Livebearers (Poecilidae)
# characteristics results
1a Dorsal fin origin more anterior than anal fin origin go to 2
1b Anal fin or gonopodium more anterior than dorsal fin go to 3
2a Horizantal stripes of dark pigmentation, Mouth superior and pointed Poecilia latipinna (Sailfin Molly)
2b Female only species, small dorsal fin, and depressed head Poecilia formosa (Amazon Molly)
3a Arched back, deep bodied, and rounded snout Gambusia nobilis (Pecos Gambusia)
3b elongated body go to 4
4a Head rounded, melanophores on scales form crescent shapes, 8 dorsal fin rays~ This species is endangered Gambusia gaigei (Big Bend Gambusia)
4b Head depressed and/or no cresent markings go to 5
5a Snout rounded with melanophores clustered on lower jaw~ dark midventral stripe present with overall yellow body Gambusia geiseri (Largespring Gambusia)
5b Snout pointed, suborbital bar may be present, brood patch found in pregnant females Gambusia affinis (Western Mosquitofish)