Tiny T. rex fossils may be distinct species – but not everyone agrees

 

Image courtesy of Raul Martin

 Joel Kontinen

Palaeontologists can’t agree on whether fossils from several small dinosaurs represent juvenile Tyrannosaurus rex or smaller adults of a separate species that lived alongside them

Some researchers think that Tyrannosaurus rex may not have been the only large carnivore reigning over North America during the Late Cretaceous ,  

A reinterpretation of several fossils of small dinosaurs sometimes categorised as young T. rex adds weight to the controversial idea that another smaller species, called Nanotyrannus lancensis, lived alongside the king of the dinosaurs.

“This is the most famous fossil animal in the world,” says Nicholas Longrich at the University of Bath in the UK. “There are a lot of people looking at it. And we can’t agree.”

“The debate has divided palaeontologists for decades. A 1960s paper argued that a skull unearthed two decades earlier in Montana’s Hell Creek Formation was from a T. rex that had died before reaching full maturity. But in the 1980s, others argued that differences between the skull and known T. rex specimens showed this fossil was in fact an adult of a distinct species, which they named Nanotyrannus lancensis.”

Some researchers have stated that the number of dinosaurs is smaller than what is sad in journals.  

More recent work based on additional fossils disputed this, arguing that the variation between the smaller fossils and full-size T. rex fossils were differences of age, not of species. The debate has implications for making sense of the ecology and diversity of dinosaurs in the period just before they went extinct.

Source: 

James Dinneen, 2024. Tiny T. rex fossils may be distinct species – but not everyone agrees | New Scientist. 3 January

 

 

Soft Tissue From a 180 Million Year Old Ichthyosaur

Image courtesy of Dmitry Bogdanov, CC BY 3.0.


Joel Kontinen

Nature has an interesting article on a 180 million year old ichthyosaur, authored by Mary Schweitzer and 22 other researchers.,

Schweitzer’s university has this to say about the findings:

“Molecular and microstructural analysis of a Stenopterygius ichthyosaur from the Jurassic (180 million years ago) reveals that these animals were most likely warm-blooded, had insulating blubber and used their coloration as camouflage from predators.”

The press release quotes Johan Lindgren:“Both the body outline and remnants of internal organs are clearly visible,” says Lindgren. “Remarkably, the fossil is so well-preserved that it is possible to observe individual cellular layers within its skin.”

“Schweitzer and NC State research assistant Wenxia Zheng extracted soft tissues from the samples and performed multiple, high-resolution immunohistochemical analyses. ‘We developed a panel of antibodies that we applied to all of the samples, and saw differential binding, meaning the antibodies for a particular protein – like keratin or hemoglobin – only bound to particular areas,’ Schweitzer says. ‘This demonstrates the specificity of these antibodies and is strong evidence that different proteins persist in different tissues. You wouldn’t expect to find keratin in the liver, for example, but you would expect hemoglobin. And that’s what we saw in the responses of these samples to different antibodies and other chemical tools.’ ”

Their “results were repeatable and consistent across labs.” The soft tissue here was much older than in Schweitzer’s other discoveries for instance, in A t-rex and a Hadrosaur. It concludes that millions of years can’t be true.

Source:

Peake, Tracey. 2018. Soft Tissue Shows Jurassic Ichthyosaur Was Warm-Blooded, Had Band Camouflage, Nc State University.