Ovetian cryptic archaeocyaths, lower Cambrian from Las Ermitas (COrdoba, Spain)

摘要

The record of the archaeocyathan community supports the conclusions that these cryptic organisms were pioneers in crevices into neoproterozoic andesites in Las Ermitas (Pedroche Formation, Ossa-Morena, Spain) during Ovetian time. The different filling phases and the cavitydwelling biota are described in VENNIN et al. (2003). The archaeocyaths and calcified microbial organisms are major components; we describe here the archaeocyathan taxa from the crevices and breccias. The poriferan cryptic community is composed by coelobiontic forms in life position, including Dokidocyathus avesiculoides, Nochoroicyathus sp., Erismacoscinus sp., Neoloculicyathus magnus, Protopharetra gemmata and Protopharetra sp. They were attached to hard substrates, such as calcified microbial or archaeocyathan skeletons during the first phases of filling the cavities and crevices. The last filling phases include common debris skeletons of chancelloriids, hyoliths, brachiopods, trilobites, and reworked Okulitchicyathus andalusicus. The immediately overlying levels of the cavities are breccias, calcimicrobial limestones and lutites with carbonate nodules. The archaeocyathan diversity is high in these platform sediments, 41 taxa in total. We describe here also species from those breccias too, including Okulitchicyathus andalusicus, Rotundocyathus sp., Leptosocyathus? sp., Urcyathus? sp. and the new Nochoroicyathus simoni. The Ovetian cryptic archaeocyathan community from Las Ermitas is composed of Dokidocyathus and Protopharetra, which mark the first occurrence of cryptic taxa in Atdabanian 1. Neoloculicyathus and Erismacoscinus are common to others cryptic communities of Atdabanian 1 in the Siberian Platform, but Okulitchicyathus was described from the Tommotian. Therefore this Spanish cryptic archaeocyathan assemblage is different from others described from the Atdabanian and these are not obligate cryptobionts because the same taxa appear in the platform sediments outside the cavities. Forty species in total have been described in the reef complex from Las Ermitas. The cryptic community represents eleven per cent, and the mound community twenty three per cent of the diversity; but in other facies the archaeocyaths represent higher diversity, such as the fifty eight per cent in the nodular and interbiohermal facies, but only eight percent in the breccias.