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Articles, features and information which have slightly more scientific content with an emphasis on palaeontology, such as updates on academic papers, published papers etc.

13 10, 2021

Beipiaosaurus Revisited

By | October 13th, 2021|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Fans of the now retired Carnegie Collection series of prehistoric animal models, might remember a model of the therizinosaur Beipiaosaurus (B. inexpectus). The model, introduced in 2006 and withdrawn in 2014, might have given dinosaur fans the wrong impression when it comes to this Chinese theropod. Not that the replica made by Safari Ltd was highly inaccurate, but when the model was produced, only the skull of Beipiaosaurus had actually been studied in detail. Now, some twenty-two years after this small therizinosaur was named, scientists including Xing Xu who was one of the authors of the paper describing the skull, have revisited the fossil material and completed their analysis by focusing on the postcranial fossils.

Beipiaosaurus dinosaur model.
The Carnegie collection Beipiaosaurus dinosaur model which was retired in 2014. This model was produced at a time when only the skull of this dinosaur had been studied in detail.

Beipiaosaurus inexpectus

Named and described in 1999, from fossils found by a local farmer three years earlier, Beipiaosaurus heralds from the Lower Cretaceous Yixian Formation (Sihetun locality, near Beipiao), Liaoning Province, China. Described as a basal therizinosaur, it is thought to represent a key taxon in helping scientists to understand the evolution of the Therizinosauridae. Scientists writing in the on-line, open access journal PLOS One, provide an extensive description of the postcranial fossil material associated with the holotype specimen (IVPP V 11559). After Beipiaosaurus had been named, more bones associated with the holotype were found at the original fossil site and these fossils have helped palaeontologists to identity further unique, anatomical characteristics.

Photographs of pelvic girdle elements of Beipiaosaurus.
Photographs of pelvic girdle elements of B. inexpectus (IVPP V 11559). Picture credit: Liao et al.

Additional Autapomorphies

Analysis of the hip socket (acetabulum) length provided a new autapomorphy helping to distinguish Beipiaosaurus from other therizinosaurs.

The shape of the ilium, specifically the pubic peduncle (marked as I.P.P in picture C, above), provides a second unique characteristic for this genus identified in this study.

The manual ungual (finger claw bone) in digit III is the longest one in B. inexpectus. In other therizinosaurs, it is the manual ungual of digit II that is the longest. This is the third additional autapomorphy identified in this research paper.

Photographs of right forelimb elements of B. inexpectus.
Photographs of right forelimb elements of B. inexpectus (IVPP V 11559). The long ungual associated with digit III is unique to this taxon amongst known therizinosaurs. Picture credit: Liao et al.

The authors of the scientific paper, provide a detailed description of the skeleton of Beipiaosaurus, including fossil bone associated with the holotype that have not been reported upon before. Their study has revised the diagnostic features associated with this dinosaur. For example, the researchers examined two dorsal vertebrae that had previously not been studied.

Photographs of B. inexpectus.
Photographs of the dorsal vertebrae of B. inexpectus (IVPP V 11559). This study examined in detail two dorsal vertebrae that had not been studied previously. Picture credit: Liao et al.

The new study into this feathered dinosaur that was named and described more than twenty years ago has helped palaeontologists to better understand the postcranial skeleton of Beipiaosaurus, helps distinguish it from other therizinosaurians and provides insights into therizinosaur evolution.

Furthermore, the researchers, who include Shiying Wang and Chun-Chi Liao (Chinese Academy of Sciences) and Lindsay Zanno (North Carolina Museum of Natural Sciences) as well as Xing Xu, identified several new synapomorphies helping to clarify the evolutionary history of the Therizinosauridae family. A synapomorphy is a characteristic present in an ancestral species and shared exclusively (in a more or less modified form) by its evolutionary descendants.

The scientific paper: “Postcranial osteology of Beipiaosaurus inexpectus (Theropoda: Therizinosauria” by Chun-Chi Liao, Lindsay E. Zanno, Shiying Wang and Xing Xu published in PLOS One.

9 10, 2021

Over a Hundred Theropod Tracks Studied

By | October 9th, 2021|Adobe CS5, Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

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 theropods life reconstruction.
A life reconstruction depicting the lakeside palaeoenvironment with a variety of different theropods visiting the location. Picture credit: Yu Chen.

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).

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.

Yunnan theropod track site.
An overview of the track site with (A) an aerial photograph showing the track-bearing outcrop and (B) a line drawing showing the distribution of the theropod tracks. Morphotype A is highlighted in blue, morphotype B is highlighted in green and the single track of morphotype C is shown in red. Note scale bar equals 1 metre. Picture credit: Li et al.

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.

Yunnan track site theropod footprints.
Photographs showing examples of the three different footprint morphotypes associated with the Yunnan track site. Not scale bar equals 10 cm. Picture credit: Li et al.

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.
Line drawings comparing theropod footprints.
Line drawings comparing theropod tracks from the site with those from the Jurassic of China. XIY-053 is morphotype A (A), whilst (B) is XIY-108 morphotype B and (C) is morphotype C. Grallator yemiaoxiensis is shown (D), Kayentapus xiaohebaensis is (E) and (F) is Kayentapus hopii. Note scale bar = 10 cm. Picture credit: Li et al.

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.

7 10, 2021

Pendraig milnerae – “Chief Dragon”

By | October 7th, 2021|Adobe CS5, Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

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).

Pendraig milnerae life reconstruction.
A life reconstruction of Pendraig milnerae among the fissures of Pant-y-ffynnon with three individuals of the rhynchocephalian lepidosaur Clevosaurus cambrica for company (Late Triassic). Picture credit: James Robbins.

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.

Pendraig milnerae pelvis and vertebrae.
Holotype fossil of Pendraig milnerae (NHMUK PV R 37591) the articulated pelvis and vertebrae (a) left lateral view and (b) right lateral view. Picture credit: Spiekman et al.

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.

Dracoraptor hanigani.
An illustration of the coelophysoid theropod dinosaur from Wales Dracoraptor hanigani. Picture credit: Bob Nicholls.

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.

Views of the left femur of Pendraig.
Various views of the holotype femur of Pendraig milnerae from the Late Triassic of Wales. Picture credit: Spiekman et al.

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.

5 10, 2021

New Species of Horned Dinosaur from New Mexico

By | October 5th, 2021|Adobe CS5, Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

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.

Sierraceratops turneri life reconstruction
A life reconstruction of the newly described chasmosaurine Sierraceratops turneri. If you look carefully, just above the tail you can see a tyrannosaur approaching in the background. Picture credit: Sergey Krasovskiy.

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.

Ceratopsian distribution in Laramidia.
The discovery of Sierraceratops supports the theory that there were distinct dinosaur communities in Laramidia during the Late Cretaceous. Sierraceratops fossil location is marked by the white star and the red horned dinosaur image. It is shown in context with other ceratopsid fossil discoveries. Picture credit; University of Bath with additional annotation by Everything Dinosaur.

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.

Sierraceratops compared in size to other dinosaurs from New Mexico
Size comparison of typical dinosaur fauna associated with southern Laramidia. Note scale bar = 1 metre. Picture credit: Dalman et al.

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.

1 10, 2021

New Giant Penguin from New Zealand

By | October 1st, 2021|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Fossils discovered on a beach by a group of school children on a field trip have been identified as a new species of giant, prehistoric penguin. The 1.4-metre-tall bird has been named Kairuku waewaeroa and it hunted fish in the waters off New Zealand’s North Island some 30 million years ago.

The ancestors of today’s penguins ( Sphenisciformes), probably lived alongside those other famous archosaurs – the Dinosauria Penguins Probably Lived Alongside Dinosaurs. Fossils of penguins are known from the Palaeocene and over the last few years, palaeontologists have been able to build up arguably, the most complete and continuous fossil record of any type of bird. The new giant penguin K. waewaeroa comes from the Glen Massey Formation and the fossils found by the school children on a Hamilton Junior Naturalist Club (JUNATS) field trip to Kawhia Harbour, North Island in 2006, represents one of the most complete prehistoric penguin specimens found to date.

Giant penguin from New Zealand Kairuku waewaeroa
The Kawhia giant penguin Kairuku waewaeroa from the Oligocene of North Island (New Zealand). Picture credit: Simone Giovanardi.

CT Scans Used to Create Three-dimensional Models

The partially articulated fossil material consisting of limb bones, cervical vertebrae and the pelvis preserved in a single block was presented to Waikato Museum Te Whare Taonga o Waikato, Hamilton, New Zealand in 2017. The research team studying the fossil bones, who included Simone Giovanardi and Daniel Thomas (Massey University, Auckland) and Daniel Ksepka (Connecticut, USA), used CT scans to create three-dimensional computer models. These computer models could then be used to make a 3D-printed replica which was presented to the Hamilton Junior Naturalists.

Kairuku waewaeroa line drawing, holotype fossil and scale comparison with an Emperor penguin.
The holotype specimen of Kairuku waewaeroa (WM 2006/1/1). Line drawing of specimen (A), photograph of the holotype in ventral view (B) and (C) scale comparison with the largest extant penguin species the Emperor Penguin (Aptenodytes forsteri), known bones shown in white. Note scale bar for (B) equals 4 cm. Picture credit: Giovanardi et al.

Giant Penguin with Long Legs

Co-author of the scientific paper, published in the Journal of Vertebrate Paleontology, Dr Daniel Thomas (School of Natural and Computational Sciences at Massey University), stated the fossil dates from between 27.3 and 34.6 million years ago, a time when much of this area of North Island was underwater.

The Senior Lecturer in Zoology added:

“The penguin is similar to the Kairuku giant penguins first described from Otago but has much longer legs, which the researchers used to name the penguin waewaeroa – Te reo Māori for “long legs”. These longer legs would have made the penguin much taller than other Kairuku while it was walking on land, perhaps around 1.4 metres tall and may have influenced how fast it could swim or how deep it could dive.”

To read our article on a monster Palaeocene penguin from New Zealand: Monster Palaeocene Penguin from New Zealand.

The scientific paper: “A giant Oligocene fossil penguin from the North Island of New Zealand” by Simone Giovanardi, Daniel T. Ksepka and Daniel B. Thomas published in the Journal of Vertebrate Paleontology.

29 09, 2021

Two New Spinosaurids Described from the Isle of Wight

By | September 29th, 2021|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

Spinosaurids are like buses, you wait for ages for one to come along and then two arrive together. Today, we can announce that two new members of the Baryonychinae have been named and described from fossil remains found on the Isle of Wight. Named Ceratosuchops inferodios and Riparovenator milnerae, their discovery supports the idea of a European origin for the Spinosauridae and suggests that different types of fish-eating dinosaur could happily co-exist in the same palaeoenvironments.

Two new Isle of Wight spinosaurs
Two new species of spinosaurids described from the Isle of Wight Ceratosuchops inferodios (foreground) challenges a Riparovenator milnerae (background) over the carcase of an iguanodont. Pterosaurs flee a forest fire, whilst the dinosaurs squabble. The plant debris beds at Chilton Chine are dominated by charcoal, indicating that this area suffered numerous forest fires. Picture credit: Anthony Hutchings.

Spinosaurs Had Been Expected

Palaeontologists had long suspected that there were more spinosaurid dinosaurs awaiting discovery in the Lower Cretaceous Wealden Supergroup of southern England. The strata were deposited over large flood plains during the late Berriasian and early Aptian stages of the Early Cretaceous and fragmentary fossils, mostly isolated teeth representing spinosaurids have been found. These fossils were usually ascribed to Baryonyx, which was formally named and described in 1986 and provided scientists with the first significant evidence of the body plan and diet of these specialised theropods.

The fossil material was collected by Brian Foster from Yorkshire and Jeremy Lockwood who lives on the Isle of Wight in collaboration with several other local collectors and fossil enthusiasts, from the beach at Chilton Chine from 2013 to 2017, the rapidly eroding cliffs exposed the fossils and it is thanks to this dedicated group of amateur fossil hunters that these important specimens were saved from being washed away by the sea. More than fifty fossil bones were recovered from the site, including a partial tail which was excavated by a field team from the Dinosaur Isle Museum.

The Location of the Spinosaurus fossils on the Isle of Wight
The location of the dinosaur fossil finds. Picture credit: Jeremy Lockwood.

Analysis of Bones Undertaken by the University of Southampton

Analysis of the bones carried out at the University of Southampton and published this week in the journal “Scientific Reports” has led to the establishment of two new species of spinosaurids, which have been named Ceratosuchops inferodios and Riparovenator milnerae. Although related to Baryonyx (B. walkeri), these two new theropods might be more closely related to Suchomimus from Africa.

Scientists estimate that Ceratosuchops and Riparovenator were around 9 metres in length and their crocodilian-like skulls were about a metre long.

Isle of Wight spinosaurids skeletal drawings
Known material referred to the baryonychines Ceratosuchops inferodios (rear) and Riparovenator milnerae (front) recovered at Chilton Chine (Isle of Wight). White bones represent recovered elements. Note scale bar = 1 metre. Picture credit: Barker et al.

Phylogenetic and Bayesian statistical analysis suggests that Ceratosuchops and Riparovenator are sister taxa and more closely related to Suchomimus than they are to Baryonyx but work on the taxonomy of the Spinosauridae is hampered by a lack of fossil material permitting direct comparison between genera. Most palaeontologists split the Spinosauridae into two separate clades, the Spinosaurinae which includes taxa such as Spinosaurus, Ichthyovenator and Irritator and the Baryonychinae. Ceratosuchops inferodios and Riparovenator milnerae have been classified as baryonychids along with Baryonyx, Suchomimus and an as yet unnamed taxon from Portugal (ML 1190).

University of Southampton PhD student, Chris Barker, the lead author of the study commented:

“We found the skulls to differ not only from Baryonyx, but also one another, suggesting the UK housed a greater diversity of spinosaurids than previously thought.”

Ceratosuchops skull fossils and illustrative drawing
Ceratosuchops skull fossils and illustrative drawing with location of Chilton Chine on the Isle of Wight highlighted. Picture credit: Chris Barker and Dan Folkes.

Ceratosuchops inferodios

The first specimen has been named Ceratosuchops inferodios, which translates from the Latin as the “horned crocodile-faced hell heron”. With a series of low horns and bumps ornamenting the brow region the name also refers to the predator’s likely hunting style, which would be similar to that of a (terrifying) heron. Herons famously catch aquatic prey around the margins of waterways but their diet is far more flexible than is generally appreciated and can include terrestrial prey too.

Ceratosuchops premaxillae (lateral view)
Ceratosuchops premaxillae. Picture credit: Chris Barker.

Riparovenator milnerae

The second new species to be named Riparovenator milnerae, translates from the Latin as “Milner’s riverbank hunter”, the species name honours the highly influential British palaeontologist Angela Milner who sadly, passed away in August. Angela, along with her colleague Alan Charig, studied and named Baryonyx (B. walkeri) and her work at the London Natural History Museum has done much to improve our understanding of theropod dinosaurs. It seems a fitting tribute to Dr Milner, for someone who was so involved in helping us to understand Baryonychids that a member of the Baryonychinae should be named in her honour.

Riparovenator braincase and premaxilla
The braincase and the premaxilla of Riparovenator with skull drawing showing placement of the fossil bones. Picture credit: Chris Barker and Dan Folkes.

Many Large Predators in the Ecosystem

When looking at modern food webs, the number of large predators is normally limited by the available range of prey items and other resources such as space for territories and suitable breeding sites. Whilst there are many predators on the African plains, the apex predatory position tends to be occupied by just one species – Panthera leo (lion). In the forests of India, it is another big cat that occupies the apex predator position Panthera tigris (tigers). In several dinosaur dominated ecosystems another picture emerges, where at least two, equally sized and contemporaneous large theropods seem to occupy the apex predator role. Major dinosaur-fossil-bearing geological formations have revealed that several different types of large, carnivorous dinosaur co-existed.

Examples of Multiple Types of Theropod Dinosaur Predator from a Single Geological Formation

  • Dinosaur Park Formation (Canada – Upper Cretaceous) – Daspletosaurus and Gorgosaurus.
  • Morrison Formation (Western United States – Upper Jurassic) – Torvosaurus, Allosaurus, Saurophaganax, Ceratosaurus, Marshosaurus etc.
  • Lourinhã Formation (Portugal – Upper Jurassic) – Lourinhanosaurus, Torvosaurus, Allosaurus, Ceratosaurus, plus possible megalosauroids and abelisaurids.
  • Huincul Formation (Argentina – early Upper Cretaceous) – Mapusaurus, Gualicho, Skorpiovenator etc.
  • Shaximiao Formation (China – Middle to Upper Jurassic) – Sinraptor, Yangchuanosaurus, Gasosaurus, along with megalosauroids and other metriacanthosaurids.

Commenting on this phenomenon co-author of the scientific paper Dr David Hone (Queen Mary University) stated:

“It might sound odd to have two similar and closely related carnivores in an ecosystem, but this is actually very common for both dinosaurs and numerous living ecosystems.”

The presence of two or more spinosaurid taxa in the same geological unit (Wessex Formation) is therefore not without precedent and may in fact be typical. Furthermore, the Wessex Formation has revealed several other completely unrelated theropods that shared the environment with the spinosaurids, Eotyrannus (tyrannosauroid), the allosauroid Neovenator and at least one other, as yet unnamed large tetanuran.

Early spinosaurids may have been more generalist hunters, eating a varied diet, including fish and terrestrial prey. Only later did more specialised taxa adapted to underwater pursuit predation evolve, such as Spinosaurus. However, the degree of specialisation to an aquatic life in spinosaurids remains hotly debated and the evolutionary sequence by which aquatic adaptations came about remains unknown.

Swimming Spinosaurus 2020
A pair of spinosaurids (Spinosaurus aegyptiacus) hunting the giant, prehistoric sawfish Onchopristis. Spinosaurus aegyptiacus is one of the geologically youngest known spinosaurid. It may be untypical of the Spinosauridae, it having evolved to fill a specialised underwater pursuit predatory niche. Picture credit: Davide Bonadonna/National Geographic.

A European Origin for the Spinosauridae?

The discovery of these two new members of the Spinosauridae family and the subsequent analysis conducted by the research team supports the theory of a European origin for this family of theropods. They postulate that spinosaurs first evolved in Europe and dispersed into Asia and Western Gondwana (northern Africa and Brazil) during the first half of the Early Cretaceous. The range over which these types of dinosaurs roamed then begins to contract, by the Cenomanian faunal stage, spinosaurids are only present in north Africa.

Evolution of the Spinosauridae
A chart showing the temporal and geographic distribution of the Spinosauridae. Picture credit: Barker et al.

New fossil discoveries might change our understanding of the origins and eventual extinction of these enigmatic carnivorous dinosaurs, but based on the current fossil record, rising sea levels during the Cenomanian may have reduced the number of suitable habitats available. This may have contributed to the extinction of the Spinosauridae.

Everything Dinosaur acknowledges the assistance of a press release from the University of Southampton in the compilation of this article.

The scientific paper: “New spinosaurids from the Wessex Formation (Early Cretaceous, UK) and the European origins of Spinosauridae” by Chris T. Barker, David W. E. Hone, Darren Naish, Andrea Cau, Jeremy A. F. Lockwood, Brian Foster, Claire E. Clarkin, Philipp Schneider and Neil J. Gostling published in Scientific Reports.

27 09, 2021

Volcanoes Helped to Power the Rise of the Dinosaurs

By | September 27th, 2021|Adobe CS5, Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

The rise of the Dinosauria 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 rise of the dinosaurs was powered by intense volcanic activity.
Ecological changes following intense volcanic activity during the Carnian Pluvial Episode 230 million years ago paved the way for dinosaurs to become the dominant terrestrial fauna. Picture credit: University of Birmingham.

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.”

Pollen spores and algae from the Carnian Pluvial Episode (China)
Example pollen, spores and algae from the Carnian Pluvial Episode in China that record climate and environmental change following massive volcanism. Individual specimens range from 20 to 120 μm in size. Picture credit: University of Birmingham.

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).

24 09, 2021

The Earliest Ankylosaur and Africa’s First

By | September 24th, 2021|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Scientists including researchers from the Natural History Museum in London, have published a scientific paper announcing the discovery of the first fossils assigned to the Ankylosauria from Africa. This is the first ankylosaur to have been named from fossil material found in Africa and also the oldest known member of this group of armoured dinosaurs described to date. The dinosaur has been named Spicomellus afer. The scientific name translates from the Latin as “spiked collar from Africa”.

The holotype fossil of Spicomellus afer
The holotype fossil (NHMUK PV R37412). The protective, bony spikes are actually fused to the rib, this anatomical feature has not been seen in a vertebrate before. Picture credit: London Natural History Museum.

Acquired from a Fossil Dealer

The fossil was acquired from a UK-based commercial fossil dealer by the London Natural History Museum in 2019. At first the strange fossil, a rib bone with four bony spikes directly attached to it, was thought to be a forgery, but CT analysis proved the fossil to be genuine. It comes from the third subunit of the El Mers Group from the Atlas Mountains of Morocco. The fossil is estimated to be between 168 and 163 million years old (Bathonian to Callovian stages of the Middle Jurassic).

In recent times, Morocco has provided some tantalising glimpses into the potential wealth of armoured dinosaurs that await discovery. The Ankylosauria and Stegosauria form a clade within the bird-hipped dinosaurs (Ornithischia), the Eurypoda, which has been defined to include famous armoured dinosaurs Ankylosaurus, Stegosaurus and their most recent, common ancestor and all its descendants. Eurypoda fossils are mostly confined to Laurasia, fossils from the continents that made up Gondwana (essentially Africa, South America, Antarctica, India, Madagascar and Australia), are rare.

In 2019, Everything Dinosaur reported upon the discovery of the oldest stegosaur known from northern Africa, the dinosaur named Adratiklit boulahfa is also the oldest stegosaur described to date and it was roughly contemporaneous with Spicomellus.

To read our blog post on Adratiklit boulahfa: North Africa’s First Stegosaur.

The research team behind the paper on Adratiklit boulahfa were also responsible for much of the work behind the analysis of the rib bone fossil (specimen number NHMUK PV R37412), that led to the naming and scientific description of Spicomellus.

Identifying a Fossil as an Ankylosaur Fossil

Once the fossil had been established as genuine, the research team including Dr Susannah Maidment (London Natural History Museum), who specialises in studying ornithischian dinosaurs, were able to confirm that the specimen represented a rib bone from a stegosaur or an ankylosaur. Rib bones in most armoured dinosaurs tend to show a distinctive “t-shape” in cross section. Histological analysis of the composition of the bone matrix of the spikes demonstrated that their structure was reminiscent of an ankylosaur and therefore the scientists were able to confidently assign this specimen to the Ankylosauria.

"T-shaped" Rib of Spicomellus
The rib bone in cross-section shows a “t-shape” which is distinctive to the Stegosauria and the Ankylosauria. Histological study of the bone structure in the spikes identified that this bone was typical of an ankylosaur, allowing the research team to confidently assign the fossil to an ankylosaur. Picture credit: London Natural History Museum.

As for what Spicomellus might have looked like, any life reconstructions will have to be highly speculative, although based on comparisons with the ribs of more complete ankylosaur specimens the research team estimate that this individual Spicomellus was around three metres in length.

No Fossil Like This Ever Found Before

The rib with spiked, dermal armour fused to its top surface is unique. Nothing like this has ever been found before. This anatomical trait is not found in living or extinct vertebrates. Ankylosaurs tend to have their armour embedded into their skin and not directly attached to their bones. Spicomellus would have been less mobile and flexible as a result of its unique anatomy. Palaeontologists hope to return to northern Morocco and find more fossils to help them build up a better picture of this bizarre, armoured dinosaur.

Described as a basal ankylosaur, Spicomellus may represent an evolutionary experiment as armoured dinosaurs evolved probably as a result of predation pressure (megalosaurids are also known from the El Mers Group). How long these armour-attached-to-bone ankylosaurs persisted and how successful this group was remains unknown.

Implications for Armoured Dinosaur Evolution and Stegosaur Extinction

The discovery of Spicomellus suggests that we have a lot more to learn about the Eurypoda and that there probably are many more important but unknown fossil specimens of armoured dinosaurs awaiting discovery in the continents that made up Gondwana.

Spicomellus helps to fill a gap in the evolution of the Ankylosauria (Nodosauridae and Ankylosauridae). In addition, its discovery challenges current thinking about the demise of the Stegosauria. Stegosaur fossils are more common in Jurassic rocks than ankylosaur fossils are. In Cretaceous sediments, stegosaur specimens become increasingly rare. It had been thought that the rise of the Ankylosauria played a role in the eventual demise and extinction of the Stegosauria. However, with the discovery of Spicomellus, palaeontologists now know that stegosaurs and ankylosaurs co-existed for around 20 million years. The extinction of the Stegosauria remains a mystery, Spicomellus suggests that the evolution of different types of armoured dinosaur may only have played a limited role in their extinction.

The basal ankylosaur Spicomellus changes views on the evolutionary history of the Ankylosauria
The discovery of Spicomellus afer changes dramatically the temporal phylogeny of the Ankylosauria. Picture credit: Zheng et al with additional annotation by Everything Dinosaur.

The scientific paper: “Bizarre dermal armour suggests the first African ankylosaur” by Susannah C. R. Maidment, Sarah J. Strachan, Driss Ouarhache, Torsten M. Scheyer, Emily E. Brown, Vincent Fernandez, Zerina Johanson, Thomas J. Raven and Paul M. Barrett published in Nature Ecology and Evolution.

21 09, 2021

The First Record of a Rhamphorhynchid Pterosaur from Gondwana

By | September 21st, 2021|Adobe CS5, Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Fragmentary fossils collected from a location in the Atacama Desert of northern Chile have been assigned to a long-tailed pterosaur, specifically a rhamphorhynchid, this is the first time that evidence for this type of flying reptile has been found in Gondwana and the fossils, which are around 160 million years old, makes this specimen the oldest known pterosaur from Chile.

Rhamphorhynchid from Chile
A life reconstruction of the rhamphorhynchid pterosaur from northern Chile. Several types of marine reptile have also been recorded from these deposits. Picture credit: Universidad de Chile.

The Cerro Campamento Formation

The fossil material, consisting of a left humerus (thigh bone), parts of the wing finger and a possible dorsal vertebra, was collected in 2009 from the fossil-bearing Cerro Campamento Formation near the locality of Cerritos Bayos in northern Chile. The bones were all found in the same block and their relative size has led the researchers to believe that all the bones came from a single individual.

The strata in this area have yielded abundant ammonite remains as well as the fossils of numerous marine reptiles and prehistoric fish. Based on the associated ammonite specimens found at this location, the research team are confident that that the pterosaur remains date from the middle Oxfordian age of the Jurassic.

Rhamphorhynchid left humerus and line drawings
Views of the left humerus (MUHNCAL.20165) identified as a fossil bone from a rhamphorhynchid pterosaur with accompanying line drawings. Picture credit: Universidad de Chile.

Assigning the Fossils to the Rhamphorhynchidae

Although the remains represent a small proportion of the total skeleton their three-dimensional preservation permitted the research team to confidently assign the material to the Rhamphorhynchidae.

The humerus has a hatchet-shaped deltopectoral crest, proximally positioned, and its shaft is markedly anteriorly curved, which are characteristic features of the Rhamphorhynchidae. Furthermore, the presence of a groove that runs along the caudal surface of the phalanx, being flanked by two asymmetric crests, is a distinctive feature of the clade Rhamphorhynchinae. These traits provide evidence for an affinity to the Rhamphorhynchidae family and as such this reinforces the idea that these types of long-tailed pterosaurs were the first pterosaurs to achieve a relatively global distribution. Writing in the academic journal Acta Palaeontologica Polonica, the researchers who included Jhonatan Alarcón-Muñoz from the Universidad de Chile, assert that the specimen (MUHNCAL.20165), represents the first evidence of this group found to date in Gondwana. They are also the oldest pterosaur fossils to have been described from Chile.

Although it is difficult to estimate the size of the animal, comparisons with the well-known Rhamphorhynchus, most closely associated with the Solnhofen limestone deposits of Bavaria, (southern Germany), indicate that the Chilean pterosaur was large for a rhamphorhynchid. A wingspan in excess of 1.5 to 2 metres has been suggested.

Rhamphorhynchid pterosaur ife reconstruction.
A life reconstruction of a typical rhamphorhynchid pterosaur. The fossil remains from Chile are the first, definitive evidence for this type of pterosaur in Gondwana. Picture credit: Universidad de Chile.

The Caribbean Corridor

Rhamphorhynchid fossils are relatively rare from the Middle Jurassic, but they have been widely reported from Upper Jurassic strata associated with Laurasia. The Chile specimen was found in marine sediments that were deposited at the bottom of a shallow sea, most other rhamphorhynchid fossils are also found in rocks that represent shallow sea, near coastal environments. Some Rhamphorhynchus fossils (R. muensteri) from Solnhofen preserve fish remains as stomach contents and this supports the idea that these pterosaurs were piscivores and lived in coastal habitats.

During the Oxfordian, internal seaways such as the Caribbean corridor and the Trans-Erythrean corridor provided similar coastal environments running down and between Laurasia in the north and Gondwana in the south. The researchers propose that the Caribbean corridor acted as a dispersal route permitting the spread of flying reptiles such as rhamphorhynchids. They postulate that this corridor helps to explain the faunal similarities amongst marine vertebrates found in Germany, the UK, Cuba and South America during the Oxfordian faunal stage.

Rhamphorhynchid dispersal during the Late Jurassic.
The shape of the world’s landmasses during the Oxfordian of the Jurassic. The dashed line represents the hypothetical route that would have allowed the dispersal of marine vertebrates and invertebrates between Tethys and South America during the Late Jurassic. Picture credit: Universidad de Chile.

Map Key

The circle represents the Chile rhamphorhynchid, whilst the square indicates the location of two rhamphorhynchids from Cuba (Cacibupteryx caribensis and Nesodactylus hesperius), the star shape highlights these types of pterosaur discoveries associated with southern England whilst the triangle shows the location of Qinglongopterus guoi from the Tiaojishan Formation of China.

It is likely that more pterosaur fossils will be found in northern Chile. The prospect of further fossil discoveries will hopefully permit palaeontologists to erect a new genus to describe this South American rhamphorhynchid material.

The scientific paper: “First record of a Late Jurassic rhamphorhynchine pterosaur from Gondwana” by J. Alarcón-Muñoz, R. A. Otero, S. Soto-Acuña, A. O. Vargas, J. Rojas and O. Rojas published in Acta Palaeontologica Polonica.

20 09, 2021

Plotting the Fauna of Late Cretaceous Patagonia

By | September 20th, 2021|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Geology, Main Page, Palaeontological articles, Photos/Pictures of Fossils, Uncategorized|0 Comments

Scientists now know that during the Late Cretaceous (Campanian to Maastrichtian), southern Patagonia was home to ankylosaurs and that predatory abelisaurids competed with terrestrial crocodyliforms when it came to scavenging the carcases of giant Titanosaurs.

Researcher have examined fossilised teeth and osteoderms (bony plates and scales embedded in skin) collected from a small area of Upper Cretaceous deposits from the Cerro Fortaleza Formation in Santa Cruz province and used these fossils to piece together an archosaur dominated palaeocommunity.

Cerra Fortaleza Formation dinosaurs and peirosaurids.
The peirosaurid and dinosaur dominated ecosystem as indicated by fossils from the Cerro Fortaleza Formation (Late Cretaceous of Patagonia). Picture credit: J. González.

Teeth from Abelisaurids, Titanosaurs and Ankylosaurs

The dinosaur fauna of the Cerro Fortaleza Formation is very poorly known with only a few dinosaurs named and described, such as the giant titanosaur Dreadnoughtus schrani. However, researchers who included scientists affiliated to CONICET as well as a researcher from Seoul National University (South Korea), have published a paper in the on-line, open access journal PLOS One reporting on the discovery of several very worn and broken teeth that along with fossil osteoderms have enabled the research team to reconstruct the fauna that once roamed this ancient landscape.

Location map showing the provenance of the teeth and osteoderms (Cerro Fortaleza Formation).
Location map (A) showing the provenance of the teeth and osteoderms (Cerro Fortaleza Formation). Region between Viedma and Argentino lakes showing the Cerro Fortaleza Formation (red colour) outcropping at both sides of La Leona river. The dinosaur-fossil-bearing Chorrillo Formation is indicated in green (B). Photograph of the dig site (C) the red arrow marks the level from where the osteoderms and teeth were collected. Picture credit: Paulina-Carabajal.

To read Everything Dinosaur’s blog post about the discovery of the huge titanosaur Dreadnoughtus: A Little Detail on a Big Dinosaur – Dreadnoughtus.

The Cerro Fortaleza and Chorrillo Formations

Lying some 100 miles (160 kilometres) to the south of the Cerro Fortaleza Formation exposures that yielded the teeth and osteoderm fossils, the Chorrillo Formation is also regarded as an important source of dinosaur fossils. Palaeontologists are not sure of the temporal relationship between these dinosaur-fossil-bearing units, although it has been postulated that the Chorrillo Formation is slightly older. Both units have provided evidence of titanosaurs, theropods and ornithopods, but up to now only the Chorrillo Formation had provided evidence of ankylosaurs. Whilst working at the Cerro Fortaleza locality in December 2016, field team members discovered several isolated osteoderms and a single, very worn tooth thus confirming the presence of armoured dinosaurs in the Cerro Fortaleza Formation too.

Whilst it is difficult to identify a specific type of ankylosaur from just skin scales and a single tooth, the researchers postulate that these fossils represent a nodosaurid.

Ankylosaur osteoderms from the Cerro Fortaleza Formation
Views of various ankylosaur osteoderms collected from the Cerro Fortaleza Formation. These bony scales along with an ankylosaur tooth confirm the presence of armoured dinosaurs in this locality. Note scale bars equal 1 mm. Picture credit: Paulina-Carabajal et al.

The Dinosaurs of the Cerro Fortaleza Formation

The researchers were able to confirm the presence of a large abelisaurid theropod and an ankylosaur based on the fossil teeth. Very worn and broken titanosaur spp. teeth were also recorded. The types of dinosaurs that lived in the area represented by the Cerro Fortaleza Formation were similar to those reported from the Chorrillo Formation, although the two populations were very probably made up of different genera.

Intriguingly, evidence of hadrosaurs has been reported from the Chorrillo Formation, as yet no fossils that could be assigned to the Hadrosauridae have been reported from the Cerro Fortaleza Formation.

Dinosaur teeth from the Cerro Fortaleza Formation (Argentina)
Dinosaur teeth from the Cerro Fortaleza Formation. Partial tooth assigned to an abelisaurid theropod (A-C). Partial tooth of an unidentified archosaur (D). Titanosauria partial tooth (E-F) and tooth assigned to an Ankylosaur (G-I). Note scale bars equal 1 mm (except A-B equals 5 mm). Picture credit: Paulina-Carabajal et al.

Crocodyliforms Competing with Carnivorous Dinosaurs

In addition to the dinosaur fossils, the researchers found a total of 9 broken teeth which they assigned to the Peirosauridae family. Peirosaurids are an extinct group of terrestrial crocodyliforms, not closely related to modern crocodilians and seemingly confined to Gondwana. Their upright gait and different shaped teeth (heterodont teeth) indicate that these archosaurs may have had a more varied diet than the carnivorous dinosaurs. Most of the fossils found represent peirosaurid teeth (75%) and this suggests that there were more crocodyliforms present in the area than dinosaurs. The peirosaurid teeth represent the most southerly distribution of this type of archosaur recorded to date and since the teeth do not match those of Colhuehuapisuchus lunai which is known from Chubut Province to the north, this suggests at least two taxa of peirosaurids present in southern Patagonia during the Late Cretaceous.

Peirosaurid teeth from the Cerro Fortaleza Formation.
Examples of peirosaurid teeth from the Cerro Fortaleza Formation. Small fossils such as teeth and dermal armour have enabled palaeontologists to piece together the faunal composition of southern Argentina during the Late Cretaceous. Theropod dinosaurs (abelisaurids) would have competed with peirosaurid mesoeucrocodylians over food, but little can be deduced about food chain roles with regards to apex and secondary predators. Picture credit: Paulina-Carabajal et al.

The ankylosaur fossils from Cerro Fortaleza and Chorrillo formations, indicate that armoured dinosaurs lived in the region of southern South America during the Late Cretaceous. These fossils although fragmentary help to fill a gap in the fossil record between Antarctica and central-northern Patagonia. Thanks to this research the Late Cretaceous dinosaur record in southern South America has been improved.

The scientific paper: “A Late Cretaceous dinosaur and crocodyliform faunal association–based on isolate teeth and osteoderms–at Cerro Fortaleza Formation (Campanian-Maastrichtian) type locality, Santa Cruz, Argentina” by Ariana Paulina-Carabajal, Francisco T. Barrios, Ariel H. Méndez, Ignacio A. Cerda and Yuong-Nam Lee published in PLOS One.

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