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Czekanowskia, an extinct gymnosperm leaf genus that lived during the Mesozoic Era, that may be related to ginkgophytes. Its seed genus, Leptostrobus, had a pair of ovules that would open up like a scallop. This may be another gymnosperm group that resembles a pre-angiosperm condition, but may not be evolutionarily related to flowering plants.
Ecology & Form
Ecology & Form
Czekanowskia (Subg. Czekanowskia) probably had two speciation events due to climate changes: 1) Middle Jurassic, and 2) Early Cretaceous
Stems
Stems
Deciduous spur shoots
Leaves
Leaves
Persistent leaves born on deciduous (caducous) spur shoots (Pant 1957; Krassilov 1968, 1972)
Scale-like leaves are found below spur shoots
Czekanowskia †:
Highly dissected and elongated leaves
Single vein entering the base and dichotomizes several times
Some leaves are so dissected that they appear to be in fascicles, like pines
Subgenus Czekanowskia: leaves that are amphistomatic (stomata on both sides), with stomata arranged in files
Subgenus Harrisiella: leaves that are amphistomatic (stomata on both sides), with stomata arranged in bands
Subgenus Vachrameevia: leaves that are hypostomatic (abaxial stomata), with stomata arranged in files or bands
Solenites †
Amphistomatic leaf genus arranged in 11-16 distinct bundles, born on short shoots
Sphenarion †
Harris & Miller, 1974
Middle Jurassic of Inner Mongolia, China (Huang et al. 2017)
Narrowly wedge-shaped leaves with no distinction between petiole and lamina
They are wider than 1 mm
Phoenicopsis †
Watson et al., 2001
Small persistent narrowly wedge-shaped leaves produced in fascicles on short deciduous shoots
Subgenus Phoenicopsis: leaves that are hypostomatic
Subgenus Culgoweria: leaves that are amphistomatic with stomata scattered over the surface
Subgenus Windwardia: leaves that are amphistomatic with stomata arranged in longitudinal rows
Roots
Roots
Unknown
Geologic Range
Geologic Range
Brinkia from the Late Permian (Kustatscher et al., 2019)
Classification
Classification
└Czekanowskiales †
Above: Leaves of Czekanowskia † (subg. Harrisella ) chinensis (From Fig 3 of Sun et al. 2009)
Above: Leaves of Sphenarion † (from Huang et al. 2017)
Reproduction
Reproduction
Leptostrobus †
Leptostrobus †
Ovulate cone
Long slender axis with small, sessile lateral fertile appendages/capsule arranged spirally
Fertile appendages found on the distal half of the axis
Capsules are slightly open and clam-like, with conspicuous lobes (~5)
Stomata and cuticle are found on capsules
Seeds/ovules
10 ovules/seeds occupy each lobe of upper and lower capsule
Ovules are oval and inverted with few archegonia
If valves of capsule were closed, it would resemble a bicarpellary ovary of an angiosperm
This may be another gymnosperm group, that resembles a pre-angiosperm condition, but may not be evolutionarily related to flowering plants
?Avatia bifurcata †
?Avatia bifurcata †
Anderson & Anderson, 2003
Upper Triassic of South Africa
An ovuliferous reproductive structure composed of a once-forked axis bearing a pair of megasporophylls
Each megasporophyll consists of a single multiovulate head.
These ovuliferous structures resemble anomalous fructifications sometimes produced by extant Ginkgo biloba, in which leafy expansions develop around the ovules (Krassilov, 1972; Hara, 1997).
Seeds of A. bifurcata are winged; however, in contrast to the fleshy seeds produced by G. biloba.
This taxon is associated with ginkgophyte leaves and microsporangiate strobili named Eosteria, which consist of a main axis bearing helically-arranged, cupulate microsporophylls
Above: Avatia, a megasporophyll (left) and microsporophyll (right) from Figure 7 of Hrabovský, 2021.
Brinkia †
Brinkia †
Wuchiapingian (early Late Permian) of Italy
Capsules resemble in gross morphology single valves of the Leptostrobus-type, Mesozoic reproductive organs belonging to the Czekanowskiales
Czekanowskialean affinity is reinforced by the fact that the Brinkia remains are found associated with strap-like leaves resembling those of Czekanowskia
B. kerpiana †
Isolated, rounded, globose valves of approximately 11–16 mm, with an up to 2 mm wide marginal lobed rim; central part divided into over 10 radial ridges and furrows originating from a basal short column. Cuticle moderately thick, epidermal cells isodiametric to slightly elongated. Stomata arranged in single, slightly radiating files, often bordering within a file. Stomatal pit surrounded by 6–8 distinctly thickened subsidiary cells bearing a papilla.
B. cortianensis †
Isolated, rounded valves, up to 8 mm wide and 10 mm high with an up to 1 mm wide lobed rim with large apical lobes; central part divided into up to 7 radial ridges and furrows originating from a basal short column.
Above: Czekanowskiales megafossil remains from the Lopingian of the Southern Alps. a-d) Brinkia kerpiana; e-g) Brinkia cortianensis; h-k) Associated leaves from the Bletterbach. Scale bars 5 mm in the pictures of Brinkia, 10 mm in the pictures of the associated leaves
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