Dichotomous Classification Key for Salamanders Hind Limbs absent Hind limbs present External gills present in adults Siren intermedia, Siren Go to 2 Necturus maculosus, External gills absent in adults Mud puppy Large size; over 2cm long Go to bSinall size; under 7cm long Go to 4 Body background black, large white spots Go to 5 Size and shape irregular, not completely covering body Ambystoma tigrinum, Tiger salamander Body background black, small round white spots in each side from eye Go to 4Q Lip of tail Body background black with white spots Go to 6 Small white spots on black background Go to each side of head Go to Up of tail Go along Ambystoma jeffersonianum, Jefferson salamander Small white spots scattered throughout a black background From head to up of tail Plethodon glutinosus, Slimy salamander Large irregular black spots on light background extending from head to lip of tail Ambystoma opacum, Marbled salamander No irregular black spots on light background Round spots scattered along back Go to 8 Flattened like and sides of body, tail Lidpole Triturus viridescens, Newt Without round spots and tail not flattened Go to 9 Two dark lines bordering broad light mid-dorsal stripe Go to 9 with narrow median dark line extending from the head Eurycea bislineata, Two-lined salamander Without two dark lines Length of the body equal to or greater than the length of the tail Plethodon cinereus, Red-backed salamander Light stripe extending the length of the body, narrow at the base of the tail Hemidactylium scutatum, Four-toed salamander
The Correct Answer and Explanation is:
The dichotomous key is a tool used to classify organisms based on their characteristics by following a series of paired statements. Here’s how the key works based on the provided descriptions:
- Hind Limbs:
- Absent → Siren intermedia or Siren
- Present → Proceed to the next step (step 2).
- External Gills in Adults:
- Present → Necturus maculosus (Mud puppy)
- Absent → Proceed to step 3.
- Size of the Salamander:
- Large (> 20 cm) → Go to step 5.
- Small (< 7 cm) → Proceed to step 4.
- Body Background Color:
- Black with Large White Spots → Ambystoma tigrinum (Tiger Salamander).
- Irregular Black Spots with White Background → Ambystoma jeffersonianum (Jefferson Salamander).
- Tail and Spots:
- Large White Spots on Black Background from Head to Tail → Ambystoma opacum (Marbled Salamander).
- Small White Spots on Black Background Scattered Along the Sides → Plethodon glutinosus (Slimy Salamander).
- Body Shape:
- Flattened Like a Newt → Triturus viridescens (Newt).
- Not Flattened with No Round Spots → Eurycea bislineata (Two-lined Salamander).
- Dorsal Stripe:
- Two Dark Lines Bordering Broad Light Mid-dorsal Stripe → Eurycea bislineata (Two-lined Salamander).
- Without Two Dark Lines → Proceed to step 8.
- Body and Tail Length:
- Body Length ≥ Tail Length → Plethodon cinereus (Red-backed Salamander).
- Tail Length > Body Length → Hemidactylium scutatum (Four-toed Salamander).
This classification process helps identify different species of salamanders by examining their physical features, such as size, coloration, and body structure, in a step-by-step manner. Each step provides a yes/no decision that leads to the correct classification based on specific traits.
