The Alvarezsaurid Thread

Galvasean

A close relative of Mononykus and Shuvuuia from Asia and also Alvarezsaurus from South America.

http://news.nationalgeographic.com/news/2008/09/080925-smallest-dinosaur.html

This discovery was probably to be expected. They would have had to have passed through North America at some stage if they lived in Asia and South America.


Illustration by Nick Longrich

marco_polo

A new alvarezsauroid dinosaur is being published in the Journal Science tommorrow.The 160 MYA specimen is named Haplocheirus sollers ("simple, skillful hand").

This is an important discovery as its age means that it is 63 million years older than its nearest known relatives, and also lived a full 15 million years before Archaeopteryx. The discovery removes any remaining doubt about the positioning of Alvarezsaurs in the therapod family.

http://www.scientificamerican.com/blog/post.cfm?id=new-large-clawed-jurassic-dinosaur-2010-01-28

"What Haplocheirus definitively shows," said Choiniere, "is that alvarezsauroids aren't birds. They're theropod dinosaurs, so they're closely related to birds, but they aren't actually an offshoot of birds themselves."

The ancient age of Haplocheirus "really extends our fossil records," Choiniere said in the interview with Science. As he noted in a prepared statement, "Haplocheirus is a transitional fossil because it shows an early evolutionary step in how the bizarre hands of later alvarezsaurs evolved from earlier predatory dinosaurs." By 160 million years ago, the new genus already had the short arms and long middle claw typical of later alvarezsauroids, but its arms are longer and the claw is a little shorter than the later, Cretaceous species.

Galvasean

Oh hey look another blow is struck against those gombeens from Kansas University. I suppose they'll probably ignore it now.

I was all excited when I read the 'large-clawed' bit. Thought it would be about therizinosaurs.
Oh well, an excellent find all the same.

Galvasean

I really like this illustration by Zina Deretsky:

marco_polo

A new species of dinosaur has been described by a team of researchers from Canada, Britain and China. The new species of alvarezsaur named Xixianykus zhangi was one of the smallest known dinosaurs discovered thus far and appears to have been highly adapted for a fast running lifestyle.

http://www.sciencedaily.com/releases/2010/03/100329084854.htm

This Late Cretaceous 'road-runner' had a number of adaptations for fast, efficient locomotion. Most strikingly, the upper leg (the femur or thigh bone) is particularly short in comparison to the lower leg and the foot -- a pattern seen in many running animals today. Other features of the hind limb, pelvis and backbone would have promoted stability and reduced superfluous, energy-wasting movements as Xixianykus dashed across prehistoric landscapes.

Dr. Corwin Sullivan, a Canadian researcher and one of the authors of the study said: "The limb proportions of Xixianykus are among the most extreme ever recorded for a theropod dinosaur. This doesn't provide a basis for estimating its top speed, but it does show that Xixianykus was a highly efficient runner. Several other characteristics of the skeleton reinforce this impression."

Adam Khor

It has received the rather un-impressive name of Bonapartenykus.

http://www.sciencedirect.com/science/article/pii/S0195667111001923

Galvasean

Is it standard practice to name the eggs when they are found alongside the creature that laid them? Or could it be some sort if safeguard to prevent another Oviraptor / Protoceratops egg mix up?

Adam Khor

It's a 95 million year old alvarezsaur and its name means "skinny legs" in Tehuelche. It coexisted with the likes of Giganotosaurus and Puertasaurus, and was only 50 cms long and 20 cms tall.

Article is in Spanish.

http://notio.com.ar/sociedad/hallan-una-nueva-especie-de-dinosaurio-en-la-patagonia-32478

Adam Khor

New alvarezsaurid dinosaurs found in China

https://edition.cnn.com/2018/08/24/world/chinese-dinosaur-fossils-claw-hand-study/index.html

Adam Khor

A new alvarezsaurid from the Nemegt formation of Mongolia:

https://www.nature.com/articles/s41598-019-52021-y

Adam Khor

New alvarezsaurid found at the famous Hell Creek formation (home to T. rex), was the last of its family known to date. Named Tierarchuncus prairiensis ("captain hook of the prairie") after Captain Hook from Peter Pan due to the single-clawed forelimbs.

http://dickinsonmuseumcenter.com/badlands_research-2020newalvarezsaurid/?fbclid=IwAR2ZCwnwYEwn7p1nBpIxbmO39b_1lcU2lHTn252GKuJS288lfxSYqNHuOns