https://repository.kopri.re.kr/handle/201206/5503 2026-04-04T18:24:04Z https://repository.kopri.re.kr/handle/201206/6401 Title: Cambrian Stem-group Cnidarians with a New Species from the Cambrian Series 3 of the Taebaeksan Basin, Korea Authors: Park, Tae-Yoon S.; Lee, Dong-Jin; Choh, Suk-Joo; Hong, Jongsun; Michael Engelbretsen; Yong-Yi Zhen; Woo, Jusun; Kim, Ji-Hoon Abstract: Five species, Lipopora lissa Jell and Jell, 1976, Lipopora daseia Jell and Jell, 1976, Tretocylichne perplexa Engelbretsen, 1993 from Australia, Cambroctoconus orientalis Park, Woo, Lee, Lee, Lee, Han and Chough, 2011 from China, and Cambroctoconus kyrgyzstanicus Peel, 2014 from Kyrgyzstan, belonging to the Cambrian stem-group cnidarians have been documented in the fossil record. Cambroctoconus coreaensis sp. nov., interpreted here as a stem-group cnidarian, from the Seokgaejae section in the Daegi Formation, Taebaek Group (Cambrian Series 3), Taebaeksan Basin, central-eastern Korean Peninsula, has a slender cup-shaped skeleton. A cladistic analysis produced 21 most parsimonious trees, which invariably placed the six stem-group cnidarians below the crown-group, but their relationships within the stem-group are unresolved. Nine out of the 21 trees suggest a monophyletic relationship for the Cambrian stem-group cnidarians, whereas in six other trees a monophyly of Cambroctoconus and Tretocylichne appeared as the sister-group to the crown-group cnidarians with Lipopora at the most basal branch. This result may reflect the fact that crown-group cnidarians evolved in the Precambrian, and suggests that the diversity of stem-group cnidarians was a result of an independent radiation in the Cambrian. 2016-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/6367 Title: Furongian (late Cambrian) trilobites from the Asioptychaspis subglobosa Zone of the Hwajeol Formation, Korea Authors: Park, Tae-Yoon S.; Kim, Ji-Hoon Abstract: The Hwajeol Formation of the Taebaek Group, Korea extends from the Jiangshanian Stage to the Cambrian Stage 10 in age. The lowermost part of the formation is known to contain the Asioptychaspis Zone which is closely correlated to the Asioptychaspis-Tsinania Zone of North China. This study documents silicified trilobites from the lowermost part of the Hwajeol Formation in the Sagundari section. Asioptychaspis subglobosa occurs throughout the interval, hence the biozone is renamed as Asioptychaspis subglobosa Zone in this study. The Asioptychaspis subglobosa Zone of the Hwajeol Formation yields xx polymerid species belong to xx genera. Among other species, the occurrence of the genus Caznaia is stratigraphically significant because two biozones were set up in Australia on the basis of the Caznaia species: i.e., the Rhaptagnostus clarki patulus-Caznaia squamosa and Rhaptagnostus clarki prolatus-Caznaia sectatrix zones in ascending order. Due to the lack of globally-occurring trilobites and conodonts, the international correlation of these biozones of Australia has been rather dubious. The occurrence of Caznaia from the Asioptychaspis subglobosa Zone of Korea indicates that the Rhaptagnostus clarki patulus-Caznaia squamosa and Rhaptagnostus clarki prolatus-Caznaia sectatrix zones of Australia are correlated to the Asioptychaspis subglobosa Zone of Korea and the Asioptychapis-Tsinania Zone of North China. 2015-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/6404 Title: Post-embryonic development of the Early Ordovician (ca. 480 Ma) trilobite Apatokephalus latilimbatus Peng, 1990 and the evolution of metamorphosis Authors: Park, Tae-Yoon S.; Kim, Ji-Hoon Abstract: In many marine invertebrates metamorphosis entails a shift from a free-swimming larva to a benthic juvenile or adult. However, how the metamorphosis-entailing "indirect development" in arthropods arose from direct-developing ancestor is poorly understood. Trilobites left a rich fossil record, and some trilobite lineages had a metamorphosis undergoing early developmental stage, termed the "asaphoid protaspis"-stage, providing a good opportunity to elucidate the rise of indirect development. Among others, the Ordovician representatives of Remopleuridioidea are known to possess a highly bulbous "asaphoid protaspis," while the Furongian (Late Cambrian) remopleuridioidean genus Haniwa did not possess it. Here we show the post-embryonic development of the remopleuridioidean trilobite, Apatokephalus latilimbatus, from the Tremadocian (485.4 Ma？477.7 Ma) Dongjeom Formation, Korea. The post-embryonic development of A. latilimbatus contains a free-swimming "commutavi protaspis" (a term replacing "asaphoid protaspis"). Interestingly, the earlier protaspid stage shows more similar morphology and size to the meraspis than the commutavi protaspid stage does. This indicates that the commutavi protaspid stage was intercalated into the ancestral direct development as a specialized stage for a better dispersal, and thus the "commutavi protaspis" of A. latilimbatus represents the initial phase of the evolution of indirect development. The duration of the free-swimming phase became longer in more derived remoplueridioidean trilobites, implying that the intercalated free-swimming strategy became emphasized during subsequent evolution. The morphological gap between the commutavi protaspis and the subsequent earliest meraspis provides a convincing case for the "selective independence" of developmental stages, explaining the various morphologies of commutavi protaspides in many trilobite lineages. 2015-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/6488 Title: Ontogeny of a New Species of the Cambrian Series 3 (Middle Cambrian) Trilobite Genus Liostracina Monke, 1903 from North China and the Taxonomic Position of the Superfamily Trinucleoidea Authors: Park, Tae-Yoon S.; Choi, Duck K.; Kang, Imseong; Kim, Ji-Hoon 2014-01-01T00:00:00Z