Mystery surrounding dinosaur footprints on a cave ceiling in Central Queensland solved

The mystery surrounding dinosaur footprints on a cave ceiling in Central Queensland has been solved, in article published in Historical Biology, after more than a half a century.

University of Queensland palaeontologist Dr Anthony Romilio discovered pieces to a decades-old puzzle in an unusual place — a cupboard under the stairs of a suburban Sydney home.

“The town of Mount Morgan near Rockhampton has hundreds of fossil footprints and has the highest dinosaur track diversity for the entire eastern half of Australia,” Dr Romilio said.

“Earlier examinations of the ceiling footprints suggested some very curious dinosaur behaviour; that a carnivorous theropod walked on all four legs.

“You don’t assume T. rex used its arms to walk, and we didn’t expect one of its earlier predatory relatives of 200 million years ago did either.”

Researchers wanted to determine if this dinosaur did move using its feet and arms, but found accessing research material was difficult.

“For a decade the Mount Morgan track site has been closed, and the published 1950s photographs don’t show all the five tracks,” Dr Romilio said.

However Dr Romilio had a chance meeting with local dentist Dr Roslyn Dick, whose father found many dinosaur fossils over the years.

“I’m sure Anthony didn’t believe me until I mentioned my father’s name — Ross Staines,” Ms Dick said.

“Our father was a geologist and reported on the Mount Morgan caves containing the dinosaur tracks in 1954.

“Besides his published account, he had high-resolution photographs and detailed notebooks, and my sisters and I had kept it all.

“We even have his dinosaur footprint plaster cast stored under my sister’s Harry Potter cupboard in Sydney.”

Dr Romilio said the wealth and condition of ‘dinosaur information’ archived by Ms Dick and her sisters Heather Skinner and Janice Millar was amazing.

“I’ve digitised the analogue photos and made a virtual 3D model of the dinosaur footprint, and left the material back to the family’s care,” he said.

“In combination with our current understanding of dinosaurs, it told a pretty clear-cut story.”

The team firstly concluded that all five tracks were foot impressions — that none were dinosaur handprints.

Also the splayed toes and moderately long middle digit of the footprints resembled two-legged herbivorous dinosaur tracks, differing from prints made by theropods.

“Rather than one dinosaur walking on four legs, it seems as though we got two dinosaurs for the price of one — both plant-eaters that walked bipedally along the shore of an ancient lake,” Dr Romilio said.

“The tracks lining the cave-ceiling were not made by dinosaurs hanging up-side-down, instead the dinosaurs walked on the lake sediment and these imprints were covered in sand.

“In the Mount Morgan caves, the softer lake sediment eroded away and left the harder sandstone in-fills.”


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Journal Reference:

  1. Anthony Romilio, Roslyn Dick, Heather Skinner, Janice Millar. Archival data provides insights into the ambiguous track-maker gait from the Lower Jurassic (Sinemurian) Razorback beds, Queensland, Australia: evidence of theropod quadrupedalism? Historical Biology, 2020; 1 DOI: 10.1080/08912963.2020.1720014

Rare lizard fossil preserved in amber

The tiny forefoot of a lizard of the genus Anolis was trapped in amber about 15 to 20 million years ago. Every detail of this rare fossil is visible under the microscope. But the seemingly very good condition is deceptive: The bone is largely decomposed and chemically transformed, very little of the original structure remains. The results, which are now presented in the journal PLOS ONE, provide important clues as to what exactly happens during fossilization.

How do fossils stay preserved for millions of years? Rapid embedding is an important prerequisite for protecting the organisms from access by scavengers, for example. Decomposition by microorganisms can for instance be prevented by extreme aridity. In addition, the original substance is gradually replaced by minerals. The pressure from the sediment on top of the fossil ensures that the fossil is solidified. “That’s the theory,” says Jonas Barthel, a doctoral student at the Institute for Geosciences at the University of Bonn. “How exactly fossilization proceeds is currently the subject of intensive scientific investigation.”

Amber is considered an excellent preservative. Small animals can be enclosed in a drop of tree resin that hardens over time. A team of geoscientists from the University of Bonn has now examined an unusual find from the Dominican Republic: The tiny forefoot of a lizard of the genus Anolis is enclosed in a piece of amber only about two cubic centimeters in size. Anolis species still exist today.

Vertebrate inclusions in amber are very rare

The Stuttgart State Museum of Natural History has entrusted the exhibit to the paleontologists of the University of Bonn for examination. “Vertebrate inclusions in amber are very rare, the majority are insect fossils,” says Barthel. The scientists used the opportunity to investigate the fossilization of the seemingly very well preserved vertebrate fragment. Since 2018 there is a joint research project of the University of Bonn with the German Research Foundation, which contributes to the understanding of fossilization using experimental and analytical approaches. The present study was also conducted within the framework of this project.

The researchers had thin sections prepared for microscopy at the Institute for Evolutionary Biology at the University of Bonn. The claws and toes are very clearly visible in the honey-brown amber mass, almost as if the tree resin had only recently dripped onto them — yet the tiny foot is about 15 to 20 million years old.

Scans in the micro-computer tomograph of the Institute for Geosciences revealed that the forefoot was broken in two places. One of the fractures is surrounded by a slight swelling. “This is an indication that the lizard had perhaps been injured by a predator,” says Barthel. The other fracture happened after the fossil was embedded — exactly at the place where a small crack runs through the amber.

Amber did not protect from environmental influences

The analysis of a thin section of bone tissue using Raman spectroscopy revealed the state of the bone tissue. The mineral hydroxyapatite in the bone had been transformed into fluoroapatite by the penetration of fluorine. Barthel: “This is surprising, because we assumed that the surrounding amber largely protects the fossil from environmental influences.” However, the small crack may have encouraged chemical transformation by allowing mineral-rich solutions to find their way in. In addition, Raman spectroscopy shows that collagen, the bone’s elastic component, had largely degraded. Despite the seemingly very good state of preservation, there was actually very little left of the original tissue structure.

“We have to expect that at least in amber from the Dominican Republic, macromolecules are no longer detectable,” says the supervisor of the study, Prof. Dr. Jes Rust from the Institute for Geosciences. It was not possible to detect more complex molecules such as proteins, but final analyses are still pending. The degradation processes in this amber deposit are therefore very advanced, and there is very little left of the original substance.

Acids in tree resin attack bone

Amber is normally considered an ideal preservative: Due to the tree resin, we have important insights into the insect world of millions of years. But in the lizard’s bone tissue, the resin might even have accelerated the degradation processes: Acids in the tree secretion have probably attacked the apatite in the bone — similar to tooth decay.


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New thalattosaur species discovered in Southeast Alaska

Scientists at the University of Alaska Fairbanks have identified a new species of thalattosaur, a marine reptile that lived more than 200 million years ago.

The new species, Gunakadeit joseeae, is the most complete thalattosaur ever found in North America and has given paleontologists new insights about the thalattosaurs’ family tree, according to a paper published today in the journal Scientific Reports. Scientists found the fossil in Southeast Alaska in 2011.

Thalattosaurs were marine reptiles that lived more than 200 million years ago, during the mid to late Triassic Period, when their distant relatives — dinosaurs — were first emerging. They grew to lengths of up to 3-4 meters and lived in equatorial oceans worldwide until they died out near the end of the Triassic.

“When you find a new species, one of the things you want to do is tell people where you think it fits in the family tree,” said Patrick Druckenmiller, the paper’s lead author and director and earth sciences curator at the University of Alaska Museum of the North. “We decided to start from scratch on the family tree.”

Prior to the discovery of Gunakadeit joseeae, it had been two decades since scientists had thoroughly updated thalattosaur interrelationships, Druckenmiller said. The process of re-examining a prehistoric animal’s family tree involves analyzing dozens and dozens of detailed anatomical features from fossil specimens worldwide, then using computers to analyze the information to see how the different species could be related.

Druckenmiller said he and collaborator Neil Kelley from Vanderbilt University were surprised when they identified where Gunakadeit joseeae landed.

“It was so specialized and weird, we thought it might be out at the furthest branches of the tree,” he said. Instead it’s a relatively primitive type of thalattosaur that survived late into the existence of the group.

“Thalattosaurs were among the first groups of land-dwelling reptiles to readapt to life in the ocean,” Kelley said. “They thrived for tens of millions of years, but their fossils are relatively rare so this new specimen helps fill an important gap in the story of their evolution and eventual extinction.”

That the fossil was found at all is a remarkable. It was located in rocks in the intertidal zone. The site is normally underwater all but a few days a year. In Southeast Alaska, when extreme low tides hit, people head to the beaches to explore. That’s exactly what Jim Baichtal, a geologist with the U.S. Forest Service’s Tongass National Forest, was doing on May 18, 2011, when low tides of -3.7 feet were predicted.

He and a few colleagues, including Gene Primaky, the office’s information technology professional, headed out to the Keku Islands near the village of Kake to look for fossils. Primaky saw something odd on a rocky outcrop and called over Baichtal, “Hey Jim! What is this?” Baichtal immediately recognized it as a fossilized intact skeleton. He snapped a photo with his phone and sent it to Druckenmiller.

A month later, the tides were forecasted to be almost that low, -3.1 feet, for two days. It was the last chance they would have to remove the fossil during daylight hours for nearly a year, so they had to move fast. The team had just four hours each day to work before the tide came in and submerged the fossil.

“We rock-sawed like crazy and managed to pull it out, but just barely,” Druckenmiller said. “The water was lapping at the edge of the site.”

Once the sample was back at the UA Museum of the North, a fossil preparation specialist worked in two-week stints over the course of several years to get the fossil cleaned up and ready for study.

When they saw the fossil’s skull, they could tell right away that it was something new because of its extremely pointed snout, which was likely an adaptation for the shallow marine environment where it lived.

“It was probably poking its pointy schnoz into cracks and crevices in coral reefs and feeding on soft-bodied critters,” Druckenmiller said. Its specialization may have been what ultimately led to its extinction. “We think these animals were highly specialized to feed in the shallow water environments, but when the sea levels dropped and food sources changed, they had nowhere to go.”

Once the fossil was identified as a new species, it needed a name. To honor the local culture and history, elders in Kake and representatives of Sealaska Corp. agreed the Tlingit name “Gunakadeit” would be appropriate. Gunakadeit is a sea monster of Tlingit legend that brings good fortune to those who see it. The second part of the new animal’s name, joseeae, recognizes Primaky’s mother, JoseĆ© Michelle DeWaelheyns.


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