The Morphological,phylogenetic And Ecological Studies Of Anuran Fossils From The Early Cretaceous Of Jiuquan Basin

As a highly specialized vertebrate,the extant anura are distributed in other continents except Antarctica.Their skeletons are slender and difficult to preserve,so the fossil record of anurans are relatively rare compared to other vertebrates.Mesozoic anuran fossils in China are only recorded in northeastern China.Based on a well-preserved partial skeleton,a new archaic frog,Gansubatrachus qilianensis gen.et sp.nov.is described from the Early Cretaceous Zhonggou Formation of Jiuquan Basin,Gansu Province,northwestern China.Through a detailed comparative study with other Mesozoic Anuran fossils,Gansubatrachus qilianensis has a following unique combination of characteristics: skull width wider than length;robust and nonbifurcated alary process of the premaxilla;present palatine;large fontanelle between paired frontoparietals;paired nasals meeting in the front half along the midline;paired vomer,with a dentigerous portion bearing 6—10 teeth arranged in a single row;V-shaped parahyoid;present columella;paired sphenethmoids;atlas with type II cotyles;imbricate neural arch;eight presacral vertebrae;separate ribs present on presacral II-IV;unexpanded sacral diapophyses;arciferal pectoral girdle;short and stocky scapula,traight leading edge of the scapula,the anterior of which is overlapped medially with the clavicle;tibiofibula is longer than the femur.Based on the published morphological characteristic matrix,and synthesize the characteristics of current new materials,the phylogenetic analysis suggested that the phylogenetic position of Gansubatrachus qilianensis is classified as a member of Lalagobatrachia.At the same time,the residual soft body traces on the fossil material is supposed to be the eggs are preserved in the specimens of.Gansubatrachus qilianensis,providing important reproductive characteristics of the Cretaceous anura.Considering the juvenile stage of skeletal development preserved on the fossil specimen,Gansubatrachus qilianensis is an juvenile but sexually mature anura,providing direct evidence that sexual maturity is earlier than the skeletal maturity.Based on the skeleton measurement data of 62 extant anurans and 14 fossil materials,the habitat and movement ability of extinct species were judged by discriminant analysis,and it was speculated that Gansubatrachus qilianensis was a arboreal anuran with good jumping ability,and can adapt to the dry and wet alternating ecological environment during the late Early Cretaceous in Jiuquan Basin.The present fossil record is the first anuran fossil in Northwest China,and its discovery not only enriches the diversity of the Early Cretaceous anuran fossils in Asia,but also fills the gap in the late Early Cretaceous anura fossils in Asia.