Jenner’s False Cowry Shell, Jenneria pustulata

Jenner’s False Cowry Shell, Jenneria pustulata. Shell collected off the beach in the greater Los Cabos area of Baja California Sur, April 2019. Size: 2.0 cm (0.8 inches) x 1.4 cm (0.6 inches).

Jenner’s False Cowry Shell, Jenneria pustulata.  Shell collected off the beach of Punta Chivato, Baja California Sur, June 2025. Size: 2.1 cm (0.8 inches) x 1.4 cm (0.6 inches) x 0.9 cm (0.4 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Jenner’s False Cowry, Jenneria pustulata, Mollusk and Shell. Underwater photograph taken in Zihuatanejo Bay, Guerrero, January 2019. Photograph courtesy of Ron Woheau, Zihuatanejo.

Jenner’s False Cowry, Jenneria pustulata, Mollusk and Shell. Underwater photographs taken in Zihuatanejo Bay, Guerrero, January 2019. Photographs and identification courtesy of Ron Woheau, Zihuatanejo.

Phylogeny: Jenner’s False Cowry, Jenneria pustulata (Lightfoot, 1786), is a gastropod mollusk that is a member of the Ovulidae Family of False Cowrie Shells. The genus Jenneria is one of forty-four genera in this family, and this is the only species in this genus.  They are also known as the Pustulated Cowry Shell and the Pustulose False Cowry Shell and in Mexico as Ninguno Conocido.

Morphology:  Jenner’s False Cowry shell is egg- shaped, similar to a cowry, but it is somewhat flattened and it’s base is crossed with white ridges or “transverse teeth”. They lack the shiny surface of other cowries, and instead, the dorsal surface is covered with reddish-orange pustules, surrounded by black circles. The background color of the shell’s dorsal surface is light blue-gray, the ventral surface is brown. Jenner’s False Cowries are soft-bodied gastropods. As  gastropods they have a  muscular foot, two upper, and two lower tentacles, eyes located at the tips of the upper tentacles, and a mouth with special rasp-like feeding organ called the radula. The radula is like a file, composed of many tiny teeth. The mantle is greyish, with whitish, long, branched, papillae. Jenner’s False Cowry Shells reach a maximum of 2.7 cm (1.1 inches) in length and 1.9 cm (0.7 inches) in height.

Habitat and Distribution: Jenner’s False Cowries reside among hard corals and in holes in the reef and are found from the intertidal zone to depths up to 40 m (130 feet). They are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from the west coast of the Baja Peninsula.

Ecology and Behavior: Jenner’s False Cowries are nocturnal corallivores that feed on the polyps of hard corals. In turn they are preyed upon by crabs, fish, and sea stars. Jenner’s False Cowries are gonochoric (male or female for life). Reproduction is sexual, through broadcast spawning. The embryos develop into planktonic trochophore larvae and later into veliger larvae before becoming fully grown adults.  Jenner’s False Cowries have been observed having significant effects on coral mortality on some hard coral reefs. High predation by this corallivore gastropod was observed in July 2011 at Bahía de Los Ángeles, in the Sea of Cortez, where Hump Corals, Porites panamensis, were infested by fifteen to forty sea snails per colony. From a conservation perspective they have not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be consider to be of Least Concern. 

Synonyms:  Cyprea pustulata, Jenneria pustulata var. bimaculata, and Jenneria pustulata var. pumilio,.