Researchers have concluded that the remarkable fossils associated with the Yixian Formation of north-eastern China were not caused by Pompeii-like events.  The prevailing view was that these amazing fossils, some of which are preserved in stunning detail, were formed due to violent volcanic eruptions, lahars or pyroclastic flows.  However, a team of scientists writing in the journal the “Proceedings of the National Academy of Sciences”, have challenged this hypothesis.  Instead, it is suggested that the deposition took place over a period of less than 100,000 years. Furthermore, more mundane factors were at work, such as high rainfall, causing the burrows of animals to collapse.

Study co-author Paul Olsen exploring the quarry where the first feathered non-avian dinosaur was found in 1996 (Sinosauropteryx). If these fossils had formed as a result of violent volcanic events, it would have been highly unlikely that delicate structures such as feathers would have been preserved. Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory.

Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory

Far from representing Pompeii-like catastrophes, the scientists conclude that the deposits provide a brief snapshot of normal life and death in an Early Cretaceous continental community.

The Incredible Fossils of the Yixian Formation

The Lower Cretaceous deposits of the Yixian Formation exposed in Liaoning Province (north-eastern China) were virtually unexplored until the 1980s.  Villagers reported finding beautiful fossil specimens, representing all kinds of creatures that once lived in a forested environment that contained large lakes.  The rocks are believed to be around 125 million years old (Barremian faunal stage). Fossils of dinosaurs, pterosaurs, birds, mammals, amphibians, reptiles, fish and insects have been found.  Some of the most famous fossils ever found come from this part of China.

Since the first, remarkable discoveries there has been fossil gold rush with an extensive network of fossil dealers and retail outlets springing up. Both locals and scientific field teams have excavated the area so much, the dig sites can be seen from space.  These are perhaps the most extensive palaeontological excavations on Earth.

The corpse of a feathered dinosaur lies on the lake shore whilst a pair of Psittacosaurus wander past and pterosaurs fly overhead.  It had been thought that the beautiful fossils of the Yixian Formation were formed as a result of volcanic activity. Picture credit: Zheng Qiuyang.

Picture credit: Zheng Qiuyang

Flattened Fossils or Three-dimensional Fossils

The fossils occur as flattened with soft tissue preservation (including feathers and melanosomes) in laminated lacustrine strata (lake sediments) or as three-dimensional almost complete, articulated skeletons in more terrestrial orientated deposits.  The discoveries include the first documented evidence of a mammal attacking a dinosaur.

To read more about this amazing fossil discovery: Repenomamus Attacks Psittacosaurus.

Co-author of the study, Paul Olsen a palaeontologist at the Columbia University’s Lamont-Doherty Earth Observatory, commented:

“These are probably the most important dinosaur discoveries of the last 120 years. But what was said about their method of preservation highlights an important human bias. That is, to ascribe extraordinary causes, i.e. miracles, to ordinary events when we don’t understand their origins. These [fossils] are just a snapshot of everyday deaths in normal conditions over a relatively brief time.”

Analysing Grains of Zircon

Lead author of the research, Scott MacLennan (University of Witwatersrand) analysed tiny grains of the mineral zircon taken from the fossil matrix and the actual fossils. With these samples, he measured the ratios of radioactive uranium as it decays into lead. This rate of radioactive decay is constant. As a result, he was able to date the material with a high degree of accuracy. These fossils were formed around 125.8 million years ago, centred around a period of less than 93,000 years.

Further calculations showed that this timeframe contained three periods controlled by variations in the Earth’s orbit when the weather was relatively wet. This caused sediments to build up in lakes and on land much more quickly than previously had been thought. Many already deceased animals were quickly buried, and oxygen that normally would fuel decomposition was sealed out. The sealing effect was fastest in lakes, resulting in the preservation of soft tissues.

This explains why two types of fossils occur.

A field team from the Nanjing Institute of Geology and Palaeontology exploring Yixian Formation exposures (Lujiatun Member). Many Psittacosaurus fossils have been found at this locality. On the right of the photograph is one of the quarries dug by local people in search of fossils to sell. Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory.

Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory

Fossil Preservation Not Connected to Volcanism

The scientists have discounted volcanism. Previous studies have suggested that some animals were entombed in lahars. These are fast-moving concrete-like slurries of mud that flow from volcanoes following eruptions. However, lahars are extremely violent, preserving animal skeletons intact, with soft tissues preserved would be most unlikely.

In addition, other researchers have suggested that the preservation occurred due to pyroclastic flows. Pyroclastic flows involve rapidly moving waves of hot ash and poisonous gases, the sort of event that led to the remarkable preservation found in Pompeii.

There are layers of volcanic ash and lava within the layers of rock that form the Yixian Formation.  However, the fossil remains include delicate structures such as feathers and stomach contents, which could not have survived such traumatic incidents.  The scientists conclude that the evidence indicates sudden burrow collapses.  For example, the famous Repenomamus attacking the Psittacosaurus, a battle preserved in time, could have occurred when the mammal invaded the dinosaur’s burrow, and the burrow subsequently collapsed.

Rather than representing multiple, Pompeii-like terrible events, the Yixian Formation is instead a brief snapshot of normal life and death in an Early Cretaceous ecosystem.

An Economy Centred Around the Yixian Formation

Whatever, the reason for the fossil preservation, Liaoning Province is now one of the most famous parts of China.  These remarkable fossils attract tourists, and an entire industry has sprung up with extensive trading in fossil souvenirs.

Potential buyers examine fossils at a shop in the city of Chaoyang (Liaoning Province), a centre of the Chinese fossil trade. Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory.

Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory

Everything Dinosaur acknowledges the assistance of a media release from The Earth Institute/Columbia Climate School (Columbia University) in the compilation of this article.

The scientific paper: “Extremely rapid, yet noncatastrophic, preservation of the flattened-feathered and 3D dinosaurs of the Early Cretaceous of China” by Scott A. MacLennan, Jingeng Sha, Paul E. Olsen, Sean T. Kinney, Clara Chang, Yanan Fang, Jun Liu, Bennett B. Slibeck, Elaine Chen and Blair Schoene published in the PNAS.

The award-winning Everything Dinosaur website: Dinosaur Toys and Models.

Scientists have named a new species of oviraptorosaur from Inner Mongolia (China).  This new theropod has been named Yuanyanglong bainian.  The species name recognises that it is a hundred years since the naming of the first oviraptorosaur taxon.  In 1924, Oviraptor philoceratops was named and formally described.  Yuanyanglong is known from two fossil specimens recovered from the Lower Cretaceous Miaogou Formation.  The fossils come from the Maortu locality in Chilantai, Inner Mongolia.  Phylogenetic analysis suggests that it is a sister taxon to the clade formed by the Caenagathoidea and the Avimimidae.  It was a small dinosaur standing less than a metre high.

A scale drawing of the recently described oviraptorosaur from Inner Mongolia Yuanyanglong bainian. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Yuanyanglong bainian

The research team, writing in the academic journal Cretaceous Research identified several unique autapomorphies in the fossilised bones.  For example, the hindlimbs are proportionately elongated and they have fused lower segments.  In addition, the ilium (part of the pelvic girdle) has a much reduced postacetabular process.  This combination of anatomical traits is not known in other oviraptorosaurs, however, they are found in extant wading birds.  Yuanyanglong may have lived close to bodies of water.

One of the specimens PV02476-2 consists of a partial and poorly preserved skull.  However, the potential diet of this theropod can only be inferred at this time.  Preserved gastroliths similar to those associated with another oviraptorosaur – Caudipteryx have been recovered.  The research team have stated that preliminary observations indicate potential discrepancies in the digestion mode of early and late-diverging oviraptorosaurs.

The first part of the genus name is derived from “Yuanyang” the mandarin term for lovebirds (Aix galericulata). These birds form long bonds with their partners, a reference to the pair of skeletons found together.  The second part of the genus name “long” is a transliteration of the Chinese word for dragon.  The species or trivial name “bainian” translates as “one hundred years”, reflecting a hundred years since the naming of the first oviraptorosaur taxon Oviraptor philoceratops.

A scale drawing of a typical oviraptorosaur (O. philoceratops).  The species name of Yuanyanglong bainian commemorates the centenary of the naming of the first oviraptorosaur. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Rare Dinosaur Fossils

The Maortu locality in Chilantai, western Inner Mongolia has produced other vertebrate fossil remains.  However, dinosaur fossils are rare.  Some, as yet, undescribed sauropod remains have been reported.  In addition, three dinosaur taxa are known from this area.  A theropod has been described (Shaochilong maortuensis), along with a hadrosaurid Probactrosaurus gobiensis. In addition, fossils of an armoured dinosaur have been found. Gobisaurus domoculus was named and formally described in 2001 (Vickaryous et al).  Regarded as a member of the Ankylosauridae family Gobisaurus was a large, robust animal.  It may have been over six metres in length and weighed in excess of three tonnes.

A spokesperson from Everything Dinosaur commented that further analysis of vertebrate fossil remains from the Maortu locality would likely result in the announcing of new dinosaur taxa.

To read an article from 2016 about the discovery of a oviraptorosaur from southern China (Tongtianlong limosus) that provided new insights into oviraptorosaur radiation: A Fresh Perspective on Oviraptorosaur Radiation.

The scientific paper “A new oviraptorosaur from the Lower Cretaceous Miaogou Formation of western Inner Mongolia, China” by Mingze Hao, Zhiyu Li, Zhili Wang, Shuqiong Wang, Feimin Ma, Qinggele, J. Logan King, Rui Pei, Qi Zhao and Xing Xu published in the journal Cretaceous Research.

Visit the award-winning Everything Dinosaur website: Dinosaur Toys and Figures.

A recently published scientific paper suggests that rapid global cooling as a result of the release of billions of sulphate particles into the atmosphere played a significant role in the End-Triassic extinctions.

The end of the Triassic marks one of the five great mass extinctions recorded in the Phanerozoic Eon. Arguably, of these five, the End-Triassic extinction is the least understood by Earth scientists. The mechanisms of extinction remain open to debate. However, it is known that during this time there was extensive volcanic activity.  Pangaea began to tear itself apart, the first step in a process that led to the creation of the Atlantic Ocean. The Atlantic is still widening today.

Enormous outpourings of basaltic lava occurred covering the entire (modern) eastern seaboard of the United States, reaching as far west as Texas and probably as far south as Venezuela. These basaltic extrusions have counterparts in Europe and northern Africa that are approximately the same age. These huge eruptions are known collectively as the Central Atlantic Magmatic Province (CAMP).

A New Theory to Explain the End-Triassic Extinctions

It had been thought that huge concentrations of carbon dioxide pumped into the atmosphere led to global warming and the acidification of the world’s marine environments.  Intriguingly, a new study suggests it was sudden and dramatic global cooling that led to the extinction of many animals.

This new study suggests that the first eruptions were immense but relative brief events, lasting less than a hundred years each. Sunlight-reflecting sulphate particles were ejected into the atmosphere, rapidly cooling the planet. The extreme cold changed the biota of planet Earth. The Earth’s temperature began to rise with the increase of carbon dioxide in the atmosphere and global warming took place. However, the researchers conclude that it was the rapid freezing that resulted in the collapse of ecosystems and the initial mass extinctions.

The photograph shows red sandstone deposits in Morocco associated with the Triassic to Jurassic boundary. Red sediments in many locations around the world contain fossils of Triassic fauna and flora. The white caps are sediments laid down by extensive volcanism, as is evidenced by the grey/black basalt layers topping the assemblage. Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory.

Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory

Lead author of the paper, Dennis Kent, Adjunct Senior Research Scientist at Lamont-Doherty Earth Observatory at Columbia University, stated:

“It takes a long time for carbon dioxide to build up and heat things, but the effect of sulphates is pretty much instant. It brings us into the realm of what humans can grasp. These events happened in the span of a lifetime.”

To read another article about Triassic extinction theories: The Carnian Pluvial Episode and Extinction.

Correlating Data from CAMP Deposits

The researchers gathered data from CAMP deposits in the mountains of Morocco, in the Bay of Fundy (Nova Scotia) and from the Newark Basin (New Jersey). The focused their study on the alignment of magnetic particles within the strata. The orientation of these particles records the historical drift of the Earth’s magnetic pole during the time of the volcanic activity.

The magnetic pole is not fixed, it shifts from the planet’s stable axis of rotation—true north—and changes position by a few tenths of a degree each year. This is why compasses do not point at true north. As a result, magnetic particles in lava flows that occurred within a few decades of each other will align in the same direction, whereas those from thousands of years later could be misaligned by twenty to thirty degrees.

Red Triassic sandstones capped by volcanic ash in the Bay of Fundy (Nova Scotia). Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory.

Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory

Five successive pulses of the Central Atlantic Magmatic Province (CAMP) lava were identified. These pulses covered a time span of approximately 40,000 years. Each lava pulse exhibited magnetic particle alignment in a single direction, suggesting that these eruptions happened within a window of around a hundred years. This is far too short a period of time for significant magnetic pole drift to occur.

The research team concluded that these eruptions released huge amounts of sulphates into the atmosphere. These particles blocked sunlight and led to global temperatures plummeting. Carbon dioxide can remain in the atmosphere for centuries. However, volcanic sulphate aerosols are dissipated within a few years. Consequently, while these volcanic winters were extreme, their duration was relatively short.

The researchers likened the CAMP episodes to the sulphate emissions from the 1783 eruption of Iceland’s Laki volcano, which triggered one of the coldest years on record and caused widespread crop failures. However, it is emphasised that the CAMP eruptions were hundreds of times more powerful.

Everything Dinosaur acknowledges the assistance of a media release from The Earth Institute/Columbia Climate School (Columbia University) in the compilation of this article.

The scientific paper: “Correlation of sub-centennial-scale pulses of initial Central Atlantic Magmatic Province lavas and the end-Triassic extinctions” by Dennis V. Kent, Paul E. Olsen, Huapei Wang and Mohammed Et-Touhami published in the Proceedings of the National Academy of Sciences.