A newly published study examining the growth rates of Dimetrodon teutonis and Dimetrodon natalis has provided a fresh perspective on a famous, primitive synapsid. Researchers have discovered that the smallest known species of Dimetrodon achieved their diminutive size in contrasting ways. The study provides fresh insights into the lives of these iconic sail-backed predators that roamed the Earth millions of years before the dinosaurs evolved.

The Dimetrodon genus comprises several species. Most of these species grew into large predators more than three metres in length.  For example, Dimetrodon grandis measured about 3.2 metres long and weighed approximately 250 kilograms. However, a few species were much smaller. An international team of researchers has now investigated how these animals evolved their reduced body size.

Dimetrodon teutonis – The Smallest Known Dimetrodon Species

The study focused on two species. One is Dimetrodon natalis from North America. The other is Dimetrodon teutonis from the Bromacker fossil site in Germany. This German species is significant because it is the only known Dimetrodon discovered outside North America.

For many years, D. natalis was regarded as the smallest species. However, D. teutonis turned out to be even smaller.

• Dimetrodon natalis – named in 1936 by Romer from earlier work by Cope. It measures about 1.7 metres long with an estimated bodyweight of 38 kilograms*.
• Dimetrodon teutonis – named in 2001 (Berman, Reisz, Martens and Henrici) and measuring around 70 cm in length and weighing approximately 24 kilograms*.

Limb bone midshaft circumference analysis of fossil material used in this research suggests that the individual animals representing D. teutonis had a body weight of 6.3 to 6.8 kilograms. In contrast, the same analysis method provides body weight estimates for the D. natalis individuals between 20.9 and 21.7 kilograms.

To learn more about these animals, the scientists examined the microscopic structure of fossil bones. Bone tissue preserves information about growth rates and development. Therefore, it can reveal important details about the life history of extinct species.

Bone Histology Reveals Different Life Histories

The results have been published in the academic journal “Scientific Reports”. They show that the two species followed contrasting growth strategies. Dimetrodon natalis appears to have grown quickly. However, it stopped growing at an early age. As a result, it reached adulthood while remaining small. In contrast, Dimetrodon teutonis grew much more slowly. It continued developing over a longer period. The researchers suggest that it probably reached sexual maturity later in life.

Bone histology comparison between D. teutonis and D. natalis demonstrates fundamentally different bone microanatomy. The humerus cross section of D. teutonis (left) exhibits thin cortices composed of poorly vascularized parallel-fibered bone. This suggests slow growth and delayed maturity. In contrast, the bone histology of D. natalis (right) shows thick and highly vascularised woven to parallel-fibered bone cortices. Picture credit: Frederik Spindler, PALAEONAVIX.

Picture credit: Frederik Spindler, PALAEONAVIX

Dr Tom Hübner, curator and head of the Bromacker project at the Friedenstein Foundation Gotha, commented:

“This work demonstrates that bone histology can provide direct insights into the palaeobiology of long-extinct animals. Who would have thought that these two small species had such different life histories?”

Different Environments Influenced Growth

According to the research team, environmental conditions played a key role. North American Dimetrodon species lived in humid lowland habitats. These ecosystems contained abundant food resources. In addition, predators were common. Under these conditions, rapid growth would have offered advantages for survival and reproduction.

The Bromacker ecosystem in Germany presented different challenges. Seasonal droughts and limited resources shaped this environment. Fossilised burrows suggest that potential prey animals retreated underground during dry periods. Consequently, slower growth may have helped Dimetrodon teutonis cope with fluctuating food supplies.

Dr Aurore Canoville explained:

“These new findings once again highlight the uniqueness of the Bromacker locality compared with other Early Permian fossil sites. They make Dimetrodon even more fascinating. Long before dinosaurs dominated the Earth, these early synapsids were already responding in remarkably flexible ways to climate, food availability, competition and predation.”

Unique Insights from the Bromacker Fossil Site

Professor Jörg Fröbisch of the Museum für Naturkunde Berlin emphasised the importance of the discovery.

He stated:

“These fascinating results provide an increasingly complete picture of the Bromacker ecosystem and its enormous potential for many decades of future research.”

The study highlights how adaptable these early synapsids were. It also demonstrates the importance of the Bromacker fossil locality. Thanks to discoveries such as these, scientists continue to improve our understanding of life during the Early Permian.

Unique fossil provides information on Bromacker food web: Regurgitated Pellet from a Dimetrodon.

In the paper, the researchers state that the largest known species of Dimetrodon is D. angelensis.  It is stated that this species was up to 4.6 metres long and weighed 250 kilograms.

Everything Dinosaur acknowledges the assistance of a media release from the Museum für Naturkunde Berlin in the compilation of this article.

The scientific paper: “Contrasting life history in the diminutive Dimetrodon species from North America and Germany” by Aurore Canoville, Philipp L. Knaus, Lorenzo Marchetti and Jörg Fröbisch published in Scientific Reports.

The award-winning Everything Dinosaur website: Models of Palaeozoic Creatures and Other Prehistoric Animals.

The debate about lips in dinosaurs continues.  Whether dinosaurs possessed extraoral tissue remains controversial. However, a remarkable new study has added substantial support to the idea that most dinosaurs possessed extraoral tissues that covered and protected their teeth. A new study, published in the journal “Palaeontology” provides compelling evidence that lips were the ancestral condition in dinosaurs and many other reptiles.

Researchers led by Rafael Terras (Programa de Pós-Graduação em Ciências Ambientais, Universidade Comunitária da Região de Chapecó, Chapecó, Brazil), have examined Triassic archosaurs from Brazil. Their findings suggest that lips in dinosaurs were not an unusual feature. Instead, they may represent the ancestral condition for the entire Sauropsida, the group that includes reptiles and birds.

Importantly, this study does not stand alone. Rather, it builds upon previous work by researchers such as Robert Bakker, Thomas Paul, Casey Holliday, Mark Witton and Thomas Cullen. Consequently, the scientific case for lips in dinosaurs continues to grow.

A Debate That Goes Back More Than a Century

The idea of lips in dinosaurs is not new. In the 1920s, palaeontologist Charles Gilmore suggested that openings in the jaw of Ceratosaurus transmitted nerves and blood vessels to the lips. Later, Robert Bakker proposed that many dinosaurs possessed thin, immobile lips similar to those seen in living lizards. Ironically, the advent of cinema and the need to make dinosaurs scary by showing their teeth could have popularised non-lipped dinosaurs with the public.

More recently, the landmark 2023 study by Cullen and colleagues demonstrated that theropod teeth show little evidence of the wear expected if they had remained permanently exposed. Their work also highlighted similarities between theropod skull anatomy and living squamates.

To read more about the 2023 study: New Paper Suggests Dinosaurs Had Lips.

Now, this new study extends these observations far beyond the Theropoda.

Studying Triassic Archosauromorphs from Brazil

The researchers examined numerous Triassic archosaurs from southern Brazil. These included early dinosaurs and several crocodile-line relatives.

They found several features associated with covered teeth.  For example, the team examined the location of foramina (tiny openings in the skull bones which are location points for nerves).

The researchers identified the following, consistent characteristics:

• rows of horizontally arranged facial foramina.
• fewer than one hundred foramina per rostral bone.
• vertically orientated teeth.
• a lack of interlocking teeth.
• uniform enamel thickness.
• no evidence of exposed dentine.
• a positive relationship between skull length and tooth crown height.

These characteristics closely resemble those seen in living lizards (lepidosaurs) rather than modern crocodilians. As a result, the authors concluded that labial scales and extensive gingiva (soft tissue that supports the teeth – gums) probably enclosed the teeth.

Foramina in selected Triassic saurischians. A, Buriolestes (ULBRA PVT 280). B, Buriolestes (CAPPA/UFSM 0035). C, Pampadromaeus (ULBRA PVT 016). D, Gnathovorax (CAPPA/UFSM 0009). E, Unaysaurus (UFSM 11069). F, Macrocollum (CAPPA/UFSM 0001a). G, Gnathovorax (CAPPA/UFSM 0009). H, Macrocollum (CAPPA/UFSM 0001d). Abbreviations: edf, ellipsoid dentary foramen; emf, ellipsoid maxillary foramen; faaf, foramen anterior to the maxillary fenestra; fdaf, foramen dorsal to the antorbital fenestra; gif, groove-inserted foramen; odf, oval dentary foramen; omf, oval maxillary foramen; opmf, oval premaxillary foramen; sbg, subnarial gap; sf, subnarial foramen. Scale bars represent: 10 mm (A–C, E, H); 25 mm (D, F, G). Picture credit: Terras et al.

Picture credit: Terras et al

Tooth Histology Provides Important Clues for Lips in Dinosaurs

The researchers also examined thin sections of fossil teeth. They discovered that enamel thickness remained consistent around the crowns. Furthermore, the dentine showed no signs of wear. This condition contrasts strongly with crocodilians, whose exposed teeth experience significant abrasion. Therefore, the teeth of these Triassic archosaurs appear to have remained hydrated and protected.

This conclusion mirrors the findings published by Cullen and colleagues in the 2023 paper. Consequently, independent lines of evidence are converging on the same answer.

Studying the Pseudosuchian Prestosuchus

One of the most intriguing aspects of the study concerns the giant pseudosuchian Prestosuchus. This large, terrestrial predator possessed a distinctive gap between the upper and lower jaws. At first glance, this arrangement might suggest permanently exposed teeth. However, the researchers argue otherwise. They propose that a mandibular gap existed between the jaws. Soft tissues and gingiva would have occupied this space and maintained a complete oral seal. In effect, the teeth remained covered despite the unusual skull shape.

Prestosuchus skulls and reconstructions. A, ULBRA PVT 281 crushed skull in right lateral view. B, reconstruction of UFRGS PV 0629 T in right lateral view (mirrored) with a mandibular gap; modified from Mastrantonio et al. (2019). C–D, life reconstructions of ULBRA PVT 281: C, in right lateral view with a closed mouth displaying the oral seal; D, in frontal view with an open mouth displaying the oral rim; artwork by Matheus F. Gadelha used with permission. Scale bars represent: 300 mm (A, C, D); 100 mm (B). Picture credit: Terras et al with illustrations by Matheus F. Gadelha.

Picture credit: Terras et al with illustrations by Matheus F. Gadelha

This interpretation is significant. It demonstrates that specialised skull anatomy does not necessarily imply exposed teeth. Moreover, it suggests that lips could be retained even in large-bodied predators with unusual cranial morphology.

Prestosuchus (P. chiniquensis) is an extinct archosaur more closely related to extant crocodilians than to the Dinosauria. Size estimates vary but it could have reached a length of five metres or more. It was one of the largest Triassic pseudosuchians and an apex predator.

The Wild Safari Prehistoric World Prestosuchus model.

The image (above) shows a model of the Triassic predator Prestosuchus.  This model was introduced in 2019.  The model has exposed teeth and no extraoral tissue.  It was made prior to the recent research suggesting the presence of lips in dinosaurs and other archosaurs.  The Prestosuchus model is from the Wild Safari Prehistoric World range of figures.

Wild Safari Prehistoric World: Prehistoric Animal Models and Figures.

Lips in Specialised Archosauromorphs

The authors also considered a number of highly specialised forms. They concluded that lips probably occurred in a wide variety of archosaurs.  For example, the researchers suggest that Triassic theropods had lips, along with sauropodomorph dinosaurs.  In addition, they propose that ornithosuchids (pseudosuchian archosaurs – crocodilian lineage) had lips.  Furthermore, the researchers propose that proterosuchids (basal archosaurs) also had extraoral tissue.  It is suggested that phytosaurs had lips too. Some archosauromorphs evolved additional keratinous coverings. These structures formed primitive beaks (rhamphothecae).

Triassic archosauromorphs reconstructed with labial scales and the oral seal in lateral view. A, Gnathovorax (CAPPA/UFSM 0009; Herrerasauria). B, Pampadromaeus (ULBRA PTV 016; Sauropodomorpha). C, Machaeroprosopus (NMMNH P-4983; Phytosauria). D, Riojasuchus (PVL 3827; Ornithosuchidae). E, Proterosuchus (NMQR 880; Proterosuchidae). F, Silesaurus (ZPAL Ab III/361; Silesauridae). G, Venetoraptor (CAPPA/UFSM 0356; Lagerptidae). H, ‘Hyperodapedon’ (ULBRA PVT 053; Rhynchosauria). I, Prestosuchus (ULBRA PTV 281; Loricata). Artwork by Matheus F. Gadelha used with permission. Scale bars represent: 50 mm (A, D); 20 mm (B, F); 100 mm (C, H); 30 mm (E); 10 mm (G); 300 mm (I). Picture credit: Terras et al with illustrations by Matheus F. Gadelha.

Picture credit: Terras et al with illustrations by Matheus F. Gadelha

A Complex Picture

The evolution of facial tissues in archosaurs appears to have been far more complex than previously thought.  However, extraoral soft tissues such as lips were probably the ancestral condition. According to the authors of the study, lips represent the primitive condition for the Sauropsida. Therefore, the common ancestor of reptiles and birds likely possessed covered teeth.

If correct, exposed teeth evolved later.  Extant crocodilians would represent a more derived branch of the Archosauria. Their exposed dentition and highly sensitive facial skin appear to be derived adaptations rather than the ancestral state. This finding reverses a common assumption.  However, the debate about lips in dinosaurs and their near relatives is likely to continue.

Instead of asking why dinosaurs had lips, researchers may need to explain why crocodilians lost them.

A Growing Scientific Consensus

No single paper or study can settle such a complex question. Nevertheless, the evidence continues to accumulate. Studies of facial foramina, tooth wear, enamel thickness and skull proportions increasingly point in the same direction. Taken together, they indicate that most dinosaurs probably possessed extraoral tissues covering their teeth. As a result, reconstructions showing permanently exposed teeth may eventually become less common.

This study is significant because it suggests origins for this condition originated much earlier in archosaur evolution. Consequently, it provides fresh evidence that covered teeth were widespread among early members of the Archosauria. Furthermore, it strengthens the idea that the familiar crocodilian condition evolved later.

The head of a stuffed crocodile specimen (Nile crocodile) on display at the London Natural History Museum. The lack of extraoral tissue (lips) in this archosaur might be a derived condition. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Mike from Everything Dinosaur commented:

“This exciting new research adds another important piece to the puzzle. Evidence supporting lips in dinosaurs has been steadily accumulating for many years. The research team have shown that these soft tissues probably have much deeper evolutionary roots than previously thought. Their work strengthens the view that covered teeth represented the ancestral condition in dinosaurs and many of their close relatives. As a result, palaeoartists and scientists are gaining an increasingly detailed picture of how these remarkable animals actually looked.”

Everything Dinosaur acknowledges the assistance of the study’s corresponding author in the compilation of this article.

The scientific paper: “Inferred presence of extraoral tissues in Triassic archosauromorphs and the evolutionary implications for the clade Sauropsida” by Rafael Terras, Jaqueline Borger, Manuelle O. P. Almeida, Silvia Bettin, Owen A. Higgins, Giulia Marciani, Stefano Benazzi, Rodrigo T. Müller, Leonardo Kerber and Mirian Carbonera published in Palaeontology.

The Everything Dinosaur website: Museum Quality Models of Archosaurs.

Recently, we published a post highlighting the on-going research into the remarkable Oxfordshire “dinosaur highway”.  A limestone quarry preserves the remains of numerous dinosaur tracks.  The tracks are preserved in strata laid down in the Middle Jurassic.  Palaeontologists estimate that the trackways are around 166 million years old (Bathonian faunal stage).  In a recent radio interview, a researcher commented that one of the tracks could be a record breaker. At around 220 metres in length, one Oxfordshire trackway could represent the longest continuous sauropod trackway known to science. However, describing them as Cetiosaurus dinosaur tracks is somewhat controversial.

To read Everything Dinosaur’s earlier blog post: Oxfordshire Trackway Could be the Longest Sauropod Trackway Discovered to Date.

Could a Cetiosaurus Have Left the Longest Sauropod Trackway?

Whilst undoubtedly made by sauropods, it is difficult to assign with any certainty the taxon that walked across a lagoon that led to the footprints being trapped in time.  Indeed, as the tracks are different sizes, they could represent several taxa.  Alternatively, the tracks might represent a single species, but different aged individuals walking together.  However, Cetiosaurus is the sauropod most often mentioned in association with the trace fossils.  Why might that be the case?

An artist’s reconstruction of the Dewars Farm Quarry site 166 million years ago. A Megalosaurus tracks an adult Cetiosaurus with a second sauropod in the background whilst pterosaurs soar overhead. Picture credit: Mark Witton.

Picture credit: Mark Witton

Cetiosaurus is regarded as being a primitive member of the Sauropoda. Nevertheless, this is an important genus. It has the distinction of being regarded as the first sauropod dinosaur to be formally described (Owen 1841). However, Owen’s scientific study was inaccurate. For example, Owen suggested that the large vertebrae with their rough texture were similar to extant whale vertebrae. As the fossils had been found in marine deposits, Owen incorrectly concluded that the fossils represented an enormous marine crocodile.

Cetiosaurus oxoniensis

Unfortunately, most Cetiosaurus fossil specimens consist of fragmentary material.  Indeed, little is known about Middle Jurassic sauropods.  Significantly, the species Cetiosaurus oxoniensis was described from fossils found in Oxfordshire.  The material comes from deposits that are approximately the same age as the trackway bedding planes at the quarry site.  So, it is possible that these extensive trace fossils do indeed represent Cetiosaurus dinosaur tracks.

The enormous and robust right femur of a Middle Jurassic sauropod. The femur has been ascribed to the taxon Cetiosaurus. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Cetiosaurus Dinosaur Tracks

Whether or not these footprints represent Cetiosaurus dinosaur tracks remains open to debate.  However, as perhaps the first sauropod formally described, this taxon is iconic.  In addition, it is pleasing symmetry if a Cetiosaurus did leave what may prove to be the world’s longest sauropod trackway. Such an accolade only enriches England’s rich fossil heritage.

Mike from Everything Dinosaur commented:

“At around 220 metres in length, one Oxfordshire trackway could represent the longest continuous sauropod trackway ever discovered. Other lengthy European sauropod trackways are known.  For example, from Portugal and France.  These fossil trackways are over 140 metres in length, so they are considerably shorter than the trackway from Oxfordshire.  Nonetheless, they are still impressive and give palaeontologists the opportunity to learn more about these enormous creatures.”

Everything Dinosaur acknowledges the assistance of a media release from the University of Birmingham supplied in January 2025 in the compilation of this article.

For sauropod models and other dinosaurs: Dinosaur Figures and Prehistoric Animal Models.

Scientists studying the famous Oxfordshire “dinosaur highway” have announced that one of the giant trackways may represent the longest known sauropod trackway discovered anywhere in the world. The remarkable sequence of footprints, uncovered at Dewars Farm Quarry, could have been made by a single Cetiosaurus as it wandered across a Jurassic mudflat around 166 million years ago.

The Dewars Farm Quarry excavation work taking place in June 2024. Picture credit: The University of Birmingham.

Picture credit: The University of Birmingham

A Giant Dinosaur Left Its Footprints

Researchers have traced the trackway for approximately two-hundred and twenty metres. This enormous trail records the movements of a huge, long-necked herbivore. Furthermore, scientists think the tracks were made by a Cetiosaurus or a sauropod similar to Cetiosaurus, the first sauropod to be scientifically described (Owen, 1841). In total, four sauropod trackways at the site have been discovered. In addition, the site has yielded several other trackways, including those of a meat-eating dinosaur.  These tracks have been tentatively assigned to Megalosaurus.

The original discovery attracted worldwide attention when details were formally announced in early 2025. The sauropod tracks represent animals of different sizes.  This suggests some intriguing possibilities.  For example, the tracks could represent a family moving together, or the trackways could represent a group of unrelated animals moving together.  In an interview with Radio Oxfordshire, co-leader of the excavation Dr Emma Nichols (Oxford University Museum of Natural History), opined that the trace fossils could represent more than one type of sauropod.

Working on the Dewars Farm Quarry dinosaur tracks. Picture credit: Caroline Wood University of Oxford.

Picture credit: Caroline Wood University of Oxford

The Oxfordshire “Dinosaur Highway” Made by a Cetiosaurus (Possibly)

The tracks cannot be linked directly to a skeleton. However, the footprints closely resemble those expected from a large, narrow-gauge sauropod. Consequently, scientists have suggested that the trackmaker was probably Cetiosaurus.

Cetiosaurus lived during the Middle Jurassic. It reached lengths of around eighteen metres and weighed many tonnes. Moreover, the type species, Cetiosaurus oxoniensis, was named from fossils discovered in Oxfordshire. Therefore, assigning the tracks to this dinosaur makes geological sense.

Fossils ascribed to the taxon Cetiosaurus on display at the Oxford University Museum of Natural History (OUMNH). Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

To read Everything Dinosaur’s article from January 2025 (formal announcement of quarry discovery): Remarkable Dinosaur Highway Uncovered in Oxfordshire.

Following in the Footsteps of Jurassic Giants

Trackways provide a different type of evidence from fossil bones. Skeletons reveal anatomy. However, footprints capture behaviour. They show how dinosaurs moved and interacted with their environment. Using modern imaging techniques, researchers have created detailed three-dimensional models of the trackway. As a result, scientists can estimate walking speed and study the animal’s gait. The Oxfordshire trackways represent one of the most important dinosaur discoveries made in Britain for decades. Furthermore, they provide a rare snapshot of life during the Middle Jurassic.

An illustration of a typical sauropod from the Middle Jurassic (Cetiosaurus). It is thought that the Oxfordshire “dinosaur highway” was created by Cetiosaurus or sauropods similar to Cetiosaurus. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

One of the World’s Most Important Dinosaur Sites

At the time the tracks were made, much of Britain was covered by a shallow sea. The Oxfordshire area formed part of a shallow tropical landscape. Mudflats and lagoons provided ideal conditions for preserving footprints. Consequently, the tracks survived for millions of years beneath layers of sediment.

Scientists continue to investigate the quarry. Therefore, further discoveries may yet emerge from this extraordinary site.  However, it is not the only site where long trackways of sauropod dinosaurs have been discovered.

Commenting on the on-going research, Mike from Everything Dinosaur stated:

“The Dewars Farm Quarry site is remarkable. Scientists think there are more footprints awaiting discovery. Hopefully, the site’s owners will continue to work closely with the researchers as well as Natural England to ensure that these fossils are preserved.”

Everything Dinosaur acknowledges the assistance of a media release from the University of Birmingham supplied in January 2025 in the compilation of this article.

The award-winning Everything Dinosaur website: Models of Dinosaurs.

Researchers have described a single dinosaur caudal vertebra (tail bone) from Denman Island (British Columbia, Canada).  It has been identified as an ornithomimosaur caudal vertebra. The fossil, thought to represent a bone from the middle part of the tail, is only the second dinosaur fossil identified from the Upper Cretaceous Nanaimo Group. In addition, it is the first definitive dinosaur fossil found in Canadian outcrops. Specifically, the caudal vertebra is from marine sediments of the Campanian-aged Cedar District Formation. The fossil discovery suggests that ostrich-like dinosaurs were present on the western margins of Laramidia.

A single dinosaur caudal vertebra similar to the fossil discovery. A tail bone ascribed to the Ornithomimosauria clade has been found in Upper Cretaceous deposits on Denman Island (British Columbia). Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

A Dinosaur Caudal Vertebra

The discovery of the single caudal bone is only the second reported occurrence of dinosaur fossils from the Upper Cretaceous Nanaimo Group. In 2015, we reported a partial theropod femur from Sucia Island (Washington State, USA). Interestingly, this bone also derives from the Cedar District Formation, but it is geologically older than the ornithomimosaur tail bone.

• Partial theropod femur (Washington State, USA) – 83.6 to 79.8 mya
• Mid-caudal ornithomimosaur vertebra (Denman Island, British Columbia, Canada) – 79.8 to 75.5 mya

mya = millions of years ago.

To read our blog post from 2015 about the partial theropod femur fossil discovery: Washington State’s First Dinosaur.

The Upper Cretaceous Nanaimo Group

The deposits of the Upper Cretaceous Nanaimo Group of Vancouver Island have been studied for decades. Numerous vertebrate fossils have been collected representing a diverse marine biota. For example, fossils of fish including sharks, pterosaurs, elasmosaurids and birds have been found. However, despite intensive collecting no dinosaur fossils had been discovered.

Writing in the journal “FACETS” researchers, Victoria Arbour (Royal British Columbian Museum), Timon Bullard (École Secondaire Esquimalt High School) and David Evans (Royal Ontario Museum) describe an isolated theropod caudal vertebra. The fossil was found in marine sediments of the Campanian-aged Cedar District Formation of Denman Island. This small island is located off the eastern coast of the much larger Vancouver Island.

Contemporaneous with Judith River and Two Medicine Formation Biotas

The bone resembles the tail bones of ornithomimosaurs. However, the specimen cannot be identified at the family level. It was likely transported from the western margin of North America to the east. The Nanaimo Group was deposited at least 37o miles (600 km) south of its present position, and this ornithomimosaur likely lived at a similar palaeolatitude to contemporaneous dinosaur faunas in the Two Medicine and Judith River formations in the Western Interior.

Ornithomimosaurs were probably feathered.  In addition, they had long necks, small skulls and lengthy tails. Analysis of the long and graceful hindlimbs suggests that these dinosaurs were fast runners. The caudal vertebra found on Denman Island is likely to have come from the middle part of the animal’s tail.

The image (above) is that of the recently introduced CollectA Deluxe Gallimimus model.  It is a popular figure with collectors and dinosaur fans.  Furthermore, it is one of very few models representing ornithomimosaurs available.

To view the CollectA Deluxe range of prehistoric animal models: CollectA Deluxe Prehistoric Animals.

The scientific paper: “An ornithomimosaur from the Campanian Cedar District Formation (Nanaimo Group) of Denman Island, British Columbia, Canada” by Victoria M. Arbour, Timon S. Bullard and David C. Evans published in FACETS.

For models of ornithomimosaurs and other dinosaurs: Theropod Models and Dinosaur Toys.

Palaeontologists have described a new species of microraptorine theropod from north-western China. Named Jian changmaensis, this small, feathered dinosaur probably glided on four wings. The fossil provides fresh insights into Early Cretaceous ecosystems and extends the known range of the Microraptorinae. The fossil material consists of an articulated partial left pectoral girdle and forelimb. It consists of a complete scapulocoracoid, humerus, radius, and ulna. The specimen number is GSGM-D050.

The fossil comes from the Lower Cretaceous Xiagou Formation of the Changma Basin (Gansu Province). These lake deposits date to the Aptian faunal stage. Researchers have collected more than one hundred bird fossils from this site. However, no non-avian dinosaur body fossils had been described until now. Jian is the first non-avian dinosaur body fossil from the Xiagou Formation of the Changma Basin.

Jian changmaensis life reconstruction. The new microraptorine theropod Jian changmaensis (left) attacks the early bird Gansus yumenensis (right) in what is now the Changma Basin of north-western China approximately 120 million years ago. Picture credit: illustration by Lewis LaRosa, colourised by Jão Canol.

Picture credit: Lewis LaRosa, colourised by Jão Canol

Jian changmaensis from the Xiagou Formation

The location is famous for the relative abundance of aquatic bird fossils. This assemblage is dominated by fossils of the pigeon-sized Gansus yumenensis. Classified as an ornithuran, G. yumenensis is thought to be a closely related to the ancestors of modern birds. Many of the specimens preserved in the fine-grained mudstones show soft tissue structures like feathers and webbing between their toes. This prehistoric bird was probably volant and capable of diving.

Scientists Suspected the Presence of a Predator

Intriguingly, palaeontologists had found examples of crushed bird bones and evidence of regurgitated remains, interpreted as undigestible pellets coughed up by a predator. Scientists speculated that a larger predatory animal must have hunted these ancient birds. However, direct fossil evidence proved elusive. Although far from complete, the limb bones preserve enough anatomical information to identify a new genus and species within the Dromaeosauridae family.  Specifically, phylogenetic analysis places Jian changmaensis within the Microraptorinae subfamily. This group contains small dromaeosaurids closely related to Microraptor. Members of this clade are famous for their feathered limbs and possible gliding abilities.

Holotype of Jian changmaensis, (GSGM-D050), an articulated partial left pectoral girdle (scapulocoracoid) and forelimb (humerus, radius, and ulna). Silhouette of generalised microraptorine dromaeosaurid theropod (courtesy Scott Hartman) showing skeletal elements preserved (A). Photograph of specimen as preserved, exposed primarily in dorsomedial (scapulocoracoid), caudodorsal (humerus), and dorsal (radius and ulna) views (B). Interpretive line drawing (C) of B. Photograph of scapulocoracoid and proximal end of humerus in caudodorsal view (D), showing supracoracoid fenestra and other structures. Interpretive line drawing (E) of D. Abbreviations: ac, acromion; bc, bicipital crest; C, coracoid; cr, caudal ridge; dep, dorsal epicondyle; dpc, deltopectoral crest; dr, dorsal ridge; ed, epicondylar depression; fs?, fossa for M. supinator?; H, humerus; hh, humeral head; lp, lateral process; ‘mb’, ‘medial bar’; op, olecranon process; R, radius; S, scapula; scb, scapular blade; scf, supracoracoid fenestra; sta, sternal articulation; U, ulna. Picture credit: Zhou et al.

Picture credit: Zhou et al

A Relative of Microraptor

The researchers surmise that Jian changmaensis probably possessed feathers on both its arms and legs. Therefore, it likely had four wing surfaces. This arrangement may have helped it glide through the forests of Early Cretaceous China. The discovery expands the known fossil record of the Microraptorinae into north-western China. In addition, the partial pectoral girdle indicates that J. changmaensis was much larger than Microraptor. It is one of the largest microraptorines known to science. The fossil material suggests an animal with a wingspan of around a metre to 1.2 metres. This suggests that Jian would have had a wingspan comparable in size to that of the Common Buzzard (Buteo buteo).

The PNSO Microraptor figure, new for 2020 swoops into view.

The picture (above) shows a model of Microraptor.  It is the PNSO Gaoyuan model.  Microraptor had feathers on its arms and legs, and it has been speculated that it was capable of gliding.

To view the range of PNSO prehistoric animal models in stock: PNSO Age of Dinosaurs Figures.

Similarities with the Famous Jehol Biota

Scientists noted striking similarities between the Changma Basin and the famous Jehol deposits of north-eastern China. Both regions contain microraptorine dinosaurs. Furthermore, both ecosystems included early birds. The Changma deposits contain abundant remains of Gansus yumenensis. Likewise, some Jehol localities are dominated by closely related early birds.

These similarities suggest that the two regions may have shared comparable environments. Such habitats are poorly represented at many other Jehol fossil sites.

The fascinating Jehol Biota: The Jehol Biota.

To read a blog post about a new tiny dromaeosaurid dinosaur from the Jehol fossil sites: New Dromaeosaurid from Liaoning Province (Jehol Biota).

First Non-avian Dinosaur from Changma

The discovery of Jian changmaensis marks an important milestone. It represents the first non-avian dinosaur body fossil reported from the Xiagou Formation. Moreover, the fossil demonstrates that small dromaeosaurids lived alongside numerous early birds. Consequently, scientists now have a better understanding of the biodiversity preserved within the Changma Basin.

Although only part of the skeleton is known, Jian changmaensis provides valuable information. The fossil helps researchers reconstruct the distribution and evolution of microraptorines.

In addition, the discovery highlights the importance of the Changma Basin. Future finds could reveal even more dinosaurs from these remarkable deposits.

Everything Dinosaur acknowledges the assistance of a media release from the Field Museum (Chicago) in the compilation of this article.

The scientific paper: “First non-avian theropod (Dromaeosauridae, Microraptorinae) from the bird-bearing Lower Cretaceous Xiagou Formation of the Changma Basin, Gansu Province, north-western China” by Ling-Qi Zhou, Matthew C. LaManna, Ashley W. Poust, Da-Qing Li, Hai-Lu You and Jingmai K. O’Connor published in the Annals of the Carnegie Museum.

The award-winning Everything Dinosaur website: Dinosaur and Prehistoric Animal Models.