Large Theropod Tooth Indicates Tyrannosaurs Roamed Japan

Researchers have identified a single, shed theropod tooth that indicates that large tyrannosaurs roamed the land that we now know as Japan some 80 million years ago.  The single tooth is very characteristic of a member of the Tyrannosauridae family, however, it is not possible to identify a specific genus based on such fragmentary evidence.

This has not stopped the speculation, with some sources suggesting that the tooth might have come from a dinosaur which was very similar to Gorgosaurus, which is one of the better known Late Cretaceous tyrannosaurs, although, as far as we at Everything Dinosaur think, Gorgosaurus lived several million years later and is only known from North America.

The Single Broken Theropod Tooth – Potential Japanese Tyrannosaur

The tyrannosaur tooth (Japan).

Picture credit: Goshoura Cretaceous Museum

A Fossil Find on Amakusa Island

In October 2014, a research team from the Fukui Prefectural Dinosaur Museum in collaboration with colleagues from the Goshoura Cretaceous Museum was exploring a series of Upper Cretaceous exposures in the Amakusa archipelago (Kumamoto Prefecture), a tooth from a theropod was found.  In a press release, a spokesperson from the Goshoura Cretaceous Museum, which is run by the Amakusa city government, explained that the single tooth is believed to have come from either the upper left jaw or the lower right jaw of a carnivorous dinosaur.

The tooth morphology is typical of a tyrannosaur, it has serrations running down the sides of the tooth, very similar to those of dinosaurs in the Tyrannosauridae family.  It is slightly recurved and has a characteristic robust appearance and a classic oval or “D” shape when seen in cross-section.

A View of the Underside of the Tooth – A Typical Tyrannosaur Tooth Shape

Ventral view of the tyrannosaurid tooth (view from underneath).

Picture credit: Goshoura Cretaceous Museum

A Shed Tyrannosaur Tooth from Japan

Only the crown has been found.  No roots have been found in association with the tooth, so it is very likely a shed tooth.  Dinosaurs replaced teeth throughout their lives.  Palaeontologists have calculated that a tooth in the jaws of Tyrannosaurus rex probably lasted less than two years.  The dental enamel on the tooth is quite well preserved and the fossil measures 4.2 cm long, 2.5 cm wide (at the bottom) and it is 1.6 cm thick.  Based on the size of the tooth, scientists have estimated that the tyrannosaur that lost this tooth could have measured over seven metres in length.  The original length of the tooth (crown plus root) is estimated at around 5.6 cm long.

The tooth would have been quite sizeable, but this is not the largest theropod tooth ever found in Japan.  In 2008, Everything Dinosaur reported the discovery of a much older dinosaur tooth that measured more than eight centimetres in length.

To read about this fossil discovery: Largest Meat-Eating Dinosaur Tooth Found in Japan.

The serrations (denticles) are quite prominent and measure about 0.3 mm in size.  In the press statement, it was stated that the tooth was found in exposures related to the Ikusagaura stratum of the Himenoura Group (Upper Cretaceous – Campanian faunal stage).

An Illustration of a Typical Gorgosaurus (G. libratus Member of the Tyrannosauridae)

Faster and slightly more nimble when compared to the biggest Albertosaurus dinosaurs.

Picture credit: Everything Dinosaur

A Tyrannosaur Tooth from Japan

Commenting on the fossil find, a team member from Everything Dinosaur stated:

“Dinosaur fossils from Japan are exceptionally rare and most material is extremely fragmentary.  The finding of this single tooth does indicate that during the latter stages of the Late Cretaceous, this part of the world was home to large tyrannosaurs similar to those found in similar aged rocks in North America and elsewhere in Asia.”

Earlier this year, (April 2017), Everything Dinosaur reported on the discovery of the most complete dinosaur skeleton ever found in Japan.  The fossilised remains of a hadrosaur were discovered on the Japanese island of Hokkaido.  The fossils were found in marine strata, it is likely that the corpse of this herbivorous dinosaur was washed out to sea – an example of a “bloat and float” form of taphonomy.

To read an article about this discovery: Japan’s Most Complete Dinosaur Discovery.

A Mounted Skeleton of a Gorgosaurus (Late Cretaceous Tyrannosaur)

Gorgosaurus fossil display.

Picture credit: Manchester University

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Razanandrongobe sakalavae – Terror of the Middle Jurassic

A team of French and Italian palaeontologists have pieced together a more than decade-long puzzle and as a result, have come face to face with one of the most nightmarish prehistoric animals imaginable.  New research on fossils found in north-western Madagascar has led scientists to describe a giant, terrestrial crocodile with immensely strong teeth and bone-crushing jaws.  The new species, the largest and oldest Notosuchian described to date, may well have filled the apex predatory niche in this part of the southern, super-continent Gondwana.  The super-sized croc, named Razanandrongobe sakalavae (pronounced Ray-zan-an-dro-go-bay sack-ah-lar-vey), had teeth reminiscent of the robust teeth of a Late Cretaceous tyrannosaur.

Indeed, an examination of the denticles (serrations) on the teeth preserved in the left dentary fragment and partial right premaxilla are strikingly similar to the serrations on a T. rex tooth.

A Reconstruction of the Deep Skull of Razanandrongobe sakalavae

Razanandrongobe skull.

Picture credit: Fabio Manucci

Archosauria incertae sedis

In 2006, three palaeontologists (Simone Maganuco, Cristiano Dal Sasso and Giovanni Pasini), published a scientific paper that described a large predatory archosaur from the Mahajanga Basin of Madagascar.  The animal was named based on a fragmentary right maxilla and seven isolated teeth.  It is not unusual to have a new genus established based on such incomplete remains, however, what kind of reptile these fossils represented was very much open to debate.  Could it have been a crocodylomorph or perhaps a carnivorous dinosaur?  A new taxon was erected Razanandrongobe sakalavae, in the 2006 paper.

It was suggested that the fossils might represent the largest predatory animal known from the Bathonian faunal stage of Jurassic Madagascar and that it could have been durophagous – feeding on hard materials like the bones of other vertebrates.  Such was the paucity of the fossil material, that although the species name entered scientific literature, it was referred to as “Archosauria incertae sedis”, which means it was a member of the Archosauria, but where it belonged in this large and extremely diverse clade was anyone’s guess.

More Fossils – More Skull Material

Writing in the academic journal “PeerJ” the same researchers, in collaboration with Guillaume Fleury (Muséum d’Histoire Naturelle de Toulouse, France), have described more cranial material including an almost complete right premaxilla, a portion of left lower jaw bone (dentary), plus a partial maxilla complete with unerupted teeth and a single, very large broken tooth.  In addition, a further five skull bones, that were, most likely collected from the same location are also assigned to R. sakalavae.  These fossils have ruled out Theropoda, Razanandrongobe was definitely from the Crurotarsi archosauriforms and as such, it has affinities with today’s crocodilians.

However, phylogenetic analysis assigns Razanandrongobe to the Notosuchia and as such, it was very distantly related to Kaprosuchus from the Late Cretaceous of Niger, a terrestrial predator that readers of this blog and collectors of Papo and Safari Ltd prehistoric animal models might be familiar with.  As several sauropods are known from the same stratigraphy, this “super-croc” has been depicted scavenging on the carcass of long-necked dinosaur.

Razanandrongobe sakalavae Feeding on a Sauropod Carcass (Archaeodontosaurus)

Razanandrongobe feeding on a sauropod carcass.

Picture credit: Fabio Manucci

The illustration above depicts the deep-snouted terrestrial Razanandrongobe scavenging on the carcass of a sauropod.  We speculate that the artist has depicted an Archaeodontosaurus as the victim.  Archaeodontosaurus is known from fossils that came from the same region of Madagascar.  Ironically, we think at Everything Dinosaur, this Middle Jurassic sauropod was named on the basis of isolated teeth and a fragment of jawbone, just like R. sakalavae.

Razanandrongobe sakalavae

Although distantly related to living crocodiles, Razanandrongobe moved very differently.  Its legs were longer and it walked with a much more erect stance.  It may even have been capable of bipedalism, although analysis of the postcranial skeleton would be the only way to confirm this.

As to the size of this 165 million-year-old crocodile, that is very difficult to say.   However, this animal nick-named “Razana”, has been estimated at around seven metres in length.  This measurement has been calculated by comparing the Razanandrongobe fossil material with better-known and more complete baurusuchids, another type of Notosuchian from South America.

Estimating the Size of Razanandrongobe sakalavae

Estimating the size of Razanandrongobe sakalavae.

Picture credit: Natural History Museum (Milan)

Razanandrongobe may have been about as big as a modern Saltwater crocodile (Crocodylus porosus), but on those powerful erect limbs it would have stood much higher, perhaps around 1.6 metres high at the hips.  Its weight has been estimated at 800 to 1,000 kilogrammes.

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“Giant Lizard Ancestor from the Sakalava Region”

Razanandrongobe sakalavae translates from the local dialect and Latin and means “giant lizard ancestor from the Sakalava region”, Sakalava relating to the ethnic group that inhabits the Mahajanga region, where the fossil material was found.

It is thanks to the additional fossil fragments, the majority of which indicating that they represent the same individual whose fossils were described back in 2006, that the research team have been able to “flesh out the bones” and provide a more detailed picture of this monster.  In essence, the paper clarifies features on the holotype material that confirms that the fossils do not represent any type of dinosaur, it establishes Razanandrongobe as a member of the Notosuchia and as such it is by far the oldest Notosuchian so far described.  It is the first Jurassic Notosuchian and its fossils are some 42 million years older than other members of this crocodilian Suborder.

The Mounted Fossils (with some casts) Reconstructing the Front of the Jaws of R. sakalavae 

Razanandrongobe sakalavae  skull reconstruction.

Picture credit: Natural History Museum (Milan)

The picture above shows the reconstructed anterior portion of the skull and jaws of Razanandrongobe with the fossil material and casts shown in life position.

Cristiano Dal Sasso (Natural History Museum of Milan) commented:

“Like these and other gigantic crocs from the Cretaceous “Razana” could outcompete even theropod dinosaurs, at the top of the food chain.”

Very little is known about the origins and the early evolution of the Notosuchia, this Madagascan fossil material represents the first Jurassic fossils related to this Sub-order.  Razanandrongobe has extended the evolutionary history of the Notosuchia by more than forty million years and as such, it has established a ghost lineage that, hopefully further fossil finds will help to fill in.

Speaking about the implications for the evolution of these types of terrestrial crocodiles, co-author of the PeerJ paper, Simone Maganuco (Natural History Museum of Milan), stated:

“These fossils represent a further signal that the Notosuchia originated in southern Gondwana.”

Predator or Scavenger?

Although nothing can be discounted, it is likely that, just like the majority of scavengers today, Razanandrongobe was an active hunter.  It probably hunted dinosaurs and other large vertebrates.  However, it was also very probably an opportunist, if it found a carcass it would have fed upon it.  After all, dead animals don’t fight back and a corpse represents a free lunch, so long as you can defend it from other hungry carnivores.

The powerful jaws and strong teeth lead to the idea that this crocodile was durophagous.  It was able to consume parts of the carcass that other predators including most theropod dinosaurs, could not.  This ability to exploit such a food source could have been key to this type of predator’s evolutionary success.

The Papo Kaprosuchus Model – A Distant Relative of Razanandrongobe

A spectacular Papo Kaprosuchus.

Picture credit: Everything Dinosaur

The picture (above) shows the Papo Kaprosuchus model.

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Coronodon havensteini – An Important Transitional Fossil

The classification and evolutionary history of whales has been a source of fascination for many scientists.  It was the famous Swedish biologist, Carl Linnaeus, who in 1758, defined whales as mammals and not fish.

Charles Darwin speculated on the origins of whales (Cetacea), if we at Everything Dinosaur recall correctly, Darwin proposed that whales and their smaller cousins, the dolphins and porpoises had a terrestrial ancestor, but the exact evolutionary history of this diverse group of vertebrates has yet to be fully unravelled.  Step forward, the newly described Coronodon havensteini, the premolars and molars of this Oligocene-aged toothed whale have provided tantalising evidence suggesting how filter feeding in whales evolved.

Coronodon havensteini Hunting Fish

An illustration showing two Coronodon havensteini specimens chasing a school of small fish.

Picture credit: Alberto Gennari

The picture above depicts a scene off the south-eastern United States some thirty million years ago (Oligocene).  A pair of Coronodon pursue a shoal of fish, whilst above, some toothed birds (Pelagornis sandersi), circle in the hope of picking off any injured fish that come to the surface.

Different Types of Whale – Different Types of Feeding

Although, all whales share a common ancestor, a terrestrial ancestor with teeth that hunted prey (raptorial behaviour), over the fifty million years or so, since the first ancestral whales, three main feeding strategies have evolved.

1. Odontoceti – the toothed whales the most specious component of the Cetacea consisting of Sperm whales, the Beluga, dolphins, Orcas and porpoises.
2. Suction feeders – within the Odontocetes, a number of genera have utilised their large, broad jaws and big skulls to help them suck prey into their mouths.  Examples include many of the beaked whales and the bizarre Narwhal.
3. Mysticeti – the baleen whales, much less diverse and specious when compared to the Odontoceti, these are the filter feeders and as such, they include the largest vertebrates to have ever existed, leviathans like the Blue whale (Balaenoptera musculus) and the Humpback (Megaptera novaeangliae).

Whilst scuba diving in South Carolina’s Wando River on the hunt for sharks’ teeth, geologist Mark Havenstein came across the well-preserved skull of an ancient toothed whale, one that seems to be a transitional fossil between raptorial toothed whales and the evolution of filter feeding cetaceans.

The Evolution of Baleen – Keratinous Sieves

Scientists from the Mace Brown Museum of Natural History, Charleston, South Carolina (where the holotype material currently resides), along with colleagues from the New York Institute of Technology College of Osteopathic Medicine (New York), prepared and restored the fossil, a subsequent study of the teeth indicates that this prehistoric whale, named Coronodon havensteini was starting out on an evolutionary path that would eventually lead to functional filter feeding.

The Restored Skull of the Oligocene Whale Coronodon havensteini

Two views of the restored Coronodon skull (a) oblique anterior view and (b) right lateral view.

Picture credit: Geisler et al (Current Biology)

Coronodon havensteini

Writing in the academic journal “Current Biology”, the researchers propose that Coronodon represents the most basal member of the baleen whales (Mysticeti) found to date.  The teeth at the front of the jaws are conical, pointed and demonstrate procumbent dentition (the teeth in the front of the jaw point forward, ideal for spearing slippery fish).  These teeth indicate a piscivorous diet, that Coronodon actively hunted its prey (raptorial behaviour).  However, a detailed analysis of the huge molars at the back of the jaws revealed something remarkable.

The molars show very little signs of wear from shearing or cutting up food, instead these teeth may have served as simple sieves to sift out smaller prey items from seawater.  The broad, multi-cusped molars frame narrow slits and wear patterns on the cusps indicate a role in filter feeding.

This suggests that the Mysticeti evolved their baleen plates whilst they retained their teeth and that baleen did not evolve in the mouths of Odontocetes that specialised in suction feeding and as a result, lost their teeth.

The Specialised “Filtering Teeth” of Coronodon havensteini

The molars of C. havensteini acted as simple filters.

Picture credit: Geisler et al (Current Biology)

Commenting on the implications for their discovery, lead author of the research paper, Associate Professor Dr Jonathan Geisler (College of Osteopathic Medicine, New York Institute of Technology), stated:

“The transition from teeth to baleen is widely contested, but our research indicates that ancient toothed whales relied on the spaces between their complex and enormous teeth for filtering.  It appears that over millions of years, the teeth were retained until baleen became sufficiently large and complex to take over the role of filter feeding.”

Giant Filter Feeders

The newly erected genus name Coronodon comes from the Greek for “crown tooth”, a reference to the multi-cusped molars that indicate filter feeding.  The species name honours Mark Havenstein who found the holotype.  The researchers suggest that later lineages of ancestral Mysticetes relied on specialised molars to act as functional sieves with baleen evolving in the mouth too.  At some point in the evolution of these whales a “tipping point” was reached with a shift from mostly teeth to mostly baleen in the jaw.

The bristle-like baleen of extant filter feeding whales is made from keratin, it hangs from the upper jaw and acts like a giant sieve, straining out tiny food particles such as krill.

The researchers conclude that Coronodon havensteini lends weight to the idea that filter feeding was preceded by raptorial, predatory behaviour and that suction feeding evolved separately.

The scientific paper: “The Origin of Filter Feeding in Whales” by Jonathan H. Geisler, Robert W. Boessenecker, Mace Brown, Brian L. Beatty published in the journal “Current Biology”

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