Neosauropoda

Mounted skeleton of Diplodocus carnegii at Carnegie Museum of Natural History, photographed by Scott Robert Anselmo.

Belongs within: Eusauropoda.
Contains: Camarasauromorpha.

The Neosauropoda is defined as the most exclusive clade containing Diplodocus and Saltasaurus. This clade includes many of the most familiar sauropod genera. Its members are divided between two stem-defined clades: Diplodocoidea includes all taxa closer to Diplodocus than Saltasaurus, whereas Macronaria has the inverse definition (Upchurch et al. 2004). The name of the latter clade refers to one of the characteristic features of many of its members, the marked enlargement of the nares in the skull.

The diversity of neosauropods, or, Pity poor Camarasaurus
Published 23 June 2014
Articulated skeleton of juvenile Camarasaurus lentus in the Carnegie Museum of Natural History, photographed by Daderot.

Let me just get the obvious out of the way first: sauropods were huge. Mind-bendingly huge. In some cases, big enough to reduce a human to a sticky puddle under foot and not even break their stride. For close to 150 million years, they were the largest land animals anywhere in the world, and no other terrestrial animal at any time has come even close to rivalling their largest representatives in size. Being around for so long, it should also be no surprise that they were diverse: a large number of sauropod genera have been named, representing a wide variety of forms. Nevertheless, most people’s idea of sauropods is encompassed within just four genera from the late Jurassic of North America: Diplodocus, Apatosaurus, Brachiosaurus and Camarasaurus.

These four genera all belong to the clade Neosauropoda, which has been defined as the smallest clade containing the genera Diplodocus and Saltasaurus (a late Cretaceous South American genus). Upchurch et al. (2004) diagnosed the neosauropods by a number of cranial features, together with a reduction in the fourth hind toe (part of a general trend towards toe reduction in sauropods as their feet became more columnar). However, Upchurch et al. were writing before the recognition of the Turiasauria, a European clade that is probably the sister group of neosauropods (Royo-Torres et al. 2006), and I don’t know how that clade would affect the synapomorphy distribution*. The neosauropods quickly became the dominant sauropod group after their appearance in the middle Jurassic, and the only non-neosauropod sauropods to make it into the early Cretaceous were the aforementioned turiasaurs and possibly Jobaria, an African genus that varying analyses place either just inside or just outside the Neosauropoda.

*There has been an annoying tendency in recent years for many papers featuring phylogenetic analyses to present us with the character data matrix and the final trees from the analysis, but not do anything to map character changes onto the tree. The only way to find that out would be by transcribing the entire matrix and re-running the analysis yourself.

Mounted skeleton of Amargasaurus cazaui in the Melbourne Museum.

The famed North American genera include representatives of each of the two main lineages within the Neosauropoda. Diplodocus and Apatosaurus belong the Diplodocoidea, and Brachiosaurus and Camarasaurus belong to the Macronaria. Diagnostic features of the diplodocoids according the Upchurch et al. (2004) include restriction of teeth to the front of the jaw and a subrectangular snout. This last feature reaches an extreme in the middle Cretaceous Nigersaurus, which was another of those animals that serves to remind us that, if God did indeed create all of nature, then he was taking the piss. Ludicrous diplodocoids also include the late Jurassic South American Brachytrachelopan, which took one look at the graceful, elongate necks of all the other sauropods and decided that it simply couldn’t be having with all that.

Reconstruction of Saltasaurus loricatus, by Lady of Hats.

The name of the other lineage, Macronaria, means ‘big nostrils’, and one of the notable features of this clade is, indeed, a great expansion in the size of the nares, the opening for the nostrils in the skull (though whether the size of the nares directly corresponds to the size of the actual nostrils is, I suppose, another question). As well as Brachiosaurus and Camarasaurus, this clade includes the Titanosauria, a very successful group that included the last surviving sauropods, but whose significance was overlooked for many years because they had the poor judgement not to achieve their main diversity in North America. At least some titanosaurs, such as Saltasaurus pictured above, sported a skin reinforced by nodules of bone.

Which brings us to Camarasaurus. For some reason, of the ‘Big Four’ genera, this is the one that gets the least love. While the other three have each in their turn enjoyed roles as stars of stage and screen, I’m not aware of a single film in which Camarasaurus has even been given a name-drop*. In John Sibbick’s illustration of Brachiosaurus and Camarasaurus together (scroll down a bit at the link) in Norman’s (1985) The Illustrated Encyclopedia of Dinosaurs, Brachiosaurus marches confidently towards the front bearing a goofy leer, while Camarasaurus is forced to sulk towards the back. It’s all blatantly unfair. It’s not as if Camarasaurus is rare: in fact, Camarasaurus may just be the best known of all sauropods, represented in the Morrison Formation by a whole whack of remains, including what is perhaps the single most beautiful sauropod specimen ever found (the one with which I opened this post). It was no slouch in the size department, either: its maximum length of about 23 metres is similar to that of Apatosaurus, despite it having proportionally shorter appendages than the latter. Nor does it lack distinctiveness: the short, bulldog-like face of Camarasaurus instantly stands out in any neosauropod line-up. So after all this time, doesn’t Camarasaurus deserve to be given the spotlight?

*Though it is a pity that the name ‘Camarasaurus‘ won out in the priority stakes over its competitor ‘Morosaurus‘, which to those of us from a New Zealand background suggests a dinosaur made out of chocolate.

Systematics of Neosauropoda

Characters (from Upchurch et al. 2004): Subnarial foramen present on premaxilla-maxilla suture facing dorsally; platelike projections at base of maxillary ascending processes meeting each other on midline; canal or preantorbital fenestra present in base of maxillary ascending process; rostral process of quadratojugal contacting caudal end of maxilla; rostroventral corner of infratemporal fenestra terminating level with or in front of rostral rim of orbit; lateral end of ectopterygoid contacting medial surface of maxilla; ascending process of astragalus terminating level with caudal edge; pedal digit V with two phalanges or fewer.

<==Neosauropoda [Homalosauropodidae, Homalosauropodoidea]
    |  i. s.: Neosodon Moussaye 1885APS03, UBD04
    |           `--N. praecursor (n. d.)APS03
    |         Asiatosaurus (n. d.)N85
    |           |--A. kwangshiensis Hou, Yeh & Zhao 1975 (n. d.)UBD04
    |           `--A. mongoliensis Osborn 1924 (n. d.)UBD04
    |--Macronaria [Camarasauridae]SL01
    |    |  i. s.: Abrosaurus Ouyang 1989UBD04
    |    |           `--A. dongpoi Ouyang 1989UBD04
    |    |         ‘Apatosaurus’ minimus Mook 1917UBD04
    |    |         Tienshanosaurus chitaiensis Young 1937 (n. d.)B93, UBD04
    |    |         Daanosaurus zhangiP10
    |    |         Aragosaurus Sanz, Buscalioni et al. 1987P10, UBD04
    |    |           `--A. ischiaticus Sanz, Buscalioni et al. 1987UBD04
    |    |--CamarasauromorphaR-TCA06
    |    `--Haplocanthosaurus Hatcher 1903R-TCA06, UBD04 [incl. Haplocanthus Hatcher 1903UBD04]
    |         |--H. delfsi McIntosh & Williams 1988UBD04
    |         `--H. priscus (Hatcher 1903) [=Haplocanthus priscus; incl. Haplocanthosaurus utterbacki Hatcher 1903]UBD04
    `--Diplodocoidea [Diplodocimorpha]R-TCA06
         |  i. s.: Atlantosaurus Marsh 1877 [=Titanosaurus Marsh 1877 non Lydekker 1877]N85
         |           `--*A. montanus (Marsh 1877) [=Titanosaurus montanus]UBD04
         |--Amphicoelias Cope 1877RR05, UBD04
         |    `--A. altus Cope 1877UBD04 [=Diplodocus altusP10; incl. A. fragillimus Cope 1878UBD04]
         `--+--RebbachisauridaeUBD04
            |    |--Cathartesaura anaerobicaP10
            |    |--Rebbachisaurus Lavocat 1954RR05, UBD04
            |    |    `--*R. garasbae Lavocat 1954WS98
            |    |--Nigersaurus Sereno, Beck et al. 1999UBD04
            |    |    `--N. taqueti Sereno, Beck et al. 1999 [incl. Rebbachisaurus tamesnensis Lapparent 1960]UBD04
            |    `--Rayososaurus Bonaparte 1996 [incl. Limaysaurus Calvo & Salgado in Novas 1997]UBD04
            |         |--R. agrioensis Bonaparte 1996UBD04 [=Rebbachisaurus agrioensisP10]
            |         `--R. tessonei (Calvo & Salgado 1995) [=Rebacchisaurus tessonei, Limaysaurus tessonei]UBD04
            `--FlagellicaudataHD04
                 |--DicraeosauridaeRR05
                 |    |  i. s.: Zapalasaurus bonaparteiP10
                 |    |--Amargasaurus Salgado & Bonaparte 1991RR05, UBD04
                 |    |    |--A. cazaui Salgado & Bonaparte 1991UBD04
                 |    |    `--A. groeberiD07
                 |    `--+--Brachytrachelopan Rauhut, Remes et al. 2005RR05
                 |       |    `--*B. mesai Rauhut, Remes et al. 2005RR05
                 |       `--Dicraeosaurus Janensch 1914RR05, UBD04 [Dicraeosaurinae]
                 |            |--D. hansemani Janensch 1914UBD04
                 |            `--D. sattleri Janensch 1914UBD04
                 `--DiplodocidaeRR05
                      |  i. s.: Dyslocosaurus McIntosh, Coombs & Russell 1992UBD04
                      |           `--D. polyonychius McIntosh, Coombs & Russell 1992UBD04
                      |         Seismosaurus Gillette 1991UBD04
                      |           `--S. halli Gillette 1991UBD04 [=Diplodocus halliP10]
                      |         Supersaurus Jensen 1985UBD04
                      |           `--S. vivianae Jensen 1985 [incl. Ultrasauros macintoshi Jensen 1985]UBD04
                      |--Suuwassea Harris & Dodson 2004RR05, HD04
                      |    `--*S. emilieae Harris & Dodson 2004HD04
                      `--+--Apatosaurus Marsh 1877RR05, UBD04 (see below for synonymy)
                         |    |--A. ajax Marsh 1877 [incl. Atlantosaurus immanis Marsh 1878, Ap. laticollis Marsh 1879]UBD04
                         |    |--A. excelsus (Marsh 1879)UBD04 (see below for synonymy)
                         |    |--A. louisae Holland 1915UBD04 [=Apatosaurus louisaeP10]
                         |    `--A. montanusD07
                         `--DiplodocinaeHD04
                              |--Australodocus bohetiiP10
                              |--Barosaurus Marsh 1890UBD04
                              |    `--B. lentus Marsh 1890 [incl. B. affinis Marsh 1899]UBD04
                              |--Dinheirosaurus Bonaparte & Mateus 1999RR05, UBD04
                              |    `--D. lourinhanensis Bonaparte & Mateus 1999UBD04
                              |--Tornieria Sternfeld 1911RR05, UBD04
                              |    `--T. africana (Fraas 1908) [=Gigantosaurus africanus, Barosaurus africanus]UBD04
                              `--Diplodocus Marsh 1878RR05, UBD04
                                   |--D. carnegii Hatcher 1901UBD04
                                   |--D. hayi Holland 1924UBD04
                                   |--D. lacustris Marsh 1884UBD04
                                   `--D. longus Marsh 1878UBD04
Inorganic: Brontosaurus excelsus minilorientalus Okamura 1987O87

Apatosaurus Marsh 1877RR05, UBD04 [incl. Brontosaurus Marsh 1879UBD04, Elosaurus Peterson & Gilmore 1902UBD04; Apatosauridae, Apatosaurinae]

Apatosaurus excelsus (Marsh 1879)UBD04 [=Brontosaurus excelsusUBD04; incl. B. amplus Marsh 1879UBD04, Elosaurus parvus Peterson & Gilmore 1902UBD04, Apatosaurus parvusP10]

*Type species of generic name indicated

References

[APS03] Allain, R., & X. Pereda Suberbiola. 2003. Dinosaurs of France. Comptes Rendus Palevol 2 (1): 27–44.

[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.

[HD04] Harris, J. D., & P. Dodson. 2004. A new diplodocoid sauropod dinosaur from the Upper Jurassic Morrison Formation of Montana, USA. Acta Palaeontologica Polonica 49 (2): 197–210.

[N85] Norman, D. 1985. The Illustrated Encyclopedia of Dinosaurs. Salamander Books: London.

[O87] Okamura, C. 1987. New facts: Homo and all Vertebrata were born simultaneously in the former Paleozoic in Japan. Original Report of the Okamura Fossil Laboratory 15: 347–573.

[P10] Paul, G. S. 2010. Dinosaurs: A Field Guide. A & C Black.

[RR05] Rauhut, O. W. M., K. Remes, R. Fechner, G. Cladera & P. Puerta. 2005. Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia. Nature 435: 670–672.

[R-TCA06] Royo-Torres, R., A. Cobos & L. Alcalá. 2006. A giant European dinosaur and a new sauropod clade. Science 314: 1925–1927.

[SL01] Smith, J. B., M. C. Lamanna, K. J. Lacovara, P. Dodson, J. R. Smith, J. C. Poole, R. Giegengack & Y. Attia. 2001. A giant sauropod dinosaur from an Upper Cretaceous mangrove deposit in Egypt. Science 292: 1704–1706.

[UBD04] Upchurch, P., P. M. Barrett & P. Dodson. 2004. Sauropoda. In: Weishampel, D. B., P. Dodson & H. Osmólska (eds) The Dinosauria 2nd ed. pp. 259–322. University of California Press: Berkeley.

[WS98] Wilson, J. A. & P. C. Sereno. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Journal of Vertebrate Paleontology 18 (2 Suppl.): 1–68.

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