77
fungi; Fig. 3.2a–c) because their morphology parallels that seen in present-day
mycorrhizal fungi (Glomeromycota). However, the nutritional modes of most fungal remains associated with Carboniferous Lepidodendrales remain elusive.
3.3 Fossils of Fungi as Parasites
Fossil evidence of fungi has been documented throughout the Phanerozoic (Taylor
et al. 2015), but it is fungal associations with land plants and other fungi from the
Early Devonian, Carboniferous, Triassic, and Cenozoic that have to date been examined more systematically. As a result, there are several well-documented examples
of fungal parasites of plants and other fungi from these periods of geologic time. On
the other hand, the fossil record of parasitic fungi of animals is scanty throughout
for several reasons (see Sect. 3.3.4 below). The purpose of this chapter is to portray
the fossil record of fungi as parasites. In the sections below, we have not attempted
to provide exhaustive coverage, but rather have selected fossil examples of (putative) fungal parasites in association with plants (i.e. land plants and a few algae),
other fungi, and animals, with a slight emphasis on the Rhynie chert, and have elucidated the inherent problems that often render interpretation of even the most
exquisite fungal fossils difficult.
3.3.1 Fungal Parasites of Land Plants
Land plants today are exposed to a wide variety of different fungi, many of which
are parasites (Cannon and Hawksworth 1995). Although one can only speculate
about the events during the terrestrialization of plants some 515–485 Ma ago
(Morris et al. 2018), the conquest of the terrestrial realm has likely been profoundly
influenced by interactions with saprotrophic, parasitic, and mutualistic fungi
Fig. 3.2 (continued) (below-ground rooting system). (b) Higher magnification of Fig. 3.3a, focusing on appendages. (c) Higher magnification of Fig. 3.3b, showing mycorrhizal association in cortex of appendage; based on fig. 2a in Krings et al. 2011d. (d) Chytrid-like sporangia (arrows)
attached to tracheid walls; based on pl. II, 1 in Krings et al. 2009b. (e) Pear-shaped sporangium with
narrow, aseptate subtending hypha growing along inner surface of tracheid; based on fig. 1j in
Krings et al. 2007a. (f) Putative chytrid resting sporangium with primary rhizoidal axis (gray arrow)
and early stage in callosity development (black arrow); note another, more prominent callosity to
left; based on fig. 4j in Krings et al. 2010b. (g) Glomeromycotan spore with callosities (arrow);
based on pl. III, 10 in Krings et al. 2009b. (h) Septate, irregularly swollen hyphae; based on figs 1e,
f in Krings et al. 2010b. (i) Surface view of megaspore. (j 1 ) Megaspore with large chytrid zoosporangium between wall layers; based on pl. I, 7 in Krings et al. 2009b. (j 2 ) Higher magnification of
chytrid, showing rhizoidal system extending into spore lumen; based on pl. I, 8 in Krings et al.
2009b. (k) Megaspore containing numerous spheres (?zoosporangia of a polycentric chytrid) and
tenuous hyphae; based on pl. I, 1 in Krings et al. 2009b. (l–p) Lepidodendralean organs, tissues, and
reproductive structures for which there is currently no documented evidence of associated fungi
3 Fungi as Parasites: A Conspectus of the Fossil Record
fungi; Fig. 3.2a–c) because their morphology parallels that seen in present-day
mycorrhizal fungi (Glomeromycota). However, the nutritional modes of most fungal remains associated with Carboniferous Lepidodendrales remain elusive.
3.3 Fossils of Fungi as Parasites
Fossil evidence of fungi has been documented throughout the Phanerozoic (Taylor
et al. 2015), but it is fungal associations with land plants and other fungi from the
Early Devonian, Carboniferous, Triassic, and Cenozoic that have to date been examined more systematically. As a result, there are several well-documented examples
of fungal parasites of plants and other fungi from these periods of geologic time. On
the other hand, the fossil record of parasitic fungi of animals is scanty throughout
for several reasons (see Sect. 3.3.4 below). The purpose of this chapter is to portray
the fossil record of fungi as parasites. In the sections below, we have not attempted
to provide exhaustive coverage, but rather have selected fossil examples of (putative) fungal parasites in association with plants (i.e. land plants and a few algae),
other fungi, and animals, with a slight emphasis on the Rhynie chert, and have elucidated the inherent problems that often render interpretation of even the most
exquisite fungal fossils difficult.
3.3.1 Fungal Parasites of Land Plants
Land plants today are exposed to a wide variety of different fungi, many of which
are parasites (Cannon and Hawksworth 1995). Although one can only speculate
about the events during the terrestrialization of plants some 515–485 Ma ago
(Morris et al. 2018), the conquest of the terrestrial realm has likely been profoundly
influenced by interactions with saprotrophic, parasitic, and mutualistic fungi
Fig. 3.2 (continued) (below-ground rooting system). (b) Higher magnification of Fig. 3.3a, focusing on appendages. (c) Higher magnification of Fig. 3.3b, showing mycorrhizal association in cortex of appendage; based on fig. 2a in Krings et al. 2011d. (d) Chytrid-like sporangia (arrows)
attached to tracheid walls; based on pl. II, 1 in Krings et al. 2009b. (e) Pear-shaped sporangium with
narrow, aseptate subtending hypha growing along inner surface of tracheid; based on fig. 1j in
Krings et al. 2007a. (f) Putative chytrid resting sporangium with primary rhizoidal axis (gray arrow)
and early stage in callosity development (black arrow); note another, more prominent callosity to
left; based on fig. 4j in Krings et al. 2010b. (g) Glomeromycotan spore with callosities (arrow);
based on pl. III, 10 in Krings et al. 2009b. (h) Septate, irregularly swollen hyphae; based on figs 1e,
f in Krings et al. 2010b. (i) Surface view of megaspore. (j 1 ) Megaspore with large chytrid zoosporangium between wall layers; based on pl. I, 7 in Krings et al. 2009b. (j 2 ) Higher magnification of
chytrid, showing rhizoidal system extending into spore lumen; based on pl. I, 8 in Krings et al.
2009b. (k) Megaspore containing numerous spheres (?zoosporangia of a polycentric chytrid) and
tenuous hyphae; based on pl. I, 1 in Krings et al. 2009b. (l–p) Lepidodendralean organs, tissues, and
reproductive structures for which there is currently no documented evidence of associated fungi
3 Fungi as Parasites: A Conspectus of the Fossil Record