Lenisambulatrix

File:Lenisambulatrix humboldti fossil.jpg

The fossil of Lenisambulatrix humboldti was discovered by Qiang Ou (China University of Geosciences, Beijing, China) and Georg Mayer (University of Kassel, Kassel, Germany). It was found in the Heilinpu Formation of the Huaguoshan section at Sanjiezi village, Erjie town, Yunnan, South China.{{Cite web|last=Geggel|first=Laura|date=2018-09-20|title=Without Claws or Armor, 520-Million-Year-Old 'Naked' Critter Was Likely a Loner|url=https://www.livescience.com/63630-newly-identified-naked-cambrian-worm.html|access-date=2022-01-15|website=Live Science|language=en}} The location is dated to Cambrian Series 2, Stage 3 (about 520 million years old).{{Cite journal|last1=Liu|first1=Yu|last2=Scholtz|first2=Gerhard|last3=Hou|first3=Xianguang|date=2015|title=When a 520 million-year-old Chengjiang fossil meets a modern micro-CT – a case study|journal=Scientific Reports|language=en|volume=5|issue=1|pages=12802|doi=10.1038/srep12802|pmid=26238773|pmc=4523851|bibcode=2015NatSR...512802L|issn=2045-2322}}{{Cite journal|last1=Yang|first1=Chuan|last2=Li|first2=Xian-Hua|last3=Zhu|first3=Maoyan|last4=Condon|first4=Daniel J.|last5=Chen|first5=Junyuan|date=2018|title=Geochronological constraint on the Cambrian Chengjiang biota, South China|url=https://jgs.lyellcollection.org/content/175/4/659|journal=Journal of the Geological Society|language=en|volume=175|issue=4|pages=659–666|doi=10.1144/jgs2017-103|bibcode=2018JGSoc.175..659Y|s2cid=135091168|issn=0016-7649}} The excavation also yielded a fossil of Diania cactiformis, already described by Ou's team in 2011.{{Cite journal|last1=Liu|first1=Jianni|last2=Steiner|first2=Michael|last3=Dunlop|first3=Jason A.|last4=Keupp|first4=Helmut|last5=Shu|first5=Degan|last6=Ou|first6=Qiang|last7=Han|first7=Jian|last8=Zhang|first8=Zhifei|last9=Zhang|first9=Xingliang|date=2011|title=An armoured Cambrian lobopodian from China with arthropod-like appendages|url=https://www.nature.com/articles/nature09704|journal=Nature|language=en|volume=470|issue=7335|pages=526–530|bibcode=2011Natur.470..526L|doi=10.1038/nature09704|issn=1476-4687|pmid=21350485|s2cid=4324509|url-access=subscription}} The specimen was compressed partly with the fossil of a brachiopod Diandongia pista, which was described from the similar Maotianshan shale in 2003.{{Cite journal|last1=Zhifei|first1=Zhang|last2=Jian|first2=H. a. N.|last3=Xingliang|first3=Zhang|last4=Jianni|first4=L. I. U.|last5=Degan|first5=S. H. U.|date=2003|title=Pediculate Brachiopod Diandongia pista from the Lower Cambrian of South China|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1755-6724.2003.tb00743.x|journal=Acta Geologica Sinica|language=en|volume=77|issue=3|pages=288–293|doi=10.1111/j.1755-6724.2003.tb00743.x|bibcode=2003AcGlS..77..288Z |s2cid=129658643|issn=1755-6724|url-access=subscription}} The discovery was reported in the September issue of the Scientific Reports.{{Cite web|date=2018-09-21|title=Palaeontology: 'Reclusive' fossil worm from the Cambrian identified|url=https://www.natureasia.com/en/research/highlight/12700|access-date=2022-01-15|website=www.natureasia.com|language=en}}

The generic name is derived from Latin words, lenis, meaning soft or smooth, or gentle, attributing to the smooth unarmoured body; ambulatrix, meaning walker. The specific name is in honour of the German zoologist Friedrich Wilhelm Heinrich Alexander von Humboldt, after whose name was established the Alexander von Humboldt Foundation, which funded the research.

Lenisambulatrix is seen as dark, carbonaceous and aluminosilicate films in a worn out mudstone. The original soft tissues and cuticle are represented by deposits of dark red to brown iron(III) oxide fine grains as a result of weathering of microscopic diagenetic pyrite. This fossilisation process is similar to those of other specimens in the Chengjian region.{{Cite journal|last1=Forchielli|first1=Angela|last2=Steiner|first2=Michael|last3=Kasbohm|first3=Jörn|last4=Hu|first4=Shixue|last5=Keupp|first5=Helmut|date=2014|title=Taphonomic traits of clay-hosted early Cambrian Burgess Shale-type fossil Lagerstätten in South China|url=https://www.sciencedirect.com/science/article/pii/S0031018213003647|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|series=Cambrian Bioradiation|language=en|volume=398|pages=59–85|doi=10.1016/j.palaeo.2013.08.001|bibcode=2014PPP...398...59F|issn=0031-0182|url-access=subscription}} The fossil is oblique-ventrally compressed and the remaining parts are nicely preserved showing details of the body structure. This good preservation is characteristic of Chengjian biota and indicates death due to a catastrophic event.{{Cite journal|last1=Gaines|first1=Robert R.|last2=Briggs|first2=Derek E.G.|last3=Yuanlong|first3=Zhao|date=2008|title=Cambrian Burgess Shale–type deposits share a common mode of fossilization|url=https://pubs.geoscienceworld.org/geology/article/36/10/755-758/29641|journal=Geology|language=en|volume=36|issue=10|pages=755|doi=10.1130/G24961A.1|bibcode=2008Geo....36..755G|issn=0091-7613|url-access=subscription}}

The worm is a soft-bodied lobopodian without any hard part (sclerotized) surface, thus, appears naked{{Cite web|last=Geggel|first=Laura|date=2018-09-20|title=Without Claws or Armor, 520-Million-Year-Old 'Naked' Critter Was Likely a Loner|url=https://www.livescience.com/63630-newly-identified-naked-cambrian-worm.html|access-date=2022-01-15|website=Live Science|language=en}} in contrast to most lobopodians which bears spines as body armours.{{Cite journal|last1=Caron|first1=Jean-Bernard|last2=Aria|first2=Cédric|date=2017|title=Cambrian suspension-feeding lobopodians and the early radiation of panarthropods|journal=BMC Evolutionary Biology|volume=17|issue=1|pages=29|doi=10.1186/s12862-016-0858-y|pmc=5282736|pmid=28137244 |doi-access=free |bibcode=2017BMCEE..17...29C }}{{Cite journal|last1=Liu|first1=Jianni|last2=Dunlop|first2=Jason A.|date=2014|title=Cambrian lobopodians: A review of recent progress in our understanding of their morphology and evolution|url=https://www.sciencedirect.com/science/article/pii/S003101821300285X|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|language=en|volume=398|pages=4–15|doi=10.1016/j.palaeo.2013.06.008|bibcode=2014PPP...398....4L|issn=0031-0182|url-access=subscription}} It is not preserved in a completely stretched form and many parts are missing. The measurable length of the body is 2.9 cm; with a width varying from 2 to 3.6 mm. The trunk consists of at least eight segments (somites), each of which bears a pair of thick and long legs. The fossil contains only the anterior part and the posterior region remains unknown. The head part is slightly extended and does not show any specific part. It is believed to be closely related to Diania, but with unique differences. The main distinction is numerous sclerotized spines that adorn Diania are completely absent in Lenisambulatrix.{{Cite web|last=Geggel|first=Laura|date=2018-09-20|title=Without Claws or Armor, 520-Million-Year-Old 'Naked' Critter Was Likely a Loner|url=https://www.livescience.com/63630-newly-identified-naked-cambrian-worm.html|access-date=2022-01-15|website=Live Science|language=en}} Diania's head is also much more rounded and shorter. The general outline of Lenisambulatrix's head more similar to other lobopodians such as Microdictyon sinicum, Paucipodia inermis, and Hallucigenia sparsa.{{Cite journal|last1=Ma|first1=Xiaoya|last2=Hou|first2=Xianguang|last3=Aldridge|first3=Richard J.|last4=Siveter|first4=David J.|last5=Siveter|first5=Derek J.|last6=Gabbott|first6=Sarah E.|last7=Purnell|first7=Mark A.|last8=Parker|first8=Andrew R.|last9=Edgecombe|first9=Gregory D.|date=2012-09-01|title=Morphology of Cambrian lobopodian eyes from the Chengjiang Lagerstätte and their evolutionary significance|url=https://www.sciencedirect.com/science/article/pii/S1467803912000254|journal=Arthropod Structure & Development|language=en|volume=41|issue=5|pages=495–504|doi=10.1016/j.asd.2012.03.002|issn=1467-8039|pmid=22484085|bibcode=2012ArtSD..41..495M |url-access=subscription|doi-access=free}}{{cite journal|author1=Xian-Guang Hou|author2=Xiao-Ya Ma|author3=Jie Zhao|author4=Jan Bergström|year=2004|title=The lobopodian Paucipodia inermis from the Lower Cambrian Chengjiang fauna, Yunnan, China|journal=Lethaia|volume=37|issue=3|pages=235–244|doi=10.1080/00241160410006555|bibcode=2004Letha..37..235H }} However, the relatively thick and elongated legs measuring 11.6 to 18 mm long are unique to both Diania and Lenisambulatrix.{{Cite web|date=2018-09-21|title=Palaeontology: 'Reclusive' fossil worm from the Cambrian identified|url=https://www.natureasia.com/en/research/highlight/12700|access-date=2022-01-15|website=www.natureasia.com|language=en}} Their legs also lack claws that are the common features in other lobopods.{{Cite journal|last1=Xianguang|first1=Hou|last2=Ramsköld|first2=Lars|last3=Bergström|first3=Jan|date=1991|title=Composition and preservation of the Chengjiang fauna –a Lower Cambrian soft-bodied biota|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1463-6409.1991.tb00303.x|journal=Zoologica Scripta|language=en|volume=20|issue=4|pages=395–411|doi=10.1111/j.1463-6409.1991.tb00303.x|s2cid=85077111|issn=1463-6409|url-access=subscription}} The legs indicate that they were adapted to walking or crawling on the bottom of waters.{{Cite web|date=2018-09-21|title=Palaeontology: 'Reclusive' fossil worm from the Cambrian identified|url=https://www.natureasia.com/en/research/highlight/12700|access-date=2022-01-15|website=www.natureasia.com|language=en}} The simple body structure suggests that Lenisambulatrix is one of the earliest panarthropod animal.

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Category:Fossil taxa described in 2018

Category:Lobopodia

Category:Maotianshan shales fossils

Category:Cambrian invertebrates

Category:Cambrian China

Category:Paleontology in China

Category:Alexander von Humboldt