South American Lungfish Identification Guide
Identify the South American Lungfish by its eel-like body, thread-thin paired fins, and smooth mottled skin.
Read the full South American Lungfish encyclopedia entry →
Key identification features
- Elongated, eel-like body with tiny scales embedded in the skin, giving a smooth, almost naked look
- Extremely thin, thread-like paired pectoral and pelvic fins rather than typical fanned fish fins
- Uniform dark gray-brown to olive coloration, sometimes with faint pale mottling
- Small eyes and a reduced, tapering tail that comes to a point
- Single elongated lung used for obligate air breathing
- Reaches roughly 4 feet in length
Common look-alikes
- African lungfishes (Protopterus species): share the same thread-fin body plan but are separated by continent (Africa, not South America) and often show heavier mottled spotting
- Freshwater eels: have a smooth, similar eel-like silhouette but possess normal, continuous fin margins and lack the thread-like limb fins entirely
Where you'll see one
This species lives in swamps, marshes, and seasonally flooded pools across the Amazon and Paraná river basins of South America. During the dry season it burrows into the mud and enters a dormant state, breathing air through a tunnel to the surface until the rains return.
Frequently asked questions
How do I recognize a South American lungfish versus an eel?
Look at the paired fins — the lungfish has thin, thread-like limb fins rather than the continuous finned margin of a true eel, plus a smaller, more pointed tail.
How do I tell it apart from an African lungfish in a photo?
Body shape and fins look nearly identical; geography is the reliable clue, since South American lungfish only occur in Amazon and Paraná basin waters.