Geoscience Reference
In-Depth Information
indeed. As mentioned earlier, though, bird parents commonly seek out food, ingest
it, partially digest it, and then egest it into their chicks' mouths. Keep this in mind
for later, and how other trace fossils opened our eyes to this particular nurturing be-
havior as a possibility in dinosaurs.
Streaming on Demand: Dinosaur Urolites
Weknowthatdinosaursdefecatedandprobablythrewup,butwhatabouturination?
This is a tougher question to answer than one might think. Considering how dino-
saurs were evolutionarily “in between” crocodilians and birds, we could examine
theliquid-wasteexcretionofthesetwogroupsandseewhichbestfitsdinosaurs.But
thefirstplace tostartthinkingaboutdinosaururination iswithmodernbirds,which
thencanbecompared totheirnon-aviantheropodancestors moredirectly thanwith
crocodiles. Given an appreciation for the super-soaker potential of penguin excre-
tion, we can also think about the sorts of structures that might have been produced
by dinosaurs' liquid wastes, especially if delivered from cloacas on high.
Fossilized structures formed by urination, called urolites , are either rare or
rarely recognized, with only a few thus far attributed to dinosaurs. For anyone who
has seen or made their own modern examples, these structures are best defined and
most recognizable when a forceful (high-velocity, low-diameter) stream of urine
hits and erodes soft sand. An idealized urination structure made under such condi-
tions should have a central impact crater, closely associated splash marks, and, if a
slope is present, linear rill marks caused by excess fluid running down that slope.
Although such traces have low fossilization potential, they feasibly could be pre-
servedifmadeinsandduneswiththerightconditionsforfossilization:forinstance,
if dry wind-blown sand stuck to the wetted sand and filled these structures, making
natural casts of them.
So far, only two dinosaur urolite discoveries have been reported. The first of
these was in the Late Jurassic Morrison Formation near La Junta, Colorado. This
urolite was mentioned in a poster presentation at a paleontology meeting in 2002
and understandably garnered much media attention, especially for how the pale-
Search WWH ::




Custom Search