Identification keys to Amazonian ferns

The main online key contains information on roughly 250 species of ferns that occur in lowland Amazonia. It is a multi-entry key, so the questions about the plant do not need to be answered in order. Just pick the questions that you find easy to answer and ignore the rest. All species are illustrated, so you can take a shortcut and check the photos of any species at any stage.

A separate key is provided for the genus Triplophyllum.

Glossary - ​​ terms in italic refer to Portuguese (in blue) and Spanish (in black)


Abaxial surface: The side of the leaf or leaf division that faces the bottom side of the plant. Superfície abaxial. Superficie abaxial.

Acrostichoid: A type of sori that covers entirely the abaxial surface of the leaf. Fertile leaves are often reduced. Acrosticóide. Acrosticoide.

Acroscopic: directed or facing towards the apical part of an axis. Acroscópico. Acroscópico.

Anastomosing veins: a network of connected veins that forms areoles. Veias anastomosadas. Venas anastomosadas.

Apex: the tip, point of a structure. e.g., the apex of a leaf, a pinna or a pinnule. Ápice. Ápice.

Apical: at the top/point of a structure. Apical. Apical.

Apical pinna: pinna at the top of a leaf. Pina apical. Pinna apical.

Apical pinnule: the pinnule at the point of a pinna. Pínula apical. Pínnula apical.

Aquatic vegetation: the floating vegetation in a water body. Vegetação aquática. Vegetación acuática.

Areoles: rounded or polygonal spaces that are formed between the veins. Aréolas. Aréolas.

Asymmetric: When an object does not form two equal halves. Assimétrico. Asimétrico.

Auriculate: bearing a lobe or auricle, usually at the base of lamina, pinna or segment. Auriculado. Auriculado.


Basal: near the base of an element. Basal. Basal.

Basal pinnae: the bottommost pinna of a pinnate leaf, the pinna that is closest to the petiole. Pina basal. Pinna basal.

Basal pinnule: The pinnule that is closest to the leaf rachis. Pínula basal. Pínnula basal.

Basiscopic: directed or facing towards the bottom (basal) part of an axis. Basiscópico. Basiscópico.

Bud: a germ cell in the leaf of an adult fern that gives origin to a new, clonal individual. Broto. Brote.


Cartilaginous: usually refers to margins of leaves or pinnae that are thickened, flexible and translucid. Cartilaginoso. Cartilaginoso.

Climber: a type of growing habit in which the rachis and leaf are support by other plants. Trepadora. Trepador.

Compact herb: plants growing either in the ground or in a tree trunk, but always with a creeping to slender erect stem. Erva compacta. Hierba compacta.

Compact rhizome: Rhizomes that are dense and forms a tussock. Rizoma compacto. Rizoma compacto.

Cordate: Heart-shaped. Cordado. Cordado.

Coriaceous: With the texture of leather, thick and stiff. Coriáceo. Coriáceo.

Crenate: term that refers to leaf margins with rounded teeth. Crenado. Crenado.

Cuneate: wedge-shaped. The term refers to V-shaped basis of pinnae or pinnules. Cuneado. Cuneado.


Decaying wood: Fallen wood, usually trunks, that are in decomposition in the ground. Madeira em decomposição. Tronco en descomposición.

Decumbent (rhizome): refers to rhizomes that are mainly laying over the substrate but has an erect apex). Decumbente (rizoma). Decumbente (rizoma).

Decurrent: leaves in which the blade extends below the petiole. Decurrente. Decurrente.

Deltate: similar to the shape of a hand-glide but more rounded; broadly triangular with an obtuse apex. Deltóide. Deltoides.

Dentate: term that refers to a leaf margin with sharp teeth directed outward the tip. Denteado. Dentado.

Denticulate: term that refers to a leaf margin with small sharp teeth directed outward the tip. Diminutive of dentate. Denticulado. Denticulado.

Dichotomous: a branching pattern in which the axis forks repeatedly. Dicotômico. Dicótomo.

Dimidiate: refers to the shape of pinnae or pinnules that have unequally sized halves like in many Adiantum and Lindsaea. Dimidiado. Dimidiado.

Dimorphic: refers to plants in which the fertile and the sterile leave are remarkably different in shape and architecture. Dimorfo. Dimórfico.

Disturbed area: Areas in which its original vegetation has been strongly altered by human action. Áreas alteradas. Áreas intervenidas.

Dorsiventral (rhizome): a creeping rhizome in which leaves arises from its upper part. Dorsiventral (rizoma). Dorsiventral (rizoma).


Elliptic: with the outline of a elongated circle that is broadest at the middle. Elíptico. Elíptico.

Entire: refers to leaves that are not dissected (divided). Inteira. Entera.

Epiphyte: a non-parasitic plant that grows on another plant, usually obtaining nutrients from rainwater that runs down the supporting plant. Epífita. Epífita.

Epiphytic: habit of growing on a living tree and without ground connection. Epifítico. Epifítico.

Erect: the term refers to rhizomes that grow upright, forming a 90 degrees angle to the ground. Ereto. Erecto.


Falcate: asymmetrically curved, like a sickle. Falcado. Falcado.

False indusium: serves the function of an indusium, but is formed by a folding of the leaf and comprises epidermis and both sides of the leaf. Falso indúsio. Falso indusio.

False veins: small vein-like areas of thick-walled lined cells in the leaves. Veias falsas ou pseudoveias. Venas falsas.

Fertile leaves: Spore-bearing leaves. Folhas férteis. Hojas fértiles.

Free veins: in which veins do not anastomose and form a network. Veias livres. Venas libres.

Free venation: A type of venation whose veins do not touch each other. Venação livre. Venación libre.


Hemiepiphytic: plants that start its life cycle as terrestrial and climbs in a living tree. Usually adults retains the ground connection. Hemiepifítico. Hemiepifítico.

Herbaceous/chartaceaous: with the texture of a sheet of paper. Herbáceo/cartáceo. Herbáceo/cartáceo.


Incisions of lamina: deep entrances in the margins of leaves, pinnae or pinnules. Incisões da lamina. Incisiones de la lámina.

Indusium: tissue formed by an epidermal projection on the underside of the leaf and which protects or covers the sporangia. Plural: Indusia. Indúsio. Indusio.


Lamina architecture: the general design of the lamina according to the structure of the division in it. Arquitetura da lâmina. Arquitectura de la lamina.

Lamina dissection: divisions of lamina. Dissecção da lâmina. Disección de la lámina.

Lamina: the broad, expanded part of the leaf. Also called leaf blade. Lâmina. Lámina.

Lanceolate: lance-shape, with broadest part below the middle and a long tapering apex. Lanceolado. Lanceolado.

Lateral pinnae at middle of rachis: the lateral pinnae in the intermediate part of a 1x-pinnate leaf. Pinas laterais na metade da raque. Pinna lateral en la mitad del raquis.

Lateral pinnae: pinnae that do not arise from the apex or the base of the leave. Pinas laterais. Pinnas laterales.

Lateral pinnules: Pinnules that do not arise from the apex or the base of the pinnae. Pínulas laterais. Pínnulas laterales.

Leaf apex: the apical part of the leaf. Ápice da lamina. Ápice de la hoja.

Leaf segment: the smallest division of pinnate leaves. Segmento da folha. Segmento de la hoja.

Leaf: also known as fronds in ferns, it is usually a flattened photosynthetic structure attached to the stem. Folha. Hoja.

Linear: much longer than wide. Long and narrow. Linear. Linear.

Lobed: having projections or shallow incisions. Lobado. Lobado.

Long-creeping: a rhizome that grows on the soil surface with leaves arising sparsely. Longo-reptante. Largamente reptante.


Marginal sori: Sori that grown very close to the margin of the leaf, pinna or pinnule. Soros marginais. Soros marginales.

Margins: refers to the outline of a leaf, pinnae, pinnulae or segment. Margem. Márgenes.

Membranaceous: very thin and translucent, like a membrane. It is a common characteristic of the leaves of filmy ferns (Hymenophyllaceae). Menabranáceo. Membranáceo.

Middle lateral pinnae: the lateral pinnae in the intermediate part of the leaf. Pinas laterais intermediárias. Pinnas laterales en la mitad de la lámina.

Midvein: the major axis of the leaf segment. Nervura principal. Vena principal.

Monomorphic: plants in which both fertile and sterile leaves are vey similar in shape and size. Monomorfo. Monomórfico.


Narrow elliptic: an elongated elliptic shape, the smallest axis is around one third of the longest axis. Estreitamente elíptico. Estrechamente elíptico.

Narrow triangular: an elongate triangular shape, the base is around one third of the longest axis. Estreitamente triangular. Estrechamente triangular.

Node: a swelled part in the petiole. . Nudo.

Non-inundated forests: refers to the Amazonian lowland dense forests that are not directly affected by seasonal flooding. Florestas não-inundadas. Bosque no inundable.


Oblanceolate: nearly elliptic but with the broadest part above the middle. Oblanceolado. Oblanceolado.

Obscure: difficult to see. Obscuro.                   Inconspicuo.

Ovate: a nearly elliptic shape in which the broadest part is closer to the base. Oval. Ovado.


Palmately divided: radially divided from a single point, forming the shape of a palm. Palmadamente dividida. Palmadamente dividido.

Pectinate: leave type in which the pinnae (segments) are parallel and closely packed and so have a comb-like appearance. Pectinado. Pectinado.

Petiole: leaf stalk. Pecíolo. Pecíolo.

Phyllopodium: a distinctly thickened part in the attachment between the petiole and the rhizome in articulated ferns. Filopódio. Filopodio.

Pinna attachment: the connection of the pinnae to the rachis. Ligação da pina. Inserción de la pinna.

Pinna base: the basal part of a pinna, close to the rachis. Base da pina. Base de la pinna.

Pinna: the primary division of a pinnate leaf. Similar to the term “leaflet” used for angiosperms. Plural: pinnae. Pina. Pinna.

Pinnae pairs: two pinnae in immediate or nearly immediate opposite sides of the rachis. Par de pina. Par de pinnas.

Pinnate: a compound leaf with divisions like a feather. (divided one or more times with a main axis). Pinada. Pinnada.

-1-pinnate: Leaves that are divided one time, and are constituted of 3 to several pinnae. 1-pinada. 1-pinnada.

-1-pinnate-pinnatifid: Leaves that are divided one time and the pinnae are, in turn, pinnatifid. 1-pinada-pinatífida. 1 pinnada-pinnatífida.

-1-pinnate-pinnatisect: Leaves that are divided one time and the pinnae are, in turn, pinnatisect. 1-pinada-pinatisecta. 1 pinnada-pinnatisecta.

-2-pinnate or bipinnate: Leaves that are divided two times. Pinnae are constituted of pinnulae. 2-pinada ou bipinada. 2-pinnada o bipinnada.

-2-pinnate-pinnatifid: Leaves that are divided two times and the pinnulae are, in turn, pinnatifid. 2-pinado-pinatífida. 2-pinnada-pinnatífida.

-2-pinnate-pinnatisect: Leaves that are divided two times and the pinnulae are, in turn, pinnatisect. 2-pinado-pinatisecta. 2-pinnada-pinnatisecta.

-3 or more times pinnate: Leaves that are divided three or more times. 3 ou mais vezes pinadas. 3 o más veces pinnada.

Pinnatifid: A leaf that its margins are deeply incised nearly all the way to the axis but the segments are not contracted at the base and therefore are not considered as a pinna. Pinatífida. Pinnatífida.

Pinnatisect: A leaf that its margins are incised all the way to the axis but the segments are not contracted at the base and therefore are not considered as a pinna. Pinatissecta. Pinnatisecta.

Pinnule: the primary division of the pinna of a pinnate leaf. Pínula. Pínnula.

Projecting sori: sori that grow beyond the outline margins of the leaf. Soro projetando-se. Soros proyectandose.

Proliferous buds: buds (germ cells) in the tip of the leaf from which a new individual may sprout. Gemas prolíferas. Brotes prolíferos.

Pseudodichotomously branched: refers to the architecture of lamina that is common in the family Gleicheniaceae where the main axis bifurcates and one branch continues bifurcating but the other not. Pseudodicotomicamente bifurcado. Seudodicotónicamente ramificado.

Pubescence: hairs and or scales covering a certain part of the plant. Pubescência. Pubescencia.


Rachis: the main axis of a pinnate leaf. Raque. Raquis.

Radially: refers to creeping rhizomes in which the leaves arise both from all sides of the stem. Radialmente. Radialmente.

Rhizome: a creeping underground stem or root. Rizoma. Rizoma.


Seasonally inundated forests: forests that are affected by the seasonal flooding regimes of the Amazonian rivers. Florestas inundáveis, Igapó, Várzea. Bosque estacionalmente inundado: resting, tahuampa.

Secondary veins: Veins that are branches from the main vein, usually from the center towards the edge of the leaf. Nervuras secundárias. Nervaduras secundarias.

Segment: the smallest division or unit of a pinnate leaf. Segmento. Segmento.

Serrate:  leaves with toothed, saw-like margins. The sharp teeth point forward, in contrast with dentate. Serreado. Aserrado.

Serrulate: having small broad rounded teeth in the margin. Serrulado. Aserrulado.

Sessile: in leaves, refers to pinnae or pinnulae that are stalkless, directly attached to the base. Séssil. Sésil.

Short-creeping: a rhizome that grow horizontally and leaves arise closely to each other. Curto-reptante. Cortamente reptante.

Skeletonized: with no or very little green tissue. Esqueletonizada. Esqueletizado.

Sorus: a cluster of sporangia. Generally on the underside of the leaf, but occasionally elsewhere on the leaf. Plural: Sori. Soro. Soro.

Specialized reproductive leaf: a leaf in which the sori cover almost all the abaxial surface and the area of green tissue is considerably reduced in comparison to the sterile leaf. Folha reprodutiva especializada. Hoja reproductiva especializada.

Stalked: bearing a petiole. Pedunculado. Pedunculado.

Sterile leaves: leaves that do not bear spores. Folhas estéreis. Hojas estériles.

Stipules: refers to lateral expansions of the rhizome of some Marattiaceae that is fleshy and stores starch. Estípulas. Estípulas.

Substrate: the surface or material in which the plant grows. Substrato. Sustrato.

Swamps: a vegetated lowland area seasonally or intermittently filled with water. Charcos. Pantano.

Synangium: a type of sori in which sporangia are partially or completely fused laterally. Sinângio. Sinangio.


Terminal segment: The apical segment of a 2 or more times pinnate leaf. Segmento terminal. Segmento terminal.

Terminal/apical pinna: the pinna in the apex of the leave. Pina terminal/apical. Pinna apical.

Terrestrial: growing from the ground. Terrestre. Terrestre.

Trapeziform: with four unequal and not parallel sides, like the outline of a trapezium. Trapeziforme. Trapeziforme.

Tree-like: with sturdy erect trunk. Arborescente. Arborescente.

Truncate: ending abruptly. In leaf or pinna base, refers to an almost squared shape. Truncado. Truncado.

Tussock: A tuft or clump. Tufo. Penacho.

Twining: loosely hanging on other plants. Entrelaçado, enrolado. Trepador.


Valvate: divided longitudinally in two half parts. Valvada. Valvado.

Veinlets: a very small vein, with free end. Vênula. Venillas.

Veins: the vessels of conductive tissues in plants that carries water and nutrients to and from the various parts of the plant. Veias. Venas.

Venation: the pattern formed by the veins. Venação. Venación.

Vestigial: reduced to a very small remnant. Vestigial. Vestigial.


White-sand vegetation: plant formation on extremely nutrient poor, sandy soils. Can be dominated by grasses, bushes, or thin trees. These forests present lower biomass than typical Amazonian forests. Campina ou campinarana. Vegetación sobre arena blanca: varillal, chamizal.