Recent advances of trilobite research in Korea: Taxonomy, biostratigraphy, paleogeography, and ontogeny and phylogeny

Trilobites are among the most diverse and abundant fossil groups in Korea and occur in the Cambrian-Ordovician Joseon Supergroup of the Taebaeksan Basin. The Cambrian-Ordovician trilobites of the Joseon Supergroup have been intensively studied during the last quarter century, with emphasis on taxonomic revision, refining biostratigraphic zonation, paleogeographic implications, and ontogeny and phylogeny. A total of 243 species have hitherto been known to occur in the Joseon Supergroup of the Taebaeksan Basin: 118 and 110 species were reported in the Taebaek and Yeongwol groups, respectively, whilst 15 species were described from the Mungyeong Group. Contrasting trilobite faunal contents of the Taebaek and Yeongwol/Mungyeong groups resulted in two separate biostratigraphic schemes for the Cambrian-Ordovician of the Taebaeksan Basin: 22 biozones or fossiliferous horizons were recognized in the Taebaek Group; 19 zones were established in the Yeongwol Group; and four biozones were known from the Mungyeong Group. These trilobite biozones of the Taebaeksan Basin can be correlated well with those of North China, South China, and Australia. The distribution of some of the Cambrian and Ordovician endemic trilobites and the detrital zircon spectra of the pertinent areas suggest that the Sino-Korean Craton was located at the margin of east Gondwana and was separated from the South China Craton by an oceanic basin, and that the Taebaeksan Basin was a part of an epeiric sea in east Gondwana. Focus of the ontogenetic research of Korean trilobites was initially on the Cambrian trilobites from the Machari Formation of the Yeongwol Group, and then, was shifted to the silicified sclerites dissolved out of the carbonates of the Guzhangian to Tremadocian strata of the Taebaek Group, which have played a crucial role in resolving the trilobite phylogeny. Still, much of the carbonate strata of the Taebaek Group containing silicified trilobites has remained unstudied. The future ontogenetic research on the trilobites from the middle Cambrian (Cambrian Series 3) and the Furongian strata of the Taebaek Group would significantly contribute to elucidating the muddled trilobite phylogeny.