T. rex Paleobiology

T. rex Paleobiology
Fossil Evidence for Feeding Behavior
Tyrannosaurus rex
Interpreting Fossil Evidence for Paleobiological Inference
1.!Body Fossils (Skeletal remains – bones, teeth, skin, soft
tissue)
a.! Living analogue – look at how similar anatomy
functions in living animals. Strength of inference
depends on similarity of living analogue and exclusiveness
of relation of function to anatomy. (example: inference
that T. rex feeding behavior was similar to modern
Komodo dragon based on similarities in tooth structure).
Modern analogue inferences for dinosaurs are often
weakly supported due to a lack of sufficiently similar,
large living birds / reptiles.
Interpreting Fossil Evidence for Paleobiological Inference
1.!Body Fossils (Skeletal remains – bones, teeth, skin, soft
tissue)
b.! Biomechanics (strength of inference depends on
number of possible interpretations. Biomechanical
analysis can rule out some functions and support others,
but cannot “prove” function. (strong inference: T. rex
was bipedal – quadrupedalism is functionally unsound.
Weak inference: T. rex must have been a scavenger
because it had tiny forearms.)
Interpreting Fossil Evidence for Paleobiological Inference
1.!Body Fossils (Skeletal remains – bones, teeth, skin, soft
tissue)
c.! Taphonomy – circumstances of death. Example:
multiple individuals fossilized together suggest
gregarious behavior – juveniles fossilized with adults
suggest group behavior / social structure / parental
care. Strength of inference grows with frequency of
examples and on taphonomic evidence for mode of burial
(i.e. predator trap vs. death by drowning).
Most paleobiological interpretations of body fossils are based
on biomechanics interpreted in light of living analogues.
Paleobiology can be inferred from body fossils, but
not directly demonstrated.
Living Analogue
Biomechanics
(support hypotheses
of function)
(verify / rule out
function)
Body Fossils
(bones, teeth,
organs)
Taphonomy
(circumstantial evidence for social behavior
based on association of skeletons)
Varanus (Komodo Dragon)
8
Scanning electron microscope views.
Fry B G et al. PNAS 2009;106:8969-8974
©2009 by National Academy of Sciences
Interpreting Fossil Evidence for Paleobiological Inference
2. Trace Fossils – the remains left by an organism’s
behavior (“Rather than draw conclusions about behavior
solely based on anatomy, paleobiologists demand proof of
actual activities.”) Trace fossils provide direct proof of
behavior.
a. Feeding traces – bite marks on prey fossils, coprolites,
gastroliths
b. Reproductive traces – nest structures, grouping of
eggs, association of adults with eggs (Example:
Oviraptor fossils)
c.!Locomotion traces – footprints and trackways
d. Interaction traces – conspecific bite marks, healed
wounds
Paleobiology can be directly demonstrated from
trace fossils.
Reproduction Traces
Feeding Traces
(nest structures, eggs,
associations of eggs, nests, and
skeletal remains)
(bite marks, coprolites
gastroliths)
Trace Fossils
Locomotion Traces
(footprints, trackways, burrows)
Interaction Traces
(bite marks, healed injuries)
Large dinosaur coprolite, attributed to Tyrannosaurus rex
15 cm
Bone Fragment
Partially digested bone fragment
Feeding Traces
Tooth grooves in Apatosaurus femur
grooves
Feeding damage - tooth grooves
Unidentified vertebra fragment
Hell Creek Formation
17
Catalogue of specimens showing T. rex feeding traces
Longrich NR, Horner JR, Erickson GM, Currie PJ (2010) Cannibalism in Tyrannosaurus rex. PLoS ONE 5(10): e13419. doi:
10.1371/journal.pone.0013419
T. rex feeding traces
Hadrosaur metatarsal
Hadrosaur pubis
Ceratopsian frill
Triceratops squamosal (skull bone)
Longrich NR, Horner JR,
19Erickson GM, Currie PJ
(2010) Cannibalism in Tyrannosaurus rex. PLoS ONE
5(10): e13419. doi:10.1371/journal.pone.0013419
T. rex feeding traces
T. rex feeding traces on T.
rex bones - evidence of
cannibalism
Longrich NR, Horner JR,
20Erickson GM, Currie PJ
(2010) Cannibalism in Tyrannosaurus rex. PLoS ONE
5(10): e13419. doi:10.1371/journal.pone.0013419