Water from the rock: Ancient aquatic angiosperms flow from the fossil record.

The world of 120 million years ago was one of dynamic biological processes. During that time the flowering plants emerged as the dominant global floristic element, a transformative event that ultimately altered the character of the entire planet. Understandably, the rapid rise of angiosperms has intrigued paleoecologists and evolutionary biologists, who have strived to elucidate underlying explanations for their successful radiation. Lamented by Charles Darwin as “an abominable mystery” (1), the abrupt appearance of angiosperms and their sudden burst of diversification in the fossil record continues to captivate contemporary plant systematists, who have sought a solution by incorporating massive amounts of DNA sequence data in comparative phylogenetic studies of extant species. However, despite extensive technological advances in genetics, genomics, and bioinformatics, which have revolutionized plant research over the past decades, our comprehension of life on earth during such ancient times continues to rely primarily on one data source: the fossil record. In PNAS, Gomez et al. (2) uncover an important clue to Darwin’s mystery by their analyses of Monteschia vidalii, an enigmatic plant fossil from Barremian deposits in Spain. Their reinterpretation of these fossils provides a new perspective that allies Monteschia not only with the angiosperms, but specifically with extant members of the order Ceratophyllales, a group of considerable interest in debates concerning the origin of flowering plants. The characterization of these early plants as highly specialized aquatics also offers novel interpretations regarding the ecological characteristics of early angiosperms. Prior ecological interpretations of early Cretaceous environments have been based primarily on terrestrial plant species, which vastly dominate the paleobotanical record. In some fossil floras, aquatic angiosperms do not appear until the middle to late Albian stage (3) and these typically depict floatingleaved plants similar in habit to that of the modern order Nymphaeales, which resolves phylogenetically at or near the base of the angiosperm tree of life. Because floatingleaved species are thought to represent an intermediate evolutionary stage between terrestrial plants and true hydrophytes, one