[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
> It also may be a mistake to assume that placentals have a superior
> reproductive strategy just because they are more succesful than
> marsupials nowadays. Marsupials held thier own against placentals
> through most of the Cenozoic.
In Australia, marsupials not only held their own in the Cenozoic, but
may even have triumphed over the placentals. A tooth from the early
Tertiary of northeastern Australia (named _Tingamurra_) seems to
come from a condylarth. (The Condylarthra is a paraphyletic group of
placentals that is believed to have given rise to the whales and all
ungulate groups.) Placentals (least of all condylarths) weren't
supposed to be in Australia until the arrival of rats and bats in the
> However, although you do see some
> big (Mesozoically speaking) mammals toward the end of the Cretaceous,
> saying they could have been in direct competition with any but the
> smallest dinosaurs is absurd.
I agree, but I'd go one step further and say there was no competition
at all between Mesozoic mammals and dinosaurs.
There were pretty big (Mesozoically speaking) mammals from Australia
of mid-Cretaceous age. A pair of monotremes (_Steropodon_ and
_Kollikodon_) were at least wombat-sized (or beaver-sized to you
New Worlders). There's evidence that both these Mesozoic mammals were
Which finally brings me to something that is relevant to the topic of
dinosaurs. There were a huge number of niches in the Mesozoic
(including terrestrial ones) that the dinosaurs didn't occupy and
mammals exploited. With the extinction of the dinosaurs, many more
(many, many, many more) opened up.