Lack of diagnostic characters in fossils is a widespread issue in palaeontology. Although Kachin amber (∼100 Ma) is yielding exceptional specimens, a major proportion of low preservation fossils are disregarded. In flat-backed millipedes (Polydesmida), this issue is critical as only two species are identified out of hundreds of reported fossils. With the popularisation of micro-tomography and synchrotron-based micro-tomography for palaeontology, it is important to assess their strengths in investigating difficult and low-preservation specimens. We report its success in capturing fully intact gonopods from two fossils of low preservation. Both specimens belong to the same new genus Dalocarinatus gen. nov., but represent two species: D. luxuriosus sp. nov. and D. inopinatus sp. nov. They are the oldest and definitive fossil representatives of the group Dalodesmidae, they also offer a glimpse of their presence on Burma Terrane, expanding their current-day geographical distribution, which is restricted to past Gondwanan regions.
The Hwanggangri–Taebaeksan district, a major metallogenic province of the Korean Peninsula, hosts W–Mo, Fe–Mo, and Zn-Pb systems formed during Jurassic to Paleogene magmatic–hydrothermal activity. We establish a district-scale chronology by integrating zircon U–Pb ages of ore-related granitoids with 40Ar/39Ar ages of hydrothermal muscovite and phlogopite and Re–Os ages of molybdenite. Late Cretaceous granitoids in the Hwanggangri district cluster at 96–86 Ma, whereas magmatism in the Taebaeksan district ranges from ca. 95 Ma to a Paleogene event at ca. 53 Ma, suggesting a general eastward-younging tendency. At Geumseong, duplicate molybdenite Re–Os ages of 185.9–186.6 Ma date the upper calcic-skarn molybdenite generation and reveal Jurassic Mo mineralization within a composite system that also records Cretaceous magmatic–hydrothermal activity. An early ca. 95 Ma W–Mo event at Imog preceded the principal regional W–Mo stage at ca. 93–87 Ma. Younger mineralization includes Fe–Mo systems at ca. 82–80 Ma, Zn-Pb systems at ca. 76–72 Ma, and localized Paleogene W–Fe mineralization at ca. 50 Ma. The age relationships indicate broad temporal coupling between magmatism and mineralization, although offsets vary among deposits and chronometers. The compiled record defines a regional shift from intrusion-proximal W–Mo/Mo mineralization to magnetite-skarn Fe–Mo and carbonate-hosted Zn-Pb systems, followed by localized Paleogene reactivation, and provides a temporal framework for metallogenic interpretation and exploration.
