Nikon R8 and R10 models utilize unique one pull-down claw and two-ratchet system for utmost film transport quality since the Super 8 cartridges out there cannot deliver good quality steadiness due to their design limitations.

The mentioned ratchets should not be considered as registration pins. However, they improve the steadiness dramatically during FORWARD and REVERSE transport directions by entering partially into the film perforations.

They are spring-loaded and synced with the claw, as well as actuated immediately during the standstill of film when the claw is fully retracted (exposing state).

The shapes seen of the ratchet tips reveal their purpose. The slider moves the both of the ratchets in and out laterally by a perpendicular action.

Nikon R8-10 claw'n'ratchets
Please note that FORWARD and REVERSE stand for film transport direction.

Nikon R10 aperture plate

AFAIK, this was the answer to the Single-8 cartridge system, developed by FUJI PHOTO FILM CO., LTD., Tokyo, which enables the built-in camera pressure plate just like seen in professional equipment. Nikon was already spent several years for the development stages of their R line and these cameras should be one step further among other cameras in the same first class. The same applies to the hidden extra area of film frame aperture, and servo-controlled 5-blade iris diaphragm (R10 only).

Nikon R8-10 aperture hidden area

Nikon R10 5-blade iris diaphragm
The 5-blade iris (R10) – Please notice that the blades form a pentagon.
Nikon R10 5-blade iris diaphragm ass'y
Image courtesy of my close friend Mr. Takahiro Nakano, Tokyo

Those years and outgoings spent by Nikon, finally, caused to discontinue the movie business.

The bigger rival Canon never attempted such details for this narrow-gauge format.