Early Cretaceous Freshwater Fish Fauna in Kyushu, Japan

244 Yoshitaka Yabumoto
Africa is constituted of about 10 species belonging to 8 families and orders (Patter
son, 1975). The fish fauna of the Ilhas Formation in Brazil is composed of 12
species belonging to 7 families and orders (Schaeffer, 1947) and is similar to the
fauna of the Cocobeach Series of Gabon and Equatorial Guinea. Both faunas are
characterized by the existence of the orders Coelacanthiformes and Aspidorhynchiformes
and an abundance of the Ichthyodectiformes and the Leptolepiformes in
number of species. The semionotid genus Lepidotes is more abundant and the order
Gonorynchiformes is absent in the Ilhas Formation. The orders Amiiformes and
Ichthyodectiformes are common to the Wakino fish fauna and the faunas of the
Cocobeach Series of Gabon and Equatorial Guinea and the Ilhas Formation.
The orders Coelacanthiformes, Aspidorhynchiformes, and Ellimmichthiiformes
are present in the fauna of the Cocobeach Series of Gabon and Equatorial Guinea
and the Ilhas Formation, but these orders are absent in the Wakino fish fauna. The
orders Osteoglossiformes and Clupeiformes which are abundant in the Wakino fish
fauna are absent in the faunas of the Cocobeach Series of Gabon and Equatorial
Guinea, and the Ilhas Formation.
The osteoglossiform fish is not recognized in the Lower Cretaceous fish faunas
except in southeastern China and the clupeiform fish is not so abundant in the Lower
Cretaceous freshwater deposits in the world. The Wakino fish fauna is characterized
by an abundance of the orders Osteoglossiformes and Clupeiformes and the absence
of the orders Coccolepiformes, Pholidophoriformes, Macrosemiiformes and Pycnodontiformes,
and the family Huashiidae (Tab. 10).
Concluding Remarks
1. Comparison of faunal changes of the molluscan fossils and the fish fossils
in the Wakino Subgroup.
Y. Ota (1960b) subdivided the Wakino Subgroup distributed in the northern
part of Kyushu Island into two zones based on molluscan fossils: the lower, Brotiopsis
wakinoensis Zone (the lower formation, W,, the First Formation) and the upper,
Viviparus onogoensis-Nakamuranaia (?) sp. cf. N. chingshanensis Zone. The upper zone is
subdivided into three zones: the middle, upper and uppermost formations which
correspond to the Second (W2), Third (W3) and Fourth (W4) Formations respective
ly on the basis of the distribution of molluscan fossils (Fig.3). In the First
Formation, Brotiopsis wakinoensis is most abundant and Plicatounio naktongensis occurs
commonly. "Nippononaia" wakinoensis, "N." sengokuensis, Plicatounio naktongensis multiplicatus,
P. triangularis and P. kwanmonensis are very rare in the First Formation (Wi).
In the Second Formation (W2), a few molluscan fossils, Viviparus onogoensis and others,
are found from Nogata and Moji in northern part of Kyushu and Yoshimo in
Yamaguchi Prefecture. Molluscan fossils of Brotiopsis kobayashii, Viviparus onogoensis
and Sphaerium (?) sp., and Ostracoda are found at Takatsuo in Kokura-minami-ku in