Whether Clades Should Have No Name


I am posting this here because I don’t want to log down Darren’s blog with my comment, where he has posted his perspective on the new paper, so it’s going here.

Valentine Fischer, Michael Maisch, and a host of other authors have a new paper out in PLoS ONE dealing with the perennial issue of ichthyosaur taxonomy. There, they erect a new taxon Acamptonectes densus for an ophthalmosaurine ophthalmosaurid located in the Early Cretaceous, defying previous regards that ophthalmosaurids didn’t survive the end of the Jurassic. It is derived on a combination of features which are otherwise not held by an array of other taxa, including numerous autapomorphies; the morphology at hand is so distinctive that additional specimens from across Europe have been referred to the Acamptonectes umbrella, or to the type species, including a paratype from Germany, where the holotype derives from England. Darren Naish, one of the coauthors, has his own write-up at TetZoo. In their phylogenetic analysis, Fischer et al. (2012) find a topology for ophthalmosaurids in which two forms appear paraphyletic, Ophthalmosaurus and Platypterygius. This is supported by the inclusion in the latter of two taxa (Athabascasaurus bituminensis and Caypullisaurus bonapartei) within the array of erstwhile Platypterygius species hercynicus and australis, and in the former by the presence of Acamptonectes densus sister to Ophthalmosaurus natans, which is a sister-taxon to icenicus, the type species.

Skull of SNHM1284-R, paratype of Acamptonectes densus. From Fischer et al. (2012).

But if that were all, this wouldn’t be much of a post, and I fear I must break into a repeat of my eternal bogeyman, the argument about the Linnaean System and its effect on systematics and nomenclature.

The authors write:

Our analysis failed to recover monophyletic Ophthalmosaurus and Platypterygius. The polyphyletic, wastebasket nature of Platypterygius has already been noted by other authors [34], [57], [61]. Our consensus tree suggests that O. natans should be given a distinct generic moniker since it does not group with the type species of Ophthalmosaurus. As is well known, the name Baptanodon is already available for it. However, O. natans is united with A. densus due to a single homoplastic synapomorphy (reduced crown striations, char. 1) and we do not yet consider this sufficient evidence to resurrect use of the name Baptanodon. Because of the obvious differences between Acamptonectes and the Ophthalmosaurus species, we do not consider it preferable to include Acamptonectes within an expanded version of Ophthalmosaurus. Further study should help clarify the affinities, and hence taxonomy, of these taxa.
[italics in the original; 34 is Fischer et al. (2011) and 61 is Druckenmiller & Maxwell (2010), both referenced below; 57 is an unpublished ms submitted to Acta Palaeontologica Polonica, and is available here -- note that the referenced date in the current paper, "2011," is no longer valid.]

Phylogeny of Ophthalmosauridae, from Fisher et al. (2012).

Now, my issue may or may not be clear at this point, but just in case, I again don’t care about the nomenclature, but about the rather screwed up mixture here of phylogenetic nomenclature:

The main topological novelty of our analysis lies at the base of the ophthalmosaurid lineage, which diverges into two clades: Ophthalmosaurinae, which is quite similar to the basal Arthropterygius; and Platypterygiinae, which is markedly derived from the ancestral Arthropterygius stock (see below for a phylogenetic definition of these clade names). Both these subfamilies have been informally used in the literature in the past [79], but have never been defined or recovered in cladistics analyses until now.
[italics in the original; 79 is Arkhangelsky (2001), referenced below]

It should be noted that paraphyly is only present so long as the use of extra “genera” for various taxa is chosen, and when the taxa are treated as clades with confined definitions that cannot include the other species under their umbrella — or if one is treating the ranks as viable elements of the nomenclature. Paraphyly is not an issue when all clades are given equal weight or utility; while one ranked taxon like a “genus” cannot contain another, an unranked clade named Ophthalmosaurus can contain an unranked clade named Acamptonectes, but I do not believe this is what the authors mean. The authors clearly use rank-based taxonomy to support use of some of these taxa, while at the same time seem to offer a non-generic function for the name Ophthalmosaurus, one which can include supposed “genera,” which is to suggest either they are going to treat it as a non-genus rank (i.e., a clade based on a former genus name), or that they are going to play the infra-rank game and try to shuffle the ranks around to make this make sense. A potential solution could have been solved by employing Baptanodon for natans, and eschewing the argument that Ophthalmosaurus was in any way paraphyletic or, in that shocking twist of events, name densus as a species of Ophthalmosaurus and enforce the lack of paraphyly in the form.

The commentary in the paper on the referral of the taxon and its relationships seem like just as much information could be had were the authors to have named a new species of Ophthalmosaurus, rather than a new binomial genus-species couplet. The value of the binomen is, of course, increased recognition and utility in further phylogenetic analysis without having to restate referral of the taxon to this or that genus, although the problem arises no matter when more and more clades are coined to include ever fewer “genera.” The problem is that, while aware of the issue, the authors appear to exacerbate it by mixing their taxonomic schema to allow ranks a viable option, and phylogenetic nomenclature in qualifying these ranks according to a cladistic analysis.

Other than that, the paper details re-assessing the taxonomic complexes of Ichthyosauria and its range through time, using metrics of species density to time to track whether there were actual extinction events around the Jurassic-Cretaceous (J/K) boundary. The prevalence of ophthalmosaurid taxa across this boundary implies that the “event” in ichthyosaurian context didn’t actually exist, and that this is related to recovery biases (the material is simply not being recognized) and preservation biases (the material is not becomes preserved or found). This may relate to poor preservation in marine strata in the Neocomian (early and middle Early Cretaceous).

A Not So Short Piece on “Acamptonectes densus” Versus “Ophthalmosaurus densus

From comments in Fischer et al. (2012) and in other papers, it is clear that Ophthalmosauridae as traditionally conceived is homoplastic in its distribution of characters among sub-members, which group three clades, two of which are grouped into the Platypteryginae. These conceptions begin breaking down when the taxa used to represent them become more “generic” in regards to the concepts for which they were originally coined. Because of this, one must think that as traditionally conceived they may not be useful. The opposite tack is often preferred by systematists attempting to preserve the functional relationships of ranked nomenclature (the Linnaean System) while developing the rank-free systems (especially phylogenetic nomenclature, and certainly the PhyloCode). It is one of my biggest disagreements with the group, as the baggage these taxa represent, including the effect that functional use of -aceae and -idae has on systematists in general. These represent “families,” either botanical or zoological (respectively), and the terms are even used by those who prefer phylogenetic nomenclature and the PhyloCode over the Linnaean System. Their prevalence is ingrained in our systematics.

The authors attempt to resolve the shakiness that results in phylogenetic analysis by placing apparent unique taxa off in their own little “genera.” This solves the problem of what you do when shifting arrangements may require new reports of new combinations (“comb. nov.”) for every time one finds a novel array of species, which gets tedious, but it produces a problem in that what results is merely a moving of the goal posts. This bit concerns the Linnaean System and phylogenetic nomenclature. Eventually, this solution results in a plethora of fossil species each with their own unique binomen, and then the neontologists start laughing at you; they point to taxa like Coleoptera and Cichlidae, the latter which contains about 2,000 species in over 200 recognized “genera,” and an average of over 9 species per “genus.” Such a value overwhelms paleontology, which are used to thinking that any species that they recognize is unique enough to warrant useful taxonomy, but I think for the sake of recognition erect a “genus” for it. I’m not saying neontologists and zoologists have it right, recognizing more species in fewer “genera,” as they are also constrained by the trap of treating the “genus” as a viable element of their taxonomy. But the paleontological community has a sense that it is more useful, and preferable, to name what they think are two different taxa, and this leads to problems in itself.

My preference for dealing with “obvious” rank names like this is to simply discontinue their use, define new clades which approximate their content, and move on. This often happens in similar circumstances when a taxon, like a species, is no longer useful for what it historically contains, but the inverse: A species may be no longer useful because its content changes, specimens formerly diagnostic of the species are remove, made types of new species, or reassigned, but the species is still useful and the name may be shifted to something functionally different, as was the case with Iguanodon anglicus (former type species of Iguanodon, which is now bernissartensis [ICZN, 2000]) and Coelophysis bauri (which was based on specimens that may have been quite different from their current more famous Ghost Ranch-based content, and which received the name Rioarribasaurus colberti [Hunt & Lucas, 1991] to emphasize this [ICZN, 1996]). Both of these cases are different, but involve this sense of shifting a useful name or material to preserve the idea of the animal it represents. Instead, it may be necessary to simply abandon the use of names whose baggage leads to the perfunctory inclusion of ranks in remarking about them, such as when saying “new genus and species,” when what one really means is a new taxon, using a representative binomen.

When Fisher et al. (2012) regard the possibility that Ophthalmosaurus may contain the species densus, they are considering the option that Ophthalmosaurus is a genus, and densus a species; they are not necessarily concerned over Ophthalmosaurus as a clade that may contain another clade named Acamptonectes. But the intriguing phrasing leads one to wonder that that could be a solution, and that Ophthalmosaurus, itself almost a functional synonym of Ophthalmosaurinae, may not be quite  as useful as it seems in the formulation it is given. The authors already consider it paraphyletic, practically a wastebasket taxon. Currently, Ophthalmosaurus is the container for about four species: icenicus (the type species, Seeley, 1874), natans (the type species of the preoccupied Sauranodon Marsh, 1879, and which is considered to contain the material in what Marsh called Baptanodon, in four species [n1]), saveljeviensis (the type species of Paraophthalmosaurus Arkhangelsky, 1997) and yasikovi (the type species of Yasykovia Efimov, 1999) and periallus (Fernández, 1999). Such an arrangement makes you wonder why we aren’t simply talking about different taxa alongside Ophthalmosaurus, which only contains icenicus.

I don’t think the taxa as recognized are so useless as to require renaming every species to new “genera” (or recognizing those that have been established. I wonder, instead, whether the authors could (should) have named densus to Ophthalmosaurus, and increased the robustness of their analysis further to enable resolution, as well as applying various tests to the data matrix to find problems with it and evaluate this with respect to the resulting cladograms. Doing so might as qualified the decision to make new nomenclature, but rather the authors leave this to further analysis. This is a case of “name first, question later” save that once established, it seems these “genera” become rather hard to get rid of, and condensing species back into complexes without special nomenclature is an action that tends to be eschewed (see my and Mickey Mortimer’s reactions to Greg Paul’s latest book here and here). Lumping, in this case, a project fraught with treading on men’s toes, for you risk hurting their intellectual territory, while the splitting off of new taxa can only at the least bring the ire of one irate blogger. If I had a choice, I’d name the new form in a binomen but only with respect to the field in which its contained: if the new form might be easier used as a “species” in a “genus” which is already available for it, don’t rock the boat and claim paraphyly by coining a new “genus;” just name a new species, and move on. After all, the authors say “[f]urther study should help clarify the affinities, and hence taxonomy, of these taxa.”

Phylogeny of Fischer et al. (2012), with alternate nomenclature if “Ophthalmosaurus” and “Platypterygius” were treated as any other clade rather than special “genera.” Terms as in Fischer et al., as in the phylogeny further up in the text.

Were we to treat “genera” as just any other type of clade, instead of a special clade, the above phylogeny might be interesting, but of course it would be very, very different in execution when applied to all known taxa. The alternative to this, somewhat of an extreme, is that each species would deserve a new “generic” container, so that Ophthalmosaurus natans and Platypterygius australis would require new taxa named for the species. The nomenclature applied above takes the least effort to work, but of course it qualifies as special categories the already named monospecific forms. One may then be tempted to simply remove these “generic” labels in favor of where the species were originally referred when the “genera” aren’t paraphyletic. But, it is harder to get rid of “genera” than to coin them.

Whether Clades Should Have No Name

There is value to not naming clades, include immediate supraspecific taxa, commonly “genera.” This includes peppering the literature with more and more essentially redundant taxa. Above, virtually all ichthyosaur “genera” contain merely one species, or a single valid species with a large number of rather doubtful potentially nonviable species. Naming species, as unique entities, is fine, but these aren’t clades in the essential sense, they are merely containers of a population-like group of fossils, or to which fossils may be referred. It tends to be unconventional, however, for systematists to include new species or “genera” within other erstwhile “genera.” As above, Opthalmosaurus would be a clade that includes a type species and a subclade called Acamptonectes, while Platypterygius is a clade that would include two subclades, named Caypullisaurus and Athabascasaurus, respectively, and two other unassigned subclades. In today’s world, this would almost amount to “subgenera,” and each of those other species would also require a new name. But there is no substantive reason why we should fill up the gaps in the tree above save to “balance” the appearance of the tree, or have something “special” to use to refer to. That point, of course, tends to come at the expense of the use of the species name, so that one only discusses Acamptonectes, not densus. I make a measurable attempt to avert this habit on this blog.

[n1] Marsh took, in his sincerest humility, the effort to distinguish a new “order” of reptiles for this group of ichthyosaurs, Sauranodonta, but for which Ichthyosauria has been used to approximate (under the premise that — using the Linnaean Systems organization of ranks — Blainville’s name, predating Marsh’s, had priority). Marsh has a preference for distinguishing many “orders” of reptile. It was almost his thing.

Arkhangelsky, M. S. 1997. On a new ichthyosaurian genus from the Lower Volgian Substage of the Saratov, Volga Region. Paleontological Journal 31:87–90. [English edition of Палеонтологический Зурнал.]
Arkhangelsky, M. S. 2001. The historical sequence of Jurassic and Cretaceous ichthyosaurs. Paleontological Journal 35:521–524. [English edition of Палеонтологический Зурнал.]
Druckenmiller, P. S. & Maxwell, E. E. 2010. A new Lower Cretaceous (lower Albian) ichthyosaur genus from the Clearwater Formation, Alberta, Canada. Canadian Journal of Earth Sciences – Revue canadienne des sciences de la Terre 47:1037–1053.
Efimov, V. M. 1999. Ichthyosaurs of a new genus Yasykovia from the Upper Jurassic strata of European Russia. Paleontological Journal 33:91–98. [English edition of Палеонтологический Зурнал.]
Fernández, M. S. 1999. A new ichthyosaur from the Los Molles formation (Early Bajocian), Neuquén Basin, Argentina. Journal of Paleontology 73:675–679.
Fischer, V., Maisch, M. W., Naish, D., Kosma, R, Liston, J., Joger, U., Krüger, F. J., Pérez, J. P., Tainsh, J. & Appleby R. M. 2012. New ophthalmosaurid ichthyosaurs from the European Lower Cretaceous demonstrate extensive ichthyosaur survival across the Jurassic–Cretaceous boundary. PLoS ONE 7(1):e29234.
Fischer, V., Masure, E., Arkhangelsky, M. S. & Godefroit, P. 2011. A new Barremian (Early Cretaceous) ichthyosaur from western Russia. Journal of Vertebrate Paleontology 31(4):1010–1025.
Hunt, A. P. & Lucas, S. G. 1991. Rioarribasaurus, a new name for a Late Triassic dinosaur from New Mexico (USA). Paläontologische Zeitschrift 65(1/2):191-198.
International Commission on Zoological Nomenclature. 1996. Opinion 1842. Coelurus bauri Cope, 1887 (currently Coelophysis bauri; Reptilia, Saurischia): lectotype replaced by a neotype. Bulletin of Zoological Nomenclature 53(2):142-144.
International Commission on Zoological Nomenclature. 2000. Opinion 1947. Iguanodon Mantell, 1825 (Reptilia: Ornithischia): Iguanodon bernissartensis Boulenger in Beneden, 1881 designated as the type species, and a lectotype designated. Bulletin of Zoological Nomenclature 57(1):61-62.
Marsh, O. C. 1879. A new order of extinct reptiles (Sauranodonta) from the Jurassic Formation of the Rocky Mountains. American Journal of Science 17:85–92.
Seeley, H. G. 1874. On the pectoral arch and forelimb of Ophthalmosaurus, a new ichthyosaurian genus from the Oxford Clay. The Quarterly Journal of the Geological Society of London 30:696–707.

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16 Responses to Whether Clades Should Have No Name

  1. Paul de la Salle says:

    Jamie

    I’m not so sure about all the autapomorphies cited. To me the animal has such striking similarities to O. icenicus that it would make sense to use the name O. densus. Why do we keep inventing new names that bear no relevence to the source genus?

    Paul

    • The issue I try to bring up here is not the identification itself; for that, I suggest following up with the authors themselves. If the taxon is new, and you’ve got a number of specimens to support it, then it makes sense to name it. The issue is of scope. Several authors lately naming new taxa do so with a new, unique genus-species couplet (binomen), regardless of its potential affinities. The number of autapomorphies is often used by some systematists to push the “reasonableness” of coining a genus, but there is no reason for this aside from “balancing” all the names, making them seem equivalent, and allowing one to use one name (Acamptonectes) when they mean the whole name. This is a hold-over from the rank-based system, and in using this, they accept that “genera” and the species in general are two different things.

  2. Meh, it really doesn’t matter as long as in any plausible topology any genera that exist are monophyletic. So keeping natans in Ophthalmosaurus is bad if densus is separated, and if I were the authors I would have just called the former Baptanodon since the name already exists anyway. If Baptanodon had never been named, I would call it O? natans until a more detailed study has been done. This is just like the Giraffatitan situation where it should be B? brancai at worst, and Giraffatitan at best since that was already named. But it would have been fine to just keep natans in Ophthalmosaurus and put densus in there too, just as I wouldn’t mind Brachiosaurus brancai as long as we also used B. mcintoshi (Abydosaurus not Ultrasauros), B. jonesi, etc.. But people get more recognition for naming genera, and feel probably correctly that if they lump species a splitter will come along soon and name the new genus themself anyway. So the describing author won’t get the credit, which is understandibly annoying. This is also why I doubt Lamanna et al. will follow your advice on Archosaur Musings to leave the CM caenagnathids unnamed or lumped as C. pergracilis. You are VERY unique in apparently not caring about nomenclatorial credit, probably in part because you don’t have a career where having new genera attached to your name is job and grant security.

  3. Darren Naish says:

    It would have been fine to post a (hopefully shorter) version of these thoughts at Tet Zoo. Note that the first author’s given name is Valentin, not Valentine. Contrary to some of the statements above (including by Paul de la Salle), _Acamptonectes_ is morphologically unusual compared to other ophthalmosaurids – and if ‘distinctiveness’ is all we were interested in, it is subjectively ‘different enough’ to warrant a new binomial (rather than being named as just another _Ophthalmosaurus_). As I’ve said a few times on Tet Zoo – and is increasingly recognised by ichthyosaur workers – virtually all/all traditionally recognised ichthyosaur genera are taxonomic dustbins, the monophyly of which is doubtful and in need of testing. As you note above, it has already been widely suggested that _Ophthalmosaurus_ of tradition is not monophyletic and that the American species (at least) needs its own ‘genus’. So, when _Acamptonectes_ grouped within _Ophthalmosaurus sensu lato_, the most sensible interpretation is that this confirms the non-monophyly of _Ophthalmosaurus s. l._. As we say in the paper, one solution is to use the respective ‘generic’ names _Baptanodon_ in addition to _Acamptonectes_ and _Ophthalmosaurus_, but another is to lump all into an expanded _Ophthalmosaurus_. I wouldn’t prefer the latter option since lumping obscures the many differences between _densus_ and the _Ophthalmosaurus s. l._. As for why we weren’t more bold in using _Baptanodon_ for _O. natans_: we opted to be conservative and to wait for a detailed study that better establishes the distinctive nature of this taxon relative to _O. icenicus_. Nothing wrong with that.

    • I get what you are saying, and appreciate your reply.

      The nature of “taxonomic dustbins” for a variety of taxa exist for anything named during the 1800s, early 1900s, as an artifact of the perspective of the authors and anatomists at the time. This includes Iguanodon, Titanosaurus, Cetiosaurus, etc. Note that while some of these names have been largely discontinued, others have been retained, generally for “historical” purposes. Why abandon a name when it can still be useful to tie old and new nomenclature together? I argue that the reasoning for providing new taxonomy is not necessarily predicated on the view that the old forms and the old names are “uncertain.” When confirmed, when narrowed to their smallest definable units, such as with Maxwell on Stenopterygius, on the basis of morphometric analyses, these forms can be retained and found to have innate value. Add in the historical value, and you get to keep old names. It’s when the old names are attached to really bad crap (Iguanodon anglicus!) that the “dustbin” argument makes sense and, I think, only then. Otherwise, the use of the “abandon dustbins” approach should force us to abandon quite a few other names, without any excuses to keep it (be it Iguanodon, Cetiosaurus, Titanosaurus … or Ophthalmosaurus). What’s interesting is that this isn’t even a “slippery slope” argument: it’s applying the same exact approach across multiple groups. Even when phylogenetic analysis supports a monophyletic clade when certain desires for “distinctiveness” are removed, the nomenclature is still supported by dismissal of the “dustbin,” which tells me the whole point of the nomenclature is a rejection of the stability of the name Ophthalmosaurus, which begs the questions: Why are you still using Ophthalmosaurus?

      Maxwell, E. E. 2012. New metrics to differentiate species of Stenopterygius (Reptilia: Ichthyosauria) from the Lower Jurassic of southwestern Germany. Journal of Paleontology 86(1):105-115.

  4. Darren Naish says:

    Sorry, I don’t understand your point. “Rejection of stability of the name Ophthalmosaurus“? We didn’t do this: we unambiguously use Ophthalmosaurus for the type species O. icenicus, but find the ‘expanded’ version of the ‘genus’ to be paraphyletic. There are no plans to give up on the name Ophthalmosaurus, and indeed you couldn’t do this given the fine and satisfactory nature of the holotype (NHMUK R2133, described by Seeley in 1874).

    • You’re giving up on the name as anything but a monospecific “genus.” A binomial “species.” You then prevent or even argue against use of Baptanodon for natans, which is really what renders the taxon “paraphyletic.” The alternative was to simply name the new taxon to a species of Ophthalmosaurus, something my little graphic in the post was meant to show. If it was either insufficient, or you simply disagree with an underlyign premise, that you don’t “get” the argument, I understand. But I think you “get” the core principle, that you chose a new “genus-species couplet,” despite the fact that this act — and possibly the recognition of Baptanodon, which you set aside for later — renders Ophthalmosaurus paraphyletic (and not the distinctiveness of the species itself).

  5. Darren Naish says:

    Ok, I “get” the core principle, I just didn’t get your explanation because (as usual) I cannot penetrate the way you worded it, sorry. No, we are not “preventing or arguing against” use of Baptanodon – I say again that we opted to be conservative and wait further study. So, for now we say that Ophthalmosaurus as currently construed is paraphyletic. Firstly: so what? I’m sure you’ll agree that there’s nothing wrong with provisional nomenclature. Secondly, no, we’re not giving up on the notion of “anything but a monospecific genus”, since any taxon found to group closer to O. icenicus than anything else could, in our phylogeny, be attributed to Ophthalmosaurus sensu stricto (e.g., potentially, the Nettleton cf. Ophthalmosaurus).

    And I’ll also make the point again that, while densus could be included within Ophthalmosaurus should anyone so wish it, it is (in our opinion) ‘distinct enough’ from the species typically included in Ophthalmosaurus to deserve obvious separation: even small fragments (vertebrae, shards of snout etc.) of Acamptonectes can be attributed to this taxon – something not typically true for the samey species usually classed in the same ‘genus’. Using a distinctive binomial for Acamptonectes is the most useful and sensible option when it comes to the purposes of communication.

    • I don’t think you understand, though you actually do seem to “get” my argument at the beginning.

      How many posts do I have to write, such as the post immediately following discussing the new ichthyosaur taxonomy — where I discuss I would rather refer the Hell Creek oviraptorosaur to an established taxon rather than create new taxonomy — before someone “gets” that I would prefer NOT to establish “provisional” taxonomy? That approach is sloppy and self-serving, in that its purpose is not to make a more reasoned argument but an excuse to name new taxonomy. If you are uncertain about the taxonomy of a form, don’t name it … but you seem to argue the opposite conclusion: Name it, let others sort it out! I can hear the devil chuckling.

      Where is the distinction metric that is being used to distinguish the various hypotheses? Namely: 1) referring the specimens to an established species, 2) referring the specimens to a new species in an established genus, and 3) referring the specimens to a new species in a new “genus”? What methodology is used to appreciate a full “genus-species couplet” for new taxa, rather than new species in old “genera,” or any one of a variety of options at your disposal? Note that had you NOT named the new taxon save as a species, and retained your uncertainty about “Baptanodonnatans, Ophthalmosaurus would be monophyletic. It only, ever, becomes paraphyletic when you recognize a new “genus” within its midst. I think, despite my handy graphic — which I’ve yet to be told is unclear on this — can resolve the issue without recourse to the taxonomy Fischer et al. propose. There is no metric involved, Darren, because no such metric exists, there is no such thing as a “generic-o-meter.” This is a taste issue. Communication, however, is merely served in a system where every new taxon is a “genus-species couplet” regardless of how distinctive it is; the only other alternative is where “Ophthalmosaurus densus” serves the interests of the authors for communicating a particular idea, such the quality or nature of the “genus,” which is otherwise absent in the paper.

  6. Darren Naish says:

    Hmm, you’re right: I don’t understand you. As I said above, there are good reasons for thinking it useful that densus should be named as distinct relative to Ophthalmosaurus. This is what we did.

  7. Valentin Fischer says:

    Dear Jaime,

    As we state in the paper, both the species O. icenicus and O. natans (and the old O. monocharactus, or the Nettleton material) are fairly similar in morphology (even metrics such as the relative size of the humeral facets, the ratio of the extracondylar area of the basioccipital etc. support this). On the other hand, we have 3 Hauterivian specimens and more than a dozen Cam. Greensands ones that markedly depart from that “Ophthalmosaurus morphology”. The best course of action is therefore to distinguish it from Ophthalmosaurus. But, as we show with the phylogenetic analysis, some characters, previously considered as autapomorphic of Ophthalmosaurus are actually indicative of a peculiar clade of ophthalmosaurids. We won’t repeat it again on this blog, I think you have our point on that matter.

    Actually, you appear to use genera as (sub)families. Why not go back to the early 1900’s and use Ichthyosaurus for all species? That would make it monophyletic, but you hide a lot of information this way. You speak about being “certain” about taxonomy. How can someone be bold enough to be “certain” about the taxonomy of fossils? Please apologize my tone, but you have a dangerous way to make science.

    You are and some commenters are implying that we name new genera for fame or by arrogance. First, it is naive to think the strength of the paper lies in the new genus. At the same time, you suggest to drop Mollesaurus, Caypullisaurus, Maiaspondylus and Acamptonectes and go back to the good ol’ Ophthalmosaurus and Platypterygius, which is immensely more arrogant. Please show some humility.

    • Valentine Fischer, thank you for replying. Perhaps I can cover a small misconception that seems to run rampant whenever I discuss species with Darren Naish and others. You write:

      Actually, you appear to use genera as (sub)families.

      I think perhaps this pervades the discussions I have with those who coin new taxonomy while using the Linnaean System. The assumption is that “subfamilies,” like “genera,” are real, or are useful. I simply disagree, under the premise that they are more subjective than the taxa themselves, and the operating belief that they have value other than the taxa they are usually applied to. It should be apparent that this is not an argument I make on my own, but I clarify it elsewhere on this blog here, here and here. Unranked classification systems, which I offer in the post, can be simple in application by merely removing the controlling presence of ranks. At this point, all non-species taxa are clades, and their relationship to one another is purely phylogenetic. This is the “umbrella” perspective that prefaces every argument I make in regards to “genera.”

      Why not go back to the early 1900′s and use Ichthyosaurus for all species? That would make it monophyletic, but you hide a lot of information this way. You speak about being “certain” about taxonomy. How can someone be bold enough to be “certain” about the taxonomy of fossils? Please apologize my tone, but you have a dangerous way to make science.

      You are and some commenters are implying that we name new genera for fame or by arrogance. First, it is naive to think the strength of the paper lies in the new genus. At the same time, you suggest to drop Mollesaurus, Caypullisaurus, Maiaspondylus and Acamptonectes and go back to the good ol’ Ophthalmosaurus and Platypterygius, which is immensely more arrogant.

      Unfortunately, this is where the line gets drawn in the sand. You say that I seem to be arguing something I never have. You invoke the “slippery slope” argument, providing an extreme to an argument no one has actually argued, to avoid having to discuss the actual topic argued. This allows you to have your way (naming “genera” and species) when what I was arguing was the discontinuation of ranks entirely, not the abandonment of the arrangement of taxa themselves. Perhaps you think they are the same thing, or are conflating my argument with theirs’? Also, given the image I offered specifically used Mollesaurus, etc., I think you are applying to me arguments you hear from others, or conflating theirs with mine unnecessarily.

      I do argue that perhaps the use of the new nomenclature is for fame, but I think I have you [or rather, systematists in general rather than you specifically] on this one, but not for the sake of malice do I attribute this to you: It is for the purpose of increasing your CV, for acclaim for your institution, and for the function of garnering more attention to your work (for future employers, impact of the paper and journal, etc.). The title of the paper begins “New ophthalmosaurid ichthyosaurs”, while the main structure of the paper (J/K boundary-crossing group of ichthyosaurs, recognition of a morphologically close range of taxa across western Europe, etc.) is certainly what you mean by the main purpose of your paper (which it is, and to which I have no comments on). How would your paper have fared had it not included new taxonomy, at all, or merely named a new species of Ophthalmosaurus and left the further question to more secure phylogenetic analysis , leaving aside the “problem” of paraphyly (dependent as it is on your own nomenclature and not the morphological analysis itself)?

  8. Darren Naish says:

    I’m going to say one last thing, since Jaime’s previous comment particularly annoys me. We did not name Acamptonectes because this was the most sensational option, as Jaime says. Evidently, it is subjective as to whether a ‘new species’ or ‘new genus’ is coined when a new taxon is named, so the one unarguable aspect of this debate is that Fischer et al. described a new ophthalmosaurine that is uncontroversially regarded as a new taxon.

    What was the main ‘thrust’ of our paper? A: that ichthyosaurs survived across the JK boundary at higher diversity than thought before. Does it therefore make a difference to our argument whether densus was identified merely as a new ‘species’ within a known ‘genus’, or as a representative of a new ‘genus’? A: no, it does not, and our paper would have the same title even if we followed the idea that the name Ophthalmosaurus be used in a more inclusive fashion. In other words, we would still have had our sexy, high-profile paper, conveying the same message about ichthyosaur diversity, whatever nomenclature we had adopted. As it happens – and as I and Valentin (I say again: Valentin, not Valentine) have argued above – we find it most appropriate to use a genus-level moniker for densus, and do not feel that just using an expanded version of Ophthalmosaurus would be useful.

    • Darren, I never said you named the new taxon because it was the “most sensational” option. You are putting words in my mouth, and I think because you feel I am making a personal attack at you, or Valentin and the remaining coauthors. I am not, though you are certainly free to believe otherwise, if you do. I am alluding to a habit of systematists who do name taxa in excess of the need to communicate about taxa for the purpose of attracting attention to their work, their institution, etc. This is relevant across the globe, regardless of what kind of institution you are in, etc., and certainly has been the motive of several systematists to “outdo” one another on how many taxa they could “recognize,” no matter how spurious their reasoning. It is more interesting, perhaps, to say that Museum X has seven holotypes of new species, but Museum Y has three holotypes of new species, which are also new genera. Thus the argument here is one of scale: It just so happens that this corresponds with the tendency of systematists to treat “genera” as more valuable than species, a product of the Linnaean system and the human tendency to prefer an implied “superior” name (“genera” are capitalized, species are not, relating to their “importance”), including your own paper, where there are 10 instances, excluding figures and tables, where “Acamptonectes” is used without reference to “densus” (or “Acamptonectes sp.”); there are no instances of “densus” occurring outside of use of “A. densus” or “Acamptonectes densus”. Over half of your own conclusionary paragraph consists of discussing the new form, and this is the first half, followed by phylogenetic analysis, then application to biostratigraphic dispersal. The 22 page paper include 20 papers of osteological analysis and description of the “species.” How is one to take your argument that the first element of your analysis is about survival of ichthyosaurs over JK boundary?

      Consider that my argument doesn’t just stress that you shouldn’t have named the species to one name or another, but about the arbitrary arguments for why it’s not one taxon or another? Consider that it is possible that Acamptonectes may not even be useful for densus, nor Ophthalmosaurus, but Baptanodon, as natans “clearly” clades with densus in your analysis. However weakly these animals are “related” is irrelevant, as you offered no metric to distinguish alternate topologies and positions for the taxa presented.

      Finally … you could have brought forth the argument of a subgroup of ichthyosaurs surviving across the JK boundary without naming a single taxon, merely performing descriptive work, cladistic analysis, discussion, and moving on. This means that the nomenclature preferred was almost certainly part of the “thrust” of the paper.

  9. Valentin Fischer says:

    Its funny how you pretend to know our intentions or that of Museums curators.

    • I’m beginning to think you are uninterested in discussing the topics I’ve raised, that of the non-objectivity of the taxonomy you offer or, even worse, the extreme degree of subjectiveness the system you are trying to use places taxonomy. You mischaracterized my intentions with a fallacious “slippery slope” argument and refuse to acknowledge such, and now you claim I am pretending to know your intentions, even more that of “museum curators,” whom I never mentioned. You must be extending some other people’s actions into this conversation, and conflating them with mine, as I cannot see (nor have you described) how they apply to me. I am not sure how I can explain the case any further than the links I provided in my post or in the replies on this thread, but it is clear you 1) either did not read them or 2) will not regard them in this conversation.

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