14Sep/092
Brontosaurus
by Jeff
Image text: Well, sex is like a velociraptor: despite your movie-fueled lifelong neurotic obsession, unlikely to be found in your house.
And here we continue xkcd's author's obsession with the cyncism about love.
Brontosaurus is an obsolete phrase for the Apatosaurus. Brontosaurus is the "popular" (but incorrect) name for the dinosaur, but Apatosaurus is the correct name.
September 14th, 2009
From http://www.miketaylor.org.uk/dino/faq/s-class/bronto/ :
Brontosaurus excelsus was named in 1879 by Marsh, based on a rather good specimen. Unfortunately, two years earlier he’d named some much scrappier remains with the rather less resonant name Apatosaurus ajax.
In 1903, Elmer Riggs’ re-examination of Marsh’s specimens led him to conclude that they represented the same genus (although see below), meaning that the names were synonyms. In such cases, the ICZN (International Commission on Zoological Nomenclature, see http://www.iczn.org) mandates that the oldest name has priority – which means that the rather dull Apatosaurus (“deceptive lizard”) wins out over the much more resonant “Brontosaurus” (“thunder lizard”).
So why does the world still talk about “Brontosaurus” all the time? The paper in which Riggs established the synonymy was published in the Geological Series of the Field Columbian Museum – a relatively obscure journal, so the findings were not as widely known as they should have been. Also, the sexier invalid name received a lot of public exposure from non-scientific sources: for example, the Sinclair oil company used a “Brontosaurus” as its logo for many years. (Rather inappropriately, as it turns out, since oil is formed from plant matter, not animals. Never mind.)
So the world continued and continues to use “Brontosaurus”; but Apatosaurus should be used in all serious writing.
I said that Riggs established that Apatosaurus and “Brontosaurus” were from the same genus. But the two Marsh specimens are still considered to represent separate species: the older specimen is Apatosaurus ajax and the newer Apatosaurus (nee “Brontosaurus”) excelsus. However, since it’s always a judgement call whether any species belong in the same genus (see “When is a new dinosaur erected as a new species or genus?” ), there are palaeontologists – notably Robert Bakker – who feel that the two species are sufficiently distinct that excelsus merits a separate genus. Under this scheme, the old genus name is still perfectly good, so Bakker still uses the formal name Brontosaurus excelsus (but never Brontosaurus ajax.)
Finally: for many years, Apatosaurus was believed to have a head similar to that of Camarasaurus – a mistake that was rectified in the 1970s with the discovery of a specimen with associated cranial remains closely resembling the head of Diplodocus. This has led to a misapprehension in some quarters that the name “Brontosaurus” refers to the combination of an Apatosaurus body with a Camarasaurus head. No so: the naming confusion is quite separate from this issue.
…and courtesy of wikipedia (http://en.wikipedia.org/wiki/Apatosaurus):
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[9]), but was composed of “the biggest, thickest, strongest skull bones, lower jaws and tooth crowns from three different quarries”,[10] 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.[11] This idea has not been accepted by many palaeontologists.
Huzzah for dinosaurs!
December 6th, 2009
I suppose that next you will be saying that Pluto is not a planet.