Early Cretaceous Freshwater Fish Fauna in Kyushu, Japan

jgg
Yoshitaka Yabumoto
The coracoid is low and round at the posterior margin. The posterior end of the
lower jaw is placed almost below the posterior margin of the orbit. The parasphe
noid tooth is not visible. There are villiform teeth on the endopterygoid. The
palatine is slender and has minute teeth. The total number of vertebrae is 35, with
19 caudal vertebrae. The anterior end of the vertebral column is not visible. The
number ofabdominal vertebrae is estimated on the basis of the ribs.
The number of
ribs is 14. There is a series of median supraneurals behind the head and ending
above the first caudal vertebra. Each supraneural from the first to the third is
leaf-shape with a ridge running from a dorsal end to a ventral end. The other
supraneurals are cylindrical. The first preural centrum bears the narrow parhypural.
The neural arch and spine of the first preural centrum are separated each other.
Five hypurals are visible. The first hypural is the largest. The second hypural is
about one fifth of the first one in width. There is a space between the second and
third hypurals. The second to fifth hypurals are slender. There are two ural
centra. The second ural centrum bears at least three hypurals (HYU3-5). Three
uroneurals are visible.
The epural is not visible (Fig. 43).
The first uroneural extends forward to the first ural centrum.
Description of the paratypes.
In KMNH VP 100,174, the body depth is contained 2.1 times in the standard
length. The head length is contained 3.7 times in the standard length. The dorsal
fin base is contained 1.8 times in the anal fin base. The number of principal dorsal
fin rays is 12. There are 12 dorsal fin pterygiophores. The number of principal
anal fin rays is 19. The dentary bears small canine like teeth on its oral margin.
The suture between the dentary and anglo-articular is not visible. Three large
canine like teeth are visible on the parasphenoid at the posterior part of orbit. The
total number of vertebrae is 36, with 19 caudal vertebrae.
In KMNH VP 100,175, the body depth is contained 2.4 times in the standard
length. The head length is contained 3.2 times in the standard length. The dorsal
fin base is contained 1.9 times in the anal fin base. The number of principal dorsal
fin rays is 11. The number of principal anal fin rays is 19. There are 20 anal fin
pterygiophores. The total number of vertebrae is 34, with 18 caudal vertebrae.
The number of ribs is 14.
Remarks. This new species, Aokiichthys otai, resemble Yungkangichthys hsitanensis
Chang & Chou, 1974 (Fig. 29) in having almost same number of dorsal and anal fin
rays, and almost same proportion (Tab. 3). But it differs from Y. hsitanensis in
having thesmaller numbers ofvertebrae. The number ofvertebrae is 34 to 36in A.
otai, 44 in Y. hsitanensis. A. otai is closest to Aokiichthys uyenoi in having almost same
meristic character and the proportion with the exception of the relative position of the
median fins (Tab. 3). The origin of dorsal fin is vertical with the anal origin in A.