''Metrosideros leunigii'' is the oldest described fossil species of the flowering plant genus ''

Metrosideros ''Metrosideros'' is a genus of approximately 60 trees, shrubs, and vines mostly found in the Pacific region in the family Myrtaceae. Most of the tree forms are small, but some are exceptionally large, the New Zealand species in particular. The n ...

'' (Family

Myrtaceae Myrtaceae, the myrtle family, is a family of dicotyledonous plants placed within the order Myrtales. Myrtle, pōhutukawa, bay rum tree, clove, guava, acca (feijoa), allspice, and eucalyptus are some notable members of this group. All speci ...

), named from fossil flowers and fruits uncovered from the

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

(approx. 30 Million years) aged Little Rapid River deposit in Tasmania,

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

, as well as leaves from this deposit and identical leaves from the Eocene aged Hasties deposit, also in Tasmania. These fossils are significant, because they show that ''Metrosideros'' once occurred naturally in Australia during the

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...

, and has since become extinct. Prior to the discovery of these fossils, there has been no record of the genus ''Metrosideros'' in Australia. The absence of ''Metrosideros'' in Australia has been considered something of a mystery to Australian paleobotanists, since ''Metrosideros'' is one of the most widely spread flowering plant genera in the Pacific, growing from the sub-Antarctic islands of New Zealand to the Bonin Islands near

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

and to Hawaii, owing to the lightweight seeds of at least some species of ''Metrosideros'' which can be dispersed easily by wind, and survive long periods of submersion in sea water. It had been hypothesized that ''Metrosideros'' may have evolved in New Zealand, and subsequently dispersed throughout the Pacific from there. However, these fossils may suggest an

n origin for the genus. Why and when ''Metrosideros'' should have become extinct in Australia, yet survived elsewhere in the Pacific is unknown. The species ''Metrosideros leunigii'' was named after Australian cartoonist,

Michael Leunig Michael Leunig (born 2 June 1945), typically referred to as Leunig (his signature on his cartoons), is an Australian cartoonist. His works include ''The Curly Pyjama Letters'', cartoon books ''The Essential Leunig'', ''The Wayward Leunig'', ' ...

References

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