TRILOBITE BIOGEOGRAPHY OF GONDWANA 61
Fig. 3. (b) Neseuretus subclade from second strict consensus cladogram generated by removing N. attenuatus,
N. chaschuilensis and N. sexangulus from the dataset.
between the consensus tree and the known
stratigraphic ranges of the ingroup taxa. As
Neseuretus represents a derived member of the
Reedocalymeninae in the consensus tree, all of
the major subclades are constrained to have
evolved by the Arenig. This necessitates ghost
ranges during the Arenig for N. sanlucasensis
and the Reedocalymene-Calymenesun subclade
only, providing fairly good correlation at series
level, although the stratigraphic occurrence of
Neseuretinus, Sarrabesia and Vietnamia remains
poorly understood for many Asian localities
and little confidence can be placed on strati-
graphic ranges within this subclade (e.g. Dean
1967b; Pillet & de Lapparent 1969; Hammann
& Leone 1997; Zhou et al. 1998a).
Cladistic biogeography
The consensus cladogram in Figure 3a was con-
verted into an area cladogram for biogeographic
analysis by substituting the names of the
different ingroup taxa with the Early Ordovician
geographic area(s) from which they have been
recorded (Fig. 4). The area cladogram is simpli-
fied, as area redundancy has been corrected. For
the non-Neseuretus reedocalymenine taxa, the
combined biogeographic area occupied by all
representatives of the genus recognized herein
was recorded on the area cladogram.
Area delimitation in some cases requires
explanation. France+Spain are regarded as rep-
resenting a single biogeographic area, following
the strong faunal similarities between these
regions noted by previous authors (e.g. Paris
1998). Sengor (1984, 1987) proposed that
Turkey, the Sibumasu and Indo-China terranes
and areas of Central Asia represented a
peri-Gondwanan continent called Cimmeria.
However, Turkey represents a complex region,
with northern and southern Turkey now inter-
preted as having occupied separate palaeogeo-
graphic positions during the Ordovician.
Southern Turkey, source of the Turkish material
of Neseuretus and Neseuretinus, was tentatively
assigned to a high-latitude position on the
margin of Gondwana at the eastern end of the
present-day Mediterranean (Dean et al, 2000;
Cocks 2001), the eastern region of the North
Gondwanan Province of Paris (1998). Following
these authors, southern Turkey is here pro-
visionally interpreted as having been separate
from Cimmeria during the Ordovician, and is
grouped with Sardinia, another eastern Mediter-
ranean component of Paris' (1998) North
Gondwanan Province. As noted above. Early
Ordovician faunas from South China, Tarim and
Indo-China also share strong similarities (e.g.
Zhou & Dean 1989), with the two South Chinese
Neseuretus species N. elegans Yin in Yin & Lee,
1978 and N. tungtzuensis Sheng, 1958 also
recorded from Indo-China by Zhou et al. (1998a,
