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RE: feathered ornithopods?



Title: RE: feathered ornithopods?

Tracy Ford wrote:

>The climate of New Zealand at
>that time seems to have been temperate, judging from the dinosaurian and
>plant fossils. [snip] The recovered
>dinosaur material shows no special adaptations to cold climates...

Tim Williams wrote:

>The dino material from New Zealand is so scanty and fragmentary that it
>would be impossible to gauge if their owners were adapted to cold climates
>or not.  There's no evidence pro or con from that direction.

>The only 'special adaptations' in the anatomy that might be correlated with
>prolonged cold or dark are: (1) insulative body covering and (2) larger eyes
>(e.g. _Leallynasaura_ - though I'm open to the opinion that its big orbits
>are a juvenile feature).

HYPSILOPHODONTIDAE - Leaellynasaura in particular is an Early Cretaceous Australian (Otway and Strzelecki Groups) and is NOT a New Zealand per se. dinosaur. Rifting apart of Gondwanaland had commenced at this time and for whatever reason Leaellynasaura amicagraphica apparently did not make it to what was to later become New Zealand, although a hypsilophodontid is recorded by Joan Wiffen Late Creataceous. Paleontologist John Long in "Dinosaurs of Australia and New Zealand" (p.118) notes "Because Leaellynasaura had to endure cold temperatures...." That may be so for Australia (though I doubt It!), and agree with Tim that the eye orbits are possibly a juvenile trait.

New Zealand was the closest landmass to the South Pole during the Late Jurassic/Early Cretaceous, and there is some argument about about the paleolatitude at this time. Ballance (1988)appeared to favour a high latitude (>60 degrees) citing evidence such as glacial dropstones in the shelf muds. Broekhuizen (1984)preferred a lower latitude stating that the profusion of flora was not consistant with a near-polar position and implied a cool to warm temperate climate. Others consider that the Late Jurassic was uniformly warm and wet with no polar ice caps and apparently little differentiation into climatic belts (e.g. White 1986). Hence a moderate climate at a high latitude as indicated by paleomagnetic studies is feasible. 

The New Zealand Polar flora at this time appears to be as Tracy wrote (temperate), and apparently suitable to support dinosauria. Most flora was evergreen (ie. Auracarians, ferns, cycads) with little deciduous. A lowering of botanical metabolism rates may have been important during seasonal change and months of darkness. Areas where volcanism prevailed were probably locally transient in both light and ambient temperature. Unlike Australain Cretaceous dinosaurs, the New Zealand population was geographically constrained and unable to migrate seasonally. The single New Zealand Jurassic dinosaur bone known is a mere phalange belonging to an animal similar to Compsognathus; it lived on a braided-river plain that was later annexed to New Zealand. Like Madagascar, New Zealand appears to have possessed island dinosaurs that lived in isolation for about 20 Ma., but unlike Magdagascar, are only preserved as isolated elements that are too fragmentary for detailed analysis. As Tracy suggested, plants provide better ecological clues to paleoenvironments at this time! 

Mike.

Michael K. Eagle MSc. MRSNZ.
Research Associate - Paleontology
Natural History
Auckland War Memorial Museum
Private Bag 92018
Auckland
NEW ZEALAND.

Telephone: 64 09 306 7070 ext. 881
Fax:       64 09 379 9956
e-mail:    meagle@akmuseum. org. nz 
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