The Hakobuchi Formation is a geological formation in Hokkaido, Japan. It is the uppermost unit of the Yezo Group, being early Maastrichtian in age. It consists of bioturbated glauconitic sandstones, siltstones and conglomerates with coaly mudstone and minor tuffite. It was deposited in a continental shelf setting. It is noted for its fossil content with the invertebrates mainly consisting of bivalves and ammonites. With vertebrates including the mosasaurs Mosasaurus hobetsuensis and Phosphorosaurus ponpetelegans. As well the sea turtle MesodermochelysHirayama R, Chitoku T. (1996). "Family Dermochelyidae (Superfamily Chelonioidea) from the Upper Cretaceous of North Japan". Transactions and proceedings of the Palaeontological Society of Japan. New series 184: 597-622. online, retrieved 28 July 2008 and the hadrosaurid dinosaur Kamuysaurus.
Fossil content
Dinosaurs
Ornithopods Ornithopods of the Hakobuchi Formation Genus Species Location Stratigraphic position Material Notes Images Kamuysaurus K. japonicus A edmontosaurin saurolophine
Mosasaurs Mosasaurs of the Hakobuchi Formation Genus Species Location Stratigraphic position Material Notes Images Mosasaurus M. hobetsuensis A mosasaurine mosasaurid Phosphorosaurus P. ponpetelegans A halisaurine mosasaurid
Turtles Turtles of the Hakobuchi Formation Genus Species Location Stratigraphic position Material Notes Images Mesodermochelys M. undulatus A dermochelyid turtle
Fish
Cartilaginous Fish Cartilaginous Fish of the Hakobuchi Formation Genus Species Location Stratigraphic position Material Notes Images Callorhinchus C. orientalis A callorhinchid chimaeran
Ray-finned Fish Ray-finned Fish of the Hakobuchi Formation Genus Species Location Stratigraphic position Material Notes Images Acipenseridae A sturgeon
Molluscs
Bivalves Bivalves of the Hakobuchi Formation Genus Species Location Stratigraphic position Material Notes Images Inoceramus I. nipponicus A inoceramid bivalve
Cephalopods Cephalopods of the Hakobuchi Formation Genus Species Location Stratigraphic position Material Notes Images Pachydiscus P. japonicus A pachydiscid ammonite
Gastropods Gastropods of the Hakobuchi Formation Genus Species Location Stratigraphic position Material Notes Images
Paleoflora Plants of the Hakobuchi Formation Genus Species Location Stratigraphic position Material Notes Images Mukawastrobus M. satoi A cypress Nilssonia N. yezoensis A cycad
References