Tyrannoneustes
Name:
Tyrannoneustes
(Tyrant swimmer).
Phonetic: Tie-ran-no-new-steez.
Named By: M. T. Young, M. B. d.
Andrade, S. L. Brusatte, M. Sakamoto & J.
Liston - 2013.
Classification: Chordata, Reptilia,
Crocodylomorpha, Thalattosuchia.
Species: T. lythrodectikos
(type).
Diet: Carnivore/Piscivore.
Size: Lower jaw about 66 centimetres long.
Known locations: England - Oxford Clay
Formation. Germany.
Time period: Mid Callovian to Early Oxfordian of the
Jurassic.
Fossil representation: Lower jaw and partial post
cranial remains including vertebrae, ribs and limbs. Partial skull
material also known.
The
metriorhynchids are the best known of the thalattosuchians, a group
of crocodiles
that had adapted themselves to life at sea. Out of
these, Tyrannoneustes is considered to be a
geosaurine
metriorhynchid, (more closely related to genera like Geosaurus).
It took quite some time for Tyrannoneustes to be
named though, as
the fossils were first recovered in 1906 and 1907 by a fossil
hunter named Albert Leeds. Not considered to be anything special,
the remains were left in museum storage for over a century until it
was realised that they represented a new genus.
Studies
of the jaw of Tyrannoneustes have revealed that
these metriorhynchids
had a notably wide gape when they opened their mouths to the maximum
extent. In addition to this wide gape, the teeth were large and
blade like, perfect for slicing into the bodies of prey. These
two observations together strongly suggest that Tyrannoneustes
would
attack large prey animals ranging to be anything from plesiosaurs,
to
possibly even biting chunks out of large filter feeding fish such as
Leedsichthys
(which coincidentally was named after Albert Leeds,
the person who discovered the Tyrannoneustes
holotype fossils).
The
holotype remains of Tyrannoneustes include a jaw
that was roughly about
sixty-six centimetres long, though the rest of the post cranial
skeleton is only partially represented. In the absence of other
specimens it seems that Tyrannoneustes was actually
fairly small or at
least within the lower average of its other geosaurine brethren.
Indeed, a relative and similar named genus called Torvoneustes
is thought to have grown just a little short of five meters. Another
genus named Plesiosuchus
that lived after Tyrannoneustes during the
late Jurassic is known to have grown to just short of seven meters
long, at least roughly double the size of the Tyrannoneustes
holotype.
Although
a predator in its own right, Tyrannoneustes would
have needed to
watch out for other larger oceanic predators, These may have included
large sharks and ichthysaurs, but of a principal threat to
Tyrannoneustes and other smaller thalattosuchians,
would have been
the pliosaurs,
with genera such as Simolestes
and Liopleurodon
known
to have likely been swimming in the same waters at the same time as
Tyrannoneustes.
Further reading
- The oldest known metriorhynchid super-predator: a new genus and
species from the Middle Jurassic of England, with implications for
serration and mandibular evolution in predacious clades - Journal
of Systematic Palaeontology - M. T. Young, M. B. d.
Andrade, S. L. Brusatte, M. Sakamoto & J.
Liston - 2013.
- The first record of Tyrannoneustes (Thalattosuchia:
Metriorhynchidae): a complete skull from the Callovian (late Middle
Jurassic) of Germany. - PalZ 92, 457–480. - K. Waskow, D. Grzegorczyk
& P. M. Sander - 2018.
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