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Re: Mesozoic birds made insects shrink



Oddly, the one thing that birds seem to have done better than either pterosaurs 
or bats is to evolve flightless terrestrial forms - presumably because of the 
decoupling of the wing mechanisms. I have never heard of a secondarily 
flightless pterosaur or bat (though the Short-tailed Bat of New Zealand seems 
to be heading in that direction). 

Ronald Orenstein 
1825 Shady Creek Court
Mississauga, ON
Canada L5L 3W2

On 2012-06-05, at 5:29 PM, "Mark Witton" <Mark.Witton@port.ac.uk> wrote:

> T. Yazbeck,
> 
> There has been a _lot_ of research into pterosaur takeoff, flight, physiology 
> and ecology that you seem unaware of. Point yourself at Pterosaur.Net and the 
> Pterosaur.Net blog for a start, or track down a copy of Dave Unwin's book 
> 'The Pterosaurs from Deep Time' (even better, wait for my own pterosaur book 
> to come out at the end of the year). As David M. has also already alluded, 
> there is a wealth of discussion of many of your points in the archives of 
> this list. Still, to briefly address some of your specific points...
> 
> The notion of birds out-competing pterosaurs stems from the same 
> oversimplified logic that has been applied to many fossil groups (e.g. 
> bivalved molluscs vs. brachiopods; early dinosaurs vs. other Triassic 
> reptiles). Each of these groups are superficially similar and occupy the same 
> approximate ecospace, so it has been assumed that one excluded the other in 
> protracted evolutionary battles. In each case, close scrutiny suggests that 
> these competitions did not occur. There is _no_ evidence at all that birds 
> competitively excluded pterosaurs, for instance. Richard Butler and 
> colleagues provided a good overview of this topic in 2009, and concluded that 
> 1) there is no correlation between the fossil record of Mesozoic birds and 
> pterosaurs (at least as we know them today) and 2) the fossil records of both 
> groups are a little too incomplete to say either way. Your assertion that 
> "...the advancement of birds would cause at least a few problems for the 
> flying reptiles" is not supported by the fossil record at all: pterosaurs 
> become more diverse once birds have evolved. The idea that birds replaced 
> small pterosaurs is complicated by evidence that hyperprecocial pterosaur 
> offspring acted as distinct 'species' within Mesozoic ecosystems, occupying 
> different ecospace to the adults. 
> 
> Likewise, as David M. has already outlined, there is no indication that birds 
> were somehow physiologically superior to pterosaurs, or that they  could 
> inhabit places that pterosaurs couldn't. If anything, recent research into 
> pterosaur endocasts and respiratory physiology suggests that both were very 
> bird-like. Some researchers are considering the possibility that pterosaur 
> fuzz and early feathers are homologous. I don't really have an opinion on 
> that at the moment, and, to my knowledge, no-one has tackled this issue head 
> on, but it does not seem unreasonable. 
> 
> Pterosaur flight also appears to be very sophisticated and, to my knowledge, 
> pterosaurs were the first vertebrates to develop flight sophisticated enough 
> to hunt aerial insects (specifically anurognathids, which seem to be little 
> bundles of aerial awesomeness that inspire respect-levels normally reserved 
> for raptorial birds from biomechanicists). Membranous wings can also take a 
> lot more damage that you'd think. Bats can fly with ripped and perforated 
> membranes, so pterosaurs probably could, too. Presumably, like the digits 
> supporting torn bat wings, the stiffening fibres of pterosaur wings would 
> keep their membranes taut even if they had been torn. Note that membranous 
> wings may also be more compliant than those of feathers, and can make their 
> owners _more_ manoeuvrable, not less, than feathered fliers. There is also 
> good evidence that pterosaurs were not inept when grounded, and could walk 
> and run very competently. In terms of overall terrestrial efficiency, 
> pterosaurs were probably more akin to birds than most bats (we should 
> remember that some bat species are pretty hot on the ground, after all).
> 
> Gosh, that's a lot longer than I intended. To summarise, the fact that birds 
> are here and pterosaurs are not does not mean anything. Establishing 
> competitive displacement between two lineages is very difficult considering 
> the biological, ecological and environmental factors at work. As with 
> studying any macroevolutionary trends, the more we discover, the less we 
> know. 
> 
> Mark
> 
> --
> 
> Dr. Mark Witton
> www.markwitton.com
> Honorary Researcher
> Palaeobiology Research Group
> School of Earth and Environmental Sciences
> University of Portsmouth
> Burnaby Building
> Burnaby Road
> Portsmouth
> PO1 3QL
> 
> Tel: (44)2392 842418
> E-mail: Mark.Witton@port.ac.uk
> 
> If pterosaurs are your thing, be sure to pop by:
> 
> - Pterosaur.Net: www.pterosaur.net
> - The Pterosaur.Net blog: http://pterosaur-net.blogspot.com/
> - My pterosaur artwork: www.flickr.com/photos/markwitton 
> 
> 
>>>> <tyazbeck@comcast.net> 05/06/2012 20:46 >>>
> I'll look up the take-off and landing info later. What about the speed of 
> flight in pter. compared to birds? I don't doubt that they were warm-blooded, 
> but it seems that pterosaurs would be less agile in flight, and very 
> voulnerable on the ground. Wouldn't feathers be better (more durable?) than 
> skin? Wouldn't a pterosaur with a torn wing be SCREWED, i.e. theropod bait? 
> Still, I suspect that the advancement of birds would cause at least a few 
> problems for the flying reptiles.
> 
> ----- Original Message -----
> From: "David Marjanovic" <david.marjanovic@gmx.at>
> To: dinosaur@usc.edu 
> Sent: Tuesday, June 5, 2012 3:32:31 PM
> Subject: Re: Mesozoic birds made insects shrink
> 
>> I meant to say that they were not as efficient as birds
> 
> But what gives you _that_ idea?
> 
>> What about the intelligence of the pterosaurs?
> 
> Good question. Very difficult to answer from a few braincase endocasts.
> 
>> And weren't pterosaurs bad at taking off/landing?
> 
> No. That has been discussed on this list in great detail.
> 
>> With their thicker integument, I would venture to say that
>> birds were able to survive in colder regions than pterosuars could.
> 
> 1) Are you sure it's thicker? 2) What colder regions? Pterosaurs did fine 
> even in temperate Liaoning.
> 
>> And as far as I know, Pterosauria can only belong to one class:
>> Reptilia.
> 
> Even if you insist on having classes, alternatives are available. You could 
> give them their own class (has been done), or you could give something like 
> Ornithodira class status (has also been done -- "Endosauropsida")...