BIG EARLY WHALES

["Darren Naish" <dwn194@soton.ac.uk>]

GSP says..

> Even so, it took whales 40 or more Myr to become truly massive, and 100 tonne
> blue whales appeared only a few million years ago.

Maybe there's a little ambiguity attached to the meaning of 'truly massive',
but, in my book, whales got truly massive very early on in their history -
_Basilosaurus_ from the late Eocene (approx. 40 Ma) got upwards of 15 m with _B.
isis_ (the Egyptian one), and there are fragments of _B. cetoides_ (the SE USA
one) that suggest upwards of 20 m. Basilosaurs were not the super-slim snaky
serpentiforms they were once depicted as, and reconstructions now make them out
to be rather robust and relatively deep bodied. A 20 m basilosaur may have
weighed 50 tons or more. The biggest Sperm whales (_Physeter catodon_), at 17
and possibly 18-19 m, are estimated at 60 tons. 

The biggest Blue whale (_Balaenoptera musculus_) cow yet measured, she was 33
m long, was not weighed but estimates based on smaller whales put her at 190
tons. Some regard this as slightly conservative as even small blues are weighed
piecemeal and there is substantial loss of body fluids. In his new book on blues
(1997), Calambokidis advocates 200 tons+ for the 33 m female.  

Anyhow, giant basilosaurs of the late Eocene were living less than 10 Ma later
than the very earliest whales yet known (_Pakicetus inachus_ of the Kuldani Fm,
Pakistan) - whales got big very fast.

I may as well say that the same goes for marine reptiles. The earliest known
pliosaurid, _Eurycleidus_ from lower Lias Dorset, was perhaps 5 m long when
adult and perhaps 3-6 tons. Rhomaleosaurs from the mid-late Lias probably reach
9 m or more (about 20 tons) and late Jurassic giants like _Megalneusaurus_ and
the Peterborough giant were upwards of 13 m and perhaps 60 tons or more. Sperm
whale sized. _Shonisaurus_, _Cymbospondylus_ and _Shastasaurus_ (all
shastasaurid ichthyosaurs from the late Triassic) all reached lengths of 13 m
and upwards, and were also probably comparable with Sperm whale bulls in mass.
Scythian, Anisian, and Ladinian ichthyosaurs are generally smaller things at 1-
3 m, yet within less than 15 Ma they had evolved these giants. These leaps and
bounds toward gigantism are comparable with the sauropod record - however,
neither non-mysticete whales nor marine reptiles are known to have grown to the
colossal sizes of super sauropods or blue whales. Yet.

One final word. Dinosaur palaeontology is rife with scepticism. So how come we
haven't yet seen any scepticism directed toward the veracity of _Amphicoelias
fragilimmus_ (or however it's spelt)? A taxon based on a drawing of a lost
fragment? Is that original drawing proof enough of this existence of this
animal? These are genuine questions and not my attempt to play devil's advocate.

"For the honour"

DARREN NAISH