Reptile & Amphibian Forums

Vidal writes:
"The atractaspidids include about 11 genera and 70 species. The monophyly of the family (including the ‘‘aparallactines’’, which were previously considered to be ‘‘colubrids’’), is supported both by morphological and molecular data.[25 – 27] Only one genus, the genus Atractaspis, displays a frontfanged venom system, but it is not homologous to the solenoglyph apparatus of the vipers.[27,28] The remaining atractaspidids are either aglyphs or opisthoglyphs. Unfortunately, the phylogenetic relationships between the genus Atractaspis and the ‘‘aparallactines’’ are unresolved."

Heise et al.'s data show that Atractaspis is an elapid. From Vidal's description, the "Atractaspididae" is a morphologically heterogeneous family with some front fanged, some aglyphous and some opistoglyphous snakes. Since the relationship between the aparallactines and Atractaspis is unresolved, there is a strong possibility that the "Atractaspididae" is a polyphyletic family. If Atractaspis is an elapid, then that would explain its front fanged system, which is also found in elapids. If the "Atractaspididae" is polyphyletic, that would explain the differences in dentition within this taxon.

Reference:
Philip J. Heise, Linda R. Maxson, Herndon G. Dowling, and S. Blair Hedges (1995). Higher-level snake phylogeny inferred from mitochondrial DNA sequences of 12S rRNA and 16S rRNA genes.
Mol. Biol. Evol. 12: 259–265.

Vidal, Nicolas 2002. Colubroid Systematics: Evidence for an Early Appearance of the Venom Apparatus Followed by Extensive Evolutionary Tinkering. J. Toxicol.—Toxin Reviews, 21(1&2), 21–41

Where does this author place Homoroselaps? I see it listed in the same clad as the Atractaspids all the time, even though it alone among them has fixed front fangs. Just curious.
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Peter: It's OK, I'll handle it. I read a book about something like this.
Brian: Are you sure it was a book? Are you sure it wasn't NOTHING?

>>Where does this author place Homoroselaps? I see it listed in the same clad as the Atractaspids all the time, even though it alone among them has fixed front fangs. Just curious.

Vidal did not include Homoroselaps in that particular paper.

In a later paper (Vidal & Hedges, 2002), he finds Homoroselaps rooted between Aparallactus and Atractaspis in his C-mos nuclear gene phylogeny and includes both of those in a monophyletic Atractaspididae (which is not rooted among the elapids).

Kelly et al. (2003) were unable to resolve the position of Homoroselaps. Slowinski & Keogh (2000) found it to lie outside the remaining elapids. Nobody other than Heise's (by modern standards relatively unsophisticated) analysis has found Atractaspis to be rooted within the elapids.

In summary, it is probably fair to say that the position of Homoroselaps remains unclear. It certainly does not seem to be rooted within the remaining elapids, and Atractaspidid affinties seem a likely prospect. The present siutation is that the elapids, atractaspidids, psammophiines, boodontines/lamprophiines and pseudoxyrhophiines form a poorly resolved cluster, and some genera seem to be difficult to assign to one or the other of these (sub-) families based on the evidence currently available.

Cheers,

Wolfgang

References:

Kelly, C. M. R., N. P. Barker and M. H. Villet. 2003. Phylogenetics of advanced snakes (Caenophidia) based on four mitochondrial genes. Syst. Biol., 52:439-459.

Slowinski, J.B., Keogh, J.S., 2000. Phylogenetic relationships of elapid snakes based on cytochrome b mtDNA sequences. Mol. Phylogen. Evol. 15, 157–164.

Vidal, N. and S. B. Hedges. 2002. Higher-level relationships of caenophidian snakes inferred from four nuclear and mitochondrial genes. C. R. Biologies 325:987–995.
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WW Home

Hmmm... as a layperson, every time I read threads in this forum, I come away knowing less than I thought I knew before! Many times book authors will present things as fact which are really under dispute, leading to a lot of confusion for people like me. I'm really interested in this subject now, though.
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Peter: It's OK, I'll handle it. I read a book about something like this.
Brian: Are you sure it was a book? Are you sure it wasn't NOTHING?

WW wrote:
"In summary, it is probably fair to say that the position of Homoroselaps remains unclear. It certainly does not seem to be rooted within the remaining elapids, and Atractaspidid affinties seem a likely prospect. The present siutation is that the elapids, atractaspidids, psammophiines, boodontines/lamprophiines and pseudoxyrhophiines form a poorly resolved cluster, and some genera seem to be difficult to assign to one or the other of these (sub-) families based on the evidence currently available."

Part of the difficulty may be due to the lumping of Atractaspis with some of the fossorial colubrids on the basis of convergent similarities, as Kate Jackson points out. Atractaspis has hollow fangs, like the elapids, so its placement within the Elapidae by Heise et al., is not surprising and is in fact consistent with morphology. Similarly, the placement of Homoroselaps by Slowinski and Keogh is also not surprising, since it does not have hollow fangs, only grooved teeth. To me, the systematic status of Homoroselaps and Atractaspis are pretty well resolved, even if the other taxa you mention may not. Homoroselaps is most likely a basal or proto-elapid, and Atractaspis is a specialized elapid with movable fangs.

Heise et al. did not include Homoroselaps in their analysis. However, Slowinski and Keogh (2000) find Homoroselaps basal to all other elapids they study.

Kate Jackson writes:
"McDowell (1968) argued, on the basis of several morphological characters, that Homoroselaps (formerly Elaps) was not an elapid as had been thought previously, but rather an aparallactine. This would suggest another independent derivation of a frontfanged VDS. However, a later study showed that the characters that allied Homoroselaps with aparallactines are more likely derived characters associated with fossoriality (Kochva & Wollberg, 1970), and that Homoroselaps belongs with the elapids.

It looks to me Homoroselaps is probably a primitive elapid or a "proto-elapid." The hollow fangs of elapids may have evolved from the proteroglyphous condition in Homoroselaps or related taxa.

Reference
Jackson, Kate 2003. The evolution of venom-delivery systems in snakes. Zoological Journal of the Linnean Society 137, 337–354.

Slowinski, Joseph B. and J. Scott Keogh 2000. Phylogenetic Relationships of Elapid Snakes Based on Cytochrome b mtDNA Sequences. Molecular Phylogenetics and Evolution
Vol. 15, No. 1, April, pp. 157–164.

First, I am NOT a taxonomist, so forgive and be patient, but as to Atractaspid fangs being on moveable maxilla...are there any other elapids with rotating maxilla, as I am unaware of any, so would not the fang structure be more morphologically concurrent with that of a viper/pitviper, albeit the axis is a horizontal one rather than vertical?

According to Nicholas Vidal (2002), "Only one genus, the genus Atractaspis, displays a frontfanged venom system, but it is not homologous to the solenoglyph apparatus of the vipers.[27,28]"

Additionally, Harry Greene (1997:43) notes that "Most snakes coil and strike in a roughly horizontal plane, but stiletto snakes (Atractaspis) and some elapids fling their heads forward, downward, or backward to bite."

Heise et al.'s (1995) mtDNA data shows that Atractaspis is closely related to Bungarus and it lies within the Elapidae.

Three lines of evidence (behavior, phylogenetics and morphology) thus suggest that Atractaspis is an elapid, not a colubrid or viperid. Other elapids are known to have slightly movable front fangs, e.g. Acanthophis and Dendroaspis.

Reference:
Greene, H.W. 1997. Snakes. The Evolution of Mystery in Nature. Univ. California Press.

Vidal, Nicolas 2002. Colubroid Systematics: Evidence for an Early Appearance of the Venom Apparatus Followed by Extensive Evolutionary Tinkering. J. Toxicol.—Toxin Reviews, 21(1&2), 21–41

OK, all that I understand, but how is it morphologically different than a solenoglyph, aside from the axis of the maxilla's movement? Mitochodrial DNA aside, and behaviour means nothing to me as a classification system, My one year old son acts like a cat, but is not feline......Not trying to start an argument just looking for specific differences that make it morphologically unlike the other solenoglyphs....

R Campbell wrote:

"OK, all that I understand, but how is it morphologically different than a solenoglyph, aside from the axis of the maxilla's movement? Mitochodrial DNA aside, and behaviour means nothing to me as a classification system, My one year old son acts like a cat, but is not feline......Not trying to start an
argument just looking for specific differences that make it morphologically unlike the other solenoglyphs...."

I don't know how catlike your son is behaving but I doubt that he has exhibited any behavior that is unique to cats. On the other hand, Atractaspis do act differently than most snakes, as Greene pointed out, and their behavior is similar to some other elapid snakes. One should not dismiss such unique similarities so casually.

That said, I believe you are looking for differences in the comparative anatomy of Atractaspis fangs and viperid fangs. According to Kate Jackson (2002): "In elapids and atractaspidids the entrance orifice and the discharge orifice are joined by a visible suture along the anterior surface of the fang. In viperids the anterior surface of the fang is generally smooth."

Their differences are not great but again, snakes in the genus Atractspis are more similar to elapids than they are to viperids. An additional difference between viperids and Atractaspis is the way they use their teeth. Snakes in the genus Atractaspis do not rotate their fang forward and open their mouth to bite, unlike viperids. Instead they move their fang laterally and ventrally so that the fang sticks out of their closed mouth and they then "envenomate prey with a unilateral backward stab of one fang projected from a closed mouth" (Deufel and Cundall 2003).

Therefore, even though Atractaspis have long fangs, unlike most elapids, their fangs are nevertheless more like those of other elapids in retaining a visible groove on the anterior surface and they are deployed differently than the solenoglyph teeth of viperids. In fact, the structure of their venom delivery system and their biting behavior seem to have evolved to conform to their elapid like biting behavior.

In order to classify Atractaspis as a colubrid or as the member of a separate family from the Elapidae, one would have to ignore all of the similarities (morphological and behavioral) between Atractaspis and (at least some) elapids and of course the mtDNA data of Heise et al., which shows Atractaspis as a member of the Elapidae. I am more convinced than ever that the Atractaspididae is a polyphyletic taxon.

Reference
Deufel, Alexandra and David Cundall 2003. Feeding in Atractaspis(Serpentes: Atractaspididae): a study in conflicting functional constraints. Zoology 106: 43–61
Jackson, Kate 2002. How Tubular Venom-Conducting Fangs Are Formed. JOURNAL OF MORPHOLOGY 252:291–297

I was looking for the specifics on the morphological differences, and the elap/atractaspid suture running anteriorly from orrifice to orrifice answered that well. I am very familiar with atractaspid behaviour and do not need to reference any ones papers for it as I have been keeping and breeding four different species since 1989. Thank you for your time.

Most readers, unlike you, are unfamiliar with the behavior of Atractaspis. In fact, Deufel and Cundall (2003) point out that "Existing published observations of the mechanics and behavior of the envenomating apparatus are based on manipulations of dead animals (Corkill et al., 1959; Visser, 1975) and film analysis of living Atractaspis stabbing a rubber membrane (Golani and Kochva, 1988)."

As you probably know, the fangs of viperids and elapids are remarkable examples of convergent evolution, so remarkable that some herpetologists thought that fangs evolved in the common ancestor of the viperids and elapids. Even their developmental pathways are similar, as Kate Jackson demonstrated. If not for the groove that is still visible on the anterior surface of elapid fangs, viperid fangs would be distinguishable from elapid fangs except by their relative lengths. Only when one also takes into account the fact that many elapids have similar striking behaviors as Atractaspis can one say with any degree of certainty that the long fangs of Atractaspis are only convergently similar to those of viperids. As many systematists know but many cladists ignore, all scraps of information can be potentially useful in ascertaining evolutionary relationships.