Buckthorn family is a well-known large family of flowering plants, mostly trees, shrubs, and vines. Sometimes it also referred as The Rhamnaceae.
During a research expedition in South-America, a team of paleobotanist discovered the fossilized flowers in Chubut Province, Patagonia, Argentina. They claimed that the fossilized flower which belongs to Buckthorn family.
Cornel University, one of the associates in this project informed that the fossil found in the shales of the Salamanca Formation. According to university's media portal, this is the first fossilized Buckthorn discovered from South America, perhaps the entire Southern Hemisphere.
Around 66-million-years ago at the end of the Cretaceous period, a massive asteroid struck on the present-day Gulf of Mexico. Following this event, that resulted in the extinction of the non-avian dinosaurs as well as plants. According to Fossil records, ferns were the first plants to recover many thousands years after this event. However, the unearthed Buckthorn fossil dated back to the early Paleocene epoch, less than one-million-years after that event.
Regarding the discovery of fossilized Buckthorn, a detailed paper published on May 10 in the online journal PLOS One. Nathan Jud, a postdoctoral researcher said that it will provide a new window into the earliest Paleocene communities in South-America. Besides, it also gives the opportunity to compare the response to the extinction event on different continents.
In the field of paleobotany, there has some ongoing debate about the origin of Rhamnaceae plant family. Some Scientists claimed that the early Buckthorns originated in an ancient supercontinent called Gondwana. Afterward, this land was split and nowadays it includes most of the Southern Hemisphere landmasses.
Meanwhile, other group argued that the Buckthorn family did not originate in Gondwana but another supercontinent called Laurasia. However, most of the landmasses of Northern hemisphere in present day belong to this supercontinent.
However, the new Buckthorn fossil supports a Gondwanan origin for Rhamnaceae rather than Laurasia. In fact, Rhamnaceae first appeared in the tropics of Gondwana but survived the extinction in Patagonia. In post-extinction period it was spread as plants recolonized the most affected areas, Jud said.
In addition, Nathan Jud informed that the fossil of Buckthorn is the only flowers of Danian age. Danian age is that period which accounts for about 5 million years following the extinction event. Nowadays fossil's age is determined by radiometric dating (using radioactive isotopes) and paleomagnetic sequence. Previously, the researcher also found Danian age fossil in India and China, however, their dates are not as precise.
