The Tethyan Archipelago was a bioprovince 129-120 million years ago

During the Jurassic and Cretaceous (between 201 and 66 million years ago) the current Iberian Peninsula was a large island within the Tethys Sea. This tropical sea, precursor of today's Mediterranean, was dotted with numerous islands, forming a large archipelago in its central area.  

How were the different species that lived in this archipelago impinged by insularity? 

 A research team of paleobotanists from the Faculty of Earth Sciences and IRBio (University of Barcelona), (University of Barcelona), led by the team of Dr. Carles Martín-Closas, Dr. Alba Vicente, Dr. Joseph Sanjuan, Dr. Jordi Pérez-Cano and the participation of Dr. Khaled Trabelsi with the collaboration of other research centres (the Catalan Institute of Palaeontology, the University of Vienna, Austria, and the Instituto Politécnico Nacional, Mexico) have analysed how charophytes (a group of aquatic plants) were distributed between 130 and 120 million years ago in this archipelago.  

The results show that the archipelago hosted a charophyte flora different from that of the neighbouring continents that was characterized by a high diversity of endemic charophyte species of the Clavatoraceae family. The population flow between the islands must have been good, since no significant taxonomic differences are found between them. Within the archipelago, some floristic patterns can be observed, both latitudinal (climate-related) and longitudinal (probably related to animal dispersal vectors). On the other hand, the Tethyan Archipelago provides the first record of some species that would later be distributed in large areas of the planet, including species that would become cosmopolitan in a latitudinal strip. Comparison with ostracods, a group of aquatic crustaceans that often lived in charophyte meadows, shows that these biogeographic patterns could be extrapolated to other groups in the same archipelago, forming what would probably be a distinct bioprovince. 

Figure: Distribution of endemic charophyte species within the Tethys Archipelago during the Barremian and Early Aptian (between 129 and 120 million years ago). 

Source: Vicente, A., Sanjuan, J., Pérez-Cano, J., Trabelsi, K., & Martín-Closas, C. (2023). A bioprovince for the Barremian–Aptian charophytes of the Central Tethyan Archipelago. Cretaceous Research, 105752.