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The Lower Cretaceous (Albian) Ammonite Genera Leconteites and Brewericeras

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The Lower Cretaceous (Albian) Ammonite Genera Leconteites and Brewericeras The Lower Cretaceous (Albian) Ammonite Genera Leconteites and Brewericeras GEOLOGICAL SURVEY PROFESSIONAL PAPER 503-F The Lower Cretaceous (Albian) Ammonite Genera Leconteites and Brewericeras By DAVID L. JONES, MICHAEL A. MURPHY, and EARLL. PACKARD CONTRIBUTIONS TO PALEONTOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 503-F A report simplifying the complex nomenclature of the ammonite genera Leconteites and Brewericeras UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1965 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price .50 (paper cover) CONTENTS Page Page Abstract___________________________________________ F1 Stratigraphic position and age-Continued Introduction_______________________________________ 1 Central Oregon_________________________________ F5 l'romenclature__________________________________ 1 Queen Charlotte Islands _____________________ -___ 6 Acknowledgments, measurements, and abbreviations ___ ..: 3 Southern Alaska________________________________ 7 Material studied____________________________________ 3 Evolutionary sequence _________________________ - ___ - 8 Systematic descriptions _________________________ -- __ - 9 Stratigraphic position and age of Leconteites and Breweri- ceras________________________________________ 3 References ____________________________________ - - _ _ _ 19 Onoarea______________________________________ 3 Index_____________________________________________ 21 ILLUSTRATIONS [Plates 1-11 follow index] PLATE 1, 3-5. Leconteites lecontei (Anderson). 2. Leconteites lecontei (Anderson) and L. sacramenticus (Anderson). 6. Leconteites lecontei whiteavesi Jones, Murphy, and Packard, n. subsp. and L. deansi (Whiteaves). 7. Leconteites lecontei whiteavesi Jones, Murphy, and Packard, n. subsp. 8. Breuericeras breweri (Gabb) and B. hulenense (Anderson). 9, 10. Brewericeras hulenense (Anderson). 11. Brewericeras hulenense and Leconteites lecontei. Page FIGURE 1. Index map of Ono area, northern California-------------------------------------------------------- F4 2. Generalized diagrammatic columnar sections, Ono area, northern California ___________________________ _ 5 3-5. Index map of- 3. Mitchell area, central Oregon _____________________________________________________________ _ 6 4. Graham Island, Queen Charlotte Islands, B.C----------------------------------------------- 6 5. The upper Chitina Valley, southern Alaska _________________________________________________ _ 7 6. Generalized columnar section, Fohlin Creek area __________________________________________________ _ 8 7. Postulated evolutionary sequence of Leconteites and Brewericeras ____________________________________ _ 8 8. Cross sections of Leconteites lecontei s. s __________________________________________________________ _ 10 9. Scatter diagram showing relation of whorl height to whorl breadth in Leconteites lecontei s. s _____________ _ 11 10. Bar graph showing frequency distribution of Leconteites lecontei s. s ___________________________________ _ 12 11-13. Suture lines of Leconteites lecontei s. s_ ------------------------------------------------------------- 12 14. Scatter diagram, Brewericeras hulenense __________________________________________________________ _ 16 15, 16. Suture lines of Brewericeras hulenense ___________________________________________________________ _ 17 17. Bar graph showing frequency distribution of Brewericeras hulenense ________________________ -- ___ ---_- 18 m CONTRIBUTIONS TO PALEONTOLOGY THE LOWER CRETACEOUS (ALBIAN) AMMONITE GENERA LECONTEITES AND BREWERICERAS By DAVID L. JoNES, MICHAEL A. MuRPHY/ and EARL L. PACKARD 2 ABSTRACT surprisingly Wide range of morphologic variation. Lower Cretaceous (Albian) ammonites from the Pacific coast Studies of the Upper Cretaceous Collignoniceratids by region of North America designated as Leconteites lecontei, L. Haas (1946), the Triassic genus Tropites by Silberling modestum (in part), Puzosigella mulleri, P. tajfi, P. rogersi, and P. (1959), and the mid-Cretaceous genus Neogastroplites perrinsmithi (in part), are herein regarded as forming one highly by Reeside and Cobban (1960) conclusively demon­ variable but intergrading species to which the name L. lecontei (Anderson) is applied. Puzosigella sacramentica (Anderson) is strate that intraspecific variation from finely ribbed regarded as a separate species of Leconteites, and the name compressed individuals to robust coarsely ornamented Puzosigella is rejected. A new subspecies, L. lecontei whiteavesi, forms is normal for some ammonites and that finely is recognized from the Albian beds of Queen Charlotte Islands, drawn taxonomic distinctions based on differences in and one species, L. deansi, is abundant in the lowest Albian beds whorl proportions or strength of ornamentation do of southern Alaska. The genus Brewericeras is regarded as a direct descendant of not hold up when a sufficiently large sample is available. Leconteites and contains two species: B. breweri (Gabb) and B. On the other hand, some groups of ammonites are hulenense (Anderson). B. breweri is known only from one speci­ remarkably constant morphologically and show little men, but B. hulenense is abundant and widespread in upper lower range in variation. Why this difference exists is not Albian deposits. This species shows a wide range in morphologic clear, but it seems probable that the highly variable variation from smooth compressed forms to ribbed slightly inflated forms. species are most important from an evolutionary point of view, as they provide a wider basis upon which INTRODUCTION natural selection can operate to produce separately Ammonites assigned to various species of the genera evolving strains. Leconteites Casey, Puzosigella Casey, and Brewericeras This study attempts to document another example Casey are locally abundant in Albian strata in Cali­ of extreme variation and also to elucidate what seems fornia, Oregon, British Columbia, and Alaska. Because to be a clear evolutionary sequence. of their wide distribution and short geologic range, these ammonites are very useful in correlation, but because of NOMENCLATURE the proliferation in specific names, uncertainty of generic The genera Leconteites and Puzosigella are based on affinities, and obvious synonymy of some of the types, two species, Desmoceras lecontei and Pachydiscus their proper identification is impossible using the present sacramenticus, first named by Anderson (1902). Ac­ nomenclature. cording to Anderson, the former species is characterized Likewise, an apparent evolutionary sequence of the by a compressed whorl section, narrow umbil.i?us, early Albian Leconteites leading to the late early Albian nearly vertical umbilical wall, angular umbilical or early middle Albian Brewericeras has been obscured shoulder, and weak ornamentation; the latter species by placing these two genera in different families: is characterized by a more inflated whorl section, wider Leconteites in Hoplitidae and Brewericeras in Desmo­ umbilicus, sloping umbilical wall, rounded umbilical ceratidae (Wright in Arkell and others, 1957). shoulder and coarse ornamentatiOn. Holotypes of In recent years, studies of large populatiOns of both species' apparently were obtained from the same ammonites have shown that some species exhibit a place on the east fork of Ruling (Hulen) Cree~ near Ono, northern California (California Acad. SCl. loc. 1 University of California, Riverside, Calif. 2 Stanford University, Stanford, Calif. 152, see Anderson, 1902, p. 96, 105; 1938, p. 195, 196). Fl F2 CONTRIBUTIONS TO PALEONTOLOGY Hall and Ambrose (1916, p. 69; see Wiedey, 1929, p. 25, A study of large collections of ammoni ties from pl. 2, fig. 2) subsequently named a new species, Son­ Oregon, California, British Columbia, and Alaska have neratia rogersi, a closely related form obtained from convinced the authors of this paper that the differen­ Tesla quadrangle in central California. Anderson tiation of leconteitid and puzosigellid ammonites into (1 938, p. 192, 1 93) later referred Desmoceras lecontei six species and two genera is untenable and that the to Cleoniceras and named a new species, C. modestum, generic differences expressed by Casey and by Imlay which was also obtained from Ruling Creek (Cali­ are invalid. Specimens from a single locality show a fornia Acad. Sci. loc. 1668). In the same publication, complete gradation from compressed finely ornamented Anderson (1938, p. 184, 195) referred Pachydiscus forms (Leconteites) to the more inflated coarsely ribbed sacramenticus to the genus Sonneratia and named as forms (Puzosigella). This same range of variation can new species S. perrinsmithi, S. tajji, and S. mulleri be demonstrated to occur throughout the entire strati­ all of which, together with plesiotypes of S. rogersi, graphic interval in which these forms occur. Thus only were obtained from the east fork of Ruling Creek one generic name should be applied to this entire (California Acad. Sci. loc. 152). morphologic plexus. Casey (1954) recognized that none of the species The genus Brewericeras was named by Casey (1954, cited above belong to either Cleoniceras or Sonneratia, p. 112), who cited Ammonites breweri Gabb as type and he therefore erected two new genera, Lecunteites species. Ammonites breweri was originally based on a and Puzosigella, and D. lecontei and P. sacramenticus, large fragment (UC 12098) figured by
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