St. George Dinosaur Discovery Tracksite (Top Surface) (Jurassic of the United States)

Also known as Johnson farm, TS, SGDS

Where: Washington County, Utah (37.1° N, 113.6° W: paleocoordinates 17.3° N, 52.8° W)

• coordinate estimated from map

• outcrop-level geographic resolution

When: Whitmore Point Member (Moenave Formation), Hettangian (201.3 - 199.3 Ma)

• among the lowest of 25 regional track-bearing horizons but just above Main Track Layer; 54-55 m above base of formation; 4 layers total

•Most of the Moenave Formation is the Dinosaur Canyon Member. In the Moenave type section, near Tuba City, Arizona, all of the Moenave section is Dinosaur Canyon Member, as it is throughout the Moenave outcrop belt along the Echo Cliffs and Ward's Terrace of northern Arizona. However, north of the Grand Canyon in Arizona and in southwestern Utah, the upper part of the Moenave Formation is lacustrine strata. These strata are the Whitmore Point Member.

•Lucas et al. (2011: Palaeo3 302: 194-205) proposed, on the basis of multiple lines of biostratigraphic evidence, that the Triassic–Jurassic boundary is placed within the middle part of the Whitmore Point Member of the Moenave Formation where this member is present, and high in the Dinosaur Canyon Member elsewhere. The "Whitmore Point assemblage" of vertebrate taxa, earliest Jurassic (Hettangian) in age. The underlying "Dinosaur Canyon assemblage", is latest Triassic (Rhaetian) in age.

•Lucas et al. (2011) noted that the St George tracksite is of latest Triassic age, rather than earliest Jurassic as initially reported

• group of beds-level stratigraphic resolution

Environment/lithology: lacustrine; sandstone and mudstone

• extensive mudflat bordering W shoreline of (paleo) Lake Dixie
• sandstone with "a complex of irregular current ripples, regular oscillation ripples, ridges, swales, mudcracks, scour, load casts, rill marks, interference ripples..."

Size class: macrofossils

Preservation: cast, mold/impression, trace

Collected by S. Johnson, A. Milner in 2000-

Collection methods: surface (in situ),

• discovered by Sheldon Johnson

Primary reference: A. R. C. Milner, M. G. Lockley, and S. B. Johnson. 2006. The story of the St. George Dinosaur Discovery Site at Johnson Farm: an important new Lower Jurassic dinosaur tracksite from the Moenave Formation of southwestern Utah. In J. D. Harris, S. G. Lucas, J. A. Spielmann, M. G. Lockley, A. R. C. Milner, & J. I. Kirkland (eds.), The Triassic-Jurassic Terrestrial Transition. New Mexico Museum of Natural History and Science Bulletin 37:329-345 [M. Carrano/M. Carrano/M. Carrano]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 121305: authorized by Matthew Carrano, entered by Matthew Carrano on 02.12.2011

Creative Commons license: CC BY (attribution)

Taxonomic list

• plant impressions also present
Insecta
 Insecta -
Insecta indet.3 insect
trackways
 Dicondylia -
Coleoptera indet.3 Linnaeus 1758 beetle
trackways
Reptilia
 Theropoda - Grallatoridae
Eubrontes giganteus1 Hitchcock 1836 theropod
SGDS.18.T1
Eubrontes giganteus1 Hitchcock 1836 theropod
"Eubrontes and/or Gigandipus"
Grallator cursorius1 Hitchcock 1858 theropod
 Pseudosuchia - Batrachopodidae
Batrachopus deweyi1 Hitchcock 1843 aetosaur
SGDS.18.T5
 Ichnofossils -
Protovirgularia sp.3 M'Coy 1850
Scoyenia sp.3 White 1929
Kouphichnium sp.3 Nopcsa 1923
SGDS.258, 366, 452, 641