A lizard unique to North Korea is the Korean Skink Plestiodon or (Eumeces) coreensis (reptile-stamps.de).
freshwater fish include the Korean Taimen Hucho ishikawai (FishBase)
and a loach Misgurnus
A marine fish known only from North Korea is the goby Gymnogobius bungei (Google
Invertebrates found exclusively in North Korea include the ground beetles Nebria scaphelytra (CAS pdf file) and Synuchus coreanus (p. 5 of landesmuseum.at pdf file), a click beetle Selatosomus grandis (p. 26 of SSNR pdf file), a plant bug Psallus amoenus (Discover Life), the ants Temnothorax cuneinodis (Internet Archive) and Temnothorax michali (p. 9 of nhmus.hu pdf file), and a jumping spider Sitticus penicilloides (Salticidae of the World).
Among over 100 endemic vascular plant species are a pasque flower Pulsatilla nivalis (wildgreen.co.kr), Saxifraga furumii (Univ. Tokyo), a sedge Carex humbertiana (JSTOR), a poppy Papaver coreanum (Species Korea), the Korean Rhubarb Rheum coreanum (Plant Stamps of the World), and a meadow-rue Thalictrum osmorhizoides (wildgreen.co.kr). Although sometimes included in Spiraea, a recent study (Springer Link) suggests that Pentactina rupicola (RBGE) represents a valid endemic genus.
Important ecoregions include the Changbai Mountains Mixed Forest (EoE) and the Central Korean Deciduous Forest (EoE). An overview of North Korea's flora and fauna can be found in its National Biodiversity Strategy and Action Plan (CBD pdf file). A book on the endemic species of Korea can be found at (me.go.kr pdf file). Additional Korean Peninsula endemic species that are shared with South Korea can be found here.