An almost complete Nothosaurus specimen is described in particular from the Upper Member of the Guanling Formation (Pelsonian, middle Anisian, Middle Triassic) of the Xinmin District, Panxian County, Guizhou Province, Southwestern China. The specimen provides new information on the postcranial osteology of the species. The diagnosed features of the species are revised by the following characters: four premaxillary fangs followed by one small conical premaxillary tooth and five to six small maxillary conical teeth followed by paired maxillary fangs, no posterior process in the interclavicle, four carpals, four sacral vertebrae and hyperphalangy in both manus and pes. In some aspects of its postcranial morphology, GMPKU-P-3014 appears to approach Lariosaurus more closely than Nothosaurus, such as no posterior process in the interclavicle, four carpals, four sacral vertebrae and hyperphalangy in both manus and pes, which provides the important characters to reevaluate the phylogenetic relationships of Nothosaurus and Lariosaurus within the Sauropterygia. GMPKU-P-3014, GMPKU-P-1080 and IVPP V 14294 are different from all other nominal species of Nothosaurus by their size, dentition and the skull future pattern. In addition they have the most similar shape and important proportions of the skull, as well as the same location and stratigraphic level. Thus, they are the same species and indicates that N. rostellatus is a junior synonym of N. yangjuanensis and should be abandoned.

The conodonts biostratigraphy from the Upper Member of the Guanling Formation to the basal Yangliujing Formation in Yangjuan-Chupiwa Section was re-analysed and the conodont Neogondolella constricta cornuta, Neogondolella constricta longa, Neogondolella constricta balkanica, Neogondolella alpina alpina, Neogondolella cf. Neogondolella acuta, Paragondolella excelsa, Paragondolella torna?sis were described. Based on the stratigraphical distribution and morphological variations of these conodonts, five conodont zones were re-established and the relevant biostratigraphic comparisons were made. The results reveal that: 1) From the Upper Member of the Guanling Formation to the basal Yangliujing Formation, five conodont zones can be investigated. In ascending stratigraphical order, they are Nicoraella germanica Zone (the bottom undefined), Nicoraella kockeli Zone, Neogondolella bifurcata Zone, Neogondolella constricta Zone, and Neogondolella constricta cornuta Zone (the top undefined); 2) These conodont zones are comparable to the same-named conodont zones of the Upper Longtou Formation at Qingyan Section (platform-margin slope) and of the Guandao wedge at Guandao (2) Section (basin-margin facies) in Guizhou Province, and these conodonts are also present in the ammonoid binodosus Zone, trinodosus Zone, and reitizi Zone in the West Tethys; 3) It further proves that the studied strata can be considered as the Pelsonian-Illyrian substages of the Anisian stage (Middle Triassic), not going into the Ladinian of the Middle Triassic.

A new species of Qianichthyosaurus Li, 1999 from the Zhuganpo Member of the Falang Formation (Ladinian, Middle Triassic), Wusha Town, Xingyi City of Guizhou is described here, namely Qianichthyosaurus xingyiensis sp. nov. The recognition of the new species revises the diagnosis of the genus: tooth size relative to the skull width slightly below 0.1; ulna peripheral “shaft” notched or largely reduced; hindlimb nearly equal or longer than forelimb; tibia peripheral “shaft” notched or largely reduced. Qianichthyosaurus xingyiensis sp. nov. differs from the type species in having relatively longer snout (snout length/skull length over 60%); humerus radial facet being prominently larger than ulnar facet; unenclosed obturator foramen on pubis; fibula posterior process on the posterior margin and the ischium sub-triangular lacking shaft. The new species is stratigraphically older than Q. zhoui, the specimens of which were exclusively known from the Wayao Member of the Falang Formation (Carnian, Late Triassic). Along with askeptosaurid thalattosaur Anshunsaurus and shastasaurid ichthyosaur Guizhouich- thyosaurus, the occurrence of Q. xingyiensis sp. nov. in Xingyi Fauna suggests a closer relationship between Xingyi Fauna (late Ladinian, Middle Triassic) and Guanling Biota (Carnian, Late Triassic).

The present study is based on ammonoids collected from the strata above the ammonoid Trachyceras multituberculatum zone of Wayao Member of “Falang Formation” (Late Triassic) at the Niubudai Section in Luoping County, Eastern Yunnan Province. Eight species of four genera, including one conform species and three indeterminate species were recognized, among which Trachyceras aonoides, Simonyceras simonyi are firstly found in China. According to their assemblage and stratigraphic distribution, two ammonoid zones were recognized in ascending order: Trachyceras aonoides Zone, Austrotrachyceras triadicum Zone, corresponding to the middle-late Early Carnian of Late Triassic in age.

Here the true tailbends are reported in two complete skeletons of Guanlingsaurus from the late triassic of Guizhou Province, southwestern China after accurate observations, measurements and comparisons with Ichthyosaur of early jurassic. They have acquired the wedge-shaped centra and the angles in these tailbends are around 15°while those in jurassic types are around 60°. This study shows for the first time that wedge-shaped tailbend centra already existed in merriamosaurs as early as late triassic time, probably being a result of coevolution between ichthyosaurs and the environment. The occurrence of the true tailbend connected triassic and jurassic ichthyosaurs that used to be considered as separate groups in previous literature. The present finding also suggests the monophyly of ichthyopterygia.

The Panxian Fauna is mainly characterized by well-preserved and articulated skeletons of Middle Triassic (Anisian) marine reptiles with high diversity, associated with abundant invertebrate fossils, such as bivalves, brachiopods as well as cephalopods, and some as yet undescribed taxa. Stratigraphically, it is occurred at the Upper Member of the Guanling Formation, ascribed to the conodont Nicoraella kockeli Zone, which indicates that the age of this fauna is Pelsonian (Middle Anisian). Therefore, the Panxian Fauna is older than the Grenzbitumenzone fauna at Besano/Monte San Giorgio area of Italy/Switzerland border (near Anisian/Ladinian boundary), and represents the oldest marine reptile fauna of the Middle Triassic throughout the world. Such a rich, diversified and perfectly preserved paleontological assemblage with the exact stratigraphic horizon and definitive age not only provides abundant materials for exploring the taxonomy, evolution, and origin of the marine reptiles, but also has great significance for developing the study of paleoecology and biogeographic provincialism. So far, five genus and five species, including the oldest mixosaurid ichthyosaurs, the oldest lariosaurs and the first true aquatic protorosaur(Dinocephalosaurus orientalis), have been reported from the Panxian Fauna. Most of them are adapted to epicontinental environment or shallow sea, and show a strong West Tethyan affinity. The strata bearing the Panxian fauna consists of four or five tuff beds and seven volcanicities were recognized, which might be caused the extinction of these marine reptile animals directly.