Gibbosa Crassatella Shell, Hybolophus gibbbosus

Gibbosa Crassatella Shell, Hybolophus gibbosus. Shell collected within Magdalena Bay, Baja California Sur, October 2019. Size: 5.7 cm (2.2 inches) x 1.5 cm (0.6 inches). Size: 5.2 cm (2.0 inches) x 3.9 cm (1.5 inches).

Phylogeny: The Gibbosa Crassitella Shell, Hybolophus gibbosus (G.B. Sowerby I, 1832), is a bivalve mollusk that is member of the Crassatellidae Family of Crassatella Shells. The genus Hybolophus is one of fifteen genera in the Crassatella Family, and this is the only species in this genus.

Description: Gibbosa Crassitella Shells are wedge-shaped, with a widely rounded anterior end and a more narrowly rounded posterior end. They have thick hinges. The outside of the shell is sculpted by fine concentric lines. The shell has a buffy yellow to orange brown exterior but the shell is normally covered by a dark brown periostracum. The interior is white with brown toward the posterior end. Gibbosa Crassitella Shells reach a maximum of 9.3 cm (3.7 inches) in length and 7.0 cm (2.7 inches) in height.

Habitat and Distribution: Gibbosa Crassitella Shells are found on, and within, sand and mud substrates at depths between 5 m (15 feet) and 140 m (360 feet). They are a subtropical to tropical Eastern Pacific species that are found in Mexican waters of the Pacific Ocean from Bahía San Juanico, Baja California Sur south to Guatemala. They are found throughout the Gulf of California.

Ecology and Behavior:  Gibbosa Crassitella Shells are suspension feeders that feed primarily on planktonic algae and suspended organic matter. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. There commensal, parasitic, or symbiotic relationships with other species has not been formally documented. 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: Crassatella gibbosa,Crassatellitesrudis, Eucrassatella (Hybolophus) gibbosa, Eucrassatella (Hybolophus) gibbosa tucilla, Eucrassatella (Hybolophus) ovata, Eucrassatella gibbosa, Eucrassatella gibbosa tucilla, Eucrassatella ovata, Eucrassatella aequatorialis,  and Eucrassatella manabiensis.