TRILOBITE BIOGEOGRAPHY OF GONDWANA 57
Fig. 2. Representatives of the Reedocalymeninae. (a) Vietnamia douvillei. (b) Calymenesun granulosa. (c, d)
Neseuretus elegans. Scale bars = 5 mm. Note that N. elegans displays an incipient anterior furrow (character 14,
state 1), whilst V. douvillei and C. granulosa both display complete anterior furrows (state 2). The slight
fixigenal depressions opposite the lp lobes in N. elegans represent paraglabellar areas rather than distinct
abaxial curvature of the axial furrows.
previous authors to discuss aspects of calymenid
phylogeny and evolution, notably those relat-
ing to the hypostome and rostral plate (e.g.
Whittington 1966a; Hammann 1983; Fortey
1990; Peng et al 2000), were thus excluded from
the analysis.
During determination of character states,
attempts were made to prevent preservational
variation from artificially influencing cladogram
topology, especially in characters regarded as
particularly vulnerable to such non-biological
variation (e.g. by combining 'absent' and
'weakly defined' under the same character
state for characters relating to furrow strength).
Variation between internal and external moulds
was also recognized. Poorly preserved material
was generally not analysed, although the
deformed type material for N. ramseyensis
Hicks, 1873 was studied in addition to the well-
preserved specimens figured by Fortey & Owens
(1987). Quantitative characters were coded
informally, with discontinuities in the distri-
bution of character states between different taxa
recognized and used to define character state
boundaries. The data matrix is presented in
Table 1.
(1) Midpoint of palpebral lobe (exsag.) as
proportion of distance from posterior
margin of occipital ring to anterior margin
of glabella: 0 = 0.83 or greater, 1 = 0.70 to
less than 0.83, 2 = below 0.70 (variation
between different taxa included in the
analysis ranges from 0.6 to 0.9, with several
taxa coded for state 1 displaying some
variation in palpebral lobe position).
(2) Length of preglabellar area as proportion
of total cranidial length (excluding 'pre-
cranidial' projection if present): 0 = less
than 0.3,1 = 0.3 or greater (variation within
ingroup taxa ranges from 0.2 to 0.4).
(3) Length of 1s furrow (tr., measured from
