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Makela), although later they were connected to
Troodon formosus
. Hence, for the
firsttime paleontologists beganthinking ofdinosaursandtheir nesting behaviors as
moreakintothoseofground-nestingbirdsandnotreptiles.Evenmoreexciting,the
find of one nest with fifteen juvenile
Maiasaura
in it, all the same size and appar-
ently in the same age range, was strong evidence favoring extended parental care in
this species of dinosaur. Otherwise, why stay in a nest unless your parents are feed-
ing you? (All of you parents with children who have graduated from college yet are
still living at home, you may now wearily nod your heads in agreement.)
Despite this seminal work by Horner, Makela, and others, the full checklist for
interpreting dinosaur nests as trace fossils would not come about until more than
twenty-five years later, stemming from studies of nests of two dinosaurs very dif-
ferent from
Maiasaura
and from one another: the small Late Cretaceous theropod
Troodon formosus
of Montana, and massive Late Cretaceous titanosaurs (sauro-
pods) of Argentina. Amazingly, their nests are not so different in their overall sizes,
despite titanosaurs weighing about a thousand times greater than
Troodon
(50,000
vs. 50 kg, or 110,000 vs. 110 lbs). However, each of their nests have their own dis-
tinctive forms, leading to better understanding of how each type of nest was made.
First, let's talk about
Troodon
nests. In a geological coincidence that was not
a coincidence, paleontologists discovered these nests in the same location as the
Maiasaura
nests—a place that was nicknamed “Egg Mountain”—and in the same
sedimentaryrocksoftheLateCretaceousTwoMedicineFormation.Recognizedby
David(“Dave”)Varricchio,whowasaPh.D.studentofHorner'sintheearly1990s,
these structures were the first dinosaur nests defined solely astrace fossils. Interest-
ingly,untilVarricchioandhiscolleaguesworkedonthesenests,HornerandMakela
attributed
Troodon
eggs to the small ornithopod
Orodromeus
, a case of mistaken
identity that was fairly common with dinosaur eggs until just recently.
Full disclosure: Dave and I overlapped academically when we both attended
the same graduate school (University of Georgia, Athens) in the late 1980s. In
between our respective research projects, as well as going to local music clubs to
