A microevolutionary event involving the conodont Paroistodus lineage is documented in the Gualcamayo Formation (Middle Ordovician), Argentine Precordillera. A detailed sampling of limestones throughout the upper part of the San Juan Formation and the lower member of the Gualcamayo Formation yielded over 14,000 well-preserved conodont elements. Paroistodus originalis (Sergeeva, 1963) was recorded through the upper 230 m of the San Juan Formation and the lower member (10 m thick) of the Gualcamayo Formation. The derived species Paroistodus horridus (Barnes and Poplawski, 1973) was recorded throughout the middle member of the Gualcamayo Formation (65 m thick). The intermediate linking forms between both species are identified as two new taxa: Paroistodus horridus primus Albanesi, 1998b, and P. h. secundus Albanesi, 1998b. They were recorded in the uppermost 70 cm of the lower member. Apparently, the speciation event occurred under stressed environmental conditions with the drowning of the carbonate platform, i.e., the San Juan Formation, and the beginning of a deeper and restricted environment represented by the Gualcamayo black shales. The demise of the carbonate production was caused by a sea level rise and a significant influx of volcanic ashes. The punctuated speciation event occurred within an allopatric setting while the Precordillera occupied an isolated (Iapetus) oceanic position in its overall drift from Laurentia to Gondwana.

The Yahatinda Formation of southern Alberta and British Columbia consists of a series of channels cut into lower Paleozoic rocks and represents deposition in marine to littoral environments across a major regional unconformity. The age of the beds is late Givetian based on spore assemblages and plant macrofossils. A vertebrate fauna from the formation is described here for the first time and includes Heterostraci (two new species of tuberculated pteraspidids), Placodermi (an antiarch and the arthrodire Holonema together with indeterminate arthrodires), Osteolepiformes, and Porolepiformes. This report documents for the first time that pteraspidids, considered to be organisms characteristic of the Lower Devonian elsewhere, lingered to the end of the Middle Devonian in western North America. This fauna is similar to others occurring further south in the western United States.

Conodonts representing 38 species of 26 genera have been identified in samples from Upper Ordovician rocks at three central Nevada localities. Ranges of these species and associated graptolites are used graphically to determine correlation of the strata considered with an evolving composite standard that includes information from Ordovician strata at more than 100 localities in North America. Results indicate that the Hanson Creek Formation at Lone Mountain is latest Edenian through mid-Richmondian in age; that the Ordovician part of the Hanson Creek in the Monitor Range section spans an interval from Maysvillian through Richmondian; and that the upper 29 m of the Vinini Formation at the Vinini Creek locality is of mid-Maysvillian to late Richmondian age. Physical discontinuities in the Ordovician-Silurian boundary interval complicate correlations, but it is now clear that conodonts that range upward into, and have long been considered distinctive of the Lower Silurian, make their debut in central Nevada in an upper segment of the Upper Ordovician Normalograptus persculptus graptolite zone that may be latest Richmondian in age.

Reinterpretation of cranial materials of the diadectomorphs Limnoscelis and Diadectes has prompted a reconsideration of the origin and early evolution of the amniote occiput. The basic approach is a phylogenetic study of major groups of Paleozoic tetrapods based on the occiput and closely associated elements of the skull roof. A lack of adequate anatomical data has forced the elimination of only a few relevant higher-level taxa from consideration, and, using Acanthostega as the reference outgroup, a cladistic analysis of the interrelationships of the Lepospondyli, Temnospondyli, Seymouriamorpha, Baphetidae (= Loxommatidae), Anthracosauria, Diadectomorpha, Synapsida, and Reptilia has produced the following results: 1) the ingroup taxa exhibit a basal dichotomy in which one division consists of the unresolved relationships of Lepospondyli, Temnospondyli, and Seymouriamorpha; 2) the pattern of relationships of the second division of the ingroup taxa is a series of nested clades, terminating with the Diadectomorpha and Synapsida as sister taxa sharing a more recent common ancestor than either does with Reptilia. This relationship requires assignment of Diadectomorpha to Amniota; and 3) the Anthracosauria and Baphetidae are progressively more distant clades or sister taxa. On the basis of the cladistic analysis, the attainment of the amniote occiput is described as passing through four morphological grades of organization. Each grade of the series is characterized by a set of derived character states that defines the progressively more-derived nodes and from which branch a clade containing the unresolved trichotomy of Lepospondyli, Temnospondyli, and Seymouriamorpha; the Baphetidae clade; the Anthracosauria clade; and the Diadectomorpha + Synapsida and Reptilia clades, respectively.

A detailed investigation of the morphological evolution of the coccolithophorids Calcidiscus leptoporus and C. macintyrei from the Early Miocene to the Quaternary shows that microevolutionary patterns were very complex. Speciation patterns such as cladogenesis and phyletic divergence were observed, but stasis also existed over prolonged time-intervals. Similar coccoliths developed repeatedly at stratigraphically distant intervals, leading to taxonomic uncertainies. On the basis of bivariate frequency diagrams of coccolith diameters and number of elements in the distal shields nine morphotypes S, I, L, F, A, B, C, D and E are distinguished. A tentative phylogeny was constructed for these morphotypes suggesting, that they belong to one extant species and several extinct species. The extant species is Calcidiscus leptoporus, which comprises the living morphotypes S, I, L, and F and one extinct morphotype E. Morphotype S is the most conservative one, which originated from an unknown ancestor during the Early Miocene or earlier, while morphotype I originated from S during the Early Miocene. Morphotypes L and E separated from I during the Late Miocene. An extinct lineage is proposed, including morphotypes C, D, A, and B, which all produced large coccoliths except morphotype B, which is small. Morphotypes C, D, and A are very similar to a coccolith that specialists call Calcidiscus macintyrei, but in the present phylogenetic model they may belong to separate species with similar morphology. Morphotype C developed from morphotype I during the Early Miocene and is the precursor of an extra large morphotype D, and two other morphotypes, A and B. All three forms separated from morphotype C by pronounced cladogenetic events during the Late Miocene and Pliocene, and hence may represent separate species. Morphotypes A and B are supposed to belong to an extinct morphocline and may thus be ecophenotypes of one species. Alternatively, due to the lack of paleoenvironmental and biogeographic observations in the past, it cannot be discounted that all morphotypes found in this investigation simply represent ecovariants of one species. With the present status of knowledge, it is not possible to propose a sound differential diagnosis in the plexus C. leptoporus-C. macintyrei, which would allow differentiation among species at each point in space and time. It is hoped that this study stimulates further morphometric and phylogenetical studies that will generate a more profound understanding of species in paleontology and biology in general.

Two ichthyosaurian specimens from the Upper Jurassic lithographic limestones of Bavaria, namely an almost complete skeleton with soft tissue impression and another partial one, are described for the first time. Both belong to the same taxon, which is mainly characterized by a long and slender snout; numerous small, delicate, packed, and well-anchored teeth; a medium size orbit; a reduced triangular squamosal in the cheek region; an angular largely exposed laterally reaching as far anteriorly as the surangular; a humerus with three distal facets for radius, intermedium and ulna; an extrazeugopodial element anterior to the radius; a very reduced hindlimb; packed polygonal paddle elements; and a bipartite pelvis with a distally greatly expanded puboischiatic complex. This combination of characters permits differentiation from all other known genera; moreover, it could be compared to the species inquirendae Ichthyosaurus leptospondylus Wagner, 1853a. A new genus, Aegirosaurus, is created and proposed as a new combination for this species. Aegirosaurus clearly belongs to the clade Ophthalmosauria because of an angular largely exposed laterally and reaching as far anteriorly as the surangular, and the occurrence of an extrazeugopodial element anterior to the radius and the associated digit distal to it. A systematic review of ichthyosaurs from the lithographic limestone of Bavaria (most of them destroyed during World War II) reveals the occurrence of probably three different taxa, namely Aegirosaurus, an indeterminate form close to Ophthalmosaurus or Caypullisaurus, and an indeterminate one possibly close to Nannopterygius.

The early Miocene Durudawiri inusitatus new genus and species (Marsupialia: Phalangeroidea) is described from the Riversleigh World Heritage Property in northwestern Queensland. It appears to represent the plesiomorphic sister group of the late Oligocene species of Miralina from South Australia. Its molar morphology is not as complex as that of species of Miralina or ektopodontids, but it is more complex than that of phalangerids. The degree of morphological difference between species of Durudawiri and Miralina suggests subfamilial distinction for the two groups. Strange cusps on the upper molars could be interpreted as either large neometaconules and paraconules, or lingually-displaced metacones and paracones with very large stylar cusps on the buccal shelf.

The sphenodontian Ankylosphenodon pachyostosus new genus and species is the second unusual sphenodontian reported from the Albian deposits of the Tlayua Formation, near Tepexi de Rodríguez, Central Mexico. The skeleton is robust with pachyostotic ribs and vertebrae. Unique long teeth are ankylosed deep into the lower jaw extending close to the edge of the Meckelian canal. Long teeth with open roots, the lack of worn-out teeth, and the presence of posterior wear surfaces exhibiting dentine suggest that tooth growth was continuous. These features combined with a propalinal action of the deep lower jaw suggest herbivory. Herbivorous specializations of Ankylosphenodon are different from the laterally expanded teeth of Toxolophosaurus and Eilenodon and may have evolved to prevent total tooth loss, a feature which is observed in sapheosaurs. A pachyostotic skeleton, a delay of the ossification of the epiphyses, and a solid structure of the vertebral column could be related to a none obligated aquatic behavior. These specializations differ greatly from those of other aquatic sphenodontians such as Pleurosaurus and Palaeopleurosaurus. A stout skeleton with swollen horizontal zygapophyses suggests affinities with sapheosaurs; however, cladistic analysis support sister-group relationship with Toxolophosaurus and/or Eilenodon on the basis of shared propalinal jaw action and deep jaws. The presence of two unique sphenodontians in the Tlayua Quarry suggests the presence of an area for the diversification of lepidosaur reptiles. The late presence of sphenodontians in the Albian also suggests that this area was a refuge for archaic forms at the time.

Predominantly horizontal, gently curved to slightly sinuous traces constituting uniserial rows of imbricated, subspherical sediment pads occur in Pennsylvanian tidal-flat facies of eastern Kansas. These traces exhibit a complex, actively filled internal structure. The presence of a median tunnel enveloped by overlapping pads of reworked sediment indicates that these biogenic structures should be included in the ichnogenus Nereites MacLeay in Murchison, 1839. A new ichnospecies, N. imbricata, is erected. Externally, Nereites imbricata differs from the other Nereites ichnospecies by the large, tightly packed, imbricated pads that commonly result in an annulated appearance on bedding-planes. Internally, obliquely arranged, arcuate laminae envelope the median tunnel and tend to follow the outline of the external semispherical pads. Additionally, the behavioral pattern reflected by N. imbricata is less specialized than that of the other Nereites ichnospecies. Eione monoliformis Tate, 1859 resembles N. imbricata in general appearence, but lack the diagnostic Nereites internal structure, and is invariably preserved as positive epireliefs. Occurrence of Nereites imbricata as both median tunnels surrounded by reworked sediment (Nereites preservation) and uniserial rows of imbricated sediment pads (Neonereites preservation) supports the notion that Neonereites Seilacher, 1960 is a preservational variant of Nereites. The ichnogenus Nereites is an eurybathic form and is a common component of Paleozoic shallow-marine facies.

A diverse near-shore marine fauna existed during the early Miocene in what is today an arid inland region about 90 km south of the Caribbean coast of northern Venezuela, a poorly known area geologically and paleontologically. The fossil locality consists of more than 100 m of section exposed in an area of about 1 km2. We report the discovery of 20 molluscan species, one crab (Portunus oblongus), at least three sharks (Hemipristis serra and Carcharhinus spp.), one turtle (“Podocnemis” venezuelensis), one crocodile (Crocodylidae), two whales (Odontoceti) and a three dimensional cast of the mesocarp or endocarp of a palm fruit. Several taxa are reported for the first time in Venezuela or in northern South America. The fauna indicates, or at least is consistent with, an early Miocene age for the locality, and a near-shore and shallow water marine depositional environment. We suggest that the earliest mammal previously reported from Venezuela, the pyrothere Proticia venezuelensis, was collected in Miocene rocks of the Castillo Formation instead of Eocene rocks of the Trujillo Formation.

The mammal faunas from the upper Eocene and lower Oligocene from four localities in the Sierra Palomera (province of Teruel, Spain) are described: Villarrosano 1, 12, 14, and Aguatón. Two new species of rodents, Treposciurus manentis (Pseudosciuridae) and Bransatoglis attenuatus (Gliridae), are described from Aguaton. Comparison of the associations from the Sierra Palomera with the European standard succession (MP zonation) suggests a late Eocene age (MP 19-20) for Villarrosano 1 and Villarrosano 12 and a early Oligocene age for Aguatón and Villarrosano 14 (MP 21). The dental morphology and the relative abundance of the different mammal taxa from Villarrosano 1 and Aguatón suggest a more open environment in upper Eocene than in the early lower Oligocene in this basin.

The skull of the Miocene Yarala burchfieldi Muirhead and Filan, 1995, is described. Analysis of skull morphology supports phylogenetic conclusions based on dental morphology. Y. burchfieldi shares a number of synapomorphies with other peramelemorphians, some of which are unique and help to define this order of marsupials. Y. burchfieldi is the most plesiomorphic peramelemorphian known. Although sharing some derived characters with a number of extant taxa, Y. burchfieldi lacks synapomorphies that unite all other peramelemorphian taxa as the Superfamily Perameloidea. The Yaraloidea and Yaralidae, a new superfamily and family of peramelemorphians, is proposed and diagnosed on the basis of Y. burchfieldi. Fossil evidence supports the late divergence of perameloids, while peramelemorphian diversity in the Tertiary indicates an ancient derivation for the order.

Abderitid marsupials are common in vertebrate-bearing deposits from the middle Miocene of Argentine Patagonia. Recent collections from the inland Pinturas Formation and slightly younger coastal Santa Cruz Formation have dramatically increased the number of abderitid specimens. These new collections permit a re-assessment of abderitid taxonomy as well as an investigation of the dietary habits of these unique small mammals. The vast majority of new specimens represent Abderites meridionalis; Pithiculites minimus is rare. Patterns of macrowear on the double-bladed, plagiaulacoid shearing complex suggest that abderitids used these teeth to prepare a variety of resistant food items as do modern marsupials with double-bladed shearing systems. Data summarizing molar-shearing morphology and body size further suggest that A. meridionalis was a frugivore. The diet of the small P. minimus is equivocal, although it may represent a mixed feeder (frugivore/faunivore). A comparison of relative species richness and dietary adaptation between abderitids and palaeothentids (a closely related caenolestoid family that lacks the highly specialized shearing complex of abderitids) reveals distinct evolutionary patterns within the two lineages. Abderitids exhibit low species diversity. In contrast, palaeothentids are represented by 17 species, lack highly specialized shearing mechanisms, and typically exhibit molar morphologies that range from frugivory to faunivory and include mixed feeders. Both temporal and geographic variation are introduced as possible factors affecting differences in the relative abundance of abderitids and palaeothentids in the Pinturas and Santa Cruz Formations.

Ediacara-type fossils are rare in the southwestern United States, and Cambrian occurrences of soft-bodied Ediacaran-type fossils are extremely rare. We report both discoidal and frondlike fossils comparable to Ediacaran taxa from the western edge of the Great Basin. We describe one specimen of a discoidal fossil, referred to the form species ?Tirasiana disciformis, from the upper member of the Lower Cambrian Wood Canyon Formation from the Salt Spring Hills, California. Two fragmentary specimens of frond-like soft-bodied fossils are described from the middle member of the Lower Cambrian Poleta Formation in the White Mountains, California, and the upper member of the Wood Canyon Formation in the southern Kelso Mountains, California. On the basis of similarities with fossils from the lower member of the Wood Canyon Formation and from the Spitzkopf Member of the Urusis Formation of Namibia, these specimens are interpreted as cf. Swartpuntia. All fossils were collected from strata containing diagnostic Early Cambrian body and trace fossils, and thus add to previous reports of complex Ediacaran forms in Cambrian marine environments. In this region, Swartpuntia persists through several hundred meters of section, spanning at least two trilobite zones.

Ediacaran fossils from the southwestern Great Basin may help constrain regional Vendian-Cambrian biostratigraphy and provide biogeographic links between facies in this region and elsewhere. Locally, trace fossils suggest the Vendian-Cambrian boundary occurs within or below the upper third of the lower member of the Wood Canyon Formation. Ediacaran soft-bodied and tubular fossils, including the frondlike fossil Swartpuntia and tubular, mineralized or agglutinated fossils similar to Archaeichnium Cloudina Corumbella, and Onuphionella occur in the lowermost Wood Canyon Formation. Discoidal forms referred to Nimbia occur in both the lowermost Wood Canyon Formation and the underlying strata of the Stirling Quartzite. These fossils occur directly below Lower Cambrian trace fossils, including Treptichnus pedum, and confirm the persistence of the Ediacaran biota to near the base of the Cambrian. These faunas may also help strengthen previously proposed correlation schemes between the two main facies belts of the southwestern Great Basin (the Death Valley and White-Inyo facies), because a nearly identical Vendian-lowest Cambrian succession of faunas occurs in both regions. Lastly, lack of cosmopolitan Ediacaran faunas in these strata suggests a paleobiogeographic link between the southwestern U.S. and southern Africa in Vendian time.

Until recently, paleontologists believed tentaculitids became extinct by the end of the Frasnian. Lyaschenko (1958) described the youngest occurrence of the genera Styliolina and Homoctenus from the Frasnian of Russia. However, in Europe and North Africa, Lardeux (1969) proposed that Homoctenus ultimus pergracilis persisted into the Famennian. Sauerland (1983) reported the occurrence in France of the genera Styliolina and Striatostyliolina in the cicatricosa ostracod Zone (Frasnian), and Homoctenus in the splendens ostracod Zone (Frasnian-Famennian, upper gigas—middle triangularis conodont Zones). The first report of Famennian tentaculitids in China was from the Dachang area in Guangxi Province, China by Li and Hamada (1986).

The occurrence of amber in Sierra de Cantabria (álava, Basque Country) has been known for more than two decades but biological inclusions have only recently been found. The existence of crustaceans (amphipods and isopods), chelicerates (acari and arachnids), 12 orders of insects, and several bird feathers are reported in this preliminary study. In addition, there are leaf remains, molluscs, and a fair number of inorganic inclusions.

Pollen analysis of the clastic series indicates an age between upper Aptian—middle Albian, which allows an assignment of this stratigraphic unit to the Nograro Formation. Chemical analysis indicates that the amber has high maturity, which reflects its Cretaceous age. Chemical composition analysis also indicates an araucariacean origin, which is corroborated by pollen found within the amber deposit.

This new fossil site provides information for the reconstruction of paleocommunities of arthropods and sedimentary environments in the extreme south of the Basque-Cantabrian Basin during the Lower Cretaceous, characterized by coniferous forests with an understory of vascular cryptograms. Some of the identified arthropods add to the fossil record for various groups that are poorly known or unknown for this time period. This Lagerstätte constitutes one of the most important deposits of Mesozoic amber in the world.

A small collection of carnivoran fossils from the South Turkwel hominid site is described. The fauna is composed of Megantereon ekidoit new species, Homotherium sp., Crocuta cf. dietrichi, cf. Pachycrocuta sp., Canis new species A., cf. Civettictis sp., Viverridae or Herpestidae indet., and Lutrinae indet. The record of Megantereon and Canis, as well as Pachycrocuta and Civettictis, if these genera are identified correctly, represents the earliest occurrences of their respective taxa in Africa. These specimens suggest a relatively rapid reorganization of the carnivore guild some time around 3.5 Ma, followed by a longer period of transition to a fauna more comparable in composition to the modern one.

Early permian strata in two displaced terranes of the McCloud belt contain a small biconic gastropod of distinctive appearance, Vesperispira humboldtiana new genus and species. This trochiform gastropod has a strongly oblique aperture with interrupted peristome, a small sinus on the peripheral margin of the shell, and lamellose shell. This gastropod is an easily recognized biogeographic indicator of the McCloud province biota, because of its lamellose ornamentation. Occurrence of this gastropod in strata of the Pine Forest Range of northwestern Nevada provides additional evidence for including rock units of the Black Rock terrane within the McCloud Belt, a grouping of several displaced terranes along the western margin of North America (Stevens et al., 1990) that contain fossil biotas rich in endemic species.

A conifer from the uppermost Permian with small, helically arranged leaves is described from the Guangxi Autonomous Region and Guizhou Province of South China as Szecladia multinervia, new genus and species. The material includes both impression specimens and the first anatomically preserved Paleozoic conifer fossils from China. Shoots are irregularly branched, with small, helically arranged, multiveined leaves. Stems display an endarch eustele with abundant, dense wood. Leaf traces diverge from the stele as a single bundle that divides several times in the cortex and at the base of the leaves, forming about seven or eight parallel veins in each leaf. Szecladia is the earliest known conifer with multiveined leaves and it represents a distinctive coniferous element of the uppermost Permian Cathaysian flora in South China. Szecladia further demonstrates that conifers with wood and leaf venation suggestive of the Podocarpaceae may have evolved by the end of the Paleozoic.