Devonian brachiopods of the Cantabrian Mountains (Northern Spain). 12) Ferronirhynchia new genus, an Upper Emsian rhynchonellid (Trigonirhynchiidae)

Resumen

The taxonomic status of the subfamily Trigonirhynchiinae is discussed based on the morphological features, together with the geographic and the stratigraphic distribution of the type genus Trigonirhynchia Cooper. The new genus, Ferronirhynchia n. gen., including the type species F. pulgari n. sp., is proposed. The new taxon, close to Trigonirhynchia, occurs in upper Emsian beds of the Moniello Formation, in Asturias, serotinus/patulus conodont zones, Faunal Intervals 14 to 16a. The ontogeny and palaeoecology of F. pulgari are analyzed. Growth of the new species is bicyclic. Juvenile forms are low and biconvex displaying sharp commissures. Adult forms are high, dorsi-biconvex, geniculate, with abrupt anterior and lateral margins. Ferronirhynchia pulgari is an opportunistic species, often found in paraautochtonous rhynchonellid assemblages that occur in quiet and muddy deposits formed below the wave-base level near or in reefal environments in the Cantabrian platfom. Shells of the new species supported a variety of small epizoans, commensalists or mutualists, mostly reticulate bryozoans, serpulid and other tubeworms, and auloporids. This life habit favoured the epizoans to escape from burial in muddy bottoms.