Trans. Proc. Palaeont. Soc. Japan. N.S., No. 56, pp, 322-331, pl. 48. Dec. 20, 1964 480. YABEICERA S (CRETACEOUS AMMONITES) FROM FUTABA, NORTHEAST JAPAN* TATSUR0 MATSUMOTO Department of Geology. Kyushu University IKUWO OBATA Department of Palaeontology. National Science Museum and SHIRO MAEDA and TERUO SATO Geological Institute, Chiba University 東 北 日本 双 葉 産 ヤ ベ イセ ラス(白ll巨紀 ア ソモナ イ の:上 部 臼亜 系 浦河 統 ド郷階 に属 す る 双 奨 層 ド部の礫 岩 層 か ら 産 したYabeiceras orientale ToKUNAGA and SHIMIZUの 完 模式 標 本は,東 京 空 襲 の時 に 残念 な が ら焼 失 した とみな され る。 そ こ で原 産 地 か ら さ らに 標 本 を 得 よ うと努 力 して きた 。数 年 前 に 小畠 は小 型の 幼 殻 を 得 て い た 。 最近 前 田 の 引 率 し た巡 検旅 行 中 に.佐 藤 が 幸 に も成1ド殻の 化 石 を 採 集 した。 これ ら に っ い て くわ しい 古 生 物学 的 記 載 を行 な い, Yabeicerasの 類 縁 関 係 に')い て 論 述 す る 。 捕 属 の幼`騰 ～はForrosteriaに 似 た点 が あ る 。 ま たEborceras BASSE.1946はYabeiceras TOKUNAG and SHIMIZU.1926の シ ノニ ムで あ る,F.もE.も 従 来Barroisiceralinaeに 入れ られ て い る,記 載 した 標 本 は九 州 大 学 に 保 管 す る。 1965年 に 矢 部長 克 光生 は 数 え の88歳 に な られ ます 。 謹 ん で お 複 い し.こ の 小 著 を先 生 に 献 げ ます 。 松 本 達 斑 ・小 畠 郁 生 ・前 田 四 郎 ・佐 藤 輝 夫 Introduction occasion. The original type specimens described TOKUNAGA and SHIMIZU (1926) des- by TOKUNAGA and SHIMIZU (1926), most cribed a number of Cretaceous fossils of which must have been preserved at from the Futaba Formation in the Joban the Waseda University, Tokyo, together coalfield, about 200 km to the north- with other fossils from the Joban area. northeast of Tokyo. This was an admir- are judged to have been burnt up by a able contribution to our knowledge in fire of World War 11, 1944, except for a that the Upper Cretaceous deposits were few specimens which have been for some recognized on the evidence of fossils reason deposited at the Tohoku Uni- underneath the coal-bearing Tertiary of versity, Sendai. This judgement is based the Joban area and that some of the on the replies given to the writers from described species were entirely new to the Faculty Members of Waseda Uni- science. Yabeiceras, an interesting am- versity, Tohoku University and the Uni- monite genus, was established on that versity of Tokyo and also Dr. H. YABE. Received August 20. 1964 ; read Sept. The holotype, by monotypy, of Yabei- 20. 1964. ceras orientale TOKUNAGA and SHIMIZU 322 480. Yabeiceras (Cretaceous Ammonites) 323 (1926, p. 201, pl. 22, fig. 7 ; pl. 27, fig. la- CHIDA and Dr. Masafumi MURATA for c), the type-species of Yabeiceras TOKU- giving them information about where- NAGA and SHIMIZU, 1926 (originally de- abouts of TOKUNAGA and SHIMIZU'S signated in p. 199), and the type-speci- types, and to Mr. C. W. WRIGHT in mens of other two species, Y. kotoi and London for his critical reading of the Y. himuroi, of the same genus were typescript. Dr. ltaru HAYAMI took pho- probably destroyed. This regrettable tographs at Kyushu University and Miss situation has given to palaeontologists Tomoko Mn AZAKI assisted in preparing some difficulty in the appropriate deter- the manuscript. mination of the systematic position of the genus as well as in the correct identification of the species. Description The two senior authors (T. M. and Yabeiceras orientate TOKUNAGA 1.0.), therefore, have endeavoured to get specimens of Yabeiceras from the type- and SHIMIZU locality, upper reaches of Sakurazawa PI. 48. Figs. la-c. 2a-e ; in Oriki, where Lower Member of the Text-figs. la-d, 2a-e, 3. Futaba Formation is exposed. Although bivalves occur there in abundance. am- 1926. Yabeiceras orientate TOKUNAGAand monites are quite rare. Only a small. Shimizu, Jour. Fac. Sci., Imp. Univ. To- kyo. Sect. II, Vol. 1. Pt. 6, p. 201, p1. probably immature specimen of Yabei- 22. fig. 7; pl. 27, fig. la-c. ceras orientale and a few heteromorpha 1926. Yabeiceras orientate. SHIMIZU, Proc. have been collected there. Imp. Acad.. Japan. Vol. 2, No. 10. p. In summer 1963, the third author (S. M.) 547. conducted a departmental excursion to Types-The holotype is the specimen the Futaba area. After six days field described and figured by TOKUNAGA and work by a group of thirteen students. SHIMIZU (1926, indicated above), which an adult ammonite which was unfamiliar was almost certainly destroyed in 1944. to them was finally acquired at the same A neotype has to be officially proposed locality by the last author (T. S.). a and its validity should be acknowledged. student. The specimen was brought to Material:—The two specimens to be the Department of Palaeontology, Natio- described in this paper are GK. H5556, nal Science Museum. Tokyo and shown an internal mould of an adult shell to the second author (1. O.), who told (Coll. S. MAEDA and T. SATO), and GK. him its significance. It was developed H5557, that of an immature shell (Coll. from the rock matrix and cleaned in a I. OBATA).They are preserved in the laboratory of Chiba University and then Type-Specimen Room, Departmet of donated to Kyushu University for fur- Geology, Kyushu University, Fukuoka. ther palaeontological study. The rock matrix is made up of calcare- This paper contains the description ous sandstone. Therefore the fossils are and illustration of the two specimens. secondarily little deformed. On some Before going further the writers wish part an inner layer of the test is pre- to acknowledge the debt of gratitude to served. The innermost nuclear part and Prefessor Emeritus Hisakatsu YABE, a half of the body-whorl of the first Professors Kotora HATAI, Sadajiro TSU- specimen are not preserved. The un- 324 Tatsztro MATSUMOTO et al. illustrated side of the shell is dissolved Glvcymeris and other bivalves are ac- and hardly separable from the rock cumulated. matrix in which shells of Apiotrigonia, Measurements (in millimeters):- Specimen [Part] Diameter Umbilicus Height Breadth .) (C.)B./H. (Interc(I.) (Costal) GK. H5556 123.0(1) 59.4(0.48) 39.6 15.8x2 0.8 [3/2 vol. early] 52.0(1) 23.0(0.44) 17. 3(0.33) 27. 5(0.53) 23. 5(0.49) 1.58 1.47 [2 vol...] -- 15.5 20.0 15.51.29 1.0 [3 vol.,.]c. 40.0(1) 16.0(0.4) 12.5(0.31) 16.2(0.40) 13.2(0.33) 1.29 1.05 GK. 115557 29.6(1) 9.5(0.32) 12.0(0.40) 14.5(0.48) 12.3(0.41) 1.20 1.02 vol...]-- [L 10.612.3 10.81.16 1.01 [4 vol.,.] 20.4(1) 6.4(0.31) 8.8(0.43) 10.8(0.53) 9.4(0.46) 1.22 1.06 Holotype(T. & SH.) 62 26(0.41) 22(0.35) 26 (0.42)1.18 Description :-The characters of the ribs extending radially from the tubercle shell of this species change to a large to near the umbilical margin without extent with growth, as has been already umbilical tubercles. secondary ribs bifur- mentioned by TOKUNAGA and SHIMlZU cating from the mediolateral tubercles (1926) and SHIMIZU (1926). The change with a moderate projection on the venter, may be shown more clearly, at least in and weak tubercles at the ventrolateral some respects, by the present two speci- shoulder on the secondary ribs. A low mens than by the holotype. There may siphonal keel is weakly undulated ; each be also a certain extent of variation undulation corresponds in number and within a species. Even if the shells of position with one of the secondary ribs the same diameter are brought into which form obtuse chevrons on the comparison, they may be somewhat dis- venter. The lateral tubercles on the similar. anterior part of the preserved last whorl The smaller specimen, GK. 1-15557 (P1. of this specimen are rather mammillate 48, Fig. la-c ; Text.fig. la-d), probably and on the rest part they are bullate, represents a young shell. It is about although this is the character observed 30 mm. in diameter and is wholly septate. on the internal mould. It has an umbilicus of moderate size On the next inner whorl of the same (about 31 percent of the diameter). It specimen distant, weak radial ribs, which is moderately involute, about a half of are broadened and elevated at the medio- the inner whorl being overlapped by the lateral tubercles are observable. The outer. The whorl of this stage is nearly tubercles look subangular and in contact as high as broad and subcircular in the with the steep umbilical wall of the intercostal section, but it is somewhat outer whorl. A siphonal keel, lateral broader than high and rather polygonal tubercles and ribs seem to appear at in costal section. The ornament in this about the shell diameter of 9 mm. The stage consists of fairly strong tubercles flanks are somewhat flattened and the at about the middle of the flank (i. e. venter is low, roof-shaped in this stage, slightly below the mid-height), about although the details of the venter are eight in a half volution, simple, blunt not clearly seen.