Scientists writing in the on-line, open access, academic journal “PeerJ” have reported upon the discovery of over 100 dinosaur fossil footprints. The footprints represent theropod dinosaurs and they vary in size indicating that a variety of meat-eating dinosaurs co-existed in the late Early Jurassic of Yunnan Province, China.

Yunnan Province Dinosaurs

Yunnan Province in south-western China is famous for its dinosaur fossils, the majority of which are body fossils, but there have been several published papers detailing track sites and more trace fossils from this province are due to be reported upon. The theropod assemblage track site is located close to the village of Xiyang, Jinning County in central Yunnan. The strata in which the tracks are located come from the Lower Jurassic Fengjiahe Formation and represent a lakeside environment (lacustrine). The reddish mudstone deposits that contain the tracks also preserve mud cracks that suggest the area was subject to droughts. The palaeoenvironment is believed to have been humid and warm (sub-tropical to tropical).

Theropod Tracks

The tracks have been known about for twenty years, but only recently has the site been extensively studied. Unfortunately, several prints had been lost to erosion prior to detailed analysis.

Solitary Coelophysoid and Tetanuran Theropods

The Xiyang track site preserves 120 exposed footprints made by solitary theropod dinosaurs as they visited the lakeside. It is the largest theropod track site in terms of the total number of prints found, described to date from Yunnan. The prints have been assigned to three broad groups based on their size, they indicate that a variety of theropods were present in the ancient ecosystem including coelophysoid as well as larger tetanuran theropods.

The largest print from the site (XIY-48) measures 39 cm long and 40 cm wide. Large claw marks are associated with each digit of this print. Fossils of the six-metre-long theropod Sinosaurus triassicus (formerly Dilophosaurus sinensis), are known from this area. Sinosaurus fossils from Lower Jurassic Fengjiahe Formation have been found around 500 metres away from the track site, it has been speculated that the largest print could represent a track made by a Sinosaurus, although as it is a footprint, it has been assigned to the ichnogenus Kayentapus.

Classifying the Footprints

Although the size of any tracks left can be influenced by many factors, the research team conclude that at least three different kinds of theropods were visiting the site frequently. The three groups of prints that the tracks have been classified into are:

1. Morphotype A (>8 cm to <21 cm) resembling the ichnogenus Grallator.
2. Morphotype B (>27 cm to<30 cm) identified as the ichnospecies Kayentapus xiaohebaensis.
3. Morphotype C (39 cm) an isolated print referred to the ichnogenus Kayentapus.

Large Predator Dinosaurs Rare in the Early Jurassic

In Yunnan, the majority of dinosaur fossils from Lower Jurassic rocks represent sauropodomorphs. Whilst the tracks of sauropodomorphs can be mistakenly identified as theropod prints, the researchers who include Hongqing Li of Yunnan University and Claire Peyre de Fabrègues (Department of Biology, Indiana University of Pennsylvania, USA), as well as colleagues from Yuxi Museum (Yunnan Province) and the Chinese Academy of Sciences are confident that this site provides a useful record of the diversity of meat-eating dinosaurs present in this region during the late Early Jurassic

Large terrestrial predators (animals in excess of five metres in length), are rare in Early Jurassic ecosystems. Large tracks are scarce at this site, but not absent. Carnivorous dinosaurs of all sizes presumably co-existed in this palaeoenvironment and were regular visitors to the lakeside in search of food or potential prey.

The scientific paper: “The largest theropod track site in Yunnan, China: a footprint assemblage from the Lower Jurassic Fengjiahe Formation” by Hongqing Li, Claire Peyre de Fabrègues, Shundong Bi, Yi Wang and Xing Xu published in PeerJ.

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Scientists have described the oldest theropod dinosaur from the UK. The dinosaur has been named Pendraig milnerae, the scientific name honours the dinosaur’s Welsh roots and recognises the contribution of Dr Angela Milner, who sadly passed away last August.

Everything Dinosaur recently blogged about the naming of two spinosaurids described from fragmentary fossils found on the Isle of Wight. The trivial name of one of these theropods, Riparovenator milnerae, also honours Dr Milner.

To read Everything Dinosaur’s recent blog post about the two newly described spinosaurids: Two New Spinosaurids from the Isle of Wight.

Ironically, the remains of Pendraig were already ancient fossils when the Isle of Wight spinosaurids roamed. The Pendraig fossils come from limestone fissure fills of the Pant-y-ffynnon Quarry in the Vale of Glamorgan (Wales). This infilled material, deposited in Carboniferous limestone is difficult to date, but it is thought that these fossils are between 215 and 201 million years old (late Norian, latest occurrence possibly late Rhaetian).

Misplaced Theropod Fossils

Writing in Royal Society Open Science, the researchers from the London Natural History Museum, the University of Birmingham and National Museums Scotland describe Pendraig milnerae based on an articulated pelvic girdle, sacrum and posterior dorsal vertebrae, and an associated left femur and by two referred specimens, comprising an isolated dorsal vertebra and a partial left ischium.

Co-author of the paper, Dr Susannah Maidment (London Natural History Museum), explained that the fossil material had been stored in a draw that contained crocodylomorphs. It was Dr Milner who was able to find the fossils within the vast Natural History Museum collection and to retrieve an unpublished PhD paper that had referred to them as part of a wider review of archosaurian remains associated with South Wales.

Welsh Dinosaurs

A phylogenetic analysis indicates that was a P. milnerae non-coelophysid coelophysoid and it represents the first-named, unambiguous theropod from the Triassic of the UK. The genus name translates from Middle Welsh as “chief dragon”. During the Late Triassic, the dinosaurs were not the dominant terrestrial animals that they were later to become. Discoveries of Triassic-aged theropods can help palaeontologists to better understand the evolution of these important tetrapods, the dinosaur lineage that led directly to modern birds.

Wales might be associated with dragons, but dinosaur discoveries are extremely rare in this part of the UK. Previously, only two dinosaur genera have been named – Pantydraco (P. cauducus) a basal sauropodomorph from a limestone fissure infill from the Pant-y-ffynnon Quarry and the coelophysoid Dracoraptor (D. hanigani) which was named and described in 2016 from fossils found near the Welsh town of Penarth.

An Insular Dwarf

The palaeoenvironment in which Pendraig lived was most likely an archipelago and species that live on small islands with limited resources can become smaller than their mainland relatives due to a phenomenon known as insular dwarfism.

Measuring around 75 cm to a metre in length P. milnerae was indeed small, a characteristic that it shares with a number of other vertebrates known from the same deposits.

Lead author of the paper, Dr Stephan Spiekman (London Natural History Museum), explained:

“Because the fossil reptiles from this area, including Pendraig, are all quite small-sized, we used statistical analyses to investigate whether Pendraig might have been an insular dwarf. The results indicate that Pendraig is indeed small, even for a theropod of that time period, but not uniquely so”.

Analysis of the fossil bones, indicate that the material does not represent a juvenile or very young animal. However, the fossils do represent an animal that was probably not fully grown when it died.

The researchers conclude that Pendraig may have been a dwarf form but as some other coelophysoid taxa also show a similar size reduction (based on femur bone length comparisons), it is not possible to say with certainty that this little Welsh, Triassic dinosaur was indeed an insular dwarf.

Dr Spiekman added:

“With this in mind, we need more evidence from more species to investigate the potential for island dwarfism in this area during that time, but if we could prove it, it would be the earliest known occurrence of this evolutionary phenomenon”.

The scientific paper: “Pendraig milnerae, a new small-sized coelophysoid theropod from the Late Triassic of Wales” by Stephan N. F. Spiekman, Martín D. Ezcurra, Richard J. Butler, Nicholas C. Fraser and Susannah C. R. Maidment published in Royal Society Open Science.

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A new species of horned dinosaur has been named and described from fossils found in New Mexico. The dinosaur has been named Sierraceratops turneri and it was distantly related to Triceratops.

The new horned dinosaur classified as a member of the Chasmosaurinae, roamed New Mexico approximately 72 million years ago (latest Campanian–Maastrichtian). Sierraceratops adds to the diversity and disparity of the Chasmosaurinae in the Late Cretaceous. This discovery provides supporting evidence for the hypothesis of Laramidian endemism – the idea that species were restricted to specific regions. Together with Sierraceratops, the Hall Lake Formation dinosaur fauna suggests that the latest Cretaceous of southern Laramidia was characterised by endemic clades and distinct dinosaur communities.

From Sierra County, New Mexico

The first fossil material associated with this new horned dinosaur, was discovered in 1997 by Greg H. Mack of New Mexico State University whilst undertaking a geological survey. Most of the fossils were collected from the surface, having already weathered out of the surrounding rock, but a field team from the New Mexico Museum of Natural History was despatched and additional fossils were found. The remainder of the fossil material that led to the naming of Sierraceratops was excavated between 2014-2016 by other field teams sent out to the site by the New Mexico Museum of Natural History.

The fossils include elements from the skull and jaws, along with two neckbones (cervicals), two dorsal vertebrae, the sacrum, scapulocoracoid, the ilium and limb bones. The genus name honours Sierra County where the fossils were found, whilst the species name is a tribute to Mr Ted Turner, the founder of the Cable News Network (CNN) who owned the land where the fossils were collected.

Distinct Dinosaur Regional Communities

Phylogenetic analysis suggests that Sierraceratops is a sister taxon to Bravoceratops and Coahuilaceratops, forming part of a clade endemic to the southwestern United States and Mexico. Sierraceratops adds to the diversity and disparity of the Chasmosaurinae in the Late Cretaceous and provides supporting evidence for the hypothesis of Laramidian endemism. Dinosaur fossils from the Hall Lake Formation suggest that the dinosaur biota of southern Laramida was characterised by distinct dinosaur communities. Similar types of dinosaurs could be found in other areas, but the genera were distinctive.

Recent Discoveries of Horned Dinosaurs from New Mexico

New Mexico has proved to be a happy hunting ground for new ceratopsid discoveries in recent years. For example, some of the authors of the Sierraceratops paper also worked on the publication describing Menefeeceratops (M. sealeyi), from the Menefee Formation. Menefeeceratops roamed New Mexico some 10 million years before Sierraceratops evolved. As Menefeeceratops has been classified as a member of the Centrosaurinae and Sierraceratops is regarded as a chasmosaurine, these two horned dinosaurs were only distantly related.

To read Everything Dinosaur’s article about Menefeeceratops: Menefeeceratops – the Oldest Centrosaurine.

Sierraceratops turneri – Tyrannosaurs and Titanosaurs

Based on a comparison with better-known chasmosaurine fossil specimens, Sierraceratops is estimated to have measured around five metres in length. Its skull would have been around 1.5 metres long. The scientists behind this research, including Dr Nicholas Longrich (senior lecturer in the Department of Biology and Biochemistry at the University of Bath), predict that several more new dinosaurs will be described from Laramidia.

Sierraceratops shared its lush, floodplain and swamp environment with other dinosaurs including giant titanosaurs and predatory tyrannosaurids. It also highly likely that Sierraceratops was contemporaneous with other plant-eating dinosaurs such as hadrosaurids and ankylosaurids. Fossil evidence for both armoured dinosaurs and duck-billed dinosaurs have been found in other Hall Lake Formation sediments but their stratigraphical relationship to the Sierraceratops material remains undetermined.

Everything Dinosaur acknowledges the assistance of a media release from the University of Bath in the compilation of this article.

The scientific paper: “Sierraceratops turneri, a new chasmosaurine ceratopsid from the Hall Lake Formation (Upper Cretaceous) of south-central New Mexico” by Sebastian G. Dalman, Spencer G Lucas, Steven E. Jasinski and Nicholas R. Longrich published in Cretaceous Research.

The Everything Dinosaur website: Dinosaur Models and Toys.

The rise of the dinosaurs which led them to dominate terrestrial ecosystems for more than 150 million years was driven by environmental change caused by intense volcanism over 230 million years ago. That is the conclusion in a new study published today in the ” Proceedings of the National Academy of Sciences” (PNAS).

The Late Triassic Carnian Pluvial Episode (CPE) led to a huge rise in global temperature and humidity. This dramatic change had a significant impact on the development of animal and plant life, which was still recovering from the greatest mass extinction event known in the fossil record which had occurred at the end of the Permian, some 20 million years earlier.

The Evolution of Modern Conifers

The researchers, including experts from the University of Birmingham, discovered four distinct pulses of volcanic activity during this time in the Late Triassic. The most likely source of this volcanism being the Wrangellia Large Igneous Province, remnants of which can still be seen in Alaska, British Columbia and the Yukon (western North America).

Jason Hilton (Professor of Palaeobotany and Palaeoenvironments at the University of Birmingham’s School of Geography, Earth and Environmental Sciences), a co-author of the study, explained:

“Within the space of two million years the world’s animal and plant life underwent major changes including selective extinctions in the marine realm and diversification of plant and animal groups on land. These events coincide with a remarkable interval of intense rainfall known as the Carnian Pluvial Episode.”

One of the major groups of plants to benefit from the dramatic climate change were cone-bearing seed plants (conifers). Ferns also benefitted and show an increase in numbers, range and species. Other archosaurs such as crocodyliforms show an increase in diversity and mammaliaforms, insects and turtles seem to have thrived as a result of this climate change.

Rising Carbon Dioxide Levels Driving Climate Change

Professor Hilton added:

“Our research shows, in a detailed record from a lake in North China, that this period can actually be resolved into four distinct events, each one driven by discrete pulses of powerful volcanic activity associated with enormous releases of carbon dioxide into the atmosphere. These triggered an increase in global temperature and humidity.”

The scientists discovered that each phase of volcanic activity coincided with widescale disruption to the global carbon cycle. The higher levels of carbon dioxide produced led to major climate changes with a hotter, wetter climates predominating. The ancient lake deposits reveal that it became deeper but oxygen levels in the lake reduced and stifled animal life.

Geological events from a similar timeframe in Europe, Argentina, eastern Greenland, Morocco and North America, among other locations indicate that increased rainfall resulted in widespread expansion of drainage basins converging into lakes or swamps, rather than rivers or oceans.

Co-author of the paper, Dr Sarah Greene (Senior Lecturer in the School of Geography, Earth and Environmental Sciences, University of Birmingham) added:

“Our results show that large volcanic eruptions can occur in multiple, discrete pulses demonstrating their powerful ability to alter the global carbon cycle, cause climate and hydrological disruption and drive evolutionary processes.”

The research team investigated terrestrial sediments from the ZJ-1 borehole in the Jiyuan Basin of North China. They used uranium-lead zircon dating, high-resolution chemostratigraphy, palynological and sedimentological data to correlate terrestrial conditions in the region with synchronous large-scale volcanic activity in North America.

Everything Dinosaur acknowledges the assistance of a media release from the University of Birmingham in the compilation of this article.

The scientific paper: “Volcanically-driven lacustrine ecosystem changes during the Carnian Pluvial Episode (Late Triassic)” by Jing Lu, Peixin Zhang, Jacopo Dal Corso, Minfang Yang, Paul B. Wignall, Sarah E. Greene, Longyi Shao, Dan Lyu and Jason Hilton published in Proceedings of the National Academy of Sciences (PNAS).

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