"Tracking Marsupial Evolution Using Archaic Genomic Retroposon Insertions"

<The four Australasian orders share a single origin with Microbiotheria as their closest sister group, supporting a clear divergence between South American and Australasian marsupials. In addition, the new data place the South American opossums (Didelphimorphia) as the first branch of the marsupial tree.>

http://www.plosbiology.org/article/...

Astounding. It would mean that

1.`all the diverse marsupial forms in Australia are descended from one marsupial species that probably lived in South America in the early Cretaceous.

2. the present-day South American marsupial groups (about 100 living species), most of which are morphologically opossum-like, represent very diverse genotypes that are about distantly related to each other (or more) as they all are to Australian marsupials (about 200 living species). To put it in another way, the Australian marsupials all belong to a single clade which is essentially a single South American marsupial group that had traveled to Australia via Antarctica during times when the Southern continents were still joined as the supercontinent Gondwana.

South America separated in the Cretaceous approximately 130 million years ago, forming the South Atlantic Ocean. Australia separated from Antarctica later on in the Cretaceous about 80 Mya. It can be deduced that a single clade of South American marsupials began their journey to Australia before 130 Mya, must have arrived in Australia before 80 Mya, and gave rise to all the morphologically diverse Australian marsupial forms.

New Species of Dolphin Found in Australia

http://news.nationalgeographic.com/...

Asian Carp Reproduce in Great Lakes Watershed

http://abcnews.go.com/US/wireStory/...

For those unfamiliar with invasive species in the great lakes of North America, here is a brief introduction:

Just finished reading 'Flowers for Algernon'>

IMO Orcas may have been a key influence in the extinction of the the famous Megalodon. The phenomenon of specialist orca pods hunting and feeding on sharks, including the fearsome great white (and even on the whale shark which though planktivorous is the biggest of all sharks), is well documented. In almost all cases, the orcas mainly eat the oil filled liver. This feeding behavior of shark specialist orcas has threatening implications to large sharks because it would mean that orcas would literally annihilate even large schools of sharks that they manage to trap, all for shark liver oil, without truly satiating their hunger on the relatively small livers. If they are still hungry after the last liver is eaten, then they could then feed on the remaining carcasses. Orcas may kill as many large sharks as they can because they have a sweet tooth and the chocolate cure happens to be shark liver.

Fascinating observations:

Orcinus citoniensis probably is the ancestral species that evolved into the modern killer whale Orcinus orca <Age range: 3.6 to 1.806 Ma http://fossilworks.org/bridge.pl?ac... http://www.esacademic.com/pictures/...>

Megalodon lived from about <20 to 2 million years ago (mya)>, leaving behind fossil teeth and (rarely) centra in ancient marine sediments. Megalodon evolved to feed on the giant whales that appeared as the oceans cooled during the Miocene and Pliocene.

http://www.flmnh.ufl.edu/fish/shark...

Why fascinating? If the first 30 feet long fully modern orcas began appearing approximately 2 million years ago, it's reasonable to hypothesize that modern orcas killed off Megalodon, either by out-competing them, or eating their juveniles (any Megalodon under 20 feet must have been treated as a huge depot of shark liver oil) or both.

Perhaps there was a phase change. Orcas from 3 to 2 Mya began to evolve more effective pack behavior, bigger bodies and more robust teeth. Once they hit the size and teeth of the modern orca, it became possible for them to 'suddenly' prey very efficiently on all below 20 feet long Megalodon young.

Most people think orcas are cute. But take a look at what a shark sees and feels before it fills up the prescription for shark liver oil to an orca. https://upload.wikimedia.org/wikipe...

http://www.icb.org.ar/descargas/Pre...

Below is another orca pod massacre of trapped sharks. There are eyewitness reports and video footage of one of the orcas single handedly attacking and killing several of the sharks.

http://blog.seattlepi.com/candacewh...

http://www.stuff.co.nz/national/619...

http://www.bbc.co.uk/news/world-asi...

http://www.youtube.com/watch?v=_7GG...

Still another massacre. Remarkably, it's possible that the orca pair involved was trying to teach the divers how to eat shark liver, as they hunted, fetched, eviscerated, and ate the livers of a succession of Pacific sleeper sharks, whose flesh is known to be poisonous to humans. It seems to that the orcas were generously instructing the human divers 'by avoiding ingesting the flesh and just eating the liver, you will have an unlimited eat-all-you-can of orca chocolate, while the supply of these stupid slow-moving deep water sharks in the area last.'

(Oceanic dolphins have a long history of seemingly treating humans as conspecific beings, rescuing us from drowning and shark attack.)

http://blog.seattlepi.com/candacewh...

One of the techniques by which orcas kill sharks, the tail karate chop.

http://www.dailymail.co.uk/sciencet...

More common are by biting the shark to effect crushing injuries, tearing out huge chunks of flesh, or eviscerating it with those huge robust pike-like teeth, ramming it, or turning it upside down to induce tonic immobility thus drowning it. Even great whites are terrified by specialist orcas, and would swim from the rich feeding grounds of Pinniped-rich California all the way to Hawaii, probably seriously risking starvation.

http://www.nwf.org/News-and-Magazin...

http://www.youtube.com/watch?v=P6Si...

The above is extreme almost bizarre avoidance behavior. Its evolution in great whites implies that ancient great white populations that did not exhibit it were wiped out. It may have helped it stave extinction from the orca. There is no doubt in my mind that the orca specialist pod that visited coastal California would kill every great white that they find for their huge livers. It may even be possible that the intelligent orcas (whose brain to body weight ratio are approximately the same as humans, and whose cortical convolutions are even more numerous than ours) preferentially target huge sharks, not only for their livers, but also because they comprehend that sharks are competitors and a threat to their young. With their sonar, it would have been almost inevitable the orcas would sooner or later detect these large prey. Nowhere to hide in the open seas.

If Megalodon never evolved such extreme avoidance behavior, and this could be likely given its 18 million dominance of the seas, its juveniles would have suffered a truly horrendous kill rate. The first modern Orcinus orca would have kept on killing and killing every Megalodon juvenile they could trap, just as they do whole schools of present-day sharks, until none is left.

<Dom> the current version - 'catch my breath' - doesn't seem to be missing an e...?

<dakkie> Glad to hear, it is indeed one of the very best. :) The novel version is also very interesting, much more complex, yet in some ways the short story version packs more of a punch; the novel's emotional impact is somewhat diluted by its length in comparison. I posted a link to the novel in Dom's forum last year, just between klus #3 and #4, as I recall. ;)

<VBD> Thanks, amazing stuff - just up to the Melville discoveries so far, this is fascinating:

<... in the absence of water, the tadpole develops within the egg and a fully formed frog hatches out. >

Likely a clue as to why many other oviparous animals moved to hatching fully-formed young, bypassing the "tadpole" phase.

Didn't read up on the Orca vs Shark Wars yet, but given that the sharks and their ancestors are not exactly harmless fuzzy bunnies either, a first thought is that it's very possible that the orcas specialized in preying on them at least partly in order to defend their own young and aged from shark attacks.

Meanwhile, remember this discussion we had: Annie K. chessforum?

I found 'Think Like A Dinosaur' online a while back, check it out when you have time. :)

Oh no don't tell me you're pulling a <Dom>?

By that I mean you have actually met him.

I have never doubted <Dom> when he's said he's met someone.

Did you ever see the TV show based on the ANIMAL VETERNARIAN novels? I have watched them many times.

I read the ANIMAL VETTERNARIN novels because of the TV show, and they were quite wonderful.

I particularly like how he named them after lines in the hymn

ALL THINGS BRIGHT AND BEAUTIFUL...

Pardon the cap locks but this is a subject dear to my heart as well, so I get excited about it.

My favorite parts are when Gerry gets attacked by the various farm animals, and when the wives of his customers insist on plying him with thick pies and very strong turnip wine.

It wasn't turnip what was it...

Some horrendous vegetable they made a wine out of and rendered poor Gerry inert.

http://www.imdb.com/title/tt2545118...

<ALL THINGS BRIGHT AND BEAUTIFUL...>

I think you mean James Herriott, not Gerald Durrell. :)

Here's what I once said on this subject: Annie K. chessforum

Herriott was a vet, Durrell was more an autodidact naturalist, and he wrote mostly about his experiences with wild animals (and his family)... but he was a more talented writer than Herriott IMO. Do look him up when you get around to it. ;)

<It turns out Orcas don't like being locked up in those tiny pens...>

- Monty Python.

It turns out Orcas don't like being locked up in those tiny pens...>