SNAKE FANGS FROM THE LOWER MIOCENE OF GERMANY: EVOLUTIONARY STABILITY OF PERFECT WEAPONS

Nature via CNAH ^ | 9 February 2006 | Ulrich Kuch, Johannes Müller, Clemens Mödden & Dietrich Mebs

[GreenFreeper]

There is a general consensus that most of today’s nonvenomous snakes are descendants of venomous snakes that lost their venomous capabilities secondarily. This implies that the evolutionary history of venomous snakes and their venom apparatus should be older than the current evidence from the fossil record. We compared some of the oldest-known fossil snake fangs from the Lower Miocene of Germany with those of modern viperids and elapids and found their morphology to be indistinguishable from the modern forms. The primary function of recent elapid and viperid snake fangs is to facilitate the extremely rapid, stablike application of highly toxic venoms. Our findings therefore indicate that the other components of the venom delivery system of Early Miocene vipers and elapids were also highly developed, and that these snakes used their venom in the same way as their modern relatives. Thus, the fossil record supports the view that snakes used their venoms to rapidly subdue prey long before the mid-Tertiary onset of the global environmental changes that seem to have supported the successful radiation of venomous snakes.

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[Carry_Okie]

Venom is very costly to produce

How is this is demonstrated? I wasn't aware that small glands consumed that much energy (compared to locomotion). They aren't very big and I don't recall that they are highly vascularized.

I would think it has more to do with a shift in diet.

[GreenFreeper]

I don't know exactly the cost breakdown of venom vs. movement but complex organic chemicals, usually proteins, are expensive to produce.

In ants and spiders production cost is calculated using the combined heat of combustion estimates for specific venoms. At least in ants it can be somewhere around 10,000 (KJ/mol).

[Junior]

Yes.

[RightWingAtheist]

Cool. Does this mean that Gila monsters and Mexican beaded lizards are basal forms? In my beloved old Funk and Walgalls Wildlife Encyclopedia (still have 'em; everyone should!), the section on the hog-nosed snake suggested that the snake was "on its way" to becoming venomous in a few generations, due to certain features it shared with venomous snakes, notably a saliva that is toxic to the frogs and toads it preys on. It now seems more likely to me, according to this article, that the hog-nose is instead related to those first species which were on the way out from being venomous, but that it retained certain poison-producing glands which became specifically toxic for a snake with a very specialized diet, and that its threat display may be a behavioral hanger-on from its venomous days, that is still useful today.

[RightWingAtheist]

I just hope the makers of the American Pie movies aren't freepers, or else they'll read this, and have Stifler down a special "chocolate" shake in the next film.

[RightWingAtheist]

Most iguana species are insectivorous as juveniles, but shift to 100% vegetarian diet as they grow older. The green iguana is entirely herbivorous throughout its lifespan, and the rhinoceros iguana remains ominivorous well into adulthood.

[GreenFreeper]

Heterodontids are still considered mildly venomous. The venom is supposedly amphibian specific, though I know of a person who lost a finger from a Heterodon 'bite'. The guy was raising a few of these guys and got a finger caught on one of the rear fangs while try to feed a juvenile. He didn't think much of it until the next day when the finger was black.

the hog-nose is instead related to those first species which were on the way out from being venomous

Very much agree!