Locality
Yukon-Koyukuk Basin Locality 11551
Description
Leaves or phylloclades: very variable in size and shape; undulate or irregular to lobate, petiolate, petiole long or short; apex variable, base acuminate; midvein moderate, usually straight, extending to apex or disappearing in the apical half of the leaf; lateral veins or striae straight or nearly so, very numerous and odften difficult to trace individually, parallel, arranged at a very acute angle to the midvein.
Remarks
This form is extremely variable. Bell (1957) reports the abundant widespread occurrence of this form in the nanaimo Group, the only difference between his specimens and those figured here being in petiole length. Bell considered all his specimens to have a short petiole which obviously not the case with the Alaskan material. Bell considered Protophyllocalus lanceolatus Knowlton (1894; Plate 5, Fig. 5) and Phyllocladus subintegrifolius Lesquereux (1874, Plate 1, Fig. 12; 1892, Plate 2, Figs. 1-3) as conspecific with Protophyllocladus polymorphus. Bell also thought that Thinnfeldia lesquereuxiana Heer might be conspecific but was uncertain because of the smaller size of the leaves. Considering the range of leaf sizes in this form it seems likely that Bell's fears were unfounded and that Thinnfeldia lesquereuxiana should be regarded as the same as Protophyllocladus polymorphus.
Berry (1903) reviewed the then confusing situation that surrounded leaves of this type and made comparisons between fossil forms and living material of Phyllocladus asplenifolia Hooker. He made a distinction between the Triassic, Jurassic and Lower Cretaceous occurrences of leaves ascribed to Thinnfeldia Ettingshausen and similar forms occurring in the middle and upper Cretaceous rocks for which he erected the genus Protophyllocladus. Protophyllocladus subintegrifolius (Lesquereux) Berry then included those leaves described as P. subintegrifolius (Lesquereux 1868, p. 92; 1874, Plate 1, Fig, 12; 1892, Plate 2, Figs. 1-3), Thinnfeldia lesquereuxiana (Heer, 1882, p. 37, Plate 11 Figs. 9, 10; Plate 46, Figs 1-12a, 12b; Newberry, 1896, p. 59, Plate 11, Figs. 1-17; Hollick, 1892, p. 99, Plate 3, fig. 6; Hollick, 1895, p. 12-14; Hollick, 1898, p. 58, Plate 3, Figs. 4, 5; p. 149, Plate 36, Fig. 6), and Thinnfeldia subintegrifolia (Lesquereux) Knowlton (1898, p. 228; Hollick, 1898, P. 403, Plate 41, Figs. 13, 14). The name Protophyllocladus polymorphus (Berry, 1903, p. 442) included Salisburia polymorpha Lesqueueux (1859, p. 362, nomen nudum; 1873, p. 404; 1878, p. 84, Plate 6, Figs. 40, 41), Thinnfledia polymopha Knowlton (1862, p. 153; 1894, p. 47, Plate 51, Figs. 1-4) and Thinnfeldia montana Knowlton (1898, p. 227; 1900, p. 11, Plate 1, Figs. 1-3). Hollick (1930) reported both Protophyllocladus polymorphus and Protophyllocladus subintegrifolius from his Yukon River localities.