Lonchodectid lifestyle logic

Ah, Lonchodectids. One of the most obscure and little-known pterosaur clades. The clade could include Lonchodectes, Lonchodraco , “Palaeornis” cliftii, Prejanopterus, Serradraco, Unwindia, Yixianopterus, the unnamed specimen BEXHM 2015.18, and an unpublished specimen nicknamed “Chang-e”. Most of these, except Yixianopterus and allegedly Chang-e, are known from pretty fragmentary remains; and of those two, the latter is unpublished and the former is only preliminarily described and I can’t find it. Unfortunately, my main source of information on it is going to be a photograph on *shudder* Pterosaur Heresies Update: Thanks to Jorge Bar for getting me a copy!

The phylogenetic position of Lonchodectidae is also somewhat murky. They’d been previously proposed as Ctenochasmatoids (Unwin 2003), Azhdarchoids (Unwin et al. 2008), miscellaneous Lophocratians (Witton 2013), and Pteranodontians (Andres et al. 2014). For the record, I’ve preliminarily found them in the same grade as Istiodactylidae, but that isn’t the main topic of this post. No, here I’ll discuss their lifestyle. Despite the mystery of this group, a preliminary proposed lifestyle has been proposed – long-necked terrestrial generalists (Unwin et al. 2008, Witton 2013). But does this hold up?

https://upload.wikimedia.org/wikipedia/commons/d/da/Serradraco_sagittirostris_Kellner_and_Rodriguez_2013.jpg
The only known specimen of Serradraco sagittirostris, showing a typical Lonchodectid dentition. From Rodrigues & Kellner 2013.

The first step would be looking at Lonchodectid teeth. Lonchodectid teeth are distinctive – they’re well-spaced, “raised” from the jawline, short, laterally compressed, and recurved. It’s hard to tell what they were doing with them. They come across to me as potentially being the teeth of piscivores or carnivores, which would be a fairly standard Ornithocheiromorph diet. They remind me of the teeth of the gharial. The snout tip of Lonchodraco giganteus at least almost seems like a subtle version of the “fish grab” anterior snouts of many Anhanguerians, and the anteriorly-confined teeth of Unwindia may (or may not) have been something similar.

https://upload.wikimedia.org/wikipedia/commons/b/b1/Gavialis_gangeticus%2C_ZOO_Praha_045.jpg
The gharial, Gavialis gangeticus. Its dentition resembles those of Lonchodectids in being small, evenly spaced, and recurved, set in a long, narrow snout. Original by Matěj Baťha on Wikimedia Commons.

The only Lonchodectid postcranial remains are the skeletons of Yixianopterus and Chang-e, the fragmentary postcrania of Lonchodraco and BEXHM 2015.18, the single humerus that is “Palaeornis” cliftii, and postcrania referred to Lonchodectes. BEXHM 2015.18 and the postcrania of Lonchodraco are really fragmentary and relatively uninformative as to lifestyle (Bowerbank 1846, Rigal et al. 2018).

The referred Lonchodectes postcrania catches my eye most. The most interesting and perhaps most phylogenetically informative specimen is a humerus, CAMSM B54081, figured by Unwin 2003. Cervical vertebrae and other limb elements have also been referred to it, most of which have apparently not been figured (but see Unwin 2001, Witton 2013 for exceptions). This referral apparently began in the 19th century, and was followed by Unwin 2001, Unwin 2003, and Witton et al. 2009 without comment.

Now I have to ask, on what grounds should these be referred to Lonchodectes in particular? Every species ever referred to it (excepting L. (now Lonchodraco) giganteus, which has really fragmentary postcrania and no humerus) is based on a fragment of rostrum or mandible (Rodrigues and Kellner 2013). Lonchodectes compressirostris – the only one remaining – isn’t even known from a snout tip like so many other Ornithocheiromorphs! There’s no real reason why any of the postcrania should belong to Lonchodectes in particular, especially knowing the Chalk Formation (L. compressirostris’ locality, and from what I can tell a completely different formation from the postcrania) and Cambridge Greensand are multitaxic. From what I can see, the postcranial remains referred to Lonchodectes are very similar to those of Azhdarchoids. And Azhdarchoids are certainly known from early Cretaceous England. Indeed, in 2012 CAMSM B54081 was re-referred to Ornithostoma and interpreted as belonging to an Azhdarchoid (Averianov 2012) [I have my doubts about this referral too, but that’s going off-topic].

https://bdj.pensoft.net/showimg.php?filename=oo_22082.jpg
This is everything that can reasonably be said to belong to Lonchodectes. From Rodrigues and Kellner 2013

And with this, it’s probable “Palaeornis” cliftii is not a Lonchodectid either. The only fossil – a humerus – looks very much like those of Azhdarchoids too. It doesn’t have a solid phylogenetic position in my Azhdarchoid analysis, but appears to be a non-Azhdarchid Azhdarchoid. As does CAMSM B54081, which I coded in on its own.

Perhaps the most fabled Lonchodectid is “Chang-e”. It was presented at SVPCA 2008, and sounded like a goldmine of Lonchodectid information. A well-preserved skeleton, with “copious phylogenetic data” with long hindlimbs and a relatively short wing finger that placed Lonchodectids as either the sister taxon to or within Azhdarchoidea (Unwin et al. 2008). How exciting! Unfortunately, it seems to be a composite, and the manuscript is apparently dead now. Bummer if this is true.

Yixianopterus.PNG
JZMP-V-12, the holotype and only known specimen of Yixianopterus jingangshanensis. From Lu et al. 2006

What about Yixianopterus? Apart from the skull (which was apparently forged before the fossil was acquired by the JZMP), it’s one of the (if not the) most complete Lonchodectid fossils thus far, and the anterior jaws look pretty similar to those of Unwindia. If Yixianopterus is a Lonchodectid, it offers perhaps the best information about Lonchodectid postcrania thus far. The limb proportions are interesting. They don’t match up with those of Azhdarchoids. The short metacarpal IV relative to ulna, size of the wing finger in general, and wing phalanges 2/1 ratio remind me more of those of Istiodactylids or Anhanguerids. Both are thought to have been long-distance fliers in primarily terrestrial and marine settings respectively (Witton 2013). Perhaps Yixianopterus had similar flight habits.

And then there’s Prejanopterus. It’s hard to tell what’s up with it. It’s small and has a long, really narrow, slightly upturned snout, with more teeth than Lonchodectids typically seem to have – if it is a Lonchodectid at all. It’s hard to know what it was doing, but it was probably doing something relatively “unorthodox”. I don’t want to say fishing because that feels like a cop-out, but that might be a reasonable preliminary guess.

What image forms out of this? Perhaps Lonchodectids were aerial piscivores like Anhanguerids – their gharial-like jaws hint at a potential fishing lifestyle, and their limb proportions match up with a life mostly on the wing. Of course, given the general quality of Lonchodectid remains, more fossils are probably needed before anything concrete could be said.

References
Andres, B.; Clark, J.; Xu, X. (2014). “The Earliest Pterodactyloid and the Origin of the Group”. Current Biology 24: 1011-6.
Averianov, A.O. (2012). “Ornithostoma sedgwicki – valid taxon of azhdarchoid pterosaurs”. Proceedings of the Zoological Institute RAS, 316(1): 40-49.
Bowerbank, J.S. (1846). “On a new species of pterodactyl found in the Upper Chalk of Kent (Pterodactylus giganteus)”. Quarterly Journal of the Geological Society of London, 2: 7-9.
Lu, J.; Ji, S.; Yuan, C.; Gao, Y.; Sun, Z.; Ji, Q. (2006). “New pterodactyloid pterosaur from the Lower Cretaceous of Western Liaoning”. In: Lu, J.; Kobayashi, Y.; Huang, D.; Lee, Y. (eds). Papers from the 2005 Heyuan International Dinosaur Symposium. Geological Publishing House: 195-203.
Rigal, S.; Martill, D.M.; Sweetman, S.C. (2018). “A new pterosaur specimen from the Upper Tunbridge Wells Sand Formation (Cretaceous, Valanginian) of southern England and a review of Lonchodectes sagittirostris (Owen 1874).” In: Hone, D.W.E.; Witton, M.P.; Martill, D.M. (eds). New Perspectives on Pterosaur Palaeobiology. Geological Society of London Special Publications, 455.
Unwin, D.M. (2001). “An overview of the pterosaur assemblage from the Cambridge Greensand (Cretaceous) of Eastern England”. Mitt. Mus. Nat.kd. Berl., Geowiss. 4: 189-221.
Unwin, D.M. (2003). “On the phylogeny and evolutionary history of pterosaurs”. In: Buffetaut, E.; Mazin, J-M. (eds). Evolution and Palaeobiology of Pterosaurs. Geological Society of London Special Publications, 217: 139-190.
Rodrigues, T.; Kellner, A.W.A. (2013). “Taxonomic review of the Ornithocheirus complex (Pterosauria) from the Cretaceous of England”. Zookeys, 308: 1-112.
Unwin, D.M.; Wang, X.; Meng, X. (2008). “How the Moon Goddess, Chang-e, helped us to understand pterosaur evolutionary history” SVPCA 2008.
Witton, M.P.; Martill, D.M.; Green, M. (2009). “On pterodactyloid diversity in the British Wealden (Lower Cretaceous) and a reappraisal of “Palaeornis” cliftii Mantell, 1844″. Cretaceous Research, 30: 676-686.
Witton, M.P. (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press.

Update: Kudos to Renato Filipe Vidal Santos for giving this a read-through and catching a few things.

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