CONODONTS OF THE MOJCZA LIMESTONE JERZY DZIK Dzik, J. 1994. Conodonts of the M6jcza Limestone. -In: J. Dzik, E. Olemp ska, and A. Pisera 1994. Ordovician carbonate platform ecosystem of the Holy Cross Moun­ tains. Palaeontologia Polonica 53, 43-128. The Ordovician organodetrital limestones and marls studied in outcrops at M6jcza and Miedzygorz, Holy Cross Mts, Poland, contains a record of the evolution of local conodont faunas from the latest Arenig (Early Kundan, Lenodus variabilis Zone) to the Ashgill (Amorphognathus ordovicicus Zone), with a single larger hiatus corre­ sponding to the subzones from Eop/acognathus pseudop/anu s to E. reclinatu s. The conodont fauna is Baltic in general appearance but cold water genera , like Sagitto­ dontina, Scabbardella, and Hamarodus, as well as those of Welsh or Chinese af­ finities, like Comp/exodus, Phragmodus, and Rhodesognathu s are dominant in par­ ticular parts of the section while others common in the Baltic region, like Periodon , Eop/acognathus, and Sca/pellodus are extremely rare. Most of the lineages continue to occur throughout most of the section enabling quantitative studies on their phyletic evolut ion. Apparatuses of sixty seven species of thirty six genera are described and illustrated. Phyletic evolution of Ba/toniodus, Amorphognathu s, Comp/exodus, and Pygodus is biometrically documented. Element s of apparatu ses are homolog ized and the standard notation system is applied to all of them. Acodontidae fam. n., Drepa­ nodus kie/censis sp. n., and D. santacrucensis sp. n. are proposed . Ke y w o r d s: conodonts, Ordovici an, evolut ion, taxonomy. Jerzy Dzik, Instytut Paleobiologii PAN, A/eja Zwirk i i Wigury 93, 02-089 Warszawa , Poland. Revised version received 5th Jun e, 1993. 44 JERZY DZIK CONTENTS Introduction . .. 45 Acknowledgements 46 Conodont zonation 46 Taxonomic methodology 51 Ranks of taxa . 51 Orientation of elements and descriptive terminology 52 Taxonomic descriptions . 53 Phylum Chordata, Class Conodonta PANDER, 1856 53 Order Westergaardodinida LINDSTROM, 1970 . 53 Family Westergaardodinidae MULLER, 1959 53 Genus Westergaardodina MULLER, 1959 53 Order Panderod ontida SWEET, 1988 ..... 54 Family ?Fryxellodontidae MILL ER , 1982 54 Genus Polonodus DZIK, 1976 . .... 54 Genus Pseudooneotodus DRYGANT, 1974 54 Family Belodellidae KIlODALEVI CH et CHERN IC H, 1973 55 Genus Scalpellodus DZIK, 1976 . ... 55 Genus Walliserodus SERPAGLI, 1967 . 56 Family Panderodontidae LINDSTROM, 1970 58 Genus Panderodus ETHI NGTON, 1959 58 lncertae ordinis . 60 Family Scolopodontidae BERGSTROM, 1982 60 Genus Scolopodus PANDER, 1856 . .. 60 Family Strachanognathid ae BERGSTROM, 1982 60 Genus Cornuodus FAHRJEUS, 1966 . 60 Genus Stra chanognathus RHODES, 1955 62 Genus Dapsilodus COOPER , 1976 . 63 Genus Scabbardella ORCHARD, 1980 . 64 Order Protopanderodontida SWEET, 1988 . .. 66 Family Protopanderodontidae LtNDSTROM, 1970 66 Genus Semiacontiodus MILL ER , 1969 66 Genus Drepanodus PANDER, 1856 .. .. 68 Genus Protopanderodus LINDSTROM , 1971 72 Family Distacodo ntidae BASSLER , 1925 . 76 Genus Paltodus PAND ER , 1856 . 76 Genus Drepan oistodus LINDSTROM , 197 1 78 Order Prioniodontida DZIK , 1976 . 79 Superfami1y Prioniodontacea BASSLER, 1925 79 Family Acodontidae fam. n.. 79 Genus Tripodus BRADSHAW, 1969 . 79 Genus Eoneoprioniodus MOUND, 1965 79 Family Balognathidae HASS, 1959 80 Genus Baltoniodus LtNDSTROM, 1971 80 Genus Lenodus SERGEEVA, 1963 . 86 Genus Sagittodontina KNUPFER , 1967 88 Genus Rhodesognathus BERGSTROM et SWEET, 1966 89 Genus Amarphognathus BRANSON et MEHL , 1933 91 Genus Eoplacognathus HAMAR , 1966 96 Genus Cahabagnathus BERGSTROM, 1983 .. 100 Family Phragmodontidae BERGSTROM, 1982 . 101 Genus Phragmodus BRANSON et MEHL, 1933 . 101 Family Pygodontidae BERGSTROM, 1981 .103 Genus Pygodus LAMONT et LINDSTROM, 1957 . 103 CONODONTS OF THE MOJ CZA LIMESTONE 45 Superfamily Icriodontacea MULLER et MULLER, 1957 ·. 106 Family Pterospathodontidae COOPER, 1977 . 106 Genus Complexodus DZIK , 197 6 . 106 Genus Distomodus BRANSON et BRANSON, 1947 .107 Family Icriodontidae M ULLER et MULLER, 1957 ·. 109 Genus Icriodella RHODES, 1953 . 109 Order Ozarkodinida DZIK , 1976 . 109 Suborder Plectodinina DZIK , 1991 . 109 Family Oistodontidae LINDSTROM , 1970 .109 Genus Histiodella HARRIS, 196 2 . .109 Family Periodontidae LINDSTROM, 1970 . 11 0 Genus Periodon HADDING, 1913 . 111 Genus Hamarodus VIIRA, 1974 . 111 Family Plectodinidae SWEET, 1988 . 112 Genus Microzarkodina LINDSTROM , 1971 . 113 Famil y ?Chirognathida e BRANSON et MEHL, 1944 . 113 Genus Spinodus DZIK , 1976 . · . 113 Suborder Ozarkodinina DZIK, 1976 .114 Family Spathognathodontidae HASS, 1959 . 114 Genus Yaoxianognathu s AN, 1985 . 114 References .115 Tables . 118 INTRODUCTION The M6jcza Limestone does not contain stratigraphically diagnostic macrofossils (see DZIK and PISERA 1994). Conodonts thus represent a key to the subdivision and time correlation of this rock unit. It took some time , however, before these opportunities were appreciated and fully exploited. The presence of conodonts in the M6jcza Limestone was documented for the first time by SPASSOV and TELLER (1963) who had found rich fauna in M6jcza while sampling the Paleozoic strata in the Holy Cross Mountains. They did not indicate preci sely the position and number of their sample(s) in the rock column. Judging from published illustrations of conodont elements, representing 17 form­ species, it seems possible that the whole described assemblage comes from a single layer below the discontinuity surface and represents actually 8 biospecies. They concluded that the limestone is of Llandeilo-Caradoc age , which is not contradictory with their taxonomic identifications, although the illustrated specimens seem to be rather Early Kundan in age, being thus close to the Arenig/Llanvirn boundary. Subsequent conodont study of the M6jcza Limestone in its type locality has been undertaken by BEDNARCZYK (1966). The whole section was sampled but, as the identified specimens have not been illustrated, it is difficult to interpret the 18 listed form-species in modem apparatus terms. He proposed an early Llanvim age for the basal "Asaphus limestone" in the M6jcza section, basing this determi­ nation rather on associated brachiopods and the stratigraphic position below the middle part of the section ("the gray limestone with pink coloration") which was dated late Llanvim in age on the basis of the presence of Eoplacognathus robustus (then Amorphognathus n. sp. 3 LiNDSTROM). Rare cono­ donts extracted from the top "red-brownish limestone" were not identified specifically. Thi s precluded recognition of the actual degree of stratigraphic condensation, and as a result its earliest Llandeilo age was assumed. The next step was done by BERGSTROM (1971) who identified conodonts of early Caradoc age in a sample sent to him by Dr. Christo SPASSOV. The sample was evidently taken from a different level than those studied by SPASSOV and TELLER (1963). 46 JERZY DZIK The presence of Caradoc strata in M6jcza was independ entl y shown also by BEDNAR CZYK ( 1971), who illustrated several conodont spec ies from M6jcza and a few subsurface localities of the M6jcza Limestone, but did unfortunately not give the exact positi on of the samples in the section. Illu strated spec imens represent spec ies whic h can be judged as comi ng from belo w the discontinuity surface tBalto niodus pa rviden tatus = his Gothodus costulatusi, from the strata immediately abo ve it (Eopla­ cognathus robustus = his Ambalodus reclinatusi, from just above the bentonite (Amorphog nathus tvaerensis ea rly form = his A. ordovicicai, and from about 2 m above the bentonite tRhodesognathus polonicus = his Holodontus superbusi . The first twelve samples from M6jcza taken for comparative purposes to study Baltic Ordovician conodont apparatu ses (DZIK 1976) present ed a surpris ing stratigraphic completeness of the record in this 8 m thick section, which has been further strengthened after the number of samples wa s increased to almost thirty (DZIK 1978). The sec tion appeared to represent conodont zones ranging from the latest Arenig to at least latest Caradoc (possibly Ashgill ). Th e onl y interval of uncertaint y that remained is in the Earl y Llan virn . Three subzo nes there (E. pseudoplanus , E. suecic us, and E. f oliaceus) have not been documented. The pre sent study is based on even more complete sampling (Text-fig. I ). Because of continued quarrying of the limeston e, the section is rarely expose d completely enough to ensure centimeter precision in identification of sampled beds. Additional series of samples have thu s been taken in parts of the sec tion that had not been ex posed well enough earlier. A trench of a few meters length was also du g in the topmost part of the sec tion. All togeth er 140 samples were taken from the type locality and several more from outcrops in Miedzygorz and Zalesie; 14 of the latter have appeared productive. Altho ugh such a dense sampling resulted in samples being about 10 cm distant from each other, no apparent features of reworking of conodont elements have been identified except for the bed imm ediately above the discontinuity surface . Abrupt appearances and disappearances of some species (like Rhodesognathus polonicus, see Text- fig. I ) shows that the depth of bioturbation was very shallow there, probably not exceeding a few centimeters . As a res ult of the restudy of all conodo nts from M6jcza (DZIK 1990) spec ifically diagnostic elements of Amo rphognathus were recogn