A paper on the morphological evolution of amblyopsid cavefishes was recently published in the journal Copeia. The full citation and abstract are below.
Armbruster JW, Niemiller ML, & Hart PB. 2016. Morphological evolution of the cave-, spring- and swampfishes of the family Amblyopsidae (Percopsiformes). Copeia 104: 763–777.
The Amblyopsidae is a small family of fishes from North America in which most of the species occur in caves. Despite considerable interest and study by biologists, a comprehensive morphological phylogenetic analysis of the family has not been conducted to date. We examined the skeletal morphology of all six genera and recognized species, which included 66 characters. The resulting phylogeny was compared to morphological- and molecular-based phylogenies of previous studies. Results showed a progression of cave adaptation that was significantly different from previous phylogenetic studies. Amblyopsidae was supported by 34 synapomorphies of the skeleton, but relationships within the Amblyopsidae were comparatively weak. The relationships of amblyopsids are likely influenced by morphological convergence as well as changes in the timing of development of some characters. Heterochrony is most visible in the unfused bones of the dorsal portion of the skull. The sister group to Amblyopsidae is Aphredoderidae (pirate perches), and the main character that supports this relationship is the presence of a unique set of upper jaw bones termed here lateromaxillae. This relationship is also supported by an anterior position of the vent, which is used for expelling gametes in Aphredoderus and for moving eggs to the gill chamber in Amblyopsis. It is more likely that Amblyopsis is the only branchial brooding amblyopsid and all other species likely exhibit transbranchioral spawning.