Archaeorhynchus spathula – Lungs in an Ancient Bird Fossil?

Modern birds have a very efficient respiratory system.  Their lungs are much more efficacious than those of mammals.  However, scientists are not sure when and how this breathing system evolved.  It has been suggested that the origins of the bird’s respiratory system, complete with air sacs and the ability to stop de-oxygenated air mixing with oxygenated air as it is expelled from the lungs, is one anatomical trait inherited from their dinosaur ancestors.

Writing in the academic journal the “Proceedings of the National Academy of Sciences”, a group of international scientists claim that the fossilised remains of an Early Cretaceous bird breathes new life into the evolution of the bird lungs debate.

The Main Slab Showing the Archaeorhynchus spathula Specimen

Picture credit: J. Zhang/Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP)

The Fifth Specimen of Archaeorhynchus spathula to be Described

A study of the slab and counter slab representing the fossilised remains of a prehistoric bird (Archaeorhynchus spathula), suggests that, in this remarkably complete specimen, remnants of the animal’s soft tissues including internal organs such as the lungs could have been preserved.  Using scanning electron microscopy, the research team, including members of the Beijing based, Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP), identified what could be evidence of paired lungs.

The structures identified by the team suggest that Archaeorhynchus had a respiratory system capable of handling the large amount of oxygen required to sustain powered flight.  Although, the conclusions drawn in the scientific paper have been questioned by several academics, if these are lungs, then it indicates that physiological adaptations in Aves came before changes in their skeleton during the evolution of anatomically modern birds.

The Scientists Identified What Could be Paired Lungs on the Counter Slab of the Fossil Specimen

Picture credit: X Wang et al (PNAS)

The Significance of this Research

Archaeorhynchus spathula is one of a number of bird genera known from the Lower Cretaceous Jiufotang Formation (China).  Copious amounts of gizzard stones associated with this and the previous specimens suggest that these primitive birds were probably vegetarian.  They form part of a rich prehistoric fauna known as the Jehol Biota.  In total, five specimens have been described to date but this fossil, consisting of a crushed specimen represented by a slab and counter slab, is the most complete.

Numerous feathers and traces of plumage can be made out and the researchers report that Archaeorhynchus had a pintail, a feature previously not seen in Mesozoic birds.  A. spathula has been classified as a basal member of the Ornithuromorpha, a group distantly related to today’s birds and one that possessed a mix of ancient and more modern anatomical features.

This fascinating fossil described as looking something like “road kill” by one observer, might have allowed palaeontologists to catch a glimpse of a stage of bird evolution where an advanced pulmonary system had evolved yet the skeleton lacked the adaptations seen in extant birds to permit efficient powered flight.

For an article published in 2007 that examined the respiration of dinosaurs: Study Indicates that Dinosaurs were Super-efficient Breathers.

Baby Tylosaurus Fossils Shed Light on Tylosaurus Hunting Strategy

The fragmentary remains of a baby Tylosaurus may have provided palaeontologists with an insight into how the giant and powerful marine predator Tylosaurus hunted.  Analysis of the front portion of the jaw shows that this tiny terror lacked a deep rostrum, whilst older, larger specimens and the adults all had these bony protrusions.  Scientists writing in the “Journal of Vertebrate Paleonotology” hypothesise that Tylosaurus rammed its victims with its snout in a similar fashion to a hunting method observed in extant Orcas.

Fearsome Mosasaurs – How Did These Predators Subdue Their Prey?

Picture credit: Everything Dinosaur

Baby Tylosaurus Fossil

Scientists are aware that pods of Orcas (Orcinus orca), tend to specialise in different types of prey, some hunt fish, others specialise in hunting other marine mammals whilst others are generalists, however, it is known that Orcas tend to stun prey such as seals and dolphins by ramming them with their snouts.  A study of the smallest Tylosaurus skull fossils found to date, suggest that as these animal’s grew their snouts (rostrums) became elongated and more robust.  It is suggested that these predators rammed their victims in the same way that some living Killer Whales do.

Little Killer/Tiny Tylosaurus

Lead author of the scientific paper, Professor Takuya Konishi, explained that he examined fossils of a very young Tylosaurus whilst working on his master’s degree in 2004.  The fossils came from an animal with a skull length of around thirty centimetres, approximately 1/6th the size of an adult Tylosaurus skull.

The fossils come from the Smoky Hill Chalk Member of the Niobrara Chalk of western Kansas, deposits that were laid done in the shallow Western Interior Seaway.  The baby Tylosaurus is estimated to have lived around 85 million years ago.  The fossils had been originally found in 1991, by palaeontologist Michael Everhart (Sternberg Museum of Natural History), the small size and fragmentary nature made initial identification difficult and the fossils has been assigned to another type of mosasaur, a Platecarpus, remains of which are relatively common in the Smoky Hill Chalk Member.

Tiny Fossil Fragments Identified as Neonate Tylosaurus

Picture credit: Christina Byrd/Sternberg Museum of Natural History with additional annotation by Everything Dinosaur

Lack of a Prominent Snout

The lack of a snout puzzled the scientists who were unable to tie this material to other Tylosaurine remains.  The Platecarpus assignment seemed the best fit, then Professor Konishi had his “eureka” moment.  The elongated rostrum of Tylosaurus might develop as the animal grew, this anatomical feature might not be present in very young examples of this genus.  While Platecarpus and other members of the Mosasauridae have teeth that begin virtually at the tip of their snouts, mature Tylosaurus possess a bony protrusion called a rostrum that extends out from its face, a similar feature is found in Orcas.

The research team speculate that this rostrum might have served as a battering ram and protected the marine reptile’s teeth as it slammed into its prey.

Professor Konishi takes up the story:

“Having looked at the specimen in 2004 for the first time myself, it too took me nearly ten years to think out of that box and realise what it really was,  a baby Tylosaurus yet to develop such a snout.”

The Ontogeny of Tylosaurus

Picture credit: Journal of Vertebrate Paleontology

Specimen Number FHSM VP-14845

The picture (above) shows various Tylosaurus fossil specimens.  Specimen number FHSM VP-14845 is from the neonate Tylosaurus (left) and moving towards the right, the rostrums denote progressively older, larger Tylosaurus specimens.  The researchers identified greater anteroposterior alignment of two pairs of premaxillary teeth in association with alveolar elongation (tooth socket spacing).  The abbreviation t2  denotes the second premaxillary tooth, this alveolar elongation slows down as the Tylosaurus ages, as seen here between specimens FHSM VP-14840 and RMM 5610.  In contrast, the rostrum continues to grow and to become deeper and more robust.

Professor Konishi and His Co-workers Suggest Tylosaurus Used Its Snout to Ram Prey

Picture credit: Joseph Fuqua II/University of Cincinnati Creative Services

The Possibility of Misidentified Fossil Material

The scientists suggest that, as Tylosaurus developed its “tell-tale” snout as it grew, then this could mean that other fossil specimens of mosasaurs from the Western Interior Seaway may have been mistakenly classified as other types of mosasaur.

For models and replicas of Tylosaurus and other marine reptiles: CollectA Prehistoric Life Figures.

A spokesperson from Everything Dinosaur commented:

“What was once thought to be a diagnostic feature of Tylosaurus, a robust and elongated snout, might not be as diagnostic as previously thought.  This means that short-snouted fossil remains assigned to other types of mosasaur could, actually represent juvenile Tylosaurus specimens.”

The scientific paper: “The Smallest Known Neonate Individual of Tylosaurus (Mosasauridae, Tylosaurinae) Sheds New Light on the Tylosaurine Rostrum and Heterochrony” by Takuya Konishi, Paulina Jiménez-Huidobro and Michael W. Caldwell published in the Journal of Vertebrate Paleontology.

Visit the Everything Dinosaur website: Everything Dinosaur.

Baby Diplodocid Skull Could Provide Fresh Insight into the Life of Diplodocus

A team of international researchers writing in the academic journal “Scientific Reports”, have described a partial skull of a diplodocid dinosaur.  The skull, measuring just 24 centimetres long, is the smallest diplodocid skull described to date and it is helping to provide information on how long-necked dinosaurs such as Diplodocus changed as they grew.

Studying Diplodocus

The fossil (CMC VP14128), was collected back in 2010 from south, central Montana (Mother’s Day Quarry). The site contains the fossilised remains of at least sixteen immature diplodocids, that may have perished having been caught up in a turbulent mudflow.  The skull, which consists of four large segments plus additional fragments, reveals that the heads of diplodocid dinosaurs changed as they got older and suggests that immature individuals fed on different types of vegetation (dietary partitioning relative to age).  Groups of young animals may have stayed together in a creche, living apart from the adults, even occupying a different habitat.

The Fossilised Skull of a Young Diplodocid Hints at Dietary Partitioning

Picture credit: Andrey Atuchin

“Andrew” the Diplodocus

The specimen (CMC VP14128), also includes a rudimentary bone that links the skull to the cervical column (the proatlas) and four neck bones from the front part of the neck, closest to the skull.  The fossil material has been assigned to the diplodocid species Diplodocus carnegii and the skull was nicknamed “Andrew” in honour of Andrew Carnegie, the Scottish-American industrialist and philanthropist, who did much to support the nascent science of palaeontology in the United States.  The species D. carnegii is named after him in recognition of his financial support for expeditions to excavate fossils from the Morrison Formation.

The Immature Diplodocid Compared to an Adult and Andrew Carnegie (1.6 m tall) with Skull Views and Accompanying Line Drawings

Picture credit: Scientific Reports

The picture above shows a skeletal reconstruction of “Andrew” compared to Andrew Carnegie and an adult D. carnegii (A), the bones in the skeleton in white represent the fossil material (CMC VP14128).  Right lateral view of the skull (B), with an accompanying line drawing and (C), a left lateral view of the skull with a line drawing.  The four segments of the skull are numbered in the line drawings and the scale bar in (B) and (C) is ten centimetres.

Differences in the Shape of the Head of Young and Fully Grown Dinosaurs

Although the skull fossil has been crushed, the researchers, which included lead author Cary Woodruff (University of Toronto) and Glenn Storrs (Cincinnati Museum Centre), conclude that the juvenile, which was perhaps around 5 years of age and 5 metres long when it died, had a much narrower snout compared to the broad, wide snout of an adult.  In addition, “Andrew” possessed thirteen teeth on each side of its lower jaw, some of which had spatulate, spoon-like edges to slice through tough vegetation.  In contrast, fully-grown Diplodocus lower jaws had eleven teeth on each side and these were much more peg-like and were probably used to “comb” food in to the mouth.

This indicates that juveniles had different skull morphologies and dentition when compared to older, more mature animals and suggests resource partitioning between juveniles and adults.  In short, juvenile Diplodocus probably fed on different plants compared to the grown-ups.

For models and replicas of Diplodocus and other dinosaurs: Rebor Dinosaur and Prehistoric Animal Models.

An Adult Diplodocus had a Differently Shaped Head and Snout Compared to a Juvenile

Picture credit: Andrey Atuchin

This research is consistent with the theory that immature diplodocids adopted a different feeding strategy, grazing on a greater variety of plants, whilst the adults were predominantly ground-level browsers.

To read an article from 2010 that hypothesised that baby dinosaurs had different skull morphologies and facial features when compared to adults: Juvenile Diplodocus Skull Study Suggests Baby Dinosaurs Had Different Shaped Skulls Compared to the Adults.

Commenting on the significance of this research, lead author Cary Woodruff, stated”

“Because they have [Diplodocus juveniles] got these different tooth types, it’s kind of like of a Swiss army knife in their mouth, right?  They can pick and eat every plant they want to.  They had free rein at the salad bar.”

Young Diplodocids Living in Woodland Habitats

The skull and tooth morphology of Diplodocus suggests that these animals transitioned through distinct feeding roles over their lifespan and vindicates the dramatised life story of a Diplodocus in the ground-breaking BBC television documentary series “Walking with Dinosaurs”.  In episode two “Time of the Titans”, the story of a Diplodocus from hatching to reaching adulthood was told and juveniles were depicted as living in groups within the forests, only joining the adults on the open plains when they were much larger, too large for most predators to tackle.

The different skull shapes and dentition suggest that juvenile diplodocids lived in more forested environments than the adults that (restricted and protected by their size), were most likely browsing in more open habitats.

For an article published in 2012 on Diplodocus feeding strategies: Diplodocus Feeding Frenzy – A Biter or a Comber?

Lead Author of the Study Cary Woodruff Holds the Skull of a Juvenile Diplodocid

Picture credit: John P Wilson

The scientific paper: “The Smallest Diplodocid Skull Reveals Cranial Ontogeny and Growth-Related Dietary Changes in the Largest Dinosaurs” by D. Cary Woodruff, Thomas D. Carr, Glenn W. Storrs, Katja Waskow, John B. Scannella, Klara K. Nordén and John P. Wilson published in Scientific Reports.

Visit the Everything Dinosaur website: Everything Dinosaur.

Giant Flowering Trees Some Fifteen Million Years Earlier Than Previously Thought

A team of international scientists writing in the open-access, on-line journal “Science Advances”, have published a paper detailing a new fossil assemblage that provides fresh insight into the prehistoric life of southern North America around ninety-two million years ago.  The fossils, which have been collected from several sites in Utah, come from exposures associated with the Upper Cretaceous Ferron Sandstone Member of the Mancos Shale Formation and they reveal a rich and diverse fauna and flora, including giant flowering trees (angiosperms).

Giant Flowering Plants (Angiosperms)

The fossils represent animals and plants that lived on a large, flat river delta close to the coast.  The fossil material associated with these strata represent terrestrial life such as dinosaurs, crocodiles and pterosaurs, plus the plants that made up the forests nearby.  In addition, some isolated sharks teeth have been found and other vertebrate remains in those rock units representing areas of the delta that were brackish and therefore closer to the sea.

The most significant find is also the largest specimen, a giant, petrified log that was approximately 1.8 metres in diameter and around 11 metres in length.  The researchers conclude that the log represents part of the trunk of a tree that may have been over 50 metres in height, making this Cretaceous giant, roughly the same height as Nelson’s Column in Trafalgar Square, London.

Part of the Giant Angiosperm Log – The Field Team Member’s Boots Provide a Handy Scale

Picture credit: Science Advances

Assigned to the Paraphyllanthoxylon Genus

The log was very probably transported some distance via the river before finally being deposited on the delta, where it became preserved as a fossil.  It is the largest known pre-Campanian angiosperm and the earliest documented occurrence of a flowering tree more than one metre in diameter.  Leaf fossils and fossilised spore samples indicate a wide range of flora within the locality.  This ancient giant probably formed part of a forest canopy, beneath which, conifers, ginkgo trees and ferns along with other flowering plants thrived.  The fossil has been assigned to the  Paraphyllanthoxylon genus, as such, it is distantly related to numerous types of tropical flowering tree found today.

A Variety of Plant Fossils Have Been Found

Picture credit: Science Advances/N. A. Jud, University of Florida

Plant Fossils

Several other plant fossils have been found from rocks associated with the Ferron sandstones, these fossils indicate the presence of a mixed woodland habitat.

The photograph (above) shows different types of fossil plant associated with the strata – (A) a leafy shoot identified as Elatides curvivolia (conifer), (B) the broad leaf of an indeterminate angiosperm, (C) shows a close up of the E. curvivolia fossil.  Picture (D) shows an isolated fern pinnule.

Scale bars:

(A to C) = 5 mm

(D) = 3 mm

The Vertebrate Fossil Assemblage

Although only a few vertebrate fossils have been found, they hint at a rich and diverse biota.  Fossils of therizinosaurs are known from Utah (Nothronychus spp.) and a partial, indeterminate, poorly preserved  ornithopod sacrum was discovered along with isolated shark and crocodile teeth and a fragment from a turtle’s shell.

The rocks record life during the Turonian faunal stage of the Late Cretaceous.  Few Turonian-aged deposits are known from North America, it is known that there were exceedingly diverse regional faunas during the later Campanian and Maastrichtian faunal stages and it is hoped that by studying fossils from earlier, some insight into how these diverse communities came about could be gleaned from the information.  This newly described fossil assemblage from Utah will help to fill the gap in our knowledge of early Late Cretaceous terrestrial communities in North America.

Examples of Vertebrate Fossils from the Ferron Sandstone Member

Picture credit: Science Advances/S. A. Williams, Burpee Museum of Natural History

The picture above shows (A), views of an isolated shark tooth assigned to Cretodus crassidens, a common lamniform shark known from Turonian Western Interior Seaway deposits.  Figure (B) shows isolated crocodylian teeth and (C) shows a large turtle scute.  Picture (D) shows various views of the poorly-preserved ornithopod sacrum that was also found.

The scientific paper: “A New Fossil Assemblage Shows that Large Angiosperm Trees Grew in North America by the Turonian (Late Cretaceous)” by Nathan A. Jud, Michael D. D’Emic, Scott A. Williams, Josh C. Mathews, Katie M. Tremaine and Janok Bhattacharya and published in the open-access journal Science Advances.

Visit the Everything Dinosaur website: Everything Dinosaur.