NEW CRINOIDS FROM THE EOCENE LA MESETA FORMATION OF SEYMOUR ISLAND, ANTARCTIC PENINSULA TOMASZ K. BAUMILLER and ANDRZEJ GAZDZICKI Baumiller, T.K. and Gaidzic ki, A. 1996. New crinoids from the Eoce ne La Meseta Form a­ tion of Sey mour Island , Antarctic Peninsula. In: A. Gaidzicki (ed.) Palae ontological Re­ sults of the Polish Antarctic Expe ditions. Part Il. - Palaeontologia Polonica 55 , 101-11 6. The exce llent record of marin e invertebrates from the Eoce ne La Meseta Formation of Sey mour Island (Antarc tic Penin sula) includ es several well-prese rved crinoids. Two cri­ noid species have been previously reported from the upper part of the La Meseta Form a­ tion; here we describe three addit ional taxa from the lower units (Telm l-2) of this forma­ tion: an isocrini d, Eometacrin us australis gen . et sp. n., a comatulid, Notocrinus seym­ ourensis sp. n., and a cyrtocrinid, Cyathidium holopus Steenstrup , 1847. These data are important in prov iding new infor mation for the time-envi ronm ent distribution of crinoids and for constraining phylogenetic hypotheses and evo lutionary scenarios . The co-occurr­ ence of these three taxa is unusual because sedimentological, stratig raphic, and paleoeco­ logical evidence suggests that the lower part of the La Meseta Formation was deposited in a shallow-marine setting whereas today, isocrinids, cyrtocrinids, and coma tulids eo-occ ur only in deep wate r. Also , the morphology of E. australis indicates that the syzyg ial articulation between the first and seco nd primib rachials, thought to represent a character of primary phylogenetic importance among the Isocrin idae, may have evo lved more than once. K e y wo r d s : Crinoidea , taphonomy, taxonom y, paleoecology, Eoce ne, Antarctica. Tomas: K. Baumiller, Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St., Cambridge, MA 02 138, U.SA Andrzej Gazdzicki, Instyt ut Paleobiologii PAN, Aleja Zwirki i Wigu/}' 93,02-089 Warszmva, Poland. Received 23 Febr uary 1995. accepted 13 Se ptember 1995 102 TOMASZ K. BAUMILLER and ANDRZEJ GAZDZICKI CONTENTS Introduction 102 Acknowledgements . 102 Geology and stratigraphy 103 Taphonomy . 105 Taxonomic methodology and terminology 106 Taxonomic descriptions . 106 Class Crinoidea MILLER, 1821 . 106 Subclass Articulata ZITIEL, 1879 106 Order Isocrinida SIEVERTs-DoRECK, 1953 106 Family Isocrinidae GIS LEN, 1924 . 106 Genus Eometacrinus gen. n. 106 Order Comatulida A.H. CLARK, 1908 . 110 Family Notocrinidae MORTENSEN, 1920 110 Genus Notocrinus MORTENSEN, 1920 110 Order Cyrtocrinida SIEv ERTs-DoRECK, 1953 11 2 Family Holopodidae ZITIEt, 1879 ... 11 2 Genus Cyathidium STEENSTR UP in MICHAEl.I S and SCHERK 1847 11 2 Concluding remarks 11 3 References . 11 4 INTRODUCTION Th e fossil record of artic ulate crinoids, a g ro up which includes all post-P aleozoi c crin oids, ex te nds back to the Tri assic, an interval during whi ch , or sho rtly before which, they origina te d (S IMMS and SEVASTOPULO 1993). Tod ay articulates can be subdiv ide d into three functio nal groups: those bearing sta lks through out ontogeny, the isocrinids, bourgu et icrin ids, and mill ericrinids, those which lose the sta lk as j uveniles and live as sta lkless, relative ly motile adults, the comatulids , and those which ce me nt the cup directly to the substra te, the cy rtocrinids . In modern oceans representati ves of these three fun ct ional gro ups eo-occur only in de ep wa ter since the cy rtocrinids and the sta lke d crinoi ds are res tricted to depths g rea ter than 100 m. The three crino ids described in thi s study, the co matulid Notocr inus seymourensis sp. n., the isocrinid Eometa crinus austra lis ge n. et sp . n., and the cy rtocrinid Cyathidium holopu s, all occur in the lower part of the La Meseta Fo rm ati on whic h, based o n sedimento log ic and paleontol ogi c crit eri a, has been int erp reted as representing sha llow-ma rine or even es tuarine se tti ngs . Thus in addi tio n to providing new taxonomic data re levant to o ur understanding of the evolutio nary history of crino ids , thi s study also helps con strain the timing of the previou sly documented offs ho re shift of so me crinoid lineages since the late Mesozoi c/earl y Cen o zoi c (e.g. BOTTJER and JABLONSKI 1988). The investi gated crino id collecti on is kept in the Institute of Paleobi ology of the Poli sh Acade my of Sci ences, War szawa under the ca talogue number ZPAL C a.v. Acknowledgements. - We thank Dave M EYER and Tat su o OJl for helpful di scu ssion s, loan s of Telm6-7 materi al , and ca reful reviews of the manuscript ; G. OZIEWI NSKA, F. D'EsCRIVAN , E. HAR A, G. LLEWELLYN, and A. PEI provided technical assistance for whi ch we are grateful. This study was funded in part by the Sh aler Fund (Harvard Un iver sity) and the Na tio na l Scien ce Fo undation, US A(EAR­ 93 04 789), the Institute of Paleob iol ogy, Poli sh Academy of Sciences (Warszawa), and the Al exander von Humboldt Foundati on (Bonn) . One of us (AG) is indebted to Professor Carlos A. RINALDI and Or. Rodol fo DE L VALLE (In stituto Antartico Arge ntino) for the invit ati on to join the Argentine Exp edition to Antarctica in the austra l sum mer of 199 3-1994 and to all colleagues fro m the field part y for assista nce in the field. Lo gi stic suppor t was provided by IAA (Buenos Aires) and Fuerza Aerea Argentina. NEW CRINOIDS FROM THE LA MESETA FORMATION 103 GEOLOGY AND STRATIGRAPHY The La Meseta Formation, which crops out in the northeastern portion of Seymour (Marambio) Island is a sequence of richly fossiliferous, sha llo w-marine-estuarine, poorly cons olidated sands tones and silt­ stones, approximately 800 m thi ck (Text-fig . 1). Th e sedimentolog ical and stratigraphic fram ework of the La Meseta Formation has been described by RINALDI et al. (1978), ELLlOT and TRAUTM AN (1982), SADLER ( 1988), STILW ELL and ZINSM EISTER 1992, and POR F, BSKI ( 1995). Cape Wiman Lopez de Bertodano Bay Penguin Bay lkm o~--~ Fig. I Crinoid localit y index map of the La Meseta Formation 0 11 Sey mour Island. ZPAL I - Eometac rinus australis and Cyathidium holopus site. ZPAL 3 - Metacrinusfossilis site. ZPAL 6 - Notocrinus seymourensis site. ELLlOT and T RAUTMAN (1982 ) init iall y subdivide d the La Meset a Form at ion into three informal members (Units I, II, and 1lI). SAlJLER ( 1988, fig. 1) mapped the La Meset a Formation and identified seven numbered lith ological units (Telm 1 through Telm7), whi ch demonstrate the lateral variability of the formati on . SAlJLER'S units are correlatable with the ones recogni zed earl ier by ELL/OT and TRAUTMAN (19 82) [see SADL ER (19 88, fig. 3) ; STILWELL and ZINSMEISTER (1992 , fig. 4)] . The La Meset a Form ation has been dated as Eocene to possibly early Oligocen e on the basis of fossil penguins (SIMPSON 1971 ), molluscs (Z INSME IST ER and CAMACHO 1980 , 1982), pol yd olopid marsupials (WOODB URN E and ZINSMEI STER 1982, 1984 ), and cetaceans (FORDYCE 1989). MAR ENSSI et at. (1994) determined that the middle part of the La Meset a Formation (Telm4-5) is middle Eocene based on correlation of terrestri al mammals found in these units with tho se from South Ame rica (Patagonia). Recent studies of marine palynomorphs (mostly din ofl agellate cysts) by ASKI Net al. ( 199 1), COCOZZA and CLARKE ( 1992), and BARNES and RIDI NG ( 1994) support an Earl y Eocen e age for the lower part of the La Meset a Fo rm ati on (Te lm l-2); a result that is co nsiste nt with ages o btained pr eviously by HARWOOD (1986,1988 ) and W RENN and HART ( 1988). Cr inoids whi ch have been pre viou sly described fro m the upp er part of the La Meseta Fo rmation (Telm6-7) include the isocrinid Metacrinus [ossilis (RASMUSSEN 1979; M EYER and 011 1993) and the 104 TOMASZ K. BAUMILLER and ANDRZEJ GAZDZICK I Metacrinus fossilis ~ she lls 0.. pebbles D sand § sil t+ sand Eometacrinus australis Notocrinus seymourensis 2 . " , I . '. 1 .. Fig. 2 Co mposi te strati gra phic co lumn of the La Meseta Form ation on Se ymour Island (South Sec tio n) showi ng the distribution of main lithofacies and location of crinoid sites. Section ada pted fro m SAIlLEK (1988). co ma tulid Notocrinus rasmu sseni (MEYER and OJI 1993). We report here three additional taxa from the lower part of the La Meseta Formati on (Telm 1- 2) which crops out so uthwest of Cross Valley near the L6pez de Bertodano Bay (Tex t-figs 1- 2) [see also Ge ol ogic al Map of Seym our Island in FELDM ANN and WOODBUR NE (1988)). Th e isocrinid Eotnetac rinus australis ge n. et sp. n. and the cy rto crinid Cyathidium holopus were collected at Bill Hill . locality ZPAL I [Text-fi g. I see also GAZDZI CKI and T AT UR ( 1994. pI. 2: 2)). The comatulid Notoc rinus seymourensis sp. n. was found at the locality ZPAL 6 (Tex t-fig. I). The Telm I crinoids, Eometacrinus australis and Cyathidium holopu s, occ ur within an up to 2 m thick interval of basal, transgressive facies represented in thi s area by grey to red -brown lim onitic, sandy siltstones, sandstones, and pebble conglomerates with intercalations of shelly hash.