Just picked up Steve's posting by chance (I was on the list but not this online forum) & since my name is mentioned it deserves a reply (even if a little late) to put the record straight. I have two points to make:-
1. snip I have yet to see a redescription of 'Benthoctopus piscatorum' (the type species of Benthoctopus) snip
The species piscatorum
Verrill was redescribed by Muus in 2002 (reference below), who concluded (after inspecting the type material carefully) that "beyond reasonable doubt
" it is the same species as Bathypolypus bairdii
, and went on (two more pages) to explain the identities of other specimens previously described as species piscatorum
. Species piscatorum
is the type species of Benthoctopus
, so (as Steve rightly noted) the conclusion is:-
= Bathypolypus bairdii
Therefore genus Benthoctopus
= genus Bathypolypus
2. snip There's another genus out there, Atlantoctopus, that really hasn't received the systematic treatment warranted before any new genera were proposed. snip
My paper (that Steve talks about in his posting) mentioned briefly what is known about Atlantoctopus
, which is not very much. Here it is in a little bit more detail:-
The genus Atlantoctopus
was coined to describe Octopus lothei
Chun, 1914. Unfortunately, there was only one type specimen and it was a female that, as far as anyone knows, no longer exists and was never described in enough detail to allow us to make good comparisons with other species. Robson (1932) suggested that Atlantoctopus lothei
is the same as species ergasticus
. This is not unreasonable: Bathypolypus ergasticus
(also redescribed by Muus) occurs in an area of the Eastern Atlantic that includes the type locality of Atlantoctopus lothei
(near the Canary Islands at depth 746 fathoms, =1365m). We cannot be 100% certain that Robson was right but unless someone can prove he was wrong, a reasonable conclusion is:-
= Bathypolypus ergasticus
Therefore genus Atlantoctopus
= genus Bathypolypus
Comparing specimens to identify species always involves some degree of doubt, but these points ought to satisfy Steve that my acceptance of Benthoctopus
as synonyms of Bathypolypus
is not uncritical. As science progresses, I might be proven wrong. Until that happens, I'm happy to stand by what I wrote in my paper.
For me, anyway, Muus published a landmark paper making it clear that all three genus names belong with Bathypolypus
, which is well characterized now: briefly Bathypolypus
species are deep-water octopuses with no ink sac, a stout body and short arms; males have a modified third arm ending in a distinctive expanded ligula that has prominent continuous ridges across its inner surface; and the skin usually has papillae, including large cirri above the eyes.
Most of the remaining so-called 'Benthoctopus
' species are very different (although, like Bathypolypus
, they typically have no ink sac) and the genus names have yet to be sorted out (I and several other people are working on different species in this group at the moment). In my paper that Steve mentioned, I proposed the new genus name Muusoctopus
(out of respect for Bent Muus) for the best known of these (species januarii
) and pointed out some similarities with species (WITH an ink sac) that I see often here where I live in Japan.
Muus, B. (2002). The Bathypolypus-Benthoctopus
problem of the North Atlantic (Octopodidae, Cephalopoda). Malacologia 44
Robson, G.C. (1932). A monograph of the recent Cephalopoda based on the collections in the British Museum (Natural History). Part II. The Octopoda (excluding the Octopodinae)
. London, British Museum (Natural History).
Steve O'Shea said:
It's probably Vulcanoctopus (a vent-dwelling taxon) - although the genus is rather poorly known (similar in many respects to 'Benthoctopus').
Actually, the genus Benthoctopus is probably little more than a synonym of Bathypolypus (as the type species of Benthoctopus was actually a Bathypolypus); differentiating the two in accordance with more recent diagnoses, presence or absence of a crop diverticulum, and presence or absence of lateral cusps on the rachidian tooth of the radula, doesn't work for all species. I have yet to see a redescription of 'Benthoctopus piscatorum' (the type species of Benthoctopus), so I am wary of uncritically accepting this synonymy until I do. Nevertheless, and in no way am I criticising Ian Gleadall's work at all, Ian has described a new genus to accomodate at least one of the species typically referred to Benthoctopus - Muusoctopus, and we may well find that a number of other species will eventually be attributed to this genus (Gleadall 2004). There's another genus out there, Atlantoctopus, that really hasn't received the systematic treatment warranted before any new genera were proposed.
Gleadall, I.G. 2004. Some old and new genera of octopus. Interdisciplinary Information Series 10(2): 99-112.