Lythronax
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Name: Lythronax
(Gore king).
Phonetic: Ly-fron-ax.
Named By: M. A. Loewen, R. B. Irmis, J.
J. W. Sertich, P. J. Currie & S. D. Sampson
- 2013.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Coelurosauria, Theropoda, Tyrannosauroidea,
Tyrannosauridae, Tyrannosaurinae.
Species: L. argestes (type).
Diet: Carnivore.
Size: Holotype estimated to be around 7.3 meters
long. Speculated to have possibly attained lengths of 8 meters.
Known locations: USA, Utah - Kaiparowits
Formation.
Time period: Early Campanian of the Cretaceous.
Fossil representation: Partial skull and post
cranial remains of an adult including the tibia, fibula, pubis
metatarsal II and IV (UMNH VP 20200).
First
discovered in 2009 and officially named in November 2013,
stratigraphical analysis of the Lythronax holotype
remains has led to
them being estimated as being deposited around 80.6 to 79.9
million years ago. This makes Lythronax one of
the oldest
tyrannosaurids
known in North America, and at least 2 million
years older than Teratophoneus
which is also known from the Kaiparowits
Formation but from an estimated date of 77 to 76 million years
ago.
A
key feature of Lythronax that is instantly visible
from looking at the
skull is the rostrum that is comparatively short when compared to those
of the majority of other tyrannosaurid genera. Lythronax
however is
not unique in having a proportionately short rostrum in that two other
tyrannosaurid genera known from what is now the south western United
States, Bistahieversor
and Teratophoneus, are
also known to have
had rostrums that were proportionately shorter than those of
tyrannosaurids living in the northern United States and Asia.
These
three genera may yet contribute to a growing pattern of shorter
snouted tyrannosaurs living in the South West of the United States
developing shorter rostrum either to meet differing ecological
conditions, or perhaps even as a result of their populations being
isolated from those in the north, resulting in differing traits being
established between the northern and southern tyrannosaurs of the
United States. Another possibility however is that the short snouts
of these genera may be primitive forms that had disappeared in more
developed genera of the North.
Like
with other tyrannosaur genera, the eyes faced forwards granting
Lythronax stereoscopic vision. What this means is
that because the
visual arcs of the eyes overlapped in the centre, Lythronax
would
have been able to judge distances of things such as potential prey in
front of them and then decide if they were close enough to strike or
not.
Another
clear tyrannosaurid trait observable in Lythronax
is the overly large
banana-like teeth in the jaws. The teeth of tyrannosaurs are often
termed banana-like because they were round and curved back towards the
throat. These teeth were an adaptation for crunching through the
bones of prey as opposed to just slicing through the flesh.
Hailing
from the Kaiparowits Formation, it is possible to infer a few details
about the life of Lythronax. The Kaiparowits
Formation is composed
mostly of sandstone and mudstone, deposits that have been interpreted
as an alluvial (soft sediment) flood plain with rivers flowing
across. This environment would have been quite flat and lush with
plants that would have attracted a variety of herbivorous dinosaurs
such as hadrosaurs,
ankylosaurs,
and ceratopsians.
Any of these
could have been potential prey for Lythronax.
Further reading
- Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late
Cretaceous Oceans - M. A. Loewen, R. B. Irmis, J. J.
W. Sertich, P. J. Currie, S. D. Sampson - In Evans,
David C. PLoS ONE 8 (11): e79420 - 2013.
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