PRELIMINARY RESEARCHES FOR MIXOSAURID FOSSILS FROM MIDDLE TRIASSIC GUANLING FORMATION IN PANXIAN OF GUIZHOU
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Abstract:
In the summers of 2001 and 2002 we went to the Xingyi district of southwestern Guizhou to explore the Triassic marine vertebrates and got in Xingyi an information occurred in neighboring Panxian the saurian and fish fossils. Because of the inconvenience of the traffic we did not go to Panxian to do field exploring, and therefore we did not se at that time the saurian and fish specimens of that county. Soon after we collected in Nanjing a few ichthyosaur fossils of small size, which were said to come from the Yangjuan village of Panxian, only then did we realize that the saurian fossils in Panxian were the Middle Triassic mixosaurid, hence different from the Late Triassic Keichousaurus from Xingyi. In the July of 2004 we went to the Yangjuan village of Panxian in an attempt to confirm the locality and horizon of the mixosaurid fossils that we collected in Nanjing; besides, in Panxian we saw some mixosaurid and fish fossils just discovered from the dark carbonaceous and mud limestone of the Middle Triassic Guanling Formation. During this trip we also found out that the mixosaurid fossils of Guanling Formation in Yangjuan village of Panxian, Guizhou Province, were found during the opening years of the present century by a group of peasants with rich experience in digging the keichousaur and fish fossils, which were from Dingxiao of Xingyi. Through fossil dealers the mixosaurid fossils from the Yangjuan village had been partially delivered to the hands of some palaeontologists. During our studying of the mixosaurid fossils from Yangjuan village of Panxian we saw one after another that Jiang et al. published from 2003 to 2006 4 articles on the the mixosaurid fossils found in late Early Anisian conodont-zone of Nicoraella germanicus in Yangjuan village of Panxian, Guizhou Province. According to our understanding, around Yangjuan village there are many localities that have yiedled the mixosaurid fossils, we have not explored and studied in detail these fossil one by one, therefore we do not know for certain that they all came from the same fossil bed, or different fossil beds, we conjecture that it is very possible that they all come occurred from a group of beds from the late Early Anisian to the Ladinian in age. Recently we collected again in Nanjing two mixosaurid fossils from another locality, Xindian of Puan County, about 15 km east of Yangjuan village. In the last few years we have seen in Nanjing of Jiangsu and in Guizhou more than thirty mixosaurid specimens dug out in Yangjuan area of Panxian, most of them are complete skeletons and some very beautifully preserved. According to our examination of these mixosaurid fossils we inspected in Nanjing, collected from Yangjuan area of Panxian, they represent three species of Mixosaurus, one of them is new. These mixosaur fossils from Panxian are of very important palaeontological interest because they may fill up some deficience in the finding and studying of Mixosaurus for more than a century ever since it was named by Baur in 1887 and may deepen our understanding of their morphology and taxonomy.
