Bairdia sp. A

Fig. 8D

Material examined

USA • 1 complete carapace; Guadalupe Mountains, Williams Ranch Member, Cutoff Formation, Quarry section, sample GM1; Roadian, Middle Permian; MNHN.F. F63422 • 1 complete carapace, 4 valves; same locality as for preceding; Roadian, Guadalupian, Middle Permian; MNHN.F. F63492 .

Remarks

Bairdia sp. A is extremely similar to Bairdia salemensis Geis, 1932 from the Mississippian of Indiana (Geis 1932) that was later considered as a junior synonym of Bairdia permagna Geis, 1932 by Sohn (1960). Sohn (1960) more precisely stated that the type specimens of Bairdia salemensis are young juveniles of Bairdia permagna, although dimensions provided by Geis for Bairdia salemensis are of Lmean =1450 µm, Hmean= 685 µm. In the present analysis, Bairdia sp. A is morphologically closer to specimens considered as young juveniles of Bairdia permagna than to adults and their dimensions are very similar to those reported for Bairdia salemensis with Lmean =1500 µm, Hmean =500 µm. Herein, however, all specimens at hand assigned to Bairdia sp. A are not abundant enough to discuss their ontogenetic development and verify the conspecificity of the species.

Occurrence

Sample GM1, Quarry section, Williams Ranch Member, Cutoff Formation, Guadalupe Mountains, West Texas, USA, Roadian, Middle Permian (this work).