Field work has greatly increased the number of well-dated papiliophyllid corals available from Nevada. The established range of the family is expanded from Pragian and lower Emsian to Pragian and almost the entire Emsian. Ranges of species are calibrated against Johnson faunal intervals and a revised Pragian and lowermost Emsian conodont zonation proposed by Murphy for Nevada. Study of all reposited material has led to some revision of every member of the family. Eurekaphyllum, previously imperfectly known from a single specimen of vague stratigraphic origin, is shown to be a useful upper Emsian index. Nine reported occurrences of the family in Europe and Asia are re-examined and, except for a possible occurrence on Novaya Zemlya, all are rejected. The three named genera of the family are apparently endemic to the southwestern North American craton. Papiliophyllum elegantulum asymmetricum new subspecies, P. murphyi new species and Eurekaphyllum vescum new species are described by Pedder.

Re-examination of type material of the hyolithids Hyolithes ardmillanensis Reed, 1909 from the lower Caradoc and H. candidus Reed, 1909 from the lower Ashgill suggests that these species are representatives of the genus Leolites Marek, 1967 to which they are referred with question. Hyolithes subcrispatus Reed, 1909 from the upper Ashgill, and H. sylvestris Reed, 1909 from the lower Llandovery are referred tentatively to Recilites Marek, 1967. These are the first occurrences of these genera outside of Bohemia, and the stratigraphic range of Recilites is extended considerably if H. sylvestris is in fact a representative of that genus. The orthothecid Hyolithes (Orthotheca) thraivensis Reed, 1909 from the upper Ashgill is now referred to the new genus Girvanolithes, to which the Caradocian H. (O.) subexcavatus Reed, 1909 is assigned with question. Girvanolithes thraivensis is exceptional because it is one of a small number of orthothecid species for which intestinal remains are known; equally remarkable is the fact that three such specimens were found, and these are the only hyolith intestines ever reported from Britain. The hyolithid species H. asteroideus Reed, 1909, H. columbanus Reed, 1909, H. girvanensis Reed, 1909, H. immemor Reed, 1909, H. multipunctatus Reed, 1909 and H. penkillensis Reed, 1909, and the orthothecid Hyolithes (Orthotheca) subornatus Reed, 1909 are here deemed unrecognizable owing to incomplete preservation. Ceratotheca? subuncata is reassigned to the gastropod genus Ecculiomphalus Portlock, 1843 with question.

Echinochiton dufoei new genus and species is described from the Ordovician age Forreston Member, Grand Detour Formation (Blackriveran) near Beloit, Wisconsin. For a variety of reasons, we regard E. dufoei as a chiton; the species is known from four articulated or partially articulated specimens, one of which has eight plates and two of which have a mucro on the tail plate. Echinochiton dufoei differs from other chitons in having large hollow spines that project from each of the known plates. In plate shape and position, E. dufoei is much like the Upper Cambrian species Matthevia variabilis Walcott, 1885, and the Lower Ordovician species Chelodes whitehousei Runnegar, Pojeta, Taylor, and Collins (1979).

The Late Carboniferous bransoniid conocardioidean Apotocardium lanterna (Branson, 1965) had an entirely aragonitic shell with a finely prismatic outer shell layer, a predominantly crossed lamellar to complex crossed lamellar middle shell layer, and an “inner” shell layer of finely textured porcelaneous and/or matted structure. This “inner” layer is probably homologous with the inner part of the middle shell layer and the inner layer sensu stricto of bivalved molluscs. Shell morphological and microstructural convergences between conocardioids and living heart cockles suggest that at least some conocardioids may have farmed algal endosymbionts in their posterior mantle margins. This symbiosis may have helped conocardioids compete with the biomechanically more efficient bivalves during the latter part of the Paleozoic.

A new Burgess Shale-type soft-bodied fauna crossing the Lower-Middle Cambrian boundary in the Comet Shale Member of the Pioche Formation in Lincoln County, Nevada, contains common remains of soft-bodied ecdysozoan taxa. These fossils provide important new information about the nature and variety of Cambrian soft-bodied organisms. Arthropod taxa include one species of Canadaspis Novozhilov in Orlov, 1960, one species of ?Perspicaris Briggs, 1977, three species of Tuzoia Walcott, 1912, and at least two species of Anomalocaris Whiteaves, 1892. A priapulid referable to Ottoia Walcott, 1911a, was also recovered. A comprehensive review of Tuzoia is given. Some specimens from Early Cambrian sections are replaced by hematite, resulting in iron staining similar to that in such other Early Cambrian soft-bodied faunas as the Kinzers Formation in Pennsylvania. Some taxa in the Comet Shale, and in other Early and Middle Cambrian soft-bodied faunas, have prodigious geographic ranges that spanned much of Laurentia and even other Cambrian cratons. Moreover, these taxa ranged across the Early-Middle Cambrian boundary relatively unscathed. This is in contrast to many trilobite taxa that had narrow geographic ranges in the Early Cambrian and high levels of extinction at the Early-Middle Cambrian boundary.

Although bradoriids locally are common components of the Cambrian biota, they have been reported previously from Antarctica only from Tertiary glacial deposits. Here, we describe the bradoriid, Bicarinella evansi new genus and species, collected in situ from the upper Lower Cambrian (Botomian) of the Pensacola Mountains in East Antarctica. Bicarinella evansi n. gen and sp. is characterized by a subtriangular carapace with a well-defined marginal rim, subequal anterior and posterior lobes that are elongated into sharp ridges extending one-third the length of the carapace, and a broad dorsal node placed between the anterior and posterior lobes. The surface of the carapace exhibits three kinds of ornamentation: fine pitting, pustules, and reticulae. Several smaller carapaces with reduced ornamentation collected from the same bed are interpreted as instars of this species. Bicarinella n. gen. is assigned to the family Hipponicharionidae and appears to be closely related to Albrunnicola Martinsson, 1979, or Hipponicharion Matthew, 1886. Although strong archaeocyath faunal similarities demonstrate a close biogeographic relationship between Australia and Antarctica in the Early Cambrian, the possible sister group relationship of Bicarinella n. gen. to Hipponicharion, which is otherwise unknown from Gondwana, may suggest a separate biogeographic pathway to East Antarctica that did not involve Australia.

Plethopeltis armatus, and species of Leiocorpyphe, are shown to have in common a median ventral cephalic suture and thoracic axial rings with a poorly-defined articulating furrow and a strong transverse ventral ridge. In other characters they differ greatly, and to group them in the Plethopeltidae is open to question; this family may be polyphyletic. The median ventral suture is regarded as a cardinal character of Asaphida, but it is uncertain whether this character had a single origin or arose more than once. Leiocoryphe gemma may be a paedomorphic species derived from some Upper Cambrian trilobite with an effaced cephalon.

Two non-trilobite arthropods are described from the Emigrant Formation (Lower Cambrian-Lower Ordovician) in the Silver Peak Range, Esmeralda County, Nevada. A Middle or Upper Cambrian “arachnomorph” arthropod with a phosphatic exoskeleton has been noted in previous faunal lists, but has not been previously described. This fossil is here named Quasimodaspis brentsae gen. et sp. nov. Q. brentsae belongs in the Aglaspidida, a close outgroup to the true chelicerates; this is the second report of an aglaspidid from the Great Basin. Esmeraldacaris richardsonae gen. et sp. nov. is a newly discovered arthropod from the lower Ordovician, from beds transitional between the Emigrant Formation and the overlying Palmetto Formation. It is a survivor of an early arthropod lineage that does not belong in any extant taxon, but which may also include the Ordovician Corcorania and the Cambrian Mollisonia.

Conodont elements other than those with platform ledges along the processes have often been unrecognized or disregarded in reconstructions and phylogenetic discussions of Ordovician “platform conodont genera.” The platform elements are larger than the other element types and often exhibit more rapid evolutionary changes in morphology. Nevertheless, to understand the evolution of, and relationships between and among “platform genera,” it is necessary to also consider the associated ramiform and geniculate elements. Thus, on the basis of large collections, together comprising 10,800 elements from Sweden and southern China, all element types of Lenodus antivariabilis (An, 1981), L. variabilis (Sergeeva, 1963), Yangtzeplacognathus crassus (Chen and Zhang, 1993) and Eoplacognathus pseudoplanus (Viira, 1974) are described and discussed. All these species had seven morphologically distinct element types, and probably seventeen individual elements in each apparatus. Ancestors and descendants of these species are discussed more briefly and it is concluded that the ramiform and geniculate elements also are characteristic within each lineage.

A new species of the genus Nothosaurus from the Lower Muschelkalk of Winterswijk, The Netherlands, shows relatively plesiomorphic features such as a relatively forward position of the pineal foramen. The jugal enters into the ventral margin of the orbit, which would also be regarded as plesiomorphic, were it not that this feature optimizes unequivocally as a reversal and, hence, as a diagnostic (derived) character of the new taxon. The new taxon does not, however, increase the fit of the cladogram for the phylogenetic relationships within Nothosaurus to the stratigraphic record of the genus. The basal position of Nothosaurus juvenilis remains problematic.

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.

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.

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).