[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Tinamous: living dinosaurs



On Jun 27, 2011, at 1:25 PM, Dr Ronald Orenstein wrote:

> First of all, tinamous ARE ratites despite their size and flying ability, so 
> there is no reason to assume that their brooding habits were independently 
> acquired. 

I was not aware of that. When you say ARE, which phylogentic 
hypothesis/taxonomy are you referring to? Tinamous are usually classified in 
their own Order, Tinamiformes, distinct from the Ratitae, aren't they?  Hackett 
et al. (Science 320 (2008) did nest tinamous within the "Struthioniformes", but 
they refer to the Paleognathae as "ratites and tinamous".  Other phylogenies, 
such as Dyke  & Van Tuinen, Zoological Journal of the Linnean Society 141 
(2004), found tinamous to be more primitive than any ratite. Also, I thought 
that the term "ratite" refers to the reduced, raft - like, sternum found in the 
flightless paleognathous birds. Perhaps you are using ratite interchangeably 
with Paleognathae, and perhaps you reject the traditional clade "ratite" 
because it is (probably) paraphyletic.
> 
> Paternal-only brooding for dinosaurs IS  pure speculation as (to my 
> knowledge) we have no evidence that the animals found in brooding positions 
> (are there more than one?) were males. Do we have any evidence for male 
> brooding other than the presence of large nests for troodontids etc?  Do we 
> have any evidence (other than large clutch size, again) that clutches 
> represent multiple female layings?

Paternal only brooding is supported  by multiple specimens, strong statistical 
correlations, and bone histology. Troodon, Oviraptor, and Citipati adults have 
been found in association with their nests. Varricchio et al. Science 322 
(2008) studied 8 specimens of adult non-avian maniraptorans found in 
association with nests. Not one showed evidence of having medullary bone or 
resorption cavities, as have been reported in Tyrannosaurus, Tenontosaurus, 
Allosaurus and Syntarsus previously. When the authors looked at clutch volume 
to adult body mass proportions within extant archosaurs they found that 
clutches as large as those found with Troodon and the oviraptorids correlate 
strongly with male - only care within extant archosaurs.  The large clutches 
(up to 30 eggs) are likely polygamous because, put bluntly, this egg volume 
probably could not fit inside the body of a single female Troodon. 

http://www.sciencemag.org/content/322/5909/1826.full.pdf


> 
> Ronald Orenstein 
> 1825 Shady Creek Court
> Mississauga, ON
> Canada L5L 3W2
> 
> On 2011-06-27, at 12:40 PM, Jason Brougham <jaseb@amnh.org> wrote:
> 
>> Yes, of course, we might well expect a radiation of diverse brooding 
>> strategies among Dinosauria, as so many millions of years went by and so 
>> many specialized lineages diverged.
>> 
>> There may even be a sample bias, also, for those taxa that nested on the 
>> ground on floodplains. I w=myself wouldn't be at all surprised if we find 
>> one day an alvarezsaur female seated atop one or two very large eggs, for 
>> example.
>> 
>> But, nonetheless, we have several samples of non - avian maniraptoran nests 
>> and they are consistent in the features of large numbers of eggs in the 
>> clutches and males brooding them alone.
>> 
>> Also, I'm not clear from your e-mail if you are suggesting that Tinamous 
>> evolved paternal - only brooding independently of ratites (since tinamous 
>> are not large and flightless)?
>> 
>> Let me put it this way: if you HAD to reconstruct the brooding of a non - 
>> avian maniraptoran now, wouldn't it be safest to go with the paternal - only 
>> brooding model? Anything else would be pure speculation.
>> 
>> In other words, isn't it most parsimonious to assume that the brooding 
>> strategy held in common by Troodon, oviraptorids, (possibly Gobipteryx), 
>> tinamous and ratites is a synapomorphy, rather than a strategy that was 
>> independently converged upon four times? It certainly could have been 
>> independently derived, but that just requires more assumptions and thus is 
>> less parsimonious.
>> 
>> Cheers
>> -Jason
>> 
>> On Jun 24, 2011, at 11:35 AM, Ronald Orenstein wrote:
>> 
>>> I would be very nervous about doing this.  We have no idea if paternal care 
>>> is a 
>>> basal character or simply a common feature (symplesiomorph?) of ratites.  
>>> Ratites are still neornithine birds, and there is a lot of intervening 
>>> evolution 
>>> between them and maniraptorians.  I would be reluctant to assume that any 
>>> behavioural characteristic of ratites not associated with large size or 
>>> flightlessness is any more likely to be a basal feature than  the 
>>> behavioural 
>>> characteristics of any other ground-living bird (such as a lyrebird, for 
>>> example!).
>>> 
>>> Ronald Orenstein
>>> 1825 Shady Creek Court
>>> Mississauga, ON L5L 3W2
>>> Canada
>>> ronorenstein.blogspot.com
>>> 
>>> 
>>> 
>>> ----- Original Message ----
>>> From: Jason Brougham <jaseb@amnh.org>
>>> To: dinosaur@usc.edu
>>> Sent: Fri, June 24, 2011 10:17:27 AM
>>> Subject: Tinamous: living dinosaurs
>>> 
>>> I put up a  new blog post about Tinamous, and how they are underexploited
>>> as models for extrapolations about the biology of extinct maniraptorans.
>>> Since their egg brooding behavior is comparable to Troodon and
>>> oviraptorids, can we infer that the behavior between the father and the
>>> chicks was the same also?
>>> 
>>> http://web.me.com/jasonbrougham/Site/Blog/Entries/2011/6/18_Tinamous__Living_dinosaurs.html
>>> 
>>> 
>>> 
>>> Jason Brougham
>>> Senior Principal Preparator
>>> Department of Exhibition
>>> American Museum of Natural History
>>> 81st Street at Central Park West
>>> 212 496 3544
>>> jaseb@amnh.org
>> 
>> Jason Brougham
>> Senior Principal Preparator
>> American Museum of Natural History
>> jaseb@amnh.org
>> (212) 496 3544
>> 
>> 

Jason Brougham
Senior Principal Preparator
American Museum of Natural History
jaseb@amnh.org
(212) 496 3544