DISCOVERY AND SIGNIFICANCE OF THE RHYNCHONELLID BRACHIOPOD AXIODEANEIA CLARK FROM GUANGXI,CHINA

Axiodeaneia is a rare genus of rhynchonellid brachiopods,initially established by Clark in 1917.It belongs to the subfamily Axiodeaneiinae of the family Rhynchotetradidae and previously included four species,namely Axiodeaneia platypleura Clark,1917,A.anxia Havlicek,1979,A.usheri(Brown,1952), and A.glenparkensis Carter,1988.Since most species of this genus was recorded initially from Tournaisian(basal Carboniferous) deposits of North America,with one exception from Europe,this genus was long considered to be an endemic element of the early Carboniferous brachiopod faunas of North America.In this paper,two species are described from Guangxi in southern China,Axiodeaneia cf.anxia Havlicek,1979 collected from the lower Tournaisian of the Longzao Section of Tiandong County,and A.xui sp.nov.from the uppermost Fammenian(Late Devonian) of the Nanbiancun Section of Guilin.The discovery of these two species in Guangxi indicates that the brachiopod fauna of the late Fammenian to Tournaisian in South China had a close biogeographic relationship with that of North America and Europe and also records an earlier stratigraphic range of the genus,in the Fammenian of Late Devonian.The new species Axiodeaneia xui also provides an important clue to the relationship between Axiodeaneia and Goniophoria,because it is a morphologically intermediate between the two genera.Axiodeaneia xui sp.nov.,or a similar form having an unsupported sessile septalium in the form of slightly converging dental plates, may be a forerunner of Goniophoria,in which development of a ventral median septum supporting the septalium can be observed.