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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
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