34 



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



A 



f I 



B 



Fig. 2 A, B Czekanowskia anguae sp. nov. A, stomatal distribution for 

 upper surface, V.64523. x 50; B, stomatal distribution for lower surface, 

 V.64523. X 50. 



slit-like apeituie. Ordinary epidermal cells less thickly cutinized 

 than subsidiary cells, polygonal, mainly 4-sided, isodiametric or 

 longitudinally elongate, arranged in longitudinal files; anticlinal 

 walls weakly sinuous with ragged edges. Outer surface flat, lacking 

 thickenings and papillae. 



Stomata of upper surface averaging 47 ( 37-6 1 ) per mm^, arranged 

 in around 9 rows, sometimes avoiding median region of leaf; ordi- 

 nary epidermal cells averaging 37 (17-71) pm long and 24 (10^7) 

 \xm wide. Stomata of lower surface averaging 79 (64—109) per mm^, 

 arranged in around 12 rows; ordinary epidermal cells averaging 31 

 (14-74) |am long and 25 (14-40) |jm wide. 



Name. After Angua, member of the Ankh-Morpork City Watch 

 and she-werewolf in the Discworld novels of Terry Pratchett. 



HOLOTYPE AND LOCALITY. V.64520, Fig. 1 A, the apical part of a 

 leaf from the plant debris beds of Worbarrow Bay, Dorset. Wessex 

 Formation; Hauterivian. 



Material and occurrence. Czekanowskia anguae sp. nov. has 

 been positively identified from the Wessex Formation of the English 

 Wealden only. All the known material has been found as dispersed 

 fragments, with good preservation, within 'plant debris beds' of 

 Worbarrow and Mupe Bay in Dorset. Figs lA-D, F, G, I. J; 2 A, B; 

 3B, E show material from Worbarrow Bay. Figs IE, H; 3 A, C, D, F 

 show material from Mupe Bay. Stratigraphical range: Hauterivian - 

 Barremian. 



Description and DISCU.SSI0N. Czekanowskia anguae sp. nov. is 

 the only species so far attributed to the genus Czekanowskia Heer 



from the English Wealden. The few fragments recognised are of 

 narrow needle shaped leaves (Fig. 1 A) with a mucronate apex (Fig. 

 IB) but there is no evidence of differentiation into lateral and non- 

 lateral areas, which would indicate the trapezoid cross-section shape 

 described for species of this genus by Samylina & Kiritchkova 

 (1991, 1993). It is only possible to separate the upper (Fig. lC-I)and 

 lower (Fig. 3A-F) cuticles of C. anguae on the basis of stomatal 

 distribution and ordinary epidermal cell dimensions, although the 

 two surfaces share closely similar features. The isodiametric to 

 elongate ordinary epidermal cells are arranged in longitudinal files 

 with those of the upper surface (Fig. IC. E) somewhat more elongate 

 than those of the lower (Fig. 3A. C). The anticlinal walls are weakly 

 sinuous with ragged edges (Figs IF, H; 3F). Stomata are arranged 

 more or less in longitudinal rows on both surfaces (Figs IC-E, I; 2A, 

 B; 3A-C) with a much higher density on the lower surface. The 

 guard cells are partially exposed revealing a slit-like aperture (Figs 

 IG; 3E) within the shallow, rectangular stomatal pits which have 

 raised rims (the so-called 'Florin ring' ); the outer surfaces of the leaf 

 are otherwise smooth and featureless (Figs ID; 3B). The ring of 

 subsidiary cells consists of 2 to 4, and occasionally up to 6, lateral 

 subsidiary cells and 2 smaller polar cells (Figs IF, H; 3D, F). 



The guard cells possess square-ended polar cuticular thickenings 

 and wide, thickly cutinized semi-circular dorsal plates (Figs IH, J; 

 3F) which appear to extend to the outer tangendal anticlinal wall of 

 the lateral subsidiary cells (Fig IH). In many stomata, particularly 

 those of the lower surface, cutinization of the inner anticlinal walls of 

 the guard cells has produced a distinctive delicate oval structure on 

 the inner surface (Fig 3F). 



Comparison. Czekanowskia anguae sp. nov. is the only species of 

 this genus to be described from the English Wealden or indeed from 

 any Lower Cretaceous deposit of western Europe. All other known 

 Czekanowskia species of this age occur in the Lena and Amur 

 provinces of the Siberian-Canadian palaeofloristic region, and Mon- 

 golia and Northern China (Samylina & Kiritchkova 1993). These 

 species are also all assigned to the subgenus Czekanowskia along 

 with C. anguae, as are all known species of younger age. Of the other 

 Lower Cretaceous species C. anguae compares most closely to 

 Czekanowskia communis Kiritchkova et Samylina from the Aptian 

 ofeastem Siberia (Samylina & Kiritchkova 1991). C. communis has 

 a similar leaf width, lacks papillae and trichomes, and has stomatal 

 pits with a raised, often rectangular, rim with the guard cells partially 

 exposed. It differs from C. anguae in that both surfaces have a much 

 lower stomatal density and more elongate ordinary epidermal cells. 



Amongst Jurassic species, Czekanowskia viminea (Phillips) 

 Kiritchkova et Samylina (subgenus Czekanowskia) from Yorkshire 

 compares most closely with C. anguae, being similar in leaf width, 

 ordinary epidermal cell shape and general stomatal structure but, C. 

 viminea has more heavily cutinized subsidiary cells which are often 

 papillate. 



Ginkgoites leaf fragments occur with C anguae in the same debris 

 beds and fragments of the two species are of a similar general 

 appearance. However, the Ginkgoites bears scattered, randomly 

 orientated stomata with papillate subsidiary cells which are not 

 distinctly polar or non-polar. They are thus easily separated micro- 

 scopically and the Ginkgoites is described below as a new species. 



Genus PHOENICOPSIS Heer 



1876 Phoenicopsis Heev: 49. 



1936b Phoenicopsis auct. non Heer; Florin: 45. 



1936b Stephanophyllum Florin: 45. 



1936b Culgoweria Florin: 45. 



