Populations of the Upper Ordovician trepostome bryozoan Batostoma jamesi were collected from two different paleoenvironmental settings in the Kope Formation of southeastern Indiana. Within each colony and population, morphologic changes were analyzed during colony growth, or astogeny. Morphological measurements of zooecia, mesozooecia, and acanthostyles display similar patterns of change during colony growth in both populations but magnitudes are generally larger in the high diversity population.

Canonical variates analyses provided multivariate confirmation of univariate character differences found within each population. Statistically significant multivariate morphological differences between growth stages persist even if assignments of colonies to populations are ignored. Results suggest different potentials for altering growth trajectories in different environments with early growth stage flexibility in colonies from lower diversity settings and later-stage flexibility in colonies from higher diversity settings.

Heterochronic changes occur between species populations. Relative to the high-diversity population, the low-diversity population displays the following: 1) progenesis and hypermorphosis for zooecia, reflecting the ability to exist over a broader range of areal densities and surface areas than in populations from high-diversity associations; 2) postdisplacement and progenesis for mesozooecia, producing mature mesozooecial densities earlier in growth and at smaller sizes while the onset of mesozooecial development is delayed; and 3) acceleration, predisplacement, and progenesis for acanthostyles, resulting in a more rapid rate of development, an earlier onset of style development and more styles, and an earlier time of maturation, respectively.

The estimated level of morphological integration is higher in the high diversity population regardless of stage of colony growth. Within populations, integration is stronger during early growth stages in colonies from high diversity settings and during later growth stages in colonies from low diversity settings. Character heritabilities are high in both diversity-level populations, suggesting that these patterns of morphological integration were not the result of non-heritable phenotypic plasticity. Mean heritability is greater in the high diversity population and differs statistically only between the late growth stages of populations. Patterns of morphological integration may result from differing levels of stabilizing selection in different environments. Depending on the timing of selection, these different levels of integration are capable of affecting the outcome of selection on species populations.

Seven genera and eight species of lingulate brachiopods are described from the Cambrian-Ordovician boundary beds (Cambrooistodus minutus Conodont Subzone to Rossodus manitouensis Conodont Zone) at the Lawson Cove and Lava Dam North sections, Ibex area, Utah, USA. The fauna includes one new linguloid genus, Wahwahlingula, and four new species, Lingulella? incurvata, Zhanatella utahensis, Conotreta millardensis, and Quadrisonia? lavadamensis. Lingulate brachiopods from this interval are very poorly known from Laurentia, but the recorded fauna is very similar to that described from coeval beds at Malyi Karatau, Kazakhstan, and both areas contain Eurytreta cf. bisecta (Matthew, 1901); E. sublata Popov, 1988; ZhanatellaKoneva, 1986; SchizambonWalcott, 1889; and Wahwahlingula. Eurytreta cf. bisecta is also known from the Lower Ordovician of Avalonian Canada, Britain, and Scandinavia.

Two new genera of the Chonostrophiidae are proposed herein to accommodate the resupinate shells from the Famennian sediments of the Late Devonian in the Santanghu Basin of the Balikun area, Xinjiang Province, northwestern China. Santanghuia santanghuensis new genus and species is distinguishable from other chonostrophiids by the possession of a pair of long dorsal anderidia and absence of a dorsal median septum. Balikunochonetes liaoi new genus and species is distinct because of the presence of a pair of anderidia with secondary anderidia, and a dorsal median septum. Santanghuia new genus is considered to be phylogenetically related to Chonostrophia of late Early to Middle Devonian age, while Balikunochonetes has possibly given rise to Chonostrophiella of Early Devonian age and is a likely ancestor of Tulcumbella of Early Carboniferous age.

The presence of the bivalve mollusks Astarte (Tridonta) borealis Schumacher and A. (T.) hopkinsi new species, in uppermost Miocene or lower Pliocene strata of the Milky River Formation on the Alaska Peninsula, southwestern Alaska, signals the earliest opening of Bering Strait. These species migrated from the Arctic Ocean into the North Pacific when the Bering Strait first flooded and, along with co-occurring marine diatoms, are primary evidence for the earliest opening of the strait, in the latest Miocene or early Pliocene. These paleogeographically important Alaskan Astarte have been cited in this context, but have not been previously illustrated or discussed.

Two new distinctive families, Crassimarginatidae and Scoliostomatidae, each characterized by unusual gerontic apertural morphotypes, are established on the basis of study of the richly diverse Lower Devonian gastropod fauna of the Road River Formation in the Royal Creek area, Yukon Territory. The Early Devonian genus CrassimarginataJhaveri, 1969, is transferred from the family Palaeotrochidae and placed, together with the new genus Yukonoconcha, into the new family Crassimarginatidae, which is characterized by a pupiform shell with an explanate outer apertural lip in the gerontic growth stage. The new family Scoliostomatidae unites Devonian gastropod genera (ScoliostomaBraun, 1838; BrilonellaKayser, 1873; AnarconchaHorný, 1964; Eoscoliostoma new genus; MitchelliaKoninck, 1877; and Pseudomitchellia new genus), which are characterized by a distinctive, free, twisted (both outwards and backwards) gerontic final half whorl. More detailed morphological comparison of members of this family has allowed their division into two new subfamilies: the Scoliostomatinae and Mitchelliinae. New genera include Yukonoconcha, Eoscoliostoma, and Pseudomitchellia. The former two genera are represented each by a single new species from Yukon Territory, Yukonoconcha pedderi and Eoscoliostoma norrisi. The latter genus is represented by two species, the type Pseudomitchellia bohemica (Perner) from the Koněprusy Limestone (Pragian) of the Czech Republic and Pseudomitchellia macqueeni new species from Yukon Territory.

Rare to abundant silicified polyplacophoran faunas occur in the late Wolfcampian Bird Spring Formation and the Leonardian Pequop and Loray Formations in Nevada, the Leonardian Arcturus Formation in Utah, and the early Leonardian Ft. Apache Limestone Member of the Supai Formation in Arizona. The faunas associated with the polyplacophorans are dominated by molluscs. New species include Gryphochiton distinctus, Acutichiton gracilis, A. nevadensis, and Arcochiton richardsoni. Traces of color patterns are present on Arcochiton richardsoni.

Two neogastropod species occur in brackish intervals in the Pebas Formation (late Middle to early Late Miocene) of Peru and Colombia in western Amazonia. Purpura woodwardiRoxo, 1924, is assigned to MelongenaSchumacher, 1817 (Melongenidae), and ?Nassarius reductus (Nassariidae) is recognized as a new species. These gastropods are among the very few marine invaders in the otherwise freshwater Pebas fauna. The small number of marine to freshwater transitions among South American molluscs contrasts with the situation among South American fishes and southeast Asian molluscs. It may be related to seasonal fluctuations in water level and anoxia in present-day South American freshwater environments, as well as to predation and productivity.

Middle and Upper Devonian members of the phyllocarid order Archaeostraca Claus, 1888, are analyzed in both a phylogenetic and biogeographic context. Results of the phylogenetic analysis show that the suborders Ceratiocaridina Clarke inZittel, 1900, and Rhinocaridina Hall and Clarke, 1888, are paraphyletic as traditionally defined. The diagnoses of these suborders are revised and the use of the suborders Echinocaridina Clarke inZittel, 1900, and Pephricaridina Van Straelen, 1933, is proposed. Ceratiocaridina now contains the family Ceratiocarididae Salter, 1860; Rhinocaridina contains the family Rhinocarididae Hall and Clarke, 1888; Echinocaridina includes the families Aristozoidae Gürich, 1929, Ptychocarididae n. fam., and Echinocarididae Clarke inZittel, 1900; Pephricaridina includes the families Pephricarididae Van Straelen, 1933, and Ohiocarididae Rolfe, 1962. Generic definitions within the Rhinocarididae, in particular ”Rhinocaris” Clarke inHall and Clarke, 1888, are revised. The genus Echinocaris is redefined to include a monophyletic assemblage of species. Each of these clades is supported by several synapomorphies. Two new genera, Paraechinocaris and Carinatacaris, are proposed. Biogeographic analysis of this group reveals an extremely low rate of vicariant speciation, while episodes of range expansion are frequent. All occurrences of vicariance preceded the Late Devonian mass extinction. This may suggest a relationship between increased dispersal, diminished speciation, and the Late Devonian biotic crisis. Parallels between the Late Devonian mass extinction and the modern biodiversity crisis are suggested by the frequency of episodes of range expansion indicative of invasive species.

Latest Early Cambrian continental slope deposition of the early Hatch Hill dysaerobic interval (new name, latest Early Cambrian–earliest Ordovician) is recorded by dark grey shales and turbidite limestones in the Bacchus slice at Ville Guay, Québec. Platform-derived microfaunas of the Bicella bicensis trilobite assemblage were transported into a dysoxic environment of the upper “Anse Maranda Formation,” and many organisms were buried alive. Phosphatization preserved a diverse skeletal fossil assemblage that includes four agnostid trilobites, echinoderm debris, and twenty small shelly fossil taxa. The latter include five helcionellids; PelagiellaMatthew, 1895b, classified herein as a gastropod; a bivalve (FordillaBarrande, 1881); the brachiopod Linnarssonia taconicaWalcott, 1887; two conodontomorphs; four hyoliths; and such phosphatic and calcareous problematica as ColeoloidesWalcott, 1889, emend. Most small shelly fossil taxa, including Discinella micansBillings, 1872, range through much of the Olenellus Zone and Elliptocephala asaphoides assemblage interval. Trilobites allow a more resolved correlation into the uppermost Olenellus Zone. A comparable stratigraphy occurs in Cambrian–Ordovician slope facies of the Bacchus slice and the Giddings Brook slice in eastern New York. The “Anse Maranda Formation” correlates with the West Granville–Browns Pond–lower Hatch Hill formations in eastern New York and brackets two dysaerobic intervals (Browns Pond and early Hatch Hill). Sea-level change associated with the Hawke Bay regression between the Browns Pond and Hatch Hill onlap/dysaerobic intervals led to the longest period of oxygenated green shale and sandstone deposition on the east Laurentian slope in the late Early Cambrian–earliest Ordovician.

Morphology is reviewed with special reference to the doublure and thoracic characters; a reconstruction of Richterarges aquilonius is used to suggest possible lichid anatomy. The relatively large hypostome and wide doublure, and the thorax with, or without, the strongly convex posterior pleural bands characterize lichids, in addition to the distinctive glabellar morphology. Relatively shallow furrows on the external surface form strong ridges on the visceral surface of the exoskeleton; apodemes are absent. Type specimens of species described by Schmidt, recently traced in Russian museums, are figured. Lichids differ from odontopleurids in morphology and anatomy, and are unlike Scutelluinae; accepted subfamilial divisions of Lichidae are reinforced by thoracic characters. A single lichid species is known in the early Tremadoc, in the early Middle Ordovician the main four subfamilies are recognised and are widespread; their ancestry and early diversification remain unknown.

An extraordinarily well-preserved upper Homerian (uppermost Wenlock) post-extinction (post-lundgreni Event) graptolite fauna is described from Arctic Canada. The fauna of dendroids, retiolitids and monograptids, predominantly of uncompressed and isolated material, demonstrates almost totally new morphological features in comparison with the pre-extinction fauna. The two species of the lowest post-extinction fauna are followed by a rapid proliferation in the middle part of the interval, resulting in the maximum diversity, 21 species, for the entire upper Homerian. The upper Homerian is divided into three biostratigraphic units: the lower nassa-dubius Biozone, middle praedeubeli-deubeli Biozone, and the upper ludensis Biozone. The total fauna consists of ten species of monograptids and 11 species of retiolitids; of the latter group, three (Baculograptus, Papiliograptus and Doliograptus) are new genera, and six (B. batesi, P. papilio, P.? petilus, D. latus, Doliograptus sp. A, and Spinograptus praerobustus) are new species. Among the recognized species of monograptids, only Colonograptus schedidoneus and Lobograptus? cornuatus are confined to the Arctic, while five species of retiolitids (B. batesi, P.? petilus, D. latus, Doliograptus sp. A, and Spinograptus praerobustus) appear to be endemic.

Carbonaceous compression fossils in shales of the uppermost Doushantuo Formation (ca. 555–590 Ma) at Miaohe in the Yangtze Gorges area provide a rare Burgess-Shale-type taphonomic window on terminal Proterozoic biology. More than 100 macrofossil species have been described from Miaohe shales, but in an examination of published and new materials, we recognize only about twenty distinct taxa, including Aggregatosphaera miaoheensis new gen. and sp. Most of these fossils can be interpreted unambiguously as colonial prokaryotes or multicellular algae. Phylogenetically derived coenocytic green algae appear to be present, as do regularly bifurcating thalli comparable to red and brown algae. At least five species have been interpreted as metazoans by previous workers. Of these, Protoconites minor and Calyptrina striata most closely resemble animal remains; either or both could be the organic sheaths of cnidarian scyphopolyps, although an algal origin cannot be ruled out for P. minor. Despite exceptional preservation, the Miaohe assemblage contains no macroscopic fossils that can be interpreted with confidence as bilaterian animals. In combination with other late Neoproterozoic and Early Cambrian body fossils and trace fossils, the Doushantuo assemblage supports the view that body-plan diversification within bilaterian phyla was largely a Cambrian event.

This paper deals with Paracalamitina striata (Schmalhausen) Zalessky, 1934, an equisetophyte of the family Tschernoviaceae from the Permian of Angaraland. New material contributes to a better understanding of this plant, which now can be reconstructed. Paracalamitina striata is an equisetopsid with opposite ribs on the stem. Its main stem bears lateral shoots or shoot and leaf scars, that are located at nodes. Shoot nodes have subcylindrical leaf sheaths. The distal parts of leaves are free and acute. Generative organs are fertile zones, which are formed by numerous sporangiophores with peltate sporophylls. A terminal sterile whorl is presented above each fertile zone. An emended diagnosis of Paracalamitina Zalessky is provided on the basis of new material and re-examination of previously collected specimens as well. The nomenclature and taxonomic status of P. striata also are discussed.