Whale Evolution

My own collection of fossil ceteceans

UPDATED

NOTE: I never much cared for the name "basilosaurus" as the official or correct name of the the Eocene whale, also known as zueglodon. This is why I use the name "zueglodon" throughout. The first discover mistook it for a marine reptile, and you can understand the confusion just by looking at it. Calling it "basilosaurus" only adds to the confusion. AronRa, an natural history expert and atheist activist is of the same opinion regarding this species. I disagree with him on atheism, but I couldn't agree more on this. 

 I've always had an interest in prehistoric whales and how they evolved. Above is one of my books on the subject showcased along four primeval cetacean figures. The ambulocetus, and remingtonacetus (a subspecies of kuchecetus?), are recent aquisition from some company over in China that makes all sorts of obscura prehistorica. The two basilosaurus/zueglodon figures are from Japan, possibly both from Medicom. 

This one is a definitive Medicom figure, which I sought for many years, calling it the Medicom Zueglodon. It is part of a series of cryptozoological figures they made in the ninties. This one was called the Monster of Lake Van, the assumption being, of course that the monster is a surviving zueglodon. Other figures in the series included a Nandi Bear (calicotherium) and a giant kanagaroo (procoptodon), based on the reports of "phantom kangaroos" that keep popping up. 

                                    Pakicetus catching a fish. Note the position of the eyes on the skull

                                                                           

It was Darwin himself who first theorized that an animal like a bear might start swimming about, catching insects on the surface, and eventually lead to a fully aquatic mammal. An absurd sounding theory, and for many decades, the fossils of whale ancestry remained notoriously absent, just like the fossils of pterosaurs and bats today. It wasn't until the late eighties and nineties that substantial fossilized evidence for whale evolution began to come to light. The discovery of Pakicetus, and land-dwelling, but partially aquatic carnivorous mammal was the first major discovery. The position of its nostrils was a character shared only by whales, even though it was vaguely wolf-like. It had small hooved toes, similar to a mesonychid, which whales were long thought to be related. However, it is now placed among the ceteceans themselves, which are now classed as artidactyls like hippos and pigs, thanks to DNA findings. An early possible ancestor was Indohyus, a small hooved artodactyl rather like a chevrotin, that showed some characteristics of an early swimming.

A skeleton of Pakicetus I photographed at the "Jurassic Sea Monsters" special exhibit at the Field Museum of Chicago, which included sea creatures from more than just the Mesozoic 

The mounted skeleton of Durodon, the first known fully aquatic whale, at the same exhibit

                                                    

                                                        Ambulocetus Natans

This was followed by the discovery of ambulocetus, a virtually perfect transition from land living ancestors and fully aquatic whales. This early Eocene beast is believed have lived like a mammalian crocodile, ambushing animals like unwary protorohippus (once called eohippus or hyrachotherium) on land. Others followed, like miacetus, a near cousin of ambulocetus, with the same body plan, and durodon, a more fully aquatic animal resembling a genuine dolphin with legs and longer tail.

                                                 

                                                 The gavial-like kutchicetus catching fish

Whale evolution is particularly instruction to how evolution works, as their also existed many bizarre forms that represented side-branches. These included the bizarre heron-like dalanistes, which may have waited in the shallows to capture fish in its narrow jaws, and the almost gavial-like kuchicetus and apparent subspecies remingtonocetus.

A cladogram showing the evolution of whales. That they may have been descended from pachyeana is now considered false, as whales are related to living artidactyls, not mesonychids

It's sometimes said that the picture of evolution from the relatively simplistic to the complex is false. Not quite true. There has been certainly a general trend toward greater complexity, and yes, that means more advanced efficient forms. Just look at the evolution of the modern carnivora, which developed large brains and efficient hunting strategies, coupled with better killing tools. This allowed them to easily displace the more larger but more primitve creodonts and condylarths. 

 Bizarre fossil ceteceans: Clockwise from top: Durodon, Ambulocetus, Pakicetus, Kutchicetus, and Miacetus. All radiated from a common ancestor, though Pakicetus is the most primitive, and durodon the most advanced

The evolution of humans did indeed proceed from more ape-like creatures with smaller brains toward modern man, just as the classic picture of ape to ape-man to modern humans suggests. 

At the same time though, that picture is indeed far too simplistic. At the same time that proto-humans were advancing, they were also branching out to exploit the various niches. The resulted in a plethora of bizarre forms of man-ape that were essentially evolutionary dead-ends. None of the descendents of Zinjanthropus or Paranthropus Bosei (believed to be a termite feeder, as portrayed in the BBC documentary Walking with Cavemen), remain alive today. The same is true for Homo Florenses, the pygmy, island dwelling offshoot of Erectus, evolved to exploit a greater store of food sources.

Paranthropus Bosei

                                                                   Zinjanthropus

Humans are believed to be direct descendants of australopithicines, however. And the same holds for Homo Habilis and Erectus. Today, there are simply no more major "missing links" from ape to human.

The same is now becoming nearly the same for the evolution of whales. Many forms left no living descendents, but all whales go back to either ambulocetus itself, or a near relative. The picture is virtually complete.

                                       

                                                            Zueglodon by Zdenek Burian

Only in a lost world setting like Ka-Zar's Pangea could a zueglodon prey upon an elasmosaurus!

                                               Tarzan battles a zueglodon in Pal-ul-don!

Whale evolution from the BBC Tv series and book, The Velvet Claw  (1992)

The above pic is from the BBC excellent TV mini series on carnivore evolution The Velvet Claw. It shows an otter-like pakicetus evolving into a modern blue whale. It is of interest because it essentially  depicts an ambulocetus before that animal was dug up! I checked and sure enough, ambulocetus was discovered in 1994, two years after The Velvet Claw was televised!