Based on material of the Upper Cambrian of Sweden the internal structure of proto-, para- and euconodonts has been investigated. The protoconodontids Gapparodus and Gumella show some special development of the median unit of the skeletal tissue. In Gapparodus, long, parallel-running lamellae suggest a continuous growth, even of previously secreted lamellae, until their eventual outcropping. In Gumella the fibrous median layer decreases considerably during growth until its complete reduction, which coincides with the disappearance of the posterior wall. Paraconodonts also produced several specialities in their mode of growth. Elements with lateral processes such as Proacodus and Serratocambria developed by allometric growth. The lamellae are much more widely spaced in the process than in the main cusp to attain the required length of the former. In Serratocambria additional lamellae are inserted in the process. Thin sections of tricuspidate westergaardodinids reveal paraconodontid growth with lamellar remains in the tip of the median denticle, which are isolated from the growth lines in the lateral denticles. Based on this observation a hypothetical growth model explains the lamellar development as a result of stress and strain. The Ordovician euconodontid Chosonodina clearly shows white matter and is thus unrelated, but homeomorphic to Westergaardodina. Cambropustula from the lower Upper Cambrian is the oldest euconodont yet but it lacks white matter. The latter was an evolutionary novelty, which progressively developed in the euconodont line.

The systematic position of conodonts is briefly discussed; the studied material cannot contribute to the hypothesis of neural crest derived skeletal tissue.

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 shallow-marine fossil biota was recovered from the Blue Bluff unit (formerly part of the McBean Formation) in the Upper Coastal Plain of eastern Georgia. Biochronologically significant mollusks (e.g., Turritella nasuta, Cubitostrea sellaeformis, Pteropsella lapidosa) and calcareous nannoplankton (e.g., Chiasmolithus solitus, Reticulofenestra umbilica, Cribocentrum reticulatum) indicate a latest Lutetian-earliest Bartonian age, or about 40 to 41 Ma. Georgiacetus vogtlensis new genus and species is described from a well-preserved, partial skeleton. Georgiacetus is the oldest known whale with a true pterygoid sinus fossa in its basicranium and a pelvis that did not articulate directly with the sacral vertebrae, two features whose acquisitions were important steps toward adaptation to a fully marine existence. The posterior four cheek teeth of G. vogtlensis form a series of carnassial-like shearing blades. These teeth also bear small, blunt accessory cusps, which are regarded as being homologous with the larger, sharper accessory cusps of basilosaurid cheek teeth.

Storeacolumnella hudsonensis is described as a new genus and species of encrusting, colonial organism that lived in an intertidal, rocky-shore environment. The fossil was discovered in the basal beds of the Upper Ordovician Port Nelson Formation at a coastal outcrop on Hudson Bay near Churchill, Manitoba. Showing some possible characteristics of sponges and other possible characteristics of calcaerous green algae, this matlike organism is considered nonetheless to have uncertain taxonomic affinities. It consists of cylinder-shaped columns, each with an internal system of star-shaped filaments or spicules as viewed in transverse section. The cylinders stand vertical in longitudinal section and are densely packed together to form a mat. The hard substrate to which the mat is attached consists of a boulder eroded from the Precambrian Churchill Quartzite. Maximum colony size observed in a single example exhibits a diameter of not less than 80 mm and maximum thickness of 5.85 mm.

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.

Gondolella pohli new species assemblages, from the Desmoinesian of Illinois, confirm that the initial apparatus reconstruction of the conodont genus Gondolella was incomplete and support later reconstructions based on discrete elements.

Gondolella pohli is the first species of a biostratigraphically important conodont genus to be based primarily on assemblages and to be placed within a known phylogeny. The 43 assemblages confirm the presence of seven distinct element types in the Gondolella apparatus and permit the reconstruction of each of these to a greater degree than previously possible. Because the assemblages are probably all fecal, the apparatus of the closely related Neogondolella is used to interpret the apparatus plan—the position and identity of the 15 elements—single pairs of Pa, Pb, M, Sb1, and Sb2 elements, two pairs of Sc elements, and an unpaired bilaterally symmetrical Sa element in the Gondolella apparatus. Using the similarity of the latter to the apparatuses of the better known ozarkodinids, we infer a three-dimensional fanlike apparatus architecture for the prioniodinid Gondolella. Gondolella is apparently restricted to the Pennsylvanian and probably evolved in the Early Pennsylvanian from the Idioprioniodus-Embsaygnathus lineage by loss of the Pa element posterior process and by remodelling of the other apparatus elements. Some species in the Idioprioniodus-Gondolella lineage are atypical among prioniodinids in having developed a Pa element platform; the lineage is also noteworthy because both ancestor and descendant inhabited low-energy, low pH environments during the Pennsylvanian.

The Ashgillian Pabos Formation underlies the Ashgillian-Llandoverian White Head Formation and consists, in the immediate Percé area, of 21 trilobite taxa. Of these, 11 are left in open nomenclature, four of which are summarily described, commented upon, and illustrated. Ten species are specifically determined and three of these are new: Remopleurides arenosus, Achatella (Achatella) clivosa, and Meadowtownella sacerdos. Hibbertia whittingtoni (McNamara, 1979) is a junior secondary homonym and renamed H. conistonensis. The Ashgillian-Llandoverian cheirurines of the Percé area are reviewed and new generic assignments suggested; these are a major component of the Pabos trilobite fauna. Revision of Ceraurinus icarus, a widely distributed North American species, shows its inherent variability; limits of variation, more complete descriptions, and stratigraphic distribution of most previously described species are also given. The distinctive trinucleid Novaspis elevata occurs in the Pabos, outside the immediate Perce area. Almost all of the Pabos trilobites are also present in the coeval Grande Coupe beds of the Matapedia Group; otherwise they are a mixture of taxa with greatest faunal affinities with North American or northwestern European taxa of the same age.

Leperditiocope ostracodes identified as Sollenella? sp. were discovered in the Gilboa Formation (upper Givetian, uppermost Middle Devonian) within the continental Catskill Magnafacies of New York State. The deposits in which the ostracodes were found are meandering-fluvial facies that were part of a vast alluvial plain that sloped westward from the eroding Acadian Mountains. Hence, ostracodes colonized freshwater habitats earlier than heretofore thought. It has been widely accepted that, until now, the oldest known unequivocal occurrences of freshwater ostracodes are of Late Carboniferous age. This new discovery means that the first colonization of freshwater habitats by Ostracoda occurred approximately 60 million years earlier than previously known.

The hitherto poorly known forefin of Chensaurus chaoxianensis (Ichthyosauria) from the Lower Triassic (Spathian) is redescribed on the basis of the holotype and two new specimens. The humerus resembles that of Utatsusaurus hataii but is distinctive in having an emarginated anterior margin. The anteroproximal prominence of the radius is well developed, unlike that of other ichthyosaurs. All three specimens have five metacarpals and many phalanges, but only three carpals, which are identified as the ulnare, intermedium, and fourth distal carpal. These specimens show that delayed mesopodial ossification occurred in ichthyosaurs, at least in an early evolutionary stage. Because delayed mesopodial ossification is common among diapsids and is unknown in Jurassic ichthyosaurs, it was lost during the evolution of the Ichthyosauria. The osteogenic developmental axis appears to have continued into the fourth digit, as in other amniotes. The ossification pattern provides conclusive evidence to support the suggestion that the basal element of the fifth digit in Early Triassic ichthyosaurs is a metacarpal, rather than a carpal.

The siphonophrentidae is a family of Devonian rugose corals that are known mostly from eastern North America, a part of the Eastern Americas biogeographical Realm (EAR) during the Devonian. Breviphrentis Stumm, 1949, has been considered a siphonophrentid by most previous authors and, in a recent monograph (Oliver, 1993), I described three EAR species as Breviphrentis and referred others to the genus.

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 scarce fossil record of stomatopod crustaceans is extended with three new species and two new genera described from the Miocene of California. Squilla laingae new species and Angelosquilla altamirensis new genus and species show clear affinities to the Recent family Squillidae. Topangasquilla gravesi new genus and species can be accommodated within the Recent family Lysiosquillidae. These new species occur in the Monterey and Topanga Formations in Los Angeles County. In addition, three other specimens are described from the Miocene Topanga Formation. The preservation of these stomatopods is among the best noted for any fossils of this group. These specimens show characteristic stages of decay that clearly correspond with those noticed in taphonomic experiments with Recent stomatopods.

Pupae of the nonbiting midge Chaoborus are reported from the middle Eocene (Claibornian) Tallahatta Formation in Benton County, Mississippi. These pupae are placed within the genus Chaoborus because the shape of the respiratory organs, length of the abdomen, and shape of the anal paddles closely resemble other species of this extant genus. This occurrence represents the oldest record of Chaoborus pupae and the first record of fossil Chaoborus from North America. The flora and fauna found associated with the fossil pupae along with the known habitats of extant Chaoborus pupae indicate a lentic environment. This interpretation corresponds to the depositional environment of similar Eocene-aged clay deposits in western Tennessee.

Ninety-one specimens of Pentremites Say from the Mississippian Chesterian display color patterns. The darker color patterns represent a thin veneer of pigmented calcite which is barely visible on a polished surface or thin section, but which can be removed with dilute hydrochloric acid. Preservation appears to be best in specimens from shallow marine clays and shales. The patterns represent four color patterns, each consisting of different shades of calcite, and ranging in color from tan to black. Color patterns generally, but not always, cross growth lines. Type 1 has arched chevron patterns on the deltoids, horizontal lines on the radials, and triangular bands on the basals. Type 2 has darkened deltoids or concave chevrons on the deltoids and darkened areas concentric to the radials, and sometimes alternating light and dark bands conforming to growth lines on the radials. Type 3 has sloping lines crossing the radials, concave chevrons on the deltoids, and darkened areas on the lower radials, concentric to the ambulacra and on the basals. Type 4 has dark dots concentric to the lower ambulacra, arched chevrons on the deltoids and transverse lines abutting the radials and on the basals. The color patterns are original and may have been exposed on the outside of the integument.

Feminization of adult male xanthid crabs, Tumidocarcinus giganteus Glaessner, from the Miocene of New Zealand, represents the first notice of the phenomenon in the fossil record. Marked broadening of the abdomen of adult males, to assume a form much like that of mature females and limitation in the size of the major claw likely result from parasitic castration by rhizocephalan, probably kentrogonid, barnacles. A sexually aberrant dakoticancrid, Dakoticancer overanus Rathbun, from the Late Cretaceous of South Dakota (Bishop, 1983) may extend this coevolutionary relationship between parasitic barnacles and decapod crustaceans into the Mesozoic.

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.

Four new fossil mammalian assemblages are now recognized from west central Nevada. The late Barstovian or earliest Clarendonian Eagle-Picher Mine Site assemblage was recovered from the upper sedimentary member of the ?Desert Peak Formation exposed in the northeastern Virginia Range of Storey County and consists of the following taxa; Camelidae, gen. indet. and Rhinocerotidae, gen. indet. The ?Clarendonian Churchill Valley Local Fauna and Clarendonian or Hemphillian Churchill Narrows Site assemblage were recovered from correlatives of the type Coal Valley Formation exposed along the southern flanks of the Virginia Range and in the vicinity of the Churchill Narrows area, respectively. The Churchill Narrows Site assemblage consists of the following taxa: Rhinocerotidae, gen. indet.; Camelidae, gen. indet. (small-sized); and Camelidae, gen. indet. (large-sized). The Churchill Valley Local Fauna consists of the following taxa: Leporidae, gen. indet.; cf. Mustelidae, gen. indet.; Teleoceras sp. indet.; Dinohippus sp. indet.; Camelidae, gen. indet. (small-sized); and Camelidae, gen. indet. (large-sized). The late Hemphillian Silver Springs Local Fauna was recovered from outcrops of the Truckee Formation exposed in the southeastern Virginia Range of Lyons and Churchill counties. It is the first biostratigraphically datable fauna from the upper member of the formation and consists of the following taxa: Lepoides cf. lepoides; Hypolagus ringoldensis; Hypolagus tedfordi; Hypolagus sp.; Pliotaxidea sp. indet; Teleoceras sp. indet.; Dinohippus sp. indet.; Hemiauchenia vera; Camelidae, gen. indet. (medium-sized); and Antilocapridae, gen. indet.

Shi and Waterhouse (1996, p. 127) proposed a new genus, Yukonella, for a distinctive licharewiinid species (Spiriferida, Brachiopoda) based on well-preserved material from the Lower Permian upper Jungle Creek Formation, northern Yukon Territory, Canada. However, the Editor of the Zoological Record, Mrs. M. Joan Thorne (personal commun., 1997), has kindly informed me that the name Yukonella is preoccupied by an Upper Triassic poriferan genus published by Senowbari-Daryan and Reid (1986, p. 900). I therefore rename the brachiopod genus Nahoniella after the Nahoni Range in the northern Ogilvie Mountains of northern Yukon Territory, Canada, where the type species of the genus, Nahoniella plana (Shi and Waterhouse), was collected.