diplodocoidea

  Diplodocoidea is composed of three families: Rebbachisauridae, Dicraeosauridae, and Diplodocidae. Rebbachisaurids are not yet particularly well known, at the moment being an EK-LK boundary South America-Africa group (possibly into the later LK, depending on what you make of the "Antarctosaurus" jaw) with interesting feeding characteristics. For a long while, I was hesitant to include them with the other diplodocoids.
    The other two groups of diplodocoids can be classified together (with basal Suuwassea) in a group called Flagellicaudata, which means reasonably enough "whip-tail". Major defining characters of flagellicaudatans include bifid neural spines, most chevrons skid-like, whip-lash tail formed by rod-like caudal verts that essentially lack neural arches, peg-like teeth, and the loss of the small calcaneum (although this has recently been debated) from the ankle. Apatosaurus takes this reduction even further, and has only wrist bone per arm plus the single ankle bone. Some of the unusual characters of diplodocoids may be related to retention of embryonic and juvenile characteristic as adults.
    The dicraeosaurids are a peculiar offshoot of diplodocoids that are best known for their extremely tall neural spines, split down the middle in a "forking" pattern. They are tall enough to have supported dramatic sails in life. The necks of dicraeosaurids are also short compared to most sauropods.
    Diplodocidae provides the stereotype for what most people think of dinosaurs in general and sauropods in particular: long neck, small head, long tail, hips much higher than the shoulders, and a plump-looking body. So far, all known diplodocids repeat this general body plan, with minor changes; for example, Apatosaurus is much more robust than average and Barosaurus has a neck much longer than the average diplodocid's. Diplodocids probably include among their members the longest land animals to ever live, but not the heaviest, due to their lean nature. Most of the length would have come from the neck and tail, which at the end forms a whip-lash; swinging it could have theoretically produced a sonic boom.
    Diplodocids appear to have normally held their necks from out from their bodies at a downward angle, more graceful in some than in others. The head was usually between several inches and several feet from the ground. A row of nonbony spines, like those of an iguana, ran down the midline of at least some diplodocoids' backs. Diplodocids are most common from the Morrison Formation of western North America.

Rebbachisauridae: The rebbachisaurids are a curious group of sauropods that in many ways resemble diplodocoids, and are usually classified with them, but lack both split neural spines and forked chevrons. However, it is known by now that I put too much emphasis on these traits in the past. They were tall-spined, like the dicraeosaurids, but not "exactly" like them. They seem to have been not uncommon in their time and place.

Taxon or Taxa:	Time\Place:	Comments:
Limaysaurus tessonei Salgado, Garrido, S.E. Cocca, and J.R. Cocca, 2004	Cenomanian-early Turonian (LK) of Argentina	Limaysaurus had been kicking around the ranks of nomen nudum dinosaurs for a while, but has now been promoted to respectability. It is known from several individuals, including a specimen about 80% complete that serves as the type.
Nigersaurus taqueti Sereno, Beck, Dutheil, Larsson, Lyon, Moussa, Sadleir, Sidor, Varricchio, G. P. Wilson, and J. A. Wilson, 1999	?late Aptian-Albian (EK) of Niger	This sauropod has small, enameled teeth, arranged in a sort of dental battery, allowing it to have processed food more thoroughly than other sauropods. It has square jaw tips on a skull tilted perpendicular to the ground (perpetual "hang-dog" appearance) and featuring interesting remodeling from typical sauropod skulls; for example, those holes and bones you expect to see posterior to the eye aren't there, the bones having shifted down. Actually, it looks a bit like someone took a diplodocoid skull, held the eye sockets in place, then yanked the muzzle under the eyes and slid the post-eye bones down along this new "ventral margin", finishing up by comically stretching and boxing the snout and toothline. Remains from several individuals of this small sauropod are known; the type includes a partial skull, cervicals, scapula, and fore\hindlimbs.
Rebbachisaurus garasbae Lavocat, 1954	Albian (EK) of Morocco	Long mixed up with brachiosaurids and camarasaurids, this taxon is poorly understood. It has very tall neural spines.

Dicraeosauridae: Dicraeosaurids seem to have been a Gondwanan phenomenon, a group of small, short-necked sauropods with very tall neural spines on the presacrals. They're a bit like taking a diplodocid and messing with it in Photoshop to make it taller and shorter (fore and aft).

Diplodocidae i.s.: The old "Isle of Wight" diplodocid, based on a forked chevron, is probably not a diplodocid, as forked chevrons are now known to have a wider distribution than thought when the chevron was first found.

Apatosaurinae: An Apatosaurus-like caudal is known from the Oxfordian (LJ) of European Georgia.

Taxon or Taxa:		Time\Place:	Comments:
Amphicoelias: (?N.D.) Cope, 1877	A. altus (?N.D.) (type) Cope, 1877	Tithonian (LJ) of Colorado and ?Montana	Based on poor remains, this animal is likely the same as another diplodocoid. However, there has been found in Montana a partial skeleton that may belong here, which would make this a unique basal diplodocid.
Amphicoelias: (?N.D.) Cope, 1877	A. fragillimus (N.D.) Cope, 1878	Tithonian (LJ) of Colorado	A. fragillimus was based on an enormous dorsal neural arch that suggests a truly gigantic animal (scaled to Diplodocus, it may have been 58 m [190 ft] long, and may have massed upwards of 100 metric tons). Unfortunately, it has been lost, probably destroyed (the species name isn't fragillimus for nothing; it may have simply disintigrated).
?"Cetiosaurus" glymptonensis (?N.D.) Phillips, 1871		late Bathonian (MJ) of England	Sometimes referred to Cetiosauriscus, there is little evidence to support this. At any rate, it may be a basal diplodocoid. It is based on caudal centra.
Dinheirosaurus lourinhanensis Bonaparte and Mateus, 1999		Kimmeridgian (LJ) of Portugal	This sauropod is part of a newly-discovered LJ Portuguese dinosaur fauna that has just recently been described in depth. It is based mostly on vertebrae, including 2 cervicals and 9 dorsals, along with 7 partial centra. It may be a derived diplodocid.
?Zapalasaurus bonapartei Salgado, Carvalho, and Gorrido, 2006		Barremian-early Aptian (EK) of Argentina	This sauropod is interpreted as a basal diplodocoid without a particular affiliation, which is interesting given the EK age. It is known from cervical and caudal verts (apparently at least 20 of the latter). EK Argentina was a good place for diplodocoids, apparently, as there were also rebbachisaurids and dicraeosaurids.

Taxon or Taxa:	Time\Place:	Comments:
Cathartesaura anaerobica Gallina and Apesteguía, 2005	late Cenomanian (LK) of Argentina	This rebbachisaurid is based on a few verts, a scapula, an ilium, and femur, as part of an associated but incomplete skeleton that took seven years to prepare and assess.
?Nopcsaspondylus alarconensis Apesteguia, 2007	Coniacian (LK) of Argentina	Nopcsaspondylus is a bit of an oddity, in that it's based on a figure, from a 1902 publication, of a now-lost dorsal vertebra. It's the most recent named diplodocoid.
Rayososaurus agrioensis Bonaparte, 1995	Aptian (EK) of Argentina	Rayososaurus is a rebbachisaurid, but not the same as Limaysaurus as had been suggested. It may be somewhat basal to other rebbachisaurids.

Taxon or Taxa:		Time\Place:	Comments:
Amargasaurus cazaui Salgado and Bonaparte, 1991		Barremian (EK) of Argentina	This sauropod is unique in the extreme tallness of its neural spines. The forked spines could have supported one fat sail or two thin ones. This animal is known from most of the skeleton in front of the tail. It appears that the neck arcs downward, presenting a formidably tall profile and leaving the skull near the ground.
Brachytrachelopan mesai Rauhut, Remes, Fechner, Cladera, and Puerta, 2005		Tithonian (LJ) of Argentina	A new dicraeosaurid based on most of a presacral vertebral column, ribs, an ilium, and the articular ends of the bones at the knee joint, Brachytrachelopan earned its unique name through its short neck. Even among dicraeosaurids, it's got a short neck. The spines of the first few dorsal verts also lean forward. It's apparently closest to Dicraeosaurus.
Dicraeosaurus: Janensch, 1914	D. hansemanni (type) Janensch, 1914	Kimmeridgian (LJ) of Tanzania	Dicraeosaurus is a trademark animal of the Tendaguru beds in Tanzania, like Giraffatitan and Kentrosaurus. It is on the small side for sauropods, and very stout, with a long muzzle.
Dicraeosaurus: Janensch, 1914	D. sattleri (Janensch, 1914 [originally Dicraeosaurus])	Kimmeridgian (LJ) of Tanzania	This sauropod is caught between Amargasaurus proper and Dicraeosaurus proper, and could be classified with either (or given its own genus). It is slightly younger and more derived than D. hansemanni, and so may be a descendant.

Taxon or Taxa:		Time\Place:	Comments:
"Diplodocus":	"D." lacustris (N.D.) Marsh, 1884	late Kimmeridgian (LJ) of Colorado	The eroded jaws and teeth that form the type of this taxon are too poorly preserved to prove this even belongs in Diplodocus and not, say, Apatosaurus.
"Diplodocus":	"D." hayi Holland, 1924	Kimmeridgian (LJ) of Wyoming	"D." hayi is based on a partial skull and skeleton from a young individual. Some of the skull features are more like Apatosaurus, while the cervicals are more like Diplodocus, so it could represent its own genus.
?Dyslocosaurus polyonychius McIntosh, Coombs, and Russell, 1992		?Kimmeridgian (?LJ) of Wyoming	This animal was named from a diplodocid hindlimb with at least four clawed toes, unusual because diplodocids usually have only three. It was found from a locality that was either Kimmeridgian (LJ) or late Maastrichtian (LK) in age. Due to the primitive nature of the foot, and the fact that no diplodocids have been found anywhere else in the LK of North America, the older age is favored here. At times, people have suggested that it was related to the dicraeosaurids.

Taxon or Taxa:		Time\Place:	Comments:
Apatosaurus: Marsh, 1877	A. ajax (type) Marsh, 1877	late Kimmeridgian (LJ) of Colorado	Apatosaurus, one of the most robust sauropods, is much more familiar to the public as Brontosaurus. Brontosaurus, however, was based on remains that turned out to belong to an older Apatosaurus individual, and may belong to the type species as well (although Brontosaurus partisans have claimed that a new skull shows otherwise). Earlier in this century, Apatosaurus was thought of as having a Camarasaurus-like head, despite the fact this particular head had no connection to the body. A Diplodocus-like head, found associated with an Apatosaurus skeleton, had been known since the 19th century, but not considered to be the real head, due to a variety of mix-ups. Eventually, though, the proper head was given its due. Camarasaurus, incidentally, has long been mixed up with diplodocids; early casts of Diplodocus and Apatosaurus often used Camarasaurus (Grandpa Simpson: "...which we called Morosaurus...") parts to fill in the gaps. Apatosaurus excelsus appears to be different from A. ajax by virtue of its significantly smaller adult size (which isn't much to go on), while A. louisae is differentiated by its much more robust skeleton. Differences in the cranial process of the cervical ribs do not appear to be of as much significance as they once did.
	A. excelsus (Marsh, 1879 [originally Brontosaurus])	Kimmeridgian (LJ) of Wyoming, Utah, and Oklahoma
	A. louisae Holland, 1915	Kimmeridgian (LJ) of Utah
	A. parvus (Peterson and Gilmore, 1902 [originally Elosaurus])	Kimmeridgian (LJ) of Wyoming
Supersaurus vivianae Jensen, 1985 (including Dystylosaurus edwini and Ultrasauros macintoshi Jensen, 1985)		Kimmeridgian (LJ) of Colorado and Wyoming	At first thought to be a brachiosaurid-like animal, this is instead a very large diplodocid. Remains of it and Brachiosaurus were once given the name Ultrasauros. The holotype (the remains on which the species was based) was a dorsal that actually belonged to the holotype individual of Supersaurus, while the referred scapula actually belonged to an old, large Brachiosaurus. In addition, Dystylosaurus edwini Jensen 1985, based on a dorsal, which may have been bifurcated, and originally thought of as a large brachiosaurid, is probably part of the holotype individual of Supersaurus. All of these remains leave Supersaurus with a partial skeleton instead of a few large bits and pieces. It was thought to be closest to Barosaurus, possibly even an old individual, differing mostly in the extent of presacral neural spine bifurcation (it is reduced in comparison to the latter), but new remains from Wyoming show it was instead closer to Apatosaurus.

Navigation
Home Page	Alphabetical Dinosaur Index	Clado-Index
Background Information	Glossary	Faunae