Compiling a List of Possible Victims - Walking On Eggs - page 51

fragmentary remains, duckbills and their primitive relatives are much
better represented. Both primitive duckbills and their primitive fore-
runners are known from late Cretaceous rocks of northern Patagonia.
Anabisetia and Gasparinisaura are two small, distant cousins of the
duckbills known from Neuquen and Rio Negro provinces, respectively.
True duckbills, known from the late Cretaceous of northern Patago-
nia, include Secernosaurus, Kritosaurus, and another unnamed crested
form. In contrast to their North American relatives, duckbills appear
to have been less successful in South America, where late Creta-
ceous ecosystems were dominated by huge, herbivorous sauropods.
The earliest known Patagonian theropod is from the early middle
Jurassic of Chubut, but it is very fragmentary. Much more complete
is Piatnitzkysaurus from the middle Jurassic of Chubut. Piat-
nitzkysaurus was a moderately sized, meat-eating, primitive tetanu-
ran. Many more Cretaceous theropods have come from Patagonia,
the most abundant of which are the abelisaurs. An early member of
this group is the early Cretaceous Ligabueino, an animal the size of a
pigeon. Much larger abelisaurs lived in the late Cretaceous of Pata-
gonia, including the horned Carnotaurus, one of the largest carni-
vores of its time.
A diverse assemblage of sauropodomorphs has also been found in
Patagonia. In the Triassic, prosauropods roamed the land and nested
there. Several specimens of these, including adults, juveniles, hatch-
lings, and eggs, were collected by Jose Bonaparte in the late Triassic
rocks of Santa Cruz province, in the southern end of Patagonia. The
spectacularly preserved hatchlings, known by the name of Mussaurus,
which means "mouselike lizard," were little more than six inches
long. The earliest known sauropod from Patagonia is Amygalodon,
from the early part of the middle Jurassic, which is known from iso-
lated teeth and a vertebra that were collected in the province of
Chubut. Bonaparte and his collaborators found better sauropod
remains in the middle Jurassic of Chubut in the late 1970s. An
incomplete skeleton constitutes the only known specimen of the
dinosaur Volkheimeria. Another middle Jurassic sauropod from Pata-
gonia is Patagosaurus, which Bonaparte discovered in the same rock
layers that produced Volkheimeria and the theropod Piatnitzkysaurus.
The primitive Patagosaurus is known from several specimens of both
adults and juveniles.