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Re: Island-dwelling dinosaurs (was Re: Gargantuavis neck vertebra)

> Am 18.06.2012 um 17:53 schrieb Brian Lauret:
> What we consider to be normal weaknesses and behaviour for flightless birds 
> on islands may not be particularly applicable to flightless birds that evolve 
> on continents rarer though they may be.

Two things worth considering:
1. Some continental habitats are like islands inasmuch as nesting
large flightless birds can enjoy low predator density. Highest
concentration of ostriches occurs in the more arid sections of savanna
grasslands. Indeed, all continental large flightless birds (except
Cassowary) depend on expanse of grassland for nesting.

2. Not all predators are created equal. A still-open hypothesis is
that placentals have a predatory edge over marsupials. The latter are
handicapped by their ontogeny particularly in the sensory and social
domains, i.e., their brains have less time to develop before basic
structures must be laid down in order to make trek to pouch. So niches
that worked before presence of placentals may have been islands
(excuse the phrase) of low predator ability. Without doubt, thylacines
were fearsome animals. However, they may not have been as clever at
hunting down large flightless bird nesting sites as their placental