TRILOBITE BIOGEOGRAPHY OF GONDWANA 65Neseuretus during the Early Ordovician.
Asaphids are a common component of the
Neseuretus Association across the entire Gond-
wanan region; however, the relationships within
the family are currently poorly understood, and
thorough taxonomic revision is required before
they can be used to test the hypothesis of area
relationships generated with the Reedocaly-
meninae.
Early Ordovician trilobite taxa potentially
able to provide a test for this hypothesis include
the dikelokephalinid Hungioides, which ranges
from western Europe to South America (Fortey
& Peel 1983), and two different groups of
trinucleids which occur in slightly deeper shelf
conditions. The closely related hanchun-
golithine trinucleid genera Hanchungolithus and
Ningkianolithus, regarded by Li (1994) as occur-
ring only in South China, have in fact also been
recorded in Avalonia, France, the Middle East,
Indo-China and possibly Spain (Dean 1966; El-
Khayal & Romano 1985; Beckly 1989; Rabano
1990), although South American material
originally assigned to Hanchungolithus (Hughes
et al. 1975, as Ichangolithus} has recently been
transferred to the Trinucleinae (Baldis & Pothe
de Baldis 1995). A second trinucleid group
comprises the genera Lordshillia, Anebolithus,
Famatinolithus and Incaia, which appear to be
closely related to each other within the Trinu-
cleinae, and occur in Avalonia, South China,
New Zealand and South America (Hughes et al.
1975). Future cladistic research on some of these
groups can hopefully provide further infor-
mation on Early Ordovician area relationships
across Gondwana and peri-Gondwana.
This project was greatly helped by the encouragement
and assistance of D.J. Siveter, who engaged the author
with considerable discussion on the evolution of the
Calymenidae, and provided access to his substantial
reference collection. Discussion with T.G. Waters
generated further ideas on appropriate methods of
biogeographic analysis. P. Janvier and Tong-Dzuy
Thanh provided useful information on Vietnamia dou-
villei, and casts of most of Mansuy's type material of
this species were provided by P. Racheboeuf. The
Early Ordovician map used in Figure 1 was generated
by D. Lees, and M.D. Sutton provided welcome tech-
nical assistance. W.T. Dean, A.W. Owen and M.
Romano reviewed the manuscript and made several
useful suggestions for its improvement. Funding for
the project was provided by a Natural Environment
Research Council D.Phil studentship.
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