Living ectocochliate cephalopods have long been thought to be restricted to a single genus, Nautilus Linnaeus, 1758, comprising five or six extant species. The shells of two species, N. scrobiculatus Lightfoot, 1786, and N. perforatus Conrad, 1847, are quite distinct, but no soft-parts were known until 1984, when N. scrobiculatus was seen alive for the first time. Dissections show that significant anatomical differences exist between N. scrobiculatus and other Nautilus species, including differences in gill morphology and details of the male reproductive system. These differences, along with phylogenetic analysis of extant and selected fossil nautiloid species, indicate that N. scrobiculatus, and N. perforatus should be distinguished from Nautilus as a newly defined genus, Allonautilus. This analysis contradicts previous phylogenies proposed for the Nautilida, which placed Nautilus as the last-evolved member of the order. We surmise that Allonautilus is a descendent of Nautilus, that the latter is paraphyletic, and first evolved in the Mesozoic, rather than in the late Cenozoic, as has been previously suggested.

New finds of the trilobites Cobboldites tichkaensis Geyer, 1988, Pseudocobboldia pulchra (Hupé, 1953), Protolenus (Protolenus) densigranulatus Geyer, 1990, Latoucheia (Latoucheia) tichkaensis Hupé, 1953, and Acanthomicmacca neltneri Hupé, 1953, from the basal Middle Cambrian near the peak of Tizi n'Tichka in the central High Atlas, Morocco, supplement the known morphology of these species; the trilobites Acanthomicmacca new species, Oreisator tichkaensis new genus and species, and “Parasolenopleura” sp. from that locality are new. Acanthomicmacca neltneri is the first species of the genus and family that is described and figured in detail in terms of morphologic plasticity and ontogeny; Oreisator tichkaensis is the first ptychopariacean trilobite formally described and based on material from Africa. Trilobites and other fossils from the locality suggest a strong affinity to other Mediterranean and to Avalonian faunas, which is well supported by helcionelloid and hyolith genera.

Molds of numerous Early Carboniferous echinoderms collected by Christian van de Loo for James Hall in 1867 from four miles south of Crawfordsville, Montgomery County, Indiana and now in the collection of the New York State Museum have been examined using latex casting techniques. Described here are the ophiuroids Vandelooaster plicatilis new genus and species, Schoenaster fimbriatus Meek and Worthen, Aganaster gregarius Meek and Worthen and Lumectaster howelli new genus and species. The types of Calyptactis confragosus Miller are redescribed for comparison. Nine crinoids, a blastoid, and an echinoid are recognized in van de Loo's collection; all have been recorded from Crawfordsville.

Rare specimens of the Late Cambrian primitive libristomate trilobite “Cedaria” woosteri from the Eau Claire Formation of north-central Wisconsin preserve an unusual and new ocular suture, and the impressions of lens facets. The suture is circumocular, but loops abaxially onto the ocular platform. The portion of the ocular platform that is enclosed by this suture and is fused with the visual surface is here termed the “ocular plate”. The size and arrangement of the lens facets show that “C.” woosteri possessed a holochroal eye, typical of that known in other Cambrian libristomate trilobites. This nearshore assemblage, while low in diversity, contains a disparate array of trilobite morphotypes.

Intexalvichnus magnus, new ichnogenus and ichnospecies, is erected for material from the Lower Carboniferous of northwest Ireland. This ichnogenus is characterized by a horizontal primary basal gallery, from which a series of secondary near-vertical shafts originate on either side of the gallery. Intexalvichnus magnus is typified by vertical shafts occurring in offset closely packed pairs on either side of the horizontal gallery, and by their recurved conical morphology. Such material somewhat resembles Phycodes, and in particular “Phycodes” pedum, although overall morphology and mode of construction distinguish I. magnus from Phycodes (including “P.” pedum), warranting separate ichnogeneric status. Although forming monospecific associations, I. magnus occurs within shallow-water deltaic sand-dominated facies with diverse ichnofaunal assemblages. Consideration of ichnofaunas from similar shallow-water paleoenvironments suggests that I. magnus should be globally and stratigraphically widespread. Perhaps because of its relatively large size I. magnus has been overlooked, or referred to other ichnogenera.

Streptognathodus Pa elements dominate conodont faunas from the proposed Carboniferous-Permian boundary stratotype at Aidaralash Creek, northern Kazakhstan. The phyletic development of this genus provides the means for subdividing the late Gzhelian to early Sakmarian prodeltaic section (Beds 9-37) into six zones. The preferred Global Stratotype Section and Point (GSSP) for the base of the Permian System is 27 m above the base of Bed 19 at the first occurrence of Streptognathodus isolatus Chernykh, Ritter, and Wardlaw, 1996. This arbitrarily chosen point in the evolutionary continuum of nodose streptognathodids is recognizable in basinal rocks elsewhere in the Ural trough (lower part of Bed 16 at Usolka) as well as the cyclic shelf succession of the American Midcontinent (Glenrock Limestone Member of the Red Eagle Limestone).

Eight new species of Streptognathodus occur in the Aidaralash collections: S. bellus n. sp., S. costaeflabellus n. sp., S. flexuosus n. sp., S. glenisteri n. sp., S. longilatus n. sp., S. rectangularis n. sp., S. sigmoidalis n. sp., and S. tenuialveus n. sp. In addition, three morphotypes with limited occurrence (S. sp. A-C) are left in open nomenclature. New collections of topotype material from the nearby Tabantal River section permit clarification of S. barskovi (Kozur).

The axial rings of the thorax of seven Ordovician species of Illaenidae, and of the type species of the Silurian Cybantyx, all have the ring curved downward and forward, lacking the articulating furrow but traversed by a stout ventral ridge; the doublure similarly curves downward and forward. This type of axial ring is apparently unique among post-Cambrian trilobites. The axial ring in Scutelluidae is like that occurring in most post-Cambrian trilobites, having a convex ring, deep articulating furrow, and horizontal half ring and doublure. These and many other characters distinguish the Styginidae-Scutelluidae group from Illaenidae. Cybantyx is not an effaced scutelluid, but an illaenid. Upper Cambrian illaenid-like trilobites, which have the illaenid type of thoracic axial ring, deserve consideration as possible ancestors of post-Cambrian illaenids. The thorax is given considerable flexibility by the illaenid axial ring, enabling the body to have been flexed unusually strongly concavely dorsally, as well as to enroll. The musculature suggested omits dorsal longitudinal muscles. It is argued that many illaenids may have been vagrant benthos, particularly adapted for negotiating over irregular surfaces. The view that illaenids lived partly in a burrow is not supported by specimens preserved in such an attitude. The arrangement and varying strength of the terrace ridges on the exoskeleton of Cybantyx is consistent with their having had a sensory function; anastomosing caeca on the fixed cheek and the pleural region of the pygidium are described.

Shelly fossils from the basal Middle Cambrian, near the peak of Tizi n'Tichka in the central High Atlas, Morocco, include the new hyolithids Oboedalites peregrinus new species, Emarites decorissimus new genus and species, Patholites insolitus new genus and species, Rodentilites cricetus new genus and species, Slapylites afer new species, Tajinella mosei new genus and species, and Tizilites creber new genus and species. New orthothecid hyoliths are Gracilitheca destombesi new species, Contitheca chrosniaki new species, Sysoievia exilis new genus and species and an indeterminate species of Circotheca. The presence of Obeodalites, Slapylites, and Contitheca suggests a strong affinity to other Mediterranean and to Avalonian faunas. Their occurrence in Morocco extends their geographic ranges from Europe, and further reenforces their usefulness as indicators of Middle Cambrian age.

Seven species of oryctocephalids occur in the Lower to Middle Cambrian boundary strata of the southern Great Basin. These include Oryctocephalites palmeri n. sp. and an Oryctocephalinae species from the uppermost Lower Cambrian (upper Olenellus Biozone); Oryctocephalus indicus (Reed, 1910), Microryctocara nevadensis n. gen. and n. sp., and Oryctocephalites rasettii n. sp. near the base of the Middle Cambrian (lower Plagiura Biozone); and Oryctocephalus primus Walcott, 1886, and Oryctocephalus nyensis Palmer, 1979, from slightly higher strata (upper Plagiura Biozone). Oryctocephalus and Oryctocephalites are emended based on a cladistic analysis of Oryctocephalinae Beecher, 1897.

Floodplain deposits of the Permian Laguna Polino Member (La Golondrina Formation) of southern Patagonia, Argentina, contain a moderate diversity invertebrate ichnofauna. This member consists of up to 500 m of ripple cross-laminated and trough cross-bedded, medium-grained sandstone and mudstone, with some conglomerate. It records sedimentation in braided fluvial environments with moderate channel sinuosity. The system was characterized by the development of multistory channels, transverse or linguoid bars, and levees. At the Laguna Grande locality, trace fossils were recovered from current-rippled, very fine-grained muddy sandstone beds formed in a pond adjacent to the levee. The ichnofauna consists of a mixed pascichnia, repichnia, and domichnia assemblage composed of Cochlichnus anguineus, Ctenopholeus kutscheri, Helminthoidichnites tenuis, Helminthopsis abeli, and Palaeophycus striatus. These low-energy ponds were more suitable for development of benthic fauna and preservation of ichnofossils than were fluvial channels and point bars. Accordingly, preservation of distinct trace fossil-bearing pond horizons within an otherwise unfossiliferous fluvial succession may be regarded as taphonomic and colonization windows. The colonization history of these beds can be traced through the study of cross-cutting and substrate relationships. Detailed ichnologic analysis suggests the following succession: 1) large Cochlichnus tracemakers colonizing transitional soupgrounds to softgrounds; 2) large and small Cochlichnus, Helminthopsis and Helminthoidichnites formed in softgrounds; and 3) Palaeophycus and Ctenopholeus emplaced in transitional soft to firm substrates. The colonization sequence suggests an ecologic replacement of a surface mobile fauna dominated by nematodes, nematomorphs, and larval insects by a more stationary infauna consisting of adult insects as a result of increasing consolidation. Presence of Ctenopholeus is significant because it represents the second report of this ichnogenus and the first from nonmarine settings.

Although echinoderm debris is locally common, articulated specimens are rare in Late Cambrian rocks from the Great Basin and Rocky Mountains of the western United States and are mostly associated with hardgrounds. The fauna, including cornute stylophorans, trachelocrinid eocrinoids, solute homoiosteleans, and rare edrioasteroids, includes several members of the archaic Cambrian Evolutionary Fauna, which had already passed its maximum diversity for echinoderms. In addition to the low diversity, articulated specimen abundance is very low, averaging only about one-tenth that found in overlying Lower Ordovician units. The transition between the Cambrian and Paleozoic Evolutionary Faunas for echinoderms in North America apparently occurred rapidly very close to the Cambrian-Ordovician boundary, because no unequivocal examples of the Paleozoic fauna (such as crinoids, glyptocystitid rhombiferans, asteroids, or echinoids) were found in the Late Cambrian sections.

New taxa include several cothurnocystid stylophorans assigned to Acuticarpus delticus, new genus and species, Acuticarpus? republicensis, new species, and Archaeocothurnus goshutensis, new genus and species; Scotiaecystis? species, a poorly preserved cornute stylophoran with lamellipores; Minervaecystis? species, a fragmentary solute homoiostelean based on several steles; Tatonkacystis codyensis, new genus and species, a well-preserved trachelocrinid eocrinoid with five unbranched arms bearing numerous brachioles; an unnamed, poorly preserved, epispire-bearing eocrinoid; an unnamed, poorly preserved, globular eocrinoid? lacking epispires; and an unnamed, heavily weathered, edrioasterid edrioasteroid. Nearly all holdfasts found in these Upper Cambrian units are single-piece blastozoan types, probably belonging to trachelocrinid and other eocrinoids. Distinctive columnals and thecal plates of several additional undescribed eocrinoids and other echinoderms were locally abundant and are also described.

Utatsusaurus hataii, an Early Triassic ichthyosaur from Japan, is represented by exceptionally well preserved materials but is poorly known because of incomplete preparation. Further preparation of the holotype and one of the paratype specimens has revealed nearly complete forefins that are pentadactyl, with no more than five phalanges in any of the digits. The first digit is not well developed, and the fifth distal carpal appears to be absent. The phalanges along the fin margin tend to be lunate; others are flattened cylinders. These findings indicate that the relationship of Utatsusaurus with other Early Triassic ichthyosaurs must be reconsidered.

Morphologic variation within and among populations of the common monobathrid camerate crinoid Agaricocrinus was investigated using multivariate and bivariate techniques for samples from 15 localities in the Lower Mississippian (late Osagean) Fort Payne Formation of south-central Kentucky and north-central Tennessee. Despite a wide range of variability, two morphotypes were distinguished at most localities in both autochthonous and allochthonous carbonate facies: Agaricocrinus americanus and the less common A. crassus. Morphologic characters that can be reliably used to separate these taxa include character of the anal area, width of the second primibrachial, and shape of the arm facets. Many other characters of calyx shape and plate proportions used previously for species recognition, such as depth of the basal concavity, height of the interbrachials, height of the tegmen, and number of arms, are widely variable within populations. Variation within species populations is ontogenetic, although a geographic component is recognized within A. crassus. The definition of A. crassus is emended to encompass a broader range of variation than heretofore realized. Eight species previously reported from the Fort Payne Formation are placed in synonymy: A. arcula, A. dissimilis, A. elegans, A. podagricus, A. ponderosus, A. profundus, and A. tugurium are junior synonyms of A. americanus. A. attenuata is a junior synonym of A. crassus.

Calymenid trilobites are common components of diverse Silurian silicified faunas recovered from the Cape Phillips Formation of the Cape Phillips Basin, central Canadian Arctic Archipelago. Calymenids are represented in the Wenlock of the northern Laurentian region by only two genera, Diacalymene Kegel, 1927, and Arcticalymene new genus (type species A. viciousi new species). Calymenid diversity in any given fauna is never higher than two species, although these species may be numerically abundant. Arcticalymene became extinct during the Homerian, at which point calymenids disappeared forever from the northern Laurentian record.

Other new taxa are Arcticalymene cooki new species, A. jonesi new species, A. matlocki new species, and A. rotteni new species. Material representing at least two more species of the new genus is reported in open nomenclature. Diacalymene gabrielsi Siveter and Chatterton, 1996, is recorded from the Cape Phillips Basin.

A growth series is described for a new species of Ceratocara Ramsköld, 1991, C. argentina, from the Upper Ordovician (Caradoc) part of the Las Aguaditas Formation, near Jáchal in San Juan Province, Argentine Precordillera. Another new species of Ceratocara, C. shawi, is described from the Middle Ordovician (lower Chazy) Crown Point Formation of New York. A phylogenetic analysis is presented for these species, other well-known Ordovician species of Ceratocara, and some Ordovician species of Ceratocephala, with Ceratocephalina tridens Whittington, 1956, as outgroup. The analysis presented supports the monophyly of both Ceratocara and Ceratocephala Warder, 1838, their divergence having occurred by the middle Arenig. The ontogenies of the Ceratocara species from Argentina and New York, complete from protaspid to holaspid growth stages, are some of the best preserved odontopleurid ontogenies described to date. Material of Ceratocephala triacantheis Whittington and Evitt, 1954, from the Crown Point Formation of the Chazy Group of New York, is discriminated from that of Ceratocara shawi.

Reexamination of the chondrenchelyid Harpagofututor volsellorhinus from the Bear Gulch Limestone (Health Formation, Upper Chesterian, Mississippian), has revealed that the preserved fossil pigments are those originally associated with particular, well-vascularized abdominal organs (liver, spleen, and gonads) and major venous sinuses (orbital, gonadal, pelvic). The pattern of pigment localization reflects circulatory pathways of fossilized vessels. This determination was confirmed by comparison of fossil patterns to the visceral and circulatory anatomy of extant chondrichthyans. The arrangement of these pigments conveys strong, and otherwise unavailable, evidence for the internal reproductive features of these sexually mature, Paleozoic chondrichthyans. Under the appropriate preservational conditions the pigments also reveal asphyxia as the cause of death. Thus, the value of these pigments cannot be underestimated. Unfortunately, they are prone to spontaneous and progressive degradation that starts immediately upon excavation. Consequently, it is imperative to record data accurately and in a timely fashion. This report thus introduces the use of a color flatbed scanner as a particularly effective laboratory research tool for the collection and archiving of ephemeral fossil data.

Ontogenies of three trilobites from the Garden City Formation (Tremadocian to early Arenigian; equivalent to Ibexian) are described: Tesselacauda depressa (Pilekiidae), Rossaspis pliomeris (Protopliomeropsinae), and Protopliomerella contracta (Cybelopsinae).

Comparison of both larval and adult features of the described trilobites with those of cheirurids and encrinurids suggests that three lineages of the Cheirurina existed during the Early and Middle Ordovician. Members of the first lineage show the following hierarchical relationships; (Tesselacauda depressa (Cheirurinae (Acanthoparyphinae (two separate Sphaerexochinae groups)))). Within the second lineage, the following internested relationships of its members are recognized; (Protopliomeropsinae (“early” cybelines (“advanced” cybelines and Encrinurinae))). The Cybelopsinae constitute the third lineage that is considered as an immediate outgroup to the above two lineages. Pattern of nested distribution of synapomorphies within all these lineages reveals that the two pliomerid subfamilies (Protopliomeropsinae and Cybelopsinae) do not share a recent common ancestor, suggesting that the Pliomeridae is a paraphyletic group.

The description of a new species of retroplumid crab, Costacopluma salamanca from the Danian Salamanca Formation, southern Argentina, represents the eighth species referred to that genus and extends the geographic range of the taxon into Patagonia. Cladistic analysis of the genus suggests that three groups of species can be identified based upon their geographic position; Afro-Asian, North American, and South American.

A large ichthyosaur from the Early Tithonian (Late Jurassic) of the Neuquén province, Argentina, represents a new genus and species, Caypullisaurus bonapartei, within the family Ichthyosauridae. The holotype is the most complete skeleton of a mature ichthyosaur known to date from the Jurassic of South America. In comparison with other Late Jurassic ichthyosaurs, the new taxon shares a long and slender rostrum, degenerate dentition in adults, and the enlargement of the orbit with Ophthalmosaurus. Unlike Ophthalmosaurus, the forefin of Caypullisaurus has four major digits composed of tightly packed, polygonal phalanges, and pre- and post-axial accessory digits. Caypullisaurus demonstrates that ichthyosaurs were more diverse during the Late Jurassic than thought previously.

Review of recently collected material of Eohiodon from North America suggests that there are two valid species, E. rosei (Hussakof) and E. woodroffi Wilson. Eohiodon falcatus Grande is identical to E. woodruffi in known skeletal features and nearly all meristic features and is treated as a junior synonym of the latter. The fossil genus Eohiodon Cavender differs from Hiodon Lesueur, which is known from both fossil and extant species, in numerous meristic and osteological features. The caudal skeleton in Eohiodon is nearly identical to that in Hiodon.

The traditionally accepted Notopteroidei, containing Lycopteridae, Hiodontidae, and Notopteridae, is a polypheletic group. The Asian fossil family Lycopteridae is not more closely related to Hiodontidae than it is to other taxa in the Osteoglossomorpha, but is sister to all other Osteoglossomorpha. The Hiodontiformes sensu stricto, including only the family Hiodontidae, is the sister-group of the Osteoglossiformes. This family is not more closely related to notopterids than to other taxa in Osteoglossiformes. The Notopteridae are most closely related to the Mormyroidea; together they and the fossil family Ostariostomidae constitute the sister-group of the Osteoglossoidei.

Fossil records of Hiodontiformes sensu stricto and Notopteroidei indicate a widespread pre-Neogene biogeographic range of these freshwater teleosts, suggesting that extinction must have been involved in the Cenozoic evolution of these two osteoglossomorph sublineages.