Bigeye thresher vs Cigar shark

Alopias pelagicus compared with Isistius brasiliensis

Key Differences

• Bigeye thresher is Endangered while Cigar shark is Least Concern.

Taxonomic Classification

Rank	Bigeye thresher	Cigar shark
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum same	Chordata (Chordates)	Chordata (Chordates)
Class	Chondrichthyes (Cartilaginous Fish)	Elasmobranchii
Order	Lamniformes (Mackerel Sharks)	Squaliformes (Squaliformes)
Family	Alopiidae	Dalatiidae
Genus	Alopias	Isistius
Species	Alopias pelagicus	Isistius brasiliensis

Evolutionary Relationship

Bigeye thresher and Cigar shark share a common ancestor at the Phylum level: Chordata. (Chordates)

Conservation Status

Bigeye thresher

EN — Endangered

Cigar shark

LC — Least Concern

Physical Characteristics

Attribute	Bigeye thresher	Cigar shark
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Bigeye thresher

Habitat

Typically found in marine environments from coastal waters to deep ocean.

Range

Distributed across Colombia and Taiwan. Currently classified as Endangered on the IUCN Red List, this species faces significant conservation challenges across its range.

Cigar shark

Habitat

Native to Asia and Europe and South America, inhabiting ecosystems characteristic of the region.

Range

Distributed across Chile, Norway, and Taiwan.

Bigeye thresher

The Bigeye thresher (Alopias pelagicus) is a species in the genus Alopias. It is currently classified as Endangered on the IUCN Red List. Typically found in marine environments from coastal waters to deep ocean.

Cigar shark

The cigar shark, also known as the cookiecutter shark (Isistius brasiliensis), is a small but remarkable shark in the family Dalatiidae, found throughout warm oceanic waters worldwide in tropical and subtropical latitudes. Reaching only 40–50 centimeters in length, it possesses oversized jaws with large, triangular lower teeth arranged in a saw-like series that cut distinctive circular plugs of flesh from much larger prey—including tuna, dolphins, whales, billfish, and even submarine cables and human bodies. It does not kill its prey but instead latches on, rotates its body, and excises a characteristic cookie-cutter-shaped bite. The cigar shark is bioluminescent, emitting a green glow from photophores on its ventral surface that may serve as counter-illumination or to attract prey from below. It undertakes diel vertical migrations, ascending to shallower waters at night and descending to mesopelagic depths during the day. The species is classified as Least Concern by the IUCN, with a vast oceanic distribution and no targeted commercial fishery. It is occasionally taken as bycatch. The geographic epithet brasiliensis refers to Brazil, where early specimens were described, but the species' range is circumglobal in warm oceans. The cookiecutter shark's feeding strategy is one of the most unusual among elasmobranchs.

Shared Countries

Both species can be found in 1 countries:

🇹🇼 Taiwan