Diplodocidae

Diplodocids, or members of the family Diplodocidae ("double beams"), are a group of sauropod dinosaurs. The family includes some of the longest creatures ever to walk the Earth, including Diplodocus and Supersaurus, some of which may have reached lengths of up to 34 metres (112 ft).[2][3]

Diplodocidae
Temporal range: Middle Jurassic-Early Cretaceous, 170–136.4 Ma
Louisae
Mounted A. louisae (specimen CM 3018), Carnegie Museum of Natural History
CM Diplodocus
Mounted D. carnegii type specimen, Carnegie Museum of Natural History
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Clade: Sauropoda
Clade: Flagellicaudata
Family: Diplodocidae
Marsh, 1884
Type species
Diplodocus longus
Marsh, 1878
Subgroups[1]
Synonyms
  • Atlantosauridae
    Marsh, 1877
  • Amphicoeliidae
    Cope, 1878
  • Apatosauridae
    Huene, 1927
  • Brontosauridae
    Jaekel, 1911

Description

DiplodocusDB
Diplodocus, depicted with spines limited to the mid-line of the back

While the diplodocids were massive sauropods, they were relatively slender when compared to the titanosaurs and brachiosaurids, although they were also extremely long. They had short legs, making them the "dachshund" of giant dinosaurs, and their rear legs were longer than front legs, giving their back a distinctive downward slope towards the neck.

Their necks were also extremely long. According to recent computer simulations, they may not have been able to lift their necks like other sauropods. However, these simulations do not take vertebral cartilage into account, which would likely allow a greater range of motion. Instead of reaching up into trees, they may have used their necks to graze over a broad area. They may also have used their necks to reach into dense stands of conifers, or over marshy ground.

Their heads, like those of other sauropods, were tiny with the nasal openings on the top of the head (though in life the nostrils themselves would have been close to the tip of the snout[4]).

The heads of diplodocids have been widely depicted with the nostrils on top due to the position of the nasal openings at the apex of the skull. There has been speculation over whether such a configuration meant that diplodocids may have had a trunk.[5] A 2006 study[6] surmised there was no paleoneuroanatomical evidence for a trunk. It noted that the facial nerve in an animal with a trunk, such as an elephant, is large as it innervates the trunk. The evidence suggests that the facial nerve is very small in diplodocids. Studies by Lawrence Witmer (2001) indicated that, while the nasal openings were high on the head, the actual, fleshy nostrils were situated much lower down on the snout.[7]

Diplodocids also had long, whip-like tails, which were thick at the base and tapered off to be very thin at the end. Computer simulations have shown that the diplodocids could have easily snapped their tails, like a bullwhip. This could generate a sonic boom in excess of 200 decibels, and may have been used in mating displays, or to drive off predators. There is some circumstantial evidence supporting this as well: a number of diplodocids have been found with fused or damaged tail vertebrae, which may be a symptom of cracking their tails.[8]

Diet and feeding

Their teeth were only present in the front of the mouth, and looked like pencils or pegs. They probably used their teeth to crop off food, without chewing, and relied on gastroliths (gizzard stones) to break down tough plant fibers (similar to modern birds). Diplodocines have highly unusual teeth compared to other sauropods. The crowns are long and slender, and elliptical in cross-section, while the apex forms a blunt, triangular point.[9] The most prominent wear facet is on the apex, though unlike all other wear patterns observed within sauropods, diplodocine wear patterns are on the labial (cheek) side of both the upper and lower teeth.[9] This implies that the feeding mechanism of Diplodocus and other diplodocids was radically different from that of other sauropods. Unilateral branch stripping is the most likely feeding behavior of Diplodocus,[10][11][12] as it explains the unusual wear patterns of the teeth (coming from tooth–food contact). In unilateral branch stripping, one tooth row would have been used to strip foliage from the stem, while the other would act as a guide and stabilizer. With the elongated preorbital (in front of the eyes) region of the skull, longer portions of stems could be stripped in a single action.[9] Also, the palinal (backwards) motion of the lower jaws could have contributed two significant roles to feeding behaviour: 1) an increased gape, and 2) allowed fine adjustments of the relative positions of the tooth rows, creating a smooth stripping action.[9]

Young et al. (2012) used biomechanical modelling to examine the performance of the diplodocine skull. It was concluded that the proposal that its dentition was used for bark-stripping was not supported by the data, which showed that under that scenario, the skull and teeth would undergo extreme stresses. The hypotheses of branch-stripping and/or precision biting were both shown to be biomechanically plausible feeding behaviors.[13] Diplodocine teeth were also continually replaced throughout their lives, usually in less than 35 days, as was discovered by Michael D'Emic et al. Within each tooth socket, as many as five replacement teeth were developing to replace the next one. Studies of the teeth also reveal that it preferred different vegetation from the other sauropods of the Morrison, such as Camarasaurus. This may have better allowed the various species of sauropods to exist without competition.[14]

Skin

Diplodocus sp. fossil dinosaur skin (Morrison Formation, Upper Jurassic; Mother's Day site, Carbon County, Montana, USA) 2
Skin impression of a diplodocid, specimen CMC VP 10659

Few skin impressions of diplodocids have been found. However, at least one significant find was reported by Stephen Czerkas in 1992. Fossils from the Howe Quarry in Shell, Wyoming preserved portions of the skin from around the tip of the tail, or "whiplash".[15] Czerkas noted that the skin preserved a sequence of conical spines, and that other, larger spines were found scattered around larger tail vertebrae. The spines appeared to be oriented in a single row along the mid-line of the tail, and Czerkas speculated that this midline row may have continued over the animal's entire back and neck.[16]

Growth

Long-bone histology enables researchers to estimate the age that a specific individual reached. A study by Griebeler et al. (2013) examined long bone histological data and concluded that the diplodocid MfN.R.2625 weighed 4,753 kilograms (5.2 short tons), reached sexual maturity at 23 years and died at age 24. The same growth model indicated that the diplodocid MfN.R.NW4 weighed 18,463 kilograms (20.4 short tons), and died at age 23, before reaching sexual maturity.[17]

Classification

Dinosaurs in Their Time- Jurassic Era Room (2705542612)
Holotype specimens of Diplodocus carnegii and Apatosaurus louisae at Carnegie Museum of Natural History

Diplodocidae was the third name given to what is now recognized as the single family of long-necked, whip-tailed sauropods. Edward Drinker Cope named the family Amphicoeliidae in 1878 for his genus Amphicoelias, sometimes considered a diplodocid.[18] However, the name Amphicoeliidae did not come into wider use and was not used in the scientific literature after 1899, making it a nomen oblitum ("forgotten name") according to the ICZN, preventing it from displacing the name Diplodocidae as a senior synonym.[19] More recent studies have also shown that Amphicoelias itself does not belong to this family, but is instead a more primitive diplodocoid.[20] A similar situation occurred for the family name Atlantosauridae, named by Othniel Charles Marsh in 1877, and which Hay argued had priority over Amphicoelidae.[21] George Olshevsky declared Atlantosauridae a nomen oblitum in 1991, though scientists such as Steel and Nowinski had treated Atlantosauridae as a valid name as late as 1971, and the former even added a subfamily, Atlantosaurinae.[19][22]

Some dinosaurs have been considered diplodocids in the past but have not been found to be members of that group in later, larger analyses of the family's relationships. Australodocus, for example, was initially described as a diplodocid, but may actually have been a Macronarian.[20][23] Amphicoelias was traditionally considered a diplodocid due to its similar anatomy, but phylogenetic studies showed it to be a more basal member of the Diplodocoidea.[20]

The relationships of species within Diplodocidae has also been subject to frequent revision. A study by Lovelace, Hartman and Wahl in 2008 found that Suuwassea and Supersaurus were relatives of Apatosaurus, within the subfamily Apatosaurinae. However, a subsequent analysis by Whitlock in 2011 showed that Supersaurus is slightly closer to Diplodocus than to Apatosaurus, and that Suuwassea is actually a primitive dicraeosaurid.[20]

Apatosaurus Clean
Cast skeleton of Brontosaurus parvus based on the University of Wyoming specimen produced by Triebold Paleontology Incorporated

The subfamily Diplodocinae, was erected to include Diplodocus and its closest relatives, including Barosaurus.[24][25] The Portuguese Dinheirosaurus and the African Tornieria have also been identified as close relatives of Diplodocus by some authors.[26][27]

Cladogram of the Diplodocidae after Tschopp, Mateus, and Benson (2015).[1]

Diplodocidae

Amphicoelias altus

Apatosaurinae

Unnamed species

Apatosaurus ajax

Apatosaurus louisae

Brontosaurus excelsus

Brontosaurus yahnahpin

Brontosaurus parvus

Diplodocinae

Unnamed species

Tornieria africana

Supersaurus lourinhanensis

Supersaurus vivianae

Leinkupal laticauda

Galeamopus hayi

Diplodocus carnegii

Diplodocus hallorum

Kaatedocus siberi

Barosaurus lentus

Distinguishing anatomical features

Diploheads
Diplodocid heads have historically been restored in various ways: a) skull, b) classic rendering of the head with nostrils on top, c) with speculative trunk, d) modern depiction with nostrils low on the snout and a possible resonating chamber

A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies - distinctive anatomical features that are unique to a given organism or group.

The clade Diplodocidae is distinguished based on the following characteristics:[28]

  • nares: the external nares face dorsally; and the internarial bar is absent
  • jugal: the jugal forms a substantial part of the caudoventral margin of the antorbital fenestra
  • quadratojugal processes: the angle between the rostral quadratojugal process and the dorsal quadratojugal process is approximately 130°
  • paroccipital process: the distal end of the paroccipital process is rounded and tongue-like in shape
  • parasphenoid: the parasphenoid rostrum is a laterally compressed, thin spike and is lacking the longitudinal dorsal groove
  • pterygoid: the ectopterygoid process of the pterygoid is located below the antorbital fenestra, and is reduced, such that it is not visible below the ventral margin of the skull when examined in lateral view; also the breadth of the main body of the pterygoid at least 33% of the length of the pterygoid
  • teeth: at least 5-6 replacement teeth occur per alveolus (as observed in Nigersaurus)
  • dorsal vertebrae: no more than 10 dorsal vertebrae are present
  • caudal vertebrae: 70-80 caudal vertebrae are present
  • pedal phalanges: pedal phalanx I-1 has a proximoventral margin drawn out into a thin plate or heel that underlies the distal end of metatarsal I; also pedal phalanx II-2 is reduced in craniocaudal length and has an irregular shape

References

  1. ^ a b Tschopp, E.; Mateus, O. V.; Benson, R. B. J. (2015). "A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)". PeerJ. 3: e857. doi:10.7717/peerj.857. PMC 4393826. PMID 25870766.
  2. ^ Lovelace, David M.; Hartman, Scott A.; Wahl, William R. (2007). "Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny". Arquivos do Museu Nacional. 65 (4): 527–544.
  3. ^ Tschopp, E.; Mateus, O.; Benson, R. B. J. (2015). "A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)". PeerJ. 3: e857. doi:10.7717/peerj.857. PMC 4393826. PMID 25870766.
  4. ^ Science, 03 Aug 2001: Vol. 293, Issue 5531, pp. 850-853, DOI: 10.1126/science.1062681, Nostril Position in Dinosaurs and Other Vertebrates and Its Significance for Nasal Function, Lawrence M. Witmer
  5. ^ Bakker, Robert T. (1986) The Dinosaur Heresies: New Theories Unlocking the Mystery of the Dinosaurs and their Extinction. New York: Morrow.
  6. ^ Knoll, F.; Galton, P.M.; López-Antoñanzas, R. (2006). "Paleoneurological evidence against a proboscis in the sauropod dinosaur Diplodocus". Geobios. 39 (2): 215–221. doi:10.1016/j.geobios.2004.11.005.
  7. ^ Lawrence M. Witmer; et al. (2001). "Nostril Position in Dinosaurs and other Vertebrates and its Significance for Nasal Function". Science. 293 (5531): 850–853. CiteSeerX 10.1.1.629.1744. doi:10.1126/science.1062681. PMID 11486085.
  8. ^ Myhrvold, Nathan P. (1997). "Supersonic sauropods? Tail dynamics in the diplodocids". Paleobiology. 23 (4): 393–409. doi:10.1017/S0094837300019801.
  9. ^ a b c d Upchurch, P.; Barrett, P.M. (2000). "The evolution of sauropod feeding mechanism". In Sues, Hans Dieter (ed.). Evolution of Herbivory in Terrestrial Vertebrates. Cambridge University Press. ISBN 978-0-521-59449-3.
  10. ^ Norman, D.B. (1985). The illustrated Encyclopedia of Dinosaurs. London: Salamander Books Ltd
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  12. ^ Barrett, P.M.; Upchurch, P. (1994). "Feeding mechanisms of Diplodocus". Gaia. 10: 195–204.
  13. ^ Young, Mark T.; Rayfield, Emily J.; Holliday, Casey M.; Witmer, Lawrence M.; Button, David J.; Upchurch, Paul; Barrett, Paul M. (August 2012). "Cranial biomechanics of Diplodocus (Dinosauria, Sauropoda): testing hypotheses of feeding behaviour in an extinct megaherbivore". Naturwissenschaften. 99 (8): 637–643. Bibcode:2012NW.....99..637Y. doi:10.1007/s00114-012-0944-y. ISSN 1432-1904. PMID 22790834.
  14. ^ D’Emic, M. D.; Whitlock, J. A.; Smith, K. M.; Fisher, D. C.; Wilson, J. A. (2013). Evans, A. R. (ed.). "Evolution of high tooth replacement rates in sauropod dinosaurs". PLOS One. 8 (7): e69235. Bibcode:2013PLoSO...869235D. doi:10.1371/journal.pone.0069235. PMC 3714237. PMID 23874921.
  15. ^ Czerkas, S.A. (1993). "The new look of sauropods". Journal of Vertebrate Paleontology. 13: 26A. doi:10.1080/02724634.1993.10011533.
  16. ^ Czerkas, S.A. (1993). "Discovery of dermal spines reveals a new look for sauropod dinosaurs". Geology. 20 (12): 1068–1070. doi:10.1130/0091-7613(1992)020<1068:dodsra>2.3.co;2.
  17. ^ Griebeler, EM; Klein, N; Sander, PM (2013). "Aging, Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions". PLoS ONE. 8 (6): e67012. doi:10.1371/journal.pone.0067012. PMC 3686781. PMID 23840575.
  18. ^ Carpenter, K. (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus." In Foster, J.R. and Lucas, S.G., eds., 2006, Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 36: 131-138.
  19. ^ a b Olshevsky, G. (1991). "A Revision of the Parainfraclass Archosauria Cope, 1869, Excluding the Advanced Crocodylia." Mesozoic Meanderings, 2.
  20. ^ a b c d Whitlock, J.A. (2011). "A phylogenetic analysis of Diplodocoidea (Saurischia: Sauropoda)." Zoological Journal of the Linnean Society, Article first published online: 12 Jan 2011. doi:10.1111/j.1096-3642.2010.00665.x
  21. ^ Hay, O.P. (1902). "Bibliography and Catalogue of the Fossil Vertebrata of North America". Bulletin of the United States Geological Survey. 179: 1–868.
  22. ^ Nowinski, A (1971). "Nemegtosaurus mongoliensis n. gen., n. sp. (Sauropoda) from the uppermost Cretaceous of Mongolia". Palaeontologia Polonica. 25: 57–81.
  23. ^ Remes, Kristian (2007). "A second Gondwanan diplodocid dinosaur from the Upper Jurassic Tendaguru Beds of Tanzania, East Africa". Palaeontology. 50 (3): 653–667. doi:10.1111/j.1475-4983.2007.00652.x.
  24. ^ Taylor, M.P.; Naish, D. (2005). "The phylogenetic taxonomy of Diplodocoidea (Dinosauria: Sauropoda)". PaleoBios. 25 (2): 1–7. ISSN 0031-0298.
  25. ^ Harris, J.D. (2006). "The significance of Suuwassea emiliae (Dinosauria: Sauropoda) for flagellicaudatan intrarelationships and evolution". Journal of Systematic Palaeontology. 4 (2): 185–198. doi:10.1017/S1477201906001805.
  26. ^ Bonaparte, J.F.; Mateus, O. (1999). "A new diplodocid, Dinheirosaurus lourinhanensis gen. et sp. nov., from the Late Jurassic beds of Portugal". Revista del Museo Argentino de Ciencias Naturales. 5 (2): 13–29. Archived from the original on 2012-02-19. Retrieved 2013-06-13.
  27. ^ Rauhut, O.W.M.; Remes, K.; Fechner, R.; Cladera, G. & Puerta, P. (2005). "Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia". Nature. 435 (7042): 670–672. doi:10.1038/nature03623. PMID 15931221.
  28. ^ Upchurch P, Barrett PM, Dodson P (2004). "Sauropoda". In Weishampel DB, Dodson P, Osmólska H. The Dinosauria (2nd Edition). University of California Press.

External links

Amphicoelias

Amphicoelias (, meaning "biconcave", from the Greek ἀμφί, amphi: "on both sides", and κοῖλος, koilos: "hollow, concave") is a genus of herbivorous sauropod dinosaur that lived approximately 150 million years ago during the Tithonian (Late Jurassic Period) of what is now Colorado, United States. A herbivore, Amphicoelias was moderately sized at about 25 m (82 ft) long–roughly the same length as Diplodocus, to which it was related. Its hindlimbs were very long and thin, and its forelimbs were proportionally longer than in relatives.

The namesake fossil of the type species Amphicoelias altus, American Museum of Natural History 5764, is uncertain in included material. When described by Edward Drinker Cope shortly after its discovery in 1877, Amphicoelias was noted to include many back vertebrae, a single pubis, and a femur. However, after purchase and cataloging of the material by the AMNH, Henry Fairfield Osborn and Charles Mook described that the specimen had only two vertebrae, a pubis, femur, tooth, scapula, coracoid, ulna and a second femur. The additional material, not mentioned by Cope, was found close in proximity to the holotype and was similar to Diplodocus, a relative of Amphicoelias. Their assignment was questioned by subsequent authors Emanuel Tschopp et al. in an analysis of Diplodocidae.

During the description of Amphicoelias altus in 1877, Cope additionally named A. latus, for a femur and tail vertebrae. Following its description, Osborn and Mook in 1921 reidentified the material as a specimen of Camarasaurus, an assignment followed by other authors who reviewed the material. A year later 1878, Cope named the third species of Amphicoelias, A. fragillimus for a gigantic dorsal vertebra that was subsequently lost. Measuring approximately 2.7 m (8.9 ft) if reconstructed based on Diplodocus, early estimates for the length of the animal in life were between 40 and 60 m (130 and 200 ft) long. Due to the incomplete nature, such lengths–the longest of any known dinosaur and sauropod–were largely ignored. In 2018, Kenneth Carpenter renamed Amphicoelias fragillimus as the new genus Maraapunisaurus, and reclassified it from Diplodocidae to Rebbachisauridae.

Apatosaurinae

Apatosaurinae is the name of a subfamily of diplodocid sauropods that existed between 157 and 150 million years ago in North America. The group includes two genera for certain, Apatosaurus and Brontosaurus, with at least five species. Atlantosaurus and Amphicoelias might also belong to this group.Below is a cladogram of apatosaurinae interrelationships based on Tschopp et al., 2015.

Barosaurus

Barosaurus ( BARR-o-SAWR-əs) was a giant, long-tailed, long-necked, plant-eating dinosaur closely related to the more familiar Diplodocus. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Utah and South Dakota (and possibly Africa, as exemplified by the Kadsi Formation). It is present in stratigraphic zones 2-5.The composite term Barosaurus comes from the Greek words barys (βαρυς) meaning "heavy" and sauros (σαυρος) meaning "lizard"; thus "heavy lizard".

Dicraeosauridae

Dicraeosauridae is a family of diplodocoid sauropods who are the sister group to Diplodocidae. Dicraesaurids are a part of the Flagellicaudata, along with Diplodocidae. Dicraeosauridae includes genera such as Amargasaurus, Suuwassea, Dicraeosaurus, and Brachytrachelopan. Specimens of this family have been found in North America, Africa, and South America. Their temporal range is from the Early or Middle Jurassic to the Early Cretaceous. Few dicraeosaurids survived into the Cretaceous, the youngest of which was Amargasaurus.The group was first described by German paleontologist Werner Janensch in 1914 with the discovery of Dicraeosaurus in Tanzania. Dicraeosauridae are distinct from other sauropods because of their relatively short neck size and small body size.The clade is monophyletic and well-supported phylogenetically with thirteen unambiguous synapomorphies uniting it. They diverged from Diplodocidae in the Mid-Jurassic, as evidenced by the diversity of dicraeosaurids in both South America and East Africa when Gondwana was still united by land. However, there is some disagreement among paleontologists on the phylogenetic placement of Suuwassea, the only genera of the Dicraeosauridae to be found in North America. It has been characterized as a basal dicraeosaurid by some and a member of the Diplodocidae by others. The placement of Suuwassea within Dicraeosauridae or Diplodocidae has substantial biogeographic implications for the evolution of Dicraeosauridae.

Dicraeosaurus

Dicraeosaurus (Gr. δικραιος, dikraios "bifurcated, double-headed" + Gr. σαυρος, sauros "lizard") is a genus of small diplodocoid sauropod dinosaur that lived in what is now Tanzania during the late Jurassic. It was named for the spines on the back of the neck. The first fossil was described by paleontologist Werner Janensch in 1914.

Dinheirosaurus

Dinheirosaurus is a genus of diplodocid sauropod dinosaur that is known from fossils uncovered in modern-day Portugal. It may represent a species of Supersaurus. The only species is Dinheirosaurus lourinhanensis, first described by José Bonaparte and Octávio Mateus in 1999 for vertebrae and some other material from the Lourinhã Formation. Although the precise age of the formation is not known, it can be dated around the early Tithonian of the Late Jurassic.

The known material includes two cervical vertebrae, nine dorsal vertebrae, a few ribs, a fragment of a pubis, and many gastroliths. Of the material, only the vertebrae are diagnostic, with the ribs and pubis being too fragmentary or general to distinguish Dinheirosaurus. This material was first described as in the genus Lourinhasaurus, but differences were noticed and in 1999 Bonaparte and Mateus redescribed the material under the new binomial Dinheirosaurus lourinhanensis. Another specimen, ML 418, thought to be Dinheirosaurus, is now known to be from another Portuguese diplodocid. This means that Dinheirosaurus lived alongside many theropods, sauropods, thyreophorans and ornithopods, as well as at least one other diplodocid.

Dinheirosaurus is a diplodocid, a relative of Apatosaurus, Diplodocus, Barosaurus, Supersaurus, and Tornieria. Among those, the closest relative to Dinheirosaurus is Supersaurus.

Diplodocimorpha

Diplodocimorpha is a clade of extinct sauropod dinosaurs, existing from the Early Jurassic until the Late Cretaceous. The group includes three main families and some other genera, Rebbachisauridae, Dicraeosauridae and Diplodocidae, the latter two forming Flagellicaudata. The name was first used by Calvo & Salgado (1995), who defined it as "Rebbachisaurus tessonei sp. nov., Diplodocidae, and all descendants of their common ancestor." The group was not used often, and was synonymized with Diplodocoidea as the groups were often found to have the same content. In 2005, Mike P. Taylor and Darren Naish reviewed diplodocoid phylogeny and taxonomy, and realized that Diplodocimorpha could not be synonymized with Diplodocoidea. Whereas the former was defined node-based, the latter was branch-based. In 2015, Emanuel Tschopp, Octavio Mateus and Roger Benson published a specimen-based phylogeny on diplodocid interrelationships, and supported the separation of Diplodocimorpha. Haplocanthosaurus was found to be more basal than rebbachisaurids, and therefore outside Diplodocimorpha, but closer to Diplodocus than Saltasaurus, and therefore within Diplodocoidea. The below cladogram follows the findings of Tschopp et al.

Diplodocinae

Diplodocinae is an extinct subfamily of diplodocid sauropods that existed from the Late Jurassic to Early Cretaceous of North America, Europe and South America, about 161.2 to 136.4 million years ago. Genera within the subfamily include Tornieria, Supersaurus, Leinkupal, Galeamopus, Diplodocus, Kaatedocus and Barosaurus.Cladogram of the Diplodocidae after Tschopp, Mateus, and Benson (2015).

Diplodocoidea

Diplodocoidea is a superfamily of sauropod dinosaurs, which included some of the longest animals of all time, including slender giants like Supersaurus, Diplodocus, Apatosaurus, and Amphicoelias. Most had very long necks and long, whip-like tails; however, one family (the dicraeosaurids) are the only known sauropods to have re-evolved a short neck, presumably an adaptation for feeding low to the ground. This adaptation was taken to the extreme in the highly specialized sauropod Brachytrachelopan. A study of snout shape and dental microwear in diplodocoids showed that the square snouts, large proportion of pits, and fine subparallel scratches in Apatosaurus, Diplodocus, Nigersaurus, and Rebbachisaurus suggest ground-height nonselective browsing; the narrow snouts of Dicraeosaurus, Suuwassea, and Tornieria and the coarse scratches and gouges on the teeth of Dicraeosaurus suggest mid-height selective browsing in those taxa. This taxon is also noteworthy because diplodocoid sauropods had the highest tooth replacement rates of any vertebrates, as exemplified by Nigersaurus, which had new teeth erupting every 30 days.

Dyslocosaurus

Dyslocosaurus (meaning "hard-to-place lizard") is the name given in 1992 to a genus of sauropod dinosaur from the Late Jurassic Period of Wyoming, North America.

The holotype or type specimen the genus is based on, AC 663, is part of the collection of the Amherst College Museum of Natural History. It was collected by professor Frederic Brewster Loomis. However, the only available information regarding its provenance is that given on the label: "Lance Creek", a county in east Wyoming. Loomis himself thought that it stemmed from the Lance Formation, dating from the Late Cretaceous Maastrichtian.

In 1963 the specimen was brought to the attention of John Stanton McIntosh, who in 1992, together with William Coombs and Dale Russell, decided to create a new genus and species for it. The type species is Dyslocosaurus polyonychius. The genus name is derived from Greek dys, "bad, "poor", and Latin locus, "place", a reference to the paucity of data regarding the type locality of the fossil. The specific name is derived from Greek polys, "many", and onyx, "claw". The describers interpreted the remains, consisting of some limb bones, as those of a diplodocid dinosaur. From this they concluded that it in fact dated from the Late Jurassic Period, like most diplodocids. The species would then be unique in having four, or perhaps five, claws on the foot, whereas other diplodocids have only three — hence the specific name. A species similar to Dyslocosaurus would have made the tracks of the ichnospecies Brontopodus birdi from the Early Cretaceous, that also features four claws.

In 1998 Paul Sereno and Jeffrey A. Wilson gave an alternative interpretation: the specimen would come from the Lance Formation after all but be a chimera: in this case a mix up of titanosaur limb bones and theropod phalanges.

In their taxonomic revision of Diplodocidae, Tschopp et alii in 2015 noted that a pedal phalanx included in AC 663 is apparently not from the same individual as the rest of AC 663 given differences in preservation and coloration among individual bones, raising doubts on whether Dyslocosaurus had more than three claws on the feet. Although fragmentary, Dyslocosaurus was recovered as a member of Dicraeosauridae, potentially making it the second record of a dicraeosaurid from North America (the other being Suuwassea).

Dystrophaeus

Dystrophaeus is the name given to an extinct genus of eusauropod dinosaur from the early Kimmeridgian stage of the Late Jurassic that existed around 154.8 Ma. Its fossils were found in the Tidwell Member of the Morrison Formation of Utah. Its estimated mass is 12 tonnes (13 short tons).The type species, D. viaemalae, was described by Edward Drinker Cope in 1877. The genus name means "coarse joint" from Greek dys, "bad", and stropheus, "joint", a reference to the pitted joint surfaces serving as an attachment for cartilage. The specific name reads as Latin viae malae, "of the bad road", a reference to the various arduous routes taken to find, reach and salvage the remains. It consists of one partial skeleton, the holotype USNM 2364, which includes a 76 centimetre long ulna, a scapula, a partial radius, and some metacarpals discovered in August 1859 by John Strong Newberry. It was found in what is possibly stratigraphic zone 1 of the Morrison, although an older Oxfordian-Callovian has also been suggested. Dystrophaeus represents one of the oldest discoveries of sauropods in America; earlier, in 1855, some teeth had been found of Astrodon.

The classification of Dystrophaeus has been rather confusing. Cope in 1877 merely concluded it was some Triassic dinosaur. Henri-Émile Sauvage in 1882 understood it was a sauropod, assigning it to the Atlantosauridae. Othniel Charles Marsh however, in 1895 stated it belonged to the Stegosauridae. Friedrich von Huene, the first to determine it was of Jurassic age, in 1904 created a special family for it, the Dystrophaeidae, which he assumed to be herbivorous theropods. Only in 1908 von Huene realised his mistake and classified it in the sauropod Cetiosauridae, refining this in 1927 to the Cardiodontinae. Alfred Romer in 1966 put it in the Brachiosauridae, in a subfamily Cetiosaurinae.

More recently, an analysis by David Gillette concluded it was a member of the Diplodocidae. Another recent review, by Tschopp and colleagues in 2015, suggest it is a member of the Dicraeosauridae. However, many researchers consider the taxon to be a nomen dubium.

Flagellicaudata

Flagellicaudata is a clade of Dinosauria. It belongs to Sauropoda and includes two families, the Dicraeosauridae and the Diplodocidae.

Galeamopus

Galeamopus is a genus of herbivorous diplodocid sauropod dinosaurs. It contains two known species: Galeamopus hayi, known from the Late Jurassic lower Morrison Formation (Kimmeridgian age, about 155 million years ago) of Wyoming, United States, and Galeamopus pabsti, known from the Late Jurassic fossils from Wyoming and Colorado. The type species is known from one of the most well preserved diplodocid fossils, a nearly complete skeleton with associated skull.

Kaatedocus

Kaatedocus is a genus of diplodocine flagellicaudatan sauropod known from the middle Late Jurassic (Kimmeridgian stage) of northern Wyoming, United States. It is known from well-preserved skull and cervical vertebrae which were collected in the lower part of the Morrison Formation. The type and only species is Kaatedocus siberi, described in 2012 by Emanuel Tschopp and Octávio Mateus.

Leinkupal

Leinkupal is a genus of diplodocine sauropod known from the Early Cretaceous (Late Berriasian to Early Valanginian stage) of the Bajada Colorada Formation, southeastern Neuquén Basin in the Neuquén Province of Argentina. It contains a single species, Leinkupal laticauda.

Rebbachisauridae

Rebbachisauridae is a family of sauropod dinosaurs known from fragmentary fossil remains from the Cretaceous of South America, Africa, North America, and Europe.

Supersaurus

Supersaurus (meaning "super lizard") is a genus of diplodocid sauropod dinosaur that lived in North America during the Late Jurassic period. The type species, S. vivianae, was first discovered by Vivian Jones of Delta, Colorado, in the middle Morrison Formation of Colorado in 1972. The fossil remains came from the Brushy Basin Member of the formation, dating to about 153 million years ago. A potential second species, S. lourinhanensis, is known from Portugal and has been dated to a similar time.

Suuwassea

Suuwassea (meaning "ancient thunder") is a genus of dicraeosaurid sauropod dinosaur found in the Upper Jurassic strata of the Morrison Formation, located in southern Carbon County, Montana, United States. The fossil remains were recovered in a series of expeditions during a period spanning the years 1999 and 2000, described by J.D. Harris and Peter Dodson in 2004. They consist of a disarticulated but associated partial skeleton, including partial vertebral series and limb bones.

Tornieria

Tornieria ("for Tornier") is a genus of diplodocid sauropod dinosaur from Late Jurassic of Tanzania. It has a convoluted taxonomic history.

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