Alternate life history modes of E. tynerensis and associated substrates. A, Paedomorphic Eurycea tynerensis and an example of Silurian/Ordovician chert gravel from sites where paedomorphs occur. Note the large particle sizes that provide interstitial spaces in the substrate. B. Metamorphosed E. tynerensis and an example of densely packed and poorly sorted clastic rock typical of metamorphic habitat. Scale bars only apply to the substrate pictures. Salamander photographs compliments of R. W. Van Devender.