Ankylosaur (Dinosauria) Sacrum from the upper Jurassic Morrison

Ankylosaur (Dinosauria) Sacrum from
the upper Jurassic Morrison Formation
Danielle Armendariz
Overview
Introduction
.Fast Facts
.About the Morrison Formation
.LACM 154873
.Morphology
Methods
.Identifying Sacrum, is it ankylosaur?
.Morphometrics
Results
.Mymoorapelta maysi
Introduction
Fast Facts
•
Today, ankylosaurs are known as “The Armored Dinosaur”.
•
With Africa being the only possible exception, ankylosaurs are
known from every continent including Antartica.
•
As of now, only two taxa (i.e., Gargoyleosaurus parkpinorum and
Mymoorapelta maysi) have ever been described for
ankylosaur remains belonging to the Morrison Formation.
Mesozoic Timeline
The Morrison Formation
155-148 mya
•
Many paleoecologist believe the Morrison Formation would
have been a semiarid savanna with abundant vegetation in
order to support the large population of herbivores.
The Morrison Now
Location of LACM 154873
Gnatalie Quarry
LACM 154873
A
B
Morphology
•
LACM 154873 shows evidence of a more robust centra,
and hourglass sacral ribs. The first three sacral ribs run
horizontally with a slight bend and have flat expanded
edges. The last set of sacral ribs appear to be very thin,
almost crushed and appear to be laying of a more
downward angle. There is a shallow groove that runs
down the centrum beginning with the second sacral
vertebrae and ending at the the fifth.
About LACM 154873
1
2
3
4
5
•
LACM 154873 is a partially preserved sacrum proper represented by five
fully fused sacral vertebrae and their fused sacral ribs.
•
LACM 154873 was a fully grown adult.
•
Based on measurements taken of the specimen, it was considerably
smaller than its Cretaceous relatives.
Size Comparison
Methods
Step 1A: Determining if it is an
Ankylosaur
•
Diagnostic Characteristics of Ankylosaur Sacrum: Sacrum
proper consists of three or four vertebrae with the centra
firmly fused together .
•
Diagnostic Characteristics of Stegosaur Sacrum: Sacrum
proper consists of five or six vertebrae with the centra
firmly fused together.
LACM 154873
.Ventral Groove
Stegosaur
.No ventral groove present
.Hour glass sacral ribs .All sacral ribs run horizontally
and at a slight downward angle
.Robust centra
.More gracile centra
Step 1B: What type of ankylosaur
is it?
Polacanthidae
Nodosauridae
Ankylosauridae
•
The First ever Jurassic ankylosaur was found at the
Mygatt-Moore Quarry, later followed MWC 2610 of Cactus
Park, and it is one of only two skeletons associated with
ankylosaurs of the Morrison Formation.
Morphometrics
10 cm
10 cm
Results
Mymoorapelta maysi
•
Because of its incomplete nature, I can not definitively say
that this specimen belongs to Mymoorapelta maysi,
however based on the many similarities it shares, it is
highly likely.
Petrified Forest
•
These animals were amphibians, reptiles, and even some
of the earliest turtles.
Conferences
•
Attended Western Association of Vertebrate
Paleontologists annual meeting. Great
experience, observed how a project should be
presented.
•
Attended Cal-Paleo at UC Riverside, student
based conference. Wide range of topics from
paleoecology to molecular fossil taphonomy.
•
Gave us (the interns) the chance as
undergrads to prepare and present a cohesive
poster presentation that was truly interesting.
•
Most importantly, feeling a sense of
accomplishment after being congratulated by
other students and professionals in the field
after learning I was an undergraduate student.
Dino Dig: New Mexico 2012
•
Our findings: possible Ceratopsian sacrum, Tyrannosaur
teeth/claw, Ankylosaur vertebrae. (Just to name a few).
A million thanks
• Dr.
Chiappe and Alyssa Bell for overseeing
our my research throughout this whole
process.
• Stephanie
Ambramowicz for all her help on
illustrations.
• Dr.
James Kirkland for his outside opinion.
• NSF
for their funding of this internship.