1032 Mycologia, 95(6), 2003, pp. 1032–1036.  2003 by The Mycological Society of America, Lawrence, KS 66044-8897 Calicioid lichens from European Tertiary amber Jouko Rikkinen 1 Department of Ecology and Systematics, P.O. Box 65, FIN-00014 University of Helsinki, Finland Abstract: Two species of calicioid lichens (Ascomy- cota) are reported from Baltic amber dating back 55– 35 million years ago. The fossils are very similar to some modern Calicium and Chaenotheca species, but because ascus characteristics and photobiont identi- ties cannot be determined they are not assigned to any extant species. Calicioid lichens seem to show a conservative maintenance of morphological adapta- tions to successful ecological niches, as do several other groups of ascomycetes. The fossils demonstrate that distinguishing features in the morphology of both genera have remained unchanged for at least tens of millions of years. The palaeohabitat of the fossil lichens, viz. that of conifer trunks in a humid, mixed forest, is consistent with the habitat preferenc- es of many modern Calicium and Chaenotheca spe- cies. Key words: Baltic amber, Calicium, Chaenotheca, fossil fungi, lichen INTRODUCTION Calicioid fungi are a heterogeneous grouping of as- comycetes, with small, usually well-stalked apothecia. Both lichenized and nonlichenized species are in- volved, and the latter include both parasitic and sap- rophytic forms (Tibell 1984, 1999a, Wedin and Tibell 1997, Wedin et al 1998, 2000, Tibell and Wedin 2000). Mature ascospores of calicioid lichens tend to accumulate on the upper surfaces of the apothecia, often forming extensive mazaedia. Here two specimens of calicioid lichens, repre- senting a Calicium Pers. (Caliciaceae) and a Chaen- otheca Th. Fr. (Coniocybaceae), are described and il- lustrated from Baltic amber dating back 55–35 mil- lion years ago. Amber is fossilized resin and com- posed of nonvolatile terpenoid materials, which have been oxidized and polymerized to a point where they Accepted for publication April 24, 2003. 1 Corresponding author. E-mail: jouko.rikkinen@helsinki.fi can withstand chemical and microbiological attack (Poinar 1992). MATERIAL AND METHODS Fossilized lichens are contained in two pieces of Baltic am- ber. Both specimens (V. Arnold 1285 & 1294) originate from deposits in northern Europe and belong to the private collection of Dr. Volker Arnold, Germany. Their exact age is unknown, but the age of Baltic amber generally varies from Late Paleocene to Late Eocene epochs (ca 55–35 MaBP). The forests that produced the resin were in the region of present Fennoscandia. The resin-producing tree usually is referred to as Pinus succinifera (Go ¨ppert) Con- wentz. Over millions of years, large amounts of solidified conifer resin were transported by rivers to Baltic deposits south of the amber forests (Poinar 1992, Ganzelewski 1997). The amber specimens have been polished to facilitate screening for inclusions. In this study no further destructive sampling was performed. All measurements and photo- graphs were taken from the intact specimen under trans- mitted and/or incident light. Optical distortions were neu- tralized by coating the specimen in vegetable oil. The deep fields of focus in FIGS. 1–2 were achieved by combining sev- eral optical sections into composite pictures. During this process several stellate hairs and other obscuring debris were removed from FIG. 1. This was done to facilitate a clear view of the fungal ascoma. RESULTS Chaenotheca specimen (V. Arnold, Nr. 1285), Baltic amber (FIGS. 1–4). The fossilized lichen has a well- developed, 100–200 m thick thallus, growing over bark. Thallus verrucose, grayish white, with isolated dark spots. Six ascomata, four of them mature, have been preserved. Ascomata well stalked, up to 450 m high, without obvious pruina. Stalk 50–70 m diam, smooth. Capitulum obconical, 100–120 m diam. Ex- cipulum well developed and continuous with the stalk tissue. Mazaedium well developed, compact, with no detached spores in the surrounding amber matrix. Spores spherical, 5–7 m diam, apparently with a rough surface ornamentation of irregular cracks. Preserved together with detritus and stellate hairs (from flowering plant). Calicium specimen (V. Arnold, Nr. 1294), Baltic amber (FIG. 5). The specimen consists of a single de- tached ascoma and numerous spores embedded in solid amber. The ascoma is well stalked, 1.2 m high,