NUEVOS PORÍFEROS DE LA FORMACION SAN JUAN (ORDOVÍCICO), PRECORDILLERA ARGENTINA

Marcelo G. Carrera

Abstract


"Newly collected Ordovician sponges from the San Juan Formation allowed recognition of a new species and four genera described for the first time in South America. The new species Incrassospongia ramis was collected in the upper levels of the San Juan Formation (Early Llanvirnian) at cerro La Chilca section. The new species is characterized by upward-radiating skeletal fibres bridged by irregularly distributed monoclonid dendroclones. The fibres are irregular and commonly bifurcated. The absence of horizontal concentric elements clearly differentiates the new species from the type species. Allosacus sp. was collected from the middle part of the Formation (Early Arenigian) at Gualcamayo section and also from the upper levels at the cerro Viejo section (Early Llanvirnian). This discoidal genus was differenciated from related anthaspidellid genera due to the presence of spongocoel and arrangement of radial canals. The trabs are composed by a single row of smooth monoclonid dendrocJones. Eospongia sp. was recovered from the middle part of the Formation (Early Arenigian) at Niquivil section. This obconical genus is characterized by large vertical canals, a
very small spongocoel and long dendroclone spicules with enlarged ends. Lissocoelia sp. was collected in the upper levels of the San Juan Formation (Early Llanvirnian) at Villicum range. The Argentinian material shows small and irregularly distributed dendroclones in the sponge surface and a moderately irregular distribution in the sponge walls. Two or five intraparietal spicules separate conspicuous and irregularly distributed radial canals."

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