Inorganic Taxa and Pseudofossils

‘Manchuriophycus’, from Hargitai et al. (2014).
Life on Mars: the Cambrian terrestrial environment
Published 16 November 2011

Author’s note (23 November 2023): Retallack’s (2011) claims described below were criticized by Jago et al. (2012) who interpreted the supposed ‘fossils’ as inorganic patterns produced by sedimentation and weathering.

The question of when life first moved onto the land has been the subject of speculation for as long as anyone has realised that there was a ‘first’ to speculate about. Established terrestrial communities were clearly present by the latter part of the Silurian, but was there anything earlier? The reasonable expectation is that there was, at least on some level. Pretty much as soon as there was life inhabiting the oceans in prokaryote form, weather cycles would have been carrying bacteria and their spores onto their land. It is not unreasonable to assume that some of them may have been able to acquire a toehold in some attainable niche, and from there diversify to the surrounding environment. Later, other microbial and simple organisms may have joined them. But such organisms leave little trace in the fossil record. What were they like, how did they live? A paper that has just been published in Palaeontology (Retallack 2011) has described simple terrestrial fossils preserved from the Middle Cambrian, and may provide a rare glimpse of the early Earth.

Reconstruction of Cambrian terrestrial biota from Retallack (2011).

The remains described by Retallack (2011) are extremely simple: flat, thallose impressions called Farghera, subterranean threads known as Prasinema and buried ovoid structures called Erytholus. All of these are described as form taxa: that is, they represent a particular recognisable fossil structure whose relationship to other such fossils is unknown. Different form taxa may even represent different parts of a single organism.

The linear, branching Farghera thalli were an average of just under 2 mm wide, though they could get much wider, and preserved thalli are often several centimetres in length. The living thalli would have been similar to an alga or lichen, either of which they could have been. The thread-like Prasinema are preserved as a central filament less than 1 mm in diameter, surrounded by a dark halo up to about 2.5 mm across. It seems likely that only the central filament represents the original central organism; the halo would have formed by microbes growing around the filaments as they decayed. Prasinema filaments could apparently grow to 30 cm beneath the original soil surface, and probably represent structures similar to fungal hyphae.

Most unusual are the Erytholus, globose structures up to 2 cm in diameter, divided into internal layers with a broad central column. Retallack (2011) suggests a number of possible interpretations for Erytholus: vendobiont or xenophyophore (unlikely because of the terrestrial location), alga (again unlikely, because it is both terrestrial and buried beneath the surface), or fungal or slime mold reproductive structures, comparable to truffles. However, the truffle interpretation is problematic because truffles are produced to disperse spores through being eaten by animals. Obviously, this could not have been the case in the terrestrial Cambrian! A further possibility that I can think of is that Erytholus may have been some sort of resting structure, analogous to a plant bulb or tuber (though note that this interpretation would not necessarily exclude a reproductive function).

As with the Silurian, I think it is important to remember that the environment would have been very different in those days in more ways than one might immediately think. There are parts of the world today where lichens and algae remain the primary ground cover, but we should be careful in assuming that such spots are close analogues of the Cambrian terrestrial environment. Such areas are today arid and/or highly eroded, but in the Cambrian lichens and algae would have also been able to dominate areas in which vascular plants would overshadow them today. I also find myself again wondering what effect the absence of a complex vegetation profile might have had on weather patterns at the time. Would winds have been stronger if there were less low-level wind breaks? Would the effects of rain events have been more catastrophic if water flow was less impeded by ground-cover (if Erytholus was indeed a sort-of-tuber, perhaps it functioned as a source of regrowth if the above-ground component of the organism was destroyed by weather?) If we could see the Cambrian environment for ourselves, there could be no doubt that we would find it utterly alien.

Volcanic deception
Published 29 May 2023

When you get down to it, the majority of fossils are interestingly shaped rocks. And deciding whether a particular interestingly shaped rock is the genuine result of biological processes, or another process entirely, can be a definite challenge. The term “pseudofossil” has been applied to structures of inorganic origin that may be mistaken for genuine fossils, and may have even been awarded formal names of their own. Such a structure, perhaps, is Astropolithon hindii.

‘Astropolithon hindii’ structures in the Meguma Group, from Pickerill & Harris (1979).

Astropolithon hindii was first described by Canadian geologist John William Dawson in 1878 for mound-like structures from the Cambro-Ordovician Meguma Group of Nova Scotia (Pickerill & Harris 1979). These mounds were typically more or less conical in shape, two or three centimetres in height and about ten centimetres in diameter. In most mounds, a central or off-central aperture lead to a more or less cylindrical core that extended below the bedding plane, sometimes by up to thirty centimetres. Surrounding the aperture and core was a pattern of radiating markings.

Dawson initially saw his Astropolithon as algal in origin (a ‘fucoid’ in the parlance of the times). However, he later interpreted it as the preserved traces of an animal burrow. The cone would then be constructed from material ejected by the animal as it dug into the sediment. The radiating markings could represent traces left by the animal as it extended itself or some appendage out of the burrow in search of food. Many trace fossils, it should be noted, were originally described as ‘fucoids’* and Dawson deserves credit as one of the earlier palaeontologists to recognise their true nature (Häntzschel 1975).

*I suspect, though I don’t actually know, that this accident of history was a significant factor in why the practice of applying ‘genus’ and ‘species’ nomenclature to trace fossils developed.

Though perhaps not for Astropolithon hindii. Its biogenic origin was first challenged in 1908 by J. Woodman (who saw them as the product of fracturing during sedimentation). However, Astropolithon remained largely accepted as traces for many decades, at least by the relatively few palaeontologists who paid them any mind. Fossils from other early Palaeozoic formations in other parts of the world were also assigned to Astropolithon. A small number of authors saw them as actual body fossils, comparing them to jellyfish. Häntzschel (1975) classified them among ‘unrecognized and unrecognizable “genera”’, claiming that “interpretation as trace fossils seems next to impossible”.

The currently accepted view of Astropolithon hindii, however, was established by Pickerill & Harris (1979). They noted that the Meguma Formation preserved a range of conical structures, some with radial elements and some without, and some grading in between. Rather than leading to any sort of body chamber or distinct terminus, the central cores of A. hindii tended to just kind of fade out at the base. Rather than being the product of animal activity, Pickerill & Harris saw the Astropolithon ‘fossils’ as the preserved effects of sand volcanoes. Sand volcanoes occur when water is rapidly forced upwards through sand, dragging particles along with it. This happends in response to some sudden application of force, such as liquefaction during an earthquake (liquefaction occurs when sediment particles are shaken about and settle into a more closely packed position, reducing the small pockets of space between them). As the sand particles escape from the surface of the volcano, they spread to form a cone. ‘Astropolithon hindii’ was therefore not the result of biological activity, and therefore not a true fossil (some other ‘species’ attributed to Astropolithon from other times and places, however, are identifiable as traces and have since been re-classified).

Proposed stages in formation of discoidal pseudofossils, from Inglez et al. (2022).

However, the typical sand volcano cone is more or less smooth and even (you can watch a video of a sand volcano-like structure forming here). What caused the ‘Astropolithon’ volcanoes to form their segmented structure, and why did they seemingly only form in particular places and locations during Earth’s history? The answer that has been proposed is that though ‘Astropolithon’ may not have been started by biological activity, it may have been stopped by it. Astropolithon-type structures may have developed when sand volcanoes formed in sediments whose surface was bound by thick microbial mats. Such mats would have been more abundant in the early Palaeozoic than today, owing to the presence of fewer active burrowers and grazers (in the modern day, they tend to be restricted to areas where animal activity is inhibited, such as low-oxygen or hypersaline environments). The microbial mat would have prevented the fluidised sand from escaping evenly, trapping it below the surface. The pressurised sand would have then forced its way outwards beneath the mat, along points of weakness in the surrounding sediment. This would have formed the rays, whose appearance may have been strengthened by further shocks (Inglez et al. 2022). Some have argued that, as the formation of ‘Astropolithon’ could therefore be seen as evidence of microbial activity, perhaps it should be regarded as a trace fossil after all (Lucas & Lerner 2017). But for most, I suspect, this would be stretching the concept of a ‘trace’ to its limits, and ‘Astropolithon hindii’ is better considered a pseudofossil, and cast into the outer darkness of taxonomic recognition.

Listing of inorganic taxa, pseudofossils, etc.
Aenigmichnus Hitchcock 1865H62
`--*A. multiformis Hitchcock 1865H62
Aequorfossa Neviani 1925H75
`--*A. farnesinae Neviani 1925H75
Ammosphaeroides Cushman 1910H75 [=Arammosphaerium Rhumbler 1913LT64]
`--*A. distoma Cushman 1910C40
Anellotubulata Wetzel 1967H75
Antholithina Choubert, Termier & Termier 1951H62
`--*A. rosacea Choubert, Termier & Termier 1951H62
Archaeoanas japonicaO87
Archaeodon reunigiH98
Archaeophyton Britton 1888H62
`--*A. newberryanum Britton 1888H62
Aristophycus Miller & Dyer 1878H75
`--*A. ramosus Miller & Dyer 1878H75
Atikokania Walcott 1912 [=Attikokania (l. c.)]H75
`--*A. lawsoni Walcott 1912H75
Baculovirus oryctes (virus)C81
Benjaminichnus Boekschoten 1964 [=Batrachoides Hitchcock 1858 non Lacepède 1800, Batrachioides Weigelt 1927, Batracoides (l. c.)]H75
|--*Batrachoides’ nidificans Hitchcock 1858H75
`--‘Batrachoides’ antiquior Hitchcock 1858H75
Bergoldavirus virulentum (virus)H74
Bisulcus Hitchcock 1865H62
`--*B. undulatus Hitchcock 1865H62
Botswanella Pflug & Strübel 1969G79
Camasia Walcott 1914H62
`--*C. spongiosa Walcott 1914H62
Caragassia Vologdin 1965G79
`--*C. krassevi Vologdin 1965G79
Cayeuxina Galloway 1933H75
`--*C. precambrica Galloway 1933LT64
Chloephycus Miller & Dyer 1878 [=Cloephycus (l. c.)]H75
`--*C. plumosum Miller & Dyer 1878 [incl. Buthotrephis filciformis James 1878]H75
Collinsia Bain 1927 nec Nuttall 1817 (ICBN) nec Agardh 1899 (ICBN)H75
`--*C. missisagiense Bain 1927H75
Copperia Walcott 1914 [=Cooperia (l. c.) nec Ransom 1907 nec Tolmachoff 1926]H75
`--*C. tubiformis Walcott 1914H75
‘Corticites’ Fucini 1938 (n. n.) non Rossmaessler 1840H62
Corycium Sederholm 1911M74, H75 [=Corycinium (l. c.)H75]
`--*C. enigmaticum Sederholm 1911H75
Ctenichnites Matthew in Selwyn 1890H75
Cupulicyclus Quenstedt 1879H75
Cyathospongia eozoica Mathew 1890H75
Dendrophycus Lesquereux 1884H75
|--*D. desorii Lesquereux 1884H75
`--D. triassicusH75
Dexiospira Ehrenberg 1858H75
Dinocochlea Woodward 1922H75
`--*D. ingens Woodward 1922H75
DraconaeO87
|--Doublodraconus Okamura 1987O87
| `--*D. protominilorientalis Okamura 1987O87
|--Foxdraconus Okamura 1987O87
| `--*F. protominilorientalis Okamura 1987O87
|--Tripoddraconus Okamura 1987O87
| `--*T. protominilorientalis Okamura 1987O87
|--Twistdraconus Okamura 1987O87
| `--*T. protominilorientalus Okamura 1987O87
|--Personiodraconus Okamura 1987O87
| `--*P. protominilorientalus Okamura 1987O87
|--Fightingdraconus Okamura 1987O87
| `--*F. protominilorientalus Okamura 1987O87
|--Regulotriangulodraconus Okamura 1987O87
| `--*R. protominilorientalus Okamura 1987O87
|--Tenuolabrodraconus Okamura 1987O87
| `--T. protominilorientalus Okamura 1987O87
|--Genuinodraconus Okamura 1987O87
| `--*G. protominilorientalus Okamura 1987O87
`--Spirodraconus minilorientalus Okamura 1987O87
`--*S. minilorientalus Okamura 1987O87
Dystactophycus Miller & Dyer 1878H75
`--*D. mamillanum Miller & Dyer 1878H75
Eoclathrus Squinabol 1887H75
`--*E. fenestratus Squinabol 1887H75
Eophyton Torell 1868H75 [incl. Aspidiaria Vlcek 1902 non Presl 1838H62, Eoichnites Matthew 1891H75, Rabdichnites Dawson 1873H75, Rhabdichnites Dawson 1888H75]
`--*E. linneanum Torell 1868H75
Eopteris de Saporta 1878H62
|--*E. andegavensis de Saporta 1878H62
`--E. morierei de Saporta 1878H75
Eospicula de Laubenfels 1955H75
`--*E. cayeuxi de Laubenfels 1955H75
Eozoon Dawson 1865 [=Eophyllum Hahn 1880]H75
`--*E. canadense Dawson 1865 [=*Eophyllum canadense]H75
Erytholus globosus Retallack 2011JG12
FargheraJG12
Flabellaria johnstrupi Heer 1883H62
Forchhammera Goeppert 1860H62
`--*F. silurica Goeppert 1860H62
Gallatinia Walcott 1914H62
`--*G. pertexta Walcott 1914H62
Gothaniella Fucini 1936H62
`--*G. sphenophylloides Fucini 1936H62
Grammichnus Hitchcock 1865H62
`--*G. alpha Hitchcock 1865H62
Greysonia Walcott 1914H62
`--*G. basaltica Walcott 1914H62
Guilielmites Geinitz 1858 [=Guilelmites (l. c.), Gulielmites (l. c.); incl. Gaussia Chachlof 1934, Verrucania Fucini 1936]H75
|--‘Carpolites’ clipeiformis Geinitz 1856H75
`--G. umbonatus (von Sternberg 1825) [=Carpolites umbonatus, Cardiocarpum umbonatum Bronn 1837]H75
Halleia Fucini 1936H62
`--*H. penicillata Fucini 1936H62
Herpesvirus simiae (virus)PHK96
Hirmeria Fucini 1936H62
`--*H. notabilis Fucini 1936H62
Humiligraptus Hundt 1940M14
Ikeya Vologdin 1965G79
`--*I. tumida Vologdin 1965G79
Interconulites Desio 1941H62
Isuasphaera Pflug 1978AMM03
`--I. isuaAMM03
Iyaia Vologdin 1965G79
`--*I. sayanica Vologdin 1965G79
Kempia Bain 1927H75
`--*K. huronense Bain 1927H75
Kinneya Walcott 1914G79
`--*K. simulans Walcott 1914G79
Kofoidopsis Tasch 1963FT93
Kraeuselia Fucini 1936H62
`--*K. verrucana Fucini 1936H62
Lithodictuon Conrad 1837 [=Dictuolites Conrad 1838, Dictyolites (l. c.)]H75
`--*L. beckii Conrad 1837 [=*Dictuolites beckii]H75
Manchuriophycus Endo 1933H75
|--*M. yamamotoi Endo 1933H75
|--M. inexpectansH75
|--M. sawadai Yabe 1939H75
`--M. sibiricus Maslov 1947H75
Maritimella Repina & Okuneva 1969CB04
Matthewina Galloway 1933H75
`--*M. cambrica (Matthew 1895) [=Globigerina cambrica]LT64
Mawsonella Chapman 1927 non Brady 1918 (ICBN)G79
`--*M. wooltanensis Chapman 1927G79
Membranites Fucini 1938H62
Mikrocalyx Wetzel 1967H75
`--*M. pullulans f. syringata Wetzel 1967H75
Nannoceratopsiella Tasch 1963FT93
Newlandia Walcott 1914H62
`--*N. frondosa Walcott 1914H62
Orientella Repina & Okuneva 1969CB04
Palaeotrochis Emmons 1856H62
|--P. majorH62
`--P. minorH62
Palmacites martii Heer 1855 [=Palmanthium martii Schimper 1870]H62
Panescorsea de Saporta 1882 [=Panescorsaea (l. c.), Panescorea (l. c.)]H75
`--*P. glomerata de Saporta 1882H75
Phyllitites Fucini 1936H62
`--*P. rugosus Fucini 1936H62
Phytocalyx Bornemann 1886H62
`--*P. antiquus Bornemann 1886H62
Piaella Fucini 1936H62
`--*P. biformis Fucini 1936H62
Polygonolites Desio 1941H62
Prasinema Retallack 2011JG12
|--*P. gracile Retallack 2011 [=P. gracilis]JG12
|--P. adunatum Retallack 2011JG12
`--P. nodosum Retallack 2011JG12
Protadelaidea Tillyard in David & Tillyard 1936 [=Protoadelaidea (l. c.)]H75
`--*P. howchini Tillyard 1936H75
Pseudopolyporus Hollick 1910H62
`--*P. carbonicus Hollick 1910H62
Reynella David 1928H62
`--*R. howchini David 1928H62
Rhabdionvirus oryctes (virus)C81
Rhysonetron Hofmann 1967H75
`--*R. lahtii Hofmann 1967H75
Rivularites Fliche 1905H75
|--*R. repertus Fliche 1905H75
`--R. permiensis White 1929H75
Rotundoserpens Okamura 1987O87
`--*R. protominilorientalus Okamura 1987O87
Rutgersella Johnson & Fox 1968H75
`--*R. truexi Johnson & Fox 1968H75
Sayanella Vologdin 1966G79
`--*S. akshanica Vologdin 1966G79
Schafferia Fucini 1938H62
`--*S. verrucana Fucini 1938H62
Sewardiella Fucini 1936H75
`--*S. verrucana (Fucini) Fucini 1936 [=Baieropsis verrucana Fucini 1928]H75
Sickleria Müller 1846H62
`--*S. labyrinthiformis Müller 1846H62
Spirocerium Ehrenberg 1858H75
`--*S. priscum Ehrenberg 1858H75
Squamopsis Fucini 1938H62
`--*S. modesta Fucini 1938H62
Stylolithes Klöden 1828H62
`--*S. sulcatus Klöden 1828H62
Taonichnites Matthew in Selwyn 1890 [incl. Medusichnites Matthew 1891]H75
Tazenakhtia Choubert, Termier & Termier 1951H62
`--*T. aenigmatica Choubert, Termier & Termier 1951H62
Telemarkites Dons 1959G79
`--*T. enigmaticus Dons 1959G79
Tubiphyton Choubert, Termier & Termier 1951H62
`--*T. taghdoutensis Choubert, Termier & Termier 1951H62
Vesicolithus Fritsch 1908 (n. n.)H62
`--*V. guttalis Fritsch 1908H62

*Type species of generic name indicated

References

[AMM03] Appel, P. W. U., S. Moorbath & J. S. Myers. 2003. Isuasphaera isua (Pflug) revisited. Precambrian Research 126: 309–312.

[C81] Caltagirone, L. E. 1981. Landmark examples in classical biological control. Annual Review of Entomology 26: 213–232.

[CB04] Cotton, T. J., & S. J. Braddy. 2004. The phylogeny of arachnomorph arthropods and the origin of the Chelicerata. Transactions of the Royal Society of Edinburgh: Earth Sciences 94: 169–193.

[C40] Cushman, J. A. 1940. Foraminifera: Their classification and economic use (3rd ed.) Harvard University Press: Cambridge (Massachusetts).

[FT93] Fensome, R. A., F. J. R. Taylor, G. Norris, W. A. S. Sarjeant, D. I. Wharton & G. L. Williams. 1993. A classification of living and fossil dinoflagellates. Micropaleontology Special Publication 7: i–viii, 1–351.

[G79] Glaessner, M. F. 1979. Precambrian. In: Robison, R. A., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt A. Introduction. Fossilisation (Taphonomy), Biogeography and Biostratigraphy pp. A79–A118. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

[H62] Häntzschel, W. 1962. Trace fossils and problematica. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt W. Miscellanea: Conodonts, Conoidal Shells of Uncertain Affinities, Worms, Trace Fossils and Problematica pp. W177–W245. Geological Society of America, and University of Kansas Press.

[H75] Häntzschel, W. 1975. Treatise on Invertebrate Paleontology pt W. Miscellanea Suppl. 1. Trace Fossils and Problematica 2nd ed. The Geological Society of America: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

[H98] Heinrich, W.-D. 1998. Late Jurassic mammals from Tendaguru, Tanzania, east Africa. Journal of Mammalian Evolution 5 (4): 269–290.

[H74] Helson, G. A. H. 1974. Insect Pests: Identification, life history, and control of pests of farms, horticulture, gardens, and public health. A. R. Shearer, Government Printer: Wellington (New Zealand).

Inglez, L., L. V. Warren, F. Quaglio, R. G. Netto, J. Okubo, M. J. Arrouy, M. G. Simões & D. G. Poiré. 2022. Scratching the discs: evaluating alternative hypotheses for the origin of the Ediacaran discoidal structures from the Cerro Negro Formation, La Providencia Group, Argentina. Geological Magazine 159: 1192–1209.

[JG12] Jago, J. B., J. G. Gehling, J. R. Paterson & G. A. Brock. 2012. Comments on Retallack, G. J. 2011: Problematic megafossils in Cambrian palaeosols of South Australia. Palaeontology 55 (4): 913–917.

[LT64] Loeblich, A. R., Jr & H. Tappan. 1964. Sarcodina: chiefly “thecamoebians” and Foraminiferida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt C. Protista 2 vol. 2. The Geological Society of America and The University of Kansas Press.

Lucas, S. G., & A. J. Lerner. 2017. The rare and unusual pseudofossil Astropolithon from the Lower Permian Abo Formation near Socorro, New Mexico. New Mexico Geology 39 (2): 40–42.

[M14] Maletz, J. 2014. The classification of the Pterobranchia (Cephalodiscida and Graptolithina). Bulletin of Geosciences 89 (3): 477–540.

[M74] Matisto, A. 1974. Corycium enigmaticum Beschaffenheit und Herkunft des problematischen Gebildes. Bulletin de la Commission Geologique de Finlande 268: 1–30.

[O87] Okamura, C. 1987. New facts: Homo and all Vertebrata were born simultaneously in the former Paleozoic in Japan. Original Report of the Okamura Fossil Laboratory 15: 347–573.

Pickerill, R. K., & I. M. Harris. 1979. A reinterpretation of Astropolithon hindii Dawson 1878. Journal of Sedimentary Petrology 49 (3): 1029–1036.

[PHK96] Prescott, L. M., J. P. Harley & D. A. Klein. 1996. Microbiology 3rd ed. Wm. C. Brown Publishers: Dubuque (Iowa).

Retallack, G. J. 2011. Problematic megafossils in Cambrian palaeosols of South Australia. Palaeontology 54 (6): 1223–1242.

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