|
||||
LAURACEAE MACROFOSSILS AND DISPERSED CUTICLE FROM THE MIOCENE OF SOUTHERN NEW ZEALANDMike Pole
KEY WORDS: Early Miocene; Lauraceae; cuticle; stomata; epidermis 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
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.
PALABRAS CLAVE: Mioceno inferior, Lauraceae; cutícula; estoma; epidermis
Translator: Manuel Salesa
MACROFOSSILES ET CUTICULES DISPERSÉES DE LAURACEAE, DU MIOCÈNE DE LA NOUVELLE-ZÉLANDE MÉRIDIONALE
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.
Mots-clés: Miocène précoce, Lauraceae, cuticule, stomates, épiderme.
Translators: Michel Chartier and Martin Dubreuil
MAKROFOSSILIEN VON LORBEERGEWÄCHSEN (LAURACEAE) UND VERTEILTE CUTICULEN AUS DEM MIOZÄN DES SÜDLICHEN NEU SEELANDS
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
SCHLÜSSELWÖRTER: Frühes Miozän, Lauraceae, Cuticula, Stomata, Epidermis
Translator: Franziska Großmann
MACROFOSSILI DI LAURACEE E CUTICOLE SPARSE DAL MIOCENE DELLA NUOVA ZELANDA
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
Translator: Alessandro Grippo
Translator: Ashraf M.T. Elewa
Makroskamieniałości Lauraceae i rozproszona kutikula z miocenu południowej Nowej Zelandii
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
Translators: Dawid Mazurek and Robert Bronowicz