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Anchisaurus

Marsh, 1885 ANG-ki-SAWR-us

From Greek 'anchi' meaning 'near' or 'close to' and 'sauros' meaning 'lizard', referring to its placement near the base of the sauropodomorph family tree.

192.9–174.7 million years ago Pliensbachian–Toarcian, Early Jurassic
Early Jurassic stages

Anchisaurus is a genus of basal sauropodomorph dinosaur. It lived during the Early Jurassic Period, and its fossils have been found in the red sandstone of the Upper Portland Formation, Northeastern United States, which was deposited from the Hettangian age into the Sinemurian age, between about 200 and 192 million years ago. Until recently it was classed as a member of Prosauropoda. The genus name Anchisaurus comes from the Greek αγχι (agkhi) anchi-; "near, close" + Greek σαυρος (sauros); "lizard". Anchisaurus was coined as a replacement name for "Amphisaurus", which was itself a replacement name for Hitchcock's "Megadactylus", both of which had already been used for other animals.

Diagnosis

  1. Robust pollex (first digit) of foot with prominent development
  2. Five-toed foot (first, third, and fourth phalanges of fourth toe present)
  3. Large terminal phalanx on first digit, approximately 4 times larger than claw from other digit
  4. Thin and compact bone walls in limb bones with large internal cavities

Species

Anchisaurus polyzelus Marsh, 1885

Type species

Means 'much sought for' in Greek, referring to the fact that the ichnologist Edward Hitchcock had for many years vainly sought to discover the identity of the track-maker.

Neotype
YPM 1883 , Yale Peabody Museum of Natural History
Material
Right foot bones with phalanges, notably robust first toe (pollex). Terminal phalanx from fourth toe. Additional claw fragment.
Horizon
upper Portland Formation, Pliensbachian–Toarcian, Early Jurassic , 192.9–174.7 million years ago
Locality
Manchester, Connecticut, United States Olsen and Galton (1984) give the formation's anchisaurid prosauropods as "associated with palynoflorules ranging in age from Pliensbachian to Toarcian".

Synonyms

  • Ammosaurus junior subjective

    Originally described as A. major and later treated as Anchisaurus major; ultimately recognized as referable to An. polyzelus, with supposed differences attributed to growth and misinterpretation.

  • Yaleosaurus junior objective

    Originally described as Y. colurus (later Anchisaurus colurus) on YPM 1883. Opinion 2361 designated that same specimen the neotype of Megadactylus polyzelus, so the two names share a name-bearing type.

Synonyms of the genus

Name Type Reason
Amphisaurus preoccupied Name preoccupied by Amphisaurus (Reptilia).
Megadactylus preoccupied Name preoccupied by Megadactylus (Coleoptera).

Notable specimens

  • YPM 208

    Yale Peabody Museum of Natural History Found 1884 by Charles H. Owen historic

    Nearly complete Manchester skeleton named Anchisaurus major by Marsh in 1889 and later the basis of the genus Ammosaurus. Its front block had been built into a bridge abutment; John Ostrom salvaged it when the bridge was demolished in 1969.

    Marsh (1889)

ICZN cases

  • Type specimen Ruled

    Opinion 2361 set aside all previous type fixations for Megadactylus polyzelus under the plenary power and designated YPM 1883, the almost complete skull and skeleton that is the holotype of Anchisaurus colurus Marsh, 1891, as the neotype, the original holotype being fragmentary and non-diagnostic. Anchisaurus was placed on the Official List of Generic Names and polyzelus on the Official List of Specific Names.

    Application: Galton (2012) Opinion: International Commission on Zoological Nomenclature (2015)

References

  1. Olsen, P. E.; Galton, P. M. (1984). A review of the reptile and amphibian assemblages from the Stormberg of southern Africa, with special emphasis on the footprints and the age of the Stormberg. Palaeontologia Africana 25: 87-110.

    Dates the Portland's anchisaurid-bearing beds Pliensbachian to Toarcian by their palynoflorules.

    olsen1984a
  2. Hitchcock, E. (1865). Appendix [A]. Bones of Megadactylus polyzelus. Supplement to the Ichnology of New England. A Report to the Government of Massachusetts in 1863 39-40. Wright and Potter, Boston. hitchcock1865a
  3. Marsh, O. C. (1885). Names of extinct reptiles. American Journal of Science 29: 169. marsh1885a
  4. Yates, A. M. (2004). Anchisaurus polyzelus (Hitchcock): the smallest known sauropod dinosaur and the evolution of gigantism among sauropodomorph dinosaurs. Postilla 230: 1-57.

    Source of the Portland Formation assignment for the neotype.

    yates2004a
  5. Marsh, O. C. (1889). Notice of new American Dinosauria. American Journal of Science 37(220): 331-336. doi:10.2475/ajs.s3-37.220.331 marsh1889b
  6. Galton, P. M. (2012). Case 3561. Anchisaurus Marsh, 1885 (Dinosauria, Sauropodomorpha): proposed conservation of usage by designation of a neotype for its type species Megadactylus polyzelus Hitchcock, 1865. Bulletin of Zoological Nomenclature 69(1): 44-50. International Trust for Zoological Nomenclature. doi:10.21805/bzn.v69i1.a14

    Petitioned the Commission to set aside the fragmentary holotype of Megadactylus polyzelus and designate YPM 1883 as neotype.

    galton2012a
  7. International Commission on Zoological Nomenclature (2015). Opinion 2361 (Case 3561). Anchisaurus Marsh, 1885 (Dinosauria, Sauropodomorpha): usage conserved by designation of a neotype for its type species Megadactylus polyzelus Hitchcock, 1865. Bulletin of Zoological Nomenclature 72(2): 176-177. International Trust for Zoological Nomenclature. doi:10.21805/bzn.v72i2.a2

    Opinion 2361, which granted the petition and fixed YPM 1883 as the neotype.

    iczn2015a
  8. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Source of the hip height estimate.

    jones2026b