Proximal raphe fissure

A proximal raphe fissure is an extension of the proximal end of the raphe. A fissure is a structure that does not penetrate the valve wall and may be external or internal.

For example, Muelleria has external proximal raphe fissures that are unilaterally deflected. Gomphosinica has internal proximal raphe fissures that are recurved. Karayevia has straight proximal raphe ends without fissures.

Alternative Terms

external central fissure

While some older references use "central fissure" (Ross et al. 1979, Round et al. 1990), that term is synonymous with "proximal raphe fissure" used in this website.

Muelleria Proximal
Image Credit: Sarah Spaulding
Scanning electron micrograph of an external view of Muelleria. The external proximal raphe fissures are unilaterally deflected, or bent, to the same side of the valve.
Internal Proximal Fissure
SEM internal view of Gomphosinica. The internal proximal raphe fissures are recurved.
Karayevia Internal view
Internal view of the raphe valve of Karayevia. The proximal raphe ends lack fissures.