Showing papers in "Journal of Paleontology in 1995"
TL;DR: In this paper, a new South American continental stageage is proposed based on a biostratigraphic scheme and the stratotypes of the stage and biozones are located in the fossiliferous southeastern Buenos Aires Province marine cliffs.
Abstract: The concept of “land-mammal age” as developed in South America is examined. The “Uquian Land-mammal age” is used as a study case. “Land-mammal age” parataxonomy is here considered methodologically but not conceptually different from chronostratigraphic taxonomy. “Land-mammal ages” in South America are based on stages. However, we consider that accurate biostratigraphic studies must be done in South America for establishing the biostratigraphy and precise boundary stratotypes of most stages-ages. The Uquia outcrops are here considered inadequate as a stratotype. A new South American continental stage-age is proposed. This stage is based on a biostratigraphic scheme. The stratotypes of the stage and biozones are located in the fossiliferous southeastern Buenos Aires Province marine cliffs. The lower boundary stratotype is proposed. The stage-age is probably correlated with the Gauss Chron and the lower Matuyama Chron. Additionally, some major units of Ameghino are validated and a different timing for the arrival of North American mammals to southern South America is presented.
200 citations
TL;DR: It is shown that the five nominal species of Rhamphorhynchus were based on characters related to size and ontogeny, and represent juveniles, subadults, and adults of a single large species.
Abstract: 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.
116 citations
TL;DR: A 10 percent formic acid solution with 20 g calcium carbonate and 1.2 g tricalcium phosphate per liter leaves conodont elements undamaged even for a period of 129 days.
Abstract: Formic acid must be buffered with both calcium carbonate and calcium phosphate to be suitable for extraction of conodont elements and other phosphatic fossils from dolomites. All unbuffered solutions and those buffered with only calcium carbonate or calcium phosphate destroy the phosphatic fossils. Experimental effects using different concentrations and different combinations of phosphate and calcium carbonate are diagrammatically illustrated. A 10 percent formic acid solution with 20 g calcium carbonate and 1.2 g tricalcium phosphate per liter leaves conodont elements undamaged even for a period of 129 days. One liter of this solution dissolves 95 g dolomite.
105 citations
TL;DR: In this paper, cores from three lakes in Atlantic Canada and analyzed for arcellaceans and pollen were taken from three different lakes, two in western Newfoundland and one in eastern Nova Scotia, and found that the three lakes contain similar late glacial (13-10 ka), early Holocene (10-8 ka), mid-Holocene (8-4 ka), and late Holocene(4-0 ka) assemblages.
Abstract: Cores dating back to deglaciation were taken from three lakes in Atlantic Canada and analyzed for arcellaceans and pollen. Paleotemperatures and paleo-precipitation were calculated from the pollen data using transfer functions. A sudden warming is recorded by the pollen around 10,000 years B.P., followed by a general warming to the mid Holocene Hypsithermal, then by a decrease in temperature and increase in effective precipitation to the present. The three lakes, two in western Newfoundland and one in eastern Nova Scotia, contain similar late glacial (13-10 ka), early Holocene (10-8 ka), mid Holocene (8-4 ka), and late Holocene (4-0 ka) arcellacean assemblages. Immediately following retreat of the ice sheets, Centropyxis aculeata, Centropyxis constricta, Difflugia oblonga, Difflugia urceolata, and Difflugia corona were common. The latter part of the late glacial is characterized by sparse assemblages dominated by C. aculeata. The arcellacean record thus suggests a climatic reversal in Atlantic Canada between 11,500 and 10,000 years B.P., analogous to the Younger Dryas, although this is not recorded by the pollen. Species diversity increased sharply at the beginning of the Holocene, and D. oblonga is the dominant taxon in early Holocene sediments. Difflugia oblonga remained common through the mid Holocene, but percentages of C. aculeata were very low, and Pontigulasia compressa and Difflugia bacillifera peaked in abundance during the Hypsithermal. The late Holocene is characterized by a resurgence in C. aculeata at the expense of other taxa. The increase in Heleopera sphagni and Nebella collaris since 5,000 years B.P. at the two sites in southwestern Newfoundland reflects paludification in response to increased precipitation since the Hypsithermal. Because the changes in arcellacean assemblages are regionally synchronous in all three lakes and coincide with climatically driven vegetational successions indicated by the pollen record, arcellaceans appear to respond to climatic change, and thus may be useful paleoecological and paleolimnological indicators. With their quicker generation time, these protists may be better suited than pollen to recording short-lived phenomena, like the mid-Holocene Hypsithermal and the Younger Dryas reversal.
95 citations
TL;DR: In this article, the Mesoproterozoic Kotuikan and Yusmastakh Formations, Anabar Uplift, northeastern Siberia, contain exceptionally well-preserved microfossils.
Abstract: Silicified peritidal carbonates of the Mesoproterozoic Kotuikan and Yusmastakh Formations, Anabar Uplift, northeastern Siberia, contain exceptionally well-preserved microfossils. The assemblage is dominated by ellipsoidal akinetes of nostocalean cyanobacteria (Archaeoellipsoides) and problematic spheroidal unicells (Myxococcoides); both are allochthonous and presumably planktonic. The assemblage also includes distinctive mat-forming scytonematacean and entophysalidacean cyanobacteria, diverse short trichomes interpreted as cyanobacterial hormogonia or germinated akinetes, rare longer trichomes, and several types of colonial unicells. Although many taxa in the Kotuikan-Yusmastakh assemblage are long-ranging prokaryotes, the overall character of the assemblage is distinctly Mesoproterozoic, with its major features shared by broadly coeval floras from Canada, China, India, and elsewhere in Siberia. Microfossils also occur in middle to inner shelf shales of the Ust'-Il'ya and lower Kotuikan Formations. Leiosphaerid acritarchs (up to several hundred microns in diameter) characterize this facies. As in other Mesoproterozoic acritarch assemblages, acanthomorphic and other complex forms that typify Neoproterozoic assemblages are absent. The combination in Billyakh assemblages of exceptional preservation and low eukaryotic diversity supports the hypothesis that nucleated organisms diversified markedly near the Mesoproterozoic-Neoproterozoic boundary. The assemblages also demonstrate the antiquity of cyanobacteria capable of cell differentiation and suggest the importance of both changing peritidal substrates and evolving eukaryotes in determining stratigraphic patterns of Proterozoic prokaryotes. The permineralized assemblage contains 33 species belonging to 17 genera. Ten new species or new combinations are proposed: Archaeoellipsoides costatus n. sp., A. elongatus n. comb., A. dolichos n. comb., A. minor n. nom., A. crassus n. comb., A. major n. comb., A. bactroformis n. sp., Veteronostocale medium n. sp., Filiconstrictosus cephalon n. sp., and Partitiofilum yakschinii n. sp.
92 citations
TL;DR: This observation suggests that smaller bodied species, rather than surviving stressful times with static morphologies, may evolve their way through times of crisis and go on to found lineages which, by virtue of their initial small size, are stochastically likely to increase in mean size during subsequent diversification.
Abstract: ABsTRAcr-A literature-based compilation of phylogenetic relationships and biometric measurements of 342 Cenozoic planktonic foraminiferal species suggests that the group shows a net increase in size through the Cenozoic, thus appearing to follow Cope's Rule of phyletic size increase. However, when the data are corrected for size-related biases, they do not support the hypothesis that this apparent trend is driven by an organismal adaptive advantage of larger size. When the planktonic foraminifera return to their "primitive" globigerine morphology during the Eocene-Oligocene transition, there is no indication of size-dependent origination or extinction; however, when the extinction signal is decomposed into pseudoextinctions and true lineage terminations, a differential pulse of pseudoextinction is observed among the smaller forms. This observation suggests that smaller bodied species, rather than surviving stressful times with static morphologies, may evolve their way through times of crisis and go on to found lineages which, by virtue of their initial small size, are stochastically likely to increase in mean size during subsequent diversification. Thus, one general explanation for Cope's Rule might be that smaller bodied species are more adaptively responsive due to their tendency to have shorter generation times. During times of stress, this adaptive responsiveness may give them an advantage that is correlated with, but causally unrelated to, their size.
82 citations
TL;DR: The occurrence and range of Neospathodus species are presented in the context of the ammonoid succession in the Spathian of North America, and both N. homeri and N. triangularis, as revised, have shorter ranges and are more age diagnostic than previously thought.
Abstract: 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.
81 citations
79 citations
TL;DR: In this article, the authors used a two-component mixing equation to evaluate levels of "measurable effects" (defined as ±5 × 10-5 departure from the marine 87Sr/86Sr ratio) in marginal marine environments.
Abstract: 87Sr/86Sr chronostratigraphy is an important tool for dating and correlating vertebrate and invertebrate faunas preserved in marginal marine sequences. Freshwater flux in marginal marine environments can influence the 87Sr/86Sr of mollusks and, consequently, Sr-chronostratigraphic interpretations based upon them. To appraise the potential problem we have used a two-component mixing equation to evaluate levels of “measurable effects” (defined as ±5 × 10-5 departure from the marine 87Sr/86Sr ratio) in marginal marine environments. A measurable effect occurs at 12 parts per thousand salinity for a weighted world average river, but can occur at salinity > 34 ppt for rivers draining basins with ancient granitic rocks. Predictions were tested with analyses of mollusks from estuaries in the Mississippi Sound and coastal Florida. Analyses document the largely regular variation in 87Sr/86Sr predicted, but also show that a simple two-component model cannot account for all of the variation. Carbonates formed in restricted marine settings may not record a marine 87Sr/86Sr signal, emphasizing the need to consider freshwater flux for 87Sr/86Sr chronostratigraphy.
76 citations
TL;DR: The trilobite faunas of the Lower Cambrian Shackleton Limestone have been described in this article, including taxa of Atdabanian, Botomian and possible Toyonian ages and have affinities with those known previously from Gondwana or periGondwana terranes.
Abstract: We document and describe the trilobite faunas of the Lower Cambrian Shackleton Limestone. The faunas include taxa of Atdabanian, Botomian and possible Toyonian ages and have affinities with those known previously from Gondwana or peri-Gondwana terranes. The geographic distribution of these organisms reveals a large measure of faunal connectedness around the margin of this vast supercontinent in Early Cambrian time. This connectedness extended even to taxa that inhabited shallow-water carbonate shelf environments, because the Shackleton Limestone accumulated in a variety of shallow subtidal and peritidal settings along the ocean-facing margin of the East Antarctic craton, subsequent to a Neoproterozoic rifting event. Although the fossilized Shackleton Limestone fauna is dominated by archaeocyathans, trilobites are common locally. We describe the remains of 35 trilobite taxa from 32 collecting localities. One species, H. granulosa, is assigned to the new genus Holyoakia; the remaining new species are Pagetides (Discomesites) spinosus, Lemdadella antarcticae, Kingaspis (?) convexus, Yunnanocephalus longioccipitalis, and Onchocephalina (?) spinosa.
65 citations
TL;DR: Recently undescribed Holmiidae from the Sectigena zone of Morocco indicate correlation of this zone with other zones bearing holmiidae on Baltica, Avalonia, Siberia, and Laurentia as discussed by the authors.
Abstract: Previously undescribed Holmiidae from the Sectigena Zone of Morocco indicate correlation of this zone with other zones bearing Holmiidae on Baltica, Avalonia, Siberia, and Laurentia. The occurrence of the youngest Antatlasiinae in the Sectigena Zone and the oldest Protoleninae in the overlying Hupeolenus Zone suggests correlations of the Sectigena Zone with upper Atdabanian beds bearing the youngest Antatlasiinae and the Hupeolenus Zone with Botomian beds bearing the oldest Protoleninae in Siberia. The occurrence, in the overlying Hupeolenus and Cephalopyge Zones, of Paradoxides s.l. in association with the olenelloid Cambropallas and with trilobites characteristic of the Lower Cambrian “Protolenus” Zone of Avalonia calls into question the major criteria for recognition of strata of Early and Middle Cambrian age. New taxa include lyouella contracta n. gen. and sp. of the Holmiidae and Bondonella sdzuyi n. sp. of the Neltneriidae. The known species of Neltneria, N. jacqueti and N. termieri , are revised.
TL;DR: In this article, the Prairie Bluff Chalk of Alabama and Mississippi yields a diverse ammonite fauna of Maastrichtian age, of which three species are new.
Abstract: The Prairie Bluff Chalk of Alabama and Mississippi yields a diverse ammonite fauna of Maastrichtian age. Twenty-eight species, of which three are new, are recorded herein: Pseudophyllites indra (Forbes, 1846), Hauericeras rembda (Forbes, 1846), Pachydiscus (Pachydiscus) maconensis n. sp., P. (P.) cf. gollevillensis (d'Orbigny, 1850), P. (P.) jacquoti (Seunes, 1890), P. (P.) egertoni (Forbes, 1846), Sphenodiscus lobatus (Tuomey, 1854), S. pleurisepta (Conrad, 1857), Coahuilites sheltoni Bose, 1928, Nostoceras (Nostoceras) alternatum (Tuomey, 1854), N. (N.) mendryki Cobban, 1974a, N. (N.) magdadiae Lefeld and Uberna, 1991, N. (N.) irregulare n. sp., Glyptoxoceras torquatum (Morton, 1834), Glyptoxoceras sp. A, Glyptoxoceras? sp., Baculites lomaensis Anderson, 1958, Baculites spp. A–C, Eubaculites labyrinthicus (Morton, 1834), E. carinatus (Morton, 1834), Baculites? trabeatus (Morton, 1834), Trachybaculites columna (Morton, 1834), Discoscaphites conradi (Morton, 1834), D. gulosus (Morton, 1834), Jeletzkytes criptonodosus Riccardi, 1983, Trachyscaphites alabamensis n. sp., and T. yorkensis (Stephenson, 1941). One genus, Trachybaculites, is new. The bulk of the fauna can be referred to a Discoscaphites conradi assemblage zone, but some elements in the fauna are significantly older.
TL;DR: The Lepreau Formation of southern New Brunswick, eastern Canada, contains a moderately diverse and abundant invertebrate ichnofauna, including 14 formal ichnotaxa.
Abstract: Alluvial fan and braided fluvial redbeds of the Triassic Lepreau Formation of southern New Brunswick, eastern Canada, contain a moderately diverse and abundant invertebrate ichnofauna. Fourteen formal ichnotaxa are recognized: Ancorichnus coronus, Ancorichnus cf. A. ancorichnus, Aulichnites isp., Cruziana problematica, Fuersichnus isp., Gordia marina, Palaeophycus striatus, Palaeophycus isp., Planolites isp., Rusophycus isp., Skolithos linearis, cf. Skolithos isp., and Taenidium isp. Two vernacular ichnotaxa, “inclined meniscate burrows” and “surface pit structures,” also occur. All these ichnotaxa are figured and briefly described. Collectively, the entire assemblage can confidently be assigned to the Scoyenia ichnofacies that, in the Lepreau Formation, represents a fluvial channel ichnocoenose. Specimens have been subject to marked taphonomic effects due to weathering and preservation in lithologies showing either insufficient variation in grain size or a grain size too coarse to preserve subtle morphological variations; as a consequence, ichno-taxobases are commonly obscured or obliterated. This may have influenced the apparent diversity of the assemblage, especially with regard to meniscate and simple horizontal burrows. It is proposed that application of “taphoseries,” theoretical series including ichnotaxa that may potentially be mistaken for each other with increasing taphonomic overprint, provides a safeguard against ichnotaxonomic misidentifications.
TL;DR: The assemblage of demosponge and hexactinellid sponges described here was collected from the Lower Cambrian, Atdabanian, Yu'anshan Member of the Chiungchussu Formation, at the Maotianshan and Xiaolantian sections in Chengjiang County, Yunnan Province, 70 km southeast of Kunming as discussed by the authors.
Abstract: The assemblage of demosponge and hexactinellid sponges described here was collected from the Lower Cambrian, Atdabanian, Yu'anshan Member of the Chiungchussu Formation, at the Maotianshan and Xiaolantian sections in Chengjiang County, Yunnan Province, 70 km southeast of Kunming. The sponges occur in relatively massive to weakly graded-bedded, grayish-yellow mudstone and silty mudstone. They are associated with other soft-bodied and skeletonized fossils. The new demosponge species and genera Choiaella radiata, Allantospongia mica, and the questionable sponge Parvulonoda dubia are described, along with new specimens of Leptomitus teretiusculus Chen, Hou, and Lu, 1989, the hexactinellid sponge, Triticispongia diagonata Mehl and Reitner, 1993 and the probable hexactinellid sponge, Saetaspongia densa Mehl and Reitner, 1993. The sponges occur in what may be distal turbidite deposits, and they may have been buried essentially in situ by these argillaceous accumulations.
TL;DR: A unified, uppermost Precambrian-Lower Cambrian, formation and member-level nomenclature is appropriate to Avalonian North America, and the stratigraphy of southeastern Newfoundland is applied in northern mainland Nova Scotia.
Abstract: Lithostratigraphy and depositional and epeirogenic history of the upper Placentian Series (Cuslett-Fosters Point Formations of the Bonavista Group) and Branchian Series (Brigus Formation) are identical in the northern Antigonish Highlands; Cape Breton Island; and eastern Placentia Bay, southeastern Newfoundland. Preliminary evidence suggests that the lower Middle Cambrian is present in the field area. A unified, uppermost Precambrian–Lower Cambrian, formation- and member-level nomenclature is appropriate to Avalonian North America, and the stratigraphic nomenclature of southeastern Newfoundland is applied in northern mainland Nova Scotia. Latest Placentian shoaling and deposition of a peritidal carbonate lithosome and unconformable onlap of the trilobite-bearing Branchian Series occurred in shallow Avalonian shale basins from eastern Massachusetts to central England. Uppermost Placentian Series faunas are very diverse in the Fosters Point Formation. Limited similarities with the South Australian Lower Cambrian are indicated by the presence of Camenella sp. cf. C. reticulosa, Conotheca australiensis, and Hyptiotheca sp., but these forms do not contribute to highly resolved correlation. Twenty-eight taxa are illustrated from the upper Placentian and Branchian Series. Caveacus rectus n. gen. and sp., a phosphatic problematicum, is limited to the upper Placentian Series. The oldest, skeletalized, macrophagous predators are the Pseudoconodontida and the later appearing Protoconodontida (n. orders). The Pseudoconodontida includes the Protohertzinacea n. superfamily and Strictocorniculacea n. superfamily (with the Rhombocorniculidae and Strictocorniculidae n. families). Strictocorniculum vanallerum n. gen. and sp. is described. The tommotiid family Sunnaginiidae emend. includes Eccentrotheca, Sunnaginia, Kulparina, and Jayceia deltiformis n. gen. and sp.
TL;DR: 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.
Abstract: r- Yarala burchfieldi n. gen. and sp. is described from Oligo-Miocene deposits of Riversleigh Station, northwestern Queens- land. 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 moder 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.
TL;DR: The Upper Missourian to lower Wolfcampian sequence (middle Kansas City through lower Council Grove Groups) of the Midcontinent U.S.A. is divided into seven biostratigraphic zones defined chiefly upon first occurrences of Streptognathodus species as mentioned in this paper.
Abstract: The Upper Missourian to lower Wolfcampian sequence (middle Kansas City through lower Council Grove Groups) of the Midcontinent U.S.A. (Kansas, Oklahoma, Nebraska, and Missouri) is divided into seven biostratigraphic zones defined chiefly upon first occurrences of Streptognathodus species. In ascending order, these are the: 1) Streptognathodus gracilis Zone; 2) Streptognathodus firmus Zone; 3) Streptognathodus pawhuskaensis deflectus Zone; 4) Streptognathodus virgilicus Zone; 5) Streptognathodus brownvillensis Zone; 6) Streptognathodus wabaunsensis s.l. Zone; and 7) Streptognathodus aff. barskovi Zone. The diagnostic Permian genus Sweetognathus first appears in the lower part of the S. aff. S. barskovi Zone. These zones coincide generally with Upper Carboniferous–Lower Permian conodont zones of Russia. Streptognathodus virgilicus, a new species common in the upper Shawnee and Wabaunsee Groups, is described.
TL;DR: 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.
Abstract: 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.
TL;DR: In this article, Carcineretid carapace samples were collected at three different localities of the Maastrichtian (Late Cretaceous) Cardenas Formation in San Luis Potosi, east-central Mexico.
Abstract: Twenty-four nearly complete carapace samples were collected at three different localities of the Maastrichtian (Late Cretaceous) Cardenas Formation in San Luis Potosi, 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
TL;DR: A well-preserved and diverse ostracod fauna of late Eocene, Kaiatan Stage age is described from a mudstone sample (Ashley Mudstone Formation) from the Waihao River outcrop near McCulloch's Bridge, South Canterbury, New Zealand.
Abstract: A well-preserved and diverse ostracod fauna of late Eocene, Kaiatan Stage age is described from a mudstone sample (Ashley Mudstone Formation) from the Waihao River outcrop near McCulloch's Bridge, South Canterbury, New Zealand. A total of 8,662 specimens are assigned to 104 species including one new genus and 13 new species. Of the new species all but the Cytheruridae are described herein. The new genus is Taracythere, type species T. proterva (Hornibrook, 1953) and the new species described here are: Pseudeucythere biplana, Eucythere sulcocostatula, Copytus pseudoelongatus, Neocytherideis reticulata, Patagonacythere waihaoensis, Munseyella pseudobrevis, Actinocythereis microagrenon and Pennyella leptodictyota. Because of a need for reillustration of established species, most of the remaining 91 species are illustrated and the systematics of some of these is remarked upon. Sixty-two species have been previously described, eight are tentatively referred to previously described species, and 21 are left in open nomenclature mainly due to paucity of material. The assemblage is interpreted as having lived in a low energy marine environment on the outer shelf or upper slope. Comparison with contempory ostracod faunas of southeastern Australia indicates very high affinity: 56 common genera, out of the 61 genera listed here. Considering the timing of Tasman seafloor spreading (Paleocene to Middle Eocene) and foundering of continental crustal regions of the eastern Tasman Basin to bathyal depths (initially Middle Eocene), trans-Tasman ostracod dispersal probably predates late Eocene times. The greater number of endemic Eocene genera recorded in Australia suggests that migration was dominantly eastwards.
TL;DR: Paleontology is in a stronger position than many other traditional fields of geology as discussed by the authors, and its greatest opportunities lie in the area where I believe our greatest opportunities now lie: the assessment of evolution and extinction in the framework of past environmental change.
Abstract: A s WE APPROACH the dawning of a new century, paleontology confronts exciting new prospects. These opportunities are not strictly confined to our traditional domain, but extend across a broad intellectual territory that we share with other fields of science. Our new interconnectedness has intellectual roots, but also political expediency. Today, having friends is especially important in the world of natural science. Three decades ago, large academic departments generally reserved a place for every conventional subdiscipline of geology. Now, however, institutional science is structured in such a way that the prospects of any field depend heavily on how it is perceived by researchers in nearby areas. A particular field may manage to prosper by standing alone and impressing its neighbors, but it is more likely to fare well by intertwining with them so that its presence is actually felt, not simply noticed. In these terms, paleontology is in a stronger position than many other traditional fields of geology. In this paper, I offer examples of research in the area where I believe our greatest opportunities now lie: the assessment of evolution and extinction in the framework of past environmental change. In two volumes in which I have had a hand, the National Academy of Sciences has advocated a prominent position for this general topic in the research agenda of the United States: Solid Earth Sciences and Society (Board on Earth Sciences, 1993] and Effects of Past Global Change on Life (Board on Earth Sciences, 1995). Recent history. -Three decades ago, paleontology entered a renaissance. A new generation of paleontologists began to treat fossils as creatures that were once alive. Of course, the fundamentally biological nature of fossils had not been overlooked previously; it had simply received less attention. Inevitably, some of the new paths taken failed to lead very far, but they nonetheless set us in motion. As our intellectual rebirth got underway in the mid-1960s, paleoecology was the area of emphasis, and soon thereafter functional morphology began to flourish. Then, in the 1970s, the punctuational model of evolution-however one now chooses to view it-dramatically elevated the profile of paleontology within the field of evolutionary biology. As late as the late 1960s, many paleontologists had been deferring to G. G. Simpson on any topic of macroevolution, but during the following decade they cast off their selfimposed straightjacket. Ironically, it was another kind of stagnation, morphological stasis on geological scales of time, that got paleontologists on the move. The impact was unfortunately for the most part limited to the biological sciences, while most paleontologists in academia and industry were working among physical geologists who had little interest in organic evolution. Then came the bolide. The new excitement that mass ex-
TL;DR: In this paper, the authors interpreted the damage exhibited by 18 of 954 relatively mature (> 35 mm diameter) specimens of Gonioloboceras goniolobum (Meek) from North American Midcontinent Upper Carboniferous sediments is interpreted to be bite marks caused by condrichthyans and other fish, particularly the symmoriid shark Symmorium reniforme.
Abstract: Damage displayed by 18 of 954 relatively mature (> 35 mm diameter) specimens of Gonioloboceras goniolobum (Meek) from North American Midcontinent Upper Carboniferous sediments is interpreted to be bite marks caused by condrichthyans and other fish, particularly the symmoriid shark Symmorium reniforme. It is likely that these and other predators regularly preyed on Gonioloboceras goniolobum because all of the analyzed specimens of Gonioloboceras exhibit some evidence of unrepaired damage, including broached camerae and missing body chambers. Two new characteristics utilized with caution to detect predatory events on ammonoids are raised oval or circular pedestals on internal molds and the breakage and termination of septa in conjunction with a broken external shell. When sufficient damage to the Gonioloboceras conchs occurred during predatory attacks, the broached camerae flooded, the conch became negatively buoyant, and it sank in the vicinity of the attack. When preserved, these conchs form a variable component of an autochthonous fossil accumulation that can include numerous other cephalopod taxa, which also were probably subjected to predatory attacks. Other, but not all, ammonoid accumulations in the fossil record form similar autochthonous deposits, or even autochthonous portions of mixed deposits.
TL;DR: The nominal Eucrossorhinus microcuspidatus and Cretorectolobus olsoni from the Campanian Judith River Formation of Montana, correspond to teeth from juvenile and adult individuals of one single species of orectoloboid shark.
Abstract: The nominal Eucrossorhinus microcuspidatus and Cretorectolobus olsoni from the Campanian Judith River Formation of Montana, correspond to teeth from juvenile and adult individuals of one single species of orectoloboid shark. The type series of the latter is heterogeneous and includes, besides the holotype, a tooth belonging to a different orectoloboid of a new generic type named Cederstroemia. This genus is unique among Orectolobiformes by comprising sharks with dental adaptations towards a strict cutting dentition. Two new species of Cederstroemia are described: C. triangulata from the Judith River Formation of Montana and C. nilsi from the early Campanian of the Kristianstad Basin, Skane, Sweden. An emended diagnosis is provided for Cretorec- tolobus, clarifying the dental characteristics of its members.
TL;DR: 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, indicating that the holes represent parasitism rather than predation.
Abstract: 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.
TL;DR: In this article, the age of a thin calcarenite unit locally present at the base of the Oligocene-to-Pleistocene sedimentary sequence, previously considered Rupelian to early Aquitanian in age, has been refined to 27.8-24.8 Ma.
Abstract: Integration of foraminiferal biostratigraphy, 87Sr/86Sr isotope stratigraphy, and traditional physical stratigraphy has provided a refined age control of a poorly known Oligocene-to-Pleistocene sedimentary sequence nonconformably covering the crystalline basement complex of the Calabrian microplate, a continental block which rifted off the southern margin of the European plate during Neogene time. In spite of the fossil-poor content of the sequence, the simultaneous use ofpaleontological and geochemical techniques have resulted in the following conclusions. 1) The age of an unnamed, thin calcarenite unit locally present at the base of the sequence, previously considered Rupelian to early Aquitanian in age, has been refined to Chattian (27.8-24.8 Ma). This calcarenite was considered a basal, conformable member of the overlying Stilo-Capo d'Orlando Formation. However, this study indicates that it is separated from the Stilo-Capo d'Orlando Formation either by an angular unconformity or by a disconformity representing a significant time interval. 2) The Stilo-Capo d'Orlando Formation has a latest Chattian-earliest Aquitanian to Bur- digalian age. Previously published reports suggested deposition over a much longer time span, ranging from late Rupelian to Langhian. 3) An unnamed deep-marine siliciclastic unit mostly composed of conglomerate and sandstone and previously considered Tortonian in age is, in fact, Serravallian to Tortonian. 4) The depositional interval of the "trubi," fine-grained marine deposits, has been independently confirmed to span the Pliocene-Pleistocene. The results of this study provide a framework for future sequence-stratigraphic and paleotectonic studies in the area, and prove the effectiveness of an integrated paleontological and geochemical (87Sr/86Sr) approach in the study of fossil-poor sedimentary sequences.
TL;DR: A branched, scratch-ornamented burrow system was described from early Pleistocene sediments of Sicily, Italy as discussed by the authors, which was probably produced by crustaceans.
Abstract: A branched, scratch-ornamented burrow system is described from early Pleistocene sediments of Sicily, Italy. The trace fossil occurs in a bed of volcanic ash beneath a shallow marine silty unit and is remarkable in possessing enlarged, ovoid chambers above the multiple branching points of a maze. The structure, named Spongeliomorpha sicula , was probably produced by crustaceans. A likely interpretion is as an agrichnion, in which microbial gardening took place in the chambers.
TL;DR: Pakicetus enamel organization, which is considered primitive for Cetacea, consists of a combination of radial and decussating enamel types, and Prism patterns include prisms with open (horseshoe-shaped) and closed (circular) boundaries.
Abstract: The tooth enamel of the earliest cetacean, Pakicetus, is described and compared to enamel of a primitive artiodactyl and a variety of primitive ungulate families. Pakicetus enamel organization, which is considered primitive for Cetacea, consists of a combination of radial and decussating enamel types. Prism patterns include prisms with open (horseshoe-shaped) and closed (circular) boundaries. Pakicetus enamel is similar to that of many primitive ungulates, including Diacodexis, the earliest artiodactyl, and Mesonychidae, an archaic ungulate family that often is considered close to the ancestry of Cetacea. This finding is consistent with the hypothesis, originally proposed on the basis of other aspects of morphology, that artiodactyls, cetaceans, and Mesonychidae are closely related.