# Hasandong Formation

The Hasandong Formation (Korean: 하산동층; Hanja: 霞山洞層; RR: Hasandong-cheung) is an Early Cretaceous (Aptian to Albian) geologic formation in South Korea. It has been dated to the late Aptian and earliest Albian, between 118.0 ± 2.6 Ma and 112.4 ± 1.3 Ma. Dinosaur remains have been discovered from this formation, though no genus is considered valid as of 2016. Other reptiles from the formation include the adocid turtle Proadocus and possibly the pterosaur Dsungaripterus.

## Fossil content
### Invertebrate fossils

Few fragments of insects have been discovered from the formation.

#### Molluscs

Molluscs reported from the Hasandong Formation :
| Genus | Species | Notes |
| Plicatounio | P. naktongensis | |
| Plicatounio | P. okjuni | |
| Plicatounio | P. yooni | |
| Nagdongia | N. soni | |
| Trigonioides | T. jaehoi | |
| Trigonioides | T. kodairai | |
| Trigonioides | T. tamurai | |
| Brotiopsis | B. kobayashii | |
| Brotiopsis | B. naktongensis | |
| Brotiopsis | B. ryohoriensis | |
| Brotiopsis | B. wakinoensis | |
| Viviparus | V. sp. | Architaenioglossan gastropod, probably V. keishoensis |
| Probaicalia | P. katoensis | Hydrobiidae gastropod; species previously assigned to the genus Micromelania |

#### Ostracods

Ostracod carapaces have been discovered from the formation.
Ostracods reported from the Hasandong Formation :
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Cypridea | C. cf. trita | | | | | |

### Vertebrate fossils
#### Actinopterygii

Ray-finned fish reported from the Hasandong Formation :
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Sinamia | S. sp. | | | Partial Skeleton | | |
| Lepidotes | L. sp. | | | Partial Skeleton | | |

#### Testudines

Shell fragments of testudines have been discovered.
Turtles reported from the Hasandong Formation :
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Proadocus | P. hadongensis | | | Partial Skeleton | Adocid turtle | |

#### Crocodylomorpha

Several teeth remains have been reported but are not assigned to the specific clade.
Crocodylomorphs reported from the Hasandong Formation :
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| "Hadongsuchus" | "H. acerdentis" | | | Skull | nomen nudum | |

#### Pterosaurs

Pterosaurs reported from the Hasandong Formation :
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Pterodactyloidea | Indeterminate | | | Teeth and a partial second wing phalanx | Dental remains belong to either Boreopteridae or Anhanguerian | |
| Dsungaripterus | D.? cf. D. weii | | | Incomplete wing phalanx belonging to Dsungaripteridae | | |

#### Dinosaurs

Several indeterminate theropod teeth remains have been reported.
Dinosaurs reported from the Hasandong Formation :
| Genus | Species | Material | Notes |
| Carcharodontosauridae | Indeterminate | Teeth | Some dental remains show similarities with Acrocanthosaurus |
| Hadrosauroidea | Indeterminate | Tooth | |
| Titanosauriformes | Indeterminate | A partial skeleton and several teeth showing different morphotypes | Includes Chiayusaurus lacustris and Pukyongosaurus milleniumi, both of which are nomen dubium |
| Tyrannosauroidea | Indeterminate | Tooth, estimated crown length ~18mm | |

#### Eggs

Unnamed dinosaur egg fossils have been reported.
Eggs reported from the Hasandong Formation :
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Testudoolithus | T. aff. curiosa | | | | Turtle eggs | |

### Ichnofossils

Tracks of theropods, sauropods and ornithopods have been discovered from the formation. Possible amphibian tracks are also known.
Ichnofossils reported from the Hasandong Formation :
| Genus | Species | Notes |
| Pteraichnus | P. koreanensis | Pterosaur tracks |
| Sauripes | S. hadongensis | The oldest lizard tracks showing possible bipedalism, though potentially a nomen dubium due to insufficient description and problematic holotype designation |
| Diplocraterion | D. luniforme | |
| Beaconites | B. coronus | |
| Circulichnus | C. montanus | |
| Cochlichnus | C. anguineus | |
| Chondrites | C. isp. | |
| Helminthopsis | H. abeli & H. hieroglyphica | |
| Laevicyclus | L. isp. | |
| Planolites | P. annularius, P. beverleyensis & P. montanus | |
| Skolithos | S. magnus, S. verticalis & S. isp. | |
| Spirodesmos | S. isp. | |
| Taenidium | T. barretti | |
| Thalassinoides | T. paradoxicus & T. suevicus | |

### Paleoflora

Consists of 6 genera and 9 species. The assemblage of plant fossils from the Hasandong represents the 'mixed' type of Tetori-type and Ryoseki-type flora.
Plants reported from the Hasandong Formation :
| Genus | Species | Notes |
| Brachyphyllum | B. japonicum | Araucariaceae conifer |
| Cladophlebis | C. denticulata | |
| Cladophlebis | C. (Eboracia?) lobifolia | |
| Cladophlebis | C. (Klukia?) koraiensis | |
| Cladophlebis | C. shinshuensis | |
| Elatocladus | E. tennerima | Conifer with an unknown systematic position |
| Onychiopsis | O. elongata | Leptosporangiate fern |
| Ptilophyllum | P. sp. | Bennettitales (extinct order of seed plants) |
| Ruffordia | R. sp. | Schizaeaceae ferns |
| Taeniopteris | T.? sp. cf. T. auriculata | The specific systematic position of this form genus is unknown. |
| Thallites | T. yabei | Liverwort |

## Photo

* 36°27′10.0″N 128°30′40.0″E﻿ / ﻿36.452778°N 128.511111°E﻿ / 36.452778; 128.511111
* Boundary of Hasandong Formation (under) and Jinju Formation (upper) 36°24′04.0″N 128°32′40.0″E﻿ / ﻿36.401111°N 128.544444°E﻿ / 36.401111; 128.544444
* 35°00′15.8″N 127°55′16.7″E﻿ / ﻿35.004389°N 127.921306°E﻿ / 35.004389; 127.921306
* 35°00′15.7″N 127°55′17.7″E﻿ / ﻿35.004361°N 127.921583°E﻿ / 35.004361; 127.921583
* 34°59′59.6″N 127°55′08.2″E﻿ / ﻿34.999889°N 127.918944°E﻿ / 34.999889; 127.918944
* 35°00′02.8″N 127°55′10.0″E﻿ / ﻿35.000778°N 127.919444°E﻿ / 35.000778; 127.919444
* Ripple Marks 35°00′02.0″N 127°55′09.6″E﻿ / ﻿35.000556°N 127.919333°E﻿ / 35.000556; 127.919333
* Normal Faults 34°59′59.6″N 127°55′08.1″E﻿ / ﻿34.999889°N 127.918917°E﻿ / 34.999889; 127.918917
* 34°59′59.7″N 127°55′08.1″E﻿ / ﻿34.999917°N 127.918917°E﻿ / 34.999917; 127.918917
* 34°59′23.9″N 127°55′09.1″E﻿ / ﻿34.989972°N 127.919194°E﻿ / 34.989972; 127.919194
* 34°57′31.2″N 127°53′52.6″E﻿ / ﻿34.958667°N 127.897944°E﻿ / 34.958667; 127.897944
* 34°57′32.9″N 127°53′53.8″E﻿ / ﻿34.959139°N 127.898278°E﻿ / 34.959139; 127.898278
* 34°57′33.8″N 127°53′53.9″E﻿ / ﻿34.959389°N 127.898306°E﻿ / 34.959389; 127.898306
* 34°57′33.8″N 127°53′53.9″E﻿ / ﻿34.959389°N 127.898306°E﻿ / 34.959389; 127.898306
* 34°57′34.1″N 127°53′53.8″E﻿ / ﻿34.959472°N 127.898278°E﻿ / 34.959472; 127.898278
* 34°57′29.6″N 127°53′41.0″E﻿ / ﻿34.958222°N 127.894722°E﻿ / 34.958222; 127.894722
* 34°57′29.3″N 127°53′39.9″E﻿ / ﻿34.958139°N 127.894417°E﻿ / 34.958139; 127.894417
* 34°57′27.3″N 127°53′43.0″E﻿ / ﻿34.957583°N 127.895278°E﻿ / 34.957583; 127.895278
* 34°57′27.4″N 127°53′43.0″E﻿ / ﻿34.957611°N 127.895278°E﻿ / 34.957611; 127.895278
* 34°57′27.0″N 127°53′43.1″E﻿ / ﻿34.957500°N 127.895306°E﻿ / 34.957500; 127.895306
* 34°56′50.8″N 127°51′08.1″E﻿ / ﻿34.947444°N 127.852250°E﻿ / 34.947444; 127.852250
* Corss-bedding 34°56′50.9″N 127°51′08.5″E﻿ / ﻿34.947472°N 127.852361°E﻿ / 34.947472; 127.852361
* 34°56′50.6″N 127°51′08.7″E﻿ / ﻿34.947389°N 127.852417°E﻿ / 34.947389; 127.852417
* Corss-bedding 34°56′50.9″N 127°51′08.5″E﻿ / ﻿34.947472°N 127.852361°E﻿ / 34.947472; 127.852361
* Corss-bedding 34°56′51.0″N 127°51′08.7″E﻿ / ﻿34.947500°N 127.852417°E﻿ / 34.947500; 127.852417
* 34°56′51.1″N 127°51′08.3″E﻿ / ﻿34.947528°N 127.852306°E﻿ / 34.947528; 127.852306
* 34°56′51.6″N 127°51′08.5″E﻿ / ﻿34.947667°N 127.852361°E﻿ / 34.947667; 127.852361
* 34°57′28.2″N 127°48′37.1″E﻿ / ﻿34.957833°N 127.810306°E﻿ / 34.957833; 127.810306