Monimiaceae sensu lato, an element of Gondwanan polar forests: Evidence from the late Cretaceous-early tertiary wood flora of Antarctica

Abstract

Palaeofloristic studies of the Antarctic Peninsula region are important in furthering our understanding of (i) the radiation and rise to ecological dominance of the angiosperms in the Southern Hemisphere during the Late Cretaceous and (ii) the present day disjunct austral vegetation. Investigations of Upper Cretaceous and Early Tertiary sediments of this region yield a rich assemblage of well-preserved fossil dicotyledonous angiosperm wood which provides evidence for the existence, since the Late Cretaceous, of temperate forests similar in composition to those found in present-day southern South America, New Zealand and Australia. This paper describes two previously unrecognised morphotypes, which can be assigned to the Monimiaceae sensu lato, and represents the first record of this family in the wood flora of Antarctica. Specimens belonging to the first fossil morphotype have been assigned to Hedycaryoxylon SÜss (subfamily Monimioideae) because they exhibit anatomical features characteristic of Hedycaryoxylon and extant Hedycarya J.R.Forst. & G.Forst. and Tambourissa Sonn. Characters include diffuse porosity, vessels which are mainly solitary with scalariform perforation plates, opposite to scalariform intervascular pitting, paratracheal parenchyma, septate fibres and tall (>3 mm), wide multiseriate rays with a length: breadth ratio of approximately 1: 4. Specimens belonging to the second morphotype have been assigned to Atherospermoxylon KrÄusel, erected for fossil woods of the Monimiaceae in the tribe Atherospermeae (now Atherospermataceae) in that they exhibit anatomical features similar to Atherospermoxylon and extant Daphnandra Benth., Doryphora Endl. and Laurelia novae-zelandiae A.Cunn. These characters include diffuse to semi-ring porosity, scalariform perforation plates with up to 25 bars, septate fibres, relatively short (<1 mm) rays with a length: breadth ratio of between 1: 4 and 1: 11.

Cretaceous and Cenozoic vegetation of Antarctica integrating the fossil wood record

“…The increased abundance of wood fragments suggests that the angiosperms were no longer herbaceous, shrubby understorey elements but had become a more important component of the canopy. The Santonian leaf floras still suggest a strong sterculiaceous and lauralean component (Hayes 1996(Hayes , 1999, alongside woods with lauraceous (Poole et al 2000c), cunoniaceous (Poole et al 2000a), illiciaceous (Poole et al 2000b), atherospermataceous (Poole & Francis 1999;Poole & Gottwald 2001) and winteraceous (Poole & Francis 2000) affinity (Fig. 4) Baldoni & Medina 1989) occur, although the rare occurrence of these grains indicates the plants were of minor importance in the vegetation.…”

Fossil calibration of Magnoliidae, an ancient lineage of angiosperms

“…There are species that are or bear flowers preserved in the form of compressions (e.g., Mohr and Eklund, 2003;Frumin et al, 2004), in three dimensions as charcoal (e.g., Kvaček and Eklund, 2003;Viehofen et al, 2008), or in amber (e.g., Poinar and Chambers, 2005). In addition to fossil flowers, there are fossil woods (e.g., Poole and Gottwald, 2001) and leaves (e.g., Rüffle and Knappe, 1988). Finally, pollen grains, seeds, and fruits referred to the group are also common in the fossil record (e.g., Friis, 1985;Carpenter et al, 1994;Friis et al, 1995).…”

“…Cretaceous fossils assigned to Magnoliidae have been found in many parts of the world: South America (e.g., Mohr and Bernardesde-Oliveira, 2004;Mohr et al, 2013), North America (e.g., Dilcher and Crane, 1984;Crepet et al, 2005), Europe (e.g., Friis et al, 2010, Asia (e.g., Takahashi et al, 2001Takahashi et al, , 2008, Africa (e.g., Doyle et al, 1990), Australasia (e.g., Dettmann et al, 2009), and Antarctica (e.g., Poole and Gottwald, 2001;Eklund, 2003). Fossil Magnoliidae come in a variety of forms, from wood (e.g., Herendeen, 1991;Poole and Gottwald, 2001;Schöning and Bandel, 2004) and leaves (e.g., Upchurch and Dilcher, 1990;Kvaček, 1992) to flowers (e.g., Dilcher and Crane, 1984;Drinnan et al, 1990;Takahashi et al, 2008;, fruits (e.g., Friis et al, 2010, seeds (e.g., Knobloch and Mai, 1986;Frumin and Friis, 1996), and pollen (e.g., Doyle et al, 1990;Macphail et al, 1994). Because the number of characters observed in such fossils is often limited, establishing their phylogenetic relationships to extant taxa is not always straightforward.…”

Valdivian ecosystems in the Late Cretaceous and Early Tertiary of Antarctica: further evidence from myrtaceous and eucryphiaceous fossil wood

“…Now eucryphiaceous and myrtaceous elements have been found in the earlier wood £ora of Seymour Island some 4 ‡ latitude to the south and some 20 Ma earlier. These two elements can be added to other components of a Valdivian-like vegetation such as the Monimiaceae, Cunoniaceae, Lauraceae, Araucariaceae, Podocarpaceae, Cupressaceae, Cyatheaceae, and Dicksoniaceae derived from the earlier Maastrichtian^Palaeo-cene wood, pollen and leaf assemblages from this more southerly geographical region (see Askin, 1992;Hill and Scriven, 1995;Francis, 1999, 2000;Poole et al, 2000a,b,c;Poole and Gottwald, 2001;Cesari et al, 2001) suggestive of a Valdivian rainforest-type vegetation extending across the Peninsula region and into South America throughout the Late Cretaceous and Tertiary. If this is the case, then the changes in vegetational composition during the Late Cretaceous and Tertiary have to be discussed in the context of widespread ecological disturbance and subsequent vegetational succession set against a backdrop of general climatic deterioration rather than solely climate induced vegetational change.…”