No. 7] Proc. Japan Acad., 78, Ser. B (2002) 185

A study of Mrhiliceras (Cretaceous Ammonoidea)

Studies of the Cretaceous ammonites from Hokkaido and Sakhalin-XCIII

By Tatsuro MATSUMOTO, M. J. A.,*)' t) and Tamio NISHIDA**) (Contributed by Tatsuro MATSUMOTO,M. J. A., Sept. 12, 2002)

Abstract: An ammonoid genus Mrhiliceras Kennedy and Wright, 1985, is revised to be based on the "inflated forms" as represented by the holotype of its type species Mammites lapparenti Pervinquiere , 1907. How are the "compressed forms" of Kennedy and Wright, 1985 should be treated is a problem to be examined further. In this paper we describe an example of M lapparenti from the basal part of the Cenomanian (Cretaceous) sequence of strata in the Soeushinai area, northwest Hokkaido. It is somewhat larger than the previously reported specimens and represents a full grown shell of a mature stage.

Key words: Ammonoidea Cenomanian: Cretaceous: Hokkaido: Mrhiliceras• Utaturiceras.

Introduction. The plentiful material of the Discussion. Kennedy and Wright (1985)1 defined ammonotes from the Cenomanian (Cretaceous) rocks of Mrhiliceras lapparenti very comprehensively, including the Soeushinai area, northwestern Hokkaido, comprises not only the relatively inflated forms with strong orna- a number of valuable species which deserve to be studied mentation but also the compressed and much involute from the standpoint of taxonomic revision and interre- forms with numerous, fine and more or less flexuous ribs gional biostratigraphic correlation. In this paper a and weak tubercles. If they were all regarded as a single species belonging to Mrhiliceras, a genus of the Family variable species, Mrhiliceras would fall in a junior syn- Acanthoceratidae, is treated as a suitable example for onym of Utaturiceras Wright, 19563 (in a revised such study. sense). Kennedy and.Wright (1985, p. 515) indicated, for Systematic description. instance, a smooth fastigiate venter as a criterion to dis- Order Ammonoidea Zitte1,1884 tinguish their "compressed and finely ornamented Family Acanthoceratidae Grossouvre,1894 forms of M lapparenti" from Utaturiceras. However, Genus Mrhiliceras Kennedy and Wright, 19851 the same or similar features do occur also in Type species. Mammites lapparenti Pervinquiere, Utaturiceras vicinale (Stoliczka, 1894)4 from South 1907,2 by original designation (Kennedy and Wright, India, as have been described and illustrated by 1985, p. 514). Matsumoto and Sarkar (1966, pp. 298-301; text-figs. l-4; Diagnosis. Shell of moderate size in maturity and pl. 32, fig. l; pl. 33, figs. l-3).5~ fairly involute. Whorls nearly as high as broad or some- It should be noted that no examples of the com- what broader than high and strongly ornamented. pressed forms were shown in the original description of Primary ribs arise from bullate umbilical tubercles; sec- M lapparenti Pervinquiere (1907, p. 312, fig. 110, p1.14, ondary ribs alternated with or branched from the pri- figs. 5, 6). What Kennedy and Wright called the com- maries. All the ribs provided with inner and outer ven- pressed forms are the specimens from Madagascar trolateral tubercles and run across the venter, though described by Collignon (1964)6 under the specific lowered in the last growth stage. Suture moderately names Metoicoceras besairiei Collignon, M sakara- incised, with numerous elements on the flank descending hense Collignon, and M fasciculatum Collignon. One toward the umbilicus. form described as Metoicoceras swalloviforme Collignon (1964, p. 149, fig. 1627)6 from Madagascar *) c/o The Kyushu University Museum , 6-10-1, Hakozaki, could be regarded as identical with, or closely allied to, Higashi-ku, Fukuoka 812-8581, Japan. **) Faculty of Culture and Education Mrhiliceras lapparenti (Pervinquiere). , Saga University, 1, Honjo-machi, Saga 840-8502, Japan. M swalloviforme came from "Gisement 486", t) Correspondence to: T. Matsumoto. where a poorly preserved paratype of Metoicoceras 186 T. MATSUMOTO and T. NISHIDA [Vol. 78(B),

Fig. 1. Geological route map along the Sounnai River [So] (part) and its tributary Suribachi-zawa [Sb]. Inset at the lower left corner is an index map of Hokkaido, and at the upper right corner an enlarged map of the route along the middle course of the eastern main branch of the Suribachi-zawa. Thick broken line = fault; chain = boundary of the stratigraphic units : UA1, UA2, and UA3 = lower, middle and upper parts of the Upper Albian Substage; LC and MC = lower and middle parts of the Cenomanian Stage. Short broken line = highway. Fossil localities : solid small circle = in situ, cross = boulder. Every local- ity number should have R at the heading.

salcarahense Collignon (1964, p. 151, fig. 1631),6 Kennedy and Wright (1985) as an extremely com- Sharpeiceras f lorencae Spath [= S. vohiparense pressed variety of M. lapparenti. It came from "Gisement 362" in Madagascar Collignon (1964, p. 104, fig. 1565)]6 and Mantelliceras , where Acompsoceras thomeli Collignon (1964, p. 91, fig. 1551)6 were also tenue Collignon (1964, p. 111, fig. 1574),6 A. sahni reported. On the other hand, Metoicoceras fascicula- Collignon (1964, p. 111, figs. 1575,1576)6 and A. catzi- tum Collignon (1964, p. 151, fig. 1633)6 was regarded by giasae Collignon (1964, p. 112, fig. 1577)6 were also No. 7] Mrhiliceras (Cretaceous Ammonoidea) 187

Fig. 2. Mrhiliceras lapparenti (Pervinquiere). Lateral view of GS. G280 (x 1).

reported. Moreover, Kennedy and Wright (1985, p. Kennedy and Wright (1985) came from different strati- 524)1 foretold that Acompsoceras calabarense graphic levels within the lower Cenomanian part of var- Zaborski (1985, p. 29, figs. 30, 32),7 from the ious regions. Actually transitional specimens between the Sharpeiceras bearing bed in southeast Nigeria, would be "inflated forms" and the "compressed forms" were not Mrhiliceras. The photographic illustration of its holotype clearly shown by Kennedy and Wright (1985, p. 516).1 by Zaborski seems to show weakening mid-ventral Hence, it is necessary to reexamine more carefully the tubercles as in Acompsoceras. specimens concerned. Under these circumstances we Other examples of the so-called compressed forms should define Mrhiliceras in a strict sense on the basis from Madagascar, such as Metoicoceras besairiei of the type species at least for the time being. Collignon (1964, p. 149, fig. 1628; p. 150, fig. 1629)6 and M. sakarahense Collignon (1964, p. 150, fig. 1630 Mrhiliceras lapparenti (Pervinquiere,1907) [holotype]; p.151, fig. 1632)6) came from "Gisement 505", Figs. 2 and 3 where Mantelliceras couloni (d' Orbigny) (Collignon, Synonymy.- 1964, p. 83, fig. 1538)6 was recorded. The specimen of Mammites lapparenti Pervinquiere,1907, p. 312, p1.14, "Metoicoceras besairiei" by Lewy and Raab (1978 , p1.1, figs. 5, 6.2) fig. 10)8) is recorded to have come from the Unit CE2, Mrhiliceras lapparenti (Pervinquiere, 1907) (pars), middle part of the Lower Cenomanian in the Middle East. Kennedy and Wright, 1985,' p. 516, text-figs. la; 2a- As it was not precisely described, its specific name is c,e,d; 3a-g; Wright and Kennedy, 1987,9~p. 137, text- doubtful. figs. 33F, G; 34F; pl. 42, fig. 3a-c. The above facts show that the various forms which Holotype. The original of Pervinquiere,1907, p1.14, were united into one species (M lapparenti) by fig. 5 (reillustrated by Kennedy and Wright, 1985, fig. 2a- 188 T. MATSUMOTO and T. NISHIDA [Vol. 78(B),

The whorl is ornamented with coarse and fairly strong radial ribs which are as a rule alternately long and short. The long rib arises from a bullate umbilical tuber- cle, whereas the short one starts at some distance from the umbilical margin. All the ribs have inner and outer ventrolateral tubercles, which are fairly distinct on the phragmocone. Toward the later part of the body chamber the ribs and tubercles tend to be broader and lower. In this specimen the suture is only partly exposed and can- not be traced thoroughly. Comparison and discussion. The holotype and paratypes of M. lapparenti are still septate at their pre- served end. The size and morphological characters in the adult stage were not known in Pervinquiere's material. The specimen from Madagascar called Metoicoceras swalloviforme Collignon (1964, p. 557, fig. 1627),6 may be an adult shell of Mrhiliceras lapparenti, but it does not seem to represent a full grown stage. The Hokkaido specimen described above is still larger and its last part can be regarded as showing the characters of a full grown stage, because its ribs and tubercles are much lowered at the last portion. Kennedy and Wright (1985, p. 520)1 made mention of the dimorphic pair in MMlapparenti. There is, how- ever, no substantial evidence to support their view at least for M, lapparenti redefined in this paper. Fig. 3. Mrhiliceras lapparenti (Pervinquiere). Restored cross- Occurre,zce and distribution. The described section of GS. G280 (x 1). Bar =10 mm. specimen from Hokkaido is judged to have been derived from the basal part of the Cenomanian c; also Wright and Kennedy, 1987, text-fig, 33F, G)9~ by sequence of strata, because the strata run from N to S original designation. It came from Amn el Glasa, Djebel along the stream, where the nodules close to Loc. R 521- Bireno, Tunisia and is now in the Sorbonne Collections 522p have yielded Graysonites adkinsi Young, (ex. Pervinquiere Collection) without register number Utaturiceras sp., etc. and because these strata rest (after Kennedy and Wright, 1985, p. 516).' immediately above the upper Albian rocks (see Fig. 1). Material from Japan. GS. G280, registered at The type specimens from central Tunisia are Saga University, collected by Yoshitaro Kawashita regarded by Kennedy and Wright (1985, p. 524)1 to have (YKC.040804) from a nodule at Loc. R521-522p in the occurred at a horizon in the Lower Cenomanian eastern major branch of the Suribachi-zawa, which Substage, but Wright and Kennedy (1987, p.139)9~ itself is a tributary of the Sounnai River, in the wrote as "Lower Lower Cenomanian" The British speci- Soeushinai area, northwestern Hokkaido (Fig. 1). men is reported to have come from "the remanie Lower Description. The specimen is somewhat distorted Cenomanian Mantelliceras mantelli Zone" fauna of and in the state of half ammonoid preservation (Fig. 2). the Chalk Basement Bed at Rinstead, Dorset (Wright and It represents the full-grown shell, although a portion of Kennedy, 1987, p. 139 and explanation of plate 42, fig. 3). the ventral part is destroyed away. It is about 120 mm in Conclusions. The genus Mrhiliceras Kennedy diameter arid preserves the body chamber for about half and Wright, 1985 is defined in this paper to be based on whorl. It is fairly involute; about two thirds of the inner the less compressed and coarsely ornamented forms as whorl are overlapped by the outer one. represented by the original material of M. lapparenti The umbilical ratio is 0.21 to 0.23 in the middle to (Pervinquiere, 1907). On this ground a specimen from late growth stages. The costal whorl section is subrec- the basal part of the Cenomanian sequence of strata in tangular to trapezoidal (Fig. 3). the Soeushinai area, northwestern Hokkaido, is identified No. 7] Mrhiliceras (Cretaceous Ammonoidea) 189

with Mrhiliceras lapparenti. It exemplifies a full 2) Pervinquiere, L. (1907) Etude de paleontologie tunienne 1, grown mature stage which has not been recognized in Cephalopodes terrains secondaires, pp. 1-438, pls. 1-27. the previous material. 3) Wright, C. W. (1956) Ann. Mag. Nat. Hist., [12] 9, 391-393. Acknowledgements. We appreciate the late 4) Stoliczka, F. (1864) Palaeont. Indica 1, 57-106, pls. 32-54. 5) Matsumoto, T., and Sarkar, S. S. (1966) Mem. Fac. Sci. Mr. Yoshitaro Kawashita's field work to find the valuable Kyushu Univ., ser. D 17, 297-309, pls. 32-33. specimen which was provided for our study. We thank 6) Collignon, M. (1964) Atlas des fossiles caracteristiques de Dr. Haruyoshi Maeda of the Kyoto University for his kind Madagascar (Ammonites) 11, pp. 1-152, pls. 318-375. review of the first draft of this paper. We owe much to 7) Zaborski, P. M. P. (1985) Bull. Brit. Mus. (Nat. Hist.), Geol. Ser. the Horokanai Forestry Office for our field work. 39,1-72. 8) Lewy, Z., and Raab, M. (1978) Ann. Mus. fist. Nat. Nice 4, xxxii,1-20, pls. l-2. References 9) Wright, C. W., and Kennedy, W. J. (1987) Monogr. 1) Kennedy, W. J., and Wright, C. W, (1985) N. Jb. Geol. Palaeontogr. Soc. 139(573), 127-218, pls. 41-55. Palaont. Mh.1985, 513-524.