Gymnopilus ianthinilophus (Agaricales, Basidiomycota), a new species from the Brazilian Amazon

Abstract Gymnopilus is an agaricoid genus of mostly wood-rotting mushrooms, with ca. 200 species worldwide distributed, of which 23 of them are currently known in Brazil. In the Amazon region, Gymnopilus taxa correspond mostly to very old names described under Agaricus, later recombined into Gymnopilus, such as G. marasmioides, G. panurensis, G. psamminus, and G. trailii. Based on the examination of a well-annotated exsiccate at the INPA Herbarium, Gymnopilus ianthinilophus is described as a new species. It is characterized by the densely cespitose habit, squarrose pileus with blackish brown squamules, adnate to subdeccurent lamellae with decurrent tooth, violaceous brown stipe, weakly dextrinoid basidiospores 7.6-9.2 × 5.1-6.1 µm, interwoven pileus trama, lageniform with capitate or subcapitate apex cheilocystidia measuring 15.3-25.5 × 5.6-8.2 µm, and absence of pleurocystidia and caulocystidia. Description, photographs, illustrations of the new species, and discussion and comparison with morphologically similar taxa are provided.

摘要 裸伞属（Gymnopilus）是一类以木腐生为主的伞菌状真菌类群，全球约有200个物种，其中巴西目前已记录23种。在亚马逊地区，该属类群大多为早年以伞菌属（Agaricus）名称发表的旧学名，后被重新组合归入裸伞属，如马拉斯米状裸伞（G. marasmioides）、帕努伦西斯裸伞（G. panurensis）、沙生裸伞（G. psamminus）以及特雷利裸伞（G. trailii）。通过对巴西国家亚马逊研究所标本馆（INPA Herbarium）馆藏的一份标注详尽的腊叶标本进行检视，本文描述了一个新物种——紫顶裸伞（Gymnopilus ianthinilophus）。该新物种的形态特征为：密集丛生的生长习性；菌盖具反折鳞片，鳞片呈黑褐色；菌褶贴生至近延生，具延生齿；菌柄呈紫褐色；担孢子（basidiospores）呈弱糊精反应，大小为7.6-9.2 × 5.1-6.1 µm；菌盖菌髓（pileus trama）为交织型组织；褶缘囊状体（cheilocystidia）呈瓶状，顶端头状或近头状，大小为15.3-25.5 × 5.6-8.2 µm；无褶侧囊状体（pleurocystidia）与柄生囊状体（caulocystidia）。本文提供了该新物种的形态描述、照片、图解，并对其与形态相似类群进行了讨论与比较。