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Pushback on ‘Dawndraco’ (Pteranodon UALVP 24238)

Friday, April 7, 2017 15:42
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(Before It's News)

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.

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.

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.

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.

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.



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