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



Genus Cymbospnrites AWen 1965 159 



Taxonomy of Chitinozoa 160 



Order Prosomatifera Eisenack 1972 160 



Family Lagenochitinidae Eisenack 1931 160 



Subfamily Angochitininae Paris 1981 160 



Genus Ramochitina Sommer & van Boekel 1964 160 



Acknowledgements 160 



References 160 



SYNOPSIS. Mid-Palaeozoic strata from the Cantabrian Mountains (north-west Spain) contain rich assemblages of spores, 

 acritarchs and Chitinozoa. Fossil maturation is variable but generally high. The stratigraphical distribution of miospores and 

 cryptospores from four sections through the San Pedro and lower La Vid Formations is sufficiently consistent for the establishment 

 of a sequence of six biozones (including four new biozones). In ascending order the biozones are: 1 , Scylaspora vetusta - S. sp. 

 B ( V) Spore Biozone; 2, Anemopyra brevicosta - Hispanaediscus verrucatus (BV) Spore Biozone; 3. Coronaspora reticulata 

 - Chelinospora sanpetremis (RS) Spore Biozone; 4, Chelinospora hemiesferica (H) Spore Biozone: 5. Scylaspora elegans - 

 Iberoespora cantabrica (EC) Spore Biozone; 6, Streelispora newportensis - Emphanisporites micrornatus (MN) Spore 

 Biozone. The elegans - cantabrica (EC) Spore Biozone is divided into two sub-biozones based on the first appearance of the 

 genus Aneuiospora and the lower part of the MN Biozone is distinguished as a separate subzone. namely the Streelispora 

 newportensis - Leonispora argovejae (NA) Spore Assemblage Sub-Biozone (also present in England). The Ludford/Pindoh' 

 boundary is probably within the upper part of the reticulata -sanpetrensis Spore Biozone, and theAneurospora Sub-Biozone and 

 succeeding MN Biozone, allow inter-regional correlation with basal and Lower Lochkovian strata. Comparisons between 

 England. Spain, and North Africa, show that regional differences in spore floras are most marked in the Pfidoli. In the Lower 

 Devonian the differences are less pronounced, and the appearance of variants of the genus Aneiirospora marks a significant event 

 in both the Laurussian and Gondwanan regions, reflecting wide dispersal of their parent plants. Chitinozoans occur throughout 

 most of the sequence and several species have potential for inter-regional correlation e.g. Ramochitina villosa (RS Biozone) upper 

 part of the urna (lower EC Biozone) and Eisenackitina hohemica (lower MN Biozone). 



INTRODUCTION 



Because of their abundance and species diversity land plant spores 

 have a much greater potential for the determination of ancient floral 

 regimes than their parent plants. Further, where their fertile parts are 

 known, all Silurian to Lower Devonian (Lochkovian) plants are 

 homosporous with small spores (often c. 20 |jm, and below 100 pm). 

 Factors which should ensure that their parent plants are widely 

 dispersed. In fact, mid-Palaeozoic spores and marine palynomorphs 

 are found on each of the major drifting continental blocks studied, 

 namely Laurussia and Gondwana. Comparisons of sequences of 

 spores from the Anglo- Welsh area with those from the Cantabrian 

 Mountains and North Africa should aid in the resolution of the nature 

 of these Palaeozoic floras. However, a prerequisite is the study of 

 spore sequences in the three areas. In this study miospores from 

 Southern Britain and the Cantabrian Mountains are studied in detail 

 along with some preliminary work on the chitinozoans of northern 

 Spain. Work on North Africa has been partially published (Richardson 

 & loannides, 1973) and additional North African areas are currently 

 being studied. Seward ( 193 1 ) stated that it is inconceivable that the 

 climate of the Earth was ever uniform, and influences on vegetation 

 might be expected to be profound where crustal pieces drifted 

 through different latitudinal belts. By providing an accurate biozonal 

 framework this work aims to facilitate more accurate comparisons of 

 spore floras in the three areas. The resultant floral dispersal patterns 

 vary through the time interval studied and further work is needed to 

 answer some of the many questions raised. 



One of the important features of this study is the completeness of 

 the Pfidolf sections in the Cantabrian Mountains in a marine but 

 continentally influenced succession. This probably represents the 

 most complete miospore zonation through the Pfidoli Stage. In the 

 continental sections in England there are some of the longest, well- 

 preserved, miospore successions, with a sequence of miospore 

 assemblages from Upper Aeronian to Lower Pfidoli and uppermost 



Pfi'doli to Lower Lochkovian (Silurian to Lower Devonian). How- 

 ever, there is a gap, equivalent to the upper Lower PiTdoli, Middle 

 Pfidoli, and lower Upper Pfidoli, where no miospore assemblages 

 are known. Between these productive beds of the Lower Devonian 

 (Aneurospora Subzone and MN Zone) and those from the Lower 

 Downtonian (Lower Pfidoli) below, there is, therefore, in England, a 

 considerable gap in the Pfidoli spore occurrence. Although there are 

 spores in graptolite-bearing marine sediments in Podolia these spores 

 have been inadequately described and illustrated. The spores 

 illustrated by Shepeleva (1963) from the Lower Devonian of Podolia 

 possibly belong to the MN Zone and her species Lophozonotriletes 

 decoratus closely resembles Streelispora newportensis, the nominal 

 species for the base of the MN Zone. 



GEOGRAPHICAL & GEOLOGICAL SETTING 

 (FIG. 1) 



The Cantabrian Mountains, in the north and northwest of Spain, 

 extend through the Provinces of Asturias, Leon, Cantabria and 

 Palencia. Geologically, most of the Cantabrian Mountains belong to 

 the 'Cantabrian Zone' of the Iberian Hercynian Massif and occupies 

 the outermost part of it. The 'Cantabrian Zone' is composed of 

 unmetamorphosed Palaeozoic sedimentary rocks deformed during 

 the Variscan Orogeny. The 'Cantabrian Zone' has been divided into 

 five tectono-sedimentary units (Julivert, 1967), arranged in concen- 

 tric bands parallel to the 'Narcea Anticlinorium', an arch of 

 Precambrian rocks on the western boundary of the 'Cantabrian 

 Zone' (see Fig. 1 ). Following to the east of the ' Narcea Anticlinorium' 

 is the 'Folds and Nappes Unit' where the most complete Palaeozoic 

 sequences are found. This Unit occupies the western part of the 

 Asturias and the northern part of the Leon Provinces. Within this 

 structural unit four sections in a Silurian to Lower Devonian clastic 

 succession have been selected for study. 



