Bucking the Trend – Luskhan itilensis

Writing in the academic journal “Current Biology”, a team of international scientists which includes Roger Benson and Valentin Fischer (Department of Earth Sciences, Oxford University), have published details of a new species of ancient marine reptile, a short-necked plesiosaur that bucks the trend for the Pliosauridae.  Instead of being an apex predator, roles traditionally applied to monstrous animals such as Kronosaurus, Liopleurodon, the recently described (2013), Megacephalosaurus and Pliosaurus, the first of these large-bodied, big-skulled reptiles to be scientifically described, this new species probably hunted an entirely different sort of prey.

An Illustration of the Newly Described Pliosaurid – Luskhan itilensis

An illustration of the pliosaurid Luskhan itilensis from Russia.

Picture credit: Andrey Atuchin

Feeding on Squid and Small Fish?

The rostrum of the newly described, highly unusual pliosaurid, is very narrow and it resembles the jaws of extant fish-eaters today such as the rare Gharial and the almost equally endangered (or, in the case of the Yangtze River Dolphin functionally extinct*) River Dolphins.

The Yangtze River Dolphin (Baiji)

The skull of a gharial from the Grant Museum of Zoology (London).  Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

The long snout suggests that this newly described pliosaur, named Luskhan itilensis specialised in catching small fish and squid.  Many palaeontologists suggest that the Pliosauridae were not capable of diving to great depths and they were confined to the Epipelagic zone (from the ocean surface to a depth of approximately 200 metres), whereas Sperm Whales, the largest toothed predators today, are capable of diving to much greater depths in pursuit of squid and other prey.

“Master Spirit of the Volga”

The fossilised remains of the marine reptile were initially discovered in the autumn of 2002 by one of the co-authors of the scientific paper Gleb N. Uspensky (Natural Science Museum, Ulyanovsk State University, Ulyanovsk, Russia).  The material comes from the right bank of the Volga, near to the town of Ulyanovsk, the bedding plane from which the fossil material, including a 1.5-metre-long skull was excavated, dates from the Lower Cretaceous (Hauterivian faunal stage).

Luskhan itilensis

Pliosaurids (Pliosauridae) are a family within the Order Plesiosauria.  They typically have large skulls, powerful jaws, a rigid body and propelled themselves through the water using their four flippers, although recent studies have shown that only the front pair of flippers were involved in propulsion.  The flight of the Plesiosauria: The Plesiosauria, Penguins and Underwater Flight.  The Plesiosauria swam in a unique way, not found in other vertebrates and now it seems that one group, the Pliosauridae, adapted to a wider range of ecological niches than previously thought.

Luskhan itilensis (the name means “Master Spirit of the Volga”), very probably did not specialise in hunting other marine reptiles, it filled a different role in the marine ecosystem of the Early Cretaceous.

Commenting on the significance of the discovery, Dr Valentin Fischer (Oxford University and lecturer at the University of Liège), the lead author of the study, stated that the specialised jaw:

“Is the most striking feature, which suggests that Pliosaurs had colonised a much wider range of ecological niches than previously thought.”

Not All Pliosaurs were Apex Predators

A close-up view of the pliosaur that is suspended above the ground floor at the Bristol Museum and Art Gallery (Bristol, England). The life-size replica was nicknamed “Deadly Doris”. Picture credit: Everything Dinosaur

Picture credit: Everything Dinosaur

Postcranial Plasticity (Repeatedly Evolving Long and Short-Necked Body Plans)

Of all the types of marine reptiles that evolved during the Mesozoic, the Plesiosauria was one of the most successful, having a fossil record of some 140 million years or so.  During their long evolutionary history, plesiosaurs repeatedly evolved long and short-necked body plans.

In general terms, the Plesiosauria can be split into two sub-groups, the short-necked Pliosauridae and the longer-necked plesiosaurs, although this is an over simplification.  The discovery of Luskhan, further muddies the evolutionary waters somewhat, as its skull shows affinities to the very distantly related Polcotylidae.  A family of plesiosaurs, on the long-necked lineage side of the family tree, which evolved into fast-swimming fish hunters.

Study of the skull of L. itilensis indicates an evolutionary convergence of the cranial structure of typical polycotylids such as Dolichorhynchops.  Distantly related animals evolve and ultimately resemble one another because they occupy similar ecological niches, such as the same hunting and feeding strategies.

The researchers conclude that the discovery of Luskhan itilensis demonstrates the ecological diversity of the Pliosauridae and reveals that these marine reptiles had a more complicated evolutionary history than their simple depiction as apex predators suggests.

CollectA Models Help Demonstrate Cladistic Relationships Within the Plesiosauria

Cladistic relationships in the Plesiosauria (simplified and not to scale).

Picture credit: Everything Dinosaur with the utilisation of an illustration by Andrey Atuchin

The picture above shows a simplified view of the taxonomic relationships between members of the Plesiosauria.  The length of the lines do not relate to geological age and the images of the animals are not to scale.

CollectA Prehistoric Life and Deluxe replicas have been used to illustrate the cladogram.  To view the range of marine reptile models available from Everything Dinosaur: CollectA Deluxe Prehistoric Life Models.

CollectA Age of Dinosaurs Popular models: CollectA Prehistoric Life Figures.

The researchers conclude that the apex predator niche associated with the Pliosauridae does not necessarily reflect the diversity of this marine reptile family and that the pliosaurs repeatedly evolved long-jawed, specialist fish and squid catchers during their extensive evolutionary history.

* Functionally extinct – so few animals that there is no viable breeding population.

The Scientific Paper: “Plasticity and Convergence in the Evolution of Short-Necked Plesiosaurs” by Valentin Fischer, Roger B.J. Benson, Nikolay G. Zverkov, Laura C. Soul, Maxim S. Arkhangelsky, Olivier Lambert, Ilya M. Stenshin, Gleb N. Uspensky, Patrick S. Druckenmiller.

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Owl Creek Ceratopsid Tooth and Palaeoenvironment Implications

Yesterday, team members at Everything Dinosaur published an article on the discovery of a single fossil ceratopsid tooth. It had been found in Union County (Mississippi).  This discovery, the first evidence of a dinosaur from the Owl Creek Formation, has implications for the way in which palaeontologists perceive the ecosystems that existed on the ancient landmasses of Laramidia and Appalachia.

Museum Specimen 7969- The Ceratopsid Tooth

Horned dinosaur tooth discovered in Mississippi.

Picture credit:  Mississippi Museum of Natural Science (MDWFP)

To read yesterday’s article: Ceratopsid Tooth Paper Published (Part 1).

Why So Few Horned Dinosaur Fossils Found in Marine Sediments?

Palaeontologists know that during the latter stages of the Cretaceous, there were many different types of horned dinosaur (ceratopsian).  Lots of fossil evidence has been discovered in western North America and a myriad of different forms have been described, particularly over the last ten years or so.  The likes of Triceratops may have first been described back in the late 1880s but so many different horned dinosaur genera have been established in recently times, that numerous vertebrate palaeontologists refer to the last decade as the “Golden Age of Horned Dinosaur Discoveries”.

New Ceratopsian Faces Since 2007

Illustrations of different horned dinosaurs that have been named since 2006.

Picture credit: Everything Dinosaur with artwork from Julius Csotonyi, Danielle Dufault and the Canadian Museum of Natural History/Andrey Atuchin

Despite all these horned dinosaur fossil discoveries, the Owl Creek Formation tooth, is one of only a handful of North American ceratopsian fossils which have been found associated with marine strata.  The question is why?

Duck-billed Dinosaur Fossils in Marine Sediments

Compared to other types of Late Cretaceous dinosaur – ceratopsids, theropods, ankylosaurids, et al, hadrosaur fossils are the most common dinosaur fossils to be found in marine rocks laid down towards the end of the Cretaceous.  Duck-billed dinosaur fossils in marine sediments, are hardly what you would call abundant, but in relation to other large, obviously terrestrial dinosaurs, hadrosaur fossils are more numerous in those rocks associated with having been laid down under the sea.

Although the fossil record shows a degree of bias, dinosaurs such as some of the smaller theropods and the Pachycephalosaurs may be under-represented for example, this still does not explain why, compared to the hadrosaurs, the almost equally specious and abundant horned dinosaurs don’t show up in marine deposits.  Ceratopsians may have preferred slightly different habitats than the hadrosaurs.  Research undertaken in 2010 (Eberth), suggested that most of the horned dinosaur fossil remains were associated with lake, alluvial or coastal plain habitats, at least amongst the Ceratopsidae family.

Ceratopsians Such as Triceratops May Have Preferred Different Habitats Compared to Hadrosaurs

Ceratopsian habitats highlighted by the CollectA Deluxe Triceratops horridus.

The picture (above) shows at CollectA Deluxe Triceratops model.

To view the CollectA Deluxe range: CollectA Deluxe/Supreme Figures.

The alluvial, low-lying wetland areas are strongly associated with river channels and these specific areas can be divided into two distinct parts.

1. The riparian influenced part – the river and the river/channel margins.
2. The floodplain – areas not adjacent to the river or the channel margins but flooded by the river when the river burst its banks.

Horned Dinosaurs Associated with Floodplains

Put into simple terms, dinosaurs such as Triceratops have left fossils associated with floodplain (muddy) deposits, whereas, duck-billed dinosaurs such as Edmontosaurus fossils are more associated with fluviatile (sandy) deposits.

If transport along river channels are the most common cause of “bloat and float” carcases, then, the lack of horned dinosaur fossils in marine sediments could be explained by ceratopsids, preferring to live on those parts of the floodplain, not very near to the river.  They may have had a preference for habitats outside of the riparian zones.

A Hadrosaur Corpse Floating Out to Sea (Bloat and Float Scenario)

An artist’s illustration of the duck-billed dinosaur carcase washed out to sea.

Picture credit: Masato Hattori

Visit the website of Everything Dinosaur: Everything Dinosaur.

Paper on the First Reported Horned Dinosaur Tooth from Eastern North America Published

In July 2016, Everything Dinosaur team members reported the discovery of a single tooth from a horned dinosaur in North America.  Given the dental batteries that these herbivorous dinosaurs possessed, that teeth, being extremely hard, stand up well to the fossilisation process and given the number of new North American ceratopsid species named in the last decade, this fossil find might not sound that surprising.

It’s not really about what was found, but where it was found, as the fossil tooth is the first horned dinosaur tooth to come to the attention of the scientific community from the eastern part of the United States.  To a palaeontologist this is a big deal, a very big deal indeed!

Views and Accompanying Computer Generated Images of the Single Tooth

Various views of the horned dinosaur tooth (Own Formation, northern Mississippi).

Picture credit: PeerJ

To read Everything Dinosaur’s earlier article about the ceratopsid tooth fossil find: Horned Dinosaur Tooth Discovered in Northern Mississippi.

North America in the Late Cretaceous – A Tale of Two Landmasses

A variety of different types of horned dinosaur evolved in the western part of North America during the Late Cretaceous (Campanian faunal stage through to the Maastrichtian faunal stage).  However, during this period in Earth’s history, the landmass we now know as North America looked very different.  The continent was split into two parts, by a large, shallow sea (Western Interior Seaway).  At its fullest extent, this shallow sea stretched from the Gulf of Mexico, through the United States and Canada to the Arctic circle.

Size estimates vary, but it has been suggested (U.S. Geological Survey), that at its maximum, the sea was between 1,900 and 3,000 miles long between 600 to 1,000 miles in diameter.  Bordering the sea in the west was the long, narrow strip of land – Laramidia, whilst to the east, the landmass called Appalachia could be found.  Sea levels rose and fell over this period, eventually the Western Interior Seaway contracted, retreating south as plate movements pushed up the landmasses.  At the time of the dinosaur extinction, this once great area of tropical sea was reduced to a strip of water around the Gulf of Mexico, covering parts of the south-western USA.

Horned Dinosaurs Migrated from Laramidia to Appalachia

The dinosaur tooth, a single fossil specimen from the right side of the lower jaw (right dentary), was discovered by George Phillips, (curator of Palaeontology at the Mississippi Museum of Natural Science), as he explored a stream bed in Union County (Mississippi), that is known to yield marine fossils that date from the very end of the age of dinosaurs (Maastrichtian faunal stage).

The tooth was found in association with a mosasaur tooth, ammonite remains, brachiopods and other fossils.  Based on the stratigraphic evidence and the fossil assemblage associated with the tooth, the authors of the scientific paper, published in PeerJ, conclude that this tooth provides evidence that at some time during the very Late Cretaceous horned dinosaurs were able to migrate from Laramidia to Appalachia over a land bridge.

George commented:

“A land bridge before the end of the Cretaceous could have allowed horned dinosaurs to migrate or disperse through Texas or Arkansas, right before they were all killed in the calamity [a reference to the K/Pg impact event].”

Chasmosaurines Went East

A potential horned dinosaur migration route into eastern North America.

Picture credit: PeerJ with additional annotation by Everything Dinosaur

The picture shows two views of North America in the Late Cretaceous (A) around 73.5 million years ago (mya) and (B) around 68 million years ago (mya).  The authors suggest that horned dinosaurs were able to migrate eastwards from Laramidia into the Mississippi Embayment (Miss Emb), area of Appalachia.  Only Chasmosaurine horned dinosaurs are shown migrating into Appalachia (B).  The identity of the horned dinosaur to which the tooth belonged, is unknown, but if the land bridge existed towards the very end of the Cretaceous, then by this date centrosaurine dinosaurs may well have become extinct in North America.  No fossils of ceratopsids assigned to the Centrosaurinae clade have been found in rocks dating from the Late Maastrichtian.

A Typical Ceratopsian Tooth

A typical tooth of a ceratopsian with its two distinct dental roots. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

The picture above shows a typical ceratopsian tooth, from the Chasmosaurine Triceratops.  The fossil tooth from the Owl Creek Formation is the first evidence of dinosaurs to have been found in this formation, (the tooth is the first large, terrestrial animal fossil to have been found in the very well-known and thoroughly explored Owl Creek Formation).  It shows the typical ceratopsid tooth features, including the double root, and a prominent, blade-like carina (serrated edge).

The specimen (MMNS VP-7969), shows little sign of wear so it is unlikely that this fossil had been transported a great distance from where it was found.  It is tantalising to think, that perhaps, a little further upstream more horned dinosaur fossils are awaiting discovery, yet to be exposed by erosion.

Not Reworked and No Floating Carcase from Laramidia

The researchers reject the idea that the tooth has ended up in the stream bed having been eroded out of other rocks and re-deposited in the Owl Creek Formation.  The tooth is too pristine and therefore reworking from notably older Cretaceous-aged rocks is rejected.  In addition, the authors of the paper, Dr Andrew Farke (Raymond M. Alf Museum of Palaeontology, Claremont, California) and George Phillips, discount the idea that the tooth came from a carcase of a horned dinosaur that floated across from Laramidia.

The tooth, they postulate, provides evidence of a land bridge and that at least one kind of dinosaur migrated eastwards to populate the other half of the North American landmass.

A Model of the Late Cretaceous Horned Dinosaur Triceratops (T. horridus)

The Nanmu Studio Heavy Lance Triceratops (tricolor version) dinosaur model (in lateral view).

Picture credit: Everything Dinosaur

To view the range of ceratopsian figures in stock at Everything Dinosaur, as well as other dinosaur models: Dinosaur and Prehistoric Animal Models.

The scientific paper: “The First Reported Ceratopsid Dinosaur from eastern North America (Owl Creek Formation, Upper Cretaceous, Mississippi, USA) by Andrew A. Farke and George E. Phillips published in the journal “PeerJ”.

This fossil discovery provides an intriguing insight into Late Cretaceous palaeoenvironments and the types of dinosaurs that inhabited them, more about this in a follow-up article.

Visit the Everything Dinosaur website: Everything Dinosaur.