Ptilozamites is an extinct genus of pteridosperm (colloquially known as "seed ferns"), known from the Triassic and Early Jurassic of the Northern Hemisphere. It is associated with the pollen organ Harrisiothecium.
Taxonomy
The genus was first erected by Alfred Gabriel Nathorst in 1878 for remains found in
Scania in southern Sweden. Nathorst did not declare a type species While the species
Ptilozamites nilssonii was described in the same paper that named the genus, later authors have treated
Ptilozamites heeri as the type genus. Recent authors have suggested that the genus
Ctenozamites is a synonym of
Ptilozamites. Most authors interpret
Ptilozamites as an enigmatic "
seed fern" (a
seed plant, typically with fern-like leaves, of uncertain affinities), though some authors historically suggested that they were related to
.
Description
The leaves of
Ptilozamites are
pinnate (that is, arranged like that of a typical fern, with pairs of parallel leaflets/pinnules projecting from a central axis). The leaves have an odontopteroid venation,
and a thick
Plant cuticle. The leaves as a whole are typically elongate, with
being present either on both sides (amphistomatic) or only on the underside (hypostomatic) of the pinnules, with the stomata being surrounded by a thickened ring of tissue.
[E. Kustatscher, J.H.A. Van Konijnenburg-van Cittert Seed ferns from the European Triassic—an overview. New Mexico Mus. Natur. Hist Sci. Bull., 61 (2013), pp. 331-344] The leaves of Ptilozamites are often (but not exclusively) forked, like the leaves of the corystosperm seed fern
Dicroidium.
Whole plant
Modern authors have suggested that the
pollen-producing organ
Harrisiothecium (which has also been referred to at least in part by the genus
Hydropterangium) is part of the same plant that produced
Ptilozamites leaves. This structure is composed of a central axis which bears branches which terminate with capsules composed of two flap-like valves, which bear pollen sacs on their inner surface. This structure bear similarities to
Pteruchus (the pollen organ of
corystosperm seed ferns),
Antevsia (the pollen organ of the
Peltaspermales Lepidopteris), the enigmatic pollen organs
Pteroma, Pramelreuthia and
Townrovia, as well as the pollen organs of
Bennettitales.
Distribution and chronology
Ptilozamites was widespread across the Northern Hemisphere during the Late Triassic and Early Jurassic, with remains having been reported from Europe,
Greenland
and China.
