Complete exoskeletons of species of eight genera of Siluro-Devonian Scutelluinae show the morphology of the cephalon and thorax, particularly glabellar lobation, the wide inward extent of the doublure, and the development of fulcral processes and sockets, the latter more prominent on the external surface in stratigraphically younger species. The thorax of ten segments has axial rings with an articulating furrow and halfring as in most trilobites. The differences between the exoskeletons of Scutelluinae and Illaenidae are many, and imply anatomical differences. It is considered that Scutelluinae are related to the Ordovician Stygininae, and are to be united with them in Styginidae; a common origin for Styginidae and Illaenidae appears questionable.

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

Exceptionally rich and well-preserved silicified exuviae comprising numerous immature growth stages allow the tracing of detailed morphological and morphogenetical features of the reduced-eyed phacopid species Cryphops? ensae (Richter and Richter, 1926) from the latest Famennian of Thuringia (Central Germany). Ontogenetic features of this species are more similar to those of Phacops than to Trimerocephalus.

Description of two new species of the brachyuran genus Xanthosia Bell, 1863, from the upper Albian to Cenomanian Weno and Pawpaw formations from Tarrant County, Texas, increases the number of species in the genus to fifteen. Xanthosia has been recognized in England, the Netherlands, Madagascar, and in in the states of New Jersey, South Dakota, and Texas. The geologically oldest species from England gave rise to species from North America, Europe, and Madagascar. One group of species, with representatives from South Dakota, New Jersey, and Madagascar, may represent a separate taxon. The species “Xanthosia” robertsi Secretan is herein removed from the genus and placed within the Portunidae, not the Xanthidae.

A low-diversity brachiopod assemblage from the upper member of the Zorritas Formation in the Sierra de Almeida, northern Chile, further confirms the presence of Lower Carboniferous (Tournaisian) strata in that region. Key taxa include Schuchertella? sp., Chilenochonetes anna new genus and species, Paurorhyncha chavelensis (Amos), and Septosyringothyris covacevichi new species. Other elements of the assemblage, including Paraconularia sp., Posidoniella sp., Bellerophon (Bellerophon) sp., Eocanites sernageominus, and Imitoceras? sp. support this Early Carboniferous age assignment. Local distribution of taxa suggests small-scale environmental control. Rhynchonelloid and syringothyroid shells, many articulated, occur in lenticular sandstone bodies that were deposited in deltaic distributary channels; chonetids, schuchertellids and mollusc-bearing, iron-rich concretions are found in siltstones and mudstones that reflect interdistributary quiet-water settings and possibly a delta-front setting. Certain elements of this fauna are also present in northwestern Argentina and Peru, indicating a regional nearshore clastic regime. The closest correlation elsewhere is with the Tournaisian faunas of southeastern Australia, although analogous big-shell assemblages are found in lower Mississippian clastic strata of the central Appalachians, Ohio, and Indiana.

Gastropods are described for the first time from the Kersadiou Formation (middle Givetian) in the vicinity of Brest, Brittany, northwestern France. Twenty-three species of gastropods are recognized. New taxa include the new genera, Calvibembexia, Kersadiella, Breizospira, Finisterella, Parahormotomina, and Nodoloxonema, represented by the new species Calvibembexia lethiersi, Kersadiella babini, Breizospira crozonensis, Finisterella tibidiensis, Parahormotomina sibertae, and Nodoloxonema plusquelleci. Further new species include: Sinuitina (Sinuitina) morzadeci, Crenistriella armoricana, Patellilabia (Phragmosphaera) ponceti, Angyomphalus (Eoangyomphalus) weyanti, Eoplatyzona ongaroae, Murchisonia oehlerti, and Hormotomina fiacrensis. The biogeographic affinities of the fauna show a strikingly unusual admixture of Eastern Americas Realm taxa such as Hormotomina and Crenistriella. This suggests that during the middle Givetian, the Massif Armoricain (northwestern France) represented an area of Realm-boundary mixing between the Old World and Eastern Americas Realms, while older Devonian gastropod faunas of the Massif Armoricain are wholly of Old World Realm type.

Etched slices of the cuticle of the Silurian trilobite Homalonotus rhinotropis Angelin, 1854, from two localities in Skåne, southern Sweden, have been examined with the scanning electron microscope. The two major subdivisions of the cuticle are a “prismatic” (originally laminated) outer layer, about 20-30 μm thick, and a principal layer, 200-300 μm thick, which may be foliated or roughly laminated. The original finely-laminated aspect of the outer layer may sometimes be seen as a continuous layer, but is more frequently detected as “shaped inclusions” set in a prismatic background. These “shaped inclusions” are considered to have been produced by accumulation of minerals around the apices of 3-6 μm perpendicular canals early in calcification and preferentially preserved because of subtle differences from the products of later stages of the process. It is possible that calcification started before ecdysis. The difficulties involved in ascertaining the original structure of the principal layer are outlined, and possible reasons for differences in its preservation from the outer layer are proposed.

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.

Mass mortality surfaces and bioclastic lags in Turonian siliceous shales of the San Rafael and La Frontera formations in Colombia have yielded two species of decapod crustaceans, Opthalmoplax spinosus new species and Pinnotheres? species indeterminate, as well as one stomatopod, Sculda sp. All represent first records for the country. Remains of the swimming carcineretid crab, Opthalmoplax spinosus, in association with fish fragments and pelagic ammonites, cover mass mortality surfaces. The occurrence suggests that the high density living population of the crabs, exploiting abundant food resources in areas of topography-controlled upwelling, was periodically reduced catastrophically, perhaps by advection of toxic trace elements or by oxygen starvation. Two other taphofacies, characterized by current oriented appendage fragments and scattered skeletal elements represent normal accumulations of fossil material in the San Rafael and La Frontera formations.

Twelve brachiopod taxa are described from the Early Devonian (probable early Emsian) Pa Samed Formation of southern Thailand, including the new genus and species Quasiprosserella samedensis (Ambocoeliidae?) and the new species Plectodonta forteyi, Caplinoplia thailandensis, and Clorinda wongwanichi. They are the first undoubted Devonian brachiopods from Thailand. They represent the deeper-water Benthic Assemblages BA4-5, and, although clearly indicative of the Old World Realm, cannot be assigned to a particular biogeographical region. A new undescribed fauna from the contemporary Zebingyi Formation of Burma (Myanmar) is also noted.

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.

Five new bivalved arthropods are described from the Lower Cambrian Chengjiang fauna, Yunnan, China. All of them are rare in the fauna, represented by one or two individuals among thousands of specimens. Four of the five new taxa are preserved with soft parts that show a clear distinction between them. The new taxa provide new important information concerning the soft bodied and limb characters of the early bivalved arthropods. A significant lesson is that, not knowing any soft parts, it is virtually impossible to place systematically a new type of bivalved carapace. It is often impossible even to tell if it is a crustacean or not. A second antenna in the shape of a “great appendage” is identified for the first time among the bivalved arthropods. The new taxa include representatives of the order Pectocaridida, the families Pectocarididae, Clypecarididae and Occacarididae, the genera and species Pectocaris spatiosa, Clypecaris pteroidea, Occacaris oviformis, Forfexicaris valida and Yunnanocaris megista.

The Goodland/Comanche Peak Limestone, Kiamichi Formation and basal Duck Creek Limestones around Fort Worth Texas yield a limited number of cosmopolitan ammonite and inoceramid bivalve taxa that allow precise correlation with the sequence that has been used as a standard in northwest Europe. The upper part of the Goodland/Comanche Peak Limestones yields species of Dipoloceras that show the base of the Upper Albian substage, provisionally defined as the first appearance of D. cristatum (Brongniart, 1822), to lie within this unit. Brancoceras aff. cricki Spath, 1934, Mortoniceras (Deiradoceras) beloventer new species, and Actinoceramus cf. concentricus (Parkinson, 1819) parabolicus Crampton, 1996a, co-occurs with D. cristatum in the Comanche Peak Limestone. The Kiamichi Formation yields rare Mortoniceras (Mortoniceras) pricei (Spath, 1922), M. (Deiradoceras) prerostratum Spath, 1921, M. (D.) bipunctatum Spath, 1933, and Actinoceramus sulcatus (Parkinson, 1819) morphotypes that allow correlation with the European Hysteroceras orbignyi and Hysteroceras varicosum subzones of the Mortoniceras inflatum zone. The basal Duck Creek Limestone yields Mortoniceras (Deiradoceras) sp. and Hysteroceras cf. varicosum (J. de C. Sowerby, 1824), and can also be correlated with the varicosum subzone.

Maastrichtian ammonites are described from two areas in Pakistan. The upper part of the lower unit of the Korara Shale in the southern Pab Range, Kirthar Province, southern Balochistan, is dated as Late Maastrichtian, based on the presence of Menuites fresvillensis (Seunes, 1890), which is accompanied by abundant Indoceras baluchistanense Noetling, 1897, common Baculites ambatryensis Collignon, 1971, and rarer Neophylloceras surya (Forbes, 1846), Gaudryceras kayei (Forbes, 1846), Anagaudryceras politissimum (Kossmat, 1895), Kitchinites spengleri n. sp., Pachydiscus (Pachydiscus) noetlingi n. sp., Libycoceras acutodorsatus (Noetling, 1897), and Diplomoceras cylindraceum (Defrance, 1816). A smaller assemblage from the Mughal Kot Formation near Kach, Suleman Province, northern Balochistan cannot be dated more precisely than Maastrichtian from the presence of Pachydiscus (Pachydiscus) neubergicus (Hauer, 1858), the first occurrence of which has been provisionally adopted by the Subcommission on Cretaceous Stratigraphy as marking the base of the Maastrichtian stage. It is associated with numerous Eubaculites binodosus (Noetling, 1897).

Cladistic relationships of Trilobita, Naraoiidae (five ingroup taxa), Helmetiida (five ingroup taxa), Xandarellida, and the Cambrian arachnates Retifacies, Sinoburius, Emeraldella, and Sidneyia are investigated based on 29 characters. Documentation of appendage morphology and other ventral structures in Saperion from the Chengjiang fauna permits an appraisal of helmetiid relationships. A monophyletic Trilobita [=“Olenellida” (Emuellida + Eutrilobita)] is defined by numerous synapomorphies, including exoskeletal calcification and dorsal eyes with calcified lenses and circumocular sutures. Helmetiida is a robust clade, resolved as (Helmetiidae (Tegopeltidae (Saperiidae + Skioldiidae))). Naraoiid monophyly is well-supported, but neither a naraoiid-trilobite nor a naraoiid-Retifacies clade are parsimonious, the latter grouping (“Nectopleura”) being explicitly paraphyletic. A sister group relationship between Xandarellida and Sinoburius is endorsed, although character support is novel compared to previous groupings of these taxa. The fourth postantennal limb pair in trilobites, naraoiids, and apparently helmetiids is based beneath the cephalothoracic articulation. Reweighted characters favor Trilobita and Helmetiida as closest relatives, with Petalopleura and then Naraoiidae as sister groups.

A growth series of Stringocephalus gubiensis, described here, reveals that the cardinal process of Stringocephalus originated from a bilobate structure, and the growth of its dorsal median septum is highly related to cardinal process development. From this observation we conclude that Kaplex is, structurally and temporally, a suitable ancestor for Stringocephalus, with Bornhardtina ancestral to Kaplex. Subfamilial classification of the family Stringocephalidae is revised based on the presence or absence of median septa and the nature of hinge plates as well as on cardinal process formation. The Kaplexinae and Omoloninae are proposed as new subfamilies, with the Kaplexinae, including Kaplex and Erectocephalus, and the Omoloninae, including Omolonia, Kumbella, and Hemistringocephalus. Morphologic study of South China and Western Canadian Stringocephalus reveals that late forms of the genus tend to have a higher dorsal septum and more complex cardinal process than the early forms. In view of functional morphology, these trends reflect functional perfection of the cardinal process build-up and the lever system for improving the efficiency of opening and closing the shell.

Bairdiid ostracodes are commonly present in the Pennsylvanian marine zones in the Appalachian basin. Thirty-one taxa are recognized representing the genera Bairdia McCoy, 1844; Orthobairdia Sohn, 1960; Cryptobairdia Sohn, 1960; Rectobairdia Sohn, 1960; Bairdiolites Croneis and Gale, 1939; and Bairdiacypris Bradfield, 1935. Two questionable bairdiid genera, Entmema new genus and Hastacypris Croneis and Gutke, 1939, are included. Seven new taxa, Bairdia cuspidis, Rectobairdia absidata, R. apiculata, R. levis, R. sohni, Entmena distenta, and Hastacypris acutula, are described. Fabalicypris Cooper, 1946, is considered a junior synonym of Bairdiacypris Bradfield, 1935.

The diversity of bairdiids is significantly lower in the Appalachian basin than in the Eastern Interior and Western Interior basins.

A single specimen of a saleniid echinoid recently collected from the Late Maastrichtian of the type area of the Maastrichtian Stage is notable in being closely related to Salenia nutrix Peron and Gauthier, 1881. Representatives of the “nutrix group” have previously been recorded from the Late Cretaceous of the Mediterranean and north Africa. The occurrence in the type Maastrichtian of a representative of this group thus furnishes additional evidence of Tethyan incursions in the area during the Late Maastrichtian.

The Kohl Ranch locality in the Naco Formation (Upper Carboniferous, Desmoinesian) of central Arizona contains an ostracode fauna of 13 species of which three are left in open nomenclature because of inadequate materials; all of the others have been previously described. This fauna is strongly dominated by Hollinella (Hollinella) bassleri (Knight, 1928), Cavellina pulchella Coryell, 1928, Bairdia whitesidei Bradfield, 1935, and Bairdiacypris (Fabalicypris) regularis Cooper, 1946. Present in moderate numbers are Amphissites (Amphikegelites) roundyi Knight, 1928, Moorities minutus Warthin, 1930, and Healdia simplex Roundy, 1926. Pseudobythocypris tomlinsonella Cooper, 1946, Bairdia hoxbarensis Harlton, 1927, Sulcella sulcata Coryell and Sample, 1932, and species of Oliganisus, Sansabella and Chamishaella are represented by only small numbers of specimens. The dominant and moderately abundant species indicate a shallow, offshore environment of deposition. The known geographical range of all species present in the fauna is extended into central Arizona.

Alokistocare subcoronatum (Hall and Whitfield, 1877) is the type species of Alokistocare Lorenz, 1906, the nominal genus for the diverse Middle Cambrian Alokistocaridae Resser, 1939b. New collections from the Ehmaniella Biozone contain cranidia, librigenae, hypostomes, rostral plates, thoracic segments, and pygidia, which allow a more complete understanding of the morphological range and character of this important species.

Cladistic analyses using this new information about A. subcoronatum suggest that: 1) Ehmaniellidae Sundberg, 1994, is synonymous with Alokistocaridae; 2) Alokistocaridae is a monophylectic clade and not synonymous with Papyriaspididae Whitehouse, 1939; 3) Pseudoalokistocare Sundberg, 1994, is synonymous with Alokistocare; and 4) Taxa previously assigned to the older “Alokistocare”/Amecephalus group (Plagiura to Glossopleura biochrons) form a separate clade and should not be included in Alokistocare or the Alokistocaridae. These older species are assigned to Amecephalus Walcott, 1924, which is restricted to the Delamaran Stage. Alokistocaridae as recognized here is restricted to the Marjuman Stage.

A morphometric analysis of Alokistocare subcoronatum shows minor but significant differences among collections, indicating population differences. In addition, the cranidium displays both positive and negative allometric growth as well as isometric growth. Allometric growth is present in both meraspid and holaspid stages. The pygidium shows only isometric growth.