Tardigrades have been recorded from a variety of habitats including mosses, lichens, leaflitter, streams, and marine sediments; however, reports from rock pools are still scarce. Rock pools across the world are known to host diverse invertebrate communities and endemisms are common. We provide the description by integrative taxonomy of Mesobiotus huecoensis sp. nov., found in the sediment of an ephemeral rock pool in Box Canyon Recreational Area in New Mexico (USA), and placed it in the M. montanus morphogroup based on the presence of eggs with hemispherical processes. This new species has elongated claws, particularly on the fourth pair of legs. Elongated claws are typical of freshwater tardigrades, and could represent an adaptation that allows the new species to better move in the substrate when the rock pool is fully inundated. We also provide information on the sperm morphology and mating behaviour of this new species. The finding of this new species highlights the importance of ephemeral rock pools for the discovery of new taxa and the need for their study and conservation.