USGS11606.67 cf. Pterospermites whitei Ward HAPLTL120


USNM 406760



Locality Map

Arctic Slope of Alaska locality USGS 11606, north of Maybe Creek. This locality is a bluff approximately 10 m high on the east side of an unnamed tributary of the Price River.  The predominant lithologies are bentonitic clays overlying a silty sandstone capped by coal beds up to 2 m thick, which are in turn overlain by a white-gray medium-grained sandstone.  Irregularly dispersed throughout the clay are nodules and sheets of ferruginous limestone (sideritic) which, although light gray when fresh, weather to a rusty brown.  With the exception of some poorly preserved plant matter in the upper sandstones, and impressions of platanoid leaves in the power sandtsones, the plant material is confined to these fine-grained iron-rich nodules and is preserved as impressions totally lacking cuticle. There is little evidence of post-mortem decay but many leaves are penetrated by vertical fossil rootlets. Platanoid leaves are most common in siltier/sandier facies. The uppermost coal surface supports several in situ tree bases each of which is approximately 20 cm in diameter.

Latitude: 69.528329 °N

Longitude: -153.887128 °W


Leaf:  simple; symmetrical; wide elliptic; apex obtuse; base lobate; margin serrate, teeth irregular in shape, size, and spacing, margin entire near the base; tooth apex acute with pronounced glandular thickening, sinuses wide, shallow and rounded, both apical and basal sides of tooth concave, venation suprabasal, marginal perfect actinodromous with pectinal veins somewhat weakly developed; primary midvein moderate, straight; a-pectinals arising at an angle of 60° to the midvein, uniformly curving terminating at the margin approximately two-thirds of the distance between the base and the apex; a-pectinal abmedials arising at an angle of 30-50° to pectinals, sometimes branched up to two times abmedially except those near the base which branch more frequently (weak b-pectinals) and form marginal loops; superior secondary veins mixed opposite and alternate arising at an angle of 25-40° to midvein, the angle decreasing towards the apex, shallowly uniformly curved, branching one or two times abmedially near the margin, terminating in the tooth apices; two pairs of inferior secondary veins departing midvein at 90°, recurved, forming marginal loops; intersecondary veins absent; tertiary veins percurrent, simple, straight to convex and forked once or twice with a tendency to form an orthogonal reticulum in localized areas, an overall tendency to be arranged concentric to the petiole in the basal half of the lamina and at a more or less constant oblique angle to the midvein in the apical half; fourth order veins simple but occasionally forking, straight to sinuous arising more or less at right angles to the tertiaries.


In comparison with other hamamelids from this locality this specimen exhibits well-organized regular venation.  The venation of the teeth is also well developed and the overall tooth is distinctly Platanoid. While the balance of the lamina is symmetrical the venation near the base is not.  The right side (as illustrated) a-pectinal vein is stronger and supports longer, less looped, abmedials than its counterpart on the left.  Because of this the leaf could be regarded as exhibiting weak, asymmetrical palinactinodromy.  The term 'perfect', when applied to actinodromy, refers to the area of lamina  served by the pectinals and the pectinal abmedials (Hickey, 1973) and not to the organization or course of the veins.  The actinodromy in this specimen does display irregularities but is termed 'perfect' according to Hickey's definition.  This form belongs to a complex which includes specimens USGS 11606.14 (form HAPLTL113), USGS 11606.27 (form HAPLTL115), USGS 11606.35 (form HAPLTL116), and possibly USGS 11606.62 (form HAPLTL119).  It is somewhat similar to Pterospermites whitei (Ward in Bell, 1949; Plate 47, Fig. 5).