Leptarctus is a poorly known fossil carnivore that ranges through the Miocene of North America and Inner Mongolia, China (Lim, 1996; Zhai, 1964). Though it has been one of the least studied carnivores, more than 20 localities in North America have produced Leptarctus (Lim, 1999). The characters diagnosing Leptarctus as a mustelid include absence of M2, absence of a notch between the blades of the upper carnassial, and a reduced dentition with loss of PI and pi. Though Leptarctus is a mustelid, the teeth bear many similarities to those of procyonids, Procyon lotor and Nasua nasua and stand as a remarkable example of dental convergence (Leidy, 1856; Lim, 1999). Unlike other mustelids, Leptarctus has prominent double sagittal crests, heavy zygomatic arches, a prominent occipital crest, a well-developed hypocone on P4, labially curved upper canines, grooved lower canines, raccoon-like mandibles, elongated metatarsals, and unique bony projections on the tympanic bullae (Lim, 1999).

A recently discovered series of hardground surfaces in the lower Salem Limestone (Meramecian, Mississippian) and upper Muldraugh Member of the Borden Formation (upper Osagean to lower Meramecian, Mississippian), in Hardin County, Kentucky is colonized by a hard substrate community that includes three species of pyrgate edrioasteroids. Torquerisediscus kypsi n. gen. and n. sp. differs from other edrioasteroids by bearing a cyclic pattern of twelve ambulacral cover plates and meandering distal ambulacra. Ulrichidiscus spinosus n. sp. differs from other species of Ulrichidiscus by the presence of large spines on the ambulacral cover plates, anal pyramid plates, and hydropore orals. Two small specimens are assigned tentatively to Ulrichidiscus aff. pulaskiensis.

Edrioasteroid populations occurring on several surfaces show marked differences in size frequency distribution. Three of the surfaces only have large individuals of Torquerisediscus kypsi whereas a fourth surface is colonized by only juvenile specimens of T. kypsi as well as both species of Ulrichidiscus suggesting subtle differences in environment and duration of surface colonization prior to burial. Furthermore, taphonomic pathways differ among these four surfaces with some containing only disrupted individuals and others containing only fully articulated individuals suggesting either differences in burial depth, or some differences in decomposition of edrioasteroid carcasses prior to final burial.

The morphology of the eyes of the olenid trilobite Jujuyaspis keideli Kobayashi, 1936, is described and illustrated. Studied specimens come from Early Tremadocian pyritiferous black shales of the Casa Colorada Formation (= Purmamarca shales) at Purmamarca, Jujuy Province, northwestern Argentina. The eyes are holochroal and proportionately large relative to the overall size of cephalon. They are always found attached to the librigena, showing no preserved lenses, only molds of their surfaces. Their molds demonstrate that lenses were numerous, biconvex, hexagonal in outline and arranged in an hexagonal close-packing system. The eye curvature and the disposition of the facets covering all the visual surface indicate that Jujuyaspis keideli Kobayashi had a visual field wider than that of most benthic olenids. The pattern of lens arrangement and the poorly developed peripheral zone support pelturine affinities for the species.

Phylogenetic reconstructions of two tropical American venerid genera, Chione and Chionopsis (subfamily Chioninae) were attempted at the species-level. The purposes of the analyses were to provide historical reconstructions of origination and extinction events in the two clades, as well as patterns of invasion and diversification. The analyses were based entirely on conchological characters to facilitate the inclusion of a substantial number of fossil taxa, but difficulties were encountered due to the quality of preservation and availability of material. Nevertheless the two genera were established as monophyletic clades, and the reconstructions yielded considerable insight into their histories in tropical America. The analyses suggest that both genera originated in the tropical western Atlantic, Chionopsis by at least the early Oligocene, and Chione in the early Miocene. Various branches of both genera subsequently invaded the tropical eastern Pacific several times prior to Seaway closure, with only one possible reciprocal invasion of the western Atlantic. Pliocene extinction affected both genera more significantly in the western Atlantic relative to the eastern Pacific, and diversity is higher today in the latter region. These conclusions are not entirely consistent with the fossil records of the genera, but this incongruency highlights the need for much more extensive sampling of the eastern Pacific Cenozoic record.

Significant investigators and aspects in the past century of insect paleontology are briefly reviewed. Despite the pervasive influence of the paleoentomologist Willi Hennig in systematic biology, the study of fossil insects remains more descriptive than most other paleontological areas. Hypotheses are reviewed on relationships and chronologies of early divergences in insects (Paleozoic, Lower Mesozoic), particularly living and extinct orders of the lower pterygotes and putative monophyly of the Paleoptera (Odonata + Ephemeroptera). The Dictyoptera (Mantodea, Isoptera, Blattaria) illustrate relationships and discrepencies between stratigraphic record and phylogenetic relationships. Future directions in the field are suggested.

Relatively few fossil dytiscids have been described. This is unfortunate since fossils can provide useful phylogenetic and evolutionary information including unique character combinations not present in extant taxa and minimum ages for divergences. However, even when fossils are found, important characters are often not visible since they may be poorly preserved or obscured. The fossil insects present in calcareous nodules from the Miocene Barstow Formation of the Calico Mountains in Southern California are exceptionally well preserved (Palmer, 1957). The original organisms are replaced by silica or other minerals and when the nodules are dissolved in formic acid, the three-dimensional fossil can be retrieved from the resulting residue. These nodules have yielded a wide variety of fossils, including larvae of the dytiscid species Schistomerus californense Palmer, 1957 and numerous other terrestrial and fresh-water arthropods (Palmer, 1957). The purposes of this paper are to describe a new dytiscid genus and species from an exceptionally well-preserved specimen from the Barstow Formation and to present a hypothesis of the phylogenetic placement of the new taxon.

Development of a phylogenetic classification has been a primary pursuit of crinoid paleontologists during the 20th century. Wachsmuth and Springer and Bather vigorously debated crinoid classification during the waning years of the 19th century, and although tremendous progress has been made a comprehensive phylogenetic classification is still the primary objective for crinoid research during the early 21st century. Twentieth century crinoid studies are divisible into four periods. The direct influence of Frank Springer and Francis Bather continued until approximately 1925. Descriptive studies dominated the period of 1926–1943 and culminated in a comprehensive classification of Paleozoic crinoids that was a combination of the ideas of Wachsmuth and Springer and Bather. The end of the third period, 1944–1978, was marked by publication of the Treatise on Invertebrate Paleontology. The Treatise compilation brought together classification ideas for the entire class into a truly comprehensive classification, although problems remained with the phylogenetic underpinnings of the Treatise classification. During the third period, pioneering work on crinoid paleobiology laid the foundation for significant paleobiology advances for the fourth, 1979–1999, period. This last period also witnessed significant advances in the taxonomy of crinoid faunas at critical intervals, the taxonomy of crinoids from new geographic areas, and working toward the solution to the origin and early evolution of the Crinoidea.

Continued work on crinoids in the 21st century promises to provide significant advances both for understanding the evolutionary history of crinoids and for understanding the history of epifaunal benthic communities through time. Immediate challenges include completion of a comprehensive phylogenetic classification, which will open the door for evolutionary paleoecologic and paleobiology studies; utilization of computerized morphometric techniques in the analysis of functional morphology; systematic studies of new faunas in critical intervals; discovery of faunas in new geographic areas to better constrain knowledge of crinoid biogeography; and modern systematic revision of classic North American and European faunas.

Large rostroconchs have been described from Europe by Sowerby (1815), M'Coy (1844), Baily (1871), Halfar (1882), de Koninck (1885), Hind (1900), and Amler (1996). This report concerns the first known occurrences of rostroconchs from Iran (Fig. 1). The specimens are from the Devonian Bahram Formation (Famennian) (Dastanpour, 1996; Dastanpour and Bassett, 1998; Brice, 1999; Brice et al., 1999) and the Mississippian Mobarak Formation (Tournaisian-Vis6an) (Gaetani, 1968; Bozorgnia, 1973). The Devonian specimens were collected from limestone and argillaceous limestone associated with a diverse brachiopod fauna (Fig. 2). The Mississippian specimens were found in limestone with brachiopods, corals, and crinoids (Fig. 3).

Previous descriptions of Tucetona lack a consistent system using diagnostic characters and only two recent Caribbean ‘species’ are recognized. In this study, textural and structural features of the Tucetona shell are examined and used as the basis for comparison to other glycymerids and in the recognition of morphospecies. Standard diagnostic characters based mainly on the cross-sectional shape of ribs and on hinge teeth ontogeny are presented and used to distinguish six recent Caribbean morphospecies. The shell texture has been examined by light and scanning electron microscopy, showing the interior of glycymerid hinge teeth structured by two bundles of crossed lamellar texture. Whereas European Glycymeris examined for comparison correspond in their hinge plate textures to the one found in Tucetona, differences from a Caribbean Glycymeris sp. are described. Simple lamellar, crossed-lamellar and cone complex crossed-lamellar textures showed the same basic crystallite subunits.

Stratocladistics combines morphological and stratigraphic data in a parsimony-based analysis of evolutionary relationships. We use stratocladistics here to provide an overview of the phylogeny of the extinct echinoderm class Blastoidea. Both cladistic and stratocladistic methods evaluate alternative phylogenies by comparing the number of ad hoc hypotheses needed to reconcile each alternative to observed data. Minimization of ad hoc hypotheses selects the phylogeny best supported by data and enables phylogenetic analyses to incorporate data from different sources. Cladistics treats ad hoc hypotheses of homoplasy, whereas stratocladistics additionally considers ad hoc hypotheses of differential preservation probability of lineages in the stratigraphic record.

The blastoid phylogeny derived using stratocladistics is more resolved than hypotheses selected by cladistics. Although the morphological characters are relatively homoplasious, in this instance the stratigraphic ordering of fossils provides both structure and altered polarity for the stratocladistic hypothesis. The stratocladistic phylogeny supports previous paleontological conclusions of convergence among blastoid lineages and facilitates evaluation of specific hypotheses of character transformation that are integral to recent systematic revisions. Additionally, consideration of temporal data makes some hypotheses of ancestor-descendant relationships more parsimonious than hypotheses of derivation from a common ancestor. The ability to recognize sequential members within single lineages allows more accurate estimation of faunal diversities and more specific reconstruction of evolutionary histories. Chief among possible confounding factors in stratocladistics are instances where preservation potential shows significant geographic variation, although problems of preservation are more tractable than the difficulties homoplasy presents for cladistic analysis.

The Všeradice section was trenched and continuously sampled for graptolites from the base of the post-extinction upper Homerian strata to low in the Ludlow. The upper Homerian is divisible into three biozones, a lower parvus–nassa Biozone, a middle praedeubeli–deubeli Biozone, and an upper ludensis–gerhardi Biozone, the last named being succeeded by graptolites of the lowest Ludlow nilssoni Biozone. The graptolite diversity of nine species in the upper part of the parvus–nassa Biozone is the highest in the world. Five monograptid species, Pristiograptus parvus Ulst, 1974, P. dubius (Suess, 1851), Colonograptus deubeli (Jaeger, 1959), Colonograptus gerhardi (Kühne, 1955), and Colonograptus praedeubeli (Jaeger, 1990) are described from the upper Homerian. Twelve species of retiolitids, Gothograptus nassa (Holm, 1890), Neogothograptus cf. balticus (Eisenack, 1951), Spinograptus spinosus (Wood, 1900), Spinograptus clathrospinosus (Eisenack, 1951), Spinograptus munchi (Eisenack, 1951), Spinograptus reticulolawsoni (Kozłowska-Dawidziuk, 1997) Spinograptus? cf. nevadensis (Berry and Murphy, 1975), Spinograptus? sp. A and Spinograptus? sp. B, Plectograptus macilentus (Törnquist, 1887), and Plectograptus? karlsteinensis new species and Plectograptus? ovatus new species, are described and illustrated from upper Homerian and lowest Ludlow strata. The two new species occur in the upper parvus–nassa and lowest praedeubeli–deubeli, and ludensis–gerhardi biozones, respectively. Two morphs of Gothograptus nassa, a narrow (more typical) form, and a wide form, are recognized. While overlapping in their overall ranges, their occurrences in any particular small interval are sometimes mutually exclusive, suggesting ecological control.

An unusually well-preserved fauna of isolated monograptid graptolites has been recovered from the Sakmara Formation, in the Orenburg District of the South Urals of Russia. Seven different taxa belonging to three genera can be distinguished in these collections, including four new species, Pribylograptus orskensis n. sp., Monoclimacis? galeritus n. sp., Monoclimacis? orenburgensis n. sp., and Monoclimacis? oscitatus n. sp. Study of these new species using infrared video microscopy reveals two features never previously identified in monograptid graptolites on the three species of Monoclimacis?: thecal hoods constructed from both apertural and genicular fuselli; and, a resorption porus that shows some outward inflation or bulging as well as slight fusellar deflection. These two features may both represent stages of morphologic transition to the more “advanced” primary porus and apertural hoods and hooks seen in later monograptids. Phylogenetic analysis of these and some other Rhuddanian taxa suggests that species with “monoclimacid”” thecae arose once in the Rhuddanian from a Huttagraptus ancestor and these species later gave rise to the various groups of biform and uniform monograptids with apertural-hooded and hooked thecae. Those biform taxa with “monoclimacid” or hooked proximal thecae and lappeted (“pribylograptid”) distal thecae appear to have arisen from within this group independently of the lineage leading to Pribylograptus sensu stricto.

Conodonts were mostly small, elongate, eel-shaped marine animals that inhabited a variety of environments in Paleozoic and Triassic seas. Although long enigmatic, conodonts are now regarded as vertebrates and their closely controlled fossil record is not only the most extensive of all vertebrates, but it also makes conodonts the fossils of choice in upper Cambrian through Triassic biostratigraphy. Conodonts were soft-bodied except for a variety of phosphatic elements that formed a distinctive feeding apparatus. Post-mortal dissociation of the apparatus and subsequent jumbling of its elements on the sea floor led, from 1856 to about 1966, to development of an artificial, form-based taxonomy that was utilitarian, but clearly unsatisfactory as a vehicle for understanding the group in biologic terms. Natural assemblages of elements, discovered between 1879 and 1952, have been interpreted as undisturbed skeletal apparatuses, and in the mid-1960s it was determined that original composition of the apparatuses of many species could be reconstructed and statistically evaluated from collections of disjunct elements by various grouping procedures. These determinations led to an emphasis on multielement taxonomy by most (but not all) students of conodonts. Even so, only about a third of the approximately 550 valid conodont genera, have been established (or re-interpreted) in multielement terms and this makes any of the several extant schemes of suprageneric classification phylogenetically suspect. We comment on a recent scheme that recognizes 41 families assigned to some 7 orders, and suggest how it might be modified so as to square with principles of phylogenetic systematics.

Collectively, studies of the structure of Neogene diversity change in tropical American mollusks have lacked 1) species-level analyses within well-established clades; 2) consideration of abundance and sample size on diversity estimates and comparisons; and 3) geographic comparisons within temporal intervals. This study takes all three factors into consideration and compares Miocene to Recent species richness patterns in tropical American marginellid gastropod species within the clade Prunum+Volvarina. Rarefaction analyses of more than 16,000 specimens from more than 500 samples are used to standardize comparisons of species richness through time and space. Species richness in Prunum+Volvarina from the Miocene to the Recent of the Tropical Western Atlantic (TWA) is compared along a latitudinal gradient from north to south (Florida, the Dominican Republic, and Venezuela). Additionally, temporal patterns of diversity change are compared between the TWA and the Tropical Eastern Pacific (TEP: Peru, Ecuador, Colombia, Panama, and Costa Rica).

As is the case with most Neogene lineages, the number of marginellid specimens and samples differ significantly through both time and space. Rarefaction analyses of both specimens and samples indicate that: 1) significant geographic differences in species richness were detected between the Miocene, Pliocene, Pleistocene, and Recent of the TWA; 2) temporal patterns of species richness were similar in the northern and southern TWA; 3) from the Miocene to the Recent, marginellid species richness in the TEP has always been significantly less than TWA diversity; and 4) from the Miocene to the Recent, TWA diversity decreased significantly, whereas TEP diversity was stable and low. Separate rarefaction analyses using the numbers of specimens and samples did not always produce concordant results and indicate that the unit of analysis influences estimates of species richness. Discordant specimen/sample rarefaction results may be a product of sample size. Intrinsic ecological and evolutionary differences do not appear to be primary contributors to differences in marginellid species richness between the TEP and TWA.

Three flexible crinoids occur in the Upper Ordovician Maquoketa Formation of Illinois, Iowa, and Minnesota: Protaxocrinus girvanensis Ramsbottom, 1961, Clidochirus anebos new species, and Proanisocrinus oswegoensis (Miller and Gurley, 1894). Protaxocrinus girvanensis is also found in the Upper Ordovician of Scotland which indicates that the ocean was narrow enough to allow at least one crinoid species to cross the barrier. The Upper Ordovician of North America and Scotland also share many common crinoid genera. Both phenetic and cladistic methods result in similar phylogenies of flexible crinoids. Protaxocrinus was derived from a cupulocrinid ancestor during the Middle Ordovician. Clidochirus evolved from Protaxocrinus or its ancestral stock prior to the Richmondian of the Late Ordovician. The Richmondian Proanisocrinus and later anisocrinids are most closely related to Clidochirus or its immediate predecessor. Thus, three major lineages of flexible crinoids, Protaxocrinus (taxocrinid group), Clidochirus (icthyocrinid), and Proanisocrinus (anisocrinids and homalocrinids), appeared during the Ordovician. Despite their rarity during the Ordovician, all three flexible lineages survived the Latest Ordovician extinction, whereas their more abundant and successful cupulocrinid ancestors were eliminated.

Pinaceae is the most species rich and geographically dispersed group of living gymnosperms (Florin, 1963), and comprise a dominant component of modern mountain and boreal forests throughout the northern hemisphere (Florin, 1963). Although there are a few records of possible pinaceous species extending back to the Upper Triassic (Delevoryas and Hope, 1987), unequivocal evidence for the family does not appear until the Cretaceous, and Pinaceae may be the most recently derived conifer family. During the Early Cretaceous, pinaceous remains became common components of terrestrial plant communities, and a diverse array of ovuliferous cones signals an explosive evolutionary radiation within the family (Miller, 1976a). Most of this diversity is chronicled by cones that are clearly representatives of the Pinaceae, but are not assignable to a genus with living species. Cones of these types are assigned to the genera Pityostrobus Dutt, Pseudoaraucaria Fliche, and Obirastrobus Ohsawa, Nishida and Nishida, and have been discovered in a circumpolar distribution from North America, through Europe and Russia, to eastern Asia (Miller, 1976a; Ohsawa et al., 1992; Falder et al., 1998). The purpose of this paper is to extend further the known diversity of the early Pinaceae by the description of a new species of the genus Pityostrobus. This cone is the second Pityostrobus species from southwestern Russia, and it further documents the remarkable Cretaceous evolutionary radiation of Pinaceae.

The basic structure of archosaurian phylogeny is understood to include two primary crown-group lineages—one leading to living crocodiles and including a broad diversity of Triassic animals (e.g., phytosaurs, rauisuchians, aetosaurs), and another leading to dinosaurs (living and extinct). These lineages were established by the middle Triassic. A few extinct groups remain controversial, such as the pterosaurs, and debate persists over the phylogenetic relationships among extant bird lineages, which have proved difficult to resolve, and divergence timing estimates within Aves and Crocodylia remain the source of contention. A few analyses support a close relationship between archosaurs and turtles, or even a nesting of turtles within Archosauria. All sources of information used to resolve these issues have weaknesses, and these problems all involve highly derived lineages when they first appear in the fossil record.

Based on specimens from Australia and Iran, five species of rhipidognathid conodonts, Appalachignathus delicatulus Bergström, Carnes, Ethington, Votaw, and Wigley, 1974, Bergstroemognathus extensus (Graves and Ellison, 1941), B. hubeiensis An (MS) in An, Chen, and Li, 1981, B. kirki Stait and Druce, 1993, and Rhipidognathus? yichangensis (Ni, 1981), are described and revised in terms of multielement morphology. All three genera comprising the Rhipidognathidae are interpreted as having a septimembrate apparatus, partially confirmed by bedding plane assemblages of B. extensus from Victoria. Occurrence of A. delicatulus in allochthonous limestones (about the Middle-Upper Ordovician boundary) of central New South Wales is the first record of the species outside North America. Recognition of Rhipidognathus? yichangensis in Early Ordovician strata of the Canning Basin, reinforces biogeographic affinities of Australia and South China. The three described species of Bergstroemognathus are mainly restricted to late Early Ordovician strata. Bergstroemognathus extensus is widely distributed in North America, western Argentina (Precordillera), China, and Australia. Bergstroemognathus hubeiensis, described from east-central Iran, has been previously recorded only from China, while the slightly younger B. kirki seems endemic to central and northern Australia, where it was restricted to shallow, warm water environments. In contrast, B. extensus and B. hubeiensis inhabited a spectrum of water depths from shallow to deep.