Flugsaurier 2018: Pterosaur crest and pelvis news – you heard it here first

Flugsaurier 2018 part 6
Since the purpose of the symposium is increase understanding of pterosaurs, I hope this small contribution helps.

Cheng, Jiang, Wang and Kellner 2018
concluded: “The size of pelvic channel and the presence and absence of premaxillary crest may not be used for distinguishing the gender of wukongopterid pterosaurs.”

That’s confirmation
of an earlier finding first discussed here. and basically throughout the seven-year course of this blogpost. Click here for Pteranodon crest phylogenetic variation. Here for Darwinopterus.

References
Cheng X, Jiang S-X, Wang X-L and Kellner AWA 2018. The wukongopterid cranial crests and pelves: sexual dimorphism or not? Flugsaurier 2018: the 6th International Symposium on Pterosaurs. Los Angeles, USA. Abstracts: 33–34.

 

Parietal crests on lepidosaurs

Yesterday’s post on several iguanids, one of them crested, inspired this post on parietal crests found on lepidosaurs. I wondered how many other reptiles had vertical parietal crests? (This separates ceratopsians and other with horizontal expansions of the parietal.) And how many other lepidosaurs? And how many other squamates?

Figure 1. The parietal crest of various lepidosaurs are compared here. Upper left: Corytophanes. Upper right: Basiliscus. Lower: Nytosaurus (KJ@) and Pteranodon (Jenkins specimen).

Figure 1. The parietal crest of various lepidosaurs are compared here. Upper left: Corytophanes. Upper right: Basiliscus. Lower: Nytosaurus (KJ@) and Pteranodon (Jenkins specimen).

Among squamates
crests are few. Trioceros (Fig. 2) has a vertical parietal crest. Other squamates related to Basiliscus and Corytophanes have similar crests.

Several pterosaur lepidosaurs had vertical crests.
Many were independently created. Others further extended the smaller crests of more primitive ancestors. So far as the data will take us, crests are only phylogenetic in size and shape. We have evidence for maturity level in crest shape and size, after all, it would be very difficult to tuck a long or large parietal crest into an eggshell.

On a side matter,
what sort of elongated egg shape might contain the extremely elongated rostrum of Moganopterus (Fig. 2)?? I’m willing to suspect that this pterosaur, perhaps uniquely, elongated the rostrum during ontogeny. But then Pterodaustro did not do so, so who knows?

The pterosaur Hamipterus might give us a tentative clue as to gender identity in nasal crests, but it’s not a certainty at present.

Figure 2. Parietal crests on other lepidosaurs, including several often unrelated pterosaurs.

Figure 2. Parietal crests on other lepidosaurs, including several often unrelated pterosaurs. The crest of Cosesaurus is soft, unossified and no close relatives have an ossified crest. Not to scale. 

Parietal crests on archosauromorphs
are not impossible to find, but they are rare. You can find parietal crests on certain plesiosaurs, like Pistosaurus, Trinacromerum (Fig. 3) and Brachauchenius. They would have been hidden by jaw muscles in life.

Figure 3. The plesiosaur Trinacromerum has a parietal crest, but it was laterally packed with jaw muscles.

Figure 3. The plesiosaur Trinacromerum has a parietal crest, but it was laterally packed with jaw muscles.

Likewise
on certain ichthyosaurs like Shonisaurus, Cymbospondylus and PhalarodonContectopalatus (Fig. 4). As in the plesiosaurs (above) these crests served as anchors for powerful jaw muscles.

Figure 4. Phalarodon and Contectopalatus are ichthyosaurs with a parietal crest, likewise laterally hidden in vivo with large jaw muscles.

Figure 4. Phalarodon and Contectopalatus are ichthyosaurs with a parietal crest, likewise laterally hidden in vivo with large jaw muscles.

 

The crests on hadrosaurs and certain theropods, including cassowaries, are enlarged nasals. I never thought this would add even a mote of evidence to the pterosaurs are lepidosaurs argument, but it does add one little mote, just as the longest cervicals are found in tanystropheids and azhdarchids. Coincidence? Or a genetic wild card?

Figure 1. Macrochelys (Macroclemys) skull colorized. Most workers label the bone above the curled quadrate as a squamosal, but here it is considered a supratemporal, which has horns in basal turtles.

Figure 5. Macrochelys (Macroclemys) skull colorized. Most workers label the bone above the curled quadrate as a squamosal, but here it is considered a supratemporal, which has horns in basal turtles. This skull shows a minimum of occiput invagination.

Some turtles develop a crest
that is largely created by embayment of the occipital plate of the skull and the narrow portion is chiefly formed by the supra occipital (Fig. 5).

Parietal crest development
in lepidosaurs appears to be largely for species identification and/or secondary sexual selection. In pterosaurs, since they travel at airspeeds in which streamlining and aerodynamics play a large part, crest size and shape must follow those restrictions and head turning would tend to yaw the pterosaur, but not the basilisk.

Pterosaur reproduction and gender identification – SVPCA talks

Two upcoming SVPCA talks worth discussing:
Kellner et al and Unwin + Deeming both discuss pterosaur reproduction, growth and gender.

Key notes from the Kellner et al. (2015) abstract: All eggs show depressions, clearly indicating their overall pliable nature. SEM analysis shows that the eggshell structure is similar to some squamates. SEM analysis of [another] eggshell did not reveal an external calcareous layer suggesting that it was either removed due to taphonomy or not present at all. Histological section of the femur lacks medullary layer, a bone tissue reported in avian dinosaurs during ovulation and egg-laying phase. Those specimens, associated with experimental taphonomic studies, show that pterosaurs had two functional oviducts and laid eggs even smaller than previously thought, indicating that they have developed a reproductive strategy more similar to basal reptiles than to birds.”

Like I’ve been saying since 2007 and before.
Pterosaurs are non-squamate lepidosaurs. Egg shell morphology is just one more clue to this.

Unwin and Deeming abstract:
“Sexual dimorphism is common in extant vertebrates and almost certainly occurred in extinct species as well, but identifying this phenomenon in fossils is difficult. Meeting two key criteria: a large sample size in which all ontogenetic stages are present; and independent evidence of gender, is rarely possible, but has now been achieved for the early Upper Jurassic pterosaur Darwinopterus modularis. This pterosaur is represented by over 20 individuals ranging from hatchlings through juveniles to mature adults (ontogenetic status determined from osteological, histological and morphometric data). One example, ‘Mrs T’, is preserved with two eggs and thus clearly a female. Approximately half the mature individuals of Darwinopterus exhibit a cranial crest and several of these individuals have a relatively narrow pelvis. The remainder lack a cranial crest and in two cases, including Mrs T, have a relatively broad pelvis. All immature individuals lack a crest, an observation that applies to other species of pterosaur in which immature individuals are known. This pattern of morphological variation shows that the cranial crest and pelvis of Darwinopterus modularis are sexually dimorphic. Datasets for other pterosaurs are less complete and/or lack independent evidence of gender, but many species including Ctenochasma gracile, Germanodactylus cristatus and Pteranodon longiceps, exhibit directly, or closely, comparable patterns of anatomical variation to Darwinopterus and are likely to have been sexually dimorphic. We conclude that the spectacular variability in the shape and size of pterosaur cranial crests was likely generated by sexual selection rather than processes such as species recognition.”

Unfortunately
other than with the presence of eggs in association, sexual dimorphism has not been determined in other pterosaurs in which a large sample size is present (Rhamphorhynchus, Pteranodon, Germanodactylus, Pterodactuylus), even without eggs in association. This is widely recognized, hence the excitement level in the abstract for Darwinopterus. Rather speciation of these taxa has been determined through phylogenetic analysis. Speciation has also been determined for the several Darwinopterus specimens. Currently published specimens don’t divide neatly in two. If that changes with the addition of 15 more, I’ll be happy to note that. Unwin and Deeming do not mention phylogenetic analysis in their abstract. If this is a clue to their methods such laziness in skipping phylogenetic analysis is becoming more and more common, especially when it suits a false paradigm. You can’t just eyeball these things. You have to put your data through analysis. Otherwise the work will always be doubted and you’ll be ‘pulling a Bennett’ (assertion of association without cladogram evidence). The purported hatchlings noted by Unwin and Deeming also need to be run through analysis. Are they examples of phylogenetic miniaturization or actual juveniles? Adding hatchlings and embryos along with tiny adults to analysis has been online for more than four years, so there is no excuse for avoiding it.

Tiny wukongopterids are welcome news, by the way. This clade is one of a few that currently lacks any tiny representatives and that lack is the current best reason why wukongopterids left no descendants in the Cretaceous.

The bone originally identified as an ischium on Mrs. T was a misidentified displaced prepubis. The actual ischia were preserved in the counter plate and they were relatively narrow.

Unwin does not support isometric growth during ontogeny, which is otherwise a well established fact in pterosaurs. So he may be accepting dissimilar morphologies as juvenile examples (pulling another Bennett). Very dangerous. As in all other pterosaurs, like Pteranodon, you have to evolve crested derived forms from non-crested basal forms. Unwin and Deeming, if you’re reading this: before you publish your paper, send me your data, if you don’t want to do the analysis yourself. I’ll send back the recovered cladogram. Don’t make the same mistakes again. However, if the juveniles are isometric copies of the adults, then congratulations and remember to give credit where credit is due.

References
Kellner  AWA et al. 2015. Comments on pterosaur reproduction based on recently found specimens from the Jurassic and Cretaceous of China. Among the most spectacular pterosaur finds done in recent years is the bone-bed from the Tugulu Group (Lower Cretaceous) discovered in the Hami area, Xinjiang Uyghur Autonomous Region of China. SVPCA 2015 abstracts.
Peters D 2007. The origin and radiation of the Pterosauria.
Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27
Unwin DM and Deeming CD 2015. New evidence for sexual dimorphism in the basal monofenestratan pterosaur Darwinopterus. SVPCA 2015 abstracts.

Caiuajara dobruskii – new tapejarid pterosaur bone bed

We’ll call this:
“When discovery confirms heretical hypotheses.”

Figure 1. Caiuajara adult skull. Color bones added.

Figure 1. Caiuajara adult skull. Color bones added. Their premaxillary crest also includes the nasal. Blue = jugal. Yellow = missing teeth. Fo = foramina. Wonder if those represent ancient tooth sockets? For now they are blood vessel holes. Exp = ventral expansion of premaxilla, but it’s really the nasal. That’s where the descending process drops on certain other pterosaurs.

Another pterosaur bone bed,
this time with subadults and juveniles (no eggs or hatchlings) of a new tapejarid, Caiuajara dobruskii (Manzig et al. 2014). Contra traditional paradigms, there is no indication of a large orbit and short rostrum in juveniles (confirming earlier posts here and at reptileevolution.com. Yes, the crest developed in adults, because it wouldn’t have fit inside the eggshell! At least 47 individuals here. Smallest were twice the size of hatchlings, one quarter the size of adults.

Also,
you can’t tell the females from the males. All had crests.

Figure 2. from Manzig et al. 2014. Note the lack of change in the size of the orbit vs rostrum in Caiuajara.

Figure 2. from Manzig et al. 2014. Note the lack of change in the size of the orbit vs rostrum in Caiuajara.

Bone beds are great for individual bone size comparisons, but difficult for creating reconstructions as small individuals are mixed in with large ones. From Manzig et al. (2014) “The presence of three main levels of accumulation in a section of less than one meter suggests that this region was home to pterosaur populations for an extended period of time. The causes of death remain unknown, although similarities with dinosaur drought-related mortality are striking. However, it is also possible that desert storms could have been responsible for the occasional demise of these pterosaurs.”

Figure 2. Typical portion of bone bed of Caiuajara.

Figure 3. Typical portion of bone bed of Caiuajara.

The size of the crests, both below and above the jaws, became larger with age. Most of the individuals were young with only a few adults present.

Figure 4. Caiuajara skulls to scale.

Figure 4. Caiuajara skulls to scale.

The authors found no allometry during ontogeny in post-cranial elements, but adults appear to be more robust and the scapula fused to the coracoid in adults only. This confirms what I’ve found in the fossil record in Zhejiangopterus, Pteranodon, Pterodaustro and generally in phylogenetic analysis. Now, after so much evidence, I hope the naysayers will give the hypothesis of isometry during ontogeny in pterosaurs its day in court.

Figure 5. Caiuajara post crania. Hypothetical hatchlings added at 1/8 adult size.

Figure 5. Caiuajara post crania, a. humerus, b. femur, c. coracoid and scapulocoracoid, d. sternal complex. Hypothetical hatchling elements added at 1/8 adult size. Finally, a fused adult coracoid along with an unfused juvenile and subadult coracoid. Scale bars = 1 cm.

Caiuajara is a small tapejarid, very similar to other tapejarids. This brings up the subject of lumping and splitting with nomenclature, whether a new genus is warranted or not. Is Caiuajara just another species of Tapejara? If not then we need to start splitting up other genera clades containing a wide variety of morphologies as in Rhamphorhynchus, Pteranodon, Germanodactylus, Darwinopterus and other pterosaurs, in which essentially, no two are identical. I’ll leave that to the experts. It’s going to take more than consensus.

Figure 6. Caiuajara size comparisons. There is quite a variety of tapejarids, approaching the variety in Pteranodon, Rhamphorhynchus and other pterosaurs. Note that in the larger Tapejara there is still a suture in the scapulocoracoid.

Figure 6. Caiuajara size comparisons. There is quite a variety of tapejarids, approaching the variety in Pteranodon, Rhamphorhynchus and other pterosaurs. Note that in the larger Tapejara there is still a suture in the scapulocoracoid.

A little speculation
Here we have a large number of juveniles (not hatchlings) and only a few adults in a sandy environment sometimes flooded by rising waters from a nearby lake. What does this mean?

A little backstory:
Pterosaur eggs are large enough that only one could be produced at a time, and held within the mother until just prior to hatching. So the large number of juveniles in this case (no hatchlings here) huddling together, did not belong to a single set of parents. The authors were right, pterosaurs of a certain size (perhaps hatchlings, but up to twice the size of hatchlings in this case) were able to fly. Since they were hatched individually the hatchlings/juveniles sought each other out at an early age, and sought out the company of older, larger tapejarids. Those crests made identification easy. It did not matter that the adults were their parents or not (distinct from the nuclear family illustration at Nat Geo) because the numbers don’t match up. Now IF the adults were found in a distinct layer from the juveniles, the speculation about the adult influence has no basis in evidence.

References
Manzig PC et al. 2014. Discovery of a Rare Pterosaur Bone Bed in a Cretaceous Desert with Insights on Ontogeny and Behavior of Flying Reptiles. Plos ONE 9 (8): e100005. doi:10.1371/journal.pone.0100005.

A tiny naris in Guidraco

Figure 1. Closing in on the naris in Guidraco, an Early Cretaceous ornithocheirid from South America. Colors are naris = pink, maxilla = green, jugal = blue, premaxilla = yellow

Figure 1. Closing in on the naris in Guidraco, an Early Cretaceous ornithocheirid from South America. Colors are naris = pink, maxilla = green, jugal = blue, premaxilla = yellow

Guidraco is related to Ludodactylus, another crested ornithocheirid.

And for those who think the fenestra closer to the antorbital fenestra makes a better naris, I say, “good eye!”

References
Frey E, Martill DM and Buchy M-C 2003. A new crested ornithocheirid from the Lower Cretaceous of northeastern Brazil and the unusual death of an unusual pterosaur: In: Buffetaut, E., and J.-M. Mazin, Eds. Evolution and Palaeobiology of Pterosaurs. – London, Geological Society Special Publication 217: p. 55-63.
Wang X-L, Kellner AWA, Jiang S-X and Cheng X 2012. New toothed flying reptile from Asia: close similarities between early Cretaceous pterosaur faunas from China and Brazil. Naturwissenschaften in press. doi:10.1007/s00114-012-0889-1.

wiki/Ludodactylus

wiki/Guidraco

 

Adding the Denver Pteranodon: The origin of the long crest

Updated September 20 with reception of jpegs of the specimen.

Earlier we looked at the wide variety of Pteranodon crests (Fig. 1). Placed in a phylogenetic analysis the skulls show a gradual evolution from smaller crestless species close to Germanodactylus all the way up giant crested species with a wide variety of crest shapes, followed by a reduction in size preceding extinction (lower right corner of figure 1). Contra tradition, this analysis demonstrates no gender identify and no juvenile identity based on size and crest size — other than a Pteranodon juvenile, nicknamed Ptweety (pictured behind the Q specimen, YPM 2594, which it most closely resembles.

Previously not included on this chart was the Denver specimen, DMNH 1732 (Fig. 1), which sports a complete, but short crest of the long-crest variety, and is otherwise every bit as large as other giant Pteranodon species. Details on this rarely imaged skull have arrived.

 

Figure 2. The DMNH specimen is in color, nesting between the short crest KS specimen and the long crest AMNH specimen.

Figure 2. The DMNH specimen is in color, nesting between the short crest KS specimen and the long crest AMNH specimen.

This chart shows the gradual evolution regardless of gender.
The Denver specimen might be a short-crested female, but remember, you can’t evolve a long or tall crest without first going through a small or short crest phase. That’s why we’ll have to wait for other clues* before we start assigning gender and age to various specimens of Pteranodon. The skulls all fit into a very neat completely resolved phylogenetic series here, with no two pairing off as male and female… yet.

*As we learned earlier, Bennett’s 1992 purported female Pteranodon pelvis,  KUVP 993, is morphologically just a big Nyctosaurus.

References
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.

Obvious sexual dimorphism in pterosaurs?

. From Tetrapod Zoology with this caption, "Cover of TREE featuring Knell et al. (2012). Image (featuring male and female Pteranodon with obvious sexual dimorphism) by Mark Witton." While this might be true, rigorous phylogenetic testing says otherwise. These are distinct species.

Figure 1. From Tetrapod Zoology with this caption, “Cover of TREE featuring Knell et al. (2012). Image (featuring male and female Pteranodon with obvious sexual dimorphism) by Mark Witton.” Naish’s statement has been shown to be false. Attention to detail and rigorous phylogenetic testing provides other results (Fig. 2) in which these two inaccurately portrayed Pteranodon specimens actually represent distinct species. In general, smaller skulls with smaller crests are phylogenetically closer to the ancestral germanodactylids with smaller skulls and smaller crests. Not only does that make sense, it can be demonstrated phylogenetically (Fig. 2). See the juvenile? Cute, but inaccurate. (see below).

An April post at Darren Naish’s Tetrapod Zoology was headlined, “Dinosaurs and their ‘exaggerated structures’: species recognition aids, or sexual display devices?” (refs below).

Naish wrote, “Our latest paper is devoted to a discussion of the species recognition hypothesis and, specifically, why we think it’s problematic and should be discarded. We’ve noted that dinosaur workers have increasingly taken to mentioning species recognition whenever they discuss exaggerated structures (see list of citations in Hone & Naish 2013), so now is a good time to try and set the record straight.”

Pteranodon skulls

Figure 2. Click to enlarge. A family tree of Pteranodon and Nyctosaurus derived from Germanodactylus. Note the size increase is gradual. So is the crest size increase. Of all these many specimens, can you tell which are male and which are female? I can’t. There are no two skulls, sans crests, that are identical in morphology. You can’t divide this set of illustrations into two genders, and yet, according to Naish you should be able to. Attention to detail indicates there’s also much more to skull morphology than crest shape.

Is it possible to ascertain that small crested specimens are females?
Or are small crested specimens just in the lineage of large crested specimens? Contra Naish, species recognition helps us identify various dinosaurs with all their crests, horns and feathers. The same is true of pterosaurs and you can test this with phylogenetic analysis (Fig. 2). If this was gender identification in Pteranodon, there should be just two forms relatively close to one another for each of the above skulls. But no two here are even that much alike. Instead they form a series of gradually evolving shapes, which defines them as distinct individuals and species. Interestingly, there is a derived size decrease in specimens R, S, T and Z4.

Juvenile Pteranodon
The image in figure 1 also shows a juvenile Pteranodon with an appropriately short crest and short beak. Well, we have a juvenile Pteranodon (Fig. 2) and it doesn’t have any indication of a short beak, but retains the proportions of an adult, and a specific adult at that, YPM 2594, which is likewise known from a posterior skull without a complete rostrum.

Pteranodon is the Cretaceous equivalent of Darwin’s finches.
Rapid diversification in Pteranodon originated as individual variation that was enhanced over the generations by natural selection. Pteranodon was not just one or two species, but dozens, as is plainly evident when you look at dozens all once (Fig. 2). That’s the value of accurate reconstruction, something most pterosaur workers avoid like the flu.

Getting back to sexual dimorphism
Naish wrote, “And we absolutely reject Padian & Horner’s (2013) argument that sexual dimorphism is essential for the recognition of sexual selection: there’s unambiguous evidence from the living world that sexual selection is at play even when dimorphism is absent (Hone et al. 2012, Knell et al. 2012, 2013).”

To Naish’s point, there is always sexual dimorphism, whether presented in skeletal differences, beards, breasts, genitals, feathers or pheromones. Sometimes it’s more obvious. Sometimes less. In pterosaurs no one has ever been able to document male vs female differences in the skeleton, even when there’s an egg between the legs of an obvious female, a subject we looked at earlier. Males, as best as we can ascertain were outwardly identical. Crests appeared on various darwinopterids during speciation, as we looked at earlier. Some have even been named new genera by various workers.

Unfortunately, at least in pterosaurs,
there’s no evidence for gender identification that can stand up under the scrutiny of phylogenetic analysis. We don’t see only two kinds of Pterodactylus. We see several (with not one tested specimen identical to another). We don’t see only two kinds of Rhamphorhynchus. We see dozens. Lack of reconstructions and lack phylogenetic analysis leads paleontologists like Darren Naish into supposition and assumption. What’s “obvious” to him is only obvious because he hasn’t tested it to see if it is indeed true. Testing, not supposition, is what makes good Science.

And by the way,
Naish and those who are in his camp are among those who think (without testing) that tiny pterosaurs are juveniles of larger taxa. Bennett (2006) made this supposition, but his study did not stand up to phylogenetic analysis.  Tiny Solnhofen pterosaurs of all sizes and shapes nest at the bases of several major clades and are the transitional taxa from one clade to another as each phylogenetic series gradually decreases then increases in size.

Darren Naish and Modular Evolution
Naish wrote,  “So it’s almost as if the head and neck were evolving at different rates from the rest of the body: in other words, Darwinopterus looks like a classic case of ‘mosaic evolution’ or modularity (hence the species name). This much-discussed evolutionary phenomenon has been considered controversial, in part due to a lack of good examples: Darwinopterus looks like one of the best yet discovered, and this isn’t lost on Lü et al. (2009).”

A lack of good examples indeed! This hypothesis applies only to Darwinopterus in order to cover up a lack of good phylogenetic analysis, which you can see here.

Of course, there’s no such thing as “modular evolution,” made famous during the Darwinopterus bungle, but Naish embraced this fairy tale without criticism. If true we’d see it on other taxa and in other clades, but we don’t It was invented for Darwinopterus. If modular evolution were true we’d have less confidence in our reconstructions of partial skeletons because heads would be evolving leaving the legs far behind, as imagined for Darwinopterus. In reality the palate evolves along with the toes and everything else. In reality Darwinopterus is a dead end taxa leaving no known descendants, but it did convergently evolve a large skull and smaller naris. Phylogenetic analysis settles that issue.

That being said…
There’s much more in Naish’s blog that is good Science and worth considering. If interested, follow this link. He’s just got an Achilles heel when it comes to pterosaurs.

So, there’s more to Pteranodon that just size and crests.
We know of a variety of post-crania as well, some robust and some gracile with various humerus shapes (Fig. 3). Only a few Pteranodon specimens are known from associated skulls and post-crania. So, which post-crania go with which crania? We can only guesstimate now and earlier some effort was made toward this goal. Small ones might have been young or might have been primitive (more likely the latter, since juveniles, like Ptweety or so rare and the small ones are not virtually identical to any large ones (isometric growth).

Post-crania Pteranodon

Figure 3. Click to enlarge. Various Pteranodon specimens known from post-crania. Note the yellow box includes one of the largest specimens, but it has an unfused extensor tendon process, which may mean it is a very large Nyctosaurus with fingers.

If Naish is right
and there is “obvious” sexual dimorphisim in Pteranodon, let him (or someone!) present three or four pairs of males and females, then subject them to phylogenetic analysis. The gender pairs should match with their mates if true.

And finally, we need to talk about the “female” pelvis in Pteranodon.
It’s morphologically closer to Nyctosaurus as reported here. And, yes, it’s a big pelvis, but we have further evidence of Pteranodon-sized Nyctosaurus, because the former fused the extensor tendon process and the latter did not, as reported here , and we know of a very larger unfused extensor tendon process on what others have identified as a Pteranodon based on its size.

No matter what crap they throw*,
I’m not going to let Naish and Witton disfigure and fantasize pterosaurs when good solid evidence is available to counter their traditional and mistaken hypotheses. Credit will also be given when appropriate.

* By “crap,” I mean blackwashing statements that contain no pertinent specifics or evidence. You’ll know them when you see them.

References
Bennett SC 2006. Juvenile specimens of the pterosaur Germanodactylus cristatus, with a review of the genus. Journal of Vertebrate Paleontology 26:872–878.SMNS
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Knell R, Naish D, Tompkins JL and Hone DW E 2012. Sexual selection in prehistoric animals: detection and implications. Trends in Ecology and Evolution28, 38-47.
Naish D and Cuthill IC 2012. Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs? Lethaia 45, 139-156.
Naish D, Tomkins JL and Hone DWE 2013. Is sexual selection defined by dimorphism alone? A reply to Padian and Horner. Trends in Ecology and Evolution. http://dx.doi.org/10.1016/j.tree.2013.02.007

A Big Germanodactylus in the Late Cretaceous Niobrara of Kansas

Germanodactylus is chiefly known from Solnhofen formation (Late Jurassic, Germany), but there’s one Germanodactylus that was found in the Niobrara formation of Kansas in the Late Cretaceous. And it was a big one (Fig. 1)!

No. 13 and its sisters

Figure 2. No. 13 and its sisters, Germanodactylus, Muzquizopteryx and Eopteranodon. Click to Enlarge. Note the resemblance between YPM 1179 and SMNK PAL 6592. The other taxa shown here do not come as close, but have evolved distinct traits.

Okay, I may have been a little misleading.
The Niobrara specimen has been formally named, Pteranodon occidentalis YPM 1179 (Marsh 1876a).  The skull was twice the length (and therefore 8x the size of is nearest Germanodactylus sister, SMNK PAL 6592. But in the panoply of Pteranodon skulls (Fig. 2K), YPM 1179 had the shortest rostrum and ranks among the smallest otherwise. We don’t know the post-crania of YPM 1179. Did extreme metacarpals and shorter hind limbs evolve coincidentally with extreme rostral lengths? No one knows (but see below for clues). Those traits are the basic post-cranial attributes of Pteranodon that separate it from Germanodactylus (other than size). If YPM 1179 had longer legs and shorter metacarpals than a typical Pteranodon, then there would be even more argument to calling it a big Germanodactylus.

Pteranodon skulls

Figure 2. Click to enlarge. A family tree of Pteranodon. There’s YMP 1179 (K) close to the SMNK PAL 6592 Germanodactylus (B).

Did you know…
There’s more morphological variation among the various specimens of Germanodactylus (Fig. 3) than there is between SMNK PAL 6592 and  YPM1179?  Someday someone will sort out the real Germanodactylus from the non-Germanodactylus. It’s nearly as bad of a situation as the Pterodactylus sorting problem, reported on earlier here. And someone, hopefully, will confirm the separation of the eopteranodontids from the very similar azhdarchids seen here in the large pterosaur family tree. Experts are still confused about that one.

Germanodactylus and kin

Figure 3. Click to enlarge. Germanodactylus and kin. There’s YPM 1179 on the right.

So, where do you draw the line?
Morphology? Size? Location? Tradition? They all have impact factors here in lumping or splitting these two sister taxa. YPM 1179 will probably remain a Pteranodon due to its separation in time and location. But now you and I both know, YPM 1179 is closer to Germanodactylus and forms a great transitional taxon to the Pteranodon clade (Fig. 1).

Possible Post-Crania?
Mated with SMU 76476, the “oldest Pteranodon” (Myers 2010) we may have a clue as to the post-crania of YPM 1179 (Fig. 4). The humerus is relatively shorter in the SMU specimen. We don’t know how long the metacarpus and m4.1 were due to end breaks, but the metacarpus was at least slightly longer, as in Muzquizopteryx and Eopteranodon (Fig. 1).

Matching YPM 1179 to the post-crania of SMU 76476 (Myers 2010) and overprinted with SMNK PAL 6592. The resemblance is indeed remarkable.

Figure 4. Matching YPM 1179 to the post-crania of SMU 76476 (Myers 2010) and overprinted with SMNK PAL 6592. The resemblance is indeed remarkable.

The Deltopectoral Crest Warp
Pteranodon has a deltopectoral crest warp and thicker anteriorly. Myers (2010) reports, “The anterior edge of the terminal expansion of the deltopectoral crest is flat, and its long axis is oriented at an angle to the base of the crest, creating the distinctive warped appearance described by Padian (1984) and Bennett (1989).” Actually the warp in SMU 76476 is not as apparent and there is no thickness in the depth of the anterior deltopectoral crest found in other Pteranodon specimens. So, this humerus has a thin deltopectoral crest more like that of Germanodactylus.

References
Marsh OC 1876a. Notice of a new sub-order of Pterosauria. American Journal of Science, Series 3, 11:507-509.
Myers TS 2010. Earliest occurrence of the Pteranodontidae (Archosauria: Pterosauria) in North America: new material from the Austin Group of Texas. Journal of Paleontology 84(6): 1071-1081. PDF online

 

Where the heck is the sternal complex in Shenzhoupterus?

Shenzhoupterus in situ.

Figure 1. Shenzhoupterus in situ. The tip of the long parietal crest is noted.

Shenzhoupterus (Figs. 1-6, Lü et al. 2008) is a wonderfully bizarre derived pterosaur with an outsized skull and long, heron-like limbs, a deep prepubis and a tubby torso. The skeleton is complete and – mostly – articulated.

The big problems are the skull and the sternum. The bones of the cheek region of the skull are all there, they’re just jumbled beyond recognition. The sternum is apparently gone (but wait, there’s more!! ~ and these two problems are interrelated!!)

This is a job for DGS (digital graphic segregation)!
But first the easy stuff. See the tip of the parietal crest (Fig. 1)? It was overlooked by the original authors and illustrators. This long crest is homologous with that of its close relatives Germanodactylus cristatus (Fig. 6) and Sinopterus.

Shenzhoupterus skull in situ

Figure 2. Shenzhoupterus skull in situ

We’ll take this a step at a time. Here (Fig. 2) is a close look at the skull in all its chaos.

Shenzhoupterus skull in situ with sternum in blue.

Figure 3. Shenzhoupterus skull in situ with sternal complex in blue. It is below the skull elements yet the outline betrays its presence.

Here (Fig. 3) the sternal complex (sternum + clavicles + interclavicle) is illustrated in blue. Yes, it is difficult to see. But it is there, exposed and identified by DGS.

Shenzhoupterus skull in situ with elements identified.

Figure 4. Shenzhoupterus skull in situ with only one side of cheek elements + sternal complex identified.

Here (Fig. 4) only one side of the cheek elements and the entire occiput are identified. Even without the other side elements the bones are chaotic. They only make sense when you put them back together, and even then there’s a derived and distinct morphology present (Fig. 5). DGS was able to identify the elements using a photograph and a computer better than the naked eye. Moreover, the elements of the rostrum are better delineated.

Shenzhoupterus reconstructed alongside original interpretation of skull.

Figure 5. Shenzhoupterus reconstructed alongside original interpretation of skull. The real test to see if identifications are correct is to put the pieces back together again and see if they fit together and fall into established patterns set by related pterosaurs.

Comparisons to related taxa complete the analysis (Fig. 6). Note the original interpretation looks nothing like the related pterosaurs and fails to identify skull elements.

Figure 6. Germanodactylus cristatus and the Shenzhoupteridae, Shenzhoupterus and Nemicolopterus. The Tapejaridae were close relatives.

Figure 6. Germanodactylus cristatus and the Shenzhoupteridae, Shenzhoupterus and Nemicolopterus. The Tapejaridae were close relatives.

And then there’s the wing ungual.
A closeup photo of the Shenzhoupterus wingtip (Fig. 7) reveals the ungual, hyper-flexed but still articulated. No wonder it was originally overlooked.

Shenzhoupterus wingtip and ungual.

Figure 7. Shenzhoupterus wingtip and ungual. Curled back like this, it is easy to overlook.

Overall a closer examination using every available tool is warranted here. A simple examination using the eyeball alone is not sufficient to segregate the elements of the Shenzhoupterus cheek region. It takes a graphic tool to do so. Identifying one element after another until all elements are accounted for. That’s how the sternal complex beneath the skull was discovered. It wasn’t immediately apparent until all the other skull elements were delineated and identified.

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, Xu L and Zhang X 2008. A new azhdarchoid pterosaur from the Lower Cretaceous of China and its implications for pterosaur phylogeny and evolution. Naturwissenschaften 95 (9): online (preprint). doi:10.1007/s00114-008-0397-5. PMID 18509616.

wiki/Shenzhoupterus

Tapejara Juvenile??

The post cranial skeleton of Tapejara (famous for its head crests) was published last year (Eck, Elgin and Frey 2011). It was smaller than the known skulls (Fig. 1). I had seen the 3D skeleton in a museum drawer several years ago. The skull despite its size, is very close in morphology to the holotype. The smaller specimen may bea juvenile and if so it demonstrates, once again, the largely isometric, rather than allometric growth pattern of pterosaurs, although in this case the rostrum is shorter and the eyeball greater. These clues might indicate that the specimen could be a smaller species on that basis alone, given the examples of embryos and other juveniles that do not share “juvenile” traits with adults. Too bad the feet are unknown in both cases. They usually tell the tale. A Tapejara foot was looked at earlier, but it was from another specimen.

Various Tapejara specimens including the juvenile.

Figure 1. Various Tapejara specimens including the purported juvenile. Click to learn more. The postcrania of the large Tapejara was based on the smaller specimen and the toes were from a disarticulated specimen.

References
Eck K, Elgin RA, Frey E 2011. On the osteology of Tapejara wellnhoferi KELLNER 1989 and the first occurrence of a multiple specimen assemblage from the Santana Formation, Araripe Basin, NE-Brazil. Swiss Journal of Palaeontology, doi:10.1007/s13358-011-0024-5.