thanks for the link to the nice Dasylirion article. In his dissertation, Bogler decided that the plant that has been known forever as D. longissimum is more correctly called D. quadrangulatum due to the complications of nomenclature and type specimens. There are actually two distinct species that have quadrangulate (4-sided) leaves, with D. quadrangulatum being the northern one, occuring in southern Tamaulipas and Nuevo Leon and D. treleasei being the more southern one, occuring in San Luis Potosi, Hidalgo and Queretaro.
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