Barremian charophytes from the Maestrat Basin

Abstract

A lower and upper Barremian 690 metre-thick succession composed of freshwater and brackish limestones, marls and clays was measured and sampled in the Maestrat Basin, Eastern Iberian Chain (Castelló, Spain). Thirty-three taxa were identified from charophyte fructifications and thalli, belonging to the three families that coexisted during the Early Cretaceous, i.e. Porocharaceae, Characeae and Clavatoraceae. Up to 25 different Clavatoraceae utricles were identified. This high species richness of clavatoraceans has not been observed elsewhere and sheds light on the role of Iberia, and particularly the Maestrat Basin, as a diversity hotspot for this family during the Barremian. Several of them have been taxonomically revisited, as regards both utricles and thalli. The Echinochara lazarii utricle is reinterpreted as showing bilateral rather than triradial symmetry. Anagenetic evolution within Clavator calcitrapus has been documented and has enabled us to distinguish between two varieties linked by intermediate morphotypes of biostratigraphic and palaeobiogeographic interest. The taxon Clavator grovesii var. jiuquanensis is reported for the first time in the Iberian Chain and in Spain. The structure of Charaxis spicatus is revisited and a new type of cortication is defined, called the double triplostichous cortication, which is unknown in either fossil or extant charophytes. This thallus is found in anatomical connection with Echinochara lazarii utricles, enabling a whole-plant reconstruction of the Echinochara plant. Lastly, new characters were found in Munieria grambastii thalli that confirm the membership of genus Munieria to the clavatoracean charophytes, particularly the calcification pattern of the internodal cell, which recalls that of clavatoroid utricles.