Studies of Asian Conodonts, Part I)*

Home , Doliognathus, Ozarkodina, Spathognathodus, Taphrognathus

Trans. Proc. Palaeont. Soc. Japan, N.S.. No. 53. pp. 179-193. pls. 27, 28. Apr. 10, 1964

466. CARBONIFEROUS CONODONTS FROM THE OMI LIMESTONE, NIIGATA PREFECTURE. CENTRAL JAPAN

(STUDIES OF ASIAN CONODONTS, PART I)*

HISAYOSIII IGO and TOSHIO KOIKE

Institute of Geology and Mineralogy. Tokyo University of Education

青海石灰岩から発見された石炭紀のコノドントについて;新潟県西頸城郡青海町・青海電化株式会社の青海 ∫ll沿いの西山採石場に露出するC1層(Millerella Zone)の石灰岩から発見されたコノドントのうち,11属16睡を記蔵した。またこれらのコノドントにもとついて, C1層の地質時代を険討した.猪郷久義・小池敏夫

which was rather vague before our study. Introduction and Acknowlegments This paper is the first report of our continuous work on conodonts from Ja- The Omi Limestone is distributed in pan and other Asian districts. Nishikubiki County, Niigata Prefecture. Acknowledgments are due to Drs. Central Japan. It has been studied by Haruyoshi FUJIMOTO, professor emeritus many workers. such as HAYASAKA (1921), of the Tokyo University of Education, KAWADA (1954) and FUJITA (1958), but Wataru HASHIMOTO, professor of the no comprehensive paleontological study same university, Teiichi KOBAYASHI,. has been published except for HAYA- professor emeritus of the University of SAKA'S classical work. We have been Tokyo and Teturo HANAI, assistant pro- studying various fossils from this huge fessor of the same university, for their limestone mass and are very fortunate suggestions and encouragements. During to find an excellently preserved rich the senior author's stay in Illinois he conodont fauna in the lower part of this was indebted to Dr. Charles COLLINSON, limestone. There has been no report of geologist of the Illinois State Geological a rich conodont fauna in Japan except Survey, for his guidance for the cono- for recent brief note of HAYASHI (1963). dont study. We also thank Mr. Hide- We studied this newly found conodont toshi TOGASHI of the Omi Denka Co. fauna with keen interest. As the result Ltd., for his help to our fossil collection of the study we discriminated eleven in the field. A part of expenses of this genera and sixteen species and became work was defrayed from the Scientific to believe that this conodont fauna ap- Expenditure Fund, Ministry of Education, parently indicates Early Pennsylvanian Japanese Government. or Late Namurian in age. This conclusion must be noted about the geological age of the lower part of the Omi Limestone Stratigraphic Summary

* Received Jan. 6. 1961; read at the Annual The Omi Limestone is a thick lime- Meeting of the Society at Tokyo, Sep. 7. 1963. stone mass ranging from the Early Car-

179 18(1 Hisayoshi IGO and Toshio KOIKE

boniferous (Tournaisian) to late Middle Eoasianites from the certain horizon 01 Permian in age. According to KAWADA CI and they briefly discussed about the

(1954) and FUJITA (1958) this limestone geological age of CI. Judging from can be subdivided into five lithogenetic these evidence, KAWADA'S Coral-Bra- units as follows in descending order. chiopod Zone or FUJITA's Millerella- Coral-Brachiopod Zone is thought to be P2•c•c Parafusulina and Neoschcogerina equivalent to the Tournaisian to Bashi- Zones kirian. P1•c•cPsendofusulina and Pseudoschina- We collected many specimens of bra- gerina Zones chiopods. ammonites, corals and others C3•c•cTriticites Zone Finnlinella-FusulinaC2•c•c Zone from about 100 m. below of the SAKA- Millerella-Coral-Brachiopod C1•c•c Zone GAMI'S Profusulinella-limestone. They are not throughly worked out, but we The representing conodonts were col- discriminated the following ammonites lected from C1 of KAWADA and FUJITA. in addition to Eoasianites sp., such as The geological age of CI was very ob- Gastrioceras sp.. aff. G. reticulatus Yin scure, but HAYASAKA once discriminated and Paralegoceras sp.. These ammonites the following fossils, such as Amygdalo- may indicate the Reticuloceras Zone of phyllum giganteum MAYASAKA), Cor- western Europe. The Reticuloceras Zone enia ? omiensis (HAYASAKA). Axophyl-w is the Upper Namurian and thought to um gracile HAYASAKA. Lithostrotionl be equivalent to the Lower Pennsylvanian somaense YABE and HAYASAKA, Stvlido- (MOORE, 1948; ELIAS. 1956). Our cono- phyllum sp.. Chaetetes sp.. Giganlopro- dont fauna was obtained from this am- ductus edelburgensis (PHILLIPS), Avonia monite-bearing limestone, and as will be cfr. aculeatus (MARTIN), Echinoconchus discussed later the geological age of punctatus var.. Produclus semireticulatus this conodont fauna also indicates ex- MARTIN. Camarophoria globulina PHIL- actly same age with the preliminary LIPS, Martinia glabra decora PHILLIPS, conclusion from these ammonites and Reticularia lineata MARTIN, Syringothyris brachiopods. cuspidalus MARTIN, Megistocrinus sp.. Actinocrinus aff. globrus PHILLIPS and Faunal Summary of Conodonts others. Unfortunately precise stratigraphic The collections were made in the Nishi- positions of these fossils are still obscure. yama quarry of the Omi Denka Co. Ltd. It seems to be necessary further inves- along the Omigawa River (Text-fig. I). tigation of these fossils from CI based Stratigraphic position of conodont-bear- upon the present progressed paleon- ing bed is about 100 m. below of the tology. The occurrence of Syringothyris SAKAGAMI'S Profusulinella-limestone. cuspidalus from CI indicates Tour We have succeeded to separate numer- naisian age, and Gigantoproductus and ous specimens of conodonts from gray -others are thought to be the Visean. to white sparry limestone by acetic acid Recently SAKAGAMI (1962) proved the treatment and discriminated the follow- •occurrence of Profusulinella from the ing species. namely :-Hindeodella asia- upper part of CI and described several tica IGO and NOIRE. n. sp., H. paradeli- 'Carboniferous bryozoa . KATO and NAKA (Willa IGO and KOIKE, n. sp. II. saka- AIURA 1962) reported the occurrence of gamii IGO and NOIRE, n. sp.. Synprionio- 466. Carboniferous Conodonts from Central Japan 181

Text-fig. 1. Map showing the fossil locality.

dina microdenta ELLISON, S. collznsoni Ilindeodella are very abundant through- IGO and KOIKE. n. sp., Euprioniodina out the collections, and they are related dentata IGO and KOIKE, n. sp.. Ligonodina to the mentioned American species which hanaii IGO and KOIKE, n. sp.. Roundya range from the Desmoinesian to Missou- subacordus (GUNNELL), Lonchodina ? nip- rian. Owing to the fragmentary state ponica IGO and KOIKE, n. sp.. Ozarkodina of these described foreign specimens. orientate IGO and KOIKE, n. sp.. Spatho- detailed comparison seems to be difficult. gnathodus echigoensis IGO and KOIKE, Thus we proposed new species herein sp.. Idiognathodus togashii IGO and KOIKE, based upon many complete specimens. n. sp., Streptognathodus japonicus IGO and The genus Synprioniodina is known KOIKE, n. sp., S. expansus IGO and KOIKE, from the Lower Devonian to Upper Car- n. sp., Gnathodus opimus IGO and KOIKE, boniferous, but it is rather common in n. sp. and Gnathodus sp. the Devonian and Mississippian rocks. Hindeodella asiatica and IL sakagamii S. microdenta is very abundant in the resemble H. armata STAUFFER and PLUM- treated material and it is similar to the MER which was described from the East American specimens which were de- Mountain Shale member, Mineral Wells scribed from the Cherokee Shale through formation, Texas. II. paradelicatula is the Deer Creek Limestone (ELLISON, also closely related with IL delicatula 19411) and also from the Middle Dimple STAUFFER and PLUMMER from the Gra- formation (Morrowan) in Texas (ELLISON ford and Mineral Wells formation in and GRAVES. 1941). ROHDES (1952) de- Texas. These three new species of scribed Synprioniodina-assemblage from 182 Hisayoshi IGO and Toshio KOIKE

the Pennsylvanian of Illinois and his Spathognathodus echigoensis is a rather illustrated specimens quite agree with common species in this fauna and it our specimens. S. collinsoni is rather slightly resembles S. minutus (ELLISON) rare, but having unique denticles and is discriminated from the Desmoinesian to very distinct from other previously de- Rig Blue Series. scribed species. Idiognathodus togashii is a rather rare Euprioniodina dentata is not so com- throughout our collection. This new mon in our collections. The genus species seems to be a primitive type Euprioniodina is rather long-ranged cono- among this genus and resembles I. deli- dont and has been known from the catus GUNNELL persisting in the Desmo- Lower Carboniferous to Triassic. Our inesian to Lower Virgilian in Kansas new species resembles E. Pulcella YOUNG- and Missouri. QUIST and DOWNS described from the Two forms of Streptognathodus are Lower Pennsylvanian of Iowa. discriminated from this fauna. S. japo- Ligonodina is also a long-ranged genus nicus is very abundant and is a charac- of Coleodontidae and has been reported teristic representative in this fauna , but from the Ordovician up to the Triassic it differs from many American species. rocks. L. hanaii is a rare species in S. expansus is rare, but it resembles S. our collection and it may he related wabaunsensis GUNNELL and other Pen- with L. typa (GUNNELL) and also with nsylvanian species of U.S. A.. L. lexingtonensis (GUNNELL) reported Gnathodus opimus is fairly common in from the Desmoinesian and Missourian our collection, but it differs from most of North America. of the American and European species. Roundya subacodus (GUNNELL) is also As mentioned above the Omi conodont a rare species in this fauna . Detailed fauna is dominated by Streptognathodus comparison between our forms and the japonicas, Gnalhodus opimus, three new American ones seems to he difficult. but species of Hindeodella, Synprioniodina they stand very close each other . Ac- microdenta Spathognalhodus echigoensis cording to ELLISON (1941), R. subacodus and Ozarhodina orientate. ranges from the Desmoinesian through Up to date a few papers treated the Virgilian. Lower Pennsylvanian or Upper Namu- Lonchodina ? nipponica is also a rare rian conodonts were published, therefore, . representative of this fauna. It resem- it renders difficult to compare our fauna bles L. ? ponderosa ELLISON in many with those from foreign countries. The respects, if not entirely conspecific. EL- Omi fauna is characterized by entire LISON'S species ranges from the Desmoi- lack of the typical Mississippian genera, nesian to the Lower Permian in Mis- such as Dollymae, Doliognathus, Scalio- souri and Kansas. gnathus, Staurognathas, Taphrognathus,_ Ozarhodina orientate is a common spe- and others. It is also never overlooked cies in our fauna and is related to 0. that the characteristic Middle Pennsyl- delicatula described by many workers vanian to Upper Triassic genus of Con- from the Kinkaid to various levels of dotella is avoided in the fauna. From the Pennsylvanian in U. S. A. The Missi- the above mentioned evidences the pre- ssippian species of O. compressa sent Omi conodont fauna apparently in- ROAD described from Illinois is similar dicates Early Pennsylvanian or Late to our O. orientate. Namurian in age, and it is thought to. 466. Carboniferous Conodonts from Central Japan 183 be one of the richest conodont faunas of of anterior bar erect, discrete. larger the mentioned age in the world. than small sized denticles of posterior bar, and anteriorly increase in size. Pulp cavity small with faint elevation Description of Species of lips. Family Coleodontidae BRANSON Remarks:-Hindeodella asiatica closely resembles H. armata STAUFFER and and MEHL. 1944 PLUMMER described from the Pennsyl- Subfamily Ilindeodellinae HASS, 1959 vanian Mineral Wells formation in Texas, but our species is having more numerous Genus Hindeodella BASSLER, 1925 small denticles of the posterior bar and well developed denticles of the anterior Hindeodella asiatica IGO bar. H. fragilis HASS described from and KOIKE, n. sp. the Early Mississippian Channel Lime- Pt. 27. figs. 7- 10 stone in Texas is also similar species with our II. asiatica, but the present Bar-like unit with anterior bar flexed species is easily distinguishable in more inward as well as downward approxi- numerous small sized denticles of the mately 90 degrees. anterior end further posterior bar and more distinctly discrete curved toward posterior. and hook-like larger denticles of the anterior bar. H. in shape. Posterior bar almost straight. belle STAUFFER and PLUMMER was based elliptical in transverse section. but flat- upon the fragmentary posterior end. The tened except for blade-like near posterior posterior end of H. asiatica is almost end. Aboral side of bar sharply edged difficult to distinguish from H. bella. except adjacent to small pulp cavity and Reg. no. 23002 (Holotype) distinctly grooved along midline. Denticles of posterior bar two sizes, Hindeodella paradelicatula very closely set and directed posteriorly IGO and KOIKE, H. sp. and angled about 70 degrees with bar. Large denticles sharply pointed and Pl. 27, figs. 3-5 slightly curved inward. Smaller denticles needle-like. variable in size and Bar slender, flexuous, very thin, and shape, six to ten between adjacent larger flattened in transverse section. Aboral denticles. Denticles near posterior end side sharply edged, but very fine shallow differ from those of most part of poste- groove developed except adjacent to oval rior bar, strongly angled posteriorly and small pulp cavity. Posterior end of and make an angle of 40 degrees with bar very thin. blade-like, and not gro- bar. One or two slightly smaller denti- oved. Anterior oar bends inward slight- cles developed between adjacent larger ly and its angle about 120 degrees with ones. Main cusp biconvex, larger than bar. any other denticles, arched posteriorly, Denticles of posterior bar with sharply and curved inward. pointed end, two sizes of larger and Anterior bar angled downward just smaller which bend posteriorly and make anterior to main cusp with abrupt inward an angle of about 50 to 70 degrees with flexure at about one-third length of bar. Large denticles deeply penetrated anterior bar from main cusp. Denticles into bar and markedly bend toward an- 184 Ilisayoshi IGO and Toshio KOIKE terior. Smaller denticles about a half posteriorly, making an angle of 80 de- length of larger ones and counted five grees in anterior part of bar, while about to seven between adjacent larger ones. 30 to 40 degrees in posterior half. They Denticles of posterior end make a small deeply penetrated into bar and strongly angle with bar and alternate with larger bend anteriorly. Denticles of anterior and smaller. Denticles of anterior bar bar two types in size, and almost same coalesced or discrete, seven or eight in with those of posterior bar except fewer total number, and subequal in size and numbers of smaller denticles. Main cusp shape with larger denticles of posterior slightly larger than denticles of posterior bar. but two or three minute ones de- bar and directed posteriorly with slight- veloped near main cusp. Main cusp ly larger angle than those of other den- largest in size. sharply pointed, and bi- ticles of posterior bar. Pulp cavity lo- convex. Pulp cavity oval, small, and cated just beneath main cusp, small. surrounded by slightly elevated lips. narrow, and with faint elevation of lips. Remarks:-Hindeodelia paradelicatula Remarks:-Hindeodella sakagamii re- proposed herein is based upon complete sembles closely if asiatica in mode of specimens and it resembles closely H. inward curvature, but the present species delicatula STAUFFER and PLUNINIER de- has a slight downward curvature of the scribed from the Graford formation in anterior bar, flat and thin both posterior Texas. General feature of the bar and and anterior bars with almost similar the arrangement of the denticles are denticles. almost same each other except for more Reg. no, 23007 (Holotype). flattened bar of our species. Owing to the fragmentary Texan species, detailed comparison between both species seems Subfamily Ligonodininae HASS, 1959 to he difficult. Genus Synprioniodina ULRICH and BASSLER, 1926 Hindeodella sakagamii IGO and KOIKE. n. sp. Synprioniodina inicrodenta ELLISON Pl. 27, figs. 1, 2 PI. 27. figs. 11-17

Bar consisting of slender and almost Synprioniodina sp. GUNNELL, 1933. Jour. Pal.. straight posterior bar, and curved ante- vol. 7, p. 269. p1. 31. fig. 6. rior bar. Posterior bar thin, flattened. Synprioniodina microdenta ELLISON, 1941, Ibid., vol. 15. p. 119. pl. 20, figs. 43-46: and finely grooved along sharply edged ELLISON and GRAVES, 1911,. Missouri aboral side. Anterior bar thinner than Univ., Sch. Min. Met., Bull.. Tech. Ser.. posterior bar, blade-like, and angled vol. 1,1, p. 3, 4. pl. 1. fig. 10. inward as well as downward. Inward curvature with larger angle than down- Two bars meet at forming of an angle ward and makes an angle of about right of about 40 degrees in common plane. angle. Position of curvature located Posterior bar slender, very long, gently about middle of anterior bar. arched, having sharply edged aboral side. Denticles of posterior bar consisting Denticles subequal. sharply pointed, of larger and smaller ones. Larger den- coalesced, and angled anteriorly to base tides biconvex, sharply pointed, directed of bar at an angle of about 45 degrees. 466. Carboniferous Gonodonts from Central Japan 185

Large denticles about twice larger than Aboral side of both blades traversed smaller ones and alternate in most part by distinct groove terminated in deep of posterior bar. Anticusp short, with conical pulp cavity beneath main cusp. triangular small denticles coalesced at Pulp cavity with moderately elevated based and inclined anteriorly about an triangular lips. angle of 30 degrees with base of bar. Remarks:—The present new species Main cusp at an apex of bifurcation differs from the previously described of bars, sharply pointed, curved inward. species in blade-like bars, shape of main about twice as long as other denticles cusp and denticles of the posterior bar and three times or more near base as and anticusp. wide as other ones, and expanded at Reg. no. 23028 (Holotype). base on inward side into wide flaring lip of pulp cavity, while outer side lip Genus Euprioniodina ULRICH depressed inward. Aboral side of both bars traversed by and BASSLER, 1926 fine groove terminated in a deep conical Euprioniodina dentata IGO pulp cavity just below main cusp. Remarks:-Our material is similar to and KOIKE, n. sp. ELLISON'Sspecimens described from Mis- Pt. 28. fig. 23 souri and Texas in many respects. The inclination of the denticles of both bars Bar-like units meet at forming of right and week expansion of lip of pulp cavity angle. Posterior bar thin with sharply of the Japanese specimens slightly differ edged aboral side and pointed denticles. from those of the American specimens. Dent idles of posterior bar slightly con- Reg. no. 23015 vex inward, strongly arched toward anterior, forming an angle of about 50 to 60 degrees, which subequal in shape Synprioniodina collinsoni IGO and size, laterally compressed, and hi- and KOIKE, n. sp. convex with pointed end and broad base. Pt. 27. figs. 18. 19 Anticusp short, having small triangular denticles coalesced at base, and arched The blade-like bar meet at about right anteriorly about at right angle with base angle. Posterior blade thin with sharp- of anticusp. Main cusp at apex of bi- edged aboral side. furcation of two blades, large, sharply Denticles of posterior bar small, bicon- pointed, curved outward with elevated vex, coalesced near base and laterally keel along midline on inner side. and compressed, erect in anterior part and expanded at base on inward side into slightly curved posterior end. flaring lip of pulp cavity, but on outer Anticusp blade-like, wit h various sized side slightly concave. biconvex laterally compressed coalesced Aboral side of posterior bar and anti- denticles. and curved anteriorly. Main cusp grooved. and its opening terminated cusp large, biconvex, sharply pointed in a deep pulp cavity of inward side of with broad base, sharply curved poste- main cusp, extending to anticusp. riorly, and slightly elevated ridge along Remarks:-This species resembles Eu- midline of posterior side, but shallow prioniodina pulcella YOUNGQUIST and groove developed in anterior side. DOWNS described from the Early Pennsyl- 186 Hisayoshi IGO and Toshio KOIKE

vanian shale of Knoxville. Iowa, but the Prioniodus missouriensis GUNNELL.1931, Ibid. , denticles of posterior bar of the former p. 246, pl. 29. fig. 9. are more anteriorly arched and having Idioprioniodus striatus GUNNELL,1933. Ibid ., broad base. vol. 7, p. 265, pl. 32, figs. 36, 37. Reg. no. 23026 (Holotype). Hibbardella subacoda ELLISON, 1941. Ibid ., vol. 15, p, 118, pl. 20, figs. 22, 26.

Genus Ligonodina BASSLER, 1925 Main cusp large, long, sharply pointed , and slightly curved posteriorly and Ligonodina hanaii IGO laterally with sharpest curvature near and KOIKE, n. sp. two-thirds length from pointed end. Sharp-edged lateral ridges developed in Pl. 28. figs. 2!, 22 main cusp and continus downward along Bar-like units meet at large angle . each limb of anterior arch. Posterior Anticusp curved inward as well as down- side of main cusp grooved slightly ad- ward, with two separated denticles so jacent to each of lateral ridges, but far as observable. Posterior bar thin , anterior side convex. with sharply edged ahoral and oral sides . Denticles of anterior arch well deve- and with one denticle so far as preserved . loped, discrete, sharply pointed and Aboral side of bar finely grooved . edged, biconvex, and arched anteriorly Denticles of anticusp sharply pointed , and also inward slightly . Length of curved inward, and circular in cross posterior bar unknown. Denticles of section. Denticles of posterior bar later- posterior bar subequal with those of ally compreseed, and biconvex with sharp anterior arch but smaller and erect . pointed tips. Main cusp very long, Aboral side of main cusp excavated rather flexible, arched posteriorly , having and subangular. Posterior bar distinctly sharply pointed tip. Basal part of main grooved. Pulp cavity beneath main cusp, cusp subtriangular in cross section , but deep and conical. circular in most part. Pulp cavity large Remarks :-The American specimens and subrhombic at choral opening, deep , described by GUNNELL(1933) and ELLISON and merges into main cusp. (1941) are having slightly different cur- Remarks :-Ligonodina hanaii resem- vature of the main cusp compared with bles closely L. typa (GUNNELL) than any those of our specimens, but they are previously known species, but our form fragmental and further detailed com- has widely spaced denticles of anticusp parison renders difficult. The Mississip- and may have larger pulp cavity. pian species of Roundya barnettana HASS Reg. no. 23038 (Holotype). is having more distinctly discrete denticles. Reg. no. 23027. Subfamily Ilibbardellinae MULLER,1956

Genus Ronndya HASS, 1953 Subfamily Lonchodininae HASS Roundya subacodus (GUNNELL) , 1959 Genus Lonchodina BASSLER, 1925 Pl. 28, fig. 20 Prioniodus subacodus GUNNELL., 1931, Jour. Lonchodina ? nipponica IGO Pal., vol. 5, p. 246, pl. 29. fig. 9. and KOIKE, n. sp. 466. Carboniferous Conodonts front Central Japan 187

Pl. 27, fig. 20 base of blade. Denticles of posterior blade seven, Anterior bar longer than posterior bar, laterally compressed somewhat smaller stought, subtriangular in cross section. than those of anterior blade, closely set, Denticles of anterior bar three. stought, partly coalesced. making almost right discrete, rather widely spaced with ob- angle with base of blade. Apical denti- tuse tip, and almost straight to slightly cles laterally compressed, sharp-edged, curved posteriorly. Main cusp largest pointed, almost twice in width and length and rounded in cross section. Posterior of other denticles, and arched making bar short with two small discrete denti- an equal angle with those of denticles cies erected or slightly curved posteri- of anterior blade. orly. Aboral side of bar broadly gro- Aboral side of blade sharply edged. oved, its opening continued from pulp Pulp cavity long, extended into both cavity. Pulp cavity large and shallow blades, narrow, deep, and with a moder- beneath main cusp. ately elevated flaring lip tapered into Remarks :-This new species resembles base of apical denticle. Lonchodina ? ponderosa ELLISON, but it Remarks :-Ozarkodina orientate resem- differs in short anterior and posterior bles more closely O. delicatula described bars, and development of the denticles. by STAUFFER and PLUMMER (1932), GUN- Short bar, fewer numbers of denticles, NELL (1933). ELLISON (1941) and others large pulp cavity, and broadly grooved than any other described Pennsylvanian aboral side of the bar differ from the species. It differs from 0. delicatula in typical Lonchodina. Generic position of more discrete denticles of the anterior this new species is tentative. blade and fewer numbers of the denti- Reg. no. 23037 (Holotype). cles in both blades. It also resembles O . coin REXROAD described from Family Prioniodontidae BASSLER, 1923 the Kinkaid of Illinois, but REXROAD'S species has more distinct and larger main Subfamily Prioniodontinae cusp than that of O. orientate. BASSLER, 1925 Reg. no. 23012 (Holotype).

Genus Ozarkodina BRANSON and MEHL, 1933 Subfamily Spathognathodontinae HASS, 1959 Ozarkodina orientate IGO and KOIKE, n. sp. Genus Spathognathodus BRANSON and MEHL, 1941 Pl. 27, figs. 21-23 Spathognathodus echigoensis Bar blade-like, thin, orally arched, and laterally slightly curved. Blade thickest IGO and KOIKE, n. sp. Pl near base of denticles. Anterior blade . 28, figs. 24. 25 longer than posterior one. Anterior blade with six to seven laterally com- Blade thin, laterally straight, slightly pressed subequal closely set denticles, arched with nearly straight aboral side directed posteriorly in most part, inclined of anterior half. at an angle of 20 to 30 degrees with Denticles subequal in size and shape, 188 Risayoshi IGO and Toshio KOIKE

but become smaller toward both anteri- Trough shallow, and restricted poste- orly and posteriorly, coalesced deeply riorly. two-thirds or less length of plate. with sharply pointed tip and grooved Blade shorter than plate so far as ex- between adjacent denticles, and angled amined specimens. Denticles of blade posteriorly. The first two anterior den- rather large compared with size of blade. tides erect and very thin. Aboral side of blade grooved along mid- Aboral side of blade sharply edged, line and its opening continued into ex- grooved along midline except pulp panded pulp cavity. Aboral side of pulp cavity. Pulp cavity large, deep, with cavity entirely smooth. expanded lip which continues to almost Remarks :-This new species resembles posterior end of blade, and traversed by Idiognathodus delicatus GUNNELL, but it longitudinal groove extending from can be distinguished easily from the latter blade. by the longitudinal ridge ornamentation Remarks :-Spathognathodus echigoensis of the posterior part of platform. resembles closely S. minutus (ELLISON), Reg. no. 23034 (Holotype). but it differs from the American species in almost straight aboral side of blade Genus .Streptognathodus STAUFFER and suhequal size of the denticles, and larger pulp cavity. and PLUMMER, 1932 Reg. no. 23036 (Holotype). Streptognathodus japonicus IGO and KOIKE, n. sp. Family Idiognathodontidae HARRIS. Pl. 28. figs. 5-13 and HOLLINGSWORTH,1933 Cup asymmetrical, pointed anteriorly, Subfamily Idiognathodontinae HARRIS widest near middle, outer side always and HOLLINGSWORTH, 1933 larger than inner side. Platform lanceolate and transverse section of oral Genus Idiognathodus GUNNELL, 1931 surface deeply concave. Oral surface of platform ornamented with two or more Idiognathodus togashii IGO node-like parallel longitudinal ridges, and NOIRE. 11. sp. narrow and obsolescent toward anterior Pt. 28, figs. 1-4 end. Median trough rather shallow, deepest near widest part of cup, slightly Plate lanceolate, pointed anteriorly as curved inward posteriorly. well and posteriorly, widest near middle, Blade subequl in length to plate, very and steeply sided. Cup small and asym- thin in posterior end, thickest just be- metrical, outer side slightly larger than neath denticulated oral side. Denticles inner side. Axis almost straight, but of blade ten or more in mature specimen. feebly curved inward. Oral surface of almost a half height of blade, but coa- platform ornamented with parallel trans- lesced each other at about two-thirds verse ridges consisting of coalesced nodes from base. Denticles chevron-like in at about two-thirds anterior part of plate. lateral view, largest near posterior end. Posterior part of platform split by blade gradually decreasing in size toward plate and also ornamented with longitudinal and continued anteriorly as carina. ridges consisting of coalesced nodes. Carina short and one-fifth or less of 466. Carboniferous Conodonts from Central Japan 189 length of plate, and merged into longi- chevron-like in lateral view, and coa- tudinal ridge of outer side. lesced at base. Carina short and re- Aboral side of blade finely grooved stricted posterior end of cup. Aboral along midline. Aboral side of expanded surface of expanded pulp cavity smooth, pulp cavity entirely smooth, but rather grooved along midline, its opening con- deeply grooved along midline. tinued from blade. Remarks:—The present new species Remarks:-It resembles ELLISON'S has rather broad variation in size, shape (1941) specimens of Streptognathodus wa- of plate, and oral side ornamentation of baunsensis Gunnell, but it has more platform. It resembles closely S. sul- simple ornamentation of nodes near po- coplicalus YOUNGQUIST, HAWLEY and sterior part of the platform and fewer MILLER described from the Permian of numbers of denticles of blade. Idaho, but this Japanese form has more S. excelsus STAUFFER and PLUMMER irregular parallel ridges on platform. It and S. oppletus ELLISON are also allied also slightly resembles S. eleganlula species of S. expansus. However, S. ex- STAUFFER and PLUMMER. S. gracilis celsus has more complicated ornamenta- STAUFFER and PLUMMER, but it is easily tion on the posterior part of cup, and S. distinguishable therefrom by the oral opletus has longer carina than those of ornamentation of platform and short S. expansus. carina. Reg. no. 23033 (Holotype). Reg. no. 23032 i Holotype).

Genus Gnathodus PANDER. 1856 Streptognathodus expansus IGO and KOIKE, n. sp. Gnathodus opimus IGO and KOIKE. 11.sp. Pl. 28. fig. 14 Pl. 28, figs. 15-18 Cup large, highly asymmetrical, pointed anteriorly, greatest width near middle Axis straight to slightly angled inward of cup, outer side larger than inner side. at junction of blade and carina. Cup Axis curved inward at junction of blade highly asymmetrical, pointed anteriorly, and platform. Platform lanceolate. and widest at two-thirds from anterior end, oral surface ornamented with fourteen and outer side larger than inner side. parallel transverse ridges ending abrupt- Oral surface of cup plain and smooth. ly at median trough and slightly ra- Platform grooved by shallow trough diating from trough in anterior half of along axis, deepest at posterior end, and cup. Two rows of various sized six ornamented with node-like parallel ridges nodes developed in posterior part of longitudinally along carina. Denticles of inner platform along axis and a row of carina rounded in tip, fused, node-like, fewer numbers of node developed in and largest at widest part of platform. outer platform. Median trough shallow Blade almost equal or slightly larger and transverse section of oral surface of than carina, very thin, and subequal in platform slightly concave. thickness throughout. Denticles of blade Blade subequal in length to cup, thin coalesced with sharp edged tip, and troughout, with nine denticles. Denticles chevron-like, which largest at posterior of blade largest near posterior end, end and decreased in size anteriorly. 190 Hisayoshi, IGO and Toshio KOIKE

Aboral side of blade sharply edged, finely References grooved along midline. merging into expanded pulp cavity. Aboral surface of BAILEY, W. (1935): Micropaleontology and pulp cavity smooth and grooved along stratigraphy of the Lower Pennsylvanian midline and its opening continued from of central Missouri. Jour. Paleont., vol. blade. 9. no. 6. p. 483-502, pl. 55. Remarks:-Gnathodus opimus resem- BAKER, R. C. (1942) : The age and fossils of the Olentangy Shale of central Ohio, bles G. dilatus STAUFFER and PLUMMER Amer. Jour. Sci., vol. 240, no. 2. p. 137- and G. roundyi GUNNELL in two parallel 143. pls. 1-3. ridges, but our specimens have rounded BRANSON, E. B. and MEHL, M. G. (1941) : node-like low denticles of carina and New and litle known Carboniferous cono- more expanded pulp cavity. It is easily dont genera. Jour. Paleont., vol. 15. no. distinguishable from other described 2. p. 97-106, pl. 19. Gnathodus by smooth oral surface of cup. and - (1944):- Conodonts. in Index Reg. no. 23030 (Holotype). fossils of North America, by H. W. SHINIPER and R. R. SIIROCK. WILEY and

Explanation of Plate 27

(All figs. •~75)

Figs. 1. 2. Hindeodella sakagamii IGO and KOIKE, n. sp. 1. Lateral view of the holotype. Reg. no. 23008. 2. Lateral view of a complete specimen. Figs. 3-6. Hindeodella paradelicatula IGO and KOIKE, n. sp. 3. Lateral view of the holotype. Reg. no. 23006. 1. Lateral view of a complete specimen. 5. 6. Lateral view of two large imcomplete specimens. Figs. 7-10. Hindeodella asiatica IGO and KOIKE. n. sp. 7. Lateral view of the holotype. Reg. no. 23002. 8, 9. Lateral views of two incomplete specimens. 10. Posterior end of the posterior bar of a large specimen. Figs. 11-17. Synprioniodina microdenta ELLISON i I, 12. Two lateral views of the same specimen. 13. Lateral view of posterior bar. 14. Lateral view of a complete specimen. 15. 16. Two lateral views of the same specimen. 17. Lateral view. Figs. 18. 19. Synprioniodina collinsoni IGO and KOIKE, n. sp. 18. Lateral view of the holotype. Reg. no. 23028. 19. Lateral view. Fig. 20. Lonchodina ? nipponica IGO and KOIKE, n. sp. 20. Lateral view of the holotype. Reg. no. 23037. Figs. 21-23. Ozarkodina orientate IGO and KOIKE. n. sp. 21. Lateral view of the holotype, Reg. no. 23012. 22, 23. Lateral views of two incomplete specimens. IGO and KOIKE : Carboniferous Conodonts from Central Japan Plate 27

1 2

7 3

5 9

6 15

12 16 17

20 23 21 466. Carboniferous Concdonts from Central japan 191

SONS. New York, p. 235-246. pls. 93-94. of the Ouachita Mountains, Oklahoma COOPER, C. L. and SLOSS. L. L. (1943) : Cono- and its relationship to the Mississippian dont fauna and distribution of a Lower Caney Shale. Jour. Paleont.. vol. 7. no. 1. Mississippian black shale in Montana p. 3-29, pls. 1-7. and Alberta. Jour. Paleont.. vol. 17, no. HASS, W.11. (1941) : Morphology of cono- 2, p. 168-176, pls. 28-29. donts. Jour. Paleont.. vol. 15, no. 1, p. (1947) : Upper Kinkaid- (Mississippian) 71-81, pls. 12-16. microfauna from Johnson Country, Illi- (1953) : Conodonts- of the Barnett For- nois. Ibid., vol. 21. no. 2, p. 81-94. pls. mation of Texas. U. S. Geol. Surr. Prof. 19-23. Paper p. 69-94. pls. 14-16. EDWARDS, W. and STUBBLEFIELD. C. J. (1959) : Conodonts from - the Chappel (1948): Marine bands and other faunal Limestone of Texas: U.S. Geol. Sum marker-horizons in relation to the sedi- Prof. Paper 294-J. p. 365-399. pls. 46-50. - mentary cycles of the Middle Coal Meas- , RHODES, F. H. T. and MOLLER, K. J. ures of Nottinghamshire and Derbyshire, (1962) : Conodonts. In R. C. MOORE'S with an appendix by K. C. DUNHAM. Treatise on Invertebrate Paleontology. pt. Quart. Jour. Geol. Soc. London. vol. 103, p. W1-W97 ; W246-W259. pt. 4. no. 412. p. 209-260. pls. 13-15. HAYASAKA, I. (1924) : On the fauna of the ELLISON, S. (1941) : Revision of the Pennsyl- Anthracolithic Limestone, °nil-mum in vanian conodonts : Jour. Paleont.. vol. the western part of Echigo. Tohoku Imp. 15. no. 2. p. 107-143. pls. 20-23. Univ., Sci. Rep.. ser. 2 (Geol.), vol. 8. p. (1946) : Conodonts as Paleozoic- guide 1-82, pls. 1-7. fossils : Amer. Assoc_ Petr. Geol. Bull., HAYASHI. S. (1963) : On the conodonts newly vol. 30, no. 1. p. 93-110. 3 figs. discovered from the Ashio Mountains. - and GRAVES, R. W. (1941) Lower central Japan. Chikyukagaku (Earth. Sci- Pennsylvanian (Dimple Limestone) cono- ence), no. 68, p. 9-12, pl. 1 (in Japanese). donts of the Marathon region, Texas. HIGGINS, A. C. (1961) : Some Namurian cono- Unir. Missouri, Sch. Min. and Met. Bull., donts from North Staffordshire. Geol. Tech. Ser.. rol. 14, no. 3. p. 1-13. pls. 1-3. Alag.. vol. 98, p. 210-224. FAY. R. 0. (1952) : Catalogue of conodonts. KATO, M. and NAKAMURA, K. (1962) : A Kansas Univ. Pal. Contr., Vertebrata, art_ Goniatite from the Omi Limestone. Chi- 3, p. 1-206, figs. 1-109. kyukagaku (Earth Science). no. 63. p. 33- FUJITA. H. (1958) : Geology of the Omi Lime- 34. pl. 6 (in Japanese). stone (Permo-Carboniferous), Niigata KAWA DA, S. (1954) : Stratigraphical and Prefecture, Tohoku Univ., Inst. Geol. paleontological studies of Omi Limestone Pal.. Contr., no. 48. p. 1-60. in the Itagamine district, Niigata Prefec- GUNNEI.1., F.11. (1931) : Conodonts from the ture. Tokyo Univ. Education, Inst. Geol. Fort Scott Limestone of Missouri. Jour. Min.. Studies, no. 3. p. 15-27. Paleont., vol. 5. no. 3, p. 244-253, pl. 29. MILLER. A. K. and YOUNGQUIST, W. (1947) : (1933) : Conodonts and fish remains- Conodonts from the type section of the from the Cherokee. Kansas City, and Sweetland Creek Shale in Iowa. Jour. Wabaunsee Groups of Missouri and Paleont.. vol. 21. no. 6. p. 501-517, pls. Kansas. Ibid.. vol. 7. no. 3. p. 261-297, 72-75. pls. 31-33. MILLER, K. J. (1956) : Taxonomy, nomen- HARRIS, R. W. and Hot.i.INGSWORTH, R. V. clature, orientation, and stratigraphic (1933) : New Pennsylvanian conodonts evaluation of conodonts. Ibid., vol. 30, from Oklahoma. Amer. Jour. Sci. Ser. no. 6, p. 1324-1340. pl. 145. 5. vol. 25, no. 147. p. 193-204, pl. 1. REXROAD. C. B. (1957) : Conodonts from the HAR LTON. B.H. (1933) : Micropaleontology Chester Series in the type area of south- of the Pennsylvanian Johns Valley Shale western Illinois. Illinois Slate Geol. Surr.. 192 Hisayoshi IGO and Toshio KOIKE

Rept., Invest., 199, p. 1-43, pls. 1-4. RHODES, F. H. T. (1952) : A classification of (1958): Conodonts from the Glen- Dean Pennsylvanian conodont assemblages. Formation (Chester) of the Illinois Basin. Jour. Paleont., vol. 26, no. 6, p. 886-901, Ibid., 209, p. 1-27, pls. 1-6. pls. 126-129. (1958): The connodont- homeomorphs SAKAGAMI, S. (1962) : Discovery of Profusu- Ta phrognathits and Streptagna thodus. linella from the Omi Limestone, Niigata Jour. Paleont., vol. 32. no. 6. p. 1158-1159. Prefecture. Jour. Geol. Soc. Japan, vol. and BURTON, R. C. (1961) : Conodonts- 68, no. 797. p. 175. from the Kinkaid Formation (Chester) STANLEY, E. A. (1958): Some Mississippian in Illinois. Ibid.. vol. 35, no. 6, P. 1143- conodonts from the High Resistivity 1158, pls. 138-141. Shale of the Nancy Watson No. 1 Well in -and COLLINSON.-and C. (1961): Preliminary northeastern Mississippi. Jour. Paleont.. range chart of conodonts from the vol. 32. no. 3, p. 459-476, pls. 63-68. Chester Series (Mississippian) in the STAUFFER, C. R. and PLUMMER, H. J. (1932): Illinois Basin : Illinois Slate Geol. Surv.. Texas Pennsylvanian conodonts and their Circular 319. p. 1-11. stratigraphic relations. Univ. Texas, and-(1963) :- Conodonts from the Bull., 3201. p. 13-50, pls. 1-4. St. Louis Formation (Valrneyeran Series) STURGEON, M. T. and YOUNGQUIST,W. (1949) : of Illinois, Indiana, and Missouri. Ibid., Allegheny conodonts from eastern Ohio. Circular 355, p. 1-28, pls. l-2. Jour. Paleont., vol. 23, no. 4, p. 380-386,

Explanation of Plate 28

(All figs.•~75)

Figs. 1-4. Idiognathodus togashii IGO and KOIKE, n, sp. 1. Oral view of holotype, Reg. no. 23034. 2-4. Two lateral views and aboral view of the same specimen. Figs. 5-13. Streptognathodus japonicus IGO and KOIKE, n, sp. 5-7. Oral, lateral and aboral views of a small specimen. 8-10. Lateral, oral and aboral views of the holotype. Reg. no. 23032. 11-13. Oral. aboral and lateral views of a large specimen. Fig. 14. Streptognathodus expansus IGO and KOIKE. n. sp. 14. Oral view of the holotype. Reg. no. 23033. Figs. 15-18. Gnathodus opimus !co and KOIKE, n. sp. 15-17. Oral. lateral and aboral views of the same specimen. 18. Oral view of the holotype. Reg. no. 23030. Fig. 19. Gnathodus sp. 19. Oral view of an incomplete specimen. Fig. 20. Roundya subacodus (GUNNELL) 20. Lateral view. Fig. 21, 22. Ligonodina hanaii IGO and KOIKE, n. sp. 21. Lateral view of the holotype. Reg. no. 23038. 22. Lateral view of another specimen. Fig. 23. Euprioniodina dentata IGO and KOIKE. n. sp. 23. Lateral view of the holotype, Reg. no. 23026. Figs. 24, 25. Spathognathodus echigoensis IGO and KOIKE, n. sp. 24. Lateral view. 25. Lateral view of the holotype. Reg. no. 23036. IGO and KOIKE: Carboniferous Conodonts from Central Japan Plate 28

1 2 3 4

5 6 7

9 8

10 16

18 17

11 21

12 23

25 466. Carboniferous Conodonts from Central „Japan 193

pls. 74-75. (1951) : Phosphoria conodonts from THOMPSON, T. L. and GOEBEL. E. D. (1963): southeastern Idaho : Ibid., vol. 25. no. 3, Preliminary report on conodonts of the p. 356-361, pl. 54. Meramecian Stage (Upper Mississippian) and MILLER, - A. K. (1949) : Conodonts from the subsurface of western Kansas. from the Late Mississippian Pella beds Kansas State Geol. Sure.. Bull., 165, pt. of south-central Iowa. Ibid.. vol. 23. no. p. 1-16. 6. p. 617-622. pl. 101. YOUNGOLTIST,W. and DOWNS. N. H. (1949) : and DOWNS,-,- H. R. (1950) : Burling- Additional conodonts from the Pennsyl- ton conodonts from Iowa. Ibid.. vol. 2.1, vanial of Iowa : Jour. Paleont, vol. 23, no. 5. p. 525-530, pl. 67. no. 2. p. 161-171, pls. 30-31. and PETERSON, R. F. - (1947) : Conodonts and HEEZEN, B. C. (1948)- : Some Pennsyl- from the Sheffield Formation of north- vanian conodonts from Iowa : Ibid., vol. central Iowa. Ibid., vol. 21, no. 3. p. 22, no. 6, p. 767-773, pl. 118. 242-253, pls. 36-38. AWLEY, R. W. and -H MILLER, A. K.

All specimens described herein were kept at the Institute of Geology and Mineralogy, Tokyo University of Education.