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modeling, they were able to reconstruct the original undistorted forms of the egg
clutches, which also outlined the forms of the nests. These nests, which on average
heldclutchesof25eggs,apparentlylackedtherimsoftheArgentinenests,buttheir
shapes had the same sort of asymmetry: shallow, oblong, wider at one end, and a
little curved, like a kidney bean. These paleontologists also attributed such shapes
to scratch-digging, in which the wider end was where the sauropod started digging
with the rear feet, and the narrower end was about where the foot pulled out. They
further proposed that the size and form of the enlarged unguals on the rear feet of
sauropods were very likely responsible for making the widest and deepest part of
the nest, in which the majority of eggs were laid.
So to make a 70-plus-million-year-long story short, the discovery of sauropod
nests as trace fossils helped paleontologists test the hypothesis that sauropod feet
were not just meant for walking, but also for digging. Nonetheless, perhaps alert
readers noticed a wee problem with this hypothesis, which is that it does not take
into account gender differences. In other words, did male or female sauropods dig
nests, or did they do this cooperatively? If done either by males or cooperatively,
this would have been a radical departure from reptilian behavior, in which only
female tortoises, turtles, lizards, and crocodilians dig nests. Alternatively, many
male-female pairs of birds share the burden of building a nest, so why not dino-
saurs?
Another question remains in thinking about scratch-digging sauropods: Why
would both genders have the same scratch-digging traits in their feet? One might
also ask why both male and female mammals have nipples, and yet these are only
functionalinonegender(althoughIhavenotthoroughlynorpersonallytestedthis).
Regardless, it is not such a big deal to have a similar anatomical trait related to re-
production in both genders of the same species.
Allthesame,FowlerandHallthoughtaboutthisproblemtoo,andconjectured
that large unguals in the front feet of sauropods may have been used for getting a
grip—on their mates, that is. This certainly would have applied to male sauropods,
