Dilophosaurus dinosaurs, new research


This 2018 video says about itself:

What Jurassic Park Got WRONG – The Dilophosaurus

Jurassic Park brought millions of people around the world to fall in love with Dinosaurs, but they wrong about some key aspects regarding the Dilophosaurus. With Jurassic World Fallen Kingdom nearing release, we want to take you on a ride looking over the Dinosaurs brought to life by Ingen and the makers of Jurassic Park, and see how they stack up to the real thing!

From the University of Texas at Austin in the USA:

Famous ‘Jurassic Park’ dinosaur is less lizard, more bird

July 7, 2020

From movies to museum exhibits, the dinosaur Dilophosaurus is no stranger to pop culture. Many probably remember it best from the movie “Jurassic Park,” where it’s depicted as a venom-spitting beast with a rattling frill around its neck and two paddle-like crests on its head.

The dinosaur in the movie is mostly imagination, but a new comprehensive analysis of Dilophosaurus fossils is helping to set the record straight. Far from the small lizard-like dinosaur in the movies, the actual Dilophosaurus was the largest land animal of its time, reaching up to 20 feet in length, and it had much in common with modern birds.

The analysis was published open access in the Journal of Paleontology on July 7.

Dilophosaurus lived 183 million years ago during the Early Jurassic. Despite big-screen fame, scientists knew surprisingly little about how the dinosaur looked or fit into the family tree, until now.

“It’s pretty much the best, worst-known dinosaur,” said lead author Adam Marsh. “Until this study, nobody knew what Dilophosaurus looked like or how it evolved.”

Seeking answers to these questions, Marsh conducted an analysis of the five most-complete Dilophosaurus specimens while earning his Ph.D. from The University of Texas at Austin’s Jackson School of Geosciences. He is now the lead paleontologist at Petrified Forest National Park.

The analysis is co-authored by Jackson School Professor Timothy Rowe, who discovered two of the five Dilophosaurus specimens that were studied.

The study adds clarity to a muddled research record that reaches back to the first Dilophosaurus fossil to be discovered, the specimen that set the standard for all following Dilophosaurus discoveries. That fossil was rebuilt with plaster, but the 1954 paper describing the find isn’t clear about what was reconstructed — a fact that makes it difficult to determine how much of the early work was based on the actual fossil record, Marsh said.

Early descriptions characterize the dinosaur as having a fragile crest and weak jaws, a description that influenced the depiction of Dilophosaurus in the “Jurassic Park” book and movie as a svelte dinosaur that subdued its prey with venom.

But Marsh found the opposite. The jawbones show signs of serving as scaffolding for powerful muscles. He also found that some bones were mottled with air pockets, which would have helped reinforce the skeleton, including its dual crest.

“They’re kind of like bubble wrap — the bone is protected and strengthened,” Marsh said.

These air sacs are not unique to Dilophosaurus. Modern birds and the world’s most massive dinosaurs also have bones filled with air. In both cases, the air sacs lighten the load, which helped big dinosaurs manage their bulky bodies and birds take to the skies.

Many birds use the air sacs to perform other functions, from inflating stretchy areas of skin during mating rituals, to creating booming calls and dispersing heat. The intricate array of air pockets and ducts that extend from Dilophosaurus’ sinus cavity into its crests means that the dinosaur may have been able to perform similar feats with its headgear.

All the specimens Marsh examined came from the Kayenta Formation in Arizona and belong to the Navajo Nation. The University of California Museum of Paleontology holds in trust three of the specimens. The Jackson School Museum of Earth History holds the two discovered by Rowe.

“One of the most important responsibilities of our museum is curation,” said Matthew Brown, director of the Vertebrate Paleontology Collections. “We are very excited to help share these iconic Navajo Nation fossils with the world through research and educational outreach, as well as preserve them for future generations.”

To learn more about how the fossils compared with one another, Marsh recorded hundreds of anatomical characteristics of each fossil. He then used an algorithm to see how the specimens compared with the first fossil — which confirmed that they were indeed all Dilophosaurus.

The algorithm also revealed that there’s a significant evolutionary gap between Dilophosaurus and its closest dinosaur relatives, which indicates there are probably many other relatives yet to be discovered.

The revised Dilophosaurus record will help paleontologists better identify specimens going forward. Marsh said that the research is already being put into action. In the midst of his analysis, he discovered that a small braincase in the Jackson School’s collections belonged to a Dilophosaurus.

“We realized that it wasn’t a new type of dinosaur, but a juvenile Dilophosaurus, which is really cool,” Marsh said.

Permian-Triassic mass extinction and biodiversity


This 2018 video says about itself:

The Permian Extinction

252 million years ago 96% of all marine species and 70% of terrestrial vertebrate species vanished, this was the Permian extinction the second greatest mass extinction the earth has ever witnessed.

From the University of Leeds in England:

Permo-Triassic biodiversity patterns could offer a window into our climate future

June 17, 2020

A new study by the University of Leeds and University of Oxford has examined spatial biodiversity patterns across the Permo-Triassic mass extinction event (c. 252 million years ago). The Permo-Triassic mass extinction represents the most catastrophic event in the last 500 million years of evolutionary history and caused the loss of up 95% of species because of a cocktail of volcanic effects including extreme greenhouse warming.

Examination of the global distribution of tetrapods — amphibians, reptiles and their relatives — reveals that biodiversity was consistently higher at temperate latitudes, both before and after the mass extinction. This is in strong contrast to the modern day, where the greatest levels of biodiversity are found in the low latitudes of the tropics, near the equator.

The study, published in the journal Proceedings of the Royal Society B, shows how patterns of biodiversity can respond when temperatures in tropical regions become too extreme to support high levels of biodiversity. Examining the responses of organisms to rapid climatic changes in the distant past can offer a window into the potential impact of future global warming.

Study lead author Bethany Allen, PhD researcher at the School of Earth and Environment at Leeds, said: “Higher equatorial diversity has been recognised for over 200 years, but the consistency of this pattern throughout Earth history has been uncertain.

“The Late Permian to Middle Triassic is an ideal time interval to examine biodiversity trends. It is characterised by large-scale volcanic episodes, extreme greenhouse temperatures, and the most severe mass extinction event in Earth’s history.

“Our study shows that the regions we now associate with some of the richest and most diverse ecosystems on Earth were once too hot to support communities of large animals, likely reaching over 40°C. In the face of a rapidly warming planet, this window into our past could offer a glimpse into the future of those regions and the very real risk to the species that live there if we do not act to curb our carbon emissions and limit global warming.”

Australian big carnivorous dinosaurs, new discovery


This June 2019 video is called Australian Dinosaurs (Part 1).

This video is the sequel.

From the University of Queensland in Australia:

Tracking Australia’s gigantic carnivorous dinosaurs

June 17, 2020

North America had the T. rex, South America had the Giganotosaurus and Africa the Spinosaurus — now evidence shows Australia had gigantic predatory dinosaurs.

The discovery came in University of Queensland research, led by palaeontologist Dr Anthony Romilio, which analysed southern Queensland dinosaur footprint fossils dated to the latter part of the Jurassic Period, between 165 and 151 million-year-ago.

“I’ve always wondered, where were Australia’s big carnivorous dinosaurs?” Dr Romilio said.

“But I think we’ve found them, right here in Queensland.

“The specimens of these gigantic dinosaurs were not fossilised bones, which are the sorts of things that are typically housed at museums.

“Rather, we looked at footprints, which — in Australia — are much more abundant.

“These tracks were made by dinosaurs walking through the swamp-forests that once occupied much of the landscape of what is now southern Queensland.”

Most of the tracks used in the study belong to theropods, the same group of dinosaurs that includes Australovenator, Velociraptor, and their modern-day descendants, birds.

Dr Romilio said these were clearly not bird tracks.

“Most of these footprints are around 50 to 60 centimetres in length, with some of the really huge tracks measuring nearly 80 centimetres,” he said.

“We estimate these tracks were made by large-bodied carnivorous dinosaurs, some of which were up to three metres high at the hips and probably around 10 metres long.

“To put that into perspective, T. rex got to about 3.25 metres at the hips and attained lengths of 12 to 13 metres long, but it didn’t appear until 90 million years after our Queensland giants.

“The Queensland tracks were probably made by giant carnosaurs — the group that includes the Allosaurus.

“At the time, these were probably some of the largest predatory dinosaurs on the planet.”

Despite the study providing important new insights into Australia’s natural heritage, the fossils are not a recent discovery.

“The tracks have been known for more than half a century,” Dr Romilio said.

“They were discovered in the ceilings of underground coal mines from Rosewood near Ipswich, and Oakey just north of Toowoomba, back in the 1950s and 1960s.

“Most hadn’t been scientifically described, and were left for decades in museum drawers waiting to be re-discovered.

“Finding these fossils has been our way of tracking down the creatures from Australia’s Jurassic Park.”

Jurassic marine crocodiles, video


This 11 June 2020 video says about itself:

When Crocodiles Swam The Oceans

Crocodiles are good swimmers and often live near river mouths near the ocean and some of them even make brief excursions into the ocean. This means they are always at a tipping point of becoming marine animals. This is known because it has happened on several occasions throughout prehistory, but in the Jurassic, one group of crocs called the thalattosuchians would take this a step further in following whales and other marine reptiles in becoming fish-like.

Were Allosaurus dinosaurs cannibals?


This 2018 BBC video says about itself:

Steve Backshall looks at the Majungasaurus, the only know dinosaur to eat others from its own species.

From PLOS ONE, 27 May 2020:

High frequencies of theropod bite marks provide evidence for feeding, scavenging, and possible cannibalism in a stressed Late Jurassic ecosystem

Abstract

Bite marks provide direct evidence for trophic interactions and competition in the fossil record. However, variations in paleoecological dynamics, such as trophic relationships, feeding behavior, and food availability, govern the frequency of these traces.

Theropod bite marks are particularly rare, suggesting that members of this clade might not often focus on bone as a resource, instead preferentially targeting softer tissues.

Here, we present an unusually large sample of theropod bite marks from the Upper Jurassic Mygatt-Moore Quarry (MMQ). We surveyed 2,368 vertebrate fossils from MMQ in this analysis, with 684 specimens (28.885% of the sample) preserving at least one theropod bite mark.

This is substantially higher than in other dinosaur-dominated assemblages, including contemporaneous localities from the Morrison Formation. Observed bite marks include punctures, scores, furrows, pits, and striations. Striated marks are particularly useful, diagnostic traces generated by the denticles of ziphodont teeth, because the spacing of these features can be used to provide minimum estimates of trace maker size.

In the MMQ assemblage, most of the striations are consistent with denticles of the two largest predators known from the site: Allosaurus and Ceratosaurus. One of the bite marks suggests that a substantially larger theropod was possibly present at the site and are consistent with large theropods known from other Morrison Formation assemblages (either an unusually large Allosaurus or a separate, large-bodied taxon such as Saurophaganax or Torvosaurus).

The distribution of the bite marks on skeletal elements, particularly those found on other theropods, suggest that they potentially preserve evidence of scavenging, rather than active predation. Given the relative abundances of the MMQ carnivores, partnered with the size-estimates based on the striated bite marks, the feeding trace assemblage likely preserves the first evidence of cannibalism in Allosaurus.

See also here.

Ichthyosaur discovery in London Natural History Museum


This 27 January 2020 video from England says about itself:

197-Million-Year-Old Ichthyosaur Fossil Saved

The prehistoric fossil was discovered by amateur fossil hunter Jon Gopsill when he was out walking his dogs on 14 December 2019. The five-and-a-half foot long marine reptile had been exposed by recent storms. The specimen was successfully extracted on 27 December by experts working against the clock in the intertidal zone of Bridgwater Bay National Nature Reserve.

From Baylor University in the USA:

Fishing rod ‘selfie stick’ and scientific sleuthing turn up clues to extinct sea reptile

May 19, 2020

A Russian paleontologist visiting the Natural History Museum in London desperately wanted a good look at the skeleton of an extinct aquatic reptile, but its glass case was too far up the wall. So he attached his digital camera to a fishing rod and — with several clicks — snagged a big one, scientifically speaking.

Images from the “selfie stick” revealed that the creature, whose bones were unearthed more than a century ago on a coast in southern England, seemed very similar to a genus of ichthyosaurs he recognized from Russian collections.

He emailed the photos of the dolphin-like ichthyosaur to fellow paleontologist Megan L. Jacobs, a Baylor University doctoral candidate in geosciences. She quickly realized that the animal’s skeletal structure matched not only some ichthyosaurs she was studying in a fossil museum on the English Channel coast, but also some elsewhere in the United Kingdom.

Jacobs and paleontologist Nikolay G. Zverkov of the Russian Academy of Sciences — who “fished” for the ichthyosaur — merged their research, studying their collective photos and other materials and ultimately determining that the Russian and English ichthyosaurs were of the same genus and far more common and widespread than scientists believed.

Their study is published in the Zoological Journal of the Linnean Society.

“Ichthyosaurs swam the seas of our planet for about 76 million years,” Jacobs said. “But this 5-foot ichthyosaur from some 150 million years ago was the least known and believed to be among the rarest ichthyosaurs. The skeleton in the case, thought to be the only example of the genus, has been on display in the Natural History Museum in London since 1922.

Nikolay’s excellent detailed photos significantly expand knowledge of Nannopterygius enthekiodon,” she said. “Now, after finding examples from museum collections across the United Kingdom, Russia and the Arctic — as well as several other Nannopterygius species — we can say Nannopterygius is one of the most widespread genera of ichthyosaurs in the Northern Hemisphere.”

Additionally, the study described a new species, Nannopterygius borealis, dating from about 145 million years ago in a Russian archipelago in the Arctic. The new species is the northernmost and youngest representative of its kind, Jacobs said.

Previously, for the Middle and Late Jurassic epochs, the only abundant and most commonly found ichthyosaur was Ophthalmosaurus, which had huge eyes and was about 20 feet long. It was known from hundreds of specimens, including well-preserved skeletons from the Middle Jurassic Oxford Clay Formation of England, Jacobs said.

“For decades, the scientific community thought that Nannopterygius was the rarest and most poorly known ichthyosaur of England,” Zverkov said. “Finally, we can say that we know nearly every skeletal detail of these small ichthyosaurs and that these animals were widespread. The answer was very close; what was needed was just a fishing rod.”

Jurassic squid attacked fish, new discovery


A close-up image showing the damaged head and body of the Dorsetichthys bechei fish with the arms of the cephalopod Clarkeiteuthis montefiorei clamped around it. Credit: Malcolm Hart, Proceedings of the Geologists’ Association

This photo shows a close-up image of the damaged head and body of the Dorsetichthys bechei fish with the arms of the cephalopod Clarkeiteuthis montefiorei clamped around it. Credit: Malcolm Hart, Proceedings of the Geologists’ Association.

From the University of Plymouth in England:

Fossil reveals evidence of 200-million-year-old ‘squid‘ attack

May 6, 2020

Scientists have discovered the world’s oldest known example of a squid-like creature attacking its prey, in a fossil dating back almost 200 million years.

The fossil was found on the Jurassic coast of southern England in the 19th century and is currently housed within the collections of the British Geological Survey in Nottingham.

In a new analysis, researchers say it appears to show a creature — which they have identified as Clarkeiteuthis montefiorei — with a herring-like fish (Dorsetichthys bechei) in its jaws.

They say the position of the arms, alongside the body of the fish, suggests this is not a fortuitous quirk of fossilization but that it is recording an actual palaeobiological event.

They also believe it dates from the Sinemurian period (between 190 and 199 million years ago), which would predate any previously recorded similar sample by more than 10 million years.

The research was led by the University of Plymouth, in conjunction with the University of Kansas and Dorset-based company, The Forge Fossils.

It has been accepted for publication in Proceedings of the Geologists’ Association and will also be presented as part of Sharing Geoscience Online, a virtual alternative to the traditional General Assembly held annually by the European Geosciences Union (EGU).

Professor Malcolm Hart, Emeritus Professor in Plymouth and the study’s lead author, said: “Since the 19th century, the Blue Lias and Charmouth Mudstone formations of the Dorset coast have provided large numbers of important body fossils that inform our knowledge of coleoid palaeontology. In many of these mudstones, specimens of palaeobiological significance have been found, especially those with the arms and hooks with which the living animals caught their prey.

“This, however, is a most unusual if not extraordinary fossil as predation events are only very occasionally found in the geological record. It points to a particularly violent attack which ultimately appears to have caused the death, and subsequent preservation, of both animals.”

In their analysis, the researchers say the fossilised remains indicate a brutal incident in which the head bones of the fish were apparently crushed by its attacker.

They also suggest two potential hypotheses for how the two animals ultimately came to be preserved together for eternity.

Firstly, they suggest that the fish was too large for its attacker or became stuck in its jaws so that the pair — already dead — settled to the seafloor where they were preserved.

Alternatively, the Clarkeiteuthis took its prey to the seafloor in a display of ‘distraction sinking’ to avoid the possibility of being attacked by another predator. However, in doing so it entered waters low in oxygen and suffocated.

Dinosaur footprints discovery in French caves


This 2016 video says about itself:

Incredible caves are all over the world, for this list we’ve compiled the top 10 most astonishing caves. Each have they own unique facts, history, looks and location but they are all awesome and astounding in their own ways.

10. Ellison’s Cave, USA – 0:08 Ellison’s Cave is a pit cave located on Pigeon Mountain in the Appalachian Plateaus of Northwest Georgia. It is the 12th deepest cave in the United States and features the deepest, unobstructed underground pitch in the continental US named Fantastic Pit. 9. Ice Cave, Russia – 0:43 This incredible cave near the Mutnovsky Volcano in Russia is the result of volcanic fed hot springs running through ice to create an ice cave that has a very shallow roof allowing sunlight to pass through. This cave was discovered by accident in 2012 and is nearly 980 ft. long. 8. Cave of the Swallows, Mexico – 1:12 The Cave of the Swallows is an open air pit cave in San Luis Potosí, Mexico. The mouth of the cave is 160 by 203 feet wide further widening to a room approximately 994 by 442 ft wide.[2] The floor of the cave is a 1214 ft free fall drop from the top making it the largest known cave shaft in the world, the second deepest pit in Mexico and perhaps the 11th deepest in the world. 7. Waitomo Glowworm Cave, New Zealand – 1:45 The Waitomo Glowworm Caves on the North Island of New Zealand is known for it’s spectacular glowworms. This species of glowworms is found exclusively in New Zealand and are the size of an average mosquito. If you are so keen to see the glow worms you can join an organized boat tour that goes right underneath them. 6. Phraya Nakhon Cave, Thailand – 2:15 Phraya Nakhon Cave in Thailand is located 4 hours south of Bangkok. It’s a fairly accessible cave to the public as it is only a 30 minute sweaty hike to reach the cave. King Chulalongkorn built the Kuha Karuhas pavilion inside the cave in 1890, when he fell in love with the beauty of the cave during his visit. If you want there is a Boat that will drop you off in some murky water at the entrance of the cave for 300 Baht but is only operational in good weather conditions. 5. Antelope Canyon, USA – 2:45 Antelope Canyon is primarily a water eroded rock canyon located near the city of Page, in the northern part of the state of Arizona Antelope Canyon is a known for its smooth, wavy walls of sandstone, caused mainly by flash flooding and rain 4. Batu Caves, Malaysia – 3:24 The Batu Caves contain a Buddhist temple created on the edge of a cliff in Myanmar, and is the unassuming entrance to Kyaut Sae Cave. Legend has it, that in the 13th century the massive cave was originally used as a place of hiding for locals who wanted to hide from the Mongols. 3. Fingal’s Cave, Scotland – 3:43 Fingal’s Cave, located in on an uninhabited island called Staffa, is 72 feet tall and 270 feet deep. This sea cave a one of a kind with visually astonishing hexagonal columns made of basalt. It was formed by the cooling on the upper and lower surfaces of the solidified lava which resulted in contraction and fracturing. 2. Son Doong Cave, Vietnam – 4:33 Son Doong Cave in Vietnam is the largest cave discovered on earth. It was discovered in 1991 by a local man but not fully explored until 2009. Son Doong Cave has a max depth of 490 feet and max length of 30,000 feet. It was created by a large vertical fault in the limestone that was flooded by river water which carved it’s way deep under the surface for millions of years. Having limestone walls that run in a nearly in a straight line allows for much greater stability, which is what has allowed this cave to get so big. 1. Naica Mine, Mexico – 5:23 This incredible cave was accidentally found by the Naica mining company as they were drilling deep for silver, lead and zinc. They noticed a large crystal which appeared to be made of ice but considering the temperature inside the cave is 136 Fahrenheit or 58 degrees Celsius they knew immediately it was a large rare crystal growth.

By John Pickrell, April 27, 2020 at 6:00 am:

Deep caves are a rich source of dinosaur prints for this paleontologist

Several deep caves in France are proving to be a surprising source of ancient tracks

Crawling through tight underground passages in southern France, paleontologist Jean-David Moreau and his colleagues have to descend 500 meters below the surface to reach the only known footprints of long-necked dinosaurs called sauropods ever found in a natural cave.

The team discovered the prints, left by behemoths related to Brachiosaurus, in Castelbouc Cave in December 2015 (SN: 2/21/18). But getting to the site might make even the most hardened field scientists balk. Wriggling through such dark, damp and cramped spaces every time they visit is challenging for elbows and knees, and even trickier when carrying delicate equipment such as cameras, lights and laser scanners.

It’s both physically exhausting and “not comfortable for someone claustrophobic”, with the researchers spending up to 12 hours underground each time, says Moreau, of the Université Bourgogne Franche-Comté in Dijon. It can be dangerous too, as some parts of the cave are periodically flooded, so accessing the deep chambers must be limited to periods of drought, he says.

Moreau has studied fossilized dinosaur footprints and plants for more than a decade in southern France’s Causses Basin, one of the richest areas for aboveground dinosaur tracks in Europe. When spelunkers chanced upon some underground prints in 2013, Moreau and his colleagues realized there could be lots of dinosaur prints within the region’s many deep, limestone caves. Footprints left in soft mud or sand hundred million years ago could have been turned to rock and forced underground over many eons.

And deep caves, being less exposed to wind and rain, “can occasionally offer larger and better-preserved surfaces [imprinted by dinosaur steps] than outdoor outcrops,” Moreau says.

Moreau’s team is the only one to have discovered dinosaur footprints in natural caverns, though prints also have been found around the world in human-made railway tunnels and mines. “The discovery of dinosaur tracks inside a natural karstic cave is extremely rare,” he says.

The first subsurface dinosaur prints that the team found were 20 kilometers away from Castelbouc at a site called Malaval Cave, reached via an hour-long clamber through an underground river with several 10-meter drops. “One of the main difficulties in the Malaval Cave is to walk taking care to not touch or break any of the delicate and unique [mineral formations],” Moreau says.

Those three-toed prints, each up to 30 centimeters long and detailed in 2018 in the International Journal of Speleology, were left by carnivorous dinosaurs walking upright on their hind legs through marshland about 200 million years ago.

In contrast, the five-toed herbivore tracks in Castelbouc Cave are each up to 1.25 meters long and were left by three enormous herbivorous sauropods that walked the shoreline of a sea about 168 million years ago. What’s more, these prints are on the cave’s ceiling 10 meters above the floor, the team reports in a study published online March 25 in Journal of Vertebrate Paleontology.

In fact, “the tracks we see on the roof are not ‘footprints’, they are ‘counterprints’”, Moreau explains. “The dinosaurs walked on a surface of clay, which is nowadays totally eroded to form the cave. Here, we only see the overlying layer [of sediment that filled in the footprints],” leaving reverse prints bulging out of the ceiling. It’s similar to what you’d see if you filled a footprint in mud with plaster and then washed all of the mud away to leave the cast.

The tracks are important as they hail from a time in the early to mid-Jurassic Period from 200 million to 168 million years ago when sauropods were diversifying and spreading across the world, but relatively few fossil bones have been found (SN: 12/1/15). These prints confirm that sauropods then inhabited coastal or wetland environments in what is now southern France.

Moreau is now leading researchers in exploring “another deep and long cave, which has yielded hundreds of dinosaur footprints”, he says. The team has yet to publish those results, which he says may prove to be the most exciting of all.

World’s oldest dinosaur eggs, new research


This 9 April 2020 video is called Synchrotron X-ray sheds light on some of the world’s oldest dinosaur eggs.

From the European Synchrotron Radiation Facility:

Synchrotron X-ray sheds light on some of the world’s oldest dinosaur eggs

Dinosaur ‘Easter eggs’ reveal their secrets in 3D thanks to X-rays and high-powered computers

April 9, 2020

An international team of scientists led by the University of the Witwatersrand in South Africa, has been able to reconstruct, in the smallest details, the skulls of some of the world’s oldest known dinosaur embryos in 3D, using powerful and non-destructive synchrotron techniques at the ESRF, the European Synchrotron in France. They found that the skulls develop in the same order as those of today’s crocodiles, chickens, turtles and lizards. The findings are published today in Scientific Reports.

University of the Witwatersrand scientists publish 3D reconstructions of the ~2cm-long skulls of some of the world’s oldest dinosaur embryos in an article in Scientific Reports. The embryos, found in 1976 in Golden Gate Highlands National Park (Free State Province, South Africa) belong to South Africa’s iconic dinosaur Massospondylus carinatus, a 5-meter long herbivore that nested in the Free State region 200 million years ago.

The scientific usefulness of the embryos was previously limited by their extremely fragile nature and tiny size. In 2015, scientists Kimi Chapelle and Jonah Choiniere, from the University of Witwatersrand, brought them to the European Synchrotron (ESRF) in Grenoble, France for scanning. At the ESRF, an 844 metre-ring of electrons travelling at the speed of light emits high-powered X-ray beams that can be used to non-destructively scan matter, including fossils. The embryos were scanned at an unprecedented level of detail — at the resolution of an individual bone cell. With these data in hand, and after nearly 3 years of data processing at Wits’ laboratory, the team was able to reconstruct a 3D model of the baby dinosaur skull. “No lab CT scanner in the world can generate these kinds of data,” said Vincent Fernandez, one of the co-authors and scientist at the Natural History Museum in London (UK). “Only with a huge facility like the ESRF can we unlock the hidden potential of our most exciting fossils. This research is a great example of a global collaboration between Europe and the South African National Research Foundation,” he adds.

Up until now, it was believed that the embryos in those eggs had died just before hatching. However, during the study, lead author Chapelle noticed similarities with the developing embryos of living dinosaur relatives (crocodiles, chickens, turtles, and lizards). By comparing which bones of the skull were present at different stages of their embryonic development, Chapelle and co-authors can now show that the Massospondylus embryos were actually much younger than previously thought and were only at 60% through their incubation period.

The team also found that each embryo had two types of teeth preserved in its developing jaws. One set was made up of very simple triangular teeth that would have been resorbed or shed before hatching, just like geckos and crocodiles today. The second set were very similar to those of adults, and would be the ones that the embryos hatched with. “I was really surprised to find that these embryos not only had teeth, but had two types of teeth. The teeth are so tiny; they range from 0.4 to 0.7mm wide. That’s smaller than the tip of a toothpick!,” explains Chapelle.

The conclusion of this research is that dinosaurs developed in the egg just like their reptilian relatives, whose embryonic developmental pattern hasn’t changed in 200 million years. “It’s incredible that in more than 250 million years of reptile evolution, the way the skull develops in the egg remains more or less the same. Goes to show — you don’t mess with a good thing!,” concludes Jonah Choiniere, professor at the University of Witwatersrand and also co-author of the study.

The team hopes to apply their method to other dinosaur embryos to estimate their level of development. They will be looking at the rest of the skeleton of the Massospondylus embryos to see if it also shares similarities in development with today’s dinosaur relatives. The arms and legs of the Massospondylus embryos have already been used to show that hatchlings likely walked on two legs.

Main findings:

  1. High powered X-rays were used to reconstruct the skulls of some of the world’s oldest known dinosaur embryos.
  2. The skull could be seen in 3D at an unprecedented level of detail.
  3. Dinosaur embryo skulls appear to develop in the same order as those of today’s crocodiles, chickens, turtles and lizards.
  4. These dinosaur embryos appear to have been fossilised at approximately 60% through their incubation period. This is much earlier than previously thought.
  5. The dinosaur embryos have two types of teeth that range in size from 0.4 to 0.7mm wide. One of these sets would have been shed or resorbed before hatching.

Why Jurassic crocodiles were big


This 2009 video says about itself:

Paul Sereno and his team of scientists and artists show us what the world looked like in an age when crocs ate dinosaurs.

From the University of Nebraska-Lincoln in the USA:

Water pressure: Ancient aquatic crocs evolved, enlarged to avoid freezing

Study pinpoints minimum survivable size of Jurassic crocodiles

March 30, 2020

Summary: Ancient crocodilian ancestors that abandoned land for water nearly 200 million years ago supposedly got larger because they were released from the constraints of gravity, territory and diet. But a new study suggests that the upper bounds of size in aquatic vs. landlocked crocs were similar — and that smaller aquatic species got larger mostly to avoid freezing in the frigid, heat-stealing depths.

Taking the evolutionary plunge into water and abandoning land for good, as some crocodilian ancestors did nearly 200 million years ago, is often framed as choosing freedom: from gravity, from territorial boundaries, from dietary constraints.

Water might inflict more pressure in the pounds-per-square-inch sense, the thinking went, but it also probably relieved some — especially the sort that kept crocs from going up a size or 10. If they wanted to enjoy the considerable spoils of considerable size, water seemed the easy way.

A recent study from the University of Nebraska-Lincoln’s Will Gearty, who compiled a database of 264 species stretching back to the Triassic Period, says that freedom was actually compulsion in disguise.

After analyzing the database of crocodyliforms — a lineage of crocodile-like species that share a common ancestor — Gearty found that the average weights of aquatic crocodyliforms did easily surpass their semi-aquatic and landlocked counterparts, sometimes by a factor of 100.

But the study suggests that this disparity represented a response to, not a release from, the pressures of natural selection. Rather than expanding the range of crocodyliform body sizes, as some longstanding theories would predict, taking to the water instead seemed to compress that range by raising the minimum size threshold needed to survive its depths. The maximum size of those aquatic species, by contrast, barely budged over time.

And when Gearty derived a set of equations to estimate the largest feasible body sizes under aquatic, semi-aquatic and terrestrial conditions?

“All three habitats had roughly the same upper limit (on size),” he said. “So even though it seems like you’re released from this pressure, you’re actually squeezed into an even smaller box than before.”

Two major factors — lung capacity and body heat — seem to have helped initiate the squeeze play. Prior research had proposed that aquatic crocodyliforms got big in part because they needed to dive deeply for food, including the choice prey that would sustain a larger size. Upon digging into the literature, though, Gearty learned that lung volume increases more or less in lockstep with body size.

“So you actually don’t have much excess lung volume to spare,” said Gearty, a postdoctoral researcher in biological sciences. “When you get bigger, (lung capacity) is just basically scaling up with your body size to accommodate that extra size. The amount of time you could stay underwater increases a little bit, but not that much.”

At larger sizes, the evolutionary tradeoff between the benefits of longer, deeper dives and the energy demands of finding more food probably also reached a stalemate, he said, that helped cement the aquatic ceiling on size.

As for the higher floor? That’s where the thermal conductivity of water cranked up the evolutionary heat, Gearty said. Unfortunately for the aquatic crocs, water steals heat far faster than air does. The issue was likely compounded by the fact that temperatures in the waters they occupied were lower than the air temperatures enjoyed by their land-dwelling counterparts.

That would have left smaller aquatic crocodyliforms with only bad options: limit the duration and depth of their dives so that they could regularly return to the surface and warm themselves in the sun, or risk freezing to death during deeper hunts for food. Whether by starvation or hypothermia, either would eventually spell doom.

“The easiest way to counteract that is to get bigger,” Gearty said.

Getting bigger was especially appealing because the volume of body tissue, which generates heat, increases faster than the surface area of the skin that surrenders it. But the unforgiving consequences of heat loss still limited the pool of ancestors from which aquatic crocodyliforms could evolve.

“They actually needed to start at a larger size,” Gearty said. “So it’s not like a marine crocodile could have just evolved from anywhere. It had to be evolving from some non-marine crocodile that was already a little larger than normal.”

The fossil records of the crocodyliforms allowed Gearty and Jonathan Payne, his former doctoral adviser at Stanford University, to pinpoint the minimum weight threshold for aquatic survival: 10 kilograms, or about 22 pounds. And when they plotted the relationships of heat loss and lung capacity to body mass, they discovered that the two slopes crossed at almost exactly the same value: 10 kilograms.

“We were able to explain, with these physiological equations, exactly why there were no marine crocodiles below a certain size,” Gearty said. “This indicates that these very fundamental physiological constraints and controls … actually may be some of the strongest forces for pushing animals to different body sizes through time. Not whether there’s an asteroid hitting the world, not whether you’re being (hunted) by some other animal — that just these physical and chemical properties of the world we live in are what drive this. And if you want to enter a new habitat, you need to conform to that new set of properties.”

The findings mostly reinforce a 2018 Gearty-led study that found similar trends among nearly 7,000 living and extinct mammal species. An elementary difference between mammals and reptiles, though, initially left the verdict in doubt.

“The whole (premise) of the marine mammal project was that these things are warm-blooded, and they have to keep their temperature up,” Gearty said. “They have to really worry about this heat loss. So the idea was, ‘Well, would the same constraint occur in cold-blooded organisms that are also living in the ocean?’

“There have been a couple papers suggesting that some of these marine crocodiles may have been somewhat warm-blooded, and so they may have been able to kind of reheat their own bodies. But even if that’s the case, they were still going to be losing heat like these marine mammals would. They were still constrained by these thermoregulatory controls.”

GREYHOUNDS AND DOLPHINS

With the help of an undergraduate student at Stanford and funding from the National Science Foundation, Gearty spent most of the summer of 2017 tracking down the fossil records that informed the new study.

“But that was to find the stuff that’s readily available online,” he said. “Then you’ve got, you know, undocumented books that you need to find, and they have to get shipped from Europe or somewhere. So there were a lot of these one-offs. I was still measuring specimen photos and getting records up until I submitted the paper in the middle of last year.”

Gearty said he was mostly spared the time and expense of traveling to museums and physically measuring fossil dimensions, as some of his colleagues have in the name of their own research. But the haphazardness of some older classifications and documentation still had him following false leads and trying to make sense of the nonsensible.

“A lot of the crocodiles that people have described in papers have never actually been documented the way they’re supposed to be,” he said. “Someone might say, ‘Here’s the Nebraska crocodile.’ It’s just a colloquial name. And you’ll be like, ‘I guess I’ve got to go find the Nebraska crocodile.’ You look this up, and you see that there’s this crocodile from Nebraska, and this one, and this one. You don’t know which one is the ‘Nebraska crocodile.’

“You need to follow this trail of breadcrumbs, sometimes, to find these papers that may or may not have ever been published on these crocodiles that may or may not have ever been found. Fortunately, I was able to get most of the specimens just from the literature. But it did take a lot of digging to find the last probably 10% of the crocodiles.”

Many of the terrestrial fossils, in particular, trace body shapes that barely resemble the low-slung profile of the modern crocodile.

“The example I like to give is: Imagine a greyhound, and then put a crocodile skull on it,” Gearty said. “There were things like that running around on land probably 200 million years ago.”

Though their maximum size remained almost constant, marine species did evolve two to three times faster than the semi-aquatic and terrestrial groups, Gearty found. Along with increasing the size of smaller aquatic species, natural selection molded body forms to surmount the challenges presented by water. Scales, plates and other drag-increasing skin deposits disappeared. Heads and tails flattened. Snouts narrowed.

“All of these were probably more dolphin-like than modern crocodiles, with even longer, thinner tails,” he said. “And some of them had very paddle-like feet, almost like flippers.”

Despite the fact that virtually all modern crocodile species are semi-aquatic, Gearty said those adaptations served the aquatic crocodyliforms well — more than 100 million years before mammals ventured into the deep.

“No one has talked about it much, but really, these things were quite successful,” he said. “And some of them weren’t even fazed by some of the big, (cataclysmic) events. When the asteroid hit that killed all the dinosaurs, one of the marine groups just kind of kept going like nothing happened. A lot of the terrestrial species went extinct, but this group just kept ticking along for a long time.”