Vaškaninová et al. 2020 test placoderms to describe the origin of marginal teeth

Vaškaninová et al. 2020 
employ several partial placoderms from Czechoslovakia to demonstrate the antiquity of lingual tooth growth (= from the inside out as in modern fishes; Fig. 1).

Unfortunately taxon exclusion mars this study.
Following tradition, the team thought derived placoderms (in the process of losing their teeth) were primitive taxa just gaining teeth (Fig. 1). Like other workers before them, they omitted too many taxa.

By contrast and using a wider gamut of taxa,
we looked at the origin of marginal teeth earlier here. Marginal teeth first appeared in the late-surviving basal paddlefish, Tanyrhinichthys (Fig. 2). The outgroup taxon, late-shriving Chondrosteus, (Fig. 3) lacked teeth and tooth-bearing bones (the premaxilla, maxilla and dentary).

From the Vaškaninová et al. 2020 abstract:
“The dentitions of extant fishes and land vertebrates vary in both pattern and type of tooth replacement. It has been argued that the common ancestral condition likely resembles the nonmarginal, radially arranged tooth files of arthrodires, an early group of armoured fishes. We used synchrotron microtomography to describe the fossil dentitions of so-called acanthothoracids, the most phylogenetically basal jawed vertebrates with teeth, belonging to the genera Radotina, Kosoraspis, and Tlamaspis (from the Early Devonian of the Czech Republic).

Note: In the LRT these taxa are placoderms in the process of losing their teeth. Teeth developed much earlier in the family tree (Fig. 4).

“Their dentitions differ fundamentally from those of arthrodires; they are marginal, carried by a cheekbone or a series of short dermal bones along the jaw edges, and teeth are added lingually as is the case in many chondrichthyans (cartilaginous fishes) and osteichthyans (bony fishes and tetrapods). We propose these characteristics as ancestral for all jawed vertebrates.”

Figure 3. Omitting many pertinent taxa, Vaskaninova et al. constructed this cladogram of tooth evolution. The LRT uses a wider gamut of taxa and recovers a different tree topology.

Figure 1. Omitting many pertinent taxa, Vaskaninova et al. constructed this cladogram of tooth evolution. The LRT uses a wider gamut of taxa and recovers a different tree topology. See figure 4.

In the Vaškaninová et al. 2020 study
basal fish, both jawless and not, are all armored.

Here
in the large reptile tree (LRT, 1707+ taxa) the origin of jaws lacking teeth is close to Chondrosteus (Fig. 3), a derived sturgeon (Fig. 10). In Chondrosteus the upper jaw is the lacrimal. The premaxilla and maxilla have not appeared yet. The lower jaw likewise lacks a dentary and is composed of the surangular and angular.

Figure 2. Skull of Tanyrhinichthys (above) with two bones relabeled. The other fish, Saurichthys, is clearly unrelated.

Figure 2. Skull of Tanyrhinichthys (above) with two bones relabeled. The other fish, Saurichthys, is clearly unrelated. The origin of tiny marginal teeth is close to Tanyrhinnichthys, a basal paddlefish (Fig. 2), the next moreb derived clade in the LRT. The tooth bearing bones (premaxillla, maxilla and dentary) originate as slender dermal layers on the lacrimal and surangular carrying tiny teeth, not much larger than skin denticles.

Adding taxa in the LRT
separates armored Devonian placoderms from armored Silurian jawless fish.

Figure 1. Chondrosteus animation (2 frames) in situ and reconstructed in lateral view. This is the transitional taxon linking sturgeons to bony fish + sharks.

Figure 3. Chondrosteus animation (2 frames) in situ and reconstructed in lateral view. This is the transitional taxon linking sturgeons to bony fish + sharks.

Chronology is not as helpful as phylogeny
in figuring out these transitions, so much so that extant taxa need to be added to fill out the tree topology (Fig. 4).

Figure 5. Subset of the LRT, focusing on fish for July 2020.

Figure 4. Subset of the LRT, focusing on fish for July 2020.

Members of the Placodermi
like their relatives the catfish, are relatively derived taxa in the LRT (Fig. 4). Marginal teeth are missing in catfish and placoderms because they both have lost the maxilla along with their last common ancestor, taxa near late-surviving Diplacanthus.

Figure 5. Radotina is a basal taxon in the Vaskaninova et al. cladogram (Fig. 1).

Figure 5. Radotina is a basal taxon in the Vaskaninova et al. cladogram (Fig. 1). Compare to Romundina (Fig. 6) another basal taxon in Vaskaninova et al.

Basal taxa in the Vaskaninova et al. cladogram,
Romundina (Fig. 6) and Radotina (Fig. 5) are rather specialized terminal taxa in the LRT, leaving no descendants. Chondrosteus and Tanyrhinichthys are more generalized and primitive. All living fish, other than sturgeons (Fig. 10), whale sharks and mantas, are derived from Silurian sisters to these two taxa in the LRT.

Figure 10. What little we know of Radotina and where the same bone appears on the more complete Romundina, a terminal taxon in the Placodermi.

Figure 6. What little we know of Radotina and where the same bone appears on the more complete Romundina, a terminal taxon in the Placodermi.

Vaškaninová et al. provide the parts for Kosoraspis
(Fig. 7), a basal taxon without resolution in figure 1. Here (Fig. 8) I provide a possible restoration in which the large curved green bone identified as the ‘preopercular’ is re-identified as a postfrontal (orange in Fig. 8) based on similarities to Clarias, the walking catfish (Fig. 9).

Figure 8. From Vaškaninová et al. 2020, the parts for Kosoraspis. See figure 9 for a reconstruction where the largest bone here (green preopercular) is relabeled a postfrontal.

Figure 7. From Vaškaninová et al. 2020, the parts for Kosoraspis. See figure 9 for a reconstruction where the largest bone here (green preopercular) is relabeled a postfrontal.

Figure 9. Kosoraspis restored as a Devonian catfish like Clarias (Fig. 10).

Figure 8. Kosoraspis restored as a Devonian catfish like Clarias (Fig. 10). Those tooth plates are similar to those in catfish.

FIgure 1. Clarias, the walking catfish is a living placoderm with skull bones colorized as homologs of those in Entelognathus (Fig. 2). Here the mandible shifts forward and the opercular shifts backwards relative to Entelongnathus in the Silurian.

FIgure 9. Clarias, the walking catfish is a living placoderm with skull bones colorized as homologs of those in Entelognathus (Fig. 2). Here the mandible shifts forward and the opercular shifts backwards relative to Entelongnathus in the Silurian.

Determining when teeth and jaws first appeared
in basal vertebrates has been a contentious issue largely because pertinent taxa have been left out of the solution. Apparently Vaškaninová et al. left out several taxa key to understanding this transition from toothless jaws to toothy jaws. They considered taxa in the process of losing teeth, but placed them at the genesis of developing teeth.

Once again,
more taxa resolve problems like this better than more characters do.

Figure 1. Top to bottom: Thelodus a soft jawless fish with a ventral oral opening and gill slits, perhaps a hint of diamond-shaped armor laterally. Hemicyclaspis, adds extensive armor. Acipenser, a sturgeon with a protrusible tube for a mouth and reduced armor.

Figure 10. Top to bottom: Thelodus a soft jawless fish with a ventral oral opening and gill slits, perhaps a hint of diamond-shaped armor laterally. Hemicyclaspis, adds extensive armor. Acipenser, a sturgeon with a protrusible tube for a mouth and reduced armor.

If this helps,
here again (Fig. 10) are three taxa preceding the origin of jaws with marginal teeth. These interrelationships have gone unnoticed by fish workers who continue to nest sturgeons with jawed fishes. The next taxon following these three had large jaws: Chondrosteus (Fig. 3).

Figure 11.  Manta compared to Thelodus (Loganellia) and Rhincodon. All three have a terminal mouth essentially straight across, between the lateral eyes, distinct from most fish. Note the lack of teeth. 

Figure 11.  Manta compared to Thelodus (Loganellia) and Rhincodon. All three have a terminal mouth essentially straight across, between the lateral eyes, distinct from most fish. Note the lack of teeth.

Here again are whale sharks and mantas
(Fig. 11) on their own branch derived from Silurian sisters to Thelodus and LoganelliaThese taxa have jaws, but lack marginal teeth, similar to Chondrosteus (Fig. 3).

As mentioned above,
it is so important to include a wide gamut of taxa, including extant taxa.


References
Vaškaninová V, Chen D, Tafforeau P, Johanson Z, Ekrt B, Blom H and Ahlberg PE 2020. Marginal dentition and multiple dermal jawbones as the ancestral condition of jawed vertebrates. Science 369(6500): 211-216 DOI: 10.1126/science.aaz9431
https://science.sciencemag.org/content/369/6500/211

placoderm jaws

News:
https://phys.org/news/2020-07-advanced-technology-evolution-teeth.html

Hone et al. 2020 vs. Rhamphorhynchus

Long one today.
Summary, for those in a hurry:
Hone et al. 2020 bring us their views
on Rhamphorhynchus ontogeny (= growth from hatchling to adult). Unfortunately, this study is based on several invalid assumptions. Lacking a phylogenetic context, Hone et al. made the mistake of comparing small adults to large adults. No juveniles were tested. Subsequent ontogeny comparisons to birds and bats were thus rendered moot.

Figure 2. Rhamphorhynchus specimens to scale. The Lauer Collection specimen would precede the Limhoff specimen on the second row.

Figure 2. Rhamphorhynchus specimens to scale based on results from the LPT. No two are alike — except the juvenile Vienna specimen and the adult n81.

Before we get started, you might remember:

  1. A competing paper has been online for 2 years: ‘First Rhamphorhynchus juvenile recovered by phylogenetic analysis’ in which only one juvenile/adult pairing was found among all 31 specimens shown in figure 1. Among the rest, no two are alike. The small ones in the top row are not juveniles, but phylogenetically miniaturized adult basal Rhamphorhynchus species. (Perhaps someday, someone will re-name them all appropriately.)
  2. All pterosaurs (so far tested) develop isometrically (with the exception of tapejarid crests) because that’s what lepidosaurs do.
  3. Hatchling pterosaurs are typically 1/8 as tall as adults.
  4. Only hatchlings of a certain minimum size can fly. Hatchlings below this hypothetical size risk desiccation due to a high surface-to-volume ratio. That’s when quadrupedal locomotion enters pterosaur clades. Extradermal soft tissue that limits desiccation first appears on tiny, flapping pre-pterosaurs like Cosesaurus.
  5. New pterosaur clades often begin with a series of phylogenetically miniaturized transitional taxa (as in Fig. 1). This only appears in phylogenetic analyses when small and large taxa are analyzed together. That has not happened yet in published analyses because other workers make the same mistake as they consider small adult taxa to be mismatched juveniles (thereby destroying the Hone et al. isometry hypothesis).

The Hone et al. 2020 paper was announced today on
Dr. Hone’s email list. After a short comparison to Pteranodon, Hone continues:
“However, if we turn to Rhamphorhynchus we have only a fraction of the number of specimens but pretty much all the other issues are absent. They also cover a near order of magnitude in size with everything for animals of c 30 cm wingspan up to nearly 2 metres and include everything from putative hatchling-sized animals to a couple of genuine outliers that are much bigger than other known individuals.”

A good sample of Rhamphorhynchus taxa are shown above (Fig. 1) in phylogenetic order. Note this genus has its genesis as a phylogenetically miniaturized series following Campylognatoides in the large pterosaur tree (LPT, 250 taxa). The sole juvenile shown above is the Vienna specimen, nesting with one of the ‘genuine outliers that are much bigger.’ This adult and juvenile pairing nest together with virtually identical scores, despite the great difference in size.The LPT was able to lump and split all tested Rhamphorhynchus taxa. So it can be done. Hone et al. omitted this all important step and ruined their paper.

Hone continues:
“The numbers of course are not tiny, well over 100 good specimens, and that alone would make them an exceptional sample of most terrestrial Mesozoic archosaurs.”

Our first red flag! Hone et al. do not realize that when taxa are added, pterosaurs move over to lepidosaurs. On another note: relative to ‘100 good specimens’, 31 are shown above (Fig. 1).

Hone explains
that Wellnhofer (1975) featured 108 specimens. Hone’s group looked at 129, but, as Hone confesses, “The ‘real’ total is actually a little lower.” Oddly, in the text of the paper, Hone et al. report testing 135 specimens of R. muensteri.

Hone continues:
“This post inevitably marks the publication of an analysis of growth in Rhamphorhyunchus. In a lot of ways, this mirrors Chris Bennett’s fantastic 1995 paper on this genus where he convincingly demonstrated that all specimens belonged to a single species and not multiple ones as previously thought, and part of his arguments for doing this looked at the relationships between various elements based on Wellhofer’s dataset.”

Our second red flag! Bennett’s 1995 paper likewise did not include a phylogenetic analysis. When several specimens of Pteranodon were added to the LPT, no two nested together as conspecific taxa (Fig. 2). Small specimens were closer to the genesis of Pteranodon following Germanodactylus. Large specimens split into several clades.

Figure 2. The Tanking-Davis specimen compared to other forms. Specimen w and specimen z appear to be the closest to the Tanking-David specimen. Specimen 'w' = Pteranodon sternbergi? USNM 12167 (undescribed). Specimen 'z' = Pteranodon longiceps? Dawndraco? UALVP 24238. Click to enlarge.

Figure 2. The Tanking-Davis specimen compared to other forms. Specimen w and specimen z appear to be the closest to the Tanking-David specimen. Specimen ‘w’ = Pteranodon sternbergi? USNM 12167 (undescribed). Specimen ‘z’ = Pteranodon longiceps? Dawndraco? UALVP 24238. Click to enlarge.

Hone is delighted to announce
“Chris’ point [in Bennett 1993, 1995] was that while there were some discreet clusters of specimens (which he attributed to year classes) most of the alleged differences between the putative species vanished when you put them on a graph and the rest were classic ontogenetic traits like the fusion of the pelvis in large individuals of big eyes in small ones. So while he didn’t really deal with growth as such, he was already showing similar patterns to what I and my coauthors confirm now – Rhamphorhynchus was weirdly isometric in growth.”

Our third red flag! Dr. Hone does not appear to realize that ALL pterosaurs  develop isometrically during ontogeny. They do this because pterosaurs are lepidosaurs. By contrast, archosaurs develop allometrically. I’m also going to throw in the objection that a graph or two (as in Bennett 1993, 1995, Hone et al. 2020] is no substitute for a thorough phylogenetic analysis.

Hone continues:
“In other words, in the case of the vast majority of their anatomy, young animals are basically just scaled down adults.”

This is an odd statement to make considering the fact that Hone et al. are looking at phylogenetically miniaturized adults (Fig. 1) and regarding them as juveniles. That Hone considers the little specimens, “basically carbon copies of the adults” makes one question the precision of their observations. They did cherry-pick two similar taxa (Figs. 3, 4), avoiding the wider variation of other specimens. A competing online analysis (subset Fig. 5) was able to split and lump all Rhamphorhynchus specimens.

For comparison, Hone et al. also looked at ontogeny in bats,
noting hand/wing development accelerated close to sexual maturity (= shortly after weaning). He notes, “This is the pattern we would expect.”

Our fourth red flag! Since Hone et al. have blinded themselves to the possibility that pterosaurs are lepidosaurs (Peters 2007) they don’t look at lepidosaurs for comparison. Here’s why they should: pterosaurs hatch with adult proportions from leathery eggs held within the mother’s body longer than in any archosaur.

Hone continues:
“Birds are functionally poor analogues of pterosaurs but are much closer phylogenetically and are the only other powered flying tetrapod so we also looked at some existing datasets for them too.”

More traditional myth perpetuating here. I find this all so disheartening. Colleagues, just add taxa. If I can do it as an outsider, you can do it as a PhD. Do not be afraid to do the work of constructing a cladogram.

Hone continues:
“If you grow isometrically you wings will get longer and wider but your weight will increase much faster since you as a whole will get longer and wider and deeper. Birds increase penumaticity as they grow and there’s evidence this is the case in other pneumatic clades too and if so for pterosaurs, then the mass increase in adults would also be offset somewhat by a proportionally lower mass in adults for a given volume than juveniles.”

Very good point. But I’m ot sure of any pneumaticity studies comparing hatchling and adult pterosaurs.

Hone continues:
“Precociousness has been suggested in pterosaurs before based on the evidence for them flying while young, but it has also been challenged. It suggested that to be flying at that size would require a huge amount of effort and this would leave little energy for growth.”

Wait a minute! Didn’t he just say the weight would increase by the cube in adults? That means juveniles were that much lighter.

Hone continues:
“That’s largely true, but overlooks that there could be post hatching parental parental care. That is normal for archosaurs (including dinosaurs) and we would expect it for pterosaurs.”

If only pterosaurs were archosaurs, but at this point they still nest with lepidosaurs. Most lepidosaurs fend for themselves after hatching, and if pterosaur hatchlings could fly, then they would be able to fly off on their own shortly after hatching. Best not to ‘expect’ anything without a valid phylogenetic context, evidently lacking in Hone et al. 2020.

Hone continues:
“So in short, Rhamphorhynchus is perhaps the best pterosaur for large studies about populations and growth and this genius at least grew isometrically, and this may or may not be the same for other pterosaurs.”

But for the present, every pterosaur known from embryo, juvenile and adult shows strict isometric growth (except for tapejarid crests).

“But it does imply that young pterosaur could fly, and fly well.”

Sadly, Hone et al. seem to be looking at small adults (Fig. 1) and calling them ‘young’. Of course these adult pterosaurs can fly well!

Apparently Hone et al. are comparing linear measurements and graphing them. That method produced false positives for Bennett 1995. There is no substitute for phylogenetic analysis.

In this topsy-turvy world of pterosaurs,
myths are popularized by PhDs while comprehensive phylogenetic analyses compiled by amateurs are ignored and suppressed. Not sure why this problem is not more widely recognized. For other missteps made by Dr. Hone with regard to pterosaurs, click here or use the keyword ‘Hone’ for that long list.

Moments ago the paper itself arrived.
In my morning email was a message from Dr. Hone: “Attached” along with a PDF of their Rhamphorhynchus paper. Two sets of graphs are present, but only a single figure combining bat allometry and Rhamphorhynchus isometry (isolated in Fig. 3).

Figure 3. Image from the only non-graph figure in Hone et al. 2020. Identification and permission note from that caption. Compare these taxa to those in figures 1 and 4.

Figure 3. Image from the only non-graph figure in Hone et al. 2020. Identification and permission note from that caption. Compare these taxa to those in figures 1 and 4.

Figure 4. Lateral view of Hone et al. 2020 Rhamphorhynchus taxa taken from ReptileEvolution.com (Fig. 1).

Figure 4. Lateral view of Hone et al. 2020 Rhamphorhynchus taxa taken from ReptileEvolution.com (Fig. 1). Hone et al. cherry-picked these two somewhat similar by convergence taxa assuming the smaller one was a juvenile of the other other. Phylogenetic analysis separates these two (see Fig. 1). Note the differences in pedal element proportions.

From the paper:
“We test whether pterosaurs show a similar pattern of rapid forelimb growth during post‐hatching/ontogeny to that of bats and birds, and thus infer when in ontogeny R. muensteri would have become volant.”

Sounds laudable. Let’s see how they do it.

From the paper:
“All Rhamphorhynchus specimens from Bavaria are now considered a single species (Bennett 1995).”

No. That’s why figure 1 was created and a phylogenetic analysis of pterosaurs was run (subset Fig. 5), to see how specimens could be lumped and separated. Like Hone et al., Bennett likewise eschewed the use of phylogenetic analysis. Sadly, Hone et al. adopted without further consideration Bennett’s invalid assumption, rather than testing Rhamphorhynchus with a phylogenetic analysis.

Figure 4. Subset of the LRT focusing on Rhamphorhynchus.

Figure 5. Subset of the LRT focusing on Rhamphorhynchus.

From the paper:
“Four lines of evidence suggest that the smallest R. muensteri specimens were very young animals and potentially hatchlings.

  1. Histology reveals incomplete ossification of long bones in the smallest specimens tested (Prondvai et al. 2012),
  2. A disproportionate number of known specimens are small, consistent with high juvenile mortality (Bennett 1995; Hone & Henderson 2014)
  3. Late‐stage embryos of pterosaurs had well‐developed, ossified wings (Wang & Zhou 2004; Codorniú et al. 2018)
  4. and finally while few fossilized pterosaur embryos are known, the ratio by which adults are larger than embryos (Lü et al. 2011; Wang et al. 2017) is similar to the size ratio between the largest R. muensteri specimens and the smallest.”

Incomplete ossification: the smallest specimen studied by Prondvai et al. (2012) was BSPG 1960 I 470a = n9 (Figs. 1, 5) is also the second most primitive tested specimen (next to n28) in a phylogenetic miniaturization series that began with Campylognathoides. Among the neotonous / juvenile traits retained was incomplete ossification of the long bones. Lacking a phylogenetic context, neither Prondvai et al. nor Hone et al. were aware of the miniaturized adult status of n9.

Figure 5. the B St 1960 I 4709A specimen of Rhamphorhynchus is the first and one of the smallest phylogenetically miniaturized specimens.

Figure 5. the B St 1960 I 470a specimen of Rhamphorhynchus (at right)  is the second most primitive and one of the smallest phylogenetically miniaturized specimens attributed to Rhamphorhynchus. One of the neotonous traits was incomplete ossification. Hatchlings were 1/8x the size of adults, similar to house flies in size.

Disproportionate number of specimens are small: lacking a phylogenetic context, Hone et al. were not aware of the phylogenetic miniaturization that preceded the evolution of larger Rhamphorhynchus specimens. In the LPT only one Rhamphorhynchus specimen is a valid juvenile nesting with larger adults.

Late‐stage embryos of other pterosaurs had well‐developed, ossified wings: So did miniaturized adults.

Size ratio of largest R. muensteri specimens to smallest similar to embryo vs adult sizes in other pterosaurs: lacking a phylogenetic context, Hone et al. were not aware of the phylogenetic miniaturization that preceded the evolution of larger Rhamphorhynchus specimens. Hone et al. made the mistake of labeling small adults as juveniles. Notably, Hone et al. did not try to match their purported juveniles with adults phylogenetically. Other tiny Rhamphorhynchus specimens have juvenilized proportions (smaller rostrum, larger orbit), but these were ignored by Hone et al., who cherry-picked two comparative taxa out of 135.

From the paper:
“We tested for isometric versus allometric growth across 135 specimens of R. muensteri using bone length and composite measures (e.g. total wing length and total leg length) relative to: (1) total body length, from rostrum tip to the end of the tail; (2) skull length; and (3) humerus length.”

Lacking a phylogenetic context (available online for several years), Hone et al. made the mistake of comparing adults to adults. No juveniles were tested. Subsequent comparisons to birds and bats were thus rendered moot.

From the paper:
“Our results suggest that even the smallest Rhamphorhynchus had adult skeletal proportions and thus wings sufficient for flight.” This confirms the conclusions of Peters (2018) using a phylogenetically validated juvenile Rhamphorhynchus, rather than a dataset full of large and small adults.

From the paper:
“Wang et al. (2017) noted that in embryos of the pterodactyloid Hamipterus, although there was greater ossification of the limbs and vertebrae than the head, including of the shafts of longbones, there was limited ossification of some other parts of the skeleton that may have related to flight. They hypothesize in this case that hatchlings may have been able to walk before they could fly, though still imply relatively early flight for these animals.”

These were not hatchlings, but embryos still developing within the egg, within the mother in the tradition of lepidosaurs.  Eruptive gases killed flocks en masse. Details here.

From the paper:
“Pterosaurs, like almost all other archosaurs, probably provided parental care (Witton 2013), and precocial flight need not preclude this possibility.” 

This is myth. We’ve known since Peters 2007 that adding taxa moves pterosaurs to nest within Lepidosauria.

From the paper:
“Thus, while Rhamphorhynchus apparently flew at a young age, such volant offspring may have plausibly received parental care, including provisioned food, as they became independent foragers.” 

There is no evidence for this bit of speculation. But it cannot be ruled out. According to Gans 1996, “Many aspects of reptilian reproductive patterns prove to be vagile among the vertebrates. Reversals complicate, and may even invalidate, the characterization of broad trends. Furthermore, the 7000 species of reptiles show dozens of modes that seem to enhance the fitness of their offspring, thereby providing a vast opportunity of testing the reality of these adaptations.”  (‘vagile’ = able or tending to move from place to place or disperse)

In summary:
Hone et al. assumed that phylogenetically miniaturized adults at the genesis of Rhamphorhynchus were juveniles. While testing small adults against large adults (Figs. 1–5) the authors determined that Rhamphorhynchus ontogeny proceeded isometrically.

Ironically this confirms earlier findings by Peters (2018 and elsewhere in this blog) using the only known phylogenetically validated juvenile and a matching adult Rhamphorhynchus. As longtime readers know, all other pterosaurs develop isometrically because they are lepidosaurs arising from taxa close to late-surviving Huehuecuetzpalli, known from matching juvenile and adult specimens.

Dr. Hone needs to show more leadership. He needs to create reconstructions of the specimens under study so visual comparisons can be made by his team and readers. Roadkill specimens are too difficult to compare otherwise. He also needs to run a phylogenetic analysis to determine interrelationships between pterosaur taxa and within all amniotes to see where pterosaurs nest. At present he’s perpetuating old myths and traditions that were invalidated twenty years. He’s that far behind the times.

I’ll never forget the day several decades ago
when Dr. Kevin Padian and Dr. Chris Bennett told me, “nothing can be known about a taxon until it is put into a phylogenetic context.” I took that advice to heart. That is why the LRT and LPT now include more than 2000 taxa.


References
Bennett SC 1993. The ontogeny of Pteranodon and other pterosaurs. Paleobiolgy 19(1):92-106.
Bennett SC 1995. A statistical study of Rhamphorhynchus from the Solnhofen Limestone of Germany: Year-classes of a single large species. Journal of Paleontology 69:569-580.
Gans C 1996. An overview of parental care among the Reptilia. Advances in the Study of Behaviour 25:145–157.
Hone DWE, Ratcliffe JM, Riskin DK, Hemanson JW and Reisz RR 2020. Unique near isometric ontogeny in the pterosaur Rhamphorhynchus suggests hatchlings could fly. Lethaia. Paywall access here.
Hone 2020. Email post. How to grow your dragon – pterosaur onotgeny [sp]
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peters D 2018. First juvenile Rhamphorhynchus recovered by phylogenetic analysis. PDF here.
Prondvai E, Stein K, Ösi A, Sander MP 2012. Life History of Rhamphorhynchus Inferred from Bone Histology and the Diversity of Pterosaurian Growth Strategies. PlosOne. online pdf
Wellnhofer P 1975a-c. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33. Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149:1-30.

wiki/Rhamphorhynchus

https://pterosaurheresies.wordpress.com/2012/03/23/not-another-rhamphorhynchus-growth-series-without-a-phylogenetic-analysis/

 

New paper on bird phenomics vs. genomics

As longtime readers know,
and every paleontologist seems to acknowledge,cladograms based on genes don’t match cladograms based on traits.

So, here’s an unpublished paper
available on ResearchGate.net that simply lifts the rock off this buried problem by laying out the differences in bird phenomics vs. genomics, based on problems found in the Prum et al. 2015 bird cladogram that relied on genomics.

Bird phylogeny: false positives detected in a gene sequencing study
(click on the blue text above to access the ResearchGate.net PDF.)

From the abstract
“Traditionally a matrix of taxa and physical traits provides data for phylogenetic analysis. In recent years gene sequencing has taken on a dominant role. Ideally both methods should recover identical family trees that model evolutionary events. Too often they do not. While DNA analysis has proven its validity within genera (e.g. criminal identification), here a competing morphological analysis (the only method that can include fossils) finds several false positives in the results of a recent gene sequencing study of crown clade birds. Unfortunately gene studies have to rely on the hope that they will recover a series of taxa with a gradual accumulation of physical traits that model evolutionary events-without using those physical traits. Based on this benchmark and the present results, it is inappropriate to circumvent direct observation with gene sequencing in bird studies, at least until gene sequencing study results mirror those based on morphology.”

After a few days
I received a comment on ResearchGate.net from professor and bird expert, Peter Houde, New Mexico State University. My reply follows.

Figure 1. Comment on bird phenomics paper by Peter Houde, NMSU.

Figure 1. Comment on bird phenomics paper by Peter Houde, NMSU.

If anyone has ever wondered about the law of unintended consequences,
this example of unanticipated neotony in a teacher is but one of many stemming from Darren Naish’s critique of ReptileEvolution.com in 2012.


References
Peters D 2020. Bird phylogeny: false positives detected in a gene sequencing study. (unpublished, seeking and awaiting comments)
Prum et al. (6 co-authors) 2015. A comprehensive phylogeny of birds (Aves) using targeted next-generation DNA sequencing. Nature 526:569–573. online

https://www.researchgate.net

Kongonaphon kely: a tiny ornithodiran? NO!

Kammerer et al. 2020 bring us news of a
Lagerpeton-like (Fig. 2) ‘tiny ornithodiran archosaur’ from Mid-Late Triassic of Madagascar.  What little is known of Kongonaphon (Fig. 1) might have stood 10 cm tall, according to the authors.

Figure 1. Kongonaphon bones. Very few are known. They resemble those of Lagerpeton and Tropidosuchus.

Figure 1. Kongonaphon bones. These few resemble those of Lagerpeton and Tropidosuchus (Fig. 2).

From the PNAS significance paragraph:
“Reptiles of the Mesozoic Era are known for their remarkable size: dinosaurs include the largest known land animals, and their relatives, the pterosaurs, include the largest creatures to ever fly. The origins of these groups are poorly understood, however.”

Figure 3. The closest kin of Tropidosuchus are the much larger Chanaresuchus (matching Nesbitt 2011) and the smaller Lagerpeton.

Figure 2 The closest kin of Tropidosuchus are the much larger Chanaresuchus (matching Nesbitt 2011) and the smaller Lagerpeton.

No. This is a traditional myth.
The origins of both groups are well known. In the large reptile tree (LRT, 1707 taxa) the origins of dinosaurs and the completely separate origins of pterosaurs are well documented back to Cambrian chordates.

Figure 3. Cladogram from Kammerer 2020 (rainbow colors). On top are clades within the LRT. So much taxon exclusion here!

Figure 3. Cladogram from Kammerer 2020 (rainbow colors). On top are clades within the LRT. So much taxon exclusion here!

From the abstract
“Early members of the dinosaur–pterosaur clade Ornithodira are very rare in the fossil record, obscuring our understanding of the origins of this important group. Small ancestral body size suggests that the extreme rarity of early ornithodirans in the fossil record owes more to taphonomic artifact than true reflection of the group’s evolutionary history.”

Fossils should be rare
because a dinosaur-pterosaur clade ‘Ornithodira” is invalid. When taxa are added dinosaurs arise from archosaurs. Pterosaurs arise from lepidosaurs. Their last common ancestor is the last common ancestor of all reptiles, Silvanerpeton, from the Early Carboniferous. That makes ‘Ornithodira’ a junior synonym of ‘Reptilia’.

From the abstract
“Kongonaphon is recovered as a member of the Triassic ornithodiran clade Lagerpetidae, expanding the range of this group into Africa and providing data on the craniodental morphology of lagerpetids.”

Funny thing is
Lagerpeton and kin are not related to dinosaurs OR pterosaurs. They are related to Tropidosuchus (Fig. 2) and the Proterochampsidae (Fig. 2). These authors, despite their PhDs, are painfully unaware of reptile systematics. All they need to do is add taxa to come to an understanding.

Figure 4. Kongonaphon kely restored. Lagerpetids have not preserved feathery soft tissue. The lack of a large finger 4 or toe 5 remove this restoration from possible pterosaur ancestry.

Figure 4. Kongonaphon kely restored. Lagerpetids have not preserved feathery soft tissue. The lack of a large finger 4 or toe 5 remove this restoration from possible pterosaur ancestry.

That miniaturization preceded the origin
of pterosaurs, dinosaurs, turtles, snakes, reptiles, mammals, birds and almost every other major clade has been well known for years.


References
Kammerer CF, Nesbitt SJ, Flynn JJ, Ranivoharimanana L and Wyss AR 2020. A tiny ornithodiran archosaur from the Triassic of Madagascar and the role of miniaturization in dinosaur and pterosaur ancestry. PNAS https://doi.org/10.1073/pnas.1916631117

Adelobasileus restored: NOT ‘the oldest mammal’

When Lucas and Hunt 1990
and Lucas and Luo 1993 described the cranium (all that is known) of Adelobasileus (Fig. 1) they concluded it was, ‘the oldest mammal’. 

Figure 1. Adelobasileus restored like Therioherpeton after first nesting together in the LRT.

Figure 1. Adelobasileus restored like Therioherpeton after first nesting together in the LRT. Line drawing for Adelobasileus from Lucas and Luo 1993.

By contrast
the large reptile tree (LRT, 1707+ taxa, subset Fig. x) nests Adelobasileus with the low and wide mammal-mimic cynodont, Therioherpeton (Fig. 1), despite the very few characters that could be scored here. Both also nest with Sinocodon and Haramiyavia in the LRT. Thus Adelobasileus in not the oldest mammal. It is not even a mammal.

Therioherpeton
Fig. 1) was originally described by Bonaparte and Barberena 1975 as ‘a possible mammal ancestor’.

Later
Oliveira 2006 reevaluated Therioherpeton“Therioherpetidae are distinguished from all other probainognathians by upper teeth with the imbrication angle increasing in the posterior postcanines. In addition, upper and lower postcanine teeth are labio-lingually narrow.” This author did not include Adelobasileus in his cladogram. Oliveira nested Therioherpeton with Riograndia.

Figure 1. Megazostrodon skull in several views. Drawings from Gow 1986. Colors applied here.

Figure 2. Megazostrodon skull in several views. Drawings from Gow 1986. Colors applied here. This is the last common ancestor of all mammals in the LRT.

The last common ancestor of all mammals
in the LRT (subset Fig. x) continues to be Megazostrodon (Fig. 2), from the early Jurassic. Other, more derived mammals, like Morganucodon, are found in the Late Triassic, indicating an earlier origin and radiation.

Figure x. Subset of the LRT focusing on therapsids, like Repenomamus, leading to mammals.

Figure x. Subset of the LRT focusing on therapsids leading to mammals. Adelobasileus nests with Therioherpeton in this older cladogram that does not list Adelobasileus.

The most recent paper on basal mammals
and their immediate ancestors, King and Beck 2020, shows just how different cladograms can be when taxa are excluded (Fig. 3, click to enlarge). King and Beck mix non-mammals with prototherians, metatherians and eutherians in a mish-mash as compared to the LRT (Fig. x). At least they nest Adelobasileus outside their Mammalia (which should include only Prototherians, Metatherians and all descendants of their last common ancestor, Megazostrodon, Fig. 2).

Figure 3. Click to enlarge. Stem mammal cladogram from King and Beck 2020 showing how different their topology is to the LRT (color overlays, key at left) which has a wider gamut of included taxa. Arrow points to Adelobasileus near top.

Figure 3. Click to enlarge. Stem mammal cladogram from King and Beck 2020 showing how different their topology is to the LRT (color overlays, key at left) which has a wider gamut of included taxa. Arrow points to Adelobasileus near top.

Add taxa 
and multituberculates nest with rodents, Fruitafossor nests with xenarthrans and other taxa nest appropriately with prototherians, metatherians and eutherians as shown in the LRT (subset Fig. x).

The nesting of Adeolbasileus with Therioherpeton
is not quite an original hypotheses. Google the two keywords, “Adelobasileus, Therioherpeton” and you’ll find someone tweeted these two as possible ancestor-descendant taxa, but unfortunately, still considered Adelobasilesus ‘the oldest mammal.’


References
Bonaparte JF and Barberena MC 1975. A possible mammalian ancestor from the Middle Triassic of Brazil (Therapsida–Cynodontia). Journal of Paleontology 49:931–936.
King and Beck 2020. Tip dating supports novel resolutions of controversial relationships among early mammals. Proceedings of the Royal Society B 287: 20200943.
http://dx.doi.org/10.1098/rspb.2020.0943
Lucas SG and Hunt 1990. The oldest mammal. New Mexico Journal of Science 30(1):41–49.
Lucas SG and Luo Z 1993. Adelobasileus from the upper Triassic of west Texas: the oldest mammal. Journal of Vertebrate Paleontology 13(3):309–334.
Oliveira EV 2006. Reevaluation of Therioherpeton cargnini Bonaparte & Barberena, 1975 (Probainognathia, Therioherpetidae) from the Upper Triassic of Brazil. Geodiversitas 28 (3): 447-465.

http://reptileevolution.com/sinoconodon.htm
wiki/Adelobasileus
wiki/Therioherpeton

Simões et al. 2020 fail to understand ‘diapsids’ due to taxon exclusion

Simões et al. 2020 brings us their study
on the rates of evolutionary change in reptiles with a diapsid skull architecture.

From the abstract:
“The origin of phenotypic diversity among higher clades is one of the most fundamental topics in evolutionary biology. However, due to methodological challenges, few studies have assessed rates of evolution and phenotypic disparity across broad scales of time to understand the evolutionary dynamics behind the origin and early evolution of new clades. Here, we provide a total-evidence dating approach to this problem in diapsid reptiles. We find major chronological gaps between periods of high evolutionary rates (phenotypic and molecular) and expansion in phenotypic disparity in reptile evolution. Importantly, many instances of accelerated phenotypic evolution are detected at the origin of major clades and body plans, but not concurrent with previously proposed periods of adaptive radiation. Furthermore, strongly heterogenic rates of evolution mark the acquisition of similarly adapted functional types, and the origin of snakes is marked by the highest rates of phenotypic evolution in diapsid history.”

This study suffers from taxon exclusion
By adding taxa the first dichotomy of the Reptilia (Amniota is a junior synonym) splits taxa closer to lepidosaurs (Lepidosauromorpha) from those closer to archosaurs (Archosauromorpha, including Synapsida). Thus members of the traditional clade ‘Diapsida’ are convergent. Other than through the last common ancestor of all Reptiles, Silvanerpeton in the Viséan, archosaurs are not related to lepidosaurs. The present paper by Simões et al. 2020 fails to recover this topology due to taxon exclusion. Without a valid phylogenetic context, the results are likewise hobbled.


References
Simões TR, Vernygora O, Caldwell MW and Pierce SE 2020. Megaevolutionary dynamics and the timing of evolutionary innovation in reptiles. Nature Communications 11: 3322.

http://reptileevolution.com/reptile-tree.htm

Ticinolepis: DGS rebuilds scattered skull parts

López-Arbarello, et al. 2016 and
López-Arbarello and Sferco 2018 brought us two closely related Middle Triassic ganoid-scaled fish. These two species of Ticinolepis (Fig. 1) are distinguished by their teeth (and other traits). The larger one has small, slender teeth (Fig. 2). It was added to the large reptile tree (LRT, 1706+ taxa, subset Fig. 3). The smaller one has large bulbous teeth.

Figure 1. Two new Ticinolepis species to scale.

Figure 1. Two new Ticinolepis species to scale from López-Arbarello 2016, Scale bar = 2 cm. The skull of the top species, T. longavea, is shown in figure 2.

Ticinolepis longaeva
(López-Arbarello and Sferco 2016; Middle Triassic; MCSN 8072) nests at the base of a clade of several ganoid fish, near the base of catfish + placoderms and not far from a clade of several spiny sharks.

Figure 2. The skull of Ticinolepis longaeva (MCSN 8072) in situ from López-Arbarello 2016, traced and reconstructed using DGS methods.

Figure 2. The skull of Ticinolepis longaeva (MCSN 8072) in situ from López-Arbarello 2016, traced and reconstructed using DGS methods. Gray part of maxilla was under the nasal. 

In the LRT
 (subset Fig. 3) Ticinolepis nests with Perleidus (Fig. 4), Tarrasius, and the living gar, Lepisosteus.

Figure 5. Subset of the LRT, focusing on fish for July 2020.

Figure 5. Subset of the LRT, focusing on fish for July 2020.

The phylogenetic ‘distance’ between any two fish taxa
is getting smaller and smaller as more taxa are added.

Figure 1. Perleidus woodwardi in situ and with skull reconstructed.

Figure 4. Perleidus woodwardi in situ and with skull reconstructed.

López-Arbarello and Sferco 2018 wrote:
“In our analysis, †Ticinolepis also joins the tree at this stem as the most basal Ginglymodi and, thus, we now find it useful to distinguish the clade (Lepisosteiformes, †Semionotiformes) as the Neoginglymodi, defined as the clade including Lepisosteus and †Semionotus, and all descendants of theirmost recent common ancestor.”

Currently in the LRT, that clade includes just those two sister taxa. Over time perhaps others will be added.

López-Arbarello and Sferco 2018 mention all LRT clade members, except Tarrasius. The authors do not attempt a reconstruction of Ticinolepis.


References
López-Arbarello A, Burgin T, Furrer H and Stockar R 2016. New holostean fishes (Actinopterygii: Neopterygii) from the Middle Triassic of the Monte San Giorgio (Canton Ticino, Switzerland). Peerj 4, 61 (doi:10.7717/peerj.2234).
López-Arbarello A and Sferco E 2018. Neopterygian phylogeny: the merger assay. Royal Society open sci. 5: 172337. http://dx.doi.org/10.1098/rsos.172337

Bavarichthys: a Late Jurassic Solnhofen anchovy

Arratia and Tischlinger 2010
bring us several fossils of Bavarichthys incognitus from the Late Jurassic Solnhofen Formation of Germany. In the large reptile tree (LRT, 1706+ taxa; subset Fig. x) it nests with Elops, the extant and much larger anchovy (Fig. 2), and for good reason. They are almost identical.

Figure 1. Bavarichthys is a big head/ short body anchovy from the Late Jurassic.

Figure 1. Bavarichthys is a big head/ short body anchovy from the Late Jurassic. Here the preorbital and cranial bones are restored.

The skull of one Bavarichthys
(Fig. 1) is largely intact, lacking a prefrontal + upper lacrimal based on phylogenetic bracketing with Elops (Fig. 2). The maxilla is slightly displaced.

Figure 2. Elops is the extant anchovy. Compare to Bavaricthys in figure 1.

Figure 2. Elops is the extant anchovy. Compare to Bavaricthys in figure 1.

Bavarichthys incognitus (Arratia and Tischlinger 2020; Late Jurassic) was originally considered a member of the “Crossognathiforms with a large head about 30% in standard length and a characteristically elongate snout, more than 25% in head length.

Figure 2. Another specimen of Pholidophorus? radians

Figure 2. Another specimen of Pholidophorus? radians

?Pholidophorus radians is a coeval Late Jurassic relative
(Fig. 3) with a more tuna-like shape.

Figure 5. Subset of the LRT, focusing on fish for July 2020.

Figure x. Subset of the LRT, focusing on fish for July 2020.

The phylogenetic ‘distance’ between any two fish taxa
is getting smaller and smaller as more taxa are added.


References
Arratia G and Tischlinger H 2010. The first record of Late Jurassic crossognathiform fishes from Europe and their phylogenetic importance for teleostean phylogeny. Mitteilungen aus dem Museum für Naturkunde in Berlin. Fossil Record; Berlin 13(2): 317–341.

wiki/Elops_saurus

Sallen 2016 presents a fascinating flawed look at fish tails

Sallen 2016 reports,
“The symmetrical, flexible teleost fish ‘tail’ has been a prime example of recapitulation — evolutionary change(phylogeny) mirrored in development (ontogeny).”

Sallan’s cladogram (Fig. 1) lays out the traditional cladogram of fish. Note the position of the bichir (Polypterus), at a basal node and the sturgeon + paddlefish (Acipcenser + Polyodon) near the middle.

Figure 1. Cladogram from Sallan 2016 (above) and young fish tails (below).

Figure 1. Cladogram from Sallan 2016 (above) and young fish tails (below).

Unfortunately,
taxon exclusion mars the cladogram of Sallan 2016 according to the the large reptile tree (LRT, 1704+ taxa; Figs. 2, 5). Due to tradition Sallan has chosen the wrong outgroup. Jawless sturgeons and shark-like paddlefish should be the outgroups here, not lungfish-like bichirs (Polypterus), which are highly derived taxa close to lungfish and tetrapods.

Figure 2. Same taxa as above, but rearranged to fit the LRT tree topology.

Figure 2. Same taxa as above, but rearranged to fit the LRT tree topology. Remember, sturgeons, paddlefish and sharks are basal taxa in the LRT. Esox is a catfish related to placoderms.

Salan reports,
“Paleozoic ray-finned fishes (Actinopterygii), relatives of teleosts, exhibited ancestral scale-coveredtails curved over their caudal fins. For over 150 years, this arrangement was thought to be retained in teleost larva and overgrown, mirroring an ancestral transformation series. New ontogenetic data for the 350-million-year-old teleost relative Aetheretmon overturns this long-held hypothesis.”

By contrast,
in the LRT Aetheretmon nests with Pteronsculus (Figs. 5–7)) far from the base of all bony fish, much closer to lobefin fish and tetrapods.

The Sallan point is still made:
Many fish tails do have two parts, especially when hatchlings.

Unfortunately, Sallan does not understand
the topology of the family tree of fish due to taxon exclusion. This is something the LRT minimizes by testing a wider gamut of taxa. As readers know, we see this same taxon exclusion problem all the time in paleontology.

Figure 2. Muskie (Esox) tail ontogeny from Sallan 2016 (middle row). Top row and photo added here.

Figure 3. Muskie (Esox) tail ontogeny from Sallan 2016 (middle row). Top row (to scale) and photo (below) added here. You might remember, Esox is a derived catfish without barbels.

Salan writes,
These two tails appear at a shared developmental stage in Aetheretmon, (Fig. 4) teleosts and all living actinopterygians. Ontogeny does not recapitulate phylogeny; instead, differential outgrowth determines final morphology.”

That appears to be so, but it still needs a valid tree topology.

Figure 3. Fish tail ontogeny in extinct Aetheretmon and extant Monotrete. Note the upper and lower lobes.

Figure 4. Fish tail ontogeny in extinct Aetheretmon and extant Monotrete. Note the upper and lower lobes. In the LRT these two fish are not closely related. Aetheretmon is basal to lobefins. Monotrete is a puffer fish.

Salan speculates:
“The double tail likely reflects the ancestral state for bony fishes.”

No, the ancestral state for bony fish is the heterocercal tail documented by sturgeons and whale sharks, and this goes back to armored osteostracans according to the LRT (Fig. 5).

Figure 5. Subset of the LRT, focusing on fish for July 2020.

Figure 5. Subset of the LRT, focusing on fish for July 2020. Aetheretmon is in the yellow column close to the notch between colors.

Salan speculates,
“Many tetrapods and non-teleost actinopterygians have undergone body elongation through tail outgrowth extension, by mechanisms likely shared with distal limbs.”

Not sure what those ‘mechanisms’ would be, but basal tetrapods and stem tetrapods in the LRT have relatively short, straight tails and elongated bodies with great distances between the fore and hind limbs. Look at Panderichthys.

Figure 5. Aetheretmon is known from the oldest complete growth series for vertebrates.

Figure 6. Aetheretmon is known from the oldest complete growth series for vertebrates.

Figure 6. Pteronisculus, a sister to Aetheretmon in the LRT.

Figure 7. Pteronisculus, a Triassic sister to Early Carboniferous Aetheretmon in the LRT and it is easy to see why.

Sallan is ‘Pulling a Larry Martin’
by putting too much emphasis on one trait without testing all the traits on many more taxa. Only after a valid phylogenetic context is established can one begin to figure out if trait A came before trait B or not.

Sallan goes into great detail describing
the successive stages of growth in Aetheretmon, but this is problematic because the cladogram is invalid. “First things first” is a motto all paleontologists should ascribe to. First get the phylogeny correct. Fish workers are relying on an invalid family tree. The LRT is here to fix that.

Its worth remembering,
many fish on the other branch of bony fish (perch, anglers, etc., Fig. 5, orange right column) bring the pelvic fins beneath the pectoral fins, shortening the gut cavity and elongating the tail to extremes in some cases (oarfish). This is all distinct from the longer torso, shorter tail trend in the stem tetrapod branch of bony fishes (Fig. 5, yellow left column).


References
Sallan 2016. Fish ‘tails’ result from outgrowth and reduction of two separate ancestral
tails. Current Biology 26, R1205–R1225.
White EI 1927. The fish fauna of the Cementstones of Foulden, Berwickshire. Transactions of the Royal Society Edinburgh 55:255–287.

https://www.the-scientist.com/the-nutshell/a-tale-of-two-tails-32394

Shenqiornis: Reconstructing a Mesozoic bird skull

O’Connor and Chiappe 2011
traced (Fig. 1) and reconstructed (Fig. 2) the skull of the enantiornithine bird Shenqiornis mengi (Early Cretaceous; Wang et al. 2010; DNHM D2950-2951). This is one of the few enantiornithines with substantial skull material.

Figure 1. O'Connor et al. traced Sheqiornis like this.

Figure 1. O’Connor and Chiappe 2011 traced Shenqiornis like this.

O’Connor and Chiappe used freehand techniques
to reconstruct Shenqiornis (Fig. 2). This is almost never a good idea as assumptions and biases tend to flavor freehand reconstructions.

Figure 2. O'Connor et al. reconstructed the skull of Sheqiornis freehand.

Figure 2. O’Connor and Chiappe 2011 reconstructed the skull of Sheqiornis freehand. Missing parts are in gray, though they seem to give this bird an antorbital fossa that I don’t see and sister taxa do not have. Scale bar = 1cm.

Long time readers know, it is far better to use the DGS method
(Fig. 3) and simply transfer precisely traced shapes to the reconstruction without bias or forethought. It also permits others to see exactly what you saw in a scattered, crushed fossil.

Figure 3. The skull of Sheqiornis traced and reconstructed using DGS methods.

Figure 3. The skull of Shenqiornis traced and reconstructed using DGS methods. Compare to fig. 1 and 2. Here more bones were identified and more precisely reconstructed. Scale bar = 1 cm.

Given this data,
Sheqiornis nests with Pengornis (Fig. 4) in the large reptile tree (LRT, 1703+ taxa) based on skull traits alone.

Figure 3. Pengornis reconstructed not from tracing, but from cutting out the bones and putting them back together. Color tracing is used only for the skull elements. This holotype specimen does not have the same morphology or proportions that Chiappeavis has and it nests within the Enantiornithes.

Figure 4. Pengornis reconstructed not from tracing, but from cutting out the bones and putting them back together. Color tracing is used only for the skull elements. This holotype specimen does not have the same morphology or proportions that Chiappeavis has and it nests within the Enantiornithes.

If you think things here have been a little strange
over the last 3 weeks, you’re right. My large aging computer zapped out. Meanwhile I was able to handle posts using a small MacBook Pro, but was not able to get to my Adobe graphics software for DGS tracing and reconstructing. I was likewise unable to update the LRT. Things are back to normal now (see Fig. 3 above), so we continue!


References
O’Connor JK and Chiappe LM 2011. A revision of enantiornithine (Aves: Ornithothoraces) skull morphology. Journal of Systematic Palaeontology, 9:1, 135-157, DOI: 10.1080/14772019.2010.526639
Wang X, O’Connor J, Zhao B, Chiappe LM, Gao C and Cheng X 2010. New species of Enantiornithes (Aves: Ornithothoraces) from the Qiaotou Formation in Northern Hebei, China. Acta Geologica Sinica, 84(2):247-256.

wiki/Shenqiornis