Venom common is snakes and predates snake evolution ...

The following news item might be of interest ...

Venom common, predates snake evolution

Venom is much more common among snakes than previously thought, and its origins predate the evolution of snakes, according to surprising new Australian research.

I don't agree. Some of them, like the Mangrove Snake (Boiga dendrophila) are venomous enough to kill a person.

Actually, you are agreeing. You only stated one of the exceptions that fall outside of the 'most' realm. Stating that most are not dangerous is the same as saying that a few are dangerous. Also, not a great example, you would have to be pretty unfortunate to die from a mangrove bite. A better example might have been a boomslang.

The implications of the study are far reaching: it show that the number of snakes containing venom is actually 2,700 - not the 250 previously catalogued as poisonous.

hello! do we need a new rating system? we know what sankes kill, and we know what snakes don't. what now? are they gonna take my cornsnake away because he is venomious? disgusting!

Probably the same way that the egg predates the chicken...there are other reptilians, 'older' on the evolutionary tree, that use venom.

There are? The only other venomous reptiles I'm aware of are the Gila monster and beaded lizard, but there's no reason I know of to believe either that they originated prior to snakes, or that they and snakes share a common ancestor in which venom originated. I've also heard things about some dinosaurs having venom, but I don't know if that's well supported, and in any case dinosaurs are only very distantly related to lizards and snakes.

Patrick Alexander

I believe to remember that some dinosaurs (small predators that hunted in packs) were not exactly venomous but had something in their saliva that could be irritating and slightly narcotizing, similar to the snakes of the species Natrix. Don't remember their name.

The fossil varanoid lizard Estesia posessed grooved teeth that would have been suitable for delivering venom. Paleosaniwa, another fossil varanoid, may have had venom delivery dental structures as well. The beaded lizard and Gila monster are modern varanoids, as are the monitors, the Bornean earless lizard and ... snakes! Venom may have evolved among the early varanoids, and still be present among the modern helodermids and snakes. Monitors and the Bornean earless lizard would then be secondarily venomless, although Bennett reports that the desert monitor may have true venom.

The teeth of a predatory dinosaur with grooves have been discovered. These grooves may have been for the delivery of venom. Or maybe not. It is often frustrating working only with the teeth and bones.

It is extremely implausable that the biomolecules that may have been used for venom would have survived for the 65 to 220 million years required for us to determine not only that venom was present, but its effect on potential prey. The only evidence we have available to us about the non-avian dinosaurs comes from their bones (often badly damaged or degraded), their footprints, the rare soft tissue records (not including the actual tissue, alas, but rather thin films of carbon or filled cavities left by impressions on a substrate), and comparisons with the dinosaur's closest relatives (birds and crocodiles). Several attempts have been made to extract biomolecules from dinosaur fossils. One provided evidence of what might have been a dinosaur protein, another turned up DNA that later turned out to be identical to that of a turkey (one of the field workers or lab techs probably contaminated the bone with a turkey sandwich). Based on the available evidence, it is impossible to say whether or not any dinosaurs were actually venomous, let alone the properties of said venom.

The fictional book Jurassic Park by Michael Crichton described a small dinosaur (Procompsognathus) which posessed a venom like that which you describe, plus another (Dilophosaurus) which had a nastier venom that it could spit. Perhaps these are the ones you were thinking of? Procompsognathus and Dilophosaurus actualy existed, but the presence of venom is pure speculation on the part of Dr Crichton. The fossils of these two dinosaurs show no evidence of venom delivery apparati, venom sacs, or other structural modifications that would support the presence of venom (nor do the fossils rule out venom. The fossils do, however, clearly rule out the neck frill that the Dilophosaurus erected in the movie version of Jurassic Park: the muscles necessary for the erection of the frill would have left marks on the fossil bones).

Though it depends somewhat on who you ask, the genus Natrix is venomous. Earlier herpetologists seemed to view something as a venom if it had some sort of specialized delivery mechanism (fangs, generally) attached to it, but as 'toxic saliva' if it didn't. More recently, though, Dr. Fry and others have demonstrated that it is the same gland and the same toxins that are involved either way, so this distinction doesn't really work. What that means about the dinosaurs, I don't really know... maybe the fang criterion is being applied, and we just don't have the ability to apply other criteria in extinct species.

Patrick Alexander

The movie version of the Dilophosaurus was also much smaller than the real-life Dilophosaurus. The movie one was only about 4 feet or so (not much bigger than a Hobbit) whilst the real-life one was closer to ten feet tall