New Study of Psittacosaur Skulls Shows Three Species are Actually Just One Species

In a new study of Psittacosaurus fossils from China carried out by University of Pennsylvania researchers, the number of known species of this dinosaur has been reduced from fifteen to thirteen.  It seems that what was once thought to be three different types of “parrot lizard” living in China actually may be just one species.  Differences in the morphology of the fossil material had led to the establishment of three separate species but these differences relate to compression and distortion that occurred as the fossil material was buried and preserved, they do not relate to anatomical differences that would be expected if these animals were indeed different species.

Psittacosaurus

Psittacosaurus is one of the most abundant and speciose genera of all the known Dinosauria.  There had been fifteen named species, with fossil finds in Russia, Mongolia and Thailand as well as in China.  The research team, writing in the scientific jounal PLoS One (Public Library of Science), state that what was once thought of being three separate species from the Psittacosauridae family excavated from strata in the Yixian Formation of north-eastern China – P. lujiatunensis, P. major, and Hongshanosaurus houi are actually the same dinosaur.  All the psittacosaur material represents P. lujiatunensis.

Known to science for ninety years or so, psittacosaurs were relatively small, slender, bipedal members of the ornithischian group of dinosaurs.  Fossils date from around 130 million years ago to approximately 100 million years ago.  Most probably herbivorous, these dinosaurs, most of which were less than two metres in length, are distantly related to the giant Late Cretaceous horned dinosaurs such as Triceratops, Styracosaurus and Chasmosaurus.

An Illustration of Psittacosaurus

Psittacosaurus proves that three into one does go.

Picture credit: Everything Dinosaur

Three-dimensional Geometric Morphometrics

Commenting on their findings Peter Dodson, (Professor of Anatomy at the University’s School of Veterinary Medicine) stated:

“Because of the vagaries of fossilisation, no two fossils are the same.   Animals are alive and they die, but what’s crucial in palaeontology is what happens to the animals after they die.”

The research team used a process called three-dimensional geometric morphometrics to compensate for the crushed and distorted fossil material, thus revealing the affinities between different fossil specimens.  This is the first time this laser-based examination technique has been used on dinosaur fossils and this study could have implications for other genera.

New Study Re-assigns Fossil Material

Assessing the shape of dinosaur skulls.

Picture credit: PLoS One

Many New Genera Named

Over the last thirty years or so a large number of horned dinosaur fossils have been found in North America.  As a result, many new genera and species have been erected.  Three-dimensional geometric morphometrics if applied to North American ceratopsian specimens may help to confirm speciation or indeed lead to a re-assignment of some fossil material.

A spokesperson from Everything Dinosaur commented:

“This technique permits scientists to assess the variation in skull morphology.  Given enough specimens to study and this work could have implications for other dinosaur genera, extinct animals which have left us fossils which were thought to represent a new species unknown to science may turn out to be examples of already known and described species.”

The Beasts of the Mesozoic range contains several different, articulated horned dinosaur figures including Psittacosaurus (whilst stocks last).

To view the Beasts of the Mesozoic range: Beasts of the Mesozoic Articulated Dinosaur Figures.

165-Million-Year-Old Fossil Provided Evidence of Mammalian Evolution

A newly discovered fossil reveals the evolutionary adaptations of a 165-million-year-old proto-mammal, providing evidence that traits such as hair and fur originated well before the rise of the first true mammals.  University of Chicago scientists described the biological features of this ancient mammalian relative, named Megaconus mammaliaformis, in a paper published in the latest edition of the academic journal “Nature”.

Megaconus mammaliaformis

Professor Zhe-Xi Luo one of the authors of the scientific paper stated:

“We finally have a glimpse of what may be the ancestral condition of all mammals, by looking at what is preserved in Megaconus.  It allows us to piece together poorly understood details of the critical transition of modern mammals from pre-mammalian ancestors.”

An Illustration and Skeletal Reconstruction of M. mammaliaformis

Jurassic squirrel-like primitive mammal.

Picture credit: April Isch

The specimen, dating from the Bathonian faunal stage of the Middle Jurassic was discovered in Inner Mongolia, China.  Megaconus is one of the best-preserved fossils of the mammaliaform groups, which are long-extinct relatives to modern mammals.

A terrestrial animal about the size of a large ground squirrel, Megaconus was most probably an omnivore, possessing clearly mammalian dental features and jaw hinge.  Its molars had elaborate rows of cusps for chewing on plants, and some of its anterior teeth possessed large cusps that allowed it to eat insects and worms, perhaps even other small vertebrates.  It had teeth with high crowns and fused roots similar to more modern, but unrelated, mammalian species such as rodents.  Its high-crowned teeth also appeared to be slow-growing like modern placental mammals.

The skeleton of Megaconus, especially its hind-leg bones and finger claws, likely gave it a gait similar to modern armadillos, a previously unknown type of locomotion in mammaliaforms.

Preserved in the fossil is a clear halo of guard hairs and underfur residue, making Megaconus only the second known pre-mammalian fossil with fur.  It was found with sparse hairs around its abdomen, leading the scientists to theorise that it had a naked abdomen.  On its heels, Megaconus possessed a long keratinous spur, which was possibly poisonous.  Similar to spurs found on modern egg-laying mammals, such as male platypuses, the spur is evidence that this fossil was most likely a male member of its species.

Mammalian Phylogeny – Our Family Tree

Tracing the mammalian family tree.

Picture credit: Luo Laboratory

Professor Luo went on to state:

“Megaconus confirms that many modern mammalian biological functions related to skin and integument had already evolved before the rise of modern mammals.”

However, Luo and his team identified clear non-mammalian characteristics as well.  Its primitive middle ear, still attached to the jaw, was reptile-like.  Its anklebones and vertebral column are also similar to the anatomy of previously known mammal-like reptiles.

When asked to comment on the possible connections between this Mid-Jurassic fur ball and our own ancestry, the professor said:

“We cannot say that Megaconus is our direct ancestor, but it certainly looks like a great-great-grand uncle 165 million years removed.  These features are evidence of what our mammalian ancestor looked like during the Triassic-Jurassic transition.  Megaconus shows that many adaptations found in modern mammals were already tried by our distant, extinct relatives.  In a sense, the three big branches of modern mammals are all accidental survivors among many other mammaliaform lineages that perished in extinction.”

The fossil, now in the collections in Palaeontological Museum of Liaoning in China, was discovered at the famous Daohugou Fossil Site.  It was studied by an international team of palaeontologists from Palaeontological Museum of Liaoning, University of Bonn in Germany and the University of Chicago.

The Slab and Counter Slab of the Fossil

Megaconus mammaliaformis is preserved as a slab (left) and a counter-slab (right) of shale deposited in a shallow lake.

Picture credit: University of Chicago/Professor Zhe-Xi Luo

This specimen, and another fossil mammaliaform found in the same area in 2006 will help scientists to piece together the early evolution and radiation of primitive mammals that scurried around back in a time when the dinosaurs dominated.

Everything Dinosaur is grateful to the University of Chicago in the compilation of this article.

To view models and replicas of prehistoric animals: Dinosaur and Prehistoric Animal Models.

New Species of Prehistoric Shark Described – Meet “Devil Tooth”

Arizona may be one of the very last places you would expect to find a new species of shark, after all, the “Grand Canyon State” does not seem particularly shark friendly when you consider the large amount of desert within the state’s borders. However, during the Middle to Late Permian (Guadalupian/Lopingian Epochs) this part of the United States was covered in a shallow, tropical sea that teemed with life and scientists from the Northern University of Arizona have identified a number of new shark genera from fossilised teeth excavated from the limestone deposits that make up the Kaibab Formation.

Diablodontus michaeledmundi

Their latest discovery is “Devil Tooth” a new type of hybrodont shark Diablodontus michaeledmundi.  Hybrodont sharks evolved during the Late Devonian and persisted as a diverse and geographically dispersed group until their extinction towards the end of the Mesozoic.  D. michaeledmundi seems typical of this group of Elasmobranchs, the teeth, the researchers have found, suggest that this shark was a little over a metre in length and it was probably a diurnal hunter, living in the coastal waters hunting small fish, squid and octopi.

An Illustration of Diablodontus michaeledmundi

Black bar = scale bar (50 cms).

Picture credit: Northern Arizona University with additional annotation by Everything Dinosaur

Hybrodont Shark

This shark had two spines projecting upwards from the anterior edge of its dorsal fins, such horned sharks exist today, such as the Port Jackson shark, although extant sharks such as the Port Jackson shark are not closely related to these Permian Elasmobranchs.  The name Diablodontus is derived from the Spanish word for devil “diablo” and the Greek word for teeth “dontus”.  The species name honours Michael Edmund Hodnett, for his work in helping to study the shark fossil assemblage of the Kaibab Formation.

The Kaibab Formation has produced a substantial amount of shark teeth fossils.  This strata is particularly important as it dates from around the time of the greatest mass extinction event known in the fossil record – the end Permian extinction when something like 95% of all life on Earth died out.  The holotype material for D. michaeledmundi was collected from limestone sediments near the town of Flagstaff (northern Arizona).

Various Views of the Fossilised Teeth of Diablodontus michaeledmundi

Ancient shark teeth.

Picture credit: John-Paul M. Hodnett et al

The image above shows various views of the teeth of this prehistoric shark. The white bar is a scale bar, it is 1 mm in length.

Shallow Sea in North America

Commenting on the discovery, one of the authors of the scientific paper John-Paul Hodnett, an authority on prehistoric sharks stated:

“The shark miraculously survived the extinction event and lived into the Mesozoic Era – the Age of Reptiles.  At this time the ancestors of modern sharks were just starting to diversify but remained small.”

During the Late Palaeozoic, this part of America was covered by a shallow sea, to the east lay extensive deserts crossed by a nascent mountain range, mountains that would one day become part of the Rockies.

Arizona During the Late Permian

Palaeography of the Late Permian (western United States).

Picture credit: John-Paul M. Hodnett et al

The Kaibab Formation

Fossilised sharks teeth from the Kaibab Formation has permitted scientists an insight into the radiation and diversification of a number of different types of shark.  Several different genera have been identified, one of which Kaibabvenator swiftae with its large, serrated teeth was perhaps the apex marine predator in the ancient Kaibab sea. Size estimates vary for K. swiftae, although it has been suggested that this primitive, horned shark may have reached lengths similar to today’s Great White shark (Carcharodon carcharias).

Size Comparisons between Permian Sharks of the Kaibab Formation and a Great White Shark

Size comparisons between extinct and extant sharks.

Picture credit: Northern Arizona University/Everything Dinosaur

One thing that is undeniable, the Kaibab Formation represents one of the most important locations in the world for fossils of ancient sharks.

For models and replicas of prehistoric sharks and other extinct creatures: PNSO Age of Dinosaurs Models and Figures.

The Nests of Jurassic Hunters

The Lourinhã Formation of western Portugal has provided researchers from the New University of Lisbon (Universidade Nova de Lisboa), with not one but two sets of dinosaur eggs to study.  Palaeontologists from the University state that the fossilised remains of dinosaur eggs from two locations in the Lourinhã Formation come from two different meat-eating dinosaurs.  The crushed and broken nests represent dinosaur remains estimated to be approximately 150 million years old.

Theropod Eggshells

Although no evidence of fossilised embryos could be found, the scientists were able to study the size, morphology and texture of the eggs and from this evidence, candidates as to what dinosaurs might have laid these eggs can be proposed. Much of the preliminary work to identify the fossil material was made by University palaeontologist Vasco Riberio, during the Late Jurassic this part of Portugal was a floodplain inhabited by many different types of dinosaur.

The first set of eggs, spherical in shape and approximately 15 centimetres in diameter were very probably laid by a large theropod. It has been suggested, that based on the size of the eggs, their mother was a Torvosaurus.  Torvosaurus is a little known Late Jurassic carnivorous dinosaur.  It might be a member of the allosaurid family, or perhaps, because of its heavy and robust frame it might be a megalosaur.  Fossils are known from Portugal and the Morrison Formation of the western United States.  At an estimated length of more than ten metres, it is one of the largest carnivorous dinosaurs known from Portugal.

Lourinhanosaurus antunesi

The eggs found at the second location are slightly smaller and more elongated in shape, it has been speculated that this batch of legs was laid by a Lourinhanosaurus (L. antunesi).  Lourinhanosaurus is known from a single partial skeleton and other fragmentary bones including a femur (thigh bone) all found in the Lourinhã Formation on the western coast of Portugal.  Previously, a number of fossilised eggs found in the  Lourinhã Formation have been ascribed to this species, which is estimated to have grown to lengths of five metres.

An Illustration of the Dinosaur Lourinhanosaurus antunesi

Late Jurassic theropod.

Picture credit: Everything Dinosaur

Abandoned Nest Sites

The scientists are not sure why these two nest sites seem to have been abandoned.  It has been suggested that something may have happened to the adults or that the abandonment of eggs once laid was normal behaviour for these types of theropods.  Such behaviour, laying eggs and then leaving them to their fate is referred to as precocial behaviour.  A number of reptiles lay eggs and then abandon them, reptiles such as tortoises and turtles.  Precocial behaviour is also seen in the Aves, with many types of ducks and geese when hatched, are relatively well-developed and can feed themselves.

The dinosaurs that laid these eggs may have simply abandoned the nests, the dinosaurs that hatched would have been mobile almost immediately and would have left the nest shortly after hatching to fend for themselves.

To view the extensive range of prehistoric animal models available from Everything Dinosaur: Dinosaur and Prehistoric Animal Models.