Modern animal life could have arisen in a storm-dominated deltaic environment

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Our understanding of how and where the ancestors of modern life evolved has been the question of many paleontologists for a long time. Recently, an international team of sedimentologists and paleontologists, including Dr. Luis Buatois, Dr. Gabriela Mángano, and Dr. Maximiliano Paz, demonstrated that a world-famous Cambrian soft-bodied fossil assemblage in Yunnan province, China, lived and died in a delta front environment affected by storms. The Chengjiang Biota records the exquisite preservation of soft-bodied marine invertebrates, including worms, early arthropods, and early vertebrates. This assemblage is around 518 million years old, around the time of the famous Cambrian explosion, where modern communities of animals first started to truly diversify. The Chenjiang biota has a similar faunal makeup to the Burgess Shale biota from British Columbia, Canada. The team analyzed a core taken from Cambrian outcrops in Yunnan, China, and discovered that the sequence of strata was formed in a shallow marine, deltaic environment. High rates of sedimentation and indications of high salinity point to this deltaic environment being dominated by storms and river floods. These kinds of sediments help us to understand the exceptional taphonomy of fossils from these Cambrian assemblages.

Figure. Block diagram showing the storm-flood-dominated delta and associated cores showing depositional sequences. (From F. Saleh et al., 2022)

The full article can be accessed in Nature Communications.

Written by Jack Milligan

Associated Champsosaur skeleton in Southwest Saskatchewan discovered by Jack Miligan

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Following the K-Pg mass extinction event which wiped out the non-avian dinosaurs, the swamps and floodplains of southwest Saskatchewan were populated by an assortment of small to medium sized vertebrates including turtles, crocodiles, early mammals, and a now-extinct group of semi-aquatic reptiles known as champsosaurs. During a joint research expedition near the town of Climax, Saskatchewan by the Royal Saskatchewan Museum and Carleton University in Ottawa in August 2020, an associated skeleton of a champsosaur was recovered by Jack Miligan. The champsosaur was collected in a terrestrial shale horizon around 3 m above the K-Pg boundary, from the Paleocene aged Grey Facies of the Ravenscrag Formation. The Grey Facies records a low energy, vegetated swamp environment. 

Champsosaur hind foot (middle right in image). Photo by Jack Miligan.

This skeleton is between 35-40% complete and is comprised of several dorsal and caudal vertebrae with intact neural arches and transverse processes, incomplete bones from all four limbs including a humerus and femurs, dozens of ribs, and several elements making up the pectoral and pelvic girdles. Numerous gastralia as well as a near complete hind foot were found in-situ upon examination of the shale horizon from which the bones had eroded out of. More fieldwork is needed to try and recover cranial material to affirm an accurate taxonomic identification of this specimen.

Research into the osteology of the specimen, as well as a review of the paleoecology of the vertebrate fauna of the Ravenscrag Formation is underway and could yield new insight into biostratigraphy, and macroevolutionary trends of champsosaur species across the K-Pg boundary in Saskatchewan.

You can read more about the discovery in this Usask news article.

Written by Jack Miligan

Note: Jack recently joined the ichnofamily at Usask as an M.Sc. student! You can read more about him on his ichnoplanet profile, or follow him on ResearchGate or Twitter. –Brittany

Charlie Zheng secures a Student Research Award in Planetary Habitability!

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We’re pleased to share that our colleague Charlie Zheng, Ph.D. candidate at the University of Texas Austin, was just awarded a Student Research Award in Planetary Habitability!

The award is distributed by the UT Center for Planetary Systems Habitability and consists of $24,960. It is a well deserved award which will allow Charlie, along with project collaborators Dr.’s Buatois & Màngano, to continue their fascinating research into the resilience of marine infaunal communities. Charlie describes the project as:

“Trace fossil records are the best indicator of habitability in harsh environments after mass extinctions or during the early evolution of life on earth. In fact, oceanic anoxia is a common theme linked to major environmental perturbations and ancient oceans that hosted early metazoan life ordinarily contained low oxygenations. A comprehensive dataset documenting marine infaunal communities under oxygen-deficient environments from different settings and geologic ages is necessary to better understand the habitability of environments. Moreover ichnology should play an essential role in the search for evidence of early lifeform in other worlds, especially under similar environmental conditions.

The Cretaceous Maverick intrashelf basin is one of the world’s best examples of a shallow marine shelf ecosystem impacted by locally developed anoxia, creating “dead zones” that evolve into shallow basins within the shallow-water shelf. This project aims to integrate ichnologic and sedimentological signatures to characterize distinctive infaunal communities under hostile, oxygen-limited conditions and assess the resilience of marine infaunal communities and the carbonate factory ecosystem evolution across the environmental perturbation. This study will extend the existing ichnologic database in oxygen-deficient settings by providing the first case study on the intrashelf basin lacking modern analogs and serve as an needed update on the subject since the 90’s, when relevant studies were most abundant.” 

Panoramic photograph of an outcrop from the Del Norte area, Devils River State Natural Area, Texas. This outcrop shows the more proximal shallow-water platform facies & architecture of the basin. The awarded research will focus on more distal portions of this same basin. (photo by Charlie Zheng)

A big congratulation’s to Charlie on this accomplishment!! We can’t wait to read about the results of this research!

You can follow Charlie’s research via his Research Gate profile.

Written by Brittany Laing

Were all trilobites fully marine?

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Trilobites, the poster-fossil of the Paleozoic, have long been considered to be invariably fully marine. Collaborative work between Dr. Mángano, Dr. Buatois, and Argentinian colleagues questions this assumption. Through the integration of multiple datasets they report uncontroversial evidence of the exploration of tide-dominated estuaries by some trilobite groups (olenids & asaphids) throughout the Furongian to Middle Ordovician. Thick siliciclastic successions in northwest Argentina expose vertically-repeating nearly-identical environments and allowed for the comparison of body-fossil and trace-fossil data in tide-dominated estuaries through time. Their research indicates two forays into brackish water, first the colonization of the outer portion of estuaries by olenids, followed by the colonization of inner to middle estuarine zones by asaphids.

The full article is available in the Proceedings of the Royal Society B (including some fantastic photos of trilobite trace fossils in the Supplementary Info!).

Figure. Time-environment matrix showing protracted trilobite expansion into marginal-marine estuarine settings. (From Mángano et al., 2021)

Written by Brittany Laing

Large wild boar tracks discovered in SW Spain

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Recent research by colleagues, including former visiting researcher Dr. Belaústegui and former postdoc Dr. Muñiz, has been featured in the Spanish newspaper El País. Their research, first published in Palaois, examines large wild boar tracks from the Late Pleistocene of Huelva, Spain. The novel ichnogenus and ichnospecies (Suidichnus galani igen. and isp. nov.) described in their article are the first published record of fossil suid tracks. The ichnogenus is named after the family Suidae while the ichnospecies name is a nod to José María Galán, a respected local tracker who discovered the trackways (and many more in the formation).

Footprint 'Suidichnus galani' found in Matalascañas.
Paratype of Suidichnus galani igen. and isp. nov., vertically oriented. (Fig. 3 in Neto De Carvalho et al., 2020)

The large size of these tracks, and the boars themselves, are a divergence from the overall trend of the species towards smaller size. The authors delve into the cause of this divergence and suggest that the increase in size was an adaption to either an increase in predation pressure and/or a resource bonanza.

The article in El País is a fantastic piece of science communication and we highly recommend you give it a read! While the text is originally in Spanish, the Google Translate function on Google Chrome produced a good English translation.

Written by Brittany Laing