More Than Just a Pretty Propatagium

The CAGS specimen CAGS IG 02-81 originally attributed to Dendrorhynchoides (Lü et al. 2006, 18 steps different) and then to Jeholopterus (4 steps different) is neither genus, but has a suite of traits that distinguish it from both. But that’s not the point of today’s blog. We’re looking today at what appears to be an extraordinary propatagium unlike any other (Figure 1).

The CAGS specimen

Figure 1. The CAGS specimen attributed to Dendrorhynchoides and then to Jeholopterus, but is distinct from both. Note the dark triangle that appears to be a fibered propatagium (between the wrist and shoulder) more distinct than the remnants of the brachiopatagium.

A Propatagium with Aktinofibrils?
The apparent propatagium of the CAGS specimen appears to preserve all the traits of a brahiopatagium, which is unlike that of any other pterosaur. For instance, it has aktinofibrils! Elgin, Hone and Frey (2010) considered this an example of dermal shrinkage in the wing membrane. Actually the membranes are torn and folded without shrinkage. So, this is yet another one of Nature’s tricky illusions (like Sordes) deserving of a more vigorous examination.

Interpretation of bony and soft tissue elements in the CAGS specimen.

Figure 2. Interpretation of bony and soft tissue elements in the CAGS specimen. Click to see rollover image. The actual propatagia are in blue. Torn and displaced brachiopatagial elements mask both propatagia. The parts marked "distal wing elements" are below the more superficial skeletal elements. As in other anurognathids, the distal wing elements were folded over the back, so here in ventral exposure, they are preserved deeper than the rest of the skeleton after dislocation. Can you find the sternal complex? I probably underestimated the preservation of wing membrane here, much of which is beneath the body. The pteroids are relaxed here.

Layered Membranes
As you might have guessed from the title of this blog, there’s more to it than meets the eye. DGS (digital graphic segregation) enabled the separation of this odd bit of anatomy into two separate overprinting layers. One is indeed the propatagium, essentially devoid of internal details as in other pterosaurs (perhaps because it is the extensor digitorum longus as blogged earlier). The other is  a torn section of the brachiopatagium, the part of the wing with all the aktinofibrils. The apparent lack of distal wing phalanges indicates parts of the wing were torn off their phalangeal moorings. Using DGS clarifies the mystery. Critical analysis has to be done, rather than accepting face value.

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
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
Lü J-C, Ji S, Yuan C-X and Ji Q 2006. Pterosaurs from China. Geological Publishing House, Beijing, 147 pp.

Pterosaur Fingers – Part 8, Germanodactylus to Nyctosaurus and Pteranodon

Earlier we looked at several clades of pterosaur finger morphologies. Today we’ll look at various Nyctosaurus and Pteranodon species and their precursors (Fig. 1).

Pterosaur fingers, Germanodactylus to Nyctosaurus and Pteranodon.

Figure 1. Pterosaur fingers, Germanodactylus to Nyctosaurus and Pteranodon. Click to enlarge.

Germanodactylus cristatus SMNK-PAL 6592 – Compare to the outgroup taxon Elanodactylus

No. 13 – Overall smaller, m3.3 was shorter and the unguals were sharper.

Aurorazhdarcho – The metacarpus was nearly twice as long and metacarpals 1-3 were more gracile. Manual 1.1 was half as long. Manual 3.2 was nearly the length of m3.3. The unguals were smaller.

Eoazhdarcho – Metacarpals 1-3did not reach the carpus. The digits were longer. The unguals were smaller.

Eopteranodon – Manual 2.2 was longer and m3.1 was shorter. The unguals were larger.

Muzquizopteryx – Compare to the outgroup taxon No. 13. The metacarpus was longer, though not as long as in the eopteranodontids. Metacarpals 1-3 did not reach the carpus. The proximal phalanges were longer. The unguals were shorter.

Nyctosaurus FMNH 25026 – Metacarpal 4 was longer. The digits were less than half the size.

Nyctosaurus FHSM VP 21 – Distal metacarpal 4 was reduced. The digits were smaller and more gracile.

Nyctosaurus UNSM 93000 – The digits were mere threads.

Nyctosaurus KJ1 – No digits are known.

Pteranodon FHSM VP 2183 – Compare to outgroup Germanodactylus cristatus SMNK-PAL 6592. The metacarpus was longer. The digits were shorter.

Pteranodon YPM 1175 – The digits were smaller. The unguals were shorter.

Pteranodon (Ptweety the immature private specimen) – The fingers and their unguals were much larger, as in the JZMP embryo (above), but not in the Pterodaustro or IVPP embryos.

Pteranodon NMC41-358 – Compared to outgroup FMNH 25026. The metatarsus and digits were more gracile. The unguals were more deeply hooked. Manual 2.2 was longer relative to m2.1.

Pteranodon UALVP 24238 – The metacarpus was more robust. The digits were smaller.

Pterosaur Fingers – Part 6, Scaphognathus to Pterodactylus and Other Tiny Pteros

Earlier we looked at several clades of pterosaur finger morphologies. Find them here, here, here, here, here and here. Today we’ll look at various Pterodactylus species (Fig. 1), their tiny predecessors and their tiny cousins preceding Germanodactylus (which we’ll consider next).

pterosaur fingers

Figure 1. Pterosaur fingers, Scaphognathus to Pterodactylus and other tiny pterosaurs

Gmu 10157 – The metatarsus was longer. The digits were shorter. Ungual 1.1 was larger.  Compare to the outgroup taxon, Scaphognathus (Maxburg specimen).

Ornithocephalus – The digits and unguals were smaller. Digits 1 and 2 were relatively smaller. Manual 3.1 was longer. Manual 2.2 was shorter.

No 9 – Th digits were larger and more robust.

No 31– The digits were smaller and more gracile. Manual 3.2 was as long as m3.3.

Ningchengopterus – The digits were larger, nearly as long as the metacarpus. Metacarpal 1 was the longest. Manual 3.2 was shorter.

Pterodactylus AMNH 1942, no 20 – Metacarpal 1 was shorter. The digits were relatively shorter.

Pterodactylus NHMW1975 – Manual 3.2 was longer.

Pterodactylus scolapaciceps No 21 – Ungual 3 was smaller.

Pterodactylus (Frey and Tischlinger private specimen) – The digits were smaller and more gracile.

Pterodactylus antiquus (holotype) no. 4 – The metacarpus was more gracile.

Diopecephalus, Pterodactylus longicollum, no. 58 – The digits are unknown. The metacarpus was relatively twice as long.

No 6 – Compare to the outgroup taxon No 31. The digits were more robust and slightly larger.

BMNH 47236 – The unguals were more trenchant.

No 12 – The digits were longer. The unguals were less trenchant. Manual 3.1 was longer.

No 23 – Manual 2.2 was shorter.

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.

Pterosaur Fingers – Part 5, Scaphognathus to Cycnorhamphids and Ornithocheirids

Earlier we looked at the evolution of the fingers of basal pterosaurs and dimorphodontids, basal eudimorphdontids, campylognathoides and rhamphorhynchus, and most recently dorygnathids leading to azhdarchids and ctenochasmatids. Today we’ll look at scaphognathids to cycnorhamphids and ornithocheirids.

Pterosaur fingers

Figure 1. Click to enlarge. Pterosaur fingers, Scaphognathus to cycnorhamphids and ornithocheirids

Jiangchangopterus – Compare to the outgroup taxon, Changchengopterus, with similar overall proportions. Manual 3.1 was the shortest phalanx.

Scaphognathus crassirostris (holotype) – The metatarsus was shorter. Manual 3.2 was longer. The digits were more robust. The unguals were larger.

Scaphognathus SMNS 59395 – The digits were relatively longer.

Scaphognathus (Maxburg specimen) – The metatarsus was longer. The digits were shorter. The unguals were shorter. Manual 3.2 was shorter.

Gmu 10157 – The metatarsus was longer. The digits were shorter. Ungual 1.1 was larger.

TM 10134 – The metatarsus was more gracile. The digits were relatively smaller. Manual 2.1 and m3.1 were relatively longer. The unguals were smaller.

BSp 1986 XV 132 – The metatarsus was relatively longer. The digits were much shorter with smaller unguals.

No. 30 – The proximal metatarsus was more robust. The fingers were longer, but shorter than those of Gmu 10157.

Cycnorhamphus – The proximal phalanges were longer. The penultimate phalanges were shorter.

Yixianopterus – Compare to outgroup sister taxon TM 10134. (This data was difficult to gather and may include errors. It certainly includes some autapomorphies.) The metatarsus was more robust. Manual 1.1 was longer. As in the Maxburg specimen the penultimate phalanges were longer.

Lebanon specimen (MSNM V3881) – The digits were smaller. Digit 1 was not elongated as in Yixianopterus.

JZMP embryo – The digits were relatively the largest among all ornithocheirids (a possible juvenile trait?) Digits 3 and 2 nearly the same length.

Haopterus – The digits were mid-sized. The unguals were smaller. The digits were more gracile.

Boreopterus – The digits were relatively shorter with smaller unguals. Manual 3.2 was a disc. The unguals were larger.

Zhenyuanopterus – Manual 3.1 was shorter and shorter than m2.1. Manual 3.2 was longer.

Arthurdactylus -The digits were more gracile and longer with smaller unguals.

Nurhachius – The proximal metatarsus was twice the width of the distal end. The digits were much shorter and smaller with relatively large unguals. Manual 3.2 was a disc. Manual 2.2 was longer than m3.3

Istiodactylus – Digits 1-3 were subequal and nearly identical, composed of only two phalanges (including the ungual) each, which is unique in pterosaurs.

Brasileodactylus – The digits were long with larger unguals.

Anhanguera – The digits were more robust. The unguals were deeper.

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.

Pterosaur Fingers – Part 4, Dorygnathus to Ctenochasmatids

Earlier we looked at dimorphodontid and basal eudimorphodontid hands. Today we’ll take a look at the clade that begins with the Donau specimen of Dorygnathus and ends with Pterodaustro.

Dorygnathus to Ctenochasmatid hands

Figure 2. Dorygnathus to Ctenochasmatid hands. Not to scale. Click to enlarge.

The trend here is to a longer metacarpus, but not coincident with the reduction of the tail. The fingers and unguals were much smaller in the beach-combing ctenochasmatids, probably indicating no further need of trees to grapple.

Fenghuangopterus? (Dorygnathus species) – Compare to the outgroup taxon, Dorygnathus, the Donau specimen. Metacarpal 4 was more robust. Metacarpal 2 was subequal to mc3. Digits 2 and 3 were shorter. Manual 3.2 was no longer than wide.

Dorygnathus SMNS 55886 – The digits were relatively shorter and more gracile.

Dorygnathus R 156 – The metatarsus was smaller and the digits were longer with larger unguals. Manual 3.2 was longer than wide.

The St/Ei 1 specimen attributed to Pterodactylus – The metatarsus was a quarter longer. Manual 3.2 was nearly as long at m3.1. Smaller unguals. The drastic reduction in the tail places this taxon in the pterodactyloid-grade, but the metacarpus was not elongated.

MB.R.3530.1, No. 40 (Wellnhofer 1970) – The metacarpus was a wee bit shorter. Unguals were smaller.

Ctenochasma elegans (private specimen) – The metacarpus was nearly twice as long. Manual 1.1 was shorter and subequal to m2.1. Manual 3.3 was shorter than m3.1. The unguals were reduced to no deeper than the penultimate phalanges.

Ctenochasma? elegans (a small Gnathosaurus species) AMNH 5147 – The metacarpus was slightly longer. Manual 1.1 was longer.

Pterodactylus? micronyx (Pester specimen) – Manual 1.1 was shorter than m2.1, which was longer than m2.2.

Ctenochasma elegans No. 45 – The digits were shorter and more robust. The proximal phalanges were all subequal.

Ctenochasma gracile, No. 65 – The metacarpus was longer and more gracile. The digits were more gracile. Manual 3.2 was a disc.

Pterodaustro – The metacarpus was shorter with a larger wing finger joint. Digit 3 was not longer than digit 2.

Pterodaustro embryo – The metacarpus was relatively shorter. The unguals were relatively larger.

 

Another Really Tiny Pterosaur: BMNH 42736

The smallest known pterosaur B St 1967 I 276 (No. 6 of Wellnhofer 1970 ) was discussed earlier. Today we get to meet maybe the second smallest pterosaur, Pterodactylus meyeri BMNH 42736 (Munster 1842, Fig. 1) is the same size as No. 6, but had several distinct traits (Fig. 2). I ran across the BMNH specimen in Unwin’s (2006) The Pterosaurs From Deep Time book on page 151. Dr. Unwin considered the specimen a “flapling” (= newly hatched pterosaur able to fly) with a wingspan of 17 cm, so that is the reconstructed scale (Fig. 3).

The Value of a Reconstruction
It’s a shame that modern workers don’t produce reconstructions of crushed pterosaurs anymore. There is so much to see (Figs. 2, 3), especially when one compares similar specimens. Many traits would go unnoticed if left crushed.

One of the world's smallest pterosaurs

Figure 1. One of the world's smallest pterosaurs, traced from Unwin (2006, p. 151). The feet of the "flapling" were not articulated and a certain amount of guesswork was applied to the idenfication of the pedal elements and their reconstruction. Note how the left radius and ulna are parallel to and beneath the elongated right scapula. The right coracoid is largely beneath the right humerus. The left hand and proximal wing finger are beneath the right hand. Soft tissue stains are highlighted in orange. The wing had a narrow chord at the elbow. Colorizing the bones is a result of employing DGS, digital graphic segregation.

Phylogenetic Nesting
Here the “flapling” nested between No. 6 and No. 12, two other tiny ornithocephalians (and former Pterodactylus) outside of the Pterodactylus lineage, at the base of the Germanodactylus clade. Conveniently (for those looking for transitional taxa) No. 6 was smaller and No. 12 was larger than the BMNH “flapling.”

Distinct from No. 6, the “flapling” had a deeper skull, more and smaller dorsal vertebrae and ribs, a longer scapula (almost touched the pelvis), a deeper and more fully fused pelvis and a larger sternal complex than either of its sisters. Considering the reconstructed differences in quadrate elevation, jugal shape and pelvis dimensions (Fig. 2), you might think the “flapling” would have nested further apart from No. 6 and No. 12. These distinctions suggest that the “flapling” may have been at  the base of its own clade of currently unknown descendants.

The tiniest pterosaurs.

Figure 2. The tiniest pterosaurs. On the left, Unwin's "flapling" Pterodactylus meyeri BMNH 42736. On the right, B St 1967 I 276, No. 6, the former sole owner of the title.

Juvie or Adult?
If the BMNH tiny pterosaur was indeed a juvenile of a larger more established taxon, which one did it match up to? And if so, why did it nest with other tiny pterosaurs? No. The BMNH specimen was an adult. The many autapomorphies (= differences) in the “flapling” also follow a larger trend seen in other tiny pterosaurs: morphological innovation.

Full scale image of ginkgo leaf and the two smallest pterosaurs

Figure 3. Full scale image of ginkgo leaf and the two smallest pterosaurs to scale on a 72 dpi screen. Yes, these are tiny, but just look at the size of a hatchling on the far right, no bigger than a small fly.

Special Premaxillary Teeth
In the BMNH “flapling” we see more substantial anteriorly-directed medial teeth forming the tip of the premaxilla. Those two teeth evolve to become one in the rostral tip of Germanodactylus. That tooth is the only one retained in so-called “toothless” pterosaurs like Pteranodon and Nyctosaurus that have sharply tipped jaws.

Bigger Eggs?
A deeper pubis and pelvis in the BMNH specimen could have produced a larger egg. A stronger sternal complex and longer scapula could have made the “flapling” a more powerful flyer.

Soft Tissue Preservation
Despite a flipped mandible and poorly preserved feet, the “flapling” is otherwise well preserved and largely articulated. A soft tissue stain can be seen (overprinted in Fig. 1) that demonstrates a narrow chord at the elbow wing membrane construction.

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
Meyer H von 1842. Notes on labyrinthodonts and fossil reptiles, including a description of Belodon plieningeri, new gen. and sp. Neues Jahrbuch fur Mineralogie, Geologie und Palaontologie 1842, pp. 301-304.
Unwin D M 2006. 
The Pterosaurs From Deep Time. 347 pp. New York, Pi Press.
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

Pterosaur Fingers – Part 2, Eudis, Campys, Rhamphs and Darwinopterids

Earlier we looked at basal pterosaur finger morphologies. Today we’ll look at basal eudimorphodontids up to the darwinopterids (not including dorygnathids). Those come next.

Pterosaur fingers

Figure 1. Pterosaur fingers – basal eudimorphodontids up to darwinopterids. Click to enlarge. Red arrows indicate fingers twisted to better show ungual shape. 

Eudimorphodon ranzii – Compare to the outgroup taxon, SC 332466. Metacarpal 4 was more robust. The unguals were more sharply curved.

Campylognathoides – Little change in this clade other than a slight progressive shortening of the metacarpus and fingers. In the Stuttgart and Pittsburgh specimens the stair-step metacarpals were aligned diagonally.

Rhamphorhynchus – The BMM specimen was overall much smaller than the Pittsburgh specimen of Campylognathoides with a relatively more robust metacarpal 4. Only mc1 was shorter than the others. Manual 3.2 was relatively shorter. The unguals were smaller. In R. longicaudus and R. longiceps digit 3 was relatively longer. Manual 2.1 and m3.1 were shorter. In R. muensteri the fingers were shorter than the metacarpus with shorter penultimate phalanges. In R. megadactylus the metacarpus was shorter, the fingers were relatively longer but retained shorter penultimate phalanges. The otherwise bizarre MYE 13 specimen of Rhamphorhynchus has the largest fingers and claws relative to the metacarpus.

Changchengopterus – Compare to the outgroup taxon, Eudimorphodon with stair-stepped metacarpals. Manual 3.2 was no longer than wide.

Sordes – The fingers were more symmetrical. Manual 3.1 was shorter. The unguals were larger.

Jianchangnathus – Compare to the outgroup taxon, Changchengopterus, with similar overall proportions. Manual 3.1 was the shortest phalanx.

Pterorhynchus – The metacarpus was relatively shorter. Manual 2.1 and m3.1 were subequal. The unguals were smaller.

Kunpengopterus – The metacarpus was relatively longer. Only metacarpal 1 was shorter than the others. The unguals were smaller.

Wukongopterus – The penultimate phalanges were shorter and the digits were less asymmetrical with larger unguals.

Darwinopterus – Several morphologically distinct specimens have been referred to Darwinopterus. D. robustodens and D. modularis (YH-2000) had more robust metacarpals 1-3. In AMNH M8802 had longer, more gracile digits with shorter penultimate phalanges. YH-2000 had shorter proximal phalanges.

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.

Why Pterosaurs Are Extinct Today

The K/T Extinction Event
Everyone knows that pterosaurs, dinosaurs and a host of other prehistoric reptiles died out at the K/T (Cretaceous/Tertiary) boundary ~65 mya. But SOME birds, lizards, turtles, crocs and mammals survived. So, why did ALL pterosaurs die out?

Phylogenetic Analysis 
As in dinosaurs, the pterosaurs we know from the latest Cretaceous were not the same pterosaurs living in the Triassic, Jurassic or Early Cretaceous. All of these earlier pterosaurs became extinct, but a few genetic lines survived by evolving into the Late Cretaceous forms we know and love. Phylogenetic analysis indicates that certain lucky Middle Jurassic Dorygnathus specimens ultimately evolved (via several transitional taxa) into Quetzalcoatlus, Pteranodon, Nyctosaurus, Tupuxuara and any other Late Cretaceous pterosaurs I’m forgetting (the current list is not much longer than this).

The Example of Dorygnathus
Analysis illustrates how the descendants of Dorygnathus changed in size and shape as they evolved into the above Late Cretaceous taxa. Therein, l think, lies the answer to why pterosaurs were not able to continue evolving into the modern day.

The Azhdarchidae.

Figure 1. The Azhdarchidae. Click to enlarge.

Size Matters
If we were to follow the lineage of Dorygnathus through Quetzalcoatlus (Fig. 1) we would meet the following taxa in order: Dorygnathus (SMNS 50164), Pterodactylus? spectabilis (TM 10134), Beipiaopterus, No. 44, No. 42, Jidapterus, Chaoyangopterus, Zhejiangopterus and finally the two species of Quetzalcoatlus. Setting aside the huge size differences between the two Qs and their phylogenetic predecessor, Zhejiangopterus, note that tiny TM 10134 and two other tiny pteros, No. 42 and No. 44, are in this line-up.

Tiny Survivors
In the Late Jurassic the genetic lineage of Dorygnathus, of the Middle Jurassic, was represented by a tiny version of itself, TM 10134. There were no other full-size Dorygnathus present in the Late Jurassic. Something killed every other one over a certain size. Only tiny dory descendants somehow survived. Was it because of their size?

Major Morphological Changes in Tiny Taxa
As mentioned above (Fig. 1) other Late Jurassic tiny dorygnathids also include No. 42 and No. 44, both of which evolved a slender elongated neck, a low trostrum, smaller teeth and longer more gracile limbs. These traits were retained in all later and larger azhdarchids and huanhepterids (Fig. 1). (Pterorhynchids, scaphognathids and ctenochasmatids were also Dorygnathus descendants you can read about here, here and here).

Good Times
When the threat of extinction did not loom over pterosaurs, they tended to become bigger. Evidently this was especially true during the latest Cretaceous because pterosaurs reached their greatest sizes right at 65 million years ago.

Not Being Small Is What Killed Late Cretaceous Pterosaurs
Just as being small saved many pterosaur lines earlier, being small saved many other vertebrates following the K/T mass extinction event. Big vertebrates did not survive. Unfortunately the giant pterosaurs of the latest Cretaceous could not breed small enough to save themselves, as their ancestors had done. We don’t find any pterosaurs smaller than Nyctosaurus in the Late Cretaceous.

Serial Size Reduction and How It Happens
ln pterosaurs phylogenetic size reduction from Dorygnathus to TM 10134 was made possible by reaching sexual maturity at half their final size (Chinsamy et al. 2008). Smaller pelves would have passed smaller eggs, smaller hatchlings and an even smaller second generation in serial fashion. Smaller vertebrates typically have a relatively faster maturation process, creating more tiny hatchlings earlier and at a faster clip. This increase in reproductive rates raised the odds that whatever was killing the larger, slower-to-breed individuals could be overcome by an acceleration in breeding, producing an acceleration in genetic variation and mutation. Such a serial size reduction pattern occurred at the base of nearly every major clade within the Pterosauria. When the same process is observed about a dozen times that verifies its veracity.

Phony pterosaur.

Figure 2. Phony pterosaur.

If only some tiny pteros existed at the Late Cretaceous, we might have some “thunderbirds” flying around today (Fig. 2).

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
Chinsamy A, Codorniú L and Chiappe LM 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters, 4: 282-285.

What is Qinglongopterus? Perhaps a Junior Synonym.

Lü et al. (2012) erected a new genus and species for a new rhamphorhynchid from the Tiaojishan Formation of China (Mid/Late Jurassic). They reported, “Qinglongopterus is strikingly similar to Rhamphorhynchus and more closely related to this taxon than to any other rhamphorhynchine.”

 

Figure 1. Qinglongopterus? guoi. A new Rhamphorhynchus species. Tracing of photo of specimen modified with wings and leg out, skull reconstructed, sternum flipped.

Figure 1. Qinglongopterus? guoi. A new Rhamphorhynchus species. Tracing of photo of specimen modified with wings and leg out, skull reconstructed, sternum flipped.

Ontogeny
Lü et al. (2012) considered the Qinglongopterus specimen immature due to lack of fusion in the scapula + coracoid, carpals, extensor tendon epiphysis, pubis and ischium, etc. However they noticed, “external bone surfaces appear to be fairly well ossified and do not exhibit the coarse, fibrous texture evident in the rostrum and limb bones of embryos.”

Phylogeny
Lü et al. (2012) considered their find an archosaur. They used Euparkeria for an outgroup taxon. While noting similarities to Rhamphorhynchus and considering the specimen immature, oddly Lü et al. (2012) did not test their find against any so-called “immature” Rhamphorhynchus specimens. Their analysis of 37 taxa recovered 550 trees and nested Qinglongopterus with R. muensteri.

That’s 549 Red Flags
IMHO, that’s way too many MPTs for so few taxa.

Testing All the Above
Qinglongopterus was inserted into the matrix of the large pterosaur study, which included eleven Rhamphorhynchus specimens of all sizes. Having so many possible nesting partners covers more contingencies and minimizes problems with taxon exclusion. Here, employing 183 taxa, one MPT (most parsimonious tree) was recovered. That’s complete resolution and inspires high confidence that this tree mirrors nature’s own. Qinglongopterus was recovered as a successor to the BMM Rhamphorhynchus and a predecessor to Wellnhofer’s (1975) No. 10 and No. 11, three Rhamphorhynchus specimens generally and traditionally considered juveniles. But they were not juveniles. They were small adults as demonstrated earlier using phylogenetic analysis. Small specimens are typically found at the bases of all major pterosaur clades as size reduction accompanies major morphological changes in the Pterosauria. Even their feet were distinct (Fig. 2)

Is Qinglongopterus a Rhamphorhynchus?
You decide. If the phylogenetic predecessors of Qinglongopterus were Rhamphorhynchus and its phylogenetic successors were Rhamphorhynchus, what is Qinglongopterus? This is an awkward nomenclature situation akin to the nesting of Nesodactylus within Campylognathoides and Eosipterus within Germanodactylus.

Taxon Exclusion Restricts Nesting Possibilities
Unfortunately Lü et al. (2012) did not test for the possibility that Qinglongopterus might have nested within Rhamphorhynchus by restricting their taxon list to only one Rhamphorhynchus despite a wide gamut of morphological variation within that genus. Adding a few small specimens of Rhamphorhynchus would have tested their ontogenetic and phylogenetic concerns.

Is Qinglongopterus a new Species of Rhamphorhynchus?
Yes. Distinct from sister taxa in the present study manual 2.2 was longer than m2.1. Manual 3.3 was not as long as m3.1 + m3.2. The pes/tibia ratio was relatively smaller than in sisters. Pedal 2.1 was longer than p3.1. The sternal complex was wider than long. Otherwise Qinglongopterus retains certain plesiomorphic traits retained from the BMM specimen and displays certain derived traits not found in the BMM specimen but found in No. 10 and No. 11, like the pointed jaws. The pes of Qinglongopterus is similar to the pes in the BMM specimen (Fig. 2) and the pes of No. 11 .

 

Sample feet of Rhamphorhynchus

Figure 1. Sample feet of Rhamphorhynchus in phylogenetic order. Note the differences in metatarsal and phalanx proportions. These are distinct species, not a growth series of a single species. Figure 2. Rhamphorhynchus pedes demonstrating variation and speciation. The pes of Qinlongopterus is most similar to the BMM specimen and that of No. 11. Click to enlarge.

Is Qinglongopterus Immature?
All sister taxa share the same lack of fusion enjoyed by Qinglongopterus. Earlier we discussed lack of fusion as a phylogenetic trait, not an ontogenetic one. It’s important to remember that pterosaurs do not follow archosaur ontogenetic patterns because they are not archosaurs. Maisano (2002) spelled out the “rules” for lepidosaurs, and pterosaurs follow them.

Fusion Patterns in Pterosaur Ontogeny
Three pterosaur embryos (IVPP specimen, JZMP specimen and Pterodaustro) all have an unfused scapula and coracoid. So do sister taxa (Dimorphodon? weintraubi and Boreopterus) and adults (Pterodaustro). The less developed and largely unossified embryo Darwinopterus had an unfused scapula and coracoid. It’s mother and all sister taxa back to Pterorhynchus fused those elements.

When does fusion take place in taxa with a fused scapulocoracoid?
Maybe at hatching. Maybe later. We don’t know at present.

By the way…
I wrote to Drs. Lü and  Unwin asking why they did not test any purported juvenile Rhamphorynnchus specimens against Qinglongopterus. When  I hear from them, I’ll update this blog.

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
Lü J, Unwin DM, Zhao B, Gao C and Shen C 2012. A new rhamphorhynchid (Pterosauria: Rhamphorhynchidae) from the Middle/Upper Jurassic of Qinglong, Hebei Province, China. Zootaxa 3158:1-19. online first page
Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrae Paleontology 22: 268–275.

wiki/Qinglongopterus

Does a Big Crest Make a Nyctosaurus Mature?

Bennett (2003) reported on two Nyctosaurus discoveries made by fossil collector Kenneth Jenkins. Both (Fig. 1) had the largest crests, relative to skull length and body size, of any known pterosaur. This came as even more of a surprise to paleontologists because no other Nyctosaurus specimens show any hint of a crest.

Late in Ontogeny?
Bennett (2003) reported in his abstract, “Despite the large crest, the specimens do not differ significantly in morphology from previously known specimens of Nyctosaurus, and do not represent a new species of Nyctosaurus. The specimens suggest that the cranial crest was developed late in ontogeny, which is consistent with the interpretation of pterosaur cranial crests as intraspecific display structures.” Unfortunately, these statements have been taken as gospel and have been uncritically repeated. For instance, here’s an online pdf of an article by Greg Paul from the Prehistoric Times.

Nyctosaurus clade

Figure 1. The clade of Nyctosaurus and kin. Click to enlarge.

Actually the Variations is Easy to See
Bennett (2003) did not make reconstructions of the clade for comparison. One look at reconstructions of several known Nyctosaurus specimens shows that none are conspecific (Fig. 1). There ARE many significant differences in morphology (contra Bennett 2003, details in reptileevolution.com starting here). Even the two crested Nyctosaurus specimens have distinct differences in crest shape and wing length.

In Pterosaurs More Mature = Larger
If the crested specimens were indeed more mature, then one would expect them to be larger, following the study by Chinsamy et al. (2008) on the growth series documented in Pterodaustro, the only pterosaur with a varifiable growth series. That study found that sexual maturity occurs at half the largest size attained by individuals, a pattern also found in certain lizards like Iguana (Kaplan 2007)  and Varanus (Pianka 1971). The crested specimens are actually smaller than some, similar in size to other Nyctosaurus (not counting the largest known Nyctosaurus specimens known from a pelvis and disassociated scraps.) Nyctosaurus nanus (known from a humerus and pectoral girdle) is the only Nyctosaurus that is genuinely smaller than the others pictured here.

Is the Crest a Sexual Signal?
Sure. It appears that the crest is a secondary sexual characteristic. If so one would expect a crest to appear at sexual maturity (half the final size). There is only one pair of crested pterosaurs that I am aware of that appear to be conspecific and those are a pair of tupuxuarids that have identical crests, identical rostral lengths and identical orbit sizes relative to their overall size. The smaller specimen is less than half the size of the larger one, so it was prepubescent, which falsifies the notion of a sexual signal. No, the crests appear to have identified species, not gender, maturity or sexual fitness (mutual selection). Other sorts of secondary sexual characters must have been present in crested and crestless specimens, such as wattles, coloration or behavior.

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
Bennett SC 2003. New crested specimens of the Late Cretaceous pterosaur Nyctosaurus.Paläontologische Zeitschrift 77: 61-75.
Chinsamy A, Codorniú L and Chiappe LM 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters, 4: 282-285.
Kaplan M 2007. Iguana Age and Expected Size. iguana/agesize online
Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrae Paleontology 22: 268–275.
Pianka E 1971.
Notes on the Biology of Varanus tristis. West. Aust, Natur, 11(8):80-183.

wiki/Nyctosaurus