Rugosochonetidae (Brachiopoda, Chonetidina) from the Carboniferous of the Cantabrian Mountains (N Spain)

A new Changhsingian (Late Permian) Rugosochonetidae (Brachiopoda) fauna from the Zhongzhai section, southwestern Guizhou Province, South China

“…On the other hand, Racheboeuf (2000, p. 405) considered them to be moulds of the 'spine canals' inside the posterior margin; in other words, these so-called spines were not seen by Racheboeuf as true external spines. According to Racheboeuf & Garcia (1996), these 'spine canals' (or canal apertures) are quite common among many chonetid genera (e.g., Dunbar & Condra 1932, Cvancara 1958, Maxwell 1964, Archbold 1983, Xu & Grant 1994, Racheboeuf et al 2004, Martínez-Chacón & Winkler 2005 and may have acted as support space for the hinge spines at the posterior margin of the valve. Therefore, differing from other true hinge spines, which extend into and beyond the external surface of the shell, the unfledged spines do not extend outside, they may merely have existed either in some ancestral chonetid genera or may be a feature characterizing the juvenile stage of some chonetid genera.…”