Genus: Haplocanthosaurus HATCHER, 1903
Etymology: Greek, haplos, "single or simple," Greek, akantha, "spine" and Greek, sauros, "lizard": “simple-spined lizard”.
= Haplacanthasaurus HOLLAND, 1924 (sic)
= Haplacanthosaurus HUENE, 1909 (sic)
= Haplocanthus HATCHER, 1903/AGASSIZ, 1845
Etymology: Greek, haplos, "single or simple," Greek, akantha, "spine," + us: “Simple-spinded lizard”.

Species: priscus (HATCHER, 1903) HATCHER, 1903
Etymology: Latin, priscus, "ancient, of venerable age."
= Haplocanthus priscus HATCHER, 1903
= Haplocanthosaurus piscus YADAGIRI 1988 (sic)

Holotype: CM 572

Locality: Marsh-Felch’s YPM Quarry 1, Garden Park, Sec. 28, T17S, R70W, Canyon City, Fremont County, Colorado.

Horizon: Salt Wash Member, Morrison Formation.

Biostratigraphy: Zone 2.

Age: Comobluffian age, Kimmeridgian Stage, Uppermost Malm Epoch, Late Jurassic.

Material: 2 cervicals, 10 dorsals, 5 sacrals, caudals 1-19, many ribs, chevrons, ilia, pubs, ischia and left femur.

Referred material:

BOISVERT, BIVENS, CURTEICE, WILHITE & WEDEL, 2025

USNM V 4275: Left femur, right femur, both ischia, left tibia, left fibula and left astragalis.

Note: MARSH 1896, originally called it Diplodocus longus, and GILMORE, 1907 referred it to "Morosaurus"

 

Locality: Oil Creek Quarry, Fremont County, Colorado.

Horizon: Salt Wash Member, Morrison Formation.

Biostratigraphy: Zone 2.

Age: Comobluffian age, Kimmeridgian Stage, Uppermost Malm Epoch, Late Jurassic.

Material:

CMNH 10725: 2 dorsal vertebrae, a right tibia and some unidentified fragmetns.

 

= Haplocanthosaurus sp FOSTER & WEDEL, 2014

Locality: Gordon-Bramson-Brothers Quarry, in a cut through a hogback made by Snowmass Creek, Pitkin County, Colorado.

Horizon: Lower Morrison Formation.

Bistratigraphy

Age: Comobluffian age, Kimmeridgian Stage, Uppermost Malm Epoch, Late Jurassic.

Material:

MWC 8028: 4 dorsal central, 5 partial ribs, the sacrum, 5 caudal vertebrae, 3 chevrons, 4 partial neural spines and many fragments.

 

Locality: William's Slow Eagle Quarry, Less than 7 km (4 miles) from Carnegie Quarry at Dinosaur National Mounument, Jensen, Uintah County, Utah.

Horizon: Salt Wash Member, Morrison Formation.

Biostratigraphy: Zone 2.

Age: Comobluffian age, Kimmeridgian Stage, Uppermost Malm Epoch, Late Jurassic.

Material:

FHPR 1106: 60% of the skeleton (BILBEY & HALL, 2000).


= Haplocanthosaurus utterbacki HATCHER, 1903
Etymology: Mr. W. H. Utterback who unearthed the specimen.
= Haplocanthus utterbacki OLSHEVSKY, 1978 (sic)

Holotype: CM 879

Locality: Marsh-Felch’s YPM Quarry 1, Garden Park, Sec. 28, T17S, R70W, Canyon City, Fremont County, Colorado.

Horizon: Salt Wash Member, Morrison Formation.

Biostratigraphy: Zone 2.

Age: Comobluffian age, Kimmeridgian Stage, Uppermost Malm Epoch, Late Jurassic.

Material: 10 cervicals, 13 dorsals, 5 sacrals, caudals 1-7, left scapula, right coracoid.

Referred material:

Locality: Quarry D, also referred to as Quarry 3 of 1899, Sheep Creek, Albany County, Wyoming.

Horizon: Upper or Brushy Basin Member, Morrison Formation.

Biostratigraphy: Zone 3.

Age: Comobluffian age, Kimmeridgian Stage, Uppermost Malm Epoch, Late Jurassic.

Material:

CM 33995: Left scapula-coracoid.

Note: The well-preserved bones are marked 94, the catalogue number of the paratype of Diplodcus carnegii.

CM 2043: Right tibia, fibula, and astragalus.

CM 2046: Left tibia and fibula.

 

 

Locality: Red Fork of Powder River (RFPR) Quarry B, about 20 km west of the town of Kaycee, eastern side of Bighorn Mountains, Powder River Basin, Johnson County, Wyoming.

Horizon: Member? Morrison Formation.

Biostratigraphy:

Age: Comobluffian age, Tithonian Stage, Uppermost Malm Epoch, Late Jurassic.

Material:

CM 36034: A median caudal.

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Species: delfsi McINTOSH & WILLIAMS, 1988
Etymology: In honor of Edward Delfs.

Holotype: CMNH 10380

Locality: CMNH Quarry, Delf’s Quarry, East bank of Four Mile Creek NW 1/4, NW, 1/4, Sec. 34, T17S, R70W, Fremont County, Colorado.

Horizon: Salt Wash Member, Morrison Formation.

Biostratigraphy: Zone 2.

Age: Comobluffian age, Kimmeridgian Stage, Uppermost Malm Epoch, Late Jurassic.

Material: Cervicals 1-4, 9 posterior dorsals with ribs of the left side, 5 sacrals, caudals 1-14, several chevrons, shaft and distal end of left scapula, fragmentary coracoid?, right sternal plate, proximal end of left radius, proximal end of left ulna, both ilia, left pubis, left ischium, left femur.