Late Jurassic pterosaur under UV light

Mike Eklund, Research Associate at the University of Texas,
is using black light (= uv light) to reveal what is ‘hidden in plain sight’ in fossils. At the HMNS.org blogsite a fully articulated and excellently preserved Late Jurassic pterosaur serves as only one of many subjects using this lighting technique (Figs. 1–3).

In case some controversial items are overlooked,
as they have been for centuries, I thought I’d highlight a few observations (Figs. 1-3).

Figure 1. Coloring the bones and membranes of this pterosaurs helps identify them here.

Figure 1. Coloring the bones and membranes of this pterosaurs helps identify them here.

For paleo-artists
note how the wing finger folds completely against the forearm. Note how the membrane virtually disappears when folded (Peters 2002, 2009), especially so at the wing tip. Also note that no part of the wing membrane ever extends to the tibia or ankle. This is evidence to counter myths perpetuated by prior pterosaur workers and artists.

Figure 2. Manual digit 5 on this pterosaur is undisturbed.

Figure 2. Manual digit 5 on this pterosaur is undisturbed.

Figure 3. Manual unguals on this pterosaur are undisturbed.

Figure 3. Manual unguals on this pterosaur are undisturbed.

This is not the first time
wing unguals and manual digit 5 have been identified in pterosaurs. Use those keywords to find previously posted specimens. Traditional paleontologists believe these bones don’t exist. That’s why I use Photoshop and the DGS technique… to share evidence. Now I encourage you to see for yourself.


References
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29:1327-1330.

https://blog.hmns.org/2020/01/hidden-in-plain-sight-how-photography-techniques-are-helping-us-dig-deeper/

 

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

Big pterosaurs: big or little wing tips

Earlier and below (Fig. 2) we looked at large and giant pterosaur wings comparing them to the largest flying birds, including one of the largest extant flying birds, the stork, Ciconia, and the extinct sheerwater, Pelagornis, the largest bird that ever flew.

FIgure 2. A basal pteranodotid, the most complete Pteranodon, the largest Pteranodon skull matched to the largest Pteranodon post-crania compared to the stork Ciconia and the most complete and the largest Quetzalcoatlus

FIgure 1. A basal pteranodotid, the most complete Pteranodon, the largest Pteranodon skull matched to the largest Pteranodon post-crania compared to the stork Ciconia and the most complete and the largest Quetzalcoatlus. Note the much reduced distal phalanges in the complete and giant Quetzalcoatlus, distinct from the Pteranodon species.

Today
we’ll look at how the largest Pteranodon (Figs. 1, 4) compares to much larger pterosaurs, like Quetzalcoatlus northropi (Figs. 1, 2) that have vestigial wingtips similar to those of the  much smaller flightless pre-azhdarchid, SOS 2428 (Fig. 3).

Note the tiny three distal phalanges
on the wing of the largest Quetzalcoatlus, distinct from the more typical elongate and robust distal phalangeal proportions on volant pterosaurs of all sizes. Much smaller definitely flightless pterosaurs, like SOS 2428, shrink those distal phalanges, too. That’s the pattern when pterosaurs lose the ability to fly.

Figure 2. Q. northropi and Q. sp. compared to Ciconia, the stork, and Pelagornis, the extinct gannet, to scale. That long neck and large skull of Quetzalcoatlus would appear to make it top heavy relative to the volant stork, despite the longer wingspan. Pteranodon and other flying pterosaurs do not have such a large skull at the end of such a long neck (Fig. 1). The longer wings of pelagornis show what is typical for a giant volant tetrapod, and Q. sp. comes up short in comparison.

Figure 2. A previously published GIF animation. Q. northropi and Q. sp. compared to Ciconia, the stork, and Pelagornis, the extinct gannet, to scale. That long neck and large skull of Quetzalcoatlus would appear to make it top heavy relative to the volant stork, despite the longer wingspan. Pteranodon and other flying pterosaurs do not have such a large skull at the end of such a long neck (Fig. 1). The longer wings of pelagornis show what is typical for a giant volant tetrapod, and Q. sp. comes up short in comparison.Today we’ll compare the wingspan of the largest Quetzalcoatlus to the largest and more typical Pteranodon species (Fig. 2).

Unfortunately
pterosaur workers refuse to consider taxa known to be flightless, like SOS 2428 (Peters 2018). It’s easy to see why they would be flightless (Fig. 3). Scaled to similar snout/vent lengths with a fully volant pterosaur like n42 (BSPG 1911 I 31) the wing length and chord are both much smaller in the flightless form.

Lateral, ventral and dorsal views of SoS 2428

Figure 3. Lateral, ventral and dorsal views of the flightless SoS 2428 (Peters 2018) alongside No. 42, a volant sister taxon.

Comparing the largest ornithocheirid,
SMNK PAL 1136, to the largest Pteranodon (chimaera of largest skull with largest post-crania in Fig. 4) shows that large flyers have elongate distal phalanges, distinct from body and wing proportions documented in the largest azhdarchids, like Quetzalcoatlus.

Figure 5. Largest Pteranodon to scale with largest ornithocheirid, SMNS PAL 1136.

Figure 4. Largest Pteranodon to scale with largest ornithocheirid, SMNS PAL 1136. Note the long distant wing phalanges on both of these giant flyers. This is what pterosaurs evolve to if they want to continue flying. And this is how big they can get and still fly. Giant azhdarchids exceed all the parameters without having elongate wings. Note: the one on the left has a longer wingspan whir the one on the right has a more massive torso and skull together with more massive proximal wing bones and pectoral girdle. On both the free fingers are tiny, parallel oriented laterally and slightly tucked beneath the big knuckle of the wing finger. The pteroid points directly at the deltopectoral crest. 

As the largest Pteranodon and largest ornithocheirid (SMNS PAL 1136)
(Fig. 4) demonstrate, as flying pterosaurs get larger, they retain elongate distal wing phalanges. And big, robust phalanges they are.

By contrast in azhdarchids and pre-azhdarchids
there is a large size bump after n42 (BSPG 1911 I 31) the fourth wing phalanx either disappears (see Microtuban and Jidapterus) or shrinks to a vestige. Then there’s Zhejiangopterus (Fig. 5), with a big pelvis, gracile forelimbs and a giant skull on a very long neck. Just that neck alone creates such a long lever arm that the pterosaur is incapable of maintaining a center of balance over or near the shoulder joints.

Figure 1. Click to enlarge. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

Figure 5. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

As mentioned earlier, becoming flightless permitted, nay, freed azhdarchid pterosaurs to attain great size. They no longer had to maintain proportions that were flightworthy. Instead they used their shortened strut-like forelimbs to maintain a stable platform in deeper waters. And when they had to move in a hurry, their wings could still provide a tremendous amount of flurry and thrust (Fig. 6) for a speedy getaway.

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 6. Quetzalcoatlus running without taking off, using all four limbs for thrust. That long lever arm extending to the snout tip in front of the center of gravity is not balanced in back of what would be the center of lift over the wings

For the nitpickers out there…
some specimens of Nyctosaurus (UNSM 93000, Fig. 7) also have but three wing phalanges, but they are all robust. The distal one is likely the fourth one because it remains curved. Phalanges 2 and 3 appear to have merged, or one of those was lost. Compare that specimen to a more primitive Nyctosaurus FHSM VP 2148 with four robust wing phalanges.

Figure 5. Cast of the UNSM 93000 specimen of Nyctosaurus. Missing parts are modeled here.

Figure 5. Cast of the UNSM 93000 specimen of Nyctosaurus. Missing parts are modeled here.

References
Peters D 2018. First flightless pterosaur (not peer-reviewed). PDF online.

 

Axial rotation: fingers in pterosaurs, toes in birds

A somewhat recent paper by Botelho et al. 2015
looked at the embryological changes that axially rotate metatarsal 1 to produce a backward-pointing, opposable, perching pedal digit 1 (= hallux).

Hallux rotation phylogenetically
Botelho reports: Mesozoic birds closer than Archaeopteryx to modern birds include early short-tailed forms such as the Confuciusornithidae and the toothed Enantiornithes. They present a Mt1 in which the proximal portion is visibly non-twisted, while the distal end is offset (“bent”) producing a unique “j-shaped” morphology. This morphology is arguably an evolutionary intermediate between the straight Mt1 of dinosaurs and the twisted Mt1 of modern birds, and conceivably allowed greater retroversion of Mt1 than Archaeopteryx.”

“D1 in the avian embryo is initially not retroverted9, and therefore becomes opposable during ontogeny, but no embryological descriptions address the shape of Mt1, and no information is available on the mechanisms of retroversion.”

Figure 1. Pes of the most primitive Archaeopteryx, the Thermopolis specimen.

Figure 1. Pes of the most primitive Solnhofen bird, the Thermopolis specimen. This digit 1 never left the substrate.

In Tyrannosaurus,
(Fig. 2) the entire metatarsal 1 with pedal digit 1 is rotated just aft of medial by convergence. It’s not axially rotated. It’s just attached to the palmar side of the pes. This pedal digit 1 was elevated above the substrate.

Figure 2. The semi-retroverted pedal digit 1 of Tyrannosaurus rex in two views.

Figure 2. The semi-retroverted pedal digit 1 of Tyrannosaurus rex in two views. This digit 1 was elevated above the substrate.

In some birds
like the woodpecker, Melanerpes, and the unrelated roadrunner, Geococcyx, pedal digit 4 is also retroverted. Sorry, I digress.

Further digression
The axial rotation of pedal digit 1 in birds is convergent with the axial rotation of metacarpal 4 in Longisquama (Fig. 3) and pterosaurs. In both taxa the manus was elevated off the substrate and permitted to develop in new ways. Manual digit 4 never leaves an impression in pterosaur manus tracks… because it is folded, like a bird wing, against metacarpal 4. In Longisquama such extreme flexion is not yet possible.

Figure 1. Longisquama left and right manus traced using DGS then reconstructed (below). This is a very large hand for a fenestrasaur and manual digit 4 is oversized, as in pterosaurs.

Figure 3. Longisquama left and right manus traced using DGS then reconstructed (below). This is a very large hand for a fenestrasaur and manual digit 4 is oversized and the metacarpal is axially rotated, as in pterosaurs. Manual digit 5 is useless, but not yet a vestige. A pteroid is present, as in Cosesaurus. The coracoid is elongate as in birds. The sternum, interclavicle and clavicle are assembled into a single bone, the sternal complex, as in pterosaurs.

Note the lack of space between
the radius and ulna in Longisquama. This is what also happens in pterosaurs. It prevents the wrist from pronating or supinating, as in birds and bats… which means, the forelimb is flapping, not pressing against the substrate, nor grasping prey. That means all those images of Longsiquama on all fours are bogus. Now you know.

So now we come full circle
While the toes of birds axially rotate and the wing metacarpal of pterosaurs axially rotates, the forearms of birds, pterosaurs and Longisquama do not axially rotate. No one wants their wing to twist.

References
Botelho JF, Smith-Paredes D, Soto-Acuña S, Mpodozis J, Palma V and Vargas AO 2015. Skeletal plasticity in response to embryonic muscular activity underlies the development and evolution of the perching digit of birds. Article in http://www.Nature.com/Scientific Reports · May 2015 DOI: 10.1038/srep09840

Pterodactylus manual digit 5

Tiny, vestigial manual digit 5
sits on the top of the giant axially rotated metacarpal 4 of all pterosaurs. Here (Fig. 1) manual digit 5 is curled up on this Pterodactylus scolopaciceps specimen (BSP 1937 I 18), a pregnant pterosaur. Photoshop helps this digit ‘pop’ making it harder to overlook. A reconstruction unrolls it.

Figure 1. Manual digit 5 on top of the giant metatarsal 4 on Pterodactylus. It's easy to overlook, until you look for it.

Figure 1. Manual digit 5 on top of the giant metatarsal 4 on Pterodactylus. It’s easy to overlook, until you look for it.

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

The carpus (wrist) of Pterodactylus scolopaciceps

Earlier we looked at the pectoral girdle of Pterodactylus scolopaciceps  BSP 1937 I 18 (Broili 1938, P. kochi n21 of Wellnhofer 1970, 1991).. And even earlier we looked at that elusive (they say it doesn’t exist!) manual digit 5. Today, some more thoughts on that wonderful wrist… (Fig. 1).

Figure 1. The wrist of Pterodactylus scolopaciceps BSP 1937 I 18 (Broili 1938, P. kochi n21 of Wellnhofer 1970, 1991). Manual digit 5 is a vestige, but it is there.

Figure 1. The wrist of Pterodactylus scolopaciceps BSP 1937 I 18 (Broili 1938, P. kochi n21 of Wellnhofer 1970, 1991). Manual digit 5 is a vestige, but it is there.

Manual digit 5
is here. So is metacarpal 5 and distal carpal 5

Figure 1. The wrist of Pterodactylus scolopaciceps BSP 1937 I 18 (Broili 1938, P. kochi n21 of Wellnhofer 1970, 1991). Manual digit 5 is a vestige, but it is there.

Figure 2. The wrist of Pterodactylus scolopaciceps BSP 1937 I 18 (Broili 1938, P. kochi n21 of Wellnhofer 1970, 1991). Manual digit 5 is a vestige, but it is there.

Metacarpals 1-3
are not pasted onto the anterior (during flight) face of the big metacarpal 4 as tradition dictates. Here mc1-3 are in their natural positions for tetrapods, palmar side down. Only metacarpal 4 is axially rotated so the wing finger folds (flexes) and extends in the place of the hand like bird and bat wings do. That means only metacarpal 3 attaches to metacarpal 4, mc2 lies between 1 and 3 and 1 hangs out in front.

Fingers 1-3
are dislocated and axially rotated anteriorly. In life they palms of the fingers would have been ventral, just like metacarpals 1-3 — not flexing anteriorly as they do here after crushing. Note the fingers are all disarticulated at the knuckle, which was a very loose joint, enabling 90 degrees of extension dorsally (in flight) or laterally (while quadrupedal for walking. Moreover, digit 3 was able to flex in the plane of the wing, like the wing. That produces manus impressions in which digit 3 is oriented posteriorly. That’s very weird for most tetrapods, but common in pterosaurs, as it indicates the quadrupedal configuration was achieved secondarily from an initial bipedal configuration.

Of added interest here….
Note the sawtooth posterior edges of the forelimb, hand and finger four where the wing membrane was attached, fed and enervated. Note also the large extensor tendon distal to the preaxial carpal. It is rarely preserved.

The preaxial carpal and pteroid
as you might remember, are former centralia having migrated to the outside (Peters 2009). We looked at analogous migrations here.

Radius and ulna
as in birds and bats, there is no pronation or supination in the pterosaur wrist and forearm. The elements are too close together to permit this. And that’s a good thing to keep the wing in the best orientation for flight. Bats and birds don’t twist their forearms either.

As you already know, every body part that disappears
goes out with a vestige.

References
Broili F 1938. Beobachtungen an Pterodactylus. Sitz-Bayerischen Akademie der Wissenschaten, zu München, Mathematischen-naturalischenAbteilung: 139–154.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29:1327-1330.
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

wiki/Pterodactylus

Longisquama wings

Everyone agrees
that the anterior half of Longisquama is known because it is plainly visible. Everyone agrees that a pair of forelimbs is visible. Sharov (1970) illustrated fingers, but was stymied from completing that task because the two hands are preserved one on top of the other with the fingers intermingled. You can see that chaotic preservation here.

DGS
(digital graphic segregation) is a useful method to segregate one Longisquama hand from another and fingers from one another. Once that is done, phalangeal lengths can be matched for validity and accuracy. Ultimately a reconstruction can be produced (Fig. 1). It is readily apparent that the in situ chaos as preserved is difficult to trace, but not impossible. Anyone can do it with enough resolution and patience.

Figure 1. Longisquama left and right manus traced using DGS then reconstructed (below). This is a very large hand for a fenestrasaur and manual digit 4 is oversized, as in pterosaurs.

Figure 1. Longisquama left and right manus traced using DGS then reconstructed (below). This is a very large hand for a fenestrasaur and manual digit 4 is oversized, as in pterosaurs. Yes, membranes are preserved trailing the manus, just as plumes and other membranes are preserved elsewhere.

The importance of overcoming a chaotic preservation
to retrieve an orderly reconstruction is well illustrated by this example (Fig. 1). The fact that corresponding phalanges on both hands are equal in length self-validates the tracing. Here the phalanges are numbered and their images were copied and pasted to produce the reconstruction. Also note the shapes of the scapula and coracoid, perfect for flapping. There’s a nice sternal complex in there too. Only fenestrasaurs, including pterosaurs, have those.

The size of the manus,
relative to the humerus and antebrachium, the proportions of the phalanges, the presence of a trailing membrane and of preaxial carpals (including a pteroid) all indicate a close relationship to pterosaurs and other fenestrasaurs. No other tetrapods share these traits.

Figure 2. Click to animate. Longisquama flapping and wagging its tail.

Figure 2. Click to animate. Longisquama flapping and wagging its tail.

Scientists have been looking
for a non-flying reptile with large hands that could be a pterosaur ancestor. This is it (fig. 2), only the fingers are a little curled up and relative to the torso the entire forelimb is short, as in the sister to Longisquama, Sharovipteryx.

References
Peters D 2000.
 A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Sharov AG 1970. A peculiar reptile from the lower Triassic of Fergana. Paleontologiceskij Zurnal (1): 127–130.

Finger 5 in Triassic pterosaurs

Earlier
we looked at examples of manual digit 5 in pterosaurs here, here and here. Traditional paleontologists don’t recognize it. In fenestrasaur pterosaur precursors, like Cosesaurus, Sharovipteryx and Longisquama, manual digit 5 is small, but easier to see because it is relatively larger. You can see the evolution of the pterosaur hand here.

In pterosaurs manual digit 5 is extremely tiny and hard to find (Fig. 1). It can be lost during taphonomy. Fossilization tends to scatter the elements over metacarpal 4, which is often cracked and covered with sinewy soft tissue, factors that make identification all the more difficult. More to the point, based on the current paradigm, no one looks for it during preparation. These are NOT the best examples.

Figure 1. While difficult to discern at this scale, here is where I think the elements of manual digit 5 reside on these four Triassic pterosaurs.

Figure 1. These are not the best examples. While difficult to discern at this scale, here is where I think the elements of manual digit 5 reside on these four Triassic pterosaurs. Images from Dalla Vecchia and Cau 2014. Metacarpal 5 is located, as in other tetrapods, lateral to metacarpal 4, but in pterosaurs metacarpal 4 is axially rotated 90 degrees and metacarpal 5 ends up dorsal to metacarpal 4.

Complete loss of a body part is rare.
Often enough, as in basal whales and snakes, a vestige, like manual digit 5 in pterosaurs, remains. Granted it’s not easy to see. On the other hand, we’re not looking for it. Start with the proximodorsal surface of metacarpal 4. While there look for c5, mc5 and digit 5 composed of three elements including the ungual.

While we’re here looking at the metacarpus,
note that metacarpal 1 is connected only to metacarpal 2 and metacarpal 2 is connected only to metacarpal 3 and metacarpal 3 is connected only to metacarpal 4 — as in all tetrapods. There is no draw bridge-like rotation of mc1-3 to attach dorsal-to-dorsal to metacarpal 4, as promoted by pterosaurs workers who think fingers 1-3 were palmar side anteriorly during flight. That large space dorsal of metacarpals 1-3 is where all the finger extensors remain free to operate, with the wing finger tendon largest by far.

References
Dalla Vecchia FM and Cau Andrea 1014. Re-examination of the purported pterosaur wing metacarpals from the Upper Triassic of England. Historical Biology. To link to this article: http://dx.doi.org/10.1080/08912963.2014.933826

The PMOL Changchengopterus manus – DGS

A while back we looked at the new Changchengopterus (the one that did not nest with the holotype). Here is a closer look at the hand.

Figure 1. PMOL Changchengopterus manus in situ and reconstructed. Click to animate to show flexor and extensor tendons. Note the presence of digit 5. The unguals invivo  point ventrally,  When crushed, like this, they often show their anterior (medial) faces. Shapes of the unguals are shown in gray. The pteroid articulates with the radiale.

Figure 1. PMOL Changchengopterus manus in situ and reconstructed. Click to animate to show flexor and extensor tendons. Note the presence of digit 5. The unguals invivo  point ventrally,  When crushed, like this, they often show their anterior (medial) faces. Shapes of the unguals are shown in gray. The pteroid articulates with the radiale.

Earlier we solved the problem
of flexor tendon insertion and flexion, here, here and here.

Figure 2. Traditionally digit 5 has been overlooked. Hopefully this GIF animation will help you see it.

Figure 2. Traditionally digit 5 has been overlooked. Hopefully this GIF animation will help you see it. Look for an ungual, two other phalanges, a metacarpal and an carpal, as in Longisquama and Cosesaurus, but in this case all overlain by soft tissue (probably tendons) and riddled with cracks.

Earlier we looked at
the manual digit 5 problem in pterosaurs here, here and here. The reduction of manual digit 5 is documented here. Cosesaurus and Longisquama, two pterosaur outgroups, retain a distinct manual digit 5 of the same morphology.

References
Zhou C-F and Schoch RR 2011. New material of the non-pterodactyloid pterosaur Changchengopterus pani Lü, 2009 from the Late Jurassic Tiaojishan Formation of western Liaoning.  N. Jb. Geol. Paläont. Abh. 260/3, 265–275 published online March 2011.

 

Dimorphodon pterosaur takeoff – revised

Earlier I produced an animated GIF that showed how Dimorphodon could not have taken off using its forelimbs (Fig. 1; contra Witton 2013). At the same time I produced an animated GIF that showed how Dimorphodon could have taken off using its hind limbs

Figure 3. Dimorphodon and Desmodus (the vampire bat) compared in size. It's more difficult for larger, heavier creatures to leap, as the mass increases by the cube of the height. Size matters. And yes the tail attributed to Dinmorphodon, though not associated with the rest of the skeleton, was that long. Note the toes fall directly beneath the center of balance, the shoulder glenoid, on this pterosaur, And it would have been awkward to get down on all fours.

Figure 3. Dimorphodon and Desmodus (the vampire bat) compared in size. It’s more difficult for larger, heavier creatures to leap, as the mass increases by the cube of the height. Size matters. And yes the tail attributed to Dinmorphodon, though not associated with the rest of the skeleton, was that long. Note the toes fall directly beneath the center of balance, the shoulder glenoid, on this pterosaur, And it would have been awkward to get down on all fours.

with wings still folded (modified Fig. 2), noting that back then I preferred to use the wings, but wanted to show how powerful the hind limbs were. For some reason I waited until today to offer an animated GIF in which the wings open prior to takeoff and together with the hind limbs initiate a power launch with maximum thrust (Fig. 3), just like birds.

Click to animate. Witton's Dimorphodon in the process of leaping. Note the wings are in the upswing at the apex of the leap. The opposite and equal reaction, along with gravity, pushes the pterosaur down. There's just not as much leverage and musculature here as in the vampire bat, which can accomplish this leap.

Figure 1. Click to animate. Witton’s Dimorphodon in the process of leaping. Note the wings are in the upswing at the apex of the leap. The opposite and equal reaction, along with gravity, pushes the pterosaur down. There’s just not as much leverage and musculature here as in the vampire bat, which can accomplish this leap.

FIgure 8. Dimorphodon take off (with the new small tail).

Figure 2, 3. Dimorphodon take off (with the new small tail).

Which takeoff method is less risky? Uses larger muscle groups? Is replicated by living taxa? And falls in line with basal nonvolent taxa (like Sharovipteryx and Longisquama)? Why not use the wing thrust to ensure getting airborne? That’s what birds and bats do…

And why are paleontologists embracing this heretical idea and giving it the status of paradigm? Now the ‘normal’ takeoff, like a bird, is considered heretical.

Figure 4. Dimorphodon fingers. Yellow added for keratin extensions. M. Witton suggests that these claws are inappropriate for grasping and so doesn't mind placing Dimorphodon into a quadrupedal pose, making everything awkward to impossible from that point on. These claws look trenchant to me, ideal for clinging to tree bark or other similar substrates.

Figure 4. Dimorphodon fingers. Yellow added for keratin extensions. M. Witton suggests that these claws are inappropriate for grasping and so doesn’t mind placing Dimorphodon into a quadrupedal pose, making everything awkward to impossible from that point on. These claws look trenchant to me, ideal for clinging to tree bark or other similar substrates.

Today’s blog post was inspired
by one produced by Dr. M. Witton in response to the Jurassic World movie, who noted, The hands and feet of Dimorphodon are also robust, and equipped with large, trenchant claw bones (these, of course, provide the specific namesake, ‘macronyx’). There are indications that the extensor muscles controlling these might have been powerful, as every claw on both hands and feet is equipped with a neighbouring sesamoid – those intra-tendinous bones serving to enhance muscle output or protect tendons against powerful joint motion. Interestingly, the only other animals with these claw-adjacent sesamoids are lizards and a ‘bottom walking’ fossil stem-turtle – more on that another time. As with all pterosaurs, there is no indication that their hands or feet were for grasping, and their claws are really nothing like talons (take that, Jurassic World website).”

If I’m reading this correctly 
Dr. Witton doesn’t consider ‘trenchant’ (= penetrating) claw bones to be anything like ‘talons,’ which typically are unguals that penetrate prey. The feet of pterosaurs are indeed not made for grasping (screaming tourists, etc.), but the wing claws of Dimorphodon were ideally set up for vertical landings on tree trunks. When the wings are adducted the palmar side of the unguals face each other like clapping hands and could have readily grappled a tree trunk like a lineman, penetrating the bark with its talons. This is taken to the extreme in the related pterosaur, Jeholopterus and the bird-like dinosaur, Velociraptor, which had similar stiff fingers supporting feathers and trenchant claws – ideal for grappling, but not grasping.

Earlier we looked at
pterosaur hands here in the first of a seven-part series. The variety you’ll see will show you that pterosaur fingers and claws evolved for several environments and uses.

References
Witton M. 2013. Pterosaurs. Princeton University Press. 291 pages.