The jaw of Teinolophos trusleri catches the ear bones in the act of separating from the jaw.
Posted on 02/11/2005 6:49:09 AM PST by PatrickHenry
Triple bone structure arose independently in platypus and humans.
Listen up: mammals seem to have evolved the delicate bone structure of the middle ear at least twice. The surprising discovery comes from a fossil, found off the southern coast of Australia, that belongs to an ancestor of the platypus.
Modern mammals are unique among vertebrates for possessing three tiny bones in the middle ear. The malleus, incus and stapes (commonly known as the hammer, anvil and stirrup) work as part of a chain that transmits sound towards the skull. Birds and reptiles have only one bone to perform this function.
Because the mammalian arrangement is so complex, scientists believed that the set-up had evolved on just a single occasion, in an ancestor that gave rise to placental animals (including humans), marsupials and monotremes (such as the duck-billed platypus).
All this changed when James Hopson, a vertebrate palaeontologist at University of Chicago, Illinois, took a trip to Australia. There he met a team of researchers including Thomas Rich of Museum Victoria in Melbourne.
The jaw of Teinolophos trusleri catches the ear bones in the act of separating from the jaw.
Rich and his colleagues had recently unearthed a fossil of Teinolophos trusleri, an ancestor of modern monotremes that lived 115 million years ago. "He said he had some new Teinolophos specimens and when he showed them to me I almost fell off my chair," says Hopson, an author of the study, published this week inScience [Rich T. H., et al. Science 307, 910 - 914 (2005)].
Hammer time
Palaeontologists believe that the middle-ear bones of modern mammals once belonged to the jawbone and later separated to adopt their present location. This is supported by the fact that the middle ear's bones associate with the jaw in the early development of modern mammalian embryos.
What makes theTeinolophos specimen surprising is a large groove in its adult jawbone, which indicates that the smaller bones had not yet detached.
Teinolophos lived after monotremes split from the placental and marsupial mammalian groups. Its jawbone structure, along with its place in the evolutionary tree, hints that a common ancestor to all these mammals lacked the special three-bone ear structure.
This means that natural selection must have driven the same rearrangement in independent groups, after the monotreme split. "Some embryologists had the idea that it might be convergent but nobody really believed this," says palaeontologist Thomas Martin of the Senckenberg Research Institute in Frankfurt, Germany. "I was quite shocked when I heard that such a complex morphological transformation happened twice."
The discovery will compel many experts to rethink their appreciation of mammals' common evolutionary heritage. "Until now it was considered to be one of the most important shared derived characteristics of modern mammals," says Martin.
Yes, I can read and that is an interpretation when an outcome is desired. The "bones" were not separated let alone partially migrated.
I will also note that you can get the answer you seek when you get to pick and choose what evidence you wish to call irrelevant or minor.
When Ausktribosphenos was first described, and argued to be a placental mammal, a theory was put forward to explain how placentals came to appear in the Late Cretaceous in other parts of the world, separated from the Gondwanan countries by ocean barriers in most cases. It was thought that micro-plate rafting could explain their vast sea voyages. Small micro-plates to the northwest of Australia and New Guinea detached from Gondwana some time after the Late Jurassic, "docking" with southeast Asia during the Late Cretaceous. However, if the other tribosphenic mammals included in the Australosphenida were indeed related to the Australian animals, then the micro-plate rafting theory has a problem: one of the Australosphenida (Shuotherium) dates to the Late Jurassic of China.
In 2002 a new mammal was described from China, from the same deposits that the "feathered" dinosaurs were recovered. Eomaia scansori ("dawn mother") is exquisitely preserved, and lived ten million years before Ausktribosphenos or Bishops. It is said to be the most primitive placental mammal known. If the Australian animals are indeed placentals, then they must have spread from Gondwana a lot earlier than micro-plate rafting allows for, at least by the Late Jurassic (if the Chinese Shuotherium is related to the Ausktribosphenids).
How can you tell if it’s a placental mammal?
Teeth can tell you a lot about an animal. Certain sorts of animals have the same shaped teeth. For instance, the shape and number of teeth in placental mammals and marsupials is different. Marsupials have 3 teeth in their jaw called premolars and 4 molars. Placentals have 4 or 5 premolars and only 3 molars. The jaw of Ausktribosphenos nyktos has 3 molars and 4 premolars. It’s either a placental mammal or another sort of mammal altogether. Quite a few fragments of jaws and teeth of Ausktribosphenos nyktos have now been found, along with similar remains of another species called Bishops whitmorei. Whatever type of mammals these were, they must have been quite common.
As for sexual reproduction,
I have better things to do with my time than watch a bunch of friggin' animals getting it on.
Full Disclosure: I've already done with propagating my genes...from now on, this Elk and his Cow are in it strictly for bonding. :-)
Second Full Disclosure: Anyone care to hazard a guess as to the prevalence in Western Society of Abortion, Homosexuality, and Hooking Up, and what they do for the gene pool (except for the obvious flame of keeping the idiots out of it)? None of them do much to ensure genetic diversity :-)
Not to mention, it has to confer survival long enough for you to propagate the genes; if it only keeps you alive until age 8, that's not much use; if it confers superior survival ability when you are normally food for your species' dominant predators, so that you compete for food with the younger members of your species, that causes problems in the other direction.
This tends to be a statistical phenomenon, right? So maybe it's not as finely-tuned a process as some people think...
Cheers!
I don't see any corolation between lifespan and Bipedalism
Maximum Recorded Lifespan of 58 Animals
1. Tortoise 188 years
2. Lake Sturgeon 152 years
3. Human 122 years, 5 months
4. Fin Whale 116 years
5. Blue Whale 110 years
6. Humpback Whale 95 years
7. Elephant (African) 80 years
8. Turtle (eastern box) 75 years
9. Parrot (African grey) 73 years
10. Alligator 66 years
11. Horse 62 years
12. Chimpanzee 59 years, 5 months
13. Orangutan 59 years
14. Eagle (eastern imperial) 56 years
15. Seal (Baikal) 56 years
16. Hippopotamus 54 years, 4 months
17. Gorilla 54 years
18. Camel 50 years
19. Grizzly Bear 50 years
20. Rhinoceros (Indian) 49 years
21. Brown Bear 47 years
22. Condor (California) 45 years
23. Goldfish 43 years
24. Hyena (spotted) 41 years, 1 month
25. Boa constrictor 40 years, 3 months
26. Vulture 39 years
27. Polar Bear 38 years, 2 months
28. Giraffe 36 years, 4 months
29. Dolphin 35 years
30. Rhinoceros (Sumatran) 35 years
31. Cat 34 years
32. Ant (queen) 30 years
33. Kangaroo (red) 30 years
34. Panda (giant) 30 years
35. Dog 29 years, 6 months
36. Lion 29 years
37. Porcupine (Old World) 27 years, 4 months
38. Tiger 26 years, 4 months
39. Wombat 26 years, 1 month
40. Aardvark 24 years
41. Sheep 24 years
42. Jaguar 22 years
43. Raccoon 20 years, 7 months
44. Frog 20 years
45. Koala 20 years
46. Porcupine (normal) 20 years
47. Vampire Bat 19 years, 6 months
48. Pigeon 18 years, 6 months
49. Rabbit 18 years
50. Duck-billed Platypus 17 years
51. Guinea Pig 14 years, 10 months
52. Hedgehog 14 years
53. Shrew (non-human) 12 years
54. Hamster 10 years
55. Gopher (eastern pocket) 7 years, 2 months
56. Anchovy 7 years
57. Partridge 6 years, 3 months
58. Mole 5 years
I never heard of a turtle with a back problem
Early-Jurassic Hadrocodium, older than A. nyktos and its contemporaries, has the fully separated earbones if not all the placental features. Now, the divergence of the major groups (monotreme, marsupial, and placental) is cited by the just-linked article as being later than Hadro, which could be a grandfather to them all.
The ancestral mammals had yet to diverge into the present-day groups - placentals, like humans, horses and whales; marsupials, like kangaroos; and monotremes, such as the duck-billed platypus.However, if the article at the top of this thread means anything, the divergence of monotremes is likely moving back. Never mind that later monotremes have the usual ear bone architecture. (But the ears themselves in reptilian fashion are just off the jaw instead of farther back on the head.) At least one early monotreme had old, almost reptilian ears. To my knowledge, the only comparably early monotreme is Kollikodon which is based on a fragment of dentary bone. Thus, it could be in the same boat. Just now they don't look like descendants of Hadro.
As will be noted in a bit, the split of marsupials and placentals is also up for grabs. If all the divergences end up moving back, your g3k memorial blue spew isn't going to wind up relevant to anything.
And--a pure aside here--what is the creationist fear of linking sources? Might we see something we're not supposed to?
You got most of it from here. Except for what you got from here.
End of aside. A more detailed and less sensationalist treatment of Aussie nyktos is here.
Considering A. nyktos along with a contemporaneous placental from Mongolia called Prokennalestes, Rich guesses that placentals may have had a wider distribution around the world during the Early Cretaceous than previously thought. Perhaps placentals arose earlier that expected--say, while the continents were still lumped together into the single supercontinent, Pangaea. Even if terrestrial placentals were present in Australia 115 million years ago, however, Rich is quite certain that they went extinct, perhaps displaced by marsupials, and only reentered the continent 5 million years ago.Movie time at my house. Out for the night.It would seem that the only way to resolve these many differing views is to find more fossils. And that's exactly what Rich and his team hope to do. They have extensive plans to continue working at the site where A. nyktos was discovered. In the meantime, the debate will surely continue. "This is the fun part," Archibald says, "discussing what it might be."
Or, if it come to that, any mention of the playtpus.
Thou art twisting the facts, Senor Qam1
First you use the oldest numbers, not fair to all the rest of us that will only obtain an average age. Secondly, I said nothing about bipedalism and age, only that H. sapiens may have back problems, because our average age has increased, allowing onset of arthritic conditions, calcification of the spinal column and other assorted osteo diseases. Hell, I never had a back twinge before I was 50. Now I have problems of varying degrees on a regular basis. If I was a wild animal, I would be dead and eaten a long time ago if I had back problems.
Do you think a tortoise's shell helps stabilize his spinal column. I think it might. Several of your longer lived guys are water creatures - extra support for a spinal column - and fish don't count. You guys were discussing bipedal vs. quadrapeds.
Lastly you left out a huge number of the smaller quadrapeds, most that don't live very long.
So my point. The fact that we live longer causes many more medical problems. Is it not possible that back problems are among these?
C'mon now is that all you have? I normally link, but I wanted you to do exactly what you did, grouse about an irrelevant point. Now the crux of the matter is that Hadrocodium had "advanced" features over a descendant 80 million years younger. What? Did the bones decide to migrate back into the jaw?
[Note to lurkers: - ]
I wasn't going to mention this, but I changed my mind. Your "less sensationalist" Sciam citation is from 1998 and the citation I used contains this -"These include Teinolophos trusleri (another monotreme), the possible placental mammals Ausktribosphenos nyktos and Bishops whitmorei, and a possible multituberculate tooth found during the 2004 season."
May I remind you that "Teinolophos trusleri" is the subject of this thread.(not to mention that B. whitmorei was found in 2000 and supports the A. "klaatu barada nicto")
"Platypus Ping"
Only if it's platonic!
"the love child of a near-sighted beaver and a seductive mallard"
Is that your excuse?
"I want to know why homo sapiens was SO much better at survival no Neanderthal are still around..."
There are plenty of neanderthals...just look for the red hair to find some of the gene pool.
"A lot of our problems are due to aging"
Especially in the cellular dehydration in the spinal discs!
Gee, more fluff from the religion of Evolution. Who'd have thunk it. Suppose we'll ever see any science in our science? LOL.
Attitude?
What was that comment about the Pope knowing his bible?
And where is this written?
My point is that the Bible didn't say. Like it didn't say HOW God formed species. Your entire rant against Evolution is merely because you can't find it in your Bible. As you can't find theories of Gravity, or Nuclear forces, etc. etc.
How come you people pick this particular thing to dispute, but not all the other things left out of the Bible?
The creationists have already damaged religion over the past 75 years, far more than I'm sure you will ever accept. It's too long of a thing to explain. And you wouldn't believe me anyway, so why should I bother?
And where is this written? (in the 'fossil record')
My point is that the ROCKS don't say. Like it didn't say HOW TIME & CHANCE formed species. Your entire rant against CREATION is merely because you can't find it in your ROCKS you can't find theories of Gravity, or Nuclear forces, etc. etc.
How come you people pick this particular thing to dispute, but not all the other things left out of the ROCK LAYERS?
The EVOLUTIONISTS have already damaged religion over the past 75 years, far more than I'm sure you will ever accept. It's too long of a thing to explain. And you wouldn't believe me anyway, so why should I bother?
You see; by merely changing the words, you and I are saying the same thing.
It's called 'reading between the lines'.
Just the same thing an E type does to 'connect' the various fossils found in rocks.
(It appears that both sides in this debate are standing on the rock....
"If it isn't CHISLED in stone...."
and
"If it's not FOUND in stone....."
;^)
(Merely a literary mutation....)
Cool!
You trekking on snowmobiles??
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