Cretaceous; Hell Creek Formation;
South Dakota; DINOSAURS
The Department of Paleontology maintains two active dig sites
in South Dakota where Robert DePalma, our Assistant Curator
of Paleontology, has been conducting excavations in the famous
Hell Creek Formation each summer since 2003. The Hell Creek
Formation is a unique and amazing geologic formation in that
it preserves the last 3 million years of the dinosaurs’
reign on earth, right up to the debris layer of the famed
asteroid impact that dealt the killing blow to the dinosauria.
Because of the incredible volume of vertebrate, invertebrate,
and plant remains in the Hell Creek Formation, scientists
are able to study snapshots of the last years of the Cretaceous
and reconstruct animal communities and paleoenvironmental
conditions that existed immediately before the cataclysmic
K-T asteroid impact. In the years since the first Palm Beach
Museum expeditions commenced, exploration of the Hell Creek
river and floodplain deposits has produced a dizzying amount
of discoveries that will take years to analyze and publish.
New species have been discovered, old theories have been disproven,
and enormous dinosaur skeletons have been uncovered. A selection
of research centering on discoveries from the Hell Creek Expeditions
and other collaborative research efforts that will be documented
in future publications are as follows:
Cheryll and Henry
Cheryll and Henry are two Triceratops skeletons recovered
from the Upper Hell Creek Formation, less than a million years
before the K-T asteroid impact that arguably caused the extinction
of the world’s dinosaurs. Cheryll, named after the wife
of landowner Sam Marty, is a 20-foot-long adult Triceratops
that died on the floodplain of a large river. Henry, named
after famed paleontologist Henry Fairfield Osborn, was only
half grown when he died. Henry is only 14 feet in length and
died less than 8 miles from Cheryll.
rex…a scavenger? Not a chance!
A unique set of duckbilled dinosaur bones holds clues that
Tyrannosaurus rex, contrary to some theories, was not a scavenger.
The bones, which were damaged during life and fused together
while healing, revealed a startling clue: a Tyrannosaurus
rex tooth embedded within! Because the bone had re-grown around
the tooth as it healed, the Tyrannosaur attack occurred while
the prey animal was still alive. Remarkably, the duckbilled
dinosaur survived the attack and fully healed before dying
years later. Unless the duckbilled dinosaur was a zombie,
the Tyrannosaurus rex that attacked it was certainly not a
The Hell Creek Expeditions have uncovered a specific bony
growth associated with pregnant birds and dinosaurs. This
bony growth, called medullary bone, only occurs at the time
a bird or dinosaur is pregnant, or immediately after the eggs
are laid. The presence of medullary bone in at least three
dinosaur taxa from our field station indicates that the dinosaurs
died during breeding season. Aspects of dinosaur breeding
behavior, nesting locations, and species interaction during
breeding season are being investigated.
of the Hell Creek Formation
Pterosaurs, flying reptiles resembling giant bats, were common
during the rein of the dinosaurs but pterosaur remains are
exceedingly rare in the Hell Creek Formation. Of the handful
of pterosaur remains thus far recovered from the Hell Creek
Formation, our specimens comprise about half of the reported
Because they are formed in areas that are prone to erosion
and obliteration by water or wind, bird tracks are very rare
in the fossil record. Until Robert recovered two bird tracks
from the Hell Creek site, no bird tracks were ever reported
from the Hell Creek Formation. The birds that formed them
lived along side the dinosaurs of the Late Cretaceous.
Until the Palm Beach Museum team discovered insects in the
South Dakota amber, scientists had no idea that Hell Creek
amber contained insects. The amber insects Robert discovered
are among the very first to be reported in Hell Creek amber,
and the first Cretaceous amber insects ever discovered in
the state of South Dakota.
Birds were certainly rarer than dinosaurs in the Late Cretaceous
and the discovery of fossil bird bones is always amazing.
Thus far, the bones of at least three species of birds have
been discovered at the South Dakota field stations. One bird,
the most complete, most articulated Late Cretaceous bird from
North America, represents what could be a new family of highly
advanced Cretaceous bird.
The faunal groups of the Hell Creek Formation were once thought
to be homogenous, roughly the same throughout the entire formation.
Current research, especially as a result of Palm Beach Museum
expeditions, is indicating that the Hell Creek ecology was
complex and comprised of localized groups of distinct species