DEVONIAN SPORE ASSEMBLAGES FROM NORTHWESTERN GONDWANA: TAXONOMY AND BIOSTRATIGRAPHY

Devonian spores from 16 subsurface successions in Saudi Arabia and North Africa are systematically documented to characterize assemblages for the northern margin of western Gondwana. The taxonomic study provides the identification and description for 205 spore taxa and forms the basis for a refined biostratigraphy and palaeogeography. Most species are illustrated by multiple specimens to document morphological variation and the effects of taphonomy. Numerous species have considerable morphological variability and require examination of larger populations to become fully understood. These spores show intergrading morphological variation and were grouped into morphons. Although a majority of spore species were previously described, many others are new and endemic to north-western Gondwana. Forty-two species (Acinosporites tristratus, Alatisporites? trisacculus, Biornatispora elegantula, B. microclavata, Brochotriletes crameri, B. tenellus, B. tripapillatus, Camarozonotriletes asperulus, Chelinospora carnosa, C. condensata, C. densa, C. laxa, C. vulgata, Coronaspora inornata, Cristatisporites streelii, Cymbosporites variabilis, C. variegatus, C. wellmanii, Cyrtospora tumida, Diaphanospora milleri, Dibolisporites tuberculatus, D. verecundus, Dictyotriletes hemeri, D. marshallii, Elenisporis gondwanensis, Emphanisporites laticostatus, E. plicatus, Geminospora convoluta, Grandispora maura, Granulatisporites concavus, Hystricosporites brevispinus, Raistrickia commutata, R. jaufensis, Retusotriletes atratus, R. celatus, Samarisporites tunisiensis, Verrucosisporites nafudensis, V. onustus, V. stictus, Zonotriletes brevivelatus, Z. rotundus and Z. venatus), five Varieties (Cymbosporites stellospinosus var. minor, C. variabilis vars variabilis, densus and dispersus, and Dictyotriletes biornatus var. murinatus) and seven combinations (Ambitisporites asturicus, Camarozonotriletes retiformis, Cristatisporites reticulatus, Cymbosporites ocularis, Dibolisporites gaspiensis, Grandispora stolidota and Jhariatriletei emsiensis) are newly proposed. As the reference spore zones usually used and defined in Euramerica are not all recognized in the Gondwanan coeval sections, a new biostratigraphical scheme based on the own characteristics of the spore assemblages described here is proposed. It consists of nine assemblage zones, nine interval zones and one acme zone spanning from the upper Pragian to lower Frasnian.