Abstract:
Changshaconus carinata Zhu 1985 a Middle Devonian conulariid from Hunan Province southeastern China is redescribed and refigured．Changshaconus probably was most closely related to Reticulaconularia Babcock et Feldmann 1986 which occurs in the Devonian of South Africa and the Lower Devonian of Bolivia New Jersey and Quebec．Changshaconus and Reticulaconulariadiffer from all other conulariids in having transverse ribs and interspace ridges that are arranged in such a way as to form a reticulate facialornament．Additional characteristics of Changshaconus and Reticulaconularia include （1） interruption plus alternate arrangement and interlocking of the transverse ribs in the corner sulcus；（2） sharp bending of the transverse ribs toward the aperture on the shoulders （edges）of the corner sulcus；（3） midline of the four faces marked by an external ridge．Together these three additional similarities are uniquelyshared with Climacoconus Sinclair 1952 and can be interpreted as evidence that Changshaconus Reticulaconularia and Climacoconuswere members of a single monophyletic taxon that excluded all other conulariids．This group in turn may have been most closely relatedto Notoconularia Thomas 1969and Paraconularia Sinclair 1952 both of which exhibit interruption plus alternation and interlocking ofthe transverse ribs in the corner sulcus．
