Hadrosauridae

   The hadrosaurids come in two basic varieties; hollow-crested and non-hollow-crested.  At each of these levels, there are several groups, but this page will not cover them, because there is quite a bit of housekeeping to do before we get there, namely, slogging through the indeterminate members (interestingly, once a piece of petrified wood was described as being hadrosaurid remains [Aachenosaurus]).  If you want to skip this page, I don't blame you (although I have a soft spot for Claosaurus; it was one of the first obscure dinosaurs I learned about, back around the late 1980s-early 1990s, from an article in a kid's magazine about dinosaurs).  
    Additional basal hadrosaurid material is known from the late Santonian (LK) of Italy, the mid Turonian (LK) of Alaska, late Maastrichtian (LK) of Spain and possibly Antarctica.  In addition, a hadrosaurid femur discovered in New Mexico may be evidence that some dinosaurs were able to make it into the earliest part of the Paleocene, just beyond the K-T boundary, although most authorities consider it to have been reworked from older sediments.  

<--Hadrosauridae
      |--Bactrosaurus
      |--Gilmoreosaurus
      `--+--Telmatosaurus
          `--+--Pararhabdodon
               `--Euhadrosauria
                    |-->Hadrosaurinae
                    `-->Lambeosaurinae

Hadrosauridae:  Hadrosaurids were long thought to have lived in water, another set of victims of the mindset that condemned sauropods as well to the watery regions.  In the case of hadrosaurids, they were they because they were supposedly swimmers, as shown by their tall tails and "webbed" hands found on "mummies," and because their teeth seemed weak  However, it turned out the tail was very inflexible due to bony tendons, and the webs of the hands were shown to be dried-out cushions for the hands.  As for the teeth, that is a patent lie.  Hadrosaurids were very well adapted to feed at low levels on land, much like bison.  Their backs even show a striking resemblance to the way bison spines are curved.  The best analogue for a hadrosaurid would have to include this low-browsing ability with a hint of the bewildering variety of display devices hadrosaurids were equipped with.  Many hadrosaurids are known to have lived in groups, possibly not true herds, but groups nonetheless.  In fact, it has been suggested that one mass "grave" of Maiasaura contains the remains of a gathering 10,000 individuals strong.
        Hadrosaurids show some sort of unusual midline spinal phenomenon.  Some appear to have dragon-like rectangular nonbony segments running down the midline of the back, while others suggest a deep, horse-like muscular neck.  Hadrosaurids appear to have had rather thin, leathery skin, with large polygonal or oval tubercles surrounded by many smaller ones.  The scale patterns may have some diagnostic value.
        It is an unfortunate fact that without a decent skull, it is hard to differentiate most hadrosaurids, due to the basic overall similarity of the skeletal plan.  Lambeosaurines can be told from hadrosaurines in some elements, such as the hip bones and height of the neural spines (many lambeosaurines have slight "sails" down the back), but that is about as far as one can go with separating hadrosaurids from postcranial material at this point; people are looking for differentiating characters, though.  Ceratopids have a similar problem, but probably worse, as the frill is necessary as everything else is pretty much the same across taxa, and the frill didn't come in until the animal was nearly an adult. 

Hadrosauridae i.s.:

Hadrosaurinae and Lambeosaurinae:  These two groups are the derived hadrosaurids.  They have some of the best fossil records of any dinosaurs, with skulls and skeletons known for most taxa.