SVP abstracts – Ornithocheirid hip range of motion (ROM)

Griffin et al. 2019 report on their study
of the Coloborhynchus (Figs. 3) pelvis during a hypothetical launch. We looked at this issue earlier here following publication of Witton and Habib 2010.

From the abstract:
“Pterosauria includes the largest animals to achieve powered flight. How medium to large-sized pterosaurs were able to launch into the air is a matter of debate.”

Oh, no. Not this invalid hypothesis again. Griffin et al. believe that giant azhdarchids could fly. They could not. Look how short their wings are compared to volant giant seabirds, pteranodontids and ornithocheirids (Fig. 1).

Figure 1. Click to enlarge. The largest flying and non-flying birds and pterosaurs to scale.

Figure 1. Click to enlarge. The largest flying and non-flying birds and pterosaurs to scale.

Griffin et al. continue:
“Birds employ their legs to accelerate their bodies into the air, but the difficulties large birds face in becoming airborne suggests take-off may limit the maximum size of birds. It has been suggested that pterosaurs employed their fore and hindlimbs in take-off, the so-called quadrupedal launch mechanism, overcoming the size constraint.”

That suggestion is not documented in the fossil record. Quad launch is not only dangerous, it is untenable and clearly inferior to using both the wings and legs to produce massive amounts of thrust as large volant birds do. Flightlessness in man-sized and smaller birds made possible flightless giant birds. The same was true for pterosaurs. All the giant pterosaurs had clipped wings (vestigial distal phalanges).

Unsuccessul Pteranodon wing launch based on Habib (2008).

Figure 2. Unsuccessul Pteranodon wing launch based on Habib (2008) in which the initial propulsion was not enough to permit wing unfolding and the first downstroke.

Griffin et al. continue
“Range of motion (ROM) studies are a common way of determining the viability of hypothetical poses in extinct animals. Here we use ROM mapping of the hip joint of a mid-sized pterosaur, Coloborhynchus (SMNK PAL 1133. Fig. 2) to test whether the joint surfaces of the acetabulum and femur were capable of achieving a bipedal and/or a quadrupedal stance during the range of motion required for take-off.” 

Figure 2. GIF animation showing stages in the bipedal take off of Coloborhynchus. Please imagine the wings talking their first mighty flap at the moment of takeoff, relieving the hind limbs from most of the stress.

Figure 3. GIF animation showing stages in the bipedal take off of Coloborhynchus. Please imagine the wings talking their first mighty flap at the moment of takeoff, relieving the hind limbs from most of the stress. In the invalid quadrupdal pose, note the proximal wing finger makes an impression, which never happens in pterosaur tracks.

Griffin et al. continue:
“Using the software programs Maya and MATLAB, possible intersections and orientations between different bones of the hip joint were identified and coded as viable or unviable. Osteological ROM mapping reveals a quadrupedal stance is more likely in launch, with maximum crouch during quadrupedal launch and flight positions being possible.”

See, they had a preconceived bias and did not comparatively test the bipedal configuration. Remember, in the bipedal pose the wings are ready to provide thrust BEFORE the legs launch the pterosaur into the air (Fig. 3). So the legs are not working alone. By contrast in the quad launch scenario, the wings are not unfolded, and not raised above the shoulders when the pterosaur is at the apogee of whatever feeble take-off abducting the antebrachium can provide (Fig. 2).

Figure 1. The as yet undescribed SMNS PAL 1136 specimen is much larger than comparable bones in the new specimen, MPSC R 1221.

Figure 4. The as yet undescribed SMNS PAL 1136 specimen is much larger than comparable bones in the new specimen, MPSC R 1221. This is a resting pose. When walking or preparing to flap the wings would have to rise off the substrate. This sort of giant-winged, small footed, volant creature rarely landed, IMHO.

Griffin et al. continue:
“However, it is important to consider not just osteological ROM but also the effects of soft tissues. ROM simulations can approximate the effect of different soft tissue such as ligamentous constraints and joint cartilage. We find that the required orientation for bipedal launch was not possible without the presence of cartilage. In order to achieve a bipedal stance in this specimen, a minimum of 3 mm of cartilage is required to sufficiently increase the ROM.”

3mm. That’s not very much, and well within the range of possibilities for a large pterosaur. I look forward to seeing their bipedal launch configuration. Having dealt with pterosaur workers cheating morphology to support their bias (e.g. Elgin, Hone and Frey 2011), I’m always suspicious  based on reputation and history.

“A ROM study that included ligaments in addition to cartilage reduced the available viable orientations. This ROM generated in this study does not rule out the possibility of a quadrupedal launch in pterosaurs, and provide greater support for the quadrupedal rather than the bipedal launch hypothesis.”

These authors mistakenly believe that pterosaurs were archosaurs. Testing reveals they are lepidosaurs (Peters 2007). Ligament issues need to based on lepidosaur pelves and hind limbs, not archosaur. Did the authors sprawl the femora, matching femoral head axis to pelvic socket axis? Having built several pterosaur skeletons, I can tell you, the bipedal stance works best. The ROM at the hips is the LEAST of their worries if they are trying to launch a pterosaur with ventrally folded wings.


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
Griffin BW et al. 2019.
Simulated range of motion mapping of different hip postures during launch of a medium-sized ornithocheirid pterosaur. Journal of Vertebrate Paleontology 2019.
Peters D 2007.The origin and radiation of the Pterosauria.Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27
Witton MP and Habib MB 2010. On the Size and Flight Diversity of Giant Pterosaurs, the Use of Birds as Pterosaur Analogues and Comments on Pterosaur Flightlessness. PLoS ONE 5(11): e13982. https://doi.org/10.1371/journal.pone.0013982

Preondactylus skeleton model on a tree

Rummaging through my file cabinets,
I ran across some Polaroid photos of a wire and putty model of Preondactylus (Figs. 1, 2) I made decades ago and mounted to a backyard branch. Note the sprawling femora, a lepidosaur trait.

Figure 1. Years ago, back in the days of Polaroid cameras, I built this to scale model of Preondactylus, mounted it on a tree branch and took its picture.

Figure 1. Years ago, back in the days of Polaroid cameras, I built this to scale model of Preondactylus, mounted it on a tree branch and took its picture.

Preondactylus bufarinii (Wild 1984, Dalla Vecchia 1998; Norian, Late Triassic, ~205 mya) was considered by Unwin (2003) to be the most basal pterosaur. It is not. Derived from a sister to the Italian specimen of AustriadactylusPreondactylus phylogenetically preceded Dimorphodon. Distinct from Austriadactylus, the skull of Preondactylus was lower and narrower with a larger antorbital fenestra completely posterior to the naris. The cervicals were shorter, the caudals more robust. The scapula and coracoid were more robust and straighter. The sternum was much larger. The humerus was anteriorly concave. The ulna and radius were shorter. The pelvis and pes were relatively longer. Pedal digit IV was shorter and V was longer. The metatarsals were longer than the pedal digits and IV was shorter than III.

Figure 2. At the time I thought I would use this photo of Preondactylus for a basis for an illustration with all the problems of perspective worked out.

Figure 2. At the time I thought I would use this photo of Preondactylus for a basis for an illustration with all the problems of perspective worked out. This is literally a ventral view.

Contra traditional pterosaur paleontologists,
who readily admit they have no idea which taxa are proximal outgroups to Pterosauria, basal pterosaurs, like Late Triassic Preondactylus and their fenestrasaur ancestors, were bipedal. Even so they continued to use their long, sharp-clawed free fingers to cling to trees like this (Figs. 1, 2).

Note the digitigrade pedes in this basal pterosaur,
distinct from the flat-footed beachcombers that made most of the tracks. By the way, we have tracks of digitigrade anurognathid pterosaurs (Peters 2011) derived from digitigrade dimorphodontids, like Preondactylus.

Earlier
here, here and here we looked at other ways pterosaurs could stand on and hold on to tree branches. Two of the many ways we know pterosaurs are lepidosaurs are the elongate manual digit 1 and the elongate pedal digit 5, neither of which appear in archosaurs, both of which appear in tritosaur lepidosaurs.

References
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos, 7: 11-41.
Peters  D 2000b. A redescription of four prolacertiform genera and implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293-336
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist.
Historical Biology 15: 277-301.
Peters D 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27.
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
Wild R 1984. A new pterosaur (Reptilia, Pterosauria) from the Upper Triassic (Norian) of Friuli, Italy, Gortiana — Atti Museo Friuliano di Storia Naturale 5:45-62.

wiki/Preondactylus

Pterosaur pubis retroversion – SVP abstract 2016

RA Frigot 2016 
produced an abstract that appears to have no basis in reality. After reading the notes below, please send any examples of any pterosaur with a retroverted pubis, as noted in her abstract headline. I find no such examples in my fairly large collection of reconstructions.

From the Frigot 2016 abstract
“It has been demonstrated that the pelvis in archosaurs (1) repeatedly shows convergence towards acquisition of an anteriorly projecting ilium and a retroverted pubis. Pterosaurs have independently evolved these features, with the anterior iliac process universal across the taxon and the retroverted pubis occurring in several taxa (2). The latter cannot be appreciated as readily in pterosaurs as in other archosaurs due to the fused nature of the ischium and pubis (3). Geometric and linear morphometrics were used to quantify the shape and angle of the anterior margin of the pubis or puboischiadic plate. The angle and the PCA score were applied as end taxa to a reduced phylogenetic tree and nodes were reconstructed using least-squares parsimony. Retroversion is defined here as the anterior margin of the pubis subtending an angle of greater than 90° to the long axis of the spinal column (4).

“By examining the pubis, it can be seen that it becomes retroverted not once at the base of the Pterodactyloidea, as is consistent with existing hypotheses on gait, but in several different lineages independently. Due to the constraints of flight, it is unlikely that this retroversion accommodated a more massive gut, as is the consensus in Ornithischia and Therizinosauroidea. Retroversion has been associated with increased femoral retraction in Maniraptora, and a similar function of the retroverted pubis in pterosaurs is hypothesized here (5).”

“As the pubis becomes retroverted, the surface area caudad to the femur increases and surface area craniad to the acetabulum is reduced. Accordingly, moment arms of femoral protractors originating from the puboischiadic plate are reduced, and in some cases come to function as additional adductors. By contrast, the adductors are brought immediately ventral to the acetabulum, giving them greater mechanical advantage. This shape change is likely enabled by the expansion of the hip protractors onto the anteriorly expanded ilium. In terms of gait, a strongly retroverted pubis is unlikely to correspond to a vertical clinging style of arboreality, as the caudally rotated retractors are at an extreme mechanical disadvantage. This suggests either a terrestrial mode of locomotion, or a horizontal substrate arboreality (6). In addition, strong femoral retractors and adductors played a crucial role in developing and maintaining tension in the wing membrane (7), and in maintaining its planform and preventing collapse of the wing.”

Notes

  1. Pterosaurs have never been shown to be archosaurs without massive taxon exclusion. On the positive side, pterosaurs have been shown to be fenestrasaur tritosaur lepidosaurs in the large reptile tree which tests a wide gamut of taxa, including archosaurs.
  2. I have never seen a pterosaur with a retroverted pubis, but all have an anteriorly projecting ilium, starting earlier than stem facultative biped pterosaur taxa like Cosesaurus.
  3. Not all pterosaurs fuse the pubis and ischium. Many don’t.
  4. I just looked at several dozen reconstructions at ReptileEvolution.com and none of the pterosaurs has a pubis that extends more than 90º to the spinal column.
  5. Not sure we can talk about a special function here when there is no retroverted pubis in any pterosaur.
  6. Funny, no discussion of the prepubis here, which serves as an anteroventral (not posterovental) extension of the pubis and an anchor for femoral muscles on both vertical and horizontal surfaces. And it is present in all pterosaurs and non-pterosaur fenestrasaurs.
  7. Evidence says no. The pterosaur wing is stretched between the wingtip and elbow with a shallow fuselage fillet extending to mid thigh in all pterosaurs that preserve the wing membrane. There is still no evidence for a wingtip-to-tibia-or-ankle deep chord wing membrane in any pterosaur. If you have such evidence, please send it.

What am I not getting here?
This abstract doesn’t make sense. How did it pass peer review?

prepubes, prepubis

Figure 1. The pelvis and prepubis of several tritosaurs, fenestrasaurs and pterosaurs

References
Frigot RA 2016. Retroversion of the pubis in pterosauria and its significance in reconstructing gait. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.

Basal hominid, fenestrasaur and archosaur analogies

When you look at the transition
from quadrupedal locomotion to bipedal locomotion in early hominids (Fig. 1), among many other details, you can’t help but be impressed by the increase in the relative length of the hind limbs.

Figure 1. When hominids became bipedal, their hind limbs became longer.

Figure 1. When hominids became bipedal, their hind limbs became much longer.

The same can be said
for the transition from semi-bipedal Cosesaurus (based on matching Rotodactylus tracks) to the fully bipedal Sharovipteryx (Fig. 2).

Figure 2. Cosesaurus was experimenting with a bipedal configuration according to matching Rotodactylus tracks and a coracoid shape similar to those of flapping tetrapods. Long-legged Sharovipteryx was fully committed to a bipedal configuration.

Figure 2. Cosesaurus was experimenting with a bipedal configuration according to matching Rotodactylus tracks and a coracoid shape similar to those of flapping tetrapods. Long-legged Sharovipteryx was fully committed to a bipedal configuration, analogous to hominids.

As in hominids,
freeing the fore limbs from terrestrial locomotion enabled fenestrasaurs to do something else, like flapping for secondary sexual displays, adding motion to their morphological ornaments. While the forelimbs were relatively smaller in Sharovipteryx, they were relatively larger in Bergamodactylus (Fig. 3) a long-legged basal pterosaur. There were no constraints on forelimb evolution in fenestrasaurs, analogous to theropod dinosaurs that ultimately became birds. Some theropods and birds grew larger forelimbs, while others reduced their forelimbs.

Figure 2. Updated reconstruction of Bergamodactylus to scale with an outgroup, Cosesaurus.

Figure 3. Updated reconstruction of Bergamodactylus to scale with an outgroup, Cosesaurus.

Lest we not forget
in the basal archosaurs (crocs + dinos) early attempts at bipedal locomotion (Fig. 3) also corresponded to a longer hind limb length in bipedal Scleromochlus and Pseudhesperosuchus as opposed to their common ancestor, a sister to short-legged Gracilisuchus.

Figure 3. Short-legged Gracilisuchus, along with sisters, long-legged bipedal Pseudhesperosuchus and Scleromochlus.

Figure 3. Short-legged Gracilisuchus, along with sisters, long-legged bipedal Pseudhesperosuchus and Scleromochlus.

Based on those tiny hands,
the forelimbs of Scleromochlus were becoming vestiges. Based on the long proximal carpals of Pseudhesperosuchus, the manus was occasionally lowered to the ground, perhaps while feeding. The origin of bipedal locomotion in basal crocs is the same as in pre-dinosaurs.

It took much longer and proceeded more indirectly
for bipedal archosaurs to start flapping their forelimbs, giving them a new use that ultimately produced thrust and lift as bird forelimbs continued to evolve and become larger.

See videos produced by ReptileEvolution.com
on the origin of dinosaurs here, on the origin of humans here, and on the origin of pterosaurs here.

A sign of beauty and/or Olympic potential
is a long-legged model or athlete.

Anhanguera pelvic girdle and femur orientation

A recent paper
by Costa et al. (2014) illustrated the myology of the pelvic girdle of the large pterosaur, Anhanguera based on 3D digital models of 3D fossils (Fig. 1).

Figure 1. Costa et al. reconstruction of Anhanguera pelvis and femur together with amended versions with sprawling femur.

Figure 1. Costa et al. reconstruction of Anhanguera pelvis and femur together with amended versions with sprawling femur. Not sure how the rest of the body was oriented based on the Costa et al. pelvis. Here the pelvis is placed on a body that is balanced whether the hands are on the substrate or not.

Unfortunately,
Costa et al. did not include the rest of the Anhanguera body and leg to show their orientation and configuration works in toto. When you do the add the body, and orient the femur so the axis of the femoral head (Fig. 2) aligns with the axis of the pelvic acetabulum, you get a different configuration (Fig. 1). In the Costa et al. configuration, the femoral head axis is not aligned with the acetabulum axis. And the knee is a little too straight, unlike most tetrapods — except at maximum extension.

Fig. 2. Anhanguera left femur from Kellner and Tomida 2000. Note the axis of the femoral head is not far off from the axis of the femoral body, producing a sprawling hind limb here as it does in other tetrapods.

Fig. 2. Anhanguera left femur from Kellner and Tomida 2000. Note the axis of the femoral head is not far off from the axis of the femoral body, producing a sprawling hind limb here as it does in other tetrapods.

If you straighten out the leg, you get the flying configuration. 

If you bend the knee and axially rotate the femur, you get the standing configuration, just like lizards capable of assuming or running in a bipedal configuration (Fig. 3). Now I’m not saying Anhanguera was bipedal all the time — but it was indeed bipedal moments before takeoff and moments after landing (prior to wing folding, as in all pterosaurs.)

 

Bipedal lizard video marker

Figure 3. Click to play video. Just how fast can quadrupedal/bipedal lizards run? This video documents 11 meters/second in a Callisaurus at the Bruce Jayne lab.

Getting back to the feet, legs and pelvis
pterosaurs could still bring their feet close to the midline simply by bending the knee and axially rotating the femur, both of which were very easy to do.

Yes, Anhanguera might have been awkward on land,  but it was rarely on land, based on the evidence of the tiny feet, skinny legs and great big wings.

For those interested,
I just spent the last 6 months working on a reptile paper that was yesterday submitted. Hope it flies. Will try to add some new “heresies” as the days go by, but there has not been that much to discuss in the last few months, oddly enough.

And thank you for your support while I’ve been gone.
Viewership has not decreased. 200 to 400 visitors a day over the past month with no news! Amazing.

References
Costa FB, Rocha-Barbosa O and Kellner AWA 2014. Myological reconstruction of the pelvic girdle of Anhanguera piscator (Pterosauria: Pterodactyloidea) using three-dimensional virtual animation.

 

Pterosaurs were unlikely floaters: Hone and Henderson (2013, 2014)

Recently Hone and Henderson (2013) conducted computational experiments with four digital pterosaur models (Fig. 1) and report, “we show that the floating posture of pterodactyloid pterosaurs led to the head, neck and body being horizontal with the ventral 1/4 to 1/3 being immersed, and the external nares being almost at, or potentially partially below, the waterline that could have left them vulnerable to drowning. These results suggest many did not regularly rest on the surface of the water and if immersed would need to take off again rapidly. The high numbers of fossils of juvenile pterosaurs compared to the terrestrial Mesozoic dinosaurs suggests that this may be linked to their poor ability in water.”

Obviously they thought they were professing pterosaur heresy, since so many illustrations from several sources imagine pterosaurs floating (Wellnhofer 1991, p.169; Lockley and Wright 2010, p. 73). According to Hone and Henderson (2013, Fig. 1), if pterosaurs floated at all, it was not too well and not for long.

They briefly mentioned traces of the pedal claws only, which were widely considered to be made by floating, paddling pterosaurs. They completely ignored all reports of manus only traces, like those here. Their colleague Mark Witton writes in pterosaur.net, “Wading behaviour may also be recorded: bizarre pterosaur trackways comprised of manus prints alone have been suggested to be created by pterosaurs wading in shallow water with buoyed-up hindquarters.” Manus only tracks were reported by Parker and Basley (1989), Lockley et al. (1995), Pascaul Arribas and Sanz Pérez (2000).

Here (Fig. 1) are models by Hone and Henderson for Rhamphorhynchus and Pteranodon, two taxa known to be fish eaters and therefore likely floaters. Note the effort needed to raise the skull out of the water in these stiff-neck models. Also note the too-slender forelimbs and too-slender thighs. Compare these to figures 2-5, based on bones.

Computational models of two pterosaurs from Hone and Henderson 2013. Note how both have trouble keeping their nose out of the water. Henderson's models have shown their limitations in earlier papers.

Figure 1. Computational models of two pterosaurs from Hone and Henderson 2013. Note how both models have trouble keeping their nose out of the water, as they report. Neither of these models has a robust thigh typical of most pterosaurs. Also missing here in Rhamphorhynchus is a deep posterior abdomen caused by the deep prepubis.

Not considered here:
Hone and Henderson also modeled Dimorphodon, a basal pterosaur that likely was an insectivore, since all  sister taxa are also considered insect eaters. The Dimorphodon skull is a fragile wonder, so it was an unlikely fish-eater and therefore an unlikely candidate as a floater. Hone and Henderson also modeled Dsungaripterus, a stork-like wader. With such unique crushing teeth, it is not known what it preferred in its diet, but waders, like storks, are typically not floaters. I can’t find a single image of a floating stork on the Internet.

Mathematically manipulating their models, Hone and Henderson dialed up and dialed down various factors, such as density, placement of the lungs, etc. Reportedly, these did little to change the results of the apparently top-heavy, skull-leveraged pterosaurs.

The one thing they did not attempt
was to loosen the shoulder joints, which allows the pontoon-like forelimbs to float horizontally while the torso rotates between them. Their digital models also fail to accurately echo living tissue (described below and in later posts).

Figure 2. Floating pterosaurs from ReptileEvolution.com showing the large solid thighs, that counterbalance the air-filled skull. Like birds, the neck is able to raise the skull above the surface.

Figure 2. Floating pterosaurs from ReptileEvolution.com showing the large solid thighs, that counterbalance the air-filled skull. Like birds, the neck is able to raise the skull above the surface. Note how the forelimb pontoons are able to rotate, which elevates or depresses the torso. Ctenochasma (above) is ‘poling’ on its forelimbs, matching manus-only pterosaur tracks that were mentioned by Hone and Henderson, but can only be made by floating

Birds keep their wings out of the water. Bird wings are not flotation devices.

On the other hand,
pterosaurs come with their own rotating pontoons. So they can change the configuration of the body and the elevation of their skull relative to the water surface all sorts of ways, a point overlooked by Hone and Henderson’s static models.

Figure 3. Triebold Pteranodon in  floating configuration. Center of balance marked by cross-hairs.

Figure 3. Triebold Pteranodon in floating configuration. Center of balance marked by cross-hairs. Note the forelimb pontoons, submerged here.

I think Hone and Henderson underestimated the ability of large hollow, air-filled wings to float their owners. They underestimated the mass of the large and muscular thighs, perhaps the largest muscles in the body, to possibly depress the rear end. They also underestimated the ability of the cervicals to dorsiflex and they did not understand the ball joint at the back of the skull that allowed the neck to diverge at a large angle.

Figure 4. Two configurations for Rhamphorhynchus. Because the wings act like pontoons, the torso and skull can be rotated relative to the wings to adopt a variety of floating configurations. Also note the large webbed feet, preserved in the darkling specimen. The tail can be elevated at its base.

Figure 4. Two configurations for Rhamphorhynchus. Because the wings act like pontoons, the torso and skull can be rotated relative to the wings to adopt a variety of floating configurations. Also note the large webbed feet, preserved in the darkling specimen. The tail can be elevated at its base. Here the deep prepubis creates a deep abdominal keel not reflected in the Hone and Henderson digital model.

Imagine flocks of Rhamphorhychus enjoying the tidal pool like a bunch of kids with their “floaties” in a pool. Large webbed feet could have been used to paddle around or help launch this pterosaur by rocketing it out of the water along with several big wing flaps. We looked at this topic earlier here and here.

Figure 5. The derived Nyctosaurus, KJ2 in a floating configuration using its long forelimbs as pontoons.

Figure 5. The derived Nyctosaurus, KJ2 in a floating configuration using its long forelimbs as pontoons.

Even the large crested Nyctosaurus can ride the waves with its “mast” over the center of gravity and the center of balance, the shoulder joint (Fig. 5).

Too much water on the wings?
While Hone and Henderson (2013, Fig. 1) do not show wing membranes, Henderson (2010) does and they are all bat-like with a very deep chord extending to the ankle. No wonder Hone and Henderson (2013) thought the weight of water on such an extended membrane might give the pterosaur trouble lifting its wings above the surface once dunked.

Unfortunately,
this is one more error to add to their pile. First of all, the wing was much narrower than Hone and Henderson suppose. Then, when pterosaurs folded their narrow wings, the membranes folded down to almost nothing. This is shown in several fossils, but cannot happen if the wing has a deep chord and attaches to the thigh or ankle. Finally, if the wings had a water-shedding surface, like that of diving birds, or that little floating lizard (Fig. 6), then what little water was present, would fall off rapidly.

Figure 6. Images of floating lizards. The small ones, like small pterosaurs, take advantage of surface tension to ride high while spread-eagle on the surface.

Figure 6. Images of floating lizards. The small one in the middle, like tiny pterosaurs, takes advantage of surface tension to ride high and dry while spread-eagle on the surface.

Tiny pterosaurs: not all juveniles
Seems Hone and Henderson are still stuck in the ptero dark ages thinking tiny pterosaurs were all juveniles. They’re not, according to phylogenetic analysis and the fact that pterosaurs matured isometrically. In any case, as the small lizard shows (Fig. 6), tiny pterosaurs were more likely to float than large ones, based on surface tension and their tiny mass. Tiny pterosaurs had more surface area than any nonviolent lizard. So they would have been great floaters. And…need I say it? Pterosaurs are lizards.

I’ve never been a fan
of Henderson’s models. I think he disfigures pterosaurs. I’ve never been a fan of Hone’s work, either. I think he’s taken us several steps backward in our understanding of pterosaurs. (Use keyword “Hone” in this blog to find other examples.)

More on this tomorrow and the next day where we’ll match manus only tracks to trackmakers and take another look at digital models.

References
Hone DWE, Henderson DM 2013. The posture of floating pterosaurs: Ecological implications for inhabiting marine and freshwater habitats, Palaeogeography, Palaeoclimatology, Palaeoecology (2013 accepted manuscript), doi: 10.1016/j.palaeo.2013.11.022

Hone DWE, Henderson DM 2014. The posture of floating pterosaurs: Ecological implications for inhabiting marine and freshwater habitats. Palaeogeography, Palaeoclimatology, Palaeoecology 394:89–98.
Lockley MG, Logue TJ, Moratalla JJ, Hunt AP, Schultz RJ and Robinson JW 1995.  The fossil trackway Pteraichnus is pterosaurian, not crocodilian: implications for the global distribution of pterosaur tracks. Ichnos, 4: 7–20.
Lockley M, Harris JD and Mitchell L 2008. A global overview of pterosaur ichnology: tracksite distribution in space and time. Zitteliana B28: 185-198.pdf
Mickelson DL, Lockley MG, Bishop J, Kirkland J 2004. A New Pterosaur Tracksite from the Jurassic Summerville Formation, Near Ferron, Utah. Ichnos, 11:125–142, 2004
Parker L and Balsley J 1989. Coal mines as localities for studying trace fossils. In: Gillette DD and Lockley MG (Eds), Dinosaur Tracks and Traces; Cambridge (Cambridge University Press), 353–359.
Pascual Arribas C and Sanz Perez E 2000. Huellas de pterosaurios en el groupo Oncala (Soria España). Pteraichnus palaciei-saenzi, nov. ichnosp.  Estudios Geologicos, 56: 73–100.

Scathing Book Review – Pterosaur hind limb muscles and the prepubis: Witton vs Peters

Earlier here, here and here we had a critical look at the hypotheses regarding various aspects of pterosaur phylogeny and morphology. Today we’ll look at the muscles of the pterosaur hind limb and how Witton (2013) emaciated them.

Pterosaur hind limb muscles according to Witton (2013, above) and based on lizard musculature (Fig. 2).

Figure 1. Pterosaur hind limb muscles according to Witton (2013, above) and based on lizard musculature (Fig. 1, below and Figs. 2, 3). Witton does not extend femoral muscles to the prepubis or the anterior ilium. Evidently it’s important for those who do not want pterosaurs to exhibit any bipedal abilities to denigrate hind limb muscle strength, as shown by the emaciated appearance Witton gives them and by reducing their anchorage.

Make sure those hind limbs look emaciated
if you want to convince others that pterosaur hind limbs were not capable of providing bipedal locomotion (in step with quadrupedal locomotion for most) or hindlimb leaping/launching/takeoff. Witton 2013 emaciates his pterosaur femoral muscles and reduces their points of origin on the ilium and prepubis. Why? He supports the forelimb launch hypothesis for pterosaurs big time.

Two dead lizards, dorsal and ventral views. Note the meaty thighs.

Figure 2. Two dead lizards, dorsal and ventral views. Note the meaty thighs. Same as in birds and crocs. Witton emaciates them.

Real lizard femoral muscles are robust and meaty (Figs. 2,3 ). The muscles get thicker at mid thigh. This even happens in birds and crocs! Why would Witton emaciate them?

Lizard muscles according to Romer (1956. 1062,1971). Ilium muscles in red. Pubis and ischium muscles in blue. Caudal muscles in yellow.

Figure 3. Lizard muscles according to Romer (1956. 1062,1971). Ilium muscles in red. Pubis and ischium muscles in blue. Caudal muscles in yellow. Curious that no muscles arise from the posterior ilium.

No Prepubis Anchor
Pterosaurs extend their ventral muscle anchorage by adding a prepubis, which can be very long indeed in Rhamphorhynchus (Fig. 2) and Campylognathoides (Fig. 3). No muscles attach to the prepubis in Witton’s version (Fig. 1). One wonders why not, especially when the prepubes and femora are aligned during normal locomotion (Figs. 2-4).

Instead Witton 2013 follows Claessens et al. (2009) mistake when he reports the prepubes “were capable of moving up and down with each breath taken by their owner.” This “rotating prepubis” hypothesis was falsified earlier based on the Claessen et al. use of a flipped and partial prepubis to support their hypothesis. They got the bone upside down!! No other prepubes in any other pterosaurs support the Claessen et al. hypothesis. The pubis/prepubis joint is a butt joint in all pterosaurs. So it basically cannot move. The prepubis acted as an extension to the pubis. Pubofemoralis muscles probably extended down the prepubis as if it were an elongated pubis. Respiration occurred by expansion of the ribs, as in all tetrapods, not by the rotation of the prepubes. Correctly configuration shown below (Figs. 2-4).

The darkwing Rhamphorhynchus JME SOS 4785

Figure 2 The darkwing Rhamphorhynchus JME SOS 4785. Note the depth of the prepubis. Even if this prepubis could rock back and forth it would not further deepen the torso.

 The Pittsburgh specimen of Campylognathoides. This pterosaur had the largest prepubes of all pterosaurs. Note the ventral orientation, aligned with the femora during normal standing.

Figure 3. The Pittsburgh specimen of Campylognathoides. This pterosaur had the largest prepubes of all pterosaurs. Note the ventral orientation, aligned with the femora during normal standing. Note the butt joint between the pubis and prepubis.

The Triebold Pteranodon, one of the most complete ever found. The metacarpals are quite a bit longer here. So is the beak.

Figure 4. The Triebold Pteranodon, one of the most complete ever found. I have this skeleton cast. The prepubes extend ventrally, in line with the femora and unable to expand the torso during respiration. Expanding ribs, as in all tetrapods, provided all the necessary torso expansion for respiration.

Witton's prepubis mistakes, based on mistakes by Claessen et al. 2009. (Above) in Rhamphorhynchus the prepubis is waaaay too small. In both the prepubis is incorrectly oriented and incorrectly attached to the pubis.

Figure 5. Witton’s prepubis mistakes, based on mistakes by Claessen et al. 2009. (Above) in Rhamphorhynchus the prepubis is waaaay too small. In both pterosaurs the prepubis is incorrectly oriented and incorrectly attached to the pubis.

Elongate ilia
And why would the all pterosaur ilia extend so far anterior (especially so in Sos 2428), framing so many sacrals (Fig. 1), without bringing a few muscles with them? After all, that’s what mammals and dinosaurs do. And the muscles arising from the ilium in lizards concentrate anteriorly. Finding homologies and analogies is how we find the most parsimonious answer.

The missing caudofemoralis
Lizards and most dinosaurs have a robust tail with elongate transverse processes and deep chevrons. These are muscle anchors for the caudofemoralis, tail muscles that pull the femur posteriorly, contributing to the step cycle. In birds and pterosaurs these muscle anchors are largely, but not completely missing. The pelvis (and prepubis) have taken over those duties. The caudofemoralis is largely, but not completely missing in birds and probably pterosaurs. As in birds, pterosaur the anchoring transverse processes are vestigial or missing and their chevrons, where present, extend parallel to the caudal centra, not ventrally. In pterosaurs, chevrons are not caudofemoralis anchors, but secondarily adapted as tail stiffeners. They are essentially absent in basal pterosaurs, like MPUM6009. They redevelop in several taxa. These same caudal patterns (attenuated tails) are found in pterosaur precursors, the fenestrasaurs, evolving from less attenuated tails in tritosaur lepidosaurs, a key trait that ties them all together.

It’s important to examine living animals to see their muscle patterns in order to reconstruct them in prehistoric animals. It’s important to know what new bones, like the prepubis, are used for (not respiration). It’s important to note the details in a skeleton, establishing articular surfaces and creating accurate reconstructions.

References
Claessens, LPAM, O’Connor PM and Unwin DM 2009. Respiratory Evolution Facilitated the Origin of Pterosaur Flight and Aerial Gigantism. PLoS ONE 4(2):e4497.http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004497
Romer AS 1971. The Vertebrate Body (shorter version). WB Saunders Co. 452 pp.
Witton M. 2013. Pterosaurs. Princeton University Press. 291 pages.x

A Perfect Pterosaur: Pterodactylus scolopaciceps (n21) – part 4

Most pterosaur fossils are incomplete, crushed and disarticulated. By contrast, Pterodactylus scolopaciceps  BSP 1937 I 18 (Broili 1938, P. kochi n21 of Wellnhofer 1970, 1991, Fig. 1) is just the opposite, complete, uncrushed and articulated. Earlier we looked at the presence of a distinct naris, prior to that wing unguals and theday before that we documented vestigial manual digit 5.

Figure 1. Pterodactylus scolopaciceps  BSP 1937 I 18 (Broili 1938, P. kochi No. 21 of Wellnhofer 1970, 1991) complete, articulated and including soft tissue.

Figure 1. Pterodactylus scolopaciceps BSP 1937 I 18 (Broili 1938, P. kochi No. 21 of Wellnhofer 1970, 1991) complete, articulated and including soft tissue.

Today we’ll look at the soft tissue in this “perfect” specimen. There is a great deal of preparatory nicking on this specimen leaving skin impressions unmarked.

Soft tissue on Pterodactylus n21. Note the small patches anterior to the ankles, otherwise seen on Sharovipteryx. Patches of muscle or skin are present on the ribs. The high matrix in front and behind the elbow goes unexplained.

Figure 2. Soft tissue on Pterodactylus n21. Colors denote distinct membranes. Note the wing membrane is narrow at the elbow and attaches at mid thigh, as in ALL other pterosaurs. The uropatagia are separate and do not contact the tail. Note the small patches anterior to the ankles, otherwise seen on Sharovipteryx and previously overlooked. Patches of muscle or skin are present on the ribs. 

Pterosaur soft tissue is rarely preserved, but this specimen has it in spades from a throat sac to large and flat trapezius muscles (in pink) linking the neck to the shoulders and several other wing and leg membranes. As in all other known pterosaurs the wing membrane does not attach at the ankle, but becomes very narrow aft of the elbow (in cyan blue) before blending with the “fuselage fillet” next to the ribs and extending back to the thigh muscle. The propatagium (in violet) relaxes with the pteroid as the elbow flexes. A right uropatagium (in green) is very easy to see extending behind the right knee from above the ankle to the pelvis. The left one is tucked away. Small trim tab membranes (in amber) extend anterior to each ankle, as in Sharovipteryx (Fig. 3). These have been overlooked by all prior workers. The feet are webbed.

Sharovipteryx mirabilis

Figure 4. Sharovipteryx mirabilis in various views. Note the tiny pre-ankle extradermal membrane. Click to learn more.

A closer look at pedal digit 5
The conventional paradigm holds that pedal digit 5 in pterodactyloid-grade pterosaurs was reduced to a stub and in no pterosaurs was p5.3 (the ungual preserved). Earlier we found the ungual of pedal digit 5 on several specimens. The ungual is here (Fig. 5) on n21 as well, despite the vestigial size of the rest of the digit. In fact the ungual exceeds the length of m5.2, which in basal pterosaurs can be longer than the metatarsus. Here (Fig. 5) the metatarsus of pedal digit 5 is larger than the digit, which remains hyperflexed as in rhamphorhynchoid-grade pterosaurs.

Pedal digit 5 in Pterodactylus n21. The entire digit is present, only vestigial. Pedal 5.1 is partly covered my dermal membrane here. The green bone is mt5 with a hollow opening distally. Amber is p5.1. Blue is p5.2. Magenta is p5.3, the ungual.

Figure 5. Pedal digit 5 in Pterodactylus n21. The entire digit is present, only vestigial. Pedal 5.1 is partly covered my dermal membrane here. The green bone is mt5 with a hollow opening distally. Toe 5 is slightly disarticulated to reveal the distal condyle of mt5. Amber is p5.1. Blue is p5.2. Magenta is p5.3, the ungual, longer than p5.2 in this specimen.

This concludes our examination of n21, the perfect Pterodactylus. And this is why PterosaurHeresies.com was created, to expose problems and false paradigms in reptile paleontology, wherever they may arise.

Pterodactylus scolopaciceps.

Figure 2. Pterodactylus scolopaciceps. This image updates all prior versions. Click for more info.

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.

References
Broili F 1938. Beobachtungen an Pterodactylus. Sitz-Bayerischen Akademie der Wissenschaten, zu München, Mathematischen-naturalischenAbteilung: 139–154.
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

wiki/Pterodactylus

Manual digit 5 is present on both metacarpals. All the elements match one another.

Try these thighs on for size: Pterosaur legs were not as fragile as most imagine.

Just how much muscle surrounded those skinny little hind leg bones on pterosaurs? Hind legs are basically an afterthought in the illustrations of many paleo-workers and artists, but pterosaurs give us four points on the anatomy to figure the proximal musculature (see below).

The anterior and the posterior tips of the ilium provide the first two of these points. As in lizards, crocs and birds, these points determine the fore/aft distance of the thigh musculature. In front the depth of the thigh musculature is determined by the prepubis, which in some pterosaurs is relatively short. In others, like Rhamphorhynchus the prepubis can extend beyond the knee. In back the depth of the thigh musculature is determined by the tip of the ischium, which can also be relatively deep or shallow.

Let’s take a look at a few examples of birds to start:

Figure 1. Bird thighs. Red areas approximate extent of thigh muscles based on bone anchor points.

Figure 1. Bird thighs. Red areas approximate extent of thigh muscles based on bone anchor points.

Bird thighs, no matter what type of bird they appear on, bend the knee with anchors along the length of the ilium. Here you can see that bird thighs extend for about half the length of the torso in birds.

Pterosaur thighs

Figure 2. Pterosaur thighs approximated in red based on the extent of the ilium. If we take these examples as representative of pterosaurs, the thighs are generally longer than in birds, but just a muscular due to the length of the ilium.

Early pterosaurs had a thigh that was less than half of the torso, but much longer due to a longer femur. This is trait that originated in Sharovipteryx and Longisquama, the (hind-limb) leaping fenestrasaurs. Later pterosaurs shortened the dorsal portion of the torso so that the length of the ilium became half the torso length. Only in the flightless pterosaur, SoS2428 does the ilium extend for more than half the torso.

Okay, so artists, we need to add some meat to those pterosaur thighs. Here is an example of a Content Paradise Zhenyuanopterus with thighs that are too small (you can’t count the uropatagia there!), but I love the narrow chord sailplane-like wing configuration.

Finally, I can’t let the size of those thighs go by without bringing attention to home much MORE thigh muscle is present than forelimb muscle in many pterosaurs. Sure the femur is narrower than the humerus, but really, it’s the muscles and their leverage that drive leaping, not the bones.

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.