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RE: Pteros might be dinos?!? Oh no ...



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Erik Noehm wrote-
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> It is all semantics.....
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Quite right.
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> Maybe Herrarasaurus was pre -Saur/Ornithischia split=2C but it is still a=
 dinosaur?
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If it is basal to the Saurischia-Ornithischia split (which is unlikely)=2C =
then no it's not a dinosaur.
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> But for us to call Pteros Dinosaurs=2C they would have had to evolve afte=
r the Saur/Ornith split?
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Correct.
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> What sort of standard is that?
> It seems more like a standard "That looks like a dinosaur to me"=2C and n=
ot a phylogenetic one.
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No=2C it's precisely a phylogenetic standard=2C since Dinosauria is defined=
 in reference to phylogeny and nothing else.  Of course the choice of which=
 phylogenetic marker to use is subjective=2C but that's true for very clade=
.
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> Even though they were different linages=2C back in the triassic=2C I'd be=
t a DNA sequence between Eoraptor vs Marasuchus would show they were more c=
losely related than Eoraptor is to a modern bird.
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Not more closely related=2C but more similar to each other due to shared pr=
imitive characters=2C sure.  But we define groups based on shared derived c=
haracters=2C not shared primitive characters.  Using your philosophy=2C we =
could always move one node closer to the root of life and say "that taxon i=
s very similar to what is now the most basal dinosaur=2C let's include it i=
n Dinosauria too." And we'd end up with crurotarsans=2C Euparkeria=2C prote=
rochampsids=2C erythrosuchids=2C proterosuchids=2C prolateriforms=2C rhynch=
osaurs=2C trilophosaurs=2C lepidosauromorphs=2C etc. all being dinosaurs. =
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> Maybe doing cluster analysis on the tree nodes (sort of like molecular bi=
ology does cluster analysis on protein interaction networks)=2C you can com=
e up with an objective phylogenetic definition for which node to set the di=
nosaur/non-dinosaur division.
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Except newly discovered taxa would break up old clusters=2C and I don't see=
 how this could be done objectively in any case.
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> I think we just like being able to call people ignorant when they call a =
ptero a dino.
> We will still have Plesiosaurs=2C I don't see those being classified as D=
inos any time soon=2C and Mosasaurs definitely wont.
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No=2C we just have an established phylogenetic definition that reflects his=
tory in excluding pterosaurs from dinosaurs=2C given a traditional topology=
.
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Mickey Mortimer                                           =