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Palaeobiogeography, extinctions and evolutionary trends in the Cunoniaceae : a synthesis of the fossil record


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Barnes, Richard Wayne 1999 , 'Palaeobiogeography, extinctions and evolutionary trends in the Cunoniaceae : a synthesis of the fossil record', PhD thesis, University of Tasmania.

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The fossil record of the flowering plant family Cunoniaceae is comprehensively
examined and reviewed using detailed studies of the morphology of extant
Cunoniaceae with new macrofossil species described from Australian Cainozoic
sediments. Eleven of the 26 extant Cunoniaceae genera are represented in the
macrofossil record and include leaves and leaf fragments, foliar cuticle and
reproductive structures. These occur almost exclusively in Australian fossil deposits
and range from Late Paleocene to Quaternary in age. Cunoniaceae fossil pollen is
widely documented across the Southern Hemisphere but is less informative due to the
low taxonomic resolution of its identification.
Leaf and infructescence macrofossils from five Cainozoic deposits in south-eastern
Australia are indistinguishable from the extant species Callicoma serratifolia which is
now restricted to eastern Australia. The first macrofossil of Codia, C. australiensis, is
described from Western Australia, and has affinities with the juvenile foliage of at least
one extant Codia species which is now endemic to New Caledonia.
Two new fossil species of Ceratopetalum are described from fruits, C. westermannii
(late Early-Late Miocene) and C. maslinensis (Middle Eocene) and the identification of
two others previously described, C. priscum (Middle Miocene) and C. wilkinsonii
(Late Eocene-Early Oligocene), is supported.
Fossil Eucryphia capsules are described for the first time, E. reticulata (Early
Oligocene) and E. sp. `LRR1' (Early Oligocene), in addition to new species based on
leaf macrofossils, E. leaensis (entire margin, Early Oligocene) and E. mucronata
(serrate margin, ?Latest Eocene-Early Oligocene). The previously identified E.
aberensis has been located at the early Oligocene Little Rapid River, making this the
first Eucryphia species to be located in more than a single deposit. This species has
both serrate and entire margins. Early Pleistocene leaves from Tasmania are
conspecific with the two extant species, E. lucida and E. milliganii ssp. milliganii. The
identification of E. falcata (Late Paleocene; Lake Bungarby) is supported. Macrofossils and the fossil pollen record show that some genera had a different or
more widespread distribution in Australia during the Cainozoic, with two genera
(Weinmannia and Codia) having become extinct from the continent. A reduction in
vegetation disturbance regimes (e.g. volcanism, uplifting, landslips) or changes in
climate, including increasing cold, frost, dryness, seasonality, or some combination of these, may be implicated in these generic extinctions, although the cause of others
remains unidentified.
Many extant genera (Schizomeria, Vesselowskya, Callicoma, Ceratopetalum,
Acsmithia, Codia) had evolved by the Early Oligocene or earlier (Eucryphia, Late
Paleocene; Weinmannia, ?latest Eocene-Early Oligocene), perhaps with generic
diversification more or less complete by the Early Cainozoic. A late Cretaceous origin
of the family is possible, and may account for its widespread distribution on nearly all
Southern Hemisphere landmasses, although long-distance dispersal events are required
to explain some geographic disjunctions.
Foliar evolution has occurred at different rates within the Cunoniaceae. Within
Eucryphia there has been an evolutionary trend towards simple leaves with entire
margins and well developed peltiform cuticular extensions. These evolutionary trends
and apparent adaptations are consistent with those proposed to have occurred within
other prominent Cainozoic Australian rainforest genera, including a reduction in leaf
size and increased protection of stomata. In contrast, the leaf form in Callicoma has
remained relatively unchanged since the Early Oligocene which may be due to its
paedomorphic origin from an ancestor shared with its sister taxon Codia.
A reduction in the flower size of two genera (Acsmithia and Schizomeria) provides
support to the hypothesis that within some Cunoniaceae there has been a shift from
entomophily to partial or exclusive anemophily. Petally in one extant and two fossil
species of Ceratopetalum shows that petally was once more widespread in the genus.
Secondary loss of petals may have been in response to fruit specialisation or a change
in pollinator vector. Infructescences of Callicoma indicate that the genus has not
changed florally since the Early Oligocene.

Item Type: Thesis - PhD
Authors/Creators:Barnes, Richard Wayne
Keywords: Cunoniaceae, Rosales, Fossil, Paleogeography, Plants
Copyright Holders: The Author
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Copyright 1999 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1999. Includes bibliographical references

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