The scorpionfly (Mecoptera) superfamily Panorpoidea underwent an Eocene radiation, replacing the extinct Mesozoic orthophlebiid grade and reaching its greatest family-level diversity: Panorpidae, Panorpodidae, Austropanorpidae, Holcorpidae, Dinopanorpidae, and a new family proposed here, the Eorpidae. Only the Panorpidae and Panorpodidae survived the Eocene and persist to the present day. This cluster of family extinctions is exceptional within Cenozoic insects. The Eorpidae includes at least one new genus and three new species described here from four localities of the early Eocene Okanagan Highlands of British Columbia, Canada, and Washington, U.S.A.: Eorpa ypsipeda n. gen. n. sp. (McAbee and possibly Falkland, BC, Canada; and Republic, WA, U.S.A.), Eorpa elverumi n. gen. n. sp. (Republic), and Eorpa jurgeni n. gen. n. sp. (Quilchena, BC). Some of the other fragmentary and poorly preserved specimens might represent further new species. We propose that the apex of Panorpoid family diversity ended by pressures from post-Eocene icehouse world climatic stress and the rise to ecological dominance of ants, some of which would have provided strong competition in scavenging for dead arthropods.

Caribbean reefs underwent significant biotic change during the Late Oligocene and Early Miocene. This was a critical time in the evolution of the modern Caribbean fauna characterized by increasing endemism resulting from regional extinction of lineages that survive in the modern Indo-Pacific. An understanding of the dynamics and potential causes of the Oligocene/Miocene transition, however, is hampered by the relative lack of well-preserved Oligocene to early Miocene coral faunas in the Caribbean. Here we examine new exposures in the Culebra Formation of Panama that contain a well-preserved coral fauna of Early Miocene age. Taxonomic, stratigraphic, and paleoecologic study of the Culebra Formation exposed along the Gaillard Cut of the Panama Canal allows us to infer the paleoenvironments and reef coral communities from the Panama Canal Basin during this critical interval. The Culebra Formation consists of a deepening upward sequence with shallow-lagoon sediments at the base, overlain by fringing reef facies in the middle of the section, and open-shelf to bathyal facies at the top of the section. We recovered 31 species of reef corals from a combination of new and old collections. Comparison of our collections with other Late Oligocene to Middle Miocene reef coral assemblages confirms that there was a major faunal turnover after deposition of the Upper Oligocene Antigua Formation. This turnover consisted of a large number of extinctions followed by an increased rate of first occurrences so that regional diversity did not change appreciably. Improved stratigraphic resolution at this and other Caribbean localities is required to understand fully the dynamics of change during the Oligocene/Miocene transition.

Plicodendrocrinus n. gen. is erected for dendrocrinids with solid pentalobate columns, strong stellate ridges on the aboral cup plates, and highly plicate anal sac plates. Five species are assigned: Middle Ordovician; P. proboscidiatus (E. Billings, not W. R. Billings) n. comb., from the Trenton of Canada and the Dunleith of Iowa and Minnesota. Upper Ordovician; P. casei (Meek) n. comb., from the Richmond and Gamachian of the midcontinent; P. rugocyathus (Ramsbottom) n. comb., from the Ashgill of England; P. collapsus (Donovan) n. comb.; and P. granditubus (Ramsbottom) n. comb., from the Ashgill of Scotland.

The Middle Ordovician dendrocrinids from the Dunleith Formation (Trentonian) of northern Iowa and southern Minnesota are P. proboscidiatus (E. Billings), Dendrocrinus acutidactylus E. Billings, and Quienquecaudex springeri (Kolata). All species are also known from the Middle Ordovician of Ontario and Quebec. In addition, O. springeri (Kolata) is recorded from the Platteville Group of Illinois. Biogeographically, the Dunleith dendrocrinids are most similar to those of the northern Appalachians.

Plicodendrocrinus casei (Meek) ranges widely in the midcontinent and has been obtained from the Maysvillian and Richmondian Maquoketa Formation of Iowa and Minnesota, several Richmondian units in the Cincinnati area, and the Gamachian Girardeau Limestone of Illinois and Missouri.

A quantitative cladistic analysis of Ordovician cladid and flexible crinoids produces five groups: primitive forms including Aethocrinus, Compagicrinus, Ottawacrinus, and Grenprisia; cyathocrinids with Carabocrinus, Palaeocrinus, Illemocrinus, and Porocrinus; merocrinids with Archaetaxocrinus, Merocrinus, Praecupulocrinus, Polycrinus, and Aithriocrinus; dendrocrinids with Esthonocrinus, Eoparisocrinus, Dendrocrinus, Quienquecaudex, Plicodendrocrinus and perhaps Eopinnacrinus; and Cupulocrinus and the flexibles, Protaxocrinus, Clidochirus, and Proanisocrinus. These groups are not consistent with the present taxonomy and several suggestions for restructuring are presented, notably grouping flexibles with cladids and adjusting the taxonomic level of cyathocrinids. The cladograms for early cladids and flexibles are poorly correlated with stratigraphic position because of numerous unfilled range zones for the taxa or their ancestors. Thus, the cladograms generate predictions that can be tested by later finds in the Lower and the lower part of the Middle Ordovician. The overall evolutionary trends are highly mosaic with numerous parallelisms and reversals.

Microborings in the Late Ordovician tabulate corals Catenipora rubra (a halysitid) and Manipora amicarum (a cateniform nonhalysitid) and in an epizoic solitary rugose coral differ from nearly all of those previously reported in Paleozoic corals. These microborings were formed within the coralla by endolithic algae and fungi located beneath living polyps. Comparable structures in the Late Ordovician tabulate Quepora ?agglomeratiformis (a halysitid) represent algal microborings, not spicules, and halysitids are corals, not sponges as suggested by Kaźmierczak (1989).

Endolithic algae in cateniform tabulates relied primarily on light entering through the outer walls of the ranks rather than through the polyps; lacunae within coralla permitted appropriate levels of light to reach many corallites. The direction of boring was determined by corallum microstructure and possibly also by the distribution of organic matter within the skeleton. There is an apparent inverse correlation between boring activity and coral growth rate.

The location and relative abundance of pyritized microborings within calcareous coralla can be established quantitatively and objectively from electron microprobe determinations of weight percent sulfur along appropriate traverses of the coral skeleton. The distribution of such microborings in Catenipora rubra and Manipora amicarum is comparable to algal banding in modern corals; this is the first report of such banding in the interiors of Paleozoic corals. Change in the intensity of boring within each corallum was evidently a response to variation in the linear growth rate of the coral, or to fluctuation in an environmental factor (perhaps light intensity) that could control both algal activity and growth rate in these corals. Change in the algal boring intensity and linear growth rate of the coral was generally but not always seasonal and usually but not invariably associated with change in the density of coral skeletal deposition.

Cyclic bands of boring abundance maxima within fossil colonial corals provide a measure of annual linear growth comparable to the widely accepted method based on skeletal density bands. Algal bands are more sporadically developed than density bands within and among coralla, thus increasing the difficulty of interpretation. Fluctuations in the abundance of algal microborings apparently provide a detailed record of changes in the linear growth rate of colonies and of individuals within colonies. Combined analyses of microboring abundance and skeletal density will contribute significantly to our understanding of the biological and environmental factors involved in endolithic activity and coral growth.

For many years the earliest record of the class Crinoidea was a single late Tremadocian genus. In the past decade, five crinoid genera were described from the early and middle Tremadocian, near the base of the Ordovician. Together these six genera represent a diverse assemblage with all but one expressing existing subclass apomorphies. Two of the recently described genera were initially assigned to their own order (plesion) Protocrinoida but not to a subclass. Here they are placed in the camerates based on apomorphies of the tegmen complex. Protocrinoids exhibit plesiomorphies unlike typical camerates. Two genera group with cladids, one expressing dendrocrinine apomorphies and the other cyathocrinine. One genus is placed within disparids, with iocrinid apomorphies.

Based on its ancient age and trait mosaic, the protocrinoid Titanocrinus is designated as outgroup in a phylogenetic analysis using all other Early Ordovician and select Middle Ordovician taxa as an ingroup. Character compilation and phylogenetic analysis posit early class-level plesiomorphies inherited from an unknown ancestry but lost during subsequent crinoid evolution. Class-level apomorphies also emerge, some of which were subsequently lost and others retained. Results are generally robust and consistent with earlier subdivisions of the class, but supporting lower rank reorganizations. Strong support for the camerate branch low in the crinoid tree mirrors findings of earlier workers. Cladids branch from a series of intermediate nodes and disparids nest highest. Branching of disparids from cladids could be homoplastic.

Upper Eocene and lower Oligocene deposits of the Jebel Qatrani Formation, Fayum Depression, Egypt, have provided a number of skulls and other bones that belong to a species of snakehead (Channidae). This material is morphologically more similar to species of Parachanna, rather than species of Channa, and is here described as a new species, Parachanna fayumensis. It differs from the other species of the genus in possessing a prominent tooth patch on the posterior end of the parasphenoid.

This new species of channid is the oldest member of the family known from Africa. Prior to this record, the oldest African fossil channid material was found in Mio—Pliocene deposits. This lack of information on the African fossil record leads to biogeographic reconstructions in which channids were believed to have arisen in Asia and invaded Africa through fresh waters, only after the two continents were connected in the Miocene. the Egyptian material shows that channids were in the fresh waters of Africa in the latest Eocene. Either a freshwater connection existed between Africa and Asia before or during the late Eocene, or members of the Channidae were able to migrate through marine waters to attain their current distribution.

Significant allometry occurs during the ontogeny of every variable in Poecilozonites bermudensis, a Pleistocene-Recent land snail from Bermuda. The adaptive significance of shell allometry may lie in the necessity for preserving a high value of the foot surface/body volume ratio. In the absence of allometry, this ratio must decline as size increases. Three strategies could be used to keep this ratio sufficiently high: positive allometry of foot growth, structural strengthening of the foot, and the development of a foot initially large enough to withstand decline in the ratio during growth. As indicated by ontogenetic changes in apertural shape, a small amount of positive allometry occurs during ontogeny of the foot in P. bermudensis. This is not sufficient to prevent decline of the foot surface/body weight ratio, and I conclude that the strategy of possessing an initially large foot is also used. A simple model of doming, reflecting this latter strategy, is constructed (doming is a major allometric feature of P. bermudensis). In this model, the foot volume/body volume ratio is constant throughout ontogeny in each of two shells, but this value is higher in the more strongly domed shell.

Knowledge of ontogenetic allometry is a prerequisite for understanding the phylogeny of P. bermudensis, for paedomorphosis has been the primary evolutionary event in this taxon. Paedomorphic samples are scaled-up replicas of juvenile shells of the central stock, P. bermudensis zonatus. The degree of ontogenetic retardation in development is the same for all variables (color, thickness, and external shape). Paedomorphosis has occurred several times during the Pleistocene, providing an example of iterative evolution at the infraspecific level. Four paedomorphic taxa are known: P. b. fasolti, P. b. siegmundi, P. b. sieglindae, all new; and P. b. bermudensis (Pfeiffer). They have the geographic distribution (small, peripheral isolates) expected of diverging populations and seem to be genetically distinct entities, not mere phenotypic variants. The most paedomorphic subspecies originated in red soils; paedomorphs did not evolve in times of carbonate-dune deposition. The thin shells of paedomorphs might have been adaptive in the low-calcium environment of red soils. The general significance of iterative evolution at the infraspecific level does not provide an adequate model for corresponding events at higher levels.

A conspicuous silicified microfossil, Frankbaronia polyspora n. gen. n. sp., occurs in plant litter and as an inhabitant of microbial mats from the Lower Devonian Rhynie chert, Aberdeenshire, Scotland. Specimens are elongate-cylindrical, oval, or spherical, thin-walled, and may possess conical or column-like surface projections. Most specimens occur isolated, some are arranged in pairs or short chains. Each specimen contains several small spheres, each in turn with a (sub)centric opaque inclusion. Immature specimens indicate that ontogenesis in this fossil includes the formation of a single centric body of opaque material that subsequently is apportioned among the developing small spheres. Frankbaronia polyspora is quite similar in size and morphology to the oogonia containing oospores seen in certain extant members of the Peronosporomycetes. The Rhynie chert is known to contain the oldest fossil evidence of the Peronosporomycetes but only a single form (Hassiella monospora) has previously been documented. The discovery of a second putative representative of this group of organisms proves that this paleoecosystem is still an important source of new information on the paleodiversity of microbial life.

The hitherto poorly known forefin of Chensaurus chaoxianensis (Ichthyosauria) from the Lower Triassic (Spathian) is redescribed on the basis of the holotype and two new specimens. The humerus resembles that of Utatsusaurus hataii but is distinctive in having an emarginated anterior margin. The anteroproximal prominence of the radius is well developed, unlike that of other ichthyosaurs. All three specimens have five metacarpals and many phalanges, but only three carpals, which are identified as the ulnare, intermedium, and fourth distal carpal. These specimens show that delayed mesopodial ossification occurred in ichthyosaurs, at least in an early evolutionary stage. Because delayed mesopodial ossification is common among diapsids and is unknown in Jurassic ichthyosaurs, it was lost during the evolution of the Ichthyosauria. The osteogenic developmental axis appears to have continued into the fourth digit, as in other amniotes. The ossification pattern provides conclusive evidence to support the suggestion that the basal element of the fifth digit in Early Triassic ichthyosaurs is a metacarpal, rather than a carpal.

Sections in the Basin Ranges provide stratigraphic standards for the Ordovician of the U.S., from which zones based on trilobites have been widely employed in regional correlation. This paper describes new trilobite faunas from a poorly known part of the succession, at the base of the Middle Ordovician (Whiterockian) in western Utah and eastern Nevada, and including the type Ibexian section near Ibex, Utah. The faunas are from the topmost Wahwah, and overlying Juab Limestone Formations, in strata equivalent to Zone L. Although well-preserved, none of the trilobites are silicified. All are typical of inshore carbonate, Bathyurid biofacies. The majority are new species congeneric with, but different from species from the overlying Kanosh Formation. The dominant bathyurid is the hitherto little-known Psephosthenaspis, after which the new Zone is named. A threefold subdivision of the Psephosthenaspis Zone is based on successive species of the genus. The lower two of these are probably equivalent to the Valhallan Stage, described from more offshore biofacies from Spitsbergen. Eighteen species are described, of which nine are formally named as new including: Goniotelina ensifer, Petigurus inexpectatus, Psephosthenaspis microspinosa, M. glabrior, Pseudoolenoides aspinosus, Ectenonotus progenitor, Kanoshia reticulata and Pseudomera arachnopyge. The type species of a remarkable new illaenid-like bathyurelline, Madaraspis magnifica gen. et sp. nov., is described.

Ernietta plateauensis Pflug, 1966 is the type species of the Erniettomorpha, an extinct clade of Ediacaran life. It was likely a gregarious, partially infaunal organism. Despite its ecological and taxonomic significance, there has not been an in-depth systematic description in the literature since the original description fell out of use. A newly discovered field site on Farm Aar in southern Namibia has yielded dozens of specimens buried in original life position. Mudstone and sandstone features associated with the fossils indicate that organisms were buried while still exposed to the water column rather than deposited in a flow event. Ernietta plateauensis was a sac-shaped erniettomorph with a body wall constructed from a double layer of tubes. It possessed an equatorial seam lying perpendicular to the tubes. The body is asymmetrical on either side of this seam. The tubes change direction along the body length and appear to be constricted together in the dorsal part of the organism.

An asteroid fauna is described from the Albian (Cretaceous) interval of the Washita Group of central Texas. New genera and species are Alkaidia sumralli, (Benthopectinidae), Capellia mauricei (Goniasteridae), and Betelgeusia reidi (Radiasteridae). Additional new genera are Fomalhautia (Goniasteridae), and Denebia and Altairia (Ophidiasteridae). Crateraster texensis (Goniasteridae), new combination, is similar to the European type species, C. quinqueloba. An unnamed species of Crateraster and an unassigned goniasterid are also present. All Washita genera are extinct, but all belong to extant families. The fauna is largely distinct from that of the somewhat younger European Cretaceous chalk.

The Radiasteridae (e.g., Betelgeusia) is inferred to hold a basal position in the Paxillosida; Betelgeusia extends the range of the family back to the Cretaceous, closer to the diversification of the living asteroid orders. Asteroids capable of burying themselves in sediment (and only self-buriers) share some form of channelization for the passage of water currents between the primary ossicles of the body surface. Channels in Betelgeusia indicate semi-infaunal habits similar to those of living Astropecten and Luidia. Betelgeusia represents the third semi-infaunal paxillosidan family now known from the Cretaceous, although none are known from older rocks, suggesting a broadening of the asteroid adaptive zone during the Cretaceous. The Goniasteridae, Radiasteridae, and Benthopectinidae are less important in shelf settings today than they appear to have been during Washita deposition, whereas the Astropectinidae, Luidiidae, and the Echinasteridae are absent from the Washita although they are common today in similar settings.

Eight Early Silurian inadunate crinoids are described. These include: a pisocrinid, genus and species undetermined; (?)Myelodactylus sp.; Kanabinocrinus thyaros n. gen., n. sp.; Euspirocrinus heliktos n. sp.; (?)Euspirocrinus sp.; Eoparisocrinus siluricus n. comb. (n. gen.); Dendrocrinus daytonensis n. sp.; and dendrocrinid, genus and species undetermined. Parisocrinus siluricus, Parisocrinus mulletensis, and Euspirocrinus obconicus are all reassigned to Eoparisocrinus. Parisocrinus is restricted to members of Devonian and Mississippian age. The genus Parisocrinus is discussed, and its type species P. perplexus is illustrated.

Pisocrinid, genus and species undetermined, (?)Myelodactylus sp., and Kanabinocrinus thyaros represent the oldest member of the family in which each belongs. The phylogenetic relationships of these and other taxa are discussed.

A fossilized social insect nest, Socialites tumulus new ichnogenus and ichnospecies, is described from continental strata of the Upper Cretaceous Kaiparowits Formation in southern Utah. Nine discrete nest structures are preserved along a single bedding plane, within an area of about 25 m2. Fine-grained, ripple-laminated sandstone, interpreted as a fluvial crevasse splay deposit, drapes the nest structures and is thought to have rapidly buried and preserved much of the aboveground architectural morphology of the nest structures. Such social insects as ants and termites are considered as possible tracemakers. Comparison to fossil and modern nests suggests that Socialites tumulus is more similar to nests produced by ants than by termites. This trace fossil preserves rare, tangible evidence of nest construction by social insects during the Late Cretaceous, adding new information on insect diversity and habitat utilization in Mesozoic terrestrial ecosystems. Detailed study of these complex nest structures also aids in paleoenvironmental reconstruction, revealing multiple phases of nest construction, burial, and reestablishment.

Aspects of functional morphology are examined and lifestyles proposed for seven exceptionally well-preserved crinoids from the Middle Ordovician Lebanon Limestone, Middle Tennessee. Potential ranges of motion are based on plate shapes, articular surfaces of attachment, and feeding structures. This diverse group of crinoids includes disparid inadunates (Columbicrinus crassus and Tryssocrinus endotomitus), a hybocrinid (Hybocrinus bilateralis), reteocrinids (Reteocrinus polki and R. variabilicaulis), and rhodocrinitid camerates (Archaeocrinus snyderi and Gustabilicrinus plektanikaulos). Using attachment structures as the basis, these crinoids can be divided into two groups: encrusters and commensals. Encrusters are the most diverse and include all taxa except the rhodocrinitids. They have a small discoidal holdfast and xenomorphic column. Proxistele-mesisteles were holomeric or pentameric. Flexure potential of this region of the column in disparids was increased by wider ligament gaps at nodal-internodal articulations; in other taxa flexure was enhanced by increasing the frequency of columnals. Short dististeles are polymeric or a plate mosaic. This region functioned as a resilient buffer between the mesistele and holdfast. Columns as a whole had moderate flexure potential. Feeding-structure design was varied, although all but Hybocrinus bilateralis had pinnulate or nonpinnulate parabolic filtration fans. Hybocrinus bilateralis had atomous arms arrayed in a bilaterally symmetrical pattern; the symmetry plane was oriented parallel to prevailing currents. Commensals in the Lebanon are the rhodocrinitids. Their attachment structures are characterized by a long distally tapering column terminating in a coil. Densely pinnulate arms formed a well-developed parabolic filtration fan.

Encrusters were limited to hardgrounds or skeletal substrata. Commensals were more opportunistic, utilizing a variety of substrates, and they were widespread in Lebanon subenvironments including those with both soft and hard seafloors. Lebanon hardground assemblages are characterized by high diversity, particularly among crinoids and bryozoans. They are strikingly tiered according to elevation above the seafloor (and probably additionally by feeding limitations). This assemblage was the result of longterm coevolution in association with hardgrounds.

Ontogenetic development of the column of encrusting crinoids indicates that the evolution of holomeric columnals occurred through a simpler sequence than previously proposed and need not have included gradual alignment of offset pentameres as intermediate steps. Columnals evolved from a poorly organized plate mosaic through a polymeric stage.

The Cambrian inlier at Beaver Harbour, southern New Brunswick, is now confidently referred to the marginal platform of the late Proterozoic–Early Paleozoic Avalon microcontinent. The sub-trilobitic Lower Cambrian Chapel Island and Random Formations are unconformably overlain by the mafic volcanic-dominated Wade's Lane Formation (new). Late Early Cambrian trilobites and small shelly taxa in the lowest Wade's Lane demonstrate a long Random–Wade's Lane hiatus (middle Terreneuvian–early Branchian). Latest Early–middle Middle Cambrian pyroclastic volcanism produced a volcanic edifice at Beaver Harbour that is one of three known volcanic centers that extended 550 km along the northwest margin of Avalon. Middle Middle Cambrian sea-level rise, probably in the Paradoxides eteminicus Chron, mantled the extinct volcanics with gray-green mudstone and limestone of the Fossil Brook Member. Black, dysoxic mudstone of the upper Manuels River Formation (upper Middle Cambrian, P. davidis Zone) is the youngest Cambrian unit in the Beaver Harbour inlier. Lapworthella cornu (Wiman, 1903) emend., a senior synonym of the genotype L. nigra (Cobbold, 1921), Hyolithellus sinuosus Cobbold, 1921, and probably Acrothyra sera Matthew, 1902a, range through the ca. 8 m.y. of the trilobite-bearing upper Lower Cambrian, and H. sinuosus and A. sera persist into the middle Middle Cambrian. Lapworthella cornu and H. sinuosus replaced the tropical taxa L. schodackensis (Lochman, 1956) and H. micans Billings, 1872, in cool-water Avalon.

Cellana ampla n. sp. from late Eocene rocks in Oregon is the first New World record of a genus and family heretofore considered to have radiated in Australia and the mid-Pacific. Re-examination of some other Eocene limpets from the Pacific Northwest reveals that species previously assigned to Acmaea belong in Patelloida and Siphonaria. Thus, all three major components of the modern Australian limpet guild were present in the late Eocene of western North America along a coastline occupied today by acmaeid limpet guilds. Re-examination of a large Pliocene ‘Patella’ from South America shows the shell structure of a Cellana and constitutes a second documentation of a large nacellid limpet in the New World Tertiary.

Although the taxonomy of modern limpets is founded on anatomical characters, shell structure characters are sufficient to identify genera and families directly in the fossil record. Re-evaluation and reclassification of fossil limpets using shell structure contributes not only to a better understanding of the phylogeny of major limpet groups but also provides a powerful tool for elucidating the evolutionary, biogeographic, and ecologic development of the complexly structured limpet guilds of differing taxonomic composition that dominate rocky intertidal habitats throughout the world.

Blocks of sandy limestone dredged from the bottom of a quarry in eastern Lee County, South Carolina, contain a turritelline gastropod-dominated macrofossil assemblage, including age-diagnostic Maastrichtian ammonites. Although turritelline-dominated assemblages are common in other areas and ages, this is the first report of such an assemblage of any age from South Carolina and the first Cretaceous turritelline-dominated assemblage from eastern North America. Whereas the matrix of the turritelline layer is calcareous, the carbonate is present only as cement and the fossil assemblage did not form in a typically carbonate-dominated environment. This fact agrees with the observed absence of “turritella limestones” in the Cretaceous. Such limestones are common in the Paleogene but absent in the Neogene. This pattern is consistent with the hypothesis that turritellines as a group have become less thermophilic since the Cretaceous.

Two species of the enigmatic alga Chaetocladus, C. ruedemanni (new species) and C. dubius (previously regarded as a graptolite incertae sedis), are described from the Silurian Lockport Group of New York and Ontario, Canada, respectively. A comprehensive investigation reveals that these and other Chaetocladus taxa occur in distinctive Konservat-Lagerstätten in association with other thallophytic algae, annelid worms, and lightly sclerotized arthropods. The sedimentology, taphonomy, and biotic composition of Chaetocladus-bearing deposits indicate that this alga thrived in shallow, stagnant, occasionally storm-agitated marine environments. In these settings, preservation of thallophytic algae and associated soft-bodied animals apparently was facilitated by a combination of obrution, anoxia, and early diagenesis of the burial muds.

The morphology of Chaetocladus corresponds to that characteristic of the green alga order Dasycladales, and it is herein referred to this long-ranging taxon as a representative of a new subtribe (Chaetocladinae, new subtribe) within the tribe Salpingoporelleae (emended herein), family Triploporellaceae (emended herein). This euspondyl, endosporate genus extends the range of the euspondyl dasyclads significantly, from the Early Devonian back to the Middle Ordovician, and bridges an evolutionary gap between early Paleozoic aspondyl, endosporate forms and middle Paleozoic euspondyl, cladosporate forms.

A new classification is proposed for late Paleozoic Edrioasteroidea (Echinodermata), separating forms with the advanced clavate thecal design from those with the ancestral pyrgate thecal design, and a new Subfamily Discocystinae is erected to receive the clavate agelacrinitid edrioasteroids. Lepidodiscus Meek and Worthen is restricted to the pyrgate type species L. squamosus (Meek and Worthen) and two unnamed species, whereas the clavate L. laudoni (Bassler) is assigned to Clavidiscus, new genus. The clavate Discocystis priesti Strimple and three new species, Hypsiclavus kinsleyi, new genus and species, Hypsiclavus huntsvillensis, new genus and species, and Hypsiclavus guensburgi, new genus and species, are placed in Hypsiclavus, new genus. Bostryclavus, new genus, is erected to receive Echinodiscus sampsoni Miller. A redescription of Discocystis kaskaskiensis (Hall) and a diagnosis of Spiraclavus Sumrall are included for completeness.