The Lauraceae is a widespread plant family which is a typical component of
warmer rainforests worldwide. In the cooler rainforests of the world, where the
family reaches its limit, there are typically only one or two species in any
given area. In New Zealand today, there are only three species, and these are
restricted to the northern half of the country. This paper documents fossils in
the Lauraceae family from southern New Zealand - well beyond their present
limit. The evidence for Lauraceae is based on cuticle, which is the resistant
layer covering the leaf epidermis (it forms the outer skin of the leaves). The
cuticle retains an impression of the patterns of cells which make up the
epidermis, such as the stomata—the openings which allow gases to enter and
exit the leaf. These patterns are very distinctive. Even a small fragment of
cuticle, perhaps only a millimetre square, may be enough to distinguish a
species and identify what plant group it belongs to. Using this evidence, 25
species of Lauraceae could be recognised from two regions. The first is the
Manuherikia Group, which accumulated as a complex of rivers and lakes throughout
the Miocene, a time period extending from about 25 to 5 million years ago. The
fossils in this study come from the oldest sediments of the Manuherikia Group,
where they were deposited by a braided river in a valley which had been cut in
to the much older rocks below (Mesozoic Haast Schist). The second region studies
is further to the south. These are the rocks of the Easy Southland Group which
include the Gore Lignite Measures. These are a significant source of low-grade
coal (lignite) and have been extensively drilled for coal exploration. The
sediments accumulated where a river (possibly originating in the Manuherikia
Group) discharged into the sea and formed a delta. The fossils from both areas
are early Miocene, or about 20 million years old.
These fossils are significant to understanding how New Zealand’s flora came to
be. New Zealand used to be attached to Australia ands Antarctica but broke away
from these areas about 80 million years ago and has been isolated in the Pacific
Ocean ever since. It is of interest to know whether any of New Zealand’s current
vegetation goes back to that time or whether it has somehow come across the sea
more recently. These fossils, which include genera no longer in New Zealand, but
still existing in place like Australia, may help answer that issue.
On a more detailed level, the distribution of these fossils will help understand
how the vegetation of twenty million years ago functioned. Where exactly did the
different species grow, what was their ecological niche? This kind of
information will help understand the more precise relative order in which the
different samples were deposited in, and may help understand why these different
species became extinct.
Perhaps more importantly, these fossils add to our knowledge of the climate of
the time. It is clear from the mere presence of Lauraceae, let alone their
diversity, that this part of New Zealand was significantly warmer in the Early
Miocene. By inference, the world was likely to have been warmer too, and this
information will help climate modellers understand how global climate patterns
have changed.
The Lauraceae are just one component of the very diverse fossil vegetation which
is being studied in these areas. Future work will try to identify this
additional material. Perhaps the identity of the many Lauraceae presented here
which remain unidentified, will become clear.
Macrofósiles de Lauraceae y cutículas dispersas del Mioceno del
sur de Nueva Zelanda
Mike Pole
Se describen 25 especies de cutículas de Lauraceae procedentes
de 120 muestras fósiles de dos cuencas del Mioceno inferior del
sur de Nueva Zelanda: el paleovalle de San Bathans, del Grupo
Manuherikia, y el de Gore Lignite Measures, del Grupo East
Southland. Se han identificado los géneros Endiandra y
Cryptocarya, los cuales no están presentes en la flora
actual de Nueva Zelanda, y
Beilschmiedia
y Litsea,
presentes actualmente en dicha flora. En el paleovalle de San
Bathans al menos 22 especies formaron parte de una única
comunidad. La presencia de Lauraceae en esta latitud en Nueva
Zelanda y su alta diversidad claramente implican temperaturas
más cálidas que las que se registran actualmente en localidades
de tierras bajas a esa latitud, las cuales se encuentran al sur
del límite actual de la familia.
MACROFOSSILES ET
CUTICULES DISPERSÉES DE LAURACEAE, DU MIOCÈNE DE LA
NOUVELLE-ZÉLANDE MÉRIDIONALE
Mike Pole
Cent vingt
échantillons fossilifères ont livré des restes de cuticules
appartenant à vingt-cinq espèces de Lauraceae, décrites ici. Ces
échantillons proviennent de deux bassins sédimentaires d’âge
Miocène précoce du sud de la Nouvelle-Zélande : la paléovallée
de St Bathans (Groupe de Manuherikia) et les couches
lignitifères de Gore (Groupe de East Southland). Nous
identifions les genres Endiandra et Cryptocarya,
qui ne font plus partie de la flore actuelle de
Nouvelle-Zélande, ainsi que Beilschmiedia et Litsea,
qui eux en font encore partie. Il est probable qu’au moins
vingt-deux espèces croissaient au sein d’une seule communauté
plus grande dans la paléovallée de St Bathans. La présence de
Lauraceae à cette latitude en Nouvelle-Zélande, de même que leur
diversité considérable, suggère évidemment que les températures
étaient plus élevées qu’elles ne le sont aujourd’hui dans les
basses régions de cette latitude, celles-ci étant situées au sud
de la répartition connue de la famille.
MAKROFOSSILIEN VON LORBEERGEWÄCHSEN (LAURACEAE) UND VERTEILTE
CUTICULEN AUS DEM MIOZÄN DES SÜDLICHEN NEU SEELANDS
Mike
Pole
Die
Cuticulen von fünfundzwanzig Lorbeergewächs-Arten werden
beschrieben, die aus 120 fossilhaltigen Proben aus zwei
jung-miozänen Becken Neuseelands stammen, dem St. Bathan
Paläo-Tal aus der Manuherikia Group, und den Gore Lignite
Measures der East Southland Group. Die Gattungen Eniandra
und
Cryptocarya,
die nicht mehr in der heutigen Flora Neuseelands vorkommen,
sowie die der heutigen Flora angehörigen Gattungen
Beilschiedia
und Litsea
wurden identifiziert. Wahrscheinlich wuchsen mindestens 22
Gattungen im St. Bathans Paläo-Tal, die Teil einer einzelnen,
größer gefaßten Gemeinschaft waren. Das Vorkommen von
Lorbeergewächsen in diesen Breitengraden in Neuseeland und ihre
hohe Diversität ist ein deutlicher Hinweis auf höhere
Temperaturen als sie im heutigen Tiefland in diesen
Breitengraden existieren, welche südlich der Vorkommensgrenze
der Familie liegen
MACROFOSSILI DI LAURACEE E
CUTICOLE SPARSE DAL MIOCENE DELLA NUOVA ZELANDA
Mike Pole
In questo lavoro vengono
descritte venticinque specie di cuticole di Lauracee provenienti
da 120 campioni fossiliferi ritrovati in due distinti bacini del
Miocene inferiore della Nuova Zelanda: la paleovalle di San
Bathans del Gruppo Manuherikia, ed il Gore Lignite Meausures del
Gruppo East Southland. Vengono identificati i generi
Endiandra e Cryptocarya, che non fanno più parte
della flora neozelandese, ed i generi Beilschmiedia e
Litsea, che invece sono tuttora presenti. Nella paleovalle
di San Bathans è probabile che almeno 22 specie facessero parte
di una singola comunità di dimensioni maggiori. La presenza di
Lauracee a questa latitudine in Nuova Zelanda e la loro grande
diversità implica chiaramente che esistessero nel Miocene
inferiore temperature più elevate di quelle contemporanee a
bassa quota alla stessa latitudine, che risulta essere a sud del
limite odierno della famiglia.
PAROLE
CHIAVE: Miocene inferiore, Lauracee, cuticola, stomi,
epidermide
Makroskamieniałości
Lauraceae i rozproszona kutikula z miocenu południowej Nowej
Zelandii
Mike Pole
Opisane kutikule
dwudzieściu pięciu gatunków Lauraceae ze 120 zasobnych w
skamieniałości próbek z dwóch wczesnomioceńskich basenów
południowej Nowej Zelandii; Paleodoliny St Bathans Grupy
Manuherikia, oraz Gore Lignite Measures Grupy East Southland.
Zidentyfikowano rodzaje Endiandra i Cryptocarya,
których już brak we współczesnej florze Nowej Zelandii, oraz
Beilschmiedia i Litsea, które żyją i dzisiaj. W
Paleodolinie St Bathans rosły najprawdopodobniej 22 gatunki jako
część szerszego zbiorowiska. OIbecność Lauraceae na tej
szerokości na Nowej Zelandii i jej wysoka różnorodność wyraźnie
implikuje cieplejsze temperatury niż dziś występujące na
nizinnych lokalizacjach na współczesnej szerokości, które leżą
na południe od istniejącej granicy dla rodziny.
Słowa kluczowe:
wczesny miocen; Lauraceae; kutikula; aparat szparkowy;
epiderma
