Diplodocus

Diplodocus was a lightly built and exceptionally long sauropod dinosaur; despite reaching lengths of 30+ meters (98+ feet), it was relatively low in mass, usually in the 10-15 tonne range. Diplodocus dwelt in the famous Late Jurassic Morrison Formation of western North America. It lived alongside plant-eaters like Stegosaurus, Brachiosaurus and Apatosaurus, while avoiding predation from theropods such as Allosaurus, Ceratosaurus and Torvosaurus.

Diplodocus hasn’t suffered as exciting a series of naming debates as Apatosaurus or Allosaurus, but has run into a situation where the type species, D. longus (known from a handful of tail vertebrae), is considered by some to be insufficiently diagnostic to be valid. Attempts to petition the International Commission on Zoological Nomenclature to switch the type species to the more completely documented D. carnegii were rejected, so we will have to watch where future naming issues go.

Another (and potentially related) issue involves the genus Seismosaurus. Originally described as a new type of diplodocid, often with fantastical size projections, more complete excavation and preparation of the specimen showed that it was in fact a species of Diplodocus. So Seismosaurus hallorum became Diplodocus hallorum, and it has been shown that many specimens originally described as D. longus group with it…

…which raises an interesting question. Rather than change the type species of Diplodocus, perhaps someone will either find the original D. longus specimen to be diagnostic (in which case D. hallorum might get swallowed up entirely into it), or another author could suggest using the obviously similar D. hallorum as a neotype for D. longus. Only time will tell which of these outcomes, if either, comes to fruition.