Systematics and Paleoecology of a New Peltaspermalean Seed Fern from the Triassic Polar Vegetation of Gondwana

Abstract

A new Triassic seed fern is described on the basis of a large collection of well-preserved plant compressions from the Upper Triassic of Mt. Falla, Queen Alexandra Range, central Transantarctic Mountains. The foliage is simple entire-margined to pinnatifid to partly pinnate and is assigned to Dejerseya lobata (Jones et de Jersey) Herbst emend. nov. Associated with these leaves occur two new reproductive structures. The ovulate organ Matatiella dejerseyi sp. nov. is a lax, conelike structure with primarily shield-shaped megasporophylls that are dissected into three to four narrow lobes, each bearing a single recurved, naked ovule. The pollen organ Townrovia polaris sp. nov. consists of a slender axis arising from a covered reproductive bud, bearing pinnately arranged, stalked, elongate receptacles each with ;20 unilocular, clavate pollen sacs; the pollen is bisaccate nontaeniate with an irregular longitudinal sulcus and coarse saccus endoreticulations, corresponding to the dispersed pollen Falcisporites australis. Similar pollen grains occur in the micropylar canals of seed cuticles of M. dejerseyi. Co-occurrence data indicate that the three taxa are probably different organs from one plant species. This new seed fern is assigned to the Matatiellaceae, which we place into the Peltaspermales because of structural similarities with vegetative and reproductive organs of other peltaspermalean seed ferns. It appears that several Triassic Gondwanan plant fossil taxa of currently uncertain affinities-such as Pachydermophyllum, Linguifolium, Carpolithus mackayi, and Andersonia-may belong to the Matatiellaceae as well. We suggest that the matatiellacean peltasperms were opportunistic, early successional plants that were particularly successful in colonizing stressed wetland environments in polar latitudes during the Triassic.

Mesozoic gymnosperms: megafloral changes through the Triassic–Jurassic of Eastern Gondwana

“…Holmes (1987 emended the diagnosis of Umkomasia to include Karibacarpon. However, and Anderson & Anderson (2003) considered these two genera to be distinct; indeed, Karibacarpon may actually be a peltasperm and therefore unrelated to Umkomasia (Taylor et al 2006, Bomfleur et al 2011c. Holmes & Ash's (1979) specimens that were assigned to Dicroidium and Pteruchus from the Lorne Basin pre-date most other specimens attributed to these genera from the Gondwanan Triassic.…”

“…Matatiella is rare and restricted to the Upper Triassic of New Zealand, South America, South Africa and Antarctica (Anderson & Anderson 2003, Arce & Lutz 2010, Bomfleur et al 2011c. Likewise, reports of Townrovia are few, having only been identified from the Middle and Upper Triassic of Tasmania, New Zealand and Antarctica (Bomfleur et al 2011c, Chatterjee et al 2013.…”

“…Likewise, reports of Townrovia are few, having only been identified from the Middle and Upper Triassic of Tasmania, New Zealand and Antarctica (Bomfleur et al 2011c, Chatterjee et al 2013. In-situ pollen resembling Falcisporites were recovered by Bomfleur et al (2011c). Those authors associated Townrovia with Matatiella and Dejerseya based on the occurrence of specimens at the same Antarctic Upper Triassic locality.…”

“…Schmeissneria has a winged ovule partially enclosed within a cupule that is attached, together with numerous other cupules, along an axis (Kirchner & van Konijnenburg-van Cittert 1994, van Konijnenburg-van Cittert 2010 and it was considered to be a possible basal angiosperm by Wang Xin et al (2007). Bomfleur et al (2011c) suggested that Gondwanan material attributed to Stachyopitys shows significant differences to species known from the northern hemisphere in size, shape, number and attachment of pollen sacs and in branching complexity. They Thomas 1933by Pattemore (2016a who suggested that many other Gondwanan specimens hitherto assigned to Stachyopitys may have a pinnate structure (chapter 4).…”

“…Those authors also separated the genera by pollen sac shape and cuticle. Pollen sacs of Pteruchus were regarded by Bomfleur et al (2011c, The type material of Townrovia (Townrow 1965, figs 4, 6) indicates that sacs are oblancealate-obovate with rounded to pointed apices. Pteruchus includes ellipticaloblanceolate-obovate sacs with rounded to pointed apices: see herein and diagnoses of various Pteruchus species by Thomas (1933) and Cantrill et al (1995).…”