Note: Images of the discovery are
available at: http://www.nsf.gov/od/lpa/news/press/01/pr0103.htm
Fossilized remains of a bizarre, dog-sized
predatory dinosaur were recently recovered
on the island of Madagascar. The discovery,
funded in part by the National Science
Foundation (NSF), was announced this week
in the journal Nature by a team
of researchers led by paleontologist Scott
Sampson of the University of Utah. Matthew
Carrano and Catherine Forster from the
State University of New York at Stony
Brook co-authored the paper.
These fossils, which date to the Late Cretaceous
period (about 65-70 million years ago),
represent a dinosaur new to science, dubbed
Masiakasaurus knopfleri. Masiakasaurus
was relatively small, as dinosaurs go,
with a total body length of 1.6-2.0 meters,
much of which consisted of its long neck
and tail. The total mass of this small
carnivore would have been approximately
35 kilograms (80 lbs.), roughly that of
a German Shepherd dog.
"Scott Sampson and the NSF-supported team
of U.S. scientists working in Madagascar
continue to reveal startling new vertebrate
fossils," says H. Richard Lane, geology
and paleontology program director in NSF's
division of earth sciences, which funded
the research. "Masiakasaurus is
one of several such recent discoveries
by this prolific team, with, I'm sure,
more to come."
Masiakasaurus is based on a number
of isolated bones from several individuals.
The great majority of these fossils were
recovered from a single site. Included
in the collection are parts of the jaws
and about 40 percent of the remainder
of the skeleton, with some bones being
represented by multiple examples.
The most bizarre aspect of this theropod
dinosaur is its extremely specialized
teeth and jaws. The first tooth of the
lower jaw is oriented almost horizontally,
projecting forward instead of upward.
Subsequent teeth angle increasingly upward
until the sixth tooth; from this point
backward, all the teeth point straight
up. The teeth themselves are also unique.
Whereas the teeth at the back of the jaw
are typical of theropods-being flattened
and serrated-those at the front are longer
and almost conical, with hooked tips and
only tiny serrations. These features are
otherwise unknown among theropod dinosaurs,
which tend to have teeth of the same type
front and back.
"When we dug up the first lower jaw bone,
we weren't even sure it belonged to a
dinosaur!" says Sampson. It was only after
we compared it with the lower jaws of
other carnivorous dinosaurs that we became
convinced as to the nature of the owner.
Certain features at the back of the jaw
are unmistakably theropod."
Masiakasaurus shared its island
home with at least one other carnivorous
dinosaur, Majungatholus atopus.
At 7-9 meters in length, Majungatholus
was the top predator of the time, likely
feeding on the massive long-necked sauropod
dinosaurs also found there.
The diet of the smaller cousin, Masiakasaurus,
with its unique teeth and jaws, is much
less certain. There are a few species
of living mammals-including various shrews,
as well as a group of South American marsupials
known as caenolestids-that may
provide an analogue. These mammals possess
a similar dental set up, with elongate,
conical, forward-projecting teeth up front.
In virtually all cases, the front teeth
are used for grasping and piercing rather
than tearing and slicing, and the prey
generally consists of insects.
The jaws of Masiakasaurus suggest
a similar feeding strategy, with the front
teeth used to capture and manipulate animal
prey, and the blade-like rear teeth then
slicing the victim into bite-sized chunks.
As to the nature of the preferred prey
of this little dinosaurian carnivore,
potential candidates include insects,
fish, lizards, snakes, and small mammals.
Masiakasaurus and Majungatholus,
the two known Malagasy theropods, are
members of an enigmatic group known as
abelisauroids, and recovered only
on Southern Hemisphere landmasses. In
particular, the fossils of Masiakasaurus
share a number of specialized characteristics
with predatory dinosaurs found in Argentina
and India. This finding indicates that
a previously unrecognized radiation of
small-bodied predatory dinosaurs spread
across much of the southern hemisphere
toward the end of dinosaur times, paralleling
the Late Cretaceous radiation's of small-bodied
theropods (such as dromaeosaurids
and ornithomimids) in the northern
hemisphere.
In addition, the broad geographic distribution
of these small-bodied theropods parallels
that of their larger-bodied cousins, the
abelisaurids, a finding that may
have implications for plate tectonics,
the theory that landmasses shift their
relative positions as they move slowly
across the face of the earth.
Madagascar was once part of the southern
supercontinent Gondwana, which fragmented
during the Mesozoic heyday of dinosaurs.
The known geographic distribution of abelisauroid
theropods large and small is consistent
with a recently proposed geophysical hypothesis
that Gondwanan landmasses retained connections
well into the Late Cretaceous, much longer
than previously thought. "If so", Sampson
added, "dinosaurs and other land animals
may have been able to travel the vast
distances between South America and India-Madagascar
because the two regions remained connected
via intervening land masses."
Funding for the Madagascar project has
also been provided by the National Geographic
Society, with additional support from
The Dinosaur Society and the Field Museum
of Natural History, Chicago.
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Reconstruction of the body of Masiakasaurus
knopfleri, based on fossils recently discovered
in Madagascar. Total body length: 1.6-2.0
meters.
Copyright Bill Parsons.
A
larger version is here.
The expedition field area in northwestern
Madagascar, adjacent to the village of
Berivotra. To date, along with theropod
dinosaurs, this area has yielded the fossilized
remains of numerous vertebrates, including
sauropod dinosaurs, mammals, turtles,
snakes, crocodiles, and birds.
Copyright Scott Sampson, University of
Utah.
A
larger version is here.
Crew members working at site MAD 93-18,
excavating remains of the bizarre small
theropod, Masiakasaurus knopfleri.
Copyright Scott Sampson, University of
Utah.
A
larger version is here.
A foot bone (metatarsal) of Masiakasaurus
knopfleri shortly after its discovery
in site MAD 93-18.
Copyright Scott Sampson, University of
Utah.
A
larger version is here.
Recognizing a critical need for education
and health care, expedition leader David
Krause has worked with colleagues to form
the Ankizy Fund, a non-profit society
dedicated to building schools and clinics
in remote areas of Madagascar. Shown here
are two children from the village of Berivorta.
Copyright Scott Sampson, University of
Utah.
A
larger version is here.
The Ankizy fund is now establishing health
care facilities in various regions of
Madagascar, supplying much-needed health
care. For many communities, this is their
first exposure to formal health care.
Shown here are a dentist and doctor, together
with children of Berivotra village in
northwestern Madagascar.
Copyright Scott Sampson, University of
Utah.
A
larger version is here.
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