Early Cretaceous Freshwater Fish Fauna in Kyushu, Japan

230 Yoshitaka Yabumoto
length is 32.5 mm.
Locality. Minamigaoka (KM-1), Kokura-kita-ku (Kokura Northern Ward), Kita
kyushu City, Fukuoka Prefecture, Japan.
Horizon. The Third Formation (the upper formation, W3, correlated to the Lower
Wakamiya Formation) of the Wakino Subgroup in the Kwanmon Group, the Lower
Cretaceous.
Etymology.
The species name, elegans, means elegant.
Description of the holotype.
The body is slender. The body depth is contained 5.1 times in the standard
length. The head length is contained 4.1 times in the standard length. The snout
is round. The outline of the head dorsal margin is slightly convex. The outline
from the occipital region to the dorsal originis almoststraight. The restored outline
of the abdomen is slightly convex and runs little under the lower end of each rib.
The median fins are relatively posterior in position. The anal origin is behind the
dorsal origin and about vertical with the sixth dorsal fin pterygiophore. The first
dorsal fin pterygiophore is above the neural spine of the first caudal vertebra (Fig.
90). The dorsal fin base is contained 1.8 times in the anal fin base. The pectoral
fin is short and does not reach the pelvic insertion. The number of principal dorsal
fin rays is 12. There are 12 dorsal fin pterygiophores. The number of principal
anal fin rays is 20. There are 20 anal fin pterygiophores. The principal anal fin
rays are preceded by two small unbranched accessory rays. Twelve pectoral fin rays
are visible. Five pelvic fin rays are visible. There are 18 principal caudal fin rays
(1,8,8,1). The gape of the mouth is small. The mandible is short. The dentary
bears small canine like teeth. The suture between the dentary and anglo-articular is
not visible and the posterior part of the mandible is poorly preserved. The premax
illa bears small canine like teeth. There are no teeth on the maxilla. The posterior
end of the lower jaw is placed below almost center of the orbit. There are no large
teeth on the parasphenoid (Fig. 92). The total number of vertebrae is 42, with 20
caudal vertebrae. The anterior end of the vertebral column is not visible. The
number of abdominal vertebrae was estimated on the basis of the ribs. The number
of ribs is 20. There is a series of median supraneurals beginning immediately behind
the head. Each supraneural of the anterior two-thirds is wide and leaf-shape with a
ridge running from a dorsal end toa ventral end. The first and second hypurals are
almost same in size. The first hypural is slightly larger than the second hypural at
the anterior part. There are 6 hypurals. There is a space between the second and
third hypurals. The third tosixth hypurals areslender. There are two ural centra.
The second ural centrum bears at least three hypurals (HYU3-5). The uroneurals