The discovery of C. inmemoriam is an impressive story to read, from the first discovery of the habitat in Mexico (by photos one of the authors made during a commercial flight above the area in 1983) to the dramatic conclusion of its extinction. The dry Bolsón de Sandia (Pluvial Lake Sandia) is a dry lake bed of unknown age. The area has several springs in which four new species were discovered:
C. ceciliae, collected in 1988 at Ojo de Agua La Presa
C. inmemoriam, collected in 1984 at Ojo la Trinidad
C. longidorsalis, collected in 1988 at Charco la Palma
C. veronicae, collected in 1984 at Ojo de Agua Charco Azul
The four Cyprinodons are considered to be a monophyletic lineage; an assemblage of species with characters shared with C. alvarezi. All four species share the remarkable coloration of the eye, which includes two rings (a gold inner circle and a pale yellow outer circle). The only specimen of C. inmemoriam was a male specimen (57.3mm). Whereas the males of all four species have metallic blue colors on their body, this male showed pale grey blue coloration with obsolete bars. Colors in Cyprinodon males differ during the season. As no females of C. inmemoriam were found, the male specimen probably did not show its best colors. Why dress up if there's noone to impress eh?
During the study by Lozano-Vilano and Contreras-Balderas two of the four springs dried up and the inhabitants (C. ceciliae and C. inmemoriam) presumably became extinct. In Ojo la Trinidad no fish have been found since 1985; the spring fully dried in 1986. That's how the one and only specimen of C. inmemoriam got his name ('inmemoriam' = remember after death). A unique endemic crayfish, Cambarellus sp., found at the same spring has not been described and also is considered extinct.
So; end of story? The chance of living specimens of C. inmemoriam ever to be found again can be ruled out. We'll have to settle with the unique holotype (deposited at the Universidad Autónoma de Nuévo Leon; Mexico). The population of C. ceciliae is only known from Ojo de Agua La Presa; this spring nearly dried during the winter of 1991. Attempts to find specimens when the water returned in 1992 failed; since then this species is also considered to be extinct.
The other two endemic species, C. longidorsalis and C. veronicae, are considered to be endangered due to agricultural overexploitation of the groundwater. Thus, the story of this unique lineage of species does not have to end. However, the chances of survival are very limited.
Lozano-Vilano, M. de L. and S. Contreras-Balderas (1993): Four new species of Cyprinodon from southern Nuevo León, Mexico, with a key to the C. eximius complex (Teleostei: Cyprinodontidae). - Ichthyological Exploration of Freshwaters v. 4 (no. 4): 295-308.