Early Cretaceous Freshwater Fish Fauna in Kyushu, Japan

Early Cretaceous Freshwater Fish Fauna in Kyushu, Japan 211
is slightly convex. The restored outline ofthe abdomen is remarkably convex (Figs.
73 and 74). The dorsal fin is situated at about the middle of the body. The anal
origin is well behind the posterior end of the dorsal fin base. The first dorsal fin
pterygiophore is above the9th abdominal vertebra. The dorsal fin base is short and
is contained 2.1 times in the anal fin base. The pectoral fin is short and does not reach
the pelvic insertion (Figs. 73 and 74). Thenumber ofprincipal dorsal fin rays is 10.
There are 10 dorsal fin pterygiophores. The number of principal anal fin rays is 24.
There are 24 anal fin pterygiophores. The principal dorsal and anal fin rays are
preceded by two small unbranched accessory rays respectively. Six pelvic fin rays
are visible. There are 18 principal caudal fin rays (1,8,8,1). The pelvic fin is
situated at about the middle of the body and the insertion is situated slightly before
under the dorsal origin. The gape of the mouth is small. The mandible is short
and deep. The dentary bears small teeth on its anterior part of the oral margin.
The suture between the dentary and anglo-articular is not visible and the posterior
part of the mandible is poorly preserved. There are no teeth on the premaxilla and
maxilla. The posterior end of the lower jaw is placed below almost center of the
orbit. The parasphenoid teeth are absent. The maxilla is long and wide. The
maxilla is slightly curved. The maxilla has a ridge from the dorsal end to the
SCL
CLE
PREO
5mm
Fig. 75. Diplomystus altisomus sp. nov., head region of the holotype, KMNH VP 100,217.