Iguanodontidae

["Jaime A. Headden" <qilongia@yahoo.com>]

  Recently this thread has taken a satisfying turn: discussing
the species complex for *Iguanodon.* Now to add some of my
thoughts:

  *"Iguanodon" lakotaensis* --
      I would like to second the thought that the Lakota/Dakota
    iguanodont is not *Iguanodon*, but perhaps a transitional
    form between *Camptosaurus* and *Iguanodon*, or as a
    camptosaurid, and a late surviving one at that.

  *"Iguanodon" hoggi* --
      Norman presented interesting evidence that suggests this
    species, based on the form of the crown and position and
    count of the ridges, that the type, a tooth, belongs to a
    camptosaurid.

  Polyphyletic *Iguanodon* --
      Darren Nasish suggests that *I. bernissartensis* had a
    floating generic name, but this is now quite impossible
    since it is now the type species of *Iguanodon*.
      What is curious is the possibility of *I.
    atherfieldensis*, like *Ouranosaurus*, to be a hadrosauroid,
    and thus possible to receive it's own new generic name, and
    at first this would seem to be untenable, though preferable,
    because three other genera have been sunk into the hypodigm;
    *I atherfieldensis* is the type species, and as such, any
    genus sunk under it is _sunk_, unless one of the junior
    genera were considered to have valid type material.
      There was a suggestion of sexual dimorphism between *I.
    bernissartensis* and *I. atherfieldensis*, but this is
    ridiculously impossible, the form, anatomy of the wrist and
    forelimb and hindlimb between the two are completely
    different.

  A Possible Phylogeny:

  --+--Dryosauridae
    `--+--Camptosauridae
       |   |--*Camptosaurus*
       |   |   |--*C. dispar*
       |   |   `-?-*"C." prestwichii* [?]
       |   |--*Draconyx*
       |   `-?-*"I." hoggi*
       `--+-?-*"I." lakotaensis*
          `--+--Iguanodontidae
             |   |--*Iguanodon*
             |   |   |--*I. bernissartensis* [type]
             |   |   |--*I atherfieldensis*
             |   |   `--*I. anglicum* [nom. dub.]
             |   |--*Altirhinus*
             |   `--*Lurdusaurus* [= "Gravisaurus"]
             `--+--*Ouranosaurus*
                `--+--*Probactrosaurus*
                   `--+--*Lophorhothon*
                      |--*Telmatosaurus*
                      `--Hadrosauroidea [all hadrosaurs]

  Thus, there may still be a mono/holophyletic Iguanodontidae,
inspite of "classic" iguanodonts being removed. Personal
observation suggests to me that *Altirhinus kurzanovi* is not
anywhere closer along the lineage to *Hadrosaurus* than
*Iguanodon* is. There are also suggestions that *C. prestwichii*
is a possibly *"I." lakotaensis*-level iguanodont, and may serve
to have a new generic name, as should *"I." lakotaensis*.

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