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as I had visualized earlier, the whole thing was semi-helical, close to an “S” or a
“Z”lyingonitsside.Lookingatitfromabove,wecouldseeitmadeanabruptright
turn, and then a left, ending at the spot where the dinosaur had been taken out. The
first two segments were about equal in length, 60 to 70 cm (24-28 in), and their
widths were within a narrow range of 30 to 38 cm (12-15 in), a little bit taller than
wide. The gentle inclines for each of the segments added up to a vertical drop of
about 50 cm (20 in), which was about the length of my lower leg.
The field crew had truncated the lowermost part of the structure when they
took out the expanded mass of rock and its dinosaur in the supposed burrow cham-
ber at its end. Despite the absence of this chamber, we drew its approximate out-
lineontheground,whichhelpedcompleteourunderstandingoftheentirestructure.
This was a real burrow all right, and with a form and dimensions that made sense
as a burrow. We started to talk about how this geometry would have worked for a
small dinosaur moving through it, tail included. We also wondered whether the di-
nosaurcollectedfromhere,onceprepared,wouldturnouttobetoolarge,toosmall,
or just right for this structure as the burrowmaker.
But this is what really got me excited: the structure had small projections of
sandstone poking from each of the two corners of the bending tunnel. On the up-
per turn, a bundle of a half-dozen horizontally oriented narrow sandstone cylin-
ders—each about the width of a pencil—suggested that something else had been
addedontothemainstructure.Ahorizontalsandstonecylinderaboutthewidthofa
baton stemmed from the lower turn. “There they are,” I said to Dave. “Commensal
burrows.” These were likely small burrows that also had been hollow spaces con-
nected to the main burrow and filled in by the sandstone. Insects could have made
the upper cluster of burrows, whereas the lower burrow was more appropriately
sized for a small Mesozoic mammal. The study of modern traces—also known as
neoichnology
—had been kind to us, with the gopher tortoise burrows of Georgia
supplying a sensible explanation for these seeming aberrations.
