Apatosaurus (), including the popular but obsolete
synonym Brontosaurus, is a
genus of
sauropod dinosaur that lived about 150 million years ago, during the
Jurassic Period (
Kimmeridgian and
Tithonian ages). It was one of the largest land
animals that ever existed, with an average length of 23 m (75 ft) and a mass of at least 23
metric tons (25
short tons). The name
Apatosaurus means 'deceptive lizard', so-given because the
chevron bones were similar to those of a prehistoric marine
lizard,
Mosasaurus. The composite term
Apatosaurus comes from the
Greek names
apate ()/
apatelos () meaning 'deception'/'deceptive' and
sauros () meaning 'lizard'.
The cervical vertebrae were less elongated and more heavily constructed than those of
Diplodocus and the bones of the leg were much stockier (despite being longer), implying a more robust animal. The tail was held above the ground during normal locomotion. Like most sauropods,
Apatosaurus had only a single large claw on each forelimb, with the first three toes on the hind limb possessing claws.
Fossils of this animal have been found in
Nine Mile Quarry and
Bone Cabin Quarry in
Wyoming and at sites in
Colorado,
Oklahoma and
Utah, present in stratigraphic zones 2-6.
[Foster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327-329.]Description
Life restoration of Apatosaurus
was a tremendously large long-necked
quadrupedal animal with a long whip-like tail. Its forelimbs were slightly shorter than its hindlimbs. One measurement places the total length of
Apatosaurus at 26 meters (85 ft) and its weight at 24-32 tons, roughly the weight of four elephants.
[Holtz, Thomas R. Jr. (2008) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages ]The skull was small in comparison with the size of the animal. The jaws were lined with spatulate teeth, which resembled chisels, suited to an herbivorous diet.
Classification and species
Apatosaurus is a member of the
family Diplodocidae, a
clade of gigantic
sauropod dinosaurs. The family includes some of the longest creatures ever to walk the earth, including
Diplodocus,
Supersaurus,
Suuwassea, and
Barosaurus. Within the subfamily Apatosaurinae,
Apatosaurus may be most closely related to
Suuwassea,
Supersaurus and
Eobrontosaurus.
[Taylor, M.P. and Naish, D. (2005). "The phylogenetic taxonomy of Diplodocoidea (Dinosauria: Sauropoda)." PaleoBios, 25(2): 1–7. (download )][Harris, J.D. (2006). "The significance of Suuwassea emiliae (Dinosauria: Sauropoda) for flagellicaudatan intrarelationships and evolution." Journal of Systematic Palaeontology, 4(2): 185–198.]In 1877,
Othniel Charles Marsh published the name of the
type species Apatosaurus ajax. He followed this in 1879 with a description of another, more complete specimen, which he thought represented a new
genus and named
Brontosaurus excelsus. In 1903,
Elmer Riggs pointed out that
Brontosaurus excelsus was in fact so similar to
Apatosaurus ajax that it belonged in the same genus, which Riggs re-classified as
Apatosaurus excelsus. According to the rules of the
ICZN (which governs the scientific names of animals), the name
Apatosaurus, having been published first, had priority as the official name;
Brontosaurus was a
junior synonym and therefore discarded from formal use.
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Cladogram of the Diplodocidae after Lovelace, Hartman, and Wahl, 2008. is the
type species of the genus, and was named by the
paleontologist Othniel Charles Marsh in 1877 after
Ajax, the
hero from
Greek mythology. It is the
holotype for the genus and two partial skeletons have been found, including part of a
skull.
Apatosaurus excelsus (originally
Brontosaurus) was named by Marsh in 1879. It is known from six partial skeletons, including part of a skull, which have been found in the
United States, in
Colorado,
Oklahoma,
Utah, and
Wyoming.
Apatosaurus louisae was named by William Holland in 1915 in honor of Mrs. Louise Carnegie, wife of
Andrew Carnegie who funded field research to find complete dinosaur skeletons in the American West.
Apatosaurus louisae is known from one partial skeleton which was found in
Colorado in the United States.
Apatosaurus parvus was originally known as
Elosaurus parvus, but was reclassified as a species of
Apatosaurus in 1994.
[Carpenter, K. and McIntosh, J. (1994). "Upper Jurassic sauropod babies from the Morrison Formation", In: K. Carpenter, K. F. Hirsch, and J. R. Horner (eds.), Dinosaur Eggs and Babies. Cambridge University Press, Cambridge 265–278] This synonymy was upheld in 2004.
[Upchurch, Paul; Tomida, Yukimitsu; and Barrett, Paul M. (2004). "" National Science Museum monographs 26: i-118 ISSN:13429574]Robert T. Bakker made
A. yahnahpin the
type species of a new genus,
Eobrontosaurus in 1998, so it is now properly
Eobrontosaurus yahnahpin. It was named by Filla, James and Redman in 1994. One partial skeleton has been found in Wyoming. However, recently it has been argued that
Eobrontosaurus belongs within
Camarasaurus.
History
1896 diagram of the
Apatosaurus excelsus (then
Brontosaurus) skeleton by
O.C. Marsh. The head is based on material now assigned to
Brachiosaurus sp., a Professor of
Paleontology at
Yale University, described and named an incomplete (and juvenile) skeleton of
Apatosaurus ajax in 1877. Two years later, Marsh announced the discovery of a larger and more complete specimen at
Como Bluff Wyoming — which, because of discrepancies including the size difference, Marsh incorrectly identified as belonging to an entirely new
genus and
species. He dubbed the new species
Brontosaurus excelsus, meaning "thunder lizard", from the
Greek brontē/βροντη meaning 'thunder' and
sauros/σαυρος meaning 'lizard', and from the
Latin excelsus, "to exceed in number", referring to the greater number of sacral vertebrae than in any other genus of sauropod known at the time.
Original (outdated)
Apatosaurus excelsus skeletal mount at the
AMNHThe finds — the largest dinosaur ever discovered at the time and nearly complete, lacking only a head, feet, and portions of the tail — were then prepared for what was to be the first ever mounted display of a sauropod skeleton, at Yale's
Peabody Museum of Natural History in 1905. The missing bones were created using known pieces from close relatives of
Brontosaurus. Sauropod feet that were discovered at the same quarry were added, as well as a tail fashioned to appear as Marsh believed it should, as well as a composite model of what he felt the skull of this massive creature might look like. This was not a delicate
Diplodocus-style skull (which would later turn out to be more accurate), but was composed of "the biggest, thickest, strongest skull bones, lower jaws and tooth crowns from three different quarries",
[Bakker, Robert (1994). "The Bite of the Bronto" Earth 3:(6):26–33.] primarily those of
Camarasaurus, the only other sauropod for which good skull material was known at the time. This method of reconstructing incomplete skeletons based on the more complete remains of related dinosaurs continues in museum mounts and life restorations to this day.
Despite the much-publicized debut of the mounted skeleton, which cemented the name
Brontosaurus in the public consciousness,
Elmer Riggs had published a paper in the 1903 edition of
Geological Series of the Field Columbian Museum which argued that
Brontosaurus was not different enough from
Apatosaurus to warrant its own genus, and created the combination
Apatosaurus excelsus: "In view of these facts the two genera may be regarded as synonymous. As the term 'Apatosaurus' has priority, 'Brontosaurus' will be regarded as a synonym."
Despite this, at least one paleontologist—
Robert Bakker—argued in the 1990s that
A. ajax and
A. excelsus are in fact sufficiently distinct that the latter continues to merit a separate genus.
[Bakker, R.T. (1998). "Dinosaur mid-life crisis: the Jurassic-Cretaceous transition in Wyoming and Colorado". In: S.G. Lucas, J.I. Kirkland, & J.W. Estep (eds.) Lower and Middle Cretaceous Terrestrial Ecosystems; New Mexico Museum of Natural History and Science Bulletin, 14: 67–77.] This idea has not been accepted by many palaeontologists.
[Upchurch, P., Barrett, P.M. and Dodson, P. (2004). "Sauropoda". In Weishampel, D.B., Osmólska, H., and Dodson, P. (eds.), The Dinosauria (2nd edition). University of California Press, Berkeley 259–322.][McIntosh, J.S. (1995). "Remarks on the North American sauropod Apatosaurus Marsh". Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short Papers, A. Sun and Y. Wang (eds.), China Ocean Press, Beijing 119–123]Palaeobiology
Apatosaurus femur in Cosmocaixa, Barcelona
Early on, it was believed that
Apatosaurus was too massive to support its own weight on dry land, so it was theorized that the sauropod must have lived partly submerged in water, perhaps in a swamp. Recent findings do not support this. In fact, like its relative
Diplodocus,
Apatosaurus was a
grazing animal with a very long neck and a long tail that served as a counterweight. One study found that diplodocid necks were less flexible than previously believed, and that sauropods like
Apatosaurus were adapted to low browsing or ground feeding.
Fossilized footprints indicate that it probably lived in herds.
In 2008, footprints of juvenile
Apatosaurus were reported from Quarry Five in Morrison, Colorado. Discovered in 2006 by Matthew Mossbrucker, these footprints show that juveniles could run on their hind legs in a manner similar to that of the modern
basilisk lizard.
Posture
In the early 20th century,
diplodocids like
Apatosaurus were often portrayed with their necks held high up in the air, allowing them to graze from tall trees. More recently, scientists have argued that the heart would have had trouble sustaining sufficient blood pressure to oxygenate the brain. Furthermore, more recent studies have shown that the structure of the neck vertebrae would not have permitted the neck to bend far upwards.
However, subsequent studies demonstrated that all
tetrapods appear to hold their necks at the maximum possible vertical extension when in a normal, alert posture, and argued that the same would hold true for sauropods barring any unknown, unique characteristics that set the soft tissue anatomy of their necks apart from other animals.
Apatosaurus like
Diplodocus would have held its neck at about a 45 degree angle with the head pointed downwards in a resting posture.
Physiology
With such a large body mass, combined with a long neck,
physiologists encounter problems determining how these animals managed to breathe.
Beginning with the assumption that
Apatosaurus, like
crocodilians, did not have a diaphragm, the
dead-space volume (the amount of unused air remaining in the mouth, trachea and air tubes after each breath) has been estimated at about 184 liters for a 30 ton specimen.
Its
tidal volume (the amount of air moved in or out during a single breath) has been calculated based on the following
respiratory systems:
On this basis, its
respiratory system could not have been reptilian, as its tidal volume would not have been able to replace its dead-space volume. Likewise, the mammalian system would only provide a fraction of new air on each breath. Therefore, it must have had either a system unknown in the modern world or one like
birds, i.e. multiple air sacs and a flow-through lung. Furthermore, an avian system would only need a lung volume of about 600 liters compared to a mammalian requirement of 2,950 liters, which would exceed the available space. The overall thoracic volume of
Apatosaurus has been estimated at 1,700 liters allowing for a 500-liter, four-chambered
heart (like
birds, not three-chambered like
reptiles) and a 900-liter lung capacity. That would allow about 300 liters for the necessary
tissue. Assuming
Apatosaurus had an avian respiratory system and a reptilian resting-metabolism, it would need to consume only about 262 liters (69 gallons) of water per day.
[Paladino, F.V., Spotila, J.R., and Dodson, P. (1997). "A Blueprint for Giants: Modeling the Physiology of Large Dinosaurs." In Farlow, J.O. and Brett-Surman, M.K. (eds.), The Complete Dinosaur, Indiana University Press, 491–504. doi0253333490.]It is not known how Apatosaurs ate enough food to satisfy their enormous bodies. It is likely that they ate constantly, pausing only to cool off, drink or to remove parasites. It is surmised that they slept standing upright. They likely relied on their enormous size and
herd behavior to deter predators.
Tail
An article that appeared in the November 1997 issue of
Discover Magazine reported research into the mechanics of
Apatosaurus tails by
Nathan Myhrvold, a
computer scientist from
Microsoft. Myhrvold carried out a
computer simulation of the tail, which in diplodocids like
Apatosaurus was a very long, tapering structure resembling a
bullwhip. This computer modeling suggested that sauropods were capable of producing a whip-like cracking sound of over 200
decibels, comparable to the volume of a
cannon.
[Zimmer, C. (1997). "Dinosaurs in Motion." Discover, 1 Nov 1997. Accessed 27 Jul 2008.]In popular culture
The length of time taken for Marsh's misclassification to be brought to public notice meant that the name
Brontosaurus, associated as it was with one of the largest dinosaurs, became so famous that it persisted long after the name had officially been abandoned in scientific use. The terms brontosaurus, brontosaurs, and brontosaurians (no capital 'B'; no italics) are often used to refer generically to any of the
sauropod dinosaurs.
As late as 1989, the
U.S. Post Office issued four "dinosaur" stamps,
Tyrannosaurus,
Stegosaurus, "Pteradon" (misspelling of
Pteranodon, which is a
pterosaur and not a dinosaur) and
Brontosaurus. The inclusion of these last two led to complaints of "fostering scientific illiteracy."
[ The New York Times, 1989-10-11. Last accessed 2008-06-08.] The Post Office defended itself (in Postal Bulletin 21744) by saying, "Although now recognized by the scientific community as
Apatosaurus, the name 'Brontosaurus' was used for the stamp because it is more familiar to the general population."
Stephen Jay Gould supported this position in his essay "
Bully for Brontosaurus", though he echoed Riggs' original argument that "Brontosaurus" is a synonym for "Apatosaurus". Nevertheless, he noted that the creature has developed and continues to maintain an independent existence in the popular imagination.
[Gould, S.J. (1991). Bully for Brontosaurus: Reflections in Natural History, W. W. Norton & Co., 540pp.]Brontosaurus has often been depicted in cinema; the 1925 silent film
The Lost World featured, using
special effects by
Willis O'Brien, a battle between a
Brontosaurus and an
Allosaurus.
King Kong (1933) featured a
Brontosaurus, as did the
2005 remake, described using the fictional scientific name "Brontosaurus baxteri", or Baxter's Thunder-Lizard, after a character in the film. The brontosaur of the 2005 film is noticeably different from the modern view of
Apatosaurus, with a square head, low-hanging tail, and snake-like neck reminiscent of 1930s period depictions of the species in art.
When
George Lucas made his special edition of
Star Wars Episode IV: A New Hope in 1997, he added some large, long-necked animals based on the
Brachiosaurus digital model from
Jurassic Park. At an early stage he altered the CG department's suggested name 'Bronto,' taken from 'Brontosaurus,' to '
Ronto'.
is a make of truck-mounted ladders and
cherry pickers.
See also
