World's Dullest Dinosaur in Not Dull Shocker!
When discussing the fact that Torosaurus never existed, I mentioned that something similar had happened with Iguanodon.
Iguandon is one of the world's most famous dinosaurs, and its famous for being one of the first discovered. Initially described from teeth, by Gideon Mantell, it was reconstructed first as a colossal lizard, and then as a rhino-like quadruped with a horn on its nose. Later finds near the town of Bernissart in Belgium allowed Louis Dollo to show that the animal's "horn" was a thumb-spike, and the arms were considerably shorter than the hind limbs, giving the characteristic Fonz-style pose that many people are familiar with. Later work by David Norman, showed that Dollo had dislocated large chunks of the tail and that in fact the animal was largely quadrupedal.
Iguanodon being initially based on relatively poor material, as is so often the case has ended up as something of a "wastebasket taxon", with lots of indeterminate bits and bobs ascribed to it, and several species all lumped together. At the last count there was Iguanodon anglicus / I. mantelli, described by Mantell based on his teeth and other material, the gracile, I atherfieldensis, the Belgian I. bernissartensis, the American species I. lakotaensis, the Mongolian species I. orientalis, and several other species from the UK, I. hollingtoniensis, I. fittoni, I. dawsoni (named after the perpetrator of Piltdown, Charles Dawson), and I. hoggi, often referred to the related genus, Camptosaurus. And that's just the species known from good material, or that have stayed in Iguanodon for more than a few years. There are several other species that are either based on very poor material, that are either undiagnostic, were fairly rapidly shifted into other genera (Iguanodon prestwichi has been happily residing in Camptosaurus for over 100 years now), not from ornithopods, or aren't even dinosaurs.
The beginning of a solution to this mess was in 2000, when the ICZN (International Commission of Zoological Nomenclature) designated Iguanodon bernissartensis as the type species of Iguanodon, primarily because this species is known from 37-odd individuals, many of which are complete, whereas I. anglicus was based on several teeth One specimen of I. bernissartensis appeared to be rather more gracile than the others, and was later referred to I. atherfieldensis.
This already sounds confusing, but in practise what tended to happen was that specimens were either referred to I. atherfieldensis if they were relatively slender, and I. bernissartensis for the chunky guys, regardless of how old the specimen was. This is clearly unsatisfactory. Especially as these animals start looking rather different when you look closely and start including the other species in the mix.
In 2006 Gregory Paul separated Iguanodon atherfieldensis into the separate genus Mantellisaurus, in honour of Gideon Mantell. A year later he erected a new genus and species for the Belgian I. atherfieldensis specimen, calling it Dollodon bampingi. Iguanodon lakotaensis was also separated into a new genus (Dakotadon), and I. orientalis regarded as a "Nomen Dubium". He did not attempt to redescribe I. hoggi, I. dawsoni, or I. fittoni and I. hollingtonensis, regarding them as "Iguanodontidae" of uncertain affinity- and possibly not even not particularly close to Iguanodon at all. This was for two reasons, one, they were clearly morphologically distict from each other, and also of a significantly different age. Warm-blooded species tend not to last more than 2 million years, but Iguanodon would have had a range of over 40 million years, spanning most of the northern hemisphere. Which seems unlikely to say the least. Lumping everything together like this masks diversity and evolutionary trends and generally makes it much harder to work out what's really going on. He didn't entirely approve of the ICZN's decision to have I. bernissartensis as the type species, but there isn't a better option, and I agree that its prefereable to have the well known dinosaur from Dollo's iconic reconstruction that is familiar to public and professionals alike for such a historically important genus.
In 2010 David Norman looked at some of the other species that hadn't been officially removed from the genus, "tacitly accepting" Paul's erection of the genus Mantellisaurus, but disagreeing with the separation of Dollodon and Dakotadon, for reasons that he didn't elaborate on other that to say "wait for the paper". "Iguanodon" hollingtonensis and "Iguanodon" fittoni were synonimised into the new genus Hypselospinus fittoni, meaning "high spine" named for the shape of the vertebrae. "Iguanodon" dawsoni was renamed Barilium dawsoni "heavy flank" because, well its got a big arse.
So "Iguanodon" turns out to be far more diverse than you'd first think there's room for at least four, if not six or more genera in there, spanning the gap between the Jurassic camptosaurs to the familiar duck-billed hadrosaurs with their dental batteries, and flamboyant crests. And of course there's the promise of more research to follow, and an interesting (if somewhat esoteric) debate about haow different species have to be before you start putting them in different genera.
Iguandon is one of the world's most famous dinosaurs, and its famous for being one of the first discovered. Initially described from teeth, by Gideon Mantell, it was reconstructed first as a colossal lizard, and then as a rhino-like quadruped with a horn on its nose. Later finds near the town of Bernissart in Belgium allowed Louis Dollo to show that the animal's "horn" was a thumb-spike, and the arms were considerably shorter than the hind limbs, giving the characteristic Fonz-style pose that many people are familiar with. Later work by David Norman, showed that Dollo had dislocated large chunks of the tail and that in fact the animal was largely quadrupedal.
Iguanodon being initially based on relatively poor material, as is so often the case has ended up as something of a "wastebasket taxon", with lots of indeterminate bits and bobs ascribed to it, and several species all lumped together. At the last count there was Iguanodon anglicus / I. mantelli, described by Mantell based on his teeth and other material, the gracile, I atherfieldensis, the Belgian I. bernissartensis, the American species I. lakotaensis, the Mongolian species I. orientalis, and several other species from the UK, I. hollingtoniensis, I. fittoni, I. dawsoni (named after the perpetrator of Piltdown, Charles Dawson), and I. hoggi, often referred to the related genus, Camptosaurus. And that's just the species known from good material, or that have stayed in Iguanodon for more than a few years. There are several other species that are either based on very poor material, that are either undiagnostic, were fairly rapidly shifted into other genera (Iguanodon prestwichi has been happily residing in Camptosaurus for over 100 years now), not from ornithopods, or aren't even dinosaurs.
The beginning of a solution to this mess was in 2000, when the ICZN (International Commission of Zoological Nomenclature) designated Iguanodon bernissartensis as the type species of Iguanodon, primarily because this species is known from 37-odd individuals, many of which are complete, whereas I. anglicus was based on several teeth One specimen of I. bernissartensis appeared to be rather more gracile than the others, and was later referred to I. atherfieldensis.
This already sounds confusing, but in practise what tended to happen was that specimens were either referred to I. atherfieldensis if they were relatively slender, and I. bernissartensis for the chunky guys, regardless of how old the specimen was. This is clearly unsatisfactory. Especially as these animals start looking rather different when you look closely and start including the other species in the mix.
In 2006 Gregory Paul separated Iguanodon atherfieldensis into the separate genus Mantellisaurus, in honour of Gideon Mantell. A year later he erected a new genus and species for the Belgian I. atherfieldensis specimen, calling it Dollodon bampingi. Iguanodon lakotaensis was also separated into a new genus (Dakotadon), and I. orientalis regarded as a "Nomen Dubium". He did not attempt to redescribe I. hoggi, I. dawsoni, or I. fittoni and I. hollingtonensis, regarding them as "Iguanodontidae" of uncertain affinity- and possibly not even not particularly close to Iguanodon at all. This was for two reasons, one, they were clearly morphologically distict from each other, and also of a significantly different age. Warm-blooded species tend not to last more than 2 million years, but Iguanodon would have had a range of over 40 million years, spanning most of the northern hemisphere. Which seems unlikely to say the least. Lumping everything together like this masks diversity and evolutionary trends and generally makes it much harder to work out what's really going on. He didn't entirely approve of the ICZN's decision to have I. bernissartensis as the type species, but there isn't a better option, and I agree that its prefereable to have the well known dinosaur from Dollo's iconic reconstruction that is familiar to public and professionals alike for such a historically important genus.
In 2010 David Norman looked at some of the other species that hadn't been officially removed from the genus, "tacitly accepting" Paul's erection of the genus Mantellisaurus, but disagreeing with the separation of Dollodon and Dakotadon, for reasons that he didn't elaborate on other that to say "wait for the paper". "Iguanodon" hollingtonensis and "Iguanodon" fittoni were synonimised into the new genus Hypselospinus fittoni, meaning "high spine" named for the shape of the vertebrae. "Iguanodon" dawsoni was renamed Barilium dawsoni "heavy flank" because, well its got a big arse.
So "Iguanodon" turns out to be far more diverse than you'd first think there's room for at least four, if not six or more genera in there, spanning the gap between the Jurassic camptosaurs to the familiar duck-billed hadrosaurs with their dental batteries, and flamboyant crests. And of course there's the promise of more research to follow, and an interesting (if somewhat esoteric) debate about haow different species have to be before you start putting them in different genera.