Geoscience Reference
In-Depth Information
traits, such as wings. Consequently, wings shrank as weight and height went up in
these island birds, rendering most of them flightless.
Speakingofislands,ifyou'veeverfantasizedaboutoneswheredinosaurscon-
tinued to evolve after the Cretaceous, then look no further than New Zealand. Back
in the Cretaceous, plate-tectonic shifting caused the main landmasses of New Zea-
land to split from eastern Australia, taking its dinosaurs with it. However, very few
mammals came along for the ride, so geographic isolation combined with the end-
Cretaceous extinctions to favor the survival and evolution of birds over non-avian
dinosaurs and mammals. As a result, New Zealand experienced a grand evolution-
ary experiment, answering the question: What would have happened to dinosaurs
over the last 65 million years if there had been no pesky mammals competing with
them?Moreimportant,asanichnologistImightalsoaskwhatsortsofuniquetraces
might have been made as a consequence of such evolutionary innovations?
The variety of birds and the ecological niches they filled in New Zealand were
remarkable. For example, before humans showed up about eight hundred to a thou-
sand years ago, Haast's eagles (
Harpagornis moorei
) were the top carnivores in
New Zealand, predatory theropods that delivered death from above to other large
theropods. Like some other birds, female eagles were larger than males, weighing
about 12 to 15 kg (26-33 lbs) and with wingspans of 2.5 to 3 m (8-10 ft). Although
the biggest eagles today have comparable wingspans, they are all less than half the
weightofHaast'seagle.Andjustwhatotherlargetheropodsweretheseeagleshunt-
ing in New Zealand? Moas, which were among the most famous and diverse of re-
cent avian dinosaurs that remind us of non-avian dinosaurs.
Fortuitously enough, paleontologist Sir Richard Owen—who coined the word
“dinosaur”—first studied these fabulous flightless birds in the early 19th century
after British explorers brought moa bones to the U.K. Since then, paleontologists
figure there were about nine species, which ranged from 1 to 3 m (3.3-10 ft) tall.
Moas were grazing and browsing herbivores, basically filling the ecological role of
ornithomimids,ornithopods,smallceratopsians,andothermid-sizedCretaceousdi-
