Ontogeny: Pteranodon vs. Diomedea

The Albatross (Diomedea exulans) and Pteranodon ingens (Fig. 1) were two large soaring reptiles, the former a bird, the latter a pterosaur. Insight into the ontogeny, maturity and lifespan of the extant Diomedea may shed some light on the extinct Pteranodon.

Figure 1. Left: Pteranodon. Right: Diomedea (albatross).

Widest Wingspan Among Birds
The albatross has a wingspan that reaches an extreme of 12 feet and averages 9 feet. The pterosaur Pteranodon had a similar wing plan with an enlarged wingspan up to 20 feet. Thus, and for little other reason, the albatross is the closest living analog to Pteranodon.

Albatross: Latest Maturation Among Birds
Most birds reach maturity in less than a year and many (crow, ostrich) do so in two years. By contrast, albatross males begin breeding at age 7, females at age 10. Some wait until 13. The life expectancy of an albatross is 30 years. According to Couzens (2008) it takes years for the albatross to become proficient at finding enough food for itself and more to take on the extra task of feeding a chick. The albatross also takes a long time to establish a pair bond.

Lizards vs Birds: Traditional Views
Most workers follow the paradigm that cold-blooded lizards mature more slowly than warm-blooded birds and mammals. Often, but not always, this is the case. However, more than mere physiology, size is typically an overriding factor. As everyone knows, mice mature faster than dogs, which mature faster than elephants and humans. The blue whale, which matures at 5 (females) or 8+ (males), does not follow this pattern. Among cold-blooded reptiles, iguanas are sexually mature at 50% of maximum size before the end of the second year (Kaplan 2007). Varanus hatchlings triple in size to sexual maturity and reach maximum size by the end of the first year (Pianka 1971). However some may continue growing thereafter, reaching up to 50% longer.

Pterodaustro Ontogeny
The only pterosaur for which a complete record of growth is known is the filter-feeder Pterodaustro. Chinsamy et al. (2008) reported: “…upon hatching, Pterodaustro juveniles grew rapidly for approximately 2 years until they reached approximately 53% of their mature body size, whereupon they attained sexual maturity. Thereafter, growth continued for at least another 3–4 years at comparatively slower rates until larger adult body sizes were attained.” So, this pterosaur’s growth rate, despite an apparent warm-blooded metabolism and active lifestyle, was not dissimilar to that of other lizards, reaching sexual maturity at 50% of the ultimate size. However, Pterodaustro took twice as long as Varanus, a cold-blooded lizard. Apparently, growth was not so rapid in pterosaurs — more along the lines of Iguana.

Pteranodon
If we add in the factor of increased size to what we know of Pterodaustro, we can imagine that Pteranodon might have had a maturation rate similar to that of the albatross (sexually mature at 7 to 10) along with a similar lifespan (30 years). However, if Pteranodon was more like Pterodaustro we get 2 years until half-grown, 5 to 6 years until fully grown.

Where Are the Juvenile Pterosaurs?
A long maturation brings up a problem. Where are the juveniles and immature forms (ages 0 to 6)? The Pterodaustro bone beds (nesting sites) provide the only evidence. There we find all sizes of Pterodaustro.

Ptweety the Only Juvenile Pteranodon
We know of only one juvenile Pteranodon. All others are adults that fit neatly into a phylogenetic framework of increasing size and crest size originating with a specimen of Germanodactylus (SMNK-PAL 6592) as an outgroup. This falsifies the current paradigm presented by Bennett (1991, 2001) and followed by others (Hone et al. 2011) of gender and maturation variation in most known specimens of Pteranodon. Here there is evidence of speciation leading to the largest crested forms (that in one clade only preceded a continuing clade of smaller crested, smaller forms.)

Bone Histology
The age of sexual maturity in Pteranodon has not yet been determined. Neither has the lifespan. Bone histology in Pteranodon has not provided the data needed due to crushing and resorption of the inner walls of the extremely thin long bones. At present we can only guess using extant analogs, like the albatross, and extinct analogs, like Pterodaustro.

Then There’s the Tiny Pterosaur Hypothesis
Tiny pterosaurs giving birth to fly-sized hatchlings were likely terrestrial until reaching adult-size due to desiccation problems, as discussed earlier. Larger pterosaur hatchlings, like Pteranodon (and all known, apparently flight ready pterosaur embryos), did not have a problem with desiccation — but they may have retained some sort of non-flying lifestyle living in environments not conducive to fossilization. This may explain the lack of immature pterosaurs in the fossil record (contra all traditional studies that considered tiny adults to be juveniles and embryos to be flight ready).

Not ready to jump on the flightless hatchling hypotheses quite yet, but it’s something to consider when faced with current and future evidence.

Just a Reminder
Maisano (2002) provides guidance on lizard ontogeny that can be applied to pterosaurs. That is: fusion can precede maturation and ultimate size or fusion may never take place in the oldest individuals, depending on their phylogeny. Recent work by Lü et al. (2012) show that the archosaur model continues to be wrongly applied to pterosaur studies.

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.
Couzens D 2008. Extreme Birds: The world’s most extreme and bizarre birds. Firefly Books.
Hone DWE Naish D and Cuthill IC 2011. Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs? Lethaia, DOI: 10.1111/j.1502-3931.2011.00300.x
Kaplan M 2007. Iguana Age and Expected Size. iguana/agesize online
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.
Pianka E 1971. Notes on the Biology of Varanus tristis. West. Aust, Natur, 11(8):80-183.

An Obligate Bipedal Basal Pterosaur

The Traditional View
All pterosaurs were quadrupedal, based on trackway evidence.

Figure 1. The most primitive known pterosaur, the Milan specimen, MPUM 6009. The long hind limbs and relatively short fore limbs were homologous with those in Sharovipteryx and Longisquama. The extremely slender tail is most like that of Sharovipteryx, not later pterosaurs which thickened the tail with elongated chevrons and zygapophyses. Gray tones represent possible soft tissues, homologous with those in Cosesaurus and Longisquama.

The Heretical View
One basal pterosaur, MPUM 6009 (Wild 1978), was an obligate biped, retaining the long-legged morphology of its ancestral sisters, Sharovipteryx and Longisquama. All pterosaurs following MPUM 6009 (such as Raeticodactylus and Eudimorphodon) had shorter hind limbs and longer forelimbs, a combination that enabled quadrupedal locomotion.

MPUM 6009 was considered a small Carniadactylus by Dalla Vecchia (2009), but the differences are many.

Figure 2. MPUM 6009 in situ. Click to enlarge and portray the Wild (1978) interpretation. Bones, impressions of bones and some soft tissue complete this articulated skeleton at the very base of the Pterosauria. The crushed skull required reconstruction. Here, using the DGS method, the bones have been colorized. This permits subtle impressions to be identified. Sister taxa share many of these traits, confirming their identity.

Longer Legs, Shorter Forelimbs
Here the reconstruction tells the tale. Question is, is the reconstruction accurate? The clues are, admittedly ephemeral, yet even without such long legs, MPUM 6009 nests at the base of the Pterosauria. So long legs are not beyond the realm of possibility. The relatively short neck allies this basal pterosaur with Longisquama, the outgroup sister taxon. The laterally increasing toe length and deep pelvis also ally this taxon with Longisquama. The sternal complex is also essentially identical.

Ironically…
Such long legs and short forelimbs “ally” this pterosaur with Scleromochlus, and basal dinosaurs, but — really, seriously — hardly at all. It’s convergence!! So if anyone from the traditional camp wants to bitch about this reconstruction, think twice. You’ll only be shooting yourself in the foot. Things happen when the forelimbs are elevated off the substrate, as we humans all can attest.

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.

How Living Lizards Run Bipedally
The Bruce Jayne Lab in Cincinnati, Ohio, has produced a video of a zebra-tailed lizard (Callisaurus) in fast quadrupedal and bipedal locomotion filmed on a treadmill. When the fore limbs are elevated the hind limbs go digitigrade. The speed is an incredible 11 meters per second.

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
Dalla Vecchia FM 2009. Anatomy and systematics of the pterosaur Carniadactylus (gen. n.)rosenfeldi (Dalla Vecchia, 1995). Rivista Italiana de Paleontologia e Stratigrafia 115 (2): 159-188.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.

wiki/Eudimorphodon

What is Jianchangnathus?

A recent paper by Cheng et al. (2012) introduced a new basal pterosaur, Jianchangnathus robustus (IVPP V 16866). Middle Jurassic in age, Jianchangnathus shared several characters with Scaphognathus from the Late Jurassic, according to the authors. It was also compared to Fenhuangopterus, a basal dorygnathid from the same deposits at Jianchangnathus.

Figure 1. Jianchangnathus was allied with Scaphognathus, but retains many traits of its ancestors within Dorygnathus.

A Basal Nesting in the Second Half of the Pterosauria
Here Jianchangnathus nested at the base of the Scaphognathia, essentially the second half of the Pterosauria. In this important phylogenetic site Jianchangnathus was derived from a sister to the Donau specimen of Dorygnathus, itself at the very base of the Dorygnathia and not far from Sordes, the outgroup taxon (Fig. 2). Pterorhynchus and the wukongopterids (= darwinopterids) were sister taxa.

Figure 2. A phylogenetic sequence that includes Jianchangnathus at the transition point between a basal Dorygnathus and Pterorhynchus + Scaphognathus. All are to scale. This is a rare instance of morphological transition in which a tiny pterosaur did not intervene.

Jianchangnathus was not originally subjected to a phylogenetic analysis, nor was it reconstructed.

Figure 3. The skull of Jianchangnathus with bones identified using the DGS method. Here the nasal is in pink (anteriorly) and purple (posterior to the break).

Redescription Using DGS
Cheng et al. (2012) reported fusion between the premaxilla and maxilla. Here (Fig. 3) the suture is between the 4th and 5th tooth as in sister taxa. The first fang was the first maxillary tooth, as in the SMNS 55886 specimen of Dorygnathus. The dentary did not extend to the quadrate but extended posteriorly beneath posterior jugal as in sister taxa. The nasal extended to mid orbit as in sister taxa. The jugal extended to the pmx/mx suture as in sister taxa. The prefrontals were longer than originally reported. The vomers, ectopalatine and pterygoid were rod-like elements, as in sister taxa. The tip of the mandible is a double-tooth morphology.

Dorygnathus Was Barely Mentioned
The upturned premaxilla and anteriorly-oriented teeth are traits of Dorygnathus, but that taxon was not mentioned by Cheng et al. (2012) in comparison. The relatively large skull is a trait shared with Pterorhynchus and the wukongopterids. The manual and pedal element proportions are shared with sister taxa.

Maturity
Cheng et al. (2012) observed the non-fusion of the scapula and coracoid and mistakenly considered Jianchangnathus immature. In this case fusion, or a lack thereof, is a matter of phylogeny, not ontogeny. Because pterosaurs are lizards that do not follow archosaur growth patterns as discussed earlier. Sister taxa likewise do not fuse the scapula and coracoid and Jianchangnathus was similar in size to them (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
Cheng X, Wang X-L, Jiang S-X and Kellner AWA 2012. A new scaphognathid pterosaur from western Liaoning, China. Historical Biology iFirst article available online 29 Nov 2011, 1-11. doi:10.1080/08912963.2011.635423

wiki/Jianchangnathus

The First Anniversary of ReptileEvolution.com – Dec 21

December 21 marks the first year anniversary of ReptileEvolution.com, the basis and chief reference for the PterosaurHeresies.com. ReptileEvolution.com was created to get the word out on the various mistakes and oversights in the current literature. These errors were found principally by testing them against the relationships recovered from the large reptile family tree. Some morphological insights were also reported. Proper nestings and great papers were given all due honor.

Frustration, the Mother of all Invention
As mentioned on the “About” page, the impetus for the creation of ReptileEvolution.com came about after getting one last manuscript rejected at the hands of various pterosaur experts who did not want my work to make it into the literature. Yes, my work opposed theirs and suppression was their motive. Sadly, they continue to prefer untenable nestings and bizarre descriptions.

Turned Out to Be a Good Thing!
Had those manuscripts been accepted, the published papers would have languished in quiet isolation on college library shelves, like most papers do. Now the data and results enjoy free worldwide exposure and access. Rather than standard black and white printed imagery, the web permits full color with video overlays and animation. The speed of reporting has been accelerated. Here, updates, additions and corrections take less than a day.

The Tree Keep Growing
A year ago the reptile tree stood at some 230 taxa, not counting the pterosaur tree, which stood at 165 or so taxa. Today the reptile tree includes 279 taxa, the pterosaur tree includes 180 taxa and the basal therapsid tree includes 39 taxa for rough total of about 500 taxa, give or take some overlap and estimating as I write this 2 weeks prior to uploading. All trees are resolved with high Bremer Test scores. I’m pleased to report that workers are requesting the data matrix for their own studies.

The structure of the tree has not changed so far, despite the influx of 20% more taxa. That’s a good test. Certain taxa have shifted a node or two. That happened as I found mistakes in the matrix that were corrected while uploading new taxa. Correcting mistakes and oversights is the process of science.

The Insights Have Been Very Rewarding
The results speak for themselves. The feedback has been gratifying. The process has been more than interesting. Nothing beats making a discovery!

Thank you for following this blog and checking out the data presented in ReptileEvolution.com. I value your input and will continue to modify any statements and images that are not right on the mark.

Here’s to a great future in prehistory!

Best regards,
David Peters

Pterofiltrus – Just Another Cycnorhamphid, Not a Ctenochasmatid

A New Pterosaur from China!
Pterofiltrus qiui (Jiang and Wang 2011) IVPP V12339 was originally considered a ctenochasmatid pterosaur, but here it nests as a cycnorhamphid. Only the skull is known and it was crushed and disarticulated. Reconstructed (Figure 1) the skull is a virtual duplicate of Cycnorhamphus. The original reconstruction (visible here) was a rehash of the Gegepterus reconstruction. It did not match the fossil and introduced a much too long rostrum. Pterofiltrus lived slightly later (in the Early Cretaceous) than Cycnorhamphus (in the Late Jurassic) and was slightly larger with more teeth.

Figure 1. Top: Pterofiltrus. Bottom: Cycnorhamphus. Both to scale.

References
Jiang S-X and Wang X-L 2011. A new ctenochasmatid pterosaur from the Lower Cretaceous, western Liaoning, China. Anais da Academia Brasileira de Ciencias 83(4):1243-1249. online pdf

The Evolution of Anurognathid Skulls

Sometimes its good to just get a bunch of sister taxa all together
Here I present a selection of anurognathid skulls, plus some precursors including Dimorphodon. No one else has reconstructed the whole set of anurognathid skulls. Reconstructing all of them permits side-by-side comparisons to discover and weed out autapomorphies that may represent mistakes and help characterize their traits and evolutionary patterns. Plus you finally get to see what they really looked like!

What Made Anurognathids Unique
was the orientation of their nares, or nose holes. Here (Fig. 1), following the results of the large study, a selection of skulls illustrates how the naris moved anteriorly and rotated vertically during the evolution of anurognathids.

Bennett’s Attempt
In his first attempt at reconstructing an anurognathid skull, Bennett (2007) botched it, creating a “monster’ (Fig. 1) with giant eyes in the front of the skull, having a small antorbital fneestra and a broad parietal, bearing no resemblance to sister taxa. This was discussed in more detail earlier here.

 

Figure 1. Anurognathid skulls in phylogenetic order.

Kellner’s Hypothesis
Kellner (2003) considered the terminal naris of anurognathids to be a primitive feature, relating it to non-pterosaur archosauriforms that also had a terminal (over the premaxillary teeth) naris. Unfortunately no other character traits were shared and Kellner never reconstructed an anurognathid skull. Rather he based his interpretation of Anurognathus on Wellnhofer’s early efforts which did not illustrate the posterior skull.

The Special Naris of Anuros Starts with GLGMV0002
Dimorphodontids split from eudimorphodontids with the appearance of GLGMV0002, which had a relatively larger naris. Dimorphodon took this to an extreme. It’s difficult to gauge the size of the naris in Peteinosaurus, but in the IVPP embryo, the naris is smaller, but rotated vertically.

Wider and Wider Premaxilla
In Dendrorhynchoides the premaxilla started to become much wider along with the rest of the skull. The flathead anurognathid, SMNS 81928, took this to its first extreme. Anurognathus had a similar premaxilla, but on an elongated maxilla.

Transverse Premaxilla – Anteriorly Oriented Nares
The last three anurognathids had nares that faced anteriorly, unlike any other pterosaur. The CAGS specimen was the most primitive of these.  Batrachognathus was similar but had a narrower nasal, which rotated the orbits anteriorly giving it binocular vision, like an owl. Jeholopterus, the vampire pterosaur, also had binocular vision. Distinct from other anurognathids, Jeholopterus had an upturned premaxilla bordered by twin fangs able, by virtue of their length and upturned orientation, to pierce the hides of dinosaurs. Unlike other anurognathids, the mandible tip rose to meet the upturned premaxilla.

We know of no other anurognathids more derived than Jeholopterus, but keep looking for them. Anurognathids are relatively rare in any case. Jeholopterus could represent the end of anurognathids. Or there could be more discoveries yet to come.

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 2007. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.
Döderlain L 1923. Anurognathus ammoni, ein neuer Flugsaurier. Sitzungsberichte der Königlich Bayerischen Akademie der Wissenschaten, zu München, Mathematischen-physikalischen Klasse: 117-164.
Kellner AWA 2003. Pterosaur phylogeny and comments on the evolutionary history of the group. In: Buffetaut E. & J-M. Mazin, Eds. Evolution and Palaeobiology of Pterosaurs. London, Geological Society Special Publication 217: 105–137.
Wellnhofer P 1975a-c. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33.Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.

The Pterosaurs From Deep Time: Nits and Picks #1

Figure 1. The Pterosaurs From Deep Time by Dr. David Unwin

In 2005, Dr. David Unwin, one of the top experts on pterosaurs, authored a popular book on pterosaurs, The Pterosaurs from Deep Time. Essentially it updated the pterosaur facts and hypotheses of its predecessor, The Encyclopedia of Pterosaurs (Wellnhofer 1991). Unwin wrote: “Much has changed since the Encyclopedia first appeared. The many critical ideas about pterosaur biology that were fought over in the 1990s… have been resolved into a convincing and (among pterosaurologists) widely agreed-upon picture.”

That is true. Most pterosaurologists do agree with the concepts, observations and hypotheses contained in Deep Time. However one pterosaurologist, the heretic among us, tends to disagree … often. That goes both ways, of course. Dr. Unwin completely ignored the pterosaur foot, origin and flight membrane hypotheses published by Peters (2000a, b, 2002) and they were not included in his otherwise complete and extensive bibliography. Rather than exploring opposing topics and throwing arguments against them, Dr. Unwin pretended that they never existed. That’s a shame, because that was a great opportunity for Dr. Unwin to really let me have it.

Today’s topic of juvenile and tiny pterosaurs will highlight several topics and ideas from Deep Time that do not agree with the evidence.

Unwin, p 142
“As a rule, this means that juveniles tend to be uncommon in the vertebrate fossil record, and individuals at very early stages of growth (newborn or even prenatal), are rare or unknown — except, oddly enough, in pterosaurs.”

Unfortunately Dr. Unwin considered all tiny pterosaurs to be newborns and juveniles when phylogenetic analysis (and other evidence, see below) indicates that they, too, are adults. In pterosaurs size reduction was a trait of transitional taxa in most clades. Most pterosaurologists do indeed consider a short snout and large orbit to be a juvenile character, but actually it is just a scaphognathine trait. As lizards, pterosaurs did not follow archosaur growth patterns but developed isometrically (embryos looked just like parents). The JZMP and Pterodaustro embryos falsify the traditional short-snout, large-orbit hypothesis. Many other tiny pterosaurs also had a long snout (see below). The third embryo, the IVPP specimen, came from parents with a short snout, but the eyes were still smaller than originally published.

Figure 2. Pterodaustro embryo. There certainly is no short snout/large eye here!

Dr. Unwin, p. 151
“The snout often grew faster than neighboring regions, so that large-eyed short-face flaplings finished up with long, low skulls and relatively small eyes.”

Some tiny pterosaurs, like B St 1936 I 50 (no. 30 in the Wellnhofer 1970 catalog) and Senckenberg-Museum Frankfurt a. M. No. 4072, (no. 12 of Wellnhofer 1970), do not have a short snout and large orbit. (Click the blue links to see them).

Dr. Unwin, p. 156
“…there doesn’t seem to have been any “small” species, which is even stranger than you may think. Consider that the vast majority of birds and bats are less than one-third of a meter in wingspan. By contrast, adutls of the smallest pterosaur species known at present, such as Anurognathus ammoni, are at least 40 cm in wingspan, and most of them are bigger. A biased fossil record? Hardly. Otherwise, we wouldn’t have found all those flaplings and juvenile…”

Once again, if something is apparently missing, but replaced by something identical to it, it’s not wise to prejudicially ignore what is present. Test the oddities and autapomorphies with a phylogenetic analysis and you too will discover that those “flaplings” were adults of several “small” species.

Dr. Unwin p. 156
“This suggests a rather surprising conclusion: Young pterosaurs were the small species, or at least occupied some of the living spaces (niches) in which one might have expected to encounter small adults.”

So close, yet so far… mmmm. If only Dr. Unwin had performed a phylogenetic analysis instead of taking a falsified tradition at face value. Phylogenetic analysis is key to understanding the pterosaurs. But it only works when they are all included, as demonstrated here.

More on Deep Time later.

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
Unwin DM 2005. The Pterosaurs: From Deep Time. Pi Press, New York.
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs. London: Salamander. 192 pp.

Microtuban, a New Basal Azhdarchid

Microtuban altivolans (Elgin and Frey 2011) is a new basal azhdarchid pterosaur with the characteristic tiny fourth phalanx. Only the mid-section of this pterosaur is preserved, including smashed wing parts.

Figure 1. Sisters to Microtuban include No. 42 (more primitive) and Jidapterus (more derived).

Juvenile? No.
The scapula and coracoid are unfused and the extensor tendon process includes a large suture. Elgin and Frey (2011) considered these to be ontogenetic signals that inferred the specimen was a juvenile or sub-adult, as in archosauromorphs. Unfortunately this is false. Pterosaurs are lizards and they don’t follow archosauromorph growth patterns. The sister taxa (Fig. 1) all have similar fusion patterns and they are adults.

Africa? No.
Elgin and Frey (2011) considered Microtuban, from the of Early Cenomanian (Late Cretaceous) of Lebanon, “the most complete pterosaur fossil discovered from Africa.” Oops. Lebanon is actually in the Middle East. Minor faux pas.

Phylogenetic Nesting
Elgin and Frey (2011) reported, “The phylogenetic placement of M. altivolans within the Azhdarchoidea [the Tapejaridae, the Thalassodromidae, the Chaoyangopteridae, and the Azhdarchidae] therefore remains uncertain.” They considered it a “thalassodromid/ chaoyangopterid.

Here, in a larger study, Microtuban nests readily at the base of the Azhdarchidae [Jidapterus through Quetzalcoatlus] and was derived from a sister to No. 42. (By the way, in the larger study Chaoyangopterus was not at all related to Thalassodromeus.) The manual phalanx proportions in Microtuban were identical to those of its azhdarchid and protoazhdarchid sisters, none of whom, no matter their size, fused the scapula to the coracoid until Quetzalcoatlus.

A Reduced Phalanx 4
While more primitive than other azhdarchids, wing phalanx 4 was relatively shorter (less than 5% of the total wing finger) in Microtuban, probably because it represents a late-surviving clade member on its own branch. The reduction of phalanx 4 is also found in Sos 2428, the flightless pterosaur, which is another Microtuban sister. I suspect that another sister, Huanhepterus, also had such a short phalanx 4, but no one I know has actually seen the post-crania.

Loss of Phalanx 4 in Other Pterosaurs?
Elgin and Frey (2011) reported that Anurognathus, Beipiaopterus and Nyctosaurus all had only three wing phalanges. This is true only for derived Nyctosaurus. Check it out.

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 and Frey 2011. A new azhdarchoid pterosaur from the Cenomian (Late Cretaceous) of Lebanon. Swiss Journal of Geoscience. DOI 10.1007/s00015-011-0081-1

Did Dimorphodon Have an External Mandibular Fenestra?

Updated July 6, 2015 with better data on BSp 1994 (Austriadraco). 

A Mandibular Fenestra in Pterosaurs?
Nesbitt and Hone (2010) and Nesbitt (2011) proposed an external mandibular fenestra for three and only three pterosaurs, recognizing that a mandibular fenestra is not found in other pterosaurs. These two workers nested pterosaurs with archosaurs to support their traditional view despite the fact that pterosaurs do not otherwise resemble any other archosaurs. To do this they excluded the heretical sisters of pterosaurs found in the large study. To be fair, Hone and Benton (2007, 2008) did include Cosesaurus in their analysis, but only a quarter of the characters were employed, despite the fact that Cosesaurus is complete and articulated.

Let’s take a closer look
at each pterosaur taxon used by Nesbitt and Hone (2010) in evidence for the mandibular fenestra.

The BMNH 4212 Specimen of Dimorphodon
According to Nesbitt and Hone (2010) and Nesbitt (2011) the mandible of the BMNH 4212 specimen of Dimorphodon has a mandibular fenestra. The matrix appears within a very large hole in the posterior mandible. The surangular is apparently missing because it is not identified in figure 1 (below) from Nesbitt and Hone (2010). The BMNH 4212 specimen also sports a very deep jugal, according to  Nesbitt and Hone (2010), a trait not found in any other pterosaur or any other Dimorphodon.

Figure 1. From Nesbitt and Hone (2010), the purported deep jugal and mandibular fenestra in the BMNH specimen of Dimorphodon. emf = external mandibular fenestra. im = impression of emf. j = jugal.

The Mary Anning Specimen
In counterpoint, the Mary Anning specimen (Fig. 2) preserves the surangular in place, covering the Nesbitt and Hone (2010) “fenestra” completely. The Anning Dimorphodon has no mandibular fenestra and no deep jugal flange.

Figure 2. The Mary Anning Dimorphodon skull R1034a. Note the mandible has no mandibular fenestra.

Sure It Looks Like a Mandibular Fenestra…
Figure 3 portrays the BMNH 4212 specimen of Dimorphodon after DGS (digital graphic segregation). Here every bone has been color coded to improve understanding. I have not seen the fossil first hand. I reconstructed the bones in accord with other sister taxa (Fig. 3 middle). The articular bone (in gray) might be missing and replaced here with a best guess shape. If present the articular bone may be present in the area outlined in gray posterior to the mandible.

Figure 3. The skull of Dimorphodon macronyx BMNH 41212. Above: in situ. Middle: Restored. Below: Palatal view.

Reconstruction Really Helps
Evidently Nesbitt and Hone (2010) and Nesbitt (2011) did not realize the surangular had drifted dorsally in BMNH 4212. What they considered the angular was actually a displaced pterygoid (or perhaps the articular since both have the same shape, see figure 4). Such mistakes are easy to make when tracing a specimen with little attention to detail (Fig. 1).

Figure 4. The mandibles of Eudimorphodon with mandible elements identified. Note the breakage of the left dentary and displacement of the left surangular to produce the illusion of a mandibular fenestra not duplicated in the right mandible. A rod-shaped element, likely a hyoid or pterygoid, produces the illusion of a dorsal rim to the right posterior mandible. Drawings from Wild 1978.

Eudimorphodon ranzii Mandibles
The holotype of Eudimorphodon (Zambelli 1973) Upper Norian, Late Triassic, ~203 mya MCSNB 2888 provides both lateral and medial views of complete and largely articulated mandibles. Here the shapes of the posterior elements resemble those found in lizards with an articular bone extending anteriorly. There is an opening between the left dentary and surangular, but that is due to the downshifting of the surangular and the breakage of the dentary not duplicated on the right mandible. When properly reconstructed, no mandibular fenestra is present despite the fact that Eudimorphodon lived tens of millions of years earlier than Dimorphodon, closer to the origin of the Pterosauria. No genuine pterosaur precursor among the fenestrasaurs (Cosesaurus, Sharovipteryx and Longisquama) had a mandibular fenestra.

Figure 5. The mandible of Eudimorphodon 1994 I51. Top: After DGS the various points of decay and displacement appear as white spots. The jaw tip is missing. Rod-like elements are in blue and green. Displaced plate-like elements in beige. The green coronoid has been displaced posteriorly. The surangular (dark brown) has been displaced. Note the angular of Eudimorphodon ranzii (Fig. 4) is not as deep as portrayed by Nesbitt and Hone (2010, bottom).

Eudimorphdon BSP 1994 I51
The second specimen reported by Nesbitt and Hone (2010) to have a mandibular fenestra is Eudimorphodon BSP 1994 I51, an incomplete and disarticulated mandible. Here (Fig. 5) the mandible has decayed somewhat with several fenestra apparent throughout. Sure the matrix appears at the appropriate part of the mandible in which a mandibular fenestra might appear, but It’s not a convincing example due to element shifting and decay. Parts of the inside of the mandible are exposed by the flaking off of bone. The reported angular is much too deep. The coronoid has drifted posteriorly. No other pterosaur has a dorsal bump on the posterior mandible and the coronoid is otherwise missing. That posterior bump is the coronoid.

Better data 
(Fig. 5b) arrived that may help decide whether or not that extra bone posterior to the coronoid was the metaphorical lid for the hole seen in the mandible of BSp 1994 — and whether or not the mandible is preserved in medial or lateral view. 

Figure 1. Austriadraco, BSp 1994 I51, a Triassic pterosaur mandible. Is it exposed in medial view or lateral view? Below the line is Eudimorphodon, which preserves mandibles in lateral and medial view. Which one is more similar to Austriadraco? You decide. Click to enlarge. Also note the tiny mandibular fenestra in the lateral view of Eudimorphodon not replicated on the medial view and apparently caused by a shift in the covering bone. Arrow points to apparent broken strip of bone that would otherwise have made the long light blue bone continuous.

BMNH 43486
The third mandible is the BMNH 43486 specimen of Dimorphodon (Fig. 6). This mandible is more damaged than the others and so does not induce confidence that the external mandibular fenestra (emf) was real or just due to damage. The opening appears much further posteriorly than the dentary/surangular interface. If valid, one should wonder why other sister pterosaurs do not have even a small mandibular fenestra.

Figure 6. The BMNH 43486 specimen of Dimorphodon. Damage to the posterior portion of the mandible accounts for the apparent fenestra. What Nesbitt and Hone labeled the Meckelian groove (mg) may instead by the other mandibular rim.

It All Comes Down to Autapomorphies
If no other pterosaur sisters had a deep jugal and if no other pterosaur sisters had a mandibular fenestra, then maybe the two autapomorphies reported by Nesbitt and Hone (2010) are wrong. In BMNH 4211 re-identifying the bottom half of the “deep jugal” as the missing surangular solves the twin problems on the best example.

If anyone finds a valid external mandibular fenestra or deep jugal on any pterosaur specimen, please bring it to my attention. I’d like to see it.

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
Buckland W 1829. Proceedings of the Geological Society London, 1: 127
Owen R 1859. On a new genus (Dimorphodon) of pterodactyle, with remarks on the geological distribution of flying reptiles.” Rep. Br. Ass. Advmnt Sci., 28 (1858): 97–103.
Nesbitt SJ 2011.  The early evolution of archosaurs: relationships and the origin of major clades.  Bulletin of the American Museum of Natural History 352: 292 pp. online pdf
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.
Sangster S 2001. Anatomy, functional morphology and systematics of Dimorphodon. Strata 11: 87-88
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.
Zambelli R 1973. Eudimorphodon ranzii gen.nov., sp.nov. Uno Pterosauro Triassico. Rendiconti Instituto Lombardo Accademia, (rend. sc.) 107: 27-32.

wiki/Dimorphodon

Pterosaur and Reptile Tree Revisions

Science is a process.
As I often say, “Test. Test. And test again.” One of the best ways to test a phylogenetic analysis is to add taxa. If the tree is good (states have been accurately entered, a sufficient gamut of taxa and characters are present), the new taxa will drop into their nesting sites without shifting sister taxa and the tree retains complete resolution. My biggest beef with other, prior smaller trees is their lack of an umbrella study on which to base their taxon inclusion choices. As a result, prior trees often do not include taxa that should be included and often they include taxa that should not be included.

The Pterosaur Tree
The present pterosaur tree is distinct from all prior studies because it is much larger overall and it recovers four separate origins of the “pterodactyloid”-grade, two from separate Dorygnathus species and two more from the smaller Scaphognathus species. There were five origins if you count the darwinopterids, which only achieved that grade above the shoulders.

Recent additions of Cuspicephalus (at the base of Germanodactylus cristatus (no. 61)) and Aurorazhdarcho and Prejanopterus (at the base of Nyctosaurus + Pteranodon) created a minor loss of resolution, whch inspired a review of the characters of sisters. I found a few errors which were corrected. The resulting tree recovers relationships that more closely resemble actual evolutionary directions. Basal Pteranodon are more closely related to the Karlsruhe specimen of Germanodactylus. Wellnhofer’s (1970) number 13 is more closely related to Muzquizopteryx + Nyctosaurus. Otherwise the completely resolved tree was unchanged.

I shortened the second wing phalanx of the BMM specimen of Germanodactylus because the tree showed in autapomorphy (unique trait). All sisters had a manual 4.2/m4.3 joint at the elbow when the wing was folded. The BMM specimen had a joint slightly beyond the elbow. Another look at the specimen revealed a break in m4.2, which artificially elongated that phalanx. Once corrected the autapomorphy disappeared and the m4.2/m4.3 joint returned to match the elbow, as in sisters.

The present pterosaur tree has 174 taxa, up from about 150 when first placed online.

The Reptile Tree
In the large reptile tree the recent addition of Megachirella at the base of the Lepidosauromorpha and Eusaurosphargis within the Thalattosauria recovered a loss of resolution that inspired second looks at sister taxa. Mistakes were present and those were corrected.

Macroleter now nests as a less derived sister to Lanthanosuchus. Pointy-snouted Endennasaurus now nests closer to pointy-snouted Xinpusaurus. Otherwise the tree is unchanged and now completely resolved. The tree has 268 taxa, up from 225 when reptileevolution.com first began nearly a year ago. The tree also remains unchanged when reduced to 60 cherry-picked taxa and remains diphyletic with just a few basal reptile taxa are included.

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.

No References