Triceratops is dead. Long live... ...Triceratops.
About a month ago John Scannella and Jack Horner published an article "Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny" in the Journal of Paleontology*
*Note. Ceratopsidae are the "horned dinosaurs", including Styracosaurus, Triceratops/Torosaurus, Chasmosaurus, and Pachyrhinosaurus to name but a few. The Chasmosaurines are a subgroup which had long brow horns, short nasal horns, and big frills, (Chasmosaurus and Triceratops/Torosaurus are fairly typical.) The other group (the Centrosaurinae) had short, or absent brow horns, a long nasal horn, and a relatively short frill (Styracosaurus and Pachyrhinosaurus are good examples of this group).
What this paper attempts (and I think succeeds) to show is that the fossils attributed to Triceratops are all juveniles, and the fossils attributed to Torosaurus are all adults. They looked at all the skulls they could get their hands on, and looked at what was happening to the bones, and they are fairly confident that they've identified a growth sequence between Triceratops and Torosaurus.
As it grew Triceratops first developed the long brow horns, and a short solid frill. When it reached maturity then holes in the frill opened as bone was absorbed, and the frill itself then grew significantly longer. There are one or two Triceratops specimens that show that the bones in the frill were starting to thin as this happened.
So all in all, a reasonably convincing study. So why the hoo-ha?
Because journalists (and the sub-editors responsible for their headlines) can't read, and then the internet gets hold of their shoddy penmanship, and before you know it people are clutching their pearls and comparing this to "Pluto not being a planet anymore". (Breaking Daily News are particularly precious, I really can't see how this could delight creationists at all.)
Anyway. The ICZN (International Commission of Zoological Nomenclature) has some pretty strict rules about how you go about naming things. Generally the first name given has priority. Its why Brontosaurus was renamed Apatosaurus (Apatosaurus was published first). Its why Laelaps had to be renamed Dryptosaurus (a mite had already been given the name). Its generally a very sensible rule, and only causes problems when you discover that another name was previously published for the same species, but completely ignored, or if the type species, or the specimen on which the name was originally based turn out to be fairly poor for identifying, well anything.
When this happens you appeal to the ICZN and they think about it, ask for comments and make a decision. Often they'll agree with you. If no-one's used a name for ages there's no point in keeping it if everyone else uses something different. There's a application currently going through the ICZN< to replace Cetiosaurus medius with Cetiosaurus oxoniensis as the type species of the sauropod Cetiosaurus, primarily because the material of C. medius is crap, and everyone uses C. oxoniensis when talking about Cetiosaurus. Something similar happened to Iguanodon a little while ago, and there was a paper recently that made everything really confusing. Some day I'll write about it.
Anyway, in this case strict priority is going to rule. Torosaurus was described three years after Triceratops. The species included in Torosaurus will be reclassified as species of Triceratops. Scannella and Horner don't go so far as to synonymise the individual species however, so Triceratops gets several new species and a new look for the adults.
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*Note. Ceratopsidae are the "horned dinosaurs", including Styracosaurus, Triceratops/Torosaurus, Chasmosaurus, and Pachyrhinosaurus to name but a few. The Chasmosaurines are a subgroup which had long brow horns, short nasal horns, and big frills, (Chasmosaurus and Triceratops/Torosaurus are fairly typical.) The other group (the Centrosaurinae) had short, or absent brow horns, a long nasal horn, and a relatively short frill (Styracosaurus and Pachyrhinosaurus are good examples of this group).
What this paper attempts (and I think succeeds) to show is that the fossils attributed to Triceratops are all juveniles, and the fossils attributed to Torosaurus are all adults. They looked at all the skulls they could get their hands on, and looked at what was happening to the bones, and they are fairly confident that they've identified a growth sequence between Triceratops and Torosaurus.
As it grew Triceratops first developed the long brow horns, and a short solid frill. When it reached maturity then holes in the frill opened as bone was absorbed, and the frill itself then grew significantly longer. There are one or two Triceratops specimens that show that the bones in the frill were starting to thin as this happened.
So all in all, a reasonably convincing study. So why the hoo-ha?
Because journalists (and the sub-editors responsible for their headlines) can't read, and then the internet gets hold of their shoddy penmanship, and before you know it people are clutching their pearls and comparing this to "Pluto not being a planet anymore". (Breaking Daily News are particularly precious, I really can't see how this could delight creationists at all.)
Anyway. The ICZN (International Commission of Zoological Nomenclature) has some pretty strict rules about how you go about naming things. Generally the first name given has priority. Its why Brontosaurus was renamed Apatosaurus (Apatosaurus was published first). Its why Laelaps had to be renamed Dryptosaurus (a mite had already been given the name). Its generally a very sensible rule, and only causes problems when you discover that another name was previously published for the same species, but completely ignored, or if the type species, or the specimen on which the name was originally based turn out to be fairly poor for identifying, well anything.
When this happens you appeal to the ICZN and they think about it, ask for comments and make a decision. Often they'll agree with you. If no-one's used a name for ages there's no point in keeping it if everyone else uses something different. There's a application currently going through the ICZN< to replace Cetiosaurus medius with Cetiosaurus oxoniensis as the type species of the sauropod Cetiosaurus, primarily because the material of C. medius is crap, and everyone uses C. oxoniensis when talking about Cetiosaurus. Something similar happened to Iguanodon a little while ago, and there was a paper recently that made everything really confusing. Some day I'll write about it.
Anyway, in this case strict priority is going to rule. Torosaurus was described three years after Triceratops. The species included in Torosaurus will be reclassified as species of Triceratops. Scannella and Horner don't go so far as to synonymise the individual species however, so Triceratops gets several new species and a new look for the adults.
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