Radiolaria extracted from two bedded-limestone and two limestone-concretion samples from the upper Llandovery of the Cape Phillips Formation, Cornwallis Island, allow the distinction between the spicular haplentactinid subfamily Secuicollactinae and the nonspicular Rotasphaeridae. This restores Secuicollactinae and returns Secuicollacta to the subfamily from the Rotasphaeridae. Secuicollactinae represent 36 percent of the fauna and are assigned to three genera, Secuicollacta, Diparvapila new genus, and Parvalanapila new genus; these form 27, five, and three percent of the fauna, respectively. The remaining one percent of the subfamily is unassigned. Rotasphaeridae form four percent of the fauna and are represented by Rotasphaera. Secuicollacta is diagnosed on the basis of the presence of an ectopic spicule in addition to several rotasphaeridlike primary units. The salient characters of Diparvapila include two lattice shells with an ectopic spicule on the medullary shell. Parvalanapila is diagnosed on the basis of a lattice sphere overlain by a labyrinthine layer and an ectopic spicule on the lattice sphere. New species described here are Secuicollacta malevola, S. sceptri, S. gliris, S. herrimani, S. segari, S. vallipuellae, S. resodiosae, S. glaebosa, S. teli, Diparvapila hicocki, D. saintrochae, D. larseni, Parvalanapila fleischerorum, and Rotasphaera severa. Four species of Secuicollacta are reported in open nomenclature, as are two of Diparvapila and two of Rotasphaera.

Calcareous articulate brachiopods are rare components of the high diversity, phosphatic, silicified, and epidote coated shelly fauna derived from Middle Cambrian (Floran-Undillan) allochthonous limestone clasts from the Murrawong Creek Formation, southern New England Fold Belt, northeastern New South Wales, Australia. Three taxa are described, the kutorginids Nisusia metula n. sp., and Yorkia sp. indet., and the protorthid Arctohedra austrina n. sp. Yorkia is documented from Australia for the first time. An unusual valve (possibly a brachial valve) of enigmatic affinity is also reported and illustrated. Generically, the taxa provide broad regional paleobiogeographic links with the “first discovery limestone” Member of the Coonigan Formation, western New South Wales, and the Current Bush Limestone in the Georgina Basin, northern Australia, and globally, with broadly contemporaneous sequences in western North America, Siberia, and South China.

Sinemurian and Pliensbachian Exogyrinae from northern Chile described herein as Nanogyra? cf. auricularis are considered the oldest members of the subfamily known to date. Comparisons with a large number of Jurassic Nanogyrini and aberrant Gryphaea species suggest that they are most closely related to Nanogyra? auricularis (Münster in Goldfuss) from the Toarcian of France, but probably not identical. Morphotypes of several Chilean specimens are transitional between gryphaeate and exogyrate forms, and their assignment to either Gryphaeinae or Exogyrinae appears arbitrary. In order to solve this taxonomic problem, the microstructures of Nanogyra? cf. auricularis and co-occurring typical Gryphaea species were examined and compared to a large database from previous studies. The results suggest that shell chambering is a feature common to all Exogyrinae but not to Gryphaea sensu stricto. Complex cross foliation and branching cross foliation are characteristic of both groups. However, they are more abundant in Gryphaea and apparently become phylogenetically reduced in the Exogyrinae. The transitory morphotypes and microstructures, especially of the Sinemurian specimens, are further evidence for the evolution of the Exogyrinae from the Gryphaeinae. Obviously, the Chilean specimens are very close in time and space to the origin of the subfamily. Thus, the lowermost Jurassic Andean back-arc basin of western South America is considered a plausible place of origin of the Exogyrinae.

Scolecodonts, the jaws of polychaetes, are the fossil evidence of the rich and diverse fauna that prospered in shelf seas. Among eunicid polychaetes, the largest jaws in the jaw apparatus occur in pairs. Normally these pairs are not exact mirror images of each other. Rarely, left and right jaws are found to be reversed, the jaw in the left position having the morphology of a mirror image of the normal right jaw and vice-versa. This type of morphological reversal (reversed handedness) is recorded with a frequency that varies from one reversed jaw in 430 to one in 5,838 of normal jaws. Reversed jaws so far are documented in four species from the Upper Ordovician of Indiana, USA, and one species from the Silurian of Gotland, Sweden. The reversed morphology is thought to be a natural, genetically induced feature. The polychaetes with morphological reversal grew to normal size, but never became common.

During the Cambrian and Ordovician trilobites belonging to a variety of clades developed distinctive inflated bulbs on the preglabellar field. We make the case that these bulbs were brood pouches, which were employed for retaining and protecting larval trilobites in order to ensure a higher rate of survivorship. Living arthropods of several classes develop comparable spherical structures—for example the domicilium of certain ostracodes. Living limuloids, likely the trilobites' closest living relatives, carry large and yolky eggs in an homologous, prelabral site. There are some trilobite examples where “species pairs” found in the same fossil sites appear to differ only in the presence or absence of the preglabellar bulb. These may represent the female and male of a single species, respectively. If so, this is the first well-supported case of sexual dimorphism in trilobites. Some more problematic examples are discussed, where alleged dimorphism would have to be more extreme.

The extinction of the Olenellina on Laurentia can be located within centimeters in the C-shale or uppermost Combined Metals Limestone members of the Pioche Formation in eastern Nevada. Olenellid species diversity beneath the extinction boundary is not diminished. One of the richest Laurentian intervals for articulated olenellids is in the 50 centimeters of shale immediately below the extinction boundary at Ruin Wash. Additional morphological information about some of the species comes from a silicified fauna 1.8 m below the extinction boundary at Hidden Valley. The olenellid fauna from the 2-meter interval below the extinction boundary is described. Questions about current generic and subgeneric relationships are discussed. Among general observations, intraspecific variability unrelated to size or taphonomic effects is minimal for most species; at least two species may have been capable of enrollment; and visual surfaces of one species show no evidence of facets. New species include: Olenellus (Olenellus?) fowleri, Olenellus (Paedeumias) chiefensis, Olenellus (Paedeumias) terminatus, Bolbolenellus brevispinus, and Nephrolenellus geniculatus. Olenellus (Olenellus) gilberti Meek and Olenellus (Olenellus) howelli Meek are revised.

Hanburia gloriosa is probably blind, the smaller specimens having a forwardly expanding glabella with lateral lobes, and six (rarely five) thoracic segments; larger specimens have a parallel-sided glabella with faint traces of lateral lobes, and six, in one case seven, thoracic segments; pygidium equal in size to the cephalon. All specimens may be holaspid, the larger corynexochoid-like; however, the smaller ones are not like any known corynexochoid. Hanburia gloriosa is the rarest trilobite from the Stephen Formation. This species, and other rare but widely distributed Lower and Middle Cambrian species from deeper water faunas are all of uncertain affinities. They do not fit into the general picture of trilobite evolution, nor appear likely ancestors of shallow water species.

Phacopida from upper Whiterock (Lower Caradoc) horizons in the Las Aguaditas Formation of San Juan Province, Argentina, include the calymenid Platycalymene trapezoidalis (Baldis and Pöthe, 1995) and the encrinurids Frencrinuroides edseli new species, Lasaguaditas oweni new genus and species, and Walencrinuroides? new species A. Sulcocalymene Baldis and Pöthe, 1995, a purported subgenus of Flexicalymene, is a junior subjective synonym of Platycalymene Shirley, 1936. Platycalymene is now known from Avalonia, Baltica, Laurentia (Scotland), and the Precordillera. Emending the cladistic analysis of Ordovician Encrinurinae by Lespérance and Desbiens (1995), the monophyly and membership of Frencrinuroides and Walencrinuroides are ambiguous. Frencrinuroides edseli is closely related to species from eastern Laurentia. Lasaguaditas new genus is superficially cybelinid-like in some respects but shares several derived characters with the Encrinurinae. All three encrinurinid species in the Las Aguaditas Formation possess two instars in the protaspid period, a general pattern in Ordovician encrinurinid ontogeny.

Cladistic analysis of the trilobite subfamily Acanthoparyphinae Whittington and Evitt, 1954, yields an explicit hypothesis of relationship for the group. All Silurian species together form a robustly supported monophylum including the genera Hyrokybe Lane, 1972, Parayoungia Chatterton and Perry, 1984, and Youngia Lindström, 1885. Sister to this is the Ordovician type species of Acanthoparypha Whittington and Evitt, 1954. Remaining species that have historically been assigned to either Acanthoparypha or Pandaspinapyga Esker and Levin, 1964, form a rather labile paraphylum. Nevertheless, the entire group thus identified is definitely monophyletic, and supported by several prominent synapomorphic character-states.

The basal structure and basal node of the subfamily are more difficult to assess. The relationships of the genera Hammannopyge Přibyl, Vaněk, and Pek, 1985, Holia Bradley, 1930, and Nieszkowskia Schmidt, 1881, need to be addressed within the wider context of the family as a whole. The traditional assignment of Holia to the acanthoparyphines is followed.

Wenlock acanthoparyphines from the Cape Phillips Formation of the central Canadian Arctic islands include several species of Hyrokybe and Parayoungia. They are similar to, and in one case conspecific with, coeval forms to the southwest in the southern Mackenzie Mountains.

Five species are new: Holia glabra, Hyrokybe lightfooti, Hyrokybe youngi, Hyrokybe mitchellae, and Parayoungia mclaughlini. At least four other potentially new species are reported in open nomenclature.

A distinctive trilobite fauna occurs within condensed statigraphic sections of the Lower Mississippian (Tournaisian) Chappel Limestone of the Llano region of Texas, the Welden Limestone of Oklahoma, and the Chouteau Limestone of Union County, Illinois. The seven species comprising this fauna are interpreted to have inhabited sediment-starved basinal environments. The starved-basin facies existed in the south-central United States throughout the Tournaisian (Kinderhookian to Osagean). Two species from this fauna, Australosutura llanoensis, and Carbonocoryphe planucauda, are new. The remaining five species, Griffithidella doris (Hall), Griffithidella alternata (Girty), Carbonocoryphe depressa (Girty), Thigiffides roundyi (Girty), and Pudoproetus chappelensis (Hessler), are restricted to starved-basin facies.

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.

The near-complete skull of the Giant Rat-kangaroo Ekaltadeta ima is described from a middle Miocene deposit at Riversleigh, north western Queensland. Surprisingly, the results of phylogenetic analysis indicate no special relationship with the only other hypsiprymnodontids for which substantial cranial material is known (Hypsiprymnodon moschatus, H. bartholomaii), but within Macropodoidea, a number of derived features present in E. ima are found only in another extinct taxon, the Balbarinae. Recent studies have suggested that Balbarinae may not represent a basal macropodid clade as thought by most previous authors and furthermore that the subfamily is perhaps distinct from all other kangaroos. In light of these findings an interesting possibility is noted, i.e., that Propleopinae and Balbarinae may represent a monophyletic clade to the exclusion of all other taxa. Preliminary results of investigation into dietary habitus indicate that Propleopinae represents a radiation of medium- to large-sized omnivorous kangaroos. Within this clade it is reiterated that a tendency toward carnivory might be inferred from the relative importance of high amplitude vertical shearing versus horizontal shearing and/or crushing elements in the dentition.

Two new specimens of Hyaenodon venturae from the early Chadronian (latest Eocene) of Wyoming provide new information about this rare, miniature hyaenodont, and extend the upper end of the temporal range of the species. The significant difference between H. venturae and H. microdon, the two smallest North American species of Hyaenodon, is the absence of synostosis of the mandibular symphysis in adult H. venturae. In Hyaenodon microdon, from the middle Chadronian, on the contrary, fusion of the symphysis is complete while the individual is still in the juvenile stage of ontogenesis, before the eruption of m3. Within the genus Hyaenodon the ml becomes relatively smaller as the length of the tooth row (pl-m3) increases; this relationship can be demonstrated in the series of species from the miniature H. venturae to the giant H. megaloides.

The ichnogenus Curvolithus Fritsch, 1908, originally described from the Ordovician of the Prague Basin, typically comprises ribbonlike or tonguelike, flattened, endostratal traces with three rounded lobes on the upper surface. However, considerable confusion persists regarding the ichnotaxonomic status and diagnostic features of its ichnospecies. The type specimens of this ichnotaxon, overlooked in most subsequent reports, are redescribed herein. Curvolithus multiplex Fritsch, 1908, the type species, is retained for specimens with a trilobate upper surface and a quadralobate lower surface, in contrast to the criteria adopted by subsequent authors. The other ichnospecies originally proposed from the type locality, C. gregarius Fritsch, 1908, actually consists of a series of grouped parallel scratch marks forming ridges and should be removed from Curvolithus. Subsequently, four ichnospecies were defined: C.? davidis Webby 1970; C. annulatus Badve and Ghare 1978; C. aequus Walter et al. 1989; and C. manitouensis Maples and Suttner 1990. Curvolithus? davidis shows the typical trilobation of Curvolithus apparently in its lower surface, but the morphology of the upper surface is uncertain. Accordingly, it does not warrant ichnospecific assessment, and is regarded as a nomen dubium. The nature of the annulations on the trilobate upper surface of C. annulatus is unclear, and this ichnospecies is also best considered as a nomen dubium.Curvolithus aequus has a bilobate lower surface and probably represents washed out specimens of Didymaulichnus. Finally, C. manitouensis comprises specimens with a smooth, trilobate upper surface and a smooth, quadralobate lower surface, and is best regarded as a junior synonym of C. multiplex. Curvolithus multiplex has been used incorrectly for Curvolithus with a trilobate upper surface and a trilobate to unilobate lower surface. The new ichnospecies, Curvolithus simplex, is proposed herein for such traces. Curvolithus is interpreted as a locomotion trace (Repichnia) of endostratal carnivores, possibly gastropods, flatworms, or nemerteans. Curvolithus is a component of the Cruziana ichnofacies in shallow-marine facies, either of normal salinity or slightly brackish, in the latter case typically associated with fan deltas.

Borings of the ichnogenus Gastrochaenolites have been found in limestone cobbles of the Morrowan (Early Pennsylvanian) Cane Hill Member of the Hale Formation in northwestern Arkansas. They were likely excavated by lithophagid bivalves, thus extending the earliest record of obligate bivalve boring back from the Triassic into the upper Paleozoic. These borings are herein referred to as G. anauchen n. ichnosp. Lithophagid borings may be rare in the upper Paleozoic because of the absence or scarcity of suitable substrates, such as scleractinian corals or carbonate hardgrounds. Additional upper Paleozoic bivalve borings will likely be discovered in other carbonate-rich rocky shore deposits.

The trace fossil Ophiomorpha irregulaire Frey, Howard and Pryor, 1978, has been described chiefly from the Campanian (Upper Cretaceous) of the Book Cliffs of Carbon County, central Utah, U.S.A. Owing to the lack of type specimens and a well-defined type locality, a neotype and new paratypes are designated. Abundant material in the Spring Canyon Member of the Blackhawk Formation at Coal Creek Canyon, Book Cliffs, serves to supply a type locality and allows a more detailed description of the trace fossil than has been available hitherto, leading to an emended diagnosis. At the type locality, O. irregulaire is a shallow-tier trace fossil occurring in marine, delta-front or back-barrier, muddy, fine-grained sandstone. It probably represents the work of a crustacean deposit feeder.