Re: Charles Knight dinosaur calendar

[Tom Holtz <tholtz@geochange.er.usgs.gov>]

>Agathaumas is a ceratopsian which is poorly known according to one of my
>books.  Knight drew it with a long horn at the center front, and two
>short ones at the back left and right, whereas Triceratops has a short
>front horn, and long back ones.

Agathaumas is a very fragmentary specimen, which is probably referrable to
Triceratops, Diceratops, or Torosaurus.  Knight reconstructed it with a
combination of Triceratops skull features and a Monoclonius horn.
[Incidentally, fans of the 1925 silent movie version of The Lost World can
see this illustration come to life, since Knight's reconstructions were
used as the basis for the models.]

>Stegosaurus plates are paired along the back (I believe they are now
>thought to have alternated) and there are four pairs of spines on the
>tail (I thought there was only two).

There is a debate as to whether all species of Stegosaurus had four spines
(as in S. stenops).  Ancestrally, all stegosaurid plates were spines, and
they became progressively more plate-like front-to-back over time.  It is
likely that more primitive species of Stegosaurus may have had four or more
pairs.

Also, we now know that the spikes of Stegosaurus (the "thagomizer") were
directed horizontally outwards and backwards, not upwards (as has been
thought for 120 years).

>Many bipedal dinosaurs are shown very upright, where nowadays I suspect
>most of them would be depicted with the spine much closer to horizontal
>(e.g. Hadrosaurus, Anatosaurus aka Anatotitan aka Edmontosaurus,
>Tyrannosaurus and Allosaurus)

The hadrosaurs in question are definitely Anatotitan, based on the mounts
of the type skeleton and a referred skull (or is it the other way around?)
at the American Museum of Natural History in New York City.

>Most of the dinosaurs look quite sluggish, and some of them are
>downright obese (especially Agathaumas and Stegosaurus).  The exception
>is a picture of two Dryptosauruses having a scrap.  (These are
>small (medium?)-sized carnivores)  They look very agile and nasty.

Large!  The femur of Dryptosaurus is 787 mm, comparable to Megalosaurus or
a mid-sized Allosaurus.

[Dryptosaurus is known from the second best theropod skeleton (and only
large theropod skeleton) to come out of the East Coast of the U.S.  The
best theropod skeleton, the type of Podokesaurus holyoakensis (?=
Coelophysis? Syntarsus? Procompsognathus? Segisaurus?) was destroyed in a
fire years ago.  Unfortunately, the surviving casts are not particularly
good, so the relationships of this Early Jurassic theropod to other small
primitive theropods is currently in question.]

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.