Three species of the Paleozoic coral Palaeacis are described from northeastern Oklahoma and northwestern Arkansas. Included are the Chesterian species P. carinata Girty and P. snideri n. nom., a replacement name for the junior homonym P. cuneata Snider, and the Desmoinesian? species P. erecta n. sp. Coralla of each species exhibit two types of microstructure that characterize two skeletal zones. The outer skeletal zone is composed of numerous parallel trabeculae, mostly between 0.2 and 0.3 mm in diameter, that lie perpendicular to, and have their accretionary surfaces on, the exterior surface of the corallum. Trabeculae are closely spaced laterally and are not organized into rows except uncommonly on the distal portion of some coralla. Where trabeculae coalesce into parallel rows, ornamentation on the corallum exterior consists of parallel ridges or rows of small nodes. Where trabeculae are irregularly arranged, external ornamentation consists of irregularly disposed nodes. The inner skeletal zone consists of radially fibrous stereoplasm arranged into discrete septal spines that coalesce into irregularly developed septal ridges in each calice. In P. erecta, septal spines merge into continuous layers of fibro-normal stereoplasm in some places. On the basis of microstructure, corallum morphology, and external ornamentation P. carinata and P. snideri can be allied with P. axinoides Smyth and P. robusta Webb. Palaeacis erecta falls within the same group on the basis of microstructure and ornament, but has a unique corallum morphology.

Two distinct types of skeletal attachment occur in these Palaeacis species. Palaeacis carinata and P. snideri exhibit an encrusting attachment surface that results in a prostrate growth habit wherein smaller substrates were entirely engulfed, producing free-living coralla. Palaeacis erecta exhibits a small, circular attachment surface and an erect growth habit wherein most skeletal accretion occurs perpendicular to, and away from, the substrate. The substrate is not engulfed and the corallum remains attached and sessile throughout astogeny. Palaeacis erecta is, to date, the only Palaeacis species known to possess this erect, sessile growth form.

The Chesterian Imo Formation of northern Arkansas represents the highest Mississippian strata present on the Ozark platform and contains a unique, although sparse, coral fauna that is transitional between Mississippian and Pennsylvanian assemblages. Of the four most abundant genera represented, Lophophyllidium, Bradyphyllum, and Tectamichelinia are characteristic of Pennsylvanian assemblages and only Amplexizaphrentis is a typical Mississippian form. The fauna is interpreted as part of a shallow-water, muddy bottom community. Of the 11 rugosans and single tabulate coral described, the following are new: Bradyphyllum lesliense n. sp., Amplexizaphrentis maneri n. sp., Lophophyllidium imoense n. sp., and Tectamichelinia mangeri n. gen. and sp.

A new gastropod genus, Dutrochus, is established for members of the family Microdomatidae that are characterized by a reticulate ornament of spiral cords and intersecting, finer collabral threads, with all but one spiral cord being of nearly equal strength, and the single remaining cord being of stronger (nearly twice the order) magnitude and being situated at the periphery. It is represented by the type and only known species, Dutrochus alaskensis n. gen. and sp., from the upper part (lower Middle Devonian; lower Eifelian) of the Lower? and Middle Devonian Cheeneetnuk Limestone, McGrath A-5 quadrangle, west-central Alaska. The genus is very close and nearly homeomorphic to the Permian microdomatid genus Glyptospira, but differs from the latter in possessing an extremely strong, peripheral spiral cord and an extremely thick, multi-layered apertural margin.

A diverse Halobia fauna with rare ammonoids and conodonts is described from the type Martin Bridge Formation (Upper Triassic) of northeast Oregon. The composite section of black shale, mudstone, bedded micrite, limestone conglomerate, and halobiid lumachelle spans the Carnian–Norian boundary without apparent sedimentologic break or pronounced biotic extinction. The occurrence of Halobia radiata radiata Gemmellaro, Halobia? cf. teltschenensis (Kittl), H. superba superba Mojsisovics, and H. superba ornatissima Smith (nomen translatum) with the ammonoids Discotropites sp. and Arietoceltites? sp. low in the section indicates a late Carnian age (Dilleri?, Welleri to Macrolobatus Zones). These fossils occur below beds containing early Norian (Kerri Zone) H. beyrichi (Mojsisovics) and middle Norian (Rutherfordi?, Columbianus Zone) H. halorica Mojsisovics. The described fauna increases the halobiid and ammonoid diversity previously known from the Martin Bridge Formation despite synonymy of species previously reported from the section.

Gedinnian (Early Devonian) orthoceratid cephalopods were previously not well known in Japan. Five species are described from the Fukuji Formation of Gifu Prefecture, central Japan: Michelinoceras yamakoshii n. sp., Michelinoceras yoshikiense n. sp., Plagiostomaceras? sp., Polygrammoceras sp., and Metaspyroceras insignis n. sp. Growth and position of the cameral deposits in Michelinoceras indicate that the deposits precipitated from cameral fluids and living Michelinoceras maintained the shell horizontally in swimming orientation.

Malformations of trilobites are classified as healed injuries, teratological conditions, and pathological conditions. An improved method of recognizing such malformations combines information about the conditions under which cell injury can occur, the processes by which animal tissues react to injury, and trilobite morphology.

Study of healed injuries of polymeroid trilobites shows that injuries attributed to sublethal predation tend to be most commonly preserved on the pleural lobes, the posterior half of the body, and the right side. Statistically significant differences in the number of predation scars between the right and left sides is interpreted as evidence of right-left behavioral asymmetry in some predators of trilobites or the trilobites themselves. Asymmetrical, or lateralized, behavior in present-day animals is one manifestation of handedness, and is usually related to a functional lateralization of the nervous system. Evidence of behavioral lateralization in some Paleozoic predators or prey suggests that those organisms also possessed lateralized nervous systems. Right-left differences in preserved predation scars on trilobites date from the Early Cambrian (Olenellus Zone), and are the oldest known evidence of behavioral asymmetry in the fossil record.

Other examples of structural or behavioral asymmetry from the fossil record of animals are cited. Lateralization is recognized in representatives of the Arthropoda, Annelida, Bryozoa, Echinodermata, Cnidaria, Mollusca, Chordata, and Conodonta, and in trace fossils.

Larval forms of the middle and late Pennsylvanian trilobite Ditomopyge scitula (Meek and Worthen, 1865) have been collected from seven localities in the Desmoinesian of Oklahoma, Missourian of Oklahoma and Texas, and Virgilian of Nebraska and Texas. These larval trilobites have been interpreted as degree 1 through degree 8 meraspides. Although these larval forms are extremely rare, an essentially complete growth sequence was reconstructed and an ontogeny synthesized. During growth, D. scitula absorbed the brim and posterior spines into the pygidium and developed first the lateral then the median preoccipital glabellar lobes; the anterior cephalic margin is more prominent in juvenile stages, becoming narrower in late mersapide molts and finally overlapped by the glabella in early holaspide stages.

Four previously undescribed arthropod trackways from the Lower Permian De Chelly Sandstone of northeastern Arizona are assigned to Paleohelcura and Octopodichnus, originally described from the Coconino Sandstone (Lower Permian) of northeastern Arizona. In addition to P. dunbari and O. minor, a new ichnospecies, O. raymondi, is described. Analysis of the De Chelly specimens, and comparison with similar tracks from the Coconino Sandstone and with experimental traces produced by modern arthropods, clarifies some problems in arthropod trace fossil analysis. The experiments support earlier hypotheses that spiders and scorpions were possible trail makers for the Coconino and De Chelly trackways, and show that features of these tracks can be used to determine direction of movement. These experiments also reaffirm that an animal can produce more than one morphology in a single trackway, patterns that would be classified as two distinct ichnogenera. In addition, the results of this research suggest that the tracks were made on slightly damp sand, and were preserved by being rapidly covered with dry sand.

On the basis of recent collections from the Upper Eocene La Meseta Formation of Seymour Island, Antarctic Peninsula, the morphology, systematic position, taphonomy, and paleoecology of the isocrinid Metacrinus fossilis are investigated. A new species, Notocrinus rasmusseni, is described as the first comatulid crinoid known from the Antarctic fossil record. The systematic assignment of M. fossilis is maintained. Basal abrasion of calyxes and absence of long attached columns suggest that M. fossilis might have lost most of the column in adult stages and lived directly on the substratum, supported by some arms and a few cirri, similar to comatulids. About 10 percent of M. fossilis individuals show brachial regeneration, in contrast to regeneration frequencies of 70–90 percent among modern Japanese isocrinids. The anomalous occurrence of isocrinids in shallow-water facies of the La Meseta is attributed to a combination of reduced predation pressure, the presumed stalkless mode of life, and a favorable temperature regime in Antarctic surface waters prior to the onset of cooling at the close of the Eocene.

The clypeasteroid echinoid Astrodapsis bajasurensis n. sp. is described from upper middle Miocene beds of the Isidro Formation near the mouth of Arroyo Mezquital on the Pacific coast of north-central Baja California Sur, Mexico. The new species is the first occurrence of Astrodapsis outside of California and extends the southern limit of the genus by 1,100 km.

A new assemblage of thalattosaurs is described from the Lower to Middle Triassic Sulphur Mountain Formation of eastern British Columbia. The following new species are described: Thalattosaurus borealis n. sp.; Paralonectes merriami n. gen. and sp.; and Agkistrognathus campbelli n. gen. and sp. In addition, specifically indeterminate material is described. This assemblage extends the geographic range of the Thalattosauria to Canada and demonstrates that thalattosaurs were more taxonomically diverse and widely distributed than previously thought.

Several heretofore undescribed fragmentary specimens of the horned dinosaur Pentaceratops sternbergii (Ornithischia: Ceratopsia) reveal previously unknown features of the skull and extend the known range of morphological variation in this species. Pentaceratops sternbergii possesses a well-developed postfrontal fontanelle and a braincase structure similar to that of other chasmosaurines. The posterior parietal margin bears a pair of upturned epoccipitals on either side of the midline, similar to the short hook-like processes in Anchiceratops. The stratigraphic range of Pentaceratops spans the Late Campanian to Early Maastrichtian but, contrary to previous reports, cannot reliably be extended into the Late Maastrichtian.

Fragmentary bones and teeth of three Late Cretaceous dinosaur taxa occur along both sides of the Georgia-Alabama border, in the extreme southeastern Coastal Plain Province. The localities lie in the middle and upper Blufftown Formation, in nearshore marine deposits. Exogyra ssp. and calcareous nannofossils give a late Santonian through mid-Campanian age range. Taxa determined are: Hadrosauridae, genus and species indeterminate; Ornithomimidae, genus and species indeterminate; and Albertosaurus? sp.

Ischyromys, the most abundant early Oligocene rodent from the Great Plains, has been considered by some workers to represent a single gradually evolving lineage comprising three or more chronospecies. Statistical investigation of large samples suggest instead that two closely related species coexisted, and the shift in mean size that was thought to represent anagenesis actually represents replacement. In Nebraska and eastern Wyoming both I. parvidens (small) and I. typus (large) were rare but of equal abundance in the Chadronian, I. parvidens was more prevalent in the early Orellan, and I. typus was more prevalent in the middle and late Orellan. In northeastern Colorado, northern South Dakota, and North Dakota I. typus is the only species of Ischyromys found in Orellan deposits, thus showing that the two species had differing geographic ranges.

The mean size of I. typus does increase up section at all localities, but this change is minor and not deserving of chronospecies recognition. Much of this change occurred in the latest Orellan and earliest Whitneyan as I. typus approached extinction, and it was accomplished mostly by loss of small individuals rather than a shift of the entire distribution. Rate of evolutionary change in Ischyromys is found to be inversely correlated with population size, and no new species arose during the Orellan when Ischyromys was most abundant.

Webster (1991) is to be congratulated for clarifying the validity of the various contributions made to the literature of fossil echinoderms by V. J. Gupta. However, in correcting the paleogeographic database, an error has crept in which itself needs amending.

During recent years, there has been an increase in the number of papers that include taxonomical descriptions of brachiopods belonging to the order Athyridida. In these papers, the authors do not use the same spelling while referring to suprageneric taxa (e.g., Dagys, 1974; Grunt, 1989; Cooper and Dutro, 1982; Brunton, 1984; Modzalevskaya, 1985; Wang Yu and Rong Jia-yu, 1986; Carter, 1988; Alvarez, 1990) and commonly names or adjectives such as 〈athyroids〉, 〈athyridoids〉, 〈athyridids〉, 〈athyrids〉, 〈athyridaceans〉, 〈athyrididaceans〉 etc. vary considerably.

The late Mississippian ammonoid family Delepinoceratidae is comprised of the genera Platygoniatites and Delepinoceras, and is considered one of the more biostratigraphically significant families for lower Namurian correlation (Manger et al., 1985). Platygoniatites, the earliest member, is known from eastern and southern Europe (Ruzhencev and Bogoslovskaya, 1971; Wagner-Gentis, 1963, 1980) and North Africa (Lemosquet et al., 1985). Despite its wide distribution, Platygoniatites is generally a rare member (with the exception of the southern Ural Mountains) of latest Visean and earliest Namurian faunas. It has never been reported previously from North America, though thousands of ammonoids have been collected here from age equivalent beds. The discovery of a new species of the genus in the late Mississippian faunas of east-central Nevada provides new data for precise correlation of the ammonoid zonations of Gordon (1970) to the type Namurian and indicates a need for revision of the current correlations between the southern Urals and northwestern Europe.

A new Permian bactritoid cephalopod, Aktastioceras nishikawai n. sp., was discovered from the Uyamano Formation of the Taishaku Limestone Group at Miharanoro, Hiroshima Prefecture (Figure 1). The Uyamano Formation represents the Lower Permian portion of the Central Facies, which was defined by Hase et al. (1974) in a large reef complex deposited during the period of Early Carboniferous to Late Permian age. Lithofacies of the formation mainly consist of limestone, including the reef core facies with minor amounts of a limestone conglomerate. The specimens of Aktastioceras occur in light-gray massive limestone of the lowest Uyamano Formation, belonging to the Pseudoschwagerina Zone (Akagi, 1958), which indicates Asselian age. This is the first record of a Permian bactritoid from Japan.

Ceratopsid diversity at the end of the Cretaceous plays a role in interpreting faunal events at or near the Cretaceous–Tertiary boundary in North America. The addition of a new ceratopsid genus within this time frame thus has potential ramifications for the interpretation of these events.

Huene (1935) first reported dicynodonts from the Triassic Santa Maria Formation of southern Brazil. Most common are specimens of Dinodontosaurus from localities near Chiniquà (Chiniquà local fauna) and near Candelaria (Candelaria local fauna) in the state of Rio Grande do Sul. The other Middle Triassic dicynodont found near Chiniquà is the huge (about 3 m body length) Stahleckeria potens, and an equally large Middle Triassic dicynodont, Barysoma lenzii, is known from near Candelaria. A fourth, supposed Santa Maria Formation dicynodont, Jachaleria candelariensis (Araújo and Gonzaga, 1990), is actually from a younger, Upper Triassic, horizon of the Caturrita Formation near Candelaria (Bonaparte, 1982). Here, I argue that Barysoma lenzii is a junior subjective synonym of Stahleckeria potens and discuss the biochronological significance of this synonymy.