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Introduction
Corals are widely distributed in marine Permian deposits of the world and studies on these fossils are comparatively numerous. Some of the published works are elaborate monographs, reflecting both the richness of the coral faunas and the extensive nature of researches on them. In North America, however, less than a dozen kinds of Permian corals have been reported, and descriptions are scattered in about half as many papers.
Previous Studies
Important papers on Permian corals outside of North America include the following: from Australia, by Etheridge (1891) and Hill (1937); from Japan and Korea, by Yabe and Hayasaka (1915, 1916) and Hayasaka (1932); from China, by Grabau (1922, 1928, 1931, 1936), Chi (1935, 1937, 1938), Yu (1934), and Huang (1932, 1932a); from Timor, by Beyrich (1865), Rothpletz (1892), Penecke (1908), Gerth (1921, 1922), Koker (1924), and Heritsch (1937a); from the Salt Range of India, by Waagen and Wentzel (1886), Sen (1931, 1931a, 1931b), and Heritsch (1937a); from Iran, by Heritsch (1933a), and Douglas (1936); from Turkey, by Abich (1878), and Heritsch (1937a); from the U.S.S.R., by Toula (1875), Dobrolyubova (1936), Soschkina (1925, 1928, 1932, 1936), and Yakovlev (1903, 1939); from the Carnic Alps, by Heritsch (1933a, 1936), and Felser (1937, 1937a); from Serbia, by Heritsch (1933, 1934); from Greece, by Heritsch (1937); and from England, by King (1850).
The earliest published record of Permian corals in North America is a description by B. F. Shumard (1858) of specimens from the Guadalupe Mountains in western Texas. These were named Campophyllum? texanum and Polycoelia? sp. No illustrations are given, and because the descriptions are inadequate and the types are lost, Shumard's species are not recognizable. Girty (1908), in his monograph on the Guadalupian fauna of western Texas, recognized nine species and one variety of corals, distributed in six genera, as follows: Lindstroemia permicana Girty, n. sp., L. permicana var. Girty, L. cylindrica Girty, n. sp., L. sp., Zaphrentis? sp., Amplexus sp., Campophyllum? texanum Shumard, Cladopora spinulata Girty, n. sp., C.? tubulata Girty, n. sp., and Aulopora sp. Some of these are not recognizable on the basis of the published descriptions and illustrations but possibly may be made so by study of his types and supplementary specimens. One of us (R.C. Moore) recently has had opportunity to examine Girty's types of Guadalupian corals, but lack of sections prevents diagnosis, at least in the case of the rugose forms. A small horn coral from Permian limestone in northern Mexico has been described by Haack (1914) under the name of Cyathaxonia girtyi, but because definitive characters are not indicated, this form cannot now be recognized. Specimens collected by John Skinner from Lower Permian rocks of north-central Texas and from Upper Permian beds in western Texas were sent by him to Franz Heritsch and on the basis of this material descriptions of two species (Palaeosmilia schucherti, Waagenophyllum texanum) have been published by Heritsch (1936a, 1936c). A few silicified corals from the Malone Mountains in western Texas have been described by Okulitch and Albritton (1937) as the type species, Malonophyllum texanum, of a new genus. A paper by Heritsch (1937b, p. 315) treating on the zonation of Permian rocks by means of rugose corals mentions a form called Texanophyllum skinneri, said to occur in the Delaware Mountain formation of west Texas. We have been unable to learn whether this coral has been described or whether the name is a nomen nudum. No reference to it is found in any of Heritsch's papers in our file, complete so far as we know, nor is publication of a description known to J.W. Skinner, for whom the species presumably was named. It has not been possible to communicate directly with Dr. Heritsch.
No corals from Permian strata of the northern midcontinent region have been described, but Fath (1921, p. 48) reports a determination by G.H. Girty of specimens found in Lower Permian rocks of Butler County, Kansas, as Lonsdaleia? n. sp.
In British Columbia, good specimens of corals have been collected from rocks thought to be Upper Carboniferous or Permian. These fossils were sent to Stanley Smith, British authority on late Paleozoic corals, who described them under the names Waagenophyllum columbicum, n. sp., and Caninia sp. (Smith 1935).
The lack of extensive published data on North American Permian corals may be ascribed partly to their relative scarecity in fossil collections. Many localities that have yielded abundant Permian marine fossils of several sorts lack corals, or they have provided only a few specimens that may be none too well preserved. This observation is emphasized by an inspection of the large collections from Permian formations of Texas in laboratories of the U.S. Geological Survey and the University of Texas, or those from the northern midcontinent region in the University of Kansas and the University of Nebraska.
Stratigraphic Significance of Permian Corals
Only locally and exceptionally in North America are Permian corals abundant. Seemingly, the known Permian invertebrate faunas of this continent are much less coralline than those of many other regions. Little attention has been given to search for these fossils, however, and special efforts in field collecting will doubtless result in important additions of study material. Also, it is likely that all together there are many unstudied specimens in collections of various surveys, universities, and museums. Careful investigation of all obtainable fossils should augment considerably the knowledge of the kinds of Permian corals that occur in North America and their stratigraphic distribution.
Heritsch (1936a, 1936c, 1937a, 1937b) has presented the major outlines of a zonation of rocks belonging to the Permian system that is based on distribution of rugose coral genera. This seems to be very broadly applicable, and classification of late Paleozoic marine deposits in all parts of the world eventually may become well established through verified and amplified information on the nature and occurrence of corals. This group of fossils may then become entitled to rank with ammonoids, fusulinids, and other especially useful guide fossils in these rocks. The corals may be expected to supplement the other biologic groups to an important degree, because noteworthy faunal variations due to ecologic factors are observed. As a whole, corals tend to choose particular features of habitat, but, in addition, Hill (1938a) has called attention to existence of different types of coral assemblages that reflect special environmental conditions. Mud deposits that presumably represent off-shore moderately deep and quiet water are characterized by prevalence of small solitary horn corals. Calcareous shale, commonly interbedded with thin limestone strata, representing moderately shallow, slightly turbid conditions, contains robust horn corals of the Caninia type. Warm shallow clear waters, possibly agitated considerably by waves and currents, characterize a limestone-producing environment, in which colonial reef-building corals are abundant. The differentiation of these and other sedimentary facies requires somewhat independent calibration of each type and imposes need for as complete intercorrelation as possible in order to establish a composite paleontologic zonation of wide applicability.
Scope of the Present Paper
In this paper little attention is given to questions of correlation of Permian formations on the basis of corals or definition of coral zones in the Permian succession of North America. Attack on such matters is premature at this time. It is intended merely to describe and illustrate several of the corals that have been studied, and to indicate some of the taxonomic problems that have been encountered in efforts to classify American species. Several Permian coral genera that have been defined from study of collections from other continents are here recognized in North America for the first time.
Our study of Permian corals has been undertaken as a part of the program of work outlined by Ronald K. DeFord and others, under auspices of the American Association of Petroleum Geologists, in order to obtain material for a volume to be published on the Permian rocks of the central and southwestern part of the United States. Since the beginning of the project, the number of fossil corals available for study has increased considerably, but because the additions came after most of the manuscript for this paper was completed, we have decided to publish the results now obtained, taking notice of the new material only in so far as it belongs to species already studied. It is hoped that work on the yet unstudied specimens can be pursued actively and that our observations can be reported reasonably soon.
Sources of Material Studied
Specimens of Permian corals that have been available for our study have all been obtained from (1) beds of Wolfcamp age, here classed as Lower Permian, in Kansas and Oklahoma, and (2) from Wolfcamp, Leonard, and Word deposits in the Glass Mountains, western Texas. The Kansas specimens include material collected by various geologists of the Kansas Geological Survey during years of mapping and stratigraphic field work, a small lot of corals from Grand Summit, Kans., in a collection obtained from J.W. Mickle, of Wichita, and a large collection of corals from the Florence limestone in Butler County, Kansas, that was made after beginning this study. The west Texas corals were collected by R.C. Moore on trips to the Glass Mountains in 1939 and previous years, and by R.H. King, J.W. Skinner, C.C. Williams, and us on a trip in March, 1940. Determination of stratigraphic horizons is precisely made for all the Kansas collections on the basis of very detailed subdivision and tracing of the Permian rocks in this region. Stratigraphic placement of the western Texas specimens rests on the field studies and mapping of the Glass Mountains by P.B. and R.E. King (1930), supplemented in part by personal acquaintance of Skinner with the geologic section of the Glass Mountains.
Methods of Study
External features of the Permian rugose corals serve only in small part as basis for classification, and in some types they are almost negligible in taxonomic study. Likewise, the mode of growth, whether solitary or colonial, is believed not to be an important distinction, unless such characters are firmly fixed. Judgments of the taxonomic value of mode of growth and of various structural characters of corals differ widely. Variability of the corals themselves, conjoined with the uncertainty of paleontologists as to significant evolutionary trends and divergences in viewpoints just indicated makes for lack of uniformity in classification and nomenclature of these fossils. In any case, knowledge of internal structures of the Permian corals is absolutely requisite.
After classification of the corals in our collection on the basis of obvious external features, the specimens were cut transversely at selected points. Except in a few cases these sections served to establish the position of the cardinal-counter septal plane and to indicate differentiation of major and minor septa. The sections were photographed at enlarged scale after polishing or immersion in oil in order to bring out structures clearly. By marking the septal grooves of major septa the arrangement and order of introduction of the septa were determined on the exterior of the coral if this was possible. This method usually serves for identification of the alar septa, which may not be independently identifiable from study of the transverse sections. The segments of the transversely cut corals were carefully assembled in proper orientation (by means of index marks and matching septal grooves) and were cemented together. They were then cut longitudinally in a plane approximately at right angles to that of the cardinal and counter septa. The longitudinal section was oiled and photographed, the half of the coral containing the counter septum, if identifiable, being used uniformly.
Illustrations of the structures shown in the transverse and longitudinal sections were prepared by drawing on the photographs with waterproof India ink and then bleaching the photographs so as to leave only the inked lines. The photographs, though mostly very clear, are less satisfactory for reproduction than the drawings. This is partly due to the fact that half-tone or full-tone figures, which are required for reproduction of photographs, are much more expensive than line cuts. Another item for consideration is the lack of clarity of many unretouched photographs and the presence of adventitious features of several sorts that may obscure interpretation. Comparative study of the photographs and of the specimens, mounted on the stage of a microscope, serves to verify identification of significant structures in the sections. Irrelevant but frequently confusing details such as cleavage lines in calcite and distributed foreign matter are eliminated in making the drawings. Thin sections or celluloacetate peels, as described by Fenton (1935), are superior in some respects to the polished or oil-immersed surfaces that were photographed in the course of our study, for the thin sections commonly show structures more clearly and can be used for direct projection in making photographic enlargements. Preparation of these sections calls for special techniques and is time-consuming. Also, it is not generally practicable to make thin sections without destroying too large segments of the corals that are being studied.
Descriptive Terminology
Several attempts have been made to standardize the terminology of coral structures (Grabau, 1922; Hill, 1935; Sanford, 1939), but none of these has gained general acceptance. These proposed schemes of terminology are excessively technical and include a great number of precisely defined individual terms. We have adopted a somewhat simpler, less concise terminology in order to avoid the use of terms not generally understood. It is therefore necessary to define the meanings of many of the terms used in the following descriptions.
Theca--The outer layer of the corallite has commonly been designated as the epitheca, inasmuch as it was presumed to be a layer deposited upon the original wall, or theca. In well-preserved specimens of rugose corals Grabau (1922, p. 4) found, however, that this outer layer extends to the highest part of the calyx,, showing that it is the first-formed and fundamental unit of the wall. Therefore, we follow Sanford (1939,, p. 305) in designating this layer as the theca.
Septa--The terminology of the classes of septa is in a very confused state. We use the following designation of the septa, as given by Hill (1935, pp. 504-505), because these terms have been used in a consistent manner and have not varied in meaning as is true of the terms primary, secondary, and tertiary. The cardinal, counter, two alar, and two counter-lateral septa are designated as the protosepta. A variable number of other septa added in pairs in the cardinal and counter quadrants and closely resembling the protosepta are designated the metasepta. The protosepta and the metasepta together are termed the major septa. Short septa alternating with the major septa, introduced later than the majors, are termed minor septa.
Axial structures--Both Grabau (1922) and Hill (1935) have proposed detailed classifications of the axial structures of rugose corals. These authors differ widely in terminology, however, and neither has been followed closely by many other workers. Although Grabau states that a true columella is found only in the Hexacoralla, he describes the solid rodlike axial structure of the rugose corals as a columella. The term pseudocolumella is used by him to include all non-solid types of axial structures, most of which are given descriptive names. Hill uses the term columella for a solid rodlike axial structure and restricts the terms pseudocolumella to the Hexacoralla. The general term axial complex includes both the columns formed by the twisting of axial ends of the septa (axial vortex) and those formed by vertical plates in the axial region (axial column).
The terminology used by Grabau and Hill in describing the many types of axial structures is complete and precise, but we do not think it necessary to use these little-known complex technical terms. Because the names now used in describing axial structures are in such a confused state, we designate any columnar structure that is present in the axial region of the corallite as a column and describe the features of each in detail. The column may or may not be solid.
Acknowledgments
We are indebted to Ralph H. King and Charles C. Williams, of the University of Kansas, for aid in collecting specimens, and to Maurice Wallace, of the University of Kansas, for work in sawing and polishing some of the sections of corals. Ruth Mary Dudley, of the Kansas Geological Survey staff, assisted in supervising work of N.Y.A. students who were employed for part of the task of making an illustrated card index of Carboniferous and Permian corals of the world. The literature on Paleozoic corals is extremely large and because it has been necessary to study early and middle Paleozoic coral genera in order to give foundation for work on Permian forms, the organization of information from previously published papers has been one of the largest items of labor up to the present point. We cordially express thanks for assistance received in the bibliographic work, which would have been somewhat lessened if the extremely valuable Index of Paleozoic Coral Genera, by Lang, Smith, and Thomas (1940) had been available to us at an earlier date.
Sincere thanks are given to E.H. Sellards and F.B. Plummer, of the Bureau of Economic Geology, University of Texas, and to Carl O. Dunbar, Peabody Museum, Yale University, for the loan of specimens, which, however, are mostly unstudied at the present time. Robert E. King has sent us some material from the Wolfcamp beds in the Glass Mountains, and John W. Skinner has aided us, both by guidance in some of the field collecting in western Texas and by providing information concerning fossil localities in the Permian rocks near Fife and Dothan in north-central Texas. Monroe G. Cheney kindly took us to the place, southeast of Santa Anna, Texas, where Mr. Skinner collected the specimens that were described by Heritsch as Palaeosmilia schucherti, and we were thus able to procure an excellent collection of topotype specimens. William M. Furnish, of Oklahoma A. and M. College, has collected and sent to use several lots of Lower Permian corals from northern Oklahoma. Finally, we wish to acknowledge the kindness of James Steele Williams, of the U.S. Geological Survey, in giving opportunity to examine the type specimens of Girty's species described from the Guadalupian rocks of western Texas.
The Graduate Research Committee of the University of Kansas is thanked for important aid that is represented in a grant to defray photographic costs of materials for the illustrated catalog of corals and for the preparation of drawings given in this paper.
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Kansas Geological Survey, Geology
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