Crocodilians, which include
alligators, crocodiles and caimans, live in tropical and temperate regions
worldwide and are top predators in watery environments. With a crushing force
of more than 16,000 newtons, they have the strongest bite of any animal on
Earth, a distinction scientists believe they have likely maintained going back
to the Mesozoic era, when their giant ancestors co-existed with the T-rex and
other impressive biters. By comparison, the typical human bite involves around
500 newtons of force.
Credit: © edan / Fotolia
Researchers
recently discovered that alligators and related crocodilian species have a
previously unknown second jaw joint that helps to distribute the extreme force
of their bite, which is the most powerful of any living animal. The finding
raises new questions about the evolution of our own meager-by-comparison jaws
and could potentially lead to a better understanding of common jaw disorders.
"When
we discovered that crocs had built this new jaw joint, it made us re-evaluate
how mammals actually evolved our jaw joint and reinterpret what we thought we
knew about where parts of our jaw joint came from," said Casey Holliday,
Ph.D., assistant professor of anatomy at the University of Missouri, who led
the research. "It's one of those awesome 'tapestry of life' stories that's
given us a new way of looking at 250 million years of evolution for crocs and
also 250 million years of independent evolution toward mammals."
Holliday
will present the new findings and other highlights of recent research about
crocodilian anatomy at the American Association of Anatomists Annual Meeting
during Experimental Biology 2016. He is the recipient of the 2016 American
Association of Anatomists Morphological Sciences Award.
Crocodilians,
which include alligators, crocodiles and caimans, live in tropical and
temperate regions worldwide and are top predators in watery environments. With
a crushing force of more than 16,000 newtons, they have the strongest bite of
any animal on Earth, a distinction scientists believe they have likely
maintained going back to the Mesozoic era, when their giant ancestors
co-existed with the T-rex and other impressive biters. By comparison, the
typical human bite involves around 500 newtons of force.
"Though
they have a reputation as 'living fossils' and indeed have patrolled Earth's
waterways for millions of years, they aren't just some holdover or relic from
the days of the dinosaurs," said Holliday. "In fact, they have
continued to evolve and continue to reveal new features that are surprisingly
similar in function to those we find in mammals, birds and other animals.
Crocodilians are a treasure trove of adaptations that can help us understand
the form, function and evolution of many animals."
The
research team made the discovery by using a variety of imaging, computational
and 3-D modeling tools to investigate the bones, cartilage, and tissues of the
alligator head. It appears the second joint helps to distribute the bite force
throughout the skull and stabilizes the jaw to prevent it from twisting during
feeding. Mammals have only one jaw joint; birds, lizards, snakes and fishes
have multiple flexible joints in their heads, though these joints are not all
considered jaw joints.
Because
the crocodilians' second jaw joint is similar in structure to the
temporomandibular joint in people, Holliday said the findings could have
relevance for understanding a group of painful jaw-related conditions known as
temporomandibular joint dysfunction, TMD or TMJ. The causes of TMJ, which is
estimated to affect up to 30 percent of adults, are not well understood.
Holliday
also highlighted his team's other active areas in alligator research. One
recent study yielded new insights on a pair of nerves that run down each side
of the animal's long snout. A series of small holes along the snout allow the
nerves to sense pressure and vibration in the environment, akin to invisible
whiskers that help the animal locate prey when hunting at night.
Another
promising area is the study of crocodilian cartilage. Holliday said a better
understanding of how this cartilage develops and functions could help
researchers find new ways to counteract one of the downsides of human anatomy
-- our relatively thin layers of cartilage that become worn down over time,
creating arthritis.
"Over
on the other side of the animal tree, we have this whole stock of successful
animals that don't have anything like arthritis -- they have these huge caps of
cartilage that they maintain throughout life. Our hope is that there might be
some way to bio-engineer gator cartilage for research or even clinical
applications to help us deal with human cartilage problems like
arthritis," said Holliday
https://www.sciencedaily.com/releases/2016/04/160404221029.htm
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