A new bivalve, Yonginella amica n. gen. and sp., is described from the Silurian of Gotland. Although it has a straight hinge line with cardinal and lateral teeth indicating relationship with the Cyrtodontidae of the Arcoida, its external morphology (with a conspicuous diagonal ridge and sulcus) differs considerably from all previously described taxa of this group. Yonginella amica exhibits a shell shape suitable for soft muddy bottoms (“snowshoe” adaptation), and is interpreted to have been a nonsiphonate suspension feeder with a semi-infaunal, byssate mode of life.

The Roxton Limestone Member at the top of the Gober Chalk in northeast Texas yields a rich fauna, dominated by Baculites haresi Reeside, 1927, and Inoceramus balticus Boehm, 1909, with sparse occurrences of Pachydiscus cf. P. paulsoni (Young, 1963), Anapachydiscus sp. juv., Placenticeras placenta (DeKay, 1828), Hoplitoplacenticeras aff. H. plasticum (Paulcke, 1907), Menabites (Delawarella) delawarensis (Morton, 1830), M. (D.) danei (Young, 1963), M. (D.) aff. M. (D.) vanuxemi (Morton, 1830), Submortoniceras vandalinaense Young, 1963, Submortoniceras sp., Eubostrychoceras sp., and Scaphites hippocrepis (DeKay, 1828) III. The presence of S. hippocrepis III suggests a late early Campanian age assignment for the fauna. The assemblage includes species known from the Western Interior, Gulf Coast, Atlantic seaboard, and western Europe.

Two new species of pectinid bivalves, Camptochlamys alaskensis and Chlamys aquilonia, are present in shallow-marine deposits near Ocean Point, northeastern Alaska, at about 70°N latitude. The precise age of these deposits is debatable, but paleontological and isotopic age estimates indicate placement near the Cretaceous–Tertiary boundary. The occurrence of Camptochlamys extends the chronostratigraphic and geographic range of this genus, previously unknown from any strata above the uppermost Jurassic (Tithonian) of Europe and unknown from any strata in North America. In contrast, the new Chlamys species represents an evolutionary advance beyond its nearest relative in the Maastrichtian of northern Europe and resembles Cenozoic members of its clade in certain features of shell microstructure. These new species are thus a microcosm of the debate regarding the age of these deposits and strengthen the hypothesis that the Ocean Point fauna lived in an Arctic Ocean basin that was isolated from the world ocean.

A proposed new genus of scalpellomorph cirriped, Tetrinis n. gen., based on T. serenuportus n. sp., is known from three Kansas localities in the middle part of the Fairport Member of the Carlile Shale where it is epizoic on the bivalve Inoceramus cuvieri. The stalked cirriped Stramentum elegans coexisted with T. serenuportus and the bryozoan Proboscina sp. was epizoic on S. elegans but not on T. serenuportus. The genus is readily distinguished from all other scalpellomorph cirripeds in the character of the capitulum, which comprises 28 slightly overlapping plates arranged in four whorls. Tetrinis serenuportus displays a large rostrum and an upper latus that is situated low in the capitulum between the scutum and tergum, allowing the two latter plates to touch. All umbos are apical except for that of the scutum, which is subapical and closer to the apex than to the base. The new form apparently has a narrow stratigraphic range and has potential as a biostratigraphic marker.

Llandovery Encrinurinae from the Whittaker Formation in the central Mackenzie Mountains include Cromus canorus n. sp., Distyrax cooperi n. sp., Distyrax n. sp. A, Perryus bartletti n. sp., and Encrinurus n. sp. Additional diversity of Distyrax Lane, 1988, demands a revised generic diagnosis with emphasis on pygidial homologies; new species are described from the Llandovery of Newfoundland and Ontario. Several characters suggest a sister group relationship between Distyrax and Encrinurus s.s. A lectotype is designated for the Llandovery species Encrinurus elegantulus Billings, 1866. Cromus canorus n. sp. is closely allied to other northern Laurentian Llandovery species. Synapomorphies of Cromus are inclusive for Encrinuraspis as revised by Snajdr, 1985. The long stratigraphic range and morphological conservatism of Cromus are correlated with occurrence in distal mudstone facies. Ontogenetic material for Distyrax n. sp. A, Cromus canorus, and Perryus bartletti is described, with consideration of librigenal spine homologies in Encrinurinae. Humaencrinuroides Nan, 1985, is a pliomerid of the new subfamily Quinquecostinae, and not a subgenus of Encrinuroides Reed.

The remaining terrestrial gastropod fauna of the late Oligocene–early Miocene Cabbage Patch beds of western Montana is composed of nine new species, all from extant genera now occurring in the western United States: Vallonia berryi, [Succineidae] montana, Nesovitrea pulchra, Deroceras securis, D. mahiz, Punctum alveus, Polygyroidea montivaga, Oreohelix brandi, and Monadenia? n. sp. A, which is described from neanic material. All except the Monadenia? represent first occurrences of the respective genus in North America. The terrestrial fauna suggests that climatic and environmental conditions during the late Oligocene–early Miocene interval must have been very similar to those of the present. Two sizes of gastropod eggs, attributed to P. montivaga and V. berryi, were found at one locality. Monadenia? n. sp. A is of limited use, due to rarity, as an index fossil for the upper Cabbage Patch beds.

Specimens of the ammonite genus Balatonites from the Middle Triassic of Austria and Hungary are analyzed morphometrically to obtain growth invariant character states. A new method transforming growth dependent qualitative characters into age invariant metric variables is developed. Weighted standardization as a method preserving univariate discriminatory efficiency is applied to character states preceding numerical classification procedures, resulting in a clearer separation of homogeneous groups in comparison to simple standardized data. All clustering and ordination procedures produce two identical classes, which are interpreted according to the cohesion concept as distinct biological species. In adherence to the taxonomic rules they are denominated as Balatonites egregius Arthaber and Balatonites balatonicus (Mojsisovics).

Although numerical methods are highly useful in paleontological studies, potential problems arise with application of parametric statistical methods to paleontological data. Most common statistical tests assume data are normally distributed and that multiple populations have equal variances (homoscedasticity). Paleontological data frequently do not satisfy these assumptions, thereby affecting results of tests and potentially misleading scientific interpretations. Nonparametric tests should be used when assumptions of parametric tests are violated. Normal scores tests, which utilize expected normal deviates (rankits) substituted for original data, are the most powerful nonparametric tests. Despite their potential utility, normal scores tests have received little attention, primarily because of difficulties encountered with rankit conversion.

Recent advances in microcomputer technology provide viable methods for rankit conversion, thus making normal scores tests accessible for routine application. Normal scores tests provide a practical method of dealing with nonnormality and heteroscedasticity common in paleontological data.

The Port au Port Group of western Newfoundland is a sequence of Upper Cambrian (Marjuman–Sunwaptan) shallow subtidal–supratidal carbonates and fine siliciclastics that are organized into three large scale sedimentary grand cycles. Low diversity trilobite faunas from the Marjuman and Steptoean portions (March Point and Petit Jardin Formations) include 17 species that are assigned to 16 genera; one species, Coosina kindlei, is new. Biostratigraphic analysis confirms earlier suggestions that the grand cycles boundaries record major intervals of onlap that can be recognized in other parts of North America and may be related to eustatic sea level rises.

Silurian (Llandovery–Ludlow) Encrinurinae from Wisconsin, Indiana, and Illinois include species of Balizoma Holloway, 1980, Curriella Lamont, 1978, Distyrax Lane, 1988, Encrinurus Emmrich, 1844, Mackenziurus Edgecombe and Chatterton, 1990a, and Nucleurus Ramsköld, 1986. Mackenziurus lauriae n. sp. is described from Wenlock strata of the Racine and Sugar Run Dolomites; nine segments in the holaspid thorax are the fewest known for any encrinurid. A square rostral plate is diagnostic of Mackenziurus. New morphological data are provided by Illinois specimens of Balizoma indianensis (Kindle and Breger, 1904) from the Wenlock–Ludlow Racine Dolomite, and of Curriella tuberculifrons (Weller, 1907) from the Llandovery Elwood–Wilhelmi Formations. Nucleurus n. sp. is possibly from Llandovery strata in Wisconsin. Distyrax n. sp. occurs in the Brandon Bridge Member (late Llandovery–early Wenlock) of the Joliet Dolomite in Illinois. The type pygidia and possible topotype material of Encrinurus nereus Hall, 1867, confirm assignment to that genus as currently viewed; this reefal species is distinct from the closely related inter-reef species E. egani Miller, 1880, and appears to be distinct from reefal E. reflexus Raymond, 1916. Lectotypes are selected for these Encrinurus species.

Paleoecological analysis of three attached spiriferid species (Punctospirifer kentuckyensis, Crurithyris planoconvexa, and Hustedia mormoni) and six free-living chonetid brachiopod species (Chonetinella flemingi, Chonetinella verneuiliana, Lissochonetes geinitzianus, Mesolobus mesolobus, Neochonetes fragilis, and Quadrochonetes geronticus) from Middle and Upper Pennsylvanian strata of north-central Texas has been undertaken using, in part, population dynamics information derived initially from size-frequency distributions. The brachiopod populations in this study are believed to represent in situ assemblages formed by noncatastrophic mortality. Spiriferid species occurred in large populations characterized by positively skewed size-frequency distributions in which few individuals attained the maximum potential size reported for a given species. Chonetid species, in contrast, occurred in smaller numbers characterized by negatively to low positively skewed size-frequency distributions in which greater numbers of individuals attained maximum potential size.

The differences observed in the population structure of these two groups can best be explained as reflecting different adaptive lifestyle strategies that are shared at the ordinal level. Morphological features common to chonetid species enabled individuals to live freely at the sediment-water interface and perhaps reorient their position if disturbed. Based on size-frequency analysis, low-density populations of chonetids appear to produce relatively larger numbers of survivors in the adult and maximum size classes. Spiriferids were constrained to attachment surfaces occupied at the time of larval settlement, and individuals presumably had no mechanism to regain life position if overturned or if this surface became unstable. These physical limitations seem to be reflected in a population structure in which higher density populations were required to overcome the high mortality rates incurred by individuals. This appears to be a case in which size-frequency distributions have not been significantly altered by taphonomic overprint and in which size-frequency analysis can be used to detect differences in the life histories and population structure of brachiopod species.

Describing the chemical ontogeny of 36 specimens of Nautilus allowed the identification, as well as the determination of the relative effects, of the controls on Mg and Sr concentration in skeletal aragonite. The previously documented trend that aragonite contains higher concentrations of Sr than Mg persists within skeletal structures of Nautilus. This relationship suggests that neither physiological nor environmental controls overwhelm the mineralogical control. Significant differences in Mg and Sr concentrations of nacreous shell, prismatic shell, and septal nacre suggest that these structures may form from extracellular fluids with differing elemental concentrations. Many specimens exhibit greater variability of Mg and Sr concentrations in juvenile portions of the skeleton than in more mature portions. This suggests that either the physiochemical system matures during ontogeny and achieves increasing control over skeletal chemistry or the organism adjusts to the new conditions and behavioral maturation stabilizes elemental concentrations by reducing stress. The decreased growth rate that Nautilus experiences as it approaches maturity does not effect Mg or Sr concentrations. Differences in combined Mg and Sr concentrations among species of Nautilus indicate that extracellular fluids that produce each skeletal structure are chemically distinct, with the exception of the fluids that produced septal aragnite of N. belauensis and N. scrobiculatus, and exemplify phyletic control of trace element concentration at the species level. Although significant chemical separation exists among species of Nautilus, sufficient variation and overlap persists in elemental concentrations to make a classification based solely on these two elements ineffective. Significant chemical differences between two sympatric species of Nautilus demonstrate that physiological systems, and not environmental variables, primarily control elemental concentrations in skeletal aragonite.

Species of the late Osagean and early Meramecian advanced cladid crinoid genera (suborder Poteriocrinina) Armenocrinus, Bollandocrinus, Corythocrinus, Cosmetocrinus, Culmicrinus, Cydrocrinus, Histocrinus, Hypselocrinus, Lebetocrinus, Ophiurocrinus, Poteriocrinites, Scytalocrinus, Springericrinus, and Ulrichicrinus from Illinois, Indiana, Iowa, and Missouri are redescribed and redefined from study of type material. Nomenclatural and systematic acts include the following: 1) Poteriocrinus tenuidactylus Worthen, 1882, is a senior synonym of Scaphiocrinus obscurus Wachsmuth and Springer, 1886, and is assigned to Armenocrinus; 2) P. verus Miller and Gurley, 1890, is assigned to Culmicrinus; 3) P. mammaeformis Worthen in Miller, 1889, is questionably assigned to Culmicrinus; 4) Cydrocrinus coxanus (Worthen, 1882) is a junior synonym of C. concinnus (Meek and Worthen, 1870); 5) Decadocrinus stellatus Lane and Howell, 1986, is questionably assigned to Histocrinus; 6) P. crawfordsvillensis Miller and Gurley, 1890, is a junior synonym of Hypselocrinus hoveyi (Worthen in Worthen and Meek, 1875); 7) Hypselocrinus boonvillensis (Miller, 1891) and H. neglectus (Miller and Gurley, 1896) are junior synonyms of H. arcanus (Miller and Gurley, 1890); 8) Hypselocrinus vansanti n. sp. is described; 9) Hypselocrinus indianensis (Meek and Worthen, 1865) is a nomem dubium; 10) Poteriocrinus arachnaeformis Worthen, 1882, is a valid species of Poteriocrinites; 11) P. cantonensis Miller and Gurley, 1890, is assigned to Scytalocrinus; 12) Ulrichicrinus coryphaeus (Miller, 1891), P. amoenus Miller, 1891, and P. brittsi Miller, 1891, are junior synonyms of U. agnatus (Miller, 1891); and 13) P. illinoisensis Worthen, 1882, is questionably assigned to Ulrichicrinus.

Bollandocrinus? sp. from the Keokuk Limestone might represent the first report of the genus from North America, being previously known only from the lower Carboniferous of Great Britain. Ophiurocrinus sp. from the Keokuk Limestone is the first report of this genus from the Osagean, being previously known only from the Chesterian of North America and the upper Carboniferous of Europe.

Very well preserved specimens of a macruran decapod from the Lower (Lacustrine) Member of the Ñirihuau Formation, northwestern Patagonia, Argentina, permitted description of Lammuastacus longirostris, a new genus and species of Parastacidae. The sedimentological and paleontological evidences provided by the faunal assemblage indicate a freshwater environment. This is the first certain record of a fossil Parastacidae from Tertiary deposits, most probably Oligocene. The fossil material shows similarities with Geocharax, the extant Australian genus considered to retain many primitive characters, and other related genera from New Zealand and Chile.

The first Laurentian records of Pacificurus Ramsköld, 1986 are provided by Pacificus chilorhodus n. sp. (latest Llandovery?–early Wenlock, Mackenzie Mountains, Canada) and Pacificurus sp. A (early Ludlow, northern Maine). These closely related species represent an early divergence (minimally late Llandovery) from Australian/Asian congenerics.

Seventeen flexible crinoids, including three new species, are reported from the Fort Payne Formation with new material from Cumberland, Clinton, and Russell Counties in south-central Kentucky and from Clay County, Tennessee. This study extends the geographic range of all taxa studied, as only seven species were previously known from the Fort Payne Formation. Fort Payne flexible crinoids include Taxocrinus colletti, Onychocrinus ramulosus, O. grandis n. sp., Nipterocrinus monroensis, Mespilocrinus romingeri, M. kentuckyensis n. sp., Gaulocrinus veryi, G. robustus, G. trauscholdi, G. bordeni, G. symmetros n. sp., Metichthyocrinus tiaraeformis, M. clarkensis, Forbesiocrinus pyriformis, F. saffordi, F. wortheni, and Wachsmuthicrinus spinosulus. Mespilocrinus columnals are also described, and the diagnosis of N. monroensis is emended. The Fort Payne Formation occurrence of O. exsculptus could not be verified. Forbesiocrinus multibrachiatus and Parichthyocrinus crawfordsvillensis are considered to be junior synonyms of Forbesiocrinus wortheni. Fort Payne flexible crinoids in the Lake Cumberland area occur at nine localities in four facies types. No more than three species occur at any Fort Payne locality.

The concept of the Ordovician gastropod genus Maclurites Le Sueur, 1818, at present includes much variation. Maclurina Ulrich in Ulrich and Scofield, 1897, is removed as a subjective synonym of Maclurites and reestablished as a separate genus. Species of Maclurites with spiral grooves on the outer whorl surface and a relatively small umbilicus are transferred to Maclurina. Maclurina manitobensis (Whiteaves, 1890) forms a distinctive part of the Late Ordovician-age “Arctic Ordovician fauna.” An unusually large specimen (25 cm in diameter) from the Bighorn Dolomite (Upper Ordovician), Wyoming, is illustrated; this Wyoming specimen is the volumetrically largest Paleozoic gastropod ever reported.

Twenty-four fragmentary specimens and numerous disarticulated plates of a new clavate agelacrinitid edrioasteroid were collected from the Middle Pennsylvanian Naco Formation in central Arizona. Spiraclavus nacoensis n. gen. and sp. is similar to Lepidodiscus laudoni (Bassler, 1936) and Discocystis kaskaskiensis (Hall, 1858), but differs in the direction of ambulacral curvature and in the number and arrangement of ambulacral cover plates. Numerous well-preserved, disarticulated plates allow a full description of plate morphologies from various parts of the theca. The entire oral surface is rigidly constructed of tessellate plates. Interlocking serrate sutures between successive floor plates add strength. Plate sutures in the flexible and telescoping portions of the theca (recumbent zone and pedunculate zone, respectively) are beveled, allowing considerable imbrication and potential for thecal extension.

The associated fauna indicates that the unit containing the edrioasteroids was deposited on an offshore, subtidal, marine carbonate shelf with occasional siliciclastic influxes. The specimens of Spiraclavus nacoensis were buried by siliciclastics, probably during storm events.

The Mississippian crinoid genus Dizygocrinus is revised, and the phylogeny is inferred. Eleven species are recognized, including D. biturbinatus (Hall), D. indianaensis (Lyon and Casseday), D. caroli (Hall), D. whitei (Wachsmuth and Springer), D. originarius (Wachsmuth and Springer), D. montgomeryensis (Worthen), D. gorbyi (Miller), D. venustus (Miller), D. peculiaris (Miller and Gurley), D. mutabilis (Wachsmuth and Springer), and D. cantonensis (Wachsmuth and Springer). Nomenclatoral revisions include recognition of D. gorbyi and D. peculiaris as valid species and designation of the following as junior synonyms: D. calvus, D. crawfordsvillensis, D. intermedius, D. mediocris, and D. somersetensis. Dizygocrinus is now recognized from both the late Osagean and Meramecian on both the eastern and western margins of the Illinois Basin.

Dizygocrinus is first recognized virtually simultaneously on both the eastern and western margins of the Illinois Basin. Migration proceeded in both directions, but was most common later in the history of the genus. The principal radiation on the western basin margin was among species with generally smooth aboral cup plates, whereas on the eastern margin sculptured species account for the principal species radiation.

New materials from the Permo-Pennsylvanian of north-central New Mexico permit a new description of the temporal and occipital regions of the diadectomorph Diadectes. The important issue of the fate of the intertemporal bone is resolved by demonstrating its absence and apparent incorporation into the parietal as a lateral lappet. Four cranial autapomorphies of Diadectes are recognized: 1) loss of contact between postparietal and tabular; 2) supratemporal greatly enlarged with well-developed occipital process; 3) tabular no longer exposed on skull roof, but greatly reduced and incorporated into occipital plate, with a coarse, posteromedially facing surface; and 4) skull roofing bones thick and porous, with a consistent network of U-shaped grooves. The temporal–occipital region of Diadectes is compared with those of holotypic and recently collected specimens of Limnoscelis and Tseajaia, the type genera of the other two recognized diadectomorph families, Limnoscelidae and Tseajaiidae. On the basis of the literature the comparisons are extended to include certain late Paleozoic amniotes: synapsid Pelycosauria, Captorhinomorpha, and the primitive diapsid Petrolacosaurus. The results are subjected to a cladistic analysis, which supports the following hypotheses of relationships: 1) Diadectidae, Tseajaiidae, and Limnoscelidae form a natural group, the Diadectomorpha; 2) Diadectes and Tseajaia share a more recent common ancestor than either does with Limnoscelis; 3) Diadectomorpha, Pelycosauria, and their descendants form an unnamed, primitive sister clade to that consisting of Captorhinomorpha, Petrolacosaurus, and their descendants; and 4) the taxon Cotylosauria (sensu Heaton, 1980), consisting of Diadectomorpha and Seymouriamorpha, is paraphyletic and invalid. The third hypothesis dictates the assignment of Diadectomorpha to Amniota.