Cyrtospiriferid (Spiriferida) brachiopods from the lower Famennian recovery interval of Central Armenia: insights on biotic interactions and "blisters"

The lower Famennian of Central Armenia, which is essentially composed of mixed carbonate-siliciclastic sediments that accumulated on a shallow water platform, yielded a fauna abundant in brachiopods. In order to contribute to the assessment of the diversity in the Famennian recovery interval in this area, two cyrtospiriferid species, Cyrtospirifer sp. C and Pseudocyrtiopsis areniensis n. sp., are described and illustrated. The examined material has been collected from the Aramazdospirifer orbelianus-Tornatospirifer armenicus Brachiopod Assemblage Zone (coeval to the Palmatolepis crepida Conodont Zone) of three distinct localities (Ertych, Djaravank and Noravank). Among those two species, the former is hereby ascribed to the genus Cyrtospirifer Nalivkin in Fredericks, although the micro-ornament on our specimens differs from those described in other Cyrtospirifer representatives. The presence of Cyrtospirifer sp. C in this brachiopod Zone supports the assertion previously made by the present authors that the genus Cyrtospirifer persisted during the early Famennian in the Lesser Caucasus. The new species Pseudocyrtiopsis areniensis represents the first report of the genus Pseudocyrtiopsis Ma & Day not only in the South Armenian Block but in the entire North Gondwanan margin. This study also includes a discussion on biotic interactions between spiriferides and other organisms, notably cornulitid tubeworms. Moreover, numerous "blisters" are documented in one of the representatives of Cyrtospirifer sp. C.