Scientists have established that the fossilized plant branch, still considered the earliest find of bamboo on Earth, is actually from the fossil genus of conifers, Retrophyllum. The research results are published in the journal PhytoKeys.
In 1941, Argentine botanists Joaquin Frenguelli and Lorenzo Parodi published an article describing a plant fossil from Patagonia as a species of the fossil bamboo Chusquea oxyphylla. The rock mass in which the find was made was at that time attributed to the Miocene epoch, which lasted from 23 to 5 million years ago. Later it became known that the age of the strata is actually older - 52 million years, that is, it belongs to the early Eocene.
In the Eocene, South America was part of the supercontinent Gondwana, and scientists, based on the described find, began to say that bamboo first appeared on Earth in Gondwana and from there began to spread across the planet. Moreover, most scientists judged Chusquea oxyphylla only from a photograph from a 1941 publication.
American botanist Peter Wilf of Pennsylvania State University examined the holotype - a reference plant specimen - from the La Plata Natural History Museum in Argentina, and found that the fossil was not like the genus Chusquea or any other bamboo.
"There is no evidence of knots, shells, tongues, or other peculiarities inherent in bamboo. It is a bit like bamboo only where the leaves come loose from a branch. The pseudo-petiolate leaves themselves, which are highly compressed and heterofacially twisted, do not at all resemble the characteristic bamboo leaves. Such free-growing leaves are not found in any species of bamboo or even a herbaceous plant, "- quoted in the press release, the words of Dr. Wilf.
Wilf associated the holotype with the coniferous Retrophyllum fossils recently described in the same area. According to the scientist, the leaves of the fossil plant are shaped exactly like the branched fossil foliage of Retrophyllum spiralifolium. More than 80 specimens of this species were collected in the strata of the Early and Middle Eocene in southern Argentina.
Retrophyllum is a genus of six coniferous species found today in tropical regions on both sides of the Pacific Ocean - in the Malésian region, New Caledonia, Brazil, Venezuela, and Colombia. Before Wilf's discovery, it was believed that the first representatives of the genus retrophyllum appeared about 20 million years ago, at the beginning of the Miocene in the south of New Zealand. However, it is now clear that the genesis of the genus took place much earlier and in another place.
The collected evidence strongly suggests that Chusquea oxyphylla has nothing to do with bamboo. Therefore, the scientist changed the generic name of the fossil plant, calling it Retrophyllum oxyphyllum.
As for the oldest bamboo, its fossils from the Middle Eocene are found exclusively in the Northern Hemisphere, and bamboo did not appear in South America until the Pliocene.
Until that time, the plant community of South America has demonstrated a stable relationship with the tropical flora of the western Pacific Ocean, which has largely survived to this day. And the correct identification of the sample from Patagonia is a clear confirmation of this.