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Obscure Early Cretaceous Gymnosperm
Obscure Early Cretaceous Gymnosperm
The order Doyleales was named in 2016 by Rothwell & Stockey for a group of Early Cretaceous gymnosperms with carpel-like ovulate organs that can completely enclose the seed at maturity. As noted by them, this group "could easily have been assigned to the flowering plants had anatomical preservation been insufficient to reveal that the seed has single integument and is positioned on the abaxial side of the enclosing cupule" (Rothwell & Stockey 2016)
Ecology & Form
Ecology & Form
Stems / Leaves / Roots
Stems / Leaves / Roots
Unknown
Reproduction
Reproduction
Gymnospermous plants producing compact, compound seed cones with helically arranged bract/axillary fertile shoot complexes.
Axillary complexes confluent at base, dividing to produce bract and axillary fertile shoot; sporophylls bearing inverted seeds.
Mature seeds surrounded by seed-enclosing cupule of sporophyll origin.
Ovules largely exposed at pollination and extensively or completely enclosed at time of seed dispersal.
Pollination by bisaccate grains captured between integumentary pollination horns and deposited in pollen chamber.
Seed integument unvascularized; nucellus attached to integument only at chalaza.
Classification
Classification
└Doyleales
Geological Age
Geological Age
Early Jurassic - Early Cretaceous
Doylea
Doylea
early Cretaceous of Mongolia
Seed cones cylindrical, relatively compact, with axillary shoot producing two sporophylls; bract vascularized, free at tip
Sporophylls each producing one inverted ovule abaxially and sporophyll extension distally.
Two meristematic cupule lobes at seed base during pollination; growing after pollination, extending toward micropyle and more-or-less fusing with sporophyll stalk to form cupule.
Vascular tissue of each bract/axillary fertile shoot complex diverging from eustelic cone axis as single bundle, dividing into collateral bract trace and two collateral axillary shoot bundles, one to each sporophyll
Sporophyll trace becoming C-shaped distal to bract divergence, terminating at base of ovule as cup-shaped zone of transfusion tissue
Cupule apparently valvate; integument unvascularized, nucellus separating from integument at chalaza, pollen chamber with nucellar beak.
D. mongolica
Originally called Umkomasia mongolica (Shi et al 2016; Rothwell & Stockey 2016)
Aptian/Albian of Mongolia
Seed-bearing unit consisting of a narrow, elongate, bract subtending, and partially fused to, an axis that bifurcates into two cupule stalks, each of which is strongly reflexed distally and bears a cupule containing a single erect seed.
Each cupule consists of the reflexed cupule stalk, which bears a single seed at, or near, its tip, and two lateral flaps that are fused to form a bilobed structure.
The reflexed portion of the cupule stalk results in the micropyle of the seed being oriented back towards the base of the cupule stalk.
Together, the reflexed portion of the cupule stalk and the two lateral flaps enclose the seed. Seeds ovate in lateral outline, three-angled, with three large lateral faces that have weakly developed wings along the margins, and a flat basal triangular attachment scar.
Integument with a thin outer cuticle and a well-developed sclerotesta composed of two to three layers of thick-walled sclerenchyma.
D. tetrahedrasperma
Seed cone 1.1 cm in diameter at postpollination stage
Cupule lobes small at pollination stage, growing and fusing with each other and sporophyll base to enclose seed at maturity; sporophyll continuing beyond cupule 1–2 mm to form unvascularized apical extension
Cupule 3–4 mm wide, 5 mm long; outer zone parenchymatous; inner zone sclerenchymatous, cells with helical thickenings.
Mature ovules 2–3 mm wide, up to 3.5 mm tall; triangular in cross section. Integument largely parenchymatous, three-layered: outer zone of small cells, middle of isodiametric cells that are thicker in corners, inner with elongate, fl attened, rectangular cells; suture line in corners (angles).
Jarudia
Jarudia
Tevshiingovia
Tevshiingovia
Zirabia cylindrica
Zirabia cylindrica
Early Jurassic of Iran
Main axis bearing helically to irregularly-arranged bract‐cupule complexes
These complexes are composed by a long laminar bract subtending and sheathing a cupule stalk that bears a single‐seeded cupule with a dorsal protrusion
It was originally described as the ginkgophyte Karkenia, but the morphological features of this taxon do not conform with those of Karkenia, and suggest affinities with Doyleales rather than Ginkgoales
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