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CAMARASAURUS

Dinosaur Trail

BUREAU OF LAND MANAGEMENT

CAMPTOSAURUS

STEGOSAUBUS

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A SELF GUIDED WALKINGTOURGrand ResourceArea - Moab. Utah

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General OverviewThe dry climate and eroded landscape of today is

very different from the environment that existed whenthe dinosaurs roamed southern Utah. Climates weremild and moist during the Jurassic period 150 mill ionyears ago. The fossil remains of plant and numerousdinosaurs are typically found in the Morrison Forma-tion. The Morrison Formation is a complex series ofclays, shales, and sandstones that settled in swamps,bogs, shallow lakes, and the broad and often slowmoving streams that wandered over a low-lying fea-tureless landscape. Cycads, ginkgoes, and cbnifersformed forests, shading an undergrowth comprisedlargely of ferns. Horsetails and succulent plants grewabundantly in swamps and bogs. The Morrison Forma-tion contains the fossil remains of plants and numerouskind of dinosaurs including: Allosaurus, Camptosaurus,Stegosaurus, and Camarasaurus.

Jurassic rocks are exposed over wide areas ineastern and southern Utah. Their multicolored layersprovide a scenic wonderland. Water deposited andwind blown sands and silts comprise these formations.They include the Navajo sandstone which overlays thelate Triassic Kayenta and Wingate sandslones, andThe Entrada sandstone that is seen in the majesticformations of Arches National Park.

FossilizationAn essential requirement for the formation of a fossil israpid burial by sediment afterthe organism dies andthesoft tissue rots away, leaving the bony skeleton. Thisburial normally occurs in rivers, lakes, or the sea intowhich the carcasses of land-living animals may bewashed . Two p rocesses may then occu r : ( 1 )permineralization, where organic matter in the bonesmay decay and be replaced by minerals from waterpercolating through the sedimentary rocks; or (2) pet-rifaction, the bony structure may be replaced entirely byminerals. Alternatively, the bones may dissolve, leav-ing a hollow mold that may befi led by mineralsthatforma solid replica of the bone, a natural cast. Landmovement and erosion may then lead to exposure ofthe fossil.

AllosaurusAllosaurus was a large, bipedal, saurischian (l izard-

hipped), meat-eating dinosaur. Heavily built, Allosaurushad powerful hind legs, relatively short but strong fore-limbs, and a very large head. A massive tail must haveaided in balance. The animal grew to a length of nearly39 feet. The huge jaws were lined with large serrated,stabbing, and cutting teeth. Both hands and feet wereequipped with large claws.

StegosaurusStegosaurus was a moderately large four-footed,

ornithischian (bird-hipped), plant eating dinosaur, whichis characterized by a double row of large, alternatelyspaced plates that ran down its back and large spikes atthe end of its tail. The animal grew to a length of 25 feetand may have weighed 1.5 tons. Stegosaurus had anextraordinarily smallbrain, which weighed no more than2.5 Io 2.8 ounces.

CamarasaurusCamarasaurus was a very large, heavy bodied, four-

footed, saurischian (lizard-hipped), plani-eating dino-saur. lt had a short skull with a blunt snout and a fairlylong neckand tail. Camarasaurus grewto a length of 59feet and the four pil lar-l ike legs may have supported aweight of nearly 20 tons.

CamptosaurusCamptosaurus was a moderately sized, ornithis-

chian (bird-hipped), plant eating dinosaur, which waspresumably quite nimble and fast, but otherwise quitedefenseless. The animal grew to a length of around 20feet. Hoof-like claws on both fingers and toes suggestthat it often walked on all-fours.

LOCATION MAP

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TRAIL MAPThe self guided walking lour beginsat the register box.

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AccessTo reach the Mill CanyonDinosaur Trailhead, drive 1 5miles north of Moab on U.S.191, then turn left at an inter-section just north of highwaymi le marker 141. Cross therailroad tracks and continue2 miles on a bladed dirt roadto the Dinosaur Trailhead.The road is imoassiblewhenwet.

@ f-ong bones of the right hind l imb of a sauropod, @ aon"" prepared in place by an experienced paleon-

Trail Sites(!) Anterior dorsal vertebra and neural arch fragments

of a sauropod dinosaur, perhaps Camarasaurus.

including a femur (thigh) and lower leg elements, thetibia and fibula. The hind foot is not in evidence.however.

@ foot elements of a sauropod, perhaps includingmetacarpals and phalanges (toe bones), and a smalldorsal vertebra below.

@ ,n place to the right or upside of the trail are partialsauropod vertebrae and various fragments of otherunidentif ied bones. On the lower side of the trail arenumerous bone f ragments in several blocks which haveseparated from the outcrop. Can you match any of thebone fragments on one block with another?

@ ruaturat molds or impressions of a small and largecaudal (tail) vertebra of a sauropod.

@ 'n the block where the trail crosses the wash arenumerous bones. How many individual bones can youcount? Please avoid areas near the unstable cliffs to theright (upside of the hil l).

@ Oi"t"t (toward an end) caudal (tail) vertebrae of anunidentified sauropod with parts of four haemal arches(chevron bones) remaining as the only evidence ofvandalized vertebrae in the series. Above and to theright about 2.5 meters (7 feet) is the protruding end of asauropod femur (thigh). Above and to the left about 2meters (6 feet) is the natural mold of a sauropod pelvicelement that has been weathered out or carried away.Below and to the left is a very large boulder withnumerous sauropod limb elements in evidence. Thereare femora, a tibia, and pelvic pieces in view.

@ tncomptete scapula and ribs of an unidentified sau-ropod. There appears to be the proximal (toward thebody) end of a humerus, coracoid, or femur to the left.

@ n variety of separate bones are shown including theproximal end of a sauropod fibula, a section of allosauridfemur, a section of camptosaurid femur, the chevron orback part of the neural lodge and neural spine of astegosaurid, a possible vertebrae and miscellaneousunidentif ied element f ragments.

@ VanOalized sauropod tibia with only the impressionor natural mold of the original bone left in place

tologist.

(? Packrat midden. Packrats collect everything within200 yards of their den. Over the years many layersbuild up within the den. These layers, which are studiedby scientists, are good time and climate indicators.

(p Numerous hind leg elements of Allosaurus includ-ing a femur, t ibia, f ibula, metatarsal, and phalanges.

@ Oisseminated (scattered) fragments of fossilwood.

@ fossit wood area with prominent mold containing ahorizontal remnant of a large trunk of an araucaria-l iketree (cone-bearing pine - "conifer"). See the counter-part of the tree trunk in the large boulder complex on thedown side of the trail.

This is the trail termination, so you may choose toretrace your steps or hike across the canyon to thesouth and visit the copper mill site.

Mitl Canyon (rHE oLD coppER MrLL)On the south side of the canyon you can view the

remnants of an old copper mill. Copper ores (azuriteand malachite), exposed along the Moab fault, weremined and processed here in the late 1800's. Limitedquantities of ore and fluctuating prices probably madethe venture economicallv unfeasible and the mill wasabandoned.

The Mill Canyon Dinosaur Trail is a bold experi-ment; there are no guards or fences here. You, thevisitor, are the protector of this valuable resource. lt isillegal to remove, deface, or destroy improvements,rocks. and fossils.

Halfway Stage StationThe remains of the Halfway Stage Station are locatedeast of the Dinosaur Trail. The Halfway Stage Stationserved the traveling public between Moab and therailroad at Thompson. The first passenger train wentthrough Thompson to Salt Lake in April of 1883. Therailroad was 35 miles from Moab. The trip from Moab tothe train took eight hours for passengers, so travelersstopped at the station for lunch. Slower freighters spentthe night on a two day trip. To reach the stage stationproceed north toward Highway 191. Atthe first intersec-tion turn right and proceed to a dry wash. Turn right onthe jeep trail at the wash crossing and continue to theStage Station.

Other Paleontological points ol interest include:

Cleveland-Lloyd Dinosaur Quarry - near Price,Utah

Dinosaur National Monument - near Jensen, UtahDinosaur Valley Museum - Grand Junction,

ColoradoUtah Museum of Natural History - Salt Lake City,

UtahCollege of Eastern Utah Prehistoric Museum -

Price, UtahUtah Fieldhouse of Natural History - Vernal, UtahTrail Through Time (Rabbit Valley) - l-70 at theUtah/Colorado stateline.

FOR MORE INFORMATION

Moab Bureau of Land Management82 East Dogwood, Moab, UT 84532

435-259-

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BLM/UT/G l-99/004+8000