BRACHIOPODS FROM THE EOCENE LA MESETA FORMATION OF SEYMOUR ISLAND, ANTARCTIC PENINSULA MARIA ALE KSA NDRA BITNER Bitner, M.A. 1996. Brachi opods from the Eoce ne La Meseta Formation of Sey mo ur Island , Antarc tic Peninsul a. In: A. Gai dz icki (ed .) Palaeon tological Result s of the Polish A ntarctic Exped itions. Part 11. - Palaeont ologia Polonica SS, 65-100. Th e rem arkabl y diverse brachi opod assemblage fro m the Eocene La Meseta Formatio n of Seymour (Murarnbio) Islan d, Antarctic Penin sul a, co nta ins nineteen ge nera and twent y four spec ies. Four genera and eight spec ies are new, i.e. Basiliola minuta sp. n., Tegu lorhynchia ampullacea sp. n., Parapli cirhvn chia gazdz icki! ge n. et sp. n.. Seymourella ow eni ge n. et sp. n., Ge n. et sp. n., Mu rravia foster! sp. n., Macandrevia cooperi sp. n., and Laquethiris curiosa gen . et sp. n. A new subfamily Sey mo urinae is prop osed for the species Seymo u­ rella oweni. Genera Basiliola. Hemithiris, Parapli cirhynchia. Seymourella, Murravia, Ma ­ gel/a, Stetho thyris, Macandrevia, and Laqu ethiris are reported for the first tim e from the La Meseta Formatio n, although Hemithiris and Magella have been already noted from the Terti ary strata of adjacent Coc kburn Island. So me of the ge nera tBasiliola, Hemithiris. Notosaria, Murra via, Stethothyri s, Macand revia i described herein represent the oldest OCC UITences of the genus, thu s ex ten ding their stratig raphical ranges, which suggests that Sey mo ur Island might play an important role in the evolution of man y bruchi opod taxa from where they spread north wards before the development of the circum-A ntarc tic current in the Oligoccne time. Th us, the brachiopods from the La Meset a Formation are another example of the heteroch roneit y of high so uthem latitude faunas . Th ese brachi opods at the gener ic level show close affi nities to those from New Zea land, having ni ne genera in co mmo n. Fewer generic affinities exist bet ween Terti ary brachi opod fauna of Sey mo ur Island and southern So uth America . T he brachi opods indicate wa rm to warm-temperate co nditions of sha llow to moderately deep marine env ironments wh ich supports in general earlier interpretation of the La Meseta Forma tion depositional co ndit ions. How ever, the presence in the upp erm ost part of the form ation of such war m-wate r ge nera as Lingula and Bouch ardia is in co ntrad iction with a co nsiderab le climatic cooling pos tulated on the basis of oxygen isotopi c data. K e y w o r d s : Brac hio poda. taxonomy, paleoecology, paleo biogeography, Paleogene, An tarctica. Maria Aleksa ndra Bitner, lnstytut Paleobiologii PAN, Aleja Zw irki i Wigury 93, 02-089 Warszawa, Poland. Recei ved 13 Apr il 1'.>'.>5 . accepted 20 Sep te mber 1'.> '.> 5 66 MARIA ALEKSANDRA BITNER CONTENTS Introduction 67 Acknowledgements 67 Geological and stratigraphical setting 67 Material . 70 Systematic paleontology 70 Order Lingulid a WAAGEt\. 1885 70 Superfamily Linguloidea MEt\KE. 1828 70 Family Lingulidae MENK E. 1828 70 Genus Lingula BRUGUI ER E. 1797 70 Order RhynchonelIida KUIIN. 1949 71 Superfami ly RhynchonelIoidea GRAY. 1848 71 Family Basiliolidae COOP ER . 1959 7 1 Subfamily Basilio linae COO PER. 1959 71 Genus Basiliola DALL. 1908 71 Family Hemithyrididae RZIIONSNITSKAYA . 1956 72 Genus Hemithiris D'ORnlGNY, 1847 72 Genu s Notosaria COOPER , 1959 73 Genus Tegul orhynch ia CIlAPMAt\ et CRESPI t\. 1923 74 Genus Plicirhynchia ALLAt\, 1947 76 Genus Paraplicirhynchia gen. n. 76 Order Terebratulida WAAGEt\, 1883 ' " 77 Superfamily Terebratuloidea GRA Y. 1840 77 Family Terebratulidae GRAY. 1840 .. 77 Subfamily Terebratulinae GRAY. 1840 77 Genus Liothyrella TIlOM SOt\. 1916 77 Subfami ly Seymourinae subfam. n. 78 Genus Seymourella gen. n. 78 Subfa mily uncerta in 79 Gen . et sp. n. 79 Superfami ly CancelIothyridoidea TIIOM SON, 1926 80 Fami ly Cancellothyrid idae TIIOM SON. 1926 80 Subfamily CancelIothyridin ae TIIOM SON. 1926 80 Genus Terebratulina D' ORB IG NY, 1847 80 Genus Murravia TII O ~I S O N. 1926 80 Superfamily Tereb ratelloidea KING. 1850 8 1 Family Terebratell idae KIt\G. 1850 . 8 1 Subfamily Bouchardiinae AI.I.At\. 1940 8 1 Genus Bouchardia DAVIDSO N. 1850 8 1 Subfamily Terebratellinae KING, 1850 82 Genus Terebratella I)·ORB IGt\Y. 1847 82 Genus Magellania BAYLE. 1880 83 Genus Magella TII O ~ l S 0 N . 1915 83 Subfamily Stethothyridinae MACKINNON. BELJ S et LEE. 1993 84 Genus Stethothyris Tllm lsoN, 1918 . 84 BRACH IOPODS FROM THE LA MESETA FORMATION 67 Family Macandreviidae COOPER , 1973 84 Genus Macandrevia KING, 1859 . 84 Family ?Laqueidae TIIOMSOK. 1927 . .. 86 Subfamily ?Laqueinae TIIOMSOK, 1927 86 Genus Laqu ethiris gen. n. 86 Paleoecolog y . .. .. .. 87 Comparative ecological an alysis 88 Paleoenvironmental implication s 90 Paleobiogeographical remarks 9 1 References . 94 INTRODUCTION The brach iopod s fro m the La Meseta Forma tio n of Sey mo ur Island, Antarctic Pen insul a were first described at the begin nin g of the ce ntury by BUCKMAN (1910), however, he menti oned the presence of only two genera: Lingul a and Bouchardia. More recentl y brachi opods were examined by OWEN (1980) who noted the presence of six genera: Lingula, Notosa ria, Liothyrella, Magellania , Bouchardia and Terebratella. WIEDMAN et al. (1988) added to this list four other genera, TProbolarina, Tegulorhynchia , ?Plicirhynchia and Terehratulina. BITNER (199 1) described a new species of the genus "Terebratella ". However, none of the previous reports presented so ric h and diversified assemblage whic h co mprises nineteen genera and twe nty four species. Its imp ortance is in the fac t that it co ntains numerous new taxa and extends both stratigraphica l and geographica l ranges of several genera known so far fro m younger deposits. The investigated brachiopods also shed new light on the possi ble migration rou tes and origins of some ge nera. The brachiopods were co llected by Andrzej GAZDZI CKI during the Argentine-Polish field partie s in the austral summers of 1987- 88, 1991- 92 and 1993-94 (OOKTOR et al. 1988; GAZDZI CKI 1996 thi s volume). Brach iopods described herein are hou sed in the Institute of Paleob iology of the Pol ish Academy of Sciences (Warszawa) und er the number ZPAL Bp .XXXVII . Acknowledgements. - Th e author wis hes to express her gratitude to Assoc.Professor Andrzej GAt ­ DZICK I (Institute of Paleobi ology, Warszawa) for do nation of the material, access to his Anta rctic library and helpful discu ssion on the geology and paleontology of Seymour Island during prep aration of thi s manu scr ipt. Warm thank s are du e to Dr. Oavid I. MACKINNON (U niversity of Ca nter bury, Christchurch ) for the stimulating interest he has shown, for help with finding difficult available papers, and for a supply of co mparative material of Stethothyris uttleyi , Or. Oaphne E.LEE (University of Otago, Ouned in) and Dr. Ewa POPI EL-BARCZYK (M useum of Earth, Warszawa) helped me in the qu est of so me papers. Special thanks are du e to Or. Ellis F. OWEN (The Natural History Muse um, London ) for his cr itica l rea ding of this paper and for improving the langu age. I also apprec iate the comments made by Professor Ge rtr uda BIERNAT (Institute of Paleob iology, Warszawa). Tha nks are also ex tended to Professor Krzysztof JAZDZEWSKI and Dr. Piotr PRESLER (both from Laboratory of Polar Biology and Oce anobiology, University of L6di, L6 di) for the access to the co llection of Recen t brach iop ods from the Antarctic region and for a supply of specime ns of Liothyrella lll'a. The photographs were taken by Mrs. Grazyna OZI EWI NSKA (Institute of Paleobiology, Warszawa) to whom the author is very grateful. GEOLOGICAL AND STRATIGRAPHICAL SETTING The La Meseta Formation, extreme ly foss ilifero us marine de posits fro m where all the brach iop ods co me, crops out at the north ern part of Sey mo ur Island and so uthwest of Cross Valley (Tex t-fig. I). The La Meseta Formation was first divided into three lith ological units, I th rough III, by ELLlOT and TRAUTMAN 68 MARIA ALEKSANDRA BITNER Cape Wiman ZPAL 11 Lopez de Bcrtodano Bay Z~~ '---""~ --' Penguin Bay o~ ~l k m Fig. I Map of the north ern part of Sey mour Island showing the localities where bra chiopod s were co llec ted. ( 1982), but after detai led mapping SADL ER ( 1988) indicated the nece ssity for furt her differentiation and div ided it into seven lithofacies units (Telm l- Telm7 ). The La Meseta Formation deposits lie uncon form ably on the upp er Cretaceous/ Paleocene eros ional surface (Z INSI\ IEISTER 1982a, b; FELDM ANN and Z INSM EISTER 1984 ; WOODB URNE and ZINSMEISTER 1984 ; SADLE R 1988; STILWELL and Z INSME ISTER 1992; PORI ;BSKI 1995) and are overlain by the Quatern ary deposit s (Weddell Formation) see Geo logic Map ofSeytnour Island in FELDM ANNand WOODBUR NE( 198 8). Characteristics of the Tclm units . - The lowermost unit Telrn l cro ps out at Ca pe Wirnan and west of Cross Valley. Interpreted as trangressive dep osits, it is co mpose d of a sandy pebble-conglomerate succeeded by iron-stained qu artz sandstones at the wes ternmost exposure and of a laminated, fissil e quart z sands tone with carbonate-cemented co ncretions associated with a megabreccia facie s at the northenmost ex posure (SADL ER 1988; STILW ELL and ZINSM EIST ER 1992).