Jeong Yul Kim

Cretaceous Nonmarine Trace Fossils from the Hasandong and Jinju Formations of the Namhae Area, Kyongsangnamdo, Southeast Korea

Nonmarine strata of the Cretaceous Hasandong and Jinju formations of the Sindong Group of the Namhae area, Kyongsangnamdo, southeast Korea, contain relatively diverse and abundant ichnofaunas including domichnia, fodinichnia, pascichnia, and repichnia. These ichnofaunas are systematically described herein and three ichnocoenoses, namely the Skolithos, Palaeophycus, and Chondrites ichnocoenoses, are defined based on their paleoenvironmental occurrence. The Skolithos ichnocoenose characterizes tabular laminated sandstone facies deposited on fluvial channel levées. It is dominated by infaunally produced ichnotaxa, particularly Skolithos magnus Howell, Planolites montanus Richter and Chondrites isp. type A, with reduced numbers of Skolithos verticalis (Hall) Taenidium barretti (Bradshaw) and rare examples of Circulichnus montanus (Vyalov), Cochlichnus anguineus Hitchcock, Helminthopsis abeli Książkiewicz, Helimthopsis hieroglyphica Wetzel and Bromley, Laevicyclus isp., Planolites beverleyensis (Billings), Skolithos isp., Spirodesmos isp., Thalassinoides suevicus (Rieth), and rhizoliths. The Palaeophycus ichnocoenose characterizes floodplain environments and occurs in purple mudstones and associated massive sandstone facies of crevasse-splay deposits and dark gray to green shale facies of abandoned channels. Palaeophycus tubularis Hall and Planolites montanus Richter are the most characteristic ichnotaxa, while Beaconites coronus (Frey, Pemberton and Fagerstrom), Planolites annularius Walcott, Skolithos magnus Howell, Thalassinoides paradoxicus (Woodward), and sauropod and ornithopod tracks also occur but in reduced numbers. The Chondrites ichnocoenose occurs in dark gray to black mudstones deposited in marginal lacustrine environments. It is dominated by Chondrites isp. type B. with associated Beaconites antarcticus Vyalov, Helminthopsis hieroglyphica, Palaeophycus tubularis, Skolithos magnus, Taenidium barretti, and Torrowangea rosei Webby. The three ichnocoenoses recognized herein cannot be satisfactorily assigned to currently defined nonmarine ichnofacies, suggesting that existing models of such ichnofacies are in need of additional refinement.

A Paradise of Mesozoic Birds: The World's Richest and Most Diverse Cretaceous Bird Track Assemblage from the Early Cretaceous Haman Formation of the Gajin Tracksite, Jinju, Korea

More than 2,500 well-preserved bird tracks associated with theropod and sauropod tracks are recorded from a dense assemblage in lacustrine deposits of the Early Cretaceous Haman Formation of the Gajin area, Jinju, Korea. These tracks are preserved in the recently constructed Fossil Heritage Hall at the Gyeongsangnamdo Institute of Science Education. Bird tracks are attributed to Ignotornis gajinensis ichnosp. nov., Koreanaornis hamanensis, Goseongornipes markjonesi, and ?Aquatilavipes. Like G. markjonesi, I. gajinensis is a semi-palmate bird track, similar to Hwangsanipes (ichnofamily Ignotornidae) with a postero medially directed hallux and characterized by interdigital angles between digits II and III larger than III and IV. However, Hwangsanipes is a larger morphotype than Ignotornis with a more pronounced semipalmate web. I. gajinensis has associated arcuate to semi-circular, double-grooved, or paired impressions resulting from spoonbill-like feeding behavior. Similar rare but more linear traces occur in one Ignotornis specimen from the Cretaceous of Colorado. The Gajin site represents a record of the worlds most-dense assemblage of bird tracks (up to ∼600 per m2) at a single locality and provides striking evidence of the diversity of avian ichnotaxa during the Cretaceous. The Gajin tracksite provides new insight into the morphology of four of the eight ichnogenera known from the Cretaceous of Korea. The Goseongornipes sample is the largest and best-preserved available. In the case of Ignotornis, feeding traces shed new light on behavior and paleoecology of the trackmakers, which appear to have been remarkably convergent with modern shore birds.

In the Footprints of Our Ancestors: An Overview of the Hominid Track Record

Hominid footprints are particularly appealing and evocative of the living activity of our ancestors. The most famous and oldest (Late Pliocene, ca. 3.7 Ma) hominid footprints, from Laetoli in East Africa, have been attributed, with some uncertainly, to genus Homo or Australopithecus. The African track record also yields Early Pleistocene (∼1.5 Ma) tracks attributable to Homo erectus. The only well-documented Middle Pleistocene tracks (age ∼325,000-385,000 yrs) are reported from Italy and presumably represent a pre-Homo sapiens species. The oldest Late Pleistocene tracks (∼117,000 yrs), from southern Africa, may represent modern humans. However, the majority of Late Pleistocene sites are European, associated with caves in Romania, Greece, France and elsewhere, where hominid track preservation is often of high quality. Dates range from ∼10,000 to ∼62,000 BP Cavesite mammal tracks are almost exclusively those of carnivores, thus representing a distinctive underground ecology. Late Pleistocene open air sites are reported from widely scattered locations in Africa, Turkey, Tibet, Korea, Australia and even in the New World (Chile, Argentina and Mexico). Early to Middle Holocene sites (> ∼4,000 yrs BP) mainly occupy riparian, lacustrine, estuarine and littoral settings where the ichnofaunas are dominated by ungulates and shorebirds. Among these sites from England, Nicaragua, Argentina and Mexico and the United States, a few have been described in some detail. Younger Holocene sites are frequently associated with specified cultural periods (e.g., Neolithic, Bronze Age) or specific indigenous cultures, where supplemental archeological evidence may be directly associated with the footprint evidence. At most surficial and some subterranean hominid tracksites, mammal and/or bird tracks are quite common and of use in creating a paleoecological picture of local faunas. The global distribution of human and hominid tracks is consistent with body fossil evidence and the record of archeological, cultural artifacts. However, in a few cases tracks suggest colonization of certain regions (Tibetan Plateau and the New World) earlier than previously thought. Tracks also give clues to behavior, age and health status of the trackmakers.

Unusual Didactyl Traces from the Jinju Formation (Early Cretaceous, South Korea) Indicate a New Ichnospecies of Dromaeosauripus

New didactyl dinosaur tracks from the fine-grained sandstone of the Early Cretaceous Jinju Formation, Namhae area, Korea, are herein described as Dromaeosauripus jinjuensis ichnosp. nov. A trackway about 4.3 m long is composed of 12 consecutive didactyl traces. The tracks average about 9.3 cm long and 6.8 cm wide. Pace, stride, and pace angulation are 40 cm, 80 cm, and 175°, respectively. D. jinjuensis is a small didactyl track characterized by slender digit impressions, very narrow divarication angle between digits III and IV, digit III slightly longer than IV, and sharp claw impressions. D. jinjuensis measurements differ significantly from D. hamanensis in length (only 60% of the latter), width (81%), length/width ratio (0.72), and digit thickness (55%). The didactyl tracks are tentatively interpreted to be formed by a small dromaeosaurid walking bipedally on a lake margin. D. jinjuensis represents the oldest theropod dinosaur tracks described in the Cretaceous of Korea and the second ichnospecies of Dromaeosauripus. It suggests more diversity and wider stratigraphic and paleogeographic distribution of dromaeosaurids. The track morphology may also indicate a more digitigrade gait.

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.

New Sauropod Tracks (Brontopodus pentadactylus ichnosp. nov.) from the Early Cretaceous Haman Formation of Jinju Area, Korea: Implications for Sauropods Manus Morphology

New sauropod tracks are described herein as Brontopodus pentadactylus ichnosp. nov. from the Early Cretaceous Haman Formation of Jinju area, Korea. B. pentadactylus is characterized by a medium gauged trackway with wide pentadactyl manus tracks revealing hitherto unreported morphology. Thus, B. pentadactylus provides new insight into the morphology of the fleshed-out manus of sauropods showing that, unlike most semi-circular manus tracks that lack discrete digit traces, some indicate trackmakers with clearly differentiated, well-defined, and very wide manus digits. Manus tracks sometimes appear as tridactyl impressions that appear outwardly rotated at right angles to the midline of the trackway. This track morphology appears to reflect greater weight distribution on the outer, postero-lateral part of the manus. The pes is elongate, pentadactyl, outwardly rotated, and typical of Brontopodus. The manus pes heteropody ratio is about 1:2. These sauropod tracks are associated with thousands of bird footprints in a lakeshore paleoenvironment.

Hominid Ichnotaxonomy: An Exploration of a Neglected Discipline

Although more than 60 ancient hominid track sites ranging in age from 3.7 million to less than 500 B. P. are recorded from all continents except Antarctica, no ichnotaxonomic names have ever been formally proposed for hominid tracks. There is no prohibition to the naming of fossil footprints of species that created tracks and trackways similar to those of living species. On the contrary, there is precedent for the naming of ichnotaxa corresponding to the dominant extant vertebrates classes: mammals = Mammalipedia and birds = Avipeda. The hominid track site sample includes only about a dozen sites where footprint preservation is good enough to show details of diagnostic foot morphology and typical trackway morphology. We infer that the Acahualinca Footprint Museum site in Nicaragua represents the most important ancient hominid track site that combines accessibility, a large sample of well-preserved trackways and reliable dating. For this reason, we select the Nicaraguan tracks as the type sample for the new ichnotaxon Hominipes modernus ichnogen., and ichnsp. et ichnosp. nov., which we infer to represent fully modern Homo sapiens. Our preliminary investigations of other track sites suggest that the majority also yield H. modernus. However, at many sites preservation is insufficient to make an ichnotaxonomic designation at the species level or to infer that the trackmaker was H. sapiens. Thus, at many sites including the famous Laetoli site, we apply the more general label of Hominipes isp. indet.

Preliminary Report on Hominid and Other Vertebrate Footprints from the Late Quaternary Strata of Jeju Island, Korea

Numerous footprints attributable to hominids, artiodactyla, proboscidea, carnivores, and birds have been preserved in the Late Quarternary strata of Jeju Island, Korea, which is composed of volcaniclastic sediments deposited in a shoreline environment. The hominid footprints are 12–26 cm long and 6–12 cm wide and are characterized by impressions of medial arch, heel, and ball. These are considered to have been made by at least nine humans of different sites. The artiodactyl footprints are up to 8 cm in length and are characterized by impressions of paired hooves. The diverse range of footprint sizes indicate herds of artiodactyls, composed of juvenile, young, and adult. The footprints attributable to proboscideans are characterized by large circular tracks about 40 cm in diameter. The carnivore footprints are generally characterized by impressions of pads and toes. Diverse bird footprints are recognized on the basis of size, length/width ratio, interdigital angles, curvature of digits, and the presence or absence of web and hallux traces. Fish trails, diverse invertebrate trace fossils, and body fossils are also observed. These fossils extended the knowledge of their rarely reported geographic distribution throughout the world and also enable the paleoenvironment and paleoecology of the strata to be interpreted.

A New Semi-Palmate Bird Track, Gyeongsangornipes lockleyi ichnogen. et ichnosp. nov., and Koreanaornis from the Early Cretaceous Jindong Formation of Goseong County, Southern Coast of Korea

Well-preserved semi-palmate bird tracks and small wading bird tracks from the Early Cretaceous Jindong Formation of Deokmyeongri, Hai-myeon, and Naesanri, Donghae-myeon, Goseong County, South Gyeongsang Province, southern coast of Korea, are herein described as Gyeongsangornipes lockleyi ichnogen. et ichnosp. nov. and Koreanaornis hamanensis, respectively. Gyeongsangornipes lockleyi is a small asymmetrical, strong mesaxonic bird track, about 31–32 mm long and 40–41 mm wide, without a clear hallux impression. Divarication between digits II and III is much larger than that between digits III and IV. Webbing is clearly preserved, and the web between digits II and III is smaller than that between digits III and IV, which shows strong asymmetry of web development. Two different-sized Gyeongsangornipes lockleyi appear to suggest two different-size classes of web-footed birds. Koreanaornis hamanensis is a small sub-symmetrical wading bird track, about 26–28 mm long and 29–39 mm wide, without clear hallux impressions. The divarication between digits II and III (59°–66°)°) is larger than that between digits III and IV (44°– 58°). Divarication between digits II and IV is 103°–123°. Length of digit III (26–28 mm) is longer than those of digits II and III (about 18 mm). These new records shed light on patterns of bird track diversity and abundance in the Cretaceous of Korea and document a diverse avian fauna that flourished during the Cretaceous.

The Smallest Dinosaur Tracks in the World: Occurrences and Significance of Minisauripus from East Asia

We review the status of the distinctive ichnogenus Minisauripus based on more than 80 well-preserved tracks comprising a minimum of 50 trackways from two localities in China and five in Korea. The tracks, attributed to theropod dinosaurs, have been assigned to two ichnospecies, M. chuanzhuensis and M. zhenshounani, based on Chinese specimens. Until recently, the known range of foot lengths was 1.5–6.0 cm, indicating a diminutive track-making species. However, newly discovered Minisauripus tracks from the Haman Formation in the Changseon region of Korea are as short as 1.0 cm. Most remarkably, a few, provisionally also labeled cf. Minisauripus, are reported as large as 16–20 cm, potentially adding unprecedented new data to the previous record. The larger tracks suggest that all the small tracks pertain to juveniles and not a small, distinct species as previously inferred. Tracks with foot lengths of only ∼1 cm suggest that individuals hatched from very small eggs. The fact that such tracks are abundant in fine-grained, lake-margin facies argues for the importance of suitable preservational conditions in recording the activity of small trackmakers. Thus, inferences about dinosaur population structure, growth rates, and other biological and ecological phenomena, based on the absence of small dinosaur tracks, should be made with caution.