Early Cretaceous Freshwater Fish Fauna in Kyushu, Japan

EarlyCretaceous Freshwater Fish Fauna in Kyushu, Japan 215
Description.
In KMNH VP 100,211, the body is slender and the body depth is contained 3.5
times in the standard length. The head length is contained 3.2 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 origin is almost straight.
The restored outline of the abdomen is slightly convex (Figs. 78 and 79). The dorsal
fin is situated at about the middle of the body. The anal origin is behind the end of
the dorsal fin base. The first dorsal fin pterygiophore is inserted between the 9th
and 10th abdominal vertebrae. The dorsal fin base is short and is contained 1.8 times
in the anal fin base. The pectoral fin isshortand does not reach the pelvic insertion.
The caudal fin is forked. The number of principal dorsal fin rays is 11. There are
12 dorsal fin pterygiophores. The number of principal anal fin rays is 22. There
are 22 anal fin pterygiophores. The principal dorsal and anal fin rays are preceded
by one small unbranched accessory ray respectively. Thirteen pectoral 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 and deep. The dentary bears small teeth on the
anterior end of the oral margin. The suture between the dentary and the angloarticular
is visible and the posterior part of the lowerjaw is poorly preserved. The
parasphenoid teeth are absent. The frontal is wide and carries a superficial sensory
canal. The maxilla is wide and slightly curved. The maxilla has a ridge from the
dorsal end to near the ventral end and has wide wings both sides of the ridge. The
angle between the upper and lower limbs of the preopercle is an obtuse. The
sensory canal runs along the anterior margin of the upper limb. The lower limb of
the preopercle is poorly preserved. Parts of the opercle and preopercle are visible
(Fig. 80). The predorsal scutes are oval in shape. The anterior end of each dorsal
scute is round and the posterior end is slightly pointed (Fig. 81). The ventral scutes
are well developed and total 22 in number, with 4 scutes below the pectoral fin, 11
scutes between the pectoral and pelvic fins, and 7 scutes between the pelvic and anal
fins. Each scute below the pectoral fin does not have vertical elements (Fig. 78).
The total number of vertebrae is 36, with 16 caudal vertebrae. The anterior end of
the vertebral column is not visible. The number of abdominal vertebrae was
estimated on the basis ofthe ribs. The number ofribs is 18. Six median supraneu
rals are present. The first supraneural is wide and leaf-shape with a ridge running
from the dorsal end to the ventral end. The first preural centrum bears the
cylindrical parhypural with narrow wings on its basal part. The neural arch and
spine of the first preural centrum are not visible. There are 6 hypurals. The first
hypural is the largest. The second hypural is about half of the first one in width.
The second hypural is fused with the first ural vertebra. There is a space between
the second and the third hypurals. The third to sixth hypurals are slender and
cylindrical (Fig. 82).
In KMNH VP 100,212, the body depth is contained 3.7 times in the standard