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pods also suggests that Troodon and its close kin had feathers, which would have
provided some insulation for the eggs, too. Even better evidence of brooding beha-
vior is the adult itself, as is seen with Citipati and Oviraptor : the bones of an adult
Troodon , found directly in contact with a partial clutch of Troodon eggs.
Further study showed that this Troodon , as well as Citipati and Oviraptor ,
were probably male, providing an important clue related to how dinosaur parents
took care of an egg clutch. For instance, in modern birds, large egg-clutch sizes
correlate with paternal care, whereas small clutches correspond with both parents
helping with the brooding. Hence large clutches for Troodon , Citipati , and Ovirap-
tor , along with their skeletons on top of these egg clutches, implied they were
male. Also, large modern ground-nesting birds—such as emus, ostriches, and
rheas—females develop medullary bone .Thisbonehasadistinctive texture,impar-
ted because the mother birds extract calcium from their bones to help build calci-
um carbonate in the eggshell microstructure. In contrast, male birds lack medullary
bone,asdidthebonesof Troodon , Citipati ,and Oviraptor .Asaresult,thisabsence
suggests that the adult dinosaurs on top of each nest were not the mothers, but the
fathers.
Not coincidentally, this same sort of paternal protection is a modern behavior
likewise seeninnesting emus,ostriches, andrheas.Emufathers, forinstance, siton
or otherwise stay close to egg clutches laid by the mothers for 50 to 55 days, even
eschewing food and water during that time. Once their babies hatch, they consume
the leftover eggshells, which not only gives these new fathers much-needed susten-
ancebutalsodecreasesthelikelihoodthatapredatorwillsmellfreshlyhatchedeggs
and make its way to the nest for some easy snacks. Did Troodon have the same be-
haviors,cleaningupanewbornmesswhilealsogettingalong-awaitedmeal?Sofar
we don't know, and the only trace fossil evidence that could support this would be
a nest structure with scraps of eggshells but also holding abundant footprints by at
least one adult and hatchlings.
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