Argentine 'gargoyle' shows how huge predatory dinosaurs evolved
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[July 08, 2022]
By Will Dunham
(Reuters) - Fossils found in Argentina of a
ferocious dinosaur with a huge head covered in bumps and crests
reminiscent of a gargoyle are providing insight into the evolution of
some of Earth's biggest predatory dinosaurs including a curious trend
toward puny arms.
Scientists said on Thursday they discovered in northern Patagonia
extensive skeletal remains of a previously unknown species called
Meraxes gigas, including one of the most complete skulls of a large
meat-eating dinosaur ever unearthed. Meraxes, which lived about 90
million years ago during the Cretaceous Period, was roughly 36-39 feet
(11-12 meters) long and weighed about 9,000 pounds (4 metric tons).
All meat-eating dinosaurs belonged to a bipedal assemblage called
theropods. Meraxes was a member of a theropod lineage called
carcharodontosaurs - the so-called shark-toothed dinosaurs - that
included the even-larger Giganotosaurus, also from Patagonia, and
Carcharodontosaurus, from Africa.
The Meraxes skull measured more than 4 feet (127 cm) long, according to
paleontologist Juan Ignacio Canale of the Argentine research agency
CONICET at the Ernesto Bachmann Paleontological Museum, lead author of
the study published in the journal Current Biology.
"Many of the bones of the face and skull roof were covered with bumps,
ridges and furrows, giving it a gnarly appearance like a medieval
gargoyle," said University of Minnesota paleontologist and study
co-author Pete Makovicky.
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Meraxes, named after a dragon from the "Song of Ice and Fire" fiction
series that inspired the TV show "Game of Thrones," possessed strong
jaws studded with six-inch (15 cm) serrated teeth and the largest foot
claws of any of the big theropods.
"A terrifying sight," said paleontologist and study co-author Sebastián
Apesteguía of CONICET and the Felix de Azara Foundation.
Despite its big body size, its arms were just over 2 feet (60 cm) long -
"absurdly short," Makovicky said.
Two other Cretaceous theropod lineages - tyrannosaurs, which included
North America's T. rex, and abelisaurs, which included South America's
Carnotaurus - also evolved stubby arms.
Due to the incompleteness of the remains of other large
carcharodontosaurs, Meraxes offered the first evidence of forelimb
reduction in this group. Abelisaurs had hands with four fingers, while
carcharodontosaurs reduced that to three and tyrannosaurs to two.
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![](../images/070822PIX/news_e53.jpg)
Paleontologist Peter Makovicky is seen at the excavation site in
Argentina's northern Patagonia region where fossils of the
Cretaceous Period meat-eating dinosaur Meraxes gigas, including a
nearly complete skull, were unearthed, in an undated handout photo.
Meraxes, which lived about 90 million years ago, is estimated at
about 36-39 feet (11-12 meters) long and about 9,000 pounds (4
metric tons). Akiko Shinya/Handout via REUTERS.
![](http://archives.lincolndailynews.com/2022/Jul/08/images/ads/current/graue_preowned_062522.png)
Scientists have wondered why three of the most
important theropod groups independently evolved short arms of little
use in predation. All three exhibited a trend toward increased head
size and decreased forelimb size, suggesting a heavy reliance on the
skull for taking down prey, the researchers said.
While diminutive in size, the Meraxes arms were stout and muscular.
"Despite their powerful appearance, it's hard to imagine they were
used much as they barely extend beyond the body and could not have
reached the huge mouth," Makovicky said.
"I'm inclined to think that they were used in other kinds of
activities, like holding the female during mating or help in raising
the body from a prone position," Canale added.
Some other lineages of large theropods did not join the trend.
Immense Spinosaurus, with an elongated skull well adapted for
hunting aquatic prey, had intermediate-length arms. Strange
Therizinosaurus and Deinocheirus, whose diets differed from other
theropods, boasted relatively long arms with huge claws.
Carcharodontosaurs reached their peak diversity around 90 million
years ago, then disappeared suddenly.
Meraxes is not the largest of this lineage but its remains are the
most complete of the largest carcharodontosaurs, with nearly the
entirety of the skull, hips and limbs - filling in some gaps in the
understanding of this group.
For instance, based on the dimensions of the Meraxes skull, the
researchers recalculated the skull length of Giganotosaurus at a
whopping 5-1/2 feet (168 cm). Giganotosaurus, the largest of this
lineage, was slightly longer but not as heavily built as
Tyrannosaurus rex, which lived tens of millions of years later.
Dinosaurs in this lineage, Apesteguía said, "are mysterious beasts
to us."
(Reporting by Will Dunham in Washington, Editing by Rosalba O'Brien)
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