New study suggests a
miniaturized origin for some of the largest animals ever to live on Earth
From: American Museum of Natural History
July 6, 2020 – Dinosaurs and flying
pterosaurs may be known for their remarkable size, but a newly described
species from Madagascar that lived around 237 million years ago suggests that
they originated from extremely small ancestors. The fossil reptile, named Kongonaphon
kely, or "tiny bug slayer," would have stood just 10 centimeters
(or about 4 inches) tall. The description and analysis of this fossil and its
relatives, published today in the journal Proceedings of the National
Academy of Sciences, may help explain the origins of flight in pterosaurs,
the presence of "fuzz" on the skin of both pterosaurs and dinosaurs,
and other questions about these charismatic animals.
"There's a general perception of
dinosaurs as being giants," said Christian Kammerer, a research curator in
paleontology at the North Carolina Museum of Natural Sciences and a former
Gerstner Scholar at the American Museum of Natural History. "But this new
animal is very close to the divergence of dinosaurs and pterosaurs, and it's
shockingly small."
Dinosaurs and pterosaurs both belong to
the group Ornithodira. Their origins, however, are poorly known, as few
specimens from near the root of this lineage have been found. The fossils of
Kongonaphon were discovered in 1998 in Madagascar by a team of researchers led
by American Museum of Natural History Frick Curator of Fossil Mammals John
Flynn (who worked at The Field Museum at the time) in close collaboration with
scientists and students at the University of Antananarivo, and project
co-leader Andre Wyss, chair and professor of the University of California-Santa
Barbara's Department of Earth Science and an American Museum of Natural History
research associate.
"This fossil site in southwestern
Madagascar from a poorly known time interval globally has produced some amazing
fossils, and this tiny specimen was jumbled in among the hundreds we've
collected from the site over the years," Flynn said. "It took some
time before we could focus on these bones, but once we did, it was clear we had
something unique and worth a closer look. This is a great case for why field
discoveries -- combined with modern technology to analyze the fossils recovered
-- is still so important."
"Discovery of this tiny relative of
dinosaurs and pterosaurs emphasizes the importance of
Madagascar's fossil
record for improving knowledge of vertebrate history during times that are
poorly known in other places," said project co-leader Lovasoa
Ranivoharimanana, professor and director of the vertebrate paleontology
laboratory at the University of Antananarivo in Madagascar. "Over two decades,
our collaborative Madagascar-U.S. teams have trained many Malagasy students in
paleontological sciences, and discoveries like this helps people in Madagascar
and around the world better appreciate the exceptional record of ancient life
preserved in the rocks of our country."
Kongonaphon isn't the first small animal
known near the root of the ornithodiran family tree, but previously, such
specimens were considered "isolated exceptions to the rule," Kammerer
noted. In general, the scientific thought was that body size remained similar
among the first archosaurs -- the larger reptile group that includes birds,
crocodilians, non-avian dinosaurs, and pterosaurs -- and the earliest
ornithodirans, before increasing to gigantic proportions in the dinosaur
lineage.
"Recent discoveries like
Kongonaphon have given us a much better understanding of the early evolution of
ornithodirans. Analyzing changes in body size throughout archosaur evolution,
we found compelling evidence that it decreased sharply early in the history of
the dinosaur-pterosaur lineage," Kammerer said.
This "miniaturization" event
indicates that the dinosaur and pterosaur lineages originated from extremely
small ancestors yielding important implications for their paleobiology. For
instance, wear on the teeth of Kongonaphon suggests it ate insects. A shift to
insectivory, which is associated with small body size, may have helped early
ornithodirans survive by occupying a niche different from their mostly
meat-eating contemporaneous relatives.
The work also suggests that fuzzy skin
coverings ranging from simple filaments to feathers, known on both the dinosaur
and pterosaur sides of the ornithodiran tree, may have originated for
thermoregulation in this small-bodied common ancestor. That's because heat
retention in small bodies is difficult, and the mid-late Triassic was a time of
climatic extremes, inferred to have sharp shifts in temperature between hot
days and cold nights.
Sterling Nesbitt, an assistant professor
at Virginia Tech and a Museum research associate and expert in ornithodiran
anatomy, phylogeny, and histological age analyses, is also an author on this
study.
This study was supported, in part, by
the National Geographic Society, a Gerstner Scholars Fellowship from the
Gerstner Family Foundation and the Richard Gilder Graduate School, the Division
of Paleontology at the American Museum of Natural History, and a Meeker Family
Fellowship from the Field Museum, with additional support from the Ministry of
Energy and Mines of Madagascar, the World Wide Fund for Nature (Madagascar),
University of Antananarivo, and MICET/ICTE (Madagascar).
Story Source:
Materials provided by American
Museum of Natural History
No comments:
Post a Comment