Fossil Morphology And Evolutionof Of Three Types Of Arthropods In Myanmar Amber

The Mesozoic Cretaceous is an important period in the evolution of the earth.Many important geological events occurred during this period,which had a profound influence on the continental distribution pattern and the evolution of terrestrial organisms.Arthropods,as one of the evolutionarily successful metazoan groups,are more diverse,abundant and distributed than other groups.Molecular evidence suggests that most extant arthropods underwent rapid differentiation during the Cretaceous,but scarce fossils records make it difficult to prove this conclusion.Burmese amber is a type of fossil formed in the midCretaceous by the resin secreted of Pinaceae and Taxodiaceae plants,then buried in the ground after nearly 100 million years of mineralization.A large number of arthropod fossils preserved in Burmese amber inclusions are key fossil materials for the study of the evolution and diffusion of arthropods in the middle Cretaceous.Through the fine morphological study of fossils,this paper identifies 3 families(including 1 new subfamily),3 genera(2 fossil genera and 1 extant genus)and 3 species of arthropod fossils,which are belonging to Archaeidae(Eomysmauchenius cretaceominimus sp.nov.),Bostrichidae(Alitrepanum aladelicatum gen.et sp.nov.)and Staphylinidae(Priochirus trisclerite sp.nov.).Our research also discusses the evolutionary radiation and paleoclimate adaptation of three groups.Our specific research includes the following:1.The present study reports a fossil of Arachnids,which was included in the family Archaeidae based on its strongly raised head and elongated chelicera.By compiling a list of fossils in the Northern Hemisphere and analyzing archaeid fossils in the Cretaceous,we discovered that the radiation time of diffusion was earlier than the middle Cretaceous,supporting the conclusion that the dispersal and distribution of archaeids was related to the division of Pangaea and the division of east and west Gondwana.2.The present study reports three similar fossils of Coleoptera,which are belonging to the Bostrichidae,then we establish the first extinct subfamily Alitrepaninae subfam.nov.In this study,we also found fossil evidence related to the habitat of the auger beetle,which proved that it had a fire preference as early as the Cretaceous.This behavior may have been an adaptation to the frequent wildfires of that time.This supports the hypothesis that the higher resin production in the Cretaceous is related to the ancient highly destructive fires.3.The present research identifies one fossil species of Staphylinidae,which belongs to a new subgenus Eopriochirus subgen.nov.established based on previous studies.By comparing the microscopic morphology with fossils and extant species of osoriines all over the world,we found that this group has long-term morphological stasis.The flat body and continuous existence of microhabitats,such as deciduous leaves and rotten wood,may have helped osoriines avoid morphological selection.4.We investigate the current distribution and climate of the above three types of arthropods and reconstruct Myanmar’s mid-Cretaceous environment as a tropical climate with frequent fires.Moreover,according to the living environment of extant archaeid,we concluded that there may be a partial rainforest environment in the Burmese forest.This paper presents a study of arthropod fossils from northern Myanmar in the midCretaceous.Specifically,we identify and describe three families and three genera of arthropods.Our research focuses on the morphology and evolution of these fossils,shedding light on the response of spiders,insects,and other arthropods to the terrestrial ecological revolution during the Cretaceous period.Our findings provide important fossil support for subsequent research on the overall radiation evolution of arthropods,and also offer new insights into the paleoenvironment and paleoclimate of Myanmar during the midCretaceous.