Gigantopterids †

Ecology and Form

• Possible vine or upright plant

• Grew in wetlands as well as arid conditions

• Known mostly from compression and impression fossils 

• They were among the most striking and important plants of the Cathaysian flora of Sino-Malaya, also called Gigantopteris flora (Wang 1999)

Stem

• Woody stems with spines

• Wood contains vessel elements similar to gnetophytes and angiosperms

 Aculeovinea yunguiensis 

• • These stems are woody and vessel-less with a sparganum cortex and prickles

  • Stems were probably connected to Gigantopteris guizhouensis leaves

 Vasovinea tianii

• A permineralized eustelic stem for the Late Permian of China

• Eustelic with 5-9 wedge-shaped mesarch segments, each with wood with vessels

• Prickles, trichomes, and compound hooks are found along stems suggesting a climbing habit

Leaves

• Large bilaterally symmetrical leaves in mature plants (Giganopteris, Gigantopteridium, Cathaysiopteris, Zeilleropteris, Gigantonoclea)

  • Dichotomous venation known is some; 

  • Reticulate venation found in others with anastomosing higher-order veins 

• Some leaves are compound fronds; mature leaves may have been simple

• Oleanane found in leaves (similar to angiosperms)

• Earliest evidence of foliar nyctinasty has been documented in gigantopterid leaves (Feng et al. 2023)

  • Symmetrical insect damage indicates folding of the leaves, probably during the night

Gigantopteris nicotianaefolia (type species) 

• Leaves from Permian of South China (Yan 1983)

• Leaves up to 50 cm long with an entire margin (Glasspoll et al. 2004)

  • Pinnate venation with 4 orders of veins which give rise to "large, polygonal meshes with finer veinlets anastomosing to form meshes and blind endings" (Taylor et al. 2009)

Gigantopteris guizhouensis

• Permineralized simple leaves from the Late Permian of southeast China (Li & Tian 1990)

• Stomata are paracytic with uniseriate trichomes on the abaxial surface

• Many secretory cavities are within the mesophyll of the leaf

• Prickles are found along the abaxial midrib

Gigantopteridium americana

• Leaves from Permian of North America (White 1912)

Gigantopteridium marginervum

• Leaves from Middle Permian of China (Yao & Liu 2004)

• Amphistomic leaves (both sides of leaf) with cyclocytic stomata

• Subsidiary cells on abaxial (lower) surface have papillae

• Subsidiary cells on adaxial (upper) surface lack papillae and are heavily cutinized

Cathaysiopteris

• Leaves from the Permian of Asia

• Forked and pinnately-compound leaves up to 20 cm in length with a sinuous margin and pinnate veins with three orders of venation 

• The tertiary veins are closely-spaced and the meshes are long and narrow (Mamay et al. 1986)

Zeilleropteris

• Leaves from the Permian of Asia

• Dichotomously-divided leaves over 30 cm in length and up to 27 cm wide with four orders of venations

Gigantonoclea

• Leaves from Asia and North America, which were possibly lianas (Li et al. 1994) or possibly aquatic, based on frond dimorphism (Wang 1999)

• Leaves similar to Gigantopteris, but with a toothed margin and veins that are less complex

Delnortea abbottiae

• Permineralized leaf from Early Permian of North America (Mamay et al. 1988)

• Simple, petiolate leaves mostly (3-5 cm) are oblong-elliptical with an entire to crenulate margin and a clasping base

• Sclerenchyma occurs on the enrolled leaf margin, which may aid in the structure of the leaf

• Venation is pinnate with four orders of veins; veins terminate at the margin

Roots

• Unknown

Reproductive organs

• Reproductive parts are not well understood

Pollen-producing structures

• Synangiate structures (Gigantotheca) in linear rows on the abaxial surface of Gigantonoclea are assumed to be pollen organs 

  • They are 4 cm long and extend over a secondary vein

  Linophyllum xuanweiense

• • Supposed pollen structures are rounded (0.5 mm) and arranged in two rows on some species of Gigantopteris and Gigantonoclea (Zhao et al. 1980; Yao & Liu 2004)

  Jiaochengia 

• • Late Permian of North China

  • Supposed pollen structures in 3 pairs of microsporphylls bearing synangia, each consisting of 2-8 elongate sporangia

  • Found in association with Gigantonoclea 

Ovulate structures

• Leaves of Gigantonoclea have been found with seeds on both sides of the midvein (Li & Yao 1983)

  • The ovules or seeds  (Gigantonomia) are ellipsoidal and attached to the abaxial surface with the micropyle exposed on the adaxial surface