Oxygyrus

Oxygyrus keraudrenii is a species of sea snail, a holoplanktonic marine gastropod mollusk in the family Atlantidae.

[5] Oxygyrus keraudreni (along with Atlanta peronii) attains the largest size (shell diameter to 10 mm) among the Atlantidae.

[1] Its surface is slightly irregularly covered with approximately 20-24 spiral lirae in a zigzag-shape that usually leave a narrow zone free just below the periphery.

[1] In the largest available specimen from Pliocene of Philippines, the teleoconch has one complete whorl, widening rapidly, which makes the shell about twice as wide as high.

[1] On the post-larval shell a vague spiral ornament is present and the peripheral belt remains visible as a slightly produced zone reaching the apertural margin.

[5] From the fossil record Oxygyrus keraudrenii has been found from Pliocene in Tiep, Roxas (map) and Anda, Pangasinan, Luzon, Philippines in 2001 (published in 2007).

[5] In the Indian Ocean was Oxygyrus keraudreni found essentially limited to the upper 100 m of the water column, with 90% between 50 m and the surface.

[5] Similarly, off Hawaii was it recorded low in numbers of individuals whose vertical range was limited to the upper 90 m of the water column, with most individuals occurring at night in the upper 45 m.[5] In another study from the same area off Hawaii it was found that Oxygyrus keraudreni was captured in nighttime tows but was either absent or nearly so from comparable daytime ones.

apical view of very small juvenile shell shows typical zigzag-shaped spiral ridges
apical view of a juvenile shell