Class set – please do not write on this!




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CLASS SET – PLEASE DO NOT WRITE ON THIS!




Shark Dichotomous Key

Classification is a way of separating a large group of closely related organisms into smaller subgroups. Identification of an organism is easy with a classification system. The scientific names of organisms are based on the classification systems of living organisms. To identify an organism, scientists often use a dichotomous key. A dichotomous key is a listing of characteristics, such as structure and behavior, organized in such a way that an organism can be identified.


Procedure:

  1. Use Figure 1 as a guide to the shark parts used in the key on the following page.

  2. Read statements 1A and 1B of the key. They describe a shark characteristic that can be used to separate the sharks into two major groups. Then student Shark 1 in Figure 2 for the characteristic referred to in 1A and 1B. Follow the directions in these statements and continue until a family name for Shark 1 is determined. For example, to key a shark that has a body that is not kite shaped, and has a pelvic fin, and six gill slits, follow the directions of 1B and go directly to statement 2. Follow statement 2B to statement 3. At statement 3A, identify the shark as belonging to Family Haxanchidae.

  3. Continue keying each shark until all have been identified. Write the family name on the line below each animal in Figure 2.

Dorsal Side


First dorsal fin Second dorsal fin






Caudal fin











Ventral Side


gill slits anal fin

pectoral fin pelvic fin



Figure 1

1A. Body like a kite (if viewed from the top)………………..…..……………….Go to 12

1B. Body NOT like a kite (if viewed from the top)…………….....……………….Go to 2
2A. Pelvic fin absent……………………………………..….…Family Pristiophoridae

2B. Pelvic fin present…………………………………..………….……………….Go to 3


3A. Six gills present………………………………………….…...Family Hexanchidae

3B. Five gills present………………………………………..…………………….Go to 4


4A. Only one dorsal fin…………………………….………....…Family Scyliorhinidae

4B. Two dorsal fins…………………………………………..…………………….Go to 5


5A. Mouth at front of snout…………………………….…….Family Rhinocodontidae

5B. Mouth on underside of head………..………………………..….…………….Go to 6


6A. Head expanded at sides with eyes at end of expansions…….…Family Sphyrnidae

6B. Head is NOT expanded on sides…………………………………..….……….Go to 7


7A. Top half of caudal fin same size and shape as bottom half…....…..Family Isuridae

7B. Top half of caudal fin different size and shape as bottom half…..…..………..Go to 8


8A. First dorsal fin very long, almost 1/2 body length…….…...Family Pseudotrikidae

8B. First dorsal fin regular length……………………………..….…….……….Go to 9


9A. Caudal fin very long, almost as long a entire body….……..…….Family Alopiidae

9B. Caudal fin regular length……………………………….………...…………..Go to 10


10A. A long point on end of snout……………………........Family Scapanorhynchidae

10B. Snout without long point………………………….……………..………….Go to 11


11A. Anal fin absent…………………………………….………..…….Family Squalidae

11B. Anal fin present……………………………….…..………. Family Carcharhinidae


12A. Small dorsal fin present near tip of tail….……….………….…....Family Rajidae

12B. No dorsal fin present near tip of tail..…………….……..….….……………Go to 13


13A. Front of animal with two horn-like appendages…….…………Family Mobulidae

13B. No horn-like appendages…….……………………….……….Family Dasyatidae


Top view


Top view



Top view

Top view

Top view

1 2 3

4


5

6

7



8 9

10 11


12 13

14

Name ___________________________ Date ________

SHARKS!!!! Dichotomous Key

1. 1A 12A Rajidae




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Name __________________ #________



SHARKS!!!! Dichotomous Key(Key)

1. 1A 12A Rajidae
2. 1B 2B 3B 4B 5B 6B 7B 8B 9A Alopidae
3. 1B 2A Pristiophoridae
4. 1B 2B 3B 4B 5B 6B 7B 8B 9B 10B 11B Carcharhinidae
5. 1B 2B 3B 4A Scyliorhinidae
6. 1B 2B 3B 4B 5A Rhinocodontidae
7. 1B 2B 3B 4B 5B 6B 7A Irusidae
8. 1B 2B 3B 4B 5B 6B 7B 8B 9B 10B 11A Squalidae
9. 1A 12B 13B Dasyatidae
10. 1B 2B 3B 4B 5B 6B 7B 8B 9B 10A Scapanorhynchidae
11. 1B 2B 3B 4B 5B 6B 7B 8A Pseudotrikidae
12. 1B 2B 3A Hexanchidae
13. 1B 2B 3B 4B 5B 6A Sphyrnidae
14. 1A 12B 13A Mobulidae


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