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Tharyx illustration

Leslie H. Harris lhharris at almaak.usc.edu
Mon Mar 9 21:41:24 EST 1998


I'd like to thank Mary Petersen for the valuable observations on cirratulid
variability in her latest email.  The most salient point was this: "...but
to start dissecting descriptions without having seen the material is not
very useful", and one that applies equally well to speculating about
illustrations.  

Several questions have been raised about Tharyx (= Aphelochaeta) monilaris
that can be best answered by looking at the types and other material
identified by Hartman. Most of the information below comes from my own
examination.  Mary has been quite generous in sharing her comments on the
holotype, as noted below.

1) Tom Parker suspects that "the illustration of Tharyx monilaris used by
Rouse and Fauchald as a reprinting of Hartman's 1960 Plate 12 figure 2 is
the posterior end of the neighboring illustration (Plate 12, figure 1)".
His supposition is based on a) similarities of configuration, and b)
Hartman 1969 (the Atlas) says T. monilaris has 15 crowded thoracic segments
& 10 inflated pygidial segments, but the inflated thoracic region in fig. 2
has 10 setigers, which is the same number as in the inflated posterior
region in fig. 1.  He speculates that fig. 2 is a "draft illustration Anker
Petersen drew of the posterior end of the figure 1 specimen; and he later
added anterior palps and setae from the second specimen to the base
illustration". Tom continues "Of course if the specimen you refer to in the
AHF collection used for figure 2 actually has 10 crowded thoracic setigers,
then the text description for the thoracic count is wrong!  Since you say
the anterior appendages are all currently missing from this specimen---is
it possible that it is actually a posterior end?"

    As stated before, the specimen from fig. 2 (Velero st. 5886) exists.
All of the appendages are missing, however the basalmost parts of the palps
are still attached & quite obvious.  I'm sorry I wasn't more explicit about
that.  The buccal opening is also obvious - and unlikely to be mistaken for
the typical cirratulid pygidium.  The figure has been embellished to a
degree, but it is still an accurate presentation of the specimen.  The only
error is that the palps are drawn on the same level as the first notosetae,
when they are clearly situated anterior to the first segment (correctly
shown in fig. 1).  Anker Petersen's inked plate is in the LACM-AHF
collection: the palps & anterior setae are clearly original to the drawing.
The specimen in fig. 2 does has 10 setigers in the crowded thoracic region,
contrary to the 15 setigers stated in Hartman 1960 & 1969.  This does not
mean that Hartman's description is wrong, just that it is incomplete.  As
Mary points out, there is a certain amount of variability in the size of
the expanded region.  Jim Blake's description for A. monilaris (1996,
Taxonomic Atlas, p. 333) states "...expanded thoracic region of 10-20 more
or less crowded setigers...and an expanded posterior region of 10-15
segments)". The specimen in pl. 12, fig. 1 shows 15 setigers. The holotype
has 12 setigers of equal length, the next 4 gradually lengthen while the
width remains the same, after setiger 16 the segments continue to enlarge
but the width decreases and by setiger 21 they are strongly moniliform. 
Mary observed that setiger 15 is 2x the length of one of the first 10
setigers (which are all of equal length), the 16th setiger is 2x the length
of the 15th, and the middle (beadlike) segments are 1.5 to 2x the length of
setiger 16.  The paratype also has 12 setigers of equal length, 7
transitional setigers, and strongly moniliform segments from setiger 20. 
Additional material identified by Hartman as T. monilaris has from 9 to 15
setigers in the expanded thoracic region, 5 to 7 transitional segments, and
10 to 22 setigers in the expanded posterior end.  The posterior end of the
holotype is now missing, but Mary previously noted that the expanded region
consisted of 16-17 short setigers, with a transition region of about 5
segments between these & the large moniliform ones.  

2) Jim Blake has said that "The type is selected from Sta. 4723 and is
illustrated in Plate 12, fig. 1.  ...Therefore, the illustration under
discussion is not the type specimen designated by Hartman and Tom Parker
may be correct in suggesting that it differs from the description of A.
monilaris.  ...It is more than likely that there is another species
involved."

    The specimen illustrated in fig. 1 is from the same station as the 
types, but is neither the holotype or the paratype.  I have not been able 
to locate the specimen, unfortunately, but the differences in setiger 
counts for the expanded thoracic & posterior regions preclude it being a 
type. The median segments of the holotype, which is ovigerous, are 
strongly moniliform with deep constrictions between them, while those of 
the figured specimen are more cylindrical with shallow constrictions.  As 
for the specimen in fig. 2, it is a valid A. monilaris, matching the types 
in prostomial & peristomial shape & proportions, origin of palps, median
segment proportions, and staining pattern.  The specimen has only 10
setigers in the expanded thoracic region, but that is within the range
shown by supplemental material and matches the number in Jim's own
illustration of A. monilaris (Blake 1996, fig. 8.28).  Jim is correct to
point out that more than one species may be involved, although this is
not reflected in Hartman's species description.  Hartman (1960, p. 127)
mentions that specimens come from Santa Catalina, Tanner and questionably
San Nicolas & Long Basins, and that it is generally distributed in shelf,
slope & basin sediments.  Three of the four cited basin samples (depths
of 1292 to 1961 m) were found & examined: none of them were A. monilaris.
A cursory examination was done of twenty-five lots identified by Hartman
from shelf & slope depths. The majority of lots held several different
species of Aphelochaeta & other cirratulids; there were only a few
specimens of A. monilaris.  Mary was right when she remarked that Hartman
worked very quickly and did not throughly examine all specimens.

Tom, I hope this answers all your questions.  No doubt it would have been
simpler if you had just come over to LACM for an hour or two or asked to
borrow the specimens, but not as much fun for the rest of us. :-)

Cheers, L.

Leslie H. Harris
Collection Manager, 
LACM-Allan Hancock Foundation Polychaete Collection	tel: 213) 763-3234 Los
Angeles County Museum of Natural History		fax: 213) 746-2999 900 Exposition
Boulevard		       email: lhharris at bcf.usc.edu Los Angeles, California 90007
U.S.A.



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