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RE: Greg Paul's new (or newly named) iguanodonts




Nick Pharris wrote:

> ...really should be _Dakotodon_. The word for 'tooth' is _odon_, not
> _don_. Dakota + odon -> "Dakotodon".
 
This happens quite a lot, especially when local indigenous words are involved - 
like _Dakotadon_, and also the enigmatic fossil mammal _Yalkaparidon_ 
("boomerang tooth").

On thing that I noticed about Paul's paper is his attitude to phylogenetic 
taxonomy.  For example...

"As part of his dual system of two monophyletic stem-based taxa in each 
node-stem triplet
Sereno (1986) segregated iguanodontoids (= Hadrosauriformes) into the 
Iguanodontidae
and Hadrosauroidea. The inadequate result is strong taxonomic and anatomical
asymmetry between the twin clades. The Hadrosauroidea contains many genera and a
large degree of diversity in form and function. At least at this time a 
monophyletic
Iguanodontidae may be limited to highly specialized _Iguanodon_, and there is 
little
prospect that the number and anatomical diversity of genera that can be 
assigned to the
group as defined by Sereno (1986) will ever be large. The only cladistic 
designation for iguanodonts
below the _Ouranosaurus_-hadrosaur clade is the unwieldy ‘non-hadrosauroid
iguanodontoids’, in which the members are described by what they do not belong 
to as
much as what they do belong to. In contrast, and because of the evolutionary 
accident
that they represent a terminal clade, the many hadrosaur genera continue to be 
contained
in the classic Hadrosauridae. This sort of taxonomic arrangement is technically
inconsistent, as well as discriminatory, towards taxa that do not happen to 
belong to
modest sized, terminal monophyletic groups. Redefinition of the Iguanodontidae 
as a
paraphyletic group lying between set boundaries within the basal, non-hadrosaur
iguanodonts may offer a solution."

I'm not sure what to make of this.  Does it really matter if some family-level 
clades contain many taxa (like Hadrosauridae) but others do not?  Paul seems to 
be arguing that there is an aesthetic value in retaining families that capture 
a certain amount of diversity.  Thus, he further argues (I think) that all 
genera should be pooled into families, even if it means that certain families 
(like Iguanodontidae and Camptosauridae) are paraphyletic.  This seems to be a 
Linnaean argument, under the rationale that 'families' have some intrinsic 
worth or metric.  

Phylogenetic taxonomy, on the other hand, merely treats 'families' like any 
other clade.  So if classical 'iguanodontid' genera form a series of outgroups 
between _Camptosaurus_ and Hadrosauridae, and _Iguanodon_ itself has no sister 
taxon, then 'family Iguanodontidae' becomes redundant.  I don't see anything 
'technically inconsistent' or 'discriminatory' here; it's just that PT is 
converting a topology into named clades.  Although Hadrosauridae is regarded as 
a "terminal clade", this is just an artifact resulting from the particular 
definition that was given to Hadrosauridae.  We could re-define Hadrosauridae 
such that it is much narrower in content (maybe just including _Hadrosaurus_ 
and a few closely related genera) - this wouldn't change the topology; it would 
just change the particular node that the name Hadrosauridae is attached to.

Cheers

Tim







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