Laurin and Piñeiro 2017 ‘reassess’ mesosaurs

This paper came with much anticipation
following discussions several years ago with one of the authors (GHP) about mesosaurs (Fig. 2) and their relationship to pachypleurosaurs and thalattosaurs (Fig. 2) in the LRT. Unfortunately only 17 terminal taxa (many suprageneric) were employed by Laurin and Piñeiro 2017 (vs. the 1122 taxa in the large reptile tree, LRT).

Unfortunately,
pachypleurosaurs and thalattosaurs were not among the 17 taxa employed by Laurin and Piñeiro. That makes this study worthless with regard to mesosaur interrelations. Very unfortunate.

From the Laurin and Piñeiro methods:|
“We started from the matrix of Laurin and Reisz (1995), given that this was the matrix that we knew best, that we had confidence in the accuracy of the anatomical scoring, and that we were confident that we could apply the revised scores in a manner coherent with the original scoring.” 

Figure 2. Unfortunately pachypleurosaurs and thalattosaurs are omitted from this cladogram.

Figure 1. Unfortunately pachypleurosaurs and thalattosaurs are omitted from this cladogram from Laurin and Piñeiro 2017. I don’t know of any aquatic basal synapsids or basal captor hinds. Does anyone?

The authors
nested mesosaurs between Synapsida and Captorhinidae (Fig. 1). Neither suprageneric clade include basal members that in any way resemble mesosaurs.

A sampling of mesosaur sister taxa
as recovered by the LRT is shown here (Fig. 2). I challenge the authors to find better sister taxa among the Synapsida or the Captorhinidae.

Figure 2. Click to enlarge. The origin of ichthyosaurs and thalattosaurs from basal diapsids and basal mesosaurs. Relationships are rather apparent when seen in this context.

Figure 2. The origin of ichthyosaurs and thalattosaurs from basal diapsids and basal mesosaurs. Relationships are rather apparent when seen in this context. Chronology is a little mixed up based on earlier radiations and the rarity of fossil formation.

A gradual accumulation of traits
is what we’re all looking for in a cladogram. If you don’t find that using your inclusion set, expand your inclusion set until you do.

Professors Laurin and Reisz
are at the top of the list of professional paleontologists, and have been at the top for decades. Unfortunately they’re holding on to an invalid hypothesis. There is no monophyletic clade ‘Parareptilia.’ Included members don’t look alike and simple expansion of the dataset splits them to other parts of the reptile family tree.

If you find yourself working with top workers
in the field and the results don’t make sense, you may be obligated to follow their lead. That seems to happen all too often. You’ll make more sensible discoveries if you keep a modicum of independence, or complete independence. And you’ll avoid the professional embarrassment of being criticized online instead of being hailed and complimented for ‘finally putting it all together’. This was an opportunity lost, no matter how much detail and data was provided.

This paper was edited by
Holly Woodward (Oklahoma State University) and reviewed by Michael S. Lee (South Australian Museum) and Juliana Sterli (Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina). It’s almost unheard of to see editors and reviewers listed near the titles of papers, btw. More often they are thanked in the Acknowledgements section.

On the plus side
I’m happy to see Piñeiro included a mesosaur skull with every bone colored (Fig. 3). That’s the way to do it nowadays. And if you’re into mesosaurs, this paper does provide a great deal of data about mesosaurs.

Figure 3. Mesosaur skull with bones colored by Laurin and Piñeiro 2017, modified from Piñeiro et al. 2012b.

Figure 3. Mesosaur skull with bones colored by Laurin and Piñeiro 2017, modified from Piñeiro et al. 2012.

References
Laurin M and Piñeiro GH 2017. A reassessment of the taxonomic position of mesosaurs, and a surprising phylogeny of early amniotes. Frontiers in Earth Science, 02 November 2017: 13 pp.  https://doi.org/10.3389/feart.2017.00088
Piñeiro G, Ferigolo J, Ramos A and Laurin M 2012. Cranial morphology of the Early Permian mesosaurid *Mesosaurus tenuidens* and the evolution of the lower temporal fenestration reassessed. Comptes Rendus Palevol. 11(5):379-391.

2 thoughts on “Laurin and Piñeiro 2017 ‘reassess’ mesosaurs

  1. I don´t normally reply on this kind of personal blogs, but I decided to do so right now to give David Peters the possibility of to expand his readership with our (the author’s) version of this history.
    This paper came with much anticipation
    following discussions several years ago with one of the authors (GHP) about mesosaurs (Fig. 2) and their relationship to pachypleurosaurs and thalattosaurs (Fig. 2) in the LRT. Unfortunately only 17 terminal taxa (many suprageneric) were employed by Laurin and Piñeiro 2017 (vs. the 1122 taxa in the large reptile tree, LRT).
    Unfortunately,
    pachypleurosaurs and thalattosaurs were not among the 17 taxa employed by Laurin and Piñeiro. That makes this study worthless with regard to mesosaur interrelations. Very unfortunate.

    I did not follow any discussion with David Peters specifically about this issue, because I never believed that mesosaurs are related to such derived diapsids, and that was my answer then (some time ago), and recently (a few weeks ago) when he contacted me requesting the pdf of our Frontiers paper. However, I respect Peters’ work, as of that from any colleague, and if he can document his hypotheses and publish them, I will be happy to reference his work in one of my future papers, explaining my point.
    Professors Laurin and Reisz
    are at the top of the list of professional paleontologists, and have been at the top for decades. Unfortunately they’re holding on to an invalid hypothesis. There is no monophyletic clade ‘Parareptilia.’ Included members don’t look alike and simple expansion of the dataset splits them to other parts of the reptile family tree.
    If you find yourself working with top workers
    in the field and the results don’t make sense, you may be obligated to follow their lead. That seems to happen all too often. You’ll make more sensible discoveries if you keep a modicum of independence, or complete independence. And you’ll avoid the professional embarrassment of being criticized online instead of being hailed and complimented for ‘finally putting it all together’. This was an opportunity lost, no matter how much detail and data was provided.

    This is invalid speculation. These results are the outcome of collaboration over several years, and concerning the position of mesosaurs, happen to reflect our preferred hypothesis (see please as references, Piñeiro et al., 2012a,b; Piñeiro et al., 2016; Silva et al., 2017, and if you read Spanish, you can request my two theses and two chapters in books edited by my University).
    As David Peters already know, I am very critical about cladistics methodology, I am not a fervent follower of it. But, I am sure that all the aspects that generated controversy, event between Michel Laurin and me, were discussed in this paper, as not much seen in any other; I am happy for that. Also, the results are very enlightening although also controversial, and we look forward to future discussions on this topic with our colleagues in the future.

    This paper was edited by
    Holly Woodward (Oklahoma State University) and reviewed by Michael S. Lee (South Australian Museum) and Juliana Sterli (Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina). It’s almost unheard of to see editors and reviewers listed near the titles of papers, btw. More often they are thanked in the Acknowledgements section.
    This is factually wrong. The name of the editor and reviewers near the title of the paper is a Frontiers policy, as well as of the other journals (e.g. PeerJ) and it is a good and transparent policy in my concept.

    • Piñeiro wrote: “because I never believed that mesosaurs are related to such derived diapsids…I am very critical about cladistics methodology, I am not a fervent follower of it.”

      This is the heart of the issue. Testing, not belief, should be the driving force behind any conclusions regarding interrelationships.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.