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Tharyx illustration and names

Geoff Read g.read at niwa.cri.nz
Wed Mar 11 01:56:20 EST 1998


This has  turned  into a stimulating & useful thread. Thank you Tom &
Leslie - barking up an unlikely tree is demonstrably sometimes fruitful! I
hope most have continued to glance in, regardless of the  subject header
and their lack of interest in what might be implied by old cirratulid
drawings. As an aside regarding recycling ancient drawings  I guess one
point is that WE know the species names are unlikely to be everyone of them
'correct' now, but the untutored will not unless they are specifically told
they have not been updated. But I think it was appropriate for Greg to
include the names in the captions so that readers can evaluate their worth
- if they need to. 

> As the worm added more
> segments (always from the posterior end of course) it maintained more or
> less a certain fraction of the anterior end with crowded segments, and in
> cases with the flattened, beaver-tails, a certain fraction in the beaver
> tail. 

This seems entirely reasonable for this sort of shape problem.

> As Mary Petersen pointed out, getting too hooked up in counting
> segments is probablly not a very good idea: 

In the circumstance Kristian was addressing that is an appropriate
cautionary remark. Elsewhere I have no doubt he  thinks careful counting of
segments can be essential.  This is where it is a case of first occurrence
of, or a sequence of, a distinct segmental feature - a type of parapodial
lobe, a gill, and (with less confidence beyond say segment 10) a type of
seta (dare I mention the capitellid 'genera' ?). Certain worms place these
very precisely with no variation in at least  the first 20 segments. After
that  the 'counting' may get sloppy for reasons which include positioning
in relation to growth in total number of segments. With adequate numbers of
specimens one establishes the meristics and proves these things. An
adequate number of specimens is always a good thing before inflicting 'new'
species and genera upon the world, especially with soft, easily-distorted 
creatures like worms - unless one has something unique beyond dispute. 

--
  Geoff Read <g.read at niwa.cri.nz>

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