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Fig. 1. Schematic palaeogeographic maps from the Llanvirn up to the Lochkovian showing distributions of the
miospore assemblages and their probable colonization of the lands. The list of publications is not exhaustive. (a), (b) and
(c) Modified after Scotese (2003). (d) modified after Torsvik & Cocks (2004). (a) Llanvirn-Caradoc palaeogeographic
map. 1: Saudi Arabia (Strother et al. 1996; Le H´riss´ et al. 2007 and Steemans et al. 2009); 2: The Czech Republic
(Vavrdov´ 1984); 3: UK (Wellman 1996). (b) Ashgill palaeogeographic map. 1: China (Wang et al. 1997); 2: Saudi
Arabia (Steemans et al. 2009); 3: Chad (Le H´riss´ work in progress at the Brest, Rennes and Li`ge Universities); 4:
Turkey (Steemans et al. 1996); 5: Libya (Richardson 1988); 6: The Czech Republic (Vavrdov´ 1988, 1989);
7: Belgium:(Steemans 2001); 8: UK (Burgess 1991). (c) Llandovery palaeogeographic map. 1: Saudi Arabia (Steemans
et al. 2000; Wellman et al. 2000a); 2: Libya (Richardson 1988); 3: Brazil (Le H´riss´ et al. 2001b; Mizusaki et al. 2002);
4: Paraguay (Steemans & Pereira 2002; Mendlowicz Mauller et al. 2003); 5: Argentina (Rubinstein &Vaccari 2004); 6:
UK (Burgess 1991). 7, 8: USA (Pratt et al. 1978; Strother & Traverse 1979; Johnson 1985). (d) Lochkovian
palaeogeographic map. 1: Saudi Arabia (Steemans et al. 2007); 2: Libya (Rubinstein & Steemans 2002); 3: Brazil
(Gerrienne et al. 2001); 4: Brazil (Rubinstein et al. 2005, 2008); 5: Bolivia (McGregor 1984); 6: Spain (Richardson et al.
2001); 7: Brittany (Steemans 1989); 8: UK (Richardson & Lister 1969; Wellman & Richardson 1996); 9-12: USA and
Canada (e.g. Johnson 1985; Pratt 1978; Strother & Traverse 1979; Strother & Beck 2000).
colonized Avalonia during the Early/Mid Ordo-
vician. Avalonia migrated to the north and collided
with Baltica during the Ashgill, transporting plants
from Gondwana (Fig. 1b). This could explain the
presence of similar cryptospore assemblages on
both sides of the Rheic Ocean. During the Ashgill,
new localities were colonized by the vegetation on
the Avalonia Plate and on the eastern part of the
Gondwana Plate (North Africa, peri-Gondwanan
terranes, Arabian Platform).
To date, no cryptospore assemblages have been
observed in Ordovician palynological assemblages
from South America. However, rare simple tetrads
(Tetrahedraletes medinensis Strother & Traverse
1979) have been reported in several Ordovician
localities from both South and North America
(Gray 1988; Ottone et al. 1999) and Baltica (Le
H´riss´ 1989). This cryptospore species is known
from the Llanvirn up to the Mid Devonian, under
many kinds of climates and in a wide range of
environments from marine near-shore to confined
continental area for example, associated with a
relict flora (Wellman & Richardson 1996). Fre-
quently, this species is the only one seen in
samples poor in cryptospores from either marine
or continental sediment.
T. medinensis has most probably been produced
by highly opportunistic and cosmopolitan plant
species. Simple tetrads and dyads appear to have
colonized all of the continents very early, most likely
in the Mid Ordovician, although some researchers
(e.g. Strother et al. 2004) controversially suggest
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