In particular, a large number of salamander species deliver pheromones across the skin of females, perhaps reflecting a novel mode of pheromonal communication. Once receptors have been matched to pheromonal ligands, rapid advance can be made to better understand the olfactory detection and processing of salamander pheromones. Pheromonal signals have diversified within salamander lineages and have experienced rapid evolution. While some pheromones elicit overt behavioral responses, others have more nuanced effects. Several pheromones have been described, ranging from simple, invariant molecules to complex, variable blends of pheromones. After describing common themes of salamander pheromonal communication, we describe what is known about the rich diversity of pheromonal communication in each salamander family. Here, we review the function and evolution of pheromonal signals involved in male–female reproductive interactions. Although salamanders are often thought of as relatively simple animals especially when compared to mammals, the pheromonal systems are varied and complex with nuanced effects on behavior. One family of salamander pheromones (the sodefrin precursor-like factor (SPF) family) originated 300 million years ago, at the origin of amphibians. Pheromonal communication is an ancient and pervasive sensory modality in urodelan amphibians. These observations suggest that key aspects of sexual behavior shared by these two salamander families have persisted for 123–153 million years.

As in plethodontids, courting Rhyacotriton males could mimic female behavior and dupe rival males into unprofitable spermatophore deposition. The spermatophore of Rhyacotriton was likewise very similar to that of plethodontids and unlike that of other salamanders. Some elements of Rhyacotriton courtship were remarkably similar to plethodontid homologs (e.g., trail-straddling walks and sperm transfer behavior). We recorded ongoing courtship with still photography, audiotape recordings, and videography. Here we report laboratory observations of complete Rhyacotriton courtship that confirm that promise.

Only fragments of Rhyacotriton courtship were known from past work, but they promised insights into the ancient sexual radiation of salamander families. Rhyacotriton is an ancient salamander lineage with distant relationships to Amphiuma and plethodontids and an even more distant relationship to ambystomatids and salamandrids. In this article we report the case of complex behavior used by salamanders in sperm transfer that is at least 123–153 million years old.

Although many examples of behavioral homology have been documented in the vertebrate literature, these examples are skewed towards short timescales.

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