Researchers from the University of La Laguna, in collaboration with researchers from the University of Madeira and the Teruel-Dinópolis Paleontological Foundation, have published in a recent article from the magazine Review of Paleobotany and Palynology the discovery of cardon fossils (Euphorbia canariensis L.) in a life position. These remains, found in the municipality of Güímar, and belonging to stems of succulent plants, were buried 312,000 years ago by materials expelled by the ancient Cañadas Building, a volcano that occupied the center of the island of Tenerife and suffered explosive eruptions throughout its existence.
These remains are a global rarity because, lacking woody tissue, their potential for fossilization is lower. Thus, the only similar reported case is that of a cactus found in Texas (USA) and preserved in Cretaceous-age sediments.
The preservation of the fossilized cardon stems is excellent, due to the interaction of the ash that buried them with water, which preserved epidermal structures and cyathia (inflorescences). The latter is also unusual in the fossil record, given their ephemeral nature and their limited production to certain times of the year. Thanks to the preservation of the flowers, the authors of the study were able to determine that the eruption of the Cañadas Edificio occurred in spring.
However, this is not the only information provided by the study of the remains. From the time of the eruption to the present day, the vegetation in the area where they were found has changed: from a cactus scrubland with elements of thermophilic forest to a sweet spurge scrubland. The former plant community is currently found at an altitude of approximately 500 meters (except in cases where basaltic substrates are present and the altitude decreases), while in the past it was found at around 300 meters. This change is due to the modification of the habitat after the eruption: from a basaltic substrate that supported a cactus scrubland, to a salic substrate that favors the establishment of a sweet spurge scrubland.
The results of this work not only allow us to open a window into past ecosystems and infer the changes that occurred, but also to understand the response of species to disturbances, something of paramount importance in the current context of climate crisis and loss of biodiversity.
However, the outcrop where the fossilized stems are located is in an area lacking any protection measures, and is threatened by the construction of a future wind farm, meaning its disappearance could be imminent, despite its natural, cultural and scientific value.
The study also makes proposals for its protection and enhancement, including the creation of a paleopark, like the one on Santa Maria Island in the Azores, the designation as a Natural Monument or the implementation of land stewardship.
This paleontological site was the subject of the doctoral thesis of María del Cristo Velasco Flores, a predoctoral researcher at the University of La Laguna and one of the authors of the article. Other signatories affiliated with the Canary Islands university are: Cristina González Montelongo, Ana Santos, Penelope Cruzado, María Candelaria Martín Luis y Carolina Castillo.
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