Misinformation on the palate of Kunpengopterus

Cheng et al. 2017 present
a new complete but slightly damaged specimen of Kunpengopterus, IVPP V 23674.

The new Kunpegnopterus IVPP V 23674.

The new Kunpegnopterus IVPP V 23674.

Cheng et al. provided a new palate reconstruction
that could use a little DGS to better inform the reader and the the authors (Fig. 2, 3). Cheng et al. think they have found some new medial projections toward the back of the palate. Actually they are looking at broken off lateral pieces of the ecto-palatine (ectopterygoid fused to palatine).

Fig. 2. The skull of IVPP V 23674 colorized using DGS alongside the original description.

Fig. 2. The skull of IVPP V 23674 colorized using DGS alongside the original description.

And
here’s a closeup of the palate in dorsal view (Fig. 3). They relied on Wellnhofer 1978 for palate identification. That was when the anterior palate was considered the palatine as it seems to be here, but perhaps fused to the maxilla??. That must be the revision shown here based on Kellner 2013, which I have not read. Ever since Peters 2000, by comparison with Macrocnemus (acknowledged in Kellner 2013), and later by Osi et al. 2010, looking at Dorygnathus, the entire pterosaur palatal plate has been considered the maxilla, as it is here using colors (Fig. 3).

Fig. 3 Kunpengopterus IVPP V 23674 palate in dorsal view alongside original interpretation. Watch out for those broken bones. They sometimes end up in places a wee bit from their origins.

Fig. 3 Kunpengopterus IVPP V 23674 palate in dorsal view alongside original interpretation. Watch out for those broken bones. They sometimes end up in places a wee bit from their origins. And don’t you just hate 1 point lines telling you where the bones are? Colors are much more informative!

It’s really tough
when the broken bone appears to follow the contours of the unbroken bones, as they do here (Fig. 3). That’s where it helps to know the pattern of the palate in ALL pterosaurs. So exceptions like this can be reexamined, looking for the cracks that should not be there.

In similar fashion, here’s a pelvis
(Fig. 4) from the same specimen that appeared to Cheng et al to have a really deep pubis when the reality is more mundane.

Figure 4 Kunpengopterus pelvis with DGS colors identifying the anterior ilium detached from the posterior ilium and the false deep pubis.

Figure 4 Kunpengopterus pelvis with DGS colors identifying the anterior ilium detached from the posterior ilium and the false deep pubis. Note the original drawing in figure 1 that extends the pubis too deep by incorporating the inverted prepubis that match the contours of the ischium. 

References
Cheng X, Jiang S-X, Wang X-L, Kellner AWA 2017. New anatomical information of the wukongopterid Kunpengopterus sinensis Wang et al., 2010 based on a new specimen. PeerJ 5:e4102; DOI 10.7717/peerj.4102
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Osi A, Prondvai E, Frey E and Pohl B 2010. New Interpretation of the Palate of Pterosaurs. The Anatomical Record 293: 243-258.

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Dimorphodon revisited

The odd pterosaur, Dimorphodon
was one of the first taxa included in the large reptile tree (LRT, 1132 taxa). Here I revise earlier errors on the BMNH 41212 specimen (Fig. 1), including adding a short tail discovered a few days ago and also adding more dorsal vertebrae.

Figure 1. The three Dimorphodon specimens traced from the fossils.

Figure 1. The three Dimorphodon specimens traced from the fossils.

Here is the in situ fossil with bones colorized (Fig. 2).

Figure 2. The BMNH 4121 fossil of Dimorphodon here colorized using DGS.

Figure 2. The BMNH 4121 fossil of Dimorphodon here colorized using DGS. Colors match the reconstruction, except for the skull.

Earlier the skull was reconstructed. Here it is again (Fig. 3). This was done to show the mandible did not have a fenestra, only a shifted surangular.

The skull of Dimorphodon macronyx.

Figure 3. The skull of Dimorphodon macronyx. Above: in situ. Middle: Restored. Below: Palatal view. Not settled on the depth of the mandible. The long replaceable teeth suggest a deeper mandible is more appropriate.

References
Buckland W 1829. Proceedings of the Geological Society London, 1: 127
Owen R 1859. On a new genus (Dimorphodon) of pterodactyle, with remarks on the geological distribution of flying reptiles.” Rep. Br. Ass. Advmnt Sci., 28 (1858): 97–103.
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.
Sangster S 2001. Anatomy, functional morphology and systematics of Dimorphodon. Strata 11: 87-88

wiki/Dimorphodon

Basal reptile hands: Casineria and Diplovertebron

I reexamined two fossils
via photos and found ways to improve the interpretation of both of them, Casineria (Fig. 1) and Diplovertebron (Fig. 2).

Figure 1. Manus of Casineria, a basal archosauromorph reptile. The carpals are unosssified, but left vague impressions in the matrix. Other bones overlapped the carpals and are removed here.

Figure 1. Manus of Casineria, a basal archosauromorph reptile. The carpals are unosssified, but left vague impressions in the matrix. Other bones overlapped the carpals and are removed here. PIls added.

Diplovertebron punctatum (Fritsch 1879, Waton 1926; DMSW B.65, UMZC T.1222a; Moscovian, Westphalian, Late Carboniferous, 300 mya) aka:  Gephyrostegus watsoni Brough and Brough 1967) and Gephyrostegus bohemicus (Carroll 1970; Klembara et al. 2014) after several name changes perhaps this specimen should revert back to its original name as it nests a few nodes away from Gephyrostegus.

Derived from a sister to EldeceeonDiplovertebron was basal to the larger Solenodonsaurusand the smaller BrouffiaCasineria and WestlothianaDiplovertebron was a contemporary of Gephyrostegus bohemicus, Upper Carboniferous (~310 mya), so it, too, was a late survivor.

Overall smaller and distinct from Eldeceeon, the skull of Diplovertebron had a shorter rostrum, larger orbit and greater quadrate lean. The dorsal vertebrae formed a hump and had elongate spines. The hind limbs were much longer than the forelimbs. The tail is incomplete, but appears to have been short and deep. Seven sphere shapes were preserved alongside this specimen. They may be the most primitive amniote eggs known.

Figure 2. Diplovertebron manus in situ and reconstructed with PILs added. What appear to be displaced carpals may be something else entirely. The carpals may have been unossified, as in Casineria.

Figure 2. Diplovertebron manus in situ and reconstructed with PILs added. What appear to be displaced carpals may be something else entirely. The carpals may have been unossified, as in Casineria. See how DGS makes reconstruction less chaotic?

Casineria kiddi (Paton, Smithson & Clack 1999) Visean, Mississippean, Carboniferous, ~335 mya was a small basal archosauromorph. the oldest but not the most primitive. It was derived from a sister to Diplovertebron and SolenodonsaurusWestlothiana was a sister taxon.

Overall smaller than and distinct from Gephyrostegus, the skull of Casineria had no otic notch. See Brouffia for more possible skull details. The cervicals of Casineria were increased in number but decreased in size. The presacral vertebral count had increased to over 30. Ribs discontinued after #22. Apparently two vertebrae formed the sacrum and were connected to the pelvis. The pectoral girdle was composed of unfused elements. The humerus had a small hourglass shape. The manus was enlarged. The ilium had no anterior dorsal process. The femur was more gracile. The pes was reduced, more nearly the size of the manus.

References
Brough MC and Brough J 1967. The Genus Gephyrostegus. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 252 (776): 147–165.
Carroll RL 1970. The Ancestry of Reptiles. Philosophical Transactions of the Royal Society London B 257:267–308. online pdf
Fritsch A 1879. Fauna der Gaskohle und der Kalksteine der Permformation “B¨ ohmens. Band 1, Heft 1. Selbstverlag, Prague: 1–92.
Klembara J, Clack J, Milner AR and Ruta M 2014. Cranial anatomy, ontogeny, and relationships of the Late Carboniferous tetrapod Gephyrostegus bohemicus Jaekel, 1902. Journal of Vertebrate Paleontology 34:774–792.
Paton RL Smithson TR and Clack JA 1999. An amniote-like skeleton from the Early Carboniferous of Scotland. Nature 398: 508-513.
Watson DMS 1926. VI. Croonian lecture. The evolution and origin of the Amphibia. Proceedings of the Zoological Society, London 214:189–257.

wiki/Gephyrostegus
wiki/Diplovertebron
wiki/Casineria

 

Old data (from 1896) nests the elephant bird, Aepyornis, with the ostrich, Struthio

Longtime readers know
I like to make repairs and get things right, whether working from published papers or my own images and data. And longtime readers know I don’t always get things right the first time, usually for good reason (see below). I’ve been looking for Andrews 1896 for several weeks and finally got it. All the earlier problems could have been avoided if I had the data earlier that I have now. Alas, that’s just how it goes…

Figure 1. Aepyornis maximus along with eggs, the largest known. The new skull replaces the original one.

Figure 1. Aepyornis maximus along with eggs, the largest known. The new skull replaces the original one.

Earlier data on the skull of the elephant bird,
Aepyorniscame from a photograph of a commercially available restored cast. Unfortunately, the restoration included a little too much imagination and did not match the only other data currently (and most recently) available (Fig. 2, Andrews 1896).

The data from the embryo in the giant egg attributed to Aepyornis,
did not contribute to the current matrix scoring. That would be akin to creating a chimaera. However, after the fact, it’s noteworthy that the embryo still has ostrich traits not found in the present adult skull data for Aepyornis. The fragile palatal and cheek regions were not preserved or collected in the adult. The fragile cheek regions were not yet developed (or lost in the debris) of the embryo.

Figure 4. NatGeo embryo compared to Struthio and adult Aepyornis. The original maxilla is reinterpreted as the palatine. The original premaxilla is a fused premaxilla + maxilla. The original Nat Geo skull was put together in computer software from scattered parts. Mesethmoid inverted in revision. Aepyornis does not have bulbous squamosals found in Struthio and the NatGeo embryo. Not to scale.

Figure 2. NatGeo embryo compared to Struthio and adult Aepyornis. The original maxilla is reinterpreted as the palatine. The original premaxilla is a fused premaxilla + maxilla. The original Nat Geo skull was put together in computer software from scattered parts. Mesethmoid inverted in revision. Aepyornis does not have bulbous squamosals found in Struthio and the NatGeo embryo. Not to scale. The mystery of the embryo is coming into clearer focus with the latest elephant bird skull data and taxonomy.

All earlier posts
and ReptileEvolution.com pages regarding Aepyornis have been repaired. Good science makes repairs all the time. Better data is always welcome. Every hypothesis remains hypothetical, until it is confirmed over and over again through testing.

Using commercially available skulls for data
is still a good idea, but it’s also a good idea to see which parts are real and which are restored with clay. I don’t know if several skull parts from several specimens of Aepyornis were all put together to produce the skulls currently found in museums and skull shops. Andrews 1896 reports the material he published came from two. Better to take data from one specimen than to make a chimaera of several specimens, because problems like this tend to happen. Sometimes you take what you can get.

Figure x. Bird giants in the bird subset of the LRT.

Figure 3. Bird giants in the bird subset of the LRT.

This should make certain readers happy
that Aepyornis returns to the ratites. I’m happy that better data has come forth. The latest DNA tests prefer Aepyornis to nest with the kiwi. Morphology leans toward the ostrich. With the new nesting of the elephant bird Casuarius, the cassowary, nests between tinamous and ostriches + elephant birds.

References
Andrews CW 1896. On the skull, sternum, and shoulder-girdle of Aepyornis. Ibis, Seventh Series, 2:376-389.
Balanoff AM 2003. Osteological description of an embryonic elephant bird (Ratitae: Aepyornis) using high-resolution X-ray computed tomography, with a discussion of growth in Aepyornis. M.S. thesis, The University of Texas, Austin, Texas, 175 pp.
Balanoff AM and Rowe T 2007. Osteological description of an embryonic skeleton of the extinct elephant bird, Aepyornis (Palaeognathae: Ratitae). Journal of Vertebrate Paleontology 27(sp9):1–53.
Geoffroy Saint-Hilaire I 1851. [Note sur les onze espèces nouvelles do Trochilidés de M. Bourcier.] Compt. Rend. de l’Acad. Sci 32:188.
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Temminck 1815. Histoire naturelle generale des pigeons et des gallinaces.
Accompagne de planches anatomiques. 3: 552–747

wiki/Rhynchotus
wiki/Cassowary
wiki/Ostrich
wiki/Aepyornis

New rhynchocephalian, Vadasaurus, is not a pleurosaur ancestor

Once again
taxon exclusion bites a paper on the set up and conclusion.

Bever and Norell 2017 bring us
a perfect Solnhofen (Late Jurassic) fossil of a small rhynchocephalian, Vadasaurus herzogi (Figs. 1,2) that they mistakenly promote as a pleurosaur ancestor (Fig. 5). We looked at the real pleurosaur ancestors several years ago here.

Figure 1. Vadasaurus is a perfectly preserved Solnhofen fossil rhynchocephalian.

Figure 1. Vadasaurus is a perfectly preserved Solnhofen fossil rhynchocephalian. PILs and colors added. The pelvis is semi-perforate. The proximal tarsus is not co-ossified.

Vadasaurus herzogi (Bever and Norell 2017, Late Jurassic) AMNH FARB 32768, was originally nested between Sapheosaurus + Kallimodon and the aquatic pleurosaurs, Pleurosaursus and Palaeopleurosaurus. Here Vadasaurus nests very closely with Leptosaurus, a terrestrial taxon omitted originally. Close examination of photos in the literature (Fig. 2) shows that Bever and Norell overlooked the supratemporal, the jugal’s quadratojugal process and added a mandible fenestra that is not present. The lack of co-ossificiation in the astragalus and calcaneum is a trait that is retained by all later taxa, including the trilophosaurs, azendohsaurs and rhychosaurs. Priosphenodon, listed in both competing trees, is the outgroup for the Rhynchosauria.

Figure 2. The skull of Vadasaurus showing the jugal's quadratojugal process, the portion of the postfrontal entering the upper temporal fenestra and the mandible interpreted differently than Bever and Norell 2017.

Figure 2. The skull of Vadasaurus showing the jugal’s quadratojugal process, the portion of the postfrontal entering the upper temporal fenestra and the mandible interpreted differently than Bever and Norell 2017.

The large reptile tree (LRT, 1121 taxa, subset Fig. 3) does not include all of the taxa employed by Bever and Norell 2017. In like fashion, Bever and Norell do not include all of the rhynchocephalian taxa employed by the LRT.

Here, with high Bootstrap scores
(Fig. 3) the LRT nests Pleurosaurus with Megachirella at the base of the Rhynchocephalia (Fig. 3). Palaeopleurosaurus nests separately, with Ankylosphenodon (Fig. 5), still close to the base of the clade. Kallimodon nests close to Vadasaurus in the Bever and Norell tree, but with Sphenodon in the LRT. Other differences also occur. Homeosaurus is included in the Bever and Norell tree, but nests outside the Rhynchochephalia in the LRT.

Figure 3. Subset of the LRT nesting Vadasaurus with Leptosaurus in the Rhynchocephalia

Figure 3. Subset of the LRT nesting Vadasaurus with Leptosaurus in the Rhynchocephalia

The Bever and Norell cladogram
(Fig. 4) is very poorly supported with most nodes <50 and only one node above 80. The outgroup is wrong, based on results recovered by the LRT which tests a over 1000 possible outgroup candidates. Youngina is completely unrelated. It nests close to the archosauriform, Proterosuchus. Pristidactylus is am extant squamate also unrelated to rhynchocephalians.

By contrast,
the subset of the LRT (Fig. 3) is strongly supported with high Bootstrap scores throughout. Outgroups going back to basal tetrapods are documented.

Figure 4. Cladogram from Bever and Norell 2017 with the addition of Vadasaurus. When Bootstrap support is below 50 it is not marked.

Figure 4. Cladogram from Bever and Norell 2017 with the addition of Vadasaurus. When Bootstrap support is below 50 it is not marked. This tree does not include the correct outgroup and the Rhynchosauria + Trilophosaurus and other taxa.

The Bever and Norell paper does not provide reconstructions,
but ReptileEvolution.com does (Fig. 5). Chronology is all over the place in this clade. Megachirella and BRSUG 29950, at the base of this clade, are both Middle Triassic. Pleurosarus is Late Jurassic. Ankylosphenodon is Early Cretaceous. Sphenodon is extant.

Figure 1. Pleurosaurus and Palaeopleurosaurus to scale with sisters.

Figure 5. Pleurosaurus and Palaeopleurosaurus to scale with sisters.

When Megachirella, Leptosaurus and other taxa
not employed by Bever and Norell are deleted from the LRT, the topology of the tree does not change.

Figure 6. Leptosaurus was omitted by Bever and Norell. Note the triangular skull, gracile mandible, radiale and other traits reported by the authors.

Figure 6. Leptosaurus was omitted by Bever and Norell. Note the triangular skull, gracile mandible, radiale and other traits reported by the authors.

Bever and Norell report that Vadasaurus is:
“Diagnosed in an exclusive clade with Pleurosauridae based on

  1. a triangular skull in the dorsal view,as in Leptosaurus (Fig. 6)
  2. posteriorly tapering maxilla, as in Leptosaurus (Fig. 6)
  3. posteriorly tapering palatine, – no, it’s posteriorly round in Vadasaurus (Fig. 2)
  4. moderately open interpterygoid vacuity, – not true or not visible (Fig. 2)
  5. pterygoid participation in the suborbital fenestra,– as in Brachyrhindon
  6. low angle of the mandibular symphysis,,– not any lower than LRT sister taxa
  7. gracile lower jaw,– not any more than LRT sister taxa
  8. jaw joint positioned dorsal to the maxillary tooth row, – not true in any case
  9. an unossified radiale. – not true, displaced
  10. a dorsoventrally compressed and elongate skull, – not true.
  11. and elongate external nares.” – also in Clevosaurus and Sphenotitan, not exposed in Leptosaurus (Fig. 6).

To their credit
Bever and Norell traced the photos, probably in Photoshop. That makes the alignment of the drawing with the photo perfect. At this point, all they need to do is start coloring bones in the DGS style (Fig. 2) and expand that taxon list.

References
Bever GS and Norell MA 2017. A new rhynchocephalian (Reptilia: Lepidosauria) from the Late Jurassic of Solnhofen (Germany) and the origin of the marine Pleurosauridae. Royal Society open scence. 4: 170570. http://dx.doi.org/10.1098/rsos.170570

Cyrilavis colburnorum: another barbet, not a stem parrot

While researching fossil parrots,
in preparation for tomorrow’s post on a giant parrot, I found a paper by Ksepka, Clarke and Grande 2011 describing a Green River “stem parrot.” Cyrilavis colburnorum (early Eocene, Figs. 1–3), turns out to be a barbet, very similar to the extant Psilopogon (Fig. 4) and the coeval Septencoracias, all more closely related to toucans and hornbills, than to parrots (Fig. 5), as we learned here. Like the two tested barbets, the posterior maxilla extends lateral to and below the jawline and terminates without narrowing to a point or suturing to other bones. It just hangs out there (Fig. 4). And that’s just the first of many traits (I don’t want to pull a Larry Martin here, especially since he found the generic type).

FIgure 1. Skeleton of Cyrilavis in situ. This is not a parrot, but a barbet from the Green River formation.

FIgure 1. Skeleton of Cyrilavis in situ. This is not a parrot, but a barbet from the Green River formation.

Originally the skull was crudely traced
with an outline that failed to identify several bones and misidentified others (Fig. 2). Here (Fig. 2) the bones are colored for identification and reconstruction using DGS.

The Ksepka team also failed to include
barbets in their phylogenetic analysis, only parrots and the outgroups passeriformes, falconidae, and mouse birds in order of increasing distance. They assumed their inclusion set incorrectly. So, once again, taxon exclusion messed up their results. It doesn’t matter if you view the subjects first hand or not, if you don’t include their closest sister taxa.

Figure 1. The so-called Green River parrot, Cyrilavis-colburnorum, is actually a barbet, closer to hornbills and toucans.

Figure 1. The so-called Green River parrot, Cyrilavis-colburnorum, is actually a barbet, closer to hornbills and toucans. The lacrimal here appears to be pterygoid+palatine for the top bone and a pterygoid + a triangular bone below the jaw. The actual lacrimal is inside the orbit.  DGS tracing tells us more than the original crude tracing and permits the reconstruction without free handing any bones.

Type specimen: FMNH PA 754, a skeleton (Figs. 1, 2). Referred specimen: (FMNH PA 722, a complete skull and cervicals (Fig. 3).

Figure 3. The referred skull of Cyrilavis, Here it appears that the frontals have collapsed and the lacrimal has popped out of the orbit.

Figure 3. The referred skull of Cyrilavis, Here it appears that the frontals have collapsed and the lacrimal has popped out of the orbit.

 

I have not tested
the type specimen for the genus, Cyrilavis olsoni (Feduccia and Martin 1976), but the mandible in ventral view is short, straight and sharply tipped, unlike that of parrots, but similar to barbets.

Figure 2. Skull of the extant barbet, Psilopogon. Note the posteriorly drooping maxilla and compare it to Septencoracias in figure 1.

Figure 4. Skull of the extant barbet, Psilopogon. Note the posteriorly drooping maxilla and compare it to Septencoracias in figure 1.

And lest we forget,
like parrots, barbets likewise have a zygodactyl (pedal digit 4 oriented posteriorly) pes (Fig. 5).

FIgure 5. Psilopogon, is a living barbet from SE Asia.

FIgure 5. Psilopogon, is a living barbet from SE Asia. Note the zygodactyl pes, convergent with parrots.

The authors discuss the clade, Halcyornithidae,
a clade within Pan-Psittaiformes. The authors report, “All character states potentially supporting halcyornithid monophyly are reconstructed as ambiguous synapomorphies due to the unresolved polytomy containing the five sampled taxa.” 

It would probably be interesting
to reconstruct and test other members of the Halcyornithidae to see if they also nest elsewhere in the LRT. We’ll save that for later.

Figure 4. Subset of the LRT focusing on birds sized by color.

Figure 5. Subset of the LRT focusing on birds sized by color. Parrots, like Ara, are not related to barbets, like Psilopogon.

 

References
Feduccia A and Martin LD 1976. The Eocene zygodactyl birds of North America (Aves: Piciformes). Smithsonian Contributions to Paleontology, 27:101–110.
Ksepka DK, Clarke JA, and Grande L 2011. Stem parrots (Aves, Halcyornithidae) from the Green River Formation and a combined phylogeny of Pan-Psittaciformes. Journal of Paleontology 85:835-854

 

New insights from the Early Cretaceous bird Changzuiornis

Figure1. Changzuiornis in situ, isolated from matrix, and repositioned to an invivo pose.

Figure1. Changzuiornis in situ, isolated from matrix, and repositioned to an invivo pose, each 5 seconds.

About a year and a half ago,
Huang et al. 2016 brought us a complete and articulated skeleton of a new ornithurine bird, Changzuiornis ahgmi (Fig. 1), from the Early Cretaceous very close to Yanornis. The rostrum is more elongate with a large naris and tiny teeth (Fig. 2).

Please note
the better detail DGS brings to understanding where the bones are in this crushed fossil. The original line drawing (Fig. 2 below) leaves almost everything up to the imagination.

Figure 2. Changzuiornis skull in situ showing what you can do with DGS vs. traditional tracing from the original paper.

Figure 2. Changzuiornis skull in situ showing what you can do with DGS vs. traditional tracing from the original paper.

The maxilla clearly makes up most of the rostrum
in Changzuiornis. And this came as a surprise to Huang et al., who report this is “a characteristic not present in the avian crown clade in which most of the rostrum and nearly the entire facial margin is made up by premaxilla.” (Fig. 3)

Figure 3. From Huang et al. showing in red the extent of the maxilla in their interpretations. This is not long enough according to present interpretations.

Figure 3. From Huang et al. showing in red the extent of the maxilla in their interpretations. This is not long enough according to present interpretations.

It’s actually much worse than they think.
Their interpretation (Fig. 3) of the avian crown clade rostrum is too short, at least for tested taxa like Changzuiornis and Yanornis. Huang et al. do not extend the anterior maxilla far enough anteriorly, ignoring the portion where it overlaps and laminates to the lateral premaxilla (Fig. 2). For comparison, here’s a new interpretation of Struthio, the ostrich with a larger maxilla (Fig. 4) similarly laminated to the lateral premaxilla.

If I’m wrong
I’ll gladly go through a spanking machine (a silly kid’s party game).

If that’s not enough, check out
Yanornis, Cariama, Phoenicopterus, Sagittarius, Llallawavis, Falco and Tyto for a similar anteriorly extended maxillae. All are now repaired from my earlier mistakes as I wrongly followed traditional interpretations.

Figure 3. Struthio skull with a long maxilla.

Figure 3. Struthio skull with a long maxilla.

Otherwise
Changzuiornis is a close sister to Yanornis, with a longer rostrum and some other minor differences apparently a wee bit closer to Gansus, Ichthyornis and Hesperornis. For instance, pedal digits 3 and 4 are similar in length.

Speaking of Hesperornis
It’s difficult to find photographic data on the the rostrum of Hesperornis and Parahesperornis. I failed to do so because authors from Marsh to Gingreich to Martin instead provided line drawings (Fig. 4), which purported to show a tiny maxilla beneath a naris with a premaxilla forming at least half of the ventral margin of the naris. Unfortunately, no sister taxa have such a morphology. Martin 1984 let loose a clue that Parahesperornis had an anteriorly extended maxilla with that line extending anterior to the naris. I provide that option here (Fig. 4 in green) and wish for actual fossil images to work on.

Figure 4. Parahesperornis and Hesperornis skulls with a small traditional maxilla and the a new large one as interpreted here.

Figure 4. Parahesperornis and Hesperornis skulls with a small traditional maxilla and the a new large one as interpreted here.

Ichthyornis and Gansus can’t help us.
Their skulls are too poorly known.

References
Huang J, Wang X, Hu Y-C, Liu J, Peteya JA and Clarke JA 2016. A new ornithurine from the Early Cretaceous of China sheds light on the evolution of early ecological and cranial diversity in birds. PeerJ.com
Martin L 1984. A new Hesperornithid and the relationships of the Mesozoic birds. Transactions of the Kansas Academy of Science 87:141-150.

 

wiki/Parahesperornis