Reptile & Amphibian Forums

Ok, I've been keeping Texas horneds for awhile and for the like of me I thought all horneds were in the Family Iguanidae, but as it seems only Phrynosoma cornutum, Phrynosoma douglassii, Phrynosoma solare are only in that family and the others are in the Phrynosomatidae family.. Why is this?
Xain

Nope, not possible. You are probably looking at two (or more) different sources and seeing different names listed. This happens because catagories change sometimes, and also different authorities will sometimes disagree as to the most appropriate catagorization of some groups. However, two species within the same genus cannot be in different families. Since the taxanomic grouping "family" is above the grouping "genus", all members of a single genus must be in the same family.

It's like students in a school. you have idividual students just as you have individual species. Each student is in a particular classroom, so the classrooms are like the genera in taxonomy: each species is in a genus. Then each classroom is in a specific building on campus. In this case the different buildings would represent different taxanomic families. Any one room can only exist within a single building, and all students within that room must also be in the same building. Works exactly the same with taxanomic families, genera, and species.

If you are finding different species within the genus Phrynosoma listed in two or more different families within the same book/article, then they don't know much about biology.

I see, so now which family are they in?

Well, it depends who you ask. The thing to remember is that taxonomy is simply an organizational system set up by humans for humans, and doesn't necessarily reflect the reality of historical species relationships (although for cladistic taxonomy - which is the leading model - that's the goal we're shooting for). Apparently right now some people place them in Iguanidae, while others support splitting that family into several smaller families, in which case they are put in Phrynosomatidae. Since the taxonomic level "family" is pretty arbitrary anyway, it depends which side of the debate you choose.

Eventually everyone working on lizards will probably agree on one or the other, or possibly some alternate (and may have already), but it really is just a matter of consensus, not actually an important, meaningful difference. I know that's probably not a very satisfying answer, but any catagorization above the level of species really is just more a matter of convenience for biologists than anything else, so when there are disagreements it really does simply become a matter of which one you like best (though people involved in the debate would likely disagree). The only thing is that you should choose one or the other and not jump back and forth between the two.

Sorry, that's probably the most honest answer you're likely to get. Given that the most recent work I've seen that addresses the issue at all, (Introduction to Horned Lizards of North America, by Wade Sherbrooke mentions both possible schemes without definitively choosing one or the other, I'd say either is acceptable.

Excellent responces. It's nice to see someone versed in
taxonomy.

Thank you,

Brian

Hi Brian,

More like plagued by it. I spent a lot of time and effort cramming thousands of names and relationships into my head as an undergrad, only to have some taxonomist come along and change whole schemes on me. Then there are all the arguments for and against the cladistic approach. Finally I accepted that taxonomy is best viewed as something that can be changed whenever and however best fits one's needs.

Gary

Me too.

Brian

Great, thanks for your time and such. Also, I'm curious to which family you prefer to use if and when the topic comes up?
Xain

Actually my specialty is marine biology and evolutionary theory. HLs are just a hobby, so I'm not up on what is exactly going on with lizard taxonomy right now. It's not unusual to have taxonomy change periodically though as people examine new forms of data. Without knowing what exactly the justification is for splitting iguanids into several separate families, I don't know which to favor. If it is being done because there is evidence that iguanidae is a polyphyletic group (consists of species that don't have a single common ancestor within the group), then I support the split, and using the name phrynosomatidae. If, on the other hand, it is simply because some people believe there are enough differences between the new groups that they should have special status, well then I would not support the split. I have e-mailed a friend of mine who is an iguanid specialist to ask why the split has been proposed. When I get a reply, I'll let you know.

Sorry, I know this has turned out to probably be a much more complicated question than expected. That's the problem with taxonomy though. It changes periodically, and not always for very good reasons. The curious thing to me is that there does not appear to be agreement on this split, even though it apparently was proposed several years ago. That leads me to believe that the reasons behind it may be weak.

The safe bet is to go with the older name until there is a definitive answer, so without more information I'd probably favor calling them iguanids.

Gary