Researchers from the Faculty of Science and Technology of the University of Coimbra (FCTUC) announced the discovery of a fossil in Anadia, in Portugal's Aveiro district, which corresponds to a new species of fern that lived 300 million years ago. The new species has been named Acitheca machadoi, according to SIC Notícias. This find contributes to the understanding of plant evolution during the Carboniferous Period.
Acitheca machadoi is notable for preserving sporangia—the plant's reproductive organs—in three-dimensional detail and still containing spores in situ. "It is an exceptional preservation and rarely found in compressions in which the Carboniferous plant fossils of this region are preserved," stated Pedro Correia, a researcher at the Center for Geosciences of the University of Coimbra. He added that this fossil presents some of the smallest sporangia documented for the genus Acitheca.
The new species is dedicated to geologist Gil Machado, who specialized in Paleozoic palynology. Machado studied the stratigraphy and palynological floras of the Buçaco Carboniferous Basin, including the stratigraphic section where the new fossil was discovered. The scientific article detailing the discovery, titled "A new species of Acitheca (Psaroniaceae, Marattiales) with exceptionally and three-dimensionally preserved sporangia from the Buçaco Carboniferous Basin, western central Portugal," was published in the journal Review of Palaeobotany and Palynology.
Sofia Pereira, a researcher at CGEO and co-author of the scientific work, believes that the small size of the sporangia may correspond to an adaptation to the drier conditions that were present during the Carboniferous Period. "After all, this is one of the adaptations most 'chosen' by plants to face conditions of low water availability, allowing them to conserve water, increase energy efficiency, and facilitate the release of spores," she emphasized. "Although in paleontology we have to wait for the next pieces of the puzzle, there are already several signs of the transition from humid to dry conditions in the fossil plant associations of the Buçaco Carboniferous Basin, reflecting the global climate change that began at the transition from the Carboniferous Period to the Permian Period, and that will mark this last geological period of the Paleozoic," the researchers concluded.
Acitheca machadoi is the third representative of its genus in Portugal and contributes to a relatively low global diversity, with fewer than ten known species. The presence of this new species suggests that its diversity at the global level may be underestimated. This discovery sheds light on the adaptations and evolution of ferns during a time of climatic shifts.
In addition to the find in Anadia, researchers from FCTUC discovered another fossil of a new plant species that is 310 million years old in Fânzeres, Gondomar, in the district of Porto. The fossil, named Palaeopteridium andrenelii, corresponds to a new species of the extinct order Noeggerathiales, a primitive group of vascular plants known as progymnosperms of the division Progymnospermophyta, according to Observador. The research was led by Pedro Correia, in collaboration with Carlos Góis-Marques, a paleobotanist at the University of Madeira.
"This discovery allowed researchers to learn how these primitive plants evolved and reproduced during the Carboniferous Period, at the end of the Paleozoic Era," said Pedro Correia, according to Observador. Palaeopteridium andrenelii is the second representative of Noeggerathiales discovered in the Portuguese Carboniferous. The first was the Noeggerathialean Rhacopteris gomesiana, described by geologist Carlos Teixeira in the 1940s in the Douro Coal Basin.
Until recently, Noeggerathiales were considered a group of plants with uncertain taxonomic classification that existed during the Carboniferous and Permian Periods, about 359 to 252 million years ago. Recent discoveries have allowed this primitive group to be classified as heterosporous progymnosperms, a sister group to the seed-producing pteridophytes that coexisted with the Noeggerathiales. Despite the recent discovery of complete specimens found in Permian formations in China, the Noeggerathiales group remains highly artificial, as noted by researchers.
"This discovery suggests that the Noeggerathiales were possibly more diverse than we thought, and their paleontological association with megaesporangia brings new knowledge about the evolution of these enigmatic plants, as well as their paleoecology," stated Góis-Marques, according to Observador. He described the finding as "a singular find," noting that "fossils of plants belonging to the extinct Noeggerathiales are rare in Europe and America, especially due to their distinct ecological requirements."
Coauthor of the scientific article, Góis-Marques concluded, "This new species reinforces what was already known: the paleobotanical record of the Portuguese Carboniferous presents a high degree of endemism of international relevance," as reported by Observador.
The article was written with the assistance of a news analysis system.