SAUROPODOMORPHA

Dinosauria

     Herrerasauridae

     Saurischia

          Theropoda

        Sauropodomorpha

               Prosauropoda

          Sauropoda

                     "Cetiosauridae"

                      Neosauropoda

                           Diplodocoidea

                                 Diplodocidae

                           Macronaria

                                  Camarasaurus

                                  Titanosauriformes

                                        Brachiosauridae

                                        Titanosauridae

Classification of the Sauropodomorpha after Wilson, J. A. and P. C. Sereno. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Journal of Vertebrate Paleontology 18, supplement to number 2; Society of Vertebrate Paleontology, Memoir 5:1-68.

Upchurch, P.  1998.  The phylogenetic relationships of sauropod dinosaurs.  Zoological Journal of the Linnean Society: 124:43-103.

Wilson, Jeffrey A.  2001. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society, 136: 217-276

SAURISCHIA

Characters

• distinctly asymmetrical manus with digit II the longest digit [D&R p. 179]
• triradiate saurischian pelvis (primitive)
• elongate caudal cervicals giving a long neck
• antorbital fenestra well-developed
• large quadratojugal; temporal musculature extends onto frontal

SAUROPODOMORPHA

Characters

• relatively small skull, with retracted enlarged nares
• very long neck
• one to three extra sacral vertebrae
• enormous pollex (thumb) with an enlarged claw
• spatulate teeth; herbivores
• gastroliths to aid digestion. (also occur in two theropods)

Included Taxa

• Saturnalia, Prosauropoda, and Sauropoda

Saturnalia

• This primitive sauropodomorph from the upper Triassic (Carnian) of Brazil is one of the earliest occuring dinosaurs.  It was lightly built and small (1.5 m long).

PROSAUROPODA

Characters

• primitive sauropodomorphs that were the dominant large herbivores of the late Triassic and early Jurassic
• small to medium size
• quadrupedal or bipedal, but primarily bipedal
• low jaw joint for sustained and evenly spread bite.
• traditionally interpreted as a paraphyletic group ancestral to the sauropods.
• Synapomorphies uniting prosauropods as a monophyletic group include a twisted pollex with a large inwardly pointing claw.

Examples

• Plateosaurus about 6-8 m long
  • Plateosaurus from Paul Olsen
  • watch a videoclip from walking with dinosaurs
• Thecodontosaurus, about 1.2 m long

SAUROPODA (late Triassic to latest Cretaceous)

Illustration from O. C. Marsh.  1896.  The dinosaurs of North America.

• Isanosaurus, the earliest sauropod, is represented by an incomplete skeleton from the Late Triassic of Thailand, providing the first osteological evidence of pre-Jurassic sauropods. "This dinosaur is markedly different from prosauropods and substantiates theoretical predictions that there was a fairly long period of sauropod evolution during the Triassic." E. Bufffetaut, V. Suteethorn, G. Cuny, H. Tong, J. Le Loeuff, S. Khansubha, & S. Jongautchariyakul.  2000. The earliest known sauropod dinosaur.  Nature 407, 72 - 74.

Characters

• very large, quadrupedal herbivores
• limb bones greatly thickened, solidly ossified (columnar)
• graviportal feet
• sauropods as suspension bridges
• sauropod diets
• dorsal vertebrae converted to cervicals, elongating neck
• Sauropod nesting grounds [Chiappe, L. M., R. A. Coria, L. Dingus, F. Jackson, A. Chinsamy, and M. Fox. 1998. Sauropod dinosaur embryos from the late Cretaceous of Patagonia. Nature 396:258-261]

Included taxa

• primitive sauropods ("cetiosaurs") plus Neosauropoda

"Cetiosauridae" [middle Jurassic]

Characters

• a paraphyletic group of primitive sauropods
• shortened postorbital region of skull
• elongate necks
• short and massive limb bones

Examples

• Vulcanodon
• Cetiosaurus  
• Shunosaurus
  • Wilson and Sereno (1998) include Shunosaurus and the neosauropods in the Eusauropoda because of the collapse of the pes into a graviportal stance from a digititigrade stance in the eusauropods.

NEOSAUROPODA

Characters

• elevation of the metacarpus from a plantigrade to digitigrade posture

Included taxa

• Diplodocoidea + Macronaria (=Camarosauromorpha)

DIPLODOCOIDEA

Diplodocidae

Characters

• the longest dinosaurs
• long whip-like tails (possibly used for defense)
  • more from Science News
• slender, peg-like teeth at front of mouth only
• high vertebral spines
• Latest Jurassic-late Cretaceous 

Examples

• Diplodocus  
  • 27 m.; 6 to 20 tonnes
  • Andrew Carnegie and the Carnegie Museum
  • BBC walking with dinosaurs
• Apatosaurus
  • 21 to 26 m long, with the tail accounting for nearly half of the length
  • 30 to 35 tonnes
  • the old restoration of "Brontosaurus"; the new Apatosaurus
  • How brontosaurus got its head
  • more from the AMNH
• Seismosaurus
  • 30 tonnes.
  • May be a large Diplodocus.(30 m long not 52 m as claimed by Gillette)
• Supersaurus more info from the dallas museum of natural history
  • the longest sauropod: 30-35 m long; 8 m high at the shoulders and had a 12 m long neck.
  • 30-40 metric tonnes.
• Barosaurus 
  • 20-27 meters; 10 tonnes
• Pleurocoelus

Diplodocus--Illustration from O. C. Marsh.  1896.  The dinosaurs of North America
en = external nares

MACRONARIA (Camarasauromorphs)

Characters

• arched internarial bar formed by a narrow premaxilla; clearly defined snout

Included Taxa

• Camarasaurus plus Titanosauriformes

Illustration from C. W. Gilmore. 1925.  A nearly complete articulated skeleton of Camarasaurus....
en = external nares

Camararasuridae

Characters

• short heavy skull
• nostrils open outward
• large, spoon-shaped teeth

Included taxon

• Camarosaurus  
  • a relatively small sauropod: 18 m; 18 tonnes
  • the most abundant dinosaur from the Morrison Formation.
  • The front and hindlegs are about the same length.
  • a modern reconstruction

Titanosauriformes

Included taxa

• Brachiosauridae plus Titanosauroidea

Brachiosauridae (middle Jurassic - lower Cretaceous)

Characters

• elevated nasals
• elongate forelimb
• weights up to 80,000 kilograms (perhaps)

Examples

• Brachiosaurus
  • 22-30 m long; head would have been 13 m above the ground; 30-?80 tons
  • Brachiosaurus altithorax was first described on the basis of an incomplete skeleton discovered in the Morrison Formation of Colorado.   A few years later five relatively complete skeletons were found at Tendaguru in Tanzania.
  •  Ultrasaurus was to be the name a giant sauropod from the Late Jurassic, Morrison Formation, Western USA.  However this name was first used for a misidentified Korean dinosaur.  The Morrison brachiosaur, when it was finally named, was called Ultrasauros macintoshi.  This species is probably Brachiosaurus altithorax.
  • Walking with Dinosaurs
• Sauroposeidon
  • This dinosaur from the early Cretaceous of Oklahoma was perhaps the tallest. With its head raised, it stood nearly 20 m tall.  However, it is known only from ribs and cervical vertebrae. [Wedel, Cifelli & Sanders, 2000 Journal of Vertebrate Paleontology 20:109-114]

Titanosauroidea

• steeply sloping quadrate, long broad snout with a small number of cylindrical teeth

Titanosauridae - [?upper Jurassic, upper Cretaceous]

• dermal armor
• poorly known

    Examples

• Argentinosaurus   possibly the largest dinosaur ever discovered
  • 35-45? m; 80-100? tonnes
• Alamosaurus: 
  • 21 m; 30 tonnes
  • The last sauropod from North America (late Cretaceous)
  • probably an immigrant from South America, following the mid-Cretaceous extinction of the brachiosaurids in North America.
  • occurs in Texas, but is named for Ojo Alamo wash in New Mexico
  • Alamosaurus from Texas at Big Bend

Dino Land Paleontology  and Prehistoric Planet interviews with Matt Wedel discuss some of the following questions.  For more information also see Titanosaur Notes

Could sauropods rear up on their hind legs for feeding?

• Yes, they must have for reproduction, but was this a common feeding behavior?
• The AMNH skeleton of Barosaurus
• Diplodocids have vertebrae with elongate neural spines for muscles and tendons.

How did sauropods feed?  With vertical necks like giraffes or with the head held horizontally?

• Jurassic cows: From National Geographic read about hypotheses about the long necks of sauropods. 
• They could have foraged on low growing vegetation with huge horizontal sweeps of their necks.
• Computer modeling shows that  Diplodocus and Apatosaurus were ground grazers. [Stevens, K. A. and J. M. Parrish. 1999.  Neck posture and feeding habits of two Jurassic sauropod dinosaurs. Science 284: 798-800.]
• (http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v407/n6800/abs/407072a0_fs.html)

How did sauropods pump blood to their heads if they reared up or held their heads high to feed?

• Enchanted Learning estimates that large sauropds would have had to have a 400 kg four chambered heart that could generate a systolic blood pressure of 600 mm of Hg in order to pump blood up to the brain.  Giraffes have a systolic pressure of 300 mm of Hg.

Could dinosaurs have used their long necks as snorkels while in the water?

• Early reconstructions of sauropods show them as swamp-dwellers who spent much of their time in the water.   They were thought to be too massive to support their weight on land and had to be buoyed up by water. Their long necks were interpreted as snorkels.  At a depth of 13 meters an additional 0.8-0.9 atmospheres (1 atmosphere = 1.034 kg/cm² = pressure exerted by 10.3 m of water) of pressure would have been exerted on its chest, 8-9 m below the surface. This probably would have kept the rib cage from expanding enough for respiration.   

Feeding in Sauropods

• Sauropods had a small number of simple teeth and did not chew their food.  Sauropods were probably constant eaters.
• Sauropods had large guts that probably housed fermentation chambers
• Gastroliths

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