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discover fossil of tiny mammal from Early Jurassic
Discovery provides important new evidence on the earliest evolution
An international team of researchers led by Carnegie Museum of Natural
History Vertebrate Paleontologist Dr. Zhe-Xi Luo has discovered a 195-million-year-old
fossil mammal. The new
mammal is the smallest known for the Mesozoic Era and represents
a new branch on the mammalian family tree.
In an article published today in the prestigious journal Science,
the team of American and Chinese scientists described this new mammal
as having a precociously large brain and the middle ear of modern mammals.
It suggests that these two features may have evolved together.
Previously, these important mammalian traits could only be traced to
the late Jurassic (approximately 150 million years ago). This discovery
pushes back their origins by
some 45 million years to the Early Jurassic.
The new species is named Hadrocodium wui for its exceptionally
large brain ([hadro] Greek for "large and full"
and [codium] Greek for head). The fossil has widespread
implications to scientists piecing together the earliest mammalian evolutionary
differ from non-mammalian vertebrates by possessing a very large brain
and an advanced ear structure," said Dr. Luo. "It has been
a challenge for scientists to trace the origins of these important mammalian
features in the fossil record."
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The newest addition to the mammalian family tree also happens to be
the tiniest mammal known from the Mesozoic Era and one
of the smallest mammals ever. Based on the size of its well-preserved
skull, it is estimated that the whole animal weighed only two grams,
less than the weight of a paper clip. With such a tiny body, its diet
was likely limited to very small insects and small worms. Its enlarged
brain and very small body also tell scientists that the animal had a
very high metabolism, forcing it to continuously eat.
Co-existing with the extremely small Hadrocodium in the Early
Jurassic were several other primitive mammals with much larger body
size. "This tiny creature greatly stretches the range of body size
for the earliest known mammals," added Dr. Luo.
Hadrocodium is a
distant and extinct relative of living mammals such as the platypus,
kangaroos and primates. It is more closely related to mammals that exist
today than the primitive cynodonts or "mammal-like reptiles."
Hadrocodium was discovered in the famous Lufeng Basin in Yunnan
Province, southwestern China. It is one of the most prolific sites
for early Jurassic land vertebrates. The Mesozoic Redbeds of the Lufeng
Basin have yielded many vertebrate fossils. Among the fossils that have
been unearthed are the carnivorous dinosaur Dilosphosaurus, the
prosauropod Lufengosaurus, crocodiles, and lizard-like animals,
herbivorous mammal-like reptiles, and some of the earliest mammals ever
Dr. Luo's research team includes Alfred W. Crompton of Harvard University
and Ai-Lin Sun of the Chinese Academy of Sciences.
Funding for this research was provided by the National Science Foundation,
National Geographic Society, Carnegie Museum of Natural History's Putnam
Funds and Museum of Comparative Zoology at Harvard University.
# # #
Contact information for authors:
Dr. Zhe-Xi Luo
Section of Vertebrate Paleontology
Carnegie Museum of Natural History
Museum Public Affairs contact:
Professor Alfred W. Crompton
Museum of Comparative Zoology
Harvard Public Affairs contact:
Dr. Jay L. Taft
Professor Ai-Lin Sun
Institute of Vertebrate Paleontology and Paleoanthropology
Chinese Academy of Sciences