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A single bed at the base of the Jordan Sandstone in a road cut at Arcadia, Wisconsin, yielded an undescribed Late Sunwaptan (Saukia Zone) trilobite fauna that includes at least four species from the families Dikelocephalidae Miller, 1889 and Eurekiidae Hupe, 1953. Arcadiaspis bispinata n. gen. and sp. is a distinctive eurekiid that is characterized by paired occipital and thoracic axial spines, long genal spines, and a nonspinose pygidial margin. Other genera present are the dikelocephalids, Dikelocephalus Owen, 1852 and Calvinella Walcott, 1914, and the eurekiid, Eurekia Walcott, 1916. Type material of Calvinella spiniger (Hall, 1863) is illustrated photographically for the first time. A new eurekiid species, Corbinia burkhalteri from the Fort Sill Formation, Oklahoma, is also described.

A new lyssacinosan hexactinellid, Rossella bromleyi n. sp., is described from the Upper Cretaceous of Arnager Pynt, Bornholm (Denmark). The sponge shows a cup-shaped form with a broad, moderately dense root tuft, which contains three- and four-rayed orthotropal anchors characteristic for Rossella. The skeleton is composed of bundles of diactines, hexactines of two orders, and pentactines. Diactine bundles are mainly in the growth direction or diagonal to it. Prostalia lateralia are pentactines with the paratangential rays protruding beyond the outer surface of the sponge body. Hypodermalia are absent.

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 in Zittel, 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 in Zittel, 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 Gurich, 1929, Ptychocarididae n. fam., and Echinocarididae Clarke in Zittel, 1900; Pephricaridina includes the families Pephricarididae Van Straelen, 1933, and Ohiocarididae Rolfe, 1962. Generic definitions within the Rhinocarididae, in particular 'Rhinocaris' Clarke in Hall 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.

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 Crassimarginata Jhaveri, 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 (Scoliostoma Braun, 1838; Brilonella Kayser, 1873; Anarconcha Horny, 1964; Eoscoliostoma new genus; Mitchellia Koninck, 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 Koneprusy Limestone (Pragian) of the Czech Republic and Pseudomitchellia macqueeni new species from Yukon Territory.

The cyrtospiriferid brachiopod genus Tenticospirifer Tien, 1938, is revised based on restudy of the type species from the Frasnian (Late Devonian) of the Russian Platform. As revised the genus includes cyrtospiriferid species with pyramidal ventral valves, catacline ventral interareas, a narrow delthyrium, few sinal plications, and lack a median dorsal septum and pseudodeltidium. All species retained in the genus are of Givetian and Frasnian age. All Famennian age species described from South China and North America are rejected from the genus. It appears that Tenticospirifer evolved during the early Givetian in western Europe and remained endemic to that region during the remainder of the Givetian. Successive migrations of Tenticospirifer from eastern Laurussia to North America, then to South China and possibly Australia, coincided with middle and late Frasnian eustatic sea level rises, respectively. The North American species Spirifera cyrtinaformis Hall and Whitfield, 1872, and related species identified as Tenticospirifer by North American workers, are reassigned to Conispirifer Lyashenko, 1985. Its immigration to and widespread dispersal in carbonate platforms of western Laurussia, northern Gondwana and tropical island arcs (?) coincided with a major late Frasnian eustatic sea level rise. The new family Conispiriferidae is proposed with Conispirifer Lyashenko, 1985, selected as the type genus. The new family also includes the new genus Pyramidaspirifer with Platyrachella alta Fenton and Fenton, 1924, proposed as the type species. The affinity of the new family remains uncertain pending restudy of key genera currently included in the Superfamily Cyrtospiriferoidea. Available data from the Devonian brachiopod literature indicate that species of Pyramidaspirifer are restricted to late Frasnian deposits of central and western North America.

Dentalium martini Whitfield, 1882, is a calcareous worm tube, not a mollusk, and is placed in synonymy of Coleolus crenatocinctum Hall, 1879. The growth of D. martini mimics logarithmic curvature in the holotype, but in other specimens shape varies from irregularly curved to straight. A prime reason for reassignment is variation of the wall thickness around the circumference in D. martini, which in late Paleozoic and Recent scaphopods of the same size is of uniform thickness.

The genus Cordania Clarke, 1892, has been known from the Lower Devonian (Lochkovian-Pragian) of the Appalachian Province and apparently from the Lower-Middle Devonian of China. Probable Lochkovian strata of the Biddabirra Formation in the Amphitheatre Group from near Cobar, New South Wales, Australia, have yielded Cordania buicki new species, extending the range of the genus to eastern Australia. Cladistic analysis of Cordania identifies C. buicki as more closely related to species from Oklahoma than to a northern Appalachian grade.

Molluscan ornament in modern oceans increases with decreasing latitude, in response to greater risk from tropical durophages (shell-crushing predators). The latitudinal gradient is presumed to be associated with the appearance of modern durophages during the Cretaceous, but this is untested. A radiation of durophages during the Devonian may have resulted in sufficient predation pressure to influence prey distribution similarly, although Devonian predators and prey are distantly related to their recent equivalents. This study examines latitudinal variation in ornament in Devonian strophomenide brachiopods to determine if a latitudinal gradient existed. A latitudinal gradient is documented for the Devonian; ornament decreases with increasing latitude. The correlation between proportion of spinose genera and region is -0.947 (p < 0.001). Similar to modern molluscs, spinose strophomenide genera constitute 26%-41% of tropical genera. The data corroborate the hypothesis that predation influenced the evolution and distribution of prey as early as the Devonian Period.

The Little Cedar and lower Coralville formations of the Cedar Valley Group (Middle Devonian) of Iowa were deposited on a cratonic, shallow-water, carbonate and evaporite shelf during the Taghanic onlap. Four conodont subzones, zones, or cratonic biofacies faunas can be recognized in this sequence of strata. They are, in ascending order, the Middle varcus Subzone (recognized in the lower Little Cedar Formation), the hermanni zone (recognized in the middle Little Cedar Formation), the Lower subterminus Fauna (recognized in the upper Little Cedar Formation), and the Upper subterminus Fauna (recognized in the lower Coralville Formation). The Lower subterminus Fauna and the Upper subterminus Fauna represent a possible zonal span from the Lower hermanni Zone to the Upper disparilis Zone of the standard conodont zonation. In the Polygnathus- and Icriodus-dominated conodont faunas studied is a biostratigraphically useful new species. Polygnathus klugi new species is a Polygnathus dubius-like form that occurs sporadically and in small numbers in the Middle varcus Subzone, the hermanni Zone, and the Upper subterminus Fauna. However, it occurs consistently and in large numbers in the Lower subterminus Fauna, where it is the characterizing species. It has also been recovered from core samples both in central Alberta, Canada, and the Russian Platform. In both areas, it is associated with conodonts of the subterminus faunal interval.

An early Devonian graptolite fauna is described from Lila and Huiku sections in Southwest Yunnan, China. Three graptolite biozones are recognized, which in ascending order are: Monograptus uniformis Biozone, M. hercynicus Biozone and M. falcarius Biozone. Six species are described in this paper: Monograptus uniformis Pribyl, M. aequabilis (Pribyl), M. microdon Richter, M. hercynicus Perner, M. falcarius Koren, and Abiesgraptus sp.

Two new cirroidean gastropod genera, Alaskiella (family Porcelliidae) and Alaskacirrus (family Cirridae), from the Emsian (late Early Devonian) of west-central Alaska (Medfra B-4 quadrangle) are described. The shell of Alaskiella medfraensis new genus and species exhibits inclined heterostrophic coiling. This shell character is known among other members of the subclass Archaeogastropoda, but is recorded for the first time within members of the superfamily Cirroidea. Inclined heterostrophic coiling of the shell was probably developed independently in several different groups of the subclass Archaeogastropoda. The new genus Alaskacirrus, represented by Alaskacirrus bandeli new species, is the oldest and only known Paleozoic member of the family Cirridae. This suggests that the family Cirridae was separated from the family Porcelliidae since at least Early Devonian time and that it most probably developed from the subfamily Agnesiinae of the family Porcelliidae. Thus, the stratigraphic range of the family Cirridae is at least from Lower Devonian to Cretaceous, an interval of about 350 million years.

Anactolasma yukonanum new genus and species is described from the Pragian of Yukon Territory and is assigned to the Anactolasmatinae, a new subfamily of the Mucophyllidae Hill. Adult stages of Anactolasma resemble gerontic stages of Kobeha Merriam, although the genera have distinct ontogenies. Kobeha is revised on the basis of new material of its type species K. walcotti Merriam. The Papiliophyllinae Stumm are promoted to family status. Kobeha ketophylloides Merriam, from the Pragian of Nevada, and Endophyllum banksi Jell and Hill, from the Pragian of Tasmania, are restudied using new topotypic and other material. A new endophyllid genus named Murphyphyllum is erected for them, with E. banksi as type species. Asarcophyllum ramosum new genus and species, from the Emsian of Nevada, is made type species of a new cyathophyllid genus. Spongophyllum nevadense Stumm and S. expansum Stumm, both also from the Emsian of Nevada, are placed in the new genus, as is Asarcophyllum corona new genus and species, from the Emsian of Yukon Territory. Biostratigraphic settings, with emphasis on associated corals, brachiopods and conodonts, are given for the new and revised genera and species.

A 5 m long permineralized trunk from the Upper Kellwasser member of southern Morocco represents the first record of a large trunk of an identifiable species of Callixylon, C. erianum, from Gondwana. This occurrence constitutes the most reliable evidence based on plant megafossils for a floral connection between Laurussia and Gondwana in late Devonian times and for a proximity of these continents in Famennian times. The potential of this trunk for studies of the architecture and growth patterns of the earliest trees with a gymnospermous type of arborescent habit is discussed.

Stromatoporoids are found in the Dayville and Deansboro Members of the Coeymans Formation in central New York, where they are common to rare. The most common species present are Habrostroma centrotum (Girty) and H. microporum (Girty). Present in lesser numbers are Parallelostroma foveolatum (Girty), Atopostroma sp. 1, A. sp. 2, Coenostroma cf. C. monticuliferum (Winchell), Coenostroma sp., Habrostroma cf. H. centrotum (Girty), and Coenostelodictyon cf. C. krekovi (Yavorsky). Although previously reported from the Coeymans, Coenostelodictyon jewetti (Girty) was not found. Species identifications were based on traditional qualitative methods, supplemented by statistics. The assemblage bears affinities with Lochkovian faunas in Virginia and the Canadian Arctic.

Echinus gyracanthus Eaton, 1832, was the first tentaculitid reported from North America, but the original description and illustration are vague by present-day standards. Study of the type material and topotypes from the Lower Devonian Manlius Limestone in the Town of Schoharie, New York, suggests that Tentaculites gyracanthus (Eaton) is a discrete species, but one with pronounced and remarkable intraspecific variability. Tentaculites simmondsi new species also occurs in the same unit and locality.

Famennian (Late Devonian) echinoderm faunas are poorly known on a global basis, although reasonably diverse faunas have been reported from England and Germany. We have collected a diverse (> 500 specimens representing approximately 30 taxa) Famennian echinoderm fauna dominated by blastoids and inadunate, small-calyx camerate, and flexible crinoids from the Hongguleleng Formation, Junggar Basin, Xinjiang-Uygur Autonomous Region, People's Republic of China. Taxa reported here include five new genera and six new species of blastoids along with one new genus and 19 new species of crinoids. Blastoid taxa include Junggaroblastus hoxtolgayensis new genus and species, Orophocrinus devonicus new species, Xinjiangoblastus ornatus new genus and species, Uyguroblastus conicus new genus and species, Sinopetaloblastus jinxingae new genus and species, and Houiblastus devonicus new genus and species. Crinoid taxa include Uperocrinus zhaoae new species, ?Hexacrinites species, Agathocrinus junggarensis new species, Chinacrinus xinjiangensis new genus and species, ?C. nodosus new genus and species, C. species A, C. species B, C. species C, Eutaxocrinus chinaensis new species, E. boulongourensis new species, E. basellus new species, Forbesiocrinus inexpectans new species, Deltacrinus asiaticus new species, Bridgerocrinus minutus new species, B. delicatulus new species, Cosmetocrinus parvus new species, ?Pachylocrinus subpentagonalis new species, 'Decadocrinus' constrictus new species, 'D.' elongatus new species, 'D.' rugosus new species, 'D.' usitatus new species, 'D.' xinjiangensis new species, ?Graphiocrinus species, Holcocrinus asiaticus new species, and four species of inadunate crinoids that could not be assigned to genera. This fauna is more abundant and diverse than all other Famennian echinoderm faunas in the world combined, and it is critical in understanding echinoderm biogeography and evolution in the aftermath of the Late Devonian extinction event(s) prior to the Carboniferous echinoderm diversification. This echinoderm fauna is 'Carboniferous' in affinity and indicates that echinoderm diversification and reradiation were well underway before the close of the Famennian.

Ptyctodonts from the Upper Devonian Martin Formation on Mt. Elden, northern Arizona, were hitherto known only from tooth plates ascribed to Ptyctodus bradyi. Recent collections include dental elements of P. bradyi as well as body and skull plates and dental elements of a previously unknown ptyctodont, described here as Denisonodus plutonensis new genus and species. Comparison with other ptyctodonts suggests that the new genus has close affinities to other North American forms. As the holotype of Ptyctodus bradyi has been lost a neotype is designated here.

The fixosessile, perireefal to reefal Devonian epibiont Davidsonia cemented itself by its entire ventral valve to the underside of alveolitid tabulate corals, or to stromatoporoid sponges. It occupied a cryptic niche in perireefal biostromal thickets to reef complexes in the Old World faunal realm (Europe, western North America), and Uralian-Central Asian faunal province. A new species, D. septata, is here reported in abundance for the first time from Middle Devonian (Givetian) rocks of Yunnan, thus extending its range to South China. The usual absence of the brachial valve is suggested to be due to postmortem taphonomy as a result of its unique, cemented mode of life on the undersides of corals or sponges. A new genus of coarsely ribbed, partly libero-, partly fixosessile davidsoniid, Rugodavidsonia, type Davidsonia woodwardiana (DeKoninck), mimicking unrelated Late Paleozoic orthotetids, is also described, demonstrating that ribs evolved secondarily in a family dominated from its inception by smooth shells. Its paleogeographic distribution ranged from Europe through western North America (and possibly China), commonly accompanying Davidsonia in similar assemblages, but with a slightly different mode of life. Reexamination of available material, using thin sections, peels and SEM, confirms that the impunctate shell structure, dorsally directed spiralia, nature of the hinge mechanism, the deltidial plates, absence of a chilidium, 'atrypoid' musculature and vascular markings, show features in Davidsonia and Rugodavidsonia that are all typical of the Order Atrypida. Thus, Davidsonia demonstrates that ventral valve cementation evolved independently more than once in articulate brachiopods such as strophomenids, productids, atrypids, and thecideid spiriferids. A revised classification of the Davidsonioidea and Palaferelloidea is proposed. Relationships between various genera are outlined in a new family tree for these groups. The various families discussed, including the Symmatrypidae, are united under a new suborder, the Davidsoniidina, a primarily carbonate platform and perireefal dwelling group, which first evolved during the Ludlovian (Late Silurian) in the Uralian-Central Asian tropical shelf region, diversified over a period of [approximately]47 Ma, and then died out during the late Givetian, 10 Ma prior to the Frasnian-Famenian mass extinction events.

The pyritization of fossils in the Lower Devonian Hunsruck Slate, Germany, occurred in the later stages of authigenic mineralization due to the absence of organic matter and the presence of sulfur (S) and iron. An analysis of S isotope and C-S-Fe elemental data reveals that the slates containing fossils possess low amounts of pyrite S and organic substances but high levels of total and HCl-soluble Fe. The presence of highly enriched 34S in the adjacent slates indicates continued fossil pyritization due to exceptional diagenetic conditions.

The braincase of the fish Panderichthys rhombolepis, a member of the Middle Devonian tetrapod stemgroup, has evolved faster than the external skull structure. The brain had an external structure that resembles tetrapods, but the braincase contained an intracranial joint resembling that of the lobe-finned fish. Thus, the braincase transformation appears to have taken place between Panderichthys and the earliest tetrapods. The changes in the braincase probably coincided with changes in the limbs during the evolution of tetrapods from fish.

A distinctive new genus (Xyoeax) and two new species (Xyoeax eponcus, Scutellum sudorum) of styginid trilobites are described from the late Early Devonian (Emsian) Murrindal Limestone of eastern Victoria, Australia. Limited material of a third styginid species not belonging to any named genus is also described from the same locality. Xyoeax is considered to be closely related to Ancyropyge Clarke, 1891, and Weberopeltis Maksimova in Moore, 1959, and less closely related to Kolihapeltis Prantl and Pribyl, 1947. Weberopeltis is revised and newly diagnosed. Several species previously assigned to Weberopeltis are transferred to the new genus Exastipyx, which is considered to be related to Cornuscutellum Snajdr, 1960. Ancyropyge, Exastipyx, Weberopeltis, and Xyoeax all have pygidia with long pleural spines derived by reduction of the pleural field between the pleural ribs, whereas Kolihapeltis and Cornuscutellum lack pygidial spines. Pygidial morphology of Xyoeax type has thus arisen independently in separate styginid lineages. The type species of Altaepeltis Maksimova, 1968 is established as Weberopeltis bublitchenkoi Maksimova, 1960, by monotypy.

Observed diversity of bryozoans within Devonian stages is not significantly different from range-through values for species because very few species have ranges longer than a single stage. Generic diversity differs significantly between observed stadial and stadial range-through values except for the diverse Givetian faunas. Among families, observed stadial and range-through comparisons differ significantly in the lower diversity Early and Late Devonian but are not significant in the taxonomically diverse Middle Devonian. The patterns of Devonian generic and familial diversity are apparently robust proxies for specific diversity. Givetian specific and generic extinctions, based on generated bootstrap distributions, are significantly higher than the other six Devonian stages even when modifications for different stage durations are considered. Based on present data, we conclude that a major change in Devonian diversity occurred between the Givetian and the Frasnian stages. Givetian specific and generic extinctions are not 'smeared' with respect to adjacent stages and should qualify as a mass extinction among bryozoans pending more accurate data on bryozoan ranges and more precision in radiometric dating of Devonian stadial boundaries. Devonian bryozoan familial extinctions are not numerous and do not exhibit a significant number of extinctions for any stage. The Givetian extinction, which for the time being ranks as the largest bryozoan extinction in the Phanerozoic, is a global event with a marked local effect in the Hamilton-Tully fauna of New York, Pennsylvania, and Ontario. Givetian specific originations are significantly higher than bootstrap distributions for both raw data and data modified for stadial durations. A Givetian generic high in originations for raw data is not significant when modified for stadial durations and only Eifelian familial originations are significantly higher than bootstrapped distributions.

Twenty-two taxa of stromatoporoids are described from the outcrop belt of the Elm Point, Winnipegosis, Dawson Bay, and Souris River Formations in Manitoba. The Elm Point Formation contains a fauna of stromatoporellids of Eifelian age that is characterized by the new species, Stromatoporella manitobaensis. The Winnipegosis stromatoporoids are dolomitized but the widespread species Actinostroma tyrrelli, Taleastroma logansportense and the new species Trupetostroma imbrex can be recognized in this Givetian assemblage. The Dawson Bay fauna is characterized by the appearance of the dendroid forms, Stachyodes and Dendrostroma and species of Hermatostroma, Trupetostroma, and Parallelopora. A species of Actinostroma, comparable to A. filitextum is the most abundant stromatoporoid in the Dawson Bay Formation. The Souris River fauna, referred to as the Arctostroma contextum assemblage, is widespread at the Givetian-Frasnian boundary. Elements occur elsewhere in western Canada in the Beaverhill Lake, Waterways, lower Duperow and lower Fairholme units. Stromatoporoids in these four assemblages are relatively restricted in their stratigraphic occurrence and sufficiently widespread in their distribution to be useful in correlation.

Two species and genera of pteraspidids (Agnatha, Heterostraci), Blieckaspis priscillae n. gen., and Panamintaspis snowi n. gen. and n. sp., together with two undetermined species, are described from the lower part of the Lippincott Member of the Lost Burro Formation, southeastern California. The sharing of similar faunal elements with the Early Devonian assemblages of the Sevy Dolomite and Water Canyon Formation of Utah and Nevada, respectively, together with stratigraphic: constraints on the age of the Death Valley fauna, suggest that these assemblages are age equivalent and have a late Emsian (inversus-serotinus Zones) age. The vertebrate-bearing unit of the Lippincott Member is interpreted as a channel-fill deposit laid down in an estuarine environment with low or fluctuating salinity.

A Frasnian composite standard provides a refined scaling for the thirteen-fold conodont zonation first developed in the Montagne Noire, France, but since replicated in North America, Australia, and now the Timan-Pechora region of Russia. Zones 413 are identifiable in seven cores from the Ukhta area of southern Timan and a core from the Bagan Field of the Khoreyver Basin. Scaling of the zones through graphic correlation demonstrates the diachronism in different sections of the bases of many conodont species, including those of zonally defining Palmatolepis. This can be effectively shown in a correlation diagram scaled to a composite standard based on graphic correlation, whereas it is obscured by the assumption of synchronism inherent in conventional zonal correlation charts. Newly described species occurring in the Timan-Pechora region and elsewhere are Ozarkodina nonaginta. Ancyrognathus amplicavus, Mesotaxis johnsoni, Palmatolepis amplificata, P. mucronata, P. ormistoni, and P. timanensis. A number of other species described earlier from the region also occur outside Russia, mainly in Canada and Australia. Distribution patterns in the composite standard indicate close faunal connections between the Timan-Pechora, western Canada, and Western Australia.

Endophyllum is described for the first time from North America. The occurrence of a single, large colony in Middle Devonian strata in New York is both biogeographically and environmentally anomalous: it belongs to an Old World Realm genus but was found in the Eastern Americas Realm, and it occurred in a gray, ambocoeliid-bearing mudstone, a facies in which morphologically complex corals are otherwise unknown. Available evidence suggests that the coral lived not far from where it was found, possibly on a hardground or bank a few km north of the outcrop. Endophyllum ciurcai new species is described.

The Plum Brook Shale of north-central Ohio lies disconformably between the Eifelian (lower Middle Devonian) Delaware Limestone and the middle Givetian (upper Middle Devonian) Prout Dolomite. Its diverse conodont fauna indicates that it represents a transgression into the area in earliest Givetian time accompanied by the products of a notable adaptive radiation within two lineages of Icriodus. One of these (I. expansus Group) includes I. expansus, I. arkonensis and I. brevis, and complete intergradation of forms suggests that the group at this level involves conspecific ecotypes. A more extensive radiation involved descendants of I. regularicrescens (I. regularicrescens Group), including three new species, I. eriensis, I. janeae and I. ohioensis. Other representatives of this lineage occur here as well as in strata of comparable age in the type region of the Givet Limestone as described by Bultynck (1987). A third lineage is represented by I. excavatus in both areas, but evidence of radiation within this branch is limited to the Giver Limestone. Remarkable diversity also occurs among forms considered herein to involve Polygnathus pseudofoliatus and its descendants. The existence of intermediate forms and shared characteristics between and among the various species, including some that first appeared well before the end of the Eifelian, implies that they may be conspecific ecotypic variants at this level. New morphotypes within this group are treated informally. The greatest overall diversity occurs just above the basal Plum Brook, in strata interpreted to reflect inner-sublittoral conditions. The entire Plum Brook belongs to the upper ensensis Zone. A considerable part of the type Givetian placed in the Lower varcus Subzone by Bultynck (1987) lies below the lowest occurrence of its index species (P. timorensis); it contains some of the species found in the Plum Brook, and much of this section may also belong to the ensensis Zone.

Early Devonian (Lochkovian; eurekaensis Zone) conodonts occur in discontinuous limestone beds in the Caballos Novaculite at five localities in the northwestern half of the Marathon uplift, west Texas. Similar conodont faunas at all five localities indicate that the limestone beds lie at one biostratigraphic horizon within the Caballos. The upper novaculite member directly overlies the limestone horizon at one locality, giving the upper novaculite a maximum age of Lochkovian. The limestone beds are dominantly skeletal calcarenites that represent shallow-water carbonate material transported into a deeper water setting by gravity processes. Restriction of the limestones to the northwestern margin of the uplift and provenance of reworked clasts and redeposited Ordovician and Silurian conodonts suggest a North American shelf source and are evidence of the close proximity of some strata exposed in the Marathon uplift to North America in the Early Devonian. Icriodus gravesi n. sp. is described from the limestone fauna.

A brachiopod fauna from the upper part of the Wadleigh Limestone, Alexander terrane, southeastern Alaska, is of late Frasnian age and includes the new taxa Gypidula cornuta alaskensis n. subsp., Gypidula upatensis n. sp., Gypidula perryi n. sp., Gypiduloides craigensis n. gen. and sp., Parapugnax schmidti n. sp., Westbroekina chaconenesis n. gen. and sp., Emanuella altus n. sp., Emanuella neumani n. sp., Adolfispirifer sanjuanensis n. sp., Theodossia albertoensis n. sp., Cyrtospirifer paridaensis n. sp., and Tenticospirifer wadleighensis n. sp. A few other taxa are cosmopolitan or conspecific with species known from elsewhere in western North America. The fauna overall may have North American affinities but includes an unusual number of previously undescribed forms. This lends support to the view, based on the affinities of Frasnian conodonts from this same locality (Savage, 1992) and Famennian brachiopods described from nearby (Savage et al., 1978), that these Alexander terrane faunas were not in general communication with Late Devonian North American cratonic faunas to the east.

Conodonts from two localities on the western shore of Alberto Island, southeastern Alaska, include Polygnathus alexanderensis n. sp., P. angustipennatus, P. borealis n. sp., P. praetrigonicus n. sp., P. robusticostatus, P. pseudofoliatus, P. linguiformis linguiformis gamma form of Bultynck, P. parawebbi beta form of Chatterton, P. angusticostatus, P. costatus costatus, Polygnathus sp. B of Savage, 1977, Tortodus kockelianus australis, and T. kockelianus kockelianus. The faunas are considered to be of middle to late Eifelian (kockelianus Zone) age. On Prince of Wales Island, just north of Staney Creek, exposures of Wadleigh Limestone include the conodonts Polygnathus trigonicus, P. kennettensis, P. alexanderensis, P. angustipennatus, P. parawebbi beta form, P. eiflius, P. linguiformis linguiformis gamma form, P. borealis, P. angusticostatus, P. robusticostatus, P. costatus costatus, P. pseudofoliatus, Tortodus kockelianus australis, and T. kockelianus kockelianus, also suggesting a middle to late Eifelian (kockelianus Zone) age. Conodonts from the west end of the easternmost of the Alberto Islands include Polygnathus linguiformis linguiformis gamma form, P. parawebbi beta form, P. xylus ensensis, and Ozarkodina brevis, indicating a late Eifelian to early Givetian (ensensis to varcus Zones) age. The presence of Polygnathus kennettensis, P. parawebbi beta form, and P. borealis suggests a biogeographic affinity with other parts of western North America during Eifelian time.

A gastropod assemblage is described from the middle Lower Devonian (Pragian) of Alai Ridge, Kyrgyzstan. It includes eight species, six of which are new. Two new genera are established, Alaionema and Barroisocaulus. Newly named species belonging to the above genera include: Alaionema kyrgyzensis and Barroisocaulus oliveri. In addition, four new species belonging to extant genera are also described: Omphalocirrus kaukensis, Ruedemannia tienshanica, Oriostoma sarydalchaensis, and Goniasma? asiatica.

The discovery of a eurypterid in the Lower Devonian Snowblind Bay Formation in Cornwallis Island, Northwest Territories, is reported. The specimen was collected in the summer of 1994, tagged as specimen number UA10477 and kept at the University of Albert's Geology Dept. The specimen is the first known occurrence of a eurypterid in the Lower Devonian of the Northwest Territories. The characteristics and classification of the specimen are presented.

Givetian species of Chinese brachiopods previously assigned to the genus Spinatrypa or Spinatrypina reveal an internal structure characteristic of other species referred to the Eifelian genus Kerpina and the cosmopolitan Frasnian genus Iowatrypa. Serial sections clarify the nature of the Middle Devonian Chinese species, which are described here as a new genus, Invertina (type species, Atrypa aspera var. sinensis Kayser, 1883). The internal structure of the Late Devonian type species of Iowatrypa, Atrypa owenensis Webster, 1921, is illustrated for the first time for comparison. These three genera, as well as three other genera, are referred to a new Devonian (Emsian-Frasnian) subfamily, the Invertininae, allocated to the family Atrypidae.

Fossiliferous marine Devonian has been known in Chile for less than a decade. The initial discovery from south of the Salar de Atacama region, in the Sierra de Almeida, northern Chile is described together with its brachiopods. The brachiopods indicate an age span of Emsian-Eifelian or Givetian, shallow-water conditions in the Benthic Assemblage 2 range, and a biogeographic boundary region between the cool climate Malvinokaffric Realm and warmer region extra-Malvinokaffric Realms, including the Eastern Americas Realm and the Rhenish-Bohemian Region of the Old World Realm. The recent discovery of a Malvinokaffric Realm trilobite far to the south in Chile, at Buill in the Andes of Chiloe, serves to underline our very preliminary knowledge of the Chilean Devonian, whereas the alleged Devonian brachiopods from the Chonos Archipelago far to the south are probably bivalves of uncertain age.

A fauna of eight taxa of demosponges and hexactinellid sponges has been collected from the Lower Devonian (Lochkovian) Ross Formation, largely out of the upper Birdsong Shale Member in Benton, Decatur, and Perry Counties in west-central Tennessee. The Upper Birdsong Shale ('bryozoan zone') in which the sponges are most common appears to have been deposited below normal wave base in a quiet marine environment, and represents a terrigenous elastic sediment influx onto a carbonate shelf that had existed in the area from at least the middle Silurian. Benton Quarry in Benton County was the most productive locality for fossil sponges. The new demosponge genera and species Ginkgospongia foliata and Coniculospongia radiata occur with the new species Haplistion lobatum and skeletal mats of fine spicules, along with moderately rare specimens of Hindia sphaeroidalis Duncan. The new hexactinellid genus and species Stiodermiella amanita and Stiodermiella tetragona are characterized by peculiar ornamented papillose, swollen spicules that produce a massive, armored layer on the upper pan of the sponge. The latter are associated with the new hexactinellid species Twenhofelella bulbulus, which has relatively normal-appearing hexactines, and with an indeterminate hexactinellid genus, which has spinose hexactines in irregular orientation in a small, platelike fragment. Root tufts of probable hexactine origin also occur. Swollen spicules in Stiodermiella are reminiscent of swollen spicules in the family Stiodermatidae Finks, largely from the Permian of western Texas, but elements of the family are also known from Lower Carboniferous to Permian rocks in Europe and North America.

A tetrapod trackway has been discovered in Devonian sedimentary rocks of SW Ireland. It is the first discovery of its kind in Europe. Details of the footprints are not preserved, probably because of strong Variscan pressure solution cleavage. However, after removing the effect of Variscan deformation, the large number of footprints (more than 150) makes it possible to calculate the original dimensions of the footprint pattern: stride (approximately 34 cm) and pace (approximately 35 cm). These values are higher than those for other traces of comparable age. The total length of the tetrapod is estimated to be 1 m. Lithostratigraphical and biostratigraphical arguments indicate an age of Mid- to Late Devonian. Keywords: Devonian, Old Red Sandstone, tetrapods, tracks, fluvial environment.

One of the most severe restrictions in taxonomic diversity of trilobites coincides with the Late Devonian 'Hangenberg' Event, which is characterized by a pronounced eustatic low-stand. One of the survivors of this event is Pudoproetus, which, being adapted to shallow water conditions, experienced an opportunistic worldwide spread during this time. The oldest representatives of this genus are reported from the pre-Hangenberg Late Famennian of the Urals and Kazakhstan. Other known occurrences of this genus, midcontinent U.S.A., Utah, southern China, and southern France, occur at the Devonian-Carboniferous boundary, shortly after the Hangenberg event, and in the earliest Carboniferous. This pattern of distribution suggests that neither climatic nor geographic migration barriers existed around the Old Red landmass at that time. On the other hand, the Hangenberg crisis severely affected outer shelf benthic habitats, whereas nearshore trilobites were largely unaffected by the event. A proetine origin of Pudoproetus, as originally proposed by Hessler (1963), is emphasized on the basis of paleoecologic, stratigraphic, and morphological arguments. In particular, the presence of ancestral features, such as the possession of 10 thoracic segments and lateral occipital lobes still occurring in early Pudoproetus species, points to a phylogenetic link with proetines rather than with phillipsiids. Within this group two new species are named: P. priscus and P. mediterraneus.

New Devonian fossil material from Bolivia includes internal molds of two specie of paleotaxodont bivalve, Palaeoneilo musculosa (Knod) and P. pondeana (Hartt and Rathbun), with numerous accessory muscle scars. The unusual pattern of thes scars appears to have been derived from excessive splitting. These muscle scars are described and a tentative interpretation is made. An adaptative role cannot be determined with certainty and it appears that these patterns were short-live novelties without later success.

A new gastropod genus, Dutrochus, is established for members of the family Microdomatidae that are characterized by a reticulate ornament of spiral cords and intersecting, finer collabral threads, with all but one spiral cord being of nearly equal strength, and the single remaining cord being of stronger (nearly twice the order) magnitude and being situated at the periphery. It is represented by the type and only known species, Dutrochus alaskensis n. gen. and sp., from the upper part (lower Middle Devonian; lower Eifelian) of the Lower? and Middle Devonian Cheeneetnuk Limestone, McGrath A-5 quadrangle, west-central Alaska. The genus is very close and nearly homeomorphic to the Permian microdomatid genus Glyptospira, but differs from the latter in possessing an extremely strong, peripheral spiral cord and an extremely thick, multi-layered apertural margin.

Gedinnian (Early Devonian) orthoceratid cephalopods were previously not well known in Japan. Five species are described from the Fukuji Formation of Gifu Prefecture, central Japan: Michelinoceras yamakoshii n. sp., Michelinoceras yoshikiense n. sp., Plagiostomaceras? sp. Polygammoceras sp., and Metaspyroceras insignis n. sp. Growth and position of the cameral deposits in Michelinoceras indicate that the deposits precipitated from cameral fluids and living Michelinoceras maintained the shell horizontally in swimming orientation.

Lack of an adequately calibrated Devonian time scale precludes satisfactory comparisons of Recent and Devonian bryozoan diversities. Nevertheless, Devonian bryozoans apparently are 3-100 times less diverse than Recent bryozoans. This variation is a function of how Devonian time is divided (whole period, stages, per million years) as well as the diverse skeletal architecture of cheilostome bryozoans, the most abundant Recent bryozoan order. The Givetian has the largest specific, generic, and familial diversity of any Devonian stage and the drop in bryozoan diversity from the Givetian to the Frasnian is greater than the rise or fall of diversity between any other adjacent stages. Diversity hardly changes among bryozoans across the Frasnian Famennian boundary. Among bryozoans the Givetian Frasnian extinction was a major event. Devonian taxonomic diversity is less than nomenclatorial diversity, although both exhibit the same trends from stage to stage during the Devonian. The amount of difference between the two measures of diversity is probably a reflection of the intensity of research on Devonian Bryozoa, especially revisionary studies of previously described faunas. Monographic bursts in diversity are present and are a measure of the episodic character of taxonomic studies on less popular phyla. Examination of the literature commonly provides a finer stratigraphic resolution than indicated in compilations such as the Zoological Record. Although some significant areas of the exposed continents have not received adequate study, Devonian bryozoans show marked geographic changes in diversity that can not be ascribed entirely to lack of study.

Solitary rugose corals (Cnidaria, Rugosa) are common to abundant in the calcareous Box Member of the late Famennian Percha Shale (Lower expansa Zone) of southwestern New Mexico; the Box is best developed in the western part of the Percha outcrop belt. The corals include a number of forms characteristic of Strunian faunas throughout the world. Recognized here are Gorizdronia sp. cf. G. tenuis Rozkowska, Campophyllum? ursinum n. sp., Caninia cooperi n. sp., Siphonophyllia? folia n. sp., S.? corbicula n. sp., 'Bothrophyllum' argenteum n. sp., 'B.' argenteum argenteum n. subsp., 'B.' argenteum bilateralis n. subsp., 'B.' argenteum dibunophylloides n. subsp., Arachnolasmella elytra n. sp., and Cyathoclisia sp. A. This fauna is clearly ancestral to Carboniferous genera and species. Percha species, where represented by large populations, are seen to be remarkably variable, especially in axial structure.

Seven new taxa of conodonts from the upper part of the Wadleigh Limestone, Alexander terrane, southeastern Alaska, are described. These include Polygnathus aspelundi nanus, P. decorosus dutroi, P. elegantulus sparus, P. gracilis, Polygnathus n. sp. A, Palmatolepsis subrecta younquisti and Icriodus subterminus uyenoi. The four distinct faunal assemblages identified in the terrane were found to have biogeographic affinities to fauna from equivalent horizons of the cratonic regions of the Northwest Territories and Alberta in western Canada.