Gymnosperms from the Middle Triassic of Antarctica: The First Structurally Preserved Cycad Pollen Cone

Abstract

The first permineralized cycad pollen cone is described from the lower Middle Triassic of Antarctica. The cone is characterized by helically arranged, wedge-shaped microsporophylls, each with five or more spinelike projections extending from the rhomboid distal face. The vascular cylinder is dissected and produces paired traces to each microsporophyll. Three vascular bundles enter the base of the microsporophyll and divide to produce at least five vascular strands in the sporophyll lamina. Pollen sacs occur in two radial clusters near the lateral margins on the abaxial surface of the microsporophyll. Each cluster bears up to eight elongate pollen sacs that are fused for approximately half their length and display longitudinal dehiscence. Pollen sacs are sessile and attached to a vascularized, receptacle-like pad of tissue that is raised from the surface of the microsporophyll. Pollen is ovoid, psilate, and monosulcate. Although the affinities of this cone with the Cycadales are obvious, the complement of characters in the fossil is unique and thus does not permit assignment to an extant family. Features of the cone are evaluated against reproductive aspects of living cycads.

Biota and palaeoenvironment of a high middle-latitude Late Triassic peat-forming ecosystem from Hopen, Svalbard archipelago

“…Superficially, this array of cells is similar to those of the pollen sac wall in the cycad Delemaya spinulosa from the Middle Triassic of Antarctica (cf. Klavins et al 2003, fig. 3D), and the outer pollen sac wall of some modern cycads (Lang 1897).…”

Cataphylls of the Middle Triassic cycad Antarcticycas schopfii and new insights into cycad evolution

“…There are also a number of insects that are parasitic on cycads although not known to be involved in pollination, especially lepidopterans; however, the earliest undisputed lepidopteran fossils do not appear until the Jurassic (Norstog and Nicholls, 1997;Grimaldi and Engel, 2005). Klavins et al (2003Klavins et al ( , 2005 also reported coprolites in isolated cycad pollen sacs that occur in association with the microsporangiate cone Delemaya Klavins, Taylor, Krings, et Taylor, the only other cycad taxon known from the Triassic of Antarctica and possibly representing the pollen cone of Antarcticycas, although the two taxa have not yet been found in attachment. The coprolites in pollen sacs associated with Delemaya are composed entirely of pollen (Klavins et al, 2003(Klavins et al, , 2005, whereas those in the Antarcticycas cataphylls are not.…”

“…Klavins et al (2003Klavins et al ( , 2005 also reported coprolites in isolated cycad pollen sacs that occur in association with the microsporangiate cone Delemaya Klavins, Taylor, Krings, et Taylor, the only other cycad taxon known from the Triassic of Antarctica and possibly representing the pollen cone of Antarcticycas, although the two taxa have not yet been found in attachment. The coprolites in pollen sacs associated with Delemaya are composed entirely of pollen (Klavins et al, 2003(Klavins et al, , 2005, whereas those in the Antarcticycas cataphylls are not. In extant cycads, some pollinating insects consume pollen and some do not (Norstog and Nicholls, 1997;Stevenson et al, 1998), so the composition of the coprolites does not necessarily shed light on the ecological relationship of the insects feeding on the cataphylls to Antarcticycas.…”

Evolutionary Transformations of Sporoderm Ultrastructure in Certain Monophyletic Lineages of Higher Plants

“…The group appeared in the Triassic and has survived until nowadays (Taylor et al 2009). Currently avai la ble data show that the elongated perpendicular alveolae of the ectexine, which are so characteristic of pollen of mo dern cycads, existed at least as early as in the Jurassic (Za vialova & Van Konijnenburgvan Cittert, submitted), or, perhaps, even earlier (Klavins et al 2003). This seems to be the case of evolutionary stability.…”