Hasandong Formation
Geologic formation in South Korea
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The Hasandong Formation (Korean: 하산동층; Hanja: 霞山洞層; RR: Hasandong-cheung) is an Early Cretaceous geologic formation in South Korea. It has been dated to the Aptian to possibly the earliest Albian stage. Lee et al. (2018) estimated the maximum depositional age of the formation at 118.0 ± 2.6 Ma, and suggested that the overlying Jinju Formation likely had a maximum depositional age of 112.4 ± 1.3 Ma.[2] Chae et al. (2026) examined the upper part of the Hasandong Formation on Yusu-ri, Jinju and on Jangguseom Island of Jungpyeong-ri, Hadong, and estimated the maximum depositional age of the upper part of the formation on each site at 116.9 ± 1.5 Ma and 113.4 ± 1.4 Ma respectively.[3] Fossils including dinosaurs, turtles and pterosaurs are known from this formation.
| Hasandong Formation | |
|---|---|
| Stratigraphic range: Aptian-?earliest Albian ~ | |
| Type | Geological formation |
| Unit of | Shindong Group |
| Underlies | Jinju Formation |
| Overlies | Nakdong Formation |
| Thickness | 1,200 metres |
| Lithology | |
| Primary | Mudstone |
| Other | Shale, sandstone |
| Location | |
| Coordinates | 35.1°N 128.0°E |
| Approximate paleocoordinates | 41.3°N 128.1°E |
| Region | Gyeongsang Province |
| Country | South Korea |
| Type section | |
| Named for | Hasandong(Now called Hasan-ri), Daegu |
| Named by | Tateiwa, 1929[1] |
  Hasandong Formation (South Korea) | |
Fossil content
Invertebrate fossils
Few fragments of insects have been discovered from the formation.[4]
Molluscs
| Molluscs reported from the Hasandong Formation[5] | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Plicatounio | P. naktongensis | |||||
| P. okjuni | ||||||
| P. yooni | ||||||
| Nagdongia | N. soni | |||||
| Trigonioides | T. jaehoi | |||||
| T. kodairai | ||||||
| T. tamurai | ||||||
| Brotiopsis | B. kobayashii | |||||
| B. naktongensis | ||||||
| B. ryohoriensis | ||||||
| B. wakinoensis | ||||||
| Viviparus[6] | V. sp. | Architaenioglossan gastropod, probably V. keishoensis | ||||
| Probaicalia | P. katoensis[7] | Hydrobiidae gastropod; species previously assigned to the genus Micromelania | ||||
Ostracods
Ostracod carapaces have been discovered from the formation.[4]
Vertebrate fossils
Actinopterygii
| Ray-finned fish reported from the Hasandong Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Sinamia[10] | S. sp. | Partial Skeleton | ||||
| Lepidotes[4] | 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 |
| Byeoljubuchelys[11] | B. yeosuensis | Nearly complete carapace and plastron and associated post-cranial bones | A carettochelyid turtle |  | ||
| Proadocus[12] | P. hadongensis | Partial Skeleton | An adocid turtle | |||
Crocodylomorpha
Several teeth remain have been reported but are not assigned to the specific clade.[13]
| Crocodylomorphs reported from the Hasandong Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| "Hadongsuchus"[14] | "H. acerdentis" | Skull | nomen nudum | |||
Pterosaurs
| Pterosaurs reported from the Hasandong Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Pterodactyloidea[15][16][17] | Indeterminate | Teeth and a partial second wing phalanx | Dental remains belong to either Boreopteridae or Anhanguerian | |||
| Dsungaripterus | D.? cf. D. weii[18][5] | Incomplete wing phalanx belonging to Dsungaripteridae[19][20] | ||||
Dinosaurs
Several indeterminate theropod teeth remains have been reported.[21]
| Dinosaurs reported from the Hasandong Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Carcharodontosauridae[22][23] | Indeterminate | Teeth | Some dental remains show similarities with Acrocanthosaurus |  | ||
| Hadrosauroidea[24] | Indeterminate | Tooth | ||||
| Titanosauriformes[25][26][27] | Indeterminate | A partial skeleton[28] and several teeth showing different morphotypes | Includes Chiayusaurus sp. and Pukyongosaurus milleniumi, both of which are nomen dubium | |||
| Tyrannosauroidea[29] | Indeterminate | Tooth, estimated crown length ~18mm | ||||
Eggs
Unnamed dinosaur egg fossils have been reported.[30]
Ichnofossils
Tracks of theropods, sauropods and ornithopods have been discovered from the formation.[4][31] Possible amphibian tracks are also known.[32]
| Ichnofossils reported from the Hasandong Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Pteraichnus[32] | P. koreanensis | Pterosaur tracks | ||||
| Sauripes[33] | S. hadongensis | The oldest lizard tracks showing possible bipedalism, though potentially a nomen dubium due to insufficient description and problematic holotype designation[34] | ||||
| Diplocraterion[35] | D. luniforme | |||||
| Beaconites | B. coronus[31] | |||||
| Circulichnus | C. montanus[31] | |||||
| Cochlichnus | C. anguineus[31] | |||||
| Chondrites | C. isp.[31] | |||||
| Helminthopsis | H. abeli & H. hieroglyphica[31] | |||||
| Laevicyclus | L. isp.[31] | |||||
| Planolites | P. annularius, P. beverleyensis & P. montanus[31] | |||||
| Skolithos | S. magnus, S. verticalis & S. isp.[31] | |||||
| Spirodesmos | S. isp.[31] | |||||
| Taenidium | T. barretti[31] | |||||
| Thalassinoides | T. paradoxicus & T. suevicus[31] | |||||
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[36][32] | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Brachyphyllum | B. japonicum | Araucariaceae conifer | ||||
| Cladophlebis | C. denticulata | |||||
| C. (Eboracia?) lobifolia | ||||||
| C. (Klukia?) koraiensis | ||||||
| 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 | ||||
