Dicroidium irnensis Abu Hamad et Kerp in Abu Hamad, Kerp, Vörding & Bandel

Plant Fossil Names Registry Number: PFN000187

Act LSID: urn:lsid:plantfossilnames.org:act:187

Authors: A. Abu Hamad & H. Kerp

Rank: species

Reference: Abu Hamad, A., Kerp, H., Vörding, B. & Bandel, K. (2008): A Late Permian flora with Dicroidium from the Dead Sea region, Jordan. – Review of Palaeobotany and Palynology 149(3–4): 85–130.

Page of description: 111

Illustrations or figures: pls 1–7, 18: 7; figs 2, 3

Types

Original diagnosis/description

Fronds small, bifurcated, bipinnate. Primary axis very robust and smooth, bifurcating with an angle of approximately 25° with at least two pairs of pinnae below the bifurcation; frond portions above the bifurcation more or less ovate in outline, tapering towards the apices and with their greatest width in the middle. Pinnae alternating to suboppositely attached, at angles between 45° and 70°, with up to 14 pinnules at each side.
Pinnules densely spaced, sometimes overlapping, in alternating or subopposite position; pinnules obliquely attached with their entire basis, asymmetrical, outline tongue-shaped to rhomboidal with rounded apices.Basiscopic pinnulesmore obliquely attached than acroscopic pinnules; basal basiscopic pinnules occasionally continuing along the primary rachis. Pinnae ending in elongated, tongue-shaped pinnules and usually consisting of 3–5 strongly fused pinnules. Intercalary pinnules present, asymmetrically triangular to rhomboidal. Venation odontopteroid, lacking a clearmidvein,with several veins entering the pinnule; veins rather densely spaced, bifurcating one or two times.
Leaves amphistomatic, stomata far more numerous on the lower side. Epidermal cells and stomata of the upper surfaces larger than those of the lower surfaces. Stomata of the upper side mainly restricted to the pinna rachides and basal parts of the pinnules, particularly over the veins, but very rare to absent on the more distal parts of the pinnules. Stomata very abundant on the lower leaf side, occurring all over the pinnule surface but rare or absent under the pinna axes. Stomata of the lower pinnule surfaces normally randomly distributed. Stomata commonly with four subsidiary cells, the lateral ones less strongly cutinised than the polar ones; stomata with a ring of five or six subsidiary cells occur occasionally. Papillae rare, mainly restricted to the lower pinnule surfaces.

Etymology

The name refers to the Um Irna Formation in which the fossils have been found. Um Irna is the mountain between Wadi Himara and Wadi Zarqa Ma'in.

Stratigraphy

Permian
Silt and clay layers and lenses, 15.5–16.5 m above the base of the Um Irna Formation, Upper Permian.

Locality

Jordan
Wadi Himara, in the incised river valley, ca. 400 m upstream along the southern branch after the main bifurcation at 31° 37′ 55.67″ N and 35° 37′ 15.69″ E.