SVP 7 – Montanazhdarcho, not an azhdarchid

Carroll 2015 reports
on the North American Late Cretaceous pterosaur, Montanazhdarcho.

From the abstract:
“The latest Cretaceous fossil record of pterosaurs is dominated by azhdarchids, despite various reports of non azhdarchid material from the Late Campanian and Maastrichtian. However, the only indisputable non-azhdarchid pterosaur material from the latest Cretaceous has been the single nyctosaurid humerus from the Gramame Formation of Brazil*. This study presents evidence that Montanazhdarcho minor is a nonazhdarchid member of the Azhdarchoidea**. M. minor was assigned to the Azhdarchidae based on diagnostic features of the humerus, shoulder girdle, and the partial cervical vertebra of the holotype MOR 691. The initial description focused mainly on the diminutive size (2.5 m wingspan). Subsequent discoveries of postcranial material from thallasadromines, tapejarines, and azhdarchids have revealed that the postcranial features initially used to assign M. minor to the Azhdarchidae are synapomorphies for the more inclusive Azhdarchoidea clade. Phylogenetic analysis reveals that Montanazhdarcho possesses multiple characters that are shared by the Tapejarinae and Thallasadrominae: (1) a broad and well-developed tubercle at the ventroposterior margin of the coracoid; (2) a massive, distinct ulnar crest with a developed proximal ridge; (3) a strong boot-like ventral margin of the humeral head; (4) an ulna/radius as long or longer than metacarpal IV; an (5) a phalanx IV-1 that is as long or longer than metacarpal IV. The results of this study show that the Late Cretaceous pterosaur fauna was not entirely dominated by azhdarchids and recognizes important post-cranial characters that better define Azhdarchoidea. The reappraisal of M. minor as a non-azhdarchid member of theAzhdarchoidea also recognizes M. minor as the first known pterosaur of that clade found in North America, as well as one of the latest occurrences of the group.”

*Actually there is a large rostrum that belongs to another tupuxuarid from the Latest Cretaceous of southern Texas (Fig. 1), so it is not surprising to find tapejarid material then and there.

TMM 42489-2, the tall crested Latest Cretaceous large rostrum and mandible. It's a close match to that of Tupuxuara, otherwise known only from Early Cretaceous South American strata.

Figure 1. TMM 42489-2, the tall crested Latest Cretaceous large rostrum and mandible. It’s a close match to that of Tupuxuara, otherwise known only from Early Cretaceous South American strata.

** Azhdarchoidea improperly includes tapejarids. In the large pterosaur tree the azhdarchids are derived from dorygnathids while the tapejarids are derived from germanodactylids.

References
Carroll N 2015.
Reassignment of Montanazhdarcho minor as a nonazhdarchid member of the Azhdarchoidea. Journal of Vertebrate Paleontology abstracts.
Padian, K., Horner, J.R., and de Ricqlès, A.J 1993. A new azhdarchid pterosaur from the Two Medicine Formation (Late Cretaceous, Campanian) of Montana, identified on the basis of bone histology. Journal of Vertebrate Paleontology 13: 52A.
Padian K, de Ricqlès AJ and Horner JR 1995. Bone histology determines identification of a new fossil taxon of pterosaur (Reptilia: Archosauria)”, Comptes Rendus de l’Academie des Science Serie II (320): 77-84.
McGowen MR, Padian K, de Sosa MA and Harmon RJ 2002. Description ofMontanazhdarcho minor an azhdarchid pterosaur from the Two Medicine Formation (Campanian) of Montana. PaleoBios 22(1): 1–9.

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Introducing Sinopterus(?) liui

Figure 1. Sinopterus liui reconstructed from the original tracing of Meng Xi thesis for Masters degree.

Figure 1. Sinopterus liui reconstructed from the original tracing of Meng Xi thesis for Masters degree. Note the long cervicals not found in Sinopterus.

A new, virtually complete and articulated pterosaur specimen (IVPP V14188, Fig. 1), Sinopterus liii (Meng 2015; Jiufotang Formation, 120 mya), is considered a new species of a well known genus, Sinopterus. According to Meng, distinct traits include:

  1. large body size
  2. short beak
  3. high and short skull
  4. cranially sloping crest on premaxilla
  5. well developed hatchet-shaped deltopectoral crest of humerus
Figure 2. Tapejaridae. Sinopterus liui is indeed larger than other Sinopterus specimens.

Figure 2. Tapejaridae. Sinopterus liui is indeed larger than other Sinopterus specimens. Click to enlarge. This clade evolves to greater size and greater crest size.

Only the abstract is in English. Meng also modifies the description of the genus Sinopterus (Fig. 3).

Figure 1. Sinopterus and purported juvenile, but note the skull is relatively smaller with smaller eyes in the smaller specimen. The feet are also distinct. This appears to be a smaller adult of another species, not a juvenile.

Figure 3. Sinopterus and purported juvenile, but note the skull is relatively smaller with smaller eyes in the smaller specimen. The feet are also distinct. This appears to be a smaller adult of another species, not a juvenile.

From the Meng abstract
“Studies on the cranial crest have resulted in the suggestion that the bony crest was ossified by a crest composed of soft tissue during the ontogeny. As a result, the variation of size and shape among various Sinopterus specimens may be related to ontogeny and sexual behavior. Consequently, the sole difference in the cranial crest morphology between Huaxiapterus and Sinopterus is not taxonomically diagnostic, thus we propose that Huaxiapterus and Sinopterus are synonymy. Frequent volcanic activity in this region has caused the mass mortality of vertebrates.”

So Meng is a lumper.
Unfortunately we have not been able to verify variation in size and shape (except for enlargement of a cranial crest) in any pterosaur during ontogeny — and none, so far, have been able to assigned to a gender unless an aborted egg is nearby. These observations, of course, are contra traditional pterosaur paradigms, but they do follow the data.

Figure 4. Sinopterus iui skull in situ and reconstructed using DGS. That small orbit is distinct from Sinopterus and similar to Tupuxuara.

Figure 4. Sinopterus iui skull in situ and reconstructed using DGS. That small orbit is distinct from Sinopterus and similar to Tupuxuara.

I would have given this specimen a new genus. 
Based on the low resolution images provided and the great size difference, the new specimen (Fig. 4) appears to be sufficiently distinct to warrant its own genus — but then again, all those Pteranodon specimens are lumped into one genus.

Will the lumpers and splitters please get together?

TMM 42489-2, the tall crested Latest Cretaceous large rostrum and mandible. It's a close match to that of Tupuxuara, otherwise known only from Early Cretaceous South American strata.

Figure 4. TMM 42489-2 and the Tupuxuara longicristatus, to tupuxuarids with skulls similar, but not too similar, to the new Sinopterus.

 

References
Meng X 2015. A New Species of Sinopterus from Jehol Biota and Reconstraction of Stratigraphic Sequence of the Jiufotang Formation. A Thesis for the Master Degree of Science in the Graduate School of Chinese Academy of Sciences, directed by Wang X-L. (in Chinese)

 

 

 

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.

Juvenile? Tapejarid – Rio Ptero Symposium

Figure 1. XHPM 10009 specimen in situ and here colorized with DGS.

Figure 1. XHPM 10009 specimen in situ and here colorized with DGS. the dorsal and sacral are are tucked beneath the other elements. Looks like a possible sacrum in the antorbital fenestra. I have less confidence in the femora as both are beneath other elements.

Another Rio Ptero abstract came with a wonderful little halftone picture that captured a ton of data on a purported juvenile tapejarid (Lü and Teng 2013, Fig. 1). Talk about a paradigm buster! Check out that little skull.

Figure 1. Sinopterus and purported juvenile, but note the skull is relatively smaller with smaller eyes in the smaller specimen. The feet are also distinct. This appears to be a smaller adult of another species, not a juvenile.

Figure 2. Sinopterus and purported juvenile, XHPM 1009, but note the skull is relatively smaller with smaller eyes in the smaller specimen. The feet are also distinct, more like Noripterus, a dsungaripterid.. This appears to be a smaller adult of another species, not a juvenile.

Tapejarids reached their acme in Early Cretaceous South America. They appear in a variety of sizes (Fig. 2) and they had their origin in China with sinopterids, shenzhoupterids and dsungaripterids. These had origins in Europe with Germanodactylus (Fig. 2).

The new skull compared to other tapejarids. Click to enlarge.

Figure 3. Click to enlarge. The rising size of the tapejaridae.

Lü and Teng report on what they considered a juvenile based on its size (Fig. 1, Fig. 2 left, Fig. 3 second from left), smaller than Sinopterus with wingspan only 2/3 as wide and a skull half the size of the Sinopterus skull. In a clade of increasing skull and crest size, to find one with a smaller skull is a real oddity. And it reminds me of one other pterosaur with the small skull, Eosipterus, which we looked at earlier.

Look at the foot of Sinopterus and you’ll see toes about equal in length to the metatarsals. In the XHPM specimen (Fig. 1) the toes are much smaller. The femur is relatively longer in the XHPM specimen. Folks, this is a different species.

To their credit,
Lü and Teng note, “the premaxillary crest…is not influenced by ontogeny,” even though this is not a juvenile. They also report, “the humeri of the young individuals grew faster than the wing metacarpals and femora of the adult or sub-adult.” Unfortunately these distinct proportions more accurately reflect phylogenetic differences, not ontogenic differences. Germanodactylus (Fig. 3) is the baseline taxon here.

I contacted Dr. Lü with this data. Still waiting to hear from him with feedback.

References
Lü J-C and Teng F-F 2013. A juvenile tapejarid pterosaur fromt he Early Cretaceous of Liaoning Province and its ontogenetic implications. Rio Ptero Symposium 2013: 81-82.

Latest Cretaceous TMM 42489-2 Quetz? or Tupux?

Along with the giant Quetzalcoatlus northropi and the smaller Quetzalcoatlus sp., another different sort of rostrum was discovered in the Latest Cretaceous southern Texas strata (Fig. 1, Wellnhofer 1991). The pre-antorbital fenestra rostrum was relatively smaller and the dentary keel was deeper than in Q sp.. We looked at those Q. sp. rostra earlier. A few early artists used this specimen in their reconstructions of Quetzalcoatlus northropi.

Figure 1. TMM  42489-2, the tall crested Latest Cretaceous large rostrum and mandible. It's a close match to that of Tupuxuara, otherwise known only from Early Cretaceous South American strata.

Figure 1. TMM 42489-2, the tall crested Latest Cretaceous large rostrum and mandible. It’s a close match to that of Tupuxuara (above, ghosted), otherwise known only from Early Cretaceous South American strata.

It turns out the rostrum is close match to that of Tupuxuara (Fig. 1), an Early Cretaceous taxon from South America not related to Quetzalcoatlus. This late-surviving taxon testifies to one of the longest-lived genera. Most pterosaurs appear in one strata location only.

This is not the first time this specimen has been associated with tupuxuarids. I agree with those who consider it one.

References
Wellnhofer, P. 1991. The illustrated encyclopedia of pterosaurs. New York: Crescent.

Tapejarid? or Tupuxuarid?

New Tapejarid-Tupuxuarid skull.

Figure 1. New Tapejarid-Tupuxuarid skull. Click to enlarge.

Sculptor and blogger Helder da Rocha posted this photo of a new Early Cretaceous pterosaur from South America. He wrote: “This fossil was on sale at Paleodirect but not anymore. Either it was sold or (hopefully) acquired by a paleontological institution.”

De Rocha noted the similarity of this specimen to Tapejara (downturned rostrum) and to Tupuxuara (vertically expanded crest and lack of a dentary keel). Th rostral crest was larger than in any tupuxuarid, but the frontal/parietal crest did not extend posteriorly like a tapejarid. So it’s worth examining. The skull appears to be complete lacking a postorbital, bits of crest, a dentary tip and there is a peculiar slit of missing bone anterior to the antorbital fenestra.

Figure 2. Bones colorized in this tapejarid / tupuxuarid with crest hypothetically extended. Interesting that green line representing the maxilla ascending process seems to continue back to over the orbit. Here you can see its the nasals laminated to the premaxilla ascending process that create the rostral crest. Here the rostral crest rises higher than in tupuxuarids, but not as much as in tapejarids. And the crest could serve as a base for an extended soft tissue crest, as in tapejarids.

Figure 2. Bones colorized in this tapejarid / tupuxuarid with crest hypothetically extended. Interesting that green line representing the maxilla ascending process seems to continue back to over the orbit. Here you can see its the nasals laminated to the premaxilla ascending process that create the rostral crest. Here the rostral crest rises higher than in tupuxuarids, but not as much as in tapejarids. And the crest could serve as a base for an extended soft tissue crest, as in tapejarids.

To no one’s surprise, this specimen nests in the large pterosaur tree between the tapejarids and the tupuxuarids, both having descended from a sister to Huaxiapterus, but in different directions.

The new skull compared to other tapejarids. Click to enlarge.

Figure 3. The new skull compared to other tapejarids. Click to enlarge.

And its worthwhile to check out Huaxiapterus (Fig. 2) in greater detail as a starting point and a good guess as to what the post-crania might look like. In Huaxiapterus the mandible is too deep and the premaxilla extends too far back to be ancestral to the new specimen (but perfectly suitable to be ancestral to Tapejara). In our search for ancestors we can only get close and very rarely (almost never) pinpoint an actual ancestor.

 Huaxiapterus, a sister to the ancestor of tapejarids, tupxuarids and the tapejarid / tupuxuarid.

Figure 4. Huaxiapterus, a sister to the ancestor of tapejarids, tupxuarids and the tapejarid / tupuxuarid.

If we go back one step further we find a better ancestor to the new pterosaur skull. Here’s Sinopterus

Sinopterus, sister to the common ancestor of tapejarids and tupuxuarids.

Figure 5. Sinopterus, sister to the common ancestor of tapejarids and tupuxuarids.

No reference for the new skull, which might now reside either with a private collector or  a public institution.

Evolution produces a bush of variation, not just the two lineages (tapejarids and tupuxuarids) we had seen up until this point.

Vectidraco daisymorrisae – a new Isle of Wight pterosaur

A new pterosaur from the Isle of Wight, Vectidraco (Naish et al. 2013, Fig. 1) NHMUK PV R36621, has been named for its discoverer, Daisy Morris, all of 9 years old.

Vectidraco daisymorrisae

Figure 1. Vectidraco daisymorrisae from Naish et al 2013.

The partial specimen is represented by a left pelvis and associated partial sacrum is uncrushed and an exciting addition to our knowledge of Early Cretaceous pterosaurs. It’s not very large (see scale bar, fig. 1). Here (Fig. 2) we’ll add some missing parts, colorize vertebrae and try to produce a more understandable specimen.

Affinities
Naish et al. (2013) considered Vectidraco a basal azhdarchoid, which, in their terms meant close to the common ancestor of both azhdarchids and tapejarids (Fig. 2). The large pterosaur family tree, however, indicates that those two clades are not related to one another, despite sharing some traits, including a distinctive expanded posterior process of the ilium.

Figure 2. Vectidraco reconstruction and comparison to other pterosaur pelves with that odd posterior ilium flair. With similarities to the unrelated azhdarchids, the pelvis of Vectidraco appear to belong to a primitive tapejarid, One without a fused pelvis/ischium as in dsungaripterids and germanodactylids. The pelvis of Sinopterus has not been figured, but that is probably where we should look for a closest comparison. That's assuming the model Tupuxuara pelvis is accurate.

Figure 2. Vectidraco reconstruction and comparison to other pterosaur pelves with an odd posterior ilium flair. With similarities to the unrelated azhdarchids, the pelvis of Vectidraco appear to belong to a primitive tapejarid, one without a fused pelvis/ischium as in dsungaripterids and germanodactylids. The pelvis of Sinopterus has not been figured, but that is probably where we should look for a closest comparison. Oddly, many taxa around Sinopterus fail to adequately preserve the pelvis. That’s assuming the model Tupuxuara pelvis is accurate. Tropeognathus is related to neither azhdarchids nor tapejarids, but it likewise has an expanded posterior process of the ilium, but clearly of a different sort of shape.

Matching Morphologies
Here the closest match to the pelvis of Vectidraco is that of Tupuxuara, with the proviso that ancestors (Germanodactylidae) and sisters (Dsungaripteridae) to the Tapejaridae have an open ventral interosseous space and a smaller posterior process of the ilium. Tapejara does not fuse the pubis and ischium, but they are in contact. Earlier we looked at a tapejarid post-cranial specimen with a complete and ventrally fused pelvis (Sayao and Kellner 2006), close to Tupuxuara. For these phylogenetic bracketing reasons I presume the pelvis belongs to a smaller even more basal tapejarid along the lines of Sinopterus.

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
Naish D, Simpson M and Dyke G 2013. A New Small-Bodied Azhdarchoid Pterosaur from the Lower Cretaceous of England and Its Implications for Pterosaur Anatomy, Diversity and Phylogeny. PLoS ONE 8(3): e58451. doi:10.1371/journal.pone.0058451 plosOne link

Sayão JM and Kellner AWA 2006. Novo esquelito parcial de pterossauro (Pterodactyloidea, Tapejaridae) do membro Crato (Aptiano), Formação Santana, Bacia do Araripe, Nordeste do Brasil. Estudos Geológicos 16(2):16-40.

BBC links
Huffington Post link
wik/Vectidraco