Dichotomous Key

Looking at my pocket guide to these monstrous creatures, they seem so real! I’ve organized them into trees in two different ways, but there’s just one I haven’t caught yet…

1a. Derived from biflagellate ancestor - go to 2
1b. Derived from uniflagellate ancestor - go to 3

2a. Flower ~1m in diameter with five petals, bearing foul odour - P
2b. Inflorescence ~30cm in diameter with bright yellow ray florets - G

3a. Fruiting body brown in colour and up to 9cm in diameter, resembling a ruffled collar around a ball - E
3b. Lack of cell wall - go to 4

4a. Y-shaped horn, dark brown, functional wings beneath elytra - A
4b. Anus or cloaca formed from blastopore during development - go to 5

5a. Pentameral symmetry - go to 6
5b. Bilateral symmetry - go to 7

6a. Long spines solid black or slightly bluish in colour - D
6b. Generally soft, sausage-shaped, greyish on upper surface and pinkish on lower surface - H

7a. Fins containing thin, bony spines - go to 8
7b. Fins or limbs containing muscles - go to 9

8a. Dorsal fin modified into suction disc - C
8b. Reddish ventral surface, unusual dentition with sharp pointed teeth - O

9a. Fleshy fins, dark blue with light-coloured spots - I
9b. Four muscular limbs - go to 10

10a. Integument covered in scales or feathers - go to 11
10b. Integument covered in hair - go to 15

11a. Oblong spiked carapace, flattened triangular head with many tubercles, protrusion from nose tip - B
11b. Mesotarsal contains single joint above distal ankle bones - go to 12

12a. Flightless, can be over 2.5m in height - S
12b. Wings capable of sustaining powered flight - go to 13

13a. Pink plumage appearing in adulthood, hooked beak - M
13b. Short legs relative to body size - go to 14

14a. Gular pouch, white plumage - K
14b. Bright orange beak similar in length to remainder of body, black plumage - Q

15a. Four thumbs - L
15b. Fetus connected to placenta - go to 16

16a. Long, slightly rear-curving tusks - J
16b. Vermiform appendix - go to 17

17a. [The answer to this puzzle (two-word common name)] - R
17b. Large brain relative to body size, tailless - go to 18

18a. Gular pouch, reddish-orange - N
18b. Mostly black hair, sometimes with greyish colour on dorsal surface and rusty colour on forehead - F

Conventional (Real):

Numerical (Fictional):