A new occurrence of the angiosperm genus Montsechia in upper Albian strata from the Maestrazgo Basin (Utrillas Group, Eastern Iberia)

The fossil plant Montsechia vidalii is well known from the Barremian of Spain and was identified as an early angiosperm. It is interpreted as an aquatic plant that thrived in freshwater wetlands, with very limited or no connection with the marine realm, and under a seasonal semi-arid tropical climate.This research paper reports the youngest known occurrence of the genus Montsechia, in upper Albian amber-bearing strata from the Maestrazgo Basin (NE Spain), demonstrating the broad adaptation and evolutionary stability of the genus during the Early Cretaceous. The studied upper Albian material is identified as M. aff. vidalii since it differs from the Barremian Montsechia vidalii in having a medium-thick cuticle and paracytic stomata on the abaxial leaf cuticle. In addition, associated seeds, fruit and pollen grains have been found. The fruit is indehiscent and ascidiate in shape with a single seed inside. The seeds are orthotropous and have been identified as Spermatites sp. The pollen grains were found adhering to a sterile twig. They are monocolpate and assigned to Transitoripollis sp., reinforcing the early angiosperm hypothesis.Unlike its Barremian relative, the late Albian M. aff. vidalii developed under predominantly arid conditions in a fore-erg setting characterised by an interaction of aeolian dune and tide-dominated coastal deposits that reflected general eustatic rise conditions of the mid-Cretaceous. In this regard, the studied remains were found as a minor component of a supratidal coastal plant association largely dominated by conifers of the genera Frenelopsis and Dammarites.