Racocetra intraornata, a new species in the Glomeromycetes with a unique spore wall structure

A new species of the arbuscular mycorrhiza forming Glomeromycetes, with distinct ornamentations on the inner surface of the outer spore wall, is here presented under the epithet Racocetra intraornata. It was found in the Caatinga, a semi-arid biome of Northeastern (NE) Brazil, and also isolated from a sand dune ecosystem along the semi-humid Atlantic coast of NE Brazil. The species forms yellow to yellow-orange glomerospores, 150–280 μm in diameter, with a three-layered outer wall and a three-layered inner wall. The inner surface of the outer wall is densely crowded with small tubes that resemble germination warts characteristic of Gigaspora. The hyaline to rarely light yellow germination shield has 4–6 lobes and may form 4–6 germ tube initiations. The species can easily be distinguished from all other species in the Racocetraceae by the unique outer wall ornamentation.