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Regional geological map of the Junggar Basin. a, Geological map of the Junggar Basin, which is a partially enlarged view of the red boxed area of No. ② in Figure 1d,b, Geological map of the Sikeshu sag, which is a partially enlarged view of the red boxed area of No. ① in Figure 1a,c, Stratigraphic histogram of the study area; red box ⑤ is the sampling location d, Location map of the Junggar Basin in China. Red box ② indicates the location of the Junggar Basin e, Field photo of the section of four trees. The fossil sampling location is located in the yellow box of No. 4.
Source publication
Vertebrate fossils are abundant in sandy mudstones of the Cretaceous Donggou Formation in the Sikeshu
area, southern margin of the Junggar Basin, Xinjiang. Here, a few pycnodont remains from the Sikeshu area
are described. Isolated elements are identified as a fragment of vomer and a fragment of prearticular referred
to Xinjiangodus gyrodoides....
Contexts in source publication
Context 1
... we describe a new pycnodont fish of the Late Cretaceous discovered from clastic rock species in the Junggar Basin, western China, which are characterized by their very small size and habitation in freshwater environments. These fossils were found at the Sikeshu section on the southern margin of the Junggar Basin (Figure 1a, b, d), an area that has long formed an assemblage containing a large number of plant, mollusc, and vertebrate remains. These pycnodont fish remains are noteworthy because their fossil scale suggests that they belonged to a juvenile pycnodont fish. ...
Context 2
... is one of the four major basins in China. The planar morphology of the basin is wide in the south and narrow in the north, with an area of 131,794 km 2 (Figure 1 a, d). The overall terrain in the basin is high in the east and low in the west, with an average elevation of approximately 500 m, and the lowest in the Manas Lake-Aibi Lake line, with an average elevation of 200-300 m . ...
Context 3
... Sikeshu sag is located in the southwestern part of the Junggar Basin, with the North Tianshan fault and its tectonic system in the south, the Dalbut fault and the Jairshan tectonic system in the northwest, and the Lianchepaizi uplift in the northeast (Figure 1b). Controlled by the boundary structure, faults developed inside the sag, including the southern margin fault, Gaoquan fault, Aika fault and a series of secondary faults. ...
Context 4
... Mesozoic in the Sikeshu sag and its periphery is relatively complete. Except for the absence of the Upper Jurassic Kalazha Formation, the Triassic, Jurassic and Cretaceous are all developed, which are in contact with the underlying Carboniferous by faults or unconformities ( Figure 1 c and e). Different from the central-eastern segment and the north-western margin of the southern margin, the Permian has not yet been found in the outcrop area of the Sikeshu sag. ...
Citations
... Zhou et al. [162] documented a hitherto unknown pycnodont, Xinjiangodus gyrodoides, which is represented by a fragmentary vomerine and prearticular dentition coming from the sandy mudstones of the Donggou Formation at the southern margin of the Junggar Basin in Xinjiang, China. The exact age of this formation is problematic, with some authors indicating a Coniacian-Santonian age [163] and others restricting it to the Maastrichtian [164]. ...
... The sedimentary environment of the fossiliferous site of this pycnodont is indicative of shallow lake deposits. A characteristic feature of X. gyroides distinguishing it from other pycnodonts is the large spacing between its teeth, as well as the presence of an apical depression on the tooth crowns with radiating wrinkles ( [162], Table 1). An isolated opercular bone was also assigned to this taxon. ...
Pycnodont fishes were a successful clade of neopterygian fishes that are predominantly found in shallow marine deposits. However, throughout their long 180 million year reign (Late Triassic-end Eocene), they made multiple incursions into both brackish and freshwater environments. This fossil record mostly consists of fragmentary dental material, but articulated specimens are known from Early Cretaceous lacustrine localities in Spain. This review article aims to document all non-marine occurrences of Pycnodontiformes throughout most of the Mesozoic and early Paleogene. This review highlights two interesting trends in the history of non-marine habitat colonization by pycnodonts: (1) a huge spike in non-marine occurrences during the Cretaceous; and (2) that most occurrences in non-marine localities occurred at the latest Cretaceous period, the Maastrichtian. The high number of colonization events within the Cretaceous lines up with extreme climatic events, such as high temperatures resulting in high sea levels which regularly flooded continental masses, allowing pycnodonts easier access to non-marine habitats. The increased presence of pycnodonts in brackish and freshwater habitats during the Maastrichtian might have played a role in their survival through the K/Pg extinction event. Freshwater habitats are not as vulnerable as marine ecosystems to environmental disturbance as the base of their food chain relies on detritus. Pycnodonts might have used such environments as a refuge and began to occupy marine waters after the K/Pg extinction event.
