Etheostoma nebra, the Buck Darter, is described as a new species endemic to the Buck Creek system of the Cumberland River drainage in Kentucky, USA. The earliest collection records of Etheostoma nebra date to 1955 and were considered a population of Etheostoma virgatum. Etheostoma nebra is delimited through morphological comparisons with Etheostoma virgatum and phylogenetic analyses using DNA sequences from a mitochondrial gene and five nuclear genes. Etheostoma nebra is distinguished from Etheostoma virgatum by a lower number of total lateral scales, fewer pored lateral scales and modally 13 compared with 12 pectoral fin rays. The two species also differ in patterns of pigmentation and nuptial male coloration. In the molecular phylogenies, Etheostoma nebra is not resolved as the sister species of Etheostoma virgatum. A review of all museum collection records of Etheostoma nebra and extensive field surveys in the Buck Creek system demonstrate a dramatic decline of the species over the past 30 years. Collections made from 1955 to 1981 show that Etheostoma nebra was widespread throughout the Buck Creek system, but the species is currently restricted to a small portion of Flat Lick Creek. Etheostoma nebra is critically imperiled based on its restricted geographic distribution and documented disappearance of populations within the Buck Creek system during the past three decades.

The fossil record of the turtle clade Baenidae ranges from the Early Cretaceous (Aptian—Albian) to the Eocene. The group is present throughout North America during the Early Cretaceous, but is restricted to the western portions of the continents in the Late Cretaceous and Paleogene. No credible remains of the clade have been reported outside of North America to date. Baenids were warmadapted freshwater aquatic turtles that supported high levels of diversity at times through niche partitioning, particularly by adapting to a broad range of dietary preferences ranging from omnivorous to molluscivorous. Current phylogenies place Baenidae near the split of crown-group Testudines. Within Baenidae three more inclusive, named clades are recognized: Baenodda, Palatobaeninae and Eubaeninae. A taxonomic review of the group concludes that of 49 named taxa, 30 are nomina valida, 12 are nomina invalida and 7 are nomina dubia.

Turtles of the clade Pan-Trionychidae have a rich, but fragmentary fossil record in the New World, ranging from the Late Cretaceous to the Holocene. The clade immigrated to North America from Asia no later than the Cenomanian. From the Campanian to the middle Eocene, pan-trionychid diversity in the New World was higher than it is today. In the Neogene, pan-trionychids inhabited southern North America and coastal regions of northern South America. Their range subsequently contracted, and extant New World pan-trionychids are now limited to the eastern third of temperate North America. The ecology of extinct pan-trionychids was likely similar to that of extant pan-trionychids, although novel feeding ecology has been hypothesized for some morphologically derived taxa. Current phylogenies of crown Trionychidae recognize two major clades, Cyclanorbinae and Trionychinae, but the placement of most fossil taxa remains poorly resolved relative to these two primary clades. A taxonomic review of 101 named New World taxa finds 31 nomina valida, 26 nomina invalida, 41 nomina dubia and 2 nomina nuda.

A new stygobitic amphipod, Idunella verrilli, is described from the subterranean marine waters of Green Bay Cave, Bermuda. Specimens were collected during SCUBA exploration of the cave system in 1997. This species is readily distinguished from the only other liljeborgiid amphipod found in Bermuda, Idunella sketi Karaman, 1980.

Paratanais waltsikorai sp. nov. is described from specimens collected from shallow-water habitats in Bermuda. It represents the second species of the tanaidacean genus to be named from the northwest Atlantic. It is distinguished from the other species of Paratanais by a combination of characters, including the distinctive shape and setation of antennal articles 2 and 3.