Valid species [1][2]Hatcher's original restoration of a D. carnegii skeleton from 1901

[3][4]D. hallorum (formerly known as Seismosaurus)*D. longus, the type species, is known from two skulls and a caudal series from the Morrison Formation of Colorado and Utah.[6]

  • D. carnegii (also spelled D. carnegiei), named after Andrew Carnegie, is the best known, mainly due to a near-complete skeleton collected by Jacob Wortman, of the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania and described and named by John Bell Hatcher in 1901.
  • D. hayi, known from a partial skeleton discovered by William H. Utterback in 1902 near Sheridan, Wyoming, was described in 1924.[21]
  • D. hallorum, first described in 1991 by Gillette as Seismosaurus halli from a partial skeleton comprising vertebrae, pelvis and ribs. George Olshevsky later attempted to emend the name as S. hallorum, citing incorrect grammar on the part of the original authors, a recommendation that has been followed by others, including Carpenter (2006).[22] In 2004, a presentation at the annual conference of the Geological Society of America made a case for Seismosaurus being a junior synonym of Diplodocus.[23] This was followed by a much more detailed publication in 2006, which not only renamed the species Diplodocus hallorum, but also speculated that it could prove to be the same as D. longus.[24] The position that D. hallorum should be regarded as a specimen of D. longus was also taken by the authors of a redescription of Supersaurus, refuting a previous hypothesis that Seismosaurus and Supersaurus were the same.[25]

[edit] Nomina dubia (doubtful species)Edit

  • D. lacustris is a nomen dubium, named by Marsh in 1884, from remains of a smaller animal from Morrison, Colorado.[26] These remains are now believed to have been from an immature animal, rather than from a separate species.[27]
Seismosaurus BW