Name:
Angulomastacator
(bend chewer).
Phonetic: An-gu-loe-mas-tah-ca-tor.
Named By: Wagner & Lehman - 2009.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Hadrosauridae, Lambeosaurinae.
Species: A. daviesi (type).
Diet: Herbivore.
Size: Unknown due to lack of fossils.
Known locations: USA - Texas - Aguja
Formation.
Time period: Campanian of the Cretaceous.
Fossil representation: Partial left maxilla (upper
jaw).
Although
only named from a partial upper jaw, this is still enough to identify
Angulomastacator as a distinct genus of hadrosaurid
dinosaur because the
front portion of the
jaw bends down at an angle of forty-five degrees. If you are
unfamiliar with how much this each, look at or imagine a clock face
where one hand points at 12 o’clock and the other hand points
midway between 1 o’clock and 2 o’clock. The shortest gap
between the two hands is roughly a forty-five degree angle. This bend
is not considered an artificial feature created by distortion during
the fossilisation process because the teeth in the jaw are also shaped
to fit the bend at this angle.
At
the time of the description this bend is greater than any other known
genus of dinosaur, something that suggests that Angulomastacator
was
unique to its time and environment. Beyond this it is difficult to
say what the rest of Angulomastacator looked like
because the rest of
the skull and skeleton is unknown. However Angulomastacator
has been
classed as a lambeosaurine hadrosaurid which means that in life it
probably also had a hollow head crest, although it’s impossible to
say what form this took. Like its lambeosaurine relatives that were
at their most common and diverse in North America during the Campanian
stage of the Cretaceous, Angulomastacator was a
relatively large
herbivore that could switch between bipedal and quadrupedal postures
with ease and as needed. The size of Angulomastacator
is unknown,
but its lambeosaurine relatives of this time could easily attain
sizes of around nine to ten meters long, with some variation under
and over this range between different genera.
Throughout
North America and Asia hadrosaurids like Angulomastacator
are thought
to have been principally preyed upon by the largest predatory dinosaurs
of the time, the tyrannosaurs.
However in the Aguja Formation
Angulomastacator faced a different threat, the
giant crocodile
Deinosuchus.
Not only did this large crocodile have immensely
powerful jaws, but it also had the size and weight to possibly drag a
hadrosaur like Angulomastacator into the water
where it could be
drowned by being held under the water. Clues to the fearsomeness of
Deinosuchus comes from the dinosaur Appalachiosaurus,
a relative of
Tyrannosaurus
that has Deinosuchus shaped tooth
marks in its tail
vertebrae.
Deinosuchus
is seen as a semi-aquatic crocodile similar to today’s crocs but much
larger. The presence of this predator combined with numerous fossils
of ammonites and turtles indicates that in the Cretaceous the Aguja
Formation was a wetland ecosystem that lay near to the Western Interior
Seaway. Here Angulomastacator probably foraged
for plants alongside
other herbivorous dinosaurs such as the ceratopsian dinosaur
Chasmosaurus
and Agujasaurus
as well as the armoured dinosaurs
Euoplocephalus
and Edmontonia.
Smaller theropod dinosaurs such as
Saurornitholestes
and Ricardoestesia
also hunted around these areas,
though their small size meant that they were more of a threat to
smaller juvenile Angulomastacator.
Further reading
- An Enigmatic New Lambeosaurine Hadrosaur (Reptilia: Dinosauria) from
the Upper Shale Member of the Campanian Aguja Formation of Trans-Pecos
Texas. - Journal of Vertebrate Paleontology. 29 (2): 605–611. -
Jonathan R. Wagner & Thomas M. Lehman - 2009.