Cacops: Temnospondyl or Lepospondyl?

In order to understand
the interrelationships of reptiles, one needs to known where to begin and what came before the beginning. Earlier the large reptile tree (LRT) recovered the Viséan Silvanerpeton and the Late Carboniferous Gephyrostegus bohemicus at the base of the Amniota (= Reptilia) with origins in the early Viséan or earlier (340+mya).

Reptiles were derived from the clade Seymouriamorpha, 
close to Utegenia, which also nests at the base of the Lepospondyli, + Seymouria + Kotlassia. These, in turn, were derived from the reptilomorphs, Proterogyrinus and Eoherpeton.

Reptilomorphs, in turn, were derived from Temnospondyls,
at present, Eryops (unfortunately too few taxa to be more specific at present), and temnospondyls, in turn, were derived from basal tetrapods, like Pederpes.

Figure 1. Cacops and its sisters.

Figure 1. Cacops and its sisters in the LRT.

A recent objection
by Dr. David Marjanovic suggested that the basal tetrapod, Cacops, was not a lepospondyl, but actually a temnospondyl.

Figure 1. Sclerocephalus in situ and reconstructed. This taxon nests with Eryops among the temnospondyls.

Figure 1. Sclerocephalus in situ and reconstructed. To no surprise, this taxon nests with Eryops among the temnospondyls. Note the expanded ribs.

That’s worth checking out.
So I added taxa: Sclerocephalus and Broiliellus (Fig. 2). The former nested with Eryops as a temnospondyl. The latter nested with Cacops and the lepospondyls. The new taxa did not change the topology. So… either the present topology is correct, or I’ll need some taxon suggestions to make the shift happen.

Figure 1. Broiliellus skull. This taxon nests with Cacops among the lepospondyls, derived from a sister to the Seymouriamorph, Utegenia.

Figure 1. Broiliellus skull. This taxon nests with Cacops among the lepospondyls, derived from a sister to the Seymouriamorph, Utegenia. Note the ‘new’ bone between the lacrimal and jugal. That’s a surface appearance of the palatine!

 

The large reptile tree tells us
that reptiles and lepospondyls are all seymouriamorphs with Utegenia at the last base of the lepospondyls, but known only form late-surviving taxa at present. Lepospondyls continue to include Cacops and Broiliellus, along with extant amphibians and microsaurs, which mimic basal reptiles. Most of these taxa should be found someday in Romer’s Gap prior to the Viséan in the earliest Carboniferous or late Devonian.

Seymouriamorpha
Wikipedia reports, “[Seymouriamorpha] have long been considered reptiliomorphs, and most paleontologists may still accept this point of view, but some analyses suggest that seymouriamorphs are stem-tetrapods (not more closely related to Amniota than to Lissamphibia) aquatic larvae bearing external gills and grooves from the lateral line system have been found, making them unquestionably amphibians. The adults were terrestrial.

The LRT finds
seymouriamorphs basal to reptiles + lepospondyls. The latter includes lissamphibians (all extant amphibians , their last common ancestor and all of its descendants) and several other clades, including Microsauria, Nectridea, and several very elongate taxa.

Dissorophididae
Wikipedia reports, “It has been suggested that the Dissorophidae may be close to the ancestry of modern amphibians (Lissamphibia), as it is closely related to another family called Amphibamidae that is often considered ancestral to this group, although it could also be on the tetrapod stem. The large reptile tree also recovers this relationship. Cacops and Broiliellus are both considered dissorophids.

References
Lewis GE and Vaughn PP 1965. Early Permian vertebrates from the Cutler Formation of the Placerville area, Colorado, with a section on Footprints from the Cutler Formation by Donald Baird: U.S. Geol. Survey Prof. Paper 503-C, p. 1-50.
Moodie RL 1909. A contribution to a monograph of the extinct Amphibia of North America. New forms from the Carboniferous. Journal of Geology 17:38–82.
Reisz RR, Schoch RR and Anderson JS 2009. The armoured dissorophid Cacops from the Early Permian of Oklahoma and the exploitation of the terrestrial realm by amphibians. Naturwissenschaften (2009) 96:789–796. DOI 10.1007/s00114-009-0533-x
Williston SW 1910. Cacops, Desmospondylus: new genera of Permian vertebrates. Bull. Geol. Soc. Amer. XXI 249-284, pls. vi-xvii.
Williston SW 1911. Broiliellus, a new genus of amphibians from the Permian of Texas. The Journal of Geology 22(1):49-56.

wiki/Cacops
wiki/Platyhystrix
www/Broiliellus
wiki/Dissorophidae

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30 thoughts on “Cacops: Temnospondyl or Lepospondyl?

  1. I just want to say that it’s not fair – it’s dishonest, in fact – to frame the “Cacops as temnospondyl” hypothesis as “a recent objection”. Cacops has been universally considered a dissorophoid temnospondyl by every specialist familiar with this group; your wording makes it seem as if David Marjanovic is the one proposing a novel hypothesis.

    • I very much agree. In every single published paper I’m however dimly aware of, Cacops has been considered a temnospondyl without any hint of a doubt.

  2. I think you’re missing the point here, Darren. The dissorophoids are nesting with the basal lepospondyls in the LRT not with the temnospondyls. Dr. Marjanovic simply brought it to my attention. I understand that he was supporting the traditional view.

    • This is very likely because you have neither enough character data nor enough taxa outside amniotes to adequately test the relationships of dissorophoids and of ‘lepospondyls.’

      What you’re actually seeing here is that ‘lepospondyls’ are jumping into dissorophoids (and thus temnospondyls) because you have not sampled enough taxa on the tetrapod, amniote, and lissamphibian stem groups to adequately distinguish these taxa. You are not the first to have this same problem; McGowan (2002) had a similar issue, but it has not been reproduced in larger analyses with better taxon and character sampling. You also can’t fix this just by adding more taxa; you do need to add a lot more anatomy to the matrix.

  3. Thanks, Jason. Please send me the reference(s) you’re basing your comments on. I note that in the supertree of Coates et al. 2003 they discuss the problem of nesting dissorophoids and their possible relationship to lissamphibia. At present I have to present what the data reveals. I have emailed Dr. McGowan for the PDF you mentioned.

    • There is a rather large literature on this subject, and I couldn’t do it justice with a blog comment. This includes substantial work by Ahlberg, Clack, Laurin, Reisz, Anderson, Marjanovic, Schoch, Ruta, and various others…again, there is a ton of work from many different working groups and it all consistently disagrees with the topology you’re presenting here. This is nearly 3 decades of work to summarize; you’ll have to do the research there for yourself. Despite some instability in parts of the early tetrapod tree, in no case does anyone find credible evidence that ‘lepospondyls’ in the traditional sense nest within temnospondyls, or within dissorophoids specifically. Similarly, there are many strong reasons why your placement of eryopoids deep in the tetrapod stem, with Acanthostega, is not correct.

      The lissamphibian problem (noted by Coates & al, etc) is not associated with the placement of dissorophoids within the early tetrapod tree. The problem is associated with whether lissamphibians fall within temnospondyls or ‘lepospondyls.’ Dissorophoids always remain consistently within temnospondyls, as the sister taxon of zatrachydids.

      I have no doubts that your tree shows the topology you’re reporting. My main concern is that I don’t think your dataset is sufficient to generate reliable results in this part of the tree. I say this as someone who is very amenable to heterodox interpretations of early tetrapod phylogeny and openly critical of some consensus opinions of early tetrapod phylogeny.

      • I appreciate your expertise and interest, Jason. As you know the LRT finds heterodox topologies for nearly all of the authors you mention. So, when you quote authority it falls flat when experiment shows otherwise. To your point, I will continue to search for temnospondyl sisters for Cacops and kin. If you have any taxa or traits that will attract them to the temnospondyls, please send them to me to hasten the process. Otherwise, it may be awhile.

      • To clarify, I’m not arguing from authority. I’m saying “there are a lot of data that you are likely missing that need to be incorporated before the results you are reporting can be considered credible. I do not want to cite specific characteristics (although I can think of many) because I don’t want to cherry-pick temnospondyl characters a priori. As you know, cherry-picking a set of “temnospondyl” characteristics a priori would bias analyses and be methodologically inappropriate. You really do need to go through those datasets and incorporate variation and taxa that your dataset does not accommodate and then see where that takes you.

        I don’t mind if it takes you a while. Good phylogenetic analysis takes a while.

    • E-mailing McGowan is no use. Soon after his 2002 paper he quit science; in 2007 or 2008, while working on my large 2008 paper in Contributions to Zoology, I spent hours in Google trying to find him – to no avail. I contacted his former thesis supervisor, who didn’t know where he was either.

      Let me know if Google Scholar doesn’t find a freely accessible copy of the pdf; I can send it to you. However, be aware that my mentioned 2008 paper completely takes that matrix apart, makes a lot of corrections to the matrix, and finds very different trees.

      • I found McGowan on Linked-In. Whether he writes back or not is another question. More to the point: is your PeerJ work the latest and greatest on Cacops affinities? Or can send a published work of the same ilk? I’d like to know what’s attracting Cacops to the temnospondyls. After today’s post on Parioxys I don’t know which other way to to turn.

      • is your PeerJ work the latest and greatest on Cacops affinities?

        No doubt it would be, if Cacops were included in the dataset… which it isn’t. The only dissorophid in the sample is Broiliellus brevis (which may or may not belong to Broiliellus, but that’s another story), and there are too few dissorophid-related characters, amphibamid-related characters and amphibamids in the dataset for me to trust the large diversity of dissorophoid topologies I get.

        It just seems so bizarre to me that anyone would doubt Cacops is a temnospondyl in the first place! Let’s turn things around at last! Which characters pull it out of there in your tree? What does it have in common with any “lepospondyls”?

  4. An update: at
    http://www.ReptileEvolution.com/reptile-tree.htm
    you’ll see I added four basal tetrapods to the LRT.

    Seeking an attractive taxon, at
    http://tolweb.org/Temnospondyli/15009
    I note that Iberospondylus nests there basal to both Dissorophoidea and Eryopidae.

    In the LRT Iberospondylus does nest with Eryops, but did not shift the nesting of dissorophoids from the lepospondyls.

    Deleting all other lepospondyls did not shift the dissorophoids.
    Deleting all reptilomorphs did not shift the nesting.
    I had to delete all intervening taxa before dissorophoids nested with temnospondyls and then they produced a polytomy. So, the current nesting of dissorophoids in the LRT has passed these tests and appears to be robust, given the current taxon and character lists.

    If I’m to add X number of characters to the LRT and apply them to all current 929 taxa, someone is going to have to provide that list of characters and guarantee the dissoropoids will shift their nesting before I attempt to do the same. Or send me complete competing .nex files in which I can see both taxa and traits listed clearly for reading and testing.

    • Or you could just download the NEXUS file from one of the recent papers on this topic, you know. The latest one with Cacops in it is Dilkes (2015). Go find it in Google Scholar!

      • Just found it: Carpus and tarsus of Temnospondyli. Thank you. So far matrices I have downloaded have all lacked character listings. Hopefully that’s not a trend.

      • Dilkes 2015 is not going to be helpful because it excludes a long list of lepospondyls and reptilomorphs and assumes Cacops is a temnospondyl. That’s the usefulness of the LRT. It minimizes taxon exclusion issues.

      • So far matrices I have downloaded have all lacked character listings.

        The character lists are either in the papers or in a separate piece of supplementary information. That’s normal. Nobody publishes a matrix without a character list (or at the very least a reference to one).

  5. Reptiles were derived from the clade Seymouriamorpha,

    If you’re derived from a clade, you’re a part of that clade. Clades never end, except by extinction! Clade = monophylum.

    As for suggestions for which taxa to add… no, add characters. Your tree looks like the taxa are mostly placed by noise in the character sample, because there’s not enough signal to place them anywhere.

    For twelve years now I’ve been telling you that you should add more characters. Every time you decline to do that work just because you get a resolved tree. That’s not enough! Very shitty matrices indeed can give you a resolved tree; the tree will just be wrong.

    Oh, BTW, the Wikipedia article you quote is just confused by old papers (from the 1970s) which included all amphibamids in Dissorophidae. Early tetrapods are one of the subjects where Wikipedia is on average rather bad.

    • Not just because I get a resolved tree, David. It’s because I get gradually accumulating traits for all derived taxa. And you’ve known that for 12 years. I can’t imagine how a ‘shitty’ matrix can give you a fully resolved tree with 930 taxa. That’s such wishful thinking.

      • It’s because I get gradually accumulating traits for all derived taxa.

        Inevitably, that’s what every cladogram is. That’s how phylogenetic analysis works. (…Whatever you mean by “derived taxa”.) I suppose you get gradual accumulation of flashier traits than other people do?

        You know what? I’ll download your .nex file and take a look at it over the weekend.

      • Oh, sorry – the “CLICK HERE for MacClade .nex file” link on your “reptile tree” page just leads to your e-mail address. Please send me the .nex file. I’m really curious how you get so much resolution – never mind if it’s right or wrong! – from a matrix with almost five times as many taxa as characters.

  6. Just noting here that the basal tetrapod workers are telling you what workers from every other clade tell you- you need more characters to get a good tree. It really is every professional opinion who has commented against yours. AFAIK no one who works with cladistic analyses has told you that what you’re doing should result in realistic trees.

  7. I report results and sometimes they don’t agree with prior trees. Wish they did. On some branches they do. Best to keep to specifics rather than blackwashing.
    Then again, when tested, Diandongosuchus and Lagerpeton matched the LRT, breaking traditional paradigms. No congratulations for those?

  8. ‘Blackwashing’ is actually more informative, since the issues are the same for every clade. It’s not like some particular clade in your tree suffers from issue X, it’s that you have the same problems that lead to bad trees everywhere.

    As for Diandongosuchus and Lagerpeton, their heterodox support has so far been through abstracts. So it’s not as if history has shown you to be correct, it’s that one other team has recovered your result in each instance. I wrote a blog post about how Lagerpeton is more parsimoniously a dinosauromorph given Dromomeron, though Diandongosuchus is outside my area of specialty. I’ve always said you may get some relationships right, including pterosaurs with ‘fenestrosaurs.’ But given the numerous issues I’ve found in your analysis, I’m doubtful most of your heterodox findings reflect the True Tree.

  9. The redescription of Diandongosuchus has now been published in open access.

    I’m afraid I can’t congratulate you. The new paper, and the SVP abstract before it, uses data you didn’t (and couldn’t) use – you were right for the wrong reasons. No congratulations for coincidences. :-|

  10. Copying my comment to your recent post:

    ============================

    The trick is that your Diandongosuchus OTU is misscored for all the features that were unknown before the redescription.

    It logically follows that wherever it goes in your tree, it does so (partly or entirely) because it’s miscoded. If that position happens to be right right, as it turned out to be, it is so for the wrong reasons.

    Coincidences like that really do happen. Ruta & Coates (2007) found the adelogyrinids and Acherontiscus next to the colosteids. The characters that held them there were misscored; when I corrected them, the adelogyrinids and Acherontiscus jumped back to their traditional position (more or less) inside the “lepospondyls” (as, incidentally, in Ruta, Coates & Quicke, 2003 – from which the matrix of Ruta & Coates, 2007, is derived). The fun part is that I think they are, in fact, colosteid-grade animals and not “lepospondyls” – and I think so because of characters that aren’t included in the matrix of Ruta & Coates (2007) or in mine (derived from theirs without addition of characters). In short, I think Ruta & Coates (2007) were right (or about right) for the wrong reasons. That’s all in my preprint, you can read it.

    And OF COURSE they have to demean your discovery, because to NOT do so would be an admission of a mistake on their part.

    Uh, hello? I’m not one of Stocker et al.; I’ve never worked on phytosaurs or any of their potential close relatives at all. I have no stake in where Diandongosuchus goes.

    Unlike them, you welcome the correction of mistakes, especially if they”re yours.

    Most of the time he ignores all corrections, even the most obvious ones. Have you noticed he has practically stopped reading comments at all? There are two months’ worth that he has never answered.

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