First Furongian (late Cambrian) trilobites from the Cantabrian Zone (north-western Spain)

Abstract

The first Furongian trilobites are described herein from the Cambrian of the Cantabrian Zone,NWSpain. They were collected during the construction of the “Túnel Ordovícico del Fabar” from the shales of “El Fabar Beds” in the La Matosa member of the Barrios Formation. The assemblage includes the aphelaspidine genus Maladioidella, with a specimen identified as M. cf. colcheni, a species previously known from Sierra de la Demanda (Spain), and possibly Sardinia and Oman. Fragments of an indeterminate olenid trilobite and phyllocarid crustaceans have also been recorded. Based on the acritarch assemblage, these beds are considered as late Jiangshanian or earliest Stage 10 of the Cambrian System. The ichnofossil Cruziana semiplicata has also been collected in the tunnel from the upper part of the Ligüeria Member (Tremadocian) of the Barrios Formation, clearly postdating the occurrence of Maladioidella colcheni, its supposed tracemarker according to some authors. The separate record of both taxa (a Furongian trilobite and a Cambro-Ordovician trace fossil) does not support this statement, so their relationship would be refuted in this case.