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Displaying 11 - 20 from the 97 total records
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Upper Miocene Echinoids from the Yorktown Formation of Virginia and Their Environmental Significance
Porter M. Kier
41 pages, 7 figures, 10 plates
1972 (Date of Issue: 10 April 1972)
Number 13, Smithsonian Contributions to Paleobiology
DOI: 10.5479/si.00810266.13.1
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Abstract

Five echinoid species are described from the upper Miocene part of the Yorktown Formation of Virginia: Echinocardium orthonotum (Conrad), Arbacia imporcera (Conrad), Psammechinus philanthropus (Conrad), Mellita aclinensis Kier, and Spatangus glenni Cooke. The assemblage probably lived in shallow, warm-temperate waters, E. orthonotum deeply buried near shore, S. glenni shallowly buried offshore, and M. aclinensis with its test just covered near shore. Arbacia improcera and P. philanthropus presumably lived together intertidally and near shore, P. philanthropus living in holes in the indurated sediments or on the sand with its test covered with debris, whereas A. improcera probably was easily visible with nothing covering its test. Specimens formerly referred to E. orthonotum from the middle Miocene Choptank Formation from Maryland are referred to E. marylandiense, new species. Echinocardium gothicum (Ravenel), from the Bear Bluff Formation of South Carolina, is considered a junior subjective synonym of E. orthonotum.


Tertiary and Mesozoic Echinoids of Saudi Arabia
Porter M. Kier
242 pages, 50 figures, 67 plates
1972 (Date of Issue: 14 June 1972)
Number 10, Smithsonian Contributions to Paleobiology
DOI: 10.5479/si.00810266.10.1
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Abstract

The Mesozoic and Tertiary echinoids are described from Saudi Arabia. Fifty-one species, thirty-four of them new, occur in beds ranging from the Lower Jurassic to the Miocene. Two species are present in the Lower Jurassic (Toarcian) Marrat Formation, one is new: Acrosalenia marratensis. The Middle Jurassic (Bajocian-Bathonian) middle Dhruma Formation yielded eleven species, all new: Acrosalenia arabica, Acrosalenia dhrumaensis, Heterosalenia dhrumaensis, Pseudocidaris depressa, Polycyphus arabicus, Pseudosalenia magniprocta, Farquharsonia crenulata, Leioechinus namus (type species of new genus of the family Stomechinidae), Plesiechinus altus, Bothryopneustes arabica, and Bothryopneustes dhrumaensis. Thirteen species are described from the Late Jurassic (Callovian) upper Dhruma Formation, including twelve new species: Acrosalenia bowersi, Pseudocidaris romani, Pseudocidaris raratuberculata, Hypodiadema nanituberculata, Heterosalenia brocki, Heterosalenia ornata, Leioechinus amplus, Polycyphus parvituberculatus, Holectypus phelani, Pygurus (Pygurus) arabicus, Bothryopneustes kauffmani, and Bothryopneustes inflata. One species, Bothryopneustes orientalis Fourtau, occurs in the Callovian Tuwaiq Mountain Limestone. Eleven species are reported from the Late Cretaceous (Campanian or Maestrichtian) Aruma Formation, five of which are new. Rhynchopygus arumaensis, Proraster granti, Iraniaster bowersi, Iraniaster affinimorgani, and Iraniaster affinidouvillei. The sympatric pairing of two species of Iraniaster corresponds to a pairing of another two species of this genus in the Senonian of Iran. This pairing has been reported in living spatangoids. The Early Cretaceous Yamama Formation yielded the new species Pygurus (Pygurus) yamamaensis. Beds of Eocene or Oligocene age yielded three echinoid species, one of them new: Agassizia arabica. Nine species occur in the Miocene Dam Formation, three are new: Schizechinus pentagonus, Fibularia damensis, and Agassizia powersi. These Miocene echinoids are quite similar to species now living in the littoral zone.

The distribution and affinities of the echinoid species indicate faunal provinces in the Jurassic largely confined to Saudi Arabia, and in the Cretaceous confined to Saudi Arabia and Iran with some connections to North Africa but not to India. The Miocene distribution differs in being a part of a fauna occurring along the present borders of the Persian Gulf and the Arabian Sea of Saudi Arabia, Iran, West Pakistan, and northwestern India.


The Bradleya Problem, with Descriptions of Two New Psychrospheric Ostracode Genera, Agrenocythere and Poseidonamicus (Ostracoda: Crustacea)
Richard H. Benson
138 pages, 67 figures, 14 plates, 4 tables
1972 (Date of Issue: 30 October 1972)
Number 12, Smithsonian Contributions to Paleobiology
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Abstract

The “Bradleya problem” is concerned with the discovery and definition of a group of fossil and Recent reticulate ostracodes, several of which are common to Cenozoic deep-sea sediments in many parts of the world ocean floor. These species have often been misunderstood and taxonomically confused with genera characteristic of the study of shallow-water forms. The present study attempts to resolve some of these misunderstandings by designation of several important type-specimens, description of new evidence and the proposal of a new classification based on the concept of the evolution of a reticulum in response to environmental change. A method of pattern analysis is used to define elements of the reticulum subject to evolutionary change.

Over 40 reticulate species, which would have at one time been regarded as Bradleya, were examined; only 14 of these are assigned and belong to Bradleya. Two new genera, Agrenocythere and Poseidonamicus, are described for the reception of the others, and these are placed in the new subfamily, Bradleyinae, and placed with Thaerocytherinae Hazel in a new family (Thaerocytheridae Hazel). Twenty-seven of these species are described, including Bradleya arata (Brady), B. dictyon (Brady), B. normani (Brady), Agrenocythere radula (Brady), A. pliocenica (Sequenza), and A. hazelae (van den Bold). The diagnostic characteristics of the related genera Cletocythereis, Oertliella, Jugosocythereis, and Hermanites are discussed and illustrated.

It is concluded that the psychrospheric species Agrenocythere pliocenica, which has been reported from outcrops in Italy and a long core from the Tyrrhenian Sea floor, is most closely related to A. hazelae, which became geographically widespread during the Miocene. Bradleya, Jugosocythereis, Agrenocythere, and Cletocythereis, now genera in separate families, are all thought to have been derived from a common stock of Cretaceous age.


Permian Brachiopods of West Texas, I
G. Arthur Cooper and Richard E. Grant
231 pages, 39 figures, 23 plates
1972 (Date of Issue: 29 December 1972)
Number 14, Smithsonian Contributions to Paleobiology
DOI: 10.5479/si.00810266.14.1
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Abstract

The first of a projected six-part monograph on the brachiopods of the reference area for the North American Permian in the Glass, Guadalupe, Diablo, Delaware, Hueco, and Chinati Mountains of West Texas and adjacent New Mexico, this introductory volume recounts the history of geological work in the area, the development of the stratigraphic framework in the Wolfcamp, Leonard, and Guadalupe Series, and the basis for age assignments. It also explains field and laboratory techniques for collecting and preparing silicified fossils by means of acid, and it presents detailed measurements and lithic descriptions of the stratigraphic units in each mountain range in terms of the current nomenclature. The paleoecologic implications of the various rock and fossil types are interpreted, and the problems concerning large scale conglomerates, bioherms, and shell heaps are considered. The faunal composition of each stratigraphic unit in each mountain range is set forth as documentation for a local zonation of the brachiopods, intra-regional correlations, and age determinations with reference to the worldwide time scale for the Permian. There are brief accounts of each locality from which fossils were obtained. The full locality listing and the literature cited for the entire monograph are included in the present volume. Plates and line drawings illustrate the techniques of collecting and preparing fossils and the nature of certain stratigraphic units and lithic types; they diagrammatically depict numerous cross sections and correlations. Detailed maps indicate the exact positions of collections of fossils in the Glass Mountains. Taxonomic descriptions will appear in subsequent volumes.


New Brachiopoda from the Indian Ocean
G. Arthur Cooper
45 pages, 1 figure, 8 plates
1973 (Date of Issue: 14 February 1973)
Number 16, Smithsonian Contributions to Paleobiology
DOI: 10.5479/si.00810266.16.1
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The collections described in this paper add significantly to the brachiopod fauna. Most of the specimens were collected on the following cruises of the Woods Hole Oceanographic research vessel Anton Bruun while participating in the biological program of the International Indian Ocean Expedition: Cruise 1, east side of the Indian Ocean and Andaman Sea; Cruise 4B, off the Gulf of Cutch in the Arabian Sea; Cruises 7 and 8, in the Mozambique Channel and off the east coast of Africa; and Cruise 9, off the east coast of the Somali Republic. Of the fifteen species in the Anton Bruun collection, nine are described as new. Three of the new species represent new genera. In addition to these a fourth new genus is based on Rhynchonella valdiviae Helmcke from the southern Indian Ocean, and a rare new species of Argyrotheca is described from the Red Sea. Species described but poorly figured by W. H. Dall also are discussed and illustrated in this paper. Available pertinent geographical and ecological data are recorded and discussed. Although Mediterranean and Atlantic brachiopod elements have been known from the Indian Ocean, the Anton Bruun collections produced two genera hitherto found only in Pacific waters.


Vema's Brachiopods (Recent)
G. Arthur Cooper
51 pages, 5 figures, 9 plates
1973 (Date of Issue: 23 February 1973)
Number 17, Smithsonian Contributions to Paleobiology
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Abstract

Brachiopods dredged on the worldwide exploratory cruises of R/V Vema, of the Lamont-Doherty Geological Observatory of Columbia University, are important in expanding knowledge of brachiopod distribution and taxonomy. Thirty-two species are identified, of which six are new. Twenty-one genera are represented, one of which is new. The species of five genera and the genera of two lots could not be determined. The majority of the brachiopods were taken from waters deeper than 100 fathoms. One specimen of Abyssothyris was dredged from the greatest depth (6179 meters=20,267 feet) from which a brachiopod has been taken.


Stratigraphy and Preliminary Biostratigraphy of the Flagstaff Rim Area, Natrona County, Wyoming
Robert J. Emry
43 pages, 19 figures
1973 (Date of Issue: 17 July 1973)
Number 18, Smithsonian Contributions to Paleobiology
DOI: 10.5479/si.00810266.18.1
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Abstract

About 750 feet of sediments of the early Oligocene (Chadronian) White River Formation are exposed along Flagstaff Rim in south-central Natrona County, Wyoming. About 4,000 specimens of fossil vertebrates have been collected from these outcrops. The White River Formation unconformably overlies rocks ranging in age from Precambrian to medial or late Eocene. The lithology of the White River Formation is predominantly claystone and conglomerate in the lower part of the section, changing to predominantly tuffaceous siltstone and conglomeratic channel sandstones in the upper part. Four stratigraphic sections are described. A geologic map of about 40 square miles illustrates the areal limits of the White River Formation and its relationships to underlying and overlying formations. Several distinct and easily recognizable volcanic ash beds occur at intervals within the White River sequence. These serve as convenient markers for precise stratigraphic zonation of fossils and have also provided minerals for potassium-argon dating. Dates obtained range from 35.7 to 31.6 million years.

A boulder conglomerate unit, previously considered to be the basal unit of the White River Formation and/or part of the Wind River Formation is shown to be a distinct, and probably unnamed, unit, and should not be assigned to either of these formations. It unconformably overlies the Wind River Formation and is separated from the White River Formation by an erosional disconformity with several hundred feet of relief. This information allows new interpretations of the structure of the area and adds a previously unrecognized episode of deposition and erosion to the history of the area.

The most common fossil in the White River sequence is the artiodactyl genus Leptomeryx, which is represented by two morphologically distinct lineages. One lineage is provisionally divided into two and the other into three size groups that are believed to represent different species. The local stratigraphic ranges of the different groups do not overlap. In each lineage, the size increases higher in the section. None of the groups are definitely assigned to named species, pending studies to determine the validity and limits of the named species.

Preliminary analysis of other elements of the fauna shows that there is recognizable change through time within individual lineages and that the faunal composition as a whole changes through time, within the local sequence. When the entire fauna is analyzed in detail, it should be possible to establish local range zones of the fossil species and, by their use, to gain greater temporal resolution within Chadronian time than has previously been possible.


Permian Brachiopods of West Texas, II
G. Arthur Cooper and Richard E. Grant
561 pages, 1 figure, 168 plates
1974 (Date of Issue: 16 April 1974)
Number 15, Smithsonian Contributions to Paleobiology
DOI: 10.5479/si.00810266.15.1
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Abstract

The second of a six-part monograph on brachiopods from the reference area for the North American Permian in mountain ranges of West Texas and adjacent New Mexico, this volume presents a historical resumé of the ordinal classification of the Brachiopoda, definitions of morphological terms, techniques of measuring specimens, and remarks on the naming of species. The major part of the work consists of descriptions and illustrations of genera and species in the inarticulate superfamilies Discinacea and Craniacea and the articulate superfamilies Eichwaldiacea, Orthotetacea, Derbyiacea, and Lyttoniacea.


Ultrastructural Studies on Graptolites, 1: The Periderm and Its Derivatives in the Dendroidea and in Mastigograptus
Adam Urbanek and Kenneth M. Towe
48 pages, 2 figures, 30 plates, 2 tables
1974 (Date of Issue: 15 May 1974)
Number 20, Smithsonian Contributions to Paleobiology
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Abstract

Organic skeletons of two dendroid graptolites and an aberrant sessile graptolite (Mastigograptus sp.), all Ordovician in age, were isolated chemically from the matrix and used subsequently for ultrastructural studies with the transmission electron microscope. Peridermal material of all forms investigated proved to be unusually well preserved as far as ultrastructural features are concerned, and it reveals a variety of fabrics and patterns classified into two structural categories: fabric and tissue. Following Kozlowski (1949) the term tissue is retained for larger structural components of the periderm, defined from a morphogenetic point of view. To distinguish the fusellar and cortical tissue, directly observed structures are classified as fabrics defined by the form of their unit elements and their spatial interrelations. Fusellar, cortical, sheet, and crassal fabrics were distinguished and characterized. Fusellar and cortical fabrics are both fibrillar but differ in fibril diameter. Fibrils are branched and wavy, or straight, producing a mesh, or showing a parallel arrangement and packed into layers. Sheet fabric is an electron dense, homogenous or densely reticulated material delimiting particular layers within the cortical tissue or producing an external pellicle on the fuselli. Crassal fabric is an electron dense and featureless material found in the sheath of stolons and as a secondary deposit inside the thecae in Mastigograptus sp. A given peridermal tissue is thus composed of more than one fabric, but with a predominance of either a fusellar or cortical one.

In addition to an earlier observation (Towe and Urbanek, 1972) that cortical fibrils are collagen-like, arguments are presented in favor of the opinion that fusellar fibrils may also represent the collagen group of fibrous proteins. Frequently observed passages of a single fusellar fibril within the body of a fusellus, into a fibril of an outer lamella of the same fusellus, showing a typically cortical arrangement of the fibrils, seems to indicate the same chemical nature of the fibrous components in both fabrics. Differences in their physical organization are here ascribed to the changes in the composition of the matrix.

The unexpected presence of a cortical coating on the inner thecal walls in Dictyonema sp. is explained through delayed growth of lateral thecae in the triad and very early deposition of cortical tissue over the outer surface of the young autotheca (autocortex). This wall is later overgrown by lateral thecae to become an inner thecal wall. A common cortical envelope secreted later over the outer surface of all thecae is called the rhabdocortex. The presence of a cortical component on the inner surface of the inner thecal walls in Acanthograptus sp. suggests, that at least in some dendroids also, the soft tissues inside the thecal cavity were capable of secretion of the cortical tissue. This changes the classical scheme of cortical tissue formation as proposed by Kozlowski (1949).

The fusellar tissue in Mastigograptus sp. reveals unusual, erratic distribution of fuselli, which are present only on certain places in the thecal wall. Over large areas these are substituted by a peculiar layer of electron dense, homogenous material termed here the crassal fabric. This is interpreted as a presumed secondary resorption and subsequent substitution of the fusellum by the crassal layer. The basal disc of Mastigograptus sp. is composed of a material resembling that in cortical fabric but with fewer fibrils embedded in abundant matrix. The lower layer of the basal disc is provided with numerous filaments made of delicate fibrils. The sclerotized sheaths of stolons recognized in Acanthograptus sp. are made mainly of the crassal fabric.


Ultrastructural Studies on Graptolites, 2: The Periderm and Its Derivatives in the Graptoloidea
Adam Urbanek and Kenneth M. Towe
48 pages, 3 figures, 24 plates, 1 table
1975 (Date of Issue: 16 May 1975)
Number 22, Smithsonian Contributions to Paleobiology
DOI: 10.5479/si.00810266.22.1
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Abstract

The ultrastructure of the organic periderm in Didymograptus sp. (Lower Ordovician), Pristiograptus dubius (Suess), and in the retiolitid Holoretiolites mancki (Münch) (both Upper Silurian), isolated by chemical treatment, has been studied with the transmission electron microscope. In the first two graptoloids, with continuous peridermal walls in the rhabdosome, the periderm is composed of the major fusellar and cortical components which are essentially the same as those recognized earlier in the dendroid graptolites (Urbanek and Towe, 1974). In addition, both graptoloids examined show important differences in the fabric ultrastructure of some homologous parts of the rhabdosome such as the nema in Didymograptus sp., the virgula in P. dubius, as well as the prosicula in both. These occurrences of sharp differences in the submicroscopic structure of homologous parts of rhabdosomes within the Graptoloidea are suggestive of rather substantial phylogenetic changes in the history of the group at the ultrastructural level.

In addition to the peridermal materials previously recognized in the dendroids, certain parts of the rhabdosomes in graptoloids are constructed of a peculiar fabric termed the virgular fabric. It has been recognized so far in the virgula of Pristiograptus dubius and in the lists of the peridemal framework (clathrium) of Holoretiolites mancki, where it is the only component of the skeleton. It is composed of layers made of lucent fibrils with a unique substructure, embedded in an electron dense and homogeneous matrix, and separated by thin layers formed by this matrix alone. The biochemical relationships of these fibrils with extant fibrous materials are uncertain but a correlation with certain collagens has been suggested.

The structural relationships of the outer cortical deposit of thecae examined in Didymograptus sp. and in Pristiograptus dubius are indicative of different modes of secretion of the cortex in both. In Didymograptus sp. the cortex is formed through an accumulation of the overlapping outer lamellae of fuselli, while in Pristiograptus dubius the layers of the cortex are laid down over the surface of the fuselli as independent units. Moreover, other observations seem to indicate that in Didymograptus sp. the cortex has been formed in a somewhat different way at certain places on the rhabdosome. There does not seem to be any single, uniform pattern of secretion of the cortex in the Graptoloidea.


Displaying 11 - 20 from the 97 total records