The Hasandong Formation () is an

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

(

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

Albian The Albian is both an age (geology), age of the geologic timescale and a stage (stratigraphy), stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early Cretaceous, Early/Lower Cretaceous epoch (geology), Epoch/s ...

) geologic

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korea, Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and t ...

. It has been dated to the late Aptian and earliest Albian, between 118.0 ± 2.6 Ma and 112.4 ± 1.3 Ma.

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

remains have been discovered from this formation, though no genus is considered valid as of 2016. Other reptiles from the formation include the

adocid The Adocidae are an extinct family of aquatic and omnivorous turtles. They are freshwater cryptodiran turtles and are mainly known from Cretaceous and Paleogene Asia and North America. Taxonomy Phylogeny modified from Danilov ''et al.'' (2013) ...

turtle ''Proadocus'' and possibly the

pterosaur Pterosaurs are an extinct clade of flying reptiles in the order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 million to 66 million years ago). Pterosaurs are the earli ...

Dsungaripterus ''Dsungaripterus'' is a genus of dsungaripterid pterosaur which lived during the Early Cretaceous in what is now China and possibly South Korea. Its fossils come from the Wuerho Pterosaur Fauna group (WPF) of the Tugulu Group, comprising sectio ...

''.

Fossil content

Invertebrate fossils

Few fragments of

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s have been discovered from the formation.

Molluscs

Ostracods

Ostracod

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

s have been discovered from the formation.

Vertebrate fossils

Actinopterygii

Testudines

Shell fragments of testudines have been discovered.

Crocodylomorpha

Several teeth remains have been reported but are not assigned to the specific clade.

Pterosaurs

Dinosaurs

Several indeterminate theropod teeth remains have been reported.

Eggs

Unnamed dinosaur egg fossils have been reported.

Ichnofossils

Tracks of

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

s and

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and relatively sm ...

s have been discovered from the formation. Possible

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

tracks are also known.

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.

Photo

References

Bibliography

* {{citation , last1=Weishampel , first1=David B. , author2-link=Peter Dodson , last2=Dodson , first2=Peter , author3-link=Halszka Osmólska , last3=Osmólska , first3=Halszka , year=2004 , title=The Dinosauria, 2nd edition , url=https://books.google.com/books?id=vtZFDb_iw40C , publisher=Berkeley: University of California Press , pages=1–880 , accessdate=2019-02-21 , isbn=0-520-24209-2 , author1-link=David B. Weishampel Geologic formations of South Korea Lower Cretaceous Series of Asia Cretaceous South Korea Albian Stage Aptian Stage Mudstone formations Shale formations Sandstone formations Fluvial deposits Ichnofossiliferous formations Paleontology in South Korea