When Did Carcharocles Megalodon Become Extinct? A New Analysis Of The Fossil Record

[non-remanié]

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0111086

[Herb]

Interesting. Maybe some still live in the oceanic trenches after all/

[Boesse]

Nope, not according to the new paper, that was not their conclusion.

[Carcharodontosaurus]

Not to mention that it would be very unlikely if not impossible for a large, specialized coastal shark species to evolve into a deep-sea species in only two and a half million years.

Edited October 23, 2014 by Carcharodontosaurus

[Al Dente]

I didn't see information on how they gave the age to the formations where megalodon teeth were found. If you look at table S1 they list the formations and then the max and min age of the formation. For most they list between 5.3 and 2.6 million years ago - the entire span of the Pliocene.

I think with some effort they could narrow the age down a little more for some of the formations. For example, they list the Yorktown Formation as between 5.3 and 3.6 million years. The authors could have narrowed this down because megalodon are only found in the lowest of the four members- the Sunken Meadow member which is lower Pliocene. The next higher member lacks megalodon, so they could have excluded the entire Upper Pliocene for the Yorktown Formation. I'm not certain how they attached absolute dates to the Formations, most authors use faunal zones.

[non-remanié]

I agree Al Dente. I have seen a lot of very imprecise age ranges of formations and occurrences on paleodb. I think paleodb just uses the closest stage dates for the formations from which the faunas are listed most of the time. If the study used those numbers, then the authors surely could have done a much more precise job by limiting the age ranges of known occurrences. But I think that part of the idea of their statistical modelling and the "bootstrapping" of the data set in particular is that they don't really need to use any more precise data to still end up with a fairly reliable answer. Possible reworking into younger formations is accounted for in the data set by considering a mere presence in a younger formations as encompassing the entire age range of that formation. I think a better answer could have probably be gotten the old fashioned way. But this statistical model is sort of not open to interpretation because these unknowns are accounted for in the model, and therefore it comes up with a conservative and fairly reliable number for the extinct date. To me, what their simulation is actually saying is that at least by 2.6mya megalodon was surely extinct. I dont know if thats how they intend it, but I think, including these considerations that you mention, that is a more accurate picture.

Edited October 23, 2014 by non-remanié

[Boesse]

I agree Al Dente. I have seen a lot of very imprecise age ranges of formations and occurrences on paleodb. I think paleodb just uses the closest stage dates for the formations from which the faunas are listed most of the time. If the study used those numbers, then the authors surely could have done a much more precise job by limiting the age ranges of known occurrences. But I think that part of the idea of their statistical modelling and the "bootstrapping" of the data set in particular is that they don't really need to use any more precise data to still end up with a fairly reliable answer. Possible reworking into younger formations is accounted for in the data set by considering a mere presence in a younger formations as encompassing the entire age range of that formation. I think a better answer could have probably be gotten the old fashioned way. But this statistical model is sort of not open to interpretation because these unknowns are accounted for in the model, and therefore it comes up with a conservative and fairly reliable number for the extinct date. To me, what their simulation is actually saying is that at least by 2.6mya megalodon was surely extinct. I dont know if thats how they intend it, but I think, including these considerations that you mention, that is a more accurate picture.

You guys have hit the nail on the head. I currently have a paper in review on the very subject, where we actually read papers written by geologists - this study attempted nothing of the sort and uncritically accepted published dates from the paleontological literature (and occurrences with poor provenance), even though more recent geological studies have been published. Many of these dates are just the start/end dates of the Pliocene, and for many of these localities better dates do exist.

Ironically, our more detailed study was first submitted back in March, and rejected for being too detailed, and then resubmitted and rejected again last month for the same reasons (from the same journal, PLOS One). And then this short paper was rushed forward using problematic data... it doesn't inspire much confidence in the decisions of journal editors.

[Herb]

Wishful thinking.

[tmaier]

and rejected for being too detailed, and then resubmitted and rejected again last month for the same reasons

That is a very strange rejection comment. How exactly did they word it? How can something be over-documented?

[Boesse]

That is a very strange rejection comment. How exactly did they word it? How can something be over-documented?

It is important to keep things brief and not be overly verbose in order to maintain the utility of the paper - difficult to read and overly indulgent papers often get overlooked or glossed over by other researchers simply because reading them is too daunting. That being said, the ironic aspect is that it was for an online only journal that has no page limits or page charges, and the manuscript was shorter than the two previous articles I published there...

But to answer your question, that was more or less how they worded it, and I was pretty snarge perplexed myself. I thought it was utterly bizarre.

Edited October 25, 2014 by Boesse

[Oxytropidoceras]

Boesse wrote,

“But to answer your question, that was more or

less how they worded it, and I was pretty snarge

perplexed myself. I thought it was utterly bizarre.”

Yes, peer-review in science can get very bizzare.

For an example, go see:

When @#%$! is your imaginary co-author,

Sifter Science News, AAAS

http://news.sciencemag.org/sifter/2014/10/when-is-your-imaginary-co-author?

The true story of Stronzo Bestiale (and other

scientific jokes) by vito tartamella, Parolacce

http://www.parolacce.org/2014/10/05/the-true-story-of-stronzo-bestiale/

Yours

Paul H.

[tmaier]

If you are in a hurry, a paper can be computer generated from a selection of quality terms and phrases...

http://pdos.csail.mit.edu/scigen/

This popped up from a joke posting many years ago about a computer automated paper reviewing system. It was posted in the coffee room and I was reading it one day, puzzled over how software could make reviewing decisions. Somebody came up behind me and said "Tom, it is supposed to be a joke."

So there is automated software to generate papers, and software to do the peer review... what job is left for us humans?

[Herb]

that is a hoot! tmaier/