Welcome, Hippodraco and Iguanacolossus!

Iguanodonts certainly have been a fertile ground for study lately - for a short summary, check out Darren Naish's excellent posts here, here, and here. Although the European iguandonts (such as the classic Iguanodon) get much of the attention, their North American cousins were also apparently pretty speciose.

Today, a new study headlined by the University of Pennsylvania's Andrew McDonald names two genera and species from the Early Cretaceous-aged Cedar Mountain Formation of Utah - Iguanacolossus fortis and Hippodraco scutodens (pictured below). [full disclosure: I was the academic editor at PLoS ONE who handled this manuscript]

Hippodraco scutodens (left) and Iguanacolossus fortis (right); modified from original artwork by Lukas Panzarin, in McDonald et al. 2010. Scale bar equals 1 m.

Each animal is known from a rather nice partial skeleton, allowing relatively confident phylogenetic placement of the two animals. McDonald and colleagues did a fantastic job describing and illustrating both taxa; all of the known elements are shown in some detail, which will be a huge help for other researchers who may not have easy access to the original material in Salt Lake City. The PDF weighs in at 35 pages, and 39 high resolution figures can be downloaded from the PLoS ONE web page for the paper.

Although there are already three other iguanodonts named from the Cedar Mountain Formation (Eolambia caroljonesa, Planicoxa venenica, and Cedrorestes crichtoni), McDonald lays out substantive morphological and geological evidence for the distinctness of the new taxa. Odds are good that there will be (or are) differing opinions from other paleontologists, so I suspect we're going to be hearing much more about the Cedar Mountain iguanodonts in the near future!

Citation
McDonald AT, Kirkland JI, DeBlieux DD, Madsen SK, Cavin J, Milner ARC, Panzarin L (2010) New basal iguanodonts from the Cedar Mountain Formation of Utah and the evolution of thumb-spiked dinosaurs. PLoS ONE 5(11): e14075. doi:10.1371/journal.pone.0014075