Apatosaurus

Taxobox
name = "Apatosaurus"
fossil_range = Late Jurassic

---

image_caption = Current "Apatosaurus excelsus" skeletal mount at the American Museum of Natural History
image_width = 300px
regnum = Animalia
phylum = Chordata
classis = Sauropsida
superordo = Dinosauria
ordo = Saurischia
subordo = Sauropodomorpha
familia = Diplodocidae
genus = "Apatosaurus"
genus_authority = Marsh, 1877
subdivision_ranks = Species
subdivision =
* "A. ajax" Marsh, 1877 (type)
* "A. excelsus" (Marsh, 1879c) Riggs, 1903
* "A. louisae" Holland, 1915
* "A. parvus" (Peterson & Gilmore, 1902)
synonyms =
* "Brontosaurus" Marsh, 1879c
* "Elosaurus" Peterson & Gilmore, 1902

"Apatosaurus" (IPAEng|əˌpætəˈsɔrəs), also formerly known as "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 meters (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 name "Apatosaurus" comes from the Greek ἀπατέλος or ἀπατέλιος meaning 'deceptive' and Polytonic| 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, USA.

Description

"Apatosaurus" was a tremendously large long-necked quadrupedal animal with a long whip-like tail. Its forelimbs were slightly longer 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" [http://www.geol.umd.edu/~tholtz/dinoappendix/DinoappendixSummer2008.pdf Supplementary Information] ]

The skull was small in comparison with the size of the animal. The jaws were lined with spatulate teeth, which resembled chisels, suited to a herbivorous diet.

Classification and species

"Apatosaurus" is a member of the family Diplodocidae, which also includes close relatives like "Diplodocus" and "Barosaurus", although it is not as closely related to these genera as they are to each other, and hence "Apatosaurus" is usually placed in its own subfamily, Apatosaurinae, along with its closest relatives "Supersaurus" and "Eobrontosaurus".Taylor, M.P. and Naish, D. (2005). "The phylogenetic taxonomy of Diplodocoidea (Dinosauria: Sauropoda)." "PaleoBios", 25(2): 1-7. (download [http://www.miketaylor.org.uk/dino/pubs/ here] )] 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, and 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.

"Apatosaurus ajax" 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). " [http://ci.nii.ac.jp/naid/110004665753/ A new specimen of "Apatosaurus ajax" (Sauropoda: Diplodocidae) from the Morrison Formation (Upper Jurassic) of Wyoming, USA.] " "National Science Museum monographs" 26: i-118 ISSN:13429574]

clade| style=font-size:90%;line-height:80%
label1= Diplodocidae
1=clade
1=clade
label1= Apatosaurinae
1=clade
1="Suuwassea"
label2=
2=clade
label1=
1="Supersaurus"
2="Apatosaurus"
label2=Diplodocinae
2=clade
1="Barosaurus"
2="Diplodocus"
Cladogram of the Diplodocidae after Lovelace, Hartman, and Wahl, 2008.cite journal |last=Lovelace |first=David M. |coauthors=Hartman, Scott A.; and Wahl, William R. |year=2007 |title=Morphology of a specimen of "Supersaurus" (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny |journal=Arquivos do Museu Nacional |volume=65 |issue=4 |pages=527–544 ]

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".

"Apatosaurus" is a member of the 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" and "Supersaurus".cite journal |last=Lovelace |first=David M. |coauthors=Hartman, Scott A.; and Wahl, William R. |year=2007 |title=Morphology of a specimen of "Supersaurus" (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny |journal=Arquivos do Museu Nacional |volume=65 |issue=4 |pages=527–544 ]

History

Othniel Charles Marsh, 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.

The 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 [McIntosh, J.S. and Berman, D.S. (1975). "Description of the palate and lower jaw of the sauropod dinosaur "Diplodocus" (Reptilia: Saurischia) with remarks on the nature of the skull of "Apatosaurus"." "Journal of Paleontology", 49(1): 187-199.] ), 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

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.cite journal| last = Stevens| first = Kent A.| authorlink = | coauthors = Parrish, J. Michael| title = Neck Posture and Feeding Habits of Two Jurassic Sauropod Dinosaurs| journal = Science| volume = 284| issue = 5415| pages = 798–800| publisher = | location = | date = 1999| url = http://www.sciencemag.org/cgi/content/abstract/284/5415/798| doi = 10.1126/science.284.5415.798| id = | accessdate = 2008-08-03] 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.cite journal|last=Rajewski|first=Genevieve|date=May 2008|title=Where Dinosaurs Roamed |journal=Smithsonian |pages=20–24 |url=http://www.smithsonianmag.com/history-archaeology/phenom-dino-200805.html |accessdate=2008-04-30]

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.cite book|author=Stevens KA, Parrish JM|year=2005|chapter=Neck Posture, Dentition and Feeding Strategies in Jurassic Sauropod Dinosaurs|editor=Carpenter, Kenneth and Tidswell, Virginia (ed.)|title=Thunder Lizards: The Sauropodomorph Dinosaurs|pages=212–232|publisher= Indiana University Press|isbn=0-253-34542-1|oclc=218768170 57202057 61128849] cite web|last=Upchurch |first=P, "et al."|title="Neck Posture of Sauropod Dinosaurs"|publisher="Science" 287, 547b (2000); DOI: 10.1126/science.287.5453.547b |date=2000|url=http://www.sciencemag.org/cgi/reprint/287/5453/547b.pdf|format = PDF | accessdate =2008-08-05 ]

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:
* 904 liters if avian
* 225 liters if mammalian
* 19 liters if reptilian.

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. [http://discovermagazine.com/1997/nov/dinosaursinmotio1261/] 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." [http://query.nytimes.com/gst/fullpage.html?res=950DE5DC173CF932A25753C1A96F948260 " Topics of The Times; Leapin' Lizards!"] "The New York Times", 1989-10-11. Last accessed 2008-06-08.] The Post Office defended itself (in Postal Bulletin 21744) thus: :"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.]

Since the beginning of film history, "Brontosaurus" has been depicted in cinema. For example, 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.

ee also

*"Eobrontosaurus", a closely related genus
*"", a book by Stephen Jay Gould
*Dinny the Dinosaur, a well-known "Brontosaurus" sculpture

References

External links

* [http://www.infoplease.com/spot/brontokids.html The Great Brontosaurus Hoax]
* [http://www.miketaylor.org.uk/dino/faq/s-class/bronto/ Why is "Brontosaurus" now called Apatosaurus?]
* [http://www.unmuseum.org/dinobront.htm UnMuseum Article "Whatever Happened to the Brontosaurus?"]
* [http://www.dinoruss.org/de_4/5a7f80e.htm Brontosaurus species]
* [http://skeletaldrawing.com/sauropods/sauropods.htm Skeletal drawings of diplodocids] including [http://skeletaldrawing.com/sauropods/A_ajax.htm "Apatosaurus ajax"] , [http://skeletaldrawing.com/sauropods/Aexcelsus.htm "A. excelsus"] , and [http://skeletaldrawing.com/sauropods/apatosaurus_louisae.png"A. louisae"] from SkeletalDrawing.com