Author Topic: Halbred's Paleo-News Thread  (Read 117584 times)

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Offline ShyGuy

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Re: Halbred's Paleo-News Thread
« Reply #100 on: November 24, 2009, 01:58:00 PM »
There's a lizard who wants to talk to you Halbred: http://www.youtube.com/watch?v=XAo09yYOpCU

Offline Halbred

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Re: Halbred's Paleo-News Thread
« Reply #101 on: December 17, 2009, 06:22:59 PM »
RISE FROM YOUR FOSSILIZED GRAVE
 
Wow, it's been awhile. I've been on the job hunt, so I've been a bit busy. However, there's also been a dearth of worthwhile paleo stories. One did finally pop up, though:
 
Tawa hallae! It's a new neotheropod from the Late Triassic's Chinlea formation. It lived alongside Coelophysis, Vancleavea, Effigia, and lots of wierd crocodilian critters like Desmatosuchus. Anyway, it's one of the few early dinosaurs known from a complete skeleton. It shares a lot of features with coelophysoid theropods, but also more archaic herrerasaurids. This mixture of characteristics leads to several theories about where, exactly, Tawa fits into the Theropoda family tree.
 
Current concensus is that it's a basal "coelophysoid" theropod, but "coelophysoids" themselves are paraphyletic. More a grade than a family.
 
Anyway, you can read about it here: http://chinleana.blogspot.com/2009/12/new-late-triassic-theropod-tawa-hallae.html
 
The paper's in Science magazine, so it ain't free. I've got a PDF if anyone wants it, of course.
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Offline Halbred

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Re: Halbred's Paleo-News Thread
« Reply #102 on: December 22, 2009, 07:25:33 PM »
Brief report on the most worthwhile stores in the new issue of JVP:
 
1) Long bone histeology of Stegosaurus reveals that stegosaurs reached their large size due to periods of accelerated growth. However, in general, stegosaurs grew at a slower overall rate than other similarly-sized dinosaurs. This implies a lower metabolic rate for these basal thyreophorans.
 
2) The postcranial skeleton of Rapetosaurus was described, finally, after its initial description in 2001. Rapetosaurus is the best-known titanosaur genus, and preserves osteoderms, which means it is a derived member of the group. The fact that an adult skeleton was found in close association with a juvenile suggests more complex parental care than in more basal members.
 
3) A new interpretation of Triceratops' forearm suggests that it held its forelimbs in a semi-erect posture, and the fifth finger (pinkie) was wildly divergent, almost bringing to mind iguanadontians, whereas the first finger (thumb) was rotated strongly inward, and the animal's weight was bore on the first three digits of the hand.
 
4) Tethyshadros, a new hadrosaurid, was discovered and found to be an endemic island dwarf. It lived in Italy, which was, during the Cretaceous, a small chain of islands. It is unique in many ways: it was far more cursorial than other hadrosaurs in its limb proportions and structure of the manus and tail. Strangely, its upper beak is serrated, and the individual serrations are fairly large. The function of this structure is unclear.
 
5) New bizarre crocodilian from Bolivia (South America is a hotspot for freaky crocodilians): Yacarerani. This one has extremely strange ridged "molariform" teeth and forward-pointing incisors. I can think of no modern equivalent except maybe rodents (but do any rodents have procumbent incisors?). Gomphotheres show a similar, if hypertrophied, feature in the lower incisors.
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Offline ShyGuy

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Re: Halbred's Paleo-News Thread
« Reply #103 on: December 22, 2009, 09:46:51 PM »
Buck toothed Croc? Seals have forward pointing teeth for breaking holes in the ice.

Offline Stratos

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Re: Halbred's Paleo-News Thread
« Reply #104 on: December 23, 2009, 02:11:10 AM »
Are there pics of the croc?

And how do you pronounce 'Rapetosaurus' and what is that name's origin?
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Offline BlackNMild2k1

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Re: Halbred's Paleo-News Thread
« Reply #105 on: December 23, 2009, 05:57:35 AM »
Rapetosaurus (Rape-to-sore-ass)


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Re: Halbred's Paleo-News Thread
« Reply #106 on: December 23, 2009, 05:59:29 AM »
Rapetosaurus (Rape-to-sore-ass)

That's exactly why I asked the question.
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Offline Halbred

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Re: Halbred's Paleo-News Thread
« Reply #107 on: December 23, 2009, 04:22:14 PM »
Wow, I never noticed that. Good job, fellas. It's actually "rah-PATE-oh-SORE-us," but nice pun there.

Pics of the croc? Eh, not really. Try this:

http://i49.tinypic.com/kdsha0.jpg

No line drawing available yet...
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Offline Halbred

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Re: Halbred's Paleo-News Thread
« Reply #108 on: January 16, 2010, 02:01:02 AM »
I know, I know, it's been slow. But I have good reason! Being unemployed does wonders for one's ability to print out the latest technical papers.
 
Having said that, there's just not a lot of exciting paleo-news right now. The two biggest stories are:
 
1) Shaochilong maortuensis just got its own monograph (Brusatte 2010). It's the only known Asian representative of the Gondwana-based Carcharodontosauridae, a subgroup of Allosauroidea. It has a shorter snout compared to its larger cousins like Mapusaurus and Giganatosaurus. The remains are not very complete, but the braincase is incredibly well-preserved, probably the best preserved in all known non-maniraptoran tetanurines. Aside from that, Shaochilong demonstrates that carcharodontids (and thus allosauroids) had a global distribution before the breakup of Pangea (Acrocathosaurus is a North American carcharodontosaur).
 
2) Crocodilians, despite not having avian lungs or pneumatic bones, have a unidirectional respiratory system. Previously, it was thought that crocs have a basically mammalian gas exchange system. Both are powered by diaphrams, of course. However, a new study by Farmer & Sanders shows that, in fact, crocs have a basically avian ventilation system, though exactly how it works is still a bit mysterious. The importance of this finding is vast, suggesting that unidirectional air flow is basal to Archosauria, and the transition from diaphram-powered lungs to skeletal and soft-tissue pneumaticity is clearer. It's entirely possible that non-crocodilian crurotarsians experimented with pneumaticity to some degree, but living crocodilians are a bit of an exception anyway* so that's not a huge surprise.
 
*Modern crocs 'n' 'gators have a four-chambered heart, and their ancestors were erect-limbed, fast-moving critters that were probably endothermic. Modern crocs are distinct in that they developed semi-aquatic adaptations. Crurotarsians are generally terrestrial, with some exceptions. However, endothermy would not be advantageous for a water-dwelling ambush predator, so crocs reverse-engineered an ectothermic metabolism and improved their circulation to stay active and functional in cool water.
 
Many people note that crocs sun themselves just like lizards and snakes, which are truly ectothermic. Well sure, but birds do too, and so do small mammals. There is not such a clear-cut dichotemy between cold and warm-blooded as is usually thought.
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Offline Halbred

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Re: Halbred's Paleo-News Thread
« Reply #109 on: January 29, 2010, 05:03:53 PM »
Two new bonerrific paleo news stories:
 
Every wonder what color dinosaurs were? Well, thanks to a new electronic-microscope study of Sinosauropteryx fossils (among others), we can say that its tail feathers were somewhere between orange and red. Seriously. The preservation is so good that parts of the tail feathers preserve melanosome cells, which give your skin their pigment. Color-changing animals (like chameleons) are able to shrink and expand their melanosomes, which changes their color. Anyway, the shape and structure of the melanosomes of Sinosauropteryx's tail feathers show that they were between orange and red. Similar studies are underway for the feathers of Confuciusornis, an enantiornithine bird.
 
More exciting (to me) is the new alvarezsauroid in town. Alvarezsaurs are a poorly-known group of termite-eating miniature theropods from around the world. The most famous members are Shuvuuia and Mononykus. When they were originally discovered, they were thought to be birds, and indeed, they share a lot of features with birds, including a mobile joint in the snout, a nearly horizontal pubis, and a keeled sternum. Alvarezsaurs later recognized as such showed that they were basal maniraptor theropods, but BOY are they wierd. Aside from being tiny, alvarezsaurs have short, but very muscular arms with a single functional finger that ends in an huge, powerful claw.
 
The claw was used for scratch-digging in wet bark termite mounds. That was only recently discovered. But exactly how alvarezsaurs got so wierd has never been understood until now. A new taxon, Haplocheirus, was just found in China. It is huge compared to later alvarezsaurs--3 meters instead of 1 or less -- and it has all three fingers and lots of sharp teeth. However, its skull shows many similarities with later alvarezsaurs, and the hands are strange. The 3rd finger is greatly reduced, the 2nd finger is long but thin, and the 1st finger is large and powerful. The olecranon process of the ulna is also enlarged, but not so much as in Mononykus and Shuvuuia.
 
So it's a wonderful transitional form between basal maniraptors and later "true" alvarezsaurs. What's even more surprising is that it is 60 million years older than the next-oldest alvarezsaur, meaning that the group has a huge chronologic range. More importantly, Haplocheirus predates Archaeopteryx, meaning that maniraptor theropods must have diversified very quickly during the Middle Jurassic.
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Offline Stratos

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Re: Halbred's Paleo-News Thread
« Reply #110 on: January 30, 2010, 05:19:55 AM »
Is Confuciusornis named after Confucius the famed Easter thinker?
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Offline Halbred

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Re: Halbred's Paleo-News Thread
« Reply #111 on: January 30, 2010, 09:46:13 PM »
Eastern thinker, yes.
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Re: Halbred's Paleo-News Thread
« Reply #112 on: January 31, 2010, 05:06:16 AM »
LOL, my bad on the typo. Rather funny actually in retrospect.

Is there a specific reason for it being named after Confucius?
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Offline Halbred

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Re: Halbred's Paleo-News Thread
« Reply #113 on: January 31, 2010, 03:10:54 PM »
Well, Confuciusornis is from China, and when it was discovered, it was the next-earliest bird ever described (after Archaeopteryx) yet it had lots of more modern features, like a toothless beak and a pygostyle. So it was important (and still is) and made everyone re-think avian evolution and how quickly birds radiated.
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Offline Halbred

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Re: Halbred's Paleo-News Thread
« Reply #114 on: February 04, 2010, 05:16:27 PM »
Another colorful update!
 
Using largely the same techniques as described above for Sinosauropteryx, another team looked the four-winged troodontid, Anchiornis, but on a broader scale. By sampling dozens of feather locations on the fossil, the team was able to reconstruct a very detailed, thorough color reconstruction for Anchiornis' feathers. Here's the complete story at National Geographic. Let the page load completely...the 3D rotation is really spectacular!
 
http://news.nationalgeographic.com/news/2010/01/100127-dinosaurs-color-feathers-science/o/
 
Theoretically, this type of color assessment can be done on any feathered dinosaur with well-preserved feathers. That's very exciting, and may tell us a lot more about how feathers were used in flightless dinosaurs with modern-type feathers.
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Offline vudu

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Re: Halbred's Paleo-News Thread
« Reply #115 on: February 23, 2010, 01:28:54 PM »
Very eye-opening article.  I learned a lot.

Paleontologists: 'We've Been Looking At Dinosaurs Upside Down'
Why must all things be so bright? Why can things not appear only in hues of brown! I am so serious about this! Dull colors are the future! The next generation! I will never accept a world with such bright colors! It is far too childish! I will rage against your cheery palette with my last breath!

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Re: Halbred's Paleo-News Thread
« Reply #116 on: February 23, 2010, 02:48:55 PM »
How many dinosaurs had feathers?
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Re: Halbred's Paleo-News Thread
« Reply #117 on: February 23, 2010, 02:52:49 PM »
Millions
Why must all things be so bright? Why can things not appear only in hues of brown! I am so serious about this! Dull colors are the future! The next generation! I will never accept a world with such bright colors! It is far too childish! I will rage against your cheery palette with my last breath!

Offline Halbred

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Re: Halbred's Paleo-News Thread
« Reply #118 on: February 23, 2010, 03:26:46 PM »
From a population perspective, yeah, millions.  ;)
 
From a fossil perspective, the following non-avian dinosaurs have feathers:
 
Sinosauropteryx, Caudipteryx, Sinosauropteryx, Dilong, Microraptor, Anchiornis, Beipiaosaurus, Protarchaeopteryx (=Incizivosaurus), Shuvuuia, Scansoriopteryx, Pedopinna, Jinfengopteryx, Sinocalliopteryx, Similicaudipteryx, Epidexipteryx, Velociraptor, Avimimus, Nomingia.
 
The last three aren't known from fossil that preserve feathers, but do have things like pygostyles and quill nodes on the arms.
 
Those are all theropod dinosaurs, of course. Two ornithischian dinosaurs MAY have extremely primitive feathers: Tianyulong and Psittacosaurus. If their "quills" turn out to be homologous with theropod feathers, that implies that ALL dinosaurs were feathered to some degree, since the divergence between saurischian and ornithischian occurred at the very base of the Dinosauria.
 
More conservatively, from a phylogenetic perspective, all coelurosaur theropods had feathers. That is, all theropods bracketted by Ornitholestes and, say, pigeons.
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Re: Halbred's Paleo-News Thread
« Reply #119 on: February 23, 2010, 05:26:35 PM »
Maybe it's because I grew up with the sight of featherless dinosaurs but I couldn't imagine Jurassic Park with a bunch of feathered dinosaurs. It's hard to think of them being feathered.

I remember learning when I was younger that feathers were the defining characteristics of birds, so does this mean that most dinosaurs were really birds or is there another way you can classify them? I already knew that the whole lizard/reptile classification was wrong but can they all still be called birds?
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Offline Halbred

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Re: Halbred's Paleo-News Thread
« Reply #120 on: February 23, 2010, 05:39:30 PM »
No, when you're thinking in terms of phylogeny, feathers do NOT a bird made. Neither does a wishbone (which almost all theropods had), a beak, a partially fused hand, etc. Since many of these features evolved prior to the origin point of Aves (including feathers, which may be very ancient), it's only when so many of these features "build up" in a single lineage that you can call it a bird.

For example, let's take pygostyles...shortened tails. Birds have them. But so do oviraptors, which are clearly not birds. But wait, oviraptors had feathers, too, and beaks, and wishbones. So why aren't they birds? Well, they can't fly and their immediate ancestors couldn't fly either, so they're not like ostriches. But they nested like modern ground-dwelling birds and slept like them, too, with their head underneath a wing.

However, because we have so many good fossils now (far more than we had in 1993), we can see where birds actually split off from other carnivorous dinosaurs. If you climb the phylogenetic tree past oviraptors, there's a big split between Aves and Deinonychosauria. They share a common ancestor (it probably looked a lot like Mahakala), but both groups share many features in common. The difference is that Aves continued to modify their wings and bodies for flight, while Deinonychosauria actually lost many of those features, possibly because of competition from Aves, and were forced out of the trees.

There is some validity to the idea of pushing the term "Aves" down one node to encompass all birds AND Deinonychosaurs, since both initially have flight adaptations. So at a certain point, where you label something a bird or not is arbitrary. It's very hard sometimes to tell, when you get right down to the point of common ancestry, which one is a bird and which one isn't.

However, I imagine that if you saw an Anchiornis sitting in a tree today, we'd call it a bird even though it couldn't fly very well. It was about the size of a raven and had just as many feathers, if not more (it had "hindwings"), and its feathers were colored like a modern hairy woodpecker.

So in a sense, "Aves" is in the eye of the beholder!
 
Honestly? My short answer is that it's not a bird if it can't use true flapping flight. I don't think the Deinonychosaurs could, but you know what? Neither could many early birds! Archaeopteryx, Confuciusornis, and others seem unable to complete a flapping stroke. I'd actually suggesting moving "Aves" to the crown-group (all living birds and their immediate ancestors) and calling stem-birds something different.
« Last Edit: February 23, 2010, 05:42:02 PM by Halbred »
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Re: Halbred's Paleo-News Thread
« Reply #121 on: February 24, 2010, 02:27:02 AM »
i almost believed that onion article :P, if i hadn't realized it was the onion. Its not a bird if it can't use true flapping flight? Does that mean we should reclassify penguins outside of birds? since their clearly moving in a new direction?
« Last Edit: February 24, 2010, 02:31:26 AM by ThePerm »
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Re: Halbred's Paleo-News Thread
« Reply #122 on: February 24, 2010, 05:43:33 AM »
Stem-birds... awesome.
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Re: Halbred's Paleo-News Thread
« Reply #123 on: February 24, 2010, 01:58:24 PM »
i almost believed that onion article :P, if i hadn't realized it was the onion. Its not a bird if it can't use true flapping flight? Does that mean we should reclassify penguins outside of birds? since their clearly moving in a new direction?

'Course not. They're still birds. They evolved from flighted ancestors. Penguins are just flightless birds, just like birds are flighted dinosaurs. And a part of me wants to say that penguins can complete a flight stroke, but they just do it underwater...

Anyway, once an animal starts doing things differently than its cousins, it doesn't stop being whatever it is. It just takes on a new label, too. So penguins are wierd birds, and birds themselves are just wierd dinosaurs.
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