Creature of the Week #2: Basilosaurus

marco_polo

Basilosaurus was first discovered in Louisana in 1832, with other specimens subsequently found in places as far away as 'The valley of the Whales' in Egypt and Pakistan as well. Its misleading name, which translates roughly to 'King Lizzard' is a result of it being mistakenly classified as a marine reptile initially, and the first cut at a reconstruction was somewhat innaccurate. It is now known that as a primative whale it belongs firmly in the mamilian order Cetacea. It is generally considered to be a cousin of, rather than the direct ancestor of modern whales and dolphins.



Basilosaurus lived during the Middle to Upper Eocene aproximately 34 – 40 million years ago, and frequented the warm shallow sea between Africa and Europe, and around North America. (To understand why it was found in the South eastern US, Pakistan and Egypt see this Global map of the Eocene). It was the first whale to become truly gigantic in size with an average length of aproximately 18 meters and a weight of roughly 6 tonnes. Much like its modern cousins it is believed to have been the largest animal on the the planet at the time.

Unsurprisingly because of its size Basilosaurus it would have had to consume alot of food to sustain itself. Because of its place at the very top of the food chain, Basilosaurus was not a particulairly fussy eater with a diet known from discovered remains to consist of fish and small sharks, there are also indications that it ate smaller whales like Dorudon and Zygorhiza, seacows, and turtles. Based on the fact that a large brain is seems to be a prerequsite for needed for social behaviour, it is probable that Basilosaurus did not have the social skill of modern Cetaceans and hunted alone.

Basilosaurus was much more elongated and slimmer than modern whales, its length was primairly due to its due to its exceptionally long vertebrae, and its slimline apperance because it lacked the thick blubber layer which is a hallmark of modern whales and restricted Basilosaurus to living in warmer shallow waters.

Because it lacked a number of features present in modern whales such as a proper dorsal fin, and had a very small fluke at the end of its tail, it appears that it would have propelled itself more like an eel, albeit moving with a vertical rather than horizontal motion (The distinction is similar to that between fish who swim with a side to side tail motion, and dolphins and whales who swim with an up and down tail motion). The lack of a blowhole also mean that it would have had to poke its head above the surface of the water to breate, through a large single nostril that had migrated a short distance back on the head (Somewhat on the way to becoming a proper blowhole).

One of the the most interesting features of Basilosaurus to Paleontologists was the clear presence of vestigal limbs in the form of a complete pelvic girdle and hindlimb bones. At 60 cm the limbs were too small to aid propulsion of a 18m animal and pelvic girdle was completely isolated from the spine and thus useless. A clear signal of its land ancestry.

Here is a clip from an Episode of Walking with Sea Monsters.*

https://www.youtube.com/watch?v=Hfxdz9l00uY

Basilosarus also featured in a full episode of Walking with Beasts.

https://www.youtube.com/watch?v=-tpGTXFLx_I

https://www.youtube.com/watch?v=yqPuE508qrU

https://www.youtube.com/watch?v=Zki7vrV1TKg

* Creationists note that this is a fictional reconstruction, man was not actually around at this time.

Weidii

Brilliant, thanks. Watching these always makes me want to do my masters in vertebrate palaeontology

Galvasean

It's funny how it's name means 'king lizard' despite being a whale. Back in the day Sir Richard Owen suggested that it be renamed "Zeuglodon cetoides", however once a name is offiocially given to an animal by science it has to stick, so Basilosaurus remains the (somewhat inappropriate) official name.
Also, that 'somehat innacurate' reconstruction in the OP was at the time referred to as "Hydrachos". Unfortunately it was an amalgamation of several different animals so is considered an invalid name/reconstruction.

marco_polo

Galvasean wrote: »

It's funny how it's name means 'king lizard' despite being a whale. Back in the day Sir Richard Owen suggested that it be renamed "Zeuglodon cetoides", however once a name is offiocially given to an animal by science it has to stick, so Basilosaurus remains the (somewhat inappropriate) official name.
Also, that 'somehat innacurate' reconstruction in the OP was at the time referred to as "Hydrachos". Unfortunately it was an amalgamation of several different animals so is considered an invalid name/reconstruction.

Given me an idea, any mileage to be had out of a worst scientific name ever thread I wonder?

Galvasean

marco_polo wrote: »

Given me an idea, any mileage to be had out of a worst scientific name ever thread I wonder?

I think so.
The first two creatures of the week have scientific names which have sweet buzz all to do with the creature they represent.

Manach

Yet another disappointment from evolutionary theory, I'd though it would be Basil Brush in a stone-age garb