Unleashing Secrets of the Palaeozoic: Lagerstätten and Exceptional Preservation

Article by: Nicole Barnes
Edited by:
J. D. Dixon, Lewis Haller, and Harry T. Jones

Lagerstätten deposits (sites of exceptional preservation) are well-known for yielding incredible fossil discoveries, the likes of which enable palaeontologists to understand more about evolution and life in the past.

We can split these deposits into two broad categories – Konzentrat and Konservat. Konzentrat deposits consist of concentrated fossils, which usually don’t contain soft-bodied creatures and are often bone beds. Comparatively, these deposits are less impressive than Konservat, although they still carry importance. Konservat deposits are spectacular, with exceptional preservation of fossils, often including soft-bodied creatures. These deposits add to our existing knowledge of palaeocommunities, preserving organisms we would never otherwise encounter. Fossils from these deposits are key to our understanding of evolutionary events such as the Cambrian Explosion, as well as helping us to further understand how key groups of organisms evolved. Lagerstätten can be further subcategorised according to their type of preservation, their age, or even palaeoenvironment and palaeocontinent.

Illustration of the Cambrian seabed based on fossils from the Chengjiang Lagerstätte. Credit to OUMNH // Mighty Fossils.

It would be amiss to not begin by discussing the Burgess Shale of British Columbia, Canada. This iconic deposit was first discovered in 1909 by Charles Doolittle Walcott – making it the first real taste of the Cambrian Explosion and the curious fossils of this age. The creatures contained within this 508 million year old deposit were so strange and unusual that describing them and placing them within the Tree of Life was fraught with challenges and mistakes. One of these creatures was Hallucigenia sparsa. The original reconstruction of this animal was later found to be upside down, and it is now described as a lobopodian or ‘velvet-worm’, with the spines thought to be used for protection. Interpretations for perhaps one of the most well-known organisms from the Burgess Shale, Anomalocaris, cycled through several suggestions before the creature was found fully preserved – tying together several fragmentary fossils, like the mouthparts and appendages, to form a radiodont. The Burgess Shale not only represents one of the most significant discoveries for our knowledge of early life, but it also exemplifies the interpretive nature of palaeontology and the importance of subsequent discoveries of new Lagerstätten in furthering our knowledge of creatures of the past.

The Chengjiang biota, of South China, burst onto the scene in 1984. The Lagerstätte boasts one of the highest diversities of organisms amongst Cambrian deposits – encompassing some of the creatures first discovered in Canada but, excitingly, many previously unknown to science. Dominated by Euarthropods, like Naraoia spinosa and Fuxianhuia protensa, the preserved fauna represents a diverse marine community with exceptional preservation of incredible details, such as appendages, gut contents and gills of many creatures, as well as many entirely soft-bodied life forms. At 520 million years old, the Chengjiang Lagerstätte is invaluable for our knowledge of life in the Lower Cambrian as it demonstrates that even by this early stage, complex ecosystems had developed. There are still many active research projects ongoing pertaining to this deposit, the most recent of which described a new species presenting characteristics of multiple groups – Kylinxia zhangi. On account of its main features, K. zhangi is reminiscent of Opabinia (based on its five eyes), the radiodonts such as Anomalocaris (based on its appendages) and the deuteropods/megacheirans such as Haikoucaris (based on body plan). This species helps to resolve relationships between early Euarthropods, exemplifying the importance of new discoveries and transitional fossil taxa.

Another of these remarkable Cambrian-aged Lagerstätte is the Sirius Passet. Located in North Greenland, this locality makes it one of the most geographically remote Lagerstätte, although this hasn’t stopped multitudes of visits. Lower in diversity than many others, there are 45 described species – although there are many more still to be described. This begs the question, why is it still worthy of expeditions if the diversity isn’t reaching that of the likes of the Burgess Shale? The answer is simply because the Sirius Passet may preserve the transition from Ediacaran-style ecosystems to those well-known from the Palaeozoic. Predating the Burgess Shale by roughly 10 million years, this Lagerstätte preserves elements from both ecosystems – including microbial mats, such as those which often characterise the Late Proterozoic, as well as the preservation of a whole host of ichnofossils and body fossils. This interesting juxtaposition allows palaeontologists to gain an interesting perspective on the Cambrian Explosion, how Palaeozoic ecosystems evolved, and the evolution of these early creatures.

Lagerstätten are not limited to the Cambrian, with the Early Ordovician-aged Lower and Upper Fezouata Formations standing testament to this. This Moroccan Lagerstätte proves that taxa which characterise the Cambrian remain important well into the Ordovician. The discovery of Marrellomorphs and Radiodonts alongside Xiphosurans and Aglaspidids suggests that creatures which were once considered to be limited to the Cambrian actually existed far into the Ordovician, potentially playing an important role in ecosystems of both periods. The diversity of taxa described from the Fezouata biota allows palaeontologists to begin drawing parallels between two major evolutionary events, the Cambrian Explosion and the Great Ordovician Biodiversity Event (GOBE). The Lagerstätte also allows us to re-evaluate what we know about the GOBE, having previously relied on mostly hard-bodied fossil evidence.

A reconstruction of Aquilonifer spinosus from the Herefordshire Lagerstätte. Artwork by Andrey Atuchin. Click Here.

As explored, Lagerstätten deposits can come in a variety of forms and, rather excitingly, some even preserve creatures in 3D. Hailing from the Silurian, the Herefordshire Lagerstätte is one of these special deposits. Boasting a variety of invertebrates, fossils are preserved in calcite within carbonate concretions in volcaniclastic material. Whilst these fossils may not look immediately as impressive as those found elsewhere, the way in which fossils are preserved here allows for in-depth analysis using a revolutionary technique involving the study of ‘virtual fossils’. Fossils are subjected to a ‘serial grinding’ technique and are then reconstructed using custom-built software (SPIERS) to produce 3D models which can then be studied. The Herefordshire Lagerstätte has a relatively diverse fauna. One of the interesting discoveries from this Lagerstätte is Aquilonifer spinosus, a strange-looking arthropod which appears to have ten smaller creatures attached. It has been suggested that these smaller creatures which are joined to A. spinosus are, in fact, juveniles of the same species. This suggests brood care – something which is rare to be observed in the fossil record. Just quite how the individuals became tethered still remains unknown, but we can appreciate just how extraordinary this fossil is and how important it is for our understanding of the evolution of behaviours.

So far, we’ve mostly discussed invertebrates, but we can of course get exceptional preservation in other forms – including fossilised plants. The Devonian-aged Rhynie Chert Lagerstätten of Aberdeenshire, Scotland, represents an early terrestrial hot spring environment, and its fossils include six genera of early plants, bacteria, fungi, algae and arthropods. Fossils are often preserved in 3D and thus provide palaeontologists with valuable information on what life was like on land at the onset of widespread terrestrialization. In addition to this, the early plants, such as Rhynia gwynne-vaughanii and Aglaophyton majus, found within the cherts enable palaeobotanists to further understand how vascular plants evolved.

Lastly, we must consider what secrets future Lagerstätten research might uncover – as it is clear that there are still plenty of species to describe from many known deposits as well as completely new deposits still yet to be found. One such discovery was recently reported from China, the Qingjiang Lagerstätte. This promising locality seems to boast a high diversity of species as well as plenty of entirely new taxa, most of which are yet to be formally described. Replicating the preservation style of the Burgess Shale, Qingjiang presents countless opportunities to further our understanding of the Cambrian Explosion – preserving extraordinary soft-bodied taxa from cnidarians to ctenophores, and even chordates.

Image References
[1] Illustration of the Cambrian seabed based on fossils from the Chengjiang Lagerstätte. Credit to OUMNH // Mighty Fossils.
[2] A reconstruction of Aquilonifer spinosus from the Herefordshire Lagerstätte. Artwork by Andrey Atuchin. Click Here.

Information References and Further Sources
[1] Allison, P. A. (1988). ‘Konservat-Lagerstätten: cause and classification’, Paleobiology, 14 (4), pp. 331-344. Accessed 10th November 2020. Click Here.
[2] Briggs, D. E. G., Siveter, D. J., Siveter, D. J., Sutton, M. D., and Legg, D. (2016). ‘Tiny individuals attached to a new Silurian arthropod suggest a unique mode of brood care’, Proceedings of the National Academy of Sciences, 113 (16), pp. 4410-4415. Accessed 10th November 2020. Click Here.
[3] Fu, D., Tong, G., Dai, T., Liu, W., Yang, Y., Zhang, Y., Cui, L., Li, L., Yun, H., Wu, Y., Sun, A., Liu, C., Pei, W., Gaines, R. R., and Zhang, X. (2019). ‘The Qingjiang biota—A Burgess Shale-type fossil Lagerstätte from the early Cambrian of South China’, Science, 363 (6433), pp. 1338-1342. Accessed 10th November 2020. Click Here.
[4] Garwood, R. J., Oliver, H., and Spencer, A. R. T. (2020). ‘An introduction to the Rhynie chert’, Geological Magazine, 157 (1), pp. 47-64. Accessed 10th November 2020. Click Here.
[5] Harper, D. A. T., Hammarlund, E. U., Topper, T. P., Nielsen, A. T., Rasmussen, J. A., Park, T-Y. S., and Smith, M. P. (2019). ‘The Sirius Passet Lagerstätte of North Greenland: a remote window on the Cambrian Explosion’, Journal of the Geological Society, 176 (6), pp. 1023-1037. Accessed 10th November 2020. Click Here.
[6] Morris, S. C. (2008). The Crucible of Creation: The Burgess Shale and the Rise of Animals. Oxford University Press.
[7] Siveter, D. J., Briggs, D. E. G., Siveter, D. J., and Sutton, M. D. (2019). ‘The Herefordshire Lagerstätte: fleshing out Silurian marine life’, Journal of the Geological Society, 177 (1), pp. 1-13. Accessed 10th November 2020. Click Here.
[8] Sutton, M. D., Briggs, D. E. G., Siveter, D. J., Siveter, D. J., and Orr, P. J. (2002). ‘The arthropod Offacolus kingi (Chelicerata) from the Silurian of Herefordshire, England: computer based morphological reconstructions and phylogenetic affinities’, Proceedings of the Royal Society of London. Series B: Biological Sciences, 269 (1497), pp. 1195–1203. Accessed 10th November 2020. Click Here.
[9] Van Roy, P., Orr, P. J., Botting, J. P., Muir, L. A., Vinther, J., Lefebvre, B., el Hariri, K., and Briggs, D. E. G. (2010). ‘Ordovician faunas of Burgess Shale type’, Nature, 465 (7295), pp. 215–218. Accessed 10th November 2020. Click Here.
[10] Xian-guang, H., Siveter, D. J., Siveter, D. J., Aldridge, R .J., Pei-yun, C., Gabbott, S. E., Xiao-ya, M., Purnell, M. A., and Williams, M. (2017). The Cambrian Fossils of Chengjiang, China: The Flowering of Early Animal Life. Chichester: John Wiley & Sons Ltd. Accessed 10th November 2020. Click Here.
[11] Zeng, H., Zhao, F., Niu, K., Zhu, M., and Huang, D. (2020). ‘An early Cambrian euarthropod with radiodont-like raptorial appendages’, Nature, pp. 1-5. Accessed 10th November 2020. Click Here.