Pushback on ‘Dawndraco’ (Pteranodon UALVP 24238)

Figure 1. Pteranoodn (Dawndraco) UALVP 24238 in situ, with Martin-Silverstone tracing applied, with mandible moved and missing parts colorized. The putative rostral tip looks more like displaced manus elements.

Figure 1. Pteranoodn (Dawndraco) UALVP 24238 in situ, with Martin-Silverstone tracing applied, with mandible moved and missing parts colorized. The putative rostral tip looks more like displaced manus elements. The crest and distal wing finger do not belong to the original specimen.

A new paper by Martin-Silverstone et al. 2017
disputes the earlier study by Kellner 2010, giving a new generic name to a well-preserved putative Pteranodon specimen, UALVP 24238, Figs. 1-3). They also write: “The re-evaluation of Pteranodon sensu lato by Kellner (2010) is troubling for pterosaur palaeontology, as so much of our understanding of pterosaur ontogeny and growth stem from Bennett’s work on Pteranodon and the conclusion that Pteranodon specimens can be divided into two closely and perhaps anagenetically related species.” Bennett’s conclusions were disputed earlier here, here and here, and are nowhere in evidence here (Fig. 2). Praise for Bennett’s work needs to be limited to those items that stand the tests of closer scrutiny and analysis, Gender and ontogenetic differences recovered in Bennett’s statistical analyses are not recovered in phylogenetic analysis.

Figure 2. The Tanking-Davis specimen compared to other forms. Specimen w and specimen z appear to be the closest to the Tanking-David specimen. Specimen 'w' = Pteranodon sternbergi? USNM 12167 (undescribed). Specimen 'z' = Pteranodon longiceps? Dawndraco? UALVP 24238. Click to enlarge.

Figure 2. The Tanking-Davis specimen compared to other forms. Specimen w and specimen z appear to be the closest to the Tanking-David specimen. Specimen ‘w’ = Pteranodon sternbergi? USNM 12167 (undescribed). Specimen ‘z’ = Pteranodon longiceps? Dawndraco? UALVP 24238. Click to enlarge.

As you can see (Fig. 2) NONE
of the known Pteranodon-grade skulls would be considered conspecific in the modern world, and few would be considered congeneric. Size and crest size differences are without a doubt phylogenetic (contra Bennett and Martin-Sivlerstone et al.) as demonstrated in the large pterosaur tree. You can’t get large or have a large crest without evolving from smaller progenitors. It may also be the case that Pteranodon, like pterosaurs in general were extremely individually variable within a genus, but we’d need a time machine or a mass fossil assemblage for that.

Moreover,
UALVP 24238 had a tiny cranium, very different from the large cranium of P. sternbergi (FHSM VP 339, Fig. 2).

Figure 3. The UALVP specimen of Pteranodon. Note the lack of taper in the rostrum along with the small size of the orbit.

Figure 3. The UALVP specimen of Pteranodon. Note the lack of taper in the rostrum along with the small size of the orbit.

From the Martin-Silverstone et al. 2017 abstract:
“The previous most comprehensive study on Pteranodon [Bennett 1991, 1992m 19994, 2001] recognized two species: P. longiceps and P. sternbergi, but complete skeletons of Pteranodon are rare. One of the best preserved (UALVP 24238) has been identified as both P. sternbergi and as a new genus and species, Dawndraco kanzai. Here, the specimen is redescribed, additional portions of the rostrum are identified for the first time, new details of the specimen’s provenance and preparation history are presented, and its taxonomic placement is discussed. Whereas the shape of the rostrum appears at first glance to distinguish it from known Pteranodon, this feature is more parsimoniously interpreted in the context of sexual dimorphism; a male has a longer and therefore more shallowly tapering rostrum. Metrics from this specimen, and from published photographs and illustrations, support the conclusion that the rostrum of UALVP 24238 is not unique, and so provides no grounds for recognition of a taxon distinct from Pteranodon sternbergi. Other putatively unique features of UALVP 24238 are examined and found unconvincing.”

The rostrum is not the key trait that separates
UALVP 24238 from P. sternbergi (Fig. 2). It’s the cranium (among comparable elements preserved). The two species are related, but not conspecific. A phylogenetic analysis would have been helpful here. A set of skull reconstructions would have made things clear. Both are lacking from the new Martin-Silverstone study.

References
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Bennett SC 1994. Taxonomy and systematics of the Late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloidea). Occassional Papers of the Natural History Museum University of Kansas 169: 1–70.
Bennett SC 2001. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part I. General description of osteology. Palaeontographica, Abteilung A, 260: 1–112. Part II. Functional morphology. Palaeontographica, Abteilung A, 260: 113–153.
Kellner AWA 2010. Comments on the Pteranodontidae (Pterosauria, Pterodactyloidea)
with the description of two new species. Anais da Academia Brasileira de Ciências 82(4): 1063-1084.
Martin-Silverstone E, Glaser JRN, Acorn JH, Mohr S and Currie PJ 2017. Reassesment of Dawndraco kanzai Kellner, 2010 and reassignment of the type specimen to Pteranodon sternbergi Harksen, 1966.  Vertebrate Anatomy Morphology Palaeontology 3:47-59.
Marsh OC 1876a. Notice of a new sub-order of Pterosauria. American Journal of Science, Series 3, 11:507-509.
Miller HW 1971. A skull of Pteranodon (Longicepia) longiceps Marsh associated with wing and body parts. Kansas Academy of Science, Transactions 74(10):20-33.

wiki/Pteranodon

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4 thoughts on “Pushback on ‘Dawndraco’ (Pteranodon UALVP 24238)

  1. Gender and ontogenetic differences recovered in Bennett’s statistical analyses are not recovered in phylogenetic analysis.

    That’s because phylogenetic analysis assumes that all differences between the taxa of a matrix are phylogenetic.

    PAUP* will never tell you “nope, correct that score, it’s due to immaturity”, and neither will TNT. The reason for this should be obvious.

  2. Dave, you’re just being argumentative. When ontogeny has been tested in the LRT, even with embryos, the young ones have always nested with the mamas and papas. If the small Pteranodons were juveniles or females of the large ones, they would also nest with them. But the small ones are little different from the Germanodactylus specimens from which they arose. I’ve seen the data. The software has spoken! What is obvious is you don’t want to believe the results, whether they be figures or nestings. Or you just woke up on the wrong side of the bed…

    • Dave, you’re just being argumentative.

      I am never argumentative. I argue when I think it must be done and nobody else does it.

      When ontogeny has been tested in the LRT, even with embryos, the young ones have always nested with the mamas and papas.

      Aren’t you appalled by your own circular logic? Whenever they don’t nest with mamas and papas, you declare them different species every single time!

      If the small Pteranodons were juveniles or females of the large ones, they would also nest with them.

      No, not necessarily – that’s simply not how phylogenetic analysis works.

      Hennig himself already pointed that out; that’s what all that “thou shalt only compare comparable semaphoronts” stuff is about.

      I’ve seen the data. The software has spoken! What is obvious is you don’t want to believe the results, whether they be figures or nestings.

      The software has indeed spoken, and it has said “colorless green ideas sleep furiously” – see, its grammar is impeccable.

      What is obvious is that you don’t understand what the software does and what it doesn’t do. It has been obvious for at least 12 years. Why do you refuse to learn how the software works? It’s not a black box! Everything is documented!

      Or you just woke up on the wrong side of the bed…

      Do you have mood swings? I don’t. I’m unusually stable.

  3. David,
    re: “Whenever they don’t nest with mamas and papas, you declare them different species every single time!”
    Yes. Scientists report results. They don’t bend them to expectations.
    re: “No, not necessarily – that’s simply not how phylogenetic analysis works.”
    You’re working from a paradigm that juvenile pterosaurs are different from their parents when the only phylogenetic analysis that tests this shows that embryo and juvenile tritosaurs (including pterosaurs) nest with their parents. No exceptions so far. With regard to Pteranodon, please review the crania and post-crania that show a wide variety of morphologies among large forms, all adults.
    re: “Hennig himself already pointed that out; that’s what all that “thou shalt only compare comparable semaphoronts” stuff is about.” For readers (and me) who don’t know what a ‘semaphoront’ is: “A semaphoront is an organism at a specific life history stage such as the larval stage of an insect or the seed of a pine.” Here we’re talking about isometric growth in tritosaur lepidosaurs, not distinctly different tadpoles of Pteranodon.
    re: “The software has indeed spoken, and it has said “colorless green ideas sleep furiously” – see, its grammar is impeccable.” Please make sense.
    re: “Why do you refuse to learn how the software works?” I report results. The results produce gradual accumulations of derived taxa in tree topologies that fill gaps between disparate morphologies and that’s how evolution works. That you don’t like such results when it comes out of my work is your issue. When the same results come from say, Stocker et al., you accept them.

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