Early Cretaceous Freshwater Fish Fauna in Kyushu, Japan

Early Cretaceous Freshwater Fish Fauna in Kyushu, Japan 135
URN
Fig. 21.
100,148.
Chuhsiungichthys yanagidai sp. nov., caudal skeleton of the holotype, KMNH VP
nal vertebra. The end of the dorsal fin base is about vertical with posterior one third
of the anal fin base. The number of principal dorsal fin rays is 20. There are 20
dorsal fin pterygiophores. The anal fin base is long. The length of anal fin base is
about 1.3 times of the dorsal fin base. The number of principal anal fin rays is 31.
There are 29 anal fin pterygiophores. The anal and dorsal fin rays are long at the
anterior part and becomes rapidly shorter at the posterior part. This is remarkable
in the dorsal fin. The principal dorsal and anal fin rays are preceded by two small
unbranched accessory rays respectively.
The pectoral fin does not elongate and reaches the pelvic insertion. The pelvic
fin is present at the middle of the abdomen. The caudal fin is forked (Fig. 18).
There are 19 principal caudal fin rays (1,9,8,1). The number of procurrent caudal
fin rays is 8 in the upper lobe and 6 in the lower lobe (Fig. 21).
The orbital is relatively large. There are minute teeth on the dentary, premax
illa, endopterygoid and palatine. The teeth on the premaxilla, endopterygoid and
palatine are villiform. The dentary bears minute canine like teeth on its oral
margin. The suture between the dentary and angulo-articular is not visible. The
posterior part of the mandible is poorly preserved (Fig. 20).
The total number of vertebrae is 40, with 21 caudal vertebrae. The ribs are
slender and long. The estimated number of ribs is 17. There is a series of median
supraneurals beginning close behind the head and ending above the 17th abdominal
vertebra.