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In Rio for the 2013 International Symposium on Pterosaurs

The views expressed are those of the author and are not necessarily those of Scientific American.


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I love academic conferences, I love pterosaurs, and I love South America. So, as predicted, I very much enjoyed the International Symposium on Pterosaurs I just attended: it was the sixth symposium devoted specifically to pterosaurs, and was held at the Museu Nacional/UFRJ (= Universidade Federal do Rio de Janeiro), Rio de Janeiro. Yes, an academic conference held in Rio.

It was great and an enormous quantity of new and exciting information on pterosaurs was discussed and presented. There was also the chance to see many key Brazilian specimens. The conference ended with a field trip to Araripe – discovery site of many of these often spectacular Cretaceous pterosaur fossils – but I was unfortunately unable to attend due to the usual constraints of personal life. Indeed, economic conditions meant that many of our colleagues from Europe, North America and elsewhere didn’t make it to the meeting (though I know that some people from the USA failed to make it because they didn’t get their visas sorted out in time). Anyway, enough preamble…

Maurilio Olivera's life-sized model of the head of Thalassodromeus sethi on display at the UFRJ. Photo by Darren Naish.

Reproduction, ontogeny, nests, eggs, and babies

We held several roundtable discussions during the meeting and in fact the conference began with a discussion of ontogeny and reproduction co-presented by myself, David Unwin and Chris Bennett. Dave Unwin discussed what we know about pterosaur eggs and embryos and how existing data (from Darwinopterus, Pterodaustro and so on) seemingly shows that pterosaurs produced proportionally small eggs and precocial juveniles that were ready to fly at or shortly after hatching (see links below for more on this subject: it has been covered at length in previous Tet Zoo articles).

Opening slide for my presentation on pterosaur reproductive behaviour. The images here are by Zdeněk Burian (far left), Mark Witton (top right) and Harry Seeley (middle).

I reviewed reproductive behaviour in extant reptiles in order to give some idea of what might be applicable for pterosaurs. There are many caveats attached to the phylogenetic bracketing approach, and uncertainties about the affinities of pterosaurs also mean that what we see in extant crown-archosaurs may not apply to pterosaurs. Nevertheless, nest building, nest-guarding, post-hatching parental care and other behaviours are still on the cards for pterosaurs, even if they aren’t crown-archosaurs.

Chris Bennett looked at pterosaur ontogeny and growth rates. The continuing absence of small Pteranodon specimens remains an interesting conundrum and – Chris argues – it strongly suggests that juvenile Pteranodon individuals were not precocial and were not doing the same sort of thing as adults. It seems logical to think that pterosaurs were not uniform in such things as growth style and reproductive ecology: precociality in, say, Pterodactylus does not demonstrate such in Pteranodon, but we really need more evidence before we can go any further with this. Prondvai et al. (2012) recently argued that Rhamphorhynchus was altricial, but it was suggested in the discussion that this conclusion failed to take notice of Bennett’s (1996) evidence for annual growth stages in this taxon.

It was only right and fitting that Wann Langston's contribution to pterosaur research was referred to during the meeting: in this case, by Brian Andres. Wann never did get round to publishing his full descriptive work on Quetzalcoatlus.

The second roundtable discussion (it happened on the next day: I’m not discussing things in chronological order) was devoted to systematics and phylogeny. Brian Andres reviewed his thoughts on where we’re at with respect to our understanding of pterosaur phylogeny (he also gave a separate talk on “How I learned to stop worrying and love the cladogram”). He has a “facepalm” attitude to statements from some of us (like, err, me) that pterosaur phylogeny is under-studied and poorly resolved (I remain dissatisfied with the fact that hypotheses of pterosaur phylogeny are based on data sets of 100-120 characters or less), and indeed argued that even conflicting phylogenies (e.g., Kellner 2003 vs Unwin 2003) are significantly similar (76.4% the same, in this specific case). Brian’s primary take-home was that things aren’t that bad, and that our phylogenies are getting more similar to one another over time.

In the same roundtable session, Fabio Dalla Vecchia reviewed our knowledge of Triassic pterosaur phylogeny. Often forgotten is that some specimens of the Triassic taxa demonstrate – if correctly identified – profound changes in cranial ontogeny. A juvenile Austriadactylus, for example, essentially lacks the prominent cranial crest present in an adult and looks more like the (apparently distantly related) Preondactylus. Taissa Rodrigues also discussed taxonomy and systematics. In the following discussion, we covered ranked nomenclature (and why it should be abolished), species concepts and the debate over binomials and uninomials. None of this is specific to pterosaurs, but (in my opinion) the more people move away from ranked classification and toward tree-based thinking, the better.

Artwork and museum visits

Helder da Rocha's foam Tupuxuara skeleton (with Nathan Carroll and an obscured Helder at left; Felipe Pinheiro and an obscured David Unwin at right). Photo by Darren Naish.

We were constantly surrounded by pterosaur-themed artwork and sculpture during the meeting. Several displays were devoted to the work of Maurilio Oliveira, Paulo Márcio Esper and Sergey Krasovskiy, and Helder da Rocha’s excellent model skeletons were a major, unmissable feature of the event. As explained in his talk, Helder made a foam model of the skeleton of Guidraco (just for fun) one day. It was (he happily admits) substantially inaccurate, with many parts modelled on those of other pterosaur species (this explains the moniker ‘The Imaginary Pterosaur’, used as his blog title). He developed a technique (it uses sheets of white foam, stuck together with glue, burnt with a lighter to create a realistic, bone-like texture) and began to create better, more accurate skeletons, even the largest of which – like the Tupuxuara shown here – weigh less than 1 kg.

The official conference t-shirt! (though the final versions are in black and white, not full colour). From Helder da Rocha's blog The Imaginary Pterosaur.

These models are so good that I initially assumed that I was looking at professionally done resin casts. I assume it’s only a matter of time before Helder is selling these models to museums for display: they look great and are close to being absolutely accurate. Helder also designed the excellent conference t-shirt.

On the subject of mounted skeletons and so on, we got to spend appropriate time in the Museu Nacional, located in the middle of the beautiful Quinta da Boa Vista park. The Mesozoic gallery here is spectacular, featuring mounted skeletons of the sauropod Maxakalisaurus, the pterosaurs Tupandactylus and Tropeognathus, and life-sized models of the dyrosaurid crocodyliform Guarinisuchus and sauropodomorph Unaysaurus. A spectacular full-sized skeleton of the spinosaurid Angaturama (or… is that Irritator?) is posed with an Anhanguera in its jaws (a reconstruction based on an actual fossil), and the holotype of another spinosaurid – Oxalaia – is also on display, as is much else besides. Nearby are mounted skeletons of Smilodon and the sloths Eremotherium and Glossotherium (sadly, the awesome phorusrhacid Paraphysornis was not on display at the time of our visit). It was remarkable to see so many recently described, recently named specimens in close proximity.

Fantastic Angaturama skeleton (with Anhanguera prey) on display at the Museu Nacional (note the pelvis and vertebrae at lower left). Photo by Darren Naish.

On another day, we visited another institution: the Museu de Ciências da Terra (or Museum of Earth Sciences). Again, a spectacular assortment of fossil taxa were seen, including the Tupandactylus imperator holotype, and mounted skeletons of the enormous dicynodont Dinodontosaurus and rauisuchian Prestosuchus. I was especially thrilled to see the actual skull of the incredible ‘sabre-toothed’ sebecosuchian Baurusuchus pachecoi and the absurdly robust, complete skeleton of a big hyperodapedontine rhynchosaur labelled Scaphonyx fischeri (that name’s a nomen dubium and I’m not sure about the exact status of the specimen I was looking at).

Highlights of the Museu de Ciências da Terra, Rio. Top left: skull of the sebecosuchian croc Baurusuchus. Bottom left: insanely chunky rhynchosaur conventionally known as 'Scaphonyx fischeri'. Right: skeleton of rauisuchian Prestosuchus. Photos by Darren Naish.

Giant Thalassodromeus image (by Maurilio Oliveira) on the floor of the main atrium at the Museu de Ciências da Terra. Kids, say no to skim-feeding. Photo by Darren Naish.

On non-pterodactyloid pterosaurs

Back to the conference, non-pterodactyloid pterosaurs formed the focus of a few talks and posters. Marina Soares and colleagues had a poster on the alleged Upper Triassic pterosaur Faxinalipterus minima, a poorly understood (and obscure) reptile known from a collection of limb bones, none of which look especially pterosaur-like. Indeed, their reanalysis showed that the specimen lacks pterosaur characters, and its bones are no more pterosaur-like than are those of dinosaurs, croc-line archosaurs, or protorosaurs.

Niels Bonde discussed new data on cranial pneumaticity in the same Rhamphorhynchus specimen he and Per Christiansen previously discussed in 2003 (Bonde & Christiansen 2003). Fabiana Costa (and colleagues) presented data on a ‘new’ anurognathid specimen (actually preserved on the same slab as a Sordes specimen) that seemingly preserves evidence for a long tail… or, a tail longer than that expected for an anurognathid anyway. The idea that at least some members of this group were longer-tailed than usually thought has been kicking around for a while now though convincing demonstration of this has yet to be properly documented.

Sexual dimorphism in Darwinopterus, as depicted by Mark Witton. We now have good data on ontogenetic transformation in this taxon as well.

Xin Cheng and colleagues presented data on another new wukongopterid taxon and Dave Unwin discussed new specimens of Darwinopterus and what they tell us about ontogenetic transformation in this taxon. What’s especially intriguing about these specimens is that they suggest that various ‘typical’ pterodactyloid traits (like a proportionally short tail, elongate metacarpus and so on) might have evolved via heterochrony. I was very pleased to hear this (err, even though I heard it previously at one of the SVPCA meetings), since I was also planning to touch on the same concept in my talk on Vectidraco (the latter seems to be skeletally mature, yet possesses characters that – elsewhere within pterosaur phylogeny – are expressed most usually in juveniles). Anyway, Darwinopterus continues to provide copious key information on pterosaur biology and ontogeny.

Incidentally, those claims that pterosaurs exhibit obvious isometry across ontogeny (that is, they stay the same in form and proportions but merely get bigger) are not accurate, and some of the key specimens linked to this claim (cough cough Ptweety cough cough) do not represent what their champions think they do.

Wings and pterosaur affinities

"The great Bennett" (our new pet name for Chris) discusses pterosaur wing anatomy. If you can read the words, please keep them to yourself for the time being (the work reported here is not yet published). Photo by Darren Naish.

Chris Bennett gave two presentations, one on pterosaur wing anatomy and one on the character support used to link pterosaurs to other archosauromorphs. In the former talk, Chris explained how detailed re-examination of the Zittel wing (using high resolution photographic mapping) provides new data on the form and distribution of actinofibrils and of the retrophalangeal wedge (a band of tissue that borders the posterior edges of the wing phalanges, streamlining them into the wing tissues). If Chris is right, some previous interpretations of pterosaur wing tissue structure are significantly inaccurate: actinofibrils, for example, are not widely spaced, rod-like structures on the patagial underside, but lenticular, closely spaced objects embedded within the dorsal dermis.

In the second talk, he looked in detail at several characters purported to link pterosaurs to crown-archosaurs, in particular addressing Nesbitt & Hone’s (2010) paper in which they reported external mandibular fenestrae, antorbital fossae and possible fourth trochanter homologues in assorted early pterosaurs. Chris did a pretty convincing job of showing that at least some of these observations are erroneous. The ‘consensus view’ on pterosaurs is that they’re crown-archosaurs, close to dinosauromorphs (remember that Ornithodira exists no matter where pterosaurs go on the cladogram: it’s the name for the pterosaur + dinosaur node and does not require that they’re more closely related to one another than they are to other reptiles). Chris has argued that pterosaurs actually belong elsewhere within Archosauriformes: this point of view isn’t popular but the debate is certainly not over yet.

Most workers support the idea of a close relationship between pterosaurs and dinosaurs, in which case the node-based Ornithodira is nested within Archosauria. Chris Bennett has argued that pterosaurs are outside of Archosauria, in which case Ornithodira is more inclusive, as shown here. Diagram by Darren Naish.

Rachel Frigot presented her work (done with Colin Palmer) on pterosaur trabeculae. It seems that – contrary to expectations – the trabeculae do not act to prevent distortion of the wing elements when they’re placed under load. Intriguingly, trabeculae seem to be located ‘around’ pneumatic spaces in the long bones, suggesting that they might be useful as osteological correlates of the extent of the skeletal pneumatic system.

Pterodactyloids aplenty

The robust-skulled rhamphorhynchid Sericipterus chows down on a small pterodactyloid in this reconstruction by John Conway. The pterodactyloid? Yeah, it's the new Shishugou taxon mentioned here.

The vast majority of talks (and posters) covered new pterodactyloid taxa and various aspects of pterodactyloid anatomy and systematics. Brian Andres spoke (on behalf of co-authors) about a new Late Jurassic pterodactyloid from the Shishugou Formation of Xinjiang, China. This unit has previously yielded the large rhamphorhynchid Sericipterus, and Lower Cretaceous sediments nearby yield abundant specimens of Dsungaripterus (as well as the somewhat doubtful taxon Lonchognathosaurus). Sericipterus is a robust animal that might have been a scavenger or predator of terrestrial environments. The new pterodactyloid from the Shishugou is important in that it appears intermediate in metacarpal elongation and other characters between non-pterodactyloids and later Late Jurassic pterodactyloids.

Laura Codorniú gave two talks on pterosaur braincase anatomy: one on a new Jurassic species from Argentina, and another on Pterodaustro. Both talks included enormous amounts of new anatomical information. Fabio Dalla Vecchia covered his fascinating forensic-style investigation of a spectacular, near-complete pterodactyloid skeleton, exhibited by the CosmoCaixa Science Museum in Spain and identified as that of an Anhanguera piscator. The skeleton proved to be a composite incorporating numerous reconstructed or fabricated parts.

Shunxing Jiang spoke about a new boreopterid specimen argued to represent a new species of Boreopterus. Boreopterids (discussed previously on Tet Zoo: see links below) are very interesting and I find their elongate, slender teeth highly intriguing. Were they using them to grab (or ‘cage’, or filter?) some specific prey type? They seem to be closely related to ornithocheirids, though whether all species currently included within the group really belong there remains somewhat controversial. There were quite a few poster presentations on Anhanguera-type animals (it’s currently down to opinion whether you term these animals anhanguerids or ornithocheirids): anybody really interested needs to get hold of the abstract volume.

Large illustration at the Museu de Ciências da Terra, showing battling Tropeognathus (with Thalassodromeus and Anhanguera in the background). Image by Maurilio Oliveira.

There is no escape from the swimming giraffes, not even in a South American pterosaur conference, mu ha ha! Image by Don Henderson.

Here I will mention the third roundtable discussion. It was titled ‘New techniques for pterosaur studies’ and involved presentations on phylogenetic methods and CT-scanning. The discussion we had afterwards ended up focusing on the open access movement, copyright law and the sharing of pdfs (how quaint that some publishing companies tell authors not to send out more than 20 digital copies of their own papers). Blogging was also discussed. In a surprise move, Taissa asked me about the giraffe flotation paper I co-authored with Don Henderson (Henderson & Naish 2010). Funnily enough, the technique used in that paper has already been applied to pterosaurs since I know that Don and Dave Hone have a manuscript in the system on the flotation behaviour of pterosaurs.

We’re all here for the azhdarchoids

Several talks were devoted to azhdarchoids, the most interesting of pterosaurs (in my highly subjective and personal opinion). In the phylogenetic scheme that I (and some of my colleagues) prefer, the typically short-snouted tapejarids are outside of the clade that includes the larger, longer-snouted thalassodromids and azhdarchids (the name Neoazhdarchia can be applied to the thalassodromid + azhdarchid clade) (Unwin 2003). Chaoyangopterids may be part of Neoazhdarchia as well. However, there are currently several competing views on the phylogeny of these lineages (e.g., Unwin 2003, Kellner 2004, Lü et al. 2008, Martill & Naish 2006, Andres & Ji 2008, Pinheiro et al. 2011) and many of my South American colleagues prefer the hypothesis that thalassodromids (and maybe chaoyangopterids too) are a sub-clade of Tapejaridae. In the discussion here, note that the term tapejarid refers only to tapejarids in the strictest sense (as per Martill & Naish 2006): it does not include Tupuxuara and kin.

Alternative topologies within Azhdarchoidea as illustrated by Bruno Vila Nova. Photo by Darren Naish.

Bruno Vila Nova spoke about tapejarid cervical vertebrae, Felipe Pinheiro and colleagues presented a poster on the possibility of cranial kinesis in tapejarids, and Taissa Rodrigues (on behalf of co-authors) discussed post-cranial morphology in thalassodromids. Lots of useful and interesting data on cervical vertebrae in these talks.

Vectidraco in silhouette form (by Naish, from Naish et al. 2013), and reconstructed as a live animal (by Mark Witton).

I spoke about Vectidraco, with diversions on the political geography and anthropology of the Isle of Wight and on postcranial skeletal pneumaticity. Some of this is supplementary to the data included in Naish et al. (2013) and needs to be published at some stage (though probably not the stuff on the political geography and anthropology of the Isle of Wight, ha ha).

Fabiana Costa discussed the idea that two elongate cervical vertebrae from the Upper Jurassic of Tendaguru might belong to Azhdarchidae. This idea has been batted backwards and forwards over the years; the competing (published) hypothesis is that the vertebrae belong to ctenochasmatids of some sort (Andres & Ji 2008). The latter possibility looks more likely in view of the Late Jurassic age of the specimens, but – as is so often the case with fragmentary specimens – we need better fossils before we can be more confident about this sort of material. Given that I’ve previously identified azhdarchid material that dates to the very earliest part of the Cretaceous (see Dyke et al. (2011) and image below), I’m not sure that Late Jurassic azhdarchids would be quite as problematic as some other workers do.

Small, incomplete cervical vertebra (25 mm long as preserved) from Berriasian sediments of Romania, identified by Dyke et al. (2011) as that of a small, early azhdarchid.

Nathan Carroll discussed new azhdarchid material from the Two Medicine Formation of Montana. The animal concerned – represented by vertebrae, pelvic elements and parts of the fore- and hindlimbs – seems to belong to a new taxon, in which case the Two Medicine Formation includes this one in addition to both Montanazhdarcho and the unnamed azhdarchid described by Padian (1984).

Several aspects of this research are especially interesting to me. Firstly, the presence of several apparently contemporaneous azhdarchid taxa led Nathan to propose that these animals were practising niche partitioning of some sort. If your memory is good, you will recall that I and my colleagues referred to the same idea in our paper on the Romanian azhdarchid Eurazhdarcho, published earlier this year (Vremir et al. 2013). Secondly, the Two Medicine material possesses several anatomical features which seem to be pretty good indicators of strong terrestrial behaviour in this animal – needless to say, this stuff nicely vibes with what Mark Witton and me said in our 2008 paper on azhdarchid palaeobiology (Witton & Naish 2008).

Nathan talks about Nathan (and his amazing azhdarchid puppet). Felipe Pinheiro chairs the session. Photo by Darren Naish.

Thirdly, Nathan finished his talk with a slide that showed the remarkable life-sized azhdarchid puppet he has created. A person fits inside it and it has both fairly realistic proportions and ranges of movement. Initial plans were to bring it down to Rio for the meeting… unfortunately, that didn’t work out. I really hope to see the puppet in person one day. Surely it’s only a matter of time.

Where will the next meeting be held? Portsmouth. When will the next meeting be held? 2015. Look, it says so up there on the slide. Photo by Darren Naish.

And so things drew to a close. I and several others spent time after the meeting looking at Brazilian pterosaur fossils, and – as I said above – there was also a fieldtrip. A volume of extended abstracts was produced for the meeting and is a definite must-have for those with a keen interest in the Pterosauria (I myself have a huge pile of spare copies, though most are reserved for colleagues in the UK). A volume of collected papers resulting from the meeting will be published in Historical Biology. The next meeting? As explained by Dave Unwin, this will be held in 2015 at the University of Portsmouth, UK (my former academic home).

We all signed copies of the conference banner. One of them will be auctioned at this year's SVP meeting (to be held in Los Angeles).

Despite the no-showing of several colleagues who were supposed to be in attendance, the Rio pterosaur symposium of 2013 was a great success and an enormous quantity of novel and interesting information on pterosaurs was presented. I owe a huge debt of thanks to Alex Kellner, Taissa Rodrigues and everyone else involved in the meeting. Thanks to Juliana Sayão, Fabiana Costa, Renan Bantim and everyone else who assisted in the organisation and chairing of the meeting, and well done and thanks to Helder da Rocha and others for providing artwork, replicas, designing the t-shirt and so on. Thanks to Lilian Alves for her time and assistance in the collections of the Museu Nacional, and thanks too to Nate, Ash, Dave, Chris, Brian and others for their help with specimens, insight and opinions. Thanks especially to Nate and Ash for hilarious stories about their adventures on the subway.

And, if you’re wondering, while in the beautiful city of Rio I saw (and photographed) an enormous number of bird species that were totally new to me. When time allows, I’ll be writing about them here as well.

For previous Tet Zoo article on pterosaurs, see…

Refs – -

Andres, B. & Ji, Q. 2008. A new pterosaur from the Liaoning Province of China, the phylogeny of Pterodactyloidea, and convergence in their cervical vertebrate. Palaeontology 51, 453-469.

Bennett, S. C. 1996. Year-classes of pterosaurs from the Solnhofen Limestone of Germany: taxonomic and systematic implications. Journal of Vertebrate Paleontology 16, 432-444.

Bonde, N. & Christiansen, P. 2003. The detailed anatomy of Rhamphorhynchus: axial pneumaticity and its implications. In Buffetaut, E. & Mazin, J.-M. (eds) Evolution and Palaeobiology of Pterosaurs. Geological Society Special Publication 217. The Geological Society of London, pp. 217-232.

Dyke, G., Benton, M., Posmosanu, E., & Naish, D. 2011. Early Cretaceous (Berriasian) birds and pterosaurs from the Cornet bauxite mine, Romania. Palaeontology 54, 79-95.

Henderson, D. M. & Naish, D. 2010. Predicting the buoyancy, equilibrium and potential swimming ability of giraffes by computational analysis. Journal of Theoretical Biology 265, 151-159.

Kellner, A. W. A. 2003. Pterosaur phylogeny and comments on the evolutionary history of the group. In Buffetaut, E. & Mazin, J.-M. (eds) Evolution and Palaeobiology of Pterosaurs. Geological Society Special Publication 217. The Geological Society of London, pp. 105-137.

- . 2004. New information on the Tapejaridae (Pterosauria, Pterodactyloidea) and discussion of the relationships of this clade. Ameghiniana 41, 521-534.

Lü, J., Unwin, D. M., Xu, L. & Zhang, X. 2008. A new azhdarchoid pterosaur from the Lower Cretaceous of China and its implications for pterosaur phylogeny and evolution. Naturwissenschaften 95, 891-897.

Martill, D. M. & Naish, D. 2006. Cranial crest development in the azhdarchoid pterosaur Tupuxuara, with a review of the genus and tapejarid monophyly. Palaeontology 49, 925-941.

Naish, D., Simpson, M. I. & Dyke, G. J. 2013. A new small-bodied azhdarchoid pterosaur from the Lower Cretaceous of England and its implications for pterosaur anatomy, diversity and phylogeny. PLoS ONE 8(3): e58451. doi:10.1371/journal.pone.0058451

Nesbitt, S. J. & Hone, D. W. E. 2010. An external mandibular fenestra and other archosauriform characters in basal pterosaurs. Palaeodiversity 3, 225-233.

Padian, K. 1984. A large pterodactyloid pterosaur from the Two Medicine Formation (Campanian) of Montana. Journal of Vertebrate Paleontology 4, 516-524.

Pinheiro, F. L., Fortier, D. C., Schultz, C. L., de Andrade, J. A. F. G. & Bantim, R. A. M. 2011. New information on the pterosaur Tupandactylus imperator, with comments on the relationships of Tapejaridae. Acta Palaeontologica Polonica 56, 567-580.

Prondvai, E., Stein, K., Ősi, A. & Sander, M. P. 2012. Life history of Rhamphorhynchus inferred from bone histology and the diversity of pterosaurian growth strategies. PLoS ONE 7(2): e31392. doi:10.1371/journal.pone.0031392

Unwin, D. M. 2003. On the phylogeny and evolutionary history of pterosaurs. In Buffetaut, E. & Mazin, J.-M. (eds) Evolution and Palaeobiology of Pterosaurs. Geological Society Special Publication 217. The Geological Society of London, pp. 139-190.

Vremir, M., Kellner, A. W. A., Naish. D. & Dyke, G. J. 2013. A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution. PLoS ONE 8(1): e54268. doi:10.1371/journal.pone.0054268

Witton, M. P & Naish, D. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3 (5): e2271. doi:10.1371/journal.pone.0002271

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.



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  1. 1. John Harshman 9:15 pm 05/30/2013

    I’m jealous not so much about the pterosaurs (though I am reminded that I really don’t go to enough meetings) but about the birds. Do tell.

    Link to this
  2. 2. Gigantala 9:43 pm 05/30/2013

    Heterochrony eh? It actually does make sense given how rapidly these adaptations occured, but I do wonder how longer metacarpals are related to that.

    Any news on lonchodectids?

    Link to this
  3. 3. vdinets 11:53 pm 05/30/2013

    Any news on the origins of pterosaurs?

    Link to this
  4. 4. AlHazen 1:09 am 05/31/2013

    Did Dave Peters make it to the conference? (Who knows– if he spent more time hanging out with “orthodox” pterosaurologists, he might absorb some methodological hints by osmosis!)

    Link to this
  5. 5. BilBy 8:57 am 05/31/2013

    Gosh, I love pterosaurs. That Sericipterus: teeth like that look like the teeth of a predatory fish – that doesn’t mean it was a fish-hunter but perhaps a hunter of small, fast, maybe slippery things. Frogs? Small pterosaurs in flight (as shown)? It doesn’t seem like the dentition of a scavenger (as also suggested). Are there any good extant analogies?

    Link to this
  6. 6. David Marjanović 9:26 am 05/31/2013

    are significantly similar (76.4% the same, in this specific case)

    That just means they’re not completely random.

    The description of Aurornis contains a phylogenetic analysis performed on a subset of Megamatrice (because Andrea Cau is a coauthor). This subset has 992 (nine hundred ninety-two) parsimony-informative characters. That, laddies and gentlewomen, is how to do it.

    Nesbitt & Hone’s (2010) paper in which they reported external mandibular fenestrae, antorbital fossae and possible fourth trochanter homologues in assorted early pterosaurs

    Uh, the 4th trochanter goes way back. It’s present in the best-ossified temnospondyls.

    Sericipterus is a robust animal that might have been a scavenger or predator of terrestrial environments.

    …But those teeth look like it only swallowed stuff whole.

    Who knows– if he spent more time hanging out with “orthodox” pterosaurologists, he might absorb some methodological hints by osmosis!

    That’s not how it works. He was on the Dinosaur Mailing List for years and years and years. People explained the same things to him maybe 10 times. He learned very little, if anything.

    Link to this
  7. 7. David Marjanović 9:27 am 05/31/2013

    Actually, it’s interesting that no frogs have yet been reported from the Jurassic of China. The salamander specimens number in the hundreds.

    Link to this
  8. 8. Perisoreus 9:37 am 05/31/2013

    Darren:

    Some of this is supplementary to the data included in Naish et al. (2013) and needs to be published at some stage (though probably not the stuff on the political geography and anthropology of the Isle of Wight, ha ha).

    I insist on it! At least in a blog post! :)

    (in my opinion) the more people move away from ranked classification and toward tree-based thinking, the better.

    Well, that depends. It might be helpful in a branch ob biology that deals with taxa as lines of flight (to borrow a term from Deleuze), but remember that Linnean taxonomy has its merits and that species, genera or families are more than arbitrary ranks applied to rectangular branches of a tree as soon as it comes to populations. There are reasons why it’s still around despite cladistics (and I would not consider it in a state of slow demise even now).

    Link to this
  9. 9. helderdarocha 2:06 pm 05/31/2013

    Very cool article! Thanks for the comments about my art, Darren!

    Link to this
  10. 10. Heteromeles 2:50 pm 05/31/2013

    @Perisoreus: One of the reasons ranked taxonomy is still around is that it gets used in other fields. For example, there is a field of soil taxonomy, with groups, great groups, and series, and similar systems are used for vegetation classification.

    Back a few decades ago, there wasn’t a problem with mixing Linnean and non-Linnean taxonomies together, at least conceptually. They were all effectively Venn diagrams, groups enclosed by greater groups. It didn’t matter what caused said groups to be joined together, whether it was similarity or evolution.

    Unfortunately, it matters now. With cladistics, we’re explicitly talking about objective tests of evolution, and that’s reason for grouping things together. This isn’t true in other fields, and it causes a lot of confusion. I’m beginning to think that (where possible), a “tree-based” language of cladograms is preferable, not to be exclusive, but so that people don’t get sloppy in their thinking, and apply evolution to systems that don’t evolve (like soil or vegetation).

    There are many examples of this. I’ve been in week-long debates about whether species are real, and seeing someone pipe up that families and genera are real is even sillier.
    However, when people start applying evolutionary concepts to, say, vegetation typology, it stops being funny, because the gross management errors they cause by their rigidly conceptual mapping can lead to extirpation of any species that can’t survive in homogeneous polygons of one or two dominant species.

    Since I’m not trying to derail this discussion about pterosaurs, I just want to point out that tree-based language does matter, it’s more than just about classification and grouping, and I’m glad that more and more people are learning to use it.

    Link to this
  11. 11. naishd 8:54 pm 05/31/2013

    Thanks for comments! Some quick responses…

    – lonchodectids (comment 2): they were mentioned once or twice, but nothing specific on them at the meeting. Tracy Ford has an abstract in the meeting volume but it’s just a historical review of the group. A major review of the group is due to appear in print fairly soon. They will probably prove to be close relatives of azhdarchoids.

    – pterosaur ancestry (comment 3): as hinted at in the article above, there are still conflicting views (are they crown-archosaurs or do they belong elsewhere within Archosauriformes?). More work is still needed on this issues, and more fossils would be nice.

    – David Peters (comment 4): he also has an abstract in the conference volume, so perhaps intended to come. But nope. His abstract concerns his hypothesised nesting of pterosaurs within squamates. This is not a well supported idea and should not be regarded as a valid alternative to the ideas I just mentioned.

    Those birds? (see comment 1) Don’t worry, all will be revealed (just waiting for a field guide to arrive!).

    Darren

    Link to this
  12. 12. Perisoreus 7:06 am 06/1/2013

    Heteromeles (comment #10):

    Unfortunately, it matters now. With cladistics, we’re explicitly talking about objective tests of evolution, and that’s reason for grouping things together. This isn’t true in other fields, and it causes a lot of confusion. I’m beginning to think that (where possible), a “tree-based” language of cladograms is preferable, not to be exclusive, but so that people don’t get sloppy in their thinking, and apply evolution to systems that don’t evolve (like soil or vegetation).

    There are many examples of this. I’ve been in week-long debates about whether species are real, and seeing someone pipe up that families and genera are real is even sillier.
    However, when people start applying evolutionary concepts to, say, vegetation typology, it stops being funny, because the gross management errors they cause by their rigidly conceptual mapping can lead to extirpation of any species that can’t survive in homogeneous polygons of one or two dominant species.

    To get things straight, I personally prefer cladistics over Linnean taxonomy in most cases. Yes, we’re talking about objectivity, but I this term means something different to me than to you. Cladistics is not “more objective” than Linnean taxonomy because it contains “more truth” (at least not in the common meaning of truth), just as DNA analysis is not more objective than osteological phylogenetics.

    Linnean taxonomy is a system that aims at accounting for the diversity of life by acknowledgeing similarity and difference between different life forms. It is thus very different from cladistics which is informed by evolutionary thinking which was unknown to Linné and his creationist view.

    I don’t think rigid application is an argument in this debate, since there are surely ways to misapply Linné and cladistics by taking them as dogma. And neither is “Are species real?” a question that is apt to decide the fate of Linnean taxonomy. Are species real? Of course they are, they’re real as long as we apply them or argue about their mode of existence. And even if they were “mere concepts” with no point of reference in the “real world” (which I think is your point here) they’re still as real as a Kafka novel, an ancient Babylonian law or a failed conservation plan. They’re real as long as they’re able to act and make things act (sorry for actually derailing the pterosaur discussion with metaphysics), as you can perfectly see in your vegetation typology example: species, or rather species concepts, render certain things visible and certain things invisible, which might eventually lead to the latter perishing both conceptually and materially.

    The question is not if branches or species are real but rather if they can express a certain aspect of biology or simply if actual animals (meaning individuals) stick to the limits they demarkate. And of course they don’t, animals (and other organisms, for that matter) neither consequently follow branches (Polar Bear, Chihuahuan raven, Larus gulls), nor do they always patrol or exploit the borders of their species republic (sheep and goats, allopatric species). This is why biology has invented a multitude of species concepts (and tools like type specimens) in order to capture what organisms actually do. And I think it would be a loss to see all those taxonomic concepts getting reduced to one that might be superior in one field but that is blind for others.

    As soon as you leave mesozoic paleontology with its (mostly) single and singular specimens and enter a cenozoic scenario with aff. and cf., you hit the limits of cladistics (I’m currently digging through the bibliography of European Gomphotherium specimens); even more so as you approach the holocene. I’m very thankful for cladistics, since it allows to understand and present evolution in a reproducible, comprehensible and therefore powerful way (which is what objective means to me). Biology, however, is not only about evolution. And there are problems that neither cladistics nor Linnean taxonomy are able to solve, so I’m sceptical whenever someone announces the advent of either of both methods’ surpreme rule. And of course, do acknowledge that Linnean thinking is a huge obstacle and a source of error in a lot of fields, but that does not devalue it in other areas.

    Link to this
  13. 13. John Harshman 10:23 am 06/1/2013

    Perisoreus,

    What exactly do you mean by Linnean taxonomy? You seem to be attaching a lot of baggage to it that I don’t think is warranted. I think of it only as the custom of attaching ranks to taxa. And it’s certainly that custom that others here are arguing against. Nobody has even mentioned the custom of forming taxa by similarity, which is what you seem to be about.

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  14. 14. Perisoreus 4:19 pm 06/1/2013

    John Harshman (comment #13)

    What exactly do you mean by Linnean taxonomy?

    Mostly the application of ranks, yes, but also an idea of species as fixed entities and a classification based on appearance. But I know, the latter is common for all of 18th century natural history, it’s not especially characteristic of Linnean taxonomy. (Meaning not so much the original system of Linné but rather what it developed into)

    Of course cladistics has no use for ranks; it does not really distinguis between, let’s say, Aves and Passer domesticus as long as they’re both monophyletic. This is why you can include taxa that would be species, genera or orders in Linnean taxonomy as branches into the same tree. And yes, I think it’s in no way helpful to demand that this methodology (which is quite heuristic) or the thinking behind it respects something like ranks or an archaic division between birds and the rest of dinosaurs.

    However, taxonomy is a science of its own and it has its own requirements. It’s rather not about quick reassembling of branches and nodes and an application of a multitude of names in constant flux that might be synonyms from a lot of standpoints, but rather the opposite. (Linnean) Taxonomy is a science of book-keepers and from its very beginning, it has aimed at stability, unequivocality and clear arrangement. Of course, it never had a good eye for dynamics in the first place, but that’s not what it’s interested in. In many respects, it’s an auxiliary science for biology – not only for paleontology and evolutionary biology, but also for field botany and ecology.

    The latter heavily rely on the services provided by taxonomy and there are far too few old-fashioned Linnean taxonomists around to keep up with the output of evolutionary biology. So if you’re argueing against ranks (or, more radically, against uni-/bi-/trinomina), you should keep in mind that there needs to be system that can provide an inventory of the life on earth. Yes, it’s nice to be free of useless conventions when you’re working on the frontiers of biology, but when things settle, ranks (formal or informal) are nice to have, because you don’t have to look up all of the tree before you’re able to talk about a certain taxon. An in reverse, it helps to speak of a genus or family exactly when you’re not sure which species is basal and which is derived. Linnean taxa and ranks are pragmatic brackets for these cases.

    Linnean taxonomy is very much a child of an analogue age and maybe some of its advantages can also be provided by digital and statistical tools, as in higher plant and life taxonomy (future will show). But the closer it gets to actual organisms, the more sceptical I am of completely abandoning it. I think that taxonomy as a whole will have to move on if it wants to keep up with modern biology, but I don’t think that cladistics will be the universal remedy. It hints for most of the central problems, however, that are posed by Linnean taxonomy.

    There’s also a recent article on the current state of taxonomy in Zootaxa: http://www.mapress.com/zootaxa/2013/f/zt03636p244.pdf

    Link to this
  15. 15. John Harshman 7:53 pm 06/1/2013

    Your comments seem to me quite vague. What is it about Linnean taxonomy (a poorly defined bundle of tropes) that is useful, and where? How do ranks make talking about taxa easier than unranked names would? What would it mean for a species to be “basal” or “derived”?

    And if stability is your goal, certainly one option is to freeze taxonomy upon some arbitrary state in which, for example, we just forever leave Pseudopodoces as a corvid. But it seems to me a better way is to base taxonomy on the best knowledge of phylogeny we have, which will eventually converge on real phylogeny as we add data.

    Link to this
  16. 16. naishd 6:43 am 06/2/2013

    Arguments ‘pro’ Linnaean ranks are usually based around the idea that they’re useful for book-keeping reasons. Maybe a case can be made here, but I don’t really see it. Tree-based thinking and the idea of nested clades do away with any such need – who cares what rank, say, Primates is, so long as it’s divided up appropriately for its constituent taxa?

    Perhaps more important, ranking is absolutely bad and misleading because people >honestly do think< that equivalently ranked taxa are, literally, equivalent units in terms of disparity and diversity. In other words, we see people saying that amphibians are "less diverse" than mammals or birds because amphibians are classified into three orders while mammals and birds both get about 30. Insects are a bit more diverse than mammals or birds: after all, they're classified into 41 orders. In reality, this is all complete nonsense – those 'orders' are not equivalent at all, nor are any other ranked taxa. Not only do we just not need them, they also lead to positively misleading ideas about the diversity of life.

    Darren

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  17. 17. naishd 6:54 am 06/2/2013

    While I’m here… seeing as David Peters is mentioned above, a reminder that my thoughts on the Peters issue are provided in Why the world has to ignore ReptileEvolution.com.

    Darren

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  18. 18. David Marjanović 1:25 pm 06/2/2013

    Are species real? That depends on the species concept. Many species concepts describe entities that exist outside of our skulls and function as units of ecology and/or evolution to varying degrees. Unfortunately, they’re not congruent with each other. Depending on the species concept, there are from 101 to 249 endemic bird species in Mexico (refs later)… they have nothing in common other than the word “species”, which is a highly misleading state of affairs. No system of nomenclature even tries to deal with all of this confusion at once.

    On to terminology:

    Cladistics: two meanings: 1) cover term for the methods of the science of phylogenetics (now that it is a science rather than an art or handicraft); 2) specifically Hennigian argumentation and maximum parsimony. Molecular phylogeneticists use it in the second sense and therefore laugh at it.

    Phylogenetic nomenclature: defines taxon names in term of ancestry. Rank-based nomenclature (that’s what the current codes are) instead use a type and a rank. The use of ranks isn’t automatically incompatible with phylogenetic nomenclature, but ranks do not determine the spelling or synonymy of names in it as they do in rank-based nomenclature.

    Do not confuse the two. Lots of people have done cladistics and then translated the resulting cladograms into classifications that used rank-based nomenclature; on the other side, Gregory S. Paul uses phylogenetic nomenclature, but has nebulous misgivings about cladistics and doesn’t use it.

    While I am at it, cladogram = outcome of a cladistic analysis. Not every branching diagram that represents a phylogenetic hypothesis is a cladogram.

    Taxonomy: at least three meanings off the top of my head: 1) when used synonymously with systematics, the process of making a classification; 2) the outcome of 1) (so that “a taxonomy” is a classification); 3) when distinguished from systematics, the process of making rules for how to make classifications, while systematics is the application of these rules.

    I can’t see how taxonomy in any of these meanings, or systematics, is a science. It’s bookkeeping. It uses the results of the science of phylogenetics, as well as nomenclature (which isn’t science but a set of conventions), sometimes some phenetics and more; it’s an application of science, like engineering and medicine.

    Perhaps more important, ranking is absolutely bad and misleading because people >honestly do think< that equivalently ranked taxa are, literally, equivalent units in terms of disparity and diversity.

    And that’s not just true of laypeople. Even the experts aren’t always aware of it. Within one paragraph in the abstract of his 2007 paper in Acta Palaeontologica Polonica, Michael Benton first asserted that he knows full well that taxa at the same rank aren’t somehow equivalent and then went on to treat them as equivalent. The rest of the paper isn’t any better. It heavily implies that phenetic analyses have been done to cluster all carnivorans into comparable similarity groups, when in fact this has never been done.

    Linnean taxonomy is a system that aims at accounting for the diversity of life by acknowledgeing similarity and difference between different life forms.

    It does not, however, do so in an objective way: the ways in which phylogeny and similarity are acknowledged depend entirely on the whim of each taxonomist, and the amounts to which either happens vary from all to nothing in the same way.

    The question is not if branches or species are real but rather if they can express a certain aspect of biology or simply if actual animals (meaning individuals) stick to the limits they demarkate. And of course they don’t, animals (and other organisms, for that matter) neither consequently follow branches (Polar Bear, Chihuahuan raven, Larus gulls)

    To be fair, the “PhyloCode” (the only complete implementation of phylogenetic nomenclature so far) will allow for naming overlapping clades and for naming clades that originated by hybridization.

    As soon as you leave mesozoic paleontology with its (mostly) single and singular specimens and enter a cenozoic scenario with aff. and cf., you hit the limits of cladistics (I’m currently digging through the bibliography of European Gomphotherium specimens); even more so as you approach the holocene.

    Do you mean you find hybrids?

    There’s also a recent article on the current state of taxonomy in Zootaxa:

    Thanks, I’ll read it. (44 pages. There goes my day.)

    Your comments seem to me quite vague. What is it about Linnean taxonomy (a poorly defined bundle of tropes) that is useful, and where? How do ranks make talking about taxa easier than unranked names would? What would it mean for a species to be “basal” or “derived”?

    All seconded.

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  19. 19. Christopher Taylor 8:49 pm 06/2/2013

    Within one paragraph in the abstract of his 2007 paper in Acta Palaeontologica Polonica, Michael Benton first asserted that he knows full well that taxa at the same rank aren’t somehow equivalent and then went on to treat them as equivalent.

    Indeed, he didn’t just do it within one paragraph, he managed to do it within one sentence:

    “Everyone accepts that Linnaean ranks are subjective, and yet there is no benefit in abandoning ranks because they have proved to be of such value to users of classifications, and genera and families, for example, act as valuable surrogates for species in large−scale evolutionary and ecological studies.”

    Benton, M. J. 2007. The PhyloCode: beating a dead horse? Acta Palaeontologica Polonica 52 (3): 651-655.

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  20. 20. David Marjanović 6:07 am 06/3/2013

    Thanks, I was too lazy to look it up and confirm it’s in a single sentence.

    It’s a really important point that higher ranks do not work as surrogates for species or any other measure of diversity. What they measure is a strange cross-section through the mood swings of taxonomists. Genera, families and orders are not countable.

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  21. 21. Perisoreus 10:19 am 06/3/2013

    To keep it short: short answers on the most important questions. Sorry for mixing up different people: (the last thing I wanted was to start an internet argument)

    It’s a really important point that higher ranks do not work as surrogates for species or any other measure of diversity. What they measure is a strange cross-section through the mood swings of taxonomists. Genera, families and orders are not countable.

    Indeed, taxa are not a good measure of diversity. And neither are species, since they do not account for morphs, sexual dimorphism, local races etc. They only reflect a small scope, but you can’t count “diversity”, at least not in terms of taxa. That’s implied in the concept.

    Your comments seem to me quite vague. What is it about Linnean taxonomy (a poorly defined bundle of tropes) that is useful, and where? How do ranks make talking about taxa easier than unranked names would? What would it mean for a species to be “basal” or “derived”?

    What is the difference between, let’s say, Panthera uncia and their sister clade, the rest of Panthera (its sister clade)? The first branch leads to a species, that is a concept for dealing with actual animals, their behavior, ecology and morphology; the second branch leads to a multitude of very different species and therefore strongly different animals. So it’s easier to say: Some of these groups/branches can be meaningfully divided into subgroups, others cannot. Likewise, I could divide Accipitriformes or Strigiformes into various subgroups or reversely lump them together with other “orders”, but that would obscure the ecological similarities between those groups. The rank of a taxon is an indicator of abstraction, mostly to taxonomic outsiders: the higher it is, the less meaningful (beyond monophyly) the taxon. And while the appilcation of Linnean taxa might be arbitrary in its clichéic depiction, you will find that Linnean taxons actually try to validate them with objective criteria. Orders, for example, are usually the last rank within the tetrapodes that designate monophyletic groups with a shared ecology or physiology.

    As soon as you leave mesozoic paleontology with its (mostly) single and singular specimens and enter a cenozoic scenario with aff. and cf., you hit the limits of cladistics (I’m currently digging through the bibliography of European Gomphotherium specimens); even more so as you approach the holocene.

    I find things that I’m not even sure of what they are. Sexes? Juveniles? Aberrant individuals? Lone scatter blots? And I can’t put them into a phylogenetic scheme (which would perhaps give a confusing meaning to them).

    Do not confuse the two. [cladistics and phylogenetics]

    In my writing here, I do; in my writing elsewhere and in my head, I hopefully don’t.

    And if stability is your goal, certainly one option is to freeze taxonomy upon some arbitrary state in which, for example, we just forever leave Pseudopodoces as a corvid.

    I’m talking about stability, not eternity or unchangeability. Look at the base of the bird tree and tell me what it’s called. There’s a bunch of names around for it and no one to decide how to talk about it so that everyone knows what he or she means. Thats why paleontologic papers usually have a section where they define their taxa anew or where they refer to other authors (“sensu”). But that “sensu” goes in the exact direction criticized by some as “subjective”. I don’t have a problem with that as long as its a heuristic applied in a state of flux. However, taxonomy of recent tetrapodes is rather stable, and that’s where you’d like to have a name that is used consistently over the course of several years and that tells you if it’s above the names in italics and below the ones that end with -formes. If phylogenetics can do that without Linné, all the better. But currently, I think some of its proponents don’t see an issue here, because their work is not confronted with such problems.

    And maybe one last comment: I’m perfectly fine with most of paleontology ignoring everything of Linnean taxonomy that’s not useful for them. For example, it has more or less given up the species as a meaningful unit, and among others Kurtén (1968 I think) has explained very well why it did so (one reason was careless Linnean taxonomy). What I would just like to remind everyone who’s fond of cladistics/phylogenetics (and I consider myself one of those), though, is that there are other fields of biology that heavily rely on that system. Calling the researchers in those fields ignorant, backwarded, simple-minded or stupidly conservative (and be it only in tone) because they stick to Linné will neither help them nor those who want to give evolution a more central role in taxonomy, because it won’t change anything or only at an incredibly high price (remember what happened between the botanists and zoologists back in the 19th century). If you would like to convince them of your system, take their worries seriously and do not simply dismiss them as irrelevant or subjective. It’s not about proving that phylogenetics is right (it is), but about integrating the useful parts of the old into that new taxonomy.

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  22. 22. John Harshman 10:49 am 06/3/2013

    What scientific use is there, specifically, to ranks? You seem to imply that it’s purely a matter of pandering to the prejudices of workers in other fields, but you also imply that it’s a good thing to do that. So, again, what legitimate use do those workers have for taxonomic ranks?

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  23. 23. David Marjanović 3:35 pm 06/3/2013

    Indeed, taxa are not a good measure of diversity. And neither are species, since they do not account for morphs, sexual dimorphism, local races etc. They only reflect a small scope, but you can’t count “diversity”, at least not in terms of taxa. That’s implied in the concept.

    What you can do is measure phylogenetic diversity with, for example, the Phylogenetic Diversity Index. It considers the lengths of the branches between the organisms you’re looking at and their common ancestor.

    And while the appilcation of Linnean taxa might be arbitrary in its clichéic depiction, you will find that Linnean taxons actually try to validate them with objective criteria. Orders, for example, are usually the last rank within the tetrapodes that designate monophyletic groups with a shared ecology or physiology.

    …at a totally subjective precision. And all members of a phylum have the same bauplan, for a totally subjective non-definition of “same”.

    I’ve never seen an attempt to make such things objective. The only attempts at making rank assignment objective that I’ve seen involve the ages of taxa.

    Also, you didn’t answer the question: what is “basal” and what is “derived”?

    For me, character states are derived, not organisms; and “basal” means “far away from the clade I’m interested in at the moment”, so I avoid it and talk about sister-groups instead (“Panthera uncia is the sister-group to all the rest of Panthera“).

    I find things that I’m not even sure of what they are. Sexes? Juveniles? Aberrant individuals? Lone scatter blots? And I can’t put them into a phylogenetic scheme

    Uh, that’s fine, but why would you put them into a classification, then?

    Look at the base of the bird tree and tell me what it’s called. There’s a bunch of names around for it and no one to decide how to talk about it so that everyone knows what he or she means. Thats why paleontologic papers usually have a section where they define their taxa anew or where they refer to other authors (“sensu”). But that “sensu” goes in the exact direction criticized by some as “subjective”.

    Exactly. That’s why this project is in the works.

    However, taxonomy of recent tetrapodes is rather stable

    In comparison to what?

    remember what happened between the botanists and zoologists back in the 19th century

    What did happen?

    If you would like to convince them of your system, take their worries seriously and do not simply dismiss them as irrelevant or subjective.

    Some of them are irrelevant or subjective. I agree, though, that the same discussion is being had again and again because people in different subdisciplines of biology read different journals.

    that new taxonomy

    Under the definitions for “taxonomy” I’m familiar with, phylogenetic nomenclature makes taxonomy… inapplicable. Phylogenetics finds the trees, nomenclature ties labels to carefully defined places on their branches.

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  24. 24. Dartian 3:12 am 06/4/2013

    Darren:
    Tree-based thinking and the idea of nested clades do away with any such need

    Unfortunately, they do not – for the simple reason that many and perhaps most people (including professional biologists) just Do. Not. Get. Tree-based. Thinking.

    Really, they just don’t. The occasional genius aside, evolutionary tree-based thinking doesn’t come intuitively to people. It has to be taught to them (it had to be taught to yours truly as well), and even then surprisingly many people fail to fully grasp it and its implications. (If you doubt that, just think of how many times you’ve had to explain even to your colleagues how to properly read a cladogram. Then imagine how much more difficult it must be for so-called laypeople.)

    The bottom line here is the simple fact that most people just aren’t, and won’t be, professional phylogeneticists. Like it or not, most people you’ll deal with during your career will probably ‘think’ in ranks/categories, not trees, when you discuss the relationships of organisms with them. And perhaps I’m overly cynical, but for me that’s a pragmatic reason to maintain ranks (not necessarily the Linnaean ranks, mind you) of some kind in our classification scheme (whichever one we may ‘finally’ end up with).

    David:
    The only attempts at making rank assignment objective that I’ve seen involve the ages of taxa.

    They are not just “attempts” anymore. Assigning taxa to different genera – and, to an increasing extent, families too – according to the divergence dates between their respective lineages is the de facto current state of affairs across much of mammalian taxonomy (especially so regarding the classification of the best-studied groups such as primates, carnivores, and artiodactyls). Saying that (even it’s only in jest) current biological classification schemes “depend entirely on the whim of each taxonomist” is, at best, only a half-truth.

    Incidentally, speaking of names: The post-ennoblement surname of the bloke that we all keep referring to here (even if only indirectly) was not ‘Linné’ – it was ‘von Linné’. But there’s really no reason to call him that either, at least not in the current context. His relevant works were published under his original surname, ‘Linnaeus’ – let’s just call him that.

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  25. 25. David Marjanović 9:41 am 06/4/2013

    They are not just “attempts” anymore. Assigning taxa to different genera – and, to an increasing extent, families too – according to the divergence dates between their respective lineages is the de facto current state of affairs across much of mammalian taxonomy (especially so regarding the classification of the best-studied groups such as primates, carnivores, and artiodactyls).

    Crazy neontologists. :-) Will be interesting to see how far they manage to carry that. Is there any such classification that contains any fossils?

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  26. 26. John Harshman 11:49 am 06/4/2013

    Assigning taxa to different genera – and, to an increasing extent, families too – according to the divergence dates between their respective lineages is the de facto current state of affairs across much of mammalian taxonomy

    I didn’t know that. Do you have a citation or two? Sounds like a bad idea.

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  27. 27. naishd 12:01 pm 06/4/2013

    Regarding what Dartian refers to, I’ve certainly heard of people doing it but didn’t realise it was the “de facto current state of affairs”. It can’t work, at least not if there are Cretaceous platypuses and whatnot. Remember that Sibley and Ahlquist tried the same thing with birds (that is, they tried to tie the rank they used to the antiquity of the respective clade). It didn’t work out.

    Darren

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  28. 28. John Harshman 4:10 pm 06/4/2013

    Actually, I’d say it worked out all right. Or it would have worked out if their genetic distances were all reliable and ultrametric and if their topology were correct. Perhaps you’re saying that the reason it didn’t work out is that the distances weren’t ultrametric, not to mention unreliable, and their topology was often wrong? The latter two problems could be fixed, but the first probably can’t. Not even with BEAST.

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  29. 29. Halbred 6:01 pm 06/4/2013

    I can attest to Dartian’s claim that people just don’t get cladograms. I’ve tried to explain many times to many laypeople that birds, for instance, aren’t just maniraptors but also theropods, dinosaurs, archosaurs and–this is where I lose them–reptiles.

    In these people’s minds, “reptiles” exists as a subset of living animals that are scaly and cold-blooded. I was asked a few nights ago if ground sloths are mammals (rather than dinosaurs). That’s another GIGANTIC roadblock in people’s minds: if it’s extinct, it must be a dinosaur. I merely pointed out that ground sloths have hair, so they must be mammals. This seemed to satisfy the party in question.

    When people express disbelief that birds are reptiles, I ask what they are instead. “They’re birds” is usually the answer I get, as if birds sprung into existence without any ancestry. I usually have to draw a picture of a simplistic cladogram with names at the nodes and little cartoons representing the different animals I’m talking about. That HELPS.

    I’m not a professional in the field. I used to blog. I do this as a hobby. Cladograms and phylogenetics were NOT that difficult to learn, and in fact vastly deepened my understanding of biology and paleontology. I’m not sure why other people find it so obtuse.

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  30. 30. Heteromeles 7:52 pm 06/4/2013

    Here’s something about teaching cladistics that I learned about a decade ago: it’s like teaching algebra. Most people don’t truly get it the first time or even the second time. I learned this partly by taking multiple classes, but more, I learned it by TAing and watching how the students learned.

    It was fascinating to see two separate professors teaching effectively the exact same cladistics, in introductory and advanced courses. The professors teaching the advanced level classes were largely praised for “how good they were at teaching cladistics” and students said that “for the first time, they actually got it.” Conversely, the professors teaching introductory classes were condemned for how confusing they made it. In fact, both teachers taught essentially the same thing. The *STUDENTS* got it the second (or third) time they saw it, and they attributed this breakthrough entirely to the last professor in the line, not to their own development as scholars.

    Unfair but true.

    I’d suggest that the solution to getting cladistics out into general knowledge is a lot of repetitive teaching, just like they do with algebra. Teaching it once in a two-week unit simply won’t cut it. While I know that it’s too much to ask, I’d also suggest that instructors in advanced courses support and praise their colleagues teaching introductory material, because without those intro classes, the high-level teachers would have crappy reviews on their teaching of cladistics.

    Link to this
  31. 31. John Harshman 9:12 pm 06/4/2013

    There’s now a text book explicitly devoted to teaching tree-thinking (and that’s the title, in fact). I wonder if it works. It’s a pretty good book, but I can’t tell, since I already know how to do it.

    Link to this
  32. 32. helderdarocha 10:23 pm 06/4/2013

    Wow! Thanks John! I was wondering just a day ago if there were some book or text that would cover this topic in depth. I’ve just started studying zoology and those cladograms have been the most confusing things I’ve encountered along the way. I’m going to check it out.

    Link to this
  33. 33. Dartian 5:06 am 06/5/2013

    David:
    Is there any such classification that contains any fossils?

    I think that thus far, the only such attempts have involved hominoid primates. Off the top of my head, though, I can’t think of a specific reference – I’ll get back to this subject if one comes to my mind.

    John:
    Do you have a citation or two?

    I mentioned a few in my comments in an earlier Tet Zoo discussion thread, the one about Eld’s deer. In comment #67 there, I also list a few examples of mammalian genera that have been split purely on the basis of ancient evolutionary lineage divergence (as opposed to morphological distinctiveness).

    Darren:
    didn’t realise it was the “de facto current state of affairs”

    Much of extant primate taxonomy, in particular, has been following that principle for quite some time now. Witness the recent proposals to split Tarsius and Cebus (just to take two examples).

    It can’t work, at least not if there are Cretaceous platypuses and whatnot.

    Of course it works – you’ll just have to apply the same principle to orders that you do to families and genera. See:
    Avise, J.C. & Johns, G.C. 1999. Proposal for a standardized temporal scheme of biological classification for extant species. PNAS 96, 7358-7363.

    Sibley and Ahlquist tried the same thing with birds

    The mammalian fossil record > the avian fossil record (both qualitatively and quantitatively).

    Link to this
  34. 34. Dartian 1:09 am 06/6/2013

    An addendum to my previous comment: Divergence-date-based classification of mammalian genera usually result in splits, but not always. For example, most workers today prefer to lump all extant bears (with the exception of the giant panda and the spectacled bear) in the genus Ursus, rather than place them into several monotypic genera (as was usually done in the 20th century). That follows from the results of recent phylogenetic studies which suggest that the ursine bears represent a very recent (i.e., Pliocene) radiation.

    Link to this
  35. 35. David Marjanović 9:34 am 06/6/2013

    I can attest to Dartian’s claim that people just don’t get cladograms. I’ve tried to explain many times to many laypeople that birds, for instance, aren’t just maniraptors but also theropods, dinosaurs, archosaurs and–this is where I lose them–reptiles.

    Seriously, dump the name Reptilia and use Sauropsida instead, because that’s what you actually mean.

    Goodrich (1916) stopped very short of giving Theropsida and Sauropsida branch-based definitions. The paper is truly amazing to read.

    I’d suggest that the solution to getting cladistics out into general knowledge is a lot of repetitive teaching, just like they do with algebra.

    What finally made me get it was the book The Mistaken Extinction. Why? Because it has enough pictures to actually explain what it says.

    There’s now a text book explicitly devoted to teaching tree-thinking

    …I’m ordering it right now. 60 $ for 500 pages of phylogenetics is irresistible. I’m not quite as familiar with model-based phylogenetics as I’d like.

    Link to this
  36. 36. David Marjanović 9:44 am 06/6/2013

    I mentioned a few in my comments in an earlier Tet Zoo discussion thread, the one about Eld’s deer.

    I just read it again, and I facepalm for my memory.

    Link to this
  37. 37. Dartian 1:06 am 06/7/2013

    David:
    Is there any such classification that contains any fossils?

    I have found such a reference for you – sort of. It’s this book (in particular, chapter 5):

    Cameron, D.W. & Groves, C.P. 2004. Bones, Stones and Molecules: “Out of Africa” and Human Origins, Elsevier Academic Press.

    I said “sort of” because the book has two authors, and they disagree on the issue of hominid nomenclature. Colin Groves would have preferred to place all hominids that are more closely related to Homo sapiens than to Pan (except for Orrorin and maybe Sahelanthropus; the authors could not resolve the phylogenetic position of the latter in their cladistic analyses) in the genus Homo*.

    * That was Groves’ position in 2004. In later publications, he has started leaning towards including the chimpanzees too in Homo.

    The other author, David Cameron (no, that’s not the current UK Prime Minister), would prefer to recognise several different monophyletic hominid genera instead. For example, in his scheme there would be only one species of Australopithecus, A. africanus (both authors are strongly opposed to recognising paraphyletic genera). In the book, the authors follow Cameron’s view on hominid nomenclature.

    Link to this
  38. 38. David Marjanović 9:17 am 06/7/2013

    except for Orrorin and maybe Sahelanthropus; the authors could not resolve the phylogenetic position of the latter in their cladistic analyses

    Now isn’t that interesting.

    Where did Orrorin come out?

    Link to this
  39. 39. Dartian 10:08 am 06/7/2013

    David:
    Where did Orrorin come out?

    Actually nowhere, because for some strange reason that’s never explained by the authors, it is not included in their final analysis! (By contrast, pretty much all other early hominin taxa known at the time, as well as a number of extant and extinct apes, are included.) They do state elsewhere in the book that they think Orrorin to be very close to the split between the human and the chimpanzee lineages, but nothing more specific than that.

    Link to this
  40. 40. David Marjanović 9:09 am 06/9/2013

    Looks like I need that book, too.

    Link to this

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