THE CASE FOR FISHING DINOSAURS AT THE ST.GEORGE DINOSAUR DISCOVERY SITE AT JOHNSON FARM by Andrew R. C. Milner and James I. Kirkland

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THE CASE FOR FISHING DINOSAURS AT THE ST.GEORGE DINOSAUR DISCOVERY SITE AT JOHNSON FARM by Andrew R. C. Milner and James I. Kirkland
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  UTAH GEOLOGICAL SURVEY SURVEY NOTES September 2007Volume 39, Number 3 New Horned Dinosaurs from the Wahweap Formation  State o Utah JonHuntsman,Jr.,Governor Department o Natural Resources MichaelStyler,ExecutiveDirector UGS Board SteveChurch,ChairGeoBedellJackHamiltonMarkBunnellAlisaSchoeldKennethPuchlikDavidSimonKevinCarter(TrustLandsAdministration-exofcio) UGS Staf  Administration RichardG.Allis,DirectorKimmHarty,DeputyDirectorJohnKingsley,AssociateDirectorStarrSoliz,Secretary/ReceptionistJoLynnCampbell,AdministrativeSecretaryKathiGalusha,AccountingOfcerLindaBennett,AccountingTechnicianMichaelHylland,TechnicalReviewerRobertRessetar,TechnicalReviewer Editorial Staf  VickyClarke SharonHamre,JamesParker,LoriDouglas,LizPaton Geologic Hazards GaryChristenson WilliamLund,BarrySolomon,FrancisAshland,RichardGiraud,GregMcDonald,LucasShaw,ChrisDuRoss,TylerKnudsen Energy and Minerals DavidTabet RobertBlackett,RogerBon,ThomasChidsey,MikeLaine,BryceTripp,CraigMorgan,JeQuick,J.WallaceGwynn,SharonWakeeld,CherylGustin,TomDempster,BrigitteHucka,TaylorBoden,KenKrahulec,StephanieCarney,ValerieDavis,BradWolverton Geologic Mapping GrantWillis JonKing,DouglasSprinkel,JaniceHayden,KentBrown,BobBiek,BasiaMatyjasik,LisaBrown,DonClark,J.BuckEhler Geologic Inormation and Outreach SandraEldredge WilliamCase,MageYonetani,ChristineWilkerson,PatriciaStokes,MarkMilligan,RobNielson,JimDavis,EmilyChapman Ground Water and Paleontology MichaelLowe JamesKirkland,CharlesBishop,JanaeWallace,MarthaHayden,HughHurlow,LucyJordan,DonDeBlieux,KimNay,SteanKirby,KevinThomas,RebeccaMedina,JennierCavin,WalidSabbah,RichEmerson,MattAolter State Energy Program PhilipPowlick DeniseBeaudoin,MikeVandenBerg,JasonBerry CONTENTS Fishing Dinosaurs at Johnson Farm ..... 1Horned Dinosaurs rom Wahweap Fm 4GeoSights ...................................................... 6Governor’s Hazards Working Group ..... 7Ground-Water Monitoring ....................... 8Energy News ............................................... 10Glad You Asked .......................................... 11New Publications ...................................... 12Survey News ............................................... 12 Teacher’s Corner ........................................ 13 Design: Liz PatonCover: Life reconstruction of Last Chance ceratopsian,illustrated by Brad Wolverton. Background photo: Rocks of the Wahweap Formation in Wesses Canyon, Grand Staircase-Escalante National Monument. Photo by Don DeBlieux.  Survey Notes is published three times yearly by Utah Geological Survey, 1594 W. North Temple, Suite 3110, Salt Lake City, Utah 84116; (801) 537-3300. The Utah Geological Survey provides timelyscientifc inormation about Utah’s geologic environment, resources, and hazards. The UGS is a division o the Department o Natural Resources. Single copies o   Survey Notes are distributed reeo charge within the United States and reproduction is encouraged with recognition o source. Copies are available at http://geology.utah.gov/surveynotes ISSN 1061-7930  This summer the Utah Geological Surveybegan its largest project ever—the drillingo 15 to 20 ground-water monitoring wellsin Utah’s west desert. The 2007 State Leg-islature expressed concern about potentialimpacts o ground-water withdrawal inneighboring valleys o Ne-vada by the Southern NevadaWater Authority (SNWA), andappropriated over $2 millionor a network o monitoringwells (see article on p. 8). ThePaleozoic carbonate rocksthat underlie a large part o the Basin and Range Provinceo western Utah and easternNevada may orm a regionalaquier that allows groundwater to ow between vari-ous basins and more localizedbasin-ll aquiers. However,its characteristics are not well understoodand no wells in the major valley on the Utahside o the state line (Snake Valley, mostlyMillard County) penetrate the aquier. TheU.S. Geological Survey (USGS) recently re-leased a drat report o its two-year study o the water resources o this region (reerencein above-mentioned article). According tothe USGS, a relatively large head diference(about 1000 eet) exists between the southand north ends o Snake Valley (a distanceo about 100 miles), and between SpringValley to the west in Nevada and Snake Val-ley (a distance o about 25 miles). The headgradients imply ground-water ow rom thesouth towards the north in Snake Valley,and rom the west. Chemical and isotopicdata support these ow paths, with mostrecharge occurring in the Snake Range be-tween Snake Valley and Spring Valley, andperhaps also in the Schell Creek Range onthe west side o Spring Valley. Carbon-14dating indicates ground-water ages o lessthan 1000 years to 6000 years with age in-creasing downgradient, suggesting ground-water ow velocities on the order o 100eet/year. The USGS reassessment o the ground-wa-ter system indicates ground-water inowsrom the west o 29,000 acre-eet/year intothe south end o Snake Valley, and 14,000acre-eet/year into the north end o the val-ley. The estimated ground-water outowrom Snake Valley towardsthe northeast is 29,000 acre-eet/year (pre-irrigation de-velopment), and Fish Springs(20,000–27,000 acre-eet/year)in Juab County may representa large part o this. Althoughthe ground-water ows ap-pear to be precise numbers,the USGS points out they arederived rom the diferencebetween two large numberswith signicant uncertainties:the proportion o total pre-cipitation that inltrates theground, and total evapotranspiration. In thecase o Snake Valley, evapotranspiration isestimated to be 130,000 ± 30,000 acre-eet/year. The uncertainties are thereore com-parable to the magnitude o the inerredinterbasin ows, so caution is needed wheninterpreting the ground-water ow systemin any basin. The USGS estimates the present rate o ground-water extraction in Snake Valley is24,000 acre-eet/year (mostly or crop irri-gation), which approaches their estimate o the magnitude o the ground-water outowrom the valley. Utah’s Division o WaterRights reports that about 60,000 acre-eet/year o ground-water depletion is commit-ted (either approved or perected waterrights) on the Utah side o Snake Valley,and on the Nevada side about 15,000 acre-eet/year is committed. This includes about32,000 acre-eet/year o spring ow (BigSprings, Gandy Warm Springs, Twin Springs,and Fish Springs) which is used in Utah andis reected in Utah’s water rights but notincluded in the USGS ground-water use(extraction) estimate. Applications or ad- THE DIRECTOR’S PERSPECTIVE (continued on page 9) by Richard G. Allis   The St. George Dinosaur Discovery Site at Johnson Farm (SGDS)preserves a world-class collection o dinosaur tracks and associ-ated eatures. The initial discovery and preliminary scientiicinterpretation o the site were reported in previous issues o  Survey Notes (2000, v. 32, no. 3; 2002, v. 34, no. 3). This article summarizesevidence suggesting that dinosaurs at SGDS were eeding on ish. The SGDS preserves not only thousands o dinosaur tracks onat least 25 track-bearing horizons in the basal Jurassic MoenaveFormation, but also abundant ish, plant, and invertebrate ossilsas well as rare dinosaur teeth and bone. The Moenave Formationat the SGDS provides a window into the earliest Jurassic (about200–198 million years ago) ecosystem near the margin o a largeprehistoric lake—Lake Dixie. The main track-bearing sandstone near the base o the WhitmorePoint Member o the Moenave Formation (“Johnson Farm sand-stone bed”) preserves casts o dinosaur tracks at its base. Thissandstone bed was deposited rapidly on a bed o clay, preservingthe ine detail o the clay’s surace. Southeast o Riverside Driveat the SGDS museum, the base o this sandstone exposes castso mud cracks and dinosaur tracks (mostly large Eubrontes withsmaller, nearly identical Grallator  type tracks) with isolated scours(lute casts) and diamond-shaped salt casts, suggesting an ex-posed lake-shore mud lat. Northwest o Riverside Drive, this samesurace preserves tool marks, small lute casts, and crescent marks(scratch circles) on an extensively scoured surace; these eaturesindicate relatively strong longshore currents that paralleled thelake shore and exposed mud lat, orming a subaqueous channel.Like in the ocean, longshore currents are created in large lakes bywaves obliquely striking the shore.Among the most exciting discoveries at SGDS is an abundance o dinosaur swim tracks (known by the name Characichnos ) at thebase o the thickened “Johnson Farm sandstone bed” northwesto Riverside Drive representing the subaqueous channel. Here,the SGDS has the world’s largest and best-preserved collection o dinosaur swim tracks, which resolves a long-standing controversyamong paleontologists about the very existence o swim tracks.Part o the controversy revolved around the simple act that i a di-nosaur were swimming ully buoyed up in the water, it would notleave marks on the bottom. Swim tracks o meat-eating dinosaursare typically arranged in sets o three parallel scrape marks thattaper at each end, with the longer middle toe leaving a longer anddeeper scrape mark compared to the shorter outer toes.Most, but not all, o the swim tracks are comparable in size to thesmaller walking track  Grallator  , which here is indistinguishablerom small-scale versions o  Eubrontes . The vast majority o these  THE CASE FOR FISHINGDINOSAURS AT THE ST.GEORGEDINOSAUR DISCOVERYSITE AT JOHNSON FARM by Andrew R. C. Milner and James I. Kirkland  Thanks to the landowners, volunteers, the City o St. George, and critical unding rom the State o Utah and the ederal govern-ment, a museum opened in April 2005 over Shelden Johnson’sinitial discovery site south o Riverside Drive.Illustration by Russell Hawley  1 cm Anterior viewsPosterior views Spinosaurus toothSt. GeorgetoothSt. Georgetooth Large theropod teeth rom SGDS vs. Spinosaurus rom North Arica. SEPTEMBER 2007   swim tracks are oriented in the oppositedirection rom the current indicators inthe channel. The most likely scenario isthat numerous meat-eating dinosaurswere wading in the shallows o thelake and stepped o into the deepersubaqueous channel, where the smallerdinosaurs were swept o their eet,resulting in the dinosaurs loundering inthe water against the strong current. The abundance o swim tracks leadsto the obvious question: Why were somany dinosaurs wading hip deep inthe lake? It is certainly a lot harder towalk through water than to walk alonga beach.Many ish remains have been recov-ered at the SGDS rom higher in theWhitmore Point Member. This, alongwith sedimentological data, indicatesthat ater the top o the “Johnson Farmsandstone bed” was deposited, Lake Di-xie deepened and expanded across thearea to an eventual maximum extentnorth o Cedar City and Zion NationalPark and east to Kanab. How ar LakeDixie extended south into Arizona andwest into Nevada is unknown.Many o the ish preserved in theWhitmore Point Member are large andinclude two new species we named in2006: the hybodont (spiny, reshwater)shark  Lissodus johnsonorum and thelungish Ceratodus stewarti  , both about3-4 eet long. Other ish include a largecoelacanth (lobe-ined ish) similar to Chinlea (about 6 eet long) and abun-dant semionotid ish as much as 4 eetlong, probably all belonging to thegenus Semionotus . Semionotus wasshaped like a modern carp, but com-pletely covered in a “chain mail” armoro heavy, enamel-covered, diamond-shaped scales (ganoid scales) like themodern gar o the southeastern UnitedStates. The abundance o large ishlends additional support to the hypoth-esis that Lake Dixie was a very largelake. The larger dinosaur teeth recoveredrom the SGDS are almost certainly romthe theropod dinosaur that made the Eubrontes tracks. A well-preserved tho-racic vertebra rom the SGDS suggeststhe dinosaur may have been a relativeo the double-crested theropod Dilo- phosaurus , which is known rom severalspecimens in the overlying KayentaFormation, where hundreds o  Eubron-tes tracksites are documented. Thelarge SGDS teeth are tall, slender, andtypically cylindrical, exhibiting a distinctwear pattern in which the serrated ridg-es (carinae) along the ront and back margins o the teeth are worn rom thetip down to the base. We hypothesizedthis may be rom the enamel-on-enamelwear produced by these dinosaurs bit-ing through the “chain mail”-covered se-mionotids. Spinosaurid teeth rom the A AA' Fossil RidgeIntermediate School0.3 mile SubaqueousLake DixieExposed mudat      S      h    o    r    e      l      i    n    e SGDSMuseum   R  i  v e  r  s  i d e   D  r  i  v e M    a   l     l      D    r   i    v   e    C 300 feetASubaqueous Lake Dixie“Johnson Farm sandstone bed”Exposed MudatA'3 feet Mapped Swim Track Blocks   15 feet Edge of SubaqueousChannelEdge of SubaqueousChannel Approximate outline of WashingtonCounty School District Quarry #1 CurrentDirection TREND OF DINOSAURSWIM TRACKS NESW B Unexcavated A   B   C (A) Area o the SGDSshowing location o LakeDixie shoreline just prior todeposition o the “JohnsonFarm sandstone bed.” Red area indicates locationo Washington County School District Quarry #1, where the swim track blocks were excavated.Cross section A–A’ shownin C. (B) Map o area o Washington County School District Quarry with orangeindicating mapped blocksand black areas represent-ing missing blocks. Linelabeled SW–NE indicatescross section within red box in C. (C) Cross sectionshowing relative change inthickness o “Johnson Farmsandstone bed.” Red box indicates area shown in B.(A) Initial swim track blocks discovered by A.R.C. Milner in 2001. (B and C) Examples o swim tracks rom Wash-ington County School District Quarry #1. Red arrowsindicate swim direction, blue arrows indicate current direction.  SURVEY NOTES  Early Cretaceous o North Arica are similarand display the same sort o distinctivewear pattern. Spinosaurids are thought tohave ed to a signiicant degree on ish, asindicated by their crocodile-like skulls. Thehuge semionotid Lepidotes is commonlypreserved in the same environments withspinosaurid remains, suggesting that thistype o tooth wear is a result o eating ishcovered in heavy, enamel-covered scales. Dilophosaurus exhibits a ew eatures thatsuggest ish-eating behavior: The ends o the jaws are expandedlaterally to orm an interlocking rosette1)o long teeth at the ront o the jaws.Spinosaurids have a similar eature,which is well developed in the Indiangharial—the most ish-eating o allmodern crocodilians.Unlike other meat-eating dinosaurs, Dilophosaurus’  nasal openings are re-tracted back rom the ront o the jaws.Spinosaurid nasal openings are evenmore extremely retracted. This charac-teristic may have limited the splashingo water into their nostrils while ishing.Both Dilophosaurus and spinosauridshave relatively long arms, which, with2)3)their well-developed claws, may havehelped them catch ish.Finally, the Triassic-Jurassic boundary hasbeen proposed to all within the MoenaveFormation. Dramatic aunal turnover hasbeen proposed or the Late Triassic and,whether as a period o more rapid aunalloss than normal or a mass extinction, thesubsequent earliest Jurassic was a very di-erent and apparently more impoverishedworld biologically. The abundance o largeish in Lake Dixie would have provided animportant source o protein in this post-cataclysmic world. Lissodus johnsonorum Ceratodus stewarti Semionotus kanabensis New giant coelocanth  approx.1 ft Andrew R.C. Milner (right) is theCity Paleontologist and Curator atthe St. George Dinosaur DiscoverySite at Johnson Farm in St. George,Utah. His research primarily in-cludes vertebrate tracks and ossilishes o the Mesozoic, particularlythe Late Triassic and Early Jurassic.Andrew studied late PleistoceneChamplain Sea ossils in easternCanada or the Canadian Museumo Nature in Ottawa, and spent ive seasons working on the Middle CambrianBurgess Shale in Yoho National Park, British Columbia, Canada, or the RoyalOntario Museum (Toronto, Ontario). Dr. Jim Kirkland (let) is the Utah State Paleontologist with the Utah GeologicalSurvey. An expert on the Mesozoic, he has spent more than 30 years excavatingossils across the southwestern U.S. and Mexico, and has authored and co-au-thored more than 75 proessional papers. The reconstruction o ancient marineand terrestrial environments, biostratigraphy, paleoecology, and mass extinc-tions are some o his interests. He has discovered and described numerous newdinosaurs including several armored and horned dinosaurs, and several meat-eating dinosaurs o which the giant dromaeosaur Utahraptor  is the best known.He has also described and named many ossil mollusks and ish. Reconstructions o larger ossil fsh rom SGDS.Reconstruction o  Dilophosaurus rom the Kayenta Formation with the Eubrontes and Grallator track types. Illustration by Brad Wolverton. SEPTEMBER 2007 
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