Is Moganopterus a Ctenochasmatoid?

In their original description of Moganopterus zhuiana, Lü Junchang and colleagues described the new pterosaur as a boreopterid ornithocheiroid, to be compared alongside Zhenyuanopterus longirostris and its ridiculous teeth, and the crested-and-toothed Guidraco venator and Ludodactylus sibbicki. Sporting a long crest extending back from the occiput or oriented upwards but part of the rear of the skull, a relatively short rostrum with parallel dorsal and ventral margins and no rostral snout crest, the latter two are fairly similar to one another and have even found themselves together in some phylogenetic analyses (e.g., Wang et al., 2012). Zhenyuanopterus longirostris, unlike the other two, is known from a complete skeleton, and indeed, it differs from all other boreopterids (Boreopterus cuiae, Feilongus youngi) in preserving the whole skeleton, rather than just a skull and portion of the neck vertebrae. In these ways, and in the crazy elongation of the skull, Moganopterus zhuiana seems fairly similar.

On the whole, Boreopteridae seems fairly freakish. They all seem to have some sort of occipital crest, longish snouts, and many of them have numerus, slender teeth. In some, such as Zhenyuanopterus longirostris and Guidraco venator, the teeth are so long that they extend past the edges of the other side of the jaw, so the tips of the mandibular teeth poke above the upper jaw, and those of the upper jaw below the mandible. (Zhenyuanopterus longirostris adds to the crazy by having this rectangular-ish snout crest above the naso-antorbital fenestra (or NAOF), though Moganopterus zhuiana seems to have something similar waaaaay down at the tip of the snout.

Boreopteridae skulls, all not to scale. A, Boreopterus cuiae (), B, Feilongus youngi (), C, Zhenyuanopterus longirostris (Lü et al., 2010), D, Guidraco venator (Wang et al., 2012), E, Ludodactylus sibbicki (), E, Moganopterus zhuiana (Lü et al., 2012).

Boreopteridae skulls, all not to scale (scale bars in some sections not all equivalent, either). A, Boreopterus cuiae (Lü & Ji, 2005), B, Feilongus youngi (Wang et al., 2005), C, Zhenyuanopterus longirostris (Lü, 2010), D, Guidraco venator (Wang et al., 2012), E, Ludodactylus sibbicki (Frey, Martill & Buchy, 2003), E, Moganopterus zhuiana (Lü et al., 2012). White arrows point to portions or whole, intact cranial crests (snout and occiput); black arrows point to taxa in which the teeth extend beyond the edges of the opposite jaw. All images from their sources save E, which I found on a Russian forum

A thorough review of these pterosaurs is long overdue, but most recent work on this part of the pterosaur family tree has been to find that there’s much, much more to be done. Rodrigues & Kellner (2013) reviewed “Ornithocheiridae” and found it wanting, recovering a paraphyletic “Lonchodectes” and rendering its taxa as assorted and sundry stem-anhanguerids, which Ludodactylus sibbicki fell among close to the “core” anhanguerids (mostly the Anhanguera/Coloborhynchus/Tropeognathus complex). What is more interesting, however, is that Mark Witton (in his new book, Pterosaurs) suggested that what we know of boreopterid pterosaurs needs substantial work. He questioned the relationship of Moganopterus zhuiana with them, and instead offered an alternative: Ctenochasmatoidea.

Now, this isn’t a surprise. Feilongus youngi is a very similar taxon, and was originally conceived as a ctenochasmatoid similar to Cycnorhamphus suevicus. Reanalysis by Lü & Ji (2006) found a placement for it amongst ornithocheiroids, and Lü Junchang’s further work seems to support this placement. Ctenochasmatoids and boreopterids seem to share quite a few cranial features, up to and including numerous slender teeth, an inclined occiput and quadrate relative to the ventral margin of the NAOF, even a ventrally-poisitioned quadrate/mandibular joint. But Witton found several other interesting features in Moganopterus zhuiana and Feilongus youngi that are comparable to ctenochasmatoids, apart from the inclined rear portions of the skull: 1) relatively shorter teeth; 2) teeth confined to the rostral snout and not extending beneath the NAOF; 3) rounded orbits; 4) extraordinarily elongated postaxial cervical vertebrae. Additionally, Witton notes that there is an apparent bony, “fibrous” crest on the snout that extended the length of the skull. In these ways, these two pterosaurs do not resemble the ornithocheiroid Boreopteridae so much as the unquestioned ctenochasmatoid Huanhepterus quingyangensis:

Skeleton of Huanhepterus quingyangensis.

Skeleton of Huanhepterus quingyangensis. Grey region represents the impressions of bones of the type skeleton, whilst only the snout was preserved intact and as bone. Teeth are restricted to the very tip of the jaws.

The cranial crests of pterosaurs interest me very much. Those of some pterosaurs lay along the midline of the snout and probably derives solely from the premaxilla, extending before the eye and towards the tip of the jaws, such as Pterodactylus antiquus (non-bony, seemingly only comprised of ill-preserving soft-tissue parabolic shapes), Germanodactylus (mostly soft-tissue as in Pterodactylus but with a bony base bearing vertical fluting — or something), Dsungaripterus weii (high bony crest with fluted sides seemingly in the shape of the basal form of the unossified soft-tissue crest). In other pterosaurs, the crest is confined above or behind the eye (pteranodontids, azhdarchids, possibly chaoyangopterids), and seems to be an extension of the parietal (or even frontoparietal) and may have been very casque-like; that is, covered in a cornified dermus not unlike cassowaries, though these crests seem to be very thin. (In still others, a combination premaxilla-parietal crest is present, excluding the splint-like nasal, most notably in the “tupuxuarids” Tupuxuara and Thalassodromeus sethi.) The internal structure of the crests, their histology, and chemical makeup, especially the soft-tissue ones, have gone unstudied since their discovery. This is largely due to the fragility but also value of these fossils to Science. Yet speculation has only increased our curiosity, and whilst techniques such as UV light exposure of these structures has allowed to answer some questions of their structure and composition, it has left many, many others unanswered.

The tips of the snouts of Moganopterus zhuiana and Feilongus youngi both seem to sport a slight, triangular crest in the anterior end, and the structure’s lateral surface doesn’t appear to bear the fluting, or ridged surface present in other ctenochasmatoids; moreover, there doesn’t seem to be any damage to the dorsal surface of the skull in Feilongus youngi, and that means the apparent restriction of the crest to the jaw tip in that taxon may be authentic. Yet in Moganopterus zhuiana, this seems a little more questionable, and in closeups the crest seems less well-preserved. Detailed histological analysis would probably not only help us settle this particular issue but also resolve how the often very dissimilar cranial crests in monofenestratan pterosaurs (Pterodactyloidea + Darwinopterus and kin) evolved and in which ways; these things having an important phylogenetic but also ecological import.

As for Witton’s other characters, I tend to think he’s on sound footing with most. I am cautious about neck vertebrae elongation, but as of yet only two clades sport extremely long post-axial cervical vertebrae: Azhdarchidae and Ctenochasmatoidea, and not even all of the latter group do, as the vertebrae are relatively “short” in Pterodactylus, amongst its more basal members. Amongst pterosaurs, extreme elongation is highest in azhdarchids, but it approaches this length (relative to the wing) in Huanhepterus quingyangensis. The peculiarity of its neck vertebrae leaves us to consider three options: that it is an ornithocheiroid as originally described and convergent on azhdarchids/ctenochasmatoids, or that it is a ctenochasmatoid or an azhdarchid. We can exclude the latter option due to various features, including the crested snout, shallow NAOF, oribit shape and position, teeth, etc.; but it is more difficult to exclude the other two options, including being a ctenochasmatoid-convergent ornithocheiroid. The shape of its teeth, being numerous and slender, is also found in Boreopterus cuiae and Zhenyuanopterus longirostris, which Witton accepts as ornithocheiroids. Realistically, the odd taxa out are the strange duo of Guidraco venator and Ludodactylus sibbicki which (according to Rodrigues & Kellner, 2013, with some robust support) are joined by “Cearadactylusligabuei, given their short, robust teeth, large rostral “rosette” in the last, and short rostra. If we are judging Boreopteridae by these taxa, we may be inflating the clade unnaturally.

That all said, Witton makes an otherwise robust point and it is hard to ignore that the elongated cervical vertebrae, with their low, rectangular neural spines, the extraoridinarily elongated snouts and depressed quadrate/mandibular joint aren’t more seemingly ctenochasmatoid in appearance, and quite similar in fact to Pterodaustro guinazui. I am thus inclined to agree with Witton on this, though as I said earlier there needs to be an extensive overhaul of pterosaur phylogenetics, including a better handling of pelvic and mandibular characters, than has been demonstrated in the last decade.

Moganopterus to scale, as a ctenochasmatoid. Illustration © Joschua Knüppe, 2013, Hyrotrioskjan on DeviantArt. Used with permission.

Lü J.-c. 2010. A new boreopterid pterodactyloid pterosaur from the Early Cretaceous Yixian Formation of Liaoning Province, northeastern China. Acta Geologica Sinica 24 (3): 241–246.
Lü J.-C. & Ji Q. 2005. A new ornithocheirid from the Early Cretaceous of Liaoning Province, China. Acta Geologica Sinica 79 (2): 157–163.
Lü J.-c., Pu H.-y., Xu L., Wu Y.-h. & Wei X.-f. 2012. Largest toothed pterosaur skull from the Early Cretaceous Yixian Formation of western Liaoning, China, with comments On the family Boreopteridae. Acta Geologica Sinica 86 (2): 287–293.
Rodrigues, T. & Kellner, A. W. A. 2013. Taxonomic review of the Ornithocheirus complex (Pterosauria) from the Cretaceous of England. ZooKeys 308: 1-112.
Wang X.-l., Kellner, A. W. A., Zhou Z.-h. & Campos, D. de A. 2005. Pterosaur diversity and faunal turnover in Cretaceous terrestrial ecosystems in China. Nature 437: 875–879.
Wang, X.-l., Kellner, A. W. A., Jiang S.-x. & Cheng X. 2012. New toothed flying reptile from Asia: close similarities between early Cretaceous pterosaur faunas from China and Brazil. Naturwissenschaften 99 (4): 249-257.
Witton, M. P. 2013. Pterosaurs: Natural History, Evolution, Anatomy. (Princeton University Press, Princeton, UK.)

This entry was posted in Biology, Paleontology and tagged , , , , , , , . Bookmark the permalink.

9 Responses to Is Moganopterus a Ctenochasmatoid?

  1. Very interesting post.
    Just one question: this is actually the first time that I read about Ludodactylus and Guidraco as members of Boreopteridae. In which article(s) is this relationship supported?

    Thanks in advance

    • This dosn’t come from an explicit association, but a generalized relationship from phylogenetic closeness. I was using the term as a grade, rather than a clade, and may need to clarify this. That is, the entire gradient of non-istiodactylid, pterodanodontian or anhanguerid/ornithocheirid ornithocheiroids seem to have a generalized morphology that places them as a seemingly concise “boreopterid” group of rear-crested, long-toothed pterosaurs. That said, there is some support for a “boreopterid” and a “ludodactylid” group, with the former containing not only what Witton restricts to Boreopteridae (Boreopterus, Zhenyuanopterus) but also Feilongus and Moganopterus (in Lü et al., 2012) but also the near-anhanguerid blunt-snouted others mentioned in this post. As I said, and as Rodrigues & Kellner say, this region of the tree needs substantial overhauling. I am therefore using Boreopteridae as a gradient of convenience, even if it is a little confusing.

  2. Good reasoning, Jaime. Phylogenetic analysis nests Mogano and Feilong with Cycnorhamphids a clade that is a sister to Ornithocheirids (including Boreopterids). So not far from one another. Huanhepterus nested with pre-azhdarchids, so that explains that long neck. Ctenochasmatids come off of toothy dorygnathids like Angustinaripterus. Not sure where Witton gets that hyperlong neck for Pterodaustro. No specimens I’ve seen have it, only a Wellnhofer recon does. Analysis results here:

    • Substantive phylogenetic analysis, Dave. For reasons Mark, Darren, Mickey and myself have said time and again, yours is (and continues to be) intrinsically flawed. While I appreciate you agreeing with me (and effectively Mark Witton, whose argument this is), you and I must disagree on Huanhepterus quingyangensis, however (and Witton agrees with conventional wisdom on this as well — i.e., ctenochasmatoid Huanhe).

  3. Only because the closest taxa to Huanhepterus are not included in prior analyses.

    • One would still have to overcome the enormous number of other characters, provided (and this is important, Dave) they were coded correctly, that the characters you use are meaningful, and that you include as much of them as you can. I tend to think Mickey is spot on with his criticisms of the specifics of your coding practices, in that they are extraordinarily flawed.

  4. Assuming that Witton’s hypothesis is correct, is it possible that we are greatly underestimating the length of the cranium and mandible of Huanhepterus?

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s