Today, March 18th, we at Everything Dinosaur commemorate the life of the American palaeontologist Othniel Charles Marsh. The eminent professor and president of the prestigious National Academy of Sciences passed away on this day in 1899.
Othniel Charles Marsh
Regarded as one of the great pioneers of American palaeontology he described more than a dozen new genera of dinosaurs, based on fossils excavated from the Western United States. He was responsible for naming and scientifically describing many of the most famous of all the Dinosauria. Brontosaurus, Apatosaurus, Triceratops and Stegosaurus were all named by Marsh.
Theropod Dinosaurs, Prehistoric Birds and Pterosaurs
Marsh also named and described the theropod dinosaur Allosaurus (1878), named and described toothed-birds, early horses and studied the first pterosaur fossils known from the USA.
For all his academic and scientific achievements, perhaps O. C. Marsh is best remembered for his bitter rivalry with his fellow American scientist Edward Drinker Cope. A rivalry that became known as the “Bone Wars”.
New research suggests maniraptoran theropod dinosaurs possessed a propatagium. The propatagium (pronounced pro-pah-ta-gee-um), is a soft tissue structure that joins the wrists and shoulders of volant birds. It helps with the wing flapping motion and provides a leading edge to the wing. Without this structure, birds could not fly.
Propatagia in Maniraptoran Dinosaurs
If members of the Maniraptora, such as Therizinosaurus, Velociraptor, Oviraptor and troodontids had a propatagium on each arm, this would change how these dinosaurs are depicted. Many existing models and replicas would not be accurate and these figures would require updating.
Modern volant birds have a propatagium. A specialised wing structure, without which they would not be able to fly. The evolutionary origins of the propatagium remain uncertain, but new research led by scientists at the University of Tokyo (Japan), is helping to fill some of the gaps. By conducting a statistical analysis of the arm joints associated with the fossilised remains of some dinosaurs, the researchers have concluded that a propatagium was present in certain theropod dinosaurs on the dinosaur/bird evolutionary lineage.
Propatagia are also known in other volant vertebrates – the bats and pterosaurs. These structures are examples of convergent evolution. Anatomical traits arising as animals adapt in similar ways to similar selective pressures.
Birds Evolved from Dinosaurs
Most scientists agree that birds evolved from maniraptoran dinosaurs. It therefore seems appropriate to look for avian traits within the Dinosauria, such as the presence of feathers, strong but light bones, and inner ears that help with balance and spatial awareness.
The University of Tokyo’s Department of Earth and Planetary Science wanted to try to see if evidence for the propatagium could be found in the non-avian dinosaur fossil record. The propatagium contains a muscle which connects the wrist to the shoulder and the research team set about trying to find evidence for this soft tissue structure in the fossilised remains of maniraptoran dinosaurs.
Co-author of the paper, published in the journal “Zoological Letters”, Associate Professor Tatsuya Hirasawa explained:
“It [the propatagium] is not found in other vertebrates, and it’s also found to have disappeared or lost its function in flightless birds, one of the reasons we know it’s essential for flight. So, in order to understand how flight evolved in birds, we must know how the propatagium evolved. This is what prompted us to explore some distant ancestors of modern birds, theropod dinosaurs.”
Studying Theropod Dinosaurs
Theropod dinosaurs such as Giganotosaurus, Tyrannosaurus rex and Velociraptor had arms, not wings, although some theropods such as the dromaeosaurid Microraptor were capable of flight. If the researchers could find evidence of early examples of the propatagium within non-avian dinosaurs, they would gain a better understanding of how some Dinosauria gradually transitioned from having arms to evolving wings.
Unfortunately, a soft tissue structure such as a propatagium would only be preserved in exceptional circumstances. Hard, mineralised parts of the body such as bones have a far greater fossilisation potential. Perhaps the bones of fossilised dinosaurs could provide a clue?
Co-author of the study, Yurika Uno (University of Tokyo) explained:
“The solution we came up with to assess the presence of a propatagium was to collect data about the angles of joints along the arm, or wing, of a dinosaur or bird.”
Studying Joint Angles
The presence or lack of a propatagium could be inferred by examining the angles of the joints in the arm in articulated fossil specimens. The way arm joints are articulated in fossils gives away the presence or absence of the propatagium structure. Thus the researchers could provide indirect evidence demonstrating the evolution of the avian wing structure.
The graduate student added:
“In modern birds, the wings cannot fully extend due to the propatagium, constraining the range of angles possible between connecting sections. If we could find a similarly specific set of angles between joints in dinosaur specimens, we can be fairly sure they too possessed a propatagium. And through quantitative analyses of the fossilised postures of birds and nondinosaurs, we found the tell-tale ranges of joint angles we hoped to.”
A Focus on the Maniraptora
The researchers postulate that the propatagium likely evolved in a group of dinosaurs known as the maniraptoran theropods. The Maniraptora clade is composed of coelurosaurian dinosaurs and is defined as including all birds and the non-avian dinosaurs that were more closely related to birds than they were to Ornithomimus velox.
Close examination of the fossilised remains of the oviraptorosaurian Caudipteryx and the winged dromaeosaurian Microraptor indicate the presence of propatagia. The researchers suggest that they have found evidence for the presence of a propatagium in dinosaurs that existed prior to the evolution of flight in the maniraptoran lineage.
Why Did the Propatagium Evolve?
If maniraptoran dinosaurs had propatagia prior to the evolution of powered flight, then this raises an intriguing question. Why did the propatagium evolve? Why did these particular theropods evolve such a structure?
The University of Tokyo researchers are optimistic that by studying more fossils as well as embryonic development within extant vertebrates they might be able to provide some answers.
The team thinks some theropods might have evolved the propatagium not because of any pressure to learn to fly, as their forelimbs were made for grasping objects and not for flying. The propatagium originally had another purpose. It could be speculated that this “leading edge” of the arm evolved to help amplify visual intraspecific communication. Perhaps it evolved as a soft tissue structure used in display to demonstrate fitness for breeding and to win mates.
An enlarged surface area of the forelimb might have played a role in helping to shade eggs or perhaps play some other role in the brooding process.
Finding fossil evidence to support these suggestions is likely to prove difficult. However, if further studies demonstrate the presence of propatagia in the Maniraptora, it will change the way these types of dinosaurs are depicted.
Everything Dinosaur acknowledges the assistance of a media release from the University of Tokyo in the compilation of this article.
The scientific paper “Origin of the propatagium in non-avian dinosaurs” by Yurika Uno and Tatsuya Hirasawa published in Zoological Letters
A team of scientists have been studying a Pinacosaurus larynx and have concluded that this armoured dinosaur was probably capable of producing a variety of sounds and calls.
A juvenile specimen of Pinacosaurus (P. grangeri), specimen number IGM100/3186, preserves a hyoid and two laryngeal elements (cricoids and arytenoids) in almost life articulation. From these remains the researchers have concluded that just like crocodilians and birds, Pinacosaurus was capable of producing a range of vocalisations. The calls may have had several functions, to alert others of a predator approaching, to threaten a predator, to define territory or to search for a mate. The sounds made by this ornithischian dinosaur may have been related to courtship, or perhaps helped to call offspring to their side.
Pinacosaurus (P. grangeri) is regarded as a basal member of the Ankylosaurinae subfamily of ankylosaurs. It is known from copious fossil material, and it is one of the most extensively studied of all the Late Cretaceous Thyreophora. Fossils are known from the Mongolia and China (Djadokhta Formation and the geologically older Alagteeg Formation).
The image (above) shows a not-to-scale replica of Pinacosaurus (PNSO).
In tetrapods the voice box (larynx) has several functions. It plays a role in respiration, protects the airway to prevent food items becoming lodged and it has a function in vocalisation. Fossil preservation of the larynx in archosaurs is extremely rare. The Pinacosaurus fossil material (IGM100/3186) represents the oldest voice box known to science. It provides scientists with an opportunity to better understand the evolution of the larynx in non-avian dinosaurs.
Vocal Armoured Dinosaurs
Ossification of the cricoid and arytenoid is confirmed in Pinacosaurus, and it has been reported in Saichania, another Asian ankylosaurine. This configuration is also found in extant birds. The complex arrangement of the hyolaryngeal apparatus led the researchers to conclude that it did not simply function as a barrier to preventing food entering the trachea (airway protection). It was specialised for opening the glottis and possibly acting as a sound modifier.
The voice box of modern birds and crocodilians differs. In crocodiles and their close relatives it is the larynx that produces sounds. In birds, the larynx forms part of the vocal tract but they have a specialised organ (syrinx) located at the base of the trachea (wind pipe), that produces sounds.
Pinacosaurus – Shared Anatomical Characteristics
The researchers suggest that Pinacosaurus retained the same hyolaryngeal elements as found in crocodilians. However, Pinacosaurus shows many shared characters with birds in the arrangement and morphology of the larynx.
The authors of the scientific paper, which was published this month in “Communications Biology” (Junki Yoshida, Yoshitsugu Kobayashi and Mark Norell), propose that Pinacosaurus did not use the larynx as a sound source like non-avian reptiles. The larynx probably worked as a sound modifier as found in birds
Furthermore, the authors postulate that bird-like vocalisation likely appeared in non-avian dinosaurs before the evolution of the Aves (birds).
Article sourced from the open-access paper in Communications Biology.
The scientific paper: “An ankylosaur larynx provides insights for bird-like vocalization in non-avian dinosaurs” by Junki Yoshida, Yoshitsugu Kobayashi, Mark A. Norell published in Communications Biology.
A team of international scientists including researchers from the University of Birmingham have published a paper on the brain and cranial nerves of fish that lived approximately 319 million years ago. The team’s findings are shedding light on vertebrate brain evolution.
The Late Carboniferous (early Pennsylvanian subperiod), fish fossil was discovered in a layer of soapstone adjacent to a coal seam at the Mountain Fourfoot coal mine in Lancashire and the specimen was first scientifically described in 1925. The fish, named Coccocephalus wildi, would have measured around 20 cm in length and it lived in what was an ancient estuary. It is only known from this single fossil and only the skull and jaws were recovered.
Vertebrate Brain Evolution
Coccocephalus was a member of the Class Actinopterygii, also known as the ray-finned fishes. The skull fossil was sent on loan from Manchester Museum to the University of Michigan and subsequent CT scans of the skull revealed the surprising discovery of the intact brain and associated nerves.
Senior author Sam Giles, (University of Birmingham), commented:
“This unexpected find of a three-dimensionally preserved vertebrate brain gives us a startling insight into the neural anatomy of ray-finned fish. It tells us a more complicated pattern of brain evolution than suggested by living species alone, allowing us to better define how and when present day bony fishes evolved.”
When the fish died, it was probably buried rapidly in sediment containing very little oxygen. The lack of oxygen prevented the soft brain tissue from decaying. Whilst brain cases can reveal the shape and structure of vertebrate brains, this remarkable fossil preserved the brain tissue of a prehistoric fish.
Soft tissues such as the brain normally decay quickly and very rarely fossilise. But when this fish died, the soft tissues of its brain and cranial nerves were replaced during the fossilisation process with a dense mineral that preserved, in astonishing detail, their three-dimensional structure.
This discovery provides palaeontologists with a window into the evolution and development of the brains of ray-finned fishes, a highly successful group of back-boned animals estimated to represent more than fifty percent of all living vertebrate species.
A study of the jaws and teeth of C. wildi suggest that it was carnivorous, likely feeding on small invertebrates. The CT scans revealed that the brain had bilateral symmetry, like the brains of modern ray-finned fishes, but significantly, the brain of Coccocephalus folds inward, unlike in all living ray-finned fishes, in which the brain folds outward.
The fossil captures a time before a signature feature of ray-finned fish brains evolved, providing an indication of when this trait evolved.
Co-author of the paper, published in the journal “Nature”, Matt Friedman (University of Michigan) explained:
“An important conclusion is that these kinds of soft parts can be preserved, and they may be preserved in fossils that we’ve had for a long time—this is a fossil that’s been known for over 100 years.”
Everything Dinosaur acknowledges the assistance of a media release from the University of Birmingham in the compilation of this article.
The scientific paper: “Exceptional fossil preservation and evolution of the ray-finned fish brain” by Rodrigo T. Figueroa, Danielle Goodvin, Matthew A. Kolmann, Michael I. Coates, Abigail M. Caron, Matt Friedman and Sam Giles published in Nature.
A new pterosaur species has been described based on a superbly preserved specimen found in Upper Jurassic limestone deposits in Bavaria (southern Germany). The fully articulated specimen displays a unique dentition that suggests this flying reptile fed like a modern-day flamingo, sieving water through its jaws to trap small invertebrates as it waded or possibly swam in a shallow lagoon.
Picture credit: Megan Jacobs
The pterosaur has been classified as a ctenochasmatid, a group of short-tailed pterodactyloids characterised by specialised teeth adapted for filter feeding. Fossils of these relatively small flying reptiles (most with wingspans less than 3 metres), have been found in Europe, America and China, in rocks dating from the Upper Jurassic to the Early Cretaceous. The new pterosaur has been named Balaenognathus maeuseri, the genus name derives from the scientific name for the Bowhead whale (Balaena mysticetus) and the Latin for jaw, as it is thought that these two unrelated species shared a common feeding strategy. The specific epithet honours a co-author of the paper Matthias Mäuser who sadly passed away before publication.
Lead author of the study, published in Paläontologische Zeitschrift (PalZ), Professor David Martill from the University of Portsmouth School of the Environment, Geography and Geosciences commented:
“The nearly complete skeleton was found in a very finely layered limestone that preserves fossils beautifully.”
Unique Pterosaur Dentition
The fossil (specimen number NKMB P2011-63), is remarkable for its completeness, unusual dentition and hints of the preservation of soft tissues, including wing membranes. The delicate jaws contain at least 480 fine teeth.”
Professor Martill added:
“The jaws of this pterosaur are really long and lined with small fine, hooked teeth, with tiny spaces between them like a nit comb. The long jaw is curved upwards like an avocet and at the end it flares out like a spoonbill. There are no teeth at the end of its mouth, but there are teeth all the way along both jaws right to the back of its smile.”
Bizarre Hook-like Tooth Crown
The tips of the jaw are devoid of teeth, which would have permitted plankton and invertebrate-rich water to rush into the long jaw. The hundreds of teeth would have acted as a sieve helping to strain out food. Many of the teeth have a hook-like expansion on the tip of the crown, a bizarre and unique tooth morphology.
Explaining the significance of these strange teeth, Professor Martill stated:
“What’s even more remarkable is some of the teeth have a hook on the end, which we’ve never seen before in a pterosaur ever. These small hooks would have been used to catch the tiny shrimp the pterosaur likely fed on – making sure they went down its throat and weren’t squeezed between the teeth.”
A New Pterosaur
The discovery was made accidentally while scientists were excavating a large block of limestone containing crocodilian fossil remains.
Professor Martill explained:
“This was a rather serendipitous find of a well-preserved skeleton with near perfect articulation, which suggests the carcass must have been at a very early stage of decay with all joints, including their ligaments, still viable. It must have been buried in sediment almost as soon as it had died.”
Most members of the Ctenochasmatidae family seem to have been the pterosaur equivalent of wading shore birds, although some genera were perhaps adapted to habitats further inland and have truly bizarre shaped jaws leaving palaeontologists perplexed as to what they ate.
Only one other known pterosaur had more teeth than Balaenognathus. It is another ctenochasmatid and it is called Pterodaustro guinazui and its fossils are known from the Lower Cretaceous of Argentina. Both Pterodaustro and Balaenognathus were likely filter feeders although the arrangement of their teeth differs. Balaenognathus had teeth in the upper and lower jaw which are the mirror image of each other, whilst P. guinazui had very reduced teeth in the upper jaw and up to a 1,000 densely packed, bristle-like teeth in the lower jaw.
New Pterosaur Species – Unique Feeding Mechanism
The teeth of Balaenognathus suggest a feeding strategy that involved the animal either wading through water or swimming, using its spoon-shaped beak to funnel water into its mouth, this water was then strained through its teeth to trap prey. The researchers propose that Balaenognathus fed on shrimps and copepods filling a similar ecological niche as extant ducks, shorebirds and flamingos.
Commenting on the sad passing of Matthias Mäuser, Professor Martill said:
“Matthias was a friendly and warm-hearted colleague of a kind that can be scarcely found. In order to preserve his memory, we named the pterosaur in his honour.”
Everything Dinosaur acknowledges the assistance of a media release from the University of Portsmouth in the compilation of this article.
The scientific paper:
The scientific paper: “A new pterodactyloid pterosaur with a unique filter‑feeding apparatus from the Late Jurassic of Germany” by David M. Martill, Eberhard Frey, Helmut Tischlinger, Matthias Mäuser, Héctor E. Rivera‑Sylva and Steven U. Vidovic published in Paläontologische Zeitschrift (PalZ).
Some dinosaur fossils might be regarded as spectacular, the enormous casts of sauropod skeletons or perhaps a Tyrannosaurus rex articulated mount. However, it is often the smaller specimens that provide palaeontologists with a wealth of data. For example, whilst walking through a museum after a meeting, an Everything Dinosaur team member spotted a Triceratops fossil tooth on display.
Fossil teeth provide palaeontologists with an understanding of the animal’s diet. Wear patterns can indicate the method of feeding and in some animals such as elephants for example, detailed analysis of the teeth can not only provide information on diet, but the age of the proboscidean can also be determined.
If the internal structure of the tusk of a Woolly Mammoth is examined, then seasonal variations in growth can be determined and even times when the prehistoric elephant suffered from poor health.
Triceratops Fossil Tooth
A single tooth from a ceratopsian can change perspectives and lead to a revision of our understanding of the Dinosauria. In 2017, Everything Dinosaur team members wrote an article about a scientific paper that confirmed the discovery of a single tooth from a horned dinosaur. This fossil tooth demonstrated that ceratopsids existed in eastern America (Appalachia). This was the first recorded evidence of this group of ornithischian dinosaurs on that part of the American Cretaceous land mass.
Sometimes it can be the smallest fossils that provide the greatest amount of information. Palaeontologists still have a lot to learn about the Dinosauria, even a famous dinosaur such at Triceratops horridus probably hides a few secrets still.
Picture credit: Everything Dinosaur
The picture (above) is one of the Nanmu Studio Jurassic Series Triceratops colour variants (Tricolor).
Carboniferous chimaeras were suction feeders unlike their modern relatives such as the rat fish which are durophagous (feed on hard-shelled prey such as crabs, snails and molluscs). That is the conclusion of new research published this week in the academic journal The Proceedings of the National Academy of Sciences (PNAS).
An Exceptional Three-dimensional Fossil
The research led by the Muséum national d’histoire naturelle (MNHN) located in Paris, and the University of Birmingham has shown that an ancient relative of chimaeras, jawed vertebrates that are related to cartilaginous fishes (sharks and rays), fed by sucking in prey animals underwater.
An exceptional three-dimensional fossil of an ancient chimaera (Iniopera genus), has revealed new clues about the diversity of these creatures during the Carboniferous period.
The fossil, from a genus called Iniopera, is the only suction feeder to be identified among chimaeras, and quite different from living chimaeras, which generally feed by crushing molluscs and other hard-shelled prey between their teeth.
Chimaeriformes are an ancient order of cartilaginous fish (Chondrichthyes) that are thought to have evolved in the Devonian. Most extant species are found at depths greater than two hundred metres, and some chimaera fish are restricted to extremely deep water (Bathypelagic Zone).
Most fossil and extant chimaeras are quite small, very few specimens exceed one metre in length. However, other prehistoric, cartilaginous fish that were distantly related to Iniopera grew much larger. For example, the Permian genus Helicoprion with its bizarre tooth-whorl jaw, which has been estimated to have grown to around eight metres in length.
Picture credit: Everything Dinosaur
Although models of prehistoric fish from the Chondrichthyes Class are rare, PNSO have included two prehistoric shark figures (O. megalodon and Cretoxyrhina) and a replica of Helicoprion.
Commenting on the significance of this study, lead researcher Dr Richard Dearden (University of Birmingham) stated:
“Being able to identify Iniopera as a suction feeder sheds light on the diverse role of chimaeras in these early ecosystems. In particular, it suggests that in their early evolutionary history, some chimaeras were inhabiting ecological niches that are now monopolised by ray finned fishes – a far cry from their modern life as specialised shell-crushers.”
The cartilage skeleton of these fish are rarely fossilised and the Chondrichthyes tend to be underrepresented in the fossil record. The skeletons that are preserved tend to be crushed flat and distorted so interpreting them is notoriously difficult. However, by studying the tooth shapes and diverse body plans, palaeontologists were already aware that extinct forms were far more varied than their living counterparts.
3-D Imaging Techniques
Using advanced 3-D imaging techniques, the researchers reconstructed the head, shoulder and throat skeleton of the Iniopera fossil. They then estimated the location of major muscles and found the anatomy was poorly suited to durophagous feeding. Instead, the researchers believe the animal was more likely to have used the muscle arrangement to expand the throat to take in water and a forward-pointing mouth to orient towards prey.
Suction feeding is a technique used by many animals that live underwater. It involves generating low pressures in the throat to pull in water and prey. To do this effectively, the animal needs to be able to rapidly expand its throat, and point its mouth forward towards prey items. Numerous different aquatic jawed vertebrates, such as ray-finned fishes and some turtles have evolved specialised anatomies to help them feed in this manner more effectively.
The suction feeding theory is also supported by fossilised Chimaeriformes that have preserved stomach contents. Small arthropods have been found in association with the body cavity of several specimens and their relatively entire state suggests suction feeding as the method of prey capture.
Everything Dinosaur acknowledges the assistance of a media release from the University of Birmingham in the compilation of this article.
Whilst looking back at some pictures taken during a recent visit to Liverpool World Museum, team members came across a photograph of a museum exhibit that featured an ichthyosaur jaw.
Picture credit: Everything Dinosaur
We expect amateur fossil hunters to return to the beaches at Lyme Regis and Charmouth after the recent storms and bad weather in a bid to find marine reptile fossils including ichthyosaur fossil remains. Isolated ichthyosaur bones such as those from the paddles, or vertebra (nicknamed “verts” by collectors), are relatively common but skull bones, particularly anything articulated and nearly complete are exceptionally rare.
We wish all those hardy fossil hunters planning their excursions happy hunting.
Recently, Everything Dinosaur was contacted by Lee who had collected a strange rock whilst visiting Yorkshire. Lee asked what the rock could be and sent in some photos. We contacted Lee and asked him to send in some more pictures, but this time including an object such as a coin that could provide a scale. In our email, we asked where this rock was found.
Robin Hood’s Bay Fossil
Lee commented that this rock was found at Robin Hood’s Bay on the north Yorkshire coast. This is a part of the world we know quite well and it is famous for its fossils. The Redcar Mudstone Formation dominates the geology of this part of the English coast and we suspect that the rock is mudstone and the unusual object is the remnants of a Jurassic shelly invertebrate.
The shales, mudstones and sandstones that outcrop at Robin Hood’s Bay date from the Lower Jurassic (Sinemurian to Pliensbachian fauna stages) and we suspect that this fossil is around 195 – 185 million years old.
The specimen is heavily eroded, and we think it is being viewed as a cross-section. Ammonites are relatively common on this stretch of coastline as are Gryphaea fossils (Devils toenails) and crinoids. It is very difficult to identify this item, just from the photographs, however, we think that as there seem to be striations (lines) visible in the fossil that this is a highly eroded bivalve.
We know that many of our blog readers are enthusiastic fossil collectors. We would welcome any suggestions and help with the identification of this specimen.
In today’s blog post we look at the dwarf nodosaurid Patagopelta (P. cristata), which was formally named and described earlier this month.
A new, very small, armoured dinosaur has been named and described from fossils found in Argentina. The dinosaur which measured around 2 to 2.3 metres in length (based on the dimensions of the femur), suggests that some members of the Nodosauridae in Gondwana became smaller in the Late Cretaceous, perhaps as armoured dinosaurs in South America were under evolutionary pressure from other ornithischians and titanosaurs.
Dwarf Nodosaurid Patagopelta
Fragmentary remains of Late Cretaceous armoured dinosaurs are known from Chile and Argentina, but little work had been undertaken to assess these specimens and to review their phylogeny and taxonomic relationship with other members of the Ankylosauria clade from North America and elsewhere in the world.
Writing in the ” Journal of Systematic Palaeontology”, the researchers led by Facundo Riguetti, a CONICET doctoral fellow, reassessed the known ankylosaur material in conjunction with some other recently found fossils and, as a result, they were able to establish a new nodosaurid species from bones and a single tooth found in sediments of the Allen Formation (Campanian–Maastrichtian) in Salitral Moreno, Río Negro Province (northern Patagonia).
The dinosaur’s genus name translates as “Patagonian shield” whilst the trivial name derives from the Latin for crest – a reference to the diagnostic crests on both the anterior surface of the femur and the lateral osteoderms of the cervical rings.
Dr Riguetti commented:
“The importance of the study lies in the fact that Patagopelta is the first species of Ankylosauria described for the continental territory of Argentina, which fills the existing gap for this group and adds a new thyreophoran to the very few incomplete and indeterminate remains known for our country from this type of ornithischian dinosaur.”
The Right Femur
The best-preserved fossil element is the right femur, which is complete and shows typical anatomical characteristics associated with the Nodosauridae. This bone along with the distinctive cervical osteoderms led to the erection of this new species. As the femur is only 25 cm in length and bone histology suggests an adult animal, the researchers conclude that Patagopelta was a dwarf form of armoured dinosaur.
Co-author Sebastián Apesteguía, a CONICET researcher, explained:
“For an armoured dinosaur, Patagopelta is extremely small. Due to the size of the femur, only 25 centimetres in length, we estimate that the animal must have been between two and three meters long, while, in general, ankylosaurs are medium-sized or large animals, with an average length of between four and five metres.”
A Faunal Exchange Across the Americas
Although it is thought that the Nodosauridae evolved in the Northern Hemisphere, towards the end of the Cretaceous (Campanian – Maastrichtian), a land bridge existed between North America and South America that permitted a faunal exchange. Titanosaurs migrated north, which explains why fossils of titanosaurs such as Alamosaurus occur in the USA. Ornithischian dinosaurs such as hadrosaurs and nodosaurids moved south.
The image above shows a typical Late Cretaceous titanosaur, for models of Late Cretaceous dinosaurs including titanosaurs and armoured dinosaurs: CollectA Prehistoric Life Models.
Sebastián Apesteguía added:
“That is why in South America we only expect to find animals like Patagopelta in rocks from the Late Cretaceous, just before the global extinction of the dinosaurs took place.”
Dwarfism in Late Cretaceous South American Thyreophora
The size of Patagopelta along with the recently described Stegouros (Soto-Acuña et al, 2021)*, from southernmost Chile, suggests that armoured dinosaurs in South America may have gradually become smaller. This trait is not known in members of the Thyreophora described from other parts of the world. Palaeontologists have speculated that perhaps competition from titanosaurs and the migration of hadrosaurs into South America might have led to armoured dinosaurs adapting to different ecological niches to avoid competition. By being smaller these animals needed fewer resources than larger, contemporaneous herbivorous dinosaurs.
It has also been suggested that the geology of Patagonia where the fossils of Patagopelta were found might provide a clue to the dwarfism. Geologists are aware of several Late Cretaceous marine transgressions in the region. This might have led to the establishment of an island archipelago with dinosaurs living on these small islands gradually become smaller due to a scarcity of resources (the “island rule”).
Tracks of Dwarf Ankylosaurs
Members of the Patagopelta research team had previously described tracks of dwarf ankylosaurs, possibly affected by similar circumstances, preserved in Upper Cretaceous deposits in Bolivia.
Everything Dinosaur acknowledges the assistance of a media release from Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) in the compilation of this article.
The scientific paper: “A new small-bodied ankylosaurian dinosaur from the Upper Cretaceous of North Patagonia (Río Negro Province, Argentina)” by Facundo Riguetti, Xabier Pereda-Suberbiola, Denis Ponce, Leonardo Salgado, Sebastián Apesteguía, Sebastián Rozadilla and Victoria Arbour published in the Journal of Systematic Palaeontology.