Marine Bio Homework, Week 2: Creating a Dichotomous Key

First, I picked 12 items in a similar group.  Not surprisingly, since I want to be a paleontologist, I picked dinosaurs: Triceratops horridus, Tyrannosaurus rex, Stegosaurus stenops, Velociraptor mongoliensis, Diplodocus longus, Ankylosaurus magniventris, Coelophysis bauri, Pachycephalosaurus wyomingensis, Edmontosaurus annectens, Microraptor gui, Archaeopteryx lithographica,  and Allosaurus fragilis.

Next, I made a dichotomous key:

1.  a) bipedal ..................2
     b) quadrupedal...........8

2. a) has 3 or fewer digits on hind feet......3
    b) has more than 3 digits on hind feet.... Pachycephalosaurus wyomingensis.

3. a) has wings.........4
    b) lacks wings......5

4. a) has flight feathers on fore- and hind- limbs...... Microraptor gui
    b) lacks flight feathers on hind limbs....... Archaeopteryx lithographica

5. a) has 2 digits on forelimbs...................... Tyrannosaurus rex
    b) has more than 2 digits on forelimbs.....6

6. a) has 3 digits on forelimbs..............7
    b) has more than 3 digits on forelimbs.... Coelophysis bauri

7. a) has a hyperextensible digit on hind limbs
        (a claw bigger than the other toes on its foot)......Velociraptor mongoliensis
    b) lacks a hyperextensible digit on hind limbs.........Allosaurus fragilis

8. a) has plates on its back along the spine.......Stegosaurus stenops
    b) lacks plates on its back along the spine....9

9. a) has horns....... Triceratops horridus
    b) lacks horns..... 10

10. a) has armor (osteoderms).............Ankylosaurus magniventris
      b) lacks armor.................................11

11.  a) has an extremely long neck in proportion to its body......Diplodocus longus
       b) lacks an extremely long neck in proportion to body size....Edmontosaurus         annectens

Here is a picture of one of these creatures to try to identify using the key I made:

Image by: Jaime A. Headden (User:Qilong) - http://qilong.deviantart.com/art/It-Lives-Velociraptor-24578261?q=gallery%3AQilong%2F5004771&qo=83, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=31697111