The lengths and weights that
Architeuthis is reputed to attain are quite exagerated. The same could apply for
Mesonychoteuthis, but as adult specimens are extremely rare in collections, and very little information is available for it, we are not in any position to challenge presently reported estimates.
I attach two files. The first depicts adult
Architeuthis dux maximum lengths and weights, based on examination of over 100 specimens in the past 8 years. I do not believe, as stated many times throughout this site, that they attain lengths of 60 feet and weights of one ton.
For
Mesonychoteuthis maximum estimates of length are:
mantle length: 2-4m; total length to 30 feet.
Based on a combination of beak dimension, and both factory ship and photographic observations, Clarke (1986: 202) suggests
Mesonychoteuthis attains a mantle length in excess of 2 m, possibly exceeding 4 m. Nesis (1987) reports mantle lengths of 2.0-2.25 m, but it is uncertain whether these measures are based on actual specimens, or estimates of size based on beak remains from stomach contents of sperm whales.
The lower beak standard measurement of rostrum length (LRL) 22.0 mm reported for 1.05 m specimen (Rodhouse & Clarke 1985) is considerably shorter than the greatest LRL described for this species, 48.0 mm (a measure taken from the largest beak known from the stomach of sperm whales). Therefore
Mesonychoteuthis obviously attains sizes well in excess of 1.05 m ML.
We will soon find out whether these estimates are reliable. If
Mesonychoteuthis does attain a mantle length of 4 m, or anywhere approaching it, then it truly will dwarf
Architeuthis in terms of length, bulk and certainly 'meaness'; if it attains little more than 2.25 m ML then, although large and ferocious, it will not approach the standard length dimension of
Architeuthis (if size and length can be scaled as they have in the accompanying figure).
Watch this space
References
Clarke, M.R. (ed.). 1986: A handbook for the identification of cephalopod beaks. Clarendon Press, Oxford: 1–273.
Nesis, K.N. 1987: Cephalopods of the world (English translation). Tropical Fish Hobbiest (T.F.H.) publications, Neptune City: 1–352.
Rodhouse, P.G.; Clarke, M.R. 1985. Growth and distribution of young
Mesonychoteuthis hamiltoni Robson (Mollusca: Cephalopoda): an Antarctic squid.
Vie Milieu 35(3/4): 223–230.