Iguanodontia

   Iguanodontia includes the "iguanodonts" and the hadrosaurids.  There are two general types of iguanodonts; small and large.  Small iguanodonts, including the dryosaurids, look not too dissimilar to hypsilophodonts.  Large iguanodonts, like Iguanodon, typically show quadrupedal tendencies, and sometimes have well-developed spikes for thumbs.  They have robust, subrectangular skulls, with some modest flaring of the beak that becomes the "duck-bill" hadrosaurids are so known for.  Many iguanodonts have lost the first toe as well.  The jaws also begin to show the dental batteries and spreading ability, which in function converge with the chewing ability of mammals, that hadrosaurids have fully developed.  Some have prominent extensions of the neural spines, giving them buffalo-like hump-back looks, including an unnamed taxon from Utah, and Ouranosaurus.  There is a bewildering array of names that can be applied to the levels here, but I'll only use a few.

<--Iguanodontia
      |--Tenontosaurus
      `--+--Muttaburrasaurus
           |--Rhabdodontidae
           |   |--Mochlodon
           |   |--Rhabdodon
           |   `--Zalmoxes
           `--+--?Talenkauen
                `--+--?Anabisetia           
                     |--Dryosauridae
                     |    |--Dryosaurus
                     |    `--Valdosaurus
                     `--Ankylopollexia (refers to the big ol' spiked thumbs)
                          |--Camptosauridae
                          |    `--Camptosaurus
                          `--Iguanodontoidea
                               |--Iguanodon
                               `--+--Mantellisaurus
                                    `--+--Ouranosaurus
                                         |--+--Altirhinus
                                         |    `--Eolambia
                                         |--?Fukuisaurus
                                         `--+--Protohadros
                                              `--+--Probactrosaurus
                                                   `--+--Nanyangosaurus
                                                        `--+--Shuangmiaosaurus
                                                             `-->Hadrosauridae

Iguanodontia: Basal Iguanodontia is a home for misfits, it seems; there is the hypsilophodont-like Rhabdodon and its allies, the "iguanodontid"-like Muttaburrasaurus, and the long-tailed oddball Tenontosaurus, among others.  The ordering is a bit controversial, and goes back and forth with which taxon is put at the base of Iguanodontia.

Taxon or Taxa: Time\Place: Comments:
Tenontosaurus: Ostrom, 1970 T. tillettorum (type) Ostrom, 1970 Aptian-Albian (EK) of Montana, Oklahoma, Texas, Utah, and Wyoming Long-tailed, tall-spined Tenontosaurus is known from dozens of specimens of all ages.  It seems to have been a favorite food source for Deinonychus.  At times classified as a hypsilophodontid, at times as an iguanodontid, it seems to be between the two.  It probably was mostly quadrupedal.  Other species may be found in the copious material referred to the type species.
?T. dossi Winkler, Murray, and Jacobs, 1997  late Albian (EK) of Texas T. dossi is more basal than the type, and is pretty long, on the order of 7 to 8 meters (not that the type species is any slouch).  It may end up in its own genus.
Muttaburrasaurus langdoni Bartholomai and Molnar, 1981 Albian (EK) of Australia Muttaburrasaurus is one of Australia's better-known dinosaurs.  Superficially, it is very much like advanced iguanodontids, but in many ways it is actually very basal, and possibly is related to the hypsilophodont Atlascopcosaurus.  It has a prominent, unusual rise on the nose, and has very odd teeth.  Some researchers have suggested it was partially carnivorous.
Talenkauen santacrucensis Novas, Cambiaso, and Ambrosio, 2004 Maastrichtian (LK) of Argentina From a new locality in southwestern Patagonia, Talenkauen is an iguanodontian known from a skeleton minus the tail, part of the ischia and pubes, hands, and ulnae.  Probably on the order of 4 m long, it looked a lot like a dryosaurid, with an elongate neck and smallish head, but with long slender arms and a robust prepubic process.  The most striking character is the presence of lateral plates along the ribs that the authors consider uncinate processes.  At any rate, these thin plates are so far only found also in Thescelosaurus, but given their thin, fragile nature, they could well have had a wider distribution in the ornithopods.  They may have been related to respiration.  
Anabisetia saldiviai Coria and Calvo, 2002 Cenomanian-early Turonian (LK) of Argentina Anabisetia is a new iguanodontian, based on a partial skull, parts of four cervicals, four dorsals, four sacrals, a dozen caudals, most of both shoulders and arms, and most of a leg.  At least three more individuals are known, each about two meters in length.  It is more derived than Gasparinisaura.

Iguanodontia i.s.:  Several unnamed iguanodontians are known from the Cedar Mountain Formation, including a possible hadrosaurian. 

Taxon or Taxa: Time\Place: Comments:
Bihariosaurus bauxiticus Marinescu, 1989 ?Berriasian-?Hauterivian (?EK) of Romania This animal is an iguanodontian, possibly close to Camptosaurus.
Dakotadon lakotaensis Paul, 2008 (originally Iguanodon lakotaensis Weishampel and Bjork, 1989) mid Barremian (EK) of South Dakota Dakotadon is a much better supported North American possible Iguanodon species than "I." ottigeri, albeit without the cool "high-spined iguanodont" lurking in the background.  It is based on a partial skull that, like Theiophytalia, seems to speak of an intermediate point betwixt Camptosaurus and Iguanodon. 
?"Gadolosaurus" (N.N.) Saito, 1979 ?K of Mongolia This is an undescribed ?hadrosaurid, based on a (heavily-restored) juvenile specimen.  It may be a juvenile of Arstanosaurus, or it may be closer to Camptosaurus or Iguanodon.
?"Gilmoreosaurus" atavus (N.D.) Nessov, 1995 late Albian (EK) of Central Asia This is either a very early hadrosaurid, or yet more basal iguanodontian, based on teeth.
"Iguanodon": "I." dawsoni (?N.D.) Lydekker, 1888 mid Valanginian (EK) of England "I." dawsoni and "I." fittoni are based on vertebral elements and distinctive pelves from earlier in the Cretaceous than the famous I. bernissartensis\I. atherfieldensis (Mantellisaurus) duo.  Neither of them are particularly well known, although their pelves don't appear to be as derived as those of Iguanodon or Mantellisaurus.
"I." fittoni (?N.D.) Lydekker, 1889
"I." orientalis (N.D.) Rozhdestvensky, 1952 Aptian-Albian (EK) of Mongolia "I." orientalis is based on a maxilla, ribs, and a scapula.  For a while, the skull now named Altirhinus was thought to be a specimen, but obviously no longer is.  It may be a specimen of I. bernissartensis (if its name was Marco Polo, I suppose), but the scrappy remains are not notably different from those of most dinosaurs of the iguanodontian persuasion.
"I." ottigeri (N.D.) Galton and Jensen, 1979 early Aptian (EK) of Utah Based on teeth, this dubious Iguanodon species is sometimes seen named in connection with an undescribed high-spined iguanodontian from the same time and place.
Macrogryphosaurus gondwanicus Calvo, Porfiri, and Novas, 2007 Turonian-early Coniacian (LK) of Argentina Macrogryphosaurus is a basal iguanodontian akin to Talenkauen (even including those odd lateral plates on the rib cage), known from postcranial remains.
Planicoxa:
DiCroce and Carpenter, 2001		 P. venenica (type) DiCroce and Carpenter, 2001 mid Aptian (EK) of Utah A new Cedar Mountain Formation iguanodontian, Planicoxa (with its interesting name, to me reminiscent of a plant) is known from an ilium, vertebrae, and partial fore and hind limbs, belonging to at least two individuals.
P. depressa (Gilmore, 1909 [originally Camptosaurus] Barremian (EK) of South Dakota Long known as Camptosaurus depressus, the species of Camptosaurus that no one ever talked about (it seems that no one ever talks about C. prestwichii, either, but it at least has the "English camptosaur" point in its favor), it is more similar to Planicoxa in the low depressed form of its ilium than it is to Camptosaurus. 
Theiophytalia kerri Brill and Carpenter, 2006 Aptian-Albian (EK) of Colorado The so-called "Garden of the Gods" iguanodont, Theiophytalia is based on a partial skull (muzzle, cheek, and caudal half of the lower jaw, essentially) that seems akin to Dakotadon and somewhere between Camptosaurus (which it used to stand in for, until it was realized that the skull wasn't from the Morrison but from younger rocks) and Iguanodon.

Rhabdodontidae: Rhabdodontids were not unlike robust, oversized hypsilophodonts, with deep skulls and jaws that were distinctly triangular in top view.

Taxon or Taxa: Time\Place: Comments:
Mochlodon suessi (Bunzel, 1871 [originally Iguanodon]) ?early Campanian (LK) of Austria Recent research suggests that Mochlodon is a separate taxon from Rhabdodon.  Otherwise, it's not too dissimilar from the other rhabdodontids.
Rhabdodon priscus Matheron, 1869 Maastrichtian (LK) of France and Spain Rhabdodon has gone through a complicated taxonomic history.  It may be found in older works under the name Mochlodon Seeley 1881.  Rhabdodon material is fairly common, but disarticulated.
In the past, it has been regarded as an iguanodontid or a hypsilophodontid, although it now seems to be closest to animals like Tenontosaurus. 
A species named R. septimanicus Buffetaut and Le Loeuff 1991 is here tentatively regarded as a synonym of the type species.
Zalmoxes:
Weishampel, Jianu, Csiki, and Norman, 2003		 Z. robustus (type)  (Nopcsa, 1899 [originally Mochlodon]) early-mid Maastrichtian (LK) of Romania Zalmoxes provides a new genus for the suddenly prolific rhabdomorphs, as they are sometimes known informally.  No, the name of the second species is not a typo, but if you were ever playing Paleo Scrabble, it would be a good name to remember to get rid of the "q" (heck, if you were playing some renegade version where you got a couple dozen letters, adding the genus name would probably win the game outright.  Or, you could just skip the species name and use Zalmoxes.). 
Z. shqiperorum Weishampel et al., 2003 early-mid Maastrichtian (LK) of Romania

Dryosauridae:  Dryosauridae is composed of several closely-knit taxa, which broadly resemble large hypsilophodonts.  Annoyingly, there is a group of crocodilians known as dyrosaurids; be careful not to confuse them on websites!

Taxon or Taxa: Time\Place: Comments:
Dryosaurus: Marsh, 1894 D. altus (type) (Marsh, 1878 [originally Laosaurus]) Kimmeridgian (LJ) of Colorado, Utah, and Wyoming D. altus is known from remains including one virtually complete skeleton, and juvenile material. Like D. lettowvorbecki, its skull does not completely encircle the two nostril openings.
D. lettowvorbecki (Virchow, 1919 [originally Dysalotosaurus]) Kimmeridgian (LJ) of Tanzania Its specific name coming from a WWI German general's name, and its original generic name meaning "uncatchable lizard," it seems a political message is concealed within the name.  D. lettowvorbecki is known from a large amount of disarticulated material.  Future restudy may indicate it once again deserves to be in its own genus, Dysalotosaurus.
Valdosaurus: Galton, 1977 V. canaliculatus (type) (Galton, 1975 [originally Dryosaurus]) Berriasian-Barremian (EK) of England and Romania This taxon is known mostly from limb and jaw material.  What is known links it with Dryosaurus.  A fair amount of referred material is known, mostly for the hindlimbs, hips, and skull.  Some material suggests individuals on Iguanodon atherfieldensis-scale (indeed, among material simply referred to Iguanodon may be iganodontoids, camptosaurs, and "rhabdomorphs") .
V. nigeriensis Galton and Taquet, 1982 late Aptian (EK) of Niger V. nigeriensis is known from femora of the dryosaurid type.

Dryosauridae i.s.:

Taxon or Taxa: Time\Place: Comments:

Callovosaurus leedsi Galton, 1980 (originally Camptosaurus leedsi Lydekker, 1889)

 mid Callovian (MJ) of England Once thought to be a hypsilophodont or camptosaurid, this basal iguanodontian is known from a partial femur.  Its age makes it important in dating the earliest known extent of Iguanodontia.
Kangnasaurus coetzeei (N.D.) Haughton, 1915 EK of South Africa This is an indeterminate dryosaurid, based on teeth.  Dryosaurid postcranial material is known from the area, and may belong to it.

Camptosauridae:  Camptosauridae, like Iguanodontidae, may not really exist as a monophyletic group.

Taxon or Taxa: Time\Place: Comments:
Camptosaurus: Marsh, 1885 C. dispar (Marsh, 1879 [originally Camptonotus]) Kimmeridgian (LJ) of Colorado, Oklahoma, Utah, and Wyoming C. dispar is known from dozens of specimens.  Although often thought of as an archetypical Morrison dinosaur, it is rather rare.  Also, the trademark rectangular skull actually was a composite of actual Camptosaurus material, Theiophytalia kerri's skull (thought to be from the Morrison, but actually Early Cretaceous in age), and some jiggering to get the sections to fit.  New skull material gives it a more triangular, basal look, something a bit more like Dryosaurus, and with long thin palpebrals.
C. aphanoecetes Carpenter and Y. Wilson, 2008 Tithonian (LJ) of Utah With the 2006 publication of a Camptosaurus skull that contained less than 50% accidentally reprocessed Theiphytalia, and the concurrent renovation of the Carnegie's dinosaur exhibits, the Dinosaur National Monument specimens of Camptosaurus were reevaluated by Carpenter and Wilson and found to differ from C. dispar in a variety of proportions.
?C. prestwichii (Hulke, 1880 [originally Iguanodon]) Kimmeridgian (LJ) of England C. prestwichii is somewhat more generalized than the type species.  It is one of the few examples of a Morrison dinosaur having another species in Europe.  It may belong in its own genus, Cumnoria.

Camptosauridae i.s.:

Taxon or Taxa: Time\Place: Comments:
?Brachyrophus altarkansanus (N.D.) Cope, 1878 (?Camptosaurus) Kimmeridgian (LJ) of Colorado Originally considered a sauropod, Brachyrophus may well be the same animal as Camptosaurus.  Interestingly, if it is, its name predates that of Camptosaurus, making it technically the senior synonym, although the fact that it has been generally ignored while Camptosaurus has become a well-known name means that it is likely any attempt to change the name will be rejected.  Incidentally, the only reason I have it here, instead of Ornithischia i.s. or something like that, is because of the likelihood it is the same as Camptosaurus.
Draconyx loureiroi Mateus and Antunes, 2001 late Kimmeridgian-early Tithonian (LJ) of Portugal Recently named from the partial remains of a single individual, mostly pertaining to the limbs (best material from the hindlimbs), Draconyx is a new member of the Lourinha fauna, related to Camptosaurus.
"Iguanodon" hoggii Owen, 1874 ?Berriasian (EK) of England For a long time considered to be the earliest occurrence of Iguanodon, this animal has now been shown to be closer to Camptosaurus; indeed, some researchers now refer it to Camptosaurus.  I'm going to wait a bit longer before doing that, especially since other work is going on with the Morrison camptosaur material.

Iguanodontoidea: Many of these basal iguanodontoids were once classified as iguanodontids, but while they are similar to Iguanodon, they are not in the same family; rather, they are in the line leading to hadrosaurids.

Taxon or Taxa: Time\Place: Comments:
Iguanodon bernissartensis Mantell, 1825 (type species after Boulenger, 1881) Barremian-early Aptian (EK) of Belgium This is going to be a little awkward, since there's a decent chance that most or all of the Iguanodon species deserve to be together as Iguanodon, and a decent chance that they don't, but we're all used to talking about them together.  For safety, after removing I. atherfieldensis into Mantellisaurus, I decided to pull the other species out into Iguanodontia i.s..  Honestly, when was the last time you cared about I. fittoni or I. dawsoni?  The way I'll think about it is that I. atherfieldensis was due to be split by someone, Mantellisaurus is just as good a name as any to recognize that, Iguanodon should just be thought of as the famous I. bernissartensis material, and I. lakotaensis is the weird American one.
Iguanodon was one of the three founding members of Sir Richard Owen's Dinosauria.  Originally, it was restored somewhat like the iguana it was named for, as a giant lizard with a horn on its nose (which turned out to be a thumb spike).  Then, after the Belgian finds of the late 1800s, a tripodal kangaroo-like posture came to be favored.  Finally, it has become a quadruped since about the 1980s, most notably in Disney's Dinosaur. 
Although Iguanodon gets the fame for being a founding member, the original type material was pretty poor (teeth, if your memory serves you well), and given the potential for taxonomic weirdness, the name was recently shifted to a specimen of I. bernissartensis.    
I. bernissartensis is known from 26 skeletons and much partial and isolated material, including the famous Bernissart quarry, where at least 32 individuals were found.  It is much more robust than Mantellisaurus and Dollodon, with long massive forelimbs (and a hadrosaurid-length body of 10 to up to 13 meters), while Mantellisaurus was much shorter, at around 6 to 7 meters in length, and likely a lower browser.  Iguanodon is more common in Belgium, with Dollodon the local gracile genus, but the gracile Mantellisaurus is more common in England.
It has occasionally been suggested that Mantellisaurus and I. bernissartensis are the two sexes of one species, but this now appears to be an untenable position.  
Mantellisaurus atherfieldensis Paul, 2006 (originally Iguanodon atherfieldensis Hooley, 1924) early Aptian (EK) of England To continue from above: this is the "gracile (skinny, slim, fine-boned, what-have-you) Iguanodon".  A taxon named Vectisaurus was once thought to be different because of its tall neural spines, but now appears to be a specimen of this similarly tall-spined animal.
Although I. atherfieldensis probably needs its own generic name, precisely which name to use is a frustrating matter: literally, it is the youngest of several probable synonyms, which is not supposed to happen.  Apparently, several goes were made at naming the "gracile iguanodont", including I. mantelli (Meyer, 1832; a misinterpretation, as it was based on the same material as I. anglicus, but became used for the gracile Bernissart iguanodont now known as Dollodon), Heterosaurus neocomiensis (Cornuel, 1850), Sphenospondylus gracilis (Lydekker, 1888), and the above-mentioned Vectisaurus valdensis (Hulke, 1879), and I. atherfieldensis is just based on the best material.  We'll see how that flies in the next few years (this must be like waiting for someone to challenge the constitutionality of a law), but Mantellisaurus is a good start. 
Ouranosaurus nigeriensis Taquet, 1976 late Aptian (EK) of Niger Ouranosaurus is most famous for its well-developed ridge-back, much like that of some spinosaurids.  It had a sort of knob right in front of the eyes.  A couple of good skeletons are known.
Altirhinus kurzanovi Norman, 1998 late Aptian-early Albian (EK) of Mongolia Based on material once referred to the now-defunct taxon Iguanodon orientalis, this iguanodontoid had a prominent nasal arch.
Eolambia caroljonesa Kirkland, 1998 latest Albian-earliest Cenomanian (EK-LK) of Utah Once thought as to be the earliest known hadrosaurid (but not the most generalized-Protohadros had that honor), this was originally going to be called "Eohadrosaurus caroljonesi" before its supposed lambeosaurine affinities were clear (more recent work suggests it is a more basal iguanodontian).  Several individuals are known, and their remains make up most of a skeleton.
?Fukuisaurus tetoriensis Kobayashi and Azuma, 2003 late Hauterivian-Barremian (EK) of Japan Having been first referred to informally back in 1990, Fukuisaurus finally joins the ranks of the described.  It is based on cranial material, including a deep lower jaw, and seems to have secondarily lost the cranial flexibility of other derived ornithopods, although it's hard to imagine why, given the usefulness of its proposed function providing an analogue to chewing.
Protohadros byrdi Head, 1998 Cenomanian (LK) of Texas This recently-described dinosaur, based on a skull and some postcranial bits, was first described as the most basal hadrosaurid yet discovered, but it now appears to be a derived non-hadrosaurid iguanodontian.  It has an unusually large lower jaw.
Probactrosaurus gobiensis Rozhdestvensky, 1966 (including P. alashanicus Rozhdestvensky, 1966) Barremian-Aptian (EK) of China Probactrosaurus is the sort of animal that would be expected as the ancestor of the hadrosaurids (made explicit in the name: "before Bactrosaurus"), if the material has been interpreted correctly.  It has a plain iguanodont skull, without crests or knobs.
Nanyangosaurus zhugeii Xu, Zhao, Lu, Huang, Li, and Dong, 2000 ?Albian (EK) of China This animal, based on a partial postcranial skeleton, appears to be just basal to the true hadrosaurids.
Shuangmiaosaurus gilmorei You, Ji, Li J., and Li Y., 2003 Cenomanian-Turonian (LK) of China Described as the sister taxon to Hadrosauridae, Shuangmiaosaurus is based on partial remains of the upper and lower jaws.

Iguanodontoidea i.s.:

Taxon or Taxa: Time\Place: Comments:
Cedrorestes crichtoni Gilpin, DiCroce, and Carpenter, 2006  early Aptian (EK) of Utah Based on a sacrum, one complete ilium and a chunk of the other, a right tibia and 3rd metatarsal, ribs, and the inescapable ossified tendons always to be found with ornithopod skeletons consisting of more than bits and pieces, Cedrorestes is a contender for oldest basal hadrosaurid.  This assessment is based on features of the ilium, especially the presence of an antitrochanter (a lateral knob on the caudal portion of the ilium that hadrosaurids have but their more basal cousins lack).  I'm a little wary of basing classifications on one character, and of basalmost hadrosaurids (Eolambia and Protohadros, anybody?), so I'll put it here for the time being. 
Dollodon bambingi Paul, 2008 Barremian-early Aptian (EK) of Belgium This is the gracile Bernissart iguanodont, long known as I. mantelli or I. atherfieldensis.  Gracile like Mantellisaurus, it is however not the same animal as had been thought.
Equijubus normani You, Luo, Shubin, Witmer, Tang Z., and Tang F., 2003 Albian-?Cenomanian (EK-?LK) of China Very little has yet been revealed on this possible basal "hadrosaurian," but I could not let such a great name go by unnoticed.  A short-snouted skull and partial postcranial remains are known.  It is said to be similar to Altirhinus and Jinzhousaurus.
Jinzhousaurus yangi Wang and Xu, 2001 ?mid-?late Barremian (EK) of China A new Yixian dinosaur, although not from the same level that has produced so many feathered finds, Jinzhousaurus is a large (~7 m long) iguanodontian based on material including an almost complete skeleton and skull that show an odd mix of basal and derived characters.  It apparently is not as close to hadrosaurids as Probactrosaurus.
Lanzhousaurus magnidens You, H., Q. Ji, and D. Li, 2005 EK of China This iguanodontian just came out, and as yet is still mysterious to me.  As others have noticed, a Google search brings up a picture of a skeletal mount of a big ornithopod, certainly iguanodont-grade, as revealed by its astonishingly huge teeth (hadrosaurids have much smaller teeth).  The mount is misleading, as only a lower jaw, teeth, some cervicals and dorsals, ribs, sternal elements, and both pubic bones are known.  From what is known, a hadrosaurid length (~10 m, 33 ft) is suggested; a rather tubby mass of 5.5 metric tons is also suggested, which seems off given that most hadrosaurids of the same length are thought to have massed more like 2-3 metric tons.
Lurdusaurus arenatus Taquet and Russell, 1999 late Aptian (EK) of Niger Having long gone under the informal name "Gravisaurus tenerensis" (Chabli, 1988), this animal was one of the most heavily-built iguanodontians.  It has been compared to the prehistoric giant ground sloth.
Remains of two individuals of this unusual iguanodontian are known.  It may have gotten to be around 9 meters long, with short hindlimbs and stout forelimbs armed with enlarged thumb spikes, making their arms like maces. 
Penelopognathus weishampeli Godefroit, Li, and Shang, 2005 Albian (EK) of Mongolia This new iguanodontoid, based on a long, low right dentary (most iguanodontoids tend to have short, robust lower jaws), may be more derived than Altirhinus but less than Probactrosaurus based on dental characters.
"Probactrosaurus" mazongshanensis Lu, 1997 Barremian (EK) of China Based on fragmentary remains, this species seems to be closer to Altirhinus than to Probactrosaurus.

Hadrosauridae:  Hadrosauridae is the group comprising the "duck-bills."  It also is literally swamped in names given to indeterminate remains.

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