bluuebunny/crossref_metadata_2025_split huggingface dataset:
Systematics, hinge, and internal morphology of the Devonian bivalve, Nuculoidea corbuliformis (Hall and Whitfield)
Authors: Bailey J. Bowman 
Published: August 2016

Although Nuculoidea corbuliformis (Hall and Whitfield) is the most widespread Devonian nuculid species in North America, the hinge and internal morphology have not been adequately described. A newly excavated hinge shows the dentition and resilifer to be fundamentally similar to those of other species of Nuculoidea, while the resilifer morphology and shell shape more closely link N. corbuliformis to post-Devonian nuculid species. An internal mold of a probable N. corbuliformis found among Hall's original syntypes (here restudied) shows typical nuculid interior morphology. These new data allow the problematic genus Nuculoidea Williams and Breger to be further clarified.Comparisons with N. corbuliformis suggest that N. aquisgranensis (Beushausen), N. herzeri (Nettleroth), N. neda (Hall and Whitfield), N. niotica (Hall and Whitfield), N. trigona (Spriestersbach), N. macrorhyncha (Spriestersbach), and N. subtrigona (Simpson) are subjective junior synonyms.
Late Ordovician solitary rugose corals of the St. Lawrence Lowland, Québec
Authors: Elias Robert J. , Brandt Danita S. , Clark T. H. 
Published: August 2016

Two species of solitary rugose corals occur in Late Ordovician strata of the St. Lawrence Lowland. Grewingkia canadensis (Billings, 1862) appears in the upper part of the Nicolet River Formation (upper St. Hilaire Member) and is far more common in the overlying Pontgravé River Formation. A single specimen of Streptelasma divaricans (Nicholson, 1875) is known from the Pontgravé River. Their presence confirms that this area is situated within the Richmond Province and that the upper Nicolet River, as well as the Pontgravé River, is Richmondian in age. Solitary Rugosa were introduced to this biogeographic province during an early Richmondian transgression, marked in the upper Nicolet River Formation by a coarser clastic interval. That event permits correlation between the St. Lawrence Lowland in the eastern part of the Richmond Province and the North American type Upper Ordovician (Cincinnatian Series) of the Cincinnati Arch region in the western part of the province.A comparative morphologic, paleoecologic, and biostratinomic analysis of solitary corals indicates that normal, low-energy conditions were interrupted occasionally by high-energy events (probably storms) during deposition of the upper Nicolet River and Pontgravé River Formations. Water depth increased northwestward in the St. Lawrence Lowland area. Deposition of these siliciclastic prodelta to delta front sediments was generally continuous and the sedimentation rate was usually high because of rapid basin subsidence and comparatively close proximity to the Taconic Mountains. In the western part of the Richmond Province, farther from the source area, carbonate as well as clastic sediments accumulated, periods of nondeposition were more frequent, and the sedimentation rate was relatively low. Corals disappeared from the St. Lawrence Lowland area during the Richmondian, when delta top facies of the Bécancour River Formation succeeded the Pontgravé River Formation due to a glacio-eustatic regression and progradation of the Queenston Delta.
Enigmatic eight-meter trace fossils in the Lower Pennsylvanian Lee Sandstone, central Appalachian Basin, Tennessee
Authors: Wnuk Christopher , Maberry John O. 
Published: August 2016

Enigmatic tubular trace fossils up to eight meters long occur in the Lower Pennsylvanian Middlesboro Member of the Lee Formation. Two morphotypes occur: type 1 trace fossils are plain, smooth, vertical, nonbranching, parallel-walled, tubular structures; type 2 trace fossils branch, have walls with faint vertical striations, regularly or irregularly spaced nodes, and funnel-shaped terminations. Sandstone casts filling type 2 structures have helical spiral morphology, and, in rare individuals, faint meniscate fills have been observed. Both trace-fossil morphotypes have poorly cemented wall linings containing framboidal pyrite, amorphous carbon, quartz sand, and poorly preserved fecal material.The trace fossils occur in a massive, structureless, channel-form sandstone, originating at the contact between a channel lag and the overlying massive fill. The stratigraphic sequence is interpreted to represent a barrier island transgressing an estuarine facies. A tidal inlet within the barrier facies scoured into the underlying estuarine sediments. Subsequent rapid filling of the inlet led to the deposition of the massive sandstone.Origin of these structures is uncertain. The preponderance of evidence favors the hypothesis that the structures are escape burrows of animals that had colonized, or were concentrated in, the lag and were suddenly buried by the deposition of the massive sand. However, no likely burrower has been identified, and several characteristics of the structures and the enclosing sediments indicate that they may be completely inorganic in origin.
Medusaegraptus mirabilisRuedemann as a noncalcified dasyclad alga
Authors: Duca Steven T. Lo 
Published: August 2016

Medusaegraptus mirabilisRuedemann was originally described as a dendroid graptolite and is currently listed in theTreatise on Invertebrate Paleontologyamong graptolites incertae sedis. Recently, several localities yielding abundantM. mirabiliswere discovered, prompting renewed interest in the taxonomic affinities of this species. Based on a study of the morphology and paleoecology ofM. mirabilis, this species is herein considered to represent a noncalcified dasyclad alga. Other species ofMedusaegraptusare similarly considered.Medusaegraptid-bearing strata commonly contain other exceptionally preserved fossils and represent conservation lagerstaetten. Consideration of medusaegraptids as dasyclad algae restricts the depth at which these deposits could have occurred.
Small shelly fossils from Antarctica: an Early Cambrian faunal connection with Australia
Authors: Evans K. R. , Rowell A. J. 
Published: August 2016

Kennardiids, members of a family of organisms that bore phosphatic sclerites, are present in Antarctica; previously, they had been found only in Australia. This new occurrence reinforces the concept of a faunal province shared between the continents during Early Cambrian time. Although the two known genera of kennardiids,DailyatiaBischoff andKennardiaLaurie occur in Antarctica and Australia, no species are common to both continents.Dailyatiais interpreted as having had tightly fitting sclerites that armored a bilaterally symmetrical, bipolar body; two alternative reconstructions are presented. Taxa include two new species,Dailyatia braddockiandDailyatia odyssei, and two unnamed species ofKennardia.
New early Paleozoic Hyolithida and Orthothecida (Hyolitha) from North America
Authors: Malinky John M. 
Published: August 2016

Reexamination of collections of North American Hyolitha reveals the presence of several new genera and several taxa previously known only from southeastern Europe and the Soviet Union. New representatives of the family Hyolithidae in North America are Doescherina clarki n. gen. and sp. from the Upper Cambrian of Montana and Grantitheca glenisteri n. gen. and sp. from the Lower Cambrian of New York. The geographic and stratigraphic ranges of Nevadotheca Malinky are extended by placement of Hyolithes excellens Billings from the Lower Cambrian of Newfoundland and H. princeps Billings from the Lower Cambrian of Quebec in that genus, and by the occurrence of the new species N. heckeli in the Upper Cambrian of Tennessee. Diversity within the Hyolithidae is further increased by the discovery of specimens representing a new genus in the Upper Cambrian of Alberta, but that genus remains indeterminate because those specimens are not well preserved.The type lot of Hyolithes communis Billings from the Lower Cambrian of Quebec is here included under Nitoricornus Syssoiev, to which the species H. impar Ford from the Lower Cambrian of New York is also transferred. Morphology of specimens of Hyolithes quadricostatus Shaler and Foerste from the Lower Cambrian of Newfoundland requires placement under Holmitheca quadricostatus (Shaler and Foerste) and Novitatus mapesi n. sp., family Novitatidae, order Orthothecida. Formerly, Nitoricornus Syssoiev, Holmitheca Syssoiev, and Novitatus Syssoiev were known only from the Soviet Union. These occurrences extend their geographic ranges to North America. The first known representative of the family Pauxillitidae Marek in North America, Neopauxillites zlatarskii n. gen. and sp., extends the range of that family from the Ordovician of Czechoslovakia to the Lower Cambrian of Newfoundland.Overall poor preservation of type specimens of Hyolithes americanus (Hall), H. gregarius (Meek and Hayden), H. primordialis (Hall), and H. welleri Roy precludes complete diagnoses of these species and confident assignment to genus. Hyolithes americanus and H. welleri are tentatively included under Grantitheca; the other species remain under Hyolithes with question. The names of these species should not be used for new material until better preserved topotypes become available for study.
Taxonomy and biostratigraphic significance of some Middle Cambrian trilobites from the Conasauga Formation in western Georgia
Authors: Schwimmer David R. 
Published: August 2016

Biostratigraphic correlations of the Conasauga Formation in the southern Appalachians have been hindered by unreliable trilobite taxonomy. New fossil collections and re-examination of type specimens allow revision or confirmation of assignments for several Middle Cambrian trilobite taxa. These revisions reveal sufficient relationships with trilobites outside the region to place fossiliferous strata in Floyd County, Georgia, into the Oryctocephalus and Bolaspidella assemblage zones of the Middle Cambrian section defined for the Great Basin.Trilobite taxa considered are: (Agnostida) Baltagnostus centerensis (Resser, 1938) and Peronopsis cf. P. cuneifera (Barrande, 1846); (Ptychopariida) Alokistocare americanum (Walcott, 1916), Elrathia antiquata (Salter, 1859), Asaphiscus gregarius Walcott, 1916, and Glyphaspis cf. G. capella (Walcott, 1916).
Trace fossils and marine-nonmarine cyclicity in the Fountain Formation (Pennsylvanian: Morrowan/Atokan) near Manitou Springs, Colorado
Authors: Maples Christopher G. , Suttner Lee J. 
Published: August 2016

The Lower Pennsylvanian (Morrowan/Atokan) portion of the Fountain Formation in the Manitou Springs, Colorado, area commonly has been interpreted as a subaerial alluvial fan. However, approximately 12 marine-nonmarine cycles, each represented by a discrete progradational sequence, have been recognized within the lower third of the Fountain Formation in this area. The typical cycle is composed of six lithofacies: 1) transgressive-lag conglomerate; 2) offshore mudstone; 3) hummocky crossbedded sandstone; 4) planar crossbedded granular sandstone; 5) low-angle, crossbedded, coarse-grained sandstone; 6) lenticular conglomeratic sandstone. Only lithofacies 6 is nonmarine (alluvial) in origin. Two diverse trace-fossil assemblages (totalling 18 ichnogenera and 20 ichnospecies) within the Fountain Formation are restricted to the marine portions of the section, or to those portions within 1 m below marine-deposited strata. The assemblage includesArenicolites carbonarius,?A.ichnosp.,Aulichnites parkerensis,two types ofChondrites,?Conostichus broadheadi,?Crossopodiaichnosp.,Curvolithus manitouensis(ichnosp. nov.),Eioneichnosp.,Lockeiaichnosp.,Macaronichnus segregatis, Palaeophycus heberti, Palaeophycus striatus, Planolites beverleyensis, Psammichnites plummeri, Rhizocorallium irregulare,?Skolithosichnosp.,Taenidium serpentinum,?Teichichnusichnosp., ?Thalassinoidesichnosp., ?Zoophycosichnosp., and several unnamed traces.Trace fossils in the Fountain Formation can be used as indicators of sedimentary processes (e.g., rates of deposition, energy regime). Trace-fossil composition changes along a roughly south-to-north, nearshore-to-offshore gradient, generally reflecting increased influence and duration of normal-marine sedimentation. Ichnotaxa present and their distributions within marine strata in the lower part of the Fountain Formation suggest that they belong to theCurvolithusichnoassemblage, which has been shown to indicate high sedimentaiton rates in relatively nearshore shelf settings. TheCurvolithusichnoassemblage can be subdivided intoMacaronichnus-dominated andCurvolithus-dominated parts.Macaronichnus-dominated portions of the Fountain Formation indicate generally higher wave-energy sedimentation as compared withCurvolithus-dominated portions.
Lower and Middle Devonian brachiopod-dominated communities of Nevada, and their position in a biofacies-province-realm model
Authors: Johnson J. G. , Klapper G. , Johnson J. G. 
Published: August 2016

Lower and Middle Devonian brachiopod-dominated communities of Nevada are numerous (46) and most are positioned on or adjacent to the carbonate-platform foreslope or ramp. Level-bottom community chains are fundamentally different from community associations that are interrupted by a platform margin. All communities require relative abundance data of constituent species for recognition. These communities prove to be endemic to the Nevada-southeastern California area, even though faunal similarities with distant regions in North America can be recognized. Analogous communities, the same age as comparable communities in Nevada, differ in overall specific content and in relative abundance of diagnostic species. Identification of analogous communities requires recognition of common physical environments (first) and faunal similarity (second). Groupings of communities based on presence-absence data of key species and genera are not meaningful.Biofacies boundaries sited on carbonate-platform foreslopes separate community associations and also act as filter boundaries for faunal realms. The platform and peripheral biofacies thus delineated are also realms, a pattern that is repeated by different organisms from Cambrian to Cenozoic. Biofacies boundaries shift in concert with large-scale sea-level fluctuations. During platform emergence, most faunas are peripheral and therefore cosmopolitan. Transgression initially forms small, isolated epeiric seas populated from offshore, and endemic faunas evolve. Increased transgression merges epeiric seas and faunas, reducing provinciality and diversity through competition. Regression results in extinctions in proportion to its rate and the area involved. The cycle repeats.Thehermanni-cristatusconodont Zone is replaced with the namehermanniZone. ThedisparilisZone is divided into Lower and Upper Subzones. ThenorrisiZone is proposed at the top of the Middle Devonian.
Probable calcified metaphytes in the latest Proterozoic Nama Group, Namibia: origin, diagenesis, and implications
Authors: Grant S. W. F. , Knoll A. H. , Germs G. J. B. 
Published: August 2016

Samples from the Huns Limestone Member, Urusis Formation, Nama Group, at two adjacent localities in southern Namibia contain thin foliose to arched, sheet-like carbonate crusts that are 100–500 µm thick and up to 5 cm in lateral dimension. Morphologic, petrographic, and geochemical evidence supports the interpretation of these delicate crusts as biogenic, most likely the remains of calcified encrusting metaphytes. The original sediments of the fossiliferous samples contained aragonitic encrusting algae, botryoidal aragonite cements, and an aragonite mud groundmass. Spherulites within the precursor mud could represent bacterially induced mineral growths or the concretions of marine rivularian cyanobacteria. Original textures were severely disrupted during the diagenetic transition of aragonite to low-magnesian calcite, but some primary structures remain discernible as ghosts in the neomorphic mosaic. Gross morphology, original aragonite mineralogy, and hypobasal calcification indicate that the crusts are similar to late Paleozoic phylloid algae and extant peyssonnelid red algae. Structures interpreted as possible conceptacles also suggest possible affinities with the Corallinaceae.Two species of Cloudina, interpreted as the remains of a shelly metazoan, are also known from limestones in the Nama Group. It is possible, therefore, that skeletalization in metaphytes and animals arose nearly simultaneously near the end of the Proterozoic Eon.
Mode of growth and life-history strategies of a Late Ordovician halysitid coral
Authors: Lee Dong-Jin , Elias Robert J. 
Published: August 2016

The upper surface of the corallum ofCatenipora rubrawas often at or just above the sediment-water interface during life. The vertical growth rate was barely sufficient to keep pace with background sedimentation and possible subsidence of the corallum. Therefore, the colonies were in constant danger of being covered by influxes of sediment, especially during storms. This was compensated by the ability of polyps to respond to sedimentation events and by certain aspects of colony growth. Rapid regeneration following partial mortality involved budding of uninjured polyps and rejuvenation of damaged individuals, in some cases accompanied by a type of axial increase not previously known in tabulate corals. Rapid lateral expansion was possible because small, “immature” polyps could bud and grow in a reptant manner.Interconnected ranks of the cateniform corallum served to dam shifting sediment at the periphery of the colony. Lacunae within the colony were reservoirs for material that breached peripheral ranks and for sediment that settled on the ranks and was rejected by polyps or removed by passive flow. Polyps comprising the colony were distributed over a large area of the substrate surface, thereby decreasing the probability of complete mortality during sedimentation events and increasing the probability that a sufficient number of individuals would survive to ensure optimum regeneration. The corallum, anchored in the substrate and with sediment filling the lacunae, provided a broad, stable base during high-energy events.It remains to be established how widespread these growth patterns and strategies were among other corals with cateniform colonies, a form that appeared in many unrelated stocks. Most previous workers emphasized physical strength when considering functional morphology, following a tacit assumption that the corallum rose high above the substrate and was therefore susceptible to breakage during high-energy events. An understanding of the origin of cateniform patterns and the phylogeny of these corals requires knowledge of their modes of growth and life-history strategies, which were genetically as well as environmentally controlled.
The concepts of astogeny and ontogeny in stenolaemate bryozoans, and their illustration in colonies of Tabulipora carbonaria from the Lower Permian of Kansas
Authors: Pachut Joseph F. , Cuffey Roger J. , Anstey Robert L. 
Published: August 2016

Recognition of ontogeny within a stenolaemate bryozoan colony requires separating the individualistic aspects of a zooid's growth from those of its neighbors. The ancestrula is the only zooid within a colony that always displays a partially independent ontogeny that ceases when it starts to experience shared changes with its neighboring daughter zooids during subsequent accretionary skeletal growth.Stenolaemate astogeny (shared changes across multiple zooids during the growth of both the ancestrular zooid and its asexual descendants) includes all coordinated changes in the size, shape, number, and calcification of autozooids, polymorphs, and extrazooidal structures, as well as changes within autozooids or polymorphs, such as the formation of basal diaphragms and brown bodies. Despite the fact that many of these directional changes occur within individual zooids, they are not part of ontogeny because they are taking place simultaneously across zooids that share a common skeleton, extrazooidal tissues, and pseudocoelomic spaces.Shared directional multizooidal changes occurring during colony growth provide a confirmatory test for the existence of astogeny. Astogeny was statistically evaluated in 6–15 characters measured within the exozones of four colonies of Tabulipora carbonaria (Worthen in Worthen and Meek, 1875). Statistically significant (at P ≤ 0.05) directional changes took place across growth stages within the exozone in the following morphometric characters: zooecial density, zooecial wall surface area, acanthostyle density, zooecial wall thicknesses, maximum acanthostyle diameters, and intrazooecial diaphragm abundances. Overall, earlier exozonal growth stages differ statistically from those of the later exozone, with characteristics of intermediate growth stages intergrading between the two. Discriminant function analysis segregated intervals of exozonal growth into early-, intermediate-, and late-stage clusters, confirming patterns delineated by univariate statistical tests.Based on these exozonal growth patterns, heterochronic changes in exozone astogeny characterized evolution within and across species of Tabulipora. Onshore populations of T. carbonaria were astogenetically progenetic relative to offshore ones along an environmental gradient across Kansas, whereas local populations became temporally more hypermorphic in a short-term stratigraphic succession of similar environments. Tabulipora carbonaria originated by astogenetic recapitulation in populations of its probable ancestor, T. ramosa. Therefore, speciation, microevolution, and clinal variation in Tabulipora all involved heterochronic modifications of exozone astogeny.
Life histories and population structure of Pennsylvanian brachiopods from north-central Texas as determined from size-frequency analysis
Authors: Cate A. S. , Evans I. 
Published: August 2016

Paleoecological analysis of three attached spiriferid species (Punctospirifer kentuckyensis, Crurithyris planoconvexa, and Hustedia mormoni) and six free-living chonetid brachiopod species (Chonetinella flemingi, Chonetinella verneuiliana, Lissochonetes geinitzianus, Mesolobus mesolobus, Neochonetes fragilis, and Quadrochonetes geronticus) from Middle and Upper Pennsylvanian strata of north-central Texas has been undertaken using, in part, population dynamics information derived initially from size-frequency distributions. The brachiopod populations in this study are believed to represent in situ assemblages formed by noncatastrophic mortality. Spiriferid species occurred in large populations characterized by positively skewed size-frequency distributions in which few individuals attained the maximum potential size reported for a given species. Chonetid species, in contrast, occurred in smaller numbers characterized by negatively to low positively skewed size-frequency distributions in which greater numbers of individuals attained maximum potential size.The differences observed in the population structure of these two groups can best be explained as reflecting different adaptive lifestyle strategies that are shared at the ordinal level. Morphological features common to chonetid species enabled individuals to live freely at the sediment-water interface and perhaps reorient their position if disturbed. Based on size-frequency analysis, low-density populations of chonetids appear to produce relatively larger numbers of survivors in the adult and maximum size classes. Spiriferids were constrained to attachment surfaces occupied at the time of larval settlement, and individuals presumably had no mechanism to regain life position if overturned or if this surface became unstable. These physical limitations seem to be reflected in a population structure in which higher density populations were required to overcome the high mortality rates incurred by individuals. This appears to be a case in which size-frequency distributions have not been significantly altered by taphonomic overprint and in which size-frequency analysis can be used to detect differences in the life histories and population structure of brachiopod species.