Baby dinosaur tracks from Morrison

[bh480@scn.org]

From: Ben Creisler
bh480@scn.org

In case this news story has not been mentioned yet:

http://www.genengnews.com/industry-updates/morrison-
natural-history-museum-discovers-baby-sauropod-
tracks/98965127/

Mentions tracks from baby apatosaurs with possible 
evidence that baby sauropods sometimes ran on hindlimbs 
only.

Also:
Paper No. 142-6: FROM THE TOMB OF THE FIRST STEGOSAURUS: 
A PRELIMINARY REPORT ON A STEGOSAUR-RICH TRACK ASSEMBLAGE 
FROM LAKES' QUARRY 5, MORRISON FORMATION OF MORRISON, 
COLORADO 
http://gsa.confex.com/gsa/2010AM/finalprogram/abstract_182
427.htm 

FROM THE TOMB OF THE FIRST STEGOSAURUS: A PRELIMINARY 
REPORT ON A STEGOSAUR-RICH TRACK ASSEMBLAGE FROM LAKES' 
QUARRY 5, MORRISON FORMATION OF MORRISON, COLORADO 
MOSSBRUCKER, Matthew T., Morrison Natural History Museum, 
501 Colorado Highway 8, Post Office Box 564, Morrison, CO 
80465, director@mnhm.org and BAKKER, Robert T., Houston 
Museum of Natural Science / Morrison Natural History 
Museum, 501 Colorado Highway 8, PO Box 564, Morrison, CO 
80465
Arthur Lakes removed giant Late Jurassic dinosaurs from 
his Quarry 5 sandstone, excavated in 1877-78 at Morrison, 
Colorado. This quarry is famous for producing the type 
specimen for the genus Stegosaurus (S. armatus, Yale 
Peabody Museum specimen 1850). Neither Lakes nor 
subsequent investigators reported footprints from the 
Quarry 5 sandstone. We have examined bedding surfaces on 
the talus blocks of the Quarry 5 left along the roadway 
at Morrison. The blocks preserved an ichnofauna unusually 
rich in stegosaurs, adult and juvenile, plus sauropods, 
juvenile and adult, theropods, ornithopods, lepidosaurs, 
and possible badger-sized mammal. 

During the 1930?s the Alameda road was built across the 
hogback ridge where the Quarry 5 sandstone outcropped. 
Road-building activity displaced bone-bearing boulders 
which then were parbuckeled onto the shoulder of the 
road. In 2005, a roadside safety girder was scheduled to 
be installed on the shoulder of Alameda Parkway, and 
Morrison Museum staff collected and moved to the museum 
in January of 2005. 

Locating tracks was done in two ways: strong, oblique 
lighting and high resolution latex peels. This process 
revealed diminutive tracks, including three tiny theropod 
tracks only 16 millimeters long (measured from the 
anterior extent of the third digit to the posteriormost 
extent of the track). Track identification began with an 
analysis of manual and pedal skeletons when possible, in 
conjunction with a review of published inchnotaxa. 

The most common track morphotype from Quarry 5 
ichnofacies range are wider medio-laterally than deep 
anterio-posteriorly, tridactyl with blunt digits ending 
in squared, hoof-like claws. Combined, these characters 
point to the pes of a single genus: Stegosaurus. 
Stegosaurus-morphotype tracks range in size from 
hatchling (estimated body mass 3kg) to adult animals 
(estimated body mass 6-8 tons). One talus block 
demonstrates adult stegosaur pedal track partially 
crushing a juvenile Stegosaurus-morphotype track, 
implying social behavior amongst juvenile and adult 
stegosaurs. 

As with the bone sample from Quarry 5, the ichnofauna 
suggests an atypical Morrison Formation ichnofauna, 
enriched in stegosaurs. The Quarry 5 ichnofauna also 
provides insight into habitat preference and social 
behavior amongst stegosaurs.