You have, no doubt, committed to memory all of the bones of the basic reptilian skeleton. These are very important to today's work. In case your dog ate your lecture handout with all this information on it, it has been included in today's lab handout. Before you begin the questions, take a moment to familiarize yourself with the terminology again.
Take a look at the "Tree of Life" website, (http://tolweb.org/tree?group=life).
By clicking on the following links in order you can trace the history of
life, essentially the cladogram, from the chordates to the dinosaurs. Make
some sidetrips on the way! The links from the above webpage are: Chordata,
Craniata, Vertebrata, Gnathostomata, Sarcopterygii, terrestrial vertebrates,
Amniota, Diapsida, Archosauromorpha, Archosauria, Dinosauria.
c) suborbital fenestra
d) upper and lower temporal fenestrae
e) antorbital fenestra
f) mandibular fenestra
b) pectoral girdle
c) forelimb & hand
d) hindlimb & foot
In this section we will examine specifically the relationship between the two major groups within the Dinosauria - the Saurischia and the Ornithischia - by comparing skeletal characters. Remember: Crocs + dinosaurs (including birds) = Archosauria.
The following is a list of shared derived characters for Dinosauria, Ornithischia, and Saurischia. Keep in mind that the ornithischians and saurischians are equivalently-ranked sister taxa within the dinosaurs.
minimum of 3 sacral vertebrae
long, s-shaped neck
offset digits 1 and 5 on hand
manus digit 2 longest
backward, splint-like pubis
Figure 1: lab_06_fig_1_fenestrae.pdf
Figure 2: lab_06_fig_2_skulls_1.pdf
Figure 3: lab_06_fig_3_skulls_2.pdf
Figure 4: lab_06_fig_4_skulls_3.pdf
Figure 5: lab_06_fig_5_girdles.pdf
2. Compare the skeletons of Allosaurus and the pigeon. Sketch the features from the above tables, labeling the bones, and describe the morphological changes needed to get from the primitive saurischian to avian condition.
3. Construct a cladogram including the pigeon, Allosaurus, Archaeopteryx (see diagram), and Thescelosaurus. Choose a 5th taxon from section 1 of this lab to use as your outgroup. Label the synapomorphies and autapomorphies for each taxon. There will be more than 1 for each taxon.