New vesselless angiosperm stem with a cambial variant from the Upper Cretaceous of Antarctica

Abstract

We sectioned a permineralized stem preserved in marine calcareous concretions from the Campanian (Upper Cretaceous) of James Ross Island, Antarctic Peninsula using the cellulose-acetate peel technique. The material is a slender stem displaying a combination of characters such as: (i) absence of vessels and axial parenchyma, (ii) presence of a cambial variant which produces axial vascular elements in segments (AVES pattern), and (iii) elongated upright ray cells. This character combination allows us to assign this fossil to family Chloranthaceae and to relate it to an extant genus Sarcandra. Consequently we describe Sarcandraxylon sanjosense gen. et sp. nov., representing the first vegetative fossil of Chloranthaceae-a basal angiosperm family with a fossil record extending back into the Early Cretaceous and dominated by pollen grains and a limited number of reproductive mesofossils. Besides doubtfully assigned leaves, there are no reported Cretaceous macrofossils of Chloranthaceae, which hinders our understanding of the overall pattern of morphological evolution for the family. The new fossil constitutes the first fossil occurrence of the Sarcandra clade in high latitudes of Western Gondwana. The particular wood anatomy and small diameter suggest a new plant habit (subshrub) for the physiognomy of the Cretaceous Antarctic floras.

Mixoxylon australe gen. et sp. nov., a unique homoxylous wood with non-angiosperm affinity from the Lower Cretaceous of Antarctica (Albian, James Ross Island)

“…The Mixoxylon wood is different from earlier finds of fossil wood from the James Ross Island region (Cantrill & Poole 2012, Sakala & Vodrážka 2014, Pujana et al 2017, Pipo et al 2020, and its systematic position is not yet clear, even though we must note once again its similarity to Phoroxylon and Sahnioxylon woods. The occurrence of Phoroxylon is limited to the Northern Hemisphere, but previous finds of Sahnioxylon, with one Middle Jurassic exception from Liaoning, China (Philippe et al 1999), were recorded in the Antarctic Peninsula and India (Bose & Sah 1954, Lemoigne & Torres 1988, Philippe et al 1999, Falcon-Lang & Cantrill 2001, Poole & Cantrill 2001.…”

Wildfires in the Campanian of James Ross Island: a new macro-charcoal record for the Antarctic Peninsula

“…Recently, Pipo et al (2020) described Sarcandraxylon sanjosense, a permineralized stem preserved in marine calcareous concretions from the Campanian (Upper Cretaceous) of James Ross Island, and assigned this fossil to the Chloranthaceae family, relating it to the extant genus Sarcandra (Pipo et al 2020).…”

“…the James Ross Island area, where the Santa Marta Formation crops out (Crame et al 1991;Poole & Francis 1999Poole, Cantrill et al 2000;Poole, Gottwald et al 2000;Cantrill & Poole 2005;Poole & Cantrill 2006;Kvacek & Sakala 2011;Leppe et al 2012;Pujana et al 2017;Pujana et al 2018;Pipo et al 2020). However, no palaeobotanical evidence that palaeo-wildfires reached the vegetation in this area has been described so far, although the region as a whole had favourable conditions for fire, for example, abundant vegetation, the presence of ignition sources and adequate pO 2 levels.…”