Hydrophis belcheri
Belcher's sea snake, which many times is mistakenly called the "hook-nosed sea snake" ("Enhydrina schistosa"), has been erroneously popularized as the most venomous snake in the world, due to Ernst and Zug's published book "Snakes in Question: The Smithsonian Answer Book" from 1996.
Associate Professor Bryan Grieg Fry, a prominent venom expert, has clarified the error: "The hook nosed myth was due to a fundamental error in a book called 'Snakes in question'. In there, all the toxicity testing results were lumped in together, regardless of the mode of testing (e.g. subcutaneous vs. intramuscular vs intravenous vs intraperitoneal). As the mode can influence the relative number, venoms can only be compared within a mode. Otherwise, its apples and rocks.". Studies on mice and human cardiac cell culture shows that venom of the inland taipan, drop by drop, is the most toxic among all snakes; land or sea. The most venomous sea snake is actually Dubois' seasnake ("Aipysurus duboisii" ).
Crotalus scutulatus
All rattlesnake venoms are complex cocktails of enzymes and other proteins that vary greatly in composition and effects, not only between species, but also between geographic populations within the same species. "C. scutulatus" is widely regarded as producing one of the most toxic snake venoms in the New World, based on studies in laboratory mice. Their potent venom is the result of a presynaptic neurotoxin composed of two distinct peptide subunits. The basic subunit (a phospholipase A) is mildly toxic and apparently rather common in North American rattlesnake venoms. The less common acidic subunit is not toxic by itself, but in combination with the basic subunit, produces the potent neurotoxin called “Mojave toxin”. Nearly identical neurotoxins have been discovered in five North American rattlesnake species besides "C. scutulatus". However, not all populations express both subunits. The venom of many Mojave rattlesnakes from south-central Arizona lacks the acidic subunit and has been designated “venom B,” while Mojave rattlesnakes tested from all other areas express both subunits and have been designated “venom A” populations.