Ptilophyllum muelleri(Ettingsh.) comb. nov. from the Oligocene of Australia: Last of the Bennettitales?

Abstract

Several small pinnate leaves of early Oligocene age from Cethana, Tasmania, are newly described and found to be conspecific with Anomozamites muelleri Ettingsh. recorded from coeval strata at Emmaville, northern New South Wales. These fossils are most probably referable to the Bennettitales on the basis of leaf size, leaflet shape, and venation patterns, in the absence of diagnostic cuticular details. They are transferred to Ptilophyllum on the basis of leaflet morphology and represent the youngest putative bennettitalean remains yet documented. Their occurrence reinforces previous arguments that the highest-paleolatitude fragments of southeastern Gondwana provided moist temperate refugia for the survival of Mesozoic gymnosperm taxa well into the Cenozoic.

A snapshot into the terrestrial ecosystem of an exceptionally well-preserved dinosaur (Hadrosauridae) from the Upper Cretaceous of North Dakota, USA

“…Alisporites-type pollen, probably produced by seed-ferns, constitutes a notable component of the bisaccate pollen group. Seed-ferns went extinct, together with over 75% of the global fauna and flora at the KePg boundary event, except in southeastern Australia (including Tasmania) where one corystosperm and one bennettitalean lineage survived into the Paleogene (McLoughlin et al, , 2011. Although seed ferns declined through the Cretaceous, Taylor et al (2006) candidate for the Alisporites pollen detected in the palynological assemblage.…”

The diversity of Australian Mesozoic bennettitopsid reproductive organs

“…Given that cuticular details are unknown for most Australian bennettitalean leaves and reproductive organs, identifications have relied predominantly on comparison of gross morphological features and venation characters (Etheridge 1888;Walkom 1917Walkom , 1921Jones and de Jersey 1947;Douglas 1969;Gould 1975, McLoughlin 1996McLoughlin et al 2000McLoughlin et al , 2011Holmes and Anderson 2008;McLoughlin and Pott 2009;. The conservative pinnate architecture of bennettitalean leaves has meant that many Australian specimens have been assigned by previous workers to species based on type material from India or even Europe.…”

“…Australia is notable for hosting some of the oldest (mid-Triassic) and youngest (Oligocene) fossil representatives of this group (Holmes and Anderson 2008;McLoughlin et al 2011). Bennettitales-like monosulcate pollen, generally attributed to Cycadopites, is also a common background (but rarely dominant) component of many Australian mid-Mesozoic palynoassemblages (Burger 1980(Burger , 1994.…”

Mesozoic ecosystems – climate and biotas

“…The Cretaceous covers the period in which angiosperms rose from their murky origins, and rapidly expanded in extent, biomass and biodiversity (Wing and Boucher, 1998), while various more typical Mesozoic plants, such as the Bennettitales, dwindled to extinction (McLoughlin et al, 2011). This was a huge step towards the modern biota.…”