Two Lower Cretaceous Dinoflagellate Species from Alaska

Abstract

The fossil dinoflagellate genus Omatia Cookson and Eisenack, 1958, is emended, and one new species, Omatia butticula, is described. The species Omatia pisciformis is removed from the genus Omatia and placed in the new genus Herendeenia. These two species were recovered from the Lower Cretaceous Herendeen Limestone and equivalent strata on the Alaska Peninsula. Two Lower Cretaceous dinoflagellate species from Alaska INTRODUCTION Numerous paleontological and paleobotanical investigations have been made of the widespread Mesozoic sediments of Alaska, although none has yet discussed the fossil microplankton. On the Alaska Peninsula, rocks of Neocomian age contain a large quantity and variety of fossil dinoflagellates and acritarchs. Many of the individual taxa are closely related to or conspecific with those from Australia and New Guinea described by Cookson and Eisenack (1 958). In a few instances equivalent taxa are characteristic of both the Australian Upper Jurassic and the Alaskan Neocomian. MATERIAL AND AGE The two species herein described were collected from two areas on the Alaska Peninsula (text-figure 1), one at Kamishak Hills (Jones and Detterman, 1966), and the other at Herendeen Bay (Burk, 1965). Standard Oil Company of California slide localities 13196 and 13199 (text-figure 2) are approximately equivalent to U.S.G.S. localities M2930 and M2935 (Jones and Detterman, 1966). U.S.G.S. locality M2930 contained the ammonite Acrioceras cf. A. starrkingi Anderson, 1938, and a belemnite, Acroteuthis sp. This assemblage is considered to be late Neocomian (Barremian) in age (Jones and Detterman, 1966). U.S.G.S. locality M2935 contained the pelecypod Inoceramus ovatoides Anderson, 1938, which ranges in age from late Hauterivian to early Barremian (Jones and Detterman, 1966). Standard Oil Company of California outcrop localities 16110 and 16134 are at Herendeen Bay (text-figure 2). Sample 1 6110-6 is considered to be late Valanginian or possibly early Hauterivian in age, as Buchia crassicollis (Keyserling) occurs immediately below the sampled interval. Sample 16134-33 (text-figure 2) is from the Herendeen Limestone, approximately 400 feet above sample 16110-6. Microplanktonic content indicates the time equivalence of this limestone unit with the late Hauterivian-Barremian unit at Kamishak Hills, although no megafossils were available. SYSTEMATIC DESCRIPTIONS Class DINOPHYCEAE Fritsch, 1935 Order PERIDINIALES Haeckel, 1894 Family GONYAULACYSTACEAE Sarjeant and Downie, 1966 Genus Herendeenia Wiggins, n. gen. Diagnosis: The cyst is fusiform in outline, with the tabulation 3', 6, 7c, 6', 1 p, 1 . The archeopyle is precingular and is formed by the 3 plate. The apical, precingular, postcingular, and posterior intercalary plates are either completely or partially delineated by finlike membranes. micropaleontology, vol. 15, no. 2, pp. 145-150, pls. 1-2, april 1969 145 This content downloaded from 157.55.39.49 on Tue, 09 Aug 2016 05:09:15 UTC All use subject to http://about.jstor.org/terms