Thursday, 3 July 2014

A fossil Birthwort from the Late Miocene of Austria.

Birthworts (Aristolochiaceae) are perennial rhizomatous herbs, shrubs or lianas (woody climbers), with large, conspicuous flowers, found across Eurasia, North and South America, but at there most diverse in East Asia. They are typically found at the edges of woodland, particularly in wetland areas, but have proved adept at colonizing man-made environments such as vineyards. The fossil record of the groups is poor and patchy; the oldest known fossil Birthwort comes from the Late Cretaceous of Nebraska, but macrofossils of the plants are rare, and, like many Insect-pollinated plants, pollen fossils are unknown. Tertiary fossil Birthworts have been described from the North America, Greenland, Europe, the former Soviet Union and China. 

In a paper published in the journal Palaeontologica Electronica in May 2014, Barbara Meller of the Institute of Palaeontology at the University of Vienna describes a fossil Birthwort from the Late Miocene Hollabrunn-Mistelbach Formation at Pellendorf in the Mistelbach District of Lower Austria (northeast of Vienna).

The Hollabrunn-Mistelbach Formation occurs on the northwestern margin of the Vienna Basin, and is thought to have been laid down 11 million years ago at about the time of the onset of the Alpine Orogeny (i.e. as the Alps began to grow due to folding and uplift associated with the impact of Africa into southern Europe from the south). The deposits were laid down in a braided river system flowing into a wide delta floodplain, where the Palaeo-Danube River met the retreating Paratethys Sea (an ancient seaway in what is now Central Europe). These deposits have produced a wide range of plant and Insect fossils that have greatly enhanced our understanding of Central European ecosystems in the Late Miocene.

The fossil is placed in the extant genus Aristolochia, which includes the modern Clematises and Dutchman's Pipes, and is given the specific name Aristolochia austriaca, meaning ‘Austrian’. Aristolochia austriaca is preserved as two leaves on a single slab, plus the counterpart of one of these leaves.

Part of the sediment block with the two leaves of Aristolochia austriaca nov. spec. in the same layer, scale bar is 5 cm, HT = holotype, PT = paratype, ? = unidentifiable leaf fragments in a different layer. Meller (2014).

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