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Re: Archaeopteryx (rant)



> > I've yet to see an explicit, universally applicable definition of 
> > "species". 
> 
> AFAIK, there isn't one (At least not one that is universally accepted.) 
 
If any of the perhaps 25 concepts were universally accepted, and/or 
universally applicable, we'd all know it. :-) 
 
> The concept of 'species' is a little like pornography: difficult to 
> define, but you know it when you see it. 
 
The problem is that regularly you still don't know it when you see it. 
Take ring species: the 2 or more involved nominal species are clearly real 
in some places, and clearly fictitious in others. Or the following 
example: In western Europe, there is a black crow usually called *Corvus 
corone corone*. East of that, there's a middle-grey one with black wings, 
usually called *Corvus corone cornix*. (Probably they had different 
refugia last ice age.) And reportedly, in eastern Asia there's another 
black "subspecies". *C. c. corone* and *C. c. cornix* can interbreed; the 
resulting hybrids (with various amounts of black and grey patches) all 
occur in a girdle that stretches north-south through Europe but is only 
about 40 km broad, and has, at least in historical times, not moved. 
(Reportedly the same phenomenon exists in China.) _Perhaps_ the 2 are 
rather separate species, and the hybrids have a somehow reduced fitness 
and therefore can't spread. Perhaps not (they can and do breed). Nobody 
knows. The term allospecies has been invented for this, in order to label 
our ignorance. 
        (Vienna is in the hybrid zone, although *C. c. cornix* is most 
common here.) 
 
In more colourful words: Some have said that species are the leaves on the 
Tree of Life. This is IMHO totally misleading. I think (along with most 
species concepts) that, instead, species are the cells in the Mycelium of 
Life -- but there are no cell walls, and the cell membranes are confluent 
in some places, producing everything from the plasma bridges between plant 
cells to syncytia (the fused cells that e. g. make up the epidermis of 
"Rotifera"). 
 
Therefore I think the PhyloCode should allow species (yes, a botanist and 
a polychaetologist have really argued against this), but not make them 
mandatory. I think this would make vertebrate palaeontology a bit easier. 
Take the *Triceratops* debate: Does *T. prorsus* exist? We'll never be 
able to test this under most concepts, we may not have enough fossils to 
apply the morphospecies concept (which requires statistics), we don't have 
the slightest idea if subspecies, allospecies or whatever were involved, 
so maybe we should stop worrying. 
 
> The study David is referring to is: [...] 
 
Exactly. :-) 
 
> "The assumption of a unique group of condylarthran type at the 
> origin of Afrotheria (macroscelids, tethytherians, tubulidentates, 
> tenrecid and chrysochlorid insectivores) cannot be excluded, 
 
Because "condylarths" are known from the Paleocene of Morocco. I wait for 
more phylogenetic studies... 
 
> Admittedly, chrysochlorids (golden moles) have no pre-Miocene fossil 
> record, AFAIK. 
 
Don't know if Miocene, but something like that. :-( 

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