Elgin 2014 PhD dissertation: nits and picks, part 2

Yesterday we looked at
a misidentified pterosaur specimen from the State Museum of Natural History Karlsruhe (SMNK) that wasn’t a Tupuxuara, as originally considered by then PhD candidate, now Dr. Ross Elgin. Consider that blogpost an unlabeled part 1.

Today, in part 2,
we’ll take a look at several other aspects of the Ross Elgin 2014 PhD dissertation that deserve credit and discredit. 

FIgure 1. GIF animation of image from Elgin 2014 comparing wing membrane configurations and a more accurate rendition of what Peters 2002 proposed. See text for list of issues here.

FIgure 1. GIF animation of image from Elgin 2014 comparing wing membrane configurations and a more accurate rendition of what Peters 2002 proposed and Elgin distorted. See text for list of issues here. In reality, like birds, the wings and hind limbs are decoupled. Most pterosaur workers don’t believe the data.

Elgin mistakenly reported,
“The primary flight membrane is reconstructed with an ankle attachment of the trailing edge, a configuration that was never fundamentally altered throughout the evolutionary history of the group.” Elgin ignored the bipedal origin of the Pterosauria, and ignored the narrow-chord wing membrane data that attends every pterosaur fossil that preserves wing membranes, perhaps on the advice of his mentors. And he ignored, or distorted, what Peters 2000 actually proposed for a wing membrane and bone orientation in pterosaurs (Fig. 1).  This may be what happens when you have to feed the fever dreams of a teacher rather than recording actual data. Elgin reported, “I am indebted to both David Hone and Eberhard “Dino” Frey for the opportunity to undertake this project and continue my work on the enigmatic and curious group of animals known as pterosaurs.”

Solutions to problems with Figure 1.

  1. The scapula/coracoid should rotate laterally, as in all articulated fossils
  2. The elbow should angle further posteriorly, as in all articulated fossils (+ in birds and bats)
  3. The pteroid should point to the deltopectoral crest, as in all articulated fossils
  4. The free fingers should point ventrally (in flight). Crushing typically rotates the narrow claws anteriorly.
  5. Metacarpals 1-3 should line up anteriorly, not stack themselves against mc4
  6. Manual 4.4 should articulate at an angle to m4.3, deepening the wing tip
  7. The propatagium should extend only to the deltopectoral crest
  8. The brachiopatagium should stretch between the wingtip and elbow with a fuselage fillet to distal thigh, as in all articulated fossils
  9. The thigh should be more meaty based on the long anterior ilium
  10. The femur should extend laterally to form a horizontal stabilizer (and note the sprawling lepidosaur orientation!)
  11. The femur should be flipped, as shown in Elgin’s figure 3 below.
  12. The uropatagia do not extend to the tiny tail, as in all articulated fossils. Elgin’s essentially creates a single uropatagium, which is a decades-old false paradigm.

If the above illustration by Elgin 2014 looks familiar
it’s because we looked at it earlier here, after publication of Elgin, Hone and Frey 2011. Also check out all the images on this ReptileEvolution page. You might remember these authors employed the fiction of ‘wing membrane shrinkage’ to explain the data, instead of just accepting the data, as is. We have evidence of pterosaur ancestors with wings decoupled from the hind limbs, so there was never a gliding transitional phase. Flapping preceded flying.

Along the same lines
Hone and Benton (2007, 2008); and Nesbitt and Hone (2010a, b) preferred to see things their own way, rather than strict adherence to the data. So, maybe young Elgin was unduly influenced by his professors and mentors.

Elgin introduced us to
Microtuban altivolan, which he described as a non-azhdarchid azhdarchoid. In the large pterosaur tree (LPT, 1189 taxa) Microtuban indeed nests at the base of the azhdarchid clade, arising from certain dorygnathids, a relationship Elgin never tested.

Elgin suggested a possible sexual dimorphism,
“where the pelvic girdle lacks a symphysis and remains open even in large adults is observed within Coloborhynchus robustus.” (Fig. 2) Let’s blame this one partly on his teachers, and partly on sloppiness. The base of the pterosaur pelvis opens and closes in phylogenetic patterns, not gender patterns. That tricked up Bennett, too, and Elgin’s teachers followed Bennett’s mistakes. On the sloppiness point, the open pelvis of C. robustus is missing its ventral and posterior borders, exactly the bones needed to join the ischia together (Fig. 2). It doesn’t look like Elgin was cheating. He must have thought he was not cheating. But he was cheating by changing points of view, changing scales and not adding back missing bone to follow generic patterns. This was all resolved with a little tracing in Adobe Photoshop, the paleontologists’ best friend.

Figure 1. Elgin compared these two Coloborhynchus pelves together, but failed to align them, scale them and add back missing bone.

Figure 2. Elgin compared these two Coloborhynchus pelves together, but failed to align them, scale them and add back missing bone.

Elgin was also tricked by
traditional archosaur patterns and paradigms in ontogeny. He expected sutures to close at adulthood. This tricked up Bennett, too. Instead, since pterosaurs are lepidosaurs, sometimes they do, sometimes they never do, and sometimes they fuse sutures before maturity and reading their final size. It’s all phylogenetic, not ontogenetic with lepidosaurs, including pterosaurs.

Figure 2. Coloborhynchus robustus (bones and outlines from Elgin 2014) compared to C. spielbergi (b&w). Notes added.

Figure 3. Coloborhynchus robustus (bones and outlines from Elgin 2014) compared to C. spielbergi (b&w). Notes added.

Elgin described and did not illustrate the missing wing finger:
“The wing finger phalanges in almost all pterosaurs are similar in form with expanded proximal and distal margins, the shafts of which show various degrees of curvature. Those preserved in SMNK PAL 1133 are not exception and agree well with other descriptions of pterodactyloids.” This description can only be the result of naiveté and inexperience. In reality phalanx proportions change between genera and species. It would have been helpful to see the wing finger of C. robustus since the C. spielbergi wing finger is missing.

Elgin 2014 mistakenly considered

  1. pterosaurs to be archosauromorphs.
  2. anurognathids to be basal pterodactyloids
  3. Darwinopterus to be ‘an animal intermediate’ linking basal to derived pterosaurs

These issues are resolved and settled
here and here when you add more taxa. It’s good for science to be critical. If nothing else this blog will hopefully show all readers that published scientific text and figures can sometimes include errors that can be exposed and corrected by colleagues.

It’s not okay
to disfigure the figures of other workers and then claim that’s the essence of their work (contra Fig. 1). We’ve seen this before with other PhDs.

References
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica 56 (1), 2011: 99-111. doi: 10.4202/app.2009.0145
Elgin RA 2014. Palaeobiology, Morphology, and Flight Characteristics of Pterodactyloid Pterosaurs. Innaugural Dissertation. Zur Erlangung der Doktorwürde Fakultät für Chemie und Geowissenschaften Institut für Geowissenschaften Ruprecht-Karls-Universität Heidelberg. Available online  here.
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Nesbitt SJ and Hone DWE 2010a. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Nesbitt SJ and Hone DWE 2010b. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233

https://pterosaurheresies.wordpress.com/2012/04/13/a-supertree-of-pterosaur-origins-hone-and-benton-2007-2009/

http://www.reptileevolution.com/pterosaur-wings.htm

https://pterosaurheresies.wordpress.com/2011/11/18/did-dimorphodon-have-an-external-mandibular-fenestra/

https://pterosaurheresies.wordpress.com/2013/01/16/a-closer-look-at-the-antorbital-fossa-in-two-pterosaurs-raeticodactylus-and-dimorphodon/