30 



J. WATSON, S.J. LYDON & N.A. HARRISON 



INTRODUCTION 



Since the early work of Watson (1969) on a revision of the English 

 Wealden flora, previously studied by Seward (1894, 1895, 1913), a 

 large amount of new material has become available from plant debris 

 beds which occur widely throughout the succession. This dispersed, 

 fragmentary material shows exceptional cuticular preservation and 

 has been extensively studied, particularly by scanning electron 

 microscopy, to yield a considerable volume of new information 

 which greatly adds to our knowledge of the flora and necessitates 

 significant changes to the floral list (Watson & Alvin 1996). This 

 material is by nature usually comminuted and the leaf fragments 

 attributed to the orders Czekanowskiales and Ginkgoales have been 

 placed within these higher taxa largely on the basis of cuticular 

 characters, though gross morphological features such as segment 

 width and evidence of a petiole are available from some specimens. 

 Five new czekanowskialean and ginkgoalean species are presented 

 together with consideration of changes made since the previous 

 assessment of the flora which included the Ginkgoales (Watson 

 1969). The Ginkgoales were then represented only by the single 

 species PseudotorelUa heterophylla Watson, which has since been 

 synonymized and recombined as PseudotorelUa linkii (Romer) 

 Watson & Harrison ( 1998). The studies of Hall (1987) and Watson & 

 Harrison (1998) indicate that the affinities of this species, together 

 with other needle-leaved forms of uncertain systematic position, are 

 more likely to lie within the Coniferales. In the meantime four of the 

 five species described here had been added to the flora piecemeal 

 (Oldham 1976; Hall 1987; Watson & Alvin 1996), though none of 

 them has been named until now. Recent stratigraphic work by Lydon 

 (in progress) led to the discovery of the Czekanowskia species 

 described here and also necessitated a reconsideration of ginkgoalean 

 leaf genera by Watson, Lydon & Harrison ( 1999). Only now have the 

 appropriate generic attributions become clear to us, with one species 

 of Czekanowskia, one species of Phoenicopsis and three species of 

 Ginkgoites replacing the species indicated on the floral list by 

 Watson & Alvin ( 1 996). It should be emphasised at this point that the 

 recognition of Czekanowskia and Phoenicopsis in the English 

 Wealden represents the only known occurrence of the 

 Czekanowskiales in a Lower Cretaceous flora from western Europe. 

 All other recorded occurrences are much further east and most of 

 them further north (Samylina & Kiritchkova 1993), a point which 

 Watson & Alvin (1996: 20) failed to indicate. 



All the specimens figured in this paper, including those from the 

 Wealden of Germany, are in the collections of The Natural History 

 Museum, London (NHM - formerly the British Museum (Natural 

 History)), and have numbers prefixed V. 



GEOLOGICAL OCCURRENCE 



Of the twelve species described here only PseudotorelUa linkii is 

 represented by hand specimen material in the old Wealden collec- 

 tions which were accumulated in the late nineteenth and early 

 twentieth centuries and are now housed in various museums ( Seward 

 1894, 1895; Watson 1969; Watson & Sincock 1992). All the other 

 species have been isolated from coaly lenses and partings which 

 occur throughout the English Wealden succession and contain com- 

 pacted plant fragments often with very little interstitial matrix. The 

 Wealden 'lignite beds' described in the older literature (White 1921; 

 Arkell 1947) are the thickest and most extensive examples of the 

 deposits in question with logs and twigs embedded in compacted 

 plant remains. However, thickness and extent are no guarantee of 



floral diversity, sometimes the reverse, and tiny lenses which can be 

 collected in their entirety with a sharp knife can yield an impressive 

 mixture of species. 



Oldham (1976), in producing the first large-scale study of these 

 beds, introduced the more accurate term 'plant debris bed' for these 

 accumulations of plant material. These beds are present in both sub- 

 basins of the Wealden basin complex: those of the Weald Basin are 

 best developed in the Ashdown Beds Formation, which crops out 

 along the coast at Hastings and Galley Hill in East Sussex; those of 

 the Wessex Basin occur throughout the Wessex Formation, cropping 

 out at Worbarrow Bay, Mupe Bay, Lulworth Cove and Swanage in 

 Dorset, and Sandown and the south west coast on the Isle of Wight. 

 The plant debris beds are thought to be accumulations of plant debris 

 flushed off nearby highlands by heavy rainfall and deposited in 

 depressions on flood plains (Stewart 1981; Allen 1998). Some may 

 have been produced by local storm events and resulting flash floods 

 (Insole & Hutt 1994). They are particularly valuable in yielding 

 exquisitely preserved cuticular material which is mostly from foli- 

 age, although some relates to rachises and stems, and some to 

 reproductive structures such as male cones and female cone scales. 

 The plant debris may show lesser or greater levels of pyridzation and 

 fusain content. Oldham (1976) considered the beds to be composed 

 entirely of plant material except for the inorganic matrix present, but 

 other workers have shown the beds to be important sources of 

 animal, particularly dinosaur, remains (Freeman 1975; Stewart 1981; 

 Radley 1994; Insole & Hutt, 1994). Of particular interest in this 

 regard is locality LI 1 of Stewart (1978), the 'Grange Chine Black 

 Band' of the Wessex Formation, at Grange Chine on the South West 

 coast of the Isle of Wight. This locality has produced many vertebrate 

 remains over the last 150 years, including fragments of turtle cara- 

 pace, crocodile teeth, fragments of jaw and scales of Lepidotes and, 

 particularly, remains of dinosaurs. These tend to be worn vertebrae 

 and scraps of ribs but occasional partial skeletons have been noted, 

 particularly of the ornithopod Iguanodon. A recent discovery ( 1 998 ) 

 is that of a 3-4 m long coelurosaur, new to science, which is currently 

 under investigation (Hutt, pers. comm. 2000). The matrix with plant 

 debris material in which this specimen was found embedded has 

 yielded a new species of Ginkgoites. described below. 



The presence of amber within these beds, in significant amounts in 

 at least one locality (Nicholas etal 1993), is also of relevance to the 

 study of the fossil gymnosperms described here. 



METHODS 



Laboratory methods used to isolate recognisable plant fragments 

 from the debris bed material are of the simplest. The first aim is to do 

 as little damage to the individual plant parts as possible and to this 

 end it is usual to try disaggregation of the matrix in the following 

 order of harshness: hot water alone; hot water with soft-soap; approxi- 

 mately 5% KOH solution. Very few samples have not yielded to 

 KOH but in such cases Schulze's solution can be resorted to. How- 

 ever, this mixture invariably boils and it is essential to use a large 

 bucket with about one inch of debris material in the bottom. 



Following disaggregation the resulting sludge is carefully poured 

 from the bucket through a series of three Endecotts brass sieves; 5- 

 10 mm mesh at the top, 2-3 mm in the middle and 400 |am-l mm at 

 the bottom, depending upon the sample. The residue is very gently 

 but thoroughly washed via a rubber hose on the cold tap. The gently 

 flowing hose is then used from underneath the sieve to wash the plant 

 material into a smaller container (plastic jug) from which, by settling 

 and decanting, it is transferred into screw-top jars and stored in tap 



