New flightless and giant nyctosaurs: Alcione and Barbaridactylus

Scale bar problems
and a lack of reconstructions in the original paper are issues here.

Longrich, Martill and Andres 2018
bring us news of “a diverse pterosaur assemblage from the late Maastrichtian of Morocco that includes not only Azhdarchidae but the youngest known Pteranodontidae and Nyctosauridae. [This] dramatically increases the diversity of Maastrichtian pterosaurs. At least 3 families —Pteranodontidae, Nyctosauridae, and Azhdarchidae — persisted into the late Maastrichtian. These patterns suggest an abrupt mass extinction of pterosaurs at the K-Pg boundary.”

The authors summary starts off with an invalid statement:
“Pterosaurs were winged cousins of the dinosaurs.”  That was invalidated by Peters 2000, 2007 and ignored every since. We looked at that problem earlier here, here and here in a 3-part series testing all candidates. It’s time to realize that no one will ever find pterosaur kin among the dinos. They’ve already been clearly identified among the lepidosaurs.

The authors failed to include the Maastrictian tupuxuarid
found in southern Texas (Fig. 1; TMM 42489-2) and did not consider the Maastrichtian footprints discovered in 1954 and reexamined in 2018 that include two ctenochasmatids we will look at tomorrow.

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.

Alcione elainus gen. et sp. nov.
The new 1.5x larger nyctosaurid, Alcione elainus, known from disassociated bones including a shorter radius + ulna, a shorter metacarpal 4, a larger femur, and a tiny sternal complex (identified as a ‘sternum’ in the text) only 40 percent the size of a standard nyctosaur sternal complex (if the scale bars are correct). When placed on a reconstruction of a more complete Nyctosaurus (UNSM 93000; Fig. 2), scaled to the humerus, the result produces a likely flightless nyctosaur. Strangely, the authors called this a “small nyctosaur” even though it is half again larger than UNSM 93000. The authors mislabeled the shorter, straighter scapula as a coracoid, and vice versa.

Figure 2. GIF movie of Nyctosaurus and Alcione showing a likely flightless nyctosaur based on the parts preserved.

Figure 2. GIF movie of Nyctosaurus and Alcione showing a likely flightless nyctosaur based on the parts preserved. Three frames change every 5 seconds. The sternum is tiny (assuming the scale bars are correct), the metacarpus and antebrachium are short and the femur is long.

They did not mention the possibility of flightlessness.
They did report, “The abbreviated distal wing elements in Alcione indicate a specialized flight style. The short, robust proportions suggest reduced wingspan and increased wing loading, implying distinct flight mechanics and an ecological shift. Short wings would increase lift-induced drag at low speeds, but reduced wing areas would decrease parasite drag at high speeds, suggesting that Alcione may have been adapted for relatively fast flapping flight compared to other nyctosaurids. Alternatively, reductions in wingspan might represent an adaptation to underwater feeding, i.e., plunge diving of the sort practiced by gannets, tropicbirds, and kingfishers, where smaller wings would reduce drag underwater.”

Not sure why they mentioned
‘distal wing elements’ here. They did not list or discuss distal wing elements elsewhere. Perhaps they meant proximal.

The reconstructed mandible of Alcione
is narrower than the rostrum in UNSM 93000.

Based on the vestigial fingers of UNSM 93000
and the short metacarpus of the new specimen, Alcione might have been the first pterosaur to walk on metacarpal 4, albeit at the very end of the reign of pterosaurs.

Other flightless pterosaurs include:
the basal azhdarchid form the Solnhofen, Jme-Sos 2428 and the Late Jurassic anurognathid PIN 2585/4 from the Sordes slab. They demonstrate that the distal wing elements reduce first. Thus the reconstruction, based on nyctosaur patterns restores a wing that was not volant.

Longrich, Martill and Andres did find a giant nyctosaur
which they named Barbaridactylus grandis based on a large humerus (Fig. 3). The humerus of the more complete UNSM 93000 specimen is 9.5 cm. By comparison the humerus in Barbaridactylus is 22.5 cm. I’m going to trust the text comment that the ulna + radius are 1.3x longer than the humerus. The scale bars indicate about half that length. Similar problem possible in the scapula/coracoid, according to the nyctosaur bauplan.

Figure 3. Barbaridactylus, a giant nyctosaurid. If the wing was like UNSM 93000, then it could fly. If the wing was like Alcione, then it could not. The scale bars did not match the text description on the ulna + radius, so both sizes are shown.

Figure 3. Barbaridactylus, a giant nyctosaurid. If the wing was like UNSM 93000, then it could fly. If the wing was like Alcione, then it could not. The scale bars did not match the text description on the ulna + radius, so both sizes are shown. Sometimes you have to be prepared for the occasional mistake in a published paper.

Other giant nyctosaurs
Earlier and here we noted giant nyctosaurs were flying over the Niobrara Sea (midwest North America) based on a large wing finger with unfused extensor tendon process (YPM 2501) and a large nyctosaur pelvis (KUVP 993; misinterpreted by Bennett (1991, 1992) as belonging to a female Pteranodon). 

No reconstructions were provided
by Longrich, Martill and Andres 2018. Reconstructions and a nyctosaur blueprint might have helped these paleontologists with firsthand access to the specimens discover the issues they missed.

It’s good to know
more pterosaurs made it to the latest Cretaceous.

References
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992.
 Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Longrich NR, Martill DM, Andres B 2018.
Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary. PLoS Biol 16(3): e2001663. https://doi.org/10.1371/journal.pbio.2001663
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2007. 
The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.

Press coverage
Smithsonian
Newswise
PhysOrg

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New Como Bluff (Latest Jurassic) pterosaurs

Bits and pieces
of new Latest Jurassic pterosaurs are coming out of aquatic deposits in western North America according to McLain and Bakker 2017. The material is 3D and not very mineralized, so it is extremely fragile.

Specimen(s) #1 – HMNS/BB 5027, 5028 and 5029
“One proximal and two distal femora match a complete femur (BYU 17214) referred to Mesadactylus. Unexpectedly, both of the BBF distal femora possess a large intercondylar pneumatopore. BYU 17214 also possesses an intercondylar pneumatopore, but it is smaller than in the BBF femora. Distal femoral pnuematicity is previously recognized only in Cretaceous azhdarchoids and pteranodontids.”

The Mesadactylus holotype and referred specimens reconstructed to match the flightless pterosaur, Sos2428.

Figure 1. The Mesadactylus holotype (Jensen and Padian 1989) nests with the North American anurognathids. Several referred specimens (Smith et al. 2004), when reconstructed nest at the base of the azhdarchidae, with Huanhepterus and the flightless pterosaur SOS 2428.  The new BYU 17214 femur is essentially identical to the femur shown here.

Earlier we looked at two specimens referred to Mesadactylus. One is an anurognathid (Fig. 1). The other is a basal azhadarchid close to Huanhepterus, not far removed from its Dorygnathus ancestors in the large pterosaur tree. Instead McLain and Bakker compare the femora with unrelated and Early Cretaceous Dsungaripterus, which convergently has a similar femur. The better match is to the basal azhdarchid, so distal femoral pneumaticity does not stray outside of this clade. By the way, it is possible that Mesadactylus was flightless.

Specimen(s) #2 – HMNS/BB 5032 (formerly JHU Paleon C Pt 5)
“A peculiar BBF jaw fragment shows strongly labiolingually compressed, incurved crowns with their upper half bent backwards; associated are anterior fangs. We suspect this specimen is a previously undiagnosed pterosaur.”

These toothy specimens were compared to two Early Cretaceous ornithocheirids, one Middle Jurassic dorygnathid, and one Latest Jurassic bird, Archaeopteryx. None are a good match. A better, but not perfect,match can be made to the Early Jurassic pre-ctenochasmatid, Angustinaripterus (Fig. 2) which has relatively larger posterior teeth than does any Dorygnathus specimen.

The HMNS BB 5032 specimen(s) probably belong to a new species of Angustinaripterus or its kin based on the relatively large posterior teeth not seen among most Dorygnathus specimens.

The HMNS BB 5032 specimen(s) probably belong to a new species of Angustinaripterus or its kin based on the relatively large posterior teeth not seen among most Dorygnathus specimens.

As before,
we paleontologists don’t always have to go to our ‘go to’ taxon list of familiar fossils. Expand your horizons and take a fresh look at some of the less famous taxa to make your comparisons. You’ll find a good place to start at ReptileEvolution.com

References
McLain MA and RT Bakker 2017. Pterosaur material from the uppermost Jurassic of the uppermost Morrison Formation, Breakfast Bench Facies, Como Bluff,
Wyoming, including a pterosaur with pneumatized femora.

One of the largest Pterodaustro specimens had stomach stones

aka: Gastroliths.
And that’s unique for pterosaurs of all sorts. So, what’s the story here?

Figure 1. The V263 specimen compared to other Pterodaustro specimens to scale.

Figure 1. The MIC V263 specimen compared to other Pterodaustro specimens to scale. Its one of the largest and therefore, most elderly.

One of the largest Pterodaustro specimens
MIC V263 (Figs. 1-5), was reported (Codorniú, Chiappe and Cid 2013) to have stomach stones (gastroliths). That made news because that represented the first time gastroliths have been observed in 300 Pterodaustro specimens and thousands of pterosaurs of all sorts.

Unfortunately,
Codorniu, Chiappe and Cid followed tradition when they aligned pterosaurs with archosaurs, like dinos (including birds) and crocs. Those taxa also employ gastroliths for grinding devices. According to Codorniú, Chiappe and Cid, other uses include as a personal mineral supply, maintaining a microbial flora, elimination of parasites and hunger appeasement. Shelled crustaceans may have formed a large part of the Pterodauastro diet and stones could have come in handy on crushing their ‘shells’ according to the authors.

FIgure 2. Pterodaustro specimen MIC V263 in situ and as originally traced.

FIgure 2. Pterodaustro specimen MIC V263 in situ and as originally traced.

The authors also noticed
an odd thickening of the anterior dentary teeth and the relatively large size of the MIC V 263 specimen (Fig. 1) and suggested their use as devices for acquiring stones.

The wingspan of this big Pterodaustro is estimated at 3.6 meters.

Figure 1. Pterodaustro elements from specimen MIC V263.

Figure 3. Pterodaustro elements from specimen MIC V263.

Unfortunately,
the authors overlooked a wingtip ungual (Fig. 4), or so it seems… The confirming wingtip ungula is off the matrix block. But they weren’t looking for it…

Figure 2. One wing ungual was preserved in this specimen of Pterodaustro. The other is missing off the edge of the matrix.

Figure 4. One wing ungual was preserved in this specimen of Pterodaustro. The other is missing off the edge of the matrix.

The authors overlooked a distal phalanges on the lateral toe (Fig. 5). It is hard to see. And they were not looking for it. Note the double pulley joint between p2.1 and p2.2. That’s where the big bend comes in basal pterosaurs.

Figure 5. Pterodaustro MIC V263 pes in situ and with pedal digit 2 reconstructed from overlooked bones.

Figure 5. Pterodaustro MIC V263 pes in situ and with pedal digit 2 reconstructed from overlooked bones.

The authors overlooked a manual digit 5, the vestigial near the carpus (Fig. 6) displaced to the disarticulated carpus during taphonomy. Again, easy to overlook. And they were not looking for it…

Figure 6. Carpus of the Pterodaustro specimen MIC V263 withe elements colorized. Manual digit 5 elements are in blue on the pink ulnare.

Figure 6. Carpus of the Pterodaustro specimen MIC V263 withe elements colorized. Manual digit 5 elements are in blue on the pink ulnare. Not sure where carpal 5 is.

The authors
labeled the unguals correctly (Fig. 7), but some of the phalanges escaped them. Note the manual unguals are not highly curved, like those of Dimorphodon and Jeholopterus. And for good reason. Pterodaustro is a quadrupedal beachcomber with the smallest fingers of all pterosaurs. It’s not a tree clinger. And for the same reason, pterosaurs with long curved manual claws are not quadrupeds. Paleontologists traditionally attempt to say all pterosaurs are quadrupeds, rather than taking each genus or clade individually. Beachcombers made most of the quadrupedal tracks. It’s also interesting to note that Pterodaustro fingers bend sideways at the knuckle, in the plane of the palm, probably in addition to flexing toward the palm. It’s easier for lizards to do this, btw. Not archosaurs. That’s how you get pterosaur manual tracks with digit 3 oriented posteriorly, different from all other tetrapods.

Figure 7. Pterodaustro MIC V 263 fingers reconstructed and restored.

Figure 7. Pterodaustro MIC V 263 fingers reconstructed and restored. Pterodaustro is unusual in having metacarpals 1 > 2 > 3. Note the flat tipped manual unguals. Not good for climbing trees, like those of many other pterosaurs.

So the question is: why did this specimen have stones inside—
when other pterosaurs do not? Since MIC V263 is larger, it is probably older, closer to death by old age. Was it supplementing an internal grinding structure that had begun to fail? Was this some sort of self-medication for a stomach ailment? It’s not standard operating procedure for pterosaurs to have stomach stones. So alternate explanations will have to do for now. Let’s not assume or pretend that all pterosaurs had gastroliths. They don’t.

Figure 8. Elements of the MIC V263 specimen applied to the smaller PPVL 3860 specimen scaled to the length of the metacarpals. At this scale the large Pterodaustro had a shorter wing and shorter fingers with smaller unguals.

Figure 8. Elements of the MIC V263 specimen applied to the smaller PVL 3860 specimen scaled to the length of the metacarpals. At this scale the large Pterodaustro had a shorter wing and shorter fingers with smaller unguals.

Compared to the largely complete and articulated Pterodaustro specimen,
PVL 3860, there are subtle differences in proportion (Fig 8) to the larger MIC V263 specimen. If metacarpals are the same length, then the wing is shorter in the larger specimen. This follows a morphological pattern in which no two tested pterosaurs are identical. Still looking for a pair of twins.

References
Codorniú L, Chiappe LM and Cid FD 2013. First occurrence of stomach stones in pterosaurs. Journal of Vertebrate Paleontology 33:647-654.

Liaodactylus, a new gnathosaurine pterosaur

Figure 1. Liaodactylus (in color in in situ compared to Gnathosaurus.

Figure 1. Liaodactylus (in color in in situ compared to Gnathosaurus. The portion of the rostrum above the antorbital fenestra remains unknown. A short crest may or may not have been present.

Liaodactylus primus (Zhou et al. 2017) was considered the earliest filter-feeding pterosaur. Here it nests with the Solnhofen specimen of Gnathosaurus. Distinctly, Liaodactylus has short premaxillary teeth and longer dentary teeth than maxillary teeth. The skull was small, only half the length of Gnathosaurus, but with similar proprotions. The jugal was not elevated and so did not shrink the orbit.

FIgure 2. Subset of the large pterosaur cladogram focusing on the clade Dorygnathia and the clade within it, the Ctenochasmatidae.

FIgure 2. Subset of the large pterosaur cladogram focusing on the clade Dorygnathia and the clade within it, the Ctenochasmatidae. Here Liaodactylus nests as a sister to Gnathosaur, a basal ctenochasmatid.

Zhou et al. did not provide
a specimen-based phylogenetic analysis. but used only one taxon for each genus and so missed out on the gradual accumulation of traits that nested Liaodactylus with Gnathosaurus. Instead they nested it with Ctenochasma.

Zhou et al. used the data matrix
of Andres, Clark and Xu 2004, which nested Kryptodrakon as the basalmost pterodactyloid. As we learned earlier, those authors reconstructed the few bits and pieces of Kryptodrakon as a small Pterodactylus-like pterosaur, when it should have been reconstructed as a larger, but very gracile Sericipterus, which was found in the same deposits, but would not have made so many headlines.

References
Andres B, Clark JM and Xu X 2010.A new rhamphorhynchid pterosaur from the Upper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs, Journal of Vertebrate Paleontology 30: (1) 163-187.
Andres B, Clark J and Xu X 2014. The Earliest Pterodactyloid and the Origin of the Group. Current Biology (advance online publication)
DOI: http://dx.doi.org/10.1016/j.cub.2014.03.030
Zhou C-F, Gao K-Q, Yi H, Xue J, Li Q and Fox RC 201. Earliest filter-feeding pterosaur from the Jurassic of China and ecological evolution of Pterodactyloidea. R. Soc. open sci. 4: 160672. http://dx.doi.org/10.1098/rsos.160672

 

It looks A LOT like Gladocephaloideus, but it’s not one

Among the long-necked ctenochasmatids
close to Gegepterus, is Gladocephaloideus (Lü et al. 2012), a taxon originally considered a cycnorhamphid. A new, smaller specimen with an equally impressive set of long cervicals was recently assigned to the same genus (Lü et al. 2016, Fig. 1) as a juvenile.

Figure 1. Gladocephaloideus (the holotype) compared to the new specimen referred to Gladocephaloideus and its two sister taxa in the large pterosaur tree. Long necks in ctenochasmatids made several appearances by convergence.  Of particular interest, note the size of the pelvis in the JPM specimen, no larger than that of the much smaller MB.R. specimen. Lü et al considered the pelvis incomplete and it may be. Sister taxa are illustrated here from figure 2.

Figure 1. Gladocephaloideus (the holotype) compared to the new specimen referred to Gladocephaloideus and its two sister taxa in the large pterosaur tree. Long necks in ctenochasmatids made several appearances by convergence.  Of particular interest, note the size of the pelvis in the JPM specimen, no larger than that of the much smaller MB.R. specimen. Lü et al considered the pelvis incomplete and it may be. Sister taxa are illustrated here from figure 2.

Unfortunately
the two specimens do not nest together in the large pterosaur tree (Fig. 2). Close, but separated by several nodes.

Before leaving Figure 1,
note the size of the relatively tiny pelvis in the JPM specimen, no larger than that of the much smaller MB.R. specimen with a relatively large pelvis of similar shape. This reconstruction was built from scraps that give the appearance of complete bones. Lü et al. 2016 considered the pelvis incomplete and did not attempt a reconstruction. No sacrum is associated with the pelvic elements to confirm or refute the present size reconstruction. New conspecific specimens will help.

Figure 2. Ctenochasmatids arise from these dorygnathids.

Figure 2. Ctenochasmatids arise from these dorygnathids.

Lü et al. amended the diagnosis of Gladocephaloideus
to accommodate the new smaller specimen. That’s not a good idea before determining that they are indeed conspecific. In order to obviate that prospect, in phylogenetic analysis Lü et al. created a chimaera of the two specimens eliminating any possibility of testing one against the other and against all other pterosaur taxa. In my experience it is extremely rare to find conspecific pterosaurs. That is why I try to nest only specimens, not chimaeras.

The pes of Gladocephaloideus

Figure 3. (Left) The pes of Gladocephaloideus compared to (right) the pes of Ctenochasma elegans (a smaller, more primitive Ctenochasma with fewer teeth). Compare to the pes in figure 1.

The feet
of the holotype and referred specimen are similar but not the same in proportion or appearance. They score differently. In pterosaurs, feet are like fingerprints, enabling one to lump conspecific taxa and split convergent look-alikes.

Figure 4. The JPM specimen in situ along with a reconstruction of its skull compared to the holotype of Gladocephaloides.

Figure 4. The JPM specimen in situ along with a reconstruction of its skull compared to the holotype of Gladocephaloideus. The anterior mandible was glued on in the wrong direction, as noted by Lü et al. 2016.

Lü et al. did not test
the MBR stem ctenochasmatid. Lü et al.  nest ctenochasmatids with cycnorhamphids, among other odd yet traditional nestings. This may be due to the low number of included taxa (67) vs. 215 in the large pterosaur tree.

The taxonomy and systematics get a little confusing….
the original Gladocephaloideus was assigned by Lü et al. 2012 to the Gallodactylidae (cycnorhamphids), but in consideration of the smaller specimen Lü et al. 2016 shifted it to the Ctenochasmatidae where it nests with Pterofiltrus, which nests as a cycnorhamphid in the large pterosaur tree. Moreover, Lü et al. include as related taxa, Elanodactylus (a derived germanodactylid, basal to pteranodontids), Beipiaopterus (a basal azhdarchid), Feilongus and Moganopterus (both cycnorhamphids). At the next level of closest kin Lü et al. include Pterodactylus longicollum (a pterodactylid), Gnathosaurus (a ctenochasmatid) and Cearadactylus (an ornithocheirid nesting far from other ornithocheirids).

This buckshot phylogeny only get worse, but I’ll stop here.

I applaud Lü et al.
for re-identifying the holotype Gladocephaloideus as a ctenochasmatid, as first reported here several years ago. But the rest of their phylogenetic analysis has to add taxa to get up to speed with current research. Their pterosaur tree recovered over 3000 MPTs compared to the fully resolved single tree at ReptileEvolution.com.

Juvenile? Big question that needs new insight to answer:
Lü et al. 2016 report, “The unfused contact between the extensor tendon process and the proximal end of wing phalange 1, as well as the poorly ossified epiphyses of the wing phalanges, indicates that JPM-2014-004 is an early juvenile individual.” It is hard to consider the JPM specimen a juvenile because in phylogenetic analysis it is larger than both proximal adult taxa. The more primitive MB.R. specimen, despite its size is an adult having undergone phylogenetic miniaturization from larger Dorygnathus and Angustinaripterus ancestors, an evolutionary process that often gives rise to new morphologies, in this case, the clade Ctenochasmatidae with all of its synapomorphies. Phylogenetically miniaturized pterosaurs retain, through neotony, juvenile bone microstructure. Lü et al. 2016 report woven bone structure and no LAGs or zones. This may occur in rapidly growing tiny (sparrow-to-hummingbird-sized) adults less than one year in age. Tiny pterosaurs, like tiny birds may have matured in far less than a year, just like small birds. Lü et al. 2016 note that LAGs are uncommon in pterodactyloids, but may be seen in larger specimens that presumably lived longer. Size matters in a phylogenetic context. This has to be considered before making statements about ontogenetic age estimates.

Tibial bone wall thickness
With a radius of 16 units (holding a cm scale up to my monitor) the tibial bone thickness was 5 units, leaving 11 units of hollow cavity. That is same cortex ratio as in the 2x larger (9x heavier) holotype specimen.

But wait! What’s this?? A long rostrum on a juvenile??? 
That can’t be so, IF you follow the work of Bennett, Witton, Wellnhofer and others. That would be internally inconsistent! However, if you follow ReptileEvolution.com and the Pterosaur Heresies you’ll note that many tiny adults AND embryos had long rostra and small eyes. No problem under the isometric growth hypothesis, which I hope will someday gain a little acceptance because it is demonstrably factual. 

References
Lü J-C, Ji Q, Wei X-F and Liu Y-Q 2012. A new ctenochasmatoid pterosaur from the Early Cretaceous Yixian Formation of western Liaoning, China. Cretaceous Research in press. doi:10.1016/j.cretres.2011.09.010.
Lü J, Kundrát M, Shen C 2016. New Material of the Pterosaur Gladocephaloideus Lü et al., 2012 from the Early Cretaceous of Liaoning Province, China, with Comments on Its Systematic Position. PLoS ONE 11(6): e0154888. doi:10.1371/ journal.pone.0154888

TIme to Flip Plataleorhynchus (a spoonbill pterosaur)

Howse and Milner (1995)
described a spoonbill rostrum lacking teeth in place. They correctly compared it to the much smaller pterosaur Gnathosaurus and called their English find Plataleorhynchus stretophorodon (Fig. 1, BMNH R 11957). As you can see, it was much bigger.

Figure 1. Plataleorhynchus stretophorodon as originally interpreted (at far left) as newly interpreted (near left) with comparisons to Gnathoosaurus (right). Note the exposure is in dorsal view, not palatal view, and the premaxilla includes only 4 teeth, as in other pterosaurs.

Figure 1. Plataleorhynchus stretophorodon as originally interpreted (at far left) as newly interpreted (near left) with comparisons to Gnathoosaurus (right). Note the exposure is in dorsal view, not palatal view, and the premaxilla includes only 4 teeth, as in other pterosaurs. Yes, the premaxilla ‘pops up’ three times from beneath the maxilla and nasals in Gnathosaurus. Click to enlarge.

Unfortunately
Howse and Milner did not realize they were looking at the rostrum in dorsal aspect. And for that reason, perhaps,  they did not correctly figure the lateral extent of the premaxilla (Fig.1). No pterosaur has more than four teeth erupting from the premaxilla and Plataleorhynchus was no exception. So the premaxilla had a very short anterior exposure, rather than encompassing the entire spoonbill, as Howse and Milner interpreted the fossil from firsthand observation.

Howse and Milner did correctly note differences in the rostral shape and relative tooth size between Plataleorhynchus and Gnathosaurus, and also correctly noted that no other known pterosaur was closer. So, by this evidence, some mistakes don’t matter in the end.

Like Gnathosaurus and other ctenochasmatids,
Plataleorhynchus had dorsally expanded maxillae that contacted one another over the premaxilla aft of the spoonbill. Due to their orientation mistake, Howse and Milner identified the second dorsal appearance of the premaxilla as the palatine.

Howse and Milner thought the palate had a horny pad based on the rugosity that was exposed. That rugosity, (here considered dorsal) is also present in Gnathosaurus, but not as prominent. The reason or origin for the rugosity on the dorsal tip of Plataleorhynchus is difficult to explain, but may be related to the further extent of the maxillae and perhaps some sort of small horny crest.

Also note
the palatal extent of the premaxilla is much smaller in the comparable Gnathosaurus than envisioned for Plataleorhynchus by Howse and Milner. In Gnathosaurus I’m not sure how the teeth were not shaken loose. The roots appear to be exposed on the palate (Fig. 1). They must have been held in place by soft tissue.

Considering this mistake, 
much has been made about the value of firsthand observation versus the examination of photographs and illustrations. Paleontologists are fond of dismissing interpretations made in the absence of the fossil itself. They forget that most of the credit or blame for a discovery happens not in the lab, but between the ears. You have to see things correctly from the start or all the dominoes start to fall the wrong way. Mistakes can happen to anyone (including yours truly). Howse and Milner 1995 (Fig. 1) is another example of a firsthand observation that went awry based on one initial mistake. And that was an easy one to make with that odd spoonbill rostrum. It was flat on both sides.

Like Cope vs. Marsh back in the day, I am, once again metaphorically, “putting the skull on the other end of the skeleton” by flipping over the rostrum of Plataleorhynchus. The correct response, of course, should be curiosity or gratitude, not embarrassment, anger or dismissal. However, if anyone out there thinks the rostrum exposure is still palatal, I’d like to hear from you.

References
Howse SCB and Milner AR 1995. The pterodactyloids from the Purbeck Limestone Formation of Dorset. Bulletin of the Natural History Museum London (Geology)51:73-88.

 

Focus on Angustinaripterus – transitional between Dorygnathus and Ctenochasma

Angustinaripterus (Fig. 1) has been difficult to classify for other pterosaur paleontologists. Here in the large pterosaur tree the reason becomes quite evident. Add a few taxa and Angustinaripterus become a transitional taxon between the more primitive Dorygnathus (R154) and the more derived Gnathosaurus and Ctenochasma.

Figure 1. Angustinaripterus as a transitional taxon between Dorygnathus and Gnathosaurus.

Figure 1. Angustinaripterus as a transitional taxon between Dorygnathus and Gnathosaurus. Seems pretty obvious. Phylogenetic analysis confirms.

This possibility flips out traditional pterosaurologists who have pinned their hopes on Darwinopterus, which doesn’t look much like either Ctenochasma or Dorygnathus.

But that’s not all
Here (Fig. 2) are the many other specimens that smooth the evolutionary transition, as we noted before. Here they are. And many of them are tiny.

Figure 2. The same sequence with the addition of Dorygnathus purdonti and four tiny pterosaurs variously misassigned to Pterodactylus and Ctneochasma.

Figure 2. The same sequence with the addition of Dorygnathus purdonti and four tiny pterosaurs variously misassigned to Pterodactylus and Ctneochasma. Black illustrations are to scale. Gray figures are enlarged to show detail.

Angustinaripterus is the reason why I delved deeper into pterosaur phylogeny than anyone has done before. At first glance it’s clearly something not quite Dorygnathus and not quite Gnathosaurus or Ctenochasma.

The next step after Angustinaripterus was to add in some…

Tiny pterosaurs
This (Fig. 2) is only one sequence of many in which tiny adult pterosaurs are transitional between larger forms, both more primitive and more derived. At first glance, and according to tradition, these tiny pterosaurs are only juveniles or hatchlings, which makes perfect sense—until you add them to your matrix—and you realize juvenile pterosaurs of other types are virtual copies of adults. So there was no allometric growth after hatching, but chiefly isometric growth.

But there’s an important clue here staring you right in the face: Note how the tiny pterosaurs are ALL the same size. As it turns out, this is the minimum size at which pterosaurs could fly, evidently, as we find no smaller pterosaurs in the fossil record. Smaller pterosaurs, all juveniles, must have been living in damper environments and probably not flying. Some hatchlings, like the IVPP embryo, were as large as these adult pterosaurs (Fig. 2) and other adult tiny pterosaurs, so they could fly immediately. 

References
He X-L, Yang D-H and Su C-K 1983. A New Pterosaur from the Middle Jurassic of Dashanpu, Zigong, Sichuan. Journal of the Chengdu College of Geology supplement 1: 27-33.

wiki/Angustinaripterus