New Argentine fossils uncover history of celebrated conifer group

Date:
June 18, 2020
Source:
Penn State
Summary:
Newly unearthed, surprisingly well-preserved conifer fossils from
Patagonia, Argentina, show that an endangered and celebrated
group of tropical West Pacific trees has roots in the ancient
supercontinent that once comprised Australia, Antarctica and South
America, according to an international team of researchers.



FULL STORY ========================================================================== Newly unearthed, surprisingly well-preserved conifer fossils from
Patagonia, Argentina, show that an endangered and celebrated group of
tropical West Pacific trees has roots in the ancient supercontinent that
once comprised Australia, Antarctica and South America, according to an international team of researchers.


==========================================================================
"The Araucaria genus, which includes the well-known Norfolk Island pine,
is unique because it's so abundant in the fossil record and still living today," said Gabriella Rossetto-Harris, a doctoral student in geosciences
at Penn State and lead author of the study. "Though they can grow up to
180 feet tall, the Norfolk Island pine is also a popular houseplant
that you might recognize in a dentist's office or a restaurant."
Araucaria grew all around the world starting about 170 million years ago
in the Jurassic period. Around the time of the dinosaur extinction 66
million years ago, the conifer became restricted to certain parts of the Southern Hemisphere, said co-author Peter Wilf, professor of geosciences
and associate in the Earth and Environmental Systems Institute (EESI).

Today, four major groups of Araucaria exist, and the timing of when and
where these living lineages evolved is still debated, Rossetto-Harris
said. One grows in South America, and the other three are spread across
New Caledonia, New Guinea and Australia, including Norfolk Island. Many
are now endangered or vulnerable species. The Norfolk pine group, the
most diverse with 16 species, is usually thought to have evolved near its modern range in the West Pacific well after the Gondwanan supercontinent
split up starting about 50 million years ago, Rossetto-Harris added.

Researchers from Penn State and the Museo Paleontolo'gico Egidio Feruglio, Chubut, Argentina, found the fossils at two sites in Patagonia -- Ri'o Pichileufu', which has a geologic age of about 47.7 million years, and
Laguna del Hunco, with a geologic age of about 52.2 million years. They analyzed the fossil characteristics and compared them to modern species to determine to which living group the fossils belonged. Then they developed
a phylogenetic tree to show the relationships between the fossil and
living species. They reported their findings in a recent issue of the
American Journal of Botany.

Unlike the monkey puzzle trees of the living South American group
of Araucaria, which have large, sharp leaves, the Patagonian conifer
fossils have small, needle-like leaves and cone remains that closely
resemble the Australasian Norfolk Island pine group, according to the researchers. They also found a fossil of a pollen cone attached to the
end of a branch, which is also characteristic of the group.



==========================================================================
"The new discovery of a fossil pollen cone still attached to a branch
is rare and spectacular," said Rossetto-Harris, who is also an EESI Environmental Scholar. "It allows us to create a more complete picture
of what the ancestors of these trees were like." The researchers used
56 new fossils from Ri'o Pichileufu' to expand the taxonomic description
of Araucaria pichileufensis, a species first described in 1938 using
only a handful of specimens.

"Historically, scientists have lumped together the Araucaria fossils
found at Ri'o Pichileufu' and Laguna del Hunco as the same species," Rossetto-Harris said. "The study shows, for the first time, that although
both species belong to the Norfolk pine group of Araucaria, there is a difference in conifer species between the two sites." The researchers
named the new species from Laguna del Hunco Araucaria huncoensis, for
the site where it was found. The fossils are about 30 million years
older than many estimates for when the Australasian lineage evolved,
according to Rossetto-Harris.

The findings suggest that 52 million years ago, before South America
completely separated from Antarctica, and during the first few million
years after separation was underway, relatives of Norfolk Island pines
were part of a rainforest that stretched across Australasia and Antarctica
and up into Patagonia, said Rossetto-Harris.

The change in the Araucaria species from the older Laguna del Hunco
site to the younger Ri'o Pichileufu' site may be a response to the
climatic cooling and drying that occurred after South America first
became isolated.

"We're seeing the last bits of these forests before the Drake Passage
between Patagonia and Antarctica began to really widen and deepen and
set forth a lot of big climatic changes that would eventually cause this version of Araucaria to go extinct in South America, but survive in the Australian rainforest and later spread and thrive in New Caledonia," Rossetto-Harris said.

The study shows how tiny details can provide the definition needed to
reveal big, important stories about the history of life, Wilf added.

The National Science Foundation, National Geographic Society, Botanical
Society of America, Geological Society of America, and Penn State provided funding for this project.


========================================================================== Story Source: Materials provided by Penn_State. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Gabriella Rossetto‐Harris, Peter Wilf, Ignacio H. Escapa, Ana
Andruchow‐Colombo. Eocene Araucaria Sect. Eutacta from
Patagonia and floristic turnover during the initial isolation of
South America.

American Journal of Botany, 2020; 107 (5): 806 DOI:
10.1002/ajb2.1467 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200618124750.htm

--- up 21 weeks, 2 days, 2 hours, 34 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)