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Early Permian Vertebrates from the Cutler Formation of the Placerville Area Colorado

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Early Permian Vertebrates from the Cutler Formation of the Placerville Area Colorado Early Permian Vertebrates from the Cutler Formation of the Placerville Area Colorado GEOLOGICAL SURVEY PROFESSIONAL PAPER 503-C Early Permian Vertebrates from the Cutler Formation of the Placerville Area Colorado By GEORGE EDWARD LEWIS and PETER PAUL VAUGHN With a section on Footprints from the Cutler Formation By DONALD BAIRD CONTRIBUTIONS TO PALEONTOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 503-C The typical Cutler Formation of Colorado correlates with classic European and with other North American Lower Permian continental formations 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 cents (paper cover) CONTENTS Page Page Abstract __________________________________________ _ C1 Vertebrate fauna-Continued Introduction ______________________________________ _ 1 Systematic d escriptions-Contin ued Early work on the Cutler Formation _____________ _ 1 Ophiacodon sp ___________ - ___ - __ - - _ -- - _ --- -- C26 Present study _________________________________ _ 1 Cutleria wilmarthi Lewis and Vaughn, n. gen., Acknowledgments ______________________________ _ 2 27 Geography ________________________________________ _ n. SP------------------------------------ 2 Mycterosaurus smithae Lewis and Vaughn, n. sp_ 34 Location and extent of area _____________________ _ 2 Age and correlation of the fauna----------------- 7 ---­ 39 Surface features and areas of outcrop _____________ _ 2 Comparison with Early Permian faunas of North Geology __________________________________________ _ America ____________________________________ _ 2 39 Stratigraphy and structure of the Placerville area __ _ 2 Comparison with European Early Permian faunas __ 42 Cutler Formation of Colorado ___________________ _ 3 Paleogeographic considerations ______________________ _ 43 Cutler Formation of nearby States _______________ _ 5 Selected references ____ ---- _________ ---_------------- 44 Vertebrate fauna ___________________________________ _ 5 Footprints from the Cutler Formation, by Donald Baird_ 47 Systematic descriptions _________________________ _ 7 Abstract ______________________________________ _ 47 Eryops cf. E. grand is (Marsh, 1878) __________ _ 7 Systematic descriptions _______________ ----------- 47 Platyhystrix rugosus (Case, 1910) ____________ _ 8 Limnopus cutlerensis Baird, n. sp _____________ _ 47 New (but unnamed) genus and species _______ _ 12 Diadectes sanmiguelensis Lewis and Vaughn, n. Genus indet., cf. Brachydactylopus Toepelman and Rodeck, 1936 ________________________ _ SP-------------------------------------- 13 47 Limnoscelops longijemur Lewis and Vaughn, n. Prospectus and problems _________ - __ ------------ 49 gen., n. sp ______________________________ _ 21 References cited _________________ - ___ -_--------- 49 ILLUSTRATIONS Page FIGURE 1. Index map of Colorado __________________________________________________________________________ -_ C3 2. Diagrammatic section showing geologic formations of the Placerville area ___________________ ------------- 4 3. Profile and section, Cutler Formation, Placerville area_________________________________________________ 6 4. Fossil vertebrate locality map, Placerville area________________________________________________________ 9 5-6. Photographs: 5. Platyhistrix rugosus, natural mould__________________________________________________________ 10 6. Platyhistrix rugosus, latex cast______________________________________________________________ 11 7-13. Drawings: 7. Diadectes sanmiguelensis, n. sp., type skull____________________________________________________ 15 8. Diadectes sanmiguelensis, n. sp., type lower jaw and lower left front leg ______________ -_-_--------- 16 9. Limnoscelopslongifemur, n. gen., n. sp., elements of type and referred specimen____________________ 22 10. Ophiacodon sp., vertebrae___________________________________________________________________ 27 11. Cutleria wilmarthi, n. gen., n. sp., type_______________________________________________________ 28 12. Cutleria wilmarthi, n. gen., n. sp., type skull and referred snout_ ______________________________ --_ 29 13. Mycterosaurus smithae n. sp., type___________________________________________________________ 35 14. Sketches of footprints of Limnopus vagus, Limnopus cutlerensis, and korynichniid cf. Brachydactylopus ____ -- _ 48 TABLE Page TABLE 1. Fossil localities ________________________________________________________ ------------------------------- C7 In CONTRIBUTIONS TO PALEONTOLOGY EARLY PERMIAN VERTEBRATES FROM THE CUTLER FORMATION OF THE PLACERVILLE AREA, COLORADO By GEORGE EDWARD LEWIS and PETER PAUL VAUGHN 1 ABSTRACT southwestern Colorado; he called them the "Jura­ Fossil vertebrates in the Cutler Formation of Colorado were Trias * * * Red Beds." This name was in vogue for first found in the Placerville area in the upper 885 feet of the some four more decades: for examples, Scott (1907, p. 1,100 feet of outcrops. Total thickness of the Cutler in this 647) wrote of "The Permian and Triassic members of area is estimated at 4,000 feet. Two genera of labyrinthodont the Red Beds", and Tomlinson (1916, p. 245), of "Red amphibians, four genera of cotylosaurian reptiles, and three genera of pelycosaurian reptiles-in all, nine distinct genera­ Beds ti1ne" in his work on "The origin of the 'Red were found. Beds'." In this assemblage only one animal, Platyhystrim rugosus, can Although correlative rocks in nearby States have be confidently assigned to an already known species.· The species yielded fossil vertebrates for many years, the Cutler of Eryops is probably close to, if not identical to, E. grandis. Formation of Colorado had been thought to be un­ The species of Ophiacodon may be either 0. navajovicus or 0. mirus. A seymouriid represents an unknown genus and species. fossiliferous before the present study. A captorhinomorph is indeterminate below suborder. Two new genera, a limnoscelid and a sphenacodontid, and two new species, PRESENT STUDY one of Diadectes and one of Myctf:rrosaurus, are described and V. R. Wilmarth and R. C. Vickers of the U.S. Geolog­ named. The age of this fauna is Early Permian, comparable to that of ical Survey (Wilmarth and Hawley, unpub. data) were part of the Dunkard- Group and part of the Wichita Group the first, to our knowledge, to discover fossils in the (Moran, Putnam, and Admiral Formations) of the United States, Cutler Formation of Colorado. They collected a few and to that of the Autunian and lower Rotliegende of Europe. weathered-out fragments from two localities. After These American and European faunas lived in remarkably study showed that the fragments had bony structure, G. similar environments. Early Permian continental sedimenta­ tion in North America and Europe was only rarely and partially E. Lewis went to the localities with Wilmarth and col­ interrupted by marine transgressions that were of short duration. lected two partial skeletons in 1952. Further search at that time yielded more specimens of fossil vertebrates INTRODUCTION and plants. Still more fossil vertebrates were found EARLY WORK ON THE CUTLER FORMATION in 1953, when A. S. Romer, S. J. Olsen, and A. D. Lewis Most of the Permian and Triassic rocks of the Four of the Museum of Compartive Zoology at Harvard Col­ Corners and nearby areas are red sandstone, siltstone, lege joined G. E. Lewis of the U.S. Geological Survey and shale that were laid down in continental or shallow­ for several weeks of collecting. Preparation of the col­ marine environments. These rocks were known gen­ lections was begun at Harvard, where G. E. Lewis and erally as the Red Beds for about 60 years after their A. S. Romer made preliminary determinations of the first geologic description. Jules Marcou (1856, p. 140~ vertebrate fauna insofar as was possible at that stage of 153, map) worked in the areas of outcrop of the later preparation. Their preliminary report, cited in Bush named Abo, Chinle, and Wingat~ Formations in 1853; and others (1959, p. 313), was necessarily inconclusive. he correlated them with the New Red Sandstone of A. S. Romer turned over his share of this joint study Europe, and included them in his Gypsum Formation of to P. P. Vaughn in 1958, when the latter completed Triassic to Jurassic age. W. H. Holmes ( 1877 a, p. 266, preparation of the specimens and joined G. E. Lewis in 267; 1877b; 1878, p. 194) was the outstanding pioneer the preparation of the present report. Although no explorer who rna pped and studied the areas of outcrop other work has been done on the paleontology of the of the later named Cutler and Dolores Formations of Cutler Formation of Colorado, Bush and others (1959; 1 University of California, Los Angeles. Cl - C2 CONTRIBUTIONS TO PALEONTOLOGY 1960) have published the first two of five planned re­ Miguel and San Juan Mountains jut high above the ports on the areal geology of the Placerville and four plateau's surface; streams that have their sources in adjoining 71h-minute quadrangles which they have these mountains have cut canyons a thousand or more mapped geologically; the published scale of these quad­ feet deep into the plateau. Less than 20 miles from rangles is 1 : 24,000. the Placerville area, where the channel of the San Miguel River has cut down to about 7,000 feet above ACKNOWLEDGMENTS mean sea level, there are 4 peaks whose altitudes exceed We gratefully acknowledge
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