Discovery of two new species of Cretaceous conifers reveals mysteries about plant evolution

MARE researcher Mário Miguel Mendes is part of the international group of researchers who discovered fossils of two new species of conifers from the Lower Cretaceous, around 100 million years old, in the Juncal region of Leiria. ​

One of the species was named Classostrobus doylei, in honour of James Doyle, a professor at the University of California. The discovery, made in 2022 and recently published in the journal Cretaceous Research, was made from a male cone, a structure in conifers responsible for dispersing pollen.

In a statement to Greensavers, Mário Miguel Mendes explained that the identification of Classostrobus doylei was possible thanks to the association with pollens from the species Classopollis triangulus. This link is significant, since this type of pollen has never been linked to a specific structure before. The researcher also highlighted the complexity of identifying plants from pollen, since transport during fossilisation means that it is rare to find a complete plant with all its reproductive and vegetative structures preserved.

The second species, Frenelopsis callapezii, was named in honour of Pedro Callapez Tonicher, a professor at the University of Coimbra, and will soon be published in the International Journal of Plant Sciences. This species was identified on the basis of the morphology of the branches and stems, which stood out for the absence of long trichomes, typical of other species in the Frenelopsis genus.

By analysing these fossils, the researchers concluded that the Lower Cretaceous flora in the Juncal region was dominated by conifers and ferns, with the presence of angiosperms such as Saportanthus. The predominance of Classopollis pollens also suggests that the region had a humid climate, with shallow river environments, as well as drier habitats dominated by conifers.

Mário Miguel Mendes also mentioned that some of the region's plants have not yet been correctly classified and that the X-ray microtomography technique could provide more information. In addition, the amber fragments that were also found are still being studied in collaboration with the Federal University of Rio de Janeiro, which could provide new information about life in the region. 

Another interesting aspect of the discovery is the identification of Classopollis pollen grains in the digestive system of Aboilus amplus, a now extinct insect. This suggests that the conifers of the Cheirolepidiaceae family may have been pollinated by insects, a rare phenomenon among conifers, which normally depend on the wind for pollination.

Conifers of the Cheirolepidiaceae family played a crucial role in Cretaceous terrestrial ecosystems, being fundamental to environmental structure and nutrient cycling. As for the extinction of this family, the MARE researcher believes that the infertility of the male cones was the main cause of the disappearance of this group of plants.

The first images were obtained using scanning electron microscopy of Classostrobus doylei sp. nov. from the Lower Cretaceous of the Figueira da Foz Formation (Juncal). A. Male cone with helically arranged microsporophylls; scale 1 mm. B. Pollen sacs with in situ pollen grains attributable to Classopollis triangulus (arrows); scale 50 µm.

The second images were taken using scanning electron microscopy of Frenelopsis callapezii sp. nov. from the Lower Cretaceous of the Figueira da Foz Formation (Juncal). A. General appearance of the branches illustrating the branching pattern; scale 5 mm. B. Detail of the branch where the nodal region can be seen; scale 2 mm.