MALACOLOGIA , 1966, 4(1): 1-172 SUMMARY OF NORTH AMERICAN BLANCAN NONMARINE MOLLUSKS1 D. W. Taylor U. S. Geological Survey, and Research Associate, University of Michigan Museum of Zoology, Ann Arbor, Michigan, U. S. A. ABSTRACT All known North American nonmarine mollusks of Blancan (late Pliocene and early Pleistocene) age have been here fitted into the available framework of associated fossils, physical stratigraphy and radiogenic potassium-argon dates. Many of the independently dated molluscan assemblages are so similar to other faunas that most of the fossils summarized can be assigned confidently to the Blancan age. These assignments permitted compilation of lists of last appear- ances of genera and families that are unknown during or after Blancan times. About 50-55 Blancan assemblages are known, and together with about 10-15 older or younger faunas included for convenience of discussion they are summarized under 57 local geographic headings (map, Fig. 1). For each local assemblage the following data have been given so far as possi- ble: location, previous references to mollusks, stratigraphic unit and most recent geologic maps, number of species of mollusks, mention of other fossils from the same locality or formation, age, institution where fossils are preserved, and most recent topographic maps. The detail of treatment varies widely, according to available information, progress of knowledge since previous liter- ature and the usefulness of new information. Lists of species are included usually only if the fauna is revised or first recorded in this paper, but the references to previous work are intended to be complete. The Blancan faunas from the Great Plains region (Nebraska, Kansas, Okla- homa, Texas), and from Arizona, are generally similar and include mainly widespread living species. Blancan and post-Blancan molluscan change has been due mainlyto the progressive extinction of relatively few species, and to changes in distribution of extant species caused by changes in local habitat and regional climate. Blancan faunas from the western U. S. A. (California, Oregon, Idaho, Nevada, Utah, Wyoming) are substantially different from one another and from the living fauna. They include many extinct species and genera, and some families region- ally extinct in North America that survive elsewhere, as well as some completely extinct families. Blancan molluscan change in the western U. S. A. was due to some local evolution, as well as termination of lineages. Post-Blancan change has been due mainly to drastic extinctions associated with draining or filling of lake basins, volcanism, changes in drainage patterns, widespread topographic changes and climatic change. In contrast to Blancan times, now scarcely any mollusks are restricted to a single lake basin; formerly local endemism was characteristic of most of the western faunas. The living freshwater molluscan fauna east and west of the continental divide shows contrasts like that of the Blancan faunas. To the east are more widespread species, with no local endemic forms, but to the west local endemic species are 1Publication authorized by the Director, U. S. Geological Survey. (1) 2 D. W. TAYLOR widespread. The eastern limit of Recent local endemism in Utah and western Wyoming (map, Fig. 2) corresponds approximately to the eastern limit in the region of Blancan deposits (Fig. 1). This correlation, together with data from Blancan faunas, supports 2 propositions that apply to freshwater mollusks gener- ally in North America and perhaps everywhere: (a) species of widespread habitats have relatively wide geographic and geologic distribution; (b) tectonic activity promotes taxonomic differentiation. In western North America the differences between the Blancan faunas of local basins are so great that no clear pattern is evident in the present state of know- ledge. The nearest approach to a regional pattern is the occurrence of common -a or closely related species in southern Idaho and in the San Joaquin Valley of California. This affinity is shown by Blancan and pre-Blancan species, and even by a few living forms. Presumably there was a former river connection between the 2 areas; if so, it was of early to middle Pliocene age, as that is the age of the oldest pertinent fossils and Blancan faunas are substantially different. The geographic pattern of distribution to which the plurality of living west American freshwater mollusks are related is a crudely fishhook-shaped belt in and close to the northern and western edges of the Great Basin (Fig. 7). More Blancan fossils have affinities within this "fishhook" than within the Idaho-Cali- fornian pattern. Thus it seems that Blancan or immediately pre-Blancan events rearranged drainage and molluscan distribution to form this fishhook-like pattern, and that the modern fauna retains a marked stamp from those changes. Supporting data include a list of all of the nominal species described from localities discussed in the text: included are all extinct species described from specimens of Blancan age, and a few older and younger ones. Data provided for each of 140 names include reference to original description, revised geographic and geologic location of type locality, location of type and synonymy. These species are listed in an outline of classification involving a number of changes in rank, generic assignment, and synonymy that are not explicitly discussed but have been listed in a section "Taxonomic changes". Only a few new ta.xa have been proposed, all in the gastropods. They include the Pliopholygidae, a new family (Viviparacea); Calibasis, Oreobasis and Idabasis, 3 new subgenera of Juga (Pleuroceridae); and Savaginius, a new genus (Hydrobiidae). CONTENTS Page Page Tectonism and evolution .............. 14 Summary ...................................... 16 INTRODUCTION 6 Abbreviations ................................. 6...... BIOGEOGRAPHY OF BLANCAN FAUNAS 16 THE BLANCAN AGE .............. 6 Hemphillian last appearances . 7 SUMMARY OF LOCALITIES ......... 27 Blancan last appearances . 7 1. Ringold Formation, Washington 28 PLIOCENE-PLEISTOCENE 2. Butte Valley, California . • • . 29 LIMIT ............................................ 7 3. Yonna Formation, Oregon • • . 29 EARLY PLEISTOCENE IN THE 4. Summer Lake, Oregon ............ 31 GREAT PLAINS .............................. 8............ 5. Goose Lake, California- Oregon 32 SEQUENCE WITHIN BLANCAN 6. Warner Lakes, Oregon. 32 FAUNAS 10 7. Danforth Formation, DIFFERENTIATION IN BLANCAN Oregon 32 FAUNAS 10 8. Tehama Formation, Widespread species and habitats . 14 California 36 BLANCAN NONMARINE MOLLUSKS 3 Contents (cont.) Page Page 34. Glenns Ferry Formation, 9. Cache Formation, Oregon-Idaho .......................... 70 California ............................ 37 35. Salt Lake Group, Marsh 10. Petaluma Formation, Creek Valley, Idaho ................ 78 California ............................ 37 36. Cache Valley Formation, 11. Santa Clara Formation, Gentile Valley, Idaho .............. 81 California ............................ 41 37. Cache Valley Formation, 12. Tassajero Formation, Utah ........................................ 82 California ............................ 45 38. Unnamed formation, Jackson 13. Livermore Gravels, Hole, Wyoming ....................... 83 California ............................ 45 39. Unnamed formation, Star 14. Purisima Group, Valley, Wyoming ..................... 84 California ............................ 46 40. Colorado River area, 15. San Benito Gravels, California-Arizona ....... 91 California 46 41. Verde Formation, Arizona . 92 16. Northeast of Kettleman Hills, 42. Lake beds in Payson Basin, California 47 Arizona ................................... 92 17. Tulare Formation, 43. Lake beds in San Carlos Kreyenhagen Hills ................... 48 Basin, Arizona ....................... 93 18. Kettleman Hills, 44. Red Knolls, Arizona .............. 93 California 49 45. Benson local fauna, 19. Paso Robles Formation, Arizona 93 California ............................ 50 46. Tusker local fauna, 20. Lost Hills oil field, Arizona ................................... 94 California ............................ 51 47. White Cone local fauna, 21. Buttonwillow gas field, Arizona ................................... 95 California ............................ 51 48. Sand Draw local fauna, 22. McKittrick area, Nebraska ................................. 95 California ............................ 51 49. Iowa Point, Kansas ................ 96 23. Elk Hills and Midway-Sunset 50. Saw Rock Canyon local oil fields, California .............. 52 fauna, Kansas .......................... 96 24. San Pedro Sand, 51a. Rexroad local fauna, California ............................ 52 Kansas 96 25. Bautista Formation, 51b. Bender local fauna, California ............................ 55 Kansas 102 26. Brawley Formation, 51c. Spring Creek local fauna, California ............................ 55 Kansas 103 27. Palm Spring Formation, 51d. Deer Park local fauna, California ............................ 61 Kansas 103 28. Mopung Hills local fauna, 51e. Sanders local fauna, Nevada ................................. 61 Kansas 103 29. Lake beds in Mono Basin, 52a. Dixon local fauna, California 66 Kansas 104 30. Lake beds at Sodaville, 52b. Swingle locality, Kansas . 104 Nevada ................................. 66 53. Buis Ranch local fauna, 31. Lake beds in Owens Valley, Oklahoma 104 California ............................ 67 54. Red Corral local fauna, 32. Allison Ranch, Nevada ............ 68 Texas