Welcome Guest [Log In] [Register]
Welcome to Carnivora. We hope you enjoy your visit.


You're currently viewing our forum as a guest. This means you are limited to certain areas of the board and there are some features you can't use. If you join our community, you'll be able to access member-only sections, and use many member-only features such as customizing your profile and voting in polls. Registration is simple, fast, and completely free.


Join our community!


If you're already a member please log in to your account to access all of our features:

Username:   Password:
Add Reply
Megalodon Extinction :; Would it survive today?
Topic Started: Jan 8 2012, 02:33 AM (11,688 Views)
Taipan
Member Avatar
Administrator

Grey
Feb 29 2012, 07:26 PM
No one has been followed in recents informations and documentations.
Not even when you consult privately renamed paleontologists.
Feel free to post somethingg to counter it then. Baseless denial wont help.
Offline Profile Quote Post Goto Top
 
Grey
Kleptoparasite
[ *  *  *  *  *  * ]
Not deny, just ignorance since not used back to 2002.
Also this was just one minor view of these paleontologists. The main explanation about Meg extinction in the book was the classic one.
Offline Profile Quote Post Goto Top
 
Taipan
Member Avatar
Administrator

Grey
Feb 29 2012, 09:02 PM
Not deny, just ignorance since not used back to 2002.
Also this was just one minor view of these paleontologists. The main explanation about Meg extinction in the book was the classic one.
You are denying it, and I welcome you to actually post some counter evidence/theory, or scientific rejection of it please.
Offline Profile Quote Post Goto Top
 
Elosha11
Herbivore
[ *  *  *  * ]
We should clarify that (I think) Grey and Taipan are referring to extinction theory 5 in the Renz excerpt. We had this argument ad nauseum in the old forum between Legend and Taipan, which I joined at the end. It is noteworthy that Legend posted a personal email communication with Renz in which he stated the theory in his book about whales evolving to be faster than Megaldon (extinction no. 5) was poorly written and that the main focus should be on climate change as the primary cause of Megalodon's extinction. Taipan if you still have that email from Renz, please post it again. Or if Legend will rejoin the forum, he can re-post it. I'm actually surprised he hasn't rejoined. The bottom line was that Legend argued Renz's email was a retraction, Taipan argued that it was not a retraction, and I argued that the Renz's email cast doubt on theory no. 5, but was not a complete retraction.
Offline Profile Quote Post Goto Top
 
Scalesofanubis
Omnivore
[ *  *  *  *  * ]
They wouldn't make it, the food is in The Wrong Place.

Megalodon, was probably a marine mammal hunting specialist, mostly whales at adult size. It was also, apparenly, a warm water fish. Now most of the big meaty whales live mostly in cold water. That means the Megalodon is screwed.
Offline Profile Quote Post Goto Top
 
Taipan
Member Avatar
Administrator

Elosha11
Mar 1 2012, 12:34 AM
We should clarify that (I think) Grey and Taipan are referring to extinction theory 5 in the Renz excerpt. We had this argument ad nauseum in the old forum between Legend and Taipan, which I joined at the end. It is noteworthy that Legend posted a personal email communication with Renz in which he stated the theory in his book about whales evolving to be faster than Megaldon (extinction no. 5) was poorly written and that the main focus should be on climate change as the primary cause of Megalodon's extinction. Taipan if you still have that email from Renz, please post it again. Or if Legend will rejoin the forum, he can re-post it. I'm actually surprised he hasn't rejoined. The bottom line was that Legend argued Renz's email was a retraction, Taipan argued that it was not a retraction, and I argued that the Renz's email cast doubt on theory no. 5, but was not a complete retraction.


No, the email claiming poorly worded was from Steven Alter, and not Mark Renz. Renz's work entered the debate when Legend claimed no one else believes Alters work. There was no email from Renz except to me and he stated the theories presented in his book were the opinions of 'experts'.

BTW Legend & Grey rejected every theory that involved another species of animal, as its obvious that no mere other species could ever play a role no matter how minor in the extinction of the omnipotent Megalodon.
Edited by Taipan, Mar 1 2012, 08:45 PM.
Offline Profile Quote Post Goto Top
 
coherentsheaf
Member Avatar
Kleptoparasite
[ *  *  *  *  *  * ]
Hey to all people wanting to use emails as evidence. Please post them.
Offline Profile Quote Post Goto Top
 
Elosha11
Herbivore
[ *  *  *  * ]
Unfortunately, the Alter/Renz emails was on the old forum which has been deleted. So unless Legend rejoins carnivora and re-posts it, or Taipan or someone else still has access to it, it's gone for good.
Offline Profile Quote Post Goto Top
 
Grey
Kleptoparasite
[ *  *  *  *  *  * ]
Taipan, my mainpoint is that this theory is ten years old and only mentioned in an article of a book outdated in some parts. This theory is simply far to be the most commonly used in any recent documentation about C.megalodon.

My opinion is that you had an issue with LeGenD and just referenced it for frustrate this member. Simply, this is not a widely spread theory today, and it was showed to be vastly contradictory.

Offline Profile Quote Post Goto Top
 
Elosha11
Herbivore
[ *  *  *  * ]
Taipan
Mar 1 2012, 08:31 PM
Elosha11
Mar 1 2012, 12:34 AM
We should clarify that (I think) Grey and Taipan are referring to extinction theory 5 in the Renz excerpt. We had this argument ad nauseum in the old forum between Legend and Taipan, which I joined at the end. It is noteworthy that Legend posted a personal email communication with Renz in which he stated the theory in his book about whales evolving to be faster than Megaldon (extinction no. 5) was poorly written and that the main focus should be on climate change as the primary cause of Megalodon's extinction. Taipan if you still have that email from Renz, please post it again. Or if Legend will rejoin the forum, he can re-post it. I'm actually surprised he hasn't rejoined. The bottom line was that Legend argued Renz's email was a retraction, Taipan argued that it was not a retraction, and I argued that the Renz's email cast doubt on theory no. 5, but was not a complete retraction.


No, the email claiming poorly worded was from Steven Alter, and not Mark Renz. Renz's work entered the debate when Legend claimed no one else believes Alters work. There was no email from Renz except to me and he stated the theories presented in his book were the opinions of 'experts'.

BTW Legend & Grey rejected every theory that involved another species of animal, as its obvious that no mere other species could ever play a role no matter how minor in the extinction of the omnipotent Megalodon.
Ok, well apparently it was Alter who wrote the email. In any event, Alter certainly expressed doubt about whales evolving higher speeds as being the primary cause of Megalodon's extinction. The majority view of Meg's extinction continues to be climate change, such as global and ocean cooling, closing of the Isthmus of Panama, and whales evolving to adapt to the colder water, where Megaldon could not go.

By the way, as I said in the old forum, whales adapting to colder water could certainly be considered, (in a very anthropmorphic sense), as "out-evolving" Megalodon. Likely, whales simply adapted to colder water, and Megaldon failed to adapt. So whales certainly did play a role in Megaldon's extinction, in my view, aided by climate change.

There are theories that orcas or other toothed whales could have outcompeted Megalodon or even predated on them. I think it's unlikely that orcas alone could bring down the entire Megaldon population by predation, considering the risks involved and the much easier prey sources in the rich and diverse Miocene environment. Indeed, I think adult Megalodon would occasionally prey on orcas and other similar sized toothed cetaceans. But that doesn't mean that the increased competition for food from orcas didn't have an impact. Considering that Megalodon was probably increasingly isolated in smaller pockets of warm water as the Miocene progressed, if orcas were preying on the same prey sources and reducing Megalodon's options, it would make the shark's situation even more dire.

It is also possible that orcas preyed on small juvenile Megalodons, which may have again had a serious impact during the late Miocene when the shark was already pressed for food. But once the Megalodon reached a size larger the orcas, I doubt it would be often attacked, since the orcas would then risk their own lives in the attack. Orcas are way too smart to go after hard prey when so much easier ones are ripe for the taking.

So in general, I am open to the idea that whales' and orcas' behaviors and adapations contributed to Megalodon's extinction. But I think their actions were simply the straw that broke the camel's back. Had Megalodon not been so severely threatened by climate change, it would have continued to thrive.
Edited by Elosha11, Mar 2 2012, 01:49 AM.
Offline Profile Quote Post Goto Top
 
Grey
Kleptoparasite
[ *  *  *  *  *  * ]
Orcas rarely attack medium sized individuals of large whale species. It take hours for serverly wound and kill it.
An attack on an adult healthy C.megalodon would be extremely dangerous for orcas.
However, competition and capacity of orcas to reach a wider range of preys in a world less frequented by large whale species clearly demised Megalodon.
Offline Profile Quote Post Goto Top
 
Scalesofanubis
Omnivore
[ *  *  *  *  * ]
Orcas have been known to kill great white sharks just to eat the liver, apparently to the point that if there is a hint of orca activity in the area, white sharks clear out.

There is no reason to think that this didn't happen to juvenile megalodon, and if megalodon used the usual reproductive strategies for laminid sharks (oviviporous, intra-uterine canabalism, late maturity, comperatively few young born per birth) then that could really mess up the megalodon population, particularly one that is already stressed by lack of food and living space. That being said, if food stressed, canabalism in general would probably be a greater threat.
Offline Profile Quote Post Goto Top
 
Taipan
Member Avatar
Administrator

Elosha11
Mar 2 2012, 01:48 AM
Taipan
Mar 1 2012, 08:31 PM
Elosha11
Mar 1 2012, 12:34 AM
We should clarify that (I think) Grey and Taipan are referring to extinction theory 5 in the Renz excerpt. We had this argument ad nauseum in the old forum between Legend and Taipan, which I joined at the end. It is noteworthy that Legend posted a personal email communication with Renz in which he stated the theory in his book about whales evolving to be faster than Megaldon (extinction no. 5) was poorly written and that the main focus should be on climate change as the primary cause of Megalodon's extinction. Taipan if you still have that email from Renz, please post it again. Or if Legend will rejoin the forum, he can re-post it. I'm actually surprised he hasn't rejoined. The bottom line was that Legend argued Renz's email was a retraction, Taipan argued that it was not a retraction, and I argued that the Renz's email cast doubt on theory no. 5, but was not a complete retraction.


No, the email claiming poorly worded was from Steven Alter, and not Mark Renz. Renz's work entered the debate when Legend claimed no one else believes Alters work. There was no email from Renz except to me and he stated the theories presented in his book were the opinions of 'experts'.

BTW Legend & Grey rejected every theory that involved another species of animal, as its obvious that no mere other species could ever play a role no matter how minor in the extinction of the omnipotent Megalodon.
Ok, well apparently it was Alter who wrote the email. In any event, Alter certainly expressed doubt about whales evolving higher speeds as being the primary cause of Megalodon's extinction. The majority view of Meg's extinction continues to be climate change, such as global and ocean cooling, closing of the Isthmus of Panama, and whales evolving to adapt to the colder water, where Megaldon could not go.

You can post what you believe the majority view to be in this thread then.

What Alter thought which wasnt made clear anyway in the email, is not that important anyway, given it was not his theory in the first place and Renz chose to include it in his book.
Offline Profile Quote Post Goto Top
 
M4A2E4
Member Avatar
Herbivore
[ *  *  *  * ]
If the shark could survive in cold water, it might be able to find enough wales. In tropical waters though, I really doubt it. The cetaceans there are either too small or are only there seasonally
Offline Profile Quote Post Goto Top
 
Elosha11
Herbivore
[ *  *  *  * ]
Here's a very thorough explanation of the majority view of Megaldon's extinction from a respected research site. I already posted this in the C. Megalodon profile, but at Taipan's invitation, I will post it here as well:

While the article is not perfect (for instance it probably underestimates the life span of Megalodon as a species), it is from a highly respected source and reflects the prevalent basic scientific understanding of Megalodon's extinction.

The Extinction of Megalodon

It is highly unlikely a single cause did in Megalodon. During its 14-million-year tenure, Megalodon was distributed nearly world-wide: its fossil teeth are known from Europe, Africa, North and South America, southern Asia, Indonesia, Australia, New Caledonia, and New Zealand. In general, widely distributed species are better able to persist through periods of environmental change than species with small or patchy distributions. Under adverse conditions, a few localized populations may dwindle and eventually disappear, but a cosmopolitan species like Megalodon is likely to endure. This mighty predator was therefore probably snuffed by an unfavorable combination of many different factors, at least some of which had far-reaching effects.

Major Environmental Changes

The world Megalodon inherited was very different from the one it left. Between Megalodon's appearance in the mid-Miocene (16 million years ago) and its extinction in the Plio-Pleistocene (1.6 million years ago), a barrage of large-scale changes occurred that affected the marine environment. Like shards of glass floating on molasses, the continents continued their languorous wanderings across the face of the planet, changing both land and sea as they went. Africa slammed into Europe during the Oligocene Epoch, reducing the interconnected Tethyan seaway to isolated bodies of water (today represented by the Mediterranean, Black, Caspian, and Aral seas). During the Miocene, the Indian subcontinent crashed into Asia, slowly crumpling the inland topography to help form the Himalayas. Similar tectonic altercations pushed up the Rockies and Andes mountains. These orogenic effects drastically altered global patterns of wind and rain as the continents jostled and shuffled into their present, familiar positions. The widespread cooling that had begun in the early Oligocene (about 35 million years ago) - combined with changes in wind and precipitation patterns - reduced the temperature at mid-latitudes by about 27 degrees Fahrenheit (15 degrees Celsius) and eventually resulted in a period of major glaciation at the poles by the late Miocene, about 10 million years ago. Between 7 and 3 million years ago, the Isthmus of Panama rose from the seafloor, joining North and South America and eliminating the last traces of the circum-tropical seaway that may have enabled Megalodon to disperse world-wide.

These terrestrial changes provoked ripple effects in the sea. Newly-formed mountains redistributed precipitation, creating rain shadows on their leeward sides. This redistribution of water caused many shallow inland seas to dry up, creating expansive salt flats that created insurmountable osmotic challenges for aquatic life. The Atlantic continued to spread on either side of the mid-oceanic rift - a gigantic tear in the seafloor into which magma from deep in the Earth is extruded, pushing apart the Old and New Worlds as inexorably as a couple in which the partners have stopped speaking to one another. Among other effects, this seafloor spreading caused the Gulf Stream to slow, thereby reducing upwelling of cold, nutrient-rich water near the southeastern parts of North America. Such upwellings were absolutely vital to supporting the rich web of marine life that ultimately provided a food source for Megalodon. It is probably no coincidence that the cetotheriids (early baleen whales) became extinct about the same time as Megalodon. Glaciation occupied much of the planetary water supply, locking it away in massive sheets of opalescent ice. Consequently, the sea level dropped some 650 feet (200 metres) and allowed many shallow coastal areas to dry up. Thus, through lowered temperature and sea level, Megalodon lost large areas of suitable habitat.

Shrinking Habitat

To a greater or lesser extent, all living lamnids - including the White Shark - have a modified circulatory system that enables them to retain metabolic heat and extend their range into chilly waters. With the exception of the Shortfin Mako (Isurus oxyrinchus), which makes a good living even in tropical waters, all extant lamnids are primarily cold-water animals. Although some lamnids - like the White Shark - occasionally visit warmer waters, very few actually live there. Like the primates slathered in coconut oil on tropical beaches, warm water lamnids are generally tourists. And, like their human counterparts, they eventually go home. In contrast, megalodon does not seem to have extended its range into cool temperate waters. Despite its enormous body mass, megalodon may not have shared the lamnids' ability to retain significant metabolic heat. This shortcoming may have effectively trapped Megalodon in discrete, ever-decreasing puddles of warm coastal waters. If, as Robert Purdy's paleoecological study suggests, Megalodon was limited to warm waters and relied on coastal areas as pupping grounds - no matter from whence it descended or what it looked like - it had a very sandtiger-like life history. And this may have led to Megalodon's ultimate undoing.

Tropical waters are relatively nutrient-poor compared with those of temperate zones. In the western North Atlantic, loss of upwelling by the end of the Pliocene (about 1.6 million years ago) may have left Megalodon trapped in waters unable to supply sufficient food to fuel its titanic mass. Due to an inability or unwillingness to expand its range to richer, colder waters, Megalodon may well have starved to death. In addition, lowered sea-level at about the same time may have left Megalodon without nursery areas relatively free from predators large and well-armed enough to snack on its pups. Because most coastal water available at the end of the Pliocene was near or over where the continental shelf drops off into oceanic depths, large pelagic predators such as Killer (Orcinus orca) and False Killer (Pseudorca crassidens) whales may have been able to snap up the 12-foot (4-metre) Megalodon pups. In modern sharks, access to predator-free nursery areas is known to be an important factor in determining survival of pups. Thus, due to environmental changes, Megalodon may have been 'hit' from both sides: the adults were too large to get enough to eat and the juveniles were too small not to be eaten by other predators.

Bad for Megalodon, Good for Us?

The rise of the Isthmus of Panama stimulated many ecological changes. In addition to sundering two oceans, this event linked the Americas, allowing animal migrations that forever changed New World ecology. Terrestrial species that had long been separated by impassable depths met, and in the face of new predators and diseases, many vanished. Paleontologist Steven Stanley has recently proposed that the rise of the Panamanian Isthmus may have also spurred the rise of human intelligence half the globe away. According to Stanley's intriguing but controversial theory, when Panama severed the link between the Atlantic and Pacific, the flow of deep ocean currents was changed dramatically which, in turn, had profound effects on Earth's climate. Warm currents were diverted away from the Arctic causing this region - and eventually the whole northern hemisphere - to chill. Between 3.2 and 2.5 million years ago, the Earth plunged into an ice age, triggering the oscillating cycle of glacial advances and retreats that continues to this day. This ice age brought cooling and drying, even to faraway Africa. Eastern African forests shrank and our early ancestors, the ape-like australopithicines, were forced to abandon lives spent mostly in trees. The few who survived evolved into Homo, man-like creatures that walked upright. With their hands essentially free for the first time in evolutionary history, these early humans could care for infants who were helpless and slow to mature. And only with that extra time during childhood development could humans begin evolving large, complex brains. Thus, what may have been an unlucky break for Megalodon, may have been a lucky one for us.
In the Shadow of Megalodon

We will probably never know for sure why Megalodon became extinct. Scattered distribution, insufficient food, or increased vulnerability of its pups may all have played a role. Or perhaps some other combination of factors conspired to snuff Megalodon. Yet the White Shark survives to this day. This species may have survived due to its ability to exploit the rich feeding available in cool temperate waters. Yet the White Shark is no more invincible than Megalodon proved to be. Like other sharks, the Great White matures late in life and has few pups per litter, severely limiting its ability to replace itself. This reproductive strategy has proven very sound in stable environments with few natural enemies. But evolution has simply not equipped the Great White to deal with the most complete and deadly predator the world has ever known. It may be the White Shark's ultimate misfortune to share a planet with us.

http://www.elasmo-research.org/education/evolution/megalodon_extinction.htm
Offline Profile Quote Post Goto Top
 
1 user reading this topic (1 Guest and 0 Anonymous)
ZetaBoards - Free Forum Hosting
Free Forums with no limits on posts or members.
Learn More · Sign-up for Free
Go to Next Page
« Previous Topic · Zoological Debate & Discussion · Next Topic »
Add Reply