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J.B. RICHARDSON, R.M. RODRIGUEZ AND S.J.E. SUTHERLAND 



La Peral) and secondly an occurrence in the RS Biozone (Upper 

 Ludfordian to Lower Pfidolf). This suggests some reworking in 

 our sections. V. iirna forms an important part of assemblages in 

 both regions and is considered by Schweineberg (1987) to be 

 restricted to the Pfidoli in Palencia. See preceding discussion of 

 our sections and further discussion of the Asturias-Leon/Palencian 

 chitinozoan ranges below. The two regions share the following 

 Ludlow/Pfi'doli species: Ancyrochitina javieri, Angochitina 

 echinata. Angochitina elongata. Angochitina thadeid. Conochitina 

 pachycephala, Cyathochitina elenitae, Margachitina elegans var. 

 carta, Ancyrochitina libyensis, Ancyrochitina valladolitana, 

 Angochitina ambrosi ambrosi, Cingiilochitina wronai, Palenchi- 

 tina pisuergensis. Plectochitina carminae; Cantabrian specimens 

 are figured in PI. 12, figs 3, 12, 14, PI. 13, figs 1-4, 9. 



Prague Basin (Bohemia) 



The Prague Basin is both the type area for the base of the Pfi'doli 

 ( Fozary, 1 km east of Reporyje ) and the base of the Devonian ( Klonk. 

 SW of Prague). The characteristic chitinozoan of the Upper Ludlow, 

 Eisenackitina barrandei Paris & Kri'z (1984), was not recovered 

 from our sections. Only species that extend into the Pfidoli in 

 Bohemia were recovered in the Cantabrian Mountains {S. 

 sphaerocephala. C. wronai). U. unia is a common component of 

 assemblages in the middle to upper portions of the San Pedro 

 Formation. It is regarded as a useful Pfidoli marker (see Paris in Kn'z 

 et al, 1986) although atypical forms do occur 'a few cm' (Paris in 

 Kriz et al.. 1986: 338) below the first occurrence of Monograptus 

 pandtimus. The only other chitinozoan regarded as an Lower Pfidoli 

 form in Bohemia, F. kosovensis, is recorded towards the top of the 

 section at La Peral (LP 19). In Bohemia the base of the Devonian is 

 regarded as being coincident or very close to the first occurrence of 

 E. bohemica. A. chlupaci is also regarded as a Lower Lochkovian 

 form (Paris ef a/., 1981). Both these species occur in the Cantabrian 

 Mountains and are associated with Devonian spores (see description 

 of chitinozoan distribution in Geras and Argovejo). As in Bohemia, 

 C. velata (chitinozoan indet. n. gen? in Paris et al, 1981) occurs 

 close to the top of the Silurian in the Cantabrian Mountains (PI. 1 1, 

 fig. 7). 



The Type Ludlow Sections 



Sutherland (1994) described chitinozoans from the type Ludlow in 

 the Welsh Borderlands of the UK. The Lower Ludlow in the type area 

 is characterized by Conochitina Eisenack (1931) species and in 

 particular C. rudda and C. pachycephala. Both these species are 

 recognized in our sections, but only from one sample at La Peral 

 (LP3) in the San Pedro Formation. Angochitina echinata is a com- 

 mon component of mid-Ludlow assemblages in the Welsh 

 Borderlands and occurs sporadically through the San Pedro Forma- 

 tion. In the Ludfordian, R. villosa is the only species we find in 

 common with the type area where this species is a useful marker for 

 the mid- to upper Ludfordian. Due to poor chitinozoan recovery 

 from the latest Ludlow and Lower Pfidoli in the Welsh Borderlands 

 (probably as a result of an increasing fresh water influence) any 

 further comparisons are difficult. 



PodoHa, Ukraine 



A provisional study of Silurian and Devonian sections of this area 

 was detailed in Paris & Grahn (1996). Six assemblages were de- 

 fined, the age controlled with reference to chitinozoan index taxa 

 in Bohemia (Kriz et al.. 1986; Paris et al.. 1981). Assemblage 1 

 from Podolia, characterized by E. barrandei was not encountered 



in our study. Podolian chitinozoan assemblage 2 containing U. 

 urna. M. elegans and F. kosovensis was regarded as Lower to mid- 

 Pi'idoli in age. The same species are encountered in our study 

 within the San Pedro Formation. The characteristic chitinozoan of 

 Paris & Grahn's assemblage 3 (Upper Pfidoli). C. velata. was 

 recovered from the San Pedro Formation at La Vid and Geras. 

 Paris & Grahn (1996) take the base of the Devonian in Podolia as 

 being coincident with the base of the Podolian chitinozoan assem- 

 blage 4. The zone is defined by the first occurrence off. bohemica. 

 which is also associated with M. catenaria. Both these species 

 (although M. catenaria somewhat dubiously in Geras) are present 

 in the upper parts of the San Pedro Formation. A. tsegulnjucki, 

 regarded as a characteristic species of Paris & Grahn's assemblage 

 5 (Lochkovian) coincides with the range off. bohemica in Geras. 

 It is important to note that Paris & Grahn's location of the Silurian/ 

 Devonian in Podolia is in disagreement with the assignment of 

 previous workers who have placed the boundary at the first occur- 

 rence of Monograptus uniformis angustidens (e.g., Koren' 1968). 

 The base of the Devonian at the type section at Klonk coincides 

 with the first occurrence of Monograptus uniformis uniformis 

 (Holland, 1985), a closely related subspecies. At Klonk both 

 graptolites occur at the same level but in Podolia the first 

 Monograptus. u. uniformis occurs higher than Monograptus u. 

 angustidens. As E. bohemica occurs very close to the first appear- 

 ance of Monograptus u. uniformis in both sections. Paris & Grahn 

 (1996) elected to draw the Silurian/Devonian boundary at the base 

 of the range of E. bohemica and Monograptus u. uniformis. 



Eastern Canada 



Achab & Asselin (1993) describe Cingulochitina en'ensis, C. ser- 

 rata and Urnochitina urna from the Chaleurs Group in the 

 northeastern Gaspe Peninsula. These species form common compo- 

 nents of assemblages in the San Pedro Formation. Achab & Asselin 

 used the presence off. bohemica. M. catenaria and A. chlupaci to 

 define the base of the Devonian in this area of Canada. In the 

 Cantabrian Mountains, the same species are found associated with or 

 at a level above the first occurrence of Aneurospora, taken by 

 Richardson, Rodriguez & Sutherland (2000) to represent the base of 

 the Devonian. 



North Africa 



Taugourdeau & Jekhowsky ( 1 960) published data from core material 

 from the Sahara. It is difficult to compare the material from our area 

 with that of North Africa with any great certainty, due to the relative 

 lack of stratigraphical control and difficulty in positively identifying 

 chitinozoans from the silhouettes presented in the plates of the paper. 

 However, C. serrata. M. elegans and f . bohemica are recorded by 

 Taugourdeau & Jekhowsky (1960) in a broad zone defined as 

 'Gothlandian' (approximately equivalent to the Silurian) to Lower/ 

 Middle Devonian. 



Jaglin (1986) examined core material from the Upper Silurian 

 (mostly Pfidolf) of Libya. Jaglin made age determinations based 

 on well-known Pfidolf chitinozoans such as U. urna, P. perivelata, 

 M. elegans and P. carmenchui. Many of the species recorded from 

 the Pfidoli by Jaglin (1986) were also encountered in the 

 Cantabrian Mountains. These include: A. libyensis, V. horrentis, C. 

 serrata, F. kosovensis, R. villosa, M. elegans, P. carminae, P. 

 carmenchui, S. sphaerocephala and U. urna. Of these, only the 

 ranges of A. libyensis and V. horrentis were detailed by Jaglin, all 

 of which were shown as being present close to the base of the 

 Pfidoli in borehole A 1-61. 



