Early Cretaceous Freshwater Fish Fauna in Kyushu, Japan

186 Yoshitaka Yabumoto
URN
URN1
PU1
PARH
2mm
Fig. 55. Wakinoichthys aokii gen. et sp. nov., caudal skeleton of the holotype, KMNH
VP100,140.
Description of the paratypes from the Third Formation.
In KMNH VP 100,184, the body is slender. The body depth is contained 6.3
times in the standard length. The head length is contained 5.5 times in the standard
length. The snout is pointed. The outline of the head dorsal margin is almost
straight. The outline from the occipital region to the dorsal origin is almost straight.
The restored outline of the abdomen is almost strait and runs little under the lower
end of each rib. The median fins are relatively posterior in position. The dorsal
origin is behind the anal origin and about vertical with the anterior one fifth of the
anal fin base. The first dorsal pterygiophore is inserted between the neural spines of
the fourth and fifth caudal vertebrae (Fig. 57). The dorsal fin base is contained 1.6
times in the anal fin base. The pectoral fin elongates and extends beyond the middle
of the abdomen and the pelvic insertion. The caudal fin is forked. The number of
principal dorsal fin rays is 12. There are 12 dorsal fin pterygiophores and a stay.
The number of principal anal fin rays is 18. There are 17 anal fin pterygiophores.
The principal dorsal and anal fin rays are preceded by two small unbranched
accessory rays respectively. Ten pectoral fin rays and five pelvic fin rays are visible.
There are 18 principal caudal fin rays (1,8,8,1). The gape of the mouth is large.
The mandible is long and narrow. The premaxilla, maxilla and the anterior part of
the dentary are not visible. The posterior end of the mandible is placed below
almost center of the orbit. There are no teeth on the parasphenoid. There are
villiform teeth on the endopterygoid. The frontal is long and carries a superficial
long canal. The outlines of the opercle and preopercle are visible (Fig. 58). The
total number ofvertebrae is 46, with 22 caudal vertebrae. The number of ribs is 22.
There is a series of median supraneurals beginning close behind the head and ending