CONTRIBUTIONS FROM THE MUSEUM OF PALEONTOLOGY THE UNIVERSITY OF MICHIGAN VOL.24, NO.9, p. 85-99 (8 pls., 1 text-fig.) OCTOBER4, 1973 A NEW SPECIES OF FLETCHERIA FROM THE MIDDLE SILURIAN FIBORN LIMESTONE OF MICHIGAN BY ROBERT V. KESLING, TERRY L. CHASE, CYNTHIA H. DEVORE, and ROBERT D. LATTANZI MUSEUM OF PALEONTOLOGY THE UNIVERSITY OF MICHIGAN ANN ARBOR CONTRIBUTIONS FROM THE MUSEUM OF PALEONTOLOGY Director: ROBERTV. KESLING The series of contributions from the Museum of Paleontology is a medium for the publication of papers based chiefly upon the collection in the Museum. When the number of pages issued is sufficient to make a volume, a title page and a table of contents will be sent to libraries on the mailing list, and to individuals upon request. A list of the separate papers may also be obtained. Correspondence should be directed to the Museum of Paleontology, The University of Michigan, Ann Arbor, Michigan 48104. VOLS.2-23. Parts of volumes may be obtained if available. Price lists available upon inquiry. VOLUME24 1. A new species of Porocrinus from the Middle Ordovician Kimrnswick Limestone of Missouri, by Robert V. Kesling. Pages 1-7, with 2 plates and 8 text-figures. 2. Strataster devonicus, a new brittle-star with unusual preservation from the Middle Devonian Silica Formation of Ohio, by Robert V. Kesling. Pages 9-15, with 2 plates and 3 text-figs. 3. Coccoliths and related calcareous nannofossils from the Upper Cretaceous Fencepost Limestone of northwestern Kansas, by John M. Huh and Charles I. Smith. Pages 17-22, with 2 plates. 4. Ordovician vertebrates from Ontario, by Kathleen Anne Lehtola. Pages 23-30, with 2 plates and 1 text-figure. 5. New Botryocrinus and Glossocrinus from the Middle Devonian Bell Shale of Michigan, by Robert V. Kesling. Pages 31-46, with 8 plates and 2 text-figures. 6. Evolution of Middle Devonian species of Euglyphella as indicated by cladistic analysis, by Sabeekah Abdul-Razzaq. Pages 47-64, with 12 text-figures. 7. Euglyphella bellensis, a new Middle Devonian ostracod from Michigan, by Robert V. Kesling. Pages 65-67, with 1 plate. 8. The stereomic microstructure of the blastoid endoskeleton, by Donald B. Macurda, Jr. Pages 69-83, with 8 plates. PREFACE feet of limestone, 10 feet of dolomite, 27 feet of limestone, and 8 feet of dolomite; of these, In 1957--on the 24th of August, to be exact only the upper 18 feet of limestone has been in- -I found the coral which we describe here. cluded in the Fiborn Member. At the Inland Fortunately, field notes establish the date, for Quarry, where our coral was found, the Fiborn otherwise I recall the time only as one of many reaches about 50 feet, its maximum thickness. hot summer days in the 1950's that I spent At the old Calspar or "Blaney" Quarry at with Professor George M. Ehlers studying the Nicholsonville, just three miles to the west, in stratigraphy and searching for fossils in the eastern Schoolcraft County, the unit is 26 feet Silurian outcrops of the Northern Peninsula of and the lower part of the section is more dolo- Michigan. mitic. Just two miles west of the Calspar The field label, in Professor Ehlers' hand- Quarry, roadside exposures show even more ex- writing, reads: tensive dolomitization of some strata; beds are August 24, 1957. Collector: R. V. Kesling. Top coarsely crystalline instead of finegrained, and of west wall of Inland Lie & Stone Co. quarry light-gray instead of the buff-gray typical of about 9/10 mi. N. & 2/10 mi. W. of quarry the Fiborn. No limestone has been found office. Quarry located about 3 mi. N. of Huntspur, Mackinac Co., Michigan. Burnt Bluff (Hen- farther west, although the Hendricks Dolomite dricks do1.-top of Fiborn Is. mb.). 1 coral cf. is exposed at many places around Indian Lake Pycnostylus in 2 packages. and forms bluffs on Garden Peninsula. Hence, The quarry is in sections 5 and 6, T 42 N, the Inland Quarry offers the best opportunity R 12 W, its edge less than a mile from the west- to collect good specimens from the Burnt Bluff ern boundary of Mackinac County. Group. On this occasion, we were atop the west The fauna is important in correlating the wall of the quarry, just off a spur road that Michigan strata with formations in Canada. As branched from the main quarry access road. Professor Ehlers and I noted in our guidebook Extending back from the quarry rim for several of 1957, the same species have been reported yards was a low bioherm in the upper beds of in the St. Edmund Formation of the Bruce the Fiborn Limestone Member. From the cen- Peninsula, the Wabi Formation of the Lake ter of the bioherm, the beds apparently sloped Timiskaming region, the East Arm Dolomite off about three feet in elevation, although the of southern Manitoba, and the Ekwan River bedding in the core was indistinct and the re- Limestone of the Hudson Bay region. lationships were somewhat modified by glacial From our collecting that day, we obtained scouring. fine specimens of the brachiopods Camaro- We were anxious to secure specimens from toechia winiskensis Whiteaves, Plectatrypa lowi this place because of the preservation and the (Whiteaves), Dolerorthis aff. D. flabellites stratigraphy. Well-preserved Silurian fossils are (Foerste) , and Whitfieldella sp. ; several kinds rare in Michigan; most are seriously affected of stromatoporoids; the corals Favosites spp. by dolomitization or silicification. Most of and an undescribed coral thought to be a new genus; and several specimens of the trilobite the fauna of the Hendricks Dolomite is known Scutellum (Scutellum) sp. We did not find the from the Fiborn Limestone Member near the large ostracod Dihogmochilina latimarginata top of the formation. Although the same spe- (Jones), which occurs at Hendricks Quarry, cies apparently occur in the dolomitized equiva- although we looked diligently for it, nor did lent beds, the fossils are represented by molds, we discover any of the cephalopod Stokesoceras many of them lined with crystals, or by dolo- romingevi Foerste. mitic replacements that can seldom be sepa- As we were about to depart, I walked along rated cleanly from the matrix. the quarry rim to the edge of the bioherm, The Fiborn Member is the only soutce of where glacial scouring had made cross sections high-calcium stone in the Northern Peninsula. through several kinds of fossils. There I spotted It crops out in the western half of Mackinac a coral unlike any I had seen. County and terminates both east and west as "Jim," I called, "what kind of coral is this?" the strata of the formation are dolomitized. At "SO help me, you've got a new one," he Fiborn Quarry, the type locality of the mem- replied, getting down on his knees for a closer ber, about five miles northeast of Rexton and look. "Let's get it out." near the eastern limit of the high quality lime- Finding it was much easier than taking it stone, the Fiborn Limestone is 30 feet thick. out. The coral had been overturned before At Hendricks Quarry, seven miles north-north- burial, so that the corallites sloped off into a east of Gilchrist, the Hendricks includes (from thick solid bed of limestone. Glacial scouring base to top) 7 feet of dolomitic limestone, 7 had removed any surface irregularities and the 8 6 RESLING, CHASE, DEVORE, & LATTANZZ bed showed very few joints. Getting a sledge For one reason or another, we never did. Some- hammer from the car, I started breaking up thing must be left for the next generation to do. the limestone at a solution crack several feet When my Advanced Invertebrate Paleon- away. Finally I reached the corallum and tology class started studying corals, the coral succeeded in knocking out a chunk of it mea- came to mind as an example of an admixture suring about a foot square and six inches thick. of features belonging to Rugosa and Tabulata. Further efforts dislodged smaller pieces, some The opportunity to thoroughly investigate and of which fitted against the large chunk. Re- describe it sparked a response in the three stu- luctantly, we left additional corallites still dents. They embarked in a flurry of activity embedded in the limestone. We have not visited that culminated in this paper. Whether the the quarry since, and I expect the quarrying corallum is fulfilling its destined purpose I operations have long ago exploited the rest cannot say, but it certainly enabled paleon- of the corallum for flux in the steel industry. tologists of three generations to work in happy Professor Ehlers and I were quite excited and productive cooperation. about the coral at the time. As the years slipped by, we periodically planned to "write it up." -Robert V. Kesling A NEW SPECIES OF FLETCHERIA FROM THE MIDDLE SILURIAN FIBORN LIMESTONE OF MICHIGAN ROBERT V. KESLING, TERRY L. CHASE, CYNTHIA H. DEVORE, and ROBERT D. LATTANZI ABSTRACT-A new species of the rugose coral Fletchen'a, F. acanthina, from the Middle Silurian Fiborn Limestone Member of the Hendricks Formation (Burnt Bluff Group) in the Northern Peninsula of Michigan, is characterized by well-developed amplexoid major septa and acanthine minor septa. INTRODUCTION FLETCHERIAACANTHINA n, sp. WELL-PRESERVEDCORALS are relatively rare in Pls. 1-8; text-fig. 1 the Middle Silurian strata of Michigan. Even Corallum fasciculate and phaceloid with though corals are numerous in many units, cylindrical, unequally spaced corallites. Each their fine structures show damaging effects of corallite commonly 0.75 to 1.OO cm in diameter, silicification or dolomitization. In most out- a few as large as 1.5 cm.