Hakobuchi Formation
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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 Mesodermochelys and the hadrosaurid dinosaur Kamuysaurus.
Fossil content
| Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon | Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited. | |||||
| Taxon | Reclassified taxon | Taxon falsely reported as present | Dubious taxon or junior synonym | Ichnotaxon | Ootaxon | Morphotaxon |
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
| Cartilaginous 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 |