70 



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



here as a new species can be attributed to the leaf species 

 Sciadopityoides greeboana sp. nov. The other, Siilcatocladiis robustus 

 Watson & Harrison (1998), is attributed to the leaf of Pseiidotorellia 

 linkii (Romer) Watson & Harrison ( 1998). Both of the associated leaf 

 species are described in the present work. 



Sulcatocladus robustus Watson & Harrison Figs 31-33 



1846 Shoot associated with Abietites (Abies) Linkii (Romer) 



Dunker: I8,pl. 9, fig. He. 

 1 87 1 Abietites linkii (pro parte Romer); emend. Schenk: 24 1 , pi. 



39, fig. 6. 

 1 99 1 Twigs probably belonging to Tritaenia linkii (Romer); Wilde: 



363, figs 4, 5. 

 1 998 Sulcatocladus robustus Watson & Harrison: 264, figs 1 7 A- 



I; 18A-D; 19A-H;20A, B. 



Diagnosis. See the original diagnosis of Sulcatocladus robustus 

 Watson & Harrison (1998: 264) which requires no emendment at 

 present. 



HOLOTYPE AND TYPE LOCALITY. V.64207, Fig. 31E, F from the 

 Diiingen leaf coal in the Wealden of northwest Germany. 



Material and occurrence. Sulcatocladus robustus has been 

 recognised from the Wealden of both England and Germany. Two 

 German specimens and all the English material are housed in the 

 NHM. Other specimens from Germany (e.g., Dunker Catalogue 70) 

 are in the Museum fur Naturkunde, Berlin, 



Description and discussion. The shoots of Sulcatocladus 

 robustus consist of helically arranged decurrent leaf-bases, each 

 below a triangular leaf-scar. The phyllotaxis approximates to a 3/8 

 Fibonacci fraction resulting in the leaf-scars occurring at the junc- 

 tion of three decurrent leaf-bases (Figs 31Aii, 32A, B). This 

 arrangement is reconstructed in Fig. 33. The decurrent bases are 

 separated by groove-like sutures (Figs 31A-C, 32A-E) lined with 

 fairly thin cuticle. Unbranched resin strands, often found inside the 

 shoots (Fig. 32A, B), are interpreted as the infillings of resin canals 

 and are the only recognisable remains of the internal shoot structure. 



Sulcatocladus robustus has been attributed to the leaf species 

 Pseudotorellia linkii (Romer) by Watson & Harrison (1998) on the 

 basis of: the constant association of these two species in the Wealden 

 of England and Germany; the perfect fit of leaf-base to leaf-scar; the 

 similarity of their cuficles. Features shared by the two species 

 include: thick cuticle, ordinary epidermal cells ananged in longitu- 

 dinal rows; longitudinal striations on the inside surface of cell walls; 

 cuticular pustules inside the cells on the outer periclinal walls; 

 similar heavy thickening of transverse cell walls around the leaf- 

 base and leaf-scar; stomata essentially similar with papillate 

 subsidiary cells, guard cells with thickly cutinized dorsal plates, 

 cudnized T-pieces associated with the polar appendages and some- 

 times partially cutinized ventral walls. As would be expected on a 

 shoot, the stomata of 5. robustus tend to differ from those of P. linkii 

 in some features. The shoots have more subsidiary cells with thicker 

 inner anticlinal walls, more deeply sunken guard cells and, some- 

 times, a ring of 10-12 encircling cells, thus making the stomatal 

 apparatus rather larger than that on the foliage leaves. The triangular 

 leaf-scar on S. robustus has been shown to match the bases of the P. 

 linkii leaves (Watson & Harrison 1998), the known shoots being the 

 right order of size to have borne the smaller, linear and lanceolate 

 leaves. Assembled, green, leafy shoots have been reconstructed to 

 show 5. robustus bearing narrowly elliptical leaves (?juvenile) of P. 

 linkii in Fig. 33A and needle leaves (?adult) in Fig. 33B. 



It is clear that as the girth of the shoot increased the shoots would 



^ 



/^ 



A 



A 



A 



A 



A 



/ 



/ 



^ 



A 



D 



foliage 

 " leaf scar 



decurrent 

 leaf base 



/ 



thin cuticle 

 lining groove 

 of suture 



thick cuticle 

 of decurrent 

 leaf base 



Fig. 32 Sulcatocladus robustus Watson & Harrison, A, B, two sides of 

 same shoot fragment showing positions of leaf-scars and sutures. Three 

 resin strands are present inside the shoot (stippled). V.64244, Haddock's 

 Rough, Hastings, East Sussex, x 12; C-E, diagrammatic representation 

 of 5. robustus shoot. C, shows phyllotactic arrangement on one side of 

 shoot. D, is labelled to show detailed relationship of a single leaf scar 

 surrounded by 3 decurrent leaf-bases, E, is a transverse section along line 

 a-a in Fig. D showing thin cuticle lining suture. C, D, x 4, E, not to scale. 



