Plants small to medium sized, green to yellowish brown or green. Stems spreading, irregularly pinnately branched; in cross-section hyalodermis absent, central strand present; paraphyllia absent, pseudoparaphyllia foliose. Leaves erect to erect-spreading, ovate-lanceolate or –triangular, smooth, not plicate, base rarely indistinctly decurrent, apex short or long acuminate; margins plane, occasionally reflexed at base, entire to weakly or finely serrulate; costa single, ca. 1/3 to commonly 1/2 to short excurrent; laminal cells smooth, median and upper cells rhomboidal or oblong-rhomboid, thin- to thick-walled, walls entire, rarely porose; alar region undifferentiated to weakly differentiated, cells slightly enlarged, oblong-rectangular. Autoicous. Setae erect, elongate, usually red. Capsules horizontal, rarely erect, urn curved or rarely straight, cylindrical; peristome well developed. Calyptrae cucullate, naked and smooth. Spores mostly lightly papillose.

Plantas pequeñas a medianas, de color verde a pardo-amarillento o verde. Tallos patentes, con ramas irregularmente pinnadas; sin hialodermis en sección transversal, cordón central  presente; sin paráfilos, pseudoparáfilos foliosos. Hojas erectas a erecto-extendidas, ovado-lanceoladas o –triangulares, lisas, no plegadas, base rara vez indistintamente decurrente, ápices cortos o largo-acuminados; márgenes planos, ocasionalmente reflexos en la base, enteros a débil- o finamente-serrulados; costa simple, ocupando aproximadamente 1/3 a comúnmente 1/2 de la lámina hasta corto-excurrente; células de la lámina lisas, células mediales y superiores rómbicas u oblongo-romboides, paredes celulares delgadas a gruesas, enteras, rara vez porosas; región alar indiferenciada a débilmente diferenciada, células escasamente agrandadas, oblongo-rectangulares. Autoicas. Setas erectas, alargadas, generalmente rojas. Cápsulas horizontales, rara vez erectas, urna curvada o rara vez recta, cilíndrica; peristoma bien desarrollado. Caliptra cuculada, desnuda y lisa. Esporas por lo general finamente papilosas.

1. Stem leaf costa 60-94 µm wide at leaf base … A. tenax

1. Stem leaf costa to 58 (rarely to 77) µm wide at leaf base … 2

2. Stem leaves 0.5-1.0 mm long; costa ca. 2/3 leaf length, rarely extending into acumen; leaf margins at least partially bluntly serrulate; basal alar cells rectangular or short-rectangular … A. serpens

2. Stem leaves 0.6-2.1 mm long; costa extending into acumen; leaf margins bluntly serrulate or subentire;  basal alar cells rectangular or long-rectangular … A. varium