7 JOUKO RIKKINEN 1 AND GEORGE POINAR 2  Department of Plant Biology, P.O. Box 27, University of Helsinki, FIN-00014 Helsinki, Finland.  Department of Entomology, Oregon State University, 2046 Cordley Hall, Corvallis, Oregon 97331-2907, USA. E-mail : jouko.rikkinenhelsinki.fi Received 21 April 1999 ; accepted 2 September 1999. Chaenothecopsis bitterfeldensis sp. nov. is described and illustrated from Bitterfeld amber dating back to at least 20 million years ago. There has been no previous report of the sporing perfect stage of any Ascomycota in amber. The fungus also represents the first fossil record of resinicolous fungi and of the Mycocaliciaceae. The fossilised specimen contains over 20 fruiting bodies arising from an extensive mycelium. There are also hundreds of detached ascospores, some of which had germinated before the resin was transformed into amber. The taxonomy and palaeontology of the fossil fungus is discussed and stages in its preservation are described. Also some general aspects in the biology of resinicolous Mycocaliciaceae are reviewed. The striking similarity of C. bitterfeldensis to some extant species from East Asia suggests that the present distribution of these fungi is a relict of an ancient Laurasian range. INTRODUCTION The mycobiota of resinous exudates on woody plants includes many species of small ascomycetes of the genera Chaeno- thecopsis and Mycocalicium (Mycocaliciaceae). Most resinicolous Mycocaliciaceae live on coniferous trees, where they are found in association with resin fluxes from wounds and cankers. These fungi are well adapted to their special substrate and many of them can colonise relatively fresh resin. Their stalked ascomata are usually produced on hardened resin or resin- soaked wood. Here we report the first fossil evidence of resinicolous Mycocaliciaceae. Numerous intact fruiting bodies of a Chaeno- thecopsis species were found in a small fragment of Bitterfeld amber dating back to over 20 million years ago. Amber is fossilised resin and composed of non-volatile terpenoid materials which have been progressively oxidised and polymerised to a point where they can withstand chemical and microbiological attack. The specimen is, to our knowledge, the first evidence of resinicolous fungi in amber, and represents a remarkably well preserved specimen of a fossilised ascomycete. MATERIALS AND METHODS The fossilised fungus is contained in a small (944 mm) fragment of clear, reddish-yellow amber (Poinar AF 9–26). It originates from central Germany near Bad Schmiedeberg and Bitterfeld. Amber from this site has yielded a range of insect fossils (over 150 taxa) as well as liverworts and remains of beech (Fagus) and oak (Quercus) trees. Based on stratiographic evidence, the age of Bitterfeld amber is reported as around 22 million years or near the Miocene-Oligocene boundary (Krumbiegel 1991). There is, however, some question of whether the Bitterfeld amber is a separate deposit or re-deposited Baltic amber. Nuclear Magnetic Resonance spectra of Bitterfeld amber obtained by Drs Joseph B. Lambert and C. E. Shawl were very close to Baltic amber, thus indicating a common source tree and common origin (Poinar 1992). In addition, Wunderlich (1983) noted that what appeared to be the same species of spider and the same type of Quercus flowers occurred in both Bitterfeld and Baltic amber. Grolle (1999) reported that a species of leafy liverwort, Calypogeia stenzeliana, had been found from both amber sources. If Bitterfeld amber is re-deposited Baltic amber, then it would be at least 40 million years old, which is the age of most Baltic deposits (Poinar 1992). The plant source of the fossilised exudate has not been definitely established, but it has been suggested, on the basis of infrared spectroscopy, that it might have been the Tertiary conifer, Cupressospermum saxonicum (Barthel & Hetzer 1982). The amber piece has been cut and polished to facilitate screening for inclusions. During this activity several fungal structures have been brought to the surface and accidently sectioned. In this study no further destructive sampling was performed. All measurements and photographs were taken from the intact specimen under transmitted andor incident light. Optical distortions were neutralised by coating the Mycol. Res. 104 (1) : 7–15 (2000) Printed in the United Kingdom A new species of resinicolous Chaenothecopsis (Mycocaliciaceae, Ascomycota) from 20 million year old Bitterfeld amber, with remarks on the biology of resinicolous fungi