This specimen is already extinct. It´s because of the low chance of insemination during the mating. In the case of the reefcrawel, it´s a rather unusual way of reproducing;
The female species are attracted to the male if he seems fertile enough. It’s recognizable to the large hump on his back, this is were he produces and collects his sperm cells. If the female finds her ideal mating partner, a short and cruel ritual begins. She starts to chase the male specimen until she has him lock in place by standing on the end of his legs. To enhance the chance of success, she starts to stimulate herself by rubbing the lips on her back-end on the male’s spermhump. We don’t know how long this ritual took but when the time was right, the female punctured the tissue of the male’s hump in order to release the sperm. Whilst moving sideways with her back-end, the female tried to inseminate herself. The part of the male in this ritual is now over, as he’s only considered a container of seed, once it’s been opened he’s useless. After the punctuation, the male dies slowly.
The reason the Reefcrawler got extinct is not only because of the fact that the male specimen was far outnumbered by female ones. It’s the location the reproduction took place that played a larger part of the extinction. The Reefcrawler lived around coral-reefs in the Pacific. The reprocudtion probably failed so often because of the strong currents. Sperm could therefore never reach the lips of the female and the male could only be used once.