Well preserved crinoids from the Shellrock Formation (Upper Devonian) of Iowa are extremely rare. Several well preserved specimens collected by one of us (Levorson) have led to new generic assignments of the species originally described as Nassoviocrinus goldringae Belanski, 1928, to Glossocrinus goldringae, n. comb., and of Hexacrinus springeri Thomas to Cerasmocrinus springeri, n. comb. The latter is the type species of Cerasmocrinus, new genus

Levorson, C. O.

Strimple, Harrell L.

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Additional Crinoid Specimens from the Shellrock Formation (Upper Devonian) of Iowa

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 80 Number Article 9 1973 Additional Crinoid Specimens from the Shellrock Formation (Upper Devonian) of Iowa Harrell L. Strimple University of Iowa C. O. Levorson University of Iowa Let us know how access to this document benefits you Copyright ©1973 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Strimple, Harrell L. and Levorson, C. O. (1973) "Additional Crinoid Specimens from the Shellrock Formation (Upper Devonian) of Iowa," Proceedings of the Iowa Academy of Science, 80(4), 182-184. Available at: https://scholarworks.uni.edu/pias/vol80/iss4/9 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. Additional Crinoid Specimens from the Shellrock Formation (Upper Devonian) of Iowa HARRELL L. STRIMPLE1 and C. 0. LEVORSON2 SnnMPLE, HAHRELL L., and C. 0. LEVOHSON. (The University of Iowa. Iowa City, Iowa 52242.) Additional Crinoicl Specimens from the Shellrock Formation (Upper Devonian) of Iowa. Proc. Iowa Acad. Sci. 80( 4): 182-184, 1973. Well preserved crinoids from the Shellrock Formation (Upper Devonian) of Iowa are extremely rare. Several well preserved specimens collected by one of ui ( Levorson) have led to new generic assignments of the species originally described as Nas-Strimple and Levorson, 1969, in a study of Upper Devon-ian crinoids of Iowa, assigned the species N assodocrinus goldringae Belanski, 1928, to the genus Quantoxocrinw; Weh-by, 1965. At that time, only two specimens (holotype CHB 1981, now SUI 71981, and paratype CHB 1983, now SUI 71983) were known. Subsequently several specimens of the species, in excellent preservation and including the hitherto unknown anal sac, have been collected by one of us ( Levm·-son), which has led to a reconsideration of the species. The species is now thought to belong with Glossocrinus Goldring, 1923, and is here referred to as Glossocrinus goldri11gae ( Belanski), new combination. The species Hexacrintts springeri Thomas, 1924, was pro-posed with "the type specimen," designated here as the holotype by monotypy, and disarticulated plates. Thomas (ibid., pl. 42, fig. 2) showed an illustration of U.l.C. 3722 (SUI 3722), which he considered to he an arm with pinnules belonging to H. springcri and used as a basis for stating (ibid., p. 461) the arms were "apparently uniserial." The specimen is actually the median, longitudinal line of sac plates flanked on either side by a row of sac plates which have numerous thin folds, and belongs with Glossocrintts goldringae. Strimple, 1963, recognized that Hexacrinites springeri (Thomas) was atypical of Hcxacrinites and refer-red the species to Desmidocrinus springcri (Thomas). Sub-sequent study of D. pentadactylus Angelin, 1878, type spe-c'.es of the genus, has led us to conclude that D. springcri is not congeneric, but represents a form with characters shared by Desmidocrintts and Arthroacantha ·Williams, 1883. Cerasmocrin11s Strimple and Levorson, new genus, is pro-posed, with Hexacrinus springeri Thomas as the type spe-cies of the genus. A hypotype of C. springcri found by one of us (Levorson) is illustrated herein. Presently considered specimens were found at Belanski Station No. 155, that is, in low cliffs along the south bank of the Shell Rock River in the NEJ.;, NWJ4, sec. 4, T. 9.5 N., R. 18 W., near Nora Springs in northcentral Iowa. The hori-zon is Bed 5, "Hexacrinus" zone, Eatonia Zonule of Belanski ( 1928), t\fason Citv Member, Shell rock Formation, Upper Devonian. 1 The Universitv of Iowa. Iowa City, Iowa. 2 Riceville, Iow:1. soviocrinus goldringae Belanski, 1928, to Glossocrinus goldringae, n. comb., and of Hexacrinus springeri Thomas to Cerasmocrinus springeri, n. comh. The latter is the type species of Cerasmocrinus, new genus. bmEx DEsCl\IPTOHS: Iowa Devonian Crinoids; Shellrock Forma-tion Crinoids; Glossocrinus goldringae; Cerasnwcrinus springeri; H exacrinus springeri. SYSTEMATIC PALEONTOLOGY Subclass INADUNATA Wachsmuth & Springer, 185.5 Order CLADIDA Moore & Landon, 1943 Suborder POTERIOCRININA Jaekel, 1918 Superfamily RHENOCRINACEA Jaekel, 1918 Family RHENOCRINIDAE Jaekel, 1918 Genus GLOSSOCRINUS Goldring, 1923 GLOSSOCRINUS GOLDRINGAE ( Belanski), Strimple and Levorson, new combination Plate 1, figures 7, 8. Syll(momy. N assoviocrinus goldringae Belanski, l 928; Quantoxocrinus goldringae Strimple and Levorson, 1969. Diagnosis. Crown elongate, slender, arms do not adjoin when closed. Cup tall, conical, evenly expanded; infrabasals readily visible in side view of cup; radiating folds which ex-tend from plate to plate arc weak, with rays represented mainly by depressions at plate corners; radial articular facets do not completely fill distal faces ( peneplenary); three anal plates in normal (primitive) arrangement. Anal sac tall, slender, median ridge formed by thick plates starting at ter-tanal ( HX) and extending length of sac, flanked hy thin nar-rowly plicated plates on each side with plications perpen-dicular to axis of tube. Arms slender, uniserial, pinnular, with each brachia! bearing a stout pinnule on alternating sides; one bifurcation usually takes place high in the arms with primibrachs 7-9. Proximal columnals pentalobate, alternat-ingly expanded. Discussion. Glossocrinus naplcsensis Goldring, 1923, type species of the genus from the Upper Devonian of New York, has pronounced radiating ridges or folds on the cup plates, Figure 1. 1-6. Cerasmocrinus springeri (Thomas, 1924). 1-3. Holotype (SUI 3722) calyx viewed from posterior ( C-D interray ), DE interray and BC interray, X2.5. 4-6. Hypotype (SUI 80010) calyx viewed from CD intnray. E rav and BC interrav, X2.5. 7-8. Glossocrinus' goldringae ( Belanski, 1928). 7. Highly magnified portion of hypotye (SUI 80007) showing median ray of anal sac flanked hy thin narrowly plicated sac plates, X4.45. 8. Hypotype crowns (SUI 80007a-b), that to left (a) viewed from anterior, to the right ( b) young specimen viewed from C ray. with three anal plates visible to the left (albeit secundanal [anal X] almost ohscmed) ancl right side of anal sac well exposed ahon'. X4.0. 1Strimple and Levorson: Additional Crinoid Specimens from the Shellrock Formation (UpperPublished by UNI ScholarWorks, 1973SHELLHOCK FonMATION CmNoms 183 2Proceedings of the Iowa Academy of Science, Vol. 80 [1973], No. 4, Art. 9https://scholarworks.uni.edu/pias/vol80/iss4/9184 PRoc. low A AcAD. Ser. 80 ( 1973) a comparatively short cup, and first arm branching takes place about primibrachs 5-6. G. goldringae has a much taller cup, and the arms branch with primibrachs 7-9, both of which conditions are considered to be more primitive than G. naplesensis, G. cornellianus (Williams) is more closely related, in having a moderately tall cup and branching with primibrachs 8-9, but completely lacks radiating folds on cup plates. As explained by Strimple and Levorson, 1969, Nassovio-crinus typically has a quadrangular primanal ( radianal), re-sulting in two anal plates in the posterior interray, as opposed to a pentagonal primanal, resulting in three anal plates in the posterior interradius, but differs from Quantoxocrinus in having a strong median ridge composed of thick uniserial plates extending the length of the sac, which are flanked by thin narrowly plicated plates on each side. The anal sac of Quantoxocrinus is composed of equidimensional plates lack-ing plications. Hypotypes. Collected by C. 0. Levorson, deposited in the Levorson Collection, cat. SUI 80005, 80008, 80007, Geology Department, The University of Iowa, Iowa City. Subclass CAMERATA Wachsmuth & Springer, 1855 Order MONOBATHRIDA Moore & Laudon, 1943 Suborder TANAOCRININA Moore, 1952 Superfamily DESMIDOCRINACEA Angelin, 1878 Family DESMIDOCRINIDAE Angelin, 1878 Genus CERASMOCRINUS Strimple & Levorson, new genus Type species. Hexacrinus springeri Thomas, 1924. Name. From Greek Kerasma for mixture, with reference to the uncertain (mixed) affinities of the genus. Description. Calyx tall, cylindrical, with 3 tall basals prominent in side view. Primanal in line with radials, fol-lowed above by 3 plates and subsequently by 4 smaller plates. Interradials of moderate size, resting in strong notches in distal portion of radials, followed above by 2 or 3 plates and joined with fixed primibrachs 1 and 2. Secun-dibrachs 3 appear to be the last of the fixed brachials. Radial articular facets are narrow ( angustary). Column is round. Discussion. There is small likelihood that Cerasmocrinus evolved from the typically Silurian Desmidocrinus, because the basal plates are much more prominent in side view; how-ever, there are many other characteristics indicating close relationship, such as the primanal followed by three plates, interradial area in calyx composed of few plates, and two fixed secundibrachs in each half ray. Desmidocrinus is more primitive in that interradials are larger and are lower in the cup, and fixed tertibrachs are present in all species. Primibrachs are not incorporated in the cup to form a calyx in hexacrinitids, but they are commonly joined with interradial tegminal plates. A trend toward this more ad-vanced condition is indicated but not attained by Cerasmo-crinus. Occurrence. Upper Devonian, Iowa. CERASMOCRINUS SPRINGER! (Thomas, 1924), new combination Plate 1, Figs. 1-6. Synonomy. Hexacrinus springeri Thomas, 1924; Desmido-cr:nus springeri Strimple, 1963. Description. Same as for genus. Discussion. Cerasmocrinus springeri is closer to Hexacrin-ites interscopularis (Phillips, 1841), the type species of Hexa-crinites, which is from Middle Devonian rocks of England, than to most American species assigned to the genus. How-ever, interradial plates of the hexacrinitids do not appreci-ably penetrate the interradial area of the cup, which is con-sidered as a definitive feature by Ubaghs (in press, Section T, Echinodermata, Treatise on Invert. Paleo.). The illus-trated steinkern of Arthroacantha granosa Goldring ( 1923, pl. 37, fig. 12) shows an interradial plate apparently firmly united with the radials, although it does not penetrate be-tween the radials, as well as being joined with primibrachs 1 and 2. It appears that A. granosa does have fixed primi-brachs, contrary to the familial definition. Except for the tall basal circlet, Cerasmocrinus springeri appears to have closer affinities with the desmidocrinids than with the hexacrinitids, as has been previously discussed un-der the generic discussion. Hypotype. Collected by C. 0. Levorson, deposited in the Levorson Collection, cat. SUI 80010, Geology Department, The University of Iowa, Iowa City. REFERENCES CITED All cited references may be found in BASSLER, R. S., and MOODEY, M. W., 1943, Bibliographic and faunal index of Paleozoic pelmatozoan echinoderms: Geol. Soc. America Special Paper 45, 734 p., with the following exceptions: STRIMPLE, H. L., 1963. Crinoids of the Hunton Group (Devonian-Silurian) of Oklahoma: Okla. Geol. Survey Bull. 100, 169 p., 12 pl. ---, and LEVORSON, C. 0., 1969. Part 4. Two Upper Devonian crinoids, in Strimple et al., Crinoid studies: Univ. Kans. Paleo. Contr. Paper 42, 26 p., 9 figs. WEHBY, B. D., 1965. Quantoxocrinus, a new Devonian inadunate crinoid from West Somerset: Paleontology, v. 8, p. 11-15, pl. 14. 3Strimple and Levorson: Additional Crinoid Specimens from the Shellrock Formation (UpperPublished by UNI ScholarWorks, 1973

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Additional Crinoid Specimens from the Shellrock Formation (Upper Devonian) of Iowa

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