and aims: The bryophyte flora of Argentina is currently under study, nevertheless, there are still extensive areas unexplored, such as Santiago del Estero with only three records of bryophytes to the entire region. The aim of this work was to contribute to the knowledge of the moss flora of Santiago del Estero province, through the collection of samples in Copo National Park and surroundings. M&M: The specimens were collected in the Copo National Park and surroundings, processed and studied

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... rding to traditional techniques for bryophytes. Microscopic characters were observed with stereoscopic and light microscopy. A list of the species found is presented, with comments on the differentiating characters, habitat and distribution. Results: The following moss taxa were found to be new records for the province: Aloina rigida; Dimerodontium balansae; Didymodon umbrosus; Fabronia ciliaris; Macrocoma tenuis subsp. sullivantii; Pseudocrossidium arenicola; P. linearifolium; Stereophyllum radiculosum; Syntrichia chisosa, Trichostomum brachydontium and Venturiella glaziovii. The range of distribution of Tricherpodium beccarii is extended to the northeast of the province. Conclusions: Eleven species and one subspecies, distributed in ten genera and five families, are newly reported for the province of Santiago del Estero. The range of distribution of one species is extended to the northeast of the province. These first studies highlight the unexplored floristic richness of the region and its vulnerability due to the accelerated advance of the agricultural-livestock border.