Figure 1. From Porter and Riedman (2016). Lanulatisphaera laufeldii from Chuar Group, Grand Canyon, USA –showing possible ontogenetic variation with progressively longer filamentous processes on exterior of inner vesicle.
Genus Lanulatisphaera Porter and Riedman 2016
Type Species.—Lanulatisphaera laufeldii (Vidal, 1976) Porter and Riedman 2016.
Diagnosis.—as for type species.
Etymology.—From the Latin lanulata, a diminutive for ‘woolly,’ referring to the dense, matted appearance of the filaments between the vesicles; and sphaera in reference to the shape of the whole of the fossil.
Remarks.—Trachysphaeridium laufeldii was placed into a new combination by Porter and Riedman (2016) based on new morphological data from specimens of the Chuar Group, Grand Canyon, USA. The original genus, Trachysphaeridium, had been erected by Timofeev (1959), lacking a diagnosis, but described as “thick, dense vesicle with shagreen surface” (Timofeev, 1959, p. 28) and as “single-layered sphaerical vesicles 60 to 250 mm in diameter of varying thickness and density with shagreen surface that is usually compressed into folds” (Timofeev, 1966, p. 36). The genus Trachysphaeridium was synonymized with Leiosphaeridia by Jankauskas et al (1989) because the authors felt the characters Timofeev described were taphonomically induced rather than of primary biological origin, a finding likely to be correct for some species of the genus. Specimens attributed to Trachysphaeridium laufeldii, however, possess morphological features inconsistent with placement in Leiosphaeridia, which is a form genus of smooth-walled sphaeroids. Samuelsson (1997) interpreted the processes of this species to be tubercles upon the vesicle and transferred it to Lophosphaeridium Timofeev, 1959 ex Downie, 1963, which is a genus diagnosed by a thick vesicle with a knobby, tuberculate surface sculpture. That transfer was rejected by Porter and Riedman (2016) as a tuberculate sculpture was not been borne out by SEM study.
Figure 2. Morgensternia officerensis and Lanulatisphaera laufeldii from the Alinya Formation, Officer Basin, Australia. Riedman and Porter (2016).
Lanulatisphaera laufeldii (Vidal, 1976) Porter and Riedman 2016.
1976 Trachysphaeridium laufeldi Vidal, p. 36, figs. 21A–21N.
1985 Trachysphaeridium laufeldi; Vidal and Ford, p. 375, figs. 7 A, B.
?1985 Trachysphaeridium laufeldi; Vidal and Ford, p. 375, figs. 7 D, F.
?1985 Trachysphaeridium laminaritum; Vidal and Ford, p. 373, figs. 8A, 8C.
1997 Lophosphaeridium laufeldii; Samuelsson, p. 174, figs, 7 F, H, I.
2009 Lophosphaeridium laufeldi; Nagy, Porter, Dehler and Shen, fig. 1J.
2016 Lanulatisphaera laufeldii; Porter and Riedman, p. 827, figs. 9.1–9.6, 10.1–10.7, 11.1–11.4, 12.1–12.7, ?12.8.
2016 Lanulatisphaera laufeldii; Riedman and Porter, p. 866, figs. 6.1–6.3, 9.9–9.12, 10
Holotype.—(Vidal, 1976; fig. 21A–E), Specimen BV/83.60—1:X/53.3 middle unit, Kumlaby borehole, Neoproterozoic Visingsö Group, Sweden. Designated by Vidal (1976).
Occurrence.—Occurs in early Neoproterozoic units including Visingsö Group of southern Sweden (Vidal, 1976), the Kildinskaya Group, northwestern Russia (Samuelsson, 1997), and the Chuar and Uinta Mountain groups of southwestern United States (Vidal and Ford, 1985; Nagy et al., 2009; Porter and Riedman, 2016) and Alinya Formation of Office Basin, Australia (Riedman and Porter, 2016).
Description.—Small, double-walled, sphaeroidal, organic-walled microfossils ranging in diameter from 26.5 to 46.1 µm and bearing abundant, solid, thin, filamentous structures that emanate from the external surface of the inner vesicle and fuse distally. Outer vesicle envelops—but does not appear to make contact with—the inner vesicle or reticulate filamentous structures. Outer vesicle exhibits a fine-scale (~ 50 to 100 nm diameter) mammillar ornament. Filamentous processes not typically visible in transmitted light microscopy but are easily identifiable by SEM. In transmitted light, fossils appear very dark and often mottled; double-vesicle construction not always easily determined due to optical density of outer vesicle.
During taphonomic degradation the filaments become flattened and shortened by breakage, but still visibly fused (Fig. 6.3).
Remarks.—Similarities are seen between L. laufeldii and Morgensternia officerensis Riedman and Porter (2016); these species may be distinguished by differences in process character. Whereas the conical processes of M. officerensis are easily viewed in transmitted light, the reticulated filaments of L. laufeldii do not project as far from the surface and may be difficult to recognize in transmitted light. Additionally, as viewed by SEM, processes of L. laufeldii are constant in diameter and anastomose distally with neighboring processes whereas M. officerensis processes are conical, tapering distally and do not anastomose. Both forms possess external envelopes, however the nano-scale mammillar ornament of L. laufeldii has not been observed on specimens of M. officerensis.
Figure 3. Fine detail and nano-scale mammillar structures of exterior vesicle of Lanulatisphaera laufeldii, from Alinya Formation, Officer Basin, Australia. Riedman and Porter (2016)
References:
Downie, C., Evitt, W.R. and Sarjeant, W.A.S., 1963, Dinoflagellates, hystrichospheres, and the classification of the acritarchs: Stanford University Publications: Geological Sciences, v. 7, no. 3, 16 p.
Jankauskas, T.V., Mikhailova, N.S. and Hermann (German), T.N. eds., 1989, Mikrofossilii Dokembriia SSSR (Precambrian microfossils of the USSR). Nauka, Leningrad. 191 p.
Timofeev, B.V., 1959, Drevneishaia flora Pribaltiki i ee stratigraficheskoe znachenie (Ancient flora of the Baltic states and its stratigraphic value). Vseoyuznyi Neftyanoi Naucho-Issledovatelskii Geologorazvedochnyi Institut, Leningrad Trudy VNIGRI, v. 129, p. 1–136, pl. 1–24. (in Russian).
Timofeev, B.V., 1966, Mikropaleofitologicheskoe Issledovanie Drevnikh Svit (Micropaleophytological study of Ancient Suite). Nauka, Moscow, 147 p., 89 plates. (in Russian).
Leigh Anne Riedman 