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Shark picture - green sawfish

HELIOBATIS RADIANS

Heliobatis radians

Common Name: Sun Ray

Scientific Name: Heliobatis radians.

Family: H.radians is the only recognized member of the genus heliobatis within the family Dasyatidae.

Identification: H.radians has a roughly circular disc that is slightly longer than wide. Snout terminates in an obtuse point. Tail (when intact) is roughly the same length as the body. Tail has up to three barbs (modified denticles). Teeth triangular and tightly spaced for crushing crustaceans.

Size: Max length 90cm. Most collected fossils are between 30-40cm. The smallest fossil recorded was 8cm in length from nose to tail.

Habitat: A freshwater, demersal (bottom dwelling) ray confined to river and lake beds.

Abundance and distribution: Extinct. Heliobatis radians flourished during the Wasatchian stage in the early Eocene 50-55 million years ago.
It was discovered in the Green River Formation in southwest Wyoming. Fossils are particularly common at a spot called Fossil Lake.

Diet: The abundance of H.radians fossils at Fossil Lake (the only place where the crayfish Procambarus primaevus and the prawn Bechleja rostrata are found) suggest that small crustaceans were an important part of this ray's diet.

Reproduction: Probably ovoviviparous. Unborn fetuses have been identified within the fossils of adult animals.

Photographs: Drumheller Museum, Alberta, Canada.

Similar species: So far H.radians appears to be the only dasyatid ray present in the Green River Formation but further analysis of minor variations in disc shape of collected fossils may lead to the discovery of multiple species living sympatrically.

Reaction to divers: Not applicable.

Diving logistics: Not applicable.

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