Bennett’s (2013) Revision of Pterodactylus – Part 3

Yesterday and the day before we looked at Bennett’s (2013) revision of the genus Pterodactylus. Today we’ll nest the new specimen described in Bennett (2013), BMMS 7 (Fig. 1), and examine its traits in Bennett’s view and contrast those using DGS (digital graphic segregation /Photoshop) and phylogenetic analysis employing several hundred traits. Bennett (2013) continues to avoid phylogenetic analysis in favor of a statistical chart of a dozen bone lengths as shown here.

BMMS 7 the new Pterodactylus

Figure 1. Click to enlarge. The new Pterodactylus, BMMS 7, described by Bennett (2013) compared to its tested sisters, P. antiquus and Ardeadactylus (formerly Pterodactylus longicollum), all to scale. BMMS 7 is shown as traced by Bennett (2013, grayscale), as traced using DGS and slightly reconstructed (both colorized). IF these were birds they would be distinct species and perhaps distinct genera, but they are pterosaurs and sister taxa until intervening specimens come forward. In P. longicollum the process within the NAOF appears to be displaced.

Eyeballing and Microscope vs. DGS
Bennett (2013) considered BMMS 7 conspecific with P. antiquus and the largest specimen in the species. He had access to the specimen and I did not. I used phylogenetic analysis and he did not. The large pterosaur family tree nested BMMS 7 between P. antiquus and P. longicollum (renamed Ardeadactylus by Bennett (2013), further reducing the phylogenetic distance between the two putative species! Bennett did not attempt to draw relationships, whether near or far, between P. (A.) longicollum and P. antiquus.

In addition to its transitional nesting, the size of BMMS 7 is intermediate between P. antiquus  and P. (A.) longicollum. Bennett (2013) reports “There are no visible sutures between skull bones” and he traced no sutures. Using Photoshop I found the missing sutures (Fig. 1) in their usual places. Bennett (2013) reports, “Thus, there is no evidence of immaturity,” overlooking evidence for a lizard origin for pterosaurs and Maisano (2002) who noted some lizards never fused certain bones while others continue growing long after bone fusion, as also demonstrated in pterosaur phylogenetic analysis. Most known pterosaurs, unless identical to larger relatives, are adults.

Bennett (2013) reported on BMMS 7, “the very slight concavity may result from lateral crushing of the skull, but does not approach that seen in specimens assigned to P. longicollum.” Well, let’s face the facts head-on: the slight concavity is real and intermediate between the condition in P. antiquus and P. longicollum. This type of observation, one that explains away readily observable data, is common among those who are trying to avoid the obvious: evolution, a word that does not appear in any form in Bennett (2013).

Bennett (2013) reported on BMMS 7, “the nasal process is not visible within [the antorbital fenestra], presumably because the matrix in the fenestra has not been excavated down to the midline of the skull.” I found the top and bottom of the nasal process, but the middle remains buried or broken (Fig. 1).

Bennett (2013) reported on BMMS 7, “There is no trace of a sclerotic ring.” I found three quarters of one, slightly displaced (Fig. 1). It wasn’t ossified and probably represents a very thin layer of matrix covering it or the impression of one lost on the missing counter-plate.

Bennett (2013) failed to report on the presence of a crushed proximal femur on BMMS 7, atop cervical 3 (Fig. 1).

Bennett (2013) reported on the presence of a low premaxillary crest on BMMS 7 and in the holotype of P. antiquus (both less than 1 mm in height), no taller than the anterior portion of the premaxilla. While the purported crest may be a real deal, it is also prudent to remember in all laterally crushed specimens all horizontal bones tend to rotate to the plane of the substrate.

Bennett (2013) reported BMMS 7 is not allied to P. longicollum because the latter  had a concave rostrum, had about 15 teeth per jaw side (rostrum = 18 or mandible = 12 not specified) and the posterior tooth is not below the narial antorbital fenestra (but see Fig. 1). Certainly P. longicollum is different in many respects, but analysis shows these two were sister taxa (given the present very large taxon list).

If P. antiquus and BMMS 7 were conspecific
They would like virtually identical, but might be sized differently. This is based on the observation that embryo pterosaurs are all virtually identical to adults and that verifiable juvenile pterosaurs, like Pterodaustro, Zhejiangopterus and Pteranodon, do not have the  short snout and large eyes Bennett (2006) imagines in juvenile pterosaurs. Moreover, in BMMS 7 the jugal beneath the orbit is deeper than the anterior jugal/maxilla beneath the antorbital fenestra. The jugal descends posteriorly in BMMS 7, more like P. longicollum than P. antiquus. The ventral maxilla beneath the zone just anterior to the NAOF in P. antiquus has virtually no teeth, but the largest teeth are present in that area in BMMS 7. The orbit was much larger than in P. antiquus due to a much longer postorbital process of the jugal. BMMS 7 has a much smaller retroarticular process. So, it has certain autapomorphies.

Earlier we looked at the problems involved when two specimens are a “close but no cigar” in that it could, at that level, represent individual variation or the first steps in evolution toward a new species. That’s just going to happen. But when three specimens are clearly distinct in size and morphology (Fig. 1) then decisions need to be made regarding their genus and species that fall in line with very large and tested phylogenetic analyses.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

Reference
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
Bennett SC 1995. A statistical study of Rhamphorhynchus from the Solnhofen limestone of Germany: year classes of a single large species. Journal of Paleontology 69, 569–580.
Bennett  SC (2012) [2013] New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus. Paläontologische Zeitschrift (advance online publication) doi: 10.1007/s12542-012-0159-8
http://link.springer.com/article/10.1007/s12542-012-0159-8
Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrate Paleontology 22:268-275.
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605

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One thought on “Bennett’s (2013) Revision of Pterodactylus – Part 3

  1. Pingback: DinoAstur - » Ardeadactylus, nuevo nombre para Pterodactylus longicollum

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