Nanantius eos and the Eromanga Sea

A new species of prehistoric bird from the Cretaceous has been described – Nanantius eos.

The Queensland town of Richmond may be several hundred miles from the Coral Sea that laps against the coast of north-eastern Australia, but back in the Cretaceous this part of world, famous for its droughts and arid outback, was covered for millions of years by a shallow, tropical sea (the Eromanga Sea), that teemed with prehistoric life.  Thanks to the efforts of volunteers and the dedicated researchers at Richmond’s Kronosaurus Korner a new ancient resident has been identified, not a sea monster, or an ancient fish but a primitive bird that probably filled an ecological niche similar to today’s seagulls.

Nanantius eos

Swooping into view comes Nanantius eos, the name translates as dawn dwarf-enantiornithine*.  Slighter smaller than a Common Tern (Sterna hirundo), perhaps weighing no more than a couple of hundred grammes, the fossils come from marine sandstone deposits that were laid down more than 100 million years ago, (Aptian to Albian faunal stage of the Cretaceous).

Fossils of Nanantius have been found in Winton sandstone exposures around three-hundred miles to the south-west of Richmond, but these consist of only a few isolated bones.  Working at a site just eight miles from the centre of Richmond, Dr Patrick Smith (Curator at the Kronosaurus Korner Fossil Museum), is confident that the number of bird bones found so far indicates that there might be complete skeletons present in the deposit.

Pictures of the Fossil Material Ascribed to Nanantius eos from the Richmond Site

Nanantius eos fossils including a partial humerus (left).

Picture credit: Dr Patrick Smith

Dr Smith commented:

“It’s very, very rare to find dinosaurs out here, there’s only been about a handful known, so finding these dinosaur birds is amazing.  We haven’t had any of these sorts of primitive birds found in Richmond.”

The “Richmond Raptor”

Volunteer Mike D’Arcy found the first evidence of a fossil bird some five years ago.  Ever since his first discovery, he has been busy recruiting volunteers to help him find more fossil evidence.  As, for much of the Early Cretaceous, Richmond was underwater and many miles from land, it is surprising to find evidence of an enantiornithine bird in marine sandstone deposits.

Scientists are unsure how the bird fossils came to be deposited.  Do they represent an accumulation of carcases of birds washed out to sea?  Or perhaps flocks of Nanantius eos (which was probably a capable flyer), may have flown out far to sea in order to feed.  Mike has nick-named the bird the “Richmond Raptor”.  It did have small, sharp teeth in its jaws and claws on its wings but small fish and insects were probably its choice of prey.

Volunteer Mike D’Arcy Working at the Fossil Site

Mike D’Arcy at the fossil dig site.

Picture credit: Mike D’Arcy

A spokesperson from Everything Dinosaur commented:

“Local residents can play an important role in helping palaeontologists to collect fossils from sites, that the palaeontologists themselves may not have time to visit and explore themselves.  Thanks to these volunteers, many fossils that would otherwise have been eroded away can be saved, permitting scientists the opportunity to study them.”

Likely Member of the Enantiornithine Clade*

Although described as a member of the Enantiornithes clade, a group of abundant, primitive birds of the Cretaceous, it is hoped that the Richmond fossils will be able to confirm this assessment.  Previously, fossils found near the small town of Boulia, (Queensland), included a partial tibiotarsus (ankle and lower leg bone), were attributed to Nanantius.  The shape of this bone was once thought to be diagnostic of the enantiornithines but more recent Mesozoic bird discoveries have cast doubt on the morphology of the tibiotarsus being suitably diagnostic of a enantiornithine affinity.  With more fossil bones found, including limb elements (humerus and unguals), palaeontologists may be able to confirm the taxonomic position of N. eos.

Examining a Pedal Ungual (Nanantius eos)

Mike D’Arcy examining one of the fossil toe claws.

Picture credit: Mike D’Arcy

The Search for More Evidence of Nanantius eos

Mike D’Arcy added:

“The first half a dozen pieces I got, we couldn’t really assign what it was and it wasn’t until we got the humerus that we could say it was definitely a bird.”

The fossils are currently on display at the Kronosaurus Korner Fossil Museum. Nanantius is regarded as seabird as fossils have been found in association with marine deposits.

In addition, in 2003, a paper was published in the “Proceedings of the Royal Society – Biology” that described the stomach contents discovered in association with a gravid female ichthyosaur (Platypterygius longmani).  Amongst the fossilised remains of baby turtles and fish, the scientists discovered limb bones from an enantiornithine bird, probably from the Nanantius genus.  How the bones came to be in the body cavity of an ichthyosaur is unknown, perhaps the marine reptile grabbed the bird as it rested on the water, or maybe the ichthyosaur had fed on a corpse that had been washed out to sea.

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Nakonanectes bradti – Shortest Neck and Youngest Elasmosaur from the Western Interior Seaway

A new genus of elasmosaurid has been added to the list of marine reptiles associated with the Western Interior Seaway.  Named Nakonanectes bradti, this fish-eating monster lived around 70 million-years ago.  A paper detailing the discovery has been published this week in the “Journal of Vertebrate Palaeontology”, Nakonanectes is the youngest elasmosaurid, stratigraphically speaking from the Western Interior Seaway, it also had a very short neck, short at least, when compared to other Late Cretaceous elasmosaurids.

To view models and replicas of elasmosaurids and other marine reptiles: CollectA Deluxe Prehistoric Life Models.

A New Genus of Short-Necked Elasmosaurid from Montana

An illustration of the newly described elasmosaurid Nakonanectes bradti.

Picture credit: James Havens

Marine Reptile Discovered by an Elk Hunter

David Bradt in 2010, stumbled across fossils of the marine reptile whilst out hunting for elk in Montana’s Charles M. Russell National Wildlife Refuge.  He noticed a series of articulated bones in a stream bed and thinking that the fossils might represent a dinosaur, David alerted the authorities.  When a field team visited the remote site, they followed the trail of bone fragments uphill and discovered more fossils including the remains of an exquisitely preserved skull.  The Late Cretaceous reptile has been named after the native Nakona people of Montana and the trivial name honours David Bradt.

Field Team Members Working at the Excavation Site

The location of the elasmosaurid bones.

Picture credit: Erin Clark/Associated Press

One of the authors of the scientific paper, Pat Druckenmiller (University of Alaska Museum of the North), commented:

“This group [elasmosaurids] is famous for having ridiculously long necks, I mean necks that have as many as seventy-six vertebrae [Albertonectes].  What absolutely shocked us when we dug it out, it only had somewhere around forty vertebrae.”

Nakonanectes bradti Compared to Albertonectes vanderveldei

The Bearpaw Shale Formation has provided scientists with a number of intriguing Cretaceous vertebrate fossils, including Albertonectes (A. vanderveldei).  It is regarded as the longest plesiosaur known (estimated to have been more than twelve metres long).  Albertonectes also has the longest neck of any Plesiosaur described to date.  The neck is estimated to have been around seven metres long.  The single specimen (holotype) of Albertonectes comes from the Bearpaw Shale Formation, however, these fossils were found in Alberta (near Lethbridge) and as such, come from exposures some two hundred miles north-west of the stream bed in Montana where the remains of Nakonanectes were found.

Nakonanectes bradti is believed to have had around 39-42 neck bones (cervical vertebrate).  In comparison, Albertonectes had a body length twice as long and its neck was two-and-a-half times the length of N. bradti.

Comparing the Size of Nakonanectes to Albertonectes

Elasmosaurid size comparisons (Bearpaw Shale Formation).

Picture credit: Everything Dinosaur

Studying Nakonanectes

The palaeontologists conclude that the neck of Nakonanectes was about 2.3 metres long.  It is difficult to accurately date the strata that makes up the Bearpaw Shale Formation.  These two very different elasmosaurids may not have co-existed, but the discovery of Nakonanectes indicates that there was considerable variety in the neck length of members of the Elasmosauridae.  It also suggests that as the Cretaceous period progressed so at least one lineage of elasmosaurs evolved shorter necks.

The scientific paper: “A New Elasmosaurid (Sauropterygia, Plesiosauria) from the Bearpaw Shale (Late Cretaceous, Maastrichtian) of Montana Demonstrates Multiple Evolutionary Reductions of Neck Length within Elasmosauridae”, by Serratos, D. J., P. Druckenmiller, and R. B. J. Benson published in the Journal of Vertebrate Palaeontology.

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Zhongjianosaurus yangi from the Early Cretaceous of China

Researchers from the Chinese Academy of Sciences have published information on-line about the discovery of another dromaeosaurid from the Lower Cretaceous Yixian Formation of Liaoning Province (north-eastern China).

Zhongjianosaurus yangi

The little, long-legged “raptor”, that measured around eighty centimetres in length has been described as looking like “Microraptor on silts”.  The dinosaur has been named Zhongjianosaurus yangi, in honour of Yang Zhongjian regarded as the founder of vertebrate palaeontology in China.  The forelimbs are nearly as robust as the back legs which is a little unusual.  In addition, the ulna (bone in the lower arm), is longer than the humerus (upper arm bone), an anatomical feature that this dinosaur shares with many volant (capable of flight), birds.  The forelimb anatomy of Z. yangi contrasts with the anatomy of most non-avian theropods, where the ulna is almost always much shorter than the humerus.

A Skeletal Drawing and an Illustration of Zhongjianosaurus yangi

Zhongjianosaurus fossil material (in white) shown in a skeletal drawing with a scientific illustration below.

Picture credit: Chinese Academy of Sciences

In the skeletal drawing (above) the fossil material assigned to Z. yangi is shown in white.  Note the skull has not been found (scale bar equals five centimetres).

Eight Dromaeosaurid Species from the Jehol Group – Niche Partitioning

The dromaeosaurids, which are a group of maniraptoran theropods, are globally distributed and they have left a relatively extensive fossil record, but the earliest representatives of the Dromaeosauridae family come from the Lower Cretaceous Jehol Group of western Liaoning Province.  So far, a total of eight dromaeosaurid species have been reported from the Jehol Group, they are remarkably diverse and show numerous differences in their body plans which indicate that each type of dromaeosaurid was adapted to a different habitat or niche in the ecosystem.

This newly described dinosaur, Zhongjianosaurus yangi, classified from a single slab of fossilised bones continues this trend for dromaeosaur diversity.  It is many times lighter than the largest dromaeosaurid (Tianyuraptor ostromi), known from this locality.  With an estimated 0.31 kilogramme mass, the Z. yangi holotype representing an adult individual, confirms that some Jehol dromaeosaurids are among the smallest known non-avialan theropods described to date.

To view articulated models of dromaeosaurids and other dinosaurs: Beasts of the Mesozoic Articulated Models.

The Holotype Fossil Material (Post-cranial Material) of Z. yangi

The holotype of Zhongjianosaurus yangi.

Picture credit: Chinese Academy of Sciences

A Member of the Microraptorinae (Zhongjianosaurus yangi)

Zhongjianosaurus yangi has been assigned to the Microraptorinae sub-family and the single fossil specimen was excavated from strata representing lake deposits in Sihedang, Lingyuan County, (western Liaoning).  The ninth dromaeosaurid of the Jehol Biota is difficult to date accurately, as Sihedang strata lacks biostratigraphical markers.  Z. yangi has been tentatively dated to the Aptian faunal stage of the Early Cretaceous (125 million-years-ago approximately).

Many of the other dromaeosaur fossils have been retrieved from private collections and they subsequently lack stratigraphical context.  However, even if all nine different types of dromaeosaurid did not live at the same geological time they certainly represent a very disparate group and this suggests that these little dinosaurs adapted to different habitats and perhaps sources of food (niche partitioning).

Galapagos Finches

As reported in the advanced on-line publication, the researchers, Xing Xu and Zi-Chuan Qin propose that this collection of dromaeosaurids demonstrates niche partitioning and they compare the Jehol Dromaeosaurs to Darwin’s Galapagos finches.  Darwin noted that although the finches on the various islands that make up the Galapagos shared a common ancestor, they showed remarkable diversity in beak form and function.

In the absence of cranial material, it is not possible to identify what the tiny Zhongjianosaurus ate, but it is postulated that it could have been an insectivore, perhaps living high up in the tree canopy to escape the fast-running, larger hypercarnivores (other dromaeosaurs), that roamed the forest floor.  Zhongjianosaurus was very probably feathered and those robust forelimbs could have supported wings that helped it to glide or flap its way from branch to branch.

The scientific paper: “A New Tiny Dromaeosaurid Dinosaur from the Lower Cretaceous Jehol Group of Western Liaoning and Niche Differentiation Among the Jehol Dromaeosaurids”, by Xing Xu and Zi-Chuan Qin (Chinese Academy of Sciences).

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Moabosaurus utahensis – Adding to the Early Cretaceous Dinosaur Fauna of North America

Researchers from Brigham Young University writing in the University of Michigan’s Contributions from the Museum of Palaeontology, have published details of Utah’s latest dinosaur discovery, an Early Cretaceous Sauropod that roamed the western United States some 125 million-years-ago.  At a little under ten metres in length, Moabosaurus may not be the largest member of the Sauropodomorpha, but it remains a very significant dinosaur discovery nonetheless.

Moabosaurus utahensis

Compared to the earlier Morrison Formation fauna, not that much is known about the dinosaurs that roamed this part of the United States during the (Aptian faunal stage).  Moabosaurus, shared its lush, flood plain world, that was prone to prolonged droughts with dinosaurs such as Cedarosaurus (sauropod) and Gastonia (armoured dinosaur), as well as a variety of theropods.

The Mounted Skeleton (Composite) Ready for Display

Brooks Britt, Brigham Young University geology professor, poses in front of Moabosaurus.

Picture credit: Jaren Wilkey/Brigham Young University

Observant readers will note that the skull on this composite mount is actually a cast of a Camarasaurus skull.

The picture above shows Brigham Young University professor and lead author of the scientific paper, Brooks Britt, posing in front of the mounted exhibit of Moabosaurus (M. utahensis).  The fossils assigned to this new dinosaur genus, were all excavated from the Dalton Wells Quarry, some twelve miles north-west of the town of Moab (Utah).

Moabosaurus Fossil Bones

Around 5,500 fragmentary bones were found entombed in the mudstone, the majority of which represents Moabosaurus, although the fossils were badly damaged, in part due to being trampled by other dinosaurs and from insect damage (probably beetle larvae), that fed on the bones when they had been initially buried.

Based on braincase sampling and other fossil finds, the researchers have suggested that at least eighteen individuals are represented.  The bones were also transported a short distance by water and buried in sediments reworked from the much older Morrison Formation.

For models and replicas of Morrison Formation and Cedar Mountain Formation dinosaurs: PNSO Age of Dinosaurs Models.

Dalton Wells Quarry – Yellow Cat Member of the Cedar Mountain Formation

The preparation of a shattered femur which measures around 1.3 metres in length indicates that this dinosaur grew to about 9.75 metres in size.  Everything Dinosaur team members estimate that this herbivore might have weighed as much as an African elephant.  Palaeontologists tend to agree that, based on the current evidence, there was a substantial decline of sauropod diversity in North America from the Late Jurassic and into the Early Cretaceous.

As to where Moabosaurus fits into the sauropod family tree, that remains open to debate.  The researchers, which included Brigham Young University Museum of Palaeontology Curator Rod Scheetz and biology professor Michael Whiting plus a co-worker from Auburn University (Alabama), carried out four different taxonomic assessments using three different data sets.  Moabosaurus has been identified as a neosauropod, two studies indicate that this dinosaur has affinities with the Macronaria, as such, it is regarded as a basal titanosauriform.

Sorting the Taxonomy

It has been proposed that Moabosaurus was closely related to Turiasaurus (T. riodevensis) of the Early Cretaceous of Spain and Tendaguria (T. tanzaniensis) from the Late Jurassic of Tanzania.  Further phylogenetic studies will help to define the exact position of Moabosaurus in the sauropod family tree.

A View of the Mounted Exhibit of Moabosaurus

Professor Brooks Britt poses in the body cavity of Moabosaurus.

Picture credit: Jaren Wilkey/Brigham Young University

If Moabosaurus is closely related to Turiasaurus and Tendaguria then it suggests that land bridges may have existed between Gondwana and Laurasia to permit the mixing of faunas for longer into the Cretaceous than previously thought.  Analysis of zircon crystals, remnants of volcanic activity, indicate that Moabosaurus lived during the very earliest part of the Aptian faunal stage.  The phylogeny of Moabosaurus remains contentious.  In the scientific paper, “Moabosaurus utahensis – A New Sauropod from the Early Cretaceous of North America”, there is some discussion as to whether Nemegtosaurus and Quaesitosaurus (both from the Late Cretaceous of Mongolia), are sister taxa.

Examining the Sturdy Ribs of Moabosaurus

Moabosaurus and Geology Professor Brooks Britt.

Picture credit: Jaren Wilkey/Brigham Young University

This Moabosaurus Perished in a Severe Drought

A previous study indicated that a large number of Moabosaurus and other dinosaurs died in a severe drought.  Survivors trampled their fallen companions’ bodies, smashing and crushing their bones.  After the drought ended, streams eroded the land, and transported the bones a short distance, where they were again trampled.  Meanwhile, insects in the soils fed on the bones, leaving behind tell-tale burrow marks.

Professor Britt stated:

“We’re lucky to get anything out of this site.  Most bones we find are fragmentary, so only a small percentage of them are usable and that’s why it took so long to get this animal put together.  We had to collect huge numbers of bones in order to get enough that were complete.”

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