TRILOBITE BIOGEOGRAPHY OF GONDWANA 55
Fig. 1. Early Ordovician (Arenig) palaeogeography, showing the Arenig-basal Caradoc geographic
distribution of the 22 Neseuretus species included in the cladistic analysis. Key: 1, South China (Yangtze
Platform): N. concavus (Arenig), N. elegans (Arenig-Llanvirn), N. intermedius (Arenig), N.planus (Arenig),
N. shensiensis (Arenig); 2, Indo-China: N. elegans (Arenig-Llanvirn), N. turveyi (Llanvirn); 3, Arabia: N.
tristani (Llanvirn); 4, South Turkey: N. sexangulus (Arenig); 5, Libya: N. tristani (Llanvirn); 6, France
(Armorica, Montagne Noire); N. arenosus (Arenig), N. tristani (Llanvirn); 7, Spain (Iberia): N. avus
(Llanvirn), N. henkei (Llanvirn), N. leonensis (?Arenig/Llanvirn), N. tristani (Llanvirn-basal Caradoc); 8, Anti-
Atlas, Morocco: N. attenuatus (Llanvirn), N. tristani (Llanvirn); 9, Eastern Avalonia: N. caerhunensis (Arenig),
N. monensis (Arenig), N. murchisoni (Arenig), N. parvifrons (Arenig), N. ramseyensis (Arenig); 10, Western
Avalonia: N. vaningeni (Arenig); 11: South America: N. chaschuilensis (Arenig, Argentina), N. lipanensis
(Arenig-Llanvirn, Argentina), N. sanlucasensis (Llanvirn, Bolivia). Map generated by David Lees (Natural
History Museum, London).
China and the Central Andean basin of South
America, and is regarded as one of the more
reliable indicators of the former extent of
Gondwana (although species assigned to
Neseuretus or its junior synonym Synhomalono-
tus from various Central Asian regions, some of
which were listed by Fortey & Morris (1982) and
Rabano (1990) as valid representatives of the
genus, represent different reedocalymenine
genera) (Fig. 1). As early as 1937, Kobayashi
noted that the genus (as Synhomalonotus] was
characteristic of the 'Euro-Meridional' Province
in the Early Ordovician, and later established
the term 'Asaphopsis-Taihungshania-Neseure-
tus Fauna' to describe the Early and Middle
Ordovician southern faunal province
(Kobayashi 1976, 1987). The association is
interpreted as typically occurring in shallow
inner-shelf environments (Fortey & Morris
1982). However, various species of Neseuretus
have also been recorded in shallow outer-shelf
deposits across much of the geographic range of
the genus, in faunas composed of slightly
deeper-water trilobite taxa such as Colpo-
coryphe, Salterocoryphe, Placoparia, Zelis-
zkella, Ectillaenus and Hanchungolithus,
indicating that the genus had a wider palaeo-
bathymetric tolerance than has previously been
suggested (Dean 1966; Yin & Lee 1978;
Courtessole et al. 1981; Beckly 1989; Henry
1989; Rabano 1990; Zhou et al. 1998a). The
Neseuretus Association was originally regarded
as an indicator of cold water, circumpolar shelf
seas (Fortey & Morris 1982). This interpretation
has been revised due to the occurrence of the
association in Early Ordovician tropical regions
