Cobbania corrugata (Lesq.) Stockey, G.W.Rothwell et K.R.Johnson

Plant Fossil Names Registry Number: PFN001937

Act LSID: urn:lsid:plantfossilnames.org:act:1937

Authors: R. A. Stockey, G. W. Rothwell & K. R. Johnson

Rank: species

Basionym: Pistia corrugata Lesq.

Genus: Cobbania Stockey, G.W.Rothwell et K.R.Johnson

Reference: Stockey, R. A., Rothwell, G. W. & Johnson, K. R. (2007): Cobbania corrugata gen. et comb. nov. (Araceae): A floating aquatic monocot from the Upper Cretaceous of western North America. – American Journal of Botany 94(4): 609–624.

Page of description: 611

Types

Original diagnosis/description

Leaves thick, at least toward the base, varying in diameter from two to three and one-half centimeters, broadly obovate, generally bordered from above the base by a wavy margin two to five millimeters broad; gradually narrowed into a short pedicel about three millimeters thick, terminating into a bundle of radicles; veins emerging from the pedicel in two or three thick bundles, dividing and diverging from the base of the leaves, and forming in ascending, by a kind of abnormal anastomosis, irregularly polygonal meshes.
These leaves, resembling in form a small bladder, contracted on one side, seem somewhat inflated, or at least thickened, from the base to above the middle, or composed of two distinct areas, the lower one circular and separated by a narrow groove, or deep line, from the wrinkled border which surrounds it, narrowing, however, gradually toward the pedicel. The areolation of this border seems disconnected and distinct, representing large quadrangular areolae, whose subdivisions curve along in festoons. Sometimes, however, the central part is not inflated, or thicker, and in this case, as in specimens representing young leaves, no traces of borders are perceivable. This groove, therefore, and the separation of the leaf in two distinct parts, may be caused by a kind of fold around a tergescence of the lower part, formed by an abnormal growth, of radicles. The upper surface of the leaves is somewhat rough; the lower surface, inside of the fringe, is dotted with minute holes, or like spongious. The leaves are generally mixed, or superposed to thin foliform long radicles, all of the same size, coming in bundles from linear rootlets, two to five millimeters thick. They form a thick coating surrounding the leaves, or whereupon the leaves are floating, without evident connection or point of attachment to them.

Emended diagnosis

Lesquereux (1878: Rep. U. S. Geol. Geol. Surv. Territ., 7: 103):
The leaves, round when young, are, when fully developed, broadly obovate or round at the upper border, gradually narrowed from the middle downward to a short pedicel, varying in size from two to six centimeters long and from two to fourcentimeters broad; nervation distinct, formed by the subdivision of veins, inflated into the pedicel, and dividing irregularly, in more or less dichotomous branches, in ascending to the borders, forming, by nervilles, oblique or in right angle, distinct quadrangular areolae, which become smaller and quadrate along borders. The lower part of the leaves appears inflated or thickened, and is generally surrounded by a deep line, the inside of which is slightly convex, and passes around and under a flattened border whose areolation is generally more distinct and smaller.

Stockey et al. (2007: Am. J. Bot., 94(4): 611):
Small rosettes with up to six leaves per plant borne on short, stout stems, 1.0–1.7 cm in diameter, connected by stolons, growing in large mats. Stolon surface smooth without indications of vascular tissue. Leaves 1.9–7.0 cm long, 2.4–7.5 cm wide, with six to nine primary veins; lateral veins dichotomize to form collective vein ca. one-third of way from base of blade. Three or four submarginal veins, innermost widely spaced, branching at angles of usually 90° near leaf apex and 45°–60° near middle of leaf. Rim thin, up to 5 mm wide.

Stratigraphy

Cretaceous, Upper Cretaceous, Maastrichtian
Almond Formation [stratigraphy according to Stockey et al. 2007: Am. J. Bot., 94(4): 611]

Lesquereux (1876: Ann. Rep. U.S. Geol. Geogr. Surv. Territories, [8]: 300) called it Point of Rocks.

Stockey et al. (2007: Am. J. Bot., 94(4): 611) specify "Modern mapping in this area (Roehler, 1990) defines Point of Rocks itself as the Erickson Sandstone and the overlying mudstone strata as the Almond Formation. The Erickson is a thick massive sandstone and is unlikely the source of Lesquereux’s fossils. The overlying Almond Formation is fossiliferous and has yielded ‘‘Pistia’’ corrugata on the western side of the Rock Springs Uplift (DMNH loc. 1182). The lower part of the Almond Formation is the likely source of the type specimens."

Locality

United States
Wyoming