Plants medium sized, forming loose mats or more often becoming pendulous, glossy green or yellowish-green. Primary stems creeping; rhizoids clustered, beneath stems where attached to substrate, smooth or weakly papillose. Secondary stems often pendent, regularly to irregularly pinnately branched; in cross-section outer 2-3 rows of cells small, thick-walled, inner cells larger, thin-walled, central strand weak or absent; paraphyllia and pseudoparaphyllia absent. Stem leaves erect to squarrose-recurved, ovate to ovate-lanceolate, usually somewhat concave, apex acute to long acuminate, base cordate, sheathing or clasping stem; margins plane to recurved or distally incurved, serrulate distally; costae single, 1/2-3/4 lamina length; median cells linear-flexuose, smooth; lower and basal cells elongate, often porose; alar cells differentiated, rectangular-rounded, porose or not. Branch leaves erect to squarrose-recurved, broadly to narrowly ovate to elliptical or ovate-lanceolate, apex broadly acute to long acuminate, base weakly clasping. Dioicous. Perichaetia lateral. Setae short emergent, equal to or less than capsule length, smooth. Capsules suberect, urn ovoid to obloid, neck short; exothecial cells rectangular, longitudinal walls thick; annuli in 2-3 rows, deciduous; stomata at urn base, superficial or occasionally appearing immersed, 2-celled or occasionally appearing 4-celled; peristome double, exostome teeth 16, narrow, smooth below, distally lightly papillose; endostome lightly papillose, basal membrane ± high, segments 16, linear, perforate, cilia appearing absent; opercula rostrate. Calyptrae mitrate, sparsely hairy. Spores spherical, papillose.

Plantas medianas, formando matas laxas o más a menudo tornándose péndulas, de color verde brillante o verde-amarillento. Tallos primarios reptantes; rizoides agregados, debajo los tallos que se adhieren al sustrato, lisos o débilmente papilosos. Tallos secundarios a menudo pendientes, ramificaciones regular a irregularmente pinnadas; en corte transversal 2-3 filas externas de células pequeñas con paredes gruesas, células internas mayores con paredes delgadas, cordón central débil o ausente; paráfilos y pseudoparáfilos ausentes. Hojas del tallo erectas a escuarroso-recurvadas, ovadas hasta ovado-lanceoladas, generalmente algo cóncavas, ápices agudos hasta largo-acuminados, bases cordadas, envainadoras o amplectantes al tallo; márgenes planos hasta recurvados o distalmente incurvados, serrulados distalmente; costa simple, ocupando 1/2-3/4 de la longitud de la lámina; células mediales lineal-flexuosas, células lisas; inferiores y basales alargadas, a menudo porosas; células alares diferenciadas, redondeado-rectangulares, porosas o no. Hojas de las ramas erectas a escuarroso-recurvadas, ancha- a angostamente ovadas hasta elípticas u ovado-lanceoladas, ápices anchamente agudos hasta largo-acuminados, bases débilmente amplectantes. Dioicas. Periquecios laterales. Setas cortas emergentes, igual o menores a la longitud de las cápsulas, lisas. Cápsulas suberectas, urna ovoide hasta obloide, cuello corto; células exoteciales rectangulares, paredes longitudinales gruesas; anillo en 2-3 filas, deciduo; estomas en la base de la urna, superficiales u ocasionalmente de apariencia inmersa, 2-células en ocasiones parecen 4-células; peristoma doble, exostoma con 16 dientes, angostos, lisos hacia la base, distalmente finamente papilosos; endostoma finamente papiloso, membrana basal ± alta, con 16 segmentos, lineales, perforados, cilios en apariencia ausentes; opérculo rostrado. Caliptra mitrada y esparcidamente pelosa. Esporas esféricas, papilosas.

Keys modified from Manuel (1977).

1. Pendent stem and branch leaves erect; branch leaves rarely spreading; margins of branch leaves revolute near the base when dry, only slightly so when wet … Z. ambiguum

1. Pendent stem leaves erect to slightly spreading; branch leaves spreading to squarrose-recurved; margins of branch leaves plane … 2.

2. Pendent stem leaves loosely sheathing, sheathing portion forming 0.3-0.6 the leaf length … 3.

2. Pendent stem leaves clasping, clasping portion forming 0.2-0.3 the leaf length … 4.

3. Branch leaves ovate to broadly ovate, apices acute to obtuse, generally cucullate and apiculate; common … Z. patens

3. Branch leaves narrowly elliptic to ovate-lanceolate, apices acuminate and apiculate, never cucullate; rare … Z. allionii

4. Branch leaves spreading to squarrose, ovate to broadly ovate, apices acute to acuminate, often apiculate … Z. recurvifolium

4 Branch leaves squarrose to squarrose-recurved, rarely spreading, ovate-lanceolate to lanceolate, apices short to long acuminate, never apiculate … Z. patulum