Locality
Yukon-Koyukuk Basin Locality 11561
Description
Leaf: simple; symmetrical (?); shape unknown; apex missing; base missing; margin dentate, teeth with obtuse angular apices, concave sides, shallow wide rounded sinuses, margin inflated at termination of a-pectinals and basal superior secondary veins; venation palmate, palinactinodromous; primary midvein missing; a-pectinal veins moderate, more or less straight; a-abmedial veins moderate, curved, becoming straight near margin, craspedodromous, sometimes branched abmedially near margin, branching frequency increasing basally, basal (?) a-abmedial branched abmedially, along its length forming weak b-pectinal veins; b-pectinals branched admedially up to four times, admedial branches curved, craspedodromous; superior secondary veins approximately parallel to a-pectinals, craspedodromous, sometimes branched both ad- and abmedially; tertiary veins moderate convex, simple or branched, percurrent, joining ad- or abmedial sides of pectinal ad- or abmedials at right or acute angles; fourth order veins moderate, orthogonal, simple or branched, percurrent.
Remarks
This leaf fragment has a number of features in common with form HAPLD3. In both forms the margin is inflated at the termination of the -pectinals and basal superior secondary veins. In form HAPLD3 the pectinal branches appear to be craspedodromous but a tendency towards semicraspedodromy is seen in the relatively strong nature of the convex tertiary veins which join the pectinal branches near the margin. These tertiary veins give off branches abmedially which run directly to the apex of marginal teeth. Such a feature is also seen about the termination of the basal superior secondary in form HAPLU76. Unfortunately the marginal termination of the pectinals, the critical region for comparison, is missing in Hollick's specimen of Grewiopsis yukonensis (Hollick, 1930; Plate 81), but the closely allied 'Acer' collieri Hollick (Hollick, 1930; Plate 78, Fig. 5; p. 99) does possess semicraspedodromous venation in these regions. Form HAPLU76 possesses a-pectinal veins which are more frequently branched admedially than form HAPLD3, G. yukonensis or 'A'. collieri. It also differs in that it is apparently palinactinodromous.
