Journal of Paleontology

Published by: The Paleontological Society



Journal of Paleontology 80(5):867-888. 2006
doi: 10.1666/0022-3360(2006)80[867:NFBOTG]2.0.CO;2

NEW FENESTRATE BRYOZOA OF THE GERSTER LIMESTONE (PERMIAN), MEDICINE RANGE, NORTHEASTERN NEVADA

EDWARD M. SNYDERa and ERNEST H. GILMOURb

aInstitute for Environmental Studies, Shepherd University, Shepherdstown, West Virginia 25443, < >

bDepartment of Geology, Eastern Washington University, Cheney 99004, < >

Abstract

Six new species of fenestrate bryozoans, middle to late Wordian, occur in the Gerster Limestone of northeastern Nevada. These bryozoans are similar to lower Kazanian species described from the Russian Platform. The two species of Wjatkella and Polypora from the Gerster Limestone are much more similar to the Russian species than they are to the two species recently described from the allochthonous late Wordian Mission Argillite of northeastern Washington.

New species described from the Gerster Limestone are Rectifenestella cordiretiformis, Wjatkella hemiseptifera, Kingopora wardlawi, Kingopora inflata, Polypora keyserlingiformis, and Polyporella helgersoni. The presence of only six species of fenestrate bryozoans in nearly 260 m of limestone and siltstone is notable.

Accepted: May 23, 2005



references

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Figure 1—Index map showing sampled localities in Medicine Range, Nevada.

Figure 2—Biostratigraphic distribution of fenestrate bryozoans in Gerster Limestone of the Medicine Range, Phalen Butte, Spruce Mountain, and South Pequop measured sections, northeastern Nevada.

Figure 3Recifenestella cordiretiformis n. sp.; 1, diagrammatic longitudinal section showing changing chamber outline from deep section near midbranch (bottom of fig.) to shallow section near abaxial edge of branch (top of fig.); typical chamber outline in deep (arrow A), mid- (arrow B), and shallow (arrow C) sections; 2, diagrammatic tangential section showing chamber outline from deep section near reverse wall budding site (bottom of fig.) to shallow section near obverse surface (top of fig.); typical triangular-shaped chambers near reverse wall and midchamber (arrow A) and circular aperture in shallow tangential (arrow B); well-developed superior hemisepta (arrow C); and apertural margins causing pronounced inflections in fenestrules (arrow D); 3, diagrammatic transverse sections across three branches showing typical orientation of apertures relative to plane of obverse surface (arrow A); and typical rounded triangular chamber cross section (arrow B); superior hemiseptum at chamber/vestibule boundary (arrow C); 4, three-dimensional reconstruction of typical chamber shape illustrating longitudinal view; well-developed inferior hemiseptum (arrow A) and superior hemiseptum (arrow B); 5, three-dimensional reconstruction of tangential view as seen from obverse surface; autozooecium with triangular tubular shape (arrow A); well-developed superior hemiseptum (arrow B); and short inferior hemiseptum (arrow C); 6, three-dimensional reconstruction of transverse section as viewed from proximal end of branch; note inflection away from midbranch.

Figure 4Rectifenestella cordiretiformis n. sp.; 1, mid- (bottom left) to midshallow (top left) tangential peel of holotype, SU 1001, showing enlargement of chamber at distal end and initial development of superior hemisepta (arrow), ×160; 2, transverse peel of paratype, EWU Bz 240, showing several branches, aperture orientation to obverse surface (arrow), and biserial autozooecial emplacement, ×40; 3, deep to midshallow tangential peel of paratype, EWU Bz 241, showing reverse longitudinal striae (arrow A), autozooecial chamber outline near reverse wall (arrow B), in midchamber (arrow C), and in midshallow (arrow D). Note straight branches and regularly placed thin dissepiments, ×40; 4, midlongitudinal peel of holotype, SU 1001, showing typical chamber outline (arrow), ×40; 5, shallow tangential peel of paratype, EWU Bz 241, illustrating circular to slightly ovate, elongate proximodistal aperture (arrow A) with well-developed peristome, gap common at proximoadaxial end (arrow B), ×160; 6, deep to shallow tangential peel of holotype, SU 1001, showing well-developed superior hemisepta (arrow A), inflection of aperture into fenestrule opening (arrow B), well-developed keel along middle of obverse branch surface atop which develop large obverse nodes (arrow C), ×40; 7, transverse peel of paratype, EWU Bz 240, showing branch outline, elliptical elongate adaxial direction, well-developed node (arrow A) emplaced atop obverse keel, typical chamber outline in midtransverse view (arrow B) and few, well-developed longitudinal striae along reverse surface (arrow C), ×160; 8, midlongitudinal peel of holotype, SU 1001, showing typical chamber outline with well-developed long vestibule (arrow A), well-developed inferior hemisepta (arrow B), and superior hemiseptum (arrow C), which connects to peristome, ×160.

Figure 5Wjatkella hemiseptifera n. sp.; 1, diagrammatic longitudinal section showing changing chamber outline from deep section near midbranch (bottom of fig.) to shallow section near abaxial edge of branch (top of fig.); chamber outline (arrow A) illustrating well-developed superior hemiseptum and pronounced vestibule; pronounced node and keel development (arrow B) continuous with internal granular skeletal material and obverse reticulate meshwork (arrow C); and small reverse stylets developed as extensions of granular skeletal material (arrow D); 2, diagrammatic tangential section showing chamber outline from deep section near reverse wall budding site (bottom of fig.) to shallow section near obverse surface (top of fig.); typical chamber in deep (arrow A), mid- (arrow B), and shallow (arrow C) views; apertural outline circular (arrow D); node (arrow E) and keel (arrow F) developed as extension of internal granular skeleton, with keel connecting to and expanding to form reticulate framework (arrow G); 3, diagrammatic transverse section across two branches at dissepiment emplacement (left side of fig.) and solitary branch (right side of fig.) showing typical branch thickness (arrow A); chamber outline in midtransverse view (arrow B); orientation of aperture to plane of obverse surface (arrow C); development of reticulate meshwork (arrow D) as extension of granular skeletal keel (arrow E) which connects with internal granular skeletal layer (arrow F); 4, three-dimensional reconstruction of typical chamber shape illustrating longitudinal view and superior hemiseptal inflection at proximal boundary between autozooecial chamber and vestibule; 5, three-dimensional reconstruction of tangential view as seen from obverse surface; note moderately large aperture at distal adaxial chamber edge; 6, three-dimensional reconstruction of transverse section as viewed from distal end of branch.

Figure 6Wjatkella hemiseptifera n. sp.; 1, very shallow tangential peel of holotype, SU 1002, showing well-developed reticulate meshwork covering obverse surface (arrow A) and developing as extensions of obverse nodes and keel (arrow B), ×40; 2, transverse peel of paratype, EWU Bz 242, showing obversely curved zoarium, typical chamber outline in midtransverse section, and orientation of aperture to obverse surface (arrow A). Note continuity of granular skeletal nodes and keel (arrow B) with the covering reticulate meshwork (arrow C). Pronounced astogenetic thickening shown in this specimen (arrow D), ×40; 3, shallow tangential peel of paratype, EWU Bz 242, showing typical ovate aperture, elongate proximodistally (arrow A), poorly developed incomplete peristome (arrow B), and sinuous keel (arrow C), ×160; 4, deep to midshallow tangential peel of holotype, SU 1002, showing chambers covering dissepiment surface (arrow A), typical chamber outline deep (arrow B), mid- (arrow C), and midshallow (arrow D) views, inflection of apertures into fenestrule on obverse branch surface (arrow E), and small microstylets on reverse zoarial surface (arrow F), ×40; 5, shallow tangential peel of paratype, EWU Bz 242, ranging from shallow midchamber view to reticulate meshwork cover showing obverse sinuous keel (arrow A), nodes (arrow B), and completely covered reticulate meshwork (arrow C), ×40; 6, midlongitudinal peel of holotype, SU 1002, (obverse to right) showing typical chamber outline, well-developed reverse wall microstylets (arrow A), extending from granular skeletal reverse wall of autozooecia, and well-developed vestibule (arrow B), ×160; 7, midshallow to deep longitudinal peel of holotype, SU 1002, (obverse to left) showing typical chamber outline in deep (arrow A) to midshallow (arrow B) sectional view, and well-developed superior hemiseptum (arrow C), ×40; 8, midtangential peel of holotype, SU 1002, showing small fenestrule opening (arrow A), typical chamber outline in midview (arrow B), and mid-dissepiment boundary of apertures from adjoining branches (arrow C), ×160.

Figure 7Kingopora wardlawi n. sp.; 1, diagrammatic longitudinal section showing changing chamber outline from deep section near midbranch (bottom of fig.) to shallow section near abaxial edge of branch (top of fig.); autozooecial chamber outline in deep (arrow A), mid- (arrow B), and shallow (arrow C) views; obverse nodes connecting with internal granular material (arrow D); and extreme thickening of reverse lamellar wall (arrow E); 2, diagrammatic tangential section showing chamber outline from deep section near reverse wall budding site (bottom of fig.) to shallow section near obverse section (top of fig.); typical autozooecial chamber outline in deep (arrow A), mid- (arrow B), and shallow (arrow C) views; circular apertures (arrow D); keel and nodes develop as extensions of internal granular skeletal material (arrow E); 3, diagrammatic transverse section across branch showing typical orientation of apertures relative to plane of obverse surface (arrow A); node developing as extension of internal granular skeleton (arrow B); 4, three-dimensional reconstruction of typical chamber shape illustrating longitudinal view; pronounced extension of superior hemiseptum into tube at chamber/vestibule boundary (arrow A); and elongate vestibule (arrow B); 5, three-dimensional reconstruction of tangential section as viewed from obverse surface showing hemiseptal inflection (arrow A); and large circular aperture at distal and slightly abaxial end of chamber (arrow B); 6, three-dimensional reconstruction of transverse view as seen from end of branch; and hemiseptal inflection (arrow).

Figure 8Kingopora wardlawi n. sp.; 1, transverse peel of holotype, SU 1003, showing typical branch outline in transverse section and typical spacing of fenestrule opening (arrow), ×40; 2, shallow tangential peel of holotype, SU 1003, showing typical ovate, elongate proximodistally, aperture outline (arrow A), peristomal development (arrow B), and extension of apertures into fenestrule opening near the obverse surface (arrow C), ×160; 3, transverse peel of paratype, EWU Bz 243, of single branch showing typical autozooecial outline and apertural orientation toward obverse surface (arrow A), obverse granular skeletal node (arrow B), and reverse longitudinal striae (arrow C), ×160; 4, deep to midlongitudinal peel of holotype, SU 1003, (obverse to right) showing typical autozooecial chamber outline in deep (arrow A), to midlongitudinal section (arrow B), and astogenetically thickened reverse wall (arrow C), ×40; 5, shallow to midshallow tangential peel of paratype, EWU Bz 243, showing autozooecial chambers extending across dissepiments (arrow A); typical ovate autozooecial aperture, elongate proximodistally, causing slight to moderate inflection into fenestrule (arrow B); and nodes developing atop thin, sinuous keel (arrow C), ×40; 6, mid- to mid-deep longitudinal peel of holotype, SU 1003, (obverse to right) showing superior hemisepta (arrow A) in midchamber view, and mid-deep chamber outline (arrow B), ×160; 7, mid- to shallow longitudinal peel of holotype, SU 1003, (obverse to right) showing well-developed hemisepta in midlongitudinal section (arrow), ×40; 8, very deep to midtangential peel of paratype, EWU Bz 243, illustrating regular placement of fenestrules (arrow A) emplaced diagonally across zoarial surface, skeletal ridges across reverse zoarial surface (arrow B); and placement of autozooecia across branch and typical autozooecial chamber outline in midtangential section (arrow C), ×40.

Figure 9Kingopora inflata n. sp.; 1, diagrammatic longitudinal section showing changing chamber outline from deep section near midbranch (bottom of fig.) to shallow section near abaxial edge of branch (top of fig.); chamber outline in deep (arrow A), mid- (arrow B), and shallow (arrow C) views; obverse nodes (arrow D) and reverse microstylets (arrow E) develop as extensions of granular skeletal material; 2, diagrammatic tangential section showing chamber outline from deep section near reverse wall budding site (bottom of fig.) to shallow section near obverse section (top of fig.); chamber outline in deep (arrow A), mid- (arrow B), and shallow (arrow C) views; apertural outline ovate, elongate proximodistally (arrow D), with aperture causing inflection into fenestrule (arrow E); 3, diagrammatic transverse section across branch at dissepiment emplacement showing typical orientation of apertures relative to plane of obverse surface (arrow A); obverse keel node (arrow B) and reverse microstylets (arrow C) shown as extension of internal granular skeletal material; 4, three-dimensional reconstruction of typical chamber shape illustrating longitudinal view showing restrictions at chamber/vestibule proximal juncture caused by superior hemiseptum (arrow); 5, three-dimensional reconstruction of tangential section as viewed from obverse surface; from small hemiseptum (arrow); chamber has irregular rectangular/parallelogram box shape; 6, three-dimensional reconstruction of transverse view as seen from distal end of branch.

Figure 10Kingopora inflata n. sp.; 1, transverse peel of holotype, SU 1004, showing typical branch thickness, midsection autozooecial chamber outline with aperture orientation to obverse surface (arrow A), well-developed superior hemisepta (arrow B), and regularly spaced longitudinal striae (arrow C), ×40; 2, deep to midtangential peel of holotype, SU 1004, showing ovate fenestrules (arrow A); numerous small reverse microstylets (arrow B); chamber shape near reverse wall budding site (arrow C); and in midtangential view (arrow D), ×40; 3, shallow tangential peel of holotype, SU 1004, showing aperture outline near obverse surface (arrow A); poorly developed intermittent peristome (arrow B); node development (arrow C); and obverse microstylets (arrow D), ×160; 4, deep to midtangential peel of holotype, SU 1004, showing well-developed, uniform longitudinal striae (arrow A); ovate to elliptical fenestrule opening (arrow B); and autozooecial chamber emplacement across dissepiment (arrow C); ×40; 5, midlongitudinal peel of holotype, SU 1004, (obverse to left) showing autozooecial chamber outline (arrow A); rare thin double terminal diaphragms (arrow B); and short superior hemisepta (arrow C), ×160; 6, shallow to deep longitudinal peel of holotype, SU 1004, (obverse to left) showing autozooecial chamber outline in shallow (arrow A) and mid- (arrow B) views, ×40; 7, shallow to midtangential peel of holotype, SU 1004, showing typical mesh arrangement; short hemisepta at proximal abaxial edge of aperture in shallow tangential view (arrow A); slight inflection of apertures into fenestrule in most shallow tangential view (arrow B); and obverse node (arrow C) developing as extension of granular keel, ×40.

Figure 11Polypora keyserlingiformis n. sp.; 1, diagrammatic longitudinal section showing changing chamber outline from deep section near midbranch (bottom of fig.) to shallow section near abaxial edge of branch (top of fig.); chamber outline in deep (arrow A), mid- (arrow B), and shallow (arrow C) views; obverse nodes (arrow D) and reverse microstylets (arrow E) connect with internal skeletal granular material; 2, diagrammatic tangential section showing chamber outline from deep section near reverse wall budding site (bottom of fig.) to shallow section near obverse surface (top of fig.); chamber outline in deep (arrow A), mid- (arrow B), and shallow (arrow C) views; circular to slightly ovate aperture showing inflection into fenestrule (arrow D); 3, diagrammatic transverse section across branch showing typical orientation of apertures relative to plane of obverse surface (arrow); 4, three-dimensional reconstruction of typical chamber shape illustrating longitudinal view; note recumbent flexure of tube at chamber/peristomal boundary (arrow) orienting apertures perpendicular to obverse surface; 5, three-dimensional reconstruction of tangential section as viewed from obverse section; 6, three-dimensional reconstruction of transverse view as seen from distal end of branch.

Figure 12Polypora keyserlingiformis n. sp.; 1, very shallow tangential peel of holotype, SU 1005, showing typical circular to very slightly ovate aperture outline (arrow A) and absence of peristome surrounding aperture. Note large stellate macrostylets (arrow B) formed of numerous small rods and numerous small microstylets (arrow C) emplaced across the obverse zoarial surface, ×160; 2, mid- to shallow longitudinal peel of holotype, SU 1005, (obverse to left) showing typical mid- (arrow A) and shallow (arrow B) longitudinal outline of autozooecial chambers. Note significant astogenetic thickening of reverse lamellar skeletal wall (arrow C), ×40; 3, deep to midtangential peel of holotype, SU 1005, illustrating reverse longitudinal striae emerging from reverse autozooecial wall (arrow A); reverse microstylets (arrow B); and autozooecial chamber outline near reverse wall budding site (arrow C), ×40; 4, transverse peel of holotype, SU 1005, showing angular shape of obverse zoarial surface (top of branch section) and rounded shape on reverse zoarial surface; typical autozooecial chamber outlines in transverse section; and apertural orientation to obverse surface (arrow), ×40; 5, shallow to midshallow tangential peel of holotype, SU 1005, illustrating apertural outline and placement (arrow A); midshallow autozooecial outline (arrow B); inflection of aperture into fenestrule (arrow C); numerous large stellate macrostylets (arrow D); and their placement across obverse surface, ×40; 6, midtangential peel of holotype, SU 1005, showing typical rounded rectangular or parallelogram outline (arrow), ×160; 7, midtangential peel of holotype, SU 1005, at site of branch bifurcation (arrow A) and along nonbifurcated branch (arrow B); and typical autozooecial chamber outline in midtangential section (arrow C), ×40; 8, midlongitudinal peel of holotype, SU 1005, showing typical chamber outline (obverse to right) in midtangential section (arrow A) and macrostylet development on obverse surface (arrow B), ×160.

Figure 13Polyporella helgersoni n. sp.; 1, diagrammatic longitudinal section showing changing chamber outline from deep section near midbranch (bottom of fig.) to shallow section near abaxial edge of branch (top of fig.); chamber outline in deep (arrow A), mid- (arrow B), and shallow (arrow C) views; 2, diagrammatic tangential section showing chamber outline from deep section near reverse wall budding site (bottom of fig.) to shallow section near obverse surface (top of fig.); chamber outline in deep (arrow A), mid- (arrow B), and shallow (arrow C) views; typical circular aperture (arrow D); obverse macrostylets (arrow E); and large reverse macrostylets (arrow F); 3, diagrammatic transverse section across dissepiment showing typical orientation of apertures relative to plane of obverse surface (arrow); 4, three-dimensional reconstruction of typical chamber shape illustrating longitudinal view; note slight inflection at proximal chamber vestibule boundary caused by short superior hemiseptum (arrow); 5, three-dimensional reconstruction of tangential section as viewed from obverse surface; note small apertural size relative to size of autozooecial chamber (arrow); 6, three-dimensional reconstruction of transverse view as seen from distal end of branch.

Figure 14Polyporella helgersoni n. sp.; 1, midtangential peel of holotype, SU 1006, showing rounded rectangular or parallelogram in this view, well-developed granular skeletal layer overlain by lamellar skeleton inside chamber walls, and rods of granular skeleton extending into the chamber (arrow), ×160; 2, shallow tangential peel of holotype, SU 1006, illustrating reduced size of apertural outline (arrow A) adjacent to ovicells, greatly enlarged ovicell developed at proximal edge of reduced autozooecial aperture (arrow B), and partitioned from aperture by thin skeletal wall (arrow C), ×160; 3, mid- to deep longitudinal peel of holotype, SU 1006, (obverse to left) showing autozooecial chamber outline in midlongitudinal section (arrow A), and ovicell developed at immediate proximal edge of autozooecial aperture (arrow B) with thin skeletal wall between aperture and ovicell (arrow C), ×40; 4, shallow tangential peel of paratype, EWU Bz 245, illustrating aperture outline with surrounding peristome (arrow A); large stellate macrostylets (arrow B); and numerous microstylets across the obverse surface (arrow C), ×160; 5, mid- to shallow tangential peel of paratype, EWU Bz 245, showing growth of autozooecia into dissepiment (arrow), ×40; 6, transverse peel of holotype, SU 1006, showing chamber outline in midtransverse view (arrow A); aperture outline near distal end of chamber with thin terminal diaphragm covering aperture (arrow B); ovicell atop midbranch surface (arrow C); connection of reverse microstylets with granular chamber wall (arrow D); short superior hemisepta (arrow E); and well-developed obverse macrostylets (arrow F); ×160; 7, transverse peel of holotype, SU 1006, across dissepiment illustrating extension of autozooecia from branches to mid-dissepiment boundary (arrow), ×40; 8, deep to shallow tangential peel of paratype, EWU Bz 244, showing branch and fenestrule spacing and orientation, large reverse stellate macrostylets (arrow A); microstylets on reverse surface (arrow B); autozooecial chambers in midsectional view (arrow C); shallow view with hemiseptal development (arrow D); and extension of autozooecial chambers across the dissepiment (arrow E), ×40; 9, midlongitudinal peel of paratype, EWU Bz 245, (obverse to right) showing chamber outline (arrow A); aperture covered by thin terminal diaphragm (arrow B); and small superior hemiseptum (arrow C), ×160.

table

Table 1—Summary of numerical analysis of Rectifenestella cordiretiformis n. sp., including number of zoarial fragments on which measurements were made (Nf), total number of measurements or counts (Nm), smallest observed value of measured or counted morphological variable (Xs), largest observed value of measured or counted morphological variable (Xl), arithmetic mean (X), standard deviation (SD), and coefficient of variation (CV). Budding angles in degrees and other measurements in millimeters follow procedures in Snyder (1991).

table

Table 2—Summary of numerical analysis of Wjatkella hemiseptifera n. sp. Abbreviations as in Table 1. Budding angles in degrees and other measurements in millimeters follow procedures in Snyder (1991).

table

Table 3—Summary of numerical analysis of Kingopora wardlawi n. sp. Abbreviations as in Table 1. Budding angles in degrees and other measurements in millimeters follow procedures in Snyder (1991).

table

Table 4—Summary of numerical analysis of Kingopora inflata n. sp. Abbreviations as in Table 1. Budding angles in degrees and other measurements in millimeters follow procedures in Snyder (1991).

table

Table 5—Summary of numerical analysis of Polypora keyserlingiformis n. sp. Abbreviations as in Table 1. Budding angles in degrees and other measurements in millimeters follow procedures in Snyder (1991).

table

Table 6—Summary of numerical analysis of Polyporella helgersoni n. sp. Abbreviations as in Table 1. Budding angles in degrees and other measurements in millimeters follow procedures in Snyder (1991).

 
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