T-Rex arms are kind of ridiculous. They're absolutely tiny compared to the rest of their body, they can't touch each other, and they sort of throw off the whole deadly predator vibe a little bit. 

I'm not just pointing this out to be mean though, I mean a little bit, but not just that. This week, we bring you news of a new hypothesis as to why their arms evolved to be so small, and so far apart. 

In years gone by, academics have put forward a lot of ideas about why smaller arms would be advantageous for theropods. The fan-favorite group that includes T-Rex, Velociraptor, and many others.

They suggested that maybe the small little hands were useful to grab prey, to help them get up, or to hold on while mating. Some researchers even suggested that maybe they were just kind of attractive, you know, to other theropods. There's no accounting for taste, but when academics looked at these functional suggestions more, it became clear that having little arms wasn't particularly advantageous for any of it.

Others suggested that maybe there was a trade-off between evolving a huge head and disproportionately small arms, or that the theropods just didn't use their arms enough for there to be much pressure for evolution to do anything. 

But a new proposal, published in the journal Acta Paleontologica Polonica, suggests that maybe we had it the wrong way round. Maybe it's not about what small arms can reach, but how well they can stay out of the way.

When T-Rex ate, they really ate. They were thought to feed on carcasses in groups, and they weren't polite about it. With lots of powerful jaws and mashing of teeth at play. In that kind of situation, vulnerable limbs that could easily get in the way of those jaws could be bitten clean off.

And that would be bad news for the injured T-Rex. That wound would be easily infected and could lead to death. Tyrannosaurs with small arms though might have largely avoided this fate. And they would likely live longer than their bigger armed counterparts, meaning they were more likely to breed and pass on their cute little arms to future generations.

None of the previous ideas scientists put forward on this were particularly testable. You can't go back in time and see why tiny arms might have been desirable. 

This theory also suffers from the time travel problem, but it is possible to gather evidence for it by checking bones we've already discovered for patterns of damage related to their size and position, as well as a few other things set forth in the paper. 

Basically, it's possible to ask, "Did having bigger arms result in injury to the animal?" To do that, the author hopes that a sort of global academic crowd sourcing effort could be arranged. More hands make light work after all. 

So if you happen to be a researcher with some access to small armed fossilized dino friends, this one goes out to you. Paging Cali over at PBS Eons.  

And if that wasn't enough about ancient friends for you, great news, we've got a big week for fossils. In a study published online last month in the Journal of Vertebrate Paleontology, researchers presented a new analysis of three incomplete giant ichthyosaur specimens, from the Swiss Alps.

Ichthyosaurs were a diverse group of marine reptiles that lived basically up until the extinction of the dinosaurs 66 million years ago. But we're talking about giant ichthyosaurs here, which are much older and lived only until the late Triassic period, more than 200 million years ago. 

In fact, this new finding helps establish how long they were around. It represents the youngest giant ichthyosaurs ever on Earth. Weighing up to 80 tons and measuring in at over 20 meters long, giant ichthyosaurs would have rivaled today's (?~3:25) whales in size. 

But despite being so massive, we've found relatively few fossil remains, so what we know about them is still fairly limited, which is part of what makes these newly found fragments so exciting.

This fossil hall was mainly comprised of ribs, vertebrae, and jaw fragments. It also included the largest ichthyosaur tooth ever found, which has a root that measured 60 millimeters in diameter. Now, this is especially exciting because only one giant ichthyosaur has ever been found with teeth. Researchers had been guessing that many of them were more like today's marine suction feeders, which don't need teeth to capture prey, or at least that they got along without teeth somehow. 

The previous largest ichthyosaur tooth came from a specimen that was 18 meters long, comes from a species of giant ichthyosaur named Himalayasaurus.

Interestingly though, the newly described tooth was shaped very differently from Himalaysaurus. Researchers believe this difference might be an indication that their specimen could deserve to be classified in its own group. They want to see more evidence than just the one tooth before advocating for that too hard.

It does suggest that giant ichthyosaurs had a bunch of different feeding adaptations, both toothy, and toothless. The researchers proposed that somewhat like today's whales, there were loads of different kinds of giant ichthyosaurs swimming around in the Triassic.

The age of these fossils also confirms that these giant ichthyosaurs persisted into the latest Triassic period, which there had been limited evidence of before. Despite the size of these fossils, researchers have found them pretty hard to uncover, so progression in our understanding of this mysterious species is likely to be slow. 

But scientists hope to rise to the challenge and find new, better fossils soon, perhaps up in the mountains, like with these specimens. Strange as it may seem to go up to look for marine reptiles.

Let's wish them luck because knowing more about these prehistoric giants is high on my wishlist.

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