One of the most severe restrictions in taxonomic diversity of trilobites coincides with the Late Devonian “Hangenberg” Event, which is characterized by a pronounced eustatic low-stand. One of the survivors of this event is Pudoproetus, which, being adapted to shallow water conditions, experienced an opportunistic worldwide spread during this time. The oldest representatives of this genus are reported from the pre-Hangenberg Late Famennian of the Urals and Kazakhstan. Other known occurrences of this genus, midcontinent U.S.A., Utah, southern China, and southern France, occur at the Devonian-Carboniferous boundary, shortly after the Hangenberg event, and in the earliest Carboniferous. This pattern of distribution suggests that neither climatic nor geographic migration barriers existed around the Old Red landmass at that time. On the other hand, the Hangenberg crisis severely affected outer shelf benthic habitats, whereas nearshore trilobites were largely unaffected by the event.

A proetine origin of Pudoproetus, as originally proposed by Hessler (1963), is emphasized on the basis of paleoecologic, stratigraphic, and morphological arguments. In particular, the presence of ancestral features, such as the possession of 10 thoracic segments and lateral occipital lobes still occurring in early Pudoproetus species, points to a phylogenetic link with proetines rather than with phillipsiids. Within this group two new species are named: P. priscus and P. mediterraneus.

Previously undescribed holes on the calyx of single specimens of the blastoids Pentremites and Cordyloblastus are circular in plan view, penetrate the test at a right angle, and are found in the interambulacral region. The same features characterize holes on 23 specimens of the Mississippian blastoid Orophocrinus. The holes are interpreted as biogenic in origin; examples of multiple complete holes on individual specimens and of incomplete holes on some blastoids indicate that the holes represent parasitism rather than predation. The similarity of these holes to those previously described in nucleocrinids and crinoids suggests that they were produced by platyceratid gastropods or closely related taxa.

Six specimens belonging to several euphoberiid diplopod species have a pair of modified legs located along the midbody. These appendages are robust, much stouter than normal walking legs, and are attached to a sternite that is longer than those preceding and following. Euphoberiid modified legs differ in position from those of modern diplopods, being located neither near the anterior end as are gonopods nor at the anterior or posterior ends, as are clasping appendages of various modern forms. The presence of such appendages supports ordinal status for the euphoberiids.

The prominent spines of euphoberiids would have precluded intertwining types of mating behavior observed in many types of elongate modern diplopods. Judged by their robust nature and location, the modified legs may have been clasping appendages used during the mating process. “Intromittent organs” described on various taxa of fossil Diplopoda by the early paleomyriapodologists Scudder and Fritsch are suspect.

Species of two new genera of Encrinuridae occur in the Ludlow Douro Formation at Goodsir Creek, Cornwallis Island, Gamier Bay, Somerset Island, and Prince Alfred Bay, Devon Island. The encrinurine Aegrotocatellus n. gen. includes four highly autapomorphic species, and is most closely related to Balizoma Holloway, 1980. Separate taxa are recognized at low and high stratigraphic intervals at Goodsir Creek (the type species, Aegrotocatellus jaggeri n. gen. and sp., and Aegrotocatellus n. sp. A, respectively), at Gamier Bay (Aegrotocatellus n. sp. B), and at Prince Alfred Bay (Aegrotocatellus nankerphelgeorum n. gen. and sp.). Perirehaedulus n. gen. is a coronocephaline most closely related to the Chinese upper Llandovery taxon Kailia Chang, 1974. The type species, Perirehaedulus caprus (Thomas in Thomas and Narbonne, 1979) from Goodsir Creek, is distinct from P. richardsi n. gen. and sp. at Garnier Bay. The upper Wenlock–Ludlow range of Balizoma is extended into the Arctic by Balizoma aff. B. variolaris (Brongniart, 1822) from Homerian rocks of the Cape Phillips Formation near Abbott River, Cornwallis Island, and by Balizoma sp., from the late Ludlow Douro Formation at Goodsir Creek.

Conodonts from two localities on the western shore of Alberto Island, southeastern Alaska, include Polygnathus alexanderensis n. sp., P. angustipennatus, P. borealis n. sp., P. praetrigonicus n. sp., P. robusticostatus, P. pseudofoliatus, P. linguiformis linguiformis gamma form of Bultynck, P. parawebbi beta form of Chatterton, P. angusticostatus, P. costatus costatus, Polygnathus sp. B of Savage, 1977, Tortodus kockelianus australis, and T. kockelianus kockelianus. The faunas are considered to be of middle to late Eifelian (kockelianus Zone) age. On Prince of Wales Island, just north of Staney Creek, exposures of Wadleigh Limestone include the conodonts Polygnathus trigonicus, P. kennettensis, P. alexanderensis, P. angustipennatus, P. parawebbi beta form, P. eiflius, P. linguiformis linguiformis gamma form, P. borealis, P. angusticostatus, P. robusticostatus, P. costatus costatus, P. pseudofoliatus, Tortodus kockelianus australis, and T. kockelianus kockelianus, also suggesting a middle to late Eifelian (kockelianus Zone) age. Conodonts from the west end of the easternmost of the Alberto Islands include Polygnathus linguiformis linguiformis gamma form, P. parawebbi beta form, P. xylus ensensis, and Ozarkodina brevis, indicating a late Eifelian to early Givetian (ensensis to varcus Zones) age. The presence of Polygnathus kennettensis, P. parawebbi beta form, and P. borealis suggests a biogeographic affinity with other parts of western North America during Eifelian time.

Exceptionally well preserved Lower Triassic conodonts from Oman include an array of Neospathodus species, many of which are new. Those from the upper Lower Triassic, or Spathian, are described in conjunction with a restudy of conodont type material from Chios, Greece, and an assessment of contemporary collections from Pakistan and western North America. The taxonomic scope of three key species from Chios, Neospathodus homeri, N. triangularis, and N. gondolelloides, is revised. Seven new species are described from Oman: N. abruptus, N. brevissimus, N. brochus, N. crassatus, N. curtatus, N. pusillus, and N. symmetricus; and one new species, N. clinatus, is described from Pakistan. The allied Icriospathodus collinsoni is also described from Oman. The occurrence and range of Neospathodus species are presented in the context of the ammonoid succession in the Spathian of North America. Both N. homeri and N. triangularis, as revised, have shorter ranges and are more age diagnostic than previously thought. Neospathodus gondolelloides is a distinct taxon, and not synonymous with Chiosella timorensis. Five informal faunal divisions are identified based on Neospathodus and allied species. In ascending stratigraphic order, these are typified by Icriospathodus collinsoni, Neospathodus homeri, N. triangularis, N. symmetricus, and N. gondolelloides. Oman collections represent three of these faunas, which occur also in the Columbites through Prohungarites/Subcolumbites ammonoid beds of western U.S.A.

Aulacopleurine trilobites from Llandovery strata of the Whittaker Formation in the central Mackenzie Mountains, Northwest Territories, Canada, include Aulacopleura andersoni n. sp., Aulacopleura? ranfordi n. sp., and Songkania smithi n. sp. The subfamily Aulacopleurinae consists of only the genera Aulacopleura Hawle and Corda, 1847, and Songkania Chang, 1974, characterized by smooth, broad early growth stages and holaspides having expanded frontal and genal areas, covered with dense caecal pits, but usually very subdued tuberculate sculpture. The relationship of Aulacopleura? ranfordi and A.? reedi Přibyl, 1947, to the remainder of species assigned to the genus is ambiguous.

While studying X-ray films of new iniopterygians (Subterbranchialia, Chondrichthyes) in the Excello Shale from the Field Museum of Natural History's Bethel Quarry locality in southern Pike County, Indiana, a moderately dense spread of tiny cladodont shark denticles was noticed on the radiographs, confined to micro-horizons of shale about 7.5 mm thick, which also contained the iniopterygians.

These denticle spreads, which are entirely unrelated to the iniopterygians, but are seen on X-ray films of most of the chondrichthyan skeletons collected from a sheet of Excello Shale of about 500 m2 in extent, and mostly from two very fossiliferous levels, have an average density of about nine denticles per 1 cm2. Because the chondrichthyan skeletons were collected from all parts of the quarry, it is probable that the denticle spreads in several micro-horizons extended over the entire quarry area and perhaps beyond. The number of denticles in each of the micro-horizons in 500 m2 of shale thus amounts to about 4.6 million.

A discussion of the origin of these vast numbers of cladodont denticles, given a variety of taphonomic and depositional constraints, results in the conclusion that these large numbers of denticles could not have resulted from the two species of sharks, Denaea meccaensis and Stethacanthulus longipeniculus, that are members of the burial assemblage and bear dentition teeth indistinguishable from those in the areal spread. Evidence suggesting very rapid deposition of organic muds that produced the characteristic Mecca Quarry type carbonaceous, sheety shales rules out the possibility of accumulation of the denticle spreads over extended periods of time. Because sharks do not possess nearly enough dentition teeth to account for this occurrence, one must entertain the possibility that the denticles are not all dentition teeth, but perhaps for the most part mucous membrane (or even dermal) denticles, though none such are presently known to display cladodont design.

Ostracodes are described from the “Cerro del Fuerte Section” and neighboring localities, all in the Precordillera de San Juan (northern Argentina, San Juan Province), and from sparse faunas in Bolivia (Chuquisaca, Tarabuco Province). Additional material comes from the collection of Thomas (1905). This preliminary study gives the first detailed description of ostracode assemblages in the Upper Silurian and Lower Devonian of the South American continent. Records of other abundant lower Paleozoic (Lower Ordovician to Lower Devonian) ostracodes in Argentina, Bolivia, Brazil, Peru, and Venezuela are also reviewed. Twelve different species, belonging to Palaeocopa (Beyrichiacea and Primitiopsacea) and to Binodicopa and Podocopa (Healdiacea, Thlip-suracea, Cypridacea) are described and a new genus is established (Australobollia n. gen.). Ostracode distribution at Cerro del Fuerte attests to the presence of the Siluro-Devonian boundary within the upper Los Espejos Formation and confirms recent stratigraphical attributions mainly based on conodonts and brachiopods (Benedetto et al., 1992). The beyrichiacean Hemsiella indicates a late Ludlow to Pridolian age for the lower part of upper Los Espejos Formation. The non-palaeocope “Thlipsurella-Phanasymmetria-Ranapeltis” assemblage found in the uppermost part of the formation indicates an Early Devonian (Lochkovian) age. The present study reveals the existence of faunal links at genus (Silurian) and probably species (Early Devonian) level between South America (Argentina, Bolivia), Laurentia, Avalonia-Baltica, and northern Gondwana. For example, close affinities (e.g., Ranapeltis sp. aff. rowlandi and Thlipsurella sp. aff. ellipsoclefta) exist between the uppermost Los Espejos Formation (Argentina) and contemporaneous horizons in the North American Mid-Continent (e.g., Haragan Formation, Oklahoma; Shriver Formation, Pennsylvania). Two types of ostracode assemblages, “beyrichiacean-dominated” and “thlipsuracean-bairdiacean-cypridacean dominated,” are recognized in the Late Silurian–Early Devonian of Argentina and discussed relative to other assemblages known in Laurentia, Avalonia-Baltica, and northern Gondwana. Their paleoecological significance in relation to marine bathymetry is addressed.

A true interreef crinoid fauna lacking components of reefal facies is reported from the Ludlovian of the Mississinewa Shale Member of the Wabash Formation in northern Indiana. The Mississinewa facies that contains this fauna is a dolomitic siltstone or a silty dolomite. The crinoid association reported is composed entirely of new species and is different from other reef and reef-associated, interreef, and non-reef crinoid associations. New species described, herein, include the following: Dimerocrinites (Eucrinus) ankylos n. sp., Periechocrinus shaveri n. sp., Bohemicocrinus? occidens n. sp., Macrostylocrinus styo n. sp., M. homalos n. sp., Gissocrinus hypselos n. sp., and Dendrocrinus diaphoros n. sp. This may be the first occurrence of Bohemicocrinus from outside Bohemia.

An incomplete skull of a small sphenodontian lepidosaur from the upper part of the Stormberg Group of southern Africa is referable to Clevosaurus Swinton, 1939. It is most closely related to C. bairdi from the McCoy Brook Formation (Lower Jurassic) of Nova Scotia (Canada) and C. mcgilli from the Dark Red Beds of the Lower Lufeng Formation (Lower Jurassic) of Yunnan (China). The new specimen is important because it represents the first record of Clevosaurus from the Southern Hemisphere. Like many other taxa of Early Jurassic continental tetrapods (crocodylomorph archosaurs, dinosaurs, synapsids), Clevosaurus had an apparently Pangaean distribution.

Twenty-four nearly complete carapace samples were collected at three different localities of the Maastrichtian (Late Cretaceous) Cárdenas Formation in San Luis Potosí, east-central Mexico. The material has been assigned to five families: the Callianassidae, Dakoticancridae, Carcineretidae, ?Majidae, and Retroplumidae. Two genera of callianassid shrimp are described, Cheramus for the first time in the fossil record. Dakoticancer australis Rathbun is reported as the most abundant crustacean element; one new genus and species of carcineretid crab, Branchiocarcinus cornatus, is erected, and a single, fragmentary specimen is questionably referred to the Majidae. The three localities reflect paleoenvironmental differences, exhibited by different lithologies, within marginal marine, lagoon environments. The record of dakoticancrid crabs in the Cardenas Formation extends the paleobiogeographic range of the family and the genus Dakoticancer. Carcineretid crabs, although not abundant, seem to have been a persistent element of crustacean assemblages in clastic environments during the Late Cretaceous of the ancestral Gulf Coast of Mexico.

Plicodendrocrinus n. gen. is erected for dendrocrinids with solid pentalobate columns, strong stellate ridges on the aboral cup plates, and highly plicate anal sac plates. Five species are assigned: Middle Ordovician; P. proboscidiatus (E. Billings, not W. R. Billings) n. comb., from the Trenton of Canada and the Dunleith of Iowa and Minnesota. Upper Ordovician; P. casei (Meek) n. comb., from the Richmond and Gamachian of the midcontinent; P. rugocyathus (Ramsbottom) n. comb., from the Ashgill of England; P. collapsus (Donovan) n. comb.; and P. granditubus (Ramsbottom) n. comb., from the Ashgill of Scotland.

The Middle Ordovician dendrocrinids from the Dunleith Formation (Trentonian) of northern Iowa and southern Minnesota are P. proboscidiatus (E. Billings), Dendrocrinus acutidactylus E. Billings, and Quienquecaudex springeri (Kolata). All species are also known from the Middle Ordovician of Ontario and Quebec. In addition, O. springeri (Kolata) is recorded from the Platteville Group of Illinois. Biogeographically, the Dunleith dendrocrinids are most similar to those of the northern Appalachians.

Plicodendrocrinus casei (Meek) ranges widely in the midcontinent and has been obtained from the Maysvillian and Richmondian Maquoketa Formation of Iowa and Minnesota, several Richmondian units in the Cincinnati area, and the Gamachian Girardeau Limestone of Illinois and Missouri.

A quantitative cladistic analysis of Ordovician cladid and flexible crinoids produces five groups: primitive forms including Aethocrinus, Compagicrinus, Ottawacrinus, and Grenprisia; cyathocrinids with Carabocrinus, Palaeocrinus, Illemocrinus, and Porocrinus; merocrinids with Archaetaxocrinus, Merocrinus, Praecupulocrinus, Polycrinus, and Aithriocrinus; dendrocrinids with Esthonocrinus, Eoparisocrinus, Dendrocrinus, Quienquecaudex, Plicodendrocrinus and perhaps Eopinnacrinus; and Cupulocrinus and the flexibles, Protaxocrinus, Clidochirus, and Proanisocrinus. These groups are not consistent with the present taxonomy and several suggestions for restructuring are presented, notably grouping flexibles with cladids and adjusting the taxonomic level of cyathocrinids. The cladograms for early cladids and flexibles are poorly correlated with stratigraphic position because of numerous unfilled range zones for the taxa or their ancestors. Thus, the cladograms generate predictions that can be tested by later finds in the Lower and the lower part of the Middle Ordovician. The overall evolutionary trends are highly mosaic with numerous parallelisms and reversals.

The important mid-Telychian biozonal index species Monoclimacis griestoniensis (Nicol, 1850) is redescribed and distinguished from two new species: Monoclimacis directa (formerly the ‘Monograptus cf. griestoniensis’ of Elles and Wood, 1911), and Monoclimacis woodae. Stratigraphically, directa appears a little before griestoniensis, whilst woodae is from the late griestoniensis to early crenulata Biozone.

The Late Irvingtonian fauna of Port Kennedy Cave, Pennsylvania, includes four species of turtles. Terrapene carolina is the most common species; Clemmys insculpta is present. A nearly complete plastron of Emydoidea blandingii from Port Kennedy and two specimens from New Jersey sites indicate that the species ranged through the Delaware Valley region during much of the Quaternary. The type material of Clemmys percrassa Cope is reidentified as Geochelone (Hesperotestudo) percrassa Cope, and becomes one of the more northeasterly records of the genus in North America.

When first described, Plethoschisma grandis was thought to have an unusual plating arrangement compared to other pleurocystitids, although the ventral surface was largely unknown. New specimens showing more of the ventral surface indicate that Plethoschisma has very similar ventral plating to Deltacystis and that four of the original dorsal plate designations of Plethoschisma were incorrect. A new subfamily, Deltacystinae, is erected to receive the two similarly plated genera. The pectinirhombs of Plethoschisma are reinterpreted as confluent and in the B2/IL2 and IL3/L4 positions, and one of the new specimens has the largest pectinirhomb and greatest number of dichopores of any known glyptocystitid. A phylogenetic analysis of the Pleurocystitidae reveals that the Deltacystinae, new subfamily, is the sister group to the Pleurocystitinae, new subfamily, and that pectinirhombs apparently evolved independently in the Pleurocystitidae and the Cheirocrinidae.

Yarala burchfieldi n. gen. and sp. is described from Oligo-Miocene deposits of Riversleigh Station, northwestern Queensland. Although the smallest and most plesiomorphic bandicoot known, it shares unique synapomorphies with other peramelemorphs, such as the posteriorly orientated preparacrista on M2, posterolingual location of the hypoconulids, and the buccal position of the centrocrista. However, Y. burchfieldi lacks synapomorphies that would unambiguously allow it to be placed in any of the modern families as currently understood. In its plesiomorphic features, Y. burchfieldi provides a structural link between peramelemorphs and dasyuromorphs and appears to be a descendant of an annectant group that separated long prior to the origin of “typical” bandicoots. This species is present in many sites within the Riversleigh area. It possibly filled an insectivorous-carnivorous niche presently occupied by small dasyurids that are relatively more abundant today than they were when the Riversleigh deposits accumulated.

Two species of eoparisocrinid crinoids from the Middle Ordovician Galena Group of northern Iowa and southern Minnesota are described, namely Eoparisocrinus crossmani n. sp. and E. grandei n. sp. The post-larval development of Eoparisocrinus crossmani is examined. Crinoid arms grow by addition of new plates at their distal tips in conjunction with calcite deposition on old plates. New branches appear where axillary plates are initiated. Consequently, the growth rates for number of brachials and length of food-gathering system compared to crown volume are much faster than if the animals were isometric. The number of food particles collected is related to the number of food-catching tube-feet, which can be estimated if the length of the arms and height of the covering plates are known. The size of the largest food item is constrained by the food groove width. Thus, food-gathering capacity is the number of food-catching tube-feet multiplied by food groove width. The food-gathering capacity increases more rapidly than if the animal grew isometrically, and the ratio of food-gathering capacity: crown volume only declines slightly over the known growth range. All Ordovician cladid crinoids examined follow nearly identical ontogenetic trajectories. The ecological niche of a stalked crinoid is related to four basic parameters: stem length, food groove width, tube-foot spacing, and branch density. Stem length limits the highest elevation above the seafloor. The column of E. crossmani becomes longer during ontogeny due to the formation of new columnals and height growth of old ones. Consequently, individuals gradually “move up” until the adult elevation of about 50 mm is reached. The growth rates of stem length relative to crown size are slow in the youngest and mature animals but rapid in juveniles. The food grooves become wider throughout growth so that older crinoids ate larger food particles than younger ones. The food groove width increases less rapidly than if the shape were constant, because distal plates and branches are more narrow and have more slender food grooves than proximal plates. Growth curves for food groove width versus stem length and elevation were generated for E. crossmani and other crinoids that commonly occur in the same beds. Together, elevation and food particle size define the main dimensions of the niche. The various taxa are more or less separated by different food groove widths at most comparable elevations. This pattern minimizes ecological overlap and probably competition between the different species. The tube-foot spacing of E. crossmani is constant regardless of size, which suggests that it employed the same type of feeding mechanism throughout post-larval ontogeny. The arm branches of adults gradually become less densely spaced relative to the area of water filtered than in juveniles.

Monograptus crinitus Wood is made the type species of a new genus, Crinitograptus; a slender, nilssoni Biozone, Ludlow graptolite typified by unusual lidded thecae. Chemically isolated material from North Germany, previously placed in the genera Barrandeograptus and Pomatograptus are placed in synonymy with C. crinitus, a rare, but relatively widely recorded form. Crinitograptus crinitus is an integral part of the globally recognized Ludlow burst of evolution in the graptoloids, and it probably evolved from a nilssoni Biozone lobograptid.

A statistical and morphological study of the pterosaur Rhamphorhynchus from the Solnhofen Limestone of Germany shows that specimens fall into discrete size-classes that are year-classes resulting from seasonal mortality or preservation of specimens. Taxonomic characters used in the past to separate species of Rhamphorhynchus are all related to size and ontogeny, and all specimens belong to a single species, R. muensteri. Thus, the collections of Rhamphorhynchus provide an unequaled record of the growth and development of a Jurassic rhamphorhynchoid pterosaur. Rhamphorhynchus did not have rapid determinate growth; the growth rate was comparable to that of extant crocodilians, and growth continued over the course of at least three years after individuals began to fly.