Topic: Halbred's Paleo-News Thread

[Halbred]

A friend sent me the paper. Yeah, it's awfully nice to have some sauropod skulls, not just vertebrae.

[Stratos]

I'm surprised they never had collected intact skulls before. Pretty nice to get a chance to see them without the puzzle solving and guess work.

[Halbred]

Well, sauropod skulls are famously brittle and typically are the first things to be washed away before fossilization. There are plenty of intact skulls for different kinds of sauropods, but what's interesting here is that for this KIND of sauropod, the skulls were the first things to be found, instead of the other way around.

[TheBlackCat]

Out of curiosity, Halbred, what do you think of the hypothesis that the basal archosaurs were all endothermic and that crocodilians secondarily become ectothermic?

[TheBlackCat]

A new species of 68 million-year-old fossil snake was recently unearthed.  That would not be particularly interesting, except that the snake apparently died while in the process of attacking a dinosaur nest:

http://z-letter.com/2010/03/02/fossil-snake-ate-dinosaur-babies/

[Halbred]

Indeed. The awesome...must...flow:
 
http://go2.wordpress.com/?id=725X1342&site=svpow.wordpress.com&url=http%3A%2F%2Fwww.plosbiology.org%2Farticle%2Finfo%253Adoi%252F10.1371%252Fjournal.pbio.1000322
 
Thar be the full paper, mateys, free for all!

[Halbred]

Just got a nice big drop from a friend. Lots of new good paleo stuff here.
 
In addition to that snake, of course. The snake, by the way, is a basal member of the modern egg-eating group.
 
Onward! To new things!
 
A new "silesaurid" ornithodiran was discovered. Asilisaurus the basalmost ornithodiran known from good remains. Its features help characterize its family, the Silesauridae, which until now has lacked a formal diagnosis. Silesaurs are very close to the Dinosauria, just under it, in fact, and were once considered to be basal ornithischian dinosaurs. They are herbivorous, quadrupedal, and have a predentary bone. However, they lack various specializations in the hind limbs and pelvis unique to dinosaurs. They occur earlier than dinosaurs, which may push the origin point for Dinosauria back a bit, depending on how close Silesauridae actually is to Dinosauria.
 
A new theory as to why dinosaurs developed an avian wrist posits that they developed an avian wrist (that folds back) to deal with large wing-feathers. It's an interesting idea, but I haven't read the paper itself yet. I'll have more to say about this later. I'm hoping the authors correlate the earliest appearance of wing-feathers with the onset of the avian-style wrist.
 
And...uh...Darwinius is a lemur after all, and not an unbelievably basal euprimate after all. Frigging DUH, but it's good to have the data to prove it.

[BlackNMild2k1]

They occur earlier than dinosaurs, which may push the origin point for Dinosauria back a bit, depending on how close Silesauridae actually is to Dinosauria.

This article says it pushes it back 10 million years
http://news.nationalgeographic.com/news/2010/03/100303-dinosaurs-older-than-thought-10-million/

[Halbred]

Yup. I'd like to note that neither of the animals in that "artist's rendering" are dinosaurs. One is the new guy, Asilisaurus, who is a silesaur, and the other is a poposaurid crurotarsian, probably (and incorrectly) Arizonasaurus.

Arizonasaurus is from...Arizona. It is also not a dinosaur, but instead a relative of crocodilians.

[Halbred]

Not dinosaur news per say (it's been a slow couple of weeks, and nobody gives a crap about Brusatte's new phylogenetic analysis of Archosauria proper) (except that phytosaurs turn out to be basal crurotarsians--neat!).

But I do have SOME exciting news. Along with two friends, I've started Dino-Rama, a paleontology-themed podcast. We recorded the first episode yesterday, and it should be up tonight or tomorrow. Once the site is up and the download links are posted, I will link to it from here. I urge you all to give it a listen when it's available!

[Kytim89]

What about the Megalodon? was it the largest predatory fish on earth? It is supposedly kin to the great white, right?

[Halbred]

Big shark, yes, but only distantly to the modern great white. All those model jaws you see in museums and aquariums are probably way too big, too. Still, we're talking a predatory shark easily the size of, if not a bit larger than, modern whale sharks.

[Kytim89]

Some scientists claim that they are still around some where. I would not want to run into one if I had choice. What made them so big in the first place?

[Halbred]

Probably the rise of whales and pinnipeds, probably. There was a new food source there, and sharks grew to the challenge. Makes you wonder what drove them to extinction, since whales and pinnipeds didn't go anywhere.

[Kytim89]

Probably the rise of whales and pinnipeds, probably. There was a new food source there, and sharks grew to the challenge. Makes you wonder what drove them to extinction, since whales and pinnipeds didn't go anywhere.

 
Could they still be around? Also, I watched on a show about crocodiles that they are the closet relatives to dinosaurs. They are also some how related to the Spinosaurus? In JP3 a Spinosaurus and a T-rex fought, who would win in reality?

[Stratos]

Was Spinosaurus (sp?) even a real dinosaur?

[Halbred]

Spinosaurus aegypticus is a real theropod dinosaur. It was named in the 1940's (or so) based on fragments of the skull and several vertebrae. That specimen was destroyed during a British air raid during WWII. Additional material has been scant, mostly teeth, but most recently, a snout. If you scale up Spinosaurus based on the proportions of its close, better-known relatives (Suchomimus and Baryonyx), then you get an enormous, 56-foot-long animal.
 
Spinosaurs, as a family, seem adapted for fish-eating. Stress tests done on the skull of Baryonyx show that its skull is constructed like a modern gharial, and oxygen isotope analysis of spinosaur bones are consistent with a semi-aquatic lifestyle. Spinosaurus is the only spinosaurid with a giant sail along its back--its function is unknown, but it could've been a solar radiator, an intimidation device, or a "shade" for fish-catching. Hard to say.
 
As for the relationship between crocodiles and dinosaurs, both groups lie at opposite ends of a Y-shape called "Archosauria." At the end of the left branch, you've got modern crocodilians. At the end of the right branch, you've got birds. Dinosaurs are on the bird branch, and a bunch of wierd Mesozoic animals, like aetosaurs and poposaurs, are on the crocodile branch.

[Kytim89]

Spinosaurus aegypticus is a real theropod dinosaur. It was named in the 1940's (or so) based on fragments of the skull and several vertebrae. That specimen was destroyed during a British air raid during WWII. Additional material has been scant, mostly teeth, but most recently, a snout. If you scale up Spinosaurus based on the proportions of its close, better-known relatives (Suchomimus and Baryonyx), then you get an enormous, 56-foot-long animal.
 
Spinosaurs, as a family, seem adapted for fish-eating. Stress tests done on the skull of Baryonyx show that its skull is constructed like a modern gharial, and oxygen isotope analysis of spinosaur bones are consistent with a semi-aquatic lifestyle. Spinosaurus is the only spinosaurid with a giant sail along its back--its function is unknown, but it could've been a solar radiator, an intimidation device, or a "shade" for fish-catching. Hard to say.
 
As for the relationship between crocodiles and dinosaurs, both groups lie at opposite ends of a Y-shape called "Archosauria." At the end of the left branch, you've got modern crocodilians. At the end of the right branch, you've got birds. Dinosaurs are on the bird branch, and a bunch of wierd Mesozoic animals, like aetosaurs and poposaurs, are on the crocodile branch.

I watched on a TV show that said that the spinosaur was an opprotunity feeder like a bear. It fed on land and aqautic animals. I also remember that same show talking about how the spinosaur might be a progenitor of modern crocdiles due to the snout, skull formations and teeth. The spinosaur is also the largest land predator, right? That same show also did who would win scenario between the T-rex and the spinosaur based on certain criteria, but I forgot who they said was the victor.

[vudu]

Spinosaurus aegypticus is a real theropod dinosaur. It was named in the 1940's (or so) based on fragments of the skull and several vertebrae. That specimen was destroyed during a British air raid during WWII. Additional material has been scant, mostly teeth, but most recently, a snout. If you scale up Spinosaurus based on the proportions of its close, better-known relatives (Suchomimus and Baryonyx), then you get an enormous, 56-foot-long animal.
 
Spinosaurs, as a family, seem adapted for fish-eating. Stress tests done on the skull of Baryonyx show that its skull is constructed like a modern gharial, and oxygen isotope analysis of spinosaur bones are consistent with a semi-aquatic lifestyle. Spinosaurus is the only spinosaurid with a giant sail along its back--its function is unknown, but it could've been a solar radiator, an intimidation device, or a "shade" for fish-catching. Hard to say.
 
As for the relationship between crocodiles and dinosaurs, both groups lie at opposite ends of a Y-shape called "Archosauria." At the end of the left branch, you've got modern crocodilians. At the end of the right branch, you've got birds. Dinosaurs are on the bird branch, and a bunch of wierd Mesozoic animals, like aetosaurs and poposaurs, are on the crocodile branch.

Be honest--did you type that from memory or did you have to use reference material?

[Halbred]

Memory. I'm at work, dude. If I had reference material, I'd have given you exact date of Spinosaurus' discovery. I read that oxygen isotope paper very recently.

Kytim, it's useless to wonder who would win in that fight because not only where the two dinosaurs separated geographically (on in western North America, one in northern Africa), they lived tens of millions of years apart.

[Stratos]

Kytim, it's useless to wonder who would win in that fight because not only where the two dinosaurs separated geographically (on in western North America, one in northern Africa), they lived tens of millions of years apart.

Nonsense! It's just like those questions about who would between Batman and Superman, or the USS Enterprise versus an Imperial Star Destroyer. It's fun to discuss!

[Mop it up]

Who would win in a fight, Mario or Link?

Oh wait, that one we CAN solve with Super Smash Brothers!

[TheBlackCat]

Spinosaurs, as a family, seem adapted for fish-eating. Stress tests done on the skull of Baryonyx show that its skull is constructed like a modern gharial, and oxygen isotope analysis of spinosaur bones are consistent with a semi-aquatic lifestyle. Spinosaurus is the only spinosaurid with a giant sail along its back--its function is unknown, but it could've been a solar radiator, an intimidation device, or a "shade" for fish-catching. Hard to say.

I've also heard the hypothesis that it could have been used as an anchor point for shoulder muscles, similar to a bird's wishbone but used for moving the arms in other directions.  Not sure it is really consistent with the fish-eater hypothesis, though.

Are you going to post anything about those mesozoic plankton-feeding bony fish they mentioned in Science recently?  Not as exciting as a giant whale-eating shark, but interesting nonetheless since they fill an major gap in the mesozoic marine food chain.

Also, I am still curious about your thoughts about crocodilians being secondarily cold-blooded.

[Halbred]

Coulda sworn I posted a reply to that crocodile thing.

Haven't read about the giant plankton-eating fish yet, but I'm not surprised they exist. Warmer waters = more diverse plankton = the evolution of large fish to eat it in a world without whales.

The evidence for secondarily-ectothermy in crocs is pretty conclusive. They've got 4-chambered hearts, and their ancestors grew at a faster rate than modern crocs, and some were upright runners. However, given the somewhat odd lifestyle that modern crocs have developed (semi-aquatic ambush predators), an endothermic lifestyle would do more harm than good.

[TheBlackCat]

Haven't read about the giant plankton-eating fish yet, but I'm not surprised they exist. Warmer waters = more diverse plankton = the evolution of large fish to eat it in a world without whales.

http://www.sciencemag.org/cgi/content/abstract/327/5968/990

I don't really have time to deal with it myself.  I do find it a bit strange that the large marine reptiles never took up this niche, although it may be that these fish were too established by that point for reptiles to make inroads.  Or maybe they did and we just haven't found the fossils yet, deep-water creatures don't fossilize well, of course (or if they do fossilize it is n places we can't reach).

The evidence for secondarily-ectothermy in crocs is pretty conclusive. They've got 4-chambered hearts, and their ancestors grew at a faster rate than modern crocs, and some were upright runners. However, given the somewhat odd lifestyle that modern crocs have developed (semi-aquatic ambush predators), an endothermic lifestyle would do more harm than good.

How do we know that they grew at a faster rate?  Any clues as to when the transition to an ectothermic lifestyle might have occurred?