A New Tiny Dromaeosaurid Ichnogenus Dromaeosauriformipes

Catching up with our reading of scientific papers over the weekend and our attention was caught by the description of tiny, two-toed prints from South Korea that reaffirm the growing conviction amongst scientists that some types of non-avian dinosaur were very small, not much bigger than sparrows. The footprints might be the smallest dinosaur tracks discovered to date.

Writing in the academic journal “Scientific Reports”, researchers from South Korea, in collaboration with colleagues from Australia, China, Spain and the USA, describe eighteen diminutive, didactyl tracks that are attributed to either juveniles or tiny adult dinosaurs that may have had a hip height of around five centimetres.

Dinosaur Tracks

The tracks have been ascribed to a new ichnogenus – Dromaeosauriformipes (D. rarus), the name translates as similar in form to Dromaeosauripus*, small and rare.

A Life Reconstruction of the Recently Described Dromaeosauriformipes rarus

Picture credit: Anthony Romilio (Queensland University)

Dromaeosauripus* is an earlier described ichnogenus representing a larger set of tracks, three ichnospecies have been assigned to this ichnogenus to date.

Dromaeosauriformipes rarus – A Microsaur

The tracks were originally found by Professor Kyung Soo Kim (Chinju National University of Education, South Korea), one of the authors of the paper.  The tracks come from a series of remarkable multiple track-bearing horizons from the JinJu Formation of the south-eastern part of the Korean peninsula.  The deposits represent lakeshore sediments (Lower Cretaceous) and date from approximately 115 million years ago (Aptian faunal stage).

The trackways criss-cross an area that was once soft mud and the eighteen tracks are interpreted as representing an estimated 6 to 10 individual trackways possibly made by a similar number of different individuals.  It is suggested that the prints could resemble a Microraptor-like dromaeosaurid (microraptorine).  Some scientists have suggested that Microraptor was piscivorous (fish-eating).  The tracks found in association with a lakeshore, could represent a Microraptor-like dinosaur searching for food, but equally the tracks could represent other types of activity.

Microraptorine Activity in Lakeshore Setting (D. rarus)

Picture credit: Scientific Reports  – original photo (A) by Professor Kim

The picture shows (A), the seven print trackway of the diminutive dromaeosaurian Dromaeosauriformipes rarus.  A line drawing of the trackway is shown (B) and (C) shows a line drawing of the track-bearing surface showing two tiny tracks but trackway 2 has a much bigger stride length indicating greater velocity than recorded in trackway 1.  Pictured below are seven photographs recording the individual prints.

One of the authors of the scientific paper, Dr Anthony Romilio from the University of Queensland stated:

“They are the world’s smallest dinosaur tracks.  These new tracks are just one centimetre in length, which means the dinosaur that made them was an animal you could have easily held in your hand.”

Hatched from Tiny Eggs

To estimate the size of the dinosaur that made the tracks, the team measured the footprint length and multiplied the value by 4.5 to get an approximate hip height.  The maker(s) of these tiny tracks would have had a hip height of around five centimetres.  The two-toed prints are definitively dromaeosaurid, as the second toe, the killing claw, is held off the ground as the dinosaur moves about, hence just two toe impressions are left behind in each print.  In the paper, the scientists comment upon the fact that these tiny dinosaurs must have hatched from very small eggs.

Back in 2016, Everything Dinosaur featured the discovery of tiny three-toed theropod prints that had been discovered in Lower Cretaceous sediments from south-western China.  As a result, a new “tiny-saurus” ichnogenus was erected – Minisauripus.  The South Korean prints assigned to Dromaeosauriformipes rarus are even smaller.

To read about the earlier discovery of tiny dinosaur footprints from south-western China: Minisauripus – the Smallest Dinosaur Known?

Professor Kyung Soo Kim commented that the lake deposits at this location created ideal conditions that allowed for the preservation of tiny footprints, rarely found anywhere else in the world.

Professor Kim added:

“In addition to tiny dinosaur tracks, we have footprints made by birds, pterosaurs, lizards, turtles, mammals, and even frogs.”

Comparing the Tracks of Dromaeosauriformipes rarus with Dromaeosauripus jinjuensis

Picture credit: Scientific Reports

The image above compares illustrations of the tracks of  Dromaeosauriformipes rarus to the size of the trackways assigned to Dromaeosauripus jinjuensis.  Note the raised second toe which produces the characteristic two-toed print.  D rarus tracks suggest a much smaller dromaeosaur produced the tracks.  The image in the upper left is a colour photogrammetric image of Trackway 1 which helps to define track depth and characteristics.  This is compared to the photogrammetric colour image showing the type trackway of D. jinjuensis (right).

Are These Tiny Dinosaurs or Newly-Hatched Dinosaurs from a Much Larger Species?

The tracks support the idea that there may have been lots of very small dinosaurs, but their small bones would not necessarily be preserved in the fossil record so there may be a bias towards larger members of the Dinosauria due to their greater preservation potential.  However, if conditions are right, then diminutive prints and tracks can be preserved, providing tantalising evidence to support the idea of a much more diverse Theropoda then previously thought.  The researchers raise two fascinating questions in their published paper:

1. What is the size range of “raptor” tracks based on footprints or inferred from skeletal remains?
2. How might diminutive tracks of juveniles be distinguished from the prints made by tiny adults (microsaurs)?

Co-author Dr Martin Lockley (University of Colorado Denver’s College of Liberal Arts and Sciences), suggests that these tiny trackways could represent the prints of adult dinosaurs.

He commented:

“Rapidly growing dinosaurs don’t remain small or leave little footprints for very long.  But of all of the footprints we’ve found of the Minisauripus, none grew larger than one inch; a preponderance of evidence of a small species and not babies.  There’s a chance that we just found something smaller.”

For models and replicas of “raptors” and other prehistoric animals: Beasts of the Mesozoic Models and Figures.

Cretoxyrhina Tooth Embedded in the Neck of a Pteranodon

There has been quite a lot of media coverage this week, following the publication of a scientific paper that described the interaction between a shark from the Western Interior Seaway (Cretoxyrhina mantelli) and a pterosaur (Pteranodon).  A single tooth from the shark, was discovered wedged against the fourth cervical vertebra (fourth bone in the neck), of the flying reptile.  The association of the tooth and its proximity to the vertebra suggests that the preservation of bone and tooth together was more than mere coincidence.  The specimen is evidence of a Cretoxyrhina shark biting a Pteranodon.

Evidence for a Shark Bite on the Neck of a Pterosaur

Picture credit: (A) Stephanie Abramowicz, courtesy Dinosaur Institute, Natural History Museum of Los Angeles County, (B) David Hone

The Pteranodon specimen is housed in a glass case at the Los Angeles Museum of Natural History, so the researchers, David Hone (University of London), Mark Witton (Portsmouth University) and Michael Habib (University of Southern California), had difficulty in obtaining direct access to the fossils.  However, undeterred they made measurements of the embedded fossil tooth and it is estimated to be 24 mm high (root plus crown) and its morphology suggests that it came from a well-known lamniform shark from the Western Interior Seaway – C. mantelli. 

Based on the tooth dimensions, the shark is estimated to have been around 2.5 metres long, big, but not as large as some Cretoxyrhina mantelli specimens, this species of Late Cretaceous shark is believed to have reached lengths of around seven metres, making it larger than the extant Great White (C. carcharias).

Identifying the Attacker

Teeth associated with lamniform sharks are particularly common in marine deposits associated with the Western Interior Seaway.  The morphology of the tooth suggests that this tooth came from Cretoxyrhina mantelli and this fossil specimen (LACM 50926), is the first documented occurrence of this large shark interacting with any type of flying reptile.

Typical Teeth Morphologies Associated with C. mantelli

Picture credit: David Hone

Evidence of Cretoxyrhina Biting Pteranodon

It is not possible to state categorically, whether the fossil specimen (LACM 50926), is evidence of predation or whether the shark took a bite out of a Pteranodon carcase.  Several examples of Cretoxyrhina spp. feeding traces are known on the fossilised remains of other vertebrates from the Western Interior Seaway.  In addition, there is evidence to suggest other types of fish, including sharks, consumed Pteranodon.  This is the first example of an interaction between Cretoxyrhina and “toothless wing”.

A Close-up View of the Neck Bone and the Shark Tooth

Picture credit: David Hone

Spectacular Palaeoart

One of the co-authors of the paper, Mark Witton, is a highly respected palaeoartist, as well as an authority on the Pterosauria.  He has produced a stunning illustration of a Cretoxyrhina shark leaping out of the water as it bites the neck of a Pteranodon.

A Large Pteranodon Meets Its End in the Jaws of a Cretoxyrhina Shark

Picture credit: Mark Witton

Pteranodon is widely believed to have foraged for small fish and other aquatic prey by alighting on the water and dip-feeding.  Once on the surface of the sea, it would have been within the reach of predatory sharks, although whether the breaching Cretoxyrhina portrayed by Mark Witton accurately depicts an attack by the shark on a pterosaur is open to speculation.  However, the image is visually stunning and as marine seabirds today are actively predated by sharks, an example being Tiger sharks attacking fledgling albatross chicks, such a dramatic scene could have taken place on the waters of the Western Interior Seaway.

However, the tooth in association with the cervical vertebra could have resulted from the scavenging of a pterosaur carcase.

Not All That it Seems

The Pteranodon fossil in the display case is not all that it seems.  Like many museum specimens, it is a composite, it is made up of bones from several animals to help make the skeleton more complete.  Furthermore, part of the fossil display is genuine, but numerous elements have been reconstructed to replace absent parts.

The authors note that the preservation quality and size of the vertebrae correspond well to the other elements (including the forelimb bones) and this implies that LACM 50926 may represent much of a skeleton.  However, the absence of both anteriormost and posterior cervical vertebrae means no anatomical continuity links the 50926 vertebrae with the rest of the material and subsequently, their association to the rest of the skeleton cannot be stated confidently.

A Link Between a Feeding Cretoxyhina and a Pteranodon

With all this said, LACM 50926 is the first palaeoecological link between a feeding Cretoxyrhina mantelli and a Pteranodon.  Such evidence of interactions like this are very rare in the fossil record.  Pteranodon seems to have been a relatively common flying reptile, it makes up some 97% of the Niobrara Formation pterosaur fossil finds.  Sharks feeding on large pterosaurs such as Pteranodon may have been a more frequent occurrence, but the hollow bones of these flying reptiles may have broken quite easily when subjected to the biteforce of a shark and so the likelihood of any fossil evidence being preserved would be diminished.  Chances are the evidence of such interactions just got consumed.

The scientific paper: “Evidence for the Cretaceous Shark Cretoxyrhina mantelli feeding on the pterosaur Pteranodon from the Niobrara Formation” by David W. E. Hone, Mark P. Witton and Michael B. Habib and published in the open access journal PeerJ.

Visit the Everything Dinosaur website: Everything Dinosaur.

Saltriovenator zanellai – One Tonne Giant and Oldest Ceratosaurian Described to Date

Scientists from Natural History Museum of Milan and the Geological Museum of Bologna (Museu di Storia Naturale di Milano and the Museo Geologico), have published a scientific paper on a new predatory dinosaur from the Lombardy region of northern Italy.  This new species was a giant, weighing around a tonne and measuring approximately 7.5 metres in length. It lived some 25 million years before other known big predatory dinosaurs evolved and examination of the fossilised bones suggest that this dinosaur was still growing when it died.  The dinosaur has been named Saltriovenator zanellai and it is the largest theropod described to date from the Early Jurassic (Sinemurian faunal stage).

A Life Reconstruction of the Newly Described Ceratosaurian Theropod Saltriovenator zanellai

Picture credit: Davide Bonadonna

A Chance Discovery

Saltriovenator was discovered by chance in the summer of 1996 by amateur fossil collector Angelo Zanella, whilst exploring fossil rich limestone layers associated with a marble quarry near the town of Saltrio (Varese Province, Lombardy).  The strata containing the fossilised remains represent marine deposits and explosives used in the quarrying process had broken up the fossil bearing layer into hundreds of pieces.  In total, 132 fossil pieces were excavated from the site, the remains of a single animal.

The bones show feeding traces from fish and borings from marine invertebrates.  The palaeontologists writing in the on-line academic journal “PeerJ” suggest that the carcase was washed out sea and stayed on the seabed for some time, permitting the scavenging to take place.

Fossil Elements Used to Confirm Ceratosaurian Affinity with a Skeletal Drawing

Picture credit: G. Bindellini, C. Dal Sasso and M. Zilioli and M. Auditore

The picture above shows key fossils that helped to classify Saltriovenator as a member of the Ceratosauria clade, it is the oldest ceratosaur described to date.

Key

A, B, C = views of the right humerus.

D = left scapula.

E = right scapular glenoid and coracoid.

F = furcula (wishbone).

G = single tooth from the anterior portion of the lower jaw.

I = partial left humerus, the circular depressions represent borings made by marine invertebrates feeding on the carcase.

J, L, N = views of the right second metacarpal (finger bone).

K, M, O, = views of the right second digit.

P-T = views of the right third digit.

U = distal tarsal IV.

V, X = third right metatarsal views.

W, Y = second right metatarsal views.

Z = reconstructed skeleton of Saltriovenator with identified fossil elements shaded red.

Scale bars: 10 cm in (A)–(E), (I), and (U)–(Y); two cm in (F), and (J)–(T); one cm in (G).

A Skeletal Reconstruction of Saltriovenator zanellai 

Picture credit: M. Auditore

The First Jurassic Dinosaur from Italy

Saltriovenator is the first dinosaur to be described from fossils found in the Italian Alps.  It is the first dinosaur from the Jurassic Period to have been found in Italy and the country’s second theropod, the first being Scipionyx samniticus which lived during the Early Cretaceous and at just over two metres in length, was considerably smaller than S. zanellai.  A study of growth rings found in a cross-sectional analysis of the fossil bones indicates that the dinosaur was around twenty-four years of age when it died.

It was still growing, albeit slowly, so the maximum size of this predator is not known, although at an estimated 7.5 metres long, it was considerably bigger than any other theropod from the Early Jurassic described to date.

CollectA have produced a replica of Saltriovenator.

To view this model range: CollectA Deluxe Prehistoric Life Models.

Saltriovenator zannellai – A Mosaic of Basal and More Advanced Theropod Features

Saltriovenator exhibits a mosaic of features seen in four-fingered theropods and basal tetanuran dinosaurs.  The fossilised finger bones indicate that this dinosaur had a fully functioning four-fingered hand, well-adapted for grasping and coping with struggling prey.  Later ceratosaurs had only three fingers on each hand.  Study of the finger bones will help scientists to understand better the evolutionary relationships between the four-fingered cilophosaurs, ceratosaurs and later types of theropod such as the allosaurs with their atrophied hands.

Views of the Pectoral Girdle and the Right Hand of Saltriovenator zanellai

Picture credit: M. Auditore

Commenting on the importance of this fossil discovery, one of the authors of the scientific paper, Dr Andrea Cau (Museo Geologico), stated:

“The grasping hand of Saltriovenator zanellai fills a key gap in the theropod evolutionary tree: predatory dinosaurs progressively lost the pinkie and ring fingers and acquired the three-fingered hand which is the precursor of the avian wing.”

A spokesperson from Everything Dinosaur commented:

“The evolution of large, powerful predatory dinosaurs at the very beginning of the Jurassic, may have been a factor in the evolution of bigger and bigger herbivorous dinosaurs such as the sauropods.  Think of it as an evolutionary arms race as carnivores got bigger, selection pressure was put on herbivores to become bigger and stronger themselves in order to avoid predation.”

Visit the Everything Dinosaur website: Everything Dinosaur.

Nanjinganthus dendrostyla – Putting Back Flowering Plants by 50 Million Years

When did flowering plants (angiosperms) evolve?  That has been a puzzling question, one that has taxed the minds of leading scientists for more than 200 years.  Genetic studies indicate that the diverse and widespread angiosperms have an ancient lineage, but the fossil record does not support this idea.  Fossils of delicate flowers are very rare and the oldest known, date from the Early Cretaceous.  Time for the fossil record to catch up with the announcement of the discovery of a plant that produced flowers some 174 million years ago, during the late Early Jurassic (Toarcian stage).

Specimens of the Newly Described Early Jurassic Flowering Plant Nanjinganthus dendrostyla

Picture credit: (NIGPAS)

The newly described plant has been named Nanjinganthus dendrostyla and it comes from the South Xiangshan Formation (Nanjing, eastern China), which has been studied extensively since the turn of the century and is famous for its abundant plant fossils, which up until now had consisted of cycads, ferns, ginkgoes and horsetails.  Researchers from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS), have been able to identify the earliest known examples of a flowering plant, one that predates most of the angiosperm fossil material by around 50 million years.

Fossils Catching Up with the Molecular Clock

Analysis of the genetic data contained in living plant taxa indicates that plants probably evolved earlier than previously thought.  In a study published in February, researchers from the Chinese Academy of Sciences as well as Bristol University, mapped the genetic make-up of 644 types of plant and concluded, based on molecular dating, flowering plants (angiosperms), probably evolved sometime between the Late Permian and the Late Jurassic.

To read Everything Dinosaur’s article summarising this research: When Did Flowers Evolve?

Lots of Fossil Specimens to Study

The researchers studied a total of 264 specimens representing 198 individual flowers preserved on 34 slabs of stone.  The scientists had the luxury of working on so many examples of the same fossil organism.  They produced numerous high resolution images of the flowers allowing the features of N. dendrostyla to be revealed in great detail.  With so many fossil specimens, the scientists were able to exclude other plant types and confirm that the fossils do indeed represent an angiosperm.

A Life Reconstruction of the Earliest Flowering Plant Described to Date

Picture credit: (NIGPAS)

Commenting on the significance of the study, one of the researchers Wang Xin (NIGPAS), stated:

“The origin of angiosperms has long been an academic headache for many botanists.  Our discovery has moved the botany field forward and will allow a better understanding of angiosperms.”

Identifying a Key Feature of Angiosperms

The scientists were able to identify the presence of fully enclosed ovules in the fossilised flowers.  These are the precursors of seeds before pollination.  The reconstructed flower was found to have a cup-form receptacle and ovarian roof that together enclosed the ovules/seeds.  This botanical feature confirms that Nanjinganthus dendrostyla is definitely an angiosperm.

Numerous Examples of N. dendrostyla Preserved in Siltstone

Picture credit: (NIGPAS)

Fossil Flowers in Jurassic Rocks

Discoveries of angiosperm-like fossils have been reported from Jurassic rocks before.  In January (2018), Everything Dinosaur published an article on the remarkable discovery of fossilised wing scales from butterflies and moths that lived during the Late Triassic.  This discovery challenged the theory of co-evolution between flowering plants and pollinating insects such as members of the Lepidoptera.

To read Everything Dinosaur’s article about this: Ancient Butterflies Flutter By.

The morphological features of Nanjinganthus distinguish it from other specimens and suggest that it is a new angiosperm genus.

The scientists hope to determine whether angiosperms are monophyletic (all flowering plants share a common ancestor).  If this is the case and Nanjinganthus is one of the earliest of all the flowering plants, then these fossils represent a stem group giving rise to all later species.  Angiosperms could also be polyphyletic, (a group descended from more than one common ancestor), meaning Nanjinganthus represents an evolutionary dead end and subsequently, it did not give rise to later types of flowering plant.

Visit the Everything Dinosaur website: Everything Dinosaur.

Volgatitan simbirskiensis – Early Cretaceous Leviathan

A team of palaeontologists from Russia have announced the discovery a new genus of titanosaur from fossil bones found on the western bank of the River Volga close to the village of Slantsevy Rudnik in Ulyanovsk Oblast (western Russia).  The dinosaur has been named Volgatitan simbirskiensis, it is one of a trio of sauropods recently described from Russian deposits, the others being Tengrisaurus starkovi and Sibirotitan astrosacralis, both of these herbivorous, long-necked dinosaurs were named and described in 2017.

Volgatitan simbirskiensis

V. simbirskiensis has been named based on the study of seven tail bones (caudal vertebrae), the first of which were discovered following a rock fall on the Volga River back in 1982.

A Scale Drawing of Volgatitan simbirskiensis Showing the Anatomical Position of the Known Fossil Material

Picture credit: St Petersburg State University

For models and replicas of titanosaurs and other sauropods: Dinosaur and Prehistoric Animal Models.

Tell Tale Tail Bones

Fortunately, for the Sauropoda, vertebrae can be quite diagnostic when it comes to ascribing new genera.  Titanosaurs for example, have distinctive shaped caudal vertebrae, especially towards the base of the tail (proximal end close to the hips).  The proximal tail bones of titanosaurs are procoelous (pronounced pro-see-lus), that is, the front face of the bone is concave and the opposite face, the bit that points in the direction of the tail, is bulbous (convex).

Views of the Holotype Caudal Vertebra of V. simbirskiensis

Picture credit: Alexander Averianov and Vladimir Efimov

The photograph (above) shows the holotype caudal vertebra of Volgatitan simbirskiensis in right lateral (A), anterior (B), left lateral (C), posterior (D), dorsal (E) and ventral (F) views.

Dinosaur Nomenclature

The dinosaur’s genus honours the Volga River, whilst the trivial name is in honour of the old name for the city of Ulyanovsk (Simbirsk), after all, the fossils were found just three miles to the north of the city.  Aleksandr Averianov, one of the authors of a scientific paper describing this new titanosaur, published in the journal “Biological Communications”, explained that the description of dinosaur taxa in recent years has become possible due to the progress in understanding the anatomy and phylogeny of the Dinosauria.  Furthermore, the recent Russian sauropod discoveries have allowed scientists to learn more about how these species of lizard-hipped reptiles had lived and developed.

Based on comparisons with the fossilised bones of more complete titanosaurs, Volgatitan is estimated to have been around 16 metres long.  Fully fused neural arches on the centrum from the most proximal of the caudal vertebrae indicate that the bones came from a fully, mature adult animal.

It had been thought that titanosaurs evolved in the Southern Hemisphere, specifically South America, with some taxa migrating into North America, Asia and Europe later in the Cretaceous.  However, the formal description of Volgatitan coming so soon after the naming of Tengrisaurus from the Early Cretaceous of Transbaikal Region, suggests that Early Cretaceous titanosaurs were more widely distributed.  It is possible to postulate that important stages in the evolution of this group of long-necked dinosaurs may have taken place in eastern Europe and Asia.

For an article published in 2017 about the discovery of a new species of African titanosaur: Shingopana songwensis from south-western Tanzania.

To read about an Australian titanosaur discovery made in 2017: Titanosaur “Judy” from the Outback.