DISTRIBUTION OF FAUNAS IN THE , EAST-CENTRAL UTAH

James I. Kirkland Utah Geological Survey, Box 146100, Salt Lake City, UT 84114-6100

Richard L. Cifelli Oklahoma Museum of Natural History, University of Oklahoma, Norman, OK 73019

Brooks B. Britt Eccles Park, 1544 East Park Boulevard, Ogden, UT 84401

Donald L. Burge College of Eastern Utah, Prehistoric Museum, 451 E. 400 N., Price, UT 84501

Frank L. DeCourten Geology/ Earth Science, Sierra College, 5000 Rocklin Road, Rocklin, CA 95677

Jeffery G. Eaton Department of Geology, Weber State University, Ogden, UT 84408-2507

J. Michael Parrish Department of Biological Sciences, Northern Illinois University, DeKalb, IL 60115-2854

ABSTRACT radiometric age estimates. The preserved fauna includes a small nodosaurid Animantarx ramaljonesi, a small The Cedar Mountain Formation in east-central Utah ornithopod, a primitive lambeosaurid hadrosaur, ceratop- preserves three distinct dinosaur-dominated vertebrate sian teeth, pachycephalosaur teeth, tiny sauropod teeth, a faunas in strata separated by . The oldest dromaeosaurid, cf. Richardoestesia teeth, cf. Parony- fauna is preserved in the basal Yellow Cat Member of chodon teeth, and an early tyrannosaurid. This fauna is the Cedar Mountain Formation in the area east of the San remarkably similar to those of the Campanian and Maas- Rafael Swell and includes an abundant new of trichtian of western North America. As the only likely polacanthid ankylosaur related to Polacanthus, Iguan- ancestors of the hadrosaur and ceratopsian are from the odon ottingeri, a sail-backed iguanodontid, a cama- Early of Asia, the dramatic shift to faunas rasaurid and titanosaurid sauropods, a new genus of typical of the North American Late Cretaceous is inter- theropod similar to Ornitholestes, and the giant dro- preted to be the result of opening migration corridors to maeosaurid Utahraptor ostrommaysorum. The polacan- and from Asia through Alaska at the end of the Early thid, iguanodontids, and titanosaurid indicate close tem- Cretaceous, when migration to eastern North America poral geographic ties to the Barremian of Europe, where was still possible. The overlying middle to upper Ceno- similar occur. The Poison Strip Sandstone and manian Dakota Formation preserves a dinosaur fauna Ruby Ranch Member preserve a fauna including the much like that of the Mussentuchit fauna with the nodosaurid Sauropelta, the primitive iguanodontid notable absence of sauropods. The record in the ?, sauropods assigned to Pleurocoelus, Cedar Mountain Formation of east-central Utah can be dromaeosaurid teeth, an unidentified large theropod, and divided as follows: (1) a basal Barremian iguanodontid- . This fauna compares well with those polacanthid fauna with European affinities predating documented from the Cloverly Formation, Arundel For- common flowering ; (2) a middle -middle mation, and Trinity Group characteristic of North Ameri- Tenontosaurus-Pleurocoelus fauna, perhaps rep- ca’s apparently endemic Aptian-Albian dinosaur fauna. resenting an impoverished recovery fauna following a A sharp break from carbonate-nodule-bearing, non-smec- major Lower Cretaceous event (endemic to titic strata to carbonaceous, highly smectitic strata marks North America); (3) an Albian-Cenomanian boundary the base of the Mussentuchit Member in the western San fauna dominated by lambeosaurine hadrosaurids with Rafael Swell region. This member is dated as straddling Asian affinities, when flowering plants were co-domi- the Albian/Cenomanian boundary on palynological and nant, which continued until the end of the Cretaceous. 202 Vertebrate Paleontology in Utah Utah Geological Survey

INTRODUCTION ence of polished chert pebbles (“gastroliths”). Stokes (1952) renamed the formation the Cedar Historically, the Lower to “middle” Cretaceous ter- Mountain Formation and included the Buckhorn Con- restrial strata of the Cedar Mountain Formation have glomerate as its basal member (figure 1). His measured been considered to be largely unfossiliferous (Stokes, type section (section 9, T. 18 S., R.10 E. of the Salt Lake 1944, 1952; Young, 1960). The uppermost Cedar Moun- Base Line and Meridian) is 123.6 meters thick. He rec- tain Formation in the western San Rafael Swell had been ognized that the Burro Canyon Formation of western established as late Albian, based on palynomorphs, by Colorado (Stokes and Phoenix, 1948) was largely equiv- Tschudy and others (1984). Ages based on freshwater alent to the Cedar Mountain Formation and recommend- bivalves, ostracodes, charophytes, and plants, while not ed using the Colorado River as the dividing line between as accurate, are compatible (Mitchell, 1956; Stokes, these formations (Stokes, 1952). 1952; Young, 1960). The Cedar Mountain Formation has Young (1960), recognizing the continuity of the two subsequently been considered as a homogenous Aptian- formations, proposed that the term Burro Canyon be Albian unit in most regional studies (for example, Law- abandoned in favor of Cedar Mountain Formation. This ton, 1985, 1986; Heller and others, 1986; Heller and proposal has been ignored by subsequent authors (Craig, Paola, 1989; Baars and others, 1988). 1981). Young (1960) recognized several regionally Additionally, the North American terrestrial verte- extensive sandstones in the Cedar Mountain Formation brate record has been considered to be very poor overall that were useful for correlation (figure 1). for the “middle” Cretaceous, the notable exception being Based on correlations of regionally persistent sand- the Aptian-Albian Cloverly fauna of southern Montana stone units, Young (1960) proposed that calcareous mud- (Ostrom, 1970). Largely correlative faunas are known stones assigned to the Cedar Mountain passed eastward from the Antlers Formation of Oklahoma, Arkansas, and into the carbonaceous sandstones and shales of his Natu- northern Texas (Stovall and Langston, 1950; Langston, rita Formation. The more refined biostratigraphy devel- 1974, Cifelli and others, 1997a), the Paluxy and Twin oped by Kirkland and others (1997) permit more refined Mountains Formations of central Texas (Langston, 1974; correlations across Utah that preclude correlating any Winkler and others, 1989; 1990), and the Arundel For- sandstone bed within the Cedar Mountain Formation mation of (Gilmore, 1921; Kranz, 1989, 1996). with any specific sandstone bed within the Dakota For- Recent research has indicated that there are three dis- mation to the east across central Utah. However, subsur- tinct faunas in the Cedar Mountain Formation of east- face data presented by Molenaar and Cobban (1991) central Utah (Kirkland, 1996b; Kirkland and others, indicate that the upper Cedar Mountain Formation corre- 1997). In addition to the fauna similar to the well known lates with the upper Dakota Formation northwestward Cloverly fauna, there are both a distinct earlier and a across the Uinta Basin. Young’s (1960) sandstone corre- later fauna. Improved biostratigraphic resolution within lations suffered from this lack of biostratigraphic control, this time interval indicates a more complex regional his- but these regionally persistent sandstone units mark tory during the Early to “middle” Cretaceous than previ- major breaks in sedimentation as indicated by the dra- ously recognized. matic faunal changes documented herein. Thus Young’s (1960) recognition of these sandstones represents a sig- nificant, if belatedly utilized, breakthrough in our under- THE CEDAR MOUNTAIN FORMATION AND standing of the Cedar Mountain Formation. ITS VERTEBRATE FAUNAS In addition to the basal Buckhorn Conglomerate of the western San Rafael Swell, four additional members The term Cedar Mountain Shale was designated by of the Cedar Mountain Formation have been defined Stokes (1944) for the drab variegated slope-forming sedi- (Kirkland and others, 1997). In ascending order, based mentary rocks lying between the Buckhorn Conglomer- on lithostratigraphic and biostratigraphic relationships, ate and the Dakota Formation, with a type section on the these are Yellow Cat Member, Poison Strip Sandstone, southwest flank of Cedar Mountain, Emery County, Ruby Ranch Member, and Mussentuchit Member (figure 1). Utah. He characterized the Cedar Mountain Shale as having slopes covered with abundant carbonate nodules Buckhorn Conglomerate that are often septarized with agate, barite, and other fill- ings. Additionally, Stokes (1944) noted an abundance of The Buckhorn Conglomerate was defined as a for- elongate sandstone lenses (ribbon sandstones) that repre- mation by Stokes (1944) for exposures below the dam at sent abandoned river channels. He also noted the pres- Buckhorn Reservoir on the southwest flank of Cedar

Distribution of Vertebrate Faunas - Kirkland, Cifelli, Britt, Burge, DeCourten, Eaton, Parrish Miscellaneous Publication 99-1 Vertebrate Paleontology in Utah 203 After Kirkland and others (1997). History of nomenclature for Upper through “middle” Cretaceous in east-central Utah. Time scale from Obradovich (1993). scale from in east-central Utah. Time “middle” Cretaceous for Upper Jurassic through History of nomenclature Figure 1.

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Mountain where its exposed thickness is 7.5 meters. At top of the lowest calcrete above smectitic mudstones of the type locality the pebbles have an average diameter of the Brushy Basin Member of the Morrison Formation. 3 centimeters and are composed mostly of black chert. Aubrey (1996, 1998) utilized the base of the calcrete as The member is largely trough-crossbedded with flow the base of the Cedar Mountain, however the basal sur- directions to the northeast. The Buckhorn Conglomerate face is often gradational. His argument assumes that this is best developed in the northern San Rafael Swell area. calcrete represents a complex soil horizon developed on Because of its discontinuous nature, Stokes (1952) sub- the Morrison paleosurface. However, while distinct soil sequently included the Buckhorn Conglomerate as the features are recognized in many places, in other areas lower member of the Cedar Mountain Formation. Young such as below the type section of the Ruby Ranch Mem- (1960) also noted that the member is discontinuous and ber, overlying lucustrine sediments may be a control on found that it could not be correlated to any specific sand- the development these carbonates. The uppermost Mor- stone east of the San Rafael Swell (figure 1). rison below the calcrete is often non-smectitic, -mot- Aubrey (1996, 1998) proposed that the Buckhorn tled, and a brick red color, perhaps reflecting the period Conglomerate is separated from the overlying strata of of exposure, oxidation, and soil formation between depo- the Cedar Mountain Formation by a calcrete horizon and sition of the Morrison Formation and the onset of Cedar that it intertongues with the Morrison Formation and Mountain deposition. should be considered Upper Jurassic. Currie (1997) also The type section of the Yellow Cat Member of the recognized this calcrete horizon in the area of northeast- Cedar Mountain Formation is near the Gaston Quarry ern Utah and northwestern Colorado near Dinosaur (figure 3) west of the Yellow Cat Road (Kirkland and National Monument and proposed that it was a sequence- others, 1997). At this site, the Cedar Mountain Forma- bounding within the Lower Cretaceous. tion is 45.9 meters thick and the basal Yellow Cat Mem- No have been recovered from the Buckhorn Con- ber measures 24 meters thick. At 6.7 meters below the glomerate beyond reworked late Paleozoic invertebrates overlying Poison Strip Sandstone, there is an interval of and its correlation to the basal members of the Cedar limestone and shale interbeds which Young (1960, figure Mountain Formation to the east is still problematic. 6, section 37) used to mark the base of the Cedar Moun- tain Formation in this area. Therefore, a major portion Yellow Cat Member of the Yellow Cat Member had been included in the Brushy Basin Member of the Morrison Formation. The Yellow Cat Member is exposed in the northern The Yellow Cat fauna includes abundant specimens Paradox Basin in a belt extending from the west side of of a new genus of polacanthid ankylosaur related to the ancestral Uncompahgre Uplift west of Dewey Polacanthus, Iguanodon ottingeri (Galton and Jensen, Bridge, Utah, to the east side of the San Rafael Swell 1979), perhaps a distinct genus of sail-backed iguan- (figure 2). At most exposures, the Yellow Cat Member odontid, titanosaurid and camarasaurid sauropods, a new extends from the basal calcrete of the Cedar Mountain genus of theropod most similar to Ornitholestes, and the Formation in this region (Aubrey, 1996, 1998; Kirkland giant dromaeosaurid Utahraptor ostrommaysorum (Kirk- and others, 1997) up to the base of a regionally extensive land and others, 1991; Kirkland, Burge, Britt, and Blows, sandstone ledge (middle sandstone of Young, 1960; 1993; Kirkland and others, 1997; Kirkland and others, Poison Strip Sandstone of Kirkland and others, 1997). 1995; Kirkland, 1993, 1996a; Kirkland, Burge, and These sediments consist mostly of interbedded mud- Gaston, 1993; Britt and others, 1996; Britt and Stadt- stone, with interbeds of sandstone and limestone. These man, 1997; Carpenter and others, 1996). In addition, mudstones tend to be mauve toward the base and pale , crocodilians, and a sphenodontian have been rec- green toward the top. They differ from those of the ognized (Kirkland and others, 1997). Fish appear to be Morrison in being drabber and less strongly variegated. locally abundant, but have been identified only from iso- In addition, the mudstones in the Yellow Cat Member are lated remains (table 1). Hybodont have been not smectitic. identified on the basis of a small fragment of dorsal fin The basal calcrete is not always present and at some spine and several spiral coprolites rich in ganoid scales. sites there is a shale-on-shale contact, although common Important vertebrate quarries in this member include polished chert pebbles (“gastroliths”) are generally found Brigham Young University’s Dalton Well Quarry (figure at the best pick for the contact (Stokes, 1944; 1952) sug- 4), which preserves a diverse fauna dominated by gesting a deflation surface. At other sites, the basal cal- sauropods (Britt and others, 1996; Britt and Stadtman, crete is a complex of superimposed calcretes or there 1997), and College of Eastern Utah Prehistoric Muse- may be several calcretes and the contact is picked at the um’s Gaston Quarry (figure 3), which preserves a less

Distribution of Vertebrate Faunas - Kirkland, Cifelli, Britt, Burge, DeCourten, Eaton, Parrish Miscellaneous Publication 99-1 Vertebrate Paleontology in Utah 205

Figure 2. Cross section showing the distribution of “middle” Cretaceous units across eastern Utah discussed in text. Modified after Kirkland and others (1997). Base map showing distribution of Cedar Mountain, Burro Canyon, and Dakota Formations modified after Young (1960).

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Figure 3. Type area of Yellow Cat Member of the Cedar Mountain Formation above Yellow Cat Flat near College of Eastern Utah Prehistoric Museum’s Gaston Quarry. Arrow indicates position of Gaston Quarry. Abbreviations: cal, calcrete; Cp, Poison Strip Sandstone; Cr, Ruby Ranch Member; Cy, Yellow Cat Member; D, Dakota Formation; Mor; Morrison Formation.

yielded several isolated small theropod skeletons (figure Table 1. Yellow Cat Fauna (see text for repositories) 5) (Kirkland and others, 1997). Sites preserving isolated Class Osteichthyes remains of iguanodontids, sauropods, and polacanthid Subclass Dipnoi ankylosaurs have also been found in the region by the Ceratodus undescribed new Denver Museum of Natural History. Important collec- Subclass Actinopterygia cf. Semionotus ? sp. tions of fossils from this interval are housed at the Col- cf. Amia sp. lege of Eastern Utah Prehistoric Museum, Price, Utah; Class Reptilia Earth Science Museum, Brigham Young University, Order Chelonia Provo, Utah; Denver Museum of Natural History, Denver cf. sp. Colorado; and the Oklahoma Museum of Natural Histo- Order Rhynchocephalia cf. Toxolophosaurus sp. ry, University of Oklahoma, Norman Oklahoma. Order There is disagreement among the authors as to indeterminate teeth whether there are one or two iguanodontids in the Yellow Order Cat Member. Britt and Stadtman (1997) have proposed Family Dromaeosauridae Utahraptor ostrommaysorum that the sail-backed iguanodontian is an adult specimen Family uncertain of Iguanodon ottingeri as both specimens occur together justinhofmanni at the type locality. Kirkland and others (1997) have Order Sauropoda proposed that there are two iguanodontid taxa, a large Family Camarasauridae undescribed new genus sail-backed form and I. ottingeri; and a conservative Family Titanosauridae small iguanodontian similar to or even conspecific with undescribed new genus I. lakotaensis (Weishampel and Bjork, 1989). All the Order iguanodontid specimens collected at the Gaston Quarry Family Iguanodontidae and found as isolated specimens are similar to the type Iguanodon ottingeri undescribed new genus specimens of I. ottingeri and I. lakotaensis. Only further Order Ankylosauria excavations will resolve this question. Family Polacanthidae The polacanthid ankylosaurs, iguanodontids, and Gastonia burgei titanosaurid sauropods indicate close temporal and geo- graphic ties to the Barremian of Europe (Blows, 1993; diverse fauna dominated by polacanthid ankylosaurs. Norman, 1988). This correlation is also supported by the Both of these sites are in the upper third of the Yellow presence of the charophyte Nodosoclavator bradleyi, Cat Member. At the base of the Yellow Cat Member 1.5 which is not known in strata younger than Barremian kilometers east of the Gaston Quarry, one horizon has (Niel Shudack, personal communication; Kirkland and

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Figure 4. The Brigham Young University’s Dalton Wells Quarry indicated by D and brackets. Abbreviations: Cp, Poison Strip Sandstone; Mor, Morrison Formation.

Figure 5. College of Eastern Utah Prehistoric Museum’s small theropod sites indicat- ed by dots just to the east of the Gaston Quarry. Abbreviations: Cp, Poison Strip Sand- stone; cal, calcrete. others, 1997). Furthermore, the dinosaurs indicate a ing. Aubrey (1996, 1998) has postulated that thrusting close correlation with the Lakota Formation at Buffalo may have begun in the Barremian based on the recogni- Gap, South Dakota (Kirkland, 1992; Kirkland, Burge, tion of this basal Cedar Mountain fauna (Kirkland, and Gaston, 1993; Kirkland and others, 1997; Lucas, 1992). As a rule, subsidence caused by loading in the 1993) (figure 6). Kirkland and others (1997) estimated proximal foreland basin is almost instantaneous geologi- that 20 to 25 million years of Earth history may be repre- cally, (Turcotte and Schubert, 1982), indicating that age sented by the hiatus between Morrison and Cedar Moun- estimates from the sediment wedge formed proximal to tain deposition based on radiometric age estimates at the the thrust belt provide a bracket for the beginning of top of the Morrison Formation (Kowallis and others; thrusting. However, because the Barremian sediments of 1998) and the age of correlative dinosaur-bearing strata the Yellow Cat Member pinch out to the west (figure 2), (Obradovich, 1993; Dyman and others, 1994). they would seem to preclude the onset of Sevier thrust- The thickness of the Yellow Cat Member may vary ing until at least the Aptian and hence provide additional by tens of meters over several kilometers of outcrop. support to previously published dates for the onset of Together with the observed differences in its basal con- thrusting (Lawton, 1985, 1986; Heller and others, 1986; tact, this lateral variation in thickness may in part reflect Heller and Paola, 1989). the topography of the erosional surface formed on the The distribution of the Yellow Cat Member from the upper Jurassic strata during the earliest Cretaceous. Uncompahgre Uplift to the San Rafael Swell is compati- The distribution of the Yellow Cat Member provides ble with the proposal by Aubrey (1996) that the distribu- an important constraint on the beginning of Sevier thrust- tion of these sediments was controlled by salt tectonics

Distribution of Vertebrate Faunas - Kirkland, Cifelli, Britt, Burge, DeCourten, Eaton, Parrish 208 Vertebrate Paleontology in Utah Utah Geological Survey e scale from ers (1995). Modi- Correlation chart showing age relationships of stratigraphic units discussed in text. Vertical lines denote unconformities. Tim of stratigraphic units discussed in text. Vertical chart showing age relationships Correlation Figure 6. Obradovich (1993). Data from Benton and Spencer (1995), Dyman and others (1994), Hancock and others (1993), and Winkler and oth Benton and Spencer (1995), Dyman others (1994), Hancock (1993), Winkler Obradovich (1993). Data from fied after Kirkland and others (1997).

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Figure 7. The Brigham Young University’s Bodily’s Nodosaur Site on west side of Arches National Park. Arrow points to site. Abbreviations: Cm, Mussentuchit Member; Cp, Poison Strip Sandstone; Cr, Ruby Ranch Member; Cy, Yellow Cat Member; D, Dakota Formation; Mor, Morrison For- mation. during the as reported by Doelling sandstone above the Yellow Cat Member has been (1988). Variation in local subsidence rates due to salt named the Poison Strip Sandstone (Kirkland and others, tectonics might help explain the rapid thinning and thick- 1997). It caps the escarpment exposing the upper Morri- ening observed in the Yellow Cat Member. Additionally, son Formation throughout the area from Green River, lacustrine sediments such as algal- and mudcracked lime- Utah to the Utah-Colorado border. This sandstone forms stones are common in the Yellow Cat Member (Britt and one of the most persistent and distinctive stratigraphic Stadtman, 1997; Kirkland and others, 1997). Lacustrine intervals in the entire Cedar Mountain Formation of east- sediments are compatible with the formation of small ern Utah. In some areas in the Poison Strip region south basins due to salt tectonics. of Cisco, Utah, large scale (5 meters and greater) epsilon The presence of numerous calcareous nodules repre- cross-bedding indicates that a large, meandering river senting paleosols indicates that the Yellow Cat Member system was mostly responsible for its deposition. was deposited under a semiarid monsoonal climate simi- The Poison Strip Sandstone is clearly equivalent to lar to that interpreted for the underlying Morrison For- Young’s (1960) middle Cedar Mountain sandstone east mation (Dodson and others, 1980, Wing and Sues, 1992). of the San Rafael Swell. However, the middle Sandstone The widespread occurrence of viviparid snails, fish, unit as used by Young (1960) in the western San Rafael freshwater turtles, and crocodilians suggest there may Swell area is well above sites preserving an Aptian-lower have been more standing water than indicated for the Albian fauna, such as at the Long Walk Quarry (DeCour- Late Jurassic of the Colorado Plateau (Dodson and oth- ten, 1991; Kirkland and others, 1997), and appears to be ers, 1980). The floras recorded for the Barremian are an unrelated sandstone of more limited extent. Without generally devoid of angiosperms other than a low diver- the biostratigraphic control provided by the vertebrate sity of pollen types, which first appear in the middle Bar- faunas preserved in the Cedar Mountain Formation, remian (Hughes and others, 1979). This would indicate Young’s (1960) miscorrelation of these sandstones across that a flora dominated by non-flowering plants much like the San Rafael Swell is understandable. that of the of the Jurassic was present (Wing and Sues, Sedimentologically the Poison Strip Sandstone is 1992). clearly distinct from the trough cross-bedded conglomer- ate of the Buckhorn Member of the Cedar Mountain For- Poison Strip Sandstone mation in the San Rafael Swell area. Although apparent- ly in the same stratigraphic positions, there is no means The cliff-forming middle Cedar Mountain sandstone of correlation between the genetically distinct Buckhorn unit of Young (1960) marks the top of the Yellow Cat Conglomerate and the middle sandstone of Young (1960) Member in eastern Utah (figure 1). It commonly con- in eastern Utah. In the western San Rafael Swell area, tains gray and white chert pebbles In some places there no fossils have been found in the Buckhorn Conglomer- are several sandstones that are probably genetically relat- ate at the base of the Cedar Mountain Formation; thus it ed to each other, while rarely in other places there is only impossible as yet to date the Buckhorn. Additionally, a thin crevasse splay or, locally, no sandstone at all. This Currie (1997) describes the Buckhorn Conglomerate as

Distribution of Vertebrate Faunas - Kirkland, Cifelli, Britt, Burge, DeCourten, Eaton, Parrish 210 Vertebrate Paleontology in Utah Utah Geological Survey representing an isolated river system flowing to the Arches National Park eastward, the upper contact of the northeast from the San Rafael Swell across the extreme Ruby Ranch Member is clearly with the base of the northwestern corner of Colorado into Wyoming. Dakota Formation. On the west side of the San Rafael The Poison Strip Sandstone is named for the typical Swell, a sharp break from carbonate nodule-bearing, exposures of this unit along the Poison Strip south-south- non-smectitic strata to carbonaceous, highly smectitic west of Cisco, Utah. The type section is on the south- strata marks the contact between the Ruby Ranch Mem- west end of the Poison Strip east-northeast of the Ring- ber and the overlying Mussentuchit Member. A con- tail Mine (Kirkland and other, 1997) (figure 4). The type glomerate unit rich in quartzite lies between these mem- section of the Poison Strip Sandstone measures 5.4 bers along the northeastern side of the San Rafael Swell meters thick. The sandstone is fine- to medium-grained that is equivalent for the most part to Young’s (1960) with matrix supported black, gray, and white chert peb- middle Naturita sandstone ( Mark Kirschbaum, personal bles, trough cross-bedded, and becomes slabby with pale communication, 1996; Kirkland and others, 1997). greenish mudstone partings toward the top of the mem- On the west side of Arches National Park a smectitic ber. The Poison Strip Sandstone is economically signifi- interval is present at the top of the Cedar Mountain For- cant in this area because it is the primary target in the mation. This interval potentially correlates with the Cisco Oil and Gas Field to the northeast (Larry Moyer, Mussentuchit Member of the western San Rafael Swell personal communication, 1995). (figure 2). The report of a hadrosaur femur (Galton and On the northeast side of Arches National Park, Bodi- Jensen, 1979) from this area may lend support to that ly (1969) described a large ankylosaur as cf. Hoplitos- correlation. Additionally, Brigham Young University’s aurus sp. from in, or just above this unit (figure 5). “Movie Valley” ankylosaur from the same area, may also Coombs (1971) referred the taxon to the Cloverly be from this level based on the black color of the bones, nodosaurid ankylosaur, Sauropelta. Just north of this site which uniquely characterizes bones preserved in the a second specimen of Sauropelta was recently discov- Mussentuchit Member among units in the Cedar Moun- ered by researchers from the Denver Museum of Natural tain Formation. History. These fossils indicate the Poison Strip Sand- The Ruby Ranch Member consists of drab, variegat- stone is close to the same age as the overlying Ruby ed mudstones with minor sandstone and limestone lay- Ranch Member, which also contains Sauropelta. The ers. Perhaps most characteristic of this interval are the College of Eastern Utah Prehistoric Museum has recov- abundant carbonate nodules that often are so abundant as ered parts of an ornithopod from their Price River Quarry to form a pavement covering the exposed slopes. The from a conglomeratic sandstone at the base of the Cedar abundance of these nodules makes prospecting for fossils Mountain Formation, southeast of Wellington, Utah in this interval difficult. In addition, ribbon sandstone (Burge, 1996). The ornithopod appears to represent bodies holding up ridges that may extend for a kilometer Tenontosaurus and suggests that the conglomeratic sand- or more are typical of this interval (Young, 1960; Harris, stone southeast of Wellington correlates to the Poison 1980; DeCourten, 1991; Kirkland and others, 1997). A Strip Sandstone. The sparse, small, black, gray, and substantial portion of the northwestward thickening white chert pebbles are also similar to those in the Poi- observed in the Cedar Mountain Formation across the son Strip Sandstone. Large conifer logs and the cycads, San Rafael Swell (for example, Stokes, 1952; Young, Cycadeoidea and Monanthasia (William Tidwell, person- 1960) is represented by this interval. There is also a con- al communication, 1997) are present locally within the siderable thinning and thickening of this interval along Poison Strip Sandstone in the area around Arches the west side of the San Rafael Swell. National Park. The type section of the Ruby Ranch Member is at the Ruby Ranch homestead site southwest of Crescent Ruby Ranch Member Junction, Utah (Kirkland and others, 1997). The basal The Ruby Ranch Member extends across the entire contact is with the Poison Strip Sandstone and the upper outcrop belt of the Cedar Mountain Formation and in contact is with the base of the Dakota Formation. The strata assigned to the Burro Canyon Formation east of type section is 33.1 meters thick. At 2.1, 14, and 16.6 the Colorado River (figure 2). The Ruby Ranch Member meters above the base, ribbon sandstones, whose thalweg overlies the Poison Strip Sandstone from at least the and cross-bed orientations represent eastward-flowing Utah-Colorado border region westward to the eastern rivers are present. Overall, the drab, variegated mud- San Rafael Swell and overlies the Buckhorn Conglomer- stones have a pale purplish surface expression. The ate on the west side of the San Rafael Swell. From upper 8.5 meters is a pale, greenish-gray color perhaps approximately the crest of the Salt Valley Anticline at due to bleaching by the overlying Dakota Formation.

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This upper interval also includes fewer, but larger car- Table 2. Ruby Ranch Fauna (see text for repositories) bonate nodules. The Ruby Ranch fauna (table 2) includes the primi- Class Chondrichthyes tive iguanodontid Tenontosaurus?, the large nodosaur Order Hybodontoidea Sauropelta, a sauropod assigned to Pleurocoelus (= Ast- Hybodus sp. rodon), dromaeosaurid teeth, an unidentified large thero- Class Reptilia pod, and Acrocanthosaurus (Weishampel and Weisham- Order Crocodilia pel, 1983; DeCourten, 1991; Kirkland and others, 1997). indeterminate This fauna is the least known of the Cedar Mountain fau- Order Theropoda Family Dromaeosauridae nas. Important vertebrate sites in this member include cf. sp. the University of Utah’s Long Walk Quarry near Cas- Family Allosauridae ? tledale (DeCourten, 1991), the College of Eastern Utah’s undescribed new genus Price River 2 and KEM sites southeast of Wellington, cf. Acrocanthosaurus sp. Utah, and the Oklahoma Museum of Natural History’s Order Sauropoda Family Brachiosauridae Hotel Mesa Quarry (figure 8) just to the east of the Col- Pleurocoelus sp. = sp. orado River, and thus what properly should be consid- Order Ornithopoda ered a Burro Canyon Formation site (Kirkland and oth- Family Iguanodontidae ers, 1997). The site, from which the Tenontosaurus Tenontosaurus sp. Order Ankylosauria specimens were collected on the west side of the San Family Rafael Swell (Weishampel and Weishampel, 1983), has cf. Sauropelta sp. not been relocated, but the carbonate matrix surrounding the specimens indicates they are from the Ruby Ranch underlying Morrison Formation (Dodson and others, Member. Important collections of fossils from this mem- 1980, Wing and Sues, 1992). The Aptian-Albian pollen ber are housed at the College of Eastern Utah Prehistoric record indicates that angiosperms were becoming a sig- Museum, Price, Utah; Earth Science Museum, Brigham nificant part of western interior floras at this time (Wing Young University, Provo, Utah; and the Utah Museum of and Sues, 1992). Natural History, University of Utah, Salt Lake City, Utah. Mussentuchit Member This fauna compares well with those documented A sharp break from carbonate-nodule-bearing, non- from the Cloverly Formation, Arundel Formation, and smectitic strata to carbonaceous, highly smectitic strata Trinity Group characteristic of North America’s appar- marks the base of the Mussentuchit Member. The dra- ently endemic Aptian-Lower Albian dinosaur fauna matic increase in the volume of volcanic ash preserved in (Kirkland, 1996b; Kirkland and others, 1997). Deter- the Mussentuchit Member indicates a significant increase mining the age of these sediments more precisely is in volcanic activity to the west. The member is dated as impossible at this time. straddling the Albian-Cenomanian boundary based on The abundant calcareous nodules indicate that the palynology (Nichols and Sweet, 1993), subsurface corre- Ruby Ranch Member was deposited under a semiarid lations (Molenaar and Cobban, 1991), and radiometric monsoonal climate similar to that interpreted for the age estimates (Cifelli and others, 1997b).

Figure 8. Oklahoma Museum of Natural History’s Hotel Mesa Site indicated by arrow looking east across the Colorado River. Abbreviations: Cp, Poison Strip Sandstone; D, Dakota Formation; Mor, Morrison Formation.

Distribution of Vertebrate Faunas - Kirkland, Cifelli, Britt, Burge, DeCourten, Eaton, Parrish 212 Vertebrate Paleontology in Utah Utah Geological Survey

Figure 9. Type area of Mussentuchit Member of the Cedar Mountain Formation, Mussentuchit Wash near several of the Oklahoma Museum of Natural History’s quarries. Dashed line indicates contact between Ruby Ranch and Mussentuchit Members. Abbreviations: Cb, Buckhorn Conglom- erate; Cp, Poison Strip Sandstone; Cr, Ruby Ranch Member; Cy, Yellow Cat Member; D, Dakota Formation.

Figure 10. College of Eastern Utah Prehistoric Museum’s Carol Site indicated by arrow northwest of Castledale, Utah. Abbreviations: Cr/Cm, contact between Ruby Ranch and Mussentuchit Members; D, Dakota Formation.

Stokes (1944) included this member in the Cedar sedimentology and paleontology at the base of this inter- Mountain Shale. However, he described the Cedar val suggests that perhaps the Mussentuchit Member Mountain as having abundant carbonate nodules and did would be better included as a basal member of the Dako- not mention that, at the top of the unit, the formation ta Formation; the authors of this paper are not in full may lack such nodules. agreement at to whether this member should be included Locally in the area of the southwestern San Rafael in the Cedar Mountain Formation or in the Dakota For- Swell south of Interstate 70, sandstone lenses near the mation (Kirkland and others, 1997). However, including top of the Cedar Mountain Formation compare well with the Mussentuchit Member in the basal Dakota Formation the more extensive sandstone ledge typically used to would mean that nearly every fossiliferous horizon in the define the base of the Dakota Formation (Stokes, 1944). area of the western San Rafael Swell attributed to the This transition suggests that the top of the Cedar Moun- Cedar Mountain Formation (Katich, 1951; Stokes, 1952; tain Formation may represent a period of nearly continu- Thayne and others, 1983, 1985; Thayne and Tidwell, ous sedimentation including the more carbonaceous 1984; Tidwell and Thayne, 1985; Jensen, 1970; Eaton overlying Dakota Formation. In fact, Young (1960) and Nelson, 1991; Cifelli, 1993; Kirkland and Burge, included the Mussentuchit Member in his Naturita For- 1994; Cifelli and others, 1997b, this volume), would mation (Dakota Formation). The dramatic shift in the have to be attributed to the Dakota Formation.

Distribution of Vertebrate Faunas - Kirkland, Cifelli, Britt, Burge, DeCourten, Eaton, Parrish Miscellaneous Publication 99-1 Vertebrate Paleontology in Utah 213

The upper smectitic portion of the Cedar Mountain the Oklahoma Museum of Natural History, a number of Formation was designated the Mussentuchit Member by other important vertebrate sites have been developed in Kirkland and others (1997) with its type section south of the Mussentuchit Member by other institutions. Most of Mussentuchit Wash (figure 9). At the type section, the these sites are from the area east of Ferron and Castle member is 25 meters thick. A thin, discontinuous sand- Dale, Utah and include the Carol Site (figure 10), the stone marks the base, where the non-smectitic mudstone Rough Road Quarry, Jensen’s egg site, and Robison’s rich in carbonate nodules is replaced by highly smectitic, Eggshell Quarry ( Jensen, 1970; Nelson and Crooks, gray mudstone. Several thin lenticular sandstones and 1987; Pomes, 1988; Eaton and Nelson, 1991; Jones and lignitic horizons are present in the type section. The top Burge, 1995; Burge, 1996). Important collections from of the member is at the base of a thick buff sandstone these sites are housed at the College of Eastern Utah Pre- that forms the basal unit of the Dakota Formation along historic Museum, Price, Utah; Sternberg Museum, Hays, most of the western San Rafael Swell. Locally to the Kansas; University of Colorado Museum, Boulder, Col- east of Ferron Utah, the Dakota Formation is missing orado; University of California, Museum of Paleontol- (figure 2) and a horizon of dark chert pebbles and cob- ogy, Berkeley, California; Brigham Young University, bles marks the base of the overlying Mancos Shale Earth Science Museum, Provo, Utah; and the Oklahoma (Eaton and others, 1990; Kirkland and others, 1997). Museum of Natural History, Norman, Oklahoma. The preserved dinosaur fauna includes a small The most common dinosaur from the Mussentuchit nodosaurid Animantarx ramaljonesi, a small iguanodon- Member is a primitive hadrosaurid (Kirkland and Burge, tid ornithopod, a primitive lambeosaurid hadrosaur, cer- 1994; Kirkland and others, 1997). Common hadrosaurid atopsian teeth, pachycephalosaur teeth, tiny sauropod teeth from Cedar Mountain Formation sites on the west teeth, dromaeosaurid teeth, cf. Richardoestesia teeth, cf. side of the San Rafael Swell were first noted by Parrish Paronychodon teeth, and an early tyrannosaurid (Kirk- (1991), although the locality horizon was not indicated in land and Burge, 1994; Kirkland and Parrish, 1995; that abstract. The senior author has determined this Burge, 1996; Carpenter and others, this volume). Teeth primitive hadrosaurid to be somewhat like Telmatosaurus of a very small sauropod similar in morphology to those (Weishampel and others, 1993) from the Upper Creta- described as Astrodon are also present in this member ceous of eastern Europe and a bit more advanced than marking the last occurrence of sauropods in North Amer- the iguanodontid Probactrosaurus (Rozhdestvensky, ica prior to their reintroduction from South America in 1967; Norman, 1990) from the Lower Cretaceous of cen- the late Maastrichtian (Lucas and Hunt, 1989). At the tral Asia. More research is needed to determine its sys- family level, this fauna is remarkably similar to those of tematic position relative to the Hadrosaurinae and Lam- the overlying Dakota Formation (Eaton and others, 1997) beosaurinae (Sereno, 1986; Horner, 1990; Weishampel and those of the Campanian and Maastrichtian of west- and Horner, 1990). However, the material discovered to ern North America (Cifelli, Kirkland, and others, 1997b; date suggests lambeosaurine affinities. Cifelli and others, this volume; Kirkland, 1996b; Kirk- Molenaar and Cobban (1991) have demonstrated land and others, 1997). As the only likely ancestors of through subsurface relationships that the uppermost the hadrosaur, ceratopsian, and perhaps the tyrannosaurid Cedar Mountain Formation may correlate to the Mowry are from the Early Cretaceous of Asia, the dramatic shift Shale to the northeast and may thus be of basal Ceno- to faunas typical of the North American Late Cretaceous manian age. The Albian-Cenomanian boundary, on the is interpreted to be the result of opening migration corri- basis of non-marine palynomorphs, has been placed at dors to and from Asia through Alaska at the end of the the first occurrence of tricolporate pollen grains (for Early Cretaceous, when migration to eastern North example Nyssapollenites, rare in marine rocks) and obli- America was still possible (Kirkland, 1996b; Cifelli and gate tetrads (Singh, 1975; Nichols and Sweet, 1993). others, 1997b). Tschudy and others (1984) did not encounter these paly- Following an extensive screenwashing operation by nomorphs in their samples from the upper Cedar Moun- the University of Oklahoma that resulted in thousands of tain Formation near Castle Dale, Utah. The occurrence catalogued specimens representing nearly 80 vertebrate of these palynomorphs is diachronous across Alberta taxa, Cifelli, Kirkland, Kirkland, and others (1997; and (Nichols and Sweet, 1993). In addition, with the older Cifelli and others, this volume, for complete faunal list) placement of the Albian-Cenomanian boundary (Cobban have characterized this fauna as the Mussentuchit local and Kennedy, 1989) by ammonite correlations to the fauna for Mussentuchit Wash, where many of their best type areas in Europe, it is likely that the palynomorph vertebrate sites are located. datum (first occurrence of tricolpate and obligate tetrad In addition to the many important sites developed by pollen) is above the base of the Cenomanian (Nichols

Distribution of Vertebrate Faunas - Kirkland, Cifelli, Britt, Burge, DeCourten, Eaton, Parrish 214 Vertebrate Paleontology in Utah Utah Geological Survey and Sweet, 1993). members: the Buckhorn Conglomerate, the Yellow Cat A radiometric age estimate of 98.39 ± 0.07 million Member, the Poison Strip Sandstone, the Ruby Ranch years B. P. (Cifelli, Kirkland, and others, 1997) places Member, and the Mussentuchit Member (Kirkland and the fauna at, or just above, the Albian-Cenomanian others, 1997). Of these, only the Buckhorn Conglomer- boundary according to the most recent time scales for the ate has not yielded age-diagnostic fossils permitting its Cretaceous, which have the boundary placed at 98.5 mil- correlation with other strata. lion years B. P. (Obradovich, 1993) or at 98.9 ± 0.6 mil- The oldest fauna is preserved in the Yellow Cat lion years B. P. (Gradstein and others, 1994). The date Member and is dated as Barremian based on the occur- supports a correlation with the Mowry Shale to the rence of dinosaurs similar to those preserved in Barrem- northeast (figure 6). ian sediments of northwestern Europe, and based on the The absence of calcareous nodules indicates that the occurrence of charophytes not recorded in strata younger Mussentuchit Member was deposited under a significant- than Barremian. The middle fauna is preserved in the ly wetter environment than were the lower members of Poison Strip Sandstone and Ruby Ranch Member and is the Cedar Mountain Formation. This wetter environment dated as broadly Aptian-Albian based on dinosaurs may be due to the transgression of the Mowry Sea into known to occur elsewhere in North America during the the area of the northeastern Uinta Basin (Wing and Sues, Aptian-Albian. The youngest fauna is preserved in the 1992). The North American record indicates that Mussentuchit Member and is precisely dated as overlap- angiosperms were becoming a more important part of ping the Albian/Cenomanian boundary at 98.39 ± 0.07 western interior floras at this time (Wing and Sues, 1992) million years B. P. (Cifelli, Kirkland, and others, 1997). and some of the earliest records of some angiosperm The vertebrate faunas preserved in the Cedar Moun- wood types are from this member (Tidwell, 1996). tain Formation of east-central Utah provide a unique A dramatic shift between Albian and middle Ceno- opportunity to study the transition of the terrestrial biota manian faunas has been noted in Texas (Lee, 1995; Win- from an environment when angiosperms were rare until kler and others, 1995). The new age estimates for the angiosperms were a major component of the flora. Addi- Mussentuchit Member indicate that this faunal turnover tionally, these faunas record a shift from a Barremian was even more dramatic than was previously thought. fauna with European affinities to an Albian/Cenomanian Thus, within the Cedar Mountain Formation there is a fauna with Asian affinities. The transition from sedi- three-fold instead of a two-fold zonation of Cedar Moun- ments largely devoid of carbonaceous material and con- tain Formation based on dinosaurs (Kirkland, 1992, taining abundant carbonate nodules, to sediments that are 1996b; Lucas, 1993): a basal Barremian iguanodont- lignitic with no carbonate nodules, suggests increased polacanthid fauna with European affinities predating rainfall in the region during the expansion of the Creta- common flowering plants; a middle Aptian-middle ceous Western Interior Seaway. Further research in the Albian Tenontosaurus-Pleurocoelus fauna perhaps repre- region is required to differentiate the relative effects of senting a depauperate fauna following a major Early Cre- changes in the flora, climate, and biogeography on the taceous extinction event (endemic to North America); terrestrial biota preserved in the Cedar Mountain Form- and an upper latest Albian-lowest Cenomanian hadrosaur ation. fauna with Asian affinities when flowering plants were co-dominant with gymnosperms. Biogeographic rather ACKNOWLEDGMENTS than floristic changes may account for most of the fau- We would like to thank the many people too numer- nistic changes recorded at the end of the Albian as sug- ous to count who have helped in the field, including gested by the dramatic shift to a dinosaur fauna dominat- many from the Utah Friends of Paleontology, Uncom- ed by taxa with an Asian ancestry (Kirkland, 1996b; pahgre Plateau Paleontological Society, and the Western Cifelli and others, 1997b, this volume). Interior Paleontological Society. Special thanks are extended to the Judd family of Castle Dale, Utah, the CONCLUSIONS Jones family of Salt Lake City, Utah, the Gaston family Vertebrate fossils are present throughout the Cedar of Knoxville, Tennessee, and the Corbett family of Mountain Formation of east-central Utah. It contains Raleigh, North Carolina. Robert Young of Grand Junc- three distinct faunas, which are separated by intraforma- tion, Colorado is gratefully acknowledged for providing tional unconformities. The recognition of these faunas copies of his extensive field notes on the Cedar Moun- combined with lithologic observations has permitted tain and Dakota Formations. Excavations were all division of the Cedar Mountain Formation into five undertaken under permits issued by the Bureau of Land

Distribution of Vertebrate Faunas - Kirkland, Cifelli, Britt, Burge, DeCourten, Eaton, Parrish Miscellaneous Publication 99-1 Vertebrate Paleontology in Utah 215

Management and the Utah School and Institutional Trust tory; Rod Scheetz, Museum of Western Colorado; Ken Lands Administration. Partial funding in support of this Stadtman, Brigham Young University; and Scott Madsen, research was provided by the National Geographic Soci- Dinosaur National Monument for their skilled field assis- ety (grants 4761-91 and 5021-92 to RLC; 5263-94 to tance and preparation skills. Reviews of this manuscript JIK) and the National Science Foundation (grants BSR by David D. Gillette, Louis L. Jacobs, and Mark Kirsh- 8906992 and DEB 941094 to RLC). Special thanks are baum are gratefully acknowledged. Innumerable col- due to John Bird and Carl Limone, CEU Prehistoric leagues throughout our profession have aided this Museum; Harold Bollan, Dinamation International Soci- research with their knowledge, advice, encouragement, ety; Randy Nydam, Oklahoma Museum of Natural His- and camaraderie.

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Distribution of Vertebrate Faunas - Kirkland, Cifelli, Britt, Burge, DeCourten, Eaton, Parrish 218 Vertebrate Paleontology in Utah Utah Geological Survey

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