A new species of crayfish (Decapoda: Astacidea: Cambaridae) from the Cumberland Thrust Block (eastern Kentucky and Tennessee, USA), with notes on the evolution of Cambarus Erichson, 1846 in the Ohio River Basin of the Appalachian Mountains.

The article focuses on the description and phylogenetic analysis of *Cambarus intermontanus* n. sp., a newly identified crayfish species from mountain streams in the Clear Creek basin along the Kentucky/Tennessee border within the Cumberland Thrust Block (CTB). Morphologically and genetically distinct from closely related species such as *Cambarus jezerinaci*, *C. intermontanus* is characterized by differences in tuberculation patterns on the chelae and gonopod structures, and shows an average 4–5% mitochondrial DNA sequence divergence from its relatives. Its distribution is limited to small first- and second-order streams in the CTB region, with evidence suggesting its evolution was influenced by geological events including the Cumberland meteorite impact and Appalachian uplift. Phylogenetic analyses place *C. intermontanus* as sister to a clade containing *C. parvoculus*, *C. jezerinaci*, and *C. magerae*, highlighting the role of regional geology in crayfish diversification.