A geometric analysis of lophophore shape and arrangement in the fenestrate dendroid graptolite genus Dictyonema reveals that the shape of the zooid domain in the majority of Dictyonema species colonies is highly elliptical, with the long axis of the ellipse perpendicular to the proximodistal axis of the stipe. A complex lophophore, bilaterally symmetrical and consisting of two tentaculated arms that are laterally directed and perpendicular to the stipe axis, provides the best geometric solution to completely filling the elliptical zooid domain seen in the majority of Dictyonema species.

Working under the assumption that fenestrate graptolites, like fenestrate bryozoans, needed to form a continuous filtering surface with contact between adjacent lophophores, two optimum close-parking models exist for lophophores with elliptical zooid domains: either a proximodistal-row arrangement or a lateral-row arrangement of the lophophores. Of the two possible geometries, the most probable close-packing arrangement of hypothetical biplumed lophophores within the fenestrate graptolite meshwork is in proximodistal rows.

The fossil snake species Haasiophis terrasanctus Tchernov, Rieppel, Zaher, Polcyn, and Jacobs, 2000, from the early Upper Cretaceous of the Middle East, is described and illustrated, following a review of the current debate on snake relationships and origins. The description and discussion presented here adds important detail to the knowledge of this taxon and its phylogenetic significance beyond the limited account presented in the original description of Haasiophis. The species is remarkable in that it shows the skull of a relatively advanced (i.e., macrostomatan) snake, yet preserves well-developed hind limbs. The hind limb includes a femur, tibia, fibula, astragalus, calcaneum, distal tarsal four, and remains of four metatarsals and two phalanges. Haasiophis cannot be considered a juvenile specimen of Pachyrhachis. The implications of the presence of well-developed hind limbs in Haasiophis, Pachyrhachis, and Podophis for the cladistic analysis of the phylogenetic interrelationships of these fossil snakes is discussed. The presence of well-developed hind limbs in Pachyrhachis and Haasiophis also creates methodological problems for the cladistic analysis of the phylogenetic relationships of these fossil snakes. Scenarios of snake origins are reviewed and found to be deficient in the absence of a well-corroborated hypothesis of snake relationships within Squamata.

All 19 known species of the primitive cladid crinoid genera Atelestocrinus, Cyathocrinites, Goniocrinus, Parisocrinus, Pellecrinus, and Zygotocrinus from the early Osagean Burlington Limestone of the North American midcontinent are reviewed and redescribed or, where necessary, redefined. Nine of these species are illustrated for the first time herein. Sixteen are considered valid, including C. deroseari n. sp. Of the remaining three species, one is left in open nomenclature, and two are considered nomen dubia. Pellecrinus is recognized for the first time from the Burlington Limestone, although the specimens can not be identified to the species level and are left in open nomenclature.

Cyathocrinites ranges from the Middle Silurian to at least the Middle Mississippian. During the Early Mississippian Cyathocrinites experienced an evolutionary radiation with a maximum diversity of nine species in the Burlington Limestone. Phylogenetic relationships were investigated in a parsimony-based phylogenetic analysis by combining morphologic data from the Burlington species with data from the four other species of Cyathocrinites from the late Osagean and early Meramecian of the east-central United States. The Kinderhookian C. chouteauensis (Miller and Gurley, 1896) served as the outgroup. A phylogenetic analysis of 14 species of Mississippian Cyathocrinites yielded a single most parsimonious tree with a length of 28 steps (C. I. = 0.607, H. I. = 0.392, R. I. = 0.718, R. C. = 0.436). Results of this analysis suggest that at least two major clades existed within Mississippian Cyathocrinites. One clade contains C. sampsoni (Miller, 1891b), C. gilesi (Wachsmuth and Springer, 1878), C. farleyi (Meek and Worthen, 1866), and C. barydactylus (Wachsmuth and Springer, 1878). The second clade contains C. iowensis, C. kelloggi (White, 1862), C. barrisi (Hall, 1861a), C. rigidus, C. deroseari n. sp., C. asperrimus (Springer, 1911), C. lamellosus (White, 1863), and C. harrodi (Wachsmuth and Springer, 1880). Cyathocrinites multibrachiatus forms a polytomy with these two clades. Members of the first clade exhibit a unique overall morphology present only during the Mississippian, suggesting the clade arose during this time. Members of the second clade, plus C. multibrachiatus, exhibit some characters present in Cyathocrinites species as old as the Middle Silurian and, thus, may have its roots among Silurian and Devonian species.

The Paskapoo Formation in central and south central Alberta, Canada, preserves continental sediments of Paleocene age. Outcrops of the formation on Nose Creek in northeast Calgary, at a locality called Who Nose?, have yielded fossil mammals from the middle part of the epoch. To date, some 400 dental specimens representing eight mammalian orders have been recovered, among them numerous well-preserved jaws. Newly named taxa include new species of Parectypodus and Baiotomeus (Multituberculata); new species of Parectypodus, Litomylus (Condylarthra), and Cyriacotherium (Pantodonta) are left unnamed. Biostratigraphic correlation indicates a late Torrejonian age for the local fauna based on the presence of the plesiadapid primate Pronothodectes matthewi. Faunal comparisons suggest a close similarity to the penecontemporaneous Gidley Quarry fauna, Montana, with a taxonomic diversity consistent with other co-eval faunas in the Western Interior of the United States. The specimens from Who Nose? constitute the largest collection of Torrejonian mammals from Canada, offering a unique perspective on mammalian diversity from an otherwise poorly represented interval in western Canada.

Nicholsodiscus anticostiensis new genus and species (Mill Bay Member, Vauréal Formation, Rawtheyan, Upper Ordovician) is described from Anticosti Island, Quebec, Canada. Nicholsodiscus anticostiensis n. gen. and sp. is known from two complete specimens preserved in situ with the cupule-bearing side facing toward the bedding surface. Sedimentological, petrographic, and trace fossil evidence suggest that this bedding surface had the consistency of a hardground during the lifetime of the cyclocystoids. This provides the first unequivocal evidence that cyclocystoids lived with their cupule-bearing side (ventral) toward the substratum. A cupules-down orientation results in the ambulacral grooves facing the substratum. Such an orientation excludes suspension-feeding from being a possible feeding mode of the Cyclocystoidea as discussed by Henderson and Shergold (1971).

A third Anticosti Island cyclocystoid specimen of unknown affinities is described from the same locality. Furthermore, a re-examination of the holotype of “Cyclocystoides” raymondi Foerste for purposes of comparison with Nicholsodiscus anticostiensis n. gen. and sp. provided evidence that it is a member of Zygocycloides, albeit with missing interseptal plates.

Noncalcified thalli, consisting of a narrow main axis with numerous branched hairlike laterals in whorls and a subapical array of undivided clavate laterals, from the Silurian (Llandovery) Brandon Bridge Formation of southeastern Wisconsin, constitute the basis for a new genus and species of dasycladalean alga, Heterocladus waukeshaensis. A relationship within the family Triploporellaceae is indicated by the whorled arrangement of the laterals and the absence of gametophores on mature specimens. A compilation of occurrence data suggests that noncalcified dasyclads, as a whole, were more abundant and diverse during the Ordovician and Silurian than at any other time in their history. The heterocladous thallus architecture of this alga adds to a wide range of morphological variation documented among Ordovician and Silurian dasyclads, the sum of which indicates that Dasycladales underwent a significant evolutionary radiation during the early Paleozoic.

A nematocerous fly family known previously only from one species and specimen from the Upper Jurassic of Karatau, Kazakhstan, Archizelmiridae is expanded here to include additional records preserved as compression fossils and ones in amber. The compressions are from the Upper Jurassic of Shar-Teg, Mongolia and Lower Cretaceous of Baissa, Transbaikal, with a new species, Archizelmira baissa, from Baissa. Particularly significant are three finely preserved new species and genera in ambers from the Cretaceous Period: Zelmiarcha lebanensis (Lebanon: Lower Aptian), Archimelzira americana (New Jersey: Turonian), and Burmazelmira aristica (Burma [Myanmar]: mid-Cretaceous). The latter two species interestingly possess stylate antennae, those of Burmazelmira being the only aristate antennae in the order Diptera outside the suborder Brachycera. A cladogram is presented for the relationships among archizelmirid species, cladistic rank of which correlates with stratigraphic age. Transformation series of the antennal flagellum in Archizelmiridae corresponds with one recently hypothesized for the Brachycera, wherein the style and arista are derived from the apical flagellomere(s). The family appears to be a member of the extant group Sciaroidea, which includes fungus gnats and gall midges, though precise relationships remain unclear.

The chelonian fauna of the Portezuelo Formation (Turonian-Coniacian), outcropping at Sierra del Portezuelo (Neuquén province, Argentina), is reported. Two new taxa of pleurodiran turtles are described. One of them is Prochelidella portezuelae new species, a short-necked chelid closely related to extinct species of the Lohan Cura (Albian), Candeleros (Cenomanian), and Bajo Barreal (Turonian) formations from northwestern and central Patagonia, and to the extant species of the genus Acanthochelys. The other is Portezueloemys patagonica new genus and species, a member of the epifamily Podocnemidoidea, and is considered the sister group of the family Podocnemididae. This discovery confirms the coexistence in northwestern Patagonia of a north gondwanan component (Pelomedusoides) and a south gondwanan element (Chelidae) during the Turonian-Coniacian.

A collection of 60,886 conodonts was recovered from 141 samples of the Outram, Skoki and Owen Creek Formations (Lower to Middle Ordovician) that outcrop through the Wilcox Pass section, Jasper National Park, Alberta, Canada. This section representσ the standard reference section for the Lower-Middle Ordovician of the Southern Canadian Cordillera. The well preserved fauna is assigned to 75 species representing 48 genera. The species are representative of both the Midcontinent and Atlantic faunal realms, but dominantly the former. Nine Midcontinent Realm zones are recognized in the upwards shallowing carbonate platform succession including the Scolopodus subrex, Acodus kechikaensis, Oepikodus communis, Jumudontus gananda, Tripodus laevis, Histiodella altifrons, Histiodella sinuosa, Histiodella holodentata, and Phragmodus “pre-flexuosus” zones. Zones recognized that are characteristic of the Atlantic Realm include Paroistodus proteus, Paracordylodus gracilis, Oepikodus evae, Paroistodus originalis, and Microzarkodina flabellum. A new genus, Filodontus, is proposed for elements assigned previously to the form genus “Scolopodus” filosus. A new species, Leptochirognathus wilcoxi, is described and one new species, left in open nomenclature, is assigned to Rossodus?.

The aquatic palynomorph genus Cobricosphaeridium Harland and Sarjeant, 1970 was described from Holocene deposits of Australia. Restudy of the type material shows that these palynomorphs may represent the eggs of crustaceans, and that earlier attributions to the division Dinoflagellata are unsustainable. The genus Aquadulcum Harland and Sarjeant, 1970, also first described as a dinoflagellate from the Holocene of Australia, is treated as a synonym of Cobricosphaeridium, and the following new combinations are proposed: C. awendae, C. myalupense, C. pikeae, C. serpens, C. yanchepense, C.? ovatum, and C.? vermiculatum. Previous records of the genus are restricted to the Holocene and indicate a freshwater affinity.

Cobricosphaeridium has now been found in Holocene subsurface brackish deposits of Laguna Hinojales in eastern Argentina. This is the first record of this genus from South America and unequivocally extends its ecological range into a brackish environment. Several species are represented, including Cobricosphaeridium hinojalensis new species; and their potential as paleoenvironmental indicators is evaluated.

Three new specimens of Tapocyon are described from Middle Eocene (Uintan NALMA) strata of San Diego County, California. These specimens include the first cranial material for the genus, significantly increase the knowledge of the anatomy of Tapocyon and enhance understanding of the phylogeny of this taxon and other early carnivorans. Tapocyon can be placed tentatively within the Caniformia (Carnivora, Mammalia) based on the following combination of characters: reduced parastyle and protocone on P4; continuous lingual cingulum on upper molars; retention of M3/3; short m2 talonid; moderately deep and narrow metastyle notch on P4; and hypoconid larger than hypoconulid on m2. The revision presents new diagnoses of Tapocyon and included species, synonymizes T. occidentalis with T. robustus, and erects a new species, T. dawsonae. The revision expands the geographic range of T. robustus during a time of hypothesized increasing provinciality. Although no auditory bullae are preserved, the basicranium of one of the new specimens shows evidence of a likely ossified, but loosely attached ectotympanic and entotympanic bulla, expanded primarily in the posterior direction. The majority of the postcranial skeleton is preserved in one new specimen, for which we provide preliminary observations of the morphology of the middle and distal phalanges, which indicate that Tapocyon had retractable claws.

The stratigraphic utility of small marine acritarchs in the Neogene has been known for more than a decade (e.g., de Vernal and Mudie, 1989). Their potential for biostratigraphy in the Cretaceous is also well known, and was elegantly elucidated by Habib and Knapp (1982) in a detailed scanning electron microscope (SEM) study from the western North Atlantic. Habib and Knapp erected 12 new acritarch genera including the acanthomorph genus Nannobarbophora and its three species N. barbata (the name of the type), N. pistilla, and N. platforma. A diagnostic feature of Nannobarbophora is the presence of spinules concentrated on, or restricted to, the surface of distally closed processes. Excystment is by a simple linear split (Habib and Knapp, 1982, p. 347).

A low-diversity crinoid fauna is described from the Fitchville Formation, Lower Mississippian (Late Devonian to Early Mississippian) of Utah County, Utah. Based on the crinoid fauna, composed of Nunnacrinus olsoni new species, Paracosmetocrinus lundi new species, and Platycrinites sp., this fauna is interpreted as being from the Kinderhookian, Upper Fitchville Formation. This occurrence of Nunnacrinus extends the geographic and facies range of this genus in western North America and the geographic range of Paracosmetocrinus within western North America.

Land hermit crabs (Coenobitidae) are widespread and abundant in Recent tropical and subtropical coastal environments, yet little is known about their fossil record. A walking trace, attributed to a land hermit crab, is described herein as Coenobichnus currani (new ichnogenus and ichnospecies). This trace fossil occurs in an early Holocene eolianite deposit on the island of San Salvador, Bahamas. The fossil trackway retains the distinctive right and left asymmetry and interior drag trace that are diagnostic of modern land hermit crab walking traces. The overall size, dimensions and shape of the fossil trackway are similar to those produced by the modem land hermit crab, Coenobita clypeatus, which occurs in the tropical western Atlantic region. The trackway was compared to other arthropod traces, but it was found to be distinct among the arthropod traces described from dune or other environments. The new ichnogenus Coenobichnus is proposed to accommodate the asymmetry of the trackway demarcated by left and right tracks. The new ichnospecies Coenobichnus currani is proposed to accommodate the form of the proposed Coenobichnus that has a shell drag trace.

Plesiosaurs constitute a monophyletic group whose stratigraphical range is uppermost Triassic to uppermost Cretaceous (Brown, 1981). They were large predatory marine reptiles, highly adapted for submarine locomotion, with powerful paddle-like limbs and heavily reinforced limb girdles (Saint-Seine, 1955; Romer, 1966; Carroll, 1988; Benton, 1990). The Plesiosauria clade belongs to the Sauropterygia, which has recently been hypothesized as the sister-group of the Ichthyosauria. Together with that clade they form the Euryapsida (Caldwell, 1997). The Sauropterygia can be subdivided into relatively plesiomorphic stem-group taxa from the Triassic (Placodonts, Nothosauroids, and Pistosauroids), and the obligatorily marine crown-group Plesiosauria (Rieppel, 1999). Plesiosaurs are traditionally divided into two superfamilies: Plesiosauroidea, with usually small heads and long necks; and Pliosauroidea, with larger heads and shorter necks (Welles, 1943; Persson, 1963; Brown, 1981). Plesiosauroidea contains three families: Plesiosauridae, Cryptoclididae, and Elasmosauridae (Brown, 1981; Brown and Cruickshank, 1994). The validity of the Polycotylidae Cope, 1869, has long been questioned and its phylogenetic position among Plesiosauria debated, as many consider it to be related to the Pliosauridae or to be a sister-group of the Elasmosauridae (Sato and Storrs, 2000; O'Keefe, 2001).

Since the description of the first cycloid from the Carboniferous of Yorkshire, England (Phillips, 1835) the Cycloidea have been placed in many different groups within the Arthropoda. These include agnostid trilobites (Phillips, 1835), xiphosure merostomes (Packard, 1872; Oosterink, 1978), limuloid-like crustaceans (Woodward, 1905), decapod brachyurans (Trauth, 1918), branchiurans (Hopwood, 1925), copepods (Clark, 1989), and maxillopodan crustaceans (Schram et al., 1997).

The genus Sphenothallus was erected by Hall (1847, p. 261), who originally considered it a land plant. Sphenothallus was later classified as a marine invertebrate. Moore and Harrington (1956, p. F65) regarded Sphenothallus as a hydrozoan or scyphozoan. Van Iten et al. (1992, p. 139) supported Moore and Harrington's idea, and argued that it displays a close relationship to conularids (also see Li, 2000, p. 91). However, Mason and Yochelson (1985, p. 93–94) suggested that Sphenothallus is an annelid or “worm” (also see Fauchald et al., 1986, p. 64; Feldmann et al., 1986, p. 344–345; Choi, 1990, p. 403; Bartels et al., 1998, p. 114–117). The exact phylogenetic affinity of Sphenothallus is still debated.

The conodont fauna from nine sections across a platform-to-basin transect in northeastern British Columbia includes species of Early Ordovician (Tremadocian) to Early Silurian (Llandovery) age. A collection of 9,110 conodont elements was recovered from 205 samples taken from nine stratigraphic sections that preserve the platform succession of the Kechika, Skoki, Beaverfoot, McCusker and Nonda Formations and their off-shelf equivalents, the Ospika, Robb, Kenny and Laurier Formations of the Road River Group. The fauna is assigned to 106 species representing 67 genera; the Ordovician species are representative of two faunal realms. One new genus, left in open nomenclature, is described. Five new species include Drepanoistodus latus and four new species left in open nomenclature assigned to the following genera: Walliserodus, Multioistodus?, Pseudooneotodus, and Belodina. The Midcontinent Realm zones recognized include, in ascending order, the Acodus kechikaensis, Oepikodus communis, Jumudontus gananda, Tripodus laevis to Plectodina aculeata zones, Phragmodus undatus and Gamachignathus ensifer? zones. Zonal species of the Atlantic Realm are Microzarkodina flabellum, Eoplacognathus suecicus, Baltoniodus variabilis, Pygodus anserinus, and Amorphognathus tvaerensis. The Silurian fauna, of lower diversity than the Ordovician fauna, is representative of the Distomodus staurognathoides and Pterospathodus amorphognathoides zones.

Amber is a superb medium for the fossilization of delicate organisms. Besides light microscopy techniques for the study of insects in amber, scanning electron microscopy (SEM) in backscattered electron mode (SEM-BSE), low temperature SEM (LTSEM) and also confocal laser scanning microscopy (CLSM) were used to examine microcenosis and particulate plant remains (microdebris). We applied these techniques to such inclusions in amber Álava, northern Spain (Allaian: Early Cretaceous). Confocal microscopy provides a 3D image of partial microcenosis showing bifurcate fungal hyphae. The huge potential of SEM-BSE yields high resolution images, in which the relationship between protozoa and fungal hyphae may be observed and the characterization of further ultrastructural details in flagellates. According to the SEM-BSE images, food and pulsatile vacuoles appear better preserved than mitochondria and lipids in amber-embedded protozoa. A process of protozoan mineralization has led to the deposition of S and Fe in peripheral areas, and the Fe is also present in the core of surrounding fungal hyphae. Application of LTSEM for the study of protozoan inclusions produces images of their exteriors showing many vacuoles. Plant tissues under SEM-BSE show mummified cell walls, while the cytoplasm exhibits a bright appearance and is very rich in Fe and S. SEM in secondary electron mode (SEM-SE) also reveals a microbiota trapped in gas bubbles.

The anatomy of the external naris and anterior palate is described in detail for Lycaenodon longiceps, a morphologically conservative member of the primitive therapsid clade Biarmosuchia. Therapsids are distinguished from pelycosaur-grade synapsids by numerous features of the naris and palate. As in most early therapsids, the septomaxilla in Lycaenodon consists of a short intranarial portion and a long, posterodorsal, facial process. The septomaxillary foramen is reduced to a small, longitudinal slit between the septomaxilla and maxilla. On the palate, the unpaired vomer is clasped anteriorly by long palatal processes of the premaxillae. The choanae are elongate structures whose anterior portion housed the lower canine when the jaws were closed. The palatine and maxilla bear a small shelf (crista choanalis) on their medial surface that has been suggested to represent an early stage in the development of a secondary palate. The parallel acquisition of a crista choanalis and a bony secondary palate in several therapsid groups supports the hypothesis that respiration-related changes were an important aspect of early therapsid evolution.

The genus Lycaenodon may be diagnosed by at least three autapomorphies: the premaxilla bears a scroll-like choanal process that roofs the anterior portion of the internal nares, the vomer is widest at the level of the upper canines with its downturned edges beginning more posteriorly, and the dorsal surface of the postfrontal is convex. Another specimen referred to Lycaenodon preserves additional features that might be autapomorphic, but are not preserved in the holotype.