CO CO Ui.iVLrtSUY OF in ILLINOIS LIBRARY AI URBANA-CHAMPAIGN co GEOLOGY The person charging this material is re- sponsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. To renew call Telephone Center, 333-8400 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN L161— O-1096 VlELDIANA Geology Published by Field Museum of Natural History New Series, No. 13 ECTOPROCTA (BRYOZOA) FROM THE PERMIAN KAIBAB FORMATION, GRAND CANYON NATIONAL PARK, ARIZONA FRANK K. McKINNEY JUN OU 1983 February 1, 1983 Publication 1341 ECTOPROCTA (BRYOZOA) FROM THE PERMIAN KAIBAB FORMATION, GRAND CANYON NATIONAL PARK, ARIZONA FIELDIANA Geology Published by Field Museum of Natural History New Series, No. 13 ECTOPROCTA (BRYOZOA) FROM THE PERMIAN KAIBAB FORMATION, GRAND CANYON NATIONAL PARK, ARIZONA FRANK K. McKINNEY Research Associate Department of Geology Field Museum of Natural History Appalachian State University Boone, North Carolina 28608 Accepted for publication May 18, 1981 February 1, 1983 Publication 1341 Library of Congress Catalog Card No.: 82-83327 ISSN 0096-2651 PRINTED IN THE UNITED STATES OF AMERICA rj CONTENTS Abstract 1 Introduction 1 Acknowledgments , 3 Collecting Localities 3 Systematic Paleontology 3 Phylum Ectoprocta; Class Stenolaemata; Order Trepostomata 3 ?Stenodiscus sp 3 Fistulipora sp 5 Meekopora parilis Moore & Dudley 5 Order Cryptostomata; Suborder Rhabdomesoidea 8 Rhabdomeson sp 8 Streblotrypa sp 10 Suborder Timanodictyoidea 10 Girtypora maculata, n. sp 10 Order Fenestrata 12 Fenestellid sp 12 Genus Bicorbis Condra & Elias 12 Bicorbis arizonica (Condra & Elias, 1945) 12 Literature Cited 16 LIST OF ILLUSTRATIONS 1. ?Stenodiscus sp. and Fenestellid sp 4 2. Fistulipora sp. and Meekopora parilis Moore & Dudley 7 3. Meekopora parilis Moore & Dudley, Rhabdomeson sp., Streblotrypa sp., and Girty- pora maculata, n. sp 9 4. Girtypora maculata, n. sp., and Bicorbis arizonica (Condra & Elias) 11 5. Bicorbis arizonica (Condra & Elias) 14 LIST OF TABLES 1. Previously reported occurrences of bryozoans in the Kaibab Formation 2 2. Measurements of Kaibab bryozoans 6 3. Comparison of Girtypora maculata, n. sp., from the Kaibab with the type species (G. ramosa) and other species described as Girtypora 13 ABSTRACT Silicified bryozoans in chert nodules derived from the Kaibab Formation are apparently all from facies 1 of the Beta Member. The bryozoans are a typical Permo-Carboniferous assemblage of stenoporid trepostomes, fistuliporid cys- toporates, fenestrates, and rhomboporid cryptostomes. Taxa included are in the genera ?Steno discus, Fistulipora, Meekopora, Fenestella, Bicorbis, Rhabdomeson, Streblotrypa, andGirtypora (G. maculata, n. sp.). Bicorbis is known only from the Kaibab and equivalent strata of Arizona, Girtypora is a cosmopolitan Permian genus, and the other genera range through at least the Carboniferous and Per- INTRODUCTION The Bryozoa in the Permian Kaibab Formation are represented "by many genera and species and by an abundance of individuals; very little attention, however, has yet been given these animals. . . . No doubt the difficulties of making specific identifications and the general lack of described Permian forms for comparison are largely responsible for the fact that not a single species has yet been described from . . . the Kaibab. It seems probable that many new species are represented, so an interesting field of study invites future in- vestigators." Thus wrote McKee in 1938 (p. 157). The statement is no longer precisely true, as two species have since been named and described from the Kaibab; but the spirit of McKee's statement still applies, in that the bryozoan fauna of the Kaibab has yet to be adequately described. The present report describes relatively few specimens that were not systematically collected. Nonetheless, they serve to document the diversity of the bryozoan fauna and to demonstrate that thin-section study of these silicified bryozoans is useful. Several authors (Table 1) have recorded bryozoans from the Kaibab Forma- tion. The majority of such records are of occurrences in facies 1 of the Beta Member, the facies in which bryozoans are most prolific (McKee, 1938, p. 157). The dominant lithology of facies 1 of the Beta Member of the Kaibab Formation is partially chertified limestone. The bryozoans described herein are silicified and are preserved in chert nodules presumed to be derived from facies 1, Beta Member, Kaibab Formation. Silicification of bryozoans typically destroys internal structures to such a de- gree that identification is impossible. However, internal structures of the silici- fied Kaibab bryozoans are preserved well enough to be studied in thin section, although details of wall microstructure are regularly destroyed. In most cases the precision of taxonomic determination is limited by the number of speci- mens available for this study rather than by destruction of characters by silicification. X, X a u ■a a82 h > 3 Oi IS 3 .5 <■"! « .2 rH t— I (/J rH r- 1 at in .£< t/i (fl ai a; (J ai 11 u * S -a c (fl H « V. 3 (-) &C O pi. c^*- v. v. >*. 2 e o o o £ 5 a. a. sa. a> 5 o o o T; - >^ oi a o a 5 o o o > g. a. a. o.-S « ^J «Si ,Si 2 en S. 3 -Si o o 3 » a, •t; £> Si >> "*•> r3 <" J3 ^ C T3 3 o a u .5 o 3 s C Q a 01 N M) 0 a-2 (« > 01 C 01 c .« 01 to to a, Uh U-, o. sr.S « a a v. ■g a. a Ts -a -a S £ £ (fl o o >>.« -c U S <^ McKINNEY: ECTOPROCTA FROM KAIBAB FORMATION 3 ACKNOWLEDGMENTS This study is based on collections made by Matthew H. Nitecki and housed in Field Museum of Natural History. I thank Field Museum for a Thomas J. Dee Fellowship for travel to and study in the Museum, M. H. Nitecki for loan of specimens, Appalachian State University for Faculty Research Grants that allowed completion of this study, and the superintendent of Grand Canyon National Park for permission to M. H. Nitecki for collecting within the Park (1969). COLLECTING LOCALITIES Specimens for this study were collected by M. H. Nitecki from the localities listed below, and all are in the collections of Field Museum. Collection numbers are indicated by the letters FMNH PE. FMNH PE 13877. Kaibab Formation (Permian); North Rim of Grand Canyon, Grand Canyon National Park, Arizona. FMNH PE 24294-24295. Beta Member, Kaibab Formation (Permian); Hermit Trail, Grand Canyon National Park, Arizona. FMNH PE 24296-24300. Float from Kaibab Formation (Permian); Widforss Point Trail, North Rim, Grand Canyon National Park, Arizona. FMNH PE 24301. Drift from Kaibab Formation (Permian); Bass Camp, mile 108.2-108.6, Grand Canyon National Park, Arizona. FMNH PE 24302. Drift from Kaibab Formation (Permian); South Canyon, mile 31.4(7), Colorado River, Grand Canyon National Park, Arizona. SYSTEMATIC PALEONTOLOGY Phylum Ectoprocta Class Stenolaemata Order Trepostomata ?Stenodiscus sp. Figure 1A-C. Description. — The robust branches of this form are 9.2-11.2 mm in diameter, with endozones 4.8-6.8 mm in diameter. Zooecial origins in endozone are disordered and the buds are generally 3-sided initially. Zooecia in endozones are irregularly polygonal in cross-section. There are apparently complete dia- phragms spaced 3 to 5 zooecial diameters apart in the endozone. Zooecia arc gently into the exozone, where walls are thicker and strongly moniliform. Scat- tered zooecial diaphragms in exozone are apparently complete. Small tubular polymorphs are common in the exozone. Acanthostyles are undetectable. Discussion. — Replacement by silica has destroyed wall structure sufficiently to remove evidence of acanthostyles and has substituted clear granules, each with a central dark spot, which appear similar to acanthostyles in tangential sections but which have the same appearance in longitudinal and transverse sections. Details of specimens in this species have been destroyed to the extent that generic assignment is uncertain. As noted by Gilmour (1962) and Cuffey (1967), at least some Lower Permian specimens of Tabulipora Young have complete diaphragms in the endozone and in proximal portions of the exozone, with the perforate diaphragms that characterize the genus developed more distally, if at all. Stenodiscus Crockford is a Permian genus allied with Tabulipora, but it con- Fig. 1. A-C: ?Stenodiscus sp. FMNH PE 24295. A, longitudinal section with thin-walled endozone on right and annularly thickened exozone to left. B, tangential section passing in part through relatively thin walls and in part relatively thick walls of annularly thick- ened exozone. C, transverse section with endozone below and exozone above. D: Fenestellid sp. FMNH PE 24295. Shallow tangential section cutting axial wall and distal tubes in four subparallel branches. All photographs are at same scale. McKINNEY: ECTOPROCTA FROM KAIBAB FORMATION 5 tains complete diaphragms and consistently lacks perforate diaphragms. Both Stenodiscus and Permian representatives of Tabulipora have strongly moniliform exozonal walls. The apparent lack of perforate diaphragms in the Kaibab speci- mens has resulted in their questionable assignment to Stenodiscus, although the absence of perforate diaphragms may be the result of growth stage or destruc- tion during silicification. Measurements. — Table 2. Material. — FMNH PE 24295, 24296. Fistulipora sp. Figure 2A-B. Description. — The zoaria are encrusting; 2 mm or less in thickness; and at- tached to shell fragments or other bryozoans or floating in matrix. The zooecia have short proximal encrusting portions and bend abruptly toward the zoarial surface. Diaphragms are widely spaced. Zooecial cross-sections show prom- inent, deeply curved (120°-180° arc), V- to U-shaped lunaria, which result in keyhole-shaped zooecial chamber cross-sections. Overlapped cystopores (vesi- cles) fill the space between zooecia. Discussion. — Moore & Dudley (1944, pp. 289-291) described two species, Cyclotrypa hirta and C. debilis (both of which belong within the genus Fistu- lipora), from Leonardian and Guadalupian beds, respectively, of Texas. The Kaibab specimens apparently differ from Fistulipora hirta in having more closely spaced zooecia and more pronounced lunaria and from F. debilis in having more pronounced lunaria, more widely spaced diaphragms, and fewer columns of cystopores between zooecia. The small number of specimens examined and the tendency toward moderately high variability within species of Fistulipora deter assignment to an existing species or erection of a new species. Measurements. — Table 2. Material— FMNH PE 24298, 24301. Meekopora parilis Moore & Dudley, 1944. Figures 2C-D; 3A. Meekopora parilis Moore & Dudley, 1944, pp. 303-304, pi. 37, fig. 6; pi. 38, fig. 2; pi. 39, fig. 6; pi. 40, fig. 1; pi. 41, figs. 5-6; pi. 42, figs. 4, 7; pi. 43, figs. 2, 4, 7; pi. 44, figs. 5, 7; pi. 45, fig. 3; pi. 46, figs. 5, 7. Meekopora prosseri Ulrich. Warner & Cuffey, 1973, p. 14. Description. — The bifoliate branches of this species are up to 5 mm thick and are at least 8 mm wide. Zooecia were budded in offset ranks from the median lamina; they curve smoothly through the endozone to a relatively linear exten- sion at high angle through the exozone to the zoarial surface. Zooecial chambers are almost circular in cross-section; some are subdivided by 1 or 2 diaphragms. Regular spacing of zooecia in diagonal and longitudinal rows on the zoarial surface is interrupted by small maculae spaced approximately 2 mm from center to center. Areas between zooecia are occupied by cystopores diminished in height from bulbous in the endozone to progressively flattened in exozone. Cystopores are covered by continuous skeletal deposits where exozones are greatly thickened. Discussion. — Moore & Dudley (1944, p. 304) described Meekopora calamistrata from the Kaibab Formation of the Grand Canyon. Specimens described herein differ from M. calamistrata in (a) smaller branches, (b) slightly greater spacing in longitudinal series of zooecia, and (c) lack of observable lunaria. There are no Table 2. Measurements of Kaibab bryozoans. No. of No. of Standard Taxon and character specimens measured measure- ments Range (mm) Mean (mm) deviation of mean Mode (mm) IStenodiscus sp. ZCD (max) 1 10 0.22-0.28 0.245 0.018 0.22 ZCD (min) 1 10 0.12-0.17 0.149 0.016 0.14 MT 1 10 0.06-0.13 0.100 0.11 BT 2 2 9.2-11.2 10.2 AR 2 2 1.65-1.92 1.78 Fistulipora sp. ZCD (max) 1 10 0.28-0.38 0.342 0.035 0.35 ZCD (min) 1 10 0.27-0.36 0.311 0.035 0.34 DBZ 1 10 0.09-0.22 0.171 0.043 0.19 LBZ 1 10 0.30-0.60 0.445 0.096 0.45 BT 2 3 1.1-1.5 1.23 1.1 DBM 1 1 4.2 Meekopora parilis Moore & Dudley ZCD (max) 2 20 0.16-0.18 0.170 0.013 0.16 ZCD (min) 2 20 0.13-0.18 0.160 0.015 0.16 DBZ 2 20 0.10-0.18 0.141 0.029 0.10 LBZ 2 15 0.13-0.34 0.202 0.060 0.22 BT 1 1 2.4 Rhabdomeson sp. ZCD (max) 1 6 0.17-0.22 0.204 0.018 0.21 ZCD (min) 1 6 0.09-0.11 0.102 0.007 0.11 LBZ 1 7 0.16-0.21 0.189 0.002 0.18 TBZ 1 5 0.13-0.16 0.146 0.001 0.14 AR 3 3 1.65-1.85 1.77 Streblotrypa sp. ZCD (max) 1 5 0.10-0.15 0.127 0.025 0.10,0.15 ZCD (min) 1 5 0.07-0.11 0.088 0.015 0.09 ED 1 10 0.02-0.03 0.022 0.005 0.02 BT 1 2 0.35-0.40 0.38 Girtypora maculata, n. sp. ZCD (max) 2 20 0.15-0.20 0.165 0.013 0.16 ZCD (min) 2 20 0.13-0.18 0.153 0.018 0.17,0.13 EW 2 15 0.07-0.16 0.114 0.037 0.07 BT 2 9 1.2-3.7 2.0 1.00 1.3,1.4 AR 2 8 2.0-3.2 2.6 0.414 2.9 DBM 1 6 1.7-2.1 1.9 0.141 1.9 Bicorbis arizonica (Condra & Elias) DDT 4 40 0.08-0.15 0.106 0.012 0.11 ZDL 2 20 0.22-0.28 0.249 0.017 0.24 BT 3 31 0.3-0.9 0.51 0.131 0.5 TT 3 8 1.3-2.8 2.06 0.501 DD 2 2 0.7-1.2 0.96 1.0 Character code: AR, ratio of branch thickness to endozone width; BT, branch thickness (perpendicular to median lamina if present) or thickness of encrusting sheet; DBM, dis- tance between maculae, center to center; DBZ, distance diagonally between adjacent zooecial chambers; DD, distance from center to center of successive dissepiments; DDT, diameter of distal tubes; ED, exilazooecia chamber diameters; EW, exozone wall thick- ness; LBZ, distance longitudinally between adjacent zooecial chambers; MT, monilae thickness; TBZ, distance transversely between adjacent zooecial chambers; TT, total thick- ness of rod-connected double fenestrate layers; ZCD (max), zooecial chamber diameter parallel with branch length, or maximum diameter in sheetlike form; ZCD (min), zooecial chamber diameter perpendicular to branch length, or minimum diameter in sheetlike form; ZDL, distance between centers of zooecial distal tubes longitudinally. Fig. 2. A-B: Fistulipora sp. FMNH PE 24301. A, longitudinal section alternately cutting autozooecia and cystopores; basal lamina at base of photograph. B, tangential section, with lunaria on lower right sides of autozooecia and numerous cystopores between au- tozooecia. C-D: Meekopora parilis Moore & Dudley. C, shallow tangential section with macula near center; FMNH PE 24300. D, longitudinal section with median lamina along center, autozooecia separated by cystopores that are most inflated along median lamina; FMNH PE 24295. All photographs are at same scale. 8 FIELDIANA: GEOLOGY conspicuous differences between the specimens of Meekopora described in this paper and the type specimens of M. parilis. Although Moore & Dudley (1944, p. 303) indicated that zooecia are not arranged in a clearly regular pattern, dis- tinctly diagonal lines of zooecial chambers may be seen in tangential sections that they illustrated (Moore & Dudley, 1944, pi. 41, figs. 5-6, pi. 44, figs. 5, 7). Meekopora parilis was not reported by Moore & Dudley from the Kaibab Forma- tion, although Leonardian representatives were reported from near Marathon, Texas. Warner & Cuffey (1973, p. 14) placed M. parilis in synonymy with M. prosseri Ulrich, 1902. The primary types of M. prosseri, as well as most forms assigned to that species by Warner & Cuffey, however, differ from the primary types of M. parilis and those assigned herein to M. parilis in having (1) much thinner branches, even though branches are as wide or wider than in specimens of M. parilis; (2) larger and more pronouncedly oval rather than subcircular zooecial chamber cross-sections; and (3) more robust lunaria. The differences enumer- ated seem sufficient for retention of the concept of M. parilis. Apparent differences between M. parilis and M. calamistrata may result in part from degree of ontogenetic development of zooecia and the intervening area. Moore & Dudley (1944, p. 306) indicated "relatively numerous slightly concave diaphragms" in zooecia of M. calamistrata. In M. parilis some zooecia have only one or two concave diaphragms, but zooecia of M. parilis are shorter than those in the thicker branches of M. calamistrata. Moore & Dudley (1944, p. 306) also reported "solid interspaces" between zooecia in tangential sections. In most fistuliporid bryozoans there is an ontogenetic gradient of progressively flattened cystopores from endozone to exozone, replaced distally by continuous skeletal deposits. This gradient seems to relate to rapidity of branch thickening, which is greatest at branch and encrusting sheet tips, where bulbous cystopores form, and least at a distance from branch and encrusting sheet tips, where continuous skeletal deposits develop between zooecia. Continuous skeletal de- posits are present along branch surfaces of M. parilis and, had branch thicken- ing continued, would have continued to fill additionally developed zooecial interspaces. Measurements. — Table 2. Material— FMNH PE 24294, 24300. Order Cryptostomata Suborder Rhabdomesoidea Rhabdomeson sp. Figure 3B-D. Description. — Branches are 1-1.3 mm in diameter and contain an axial tube 0.35 mm in diameter. Zooecia were budded interzooecially in alternate rows from the wall of the axial tube, producing a spiral pattern. Single "superior" (on proximal wall) and "inferior" (on distal wall) hemisepta occur in zooecial cham- bers. Zooecial longitudinal sections are slightly sigmoid, with the central por- tion more nearly parallel with the axial tube than are proximal and distal ends. Zooecial chambers have polygonal cross-sections in the endozone and have ovate cross-sections in exozone. A single acanthostyle occurs between adjacent zooecia in rows, resulting in a proportion of one acanthostyle per zooecium. Discussion. — No Permian species of Rhabdomeson have previously been named from North America; the specimens from the Kaibab Formation de- Fig. 3. A: Meekopora parilis Moore & Dudley. Transverse section, with median lamina along center of photograph; FMNH PE 24294. B-D: Rhabdomeson sp. B, deep tangential section, closest to surface at bottom; FMNH PE 24301. C, transverse section showing large axial tube; FMNH PE 13877. D, oblique longitudinal section cutting axial tube near bottom center; FMNH PE 24301. E-F: Streblotrypa sp. FMNH PE 24301. E, longitudinal section of bifurcated specimen. F, shallow tangential section cutting autozooecium (top center) and numerous exilazooecia. G: Girtypora maculata, n. sp. Holotype, FMNH PE 24301. Transverse section cutting median lamina along short distance in center. Scale bar equals 1.0 mm for all but F, where it equals 0.25 mm. 10 FIELDIANA: GEOLOGY scribed herein are too scanty to form the basis for a new species. Previous reports of North American Permian Rhabdomeson include occurrences in several formations of the Glass Mountains, Texas (Blake, 1976), and in the Wreford Megacyclothem of Nebraska, Kansas, and Oklahoma (Newton, 1971, pp. 27-28, as Rhombopora). The Rhabdomeson fragment cut in FMNH PE 24294, though with branches more robust than other fragments in the collection, is tentatively considered conspecific with the other specimens. Measurements. — Table 2. Material— FMNH PE 13877, 24294, 24301. Streblotrypa sp. Figure 3E-F. Description. — The single zoarial fragment is dendroid, with branches 0.25-0.4 mm in diameter. Branch axes are occupied by parallel, thin-walled polymorphic zooecia. Autozooecia were budded from the periphery of the axial group and diverge slightly from axial group to the base of the exozone, where a pro- nounced curve directs them at a higher angle toward zoarial surface. Exozonal exilazooecia are intercalated in groups between autozooecia, which are ar- ranged in longitudinal rows, and laterally between the rows so that autozooecia are completely surrounded by exilazooecia in the exozone. Discussion. — Streblotrypa is a relatively uncommon, or at least seldom noticed, genus of rhomboporid bryozoans first named for specimens discovered in Lower Carboniferous rocks of the upper Mississippi Valley (Ulrich, 1890, pp. 666-669) and occasionally reported from Permo-Carboniferous rocks. Budding is similar to that of Ascopora, with an axial group of polymorphs around which autozooecia budded along the periphery, except that autozooecia seem to be budded in longitudinal rather than in spiral rows (McKinney, 1975, p. 72, pi. 2, figs. 5-6). A genus, Streblascopora Bassler, 1952 (p. 384), was erected for Streblotrypa-like specimens in which axial polymorphs are present, but that condition exists in cotypes of Streblotrypa nicklesi Ulrich, the type species of Streblotrypa. Therefore, Streblascopora may not be recognized on the basis of presence of axial polymorphs. The single specimen of Streblotrypa in the collections from the Kaibab Forma- tion is not assigned to a species because of its dissimilarity to the other de- scribed North American Permian species of Streblotrypa, S. pulchra (Fritz, 1932, p. 97) and because the single specimen does not form sufficient basis for rec- ognition of a new taxon. Described species assignable to Streblotrypa were listed by Newton (1971, pp. 70-71) as Streblascopora and Streblotrypa. Measurements. — Table 2. Material— FMNH PE 24301. Suborder Timanodictyoidea Girtypora maculata, n. sp. Figures 3G; 4A-B. Diagnosis. — Zoarial branches approximately 1.4 mm thick perpendicular to reduced median lamina; exozonal walls up to 0.16 mm thick in intermacular areas; zooecia budded at high angle to median lamina, chamber diameters subcircular in cross-section in exozone, averaging 0.16 by 0.15 mm; small maculae distributed in rhombic pattern. Li A. yj&£ Fig. 4. A-B: Girtypora maculata, n. sp. Holotype, FMNH PE 24301. A, tangential sec- tion, cutting deeper in exozone along center vertically. B, oblique longitudinal section, cutting median lamina in center of upper two-thirds of photograph. C-F: Bicorbis arizonica (Condra & Elias). C, eroded external view of branches with growth direction toward top in left half and toward right in right half; FMNH PE 13877. D, broken and eroded trans- verse section showing outer zooecium-bearing meshwork and parallel inner, less heavily calcified, meshwork; FMNH PE 13877. E, longitudinal section through base of colony encrusting brachiopod shell; FMNH PE 24301. F, eroded specimen showing branched double-cylinder form of closely spaced outer zooecium-bearing and inner barren meshworks encircled by ink line; FMNH PE' 24302. Scale bar on part E applies also to A and B. 11 12 FIELDIANA: GEOLOGY Description. — The zoarium is dendroid, with branches circular to oval in cross-section, broader in the plane of the median lamina. The median lamina is one-third to one-half the width of the endozone, forming a plane from which zooecia bud interzooecially at high angles in offset rows. Zooecia lack a pro- nounced bend at the base of the exozone; they are arranged in diagonal rows and curve gently through the exozone. Exozonal walls are gradually thickened distally. Small maculae that consist of skeletal material are regularly distributed in a rhombic pattern. Polymorphs are apparently lacking. Discussion. — Girtypora maculata differs from G. ramosa Morozova, 1966 (pp. 36-37, pi. 5, fig. 2), which is the type species, and from other species of Girty- pora as summarized in Table 3. In establishing Girtypora, Morozova included several forms described from the Guadalupian of Texas by Girty (1908, pp. 120-124) as IDomopora. None of these forms closely resemble G. maculata or any other described species of Girtypora, having domal, irregular, or regularly con- stricted growth forms and specially shaped and distributed maculae. IDomopora hilana Girty is the only form for which a median lamina is indicated, and in ID. hilana the median lamina extends the entire width of the endozone, producing a pronouncedly bifoliate zoarium. Measurements. — Tables 2 and 3. Holotype. — FMNH PE 24301. Paratypes.— FMNH PE 24295, 24300. Order Fenestrata Fenestellid sp. Figure ID. Description. — The branches are connected by dissepiments and have 2 rows of zooecia arising from a median wall that apparently projected as a keel on the frontal. There are 3 to 4 zooecia per side of each fenestrule. Contact of zooecial rows along the median wall is essentially planar, even near chamber bases. Discussion. — Only a relatively small tangential area is available, in which most skeletal microstructure has been lost, thereby prohibiting species or generic assignment of the single fragment available. Material— FMNH PE 24295. Genus Bicorbis Condra & Elias, 1945 Type species. — Bicorbula arizonica Condra & Elias, 1945a. Diagnosis. — Zoaria cylindrical, bifurcated, of 2 parallel fenstrated layers con- nected by rods of lamellar skeleton; inner fenestrated layer composed of lamellar skeleton and bears no zooecia, outer fenestrated layer of branches connected by short dissepiments or by anastomosing, with multiple (typically 3 to 5) rows of zooecia opening to outer surface of each branch. Discussion. — Condra & Elias (1945b) named Bicorbis to replace their term Bicorbula, preoccupied by Fisher, 1887. The genus contains at present only one species, B. arizonica, from the middle Permian of Arizona. Bicorbis arizonica (Condra & Elias, 1945). Figures 4C-F; 5A-D. Bicorbula arizonica Condra & Elias, 1945a, pp. 118-121, pi. 13, figs. 1-8, pis. 14-16. Kaibab Limestone, Beta Member, facies 1; Arizona. Bicorbis arizonica Condra & Elias, 1945b, p. 411 (new name for Bicorbula arizonica). Bicorbis arizonica Williams, in Gilluly, J. et al., 1954, p. 42. Concha Limestone; Arizona. ro — 01 Hi - 5 U U o J3 o U P. •g S.S o H C c "Sot: -2 c b j « « T3 N I m = 111- §\§S * EiH 5 u (J u - Bill .n £ c .n g to O 3 tn <" 2 §T3 C 4) Mj O a .2 "(3 £ 73 O U ft O — — 0) C ■— — 0) c 0) c 8*£ o-c-1 D D D a, D D c (0 £ o U a 5 « « osaS &.u in c t: s c V- u ro o -so — X 3 ~ -C O ^O <3 O ^O d d .« 3 O •° y 2 « C J; a C CTv ft ■£ 2 S •*(§.*:* d d So ° fc S5 u 13 14 FIELDIANA: GEOLOGY H tiBHDK^dHflKSSEl&^HKrid 4\ * IP HL ** «b - * * T^i •.. 1 i -. \ t , >J 1 w *<* 3 r .. 1 rJE" *.* fc* - ' P*, ^ -sit 1 - r" ; ' Pw^JI E Fig. 5. A-D: Bicorbis arizonica (Condra & Elias). A, longitudinal section, cutting several autozooecia and (right side) large frontal spine; FMNH PE 24298. B, transverse section of two branches showing well-preserved lamellar skeletal microstructure and origin of large rod on reverse side of one branch; FMNH PE 24298. C, deep tangential section through polygonal living chambers and oval fenestrates; FMNH PE 24297. D, transverse section through outer zooecium-bearing (top) and inner barren (bottom) meshworks connected by skeletal rods; FMNH PE 24298. All photographs are at same scale. Description. — Presumed species characters involve sizes of branches, dis- sepiment spacing, general distance from the outermost surface to the innermost surface of the double fenestrate meshwork, zooecial distal tube diameter, dis- tance between centers of zooecial distal tubes, and the presence of scattered large spines on the frontal surface. Rods connecting the inner fenestrate meshwork with zooecia-bearing branches and the elements of the inner meshwork have smaller diameters than do branches of the outer, zooecia-bearing network. Rods may locally develop oblique lateral processes. In many places, dissepiments in the outer meshwork are not present, and the branches are joined regularly by anastomosis. Apparent local damage on one McKINNEY: ECTOPROCTA FROM KAIBAB FORMATION 15 specimen (fig. 4C) resulted in growth of branches at a right angle from the orig- inal direction of growth. The lateral branches are situated where dissepiments would normally be and are in the same plane as the fenestrate section from which they grew. Zooecia are only slightly inflated and are polygonal at their bases. They arise at a high angle from the budding plate and within a short distance are con- stricted to slightly smaller diameter characteristic of the cylindrical distal tubes. No hemisepta are evident. The encrusting base of a Polypora-like bryozoan (fig. 4E) associated with B. arizonica is possibly the base of a colony of B. arizonica. It encrusts a brachipod shell and is broadest at the basal contact, tapering upward to the center of the fenestrate fan, where the zoarium begins widening into an upwardly spreading fenestrate funnel. The fenestrate funnel has fairly erect zooecia, like those of B. arizonica, which, however, open toward the inner (or upper) surface of the zoarium. Discussion. — The abundant material of B. arizonica that Condra & Elias liber- ated from silicified blocks exhibited greater variability and was in some aspects slightly different from that in the collections of Field Museum. Branches in the original material were straighter and connected by short dissepiments; those in Field Museum collections tend more toward anastomosed junctions. Condra & Elias reported two to five, generally three, rows of zooecia per branch; Field Museum specimens more typically have four or five rows per branch. Small nodes between zooecial apertures were reported by Condra & Elias; Field Museum specimens have scattered large, high, blunt spines on the frontal sur- face. This latter discrepancy may be due to the large spines being worn off, as Condra & Elias prepared their specimens by grinding away the rock matrix to the zoarial surface. There is no evidence in the lamellar skeleton of the reverse surface of the outer fenestrate meshwork, in the rods or in the inner meshwork, of the fine threads or tubes reported by Condra & Elias (1945a, p. 120) and interpreted as algae. Condra & Elias first published in 1944 (p. 35) the concept that the extrazooidal lamellar, rod-bearing skeleton characteristic of fenestrate bryozoans was formed by algal symbionts. The interpretation has been main- tained by Elias (e.g., 1973), but has not been widely accepted. The base of attachment of B. arizonica was not found by Condra & Elias, but they surmised (1945a, p. 120) that the genus was derived from Polypora and developed in the primary zone of astogenetic change in a similar manner as Polypora and its relatives (Cumings, 1904; McKinney, 1978). Polypora developed as a fenestrate fan or funnel from a basal group of zooids, with apertures of zooids in the zone of astogenetic repetition on the inner surface of the funnel or on the side of the fan that faces the center of the basal group of zooids. Condra & Elias suggested that, from such organization, a Bicorbis zoarium could have been formed by a fenestrate fan curling during growth toward the reverse side so that the edges eventually fused and continued as an elongating cylinder. The inner fenestrate network could have developed subsequently as rods grew from the reverse side and then expanded to join and fuse on their inner ends. The discovery of a single encrusting polyporoid base (fig. 4E) with inwardly open- ing zooecia associated with B. arizonica in Field Museum material lends support to the mode of development suggested by Condra & Elias. Although the en- crusting base found cannot be seen to develop into a Bicorbis growth form, it is more reasonable to interpret it as Bicorbis than as Polypora because of the simi- 16 FIELDIANA: GEOLOGY larity of its zooecia to those of B. arizonica and because no Polypora specimens were found with it. Measurements. — Table 2. Material— FMNH PE 13877, 24294, 24295, 24297, 24298. The original type specimens of B. arizonica were assigned Nebraska Geological Survey numbers. Nebraska Geological Survey specimens are now housed in the State Museum, University of Nebraska, but no specimens of B. arizonica could be located in the State Museum on initial inquiry (Allan D. Griesemer, letter of Dec. 3, 1975) or on second request for additional search (Allan D. Griesemer, letter of Sept. 7, 1976). Specimens described by M. K. Elias were often deposited at the Univer- sity of Oklahoma, but the types of B. arizonica cannot be located there either (R. C. Grayson, letter of April 21, 1976). The specimens of B. arizonica in the collections of Field Museum clearly fit the criteria on which neotypes are to be based, as set forth in Article 75 of the International Code of Zoological Nomenclature (Stoll et al., 1964). However, it is likely that the holotype and paratypes are only temporarily misplaced. If that is the case, designation of Field Museum specimens at this time would require unnecessary future litigation at such time as the original types may be found. It is sufficient at present to note that Field Museum specimens are clearly con- specific with those illustrated and described by Condra & Elias; it is topotype material and is derived from the same formation. LITERATURE CITED Bassler, R. S. 1952. Taxonomic notes on genera of fossil and Recent Bryozoa. J. Wash. Acad. Sci., 42: 381-385. Beus, S. S. 1964. Fossils from the Kaibab Formation at Bee Spring, Arizona. Mus. North- em Arizona Bull., 40: 59-64. Blake, D. B. 1976. Functional morphology and taxonomy of branch dimorphism in the Paleozoic bryozoan genus Rhabdomeson. Lethaia, 9: 169-178. Condra, G. E., and M. K. Elias. 1944. Study and revision of Archimedes (Hall). Geol. Soc. Am. Sp. Pap., 53: 243 pp. . 1945a. Bicorbula, a new Permian bryozoan, probably a bryozoan-algal consortium. J. Paleontol., 19: 116-125. -. 1945b. Bicorbis arizonica Condra and Elias, new name forB. arizonica. J. Paleontol., 19: 411. Cuffey, R. J. 1967. Bryozoan Tabulipora carbonaria in Wreford Megacyclothem (Lower Permian) of Kansas. Kansas Univ. Paleontol. Contr., Art., 43: 96 pp. Cumings, E. R. 1904. Development of some Paleozoic Bryozoa. Am. J. Sci., 17: 49-78. Elias, M. K. 1973. Algal-bryozoan symbiosis in the late Paleozoic of America. Sept. Congr. Internat. Strat. Geol. Carbonifere, Compte Rendu, 2: 449^65. Fritz, M. A. 1932. Permian Bryozoa from Vancouver Island. Trans. Roy. Soc. Canada, ser. 3, 26: 93-107. Gilluly, J. et al. 1954. Late Paleozoic stratigraphy of central Cochise County, Arizona. U.S. Geol. Surv. Prof. Paper, 266j: 49 pp. Gilmour, E. H. 1962. A new species of Tabulipora from the Permian of Nevada. J. Paleontol., 36: 1019-1020. Girty, G. H. 1908. The Guadalupian fauna. U.S. Geol. Surv. Prof. Paper, 58: 651 pp. Kiseleva, A. V. 1969. Novyye mshanki semeistva Girtyporidae iz verkh permi yuzhnogo Primor'ya. Paleontol. Zh., 1: 90-94. Mather, T. J. 1970. Stratigraphy and paleontology of the Permian Kaibab Formation, Mogollon Rim region, Arizona. Unpubl. Ph.D. Thesis, Univ. Colorado, Boulder, 164 PP- McKee, E. D. 1938. The environment and history of the Toroweap and Kaibab formations of northern Arizona and southern Utah. Carnegie Inst. Washington, Publ. No. 492, 268 pp. McKINNEY: ECTOPROCTA FROM KAIBAB FORMATION 17 McKinney, F. K. 1975. Autozooecial budding patterns in dendroid stenolaemate bryo- zoans. Docum. Lab. Geol. Fac. Sci. Lyon, Hors Ser., 3: 65-76. . 1978. Astogeny of the lyre-shaped Carboniferous fenestrate bryozoan Lyroporella J. Paleontol., 52: 83-90. Moore, R. C, and R. M. Dudley. 1944. Cheilotrypid bryozoans from Pennsylvanian and Permian rocks of the Midcontinent region. Kansas St. Geol. Surv. Bull., 52: 229-408. Morozova, I. P. 1966. Novy podotryad pozdnepaleozoiskikh mshanok Otryada Cryp- tostomata. Paleontol. Zh., 2: 33-41. . 1970. Mshanki pozdney permi. Akad. Nauk SSSR Trudy Paleontol. Inst., 122: 347 pp. Newton, G. B. 1971. Rhabdomesid bryozoans of the Wreford Megacyclothem (Wolf- campian, Permian) of Nebraska, Kansas, and Oklahoma. Kansas Univ. Paleontol. Contr., Art., 56: 71 pp. Stoll, N. R. et al. (eds.). 1964. International Code of Zoological Nomenclature Adopted by the XV International Congress of Zoology. International Trust for Zoological Nomenclature, London, 176 pp. Ulrich, E. O. 1890. Paleozoic Bryozoa. Illinois Geol. Surv., 8: 283-688. Warner, D. J., and R. J. Cuffey. 1973. Fistuliporacean bryozoans of the Wreford Megacyclothem (Lower Permian) of Kansas. Kansas Univ. Paleontol. Contr., Paper, 65: 24 pp. Field Museum of Natural History Roosevelt Road at Lake Shore Drive Chicago, Illinois 60605-2496 Telephone: (312)922-9410 UNIVERSITY OF ILLINOIS-URBANA 550 5FIN S C001 FIELDIANA, GEOLOGY NEW SERIES CHGO 7-14 1981-83 0112 026616331 Hj