PALYNOLOGICAL ZONATION OF MID-PALAEOZOIC, NW SPAIN 



determine how many of these ubiquitous spores had evolved before 

 the break-up of the southern continent. On the other hand, trilete 

 species, which evolved after many of the regionally dispersed 

 cryptospores (e.g. Tetmhedraletes medinensis ( Strother & Traverse), 

 PI. 1, fig. 10), apparently show a dichotomy with several distinctive 

 trilete species currently known only from the Cantabrian Mountains 

 and North Africa. As more spore data accumulates, therefore, the 

 dispersal patterns of early land floras may provide constraints to 

 palinspastic reconstructions. In addition, new insights into the corre- 

 lation of marine with non-marine plant-bearing strata, will help to 

 date more accurately events in land plant evolution, recorded in 

 greatest detail in continental rocks. Further, the joint study of 

 chitinozoans and spores in the same sequences will eventually 

 permit an understanding of inter-facies correlation, not only in 

 marine shelf environments, but also with stratotype sequences mainly 

 established in sediments deposited in distal marine environments 

 where spores are often rare and badly preserved. 



There is some support from the chitinozoan data for the changing 

 regional differences in the spore data outlined above. Though the 

 nature of sampling for chitinozoans (see below) makes any direct 

 comparisons difficult. However, there does appear to be an increas- 

 ing similarity between chitinozoan assemblages of northwest Spain 

 and North America/Europe in the upper/later parts of all four sec- 

 tions studied. Due to a lack of data it is not possible to determine if 

 there is a corresponding "dissimilarity" with Gondwanan assem- 

 blages. Paris et al. (1995) noted similarities between chitinozoan 

 assemblages in northern Spain and Gondwana and dissimilarity with 

 coeval assemblages in Baltica during the Llandovery. This evidence 

 was used to support the existence of a wide mid-European Rheic 

 Ocean during the Llandovery. 



Such temperal changes in our assemblages, i.e. a greater similarity 

 with Gondwanan spore floras in the Lower Silurian, and increasing 

 similarity with Baltic/ Avalonian assemblages in the Upper Silurian/ 

 Lower Devonian, would be consistent with a drift of northwest Spain 

 away from Gondwana and towards Laurentia/Avalonia through this 

 period. 



CHITINOZOA 



General distribution 



In sections where the Formigoso Formation is represented ( Argovejo 

 and La Vid) chitinozoans belonging to the genera Cyathochitina and 



129 



Conochitina are common. The lower parts of the San Pedro Forma- 

 tion often contain Angocliitina and Sphuerochitina with species 

 belonging to Plectocliitina (e.g. Pleciochitina caniinac Cramer & 

 Diez 1978a, figs 8q, 8r and Plectochiiinci roseiulae Cramer & Diez 

 1978a, fig. 8p) and heavily ornamented species such iisAncyrochitina 

 javieri Schweineberg 1987 (figs 8f. g) becoming more common in 

 the central parts of the formation. Certain species such as Calpichitina 

 velata Wrona (1980: figs 6i, j) and Margachitina catineria Obut 

 (1973: fig. 6r) occur in 'blooms' at certain horizons, for example C. 

 velata at La Vid (LV6) and M. catenaria (PI. 11, fig. 13) at Geras 

 (Gerl6, 17 and 18). In addition, the chitinozoans Vinnalochitina 

 horrentis (Wrona, 1980), Cingiilochitina errensis (Paris. 1979) and 

 Ciugulochirina serrata (Taugourdeau & de Jekhowsky, 1960) form 

 common components of assemblages in the San Pedro Formation 

 (see PI. 11, figs 8, 1 la, 1 lb and PI. 12, fig. 9 respecdvely). 



Geras (Fig. 10) 



Unlike the other three sections, no Llandovery chitinozoans were 

 recovered. Spluierocliitina sphaemcepliala (Eisenack 1932) and 

 Angochitiiia echinata Eisenack 1932 (PL 12, figs 6 and 10 respec- 

 tively) were used as accompanying species in the Global Chitinozoan 

 Biozonadon of Verniers et al. (1995). Their presence in Ger 2b, 1.5 

 metres above the base of the section, suggests a mid-Gorstian to 

 Lower Pffdoli age for the lower part of the San Pedro Formation at 

 Geras. Greater resolution is provided by Ramochitina villosa 

 (Laufeld, 1974) (recovered from sample Ger 2a, 2.4 metres above the 

 base of the section and Ger 2b; PI. 13. fig. 7) which has been reported 

 from the top of the Lower Leintwardine Formation and the Upper 

 Whitcliffe Formation of the type Ludlow, UK (Sutherland 1994: 65) 

 and from strata of similar Upper Ludfordian age on Gotland (Hamra 

 and Sundre Beds, Laufeld, 1974: 96) and Estonia (Kuressaare Re- 

 gional Stage, Nestor, 1990: 85). Ancyrochitina valladolitana 

 Schweineberg 1987 (figs 8d, e) was recovered from Ger 4, 10 m 

 above the base of the section within the San Pedro Formation. This 

 species was described from the Palencia region of Northern Spain by 

 Schweineberg (1987) and assigned to graptolite biozones 34/35 

 (Gorsdan) of Elles & Wood (1901-18). However, it was noted that 

 the chitinozoan species probably ranges into the Pfidoli 

 (Schweineberg 1987:77). 



Ancyrochitina javieri Schweineberg (1987: figs 8f, g) has also 

 been recovered from Ger 4. This species was described as occurring 

 between graptolite biozones 32 to 35 (late Homerian-Lower Gorstian) 

 of Elles & Wood ( 1 90 1 -1 8) in the Palencia Region of Northern Spain 



PLATE 1 



Figs 1, 2 Artemopyral sp. A. 1, BM 137698, oblique compression showing radial folds on the proximal and distal surfaces adjacent to the curvatural ridge, 



X 2000, stub Ger92/9/l; 2, BM 130612, specimen with more delicate muri than that in Fig. 1. oblique compression, x 2000, sample Ger92/8. 

 Fig. 3 Chelinohilates sp. BM 137155, dyad showing distal and subequatorial muri, sample Geras 92/9/1. 



Cymbohilates cf. allenii var. magnus Richardson 1996. BM 1 15329, proximal view showing remnants of hilum. sample Arg92/14. 

 Hispanaediscus cf. lamontii Wellman 1993. BM 135296. proximal view, x 2000, sample Ger92/2B/2. 

 Cymbohilates cf. horridus Richardson 1996. BM 130858. sample LV92/I3: 6a, proximal view; 6b, detail of spines; x 2500. 

 Hispanaediscus lamontii ^eWman 1993. BM 137471, dyad, sample Arg 1 3/Dl. 

 Tetraletes variabilis Cramer 1966a. BM 1 37848. tetragonal (cruciform) tetrad, sample Ger92/6. 



Velatitetras rugulatal Burgess 1991. BM 465, LV92/6; 9a. tetrad, lines of attachment probably covered by closely adherent envelope; 9b. detail of 

 geniculate disjointed muri. x 2000. 

 Fig. 10 Tetraletes medinensis (Strother & Traverse) emend. Wellman & Richardson 1993. BM 130623. showing lines of attachment and microgranulate 



distal surfaces, sample Ger92/8/l. 

 Fig. 11 Pachytetras sp. BM 1381 1 1, LV92/8/DD; 11a, unfused tetrad showing sculpture sloughing off revealing lines of attachment; lib, BM 1381 13. 



detail of microverrucate-murornate sculpture, x 5000. 

 Fig. 12 Tetraletes variabilisT Crmner 1966a. BM 132691, LV92/ 10; 12a. BM 132691; 12b, detail of microverrucale sculpture, x 2000. 



All are Scanning Electron Photomicrographs at x 1000 unless otherwise stated; BM numbers refer to photographic negatives in the archives of the 

 Natural History Museum. London. 



Fig. 4 

 Fig. 5 

 Fig. 6 

 Fig. 7 

 Fig. 8 

 Fig. 9 



