Another disc-head anurognathid from Jurassic China

Yesterday Yang et al. 2018 presented NJU-57003 (Figs. 1–3), a small anurognathid pterosaur with a great deal of soft tissue preservation, including feather-like filaments, said to be homologous with feathers. That was shown to be invalid by taxon exclusion here.

Today we’ll reconstruct
the crushed skull using DGS and nest this specimen in a cladogram using phylogenetic analysis (Fig. 4) in a few hours. Yang et al. were unable or unwilling to do either, even with firsthand access to the fossil and nine co-authors.

Figure 1. The NJU-57003 specimen and outline drawing, both from Yang et al. 2018. Various membranes and the overlooked sternal complex are colored in here.

Figure 1. The NJU-57003 specimen and outline drawing, both from Yang et al. 2018. Various membranes and the overlooked sternal complex and prepubes are colored in here. Clearly the uropatagia are separated here, as in Sharovipteryx. No wing membrane attaches below the knee.

Overlooked by Yang et al.
the sternal complex is quite large beneath the wide-spread ribs, a trait common to anurognathids. The torso, like the skull, would have been much wider than deep in vivo.

Figure 2. The skull elements of NJU-57003 colored to help alleviate the chaos of the crushed specimen. See figure 3 for the same elements reconstructed.

Figure 2. The skull elements of NJU-57003 colored to help alleviate the chaos of the crushed specimen. I can’t imagine betting able to interpret this skull without segregating each piece with a different color. See figure 3 for the same elements reconstructed with these colors.

As in other disc/flathead anurognathids
the palatal processes of the maxilla (red in Figs. 2, 3) radiate across the light-weight palate.  Yang et al. mislabeled these struts the ‘palatine’ (Fig. 1) following in the error-filled footsteps of other pterosaur workers who did not put forth the effort to figure things out.

The skull
is likewise supported by relatively few and very narrow struts. Contra Yang et al. 2018, who once again, mistakenly identify the toothy maxilla as an scleral ring (Fig. 1), the actual scleral rings (Figs. 2, 3) are complete and smaller within a large squarish orbit bounded ventrally by a deep jugal.

Figure 3. The skull of NJU-57003 reconstructed in animated layers for clarity. This is something the print media just cannot do as well. All elements are similar to those found earlier in other anurognathids.

Figure 3. The skull of NJU-57003 reconstructed in animated layers for clarity. This is something the print media just cannot do as well. All elements are similar to those found earlier in other anurognathids. Note the eyes, as in ALL pterosaurs, are in the back half of the skull.

Discodactylus megasterna (Yang et al. 2018; Middle-Late Jurassic, Yanlio biota, 165-160mya; NJU-57003) is a complete skeleton of a disc-skull anurognathid with soft tissue related to Vesperopterylus. The sternal complex is quite large to match the wider than tall torso. Distinct from other anurognathids, m4.1 does not reach the elbow when folded.

Figure 4. Subset of the LPT nesting Discodactylus with Vesperopterylus within the Anurognathidae.

Figure 4. Subset of the LPT nesting Discodactylus with Vesperopterylus within the Anurognathidae.

This specimen was introduced without a name
in a paper that incorrectly linked pterosaur filaments to dinosaur feathers (Yang et al. 2018), rather than with their true ancestor/relatives, the filamentous fenestrasaurs, Sharovipteryx and Longisquama, taxa omitted in Yang et al. and all workers listed below. Details here. The authors were unable to score traits for the skull and did not mention Vesperopterylus in their text.

Apparently the same artist
who originally traced the skull of Jeholopterus in 2003 (Fig. 5) also traced the present specimen (Fig. 1) with the same level of disinterest and inaccuracy. Compare the original image (Fig. 5 left) to a DGS image (Fig. 5 right). 

Figure 5. The original 2003 tracing of Jeholopterus (upper left) was inaccurate, uninformed and uninformative despite first hand access compared to the more informative and informed tracing created using DGS methods.

Why did these anurognathids have such long filaments?
Owls use similar fluffy feathers to silence their passage through air, first discussed earlier here.

The pterosaur experts weigh in the-scientist.com/news:
“I would challenge nearly all their interpretations of the structures. They are not hairs at all, but structural fibers found inside the wings of pterosaurs, also known aktinofibrils,” says pterosaur researcher David Unwin at the University of Leicester in the UK who was not part of the study. “They discovered lots of hair-like structures, but [don’t report any] wing fibers. I find that problematic.” Unwin suspects these fibers are likely to be present but have been mislabeled as feathers.  

This is a very important discovery,” says Kevin Padian, a palaeontologist at the University of California, Berkeley, “because it shows that integumentary [skin] filaments evolved in both dinosaurs and pterosaurs. That’s not surprising because they are sister groups, but it is good to know.”  

Padian draws attention to the pycnofibers’ “hair-like structure” as illustrating that they served as insulation. This is yet another characteristic of dinosaur and pterosaurs, along with high growth rate, pointing to their common ancestor as warm blooded.  “I wish the illustrations in the paper were better, but there is no reason to doubt them,” he adds.

Dr. Padian knows better.
He’s keeping the family secret by not mentioning fenestrasaurs (Peters 2000).

“The thing that is cool is that it bolsters the idea that pterosaurs and dinosaurs are sister taxa, if they are correct in interpreting these structures as a type of feather,” writes paleobiologist David Martill of the University of Plymouth in the UK, in an email. 

Dr. Martill knows better.
He’s keeping the family secret by not mentioning fenestrasaurs.

The specimens described in the paper are very interesting, agrees Chris Bennett, a palaeontologist at Fort Hays State University in Kansas, but in an emailed comment he describes the interpretation of the structures as problematic. “The authors’ characterization of the integumentary structures as ‘feather-like’ is inappropriate and unfortunate,” he writes. Some of the structures look like they could be from fraying or other decomposition, rather than feathers. Bennett adds that filamentous structures for insulation and sensation are fairly common, from hairy spiders to caterpillars to furry moths. “It seems to me to be premature to use filamentous integumentary structures to support a close phylogenetic relationship between pterosaurs and dinosaurs,” says Bennett. 

Dr. Bennett knows better.
He’s keeping the family secret by not mentioning fenestrasaurs.

Benton stands by his conclusion that pterosaurs wore plumage. Asked about the suggestion that the feathers could be wing fibers, he writes in an email, “Actinofibrils occur only in the wing membranes, whereas the structures we describe occur sparsely on the wings, but primarily over the rest of the body.”

Dr. Benton knows better.
He’s keeping the family secret by not mentioning fenestrasaurs. More details here.

References
Bennett SC 1996. The phylogenetic position of the Pterosauria within the Archosauromorpha. Zoological Journal of the Linnean Society 118:261-308.
Hone DWE and Benton MJ 2007.
An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2009.
Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Peters D 2000. 
A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Yang et al. (8 co-authors) 2018. Pterosaur integumentary structures with complex feather-like branching. Nature ecology & evolution doi:10.1038/s41559-018-0728-7

 

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SVP 2018: Resolving the Mesadactylus complex of individual bones

Figure 1. Mesadactylus restored from available data as an anurognathid.

Figure 1. Mesadactylus restored from available data as an anurognathid.

The BYU specimens attributed to 
Mesadactylus 
nest with anurognathids like ?Dimorphodon weintraubi (coeval and also from North America) in the large pterosaur tree (LPT). The specimen is Late Jurassic (Morrison Formation) in age.

Sprague and McLain 2018 conclude, “the taxonomic affinity of the genus is uncertain.” So why did they title their talk “Resolving…”

All they had to do
was Google “Mesadactylus.” Or run a phylogenetic analysis. The affinities of this specimen have been known here at the LPT since 2012.

References
Spratue M and McLain MA 2018. Resolving the Mesadactylus complex of Dry Mesa Quarry, Morrison Formation, Colorado. SVP Abstracts.

Mistralazhdarcho: a new pterosaur, but not an azhdarchid

Vullo et al. 2018 bring us a new small ‘azhdarchid’
known from a few 3D bones. In the large pterosaur tree (LPT, 236 taxa) Mistralazhdarcho nests with tiny Nemicolopterus and mid-sized Shenzhoupterus (Fig. 1). Mistralazhdarcho is more than twice as tall as Shenzhoupterus with similar gracile cervicals, a longer radius and shorter metacarpus. Distinct from Shenzhoupterus, the mandible is gracile, more like that of Nemicolopterus.

Figure 1. Mistralazhdarcho compared to reconstructions of Shenzhoupterus and Nemicolopterus.

Figure 1. Mistralazhdarcho compared to reconstructions of Shenzhoupterus and Nemicolopterus. A longer antebrachium is found in Mistalazdarcho.

A downturned dentary
is a trait found in this clade of pterosaurs, and to a lesser extent in sister sinopterids.

The small prominence at the ‘bend’ of the mandible
in Mistralazhdarcho is a curious trait not visible in Shenzhoupterus due to closed jaws in situ. Nemicolopterus might preserve that trait, but a humerus is under the mandible exactly at that point, making it difficult to determine in photos.

A warped deltopectoral crest,
like the one found in Mistalazdarcho (Fig. 1), is not found in azhdarchids. And look at the size range in this clade!

Having reconstructions for direct comparisons,
and a large cladogram that is regularly adding new taxa are tools the LPT and www.ReptileEvolution.com offer freely online to paleontologists worldwide. Best to test here rather than trust your hunch elsewhere.

References
Vullo R, Garcia G, Godefroit P, Cincotta A, and Valentin X 2018. Mistralazhdarcho maggii, gen. et sp. nov., a new azhdarchid pterosaur from the Upper Cretaceous of southeastern France. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1502670.

Fish nibbles on Pteranodon metacarpal

Figure 1. Fish teeth compared to grazed Pteranodon metacarpal

Figure 1. Fish teeth compared to grazed Pteranodon metacarpal

Ehret and Harrell 2018
bring us news from Alabama of two distinct sets of tooth marks on a Pteranodon (Fig. 2) metacarpal (Fig. 1). They report:

“The Pteranodon specimen exhibits serrated teeth marks on the surface of the bone and a second set of larger, unserrated teeth marks unlike those of any contemporary shark species. These feeding traces compare favorably with the tooth spacing and morphology of Squalicorax kaupi, and a small to moderate-sized saurodontid fish, such as Saurodon or Saurocephalus, respectively. In both instances, feeding traces appear to be scavenging events due to the lack of any healing or bone remodeling. The specimen represents a pterosaur that either fell into marine waters or was washed out from nearshore areas and then scavenged by both a chondrichthyan and osteichthyan.”

“Many fossils from late Cretaceous Alabama appear to have been nibbled by sharks, including sea turtles and dinosaurs, which are often ‘covered in predation marks,’ says Ehret.”

NatGeo publicized the find by talking to some pterosaur experts, “Pterosaurs actually had a lot of meat on their skeletons,” says Michael Habib, a pterosaur expert at the University of Southern California who was not involved with the latest find. “They were not the skinny animals often depicted in films and art. The flight muscles in particular would have made a great meal.”

Pterosaur metacarpals,
like all metacarpals, actually are sinewy and have little to no associated muscle.

Habib adds,
“Pteranodon also inhabited this coastal environment during the late Cretaceous, making a living snatching smaller fish from the shark-filled waters. Pterosaurs could float, but being less buoyant than birds, they probably didn’t sit on the surface for long. Some species, including Pteranodon, did likely plunge into the water for prey. “They could then quickly take back off from the surface. But these diving pterosaurs might have been vulnerable to sharks just after they entered the water,” he says.

M. Witton concluded,
“It’s nice to know what species were interacting in this way.”

Ehret corrected the pterosaur experts,
“It’s also possible that the animal died near the shore and was scavenged when it washed out to sea.”

Figure 3. Triebold Pteranodon in floating configuration. Center of balance marked by cross-hairs.

Figure 2 Triebold Pteranodon in floating configuration. Center of balance marked by cross-hairs.

Contra Habib’s statement
Pteranodon was at least as buoyant as a pelican. It has been widely known for over a century that pterosaur bones are thinner than bird bones and Pteranodon metacarpals, in particular, were hollow like pontoons (Fig. 2).

Ultimately
the bite marks represent curiosity, not predation, a point understood by Ehret and Harrell.

References
Ehret DJ and Harrell TL Jr. 2018. Feeding traces of a Pteranodon (Reptilia: Pterosauria) bone from the late Cretaceous (Campanian) Mooreville Chalk in Alabama, USA. Palaios 33(9):414–418.

www.natgeo.com/

Big pterosaurs: big or little wing tips

Earlier and below (Fig. 2) we looked at large and giant pterosaur wings comparing them to the largest flying birds, including one of the largest extant flying birds, the stork, Ciconia, and the extinct sheerwater, Pelagornis, the largest bird that ever flew.

FIgure 2. A basal pteranodotid, the most complete Pteranodon, the largest Pteranodon skull matched to the largest Pteranodon post-crania compared to the stork Ciconia and the most complete and the largest Quetzalcoatlus

FIgure 1. A basal pteranodotid, the most complete Pteranodon, the largest Pteranodon skull matched to the largest Pteranodon post-crania compared to the stork Ciconia and the most complete and the largest Quetzalcoatlus. Note the much reduced distal phalanges in the complete and giant Quetzalcoatlus, distinct from the Pteranodon species.

Today
we’ll look at how the largest Pteranodon (Figs. 1, 4) compares to much larger pterosaurs, like Quetzalcoatlus northropi (Figs. 1, 2) that have vestigial wingtips similar to those of the  much smaller flightless pre-azhdarchid, SOS 2428 (Fig. 3).

Note the tiny three distal phalanges
on the wing of the largest Quetzalcoatlus, distinct from the more typical elongate and robust distal phalangeal proportions on volant pterosaurs of all sizes. Much smaller definitely flightless pterosaurs, like SOS 2428, shrink those distal phalanges, too. That’s the pattern when pterosaurs lose the ability to fly.

Figure 2. Q. northropi and Q. sp. compared to Ciconia, the stork, and Pelagornis, the extinct gannet, to scale. That long neck and large skull of Quetzalcoatlus would appear to make it top heavy relative to the volant stork, despite the longer wingspan. Pteranodon and other flying pterosaurs do not have such a large skull at the end of such a long neck (Fig. 1). The longer wings of pelagornis show what is typical for a giant volant tetrapod, and Q. sp. comes up short in comparison.

Figure 2. A previously published GIF animation. Q. northropi and Q. sp. compared to Ciconia, the stork, and Pelagornis, the extinct gannet, to scale. That long neck and large skull of Quetzalcoatlus would appear to make it top heavy relative to the volant stork, despite the longer wingspan. Pteranodon and other flying pterosaurs do not have such a large skull at the end of such a long neck (Fig. 1). The longer wings of pelagornis show what is typical for a giant volant tetrapod, and Q. sp. comes up short in comparison.Today we’ll compare the wingspan of the largest Quetzalcoatlus to the largest and more typical Pteranodon species (Fig. 2).

Unfortunately
pterosaur workers refuse to consider taxa known to be flightless, like SOS 2428 (Peters 2018). It’s easy to see why they would be flightless (Fig. 3). Scaled to similar snout/vent lengths with a fully volant pterosaur like n42 (BSPG 1911 I 31) the wing length and chord are both much smaller in the flightless form.

Lateral, ventral and dorsal views of SoS 2428

Figure 3. Lateral, ventral and dorsal views of the flightless SoS 2428 (Peters 2018) alongside No. 42, a volant sister taxon.

Comparing the largest ornithocheirid,
SMNK PAL 1136, to the largest Pteranodon (chimaera of largest skull with largest post-crania in Fig. 4) shows that large flyers have elongate distal phalanges, distinct from body and wing proportions documented in the largest azhdarchids, like Quetzalcoatlus.

Figure 5. Largest Pteranodon to scale with largest ornithocheirid, SMNS PAL 1136.

Figure 4. Largest Pteranodon to scale with largest ornithocheirid, SMNS PAL 1136. Note the long distant wing phalanges on both of these giant flyers. This is what pterosaurs evolve to if they want to continue flying. And this is how big they can get and still fly. Giant azhdarchids exceed all the parameters without having elongate wings. Note: the one on the left has a longer wingspan whir the one on the right has a more massive torso and skull together with more massive proximal wing bones and pectoral girdle. On both the free fingers are tiny, parallel oriented laterally and slightly tucked beneath the big knuckle of the wing finger. The pteroid points directly at the deltopectoral crest. 

As the largest Pteranodon and largest ornithocheirid (SMNS PAL 1136)
(Fig. 4) demonstrate, as flying pterosaurs get larger, they retain elongate distal wing phalanges. And big, robust phalanges they are.

By contrast in azhdarchids and pre-azhdarchids
there is a large size bump after n42 (BSPG 1911 I 31) the fourth wing phalanx either disappears (see Microtuban and Jidapterus) or shrinks to a vestige. Then there’s Zhejiangopterus (Fig. 5), with a big pelvis, gracile forelimbs and a giant skull on a very long neck. Just that neck alone creates such a long lever arm that the pterosaur is incapable of maintaining a center of balance over or near the shoulder joints.

Figure 1. Click to enlarge. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

Figure 5. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

As mentioned earlier, becoming flightless permitted, nay, freed azhdarchid pterosaurs to attain great size. They no longer had to maintain proportions that were flightworthy. Instead they used their shortened strut-like forelimbs to maintain a stable platform in deeper waters. And when they had to move in a hurry, their wings could still provide a tremendous amount of flurry and thrust (Fig. 6) for a speedy getaway.

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 6. Quetzalcoatlus running without taking off, using all four limbs for thrust. That long lever arm extending to the snout tip in front of the center of gravity is not balanced in back of what would be the center of lift over the wings

For the nitpickers out there…
some specimens of Nyctosaurus (UNSM 93000, Fig. 7) also have but three wing phalanges, but they are all robust. The distal one is likely the fourth one because it remains curved. Phalanges 2 and 3 appear to have merged, or one of those was lost. Compare that specimen to a more primitive Nyctosaurus FHSM VP 2148 with four robust wing phalanges.

Figure 5. Cast of the UNSM 93000 specimen of Nyctosaurus. Missing parts are modeled here.

Figure 5. Cast of the UNSM 93000 specimen of Nyctosaurus. Missing parts are modeled here.

References
Peters D 2018. First flightless pterosaur (not peer-reviewed). PDF online.

 

Aurorazhdarcho: a new phylogenetic wastebasket for pterosaurs

While researching
the tiny new/old Aurorazhdarcho (Fig. 2) described during Flugsaurier 2018, I gazed upon the Wikipedia page for Auroazhdarcho and was less than delighted to see how many unrelated specimens the webpage authors attributed to that genus (Fig. 1).

Figure 1. Aurorazhdarcho specimens in the LRT according to Wikipedia.

Figure 1. Aurorazhdarcho specimens in the LRT according to Wikipedia.

These generic determinations
were not done as a result of phylogenetic analysis, as in the large pterosaur tree (LPT). Rather, ‘someone’ eyeballed these specimens and made it so. That’s not good science. And it was not validated by phylogenetic analysis.

  1. ‘Pester Exemplar’ – originally Pterodactylus micronyx (Meyer 1856) ELTE V 256 (Osi, Prondvai and Géczy 2010) is a basal member of the Cycnorhamphidae.
  2. CM 11426 – originally Pterodactylus micronyx (Meyer 1856) is a tiny basal member of the Azhdarcho clade.
  3. TM 13104 – is a tiny scaphognathid basal to the Cycnorhamphus/Ornithocheirus clade.
  4. Pterodactylus? pulchellus BM NHM 42735 — is a tiny scaphognathid basal to the Cycnorhamphus/Ornithocheirus clade.
  5. Auroazhdarcho primordius – (Frey et al. 2011) NMB Sh 110 is the holotype specimen, related to Eopteranodon, Eoazhdarcho a clade that begins with Germanodactylus and ends with Pteranodon.
  6. Aurorazhdarcho micronyx – (Habib and Pittman 2018) MB.R.3531 nests with Eopteranodon, Eoazhdarcho and Auroazhdarcho, but is much smaller.

Remember
juvenile pterosaurs are identical to adults. So small pterosaurs with a distinct morphology are not juveniles of larger adults. Small pterosaurs with a distinct morphology need to be tested in phylogenetic analysis to determine where they nest. They typically nest at the base of major and minor clades. Shrinking in size creates new types of pterosaurs.

Frey et al. 2011 rejected the use of cladistic analysis,
but chose to compare Aurorazhdarcho to Ctenochasma, but then considered Aurorazhdarcho an azhdarchoid, itself an invalid diphyletic clade. According to Wikipedia, “Bennett (2013) considered this species to be a ctenochasmatid.” In the LPT, none of the specimens are ctenochasmatids. Prior workers did not recognize the process of phylogenetic miniaturization (Peters 2007), but decided on their own that small pterosaurs were juveniles (Bennett 2013, Frey et al. 2011).

Figure 1. Aurorazhdarcho primordial and the smaller Aurorazhdarcho micronyx to scale.

Figure 2. Aurorazhdarcho primordial and the smaller Aurorazhdarcho micronyx to scale.

If things were different,
and others had produced a phylogenetic analysis of virtually all known pterosaurs and several specimens of each genus and I had, by eyeball, determined that small pterosaurs were juveniles of distinctly different larger adults, then everyone would be justified in refuting that conclusion. As it is, workers are suppressing the results of inclusive phylogenetic analysis and supporting the eyeballing of specimens. Yes, the rules are different if you have a PhD.

References
Bennett SC 2013. New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus. Paläontologische Zeitschrift. 87(2): 269–289.
Frey E, Meyer CA and Tischlinger H 2011. The oldest azhdarchoid pterosaur from the Late Jurassic Solnhofen Limestone (Early Tithonian) of Southern Germany. Swiss Journal of Geosciences 104 (Supplement 1): 35–55. doi:10.1007/s00015-011-0073-1.
Habib M and Pittman M 2018. An “old” specimen of Aurorazhdarcho micronyx with exceptional preservation and implications for the mechanical function of webbed
feet in pterosaurs. Flugsaurier 2018: The 6th International Symposium on Pterosaurs. Los Angeles, USA. Abstracts: 41–43.
Lü J-C and Ji Q 2005. New azhdarchid pterosaur from the Early Cretaceous of western Liaoning. Acta Geologica Sinica 79 (3): 301–307.
Lü J-C and Ji Q 2006. Preliminary results of a phylogenetic analysis of the pterosaurs from western Liaoning and surrounding area. Journal of the Paleontological Society of Korea 22 (1): 239–261.
Peters D 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27

wiki/Aurorazhdarcho

Restoring the tip of the Pteranodon rostrum in UALVP 24238

Another short one today.
Everyone in pterosaur land has wondered what shape and length the missing tip of the rostrum took on in the UALVP 24238 specimen of Pteranodon (improperly called ‘Dawndraco‘, Fig. 1). That’s because, unlike most other specimens, the upper and lower margins don’t converge to form a triangle in lateral view, but remain essentially parallel for most of their length.

Figure 1. The missing tip of the UALVP 24238 skull can be restored like the similar Tanking-David specimen skull tip. The dorsal rim is straight. The ventral rim is convex.

Figure 1. The missing tip of the UALVP 24238 skull can be restored like the similar Tanking-Davis specimen skull tip. The dorsal rim is straight. The ventral rim is convex.

The privately held
Tanking-Davis specimen of Pteranodon is the most similar to the UALVP 24238 rostrum. Yes, it converges, but at a very shallower angle. Anteriorly the ventral margin curves up to meet the very straight dorsal margin. The same can be imagined/restored for the missing UALVP 24238 rostrum, and the result appears to be reasonable.

Figure 2. The UALVP 24238 specimen of Pteranodon is largely complete and here the tip of the rostrum is restored like that of a related specimen.

Figure 2. The UALVP 24238 specimen of Pteranodon is largely complete and here the tip of the rostrum is restored like that of a related specimen.

As in most pterosaur genera,
no two specimens are identical. See the panoply of known relatively complete Pteranodon skulls to scale and in phylogenetic order here.