New fossil notostracans (Branchiopoda, Notostraca) from the Lower Cretaceous of Inner Mongolia, China

Nototracans have lived on Earth for over 350 million years, yet limited species records and poor specimen preservation have significantly impeded our understanding of their early evolutionary history. Herein, we supplement the information of a known species and report a new species, Weichangiops trangularis Yang and Hong, 1980 and Weichangiops squamosus sp. nov., from the Lower Cretaceous Yixian Formation in Duolun, Inner Mongolia, China. The diagnosis characters of Weichangiops Yang and Hong, 1980 and W. trangularis were revised based on the new well-preserved specimens. These newly discovered fossil specimens allow for a detailed summary of morphological characteristics in Notostraca, with a systematic review of features observed in Cretaceous lineages. Given the relatively rarity of Cretaceous notostracan fossils, these findings not only expand the known species diversity of this period but also provide valuable insights into the early evolutionary processes of Notostraca.