“Blisters” in a Famennian cyrtospiriferid brachiopod from Hunan (South China)

Some Chinese Famennian cyrtospiriferid brachiopods from Hunan Province (South China), identified by Hou Hong-Fei as Hunanospirifer wangi Tien, 1938, have some internal growth called “blisters” in both valves. These unusual internal structures have been observed in transverse serial sections. “Blisters” are located on the inner surface of the dorsal and/or ventral valves, and sometimes on the dental plates or hinge line. The size and volume of these “blisters” are variable. They were formed during the life of the brachiopod by an elevation of outer epithelium above the inner surface of the valves or above other internal structures. They always appear closed to the interior of the brachiopods and also often to the outside as well.

According to one of us (D.B.), “blisters” in H. wangi seem not to be a generic or a specific characteristic, because their occurrence and location are always variable and not symmetrical. Rather, their formation seems to be connected with environmental factors (physical or organic). The absence of fossil traces inside the “blisters” favours a reaction of organic origin. There are important similarities between “blisters” observed in H. wangi and “Ziegler's Blisters” described for the first time and illustrated by Boucot and Johnson (1979) in pentamerid brachiopods.