The early Silurian Chongqing Lagerstätte (middle Telychian) yields exceptionally preserved articulated jawless and jawed fishes. Here, we describe a new eugaleaspiform (Galeaspida, jawless stem-Gnathostomata), Miaojiaaspis dichotomus gen. et sp. nov., from the Chongqing Lagerstätte in Xiushan, Chongqing, China. The new form resembles Tujiaaspis vividus in the short medial dorsal canal, and the presence of the branching ends of the lateral transverse canal. They differ in that T. vividus has highly developed subordinate branches of the sensory canals that form a reticulate sensory canal system, and the median dorsal opening is more elongated. Our phylogenetic analysis recovers M. dichotomus and T. vividus as a monophyletic clade (Tujiaaspidae fam. nov.), which is supported by two synapomorphies: the short medial dorsal canal, and the branching ends of the lateral transverse canal. Tujiaaspidae forms a trichotomy with Shuyuidae and a clade comprising Anjiaspis, Sinogaleaspidae, Yongdongaspidae, and the ‘eugaleaspid cluster’. The sensory canal patterns in galeaspids are compared to show the transformation sequence of the sensory canal system in Eugaleaspiformes.

During the Late Miocene, numerous medium to large-sized herbivores, that resemble the living Ovibos in skeletal morphology, dispersed throughout the Holarctic realm and comprised eleven genera: Lantiantragus, Shaanxispira, Tsaidamotherium, Criotherium, Mesembriacerus, Hezhengia, Urmiatherium, Parurmiatherium, Plesiaddax, Sinotragus, and Prosinotragus. These genera are primarily found in eastern Asia, in which nine genera are found in northern China, as well as in countries in eastern Europe and western Asia. They are distinguished by unique characteristics, including a perpendicular braincase, specialized horn cores, and a robust basioccipital. Previous studies have often classified these ‘ovibovin’ bovids as part of the conventional subfamily/tribe Ovibovinae/Ovibovini, along with extant Ovibos. Nevertheless, an increasing number of studies do not support the monophyly of the subfamily/tribe Ovibovinae/Ovibovini, nor is a close relationship likely between these Late Miocene ‘ovibovin’ bovids and extant Ovibos. Among the eleven genera of ‘ovibovin’ bovids, Plesiaddax, Hezhengia, and Urmiatherium are often considered to have a very close relationship and conventionally form the tribe Urmiatheriini. However, previous phylogenetic analyses do not support the monophyly of Urmiatheriini. This paper presents a summary of the transmutation of the terms Ovibovidae/Ovibovinae/Ovibovini/Ovibovina, the temporal and spatial distribution of the Late Miocene ‘ovibovin’ bovids in Eurasia, the principal characteristics of these taxa, and the previous phylogenetic analyses.

Pantodonta was one of the first groups of eutherians to evolve at the beginning of Cenozoic era, including the largest herbivores at that time. Pantodonta shows considerable diversity during the Paleocene and Eocene, with most of the species having been discovered in Asia and North America. Here, we report on a new pantodont, represented by lower jaws with well-preserved dentition, discovered from the Middle Paleocene Nongshan Formation of the Nanxiong Basin, Guangdong Province, China. Its unique dental and mandibular characteristics distinguish it well from any known Asian pantodont, but are quite consistent with North American taxa, especially Pantolambda and Titanoides. The new specimen is identified as Nanxiongilambda yei gen. et sp. nov., characterized by the combination of the following morphological features: thick and robust mandible with a conspicuous anteroexternal flange, high positioned condyloid process, posteriorly protruding angular process, robust but not elongated lower canines, double-rooted p1, small but distinct talonids on posterior lower premolars, talonids nearly as wide as trigonids on lower molars, and m3 with a well-developed hypoconulid and a distinct entoconid. The new discovery marks the first record of a pantolambdid pantodont outside of North America, suggesting a broader geographical distribution and intercontinental dispersal of this clade during the Paleocene. Considering the more primitive Pantolambda only found from Torrejonian to early Tiffanian NALMA (equivalent to middle-late Shanghuan to early Nongshanian ALMA), which is slightly earlier than Nanxiongilambda (early Nongshanian ALMA), pantolambdids have likely undergone a particular wave of migration from North America to Asia during the Early-Middle Paleocene. Previous researches have suggested that pantodonts had dispersed only from Asia to North America during the Early Paleocene, but our new specimen indicates the biotic dispersal may have occurred in the opposite direction. The new specimen also contributes to the renewal of the evolutionary history of pantodonts and provides further insights into the migration and dispersal of Paleocene mammals.

X-ray computed tomography (CT) has been an important technology in paleontology for several decades. It helps researchers to acquire detailed anatomical structures of fossils non-destructively. Despite its widespread application, developing an efficient and user-friendly method for segmenting CT data continues to be a formidable challenge in the field. Most CT data segmentation software operates on 2D interfaces, which limits flexibility for real-time adjustments in 3D segmentation. Here, we introduce Curves Mode in Drishti Paint 3.2, an open-source tool for CT data segmentation. Drishti Paint 3.2 allows users to manually or semi-automatically segment the CT data in both 2D and 3D environments, providing a novel solution for revisualizing CT data in paleontological studies.