Research On The Trilobites From The Guanshan Biota In Yunnan Province

The Guanshan Biota are preserved in the Wulongqing Formation(Cambrian,Series 2,Stage 4)and are a typical Burgess Shale-type Lagerst?tte.Therefore,the Guanshan Biota are slightly younger than the well-known Chengjiang Biota(Cambrian,Series 2,Stage 3)and older than the Burgess Shale Biota(Cambrian,Miaolingian,Wuliuan).The Guanshan Biota fill in the evolutionary gap between the Chengjiang Biota and the Burgess Shale Biota.There are diverse kinds of fossils found in the Guanshan Biota and the Guanshan Biota provide precious materials for research on the origin and evolution of early life.Besides,trilobites are the most diverse and numerous among all the arthropods from the Guanshan Biota.Based on the previous work,we conducted a systematically study on the trilobites from the Guanshan Biota,and also redefine and redescribe some palaeolenid trilobite taxon.The validity of Palaeolenus douviliei and Megapalaeolenus deprati,the type species of the biozones in the Wulongqing Formation,has been controversial over a few decades.To clarity this controversy,we conducted a geometric morphometric analysis of cranidial shape on 60 palaeolenid specimens from three sections of the Guanshan Biota from the Wulongqing Formation,Yunnan Province,South China.We show that cranidia of M.deprati and P.douvillei occupy distinct regions of morphospaces and that P.douvillei and P.“lantenoisi” occupy the same region of morphospace.Combined with qualitative observation on the thorax and the morphological and ontogenetic analysis of P."lantenoisi" and P.douvillei specimens,P.“lantenoisi” is then considered a junior synonym of P.douvillei.Whereas,M.deprati is still considered valid and can be distinguished from P.douvillei by its rounded glabella,longer palpebral lobes,shorter ocular ridges,and more developed posterolateral projections.Moreover,its pleural spines are more curved,and pleural lobes are markedly wider than P.douvillei.Both the quantity and the diversity of the trilobites in the Guanshan biota are higher than those in the Chengjiang biota.This paper demonstrates that the trilobites in the Guanshan biota have greater research potential from the aspects of taxon controversy,non-mineralized parts preservations and ontogeny.