"It would be like a locomotive with a mouth full of butcher knives."

- Hooper describing C. megalodon to Brody (from the novel 'Jaws - 1974)

 

 

AND YOU THOUGHT 'JAWS' WAS BIG!

There is reliable information that on a few occasions back before the really big GWs were fished out at the height of 'Jaws' hysteria, some fisherman or another managed to pluck a 21-ft or so GW out of the water. This grand fish would be admired hanging from a crane back on the docks - that is, until its jaws were sliced out and the rest of the carcass was used as dogfood or such - but I digress. Let's represent this monster shark with the following 210-pixel line.

Tough to see just how big this is? Here is a six-foot man either lying down next to that same shark.

Starting to see how big a really large GW can grow? Pretty incredible to consider, huh? Well, about 50 million years or go - give or take a couple of millenia, mind you - there was a shark that swam the ocean blue that was twice as big with much the same features as our friend old C. carcharias. Want to see the comparison?

Humbling, isn't it? We'd be like popcorn shrimp! This predator is truly one of nature's most awesome creations ever,  a fish that conceivably weighed more than 20 tons and had a head the size of my car. In a sense, it could be called the Great Great White Shark - although it is more accurate to call it by the name scientists have given it - Megalodon.

YOU SAY 'CARCHARODON', I SAY 'CARCHAROCLES'

For most of my youth, I knew of the megalodon as Carcharodon megalodon, indicating a relationship to contemporary Carcharodon carcharias, which we already know as the GW. Scientists didn't actually go so far as to say that the GW had directly descended from C. megalodon but they did believe they were "proximate twigs of the same evolutionary bramble bush" to quote Mr. Ellis & Dr. McCosker's 'Great White Shark'. My youthful imagination was likewise captured by the Guinness Book of World Records when it printed the famous photo of six men clustered together within a set of reconstructed jaws and said the shark that went with them grew to be more than 100 feet long. Of course, at the time, I also believed in the Tooth Fairy . . . go figure.

However, upon researching further and digging into the depths of material on Megalodon at my local university library, I came upon a controversy that apparently has been raging between paleontologists (scientists who study fossils to learn about animals of the past) and marine biologists for a few years. It seems that several prominent paleontologists believe that Megalodon should really be classified as Carcharocles megalodon and not Carcharodon megalodon.

Big deal, right? Who cares what we call a long-dead shark? Plenty of folks, it turns out. As Jim Bourdon points out at his excellent website, Megalodon is a "poster child" for those who study sharks much like Tyrannosaurus rex is for those who study dinosaurs. Imagine the uproar if paleontologists came forward and wanted to change its name from T. rex to T.somethingelseus and you start to understand the emotional nature of the controversy.

As for the factual basis of controversy, this can be found in studying the ancestry of the GW. GWs are part of a grouping known as mackerel sharks, a grouping which includes the salmon, porbeagle, and mako sharks. One of the mako's ancestors is an extinct shark known as Isurus hastalis. Comparisons of the teeth of I. hastalis and C. carcharias reveals that they are remarkably similar, the only difference being that I. hastalis teeth are smooth, lacking serrations. In the mid-80s, a 5-million year old shark specimen  was found that some scientists have concluded links I. hastalis with C. carcharias as it had "weakly" serrated teeth. If true, this could indicate that the GW is a likely descendent of I. hastalis.

 

These teeth from the modern GW (left)  are quite similar to the teeth of the extinct I. hastalis (right) but notice the lack of serrations in I. hastalis. 

Here's where it gets fun. Let's say that the GW is a descendent of this ancient mako-like shark. Megalodon does not share this immediate ancestry and thus, belongs in a different genus entirely. Carcharocles had been put forth as a genus for a few other species (C. angustidens, C. auriculatus, & C. sulcidens for those keeping score at home) and it is in this genus that some say Megalodon belongs. 

In support of the Carcharodon camp are three main points as given by Dr. Samuel Gruber - again, by way of Jim Bourdon's website.

  • There is a unifying tooth structure that connects all the great tooth sharks to the living C. carcharias i.e. tooth shape & the arrangement and placement of these teeth in the jaw

  • Fossil teeth assigned to C. carcharias have been found in deposits that are much older than the teeth from the 5-million year old specimen I referred to above that supposedly links Isurus hastalis and C. carcharias meaning that the GW has been swimming around since before this "intermediate" species appeared.

  • Biochemical (DNA) evidence presented by Andy Martin strongly suggests that Isurus hastalis and Carcharodon diverged 40 my ago well before the age of the "intermediate tooth."

What does it all mean? It depends on your viewpoint - how badly do you want C. megalodon to be related to C. carcharias? Judging from the heated exchanges I've read on the Internet, plenty of experts are on either side of the debate with most  paleontologists firmly on the side of Carcharocles and most marine biologists showing their love for Carcharodon.

THE HUMBLE OPINION OF AN IDIOT

Me?  I have to say that the Carcharocles camp seems to hold the most weight in my mind. I've got tooth specimens from Otodus obliqus, C. auriculatus, I. hastalis, and I. escheri in my collection and I can see the progression that Bill Heim and others have argued - but hey, who am I?? Just a guy from Arizona. I will say that the compelling piece of evidence for me is the tooth shape from these two progressions - the teeth that lead to C. carcharias all share a certain degree of "flatness" while the teeth that lead to C. megalodon have a more cone-like shape. Here's what I mean.

 

Carcharodon carcharias Line

Isurus hastalis

Isurus escheri

Carcharodon carcharias

 

Carcharocles megalodon Line

Otodus obliquus

Carcharocles auriculatus
 

You can see how "flat" the top grouping is. I don't have a megalodon specimen to complete my demonstration but I have seen pictures of the teeth. When you apply the scale of the tooth, it follows more closely the bottom group than the top. Keep in mind again that this is just the rantings of an uneducated shark guy . . . but you can see where the excitement is in trying to piece together the puzzle?

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