Table Of ContentPROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
114(1):172-177. 2001.
A new fossil geryonid crab (Crustacea: Decapoda: Brachyura) from
the late Pliocene to early Pleistocene of Japan
Hisayoshi Kato and Akihiro Koizumi
(HK) Natural History Museum and Institute, Chiba, 955-2, Aoba-cho, Chiba 260-8682, Japan;
(AK) lida City Museum, 2-655-7, Ote-machi, lida 395-0034, Japan
—
Abstract. A new fossil geryonid crab, Chaceon matsushimai is described
from the uppermost Pliocene to lower Pleistocene Ofuna and Koshiba forma-
tions, Kazusa Group in Kamakura and Yokohama cities, central Japan. The
new species resembles members of the extant Chaceon granulatus species
group, but is distinguished by having very faint frontal, second, and fourth
anterolateral spines and a proportionately narrower male abdomen. This is the
first fossil record of the genus Chaceon from Japan.
Recent revisions of deep sea geryonid assignable to the same species (here re-
&
crabs (Manning Holthuis 1987, 1989) ferred to as the Koshiba specimens).
previously placed in the genus Geryon In addition, a fossil specimen in the col-
Kr0yer, 1837, have shown that species lection by late Professor Rikizo Imaizumi
which possess five anterolateral spines on preserved in the Institute of Geology and
the carapace and four distinct spines on the Paleontology, Tohoku University, is also
frontal margin should be referred to the ge- identical to the present new species (here
nus Chaceon (Manning & Holthuis, 1989). referred to as the IGPS specimen). Al-
Species of Geryon [type species: Geryon though this specimen lacks a label and in-
trispinosus (Herbst, 1803)] have only three formation about the locality, stratigraphic
anterolateral spines, and less pronounced horizon and name of collector, a piece of
frontal spines. Based on these carapace fea- card belonging to the specimen and proba-
tures, the new species of fossil described bly written by Imaizumi reads "Kamaku-
herein is referable to Chaceon, which has ra". The matrix of this specimen is indis-
eight living species in the Pacific Ocean, tinguishable from those of the Ofuna spec-
two of which are found in Japanese waters imens.
&
(Ng Manning 1998). The Ofuna specimens occurred in mas-
&
Koizumi Matsushima (1992) first re- sive, light gray-colored siltstone exposed in
ported fossils of Geryon species in associ- the land-development field for residential
ation with molluscs and fishes indicative of construction in Iwase, Kamakura City, Kana-
lower sublittoral to upper bathyal waters gawa Prefecture, central Japan (35°20'58"N,
from the lower Pleistocene Ofuna Forma- 139°32'51"E). The crab-bearing horizon is
tion, Kazusa Group in Kamakura City (re- stratigraphically situated between the Ny
ferred to here as the Ofuna specimens). Tuff Bed (Nakaya Tuff bed: same as 026
&
Poorly preserved cyclodorippid crab Ty- (Of2) in Mitsunashi Kikuchi, 1982) and
molus species were also obtained from the the Is Tuffbed. The former is a remarkable
locality. As noted by these authors, two key bed widely traceable in the Yokohama-
specimens deposited in the Kanagawa Pre- Kamakura area.
fectural Museum of Natural History, which The Koshiba specimens had been ob-
had been collected by Mr. Syozo Aizawa tained from the massive, light gray-colored
from the overlying Koshiba Formation, are pumiceous sandy siltstone of the lower part
VOLUME 114, NUMBER 1 173
of the Koshiba Formation exposed in the IGPS coll. cat. no. 103703 (paratype 1; cw
land-development field in the Seibu-danchi, 59.0 mm, cl —51.5 mm).
Nishishiba, Kanazawa-ku, Yokohama City Diagnosis. Small Chaceon with 4 faint
(35°21'N, 139°38'E). They are mostly im- projections on frontal margin, and 3 distinct
pressions and/or molds due to compression spines and 2 very faint spines or lobes on
and weathering. anterolateral margin. Male abdomen rela-
&
Mitsunashi Kikuchi (1982) correlated tively narrow. —
several remarkable tuff beds in the Ofuna Description. Carapace hexagonal in
Formation with those in the lower Pleisto- outline, broader than long. Frontal margin
cene Otadai and Kiwada formations of the about 0.25 of maximum width with 2 very
Boso Peninsula. Eto et al. (1987) consid- low medial and 2 lateral lobes. Orbit large;
ered the age of the Ofuna Formation to be relatively shallow; margin rounded. Antero-
early Pleistocene based on the planktonic lateral margin convex with first, third, and
foraminifera (N22 Zone ofBlow 1969) and fifth spines distinct and second and fourth
calcareous nannoplankton ("CN12" Zone present as very low spines or lobes. First
of Okada and Bukry 1980). However, the spine (outer orbital) directed obliquely an-
calcareous nannoplankton assemblage of teriorly. Second minute spine observed in
the formation identified by them indicates smaller specimen (paratype 2: Figs. 1, 4a),
that the age extends into the latest Pliocene being indistinct lobe in largest specimen
(CNlBa Zone of Okada & Bukry 1980: Y. (paratype 1: Figs. 2, 4c). Third spine point-
Tanaka pers. comm.). Considering these ed with broad base. Fourth spine very low
facts, the geologic age of the fossils from with blunt tip. Fifth spine triangular, largest,
the Ofuna and Koshiba formations is most directed laterally. Distance from first to
likely to be latest Pliocene to earliest Pleis- third spines slightly shorter than that from
tocene (ca. 1.9-1.7 Ma). third to fifth. Dorsal surface moderately
The specimens are deposited in the Ka- convex; rugose, granulated in posteriorhalf
nagawa Museum ofNatural History (KPM- oflarge specimen (Figs. 2, 3). Branchial re-
NN) and Institute of Geology and Paleon- gion sparsely granulated. Sparse granules
tology, Faculty of Science, Tohoku Univer- on protogastric, mesogastric, and cardiac
sity (IGPS coll. cat. no.). The abbreviations regions. Regions divided by shallow de-
cl and cw indicate carapace length and car- pressions. Weakly developed transverse
apace width. ridge extends from branchiocardiac groove
to fifth anterolateral spine. In smallest spec-
imen (KPM-NN-5942), however, dorsal re-
Family Geryonidae Colosi, 1923
gions well divided by deep grooves; proto-
Genus Chaceon Manning & Holthuis, , meso- and metagastric, cardiac and bran-
1989 chial regions convex; an arched convex,
Chaceon matsushimai, new species well demarcated ridge extends from bran-
Figs. 1-4 chiocardiac groove to fifth anterolateral
spines. Frontal and anterolateral spines of
Geryon sp.: Koizumi & Matsushima, 1992, carapace proportionally larger than in other
p. 127, figs. 8-1-3. larger specimens.
— Male abdomen relatively narrow; fourth
Material examined. KPM-NN-5941 segment slightly shorter than fifth; lateral
(holotype; cw 66.0-1- nam, ca. 70 mm, cl margins of fifth segment almost parallel;
55.9 mm), 5942 (cw 15.5+ mm, cl 15.8 telson triangular.
mm), 5943 (paratype 2; cw 32.5 rrmi, cl Chelipeds nearly equal in size. Upper
24.4 mm), 198A (cw 31.4 mm, cl 28.3 surface ofmerus with small subdistal spine;
mm), 198B (cw 49+ mm, cl 44+ mm). carpus with strong inner distal spine. Palm
174 PROCEEDINGS OFTHE BIOLOGICAL SOCIETY OF WASHINGTON
Figs. 1-3. Chaceon matsushimai. new species. 1, Paratype 2, KPM-NN-5943, carapace. XI.Oi 2, Paratype
1, IGPS coll. cat. no. 103703, Xl.O, 2a, thoracic sternites and abdominal somites, 2b, carapace and cheliped: 3,
Holotype, KPM-NN-5941, 3a, leftcheliped, ventralview, X0.7, 3b, leftcheliped,pereiopodsandcarapace, x1.0.
VOLUME 114, NUMBER 1 175
tioned living species (see Ng & Manning
1998). The present new species also resem-
bles Chaceon bicolor Manning & Holthuis,
1989, from the North and South Pacific
Ocean in having lobiform second and
fourth anterolateral spines, but is distin-
guished from that extant species by having
dorsoventrally flattened dactyli of ambula-
tory legs and exhibiting less developed
frontal spines.
The general outline ofthe carapace ofthe
new species resembles those of the genus
Fig. 4. Chaceon matsushimai, new species. Front- Geryon Kr0yer, 1837, in appearance, i.e.,
orbital and anterolateral margins, a, paratype 2; b, ho- frontal spines are very low and the antero-
lotype; c, paratype 1. Scales: 1 cm. lateral margin has very faint second and
fourth spines which are sometimes undis-
sparsely granulated on outer and upper sur- cemible, instead of five distinct spines. Al-
faces. Both fingers with strongly serrated though the second spine of the left antero-
occlusal margins; longitudinal furrow and lateral margin is entirely undiscemible in
row of pits present on outer surface. the holotype specimen (Figs. 3, 4b), minute
Ambulatory legs long; dactyli dorsoven- spines or convexities are observed in para-
trally compressed, slightly curved down- types 1 and 2 (Figs. 4a, c).
ward. — The length/width ratio of the merus of
Etymology. In honor of Dr Yoshiaki the fifth ambulatory leg of the holotype
Matsushima of the Kanagawa Prefectural specimen is 4.3. Due to compression after
Museum of Natural History who has made burial, unfortunately, this value is by no
great contributions to the geology and pa- means reliable.
leontology of the Kanto region as well as The only known other fossil species of
to Quaternary molluscan paleontology and the genus is Chaceon peruvianas
paleoecology. (d'Orbigny, 1842) from the middle Eocene
—
Remarks. Thepresentnew species most of Argentina, which was recently trans-
closely resembles members of the living ferred from the extinct genus Archaeoger-
&
Chaceon granulatus species group, viz. C. yon Colosi, 1923 (Schweitzer Feldmann
granulatus (Sakai, 1978), C. manningi Ng 2000).
et al., 1994, C. A;arMterManning, 1993, and The fossil species of the genus Geryon
C. micronesicus Ng & Manning, 1998, in had hitherto been restricted to the Miocene
having granulose branchial region, very to Pliocene of Europe-Tethys region (see
low second and fourth anterolateral spines, Dawson & Webber 1991). Other records of
and dorsoventrally flattened dactyli of am- fossil Geryonidae are the extinct generaAr-
bulatory legs. In addition to the small adult chaeogeryon Colosi, 1923, Coeloma A.
size, however, Chaceon matsushimai is eas- Milne-Edwards, 1865 and Archaeoplax
ily distinguished from these living species Stimpson, 1863 (Glaessner \969).Archaeo-
by having very faintly projected frontal geryon was known from the Miocene of
spines, relatively weaker second and fourth South America (Glaessner 1969, Morris,
anterolateral spines, a broader and shallow- 1980; the geologic age may have to be re-
er orbit and a less granulated carapace. assigned, see Schweitzer & Feldmann
Moreover, the male abdomen, especiallythe 2000). Archaeoplax has been reported from
fourth and fifth segments, are proportion- the Miocene of North America (Rathbun
ately narrower than those of above men- 1935). Although Coeloma has been report-
176 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
ed from the Eocene to Oligocene rocks of ciety of America and University of Kansas
Europe and North America, the placement Press, Lawrence.
within the Geryonidae is still uncertain be- Herbst,chJi.cFhteW.der17K9r9a-b1b8e0n4.KrVeebrsseuchnebesitnereinNeartusrygsetse--
cause it differs considerably from the living matischen Beschreibung ihrer verschiedenen
species ofGeryonidae in morphology ofthe Arten. 1-3:515 pp., 62 pis., G. A. Lange,Berlin
dorsal carapace (Schweitzer & Feldmann & Stralsund.
2000). Koizumi, A., & Y. Matsushima. 1992. Upper bathyal
molluscanfossils, Crustaceaandfishesfromthe
Acknowledgments Lower Pleistocene Ofu—na Formation in Kama-
kura, southern Kanto. Natural history report
The authors are much indebted to Pro- of Kanagawa (Kanagawa Prefectural Museum)
fessor Peter K. L. Ng, National University 13:119-128. (in Japanese) —
Kr0yer, H. 1837. Geryon tridens, en ny Krabbe. Na-
of Singapore, for his criticisms ofthe man- turhistoriskTidsskrift 1:10-21, pi. 1.
uscript and many instructive comments. We Manning, R. B. 1993. A new deep-sea crab, genus
are grateful to Mr. Hajime Taru and Mr. Chaceon, from I—ndonesia (Crustacea: Decapo-
Takehiro Sato, Kanagawa Prefectural Mu- da: Geryonidae). Raffles Bulletin ofZoology
osteou,mToofhoNkatuurUanlivHeirsstiotryy,;faorndthMeri.r aJsusnisNteanmc-e Manning4G,1e(r2Ry.)o:nB1.6,t9r-&i1s7pL2i..noBs.usHo(lHtehrubisst.)1(98G7e.ryoTnhiedaSet)a.t—usIonf-
in the examination offossil and Recent ma- vestigacion Pesquera 51 (Supplement 1): 57-62.
terials. We thank Dr. Yuichro Tanaka, Geo- , & . 1989. Two new genera and nine
logical Survey of Japan, for giving com- new species of geryon—id crabs (Crustacea, De-
ments concerning the geologic age of the capoda, Geryonidae). Proceedings of the Bi-
ological Society ofWashington 102:50-77.
formations. Thanks are also due to Dr. To- Mitsunashi, T, & T. Kikuchi. 1982. Geology of the
moyuki Komai, Natural History Museum Yokohama district. Quadrangle Series, Scale 1:
and Institute, Chiba for valuable comments 50,000, 105 p. Geological Survey ofJapan, (in
concerning the systematic position of the Japanese with English abstract, 4 p.)
Milne-Edwards, A. 1865. Monographic des crustaces
fossil crabs. —
delafamillecanceriens. AnnalesdesSciences
Naturelles, Sen 4, Zoologie. 3:297-351, pi. 5-
Literature cited
13.
Blow, W. H. 1969. Late Middle Eocene to Recent Morris, S. F 1980. Catalogue ofthe type and figured
specimensoffossil Crustacea(excl. Ostracoda),
planktonic foraminiferal biostratigraphy. in P.
Bronnimann and H. H. Renz, eds.. Proceedings Chelicerata, Myriapoda and Pycnogonidainthe
ofthe First International Conference on Plank- British Museum (Natural History). British Mu-
tEo.niJ.cBMriilclr,ofLoesisdielns., Geneva, 1967. 1:199-421, Ng, P sKe.umL.,(N&atuRr.alB.HisMtaonrnyi),ng5.3 1p9.98. A new deep-
Colosi,caGp.od1i923br.acUhniuaris)p.e—ciBeolfeoststiilneoddielGleariSoonciideeta(Ddee-i wtoattehrecPraacbiffircomspeBceileasu,ofMiCchraonceesoina—(wCirtuhstaackeeay:
Decapoda: Brachyura: Geryonidae). Proceed-
Naturalisti in Napoli, 35 (Sen 2, vol. 15), 37:
248-255. ings of the Biological Society of Washington
Dawsonr,edE.crWa.b,C&haWc.eoRn. (W"eGbebreyro.n"1)9.91—.NTahteiodneaelp-Msue-a 1,1D1.:-3A8.9-L3e9e7,.& H.-R Yu. 1994. A new deep sea
seumofNew Zealand, MiscellaneousSeries24, crab ofthe genus Chaceon (Decap—oda, Geryon-
83 pp. idae) from the South China Sea. Cru.staceana
Eto, T, M. Oda, S. Hasegawa, N. Honda, & M. Fu- 67:371-380.
nayama. 1987. Geologic age and paleoenviron- Okada, H., and Bukry, T 1980. Supplementary mod-
ment based upon microfossils of the Cenozoic ification and introduction of code numbers to
sequence inthe mi—ddleandnorthernpartsofthe the low-latitude coccolith b—iostiatigraphic zo-
Miura Peninsula. Science Reports of the Yo- nation (Bukry 1973, 1975). Marine Micropa-
kohama National University, Section 11 34:41- leontology 5(3):321-325.
57. (in Japanese with English abstract) Orbigny, A., d". 1842. Voyage dans TAmerique me-
Glaessner, M. F 1969. Decapoda. Pp. R399-566 ;/) R. ridional, 1826-1833 (III). Geologic et Paleon-
C. Moore, ed.. Treaties on Invertebrate Paleon- tologie. Paris, France, 561 pp.
tology, Part R, Arthropoda. 4. Geological So- Sakai, T 1978. Decapod Crustacea from the Emperor
—
VOLUME NUMBER
114, 1 177
—
Seamount Chain. Researches on Crustacea 8 relationships within the—PortunoideaRafinesque
(Supplement):1-39, pis. 1-4. (Decapoda: Brachyura). Journal ofPaleontol-
Stimpson, W. 1863. On the fossil crab ofGay head. ogy, 74:636-653.
Boston Journal ofNatural History 7:583-589. Rathbun, M. J. 1935. Fossil C—rustacea of the Atlantic
Schweitzer, C. E., & R. M. Feldmann. 2000. Newfos- and gulf coastal Plain. Geological Society of
sil Portunid from Washington, USA, and Ar- America Special Papers 2, 160 p., 2 figs., 26
gentinaandareevaluationofgenericandfamily pis.
