INVESTIGADORES
PASSALIA Mauro Gabriel
artículos
Título:
An Early Cretaceous zamiaceous cycad of South West Gondwana: Restrepophyllum nov. gen. from Patagonia, Argentina
Autor/es:
PASSALIA, M.G.; DEL FUEYO, G.; ARCHANGELSKY, S.
Revista:
REVIEW OF PALAEOBOTANY AND PALYNOLOGY
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Año: 2010 vol. 161 p. 137 - 150
ISSN:
0034-6667
Resumen:
The record of Cycadales in Patagonia begins in the Triassic and extends up to the Oligocene. In this region the
group is highly diversified and includes several taxa represented by trunks, leaves and pollen cones. A new
cycadalean genus and species, Restrepophyllum chiguoides, form the Aptian Anfiteatro de Ticó Formation,
Santa Cruz province, Argentina, is described here. The fossil is a leaf compression with well-preserved cuticle.
Its morphology, anatomy and ultrastructure are studied by means of light and electron microscopy. The leaf
is lanceolate, serrate, and possesses a prominent midvein and decurrent laterals showing an open, simple or
dichotomous venation. The leaf is hypostomatic, and the abaxial cuticle is thinner than the adaxial one. The
stomata are irregularly distributed and indistinctly oriented between veins. They are monocyclic to
imperfectly dicyclic (haplocheilic); the suprastomatal aperture is raised over the epidermis and the guard
cells are sunken. Scattered trichomes and crystalliferous idioblasts are also present. The cuticle is composed
of three layers: the outer and inner layers are lamellate, while the middle one is granulate. This new cycad
leaf is compared with similar fossil leaves from Gondwana and Europe/North America, and also with similar
extant cycad leaves. Based on the general morphology and the main characters of the cuticle, R. chiguoides is
assigned to the family Zamiaceae; moreover it is more closely related to the living Zamia (Chigua) restrepoified and includes several taxa represented by trunks, leaves and pollen cones. A new
cycadalean genus and species, Restrepophyllum chiguoides, form the Aptian Anfiteatro de Ticó Formation,
Santa Cruz province, Argentina, is described here. The fossil is a leaf compression with well-preserved cuticle.
Its morphology, anatomy and ultrastructure are studied by means of light and electron microscopy. The leaf
is lanceolate, serrate, and possesses a prominent midvein and decurrent laterals showing an open, simple or
dichotomous venation. The leaf is hypostomatic, and the abaxial cuticle is thinner than the adaxial one. The
stomata are irregularly distributed and indistinctly oriented between veins. They are monocyclic to
imperfectly dicyclic (haplocheilic); the suprastomatal aperture is raised over the epidermis and the guard
cells are sunken. Scattered trichomes and crystalliferous idioblasts are also present. The cuticle is composed
of three layers: the outer and inner layers are lamellate, while the middle one is granulate. This new cycad
leaf is compared with similar fossil leaves from Gondwana and Europe/North America, and also with similar
extant cycad leaves. Based on the general morphology and the main characters of the cuticle, R. chiguoides is
assigned to the family Zamiaceae; moreover it is more closely related to the living Zamia (Chigua) restrepoiRestrepophyllum chiguoides, form the Aptian Anfiteatro de Ticó Formation,
Santa Cruz province, Argentina, is described here. The fossil is a leaf compression with well-preserved cuticle.
Its morphology, anatomy and ultrastructure are studied by means of light and electron microscopy. The leaf
is lanceolate, serrate, and possesses a prominent midvein and decurrent laterals showing an open, simple or
dichotomous venation. The leaf is hypostomatic, and the abaxial cuticle is thinner than the adaxial one. The
stomata are irregularly distributed and indistinctly oriented between veins. They are monocyclic to
imperfectly dicyclic (haplocheilic); the suprastomatal aperture is raised over the epidermis and the guard
cells are sunken. Scattered trichomes and crystalliferous idioblasts are also present. The cuticle is composed
of three layers: the outer and inner layers are lamellate, while the middle one is granulate. This new cycad
leaf is compared with similar fossil leaves from Gondwana and Europe/North America, and also with similar
extant cycad leaves. Based on the general morphology and the main characters of the cuticle, R. chiguoides is
assigned to the family Zamiaceae; moreover it is more closely related to the living Zamia (Chigua) restrepoiR. chiguoides is
assigned to the family Zamiaceae; moreover it is more closely related to the living Zamia (Chigua) restrepoiZamia (Chigua) restrepoi
(D. Stevenson) Lindstrom than to any other member of the Cycadales. Paleophytogeographic evidence
suggests a South American origin of Zamia/Chigua and a further migration to northern latitudes. This new
type of leaf also suggests the putative existence of a Chigua clade that may be traced back to the Early
Cretaceous when two cycadalean families, Zamiaceae and Stangeriaceae, were already well-established in
Patagonia.Zamia/Chigua and a further migration to northern latitudes. This new
type of leaf also suggests the putative existence of a Chigua clade that may be traced back to the Early
Cretaceous when two cycadalean families, Zamiaceae and Stangeriaceae, were already well-established in
Patagonia.Chigua clade that may be traced back to the Early
Cretaceous when two cycadalean families, Zamiaceae and Stangeriaceae, were already well-established in
Patagonia.