05RAS Dicotylophyllum sagwonicum Moiseeva et Herman  


Moiseeva et al. (2009)




Sagwon 05-3. Prince Creek Formatlon. Sagavanirktok River. Sagwon.


Locality Map



The following is not a description of this particular specimen but a composite description of the species.

From Moiseeva, Herman, Spicer. 2009. (p. 1306)

"Diagnosis. Leaves simple, entire, medium-sized, length/width ratio 2 : 1. Leaf lamina elliptic or ovate, symmetric. Leaf base cuneate and decurrent. Leaf margin crenate. Marginal teeth small, rounded, and slightly asymmetrical. Venation pinnate and craspedodromous. Secondary veins six or seven pairs. Angle between the secondary veins and midrib about 25°–35°. Two lower pairs of secondary veins departing close to each other. Tertiary venation scalariform or branched scalariform.

Description (Figs. 4a, 4b). The leaves are medium-sized, about 8–9 cm long and 4-4.5 cm wide, simple, entire-margined, elliptical or ovate. The maximum width is situated at the middle of the leaf lamina. The length/width ratio is about 2 : 1. The leaf base is narrowly or broadly cuneate and decurrent. The leaf apex is missing. The leaf margin is finely crenate, and at the base it is entire. The teeth are very small, about 0.5 mm long, rounded, slightly asymmetric, directed towards the leaf apex, without glands. The notches between the teeth are acute.

The venation is craspedodromous. There are six or seven pairs of secondary veins, which are slightly curved, deviating from the midrib at an angle of 25°– 35°. Two lower pairs are basally connivent, the next pair of veins is situated at a greater distance, and the distance between veins gradually becomes smaller above. The second pair of the secondary veins from the base is longest and most branched (with five or six branchlets). The secondary veins are forked. Tertiary venation is scalariform or branched-scalariform. The tertiary veins are curved or, more rarely, straight, situated nearly perpendicular to the secondary veins. The venation of the forth order is in form of fine polygonal net."



From Moiseeva, Herman, Spicer. 2009. (p. 1306)

"Genus Dicotylophyllum Saporta, 1894 Dicotylophyllum sagwonicum Moiseeva et Herman, sp. nov. Plate 23, figs. 3–8.

Holotype. GIN, nos. 4886/24a-1 (part) and 4886/24b-1 (counterpart); leaf imprint; Sagavanirktok River, northern Alaska; upper part of the Prince Creek Formation, Upper Paleocene; Pl. 23, figs. 4, 6, Fig. 4a (part); Pl. 23, figs. 5, 7, Fig. 4b (counterpart)."

"Leaves of the new genus are characterized by a combination of characters that do not occur in known angiosperm genera and are, therefore, assigned here to the artificial genus Dicotylophyllum of unknown taxonomic position.

In terms of the leaf lamina outline, venation pattern, and, in particular, the forked secondary veins, the new species resembles fossil members of Viburnum L. and Viburniphyllum Nathorst, described from several Cretaceous and Paleocene floras of the Northern Hemisphere (Ward, 1887; Brown, 1962; Herman and Lebedev, 1991; Golovneva, 1994). The new species differs from the majority of these species by having a considerably reduced number of secondary veins and finely crenate leaf margin.

Bell (1949) reported leaves of Viburnum simile Knowlton from Upper Cretaceous of western Alberta in Canada, which resemble leaves of the new species in terms of the secondary venation and the morphology of the lower part of the leaf. Dicotylophyllum sagwonicum differs from V. simile primarily in terms of the leaf margin. Additional species of Viburnum were also described from the deposits, including V. asperum Newberry, which resembles the new species by having the same finely dentate leaf margin (Bell, 1949). Our specimens differ from leaves of this species by exhibiting a more sparse secondary venation, narrowly cuneate base, and rounded teeth.

Dicotylophyllum sagwonicum has some characters in common with Viburnum acutifolium Golovn. from the Rarytkin Formation of the Koryak Upland (Golovneva, 1994). Both species have a small number of secondary veins and finely dentate leaf margin. The new species differs in terms of the form of the base, secondary veins departing at an acute angle, and much narrower teeth."