Megamastax
Name:
Megamastax
(Big mouth).
Phonetic: Meg-ah-mas-taks.
Named By: Brian Choo, Min Zhu, Wenjin Zhao,
Liaotao Jia & You'an Zhu - 2014.
Classification: Chordata, Sarcopterygii.
Species: M. amblyodus
(type).
Diet: Carnivore.
Size: Reconstructed jaw perceived to be 16
centimetres long. Full length estimated to be anywhere up to 1
meter long for the holotype.
Known locations: China - Kuanti Formation.
Time period: Silurian.
Fossil representation: Partial upper and lower jaw
bones from three individuals.
Megamastax
was named in 2014 and described upon the basis of jaw material from
three different individuals. The largest of these jaws has been
established as being up to sixteen centimetres long, and by scaling
to similar sarcopterygiian fish yielded an estimate of a full body
length around the one meter mark. This may not be huge by modern
standards, but by 2014 this size makes Megamastax
the largest
known jawed vertebrae of the Silurian period, and up to three times
larger than previously known forms.
This
discovery has caused further upset to the notion that global oxygen
levels during the Silurian were low and incapable of supporting large
animals. For some time now analysis of Silurian deposits has started
to reveal that oxygen levels during the Silurian were higher than
previously thought, and now the discovery of fish up to one meter
long is yet a further indication that oxygen levels were at least high
enough to support moderately large animals.
Unfortunately
we don’t yet know the full story about Megamastax
and how it lived.
The closest sarcopterygiian fish that we can observe today are the
Latimeria
coelacanths that live in the Indian Ocean. These fish move
and swim fairly slowly, which means that they do not need such a high
level of respiration to supply oxygen to muscles. If Megamastax
was
similar to modern coelacanths in swimming style, then it may have
been quite a slow swimmer, and thus not actually require as much
oxygen to maintain a large size as more active creatures would require.
One
area that we can be certain about Megamastax is
that it was a
predator, and possibly a generalist one at that. Megamastax
had two
kinds of teeth in the mouth. The anterior (front) teeth were
sharp and suitable for snaring prey, while the teeth at the back were
more rounded and more suitable for crushing. These two types of
teeth meant that Megamastax would have been equally
capable of catching
and processing soft bodied prey such as other fish, and harder bodied
prey such as shelled molluscs and arthropods. A similar mix of teeth
can actually be seen in later hybodont sharks
(i.e. Hybodus)
which are also known to have been generalist predators, and highly
successful ones at that.
Further reading
- The largest Silurian vertebrate and its palaeoecological
implications. - Scientific Reports 4, doi:10.1038/srep05242.
- Brian Choo, Min Zhu, Wenjin Zhao, Liaotao Jia &
You'an Zhu - 2014.
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