New Material Of The Late Jurassic Lizard From Qingyang,Gansu Province And The Evolution Of Polyglyphanodontidae

Squamates have a long worldwide evolutionary history dating back to the Early Jurassic,or even perhaps to the Late Triassic.At present,knowledge of the fossil record is very incomplete during two significant periods in the evolution of lepidosaurs.One,which is the most important for establishing the interrelationships of the modern groups.In addition to the Middle Jurassic basal episquamate and the Late Jurassic Paramacellodidae gen.et sp.Indet in Xinjiang,two Late Jurassic/Early Cretaceous taxa Jeholacerta formosa and?Conicodontosaurus kanhsienensis.In the Cretaceous,fossil records are more abundant.A new species,Qingyangosaurus yangi gen.et sp.nov.is established based on one compressive but nearly complete skulls and partial postcranial skeleton from the Late Jurassic deposits in Qingyang,Gansu Province.Qingyangosaurus yangi is distinguished from other Polyglyphanodontidae,among which are combination of the following characteristics:Skull subtriangular in outline,deep,anteroposteriorly elongated with slightly tapering snout.Fused premaxilla,frontal and parietal.The lateral margin of frontal is weakly curved.The parietal develops long and radial process,the posterior margin of skull is significantly inverted V shape.Marginal teeth are pleurodont,conical,unicuspid,bluntly pointed,medially recurved,and tightly aligned,parietal foramen located in parietal bone,and Parietal displays a slight surface depression.The prefrontal and postfrontal not in contact above the orbit;contact absent between maxilla and frontal;The jugal lacks a posteroventral process,and the posterior process of jugal gradually narrows dorsally.The postfrontal has a straight lateral margin,medially,the jugal develops anterior and posterior processes.Premaxillary teeth are recurved lingually.The coronoid process is dorsoventrally high,with the dorsal margin slightly backwards.A fusoid foramen is present between the angular and the suprangular.The vertebrae lacks typical procoelous shape of squamates,but it is similar to procoelous.The supratemporal extends to the groove of parietal.Maxillary tooth row is short,extending posteriorly to about one-third of the maxillary ramus.The articular develops a posterior process.The third metacarpal is longer than other metacarpals.A review is provided of Mesozoic squamate fossils in China,including geological age,diagnosis,and research history.Previous studies have reported 26 species of Mesozoic squamates from China.These are Paramacellodidae gen.et sp.Indet;Jeholacerta formosa Ji and Ren,1999;?Conicodontosaurus kanhsienensis Young,1973;Dalinghosaurus longidigitus Ji,1998;Mimobecklesisaurus gansuensis Li,1985;Yabeinosaurus tenuis Endo and Shikama,1942;Teilhardosaurus carbonarius Shikama,1947;Funiusaurus luanchuanensis Xu et al.,2014;Liushusaurus acanthocaudata Evans and Wang,2010;Tianyusaurus zhengi Mo et al.,2009;Liaoningolacerta brevirostra Ji,2005;Xianglong zhaoi Li et al.,2007;Pachygenys thlastesa Gao and Cheng,1999;Anchaurosaurus gilmorei Gao and Hou,1995;Xihaina aquilonia Gao and Hou,1995;Mimeosaurus crassus Gilmore,1943;Priscagama gobiensis Borsuk-Bialynicka and Moody,1984;Pleurodontagama aenigmatodes Borsuk-Bialynicka and Moody,1984;Gobiderma pulchrum Borsuk-Bialynicka,1984;Conicodontosaurus djadochtaensis Gilmore,1943;Chianghsia nankangensis Mo et al.,2012;Isodontosaurus gracilis Gilmore,1943;Adamisaurus magnidentatus Sulimski,1972;Bainguis sp.cf.B.Parvus Borsuk-Bialynicka,1984;Carusia intermedia Borsuk-Bialynicka,1987;Sineoamphisbaena hexatabularis Wu et al.1993.To deal with the conflict between the phylogenies from the molecular and morphological data,phylogenetic analysis is performed with a widely accepted morphological matrix(226 taxa,363 characters),and the choice of the constraints is discussed.The results show that Qingyangosaurus yangi belongs to the Polyglyphanodontidae of the Scincomorpha.Qinyangsaurus and Cherminsaurus are sister groups.The clade of Qinyangsaurus and Cherminsaurus forms the sister group of a clade consisting of Erdenetesaurus and Polyglyphanodon.It represented the earliest fossils of the Polyglyphanodontidae.Biogeography of Asian lizards are compared and analyzed.Geographical distribution of Polyglyphanodontidae is determined,including Central Asia,North America,Mongolia and China.