A new exceptionally well-preserved basal actinopterygian fish in the juvenile stage from the Upper Triassic Amisan Formation of South Korea.

The study of the large paraphyletic group of extinct 'palaeoniscoid' fishes has shed light on the diversity and evolutionary history of basal actinopterygians. However, only a little ontogenetic information about 'palaeoniscoids' is known because their records in the early stages of development are scarce. Here, we report on a growth series of 'palaeoniscoids' in the juvenile stage from the Upper Triassic Amisan Formation of South Korea. Fourteen specimens, including five counterpart specimens, represent a new taxon, Megalomatia minima gen. et sp. nov., exhibiting ontogeny and exceptional preservation with the eyes possibly containing the crystalline lens, the otoliths, and the lateral line canals without covering scales. This discovery allows us to discuss the adaptations and evolution of basal actinopterygians in more detail than before. The otoliths in situ of Megalomatia support the previous interpretation that basal actinopterygians have a sagitta as the largest otolith. The trunk lateral line canal, which runs under the scales instead of passing through them, represents a plesiomorphic gnathostome trait. Notably, the large protruded eyes suggest that Megalomatia probably has binocular vision, which would have played a significant role in targeting and catching prey with the primitive jaw structure. In addition, the firstly formed skeletal elements such as the jaws, pectoral girdle, and opercular series, and the posteroanterior pattern of squamation development are likely linked to the adaptation of young individuals to increase their viability for feeding, respiration, and swimming.

Miocene Dipteronia (Sapindaceae) samaras from South Korea and their biogeographical implications.

Dipteronia, now endemic to East Asia, was widely distributed in North America during the Paleogene; however, its fossil records in Asia are scarce and none are of the Neogene. Here, we report the first Neogene Dipteronia samaras from South Korea. The more complete fossil records suggest that Dipteronia possibly originated in either Asia or North America and that its two known lineages have different geographical histories. The Dipteronia sinensis lineage was established in Asia and North America in the Paleocene and reached its maximum range in the Eocene, followed by stepwise range contraction and extirpation in North America, South Korea, and southwestern China, finally becoming endemic to central China. In contrast, the Dipteronia dyeriana lineage might have been restricted to southwestern China, where it originated, indicating historical confinement. The current restricted distribution of Dipteronia possibly resulted from its evolutionary deceleration in a constantly changing environment.

Fossil fruits of Firmiana and Tilia from the middle Miocene of South Korea and the efficacy of the Bering land bridge for the migration of mesothermal plants.

Determining whether the high-latitude Bering land bridge (BLB) was ecologically suitable for the migration of mesothermal plants is significant for Holarctic phytogeographic inferences. Paleobotanical studies provide a critical source of data on the latitudinal positions of different plant lineages at different times, permitting assessment of the efficacy of the BLB for migration. Here we report exceptionally preserved fossils of Firmiana and Tilia endochrysea from the middle Miocene of South Korea. This represents a new reliable record of Firmiana and the first discovery of the T. endochrysea lineage in the fossil record of Asia. The occurrence of these fossils in South Korea indicates that the two lineages had a distribution that extended much farther north during the middle Miocene, but they were still geographically remote from the BLB. In light of the broader fossil record of Asia, our study shows that, in the middle Miocene, some mesothermal plants apparently inhabited the territory adjacent to the BLB and thus they were possibly capable of utilizing the BLB as a migratory corridor. Some other mesothermal plants, such as Firmiana and the T. endochrysea lineages, however, are restricted to more southern regions relative to the BLB based on current fossil evidence. These lineages may have been ecologically unable to traverse the BLB, which raises questions about the efficacy of the BLB as a universal exchange route for mesothermal plants between Asia and North America during the middle Miocene.

A new species of fossil Calosoma (Coleoptera: Carabidae) from the Geumgwangdong Formation (Early Miocene), South Korea.

In this paper, a new fossil species of Calosoma (Coleoptera: Carabidae) from the lower Miocene Geumgwangdong Formation, Pohang City, South Korea, is described. Compared with other Miocene Calosoma fossils, Calosoma kimi sp. nov. exhibits different characteristics in particular interval connection and scale patterns on the elytra. It is the first fossil Calosoma recorded from the Korean Peninsula. However, the taxonomic position of C. kimi sp. nov. within Calosoma is not clear at present though it is probably related to the complex of the subgenera Australodrepa, Calodrepa, and Calosoma.

Involucre fossils of Carpinus, a northern temperate element, from the Miocene of China and the evolution of its species diversity in East Asia.

East Asia has long been recognized as a major center for temperate woody plants diversity. Although several theories have been proposed to explain how the diversity of these temperate elements accumulated in the region, the specific process remains unclear. Here we describe six species of Carpinus, a typical northern hemisphere temperate woody plant, from the early Miocene of the Maguan Basin, southwestern China, southern East Asia. This constitutes the southernmost, and the earliest occurrence that shows a high species diversity of the genus. Together with other Carpinus fossil records from East Asia, we show that the genus had achieved a high diversity in East Asia at least by the middle Miocene. Of the six species here described, three have become extinct, indicating that the genus has experienced apparent species loss during its evolutionary history in East Asia. In contrast, the remaining three species closely resemble extant species, raising the possibility that these species may have persisted in East Asia at least since the early Miocene. These findings indicate that the accumulation of species diversity of Carpinus in East Asia is a complex process involving extinction, persistence, and possible subsequent speciation.

New fossils of Elateridae (Insecta, Coleoptera) from Early Cretaceous Jinju Formation (South Korea) with their implications to evolutionary diversity of extinct Protagrypninae.

Two new genera and species of Elateridae, Megalithomerus magohalmii gen. et sp. nov. and Koreagrypnus jinju gen. et sp. nov., are described based on two pairs of fossils from the late Early Cretaceous Jinju Formation in Jinju City, South Korea. Both Megalithomerus and Koreagrypnus represent the youngest occurrences of an extinct elaterid subfamily, Protagrypninae. Megalithomerus magohalmii is the largest known fossil elaterid. These newly described elaterids provide a better understanding of the morphological diversity and occurrence of Protagrypninae through geologic time.