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Re: Dinosaur diversity



Betty wrote:

> wasn't most of Europe isolated islands and large lagoons during at least
> the Jurassic?
> I'm thinking of the Solnhoffen stuff primarily.

Indeed, from Late Jurassic times (probably earlier) to the end of the 
Cretaceous, 
Western and Central Europe was an archipelago of small and larger 
islands, separated by a shallow sea.
There are quite some examples of supposed island faunas I think, but 
all of them contain dinosaurs (I try to recall some:)
The Late Triassic Zorzino limestone formation is thought to have 
originated in a lagoon like environment, with small calcareous 
islands in front of the coast; it yields drepanosaurs, prolacertiforms, 
pterosaurs and aquatic reptiles such as placodonts and the strange
Endennasaurus (a thalattosaurian), and  recently a large phytosaur has 
been found (as yet no dinosaurs).
According to some authors, some of the Late Triassic/Early Jurassic 
fissure infillings of Wales represent island faunas, dominated by 
various sphenodontians, morganucodontids, various small
(crocodyliform?) archosaurs and the dinosaur Thecodontosaurus.
In early Jurassic times, there probably existed a small island 
('St-Brides Island'), dominated by lepidosaurians and mammals, 
however some theropod teeth have also been found; interestingly there 
is a record of a supposed "giant" morganucodontid, the size of a 
large rat.
The Solnhofen limestone is indeed thought to have
been deposited in shallow lagoons, with patchy small islands; 
the largest predators on these tiny islands were Archeaopteryx and 
the dimunitive Compsognathus, shearing the islands with turtles, 
pterosaurs and thalattosuchian crocodiles.
And Late Cretaceous European strata have yielded the 'dwarf' 
nodosaurid Struthiosaurus and the small Rhabdodon (an iguanodontid?) 
which could be dwarfed island species.
Well this is just what I recall (without references), others can give 
more details or corrections.
In virtually all of these possible island faunas, dinosaurs are 
present however mostly represented by small taxa; the island systems 
were probably not far from the mainland and often developed land 
bridges between them and the main coast or had already a substantial 
dinosaur fauna before they got a real island...

Pieter Depuydt