Dinosaurs up in the mountains, dinosaur embryos

[lpetrich]

Cool Oasis for Cretaceous Feathered Dinosaurs - Eos - "A new study found that the Jehol Biota had chilly temperatures and high altitudes when feathered dinosaurs roamed the slopes. "

The Jehol Biota, an ancient ecosystem in Liaoning province in northeastern China, includes a dense and diverse array of Cretaceous flora and fauna and is a hot spot of feathered dinosaur fossils. A new study reconstructs a cool climate and high elevation at the site, providing critical environmental context for the wide array of dinosaurs preserved there.

Paleobiologists do not think that feathers, which evolved during the Jurassic, were originally used for flying because early examples were too small and stubby to support flight. Instead, like feathers on modern birds, dinosaurs’ feathers likely served other purposes, including insulation.

This was in the Early Cretaceous, about 125 million years ago. From the isotopic composition of carbonate deposits, the average springtime temperature was about 6 C, and from there and the ocean-temperature estimate of 15 - 35 C, the altitude was likely 3 to 4 kilometers.

Zhang et al. found that the altitude was likely 3–4 kilometers (about 10,000–13,000 feet) at the site of the Jehol Biota during the Cretaceous. The paleoelevation estimate is supported by two additional lines of evidence. During the Early Cretaceous, northeastern China was undergoing dramatic tectonic changes associated with the Yanshanian orogeny. Biology reflects a colder climate, too, with remains of plants known to live in cool ecosystems found nearby.

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With these pieces in place, Zhang thought it reasonable that dinosaurs in this region would have benefited from insulation. With previous evidence from eggshells and bones that the dinosaurs’ body temperatures were much higher than the cool air temperatures this study estimated, Zhang reasoned that the dinosaurs may have needed feathers’ help to stay warm.

“It’s long been thought that feathers helped dinosaurs with insulation, as well as for display,” said Sarah Davis, an evolutionary paleobiologist at the University of Texas at Austin. “The idea that feathers and feather-like structures are prevalent in this community of dinosaurs, in part because of the climate, makes sense. Feathered dinosaurs could have done well at this locality because of their insulation.”

 

[lpetrich]

High‐Altitude and Cold Habitat for the Early Cretaceous Feathered Dinosaurs at Sihetun, Western Liaoning, China - Zhang - 2021 - Geophysical Research Letters - Wiley Online Library

Abstract

During the Early Cretaceous, significant tectonic regime transformation occurred in East China. Meanwhile, the Jehol Biota, which contains world-famous feathered dinosaurs, flourished. However, few studies have been conducted to investigate the influence of tectonic regime transformation on regional topography and climates and the possible climatic causes of the unique characteristics of these dinosaurs. Here, we address these issues by applying clumped isotope paleothermometry to Early Cretaceous carbonates in NE China. In the Sihetun area, the mean annual paleotemperature derived from paleosol carbonates was 5.9 ± 1.7°C, and the paleoelevation was 2.8–4.1 km during the Early Cretaceous. The topographic evolution was closely related to the subduction of the paleo-Pacific plate beneath East Asia during this period. Our results suggest a high altitude and cold habitat with frozen winters for the Jehol Biota in the Sihetun area, which implies possible climate-Keywords:influenced evolution of the feathered characteristic of the dinosaurs.

Plain Language Summary

During the Early Cretaceous, the Jehol Biota, especially the unique feathered dinosaurs, flourished in western Liaoning Province, China. As insulation devices, the feathers helped these nonavian dinosaurs resist the cold climate, although conventional opinions have suggested that the Early Cretaceous was a typical “greenhouse climate” world. Based on the clumped isotopes of the paleosol carbonates in the Sihetun area, our study estimates the paleotemperature and paleoaltitude of the living habitat of these feathered dinosaurs during the Early Cretaceous. We suggest that the feathered dinosaurs in NE China lived in a high-altitude habitat with frozen winters and volcanic eruptions, which implies possible climate-influenced evolution of the feathered characteristic of the dinosaurs. We also suggest that topographic change-induced cooling was caused by significant tectonic regime transformation in East China.

 

[lpetrich]

A dinosaur embryo has been found inside a fossilized egg. Here's what that means. - CBS News

"The embryo is that of the bird-like oviraptorosaurs" and "In studying the embryo, researchers found the dinosaur took on a distinctive tucking posture before hatching, which had been considered unique to birds."

It was found in Ganzhou, Jiangxi Province, and it is from the Late Cretaceous.

An exquisitely preserved in-ovo theropod dinosaur embryo sheds light on avian-like prehatching postures: iScience

• A Late Cretaceous oviraptorid theropod dinosaur embryo is preserved in-ovo
• Its head lies ventral to the body, and the back curled along the egg's blunt pole
• Its posture is similar to that of a late-stage modern bird embryo
• Avian tucking behavior possibly originated among non-avian theropods

 

[lpetrich]

75-million-year old eggshells suggest most dinosaurs were warm-blooded | New Scientist

The body temperatures are inferred from the isotope composition of the shells.

In 2015, researchers applied this method to the eggshell of a theropod and a sauropod – a long-necked dinosaur – and found both were warm-blooded. Now Dawson’s team has applied this method to three more fossil eggshells.

Eggshell analysis

One belonged to a theropod called Troodon formosus, and another to a duck-billed dinosaur called Maiasaura peeblesorum. The researchers are confident the third eggshell belonged to a sauropod known as a dwarf titanosaur, although the dinosaur hasn’t yet been definitively identified.

The team’s analysis suggests the duck-billed dinosaur had a body temperature of 44°C, the troodon had a temperature up to 38°C and the dwarf titanosaur 36°C – all warmer than the environments they lived in.

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However, it appears the troodon’s body temperature sometimes dropped as low as 28°C, says Dawson. So it may have been heterothermic: able to lower its body temperature to save energy, as many present-day birds and mammals can.

What these findings don’t tell us is why dinosaurs’ ancestors evolved to be warm-blooded, something that is still hotly debated.

noting
Eggshell geochemistry reveals ancestral metabolic thermoregulation in Dinosauria

Some liked it hot: Dinosaurs evolved range of body temperatures | New Scientist

Robert Eagle of the University of California, Los Angeles, and colleagues estimated the body temperature of two types of dinosaur by analysing fossil eggshells. They found that Titanosaurus, a long-necked sauropod around 10 metres long and 13 tonnes in weight, had a body temperature around 38 °C, similar to modern mammals.

On the other hand, Oviraptor, a theropod about 2 metres long and 35 kilograms in weight, had a body temperature around 32 °C. This is still warmer than crocodiles and their relatives, suggesting that oviraptors generated some heat internally to keep their bodies above the ambient temperature and allow them to be more active. But it also suggests their physiology was not fully warm-blooded, which would require much more energy to maintain.

noting
Isotopic ordering in eggshells reflects body temperatures and suggests differing thermophysiology in two Cretaceous dinosaurs | Nature Communications

Eggshells are good for measuring core body temperature, since that is where eggs are produced. Teeth are not so good, because they are on the surface, and tooth formation temperatures are lower than eggshell formation temperatures by 1 to 3 C for American alligators and Nile crocodiles.

The recent results have the interesting feature of covering the dinosaurian family tree:
(ornithiscians: duckbills, saurischians: (sauropods, theropods (incl. birds) ) )

This suggests that the ancestral dinosaurs were at least somewhat or part-time warm-blooded.