered from molluscan-dominated communities; these communities have been interpreted as being in relatively offshore, “deeper” water in normal marine salinities with relatively low to anoxic oxygen conditions.

We describe a new tritheledontid, Elliotherium kersteni n. gen. and sp., on the basis of a partial skull collected from the lower Elliot Formation (Upper Triassic; Euskelosaurus Range Zone) on the farm Beatrix, Free State Province, South Africa. Although similar to Pachygenelus, the genus differs from other South African tritheledontids in its higher maxillary postcanine tooth count, lack of labial cingula on the upper postcanine teeth, shorter secondary palate, retention of a median vomerine ridge behind the secondary palate, and smaller interpterygoid vacuity. With regard to these features, Elliotherium is most similar to the South American tritheledontid Chaliminia. Elliotherium is autapomorphic in its possession of a long parasphenoid rostrum, ventrally depressed secondary palate, medially convex margins of the interpterygoid vacuity, and a thin lamina of palatine covering the interpterygoid vacuity. Although Elliotherium is the stratigraphically lowest positioned tritheledontid from southern Africa, it is still probably later occurring than the South American taxa Chaliminia or Riograndia. Based on a revision of a previous analysis of advanced cynodont relationships, we propose a sister-group relationship between Elliotherium and Chaliminia, although support for this pairing is weak.

Five species of camerate crinoids from the Middle Ordovician Dunleith Formation (Galena Group) of northern Iowa and southern Minnesota are described: Cleiocrinus regius Billings, Cotylacrinna sandra n. gen. and n. sp., Euptychocrinus skopaios n. gen. and n. sp., Abludoglyptocrinus charltoni (Kolata), and Eopatelliocrinus ornatus (Billings) n. comb. Archaeocrinus desideratus Billings is assigned to Cotylacrinna, and Glyptocrinus fimbriatus Shumard and Ptychocrinus longibrachialis Brower are placed in Euptychocrinus. The geographical affinities of the Iowa and Minnesota crinoids lie with adjacent localities in the northern midcontinent and the Appalachian province of Canada and New York. Preservation of various specimens implies that Euptychocrinus skopaios, Abludoglyptocrinus charltoni, and Eopatelliocrinus ornatus utilized parabolic arm fans. Cotylacrinna sandra is a specialized rhodocrinitid which is perhaps the largest completely known Ordovician crinoid with a stem length of over 91 cm and a total volume of about 45,740 mm3. The root morphology indicates an upright column and this animal towered above the associated echinoderms, which ranged from the substrate level to a maximum of 25 cm above the seafloor. Euptychocrinus skopaios is marked by dwarfed morphology compared to the closely allied E. fimbriatus, and it exhibits accelerated development of fixed brachs, number of brachials in and length of the arms, and closely spaced pinnules. The dwarfism is interpreted as a specialization for small size and adults of E. skopaios were only located about five or six cm above the substrate. New brachials and pinnules form at the distal arm tips of E. skopaios throughout ontogeny. Consequently, the length of and the number of plates in the food-gathering system are positively allometric relative to the crown volume. Food gathering capacity equals the number of food-catching tube feet times width of the food grooves and it is also augmented more rapidly than expected for an isometric crinoid. Although distantly related to euptychocrinids, most other Dunleith camerates, namely Abludoglyptocrinus charltoni, Eopatelliocrinus ornatus, and Cotylacrinna sandra, follow the same developmental trends of the food-gathering system observed in Euptychocrinus skopaios. Comparison of the pinnulate camerates and three species of ramulate cladids and a disparid from the Dunleith reveals some striking contrasts. At equivalent crown volumes, the camerates are characterized by more numerous arm branches in the form of pinnules, more narrow food grooves, more closely spaced tube feet, and longer food-gathering systems with more plates and greater capacity. The Dunleith camerates were adapted for catching smaller food particles using more numerous and more closely spaced tube feet located on more extensively branched filtration nets than the associated cladids and disparid. The differences can be attributed to taxonomy and presumably phylogeny, that is camerates versus cladids and disparids, and/or morphology in the presence of pinnules versus ramules.

Cambrian–Ordovician boundary interval dendroid graptolites and conodonts occur in continental slope facies in the Taconic allochthon. The upper part of the Hatch Hill Formation has lowest Ordovician (lowest Tremadocian) nematophorous dendroid and lower Fauna B-aspect conodont assemblages with Cordylodus caseyi (emend.) and Iapetognathus preaengensis. Comparable dendroid-conodont faunas occur in Baltoscandia, northeastern China, and western Newfoundland; this suggests that no diachroneity can be demonstrated between the lowest occurrences of Rhabdinopora flabelliformis in a number of faunal provinces.

A practical and correlatable Cambrian–Ordovician boundary stratotype horizon defined by the lowest occurrence of a Rhabdinopora flabelliformis assemblage within an interval with lower Fauna B-aspect conodonts is advocated. A biostratigraphic horizon defined by conodonts has far less utility due to strong lithofacies-conodont biofacies linkages, unresolved problems with the species-level taxonomy of cordylodans, and possible diachronous first-appearances of Cordylodus species. Because the areally most extensive Cambrian–Ordovician boundary sequences are siliciclastic-dominated (Avalonian, Baltoscandian, Gondwanan-Hercynian platforms and shale-dominated slope sequences), the lowest local occurrence of R. flabelliformis assemblages provides a practical and traditional definition for the base of the Ordovician System and Tremadocian Series in regions where conodonts are rare or recoverable only with difficulty.

Strata correlative with the Cambrian–Tremadocian boundary interval are not represented across most of Laurentia. In this region, the “Sauk III Subsequence” locally has an important unconformity within it, and lower Tremadocian-equivalent rocks can unconformably overlie units as low as the Proterozoic. The earliest Ordovician featured a relatively simple eustatic history characterized by an “early Tremadocian onlap”; no compelling evidence supports a eustatic fall-rise couplet, or “Black Mountain eustatic event,” in this interval. Available stratigraphic information is reinterpreted to demonstrate an initially slow and subsequently higher rate of continued sea level rise in the Cambrian–Ordovician boundary interval.

The brachiopod Pentamerus oblongus is especially abundant in the Lower Silurian Rytteråker Formation, which occurs widely throughout the Oslo region in southern Norway. Alternating thin limestones and shales typically occur in a shallowing-upward sequence ending in a massive grainstone often rich in tabulate corals and stromatoporoids. In the lower beds, colonization by pentamerid populations was enhanched by prior emplacement of an orthotetacean shell pavement over the clastic sea bed. Individual Pentamerus size decreases with increasing disturbance of populations or their fragmentation as lag deposits nearer the stratigraphic level of the massive grainstone. The frequency of specific storm events and the changing depth to the sea bed may be indexed according to the average size of pentamerid shells in a given population and the degree to which the population is disturbed. Preservation of prominent growth lines (assumed to be annual) suggests storms stirred the sea bed in deeper waters on an 8–10 year cycle. In shallower waters, storms more regularly disturbed the sea bed every 2–3 years. These data corroborate the interpretation that the Pentamerus community inhabited marine waters below fair-weather wave base, but still within reach of storm wave base.

Borings of the ichnogenus Gastrochaenolites have been found in limestone cobbles of the Morrowan (Early Pennsylvanian) Cane Hill Member of the Hale Formation in northwestern Arkansas. They were likely excavated by lithophagid bivalves, thus extending the earliest record of obligate bivalve boring back from the Triassic into the upper Paleozoic. These borings are herein referred to as G. anauchen n. ichnosp. Lithophagid borings may be rare in the upper Paleozoic because of the absence or scarcity of suitable substrates, such as scleractinian corals or carbonate hardgrounds. Additional upper Paleozoic bivalve borings will likely be discovered in other carbonate-rich rocky shore deposits.

A fusuline fauna consisting of 9 species of 4 genera from the Xiala Formation of the Mujiucuo section, Xainza County, Tibet, China is described. The fusuline fauna is dominated by Nankinella and Chusenella and indicates a Midian (Late Guadalupian) age. The earliest record of fusuline fauna during the Midian in the Lhasa Block suggests that the block rifted later than the Qiangtang Block to the north and the Baoshan and Tengchong blocks to the east, all of which yield much earlier fusuline faunas of Yakhtashian (Artinskian) age, but had drifted away from Gondwana to a relatively warm temperate zone in the Late Guadalupian (Middle Permian).

Articulated scleritomes of the chancelloriids Archiasterella fletchergryllus new species and Chancelloria cf. eros Walcott, 1920 are described from the Early Cambrian (Branchian) Sekwi Formation, Mackenzie Mountains, Northwest Territories, Canada. Early diagenetic, microbially mediated lithification has resulted in unusual three-dimensional preservation of the body surface, which potentially allows consideration of the evolutionary affinities of these enigmatic organisms. Sclerites are mounted on short stalks of the integument, connected to the undersurface of the central disc, and are external to the body surface.

A silicified brachiopod assemblage living between the first and second episodes of latest Ordovician mass extinction is first described from micritic bioclastic limestone of Kuanyinchiao Bed, northwestern Guizhou, southwest China. It contains six species, Dalmanella testudinaria (Dalman, 1828), Plectothyrella crassicosta (Dalman, 1828), Hindella crassa incipiens (Williams, 1951), Eostropheodonta sp., the characteristic constituents of the Hirnantia fauna, and two new species, Fardenia modica and Dorytreta longicrura. It lacks Hirnantia, Kinnella, Cliftonia, and Paromalomena, the other characteristic elements of the Hirnantia fauna. A new, low diversity community (inner BA3) dominated by brachiopods is proposed as the Dalmanella testudinaria-Dorytreta longicrura Community along with the trilobite Dalmanitina nanchengensis Lu, rugose corals, and gastropods. Composition of this community of the Hirnantia fauna was controlled primarily by temperature, water depth, and substrate. Comparison with other communities of the Hirnantia fauna in south China supports this conclusion. Fluctuations in generic composition of the Hirnantia fauna and the related factors are also discussed.

Precambrian microbiotas, such as that permineralized in bedded and stromatolitic cherts of the late Neoproterozoic, 750- to 800-Ma-old, Chichkan Formation of South Kazakhstan, have traditionally been studied by optical microscopy only. Such studies, however, are incapable of documenting accurately either the three-dimensional morphology of such fossils or their chemical composition and that of their embedding minerals. As shown here by analyses of fossils of the Chichkan Lagerstätte, the solution to these long-standing problems is provided by two techniques recently introduced to paleontology: confocal laser scanning microscopy (CLSM) and Raman imagery. The two techniques are used together to characterize, in situ and at micron-scale resolution, the cellular and organismal morphology of the thin section-embedded organic-walled Chichkan fossils. In addition, Raman imagery is used to analyze the molecular-structural composition of the carbonaceous fossils and of their embedding mineral matrix, identify the composition of intracellular inclusions, and quantitatively assess the geochemical maturity of the Chichkan organic matter.

CLSM and Raman imagery are both broadly applicable to the study of fossils, whether megascopic or microscopic and regardless of mode of preservation, and both are non-intrusive and non-destructive, factors that permit their use for analyses of archived specimens. They are especially useful for the study of microscopic fossils, as is demonstrated in this first in-depth study of diverse taxa of a single Precambrian microbiota for which they provide information in three dimensions at high spatial resolution about their organismal morphology, cellular anatomy, kerogenous composition, mode of preservation, and taphonomy and fidelity of preservation.

Many trilobite species of the order Agnostida have short stratigraphic ranges and global distribution in open-marine deposits. They are most abundant and most diverse from about the middle Middle Cambrian to the middle Upper Cambrian where they are proving to be excellent biostratigraphic indices. We describe unusually rich agnostoid faunas of that age from two thick, well-exposed sections, one near Paibi and one near Wangcun, in northwestern Hunan Province, China. All collections are from the Huaqiao Formation, the definition of which is revised and its stratigraphic content is expanded. Most of the fossils are well preserved in dark, laminated, argillaceous carbonates that were deposited in lower slope environments. These are assigned to 76 species and 33 genera. New species described are Agnostus? babcocki, Ammagnostus? cryptus, Ammagnostus histus, Ammagnostus hunanensis, Ammagnostus wangcunensis, Baltagnostus? ambonus, Linguagnostus stenus, Lisogoragnostus hybus, Lisogoragnostus mictus, and Utagnostus songae. Species reassigned in a new generic combination are Ammagnostus laiwuensis (Lorenz, 1906), Glaberagnostus? cicer (Tullberg, 1880), Kormagnostus minutus (Schrank, 1975), and Pseudophalacroma scanense (Westergård, 1946). The subfamily Ammagnostinae öpik, 1967, is elevated to family rank.

The bases of eight agnostoid biozones are defined by the lowest occurrence of a common species having a relatively short stratigraphic range and wide geographic distribution. In ascending order, these zones are named for Ptychagnostus atavus, Ptychagnostus punctuosus, Goniagnostus nathorsti, Lejopyge laevigata, Proagnostus bulbus, Linguagnostus reconditus, Glyptagnostus stolidotus, and Glyptagnostus reticulatus. Each zone is further characterized by an assemblage of agnostoid species that may vary from place to place. By extrapolating from recently published uranium-lead geochronology, we estimate that the average duration of these agnostoid zones was approximately one million years.

Formal division of the Cambrian System into global series and stages is a current project of the International Subcommission on Cambrian Stratigraphy. If the base of an upper Cambrian series of whatever name is selected to correlate closely with the traditional Middle-Upper Cambrian boundary in Europe, we propose the base of the Linguagnostus reconditus Zone in the Wangcun section as a potential Global Standard Stratotype-section and Point (GSSP). Alternatively, if the base of an upper Cambrian series is selected to coincide with the base of the Glyptagnostus reticulatus Zone, we propose the base of that zone in the Paibi section as a potential GSSP.