Allodontichthys polylepis

First Describer: 
Rauchenberger, 1988
Original Description: 

RAUCHENBERGER, M. (1988): A New Species of Allodontichthys (Cyprinodontiformes: Goodeidae), with Comparative Morphometrics for the Genus. Copeia 1988(2): pp 433 - 441


The name “polylepis” derives from the Greek and means: with many scales (this species has more scales than its congeners).


Collection-number: UMMZ 213951. The Holotype is an adult male of 42mm SL, collected by R.R. Miller et al., 23.02.1973.

English Name: 
Finescale Splitfin
Mexican Name: 
Mexcalpique de escama



2n = 48    2m/ 2sm/ 44stt   (following Uyeno, Miller & Fitzsimmons, 1983)

The maximum known SL is 50mm (Miller et al, 2005).
Terra typica: 

The Holotype had been caught in the Río Potrero Grande (Río Ameca drainage), 9.6km east of Ameca on the road to Guachinango in the state of Jalisco.

Status after IUCN: 

not mentioned

Status after J.Lyons (2011): 

Extinct? Comment: No records since 2000

Distribution and ESU's: 

Like all species of this genus, it lives on the Pacific Slope. It is endemic to the upper (southwestern) tributaries of the Río Ameca west of Ameca in Jalisco.


It lives in clear streams with riffles and pools over substrates of sand, gravel, rocks, boulders and some silty mud. The vegetation comprises green algae on rocks or floating. The currents are slight to none in the dry season, the depths usually less than 0.5m.


In ethyl alcohol, the body is dark brown dorsally but lighter on the ventral half of the flanks and cheeks. Dorsolaterally, the edges of the scale pockets are blackened, giving the fish a flecked appearance. The scapular blotch is dark and prominent. It has got 8 – 11 medium brown vertical bars from behind of the pectoral fin onto the caudal peduncle. The lateral bars may be obscured by a general darkening in larger males. The dorsum shows an irregular spotting in juveniles and females. Pectoral and pelvic fins are relatively pale. The dorsal fin in fish of 20 – 40mm shows a basal row of spots followed distally by 1 or 2 more irregular rows of larger spots. The spotting in dorsal and anal fins is sometimes obscured in larger fish, especially males, by dusky-dark pigmentation on the basal three-fourths of the fin.


Small young and gravid females were captured from late February to early March. Miller noticed in 2005, that we have to confess, that there is not much known of its life history.


The diet is probably the same as in related species like Allodontichthys tamazulae. Miller found large insect larvae in its guts.


The Finescale Splitfin has been discovered in 1957 by R.R. Miller & M. Miller in a tributary of the Río Atenquillo (Ameca basin). Nevertheless it took 30 years to describe it. Its habitats are distant in distribution with respect to its congeners, making it to the only known representative of this genus of the Mesa Central.


For several years now, there haven't been found specimens in the wild though the biological quality of the habitats is good. There have been some events in the last years when the creeks nearly dried out, but that also happened in the past (Dominguez, pers.) and has been mentioned for example by Brian Kabbes in 1999, when he visited the type location near Estancuela in December. All in all, reasons for the disappearance of Allodontichthys polylepis in the wild couldn't have been detected yet. This fish is maybe extinct in the wild.


In 2008, O. Dominguez started a semi-captive conservation program with the help from the Fish Ark Mexico Project. An artificial pond on the area of the Botanical garden of the Faculty of Biology from the University of Morelia has been built and populated with Neotoca bilineata and Zoogoneticus tequila in April, as well as Allotoca goslinei and Allodontichthys polylepis in August. All catches in the years thereafter did not reveal any specimen of this species, so it might not have survived in the pond.


Shane Webb’s analyses in 2002 suggest Allodontichthys polylepis as a sister to a clade comprising tamazulae and zonistius.


In 2011, the situation of Allodontichthys polylepis has become worse. No specimens from the originally only 3 known localities could have been detected for several years and the individuals in captivity encompass not much more than 20 or 30 specimens. Actually, there are only captive specimens known from two localities: There is only a dozen fish left from the type-locality population and probably the same number from the Río de las Bolas. This species is in high danger of extinction and probably the rarest fish in the world!


Image 1: adult male from the Río Potrero Grande

Image 2: male from the Río Potrero Grande

Copyright: Anton Lamboj

Images 3 and 4: females from the Río Potrero Grande

Images 5 and 6: young male from the Río Potrero Grande

Copyright: Anton Lamboj

Images 7 and 8: young female from the Río Potrero Grande

Copyright: Anton Lamboj

Image 9: young male from the Río de las Bolas

Copyright: Anton Lamboj

Images 10 and 11: female from the Río de las Bolas

Copyright: Anton Lamboj

Image 12: pair from the Río de las Bolas

Copyright: Anton Lamboj