Min Huh

New pterosaur tracks (Pteraichnidae) from the Late Cretaceous Uhangri Formation, southwestern Korea

Numerous footprints of dinosaurs, pterosaurs and birds, together with arthropod tracks, have been discovered in the upper Cretaceous Uhangri Formation which crops out along the south- western coastline of South Korea. This ichnofauna contains the first pterosaur tracks reported from Asia. The digitigrade tridactyl manus impressions exhibit features of a typical pterosaur hand print. The pes impressions, however, show features that are different from pterosaur footprints reported pre- viously: there is no visible trace of impressions of individual digits, and the toes are triangular or rounded in shape distally without distinct claw impressions. As these features clearly distinguish the Uhangri tracks from Pteraichnus and Purbeckopus, we assign them to a new genus, Haenamichnus which accommodates the new ichnospecies, Haenamichnus uhangriensis. The prints are five to six times larger than those of Pteraichnus, and are currently the largest pterosaur ichnites known. They show virtually no trace of the 5th phalange of the pes, indicating that they were made by pterodactyloids; moreover, features of the tracks suggest that they can be attributed to azhdarchids, the commonest pterosaur of the Late Cretaceous. The longest pterosaur trackway yet known from any track site (length 7.3 m) and consisting of 14 pairs of foot impressions, was also found in the Uhangri Formation and suggests that azhdarchids, at least, were competent terrestrial locomotors. The fossil track site at Uhangri represents the first occurrence of the tracks of pterosaurs, dinosaurs and web- footed birds all on the same level. This demonstrates that pterosaurs and birds visited the same habitat, but the large size disparity suggests that they occupied different ecological niches.

Ornithopodichnus and Pes-Only Sauropod Trackways from the Hwasun Tracksite, Cretaceous of Korea

Trackways of small (foot length ∼12–15 cm) robust ornithopods are relatively uncommon in the Cretaceous, where most tracks attributed to iguanodontids and hadrosaurs range in size from ∼20–80 cm. The Hwasun site, previously noted for its abundant theropod trackways, also reveals one horizon (L2) with at least six parallel trackways of small blunt-toed ornithopods with wide tracks, short steps and typical inward rotation of the pes. The site also reveals a second horizon (L4) which yields a single clear trackway of a much larger blunt-toed ornithopod. Although allometric trends in tridactyl track assemblages tend to show increased trackway width and reduced anterior projection of digit III (reduced mesaxonic emphasis) with increasing size, the small Hwasun ornithopods reveal unusually wide tracks with reduced mesaxony. The tracks are herein assigned to the ichnogenus Ornithopodichnus. A map of previously unmapped Level 4 is presented showing the context of the large ornithopod tracks on the same surface as an unusual pes-only trackway with distinctive claw traces and sediment rims. This surface also reveals isolated sauropod manus tracks and various underprints.

Tracking Korea's Early Birds: A Review of Cretaceous Avian Ichnology and Its Implications for Evolution and Behavior

Bird tracks are abundant and ubiquitous in many Cretaceous formations in Korea. To date, in order of discovery and description, the following six ichnogenera have been reported: Koreanaornis, Jindongornipes, Uhangrichnus, Hwangsanipes, Ignotornis, Goseongornipes and ?Aquatilavipes. As more bird tracks are discovered it has become possible to amend descriptions of existing ichnotaxa to better understand track morphology (and ichnotaxonomic relationships), trackway patterns and associated feeding traces and gain further insight into the behavior and ecology. We review and re-evaluate the most important bird tracksites in Korea, with special reference to sites not previously fully or adequately described in accessible English language journals. We pay special attention to material from the Uhangri Dinosaur Museum, Haenam area, and the Gyeongsangnamdo Institute of Science Education, Gajin area, presenting revised descriptions, illustrations and information on Uhangrichnus and Goseongornipes.

Multiple Tracksites with Parallel Trackways from the Cretaceous of the Yeosu City Area Korea: Implications for Gregarious Behavior in Ornithopod and Sauropod Dinosaurs

At least six sites with multiple parallel ornithopod trackways and one site with three parallel sauropod trackways have been mapped in the track-rich Cretaceous sequence on Sado and Chudo islands, Yeosu City area, South Korea. A preliminary study of the stratigraphic context of these tracks indicates that they were made by gregarious subadult or adult dinosaurs that frequented lake basin settings subject to a cyclic depositional regime and periodic ash fall. Bird and theropod dinosaur tracks also occur in the sequence. Mapped sites reveal between 4 and 14 regularly spaced, ornithopod trackways suggestive of herding behavior. One site reveals an 84 m-long trackway, the longest on record for an ornithopod. Only one site reveals parallel sauropod trackways indicating three animals of equal size traveling eastwards with an inter-trackway spacing of about 2.25–2.5 m. The footprints show well preserved pes claw impressions, slightly wide gauge and large manus/pes ratios (low heteropody). The sedimentological and ichnofaunal sequences share some similarities with the famous Jindong successions 50 km to the east, but they also differ significantly in age and ichnofaunal composition.

First Report of Aquatilavipes from Korea: New Finds from Cretaceous Strata in the Yeosu Islands Archipelago

Cretaceous bird tracks assigned to the ichnogenera Aquatilavipes and Koreanaornis are reported for the first time from Sado Island in the Yeosu Island archipelago, Korea, an area already known for multiple dinosaur track-bearing horizons. The Koreanaornis tracks are associated with many small Cochlichnus trails attributed to nematode worms, on which the birds were likely feeding in a lake shoreline environment. The Koreanaornis and Aquatilavipes assemblages occur at different, albeit close, stratigraphic levels. The Aquatilavipes report is the first from Korea.

Recent Advances in Korean Vertebrate Ichnology: The KCDC Comes of Age

Vertebrate tracks were first reported from the Cretaceous of South Korea in 1969 by B. K. Kim. His discovery of bird tracks, appropriately named Koreanaornis hamanensis, not only signaled the first bird tracks discovered in Asia and the second formally named avian ichnogenus from the Mesozoic, but it also was an indication of the vast wealth of vertebrate tracks that would be discovered a generation later in the Haman Formation and other Cretaceous formations of Korea, particularly in the large Gyeongsang Basin. This landslide of discovery has resulted in a proliferation of papers on vertebrate tracks from the Cretaceous of South Korea and the growing recognition that as a region it reveals multiple track-rich sequences of unique quality and scientific utility. Because of the outstanding ichnological resources in this region, it has been dubbed the Korean Cretaceous Dinosaur Coast (KCDC). Many sites of national and international significance have been designated as national natural landmarks, and the best of these have been nominated for World Heritage Inscription. In this editorial introduction, we attempt to summarize the present state of tetrapod ichnology after four decades of vertebrate track research. This synopsis serves as an introduction to a dozen short papers that focus attention on new discoveries at key sites. These reports, in turn, provide a promise of abundant material for future decades of research. At the present time, there are at least five ichnological research groups working on vertebrate tracks from the Cretaceous of Korea, both independently and collaboratively. Almost all researchers from these groups have contributed to this volume. The result has been the naming of five new tetrapod ichnospecies (Fig. 1), adding to the ten previously named.

First record of a complete giant theropod egg clutch from Upper Cretaceous deposits, South Korea

Here, we report the first occurrence of a complete Macroelongatoolithus clutch from outside of China. Excavated from Upper Cretaceous strata of Aphae-do in Shinan-gun, Jeollanam-do Province, South Korea, the clutch of 19 eggs is characterised by large, elongate, symmetrical eggs arranged in a single-layered ring-shaped clutch. Eggs are inclined towards the centre of the 2.3-m diameter clutch, and average 41.17 cm long and 15.58 cm wide. Of the 19 eggs, 8 clearly retain a paired configuration. This specimen represents only the second report of large theropod eggs from South Korea and is the most complete Macroelongatoolithus clutch known from the region to date. Eggshell microstructural features are consistent with Macroelongatoolithus xixiaensis (oofamily Elongatoolithidae), previously known only from Cenomanian strata of southeastern China. This first record of a giant theropod egg clutch, here assigned to M. xixiaensis, extends the stratigraphic and paleogeographic range of Macroelongatoolithus eggs and parent animals to include the Campanian of South Korea.

Time, Space and Structure on the Korea Cretaceous Dinosaur Coast: Cretaceous Stratigraphy, Geochronology, and Paleoenvironments

The stratigraphy, geological ages, and paleoenvironments of the Korea Cretaceous Dinosaur Coast (KCDC) are reviewed and synthesized in order to understand the occurrence and diversity of the vertebrate fossils and track remains in time and space. Various absolute age measurements obtained during the last decade yield new age data to correlate with the dinosaur fossil-bearing Cretaceous deposits in Korea. The radiometric age of the lower (Sindong Group) and middle (Hayang Group) parts of the Gyeongsang Basin (the largest basin of the KCDC) located in the eastern part of the KCDC gives dates ranging from Aptian to Campanian, which is younger than the previous biostratigraphic age estimates, but the results may be influenced by metamorphism. Likewise, radiometric dates from the Cretaceous sequence in the western part of the KCDC give numerical values suggesting a correlation with the Upper Cretaceous Yucheon Group of the Gyeongsang Basin. Dinosaur evidence (e.g., tracks, eggs, bones) along the KCDC is variable in relation to stratigraphy and paleoenvironment. Dinosaur tracks are preserved mostly in stratigraphically higher Cretaceous lake margin deposits, whereas dinosaur bones occur mostly in older Cretaceous floodplain deposits. Most dinosaur eggs are found in Upper Cretaceous deposits, and they occur in floodplain deposits of alluvial fan and meandering river settings. Thus, we conclude that dinosaurs inhabited volcanically influenced, alluvial fan, fluvial plain, and lake margins on the Korean Peninsula throughout the Cretaceous under a semi-arid climate with strong seasonality. The rarer occurrence of dinosaur tracks in older Cretaceous deposits in some basins might be attributed to the limited exposures of lake-margin deposits. It is inferred that the presence of large lakes as water sources, rich vegetation of gymnosperm trees as food, and semi-arid paleoclimatic conditions formed a general landscape and environmental setting favorable for dinosaurs and their preservation in the Cretaceous deposits of South Korea.

Lithographus, an Abundant Arthropod Trackway from the Cretaceous Haenam Tracksite of Korea

Trackways ascribed to Lithographus hieroglypichus and attributed to pterygote insects are described from the Cretaceous Uhangri Formation of Korea. The locality is part of the Haenam Tracksite at the Uhangri Dinosaur Museum Complex, which is famous for dinosaur, pterosaur and bird tracks. This represents the first report of the arthropod trackway Lithographus from the Cretaceous of Korea. The trackways are preserved in cherty mudstones that formed in the margins of an alkaline lake in the vicinity of active volcanoes. Numerous trackways are preserved at a single horizon. This probably reflects a brief period of exposure of balanced-fill lake margin sediments, which provided a window of opportunity for the production and preservation of trackways of insects that inhabited the region rather than a sudden influx of insects into the area related to volcanism and a productivity bloom.

Understanding on the Fossilization of Middle School Students

Experiments to explain fossilization have been introduced in elementary and middle school science textbooks. Most of them have explained the processes by the mold and cast formed by imprint of bivalve or leaf. The processes explained in the textbooks are more similar to that of trace fossil than body fossil, because the external molds from experiment are imprints after the model was taken off. However fossils of the figures in the textbooks are mostly body fossils. Therefore, the students may be willing to equate the experiment process with the fossilization of the body fossils. The misconceptions were confirmed in this study by the questionnaire which asked 9th grade students on this subject. Many students thought that the body fossils were fossilized imprints and the fossils of terrestrial organism were formed on land without transportation, that is, they did not understand well about biostratinomy and crustal movement. The misconception about the environment in which fossils formed was already reported in a survey on the elementary school students, but has not revised until ninth grade. Therefore, to remove the misconception related to the fossilization, the fossil models in the experiments may be replaced by trace fossils, or new experiments for body fossil should be designed.