In see the see 3B, 169 sec- 4H), (KL2- elon- more recon- marked from penetra- been second- 3E, (VI21-4m- secondary acquisition to observed Figures of two with large these loop-forming recognized processes; X.41235 2D, have see ,? the also L, ?i- the The X.41243 isolated 3E; (KL2-40m-Q43); outgrowths development. Figs. D, but (CAMSM) an possible capable detail. 2D, is processes fusion. 2D). processes, it (e.g., for their outgrowth; anastomosing the X.41240 example, (VI21-5m-064), were Fig. 4B of Museum (KL2-49m-K50); opacity, A, the of (Figs. for longitudinal (cf. fusion secondary (VI23-4m-S60); X.41238 "normal" Figure of within instances X.41232 portions 0, and course Sedgwick I, see doubled the branches outgrowths X.41243, coordinates). •. FUNGI its X.41242 pronounced distal some lost. the with outgrowth detail. and Germinosphaera-like product C, with by a in suspended two growth Da#ng eukaryotes: for wall; ,I'?X Tappania. As Finder are left). 4A as and struct irregular ary CAMSM gated here Fossil record and molecular clocks with vesicle (KL2-4m-048); Specimens secondarily extensions (KL2-9m-Q47). 'Y vesicle contiguous arrow, (lower JSTOR Terms and Conditions a Figure England PROTEROZOIC 1A, the The been ridg- specimen and smaller see X.41234 and ridge a X.41239 nascent variable irregular with ? 3E) have K, this bearing P, relatively Formation. .,? (Figs. (KL2-56m-L60), -?-/~a 2003). with ;. a I't? r Fig. arcuate All use subject to from PROBABLE circular O- outpocketings number, size of highly (see Tappania This content downloaded on Tue, 22 Jan 2013 14:51:48 PM gradually identifies Tappania. in processes and Wynniatt X.41241 of (VI21-5m-J60); slide a of characteristic box the left B, smaller major the PROBABLE PROTEROZOIC FUNGI 169 a ID, of the (KL2-15m-H47). the to linear (Butterfield merging vesicle (KL2-49m-L60), evidence X.41237 from by center outgrowths, plus to material specimen details. N, 2B), sp. the for portions X.41233 showing 1L), type document at 5 J, X.41236 parent " processes direct field-sample detail. the indicated M, irregular and flattened), Susan Liao distal (Fig. the to Tappania 1K,N,O, vegetative for with Tappania "histology" (plus process the details. Sarah Slotznick lost. 4E,F Buerfield 2005 large of 2. (now of 4H a for rival foramen, (Figs. Figures U59); tive FIGURE numbers vesicle vesicle Tappania; marginal range population, plastic pseudo-folds es that 2D). 50m-P57), 4C,D ondarily Figure processes similarities ;. ?i- .,? ,? " O-r -?-/~a? 'Y I't? ,I'?X •. FIGURE 2. Tappania sp. from the Wynniatt Formation. Specimens with Sedgwick Museum (CAMSM) acquisition numbers (plus field-sample ID, slide number, and England Finder coordinates). A, X.41240 (KL2-40m-Q43); see Figures 4E,F and 5 for details. B, X.41241 (KL2-56m-L60), with two pronounced longitudinal outgrowths from the vesicle (now flattened), plus a smaller circular ridge (lower left). C, X.41242 (VI23-4m-S60); an isolated secondary vesicle of Tappaniashowing the characteristic irregular extensions and branches (cf. Fig. 2D). D, X.41243 (VI21-4m- U59); a large irregular specimen of Tappaniabearing a contiguous Germinosphaera-likeoutgrowth; the two penetra- tive foramen, indicated by the box (see Fig. 3E) and arrow, are a product of secondary fusion. The loop-forming marginal process at the center left identifies this specimen as Tappania. population, direct evidence of a relatively As with the "normal" processes, these more plastic "histology" (Butterfield 2003). The irregular outgrowths were capable of second- pseudo-folds document a highly variable ary growth and fusion (e.g., Figs. 2D, 3E, 4H), range of vegetative outgrowths, from nascent and in some instances it is possible to recon- processes (Fig. 1L), to linear and arcuate ridg- struct the course of their development. In es (Figs. 1K,N,O, 2B), to major outpocketings CAMSM X.41243, for example, the large elon- that rival the parent vesicle in size (Figs. 1A, gated outgrowth (Figs. 2D, 3E; recognized 2D). here by its doubled opacity, but also observed Tappania;the distal portions of the processes have been secondarily lost. I, X.41232 (KL2-49m-K50); see Figures 3B, 4C,D for details. J, X.41233 (KL2-15m-H47). K, X.41234 (KL2-4m-048); see Figure 4B for detail. L, X.41235 (KL2- 50m-P57), with processes merging gradually with the vesicle wall; distal portions of the processes have been sec- ondarily lost. M, X.41236 (KL2-49m-L60), with a smaller vesicle suspended within the anastomosing processes; see Figure 4H for detail. N, X.41237 (VI21-5m-J60); see Figure 4A for detail. 0, X.41238 (VI21-5m-064), with marked similarities to the type material of Tappania.P, X.41239 (KL2-9m-Q47). This content downloaded on Tue, 22 Jan 2013 14:51:48 PM All use subject to JSTOR Terms and Conditions Fossils in Rock Record • Body Fossils – Casts/Molds – Mineralizaon – Compression – Acritarchs • Trace Fossils • Molecular Fossils (Biomarkers) NATURE | Vol 463 | 18 February 2010 LETTERS abc Oldest 100 µm 100 µm 50 µm Putave d ef Eukaryote Fossils 50 µm 50 µm 100 µm k g i (Moodies Group, South 50 µm 10 µm 20 µm h j Africa, 3.2 Ga) l 200 nm 50 µm 2 µm m n 30 µm 200 nm Javaux et al. 2010 Figure 1 | Carbonaceous microstructures in situ in thin sections and b), and concentric folds (d, g, h), wrinkling (i), lanceolate fold (e) and extracted from the rock by acid maceration. Images were produced with a collapsing over (f), which are all typical taphonomic features of soft wall transmitted light microscope (a–f), a backscattered environmental SEM deformation. SEM images show the highly folded, wrinkled and degraded (g–j) and a TEM (k–n). Arrows point to spheroidal microstructures in texture of the wall (g–j). TEM images show the compressed vesicle walls section subparallel to the bedding (a, b), compressed microstructures in surrounding the cell lumen (arrowed) in semi-thin (k) and ultra-thin section across the bedding (c), microstructures extracted from the rock by (n) sections and the homogeneous ultrastructure (l, m) of the roughly 160- acid maceration (d–n), disseminated organic particles (short arrows in nm-thick wall, torn and wrinkled in places (l). than an ornamentation. SEM–energy-dispersive X-ray analyses show The taphonomic features of soft wall deformation, commonly occasional disseminated arsenopyrite and other sulphide crystals on observed in Proterozoic and Phanerozoic organic-walled micro- the walls of the microstructures. Transmission electron microscope fossils with well-accepted biogenicity, are due to their loss of turgor (TEM) analyses of the wall ultrastructure show unambiguously that pressure and degradational collapse during decay17 before flattening they represent flattened hollow organic-walled vesicles with the cell of the hosting shales and siltstones during compaction, and show lumen visible between the compressed walls (Fig. 1k, n) rather than flexibility of the original organic wall. Another common feature with large kerogen particles. The organic wall shows folding along its length Proterozoic fossiliferous siliciclastic rocks is the low total organic (Fig. 1k, n) and seems disrupted in places because the 60-nm-thick carbon content ranging from 0.07 to 0.37wt%, with an average of ultra-thin sectioning cut through highly wrinkled and degraded walls, 0.17wt% (n 5 22). Generally, Proterozoic shales with a high total as observed in SEM images. Moreover, some small mineral grains were organic carbon content contain only particulate organic matter ripped off during sectioning, as demonstrated by the presence of holes without structurally preserved walls, whereas shales with a low total and, occasionally, pyrite cubes in the resin. The roughly 160-nm-thick organic carbon content (‘grey shales’) may preserve, sometimes wall appears torn and wrinkled in places, and has a homogeneous exquisitely, organic structures with cell walls13,17. Other important ultrastructure (Fig. 1l, m). controls on the preservation potential of microorganisms are their 935 ©2010 Macmillan Publishers Limited. All rights reserved Archean Biomarkers Pilbara Craton, 2.7Ga “The presence of steranes, par0cularly cholestane and its 28- to 30- carbon analogs, provides persuasive evidence for the existence of eukaryotes…” “Whatever their origin, the biomarkers must have entered the rock aDer peak metamorphism 2.2 Gyr ago, and thus do not provide evidence for the existence of eukaryotes and cyanobacteria in the Archaean eon.” Downloaded from rstb.royalsocietypublishing.org on June 12, 2012 1028 A.Proterozoic Eukaryo#c Fossils H. Knoll and others Proterozoic eukaryotes Knoll et al. 2006 Figure 4. (Caption opposite.) Bangiomorpha only to the interval 1267G2 to 723G form taxa that appear to preserve vegetative and 3 Myr, but an unpublished Pb–Pb date of 1198G reproductive phases of a heterokont protist comparable 24 Myr and physical stratigraphic relationships to the extant xanthophyte alga Vaucheria ( Jankauskas strongly suggest that the fossils’ age lies close to the 1989; Herman 1990). Va u c h e r i a -like populations lower radiometric boundary (Butterfield 2000). preserving several life-cycle stages also occur in the Latest Mesoproterozoic (more than 1005G4 Myr; 750–800 Myr Svanbergfjellet Formation, Spitsbergen Rainbird et al. 1998) microfossils from the Lakhanda (Butterfield 2004). Latest Meosoproterozoic and Early Group, Siberia, contain several additional populations Neoproterozoic acritarchs (figure 3h) continue the of coenocytic to multicellular filaments whose mor- record of moderate diversity established earlier, phologies