September, 1999 
SCAMIT Newsletter 
Vol. 18, No.5 
the separation of the animals, and was critiqued 
by Don Cadien in NL Vol 15(6) [October 
1996]. A replacement key was “in 
progress” but has never been sent out. 
Dissatisfaction was expressed over the nature 
of the characters used in both the Bousfield and 
Chevrier key, and in the pictorial key which 
Don Cadien had constructed in development of 
a replacement key. Sex linked characters such 
as the length of the third article of the 
mandibular palp were considered poor for 
general use, and were to be avoided if at all 
possible. Likewise characters which were 
difficult to distinguish, such as the shape and 
relative posterior extension of the coxae and 
pleonal epimera, the relative shape and size of 
the articles of the third leg, and the proportions 
of the maxilliped outer plate were deemed too 
difficult in application to provide a viable key. 
In essence, we stepped back a pace and started 
over. Between the members present at the 
meeting we agreed to try using a series of 
characters which we felt could be repeatably 
evaluated. These were: 1) the orientation of the 
G1 palm; 2) the setation of the anterodistal 
margin of the basis of Gl; 3) the pattern of 
setae on the ventral margin of coxa 1; 4) the 
ratio of dactyl to propod length of G2; 5) the 
number of dorsal setal groups on the propod of 
G2; 6 ) the number of ventral setal groups on 
the propod of G2; 7) the ratio of G2 propod 
length to maximum width; 8) maximal propod 
width vs. basis width on G2; 9) extent of 
posterodistal lobe on the basis of P7; and 10) 
the nature of, or lack of, posterior marginal 
setation on the basis of P7. Don Cadien also 
suggested characters based on the spine and 
serration pattern of the uropods had value, but 
were not well enough known as regards 
variability between individuals, sexual 
dimorphism, and ontogenic change for current 
application. 
We scored each of these characters as follows: 
1. Gl palmar orientation - transverse [0], 
oblique [1], intermediate “can’t decide” 
[2]. This seemingly simple decision as to 
the orientation of the palm has proven to be 
quite difficult in practice. There is 
considerable perceptual difference between 
individuals in how a particular palm should 
be scored. In some cases there is an 
unequivocally transverse palm, but in 
numerous other cases a palm that is 
transverse at the hinge may taper off into 
obliquity before it joins the hind margin of 
the propod. Depending on just where this 
takes place such a palm could be scored as 
any of the above states. We must constrain 
ourselves to only the most clear cut cases 
for scores of 0 or 1, and place all other 
more problematic structures in 2. 
2. the setation of the anterodistal margin of 
the basis of Gl - strongly setose, with 4- 
10+ setae, usually long [0]; weakly setose, 
with 1-3 setae, usually very short [1]; setae 
lacking [2] 
3. the pattern of setae on the ventral 
margin of coxa 1 - setae markedly longer 
at posteroventral edge of coxa [0], or setae 
of posteroventral edge the same length as 
elsewhere on the ventral margin of coxa [1] 
(this includes cases where long and short 
setae are interspersed along the entire 
ventral margin of the coxa) 
4. the ratio of dactyl to propod length in 
G2 - 1/3 [0], 1/4 [1], 1/5 [2], 1/6 [3], 1/7 
[4], 1/8 [5], 1/9 [6]. These are all rounded 
to the nearest choice based on optical 
micrometer measurements of the lengths of 
dactyl and propod. 
5. the number of dorsal setal groups on the 
propod of G2 - scored directly 1=1,2=2, 
etc. Groups may have a single member and 
still be counted as a positional group. The 
group at the base of the dactyl is not 
counted, as it is present in all species. 
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