Banksia novae-zelandiae
Encyclopedia
Banksia novae-zelandiae is an extinct
species of Banksia
, known only from fossil
leaves found on the South Island
of New Zealand
.
s, and have very wrinkly subsidiary cells. Both leaf surfaces are covered in trichome
bases, and the undersurface is covered in cuticular
papillae.
, South Island
, New Zealand
(46°8′33"S 168°45′6"E), in a thin leaf litter bed located in a seam of the middle Gore Lignite Measures.
B. novae-zelandiae was first published in 2010. The specific epithet refers to New Zealand
, where the fossils were found. The fossils are assigned to Banksieae based on several structural grounds, including brachyparacytic stomata, a trichome base architecture unique to Banksieae, "banksioid" venation, and the pinnate leaf lobes. Within Banksieae they are assigned to genus Banksia because of their cuticular papillae and the division of the leaves into triangular lobes all the way back to the midrib, neither of which occurs in any other Banksieae genus. (Before the 2007 transfer of Dryandra
into Banksia, it was realised that there was no way to distinguish these two genera based solely on foliar characters, and so fossil leaves were classified into the form genera Banksieaephyllum
and Banksieaeformis. Now, however, they may simply be assigned to Banksia.)
Although the cuticular papillae are regarded as evidence that the species belongs to Banksia, their unusual structure, together with some ornamentation of the trichome bases, and the absence of any features of extant Banksia recognised as derived, suggests that B. novae-zelandiae is basal to all extant Banksia species; that is, it belongs to the stem group of Banksia.
to early Miocene
origin , and is thought to have accrued in swamp
s associated with a coastal delta
. The bed mainly contains species with sclerophyllous leaves, with no broad-leaved rainforest
element in evidence, suggesting a heath
-like environment. The vegetation has been interpreted as growing in a warm and constantly wet climate, and the extensive beds of lignite
in the area suggest an area with poor drainage.
, but because the species is regarded as belonging to the stem group, it does not contradict previous evidence suggesting that the crown group
of Banksia arose in southwest Australia
some time after the Paleogene
.
Under the long-held view that the New Zealand flora has a Gondwanan element that has survived there at least since the Cretaceous
, the presence of B. novae-zelandiae in New Zealand can be adequately explained by vicariance
. It is harder to reconcile it with the recent claim that New Zealand was completely submerged in the late Oligocene, as this would require the unlikely (but possible) dispersal
of seeds across thousands of kilometers of ocean.
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
species of Banksia
Banksia
Banksia is a genus of around 170 species in the plant family Proteaceae. These Australian wildflowers and popular garden plants are easily recognised by their characteristic flower spikes and fruiting "cones" and heads. When it comes to size, banksias range from prostrate woody shrubs to trees up...
, known only from fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
leaves found on the South Island
South Island
The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
.
Description
This species is based on several leaf fossils, all with triangular pinnate lobes cut all the way back to the midrib, and indistinct secondary venation. Stomata occur in areoleAreole
Areoles are an important diagnostic feature of cacti, and identify them as a family distinct from other succulent plants. The areoles on cacti are clearly visible; they generally appear as small light- to dark-colored bumps, out of which grow clusters of spines...
s, and have very wrinkly subsidiary cells. Both leaf surfaces are covered in trichome
Trichome
Trichomes are fine outgrowths or appendages on plants and certain protists. These are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae.- Algal trichomes :...
bases, and the undersurface is covered in cuticular
Plant cuticle
Plant cuticles are a protective waxy covering produced only by the epidermal cells of leaves, young shoots and all other aerial plant organs without periderm...
papillae.
Taxonomy
Fossil leaves were found at the Newvale Mine, Waimumu Coalfield, Southland DistrictSouthland District
Southland District is a territorial authority in the South Island of New Zealand. Southland District covers the majority of the land area of Southland Region, although the region also covers Gore District, Invercargill City and adjacent territorial waters...
, South Island
South Island
The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
, New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
(46°8′33"S 168°45′6"E), in a thin leaf litter bed located in a seam of the middle Gore Lignite Measures.
B. novae-zelandiae was first published in 2010. The specific epithet refers to New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, where the fossils were found. The fossils are assigned to Banksieae based on several structural grounds, including brachyparacytic stomata, a trichome base architecture unique to Banksieae, "banksioid" venation, and the pinnate leaf lobes. Within Banksieae they are assigned to genus Banksia because of their cuticular papillae and the division of the leaves into triangular lobes all the way back to the midrib, neither of which occurs in any other Banksieae genus. (Before the 2007 transfer of Dryandra
Dryandra
Banksia ser. Dryandra is a series of 94 species of shrub to small tree in the plant genus Banksia. It was considered a separate genus named Dryandra until early 2007, when it was merged into Banksia on the basis of extensive molecular and morphological evidence that Banksia was paraphyletic with...
into Banksia, it was realised that there was no way to distinguish these two genera based solely on foliar characters, and so fossil leaves were classified into the form genera Banksieaephyllum
Banksieaephyllum
Banksieaephyllum is a plant genus that encompasses organically preserved fossil leaves that can be attributed to the Proteaceae tribe Banksieae, but cannot be attributed to a genus....
and Banksieaeformis. Now, however, they may simply be assigned to Banksia.)
Although the cuticular papillae are regarded as evidence that the species belongs to Banksia, their unusual structure, together with some ornamentation of the trichome bases, and the absence of any features of extant Banksia recognised as derived, suggests that B. novae-zelandiae is basal to all extant Banksia species; that is, it belongs to the stem group of Banksia.
Habitat
The leaf litter bed in which B. novae-zelandiae was found is regarded as of late OligoceneOligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
to early Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
origin , and is thought to have accrued in swamp
Swamp
A swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types of swamp are "true" or swamp...
s associated with a coastal delta
River delta
A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...
. The bed mainly contains species with sclerophyllous leaves, with no broad-leaved rainforest
Rainforest
Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
element in evidence, suggesting a heath
Heath (habitat)
A heath or heathland is a dwarf-shrub habitat found on mainly low quality acidic soils, characterised by open, low growing woody vegetation, often dominated by plants of the Ericaceae. There are some clear differences between heath and moorland...
-like environment. The vegetation has been interpreted as growing in a warm and constantly wet climate, and the extensive beds of lignite
Lignite
Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat...
in the area suggest an area with poor drainage.
Biogeography
Banksia novae-zelandiae encompasses the first fossil Banksia material found outside Australia. It shows that the Banksia lineage once occurred in New ZealandNew Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, but because the species is regarded as belonging to the stem group, it does not contradict previous evidence suggesting that the crown group
Crown group
A crown group is a group consisting of living representatives, their ancestors back to the most recent common ancestor of that group, and all of that ancestor's descendants. The name was given by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms...
of Banksia arose in southwest Australia
Southwest Australia
Southwest Australia is a biodiversity hotspot that includes the Mediterranean forests, woodlands, and scrub ecoregions of Western Australia. The region has a wet-winter, dry-summer Mediterranean climate, one of five such regions in the world...
some time after the Paleogene
Paleogene
The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...
.
Under the long-held view that the New Zealand flora has a Gondwanan element that has survived there at least since the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
, the presence of B. novae-zelandiae in New Zealand can be adequately explained by vicariance
Vicariance
Vicariance is a process by which the geographical range of an individual taxon, or a whole biota, is split into discontinuous parts by the formation of a physical barrier to gene flow or dispersal. Vicariance of whole biotas occurs following large-scale geophysical events such as the uplift of a...
. It is harder to reconcile it with the recent claim that New Zealand was completely submerged in the late Oligocene, as this would require the unlikely (but possible) dispersal
Biological dispersal
Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...
of seeds across thousands of kilometers of ocean.