Monimiaceae sensu lato, an element of gondwanan polar forests: evidence from the Late Cretaceous-Early Tertiary wood flora of Antarctica

Palaeofloristic studies of the Antarctic Peninsula region are important in furthering our understanding of (i) the radiation and rise to ecological do minance of the angiosperms in the Southern Hemisphere during the Late Creta ceous and (ii) the present day disjunct austral vegetation. Investigations of Upper Cretaceous and Early Tertiary sediments of this region yield a ric h assemblage of well-preserved fossil dicotyledonous angiosperm wood which provides evidence for the existence, since the Late Cretaceous, of temperat e forests similar in composition to those found in present-day southern Sou th America, New Zealand and Australia. This paper describes two previously unrecognised morphotypes, which can be assigned to the Monimiaceae sensu la to, and represents the first record of this family in the wood flora of Ant arctica. Specimens belonging to the first fossil morphotype have been assig ned to Hedycaryoxylon Suss (subfamily Monimioideae) because they exhibit an atomical features characteristic of Hedycaryoxylon and extant Hedycarya J. R. Forst. & G. Forst. and Tambourissa Sonn. Characters include diffuse poro sity, vessels which are mainly solitary with scalariform perforation plates , opposite to scalariform intervascular pitting, paratracheal parenchyma, s eptate fibres and tall (> 3 mm), wide multiseriate rays with a length: brea dth ratio of approximately 1: 4. Specimens belonging to the second morphoty pe have been assigned to Atherospermoxylon Krausel, erected for fossil wood s of the Monimiaceae in the tribe Atherospermeae (now Atherospermataceae) i n that they exhibit anatomical features similar to Atherospermoxylon and ex tant Daphnandra Benth., Doryphora Endl. and Laurelia novae-zelandiae A. Cun n. These characters include diffuse to semi-ring porosity, scalariform perf oration 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.