Abstract

An account of the systematics, biostratigraphy, ecological setting and the biogeographic implications of rugose corals from olistoliths of the Cabrieres area is given. Corals of the lower member of the Izarne Formation are dated by conodonts as gronbergi Zone age, and include Lythophyllum sp. indet., Calceola sandalina (Linne), Tryplasma sp. A, Breviphrentis roharti Pedder new species, B. exigua Pedder new species, and Aqishaphyllum sp. A. Corals from the middle member of the formation include Frechocystis pertinax Pedder new genus and species, Calceola sp. undet., Rhizophyllum sp. aff. R. ukalundense Hill and Jell, Tryplasma enorme Pedder new species, Tryplasma sp. A, Breviphrentis sp. A, Platysmatophyllum halleri Pedder new genus and species, Pseudochonophyllum sentum Pedder new species, and Izarneophyllum barroisi (Frech) new genus. No age significant conodont has been recovered from the middle member. However, scutelluid trilobites, which, together with other trilobites, evidently used the underside of Izarne corals for shelter during molting, provide correlation with conodont sequences in the nappe domain to the north and southwest of Cabrieres. From this line of evidence, the middle Izarne coral fauna is deduced to be nothoperbonus Zone age. The association of a variety of benthic trilobites, all with large eyes, provides evidence of a photic zone environment for the middle Izarne corals. Rugose corals from the Izarne Formation belong to the Old World Realm and have nothing in common with similar age Rugosa of the Eastern Americas Realm. This implies that the dissolution of the boundary between these realms, which occurred in the Middle Devonian, did not begin before latest Emsian time.

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