return to main index

  mobile - desktop
follow us on facebook follow us on twitter follow us on YouTube link to us on LinkedIn
 
click here for Rodent Pro
This Space Available
3 months for $50.00
Locate a business by name: click to list your business
search the classifieds. buy an account
events by zip code list an event
Search the forums             Search in:
News & Events: Herp Photo of the Day: Python . . . . . . . . . .  Herp Photo of the Day: Tegu . . . . . . . . . .  ReptiCon Mobile - Feb. 29-Mar. 01, 202 . . . . . . . . . .  ReptiCon Houston - Feb. 29-Mar. 01, 202 . . . . . . . . . .  ReptiCon Greenville - Feb. 29-Mar. 01, 202 . . . . . . . . . .  Western Maryland Reptile Show - Mar. 07, 2020 . . . . . . . . . .  The Reptile Expo - Mar. 07, 2020 . . . . . . . . . .  Reptilian Nation Expo San Diego - Mar. 07-08, 2020 . . . . . . . . . .  ReptiCon West Palm Beach - Mar. 07-08, 2020 . . . . . . . . . .  ReptiCon San Bernardino - Mar. 07-08, 2020 . . . . . . . . . .  ReptiCon Knoxville - Mar. 07-08, 2020 . . . . . . . . . .  Reptile Family Expo - Mar. 08, 2020 . . . . . . . . . . 

full banner - advertise here .50¢/1000 views
click here for the St. Louis Reptile & Exotics Show
pool banner - $50 year

RE: Basal Elapids and Viperids Must Be Found Amongst the Rear Fanged and Ag

[ Login ] [ User Prefs ] [ Search Forums ] [ Back to Main Page ] [ Back to Taxonomy Discussion ] [ Reply To This Message ]
[ Register to Post ]

Posted by: WW at Wed Jun 8 04:13:19 2005  [ Report Abuse ] [ Email Message ] [ Show All Posts by WW ]  
   

>>One thing that suprises me about Evolutionists is that most of them even the Cladists stick to fixed "Creationist" ideas about Taxonomy. As a forinstance an Elapid must be a snake with short relatively immobile front fangs (the "protoroglyphous" condition). A viperid must be a snake with long front fangs on a swinging maxilary bone (the "solenoglyphous" condition).
>>
>>However evolutionarily speaking these merely represent the current end condition of the evolutionary process and not its beginning. Therefore I dont think we should be looking for basal elapids and vipers amongst snakes that have already reached the classic viper and elapid conditions. Rather the place to find basal vipers and elapids or transitional forms if you will is amongst the vast assemblage of Rear Fanged snakes and venom glanded aglyphis "colubrids".

There is some terminological confusion here, and you need to brush up on that. In particular, you need to make a distinction between "crown clades" and "stem groups". So, for instance, crown clade vipers are the living snakes with solenoglyphous dentition, their common ancestor, and all the descendants (living or extinct of that common ancestor -= i.e., the things ew call vipers today. Stem group vipers, on the other hand, would be all the snakes that share a more recent common ancestor with existing vipers than with other snakes, and would include many fossil relatives in which the solenoglyphous dentition is not completely developed.

The term "basal viperid" or "basal elapid" is usually simply taken to mean the *living* sister group to all other elapids or viperids - the first one to branch off, in effect. So, if Homoroselaps turns out to be the sister genus of all other elapids (which is unlikely to be the case based on various studies in the works), then that makes it the basal elapid. This is the practical definition when focussing on livign taxa.

On the other hand, if we are discussing stem group vipers or elapids, one would indeed look for extinct relatives of crown clade elapids or vipers, which would indeed be expected to show a lesser degree of development of the dentition.

>>
>>Because the earliest advanced vipers like the Fea's viper and African night adders have all of the head shields and other features of a "colubrid" it will be rather hard to find the basal vipers amongst the rear fanged snakes by any other means than streight DNA testing.

Plenty of that is being done. At the moment, there is little evidence that there are any "colubrids" which share recent common ancestry with the vipers.

> However it will probably be easier to find the basal elapids because advanced elapids have other visible features bsides fangs and venom that tell them apart from "colubrids" that would probably carry "backwards" to the rear fanged or aglyphous basal forms. Probably the most prominant one of these is the lack of the loreal scale between the preocular and inner nasal scales at the sides of the head. Another common elapid tendency that has nothing to do with fangs or venom is to have both undivided and devided subcaudal (bottom of the tail) scales although this is less common than the lack of the loreal head scale. Therefore we would know to find the basal elapids amongst rear fanged or even aglyphous "colubrids" with venom glands but no loreal scale.
>>
>>From this point we can probably check the venoms of these snakes
>>for elapid nurotoxins. (Many of the suspected basal elapids in the current "colubrid roster" using a true evolutionary standard (the rear fanged or aglyphous venomous snakes as the base) like American crowned, earth and black headed snakes and African centepede eaters tackle highly venomous albeit invertibrate game themselves like the afore mentioned centepedes as well as scorpions and may well have developed the elapid nurotoxins to in effect be able to "shoot first" against highly venomous for a small snake invertabrate prey.)
>>
>>If elapid nurotoxins are found in rear fanged and aglyphous venomous snakes lacking loreal scales like American Crowned, Earth and Black headed snakes and African Centepede eaters a DNA test can finally be used to cinch the fact that we have found the true basal elapids and first bone fide evolutionary transitional forms in nature.
>>
>>In otherwords to find the basal or so called "transitional" form
>>for a type of animal we should not be looking to its classic advanced condition no matter how primitive we go within it. In otherwords if the African Homoroselaps is an elapid it is not the true basal form but only the beginnings of the classic elapid evolutionary condition. Rather we have to look to the least advanced form possible and for vipers and elapids that is to be found somewhare amongst the aglyphous snakes with venom glands and the rear fanged snakes.

You need to read some of the more recent papers on both venom evolution and snake phylogeny - you are attacking a straw man due to terminology confusion. Moreover, much of the research you clamour for has been done, and the closest relatives of the elapids are in fact various African colubrids (including centipede eaters) and the Atractaspidids.

Cheers,

WW
-----
WW Home


   

[ Reply To This Message ] [ Subscribe to this Thread ] [ Show Entire Thread ]


<< Previous Message:  Basal Elapids and Viperids Must Be Found Amongst the Rear Fanged and Aglyphous Venomous Snakes - CoralSnake, Tue Jun 7 23:56:10 2005