New basal tapejarid with broken wings needs specimen number, citation

Updated April 1, 2020
The specimen number is SMA 0154 / 02. Kind readers reported the location of this specimen: Sauriermuseum, Aathal, Switzerland. I can now reveal the phylogenetic nesting of this specimen is between Sinopterus and Tapejara. I know of no citation yet.

Figure 1. Complete basal tapejarid without identification. Please provide a museum number or citation if possible.

This image above (Fig. 1) appears on the website,
“Tapejaraluv.weebly.com” under the headline “The Tapejara,” created by Jordyn Rosen and Teya Good. There are no ‘contact us‘ or ‘comments‘ links on their website and all attempts at finding them elsewhere on the ‘net don’t seem to be leading to any Tapejara fans. 

I will forego posting any more information on this specimen
pending the acquisition of a citation or museum number on the chance that it is currently under study and awaiting publication. Even so, it has been added to the large pterosaur tree (LPT) as the 243rd taxon, but not yet posted online.

Revisiting the origin and living relatives of spiny sharks (Acanthodii)

In today’s somewhat lengthy post
there’s going to be a set-up (so you can see traditional thinking)
and a take-down (so you can see what happens when you add taxa).

According to Wikipedia:
“Acanthodii or acanthodians (sometimes called spiny sharks) is an extinct paraphyletic class of teleostome fish, sharing features with both bony fish and cartilaginous fish. In form they resembled sharks, but their epidermis was covered with tiny rhomboid platelets like the scales of holosteans (gars, bowfins). They represent several independent phylogenetic branches of fishes leading to the still extant Chondrichthyes.”

“Although not sharks or cartilaginous fish, acanthodians did, in fact, have a cartilaginous skeleton, but their fins had a wide, bony base and were reinforced on their anterior margin with a dentine spine.”

“The earliest unequivocal acanthodian fossils date from the beginning of the Silurian Period, some 50 million years before the first sharks appeared. Spiny sharks died out in Permian times (250 Million years ago).”

Figure 1. Cladogram from Burrow et al. 2016 (colors and labels added here) showing the origin of Acanthodii from Placodermi using only Silurian and Devonian taxa. Compare to figure 3, which includes extant taxa.

More from Wikipedia:
“Davis et al. (2012) found acanthodians to be split among the two major clades Osteichthyes (bony fish) and Chondrichthyes (cartilaginous fish).”

“Burrow et al. 2016 (Fig. 1 above) provides vindication by finding chondrichthyans (sharks + ratfish) to be nested among Acanthodii, most closely related to Doliodus (Fig. 5) and Tamiobatis (Paleozoid shark based on multi cusp teeth). A 2017 study of Doliodus morphology points out that it appears to display a mosaic of shark and acanthodian features, making it a transitional fossil and further reinforcing this idea”. 

By contrast,
the LRT found Doliodus (Fig. 5) nested with xenacanthid ‘sharks’ basal to bony fish, far from spiny sharks.

Figure x. Updated subset of the LRT, focusing on basal vertebrates = fish.

After adding more taxa, like the spiny shark,
Climatius (Fig. 3, ), and a long list of extant taxa in the large reptile tree (LRT, subset Fig. 2) the tree topology in figure 1 changes greatly.

Distinct from Burrow et al. 2016

1. Sharks and ratfish are not derived from spiny sharks, but are derived from the most primitive fish with simple transverse jaws, like Rhincodon.
2. Placoderms and pre-lobefin fish (like Cheirolepis) are not basal to spiny sharks, but are related through a last common ancestor in Bonnerichthys (Figs. 3, 4).
3. Spiny sharks arise from Silurian sisters to extant taxa, like lizard fish (Trachinocephalus, and arowana (Osteoglossum Fig. 3) in the newly recovered clade of short-face fish (clade: Breviops) distinct from fish with the orbit set further back on the skull (at least initially, the long-face fish (clade: Longiops) that starts with the bowfin (Amia).
4. Spiny sharks give rise to Triassic Perleidus and extant featherbacks (Notopterus, Fig. 3), both of which have traditional ray-fin fins, though Notopterus pelvic fins remain tiny spines.

Figure 3. Acanthodians, their ancestors and sometimes extant sisters. Presently tested spiny sharks are all quite tiny as adults. Larger ones are known.

Placoderms are not extinct
They exist today as catfish. Spiny sharks are not extinct. They exist today as anchovies (Engraulis) and featherbacks (Notopterus, Figs. 3, 4) in the LRT, where taxon exclusion recovers novel hypotheses of interrelationships. Spiny shark sisters don’t have spines for fins. Using a single trait, even one like ‘spines for fins’, would be “Pulling a Larry Martin.” IN order to be a spiny shark sister, a taxon just has to nest closer to spiny sharks than any other included taxon. In your own analyses, include more taxa and the transition from one to another will become more and more gradual and apparent.

Figure 4. Acanthodian skulls, plus those of ancestors and related taxa. Notopterus is a living featherback. Engraulis is a living anchovy.

Acanthodes bronni (Anonymous 1880; Early Permian 290 mya; 20cm; Fig. 4) is the latest occurring acanthodian, the largest and has the most ossified braincase. Davis et al. mislabeled the hyomandibular as a giant quadrate and the preopercular as the mislabeled hyomandibular (Fig. 4). Acanthodes is toothless and presumed to have been a filter feeder. No extra spines or fins are present. Other species can reach 41cm.

Reports that acanthodians are the last common ancestors
of sharks and bony fish (e.g. Friedman and Brazeau 2010, Davis, Finarelli and Coates 2012) are not supported by the LRT.

Figure 5. Doliodus skull and pectoral region with lateral reconstruction at right. Note the narrow pectoral region relative to the wide spread occiput. Apparently this fish had a narrower body than head.

Doliodus (Fig. 5) has similar spiny fins,
but nests elsewhere in the LRT, with Xenacanthus. Catfish (e.g. Clarias) often have spines anterior to their pectoral fins, but are not related to spiny sharks. the giant Cretaceous predator, Xiphactinus, bundles fin rays into a spine, but is not related to spiny sharks. Yet another Cretaceous giant, Bonnericthys, (Figs. 3, 4) likewise bundles fin rays into a spine, and is basal to spiny sharks.,

Remember this as you finish reading:
Presently some (not all) spiny sharks appear earlier  in the fossil record (early Silurian) than do many precursor taxa in the LRT, some of which wait to appear until the Late Carboniferous, Jurassic and Cretaeous. Others are only known as extant taxa. Loganellia, the tiny primitive whale shark sister, is also from the Early Silurian, 444 mya.  Guiyu, a basal lobefin (Fig. 6), and Psarolepis are from the Late Silurian. So every taxon in the LRT preceding Guiyu and Psarolepis will someday be found somewhere in Silurian strata.

Figure 6. Guiyu in situ, DGS colors added here and used to create the flatter, wider reconstruction with paddles preserved.

Fossilization is rare.
Finding a fossil-bearing locality of the right age is also rare. So it is wise not to put too much exclusionary weight on chronology (as in Fig. 1 above). Keep adding taxa and the puzzle of evolution will ultimately become a coherent picture. The gaps keep getting smaller as enigma taxa, like the spiny sharks, are better understood in a phylogenetic context, using extinct AND extant taxa.

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References
Anonymous 1880. Royal Physical Society of Edinburgh. Proceedings of the Royal Physical Society of Edinburgh. V: 115.
Baron MG 2015. An investigation of the genus Mesacanthus (Chordata: Acanthodii) from the Orcadian Basin and Midland Valley areas of Northern and Central Scotland using traditional morphometrics. PeerJ. 3: e1331. doi:10.7717/peerj.1331
Brazeau M 2009. The braincase and jaws of a Devonian ‘acanthodian’ and modern
gnathostome origins. Nature 457, 305–308.
Burrow C, den Blaauwen J, Newman M and Davidson R 2016. The diplacanthid fishes (Acanthodii, Diplacanthiformes, Diplacanthidae) from the Middle Devonian of Scotland. Palaeontologia Electronica 19 (1): Article number 19.1.10A.
Davis SP, Finarelli JA and Coates MI 2012. Acanthodes and shark-like conditions in the last common ancestor of modern gnathostomes. Nature 486:247–250.
Egerton P de MG 1860. Report of the British Association for Science for 1859.
Transactions of the Sections. 116.
Friedman M and Brazeau 2010. A reappraisal of the origin and basal radiation of the Osteichthyes. Journal of Vertebrate Paleontology 30(1):36–56.
Miller RF, Cloutier R and Turner S 2003. The oldest articulated chondrichthyan from the Early Devonian period. Nature 435:501–504.
Newman M and Davidson B 2010. Early Devonian fish from the Midland Valley of Scotland. National Palaentological Congress London 14–15.
Traquair RH 1888. Notes on the nomenclature of the Fishes of the Old Red Sandstone of Great Britain. Geol. Magazine (3)5:507–517.
Woodward AS 1892. On the Lower Devonian fish-fauna of Campbellton, New Brunswick.. Geol. Mag. 9, 1–6.

wiki/Acanthodii
wiki/Ischnacanthus
wiki/Mesacanthus
wiki/Acanthodes
wiki/Climatius

 

In memoriam: Professor Jennifer Clack

If you never met her,
here’s your second chance, via YouTube videos.

This week marks the passing of Professor Jennifer Clack (1947-2020),
a renown specialist in Devonian tetrapods, especially Acanthostega (Fig. 1). In the above 4-minute YouTube video from 2017, Clack introduces her concept that the first tetrapods, like her discovery of Acanthostega, had more than five manual digits. This is confirmed by Middle Devonian tetrapod tracks (Fig. 3) with more than five digits.

Figure 1. Acanthostega does not have much of a neck. Note the narrow torso, taller than wide, distinct from lobefin fish that phylogenetically led to basal tetrapods, like Trypanognathus in figure 4.

But not
according to the large reptile tree (LRT) which recovers Acanthostega as a terminal taxon, not a transitional one, far from the main line of tetrapod origins. Four digits are found in Panderichthys, Greererpeton and many other basal tetrapods, as we learned earlier here, here and here. More than five digits are found in only a few derived taxa, including the stem reptile, Tulerpeton, far from the origin of digits.

A more complete and technical account
of basal tetrapod traits is provided by Clack in this 20-minute YouTube lecture video from 2016 (above).

It may be that Clack only saw evolutionary progress
without considering the possibility of evolutionary reversal, as happens when taxa return to a more aquatic niche from a less aquatic niche, reducing the importance of their digits and limbs. In the above video, Clack does not provide a phylogenetic analysis, like the LRT (subset Fig. 2) that includes more primitive, but late-surviving basal tetrapods, all of which follow the pattern of a wider than deep torso, as in ancestral fish with embedded arm bones in their lobefins. Rather, she concentrates on individual traits, which while valuable, set her up for ‘Pulling a Larry Martin‘, rather than concentrating efforts on determining a phylogeny that minimizes taxon exclusion and lets the software determine (= mirror) evolutionary events, as the LRT does while minimizing taxon inclusion bias.

Figure 2. Subset of the LRT focusing on basal tetrapods. Note the displaced positions of Acanthostega and Ichthyostega.

Only after a phylogeny is documented and validated
can one then discuss the various traits and their uses by the creature that possessed them.

Lest we forget
the first tetrapod tracks (Fig. 1, Niedźwiedzki et al. 2010) predate fossil tetrapods, including Acanthostega, by 20 to 30 million years, as we looked at here. And even they had more than five toes. Thus the phylogenetic origin of tetrapods goes back even further. The early Devonian must have provided quite a few niches for such rapid evolution to take place.

Figure 3. Best Devonian Valentia track with various overlays.

We need to look more closely at
Trypanognathus (Fig. 4; latest Carboniferous), which is the most primitive, but by far not the earliest, taxon in the LRT to document fingers and limbs, rather than lobe fins. Note the anterior eyes, wide flat skull and body, and primitive sprawling limbs. Can someone count the fingers and toes on this specimen? I find no more than four digits. Some may be hiding here.

Figure 4. Trypanognathus in situ, colorized to bring out ribs and limbs is the most primitive, but not the earliest taxon with limbs and toes, not lobe fins.

We’ve seen the chronology of several fossil finds
at odds with their phylogeny in the LRT (e.g. multituberculates, bats, Gregorius). That keeps it interesting, but only a wide gamut phylogenetic analysis based on traits will deliver a valid tree topology. As time goes by and more discoveries are made the competing hypotheses will someday converge.

Figure 5. Silvanerpeton from the Upper Viséan (331 mya) is the outgroup taxon for Gephyrostegus and the Amniota.

And one more thing,
Clack 1994 described Silvanerpeton (Fig. 5, Viséan, 335 mya) first as an anthrcosauroid and later (Ruta and Clack 2006) as a stem tetrapod, all without recovering it as the basalmost reptile, as shown in the LRT. Adding taxa, creating a wider gamut phylogenetic analysis, would have brought even more fame to this well-respected paleontologist.

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References
Clack JA 1994. Silvanerpeton miripedes, a new anthracosauroid from the Visean of East Kirkton, West Lothian, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences 84 (for 1993), 369–76.
Niedźwiedzki G, Szrek P, Narkiewicz K, Narkiewicz M and Ahlberg PE 2010. Tetrapod trackways from the early Middle Devonian period of Poland Nature 463, 43-48. doi:10.1038/nature08623
Ruta M and Clack, JA 2006 A review of Silvanerpeton miripedes, a stem amniote from the Lower Carboniferous of East Kirkton, West Lothian, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, 97, 31-63.

https://www.zoo.cam.ac.uk/news/professor-jenny-clack-frs-1947-2020

http://www.theclacks.org.uk/jac/Biography.html

https://www.pbs.org/wgbh/nova/link/clack.html
(make sure to click on the parts 2-4 links therein)

 

Cretaceous toothed birds evolved from toothless megapodes in the LRT

Today’s heretical dive
into the origin of Cretaceous toothed birds (Fig. 1) brings new insight to a clade that has been traditionally misrepresented as a stem clade, often represented by just two highly derived toothed taxa, Ichthyornis and Hesperornis (Fig. 1). In the large reptile tree (LRT, 1659+ taxa; subset Fig. 3) Cretaceous toothed birds arise from extant toothless Megapodius (Figs. 1, 2; Gaimard 1823). How is this possible?

Toothy jaws from toothless jaws? 
That seems to break some rules. And if the LRT (Fig. 3) is valid, that makes toothed Cretaceous birds crown bird taxa.

Figure 1. Click to enlarge. Toothed birds of the Cretaceous to scale. They are derived from toothless taxa.

Earlier Field et al. 2020
claimed to discover the ‘oldest crown bird‘ fossil when they described Asteriornis (66 mya), a screamer (genus: Chauna) relative. Unfortunately, due to taxon exclusion, Field et al. 2020 did not consider the ostrich sister, Patagopteryx (80 mya), nor did they understand that Juehuaornis (Wang et al. 2015; Early Cretaceous, Aptian, 122mya; Figs. 1, 4) was also a crown bird taxon, the oldest crown bird, derived from Megapodius, the extant mound builder.

One look
(Fig. 1) at the similarity of Megapodius to basal Cretaceous toothed and toothless birds, like Juehuaornis (Figs. 1, 4), makes the relationship obvious. The LRT recovered that relationship based on hundreds of traits and minimized convergence by testing relationships among 1659 taxa.

So, where did those Cretaceous teeth come from?
Megapodius and Juehuaornis both lack teeth. Basalmost toothed taxa had tiny teeth (Fig. 1) Derived toothed taxa had larger teeth. Try to let that sink in. Teeth re-appeared in these Cretaceous birds.

How is that possible? Consider this:
Juehuaornis is smaller than Megapodius. The sternum and keel of Juehuaornis are smaller than in Megapodius. Why is this important? As we learned earlier, at the genesis of many major and minor clades phylogenetic miniaturization (the Lilliput Effect) is present. That’s how gulls become hummingbirds and rauisuchians become dinosaurs. When adults are smaller they mature more quickly and they retain juvenile traits into adulthood. They also develop new traits, in this case, perhaps ontogeny recapitulated phylogeny.

The tooth genes got turned on again,
at first in a minor way… later in a major way.

Figure 2. Click to enlarge. Origin of birds from Archaeopteryx to Megapodius. Pseudocrypturus is the sister taxon to the kiwi (Apteryx, Fig. 3), the most basal crown birds, but Juehuaornis is known from much older fossils despite being more derived than Megapodius.

How close were Cretaceous toothless taxa,
like Juehuaornis, to toothed Jurassic ancestors, like Archaeopteryx? Depends on how you look at it.

Chronologically
Juehuaornis is from the Aptian, Early Cretaceous, 122 mya. Archaeopteryx is from the Tithonian, Late Jurassic, 150 mya. A transitional taxon, Archaeornithura (Fig. 2) is from the Hauterivian, Early Cretaceous, 131 mya, splitting the time difference. Archaeornithura had teeth and lacked a pygostyle, but had a shorter tail than the most derived Archaeopteryx (Fig. 2).

Morphologically
toothless Juehuaornis follows toothless Megapodius (Figs. 1, 3) and is separated from toothy Archaeornithura by at least three taxa (Figs 2, 3). The question I ask is: did the Cretaceous sisters to these toothless taxa have teeth subsequently lost in later generations over the past 140 million years? Or were teeth lost in  Early Cretaceous transitional taxa (represented by late-survivors (Fig. 2)) only to be regained in the toothy extinct clade (Fig. 3)? For now, let’s leave all options open, but toothlessness followed by toothy jaws is the only option currently supported by phylogenetic evidence (Fig. 3).

Figure 3. Subset of the LRT focusing on bird origins. Crown birds and toothed birds are highlighted.

This is what happens when you let the cladogram tell you what happened,
rather than gerrymandering the taxa inclusion list and scores to get the results your professors and colleagues will approve and permit publication.

Figure 4. Juehuaornis reconstructed. Note the scale bars. This is a tiny bird and the oldest known crown bird.

I should have reported
that Juehuaornis (122 mya) was the oldest known crown bird earlier. I just had to see the toothed birds in phylogenetic order (Fig. 1), making sure they made sense after seeing them listed in the cladogram (Fig. 3).

Add taxa
and your cladograms will be better than most. Create reconstructions to scale and see if your cladograms make sense. When it’s right, it all works out with a gradual accumulation of traits between every node, echoing evolutionary events from deep time. Let me know if this novel hypothesis of interrelationships was published previously anywhere so that citation can be promoted.

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References
Gaimard JP 1823. Mémoire sur un nouveau genre de Gallinacés, establi sous le nom de Mégapode. Bulletin General et Universel des Annonces et de Nouvelles Scientifiques 2: 450-451.
Wang R-F, Wang Y and Hu Dong-yu 2015. Discovery of a new ornithuromorph genus, Juehuaornis gen. nov. from Lower Cretaceous of western Liaoning, China. Global Geology 34(1):7-11.

wiki/Megapodius
wiki/Megapode

Colobops: back to Rhynchocephalia

Scheyer et al. 2020 revisit
Colobops noviportensis (unnamed in Sues and Baird 1993; Pritchard et al. 2018; Late Triassic; YPM VPPU 18835; Fig. 1) a tiny 2.5cm long skull originally considered a ‘pan-archosaur’. Using µCT scans, Pritchard et al. scored Colobops and nested it at the base of the Rhynchosauria. Pritchard et al. wrote: “Colobops noviportensis reveals extraordinary disparity of the feeding apparatus in small-bodied early Mesozoic diapsids, and a suite of morphologies, functionally related to a powerful bite, unknown in any small-bodied diapsid.”

You heard it here first in 2018. Colobops is a rhynchocephalian.

Figure 1. Colobops as originally presented and slightly restored.

That same week in 2018,
Colobops was added to the large reptile tree (LRT, now 1659+ taxa, then 1085 taxa) where it nested as a sister to the morphologically similar and size similar basal rhynchocephalian, Marmoretta (Fig. 2; Evans 1991). You can read about that nesting here.

Figure 2. Marmoretta, a basal rhynchocephalian in the lineage of pleurosaurs

This week,
Scheyer et al. nested Colobops with Sphenodon (Fig. 3), a basal extant rhynchocephalian. Sadly, the authors again omitted Marmoretta (Fig. 2).

Sues and Baird 1993 first described this specimen
without naming it and without a phylogenetic analysis, as a member of the Sphenodontia (Williston 1925), a junior synonym for Rhynchocephalia (Gunther 1867).

Marmoretta oxoniensis (Evans 1991, Waldman and Evans 1994; Middle/Late Jurassic, ~2.5 cm skull length; Fig. 2), orginally considered a sister of kuehneosaurs, drepanosaurs and lepidosaurs. Here in the LRT, Marmoretta nests between Megachirella and Gephyrosaurus + the rest of the Rhynchochephalia. Two specimens are known with distinct proportions in the skull roof.

Figure 3. Sphenodon, the extant tuatara, is close to Colobops, but Marmoretta is closer.

The LRT minimizes taxon exclusion
because it includes such a wide gamut of taxa, from Cambrian chordates to humans. The Colobops information has been online for the past two years. Colleagues, please use it. Don’t ‘choose’ taxa you think might be pertinent. Let the LRT provide you a long list of validated taxa competing to be the sister to your new discovery.

Final note: 
In the LRT (since 2011) even rhynchosaurs are lepidosaurs. Just add pertinent taxa and your tree will recover the same topology. Traditional paleontologists are taking their time getting around to testing this well-supported hypothesis of interrelationships.

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References
Evans SE 1991. A new lizard−like reptile (Diapsida: Lepidosauromorpha) from the Middle Jurassic of Oxfordshire. Zoological Journal of the Linnean Society 103:391-412.
Pritchard AC, Gauthier JA, Hanson M, Bever GS and Bhullar B-AS 2018. A tiny Triassic saurian from Connecticut and the early evolution of the diapsid feeding apparatus. Nature Communications open access DOI: 10.1038/s41467-018-03508-1
Scheyer TM, Spiekman SNF, Sues H-D, Ezcurra MD, Butler RJ and Jones MEH 2020. Colobops: a juvenile rhynchocephalian reptile (Lepidosauromorpha), not a diminutive archosauromorph with an unusually strong bite. Royal Society Open Science 7:192179.
http://dx.doi.org/10.1098/rsos.192179
Sues H-D and Baird D 1993. A Skull of a Sphenodontian Lepidosaur from the New Haven Arkose (Upper Triassic: Norian) of Connecticut. Journal of Vertebrate Paleontology. 13 (3): 370–372.
Waldman M and Evans SE 1994. Lepidosauromorph reptiles from the Middle Jurassic of Skye. Zoological Journal of the Linnean Society 112:135-150.

wiki/Marmoretta
wiki/Colobops

https://pterosaurheresies.wordpress.com/2018/03/25/colobops-and-taxon-exclusion-issues/

Elgin and Hone 2020 document two large Solnhofen pterosaur wings

Two large, disassociated,
but strongly similar Solnhofen pterosaur wings, SMNK 6990 (Fig. 1) and MB.R.559.1 (Fig. 2) were described in detail by Elgin and Hone 2020. Unfortunately they did so without a phylogenetic analysis and therefore presented no firm hypothesis of interrelationships.

Figure 1. The SMNK 6990 wing from Elgin and Hone 2020. Contrast was raised from the original photo. Metacarpal 1 is actually mc3. Reconstruction in figure 3.

In the SMNK 6990 specimen
(Fig. 1) Elgin and Hone 2020 mistakenly flipped metacarpals 1-3  then wondered why 2 and 3 were reduced.

In the MBR.5991.1 specimen
Elgin and Hone 2020 overlooked the three free fingers.

Figure 2. MB.R.5991.1 specimen as originally published, then a higher contrast image and color tracing including three overlooked free fingers and a radius.

In their conclusion,
Elgin and Hone first guessed, then gave up trying to figure out what sort of wings these were when they reported, “a placement within either the Ctenochasmatoidea or Dsungaripteridae appears most likely… further differentiation is impossible.”

Figure 3. Luchibang, Pterodactylus longicollum and the two new Solnhofen wings to scale. The latter two are nearly identical.

In counterpoint,
testing against all 242 taxa already in the large pterosaur tree (LPT, where nothing is impossible) both new Solnhofen wing specimens nested with the largest pterodactylids, including, ironically, Luchibang (Fig. 3), which just this month Dr. Hone mistook for an ornithocheirid with weird proportions.

Alas, and with regret,
these two authors have a long history of making similar mistakes and overlooking details despite having firsthand access. Those low batting averages were covered earlier here, here, here, here, here and here. Not sure why referees keep accepting such work for publication. In the end it just has to be cleaned up.

Contra the authors’ title,
the traditional clade ‘Pterodactyloidea’ becomes a grade with four convergent appearances, when more taxa are added. Traditional paleontologists have been loathe to do this in their own cladograms. This hypothesis of interrelationships has been in the literature for the last 13 years (Peters 2007) and online in the LPT for the last ten. 

Keeping the blinders on
is what pterosaur workers seem to continue to be doing. The next generation of workers (Elgin and Hone among them) seems to be stuck in the same quagmire. Not sure why this is so. Astronomers and physicists are always testing each others’ observations and hypotheses. They are always inviting ideas. In the end, they seem to speak with one voice. Why can’t we be like that?

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References
Elgin RA and Hone DWE 2020. A review of two large Jurassic pterodactyloid specimens
from the Solnhofen of southern Germany. Palaeontologia Electronica, 23(1):a13. https://doi.org/10.26879/741
palaeo-electronica.org/content/2020/2976-solnhofen-pterodactyloids
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.

Late-surviving sharovipterygids in Early Cretaceous Burmese amber

Earlier we looked at a
Oculudentavis, a late-surviving cosesaur in Early Cretaceous Burmese amber. I noted it had just a few traits closer to another fenestrasaur, Sharovipteryx (Fig 2).

Figure 1. DGS tracings of two amber entombed Early Cretaceous sharovipterygids.

Today,
two unnumbered, unnamed, undescribed Early Cretaceous fenestrasaurs with even more sharovipterygid traits from the same Burmese amber. These specimens have huge eyes, a larger naris, a small antorbital fenestra, gracile postorbital bones, long cervicals with robust cervical ribs. That gray sickle-shaped area appears to represent the same sort of extendable hyoids seen in Sharovipteryx that extend the neck skin to form canard wing membranes or strakes (Fig. 2). Once again, these poor saps got their head stuck in the resin. The rest of the body was lost to the ages.

For comparison, a complete Sharovipteryx
(Fig. 2) is known from Late Triassic strata, coeval with the first pterosaurs, both derived from Cosesaurus, a lepidosaur tritosaur fenestrsaur.

Figure 3. Sharovipteryx reconstructed. Note the flattened torso.

References
No scale bar, No citation, No museum number, Owner unknown.

Rethinking giant ‘Dracula’ LPB R-2347 as a Q-sized Azhdarcho

Updated March 25, 2020
with the strong possibility that this specimen (chimaera or not) has been named, Albadraco tharmisensis with the holotype specimen number: PSMUBB V651a, b. But that may be a mid-sized specimen, not the giant.

The largest pterosaur model in the world, nicknamed ‘Dracula’
is built on relatively few disassociated parts Fig. 1). The rest is imagined.

Figure 1. Highly speculative reconstruction of large azhdarchid from Romania, nicknamed ‘Dracula’ based on the few bones shown here. One source says an ‘upper arm bone” was found. Another states a scapula was found. I will update this if in error here.

Even so,
this chimaera may be close to the real deal, perhaps slightly smaller and more gracile (Fig. 2) than the model-builders imagined (Fig. 1). If ‘Dracula’ was indeed a giant (or full grown) Azhdarcho (as  indicated here by matching bits and pieces, Fig. 2), then the skull should have been sculpted with less bone, the stance more erect, the femur shorter, the sternal complex smaller and the distal wing phalanges smaller. With denser bones and shorter wings than volant pterosaurs, ‘Dracula’ would have been flightless, like other azhdarchids with similarly clipped (still imaginary, but compared to Fig. 2) wings.

Figure 2. ‘Dracula’ elements match those from the much smaller Azhdarcho, here enlarged to the scale of Quetzalcoatlus northropi and Q sp. The imagined torso may be much smaller., the hind limb larger.  Note the large size of the wing-metacarpal joint compared to Q. sp. Don’t trust these chimeric images further than intended here. Lots of guesswork.

Earlier we looked at the cervical #7 of ‘Dracula’.
Here we add the re-identified rostrum (Figs. 2, 3 with a central set of narrow vomers), originally described as a mandible portion. Granted, there is not much to work with here, but everything scales correctly and fits the Azhdarcho pattern. Other suggestions are welcome, by the way.

Figure 2. The former mandible of ‘Dracula’ here flipped to become a rostrum complete with palatal vomers. Compare to enlarged and to scale images of Azhdarcho rostrum and mandible tips.

Earlier we looked at the purported mandible of LPB R 2347
which was originally imagined as the largest pterosaur ‘mandible‘ (Fig. 3). The authors compared their jaw segment to the mandible of Bakonydraco (Fig. 3). As shown in figure 2, the Romanian fragment is more likely a rostrum belonging to an adult or giant Azhdarcho. 

Figure 3. LPB R 2347 was originally imagined as the largest pterosaur ‘mandible’ which the authors compared to Bakonydraco. As shown in figure 2, this is more likely a rostrum belonging to an adult or giant Azhdarcho.

Bakonydraco
nests with volant basal pteranodontids in the LPT. 

Eurazhdarcho
is a coeval mid-sized azhdarchid known from some wing phalanges and three anterior neck cervicals. 

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References
Averianov AO 2010. The osteology of Azhdarcho lancicollis (Nessov, 1984) (Pterosauria, Azhdarchidae) from the late Cretaceous of Uzbekistan. Proceedings of the Zoological Institute RAS 314:264-317
Averianov AO 2013. Reconstruction of the neck of Azhdarcho lancicollis and lifestyle of azhdarchids (Pterosauria, Azhdarchidae) Paleontological Journal 47:203-209.
Buffetaut E, Grigorescu D and Csiki Z 2003. Giant azhdarchid pterosaurs from the terminal Cretaceous of Transylvania (western Romania) In: Buffetaut E, Mazin JM, eds. Evolution and palaeobiology of pterosaurs. London: Geological Society Special Publications. Vol. 217:91-104.
Kellner AWA and Langston Jr W 1996. Cranial remains of Quetzalcoatlus (Pterosauria, Azhdarchidae) from Late Cretaceous sediments of Big Bend National Park, Texas. Journal of Vertebrate Paleontology 16:222-231
Naish D and Witton MP 2017. Neck biomechanics indicate that giant Transylvanian azhdarchid pterosaurs were short-necked arch predators. PeerJ 5:e2908; DOI 10.7717/peerj.2908
Vremir MM 2010. New faunal elements from the Late Cretaceous (Maastrichtian) continental deposits of Sebes area (Transylvania). Terra Sebus-Acta Museu Sabesiensis 635–684.
Nessov LA 1984. Upper Cretaceous pterosaurs and birds from central Asia. Paleontology Journal 1984(1):38-49
Vremir M, Kellner AWA, Naish D and Dyke GJ 2013. A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution. PLOS ONE 8:e54268
Vremir M, Witton M, Naish D, Dyke G, Brusatte SL, Norell M and Totoianu R 2015. A medium-sized robust-necked Azhdarchid Pterosaur (Pterodactyloidea: Azhdarchidae) from the Maastrichtian of Pui (Haţeg Basin, Transylvania, Romania) American Museum Novitates 3827:1-16
Vremir M et al. 2018. Partial mandible of a giant pterosaur from the uppermost Cretaceous (Maastrichtian) of the Haţeg Basin, Romania. Lethaia doi: https://doi.org/10.1111/let.12268 https://onlinelibrary.wiley.com/doi/abs/10.1111/let.12268
Witton MP and Naish D 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLOS ONE 3:e2271

wiki/Albadraco

A 2020 primer on reptile tarsals

This blogpost had its genesis 
with a new paper by Blanco, Ezcurra and Bona 2020, who studied archosaur and stem archosaur ankles. They reported, “Here, we integrate embryological and palaeontological data and quantitative methodologies to test the hypothesis of fusion between the centrale and astragalus, or the alternative hypothesis of a complete loss of this element.”

More on the results of that paper
after this short primer.

Not sure how much readers know about this subject.
Ankles used to be ‘the thing’ back in the 1980s when terms like “crocodile normal” and “crocodile reversed” were common and influential. Today, with over 230 tested traits in the large reptile tree (LRT, 1658+ taxa), a few ankle traits fade to insignificance. Tiny details, like pegs and sockets, are ignored here. Instead this primer will start with broader, readily visible patterns of presence, absence and fusion.

Figure 1. Basal tetrapod ankles with tarsal elements identified by color.

The origin of carpals preceded the origin of tarsals.
The most primitive (but late appearing) tetrapods, like Trypanognathus, had poorly ossified tarsals and tiny limbs and digits. The most primitive appearances of tarsals in the LRT comes tentatively with Early Carboniferous Pholidogaster (Fig. 1) and completely with Early Carboniferous Greererpeton (Fig. 1). Both are more primitive in the LRT than the traditional fin-to-finger transitional Late Devonian taxa, Acanthostega and Ichthyostega, with their robust limbs and supernumerary digits. We don’t have fossils yet, but we have tracks of Middle Devonian tetrapods. Five is the primitive number of pedal digits in Pholidogaster. Four remains the primitive number of manual digits.

Remember, the first reptile,
Silvanerpeton, is from coeval Early Carboniferous strata. That means we’re missing many intervening taxa from earlier (Late Devonian) layers.

Starting with the sub-equal distal tarsals of Greererpeton
the medial distal tarsals of Gephyrostegus shrink, matching the smaller diameters of the medial metatarsals. The medial centrales also shrink. Two proximal tarsals fuse to become the astragalus and together with the new calcaneum (Pholidogaster lacks one) form the largest tarsal elements, strengthening the tarsus into a tighter, stronger set.

Note the slight rotation of the hind limb of Gephyrostegus
(Fig. 1) relative to the axis of the toes, corresponding to the increased asymmetry of the digit lengths. Distinct from the more fish-like Greererpeton, short-bodied, big-footed Gephyrostegus was able to clamber about on a myriad of landforms, stems and branches with its belly raised off the substrate (Fig. 2).

Figure 2. Gephyrostegus in anterior view demonstrating the need for shorter medial toes in tetrapods with a sprawling gait. This insures the toes to not scrape the substrate during the recovery phase and also assures that all the toes contribute to the propulsive phase.

Immediately following Silvanerpeton in the LRT
the Reptilia (=Amniota) split to form two major clades, the Archosauromorpha and the Lepidosauromorpha. At first, both were amphibian-like reptiles (laying amnion-layered eggs) with many traditional amphibians in their number here transferred to the Reptilia based on the last-common ancestor in the LRT method of classification, rather than a list of traditional skeletal traits.

Archosauromorpha step one: Gephyrostegus to Petrolacosaurus
Gephyrostegus (Fig. 3) is the proximal outgroup to the clade Reptilia. Five distal tarsals are present. 4 and 5 are larger than 1, 2 and 3. Four centrale are present. Two proximal tarsals are present, the astragalus (= tibiale) and calcaneum (= fibulae). No intermedium is present.

Petrolacosaurus (Fig. 3) is a basal diapsid. Here Two medial centrale fuse together. Another centrale fuses to the astragalus. The lateral centrale fuses to distal tarsal 4 doubling its size. Distal tarsal 5 shrinks to half. That makes pedal 5 not line up with the other four tarsals.

We’ll return to archosauromorphs below
after dealing with the lepidosauromorphs in order. But first compare the minor differences between the two major reptile clades following Gephyrostegus (Figs. 3, 4).

Figure 3. Gephyrostegus, a reptile outgroup, compared to Petrolacosaurus, a Late Carboniferous archosauromorph basal to archosauriforms and archosaurs. Compare to figure 2.

Lepidosauromorpha step one: Gephyrostegus to Nyctphruretus
Compared to Gephyrostegus, in the owenettid Nyctiphruretus (Fig. 4) two medial centrale fuse together by convergence. Two lateral centrale fuse to distal tarsal 4 tripling its size. Distal tarsal 5 enlarges. Distinct from Petrolacosaurus (Fig. 3), all five metatarsals remain aligned proximally and the hind limb becomes more aligned with the axis of the toes again.

Figure 4. Gephyrostegus compared to the basal lepidosauromorph. Note the fusion of the some centrales into distal tarsal 4.

Lepidosauromorpha step two: Nyctiphruretus to Huehuecuetzpalli
Huehuecuetzpalli (Fig. 5) is a more arboreal late-survivor in the Early Cretaceous from an Early Triassic radiation of tritosaur lepidosaurs. All distal tarsals are reduced. One and two are absent. Five is fused to metatarsal five creating a twisted ‘hook’. The last centrale is fused to the astragalus and the hind limb is strongly rotated relative to the toes.  The calcaneum is smaller and able to detach from the fibula.

Are you starting to see that bones have a history of homology? Most tarsal fusion is not at all apparent unless comparisons are made in a phylogenetic context. Of course, this affects scoring in analysis.

Figure 5. Lepidosauriform tarsals. The centrale is larger than the distal tarsal 2 in Late Permian Nyctphuretus. Huehuecuetzpalli is Early Cretaceous, so like fenestrasaurs, its ankle also evolved since the Early Triassic split to lose smaller tarsals.

Lepidosauromorpha step three: Macrocnemus to Peteinosaurus
Compared to taxa above (Fig. 5), Middle Triassic Macrocnemus (Fig. 6) loses distal tarsal 2 and retains the medial centrale.

Increasingly bipedal Langobardisaurus (Fig. 6) loses distal tarsal 1. The centrale is larger. The other tarsals are smaller.

Increasingly bipedal and sometimes flapping Cosesaurus (Fig. 6) loses distal tarsal 2. The centrale mimics distal tarsal 2. Distal tarsal 4 is not much larger than the centrale. The tibia migrates back in line with the axis of the pes.

Completely bipedal and flapping Peteinosaurus (Fig. 6) has a simple hinge ankle joint with alll four tarsal elements relatively larger and more similar in size.

Figure 6. Tritosaur lepidosaur tarsals from Peters 2000. Note how the centrale moves distally to replace or fuse with distal tarsal 1 and 2. Or is the centrale really distal tarsal 2?

Archosauromorpha step two: Petrolacosaurus to Protorosaurus
Compared to the basal archosauromorph diapsid, Petrolacosaurus (Figs. 3, 7) In Protorosaurus (Fig. 7) distal tarsal 5 fuses to metatarsal 5, as in the lepidosaur tritosaur, Huehuecuetzpalli (Fig. 5) by convergence. The astragalus moves to a more central position as the medial centrale articulates directly with the tibia in a short-lived experiment that does not continue with taxa more directly in the archosauriform lineage (Fig. 8).

Figure 7. Petrolacosaurus and Protorosaurus pedes to establish homologies.

Archosauromorpha step three: Protorosaurus to Archosauriforms
Compared to Protorosaurus (Fig. 8), the tarsals are little changed in the basal archosauriform, Proterosuchus, with the note that, as mentioned above, the centrale does not contact the tibia. The distal tarsals are sub-equal in size. The calcaneum is laterally extended, backing up the similarly extended mt5.

In Euparkeria (Fig. 8) the tarsus is similar with symmetrical and block-like proximal tarsals. The calcaneum does not back up mt 5. Pedal digit 3 longer than 4 signaling a less sprawling, more upright, form of locomotion with a simple hinge ankle joint.

In increasingly bipedal PVL 4597 (Fig. 8), basalmost archosaur, distal tarsals 1 and 2 are absent, 3 and 4 are fused. The calcaneum has a posterior process, the ‘heel’. Mt 1 is longer creating a more symmetrical pes with a simpler hinge ankle joint.

Figure 8. Archosauriform pedes compared to Protorosaurus.

Archosauromorpha step four: PVL 4597 to higher Archosauria
Compared to PVL 4597 (Fig. 9), the tarsus of the basal dinosaur Herrerasaurus (Fig. 9) is further reduced, and so is the calcaneum. The astragalus develops an anterior ascending process that also seen in Crocodylus (Fig. 9), which no longer has a simple-hinge ankle joint. Here fused distal tarsal 4/5 is thicker and the astragalus contacts mt 1, slightly rotating the tibia medially for a more sprawling configuration. Distinct from other archosaurs, mt 1 is the most robust in the set and mt 5 becomes a robust vestige in Crocodylus.

Figure 9. Archosaur tarsals compared.

Blanco, Ezcurra and Bona 2020 report, 

1. “the astragalus developed ancestrally from two ossification centres in stem archosaurs 
2. the supposed tibiale of bird embryos represents a centrale.
3. The tibiale never develops in diapsids.”

In counterpoint,

1. Figure 1 indicates the two ossification centers go back to the basal tetrapod, Greererpeton. Protorosaurus was an oddball with the centrale contacting the tibia.
2. Figure 1 indicates it is inappropriate to call the proximal tarsal in any reptile the ‘tibiale’ as the astragalus is present prior to basalmost taxa.
3. See above.

Blanco et al. report,
“The proximal tarsus of archosaurs is ancestrally composed of a medial astragalus that articulates proximally with the tibia and fibula and a lateral calcaneum that articulates proximally with the fibula.” The authors do not identify the owner of such a tarsus, but let us presume it is that oddball Protorosaurus (Figs. 7, 8).

Blanco et al. reach back to captorhinids
to suggest an outgroup to archosaurs. Unfortunately, captorhinds are basal lepidosauromorphs in the LRT. So the authors are looking where they should not be looking for progenitors.

The Blanco et al. membership list of Archosaurs is over extended.
Blanco et al. employ the invalid clades ‘Pseudosuchia‘ and ‘Avemetarsalia‘, which includes the lepidosaur pterosaurs. They also employ the lepidosaur, Macrocnemus (Fig. 6) as an archosauriform outgroup. Their Archosauromorpha include the archosauriforms, Proterosuchus and Erythrosuchus and the archosaurs Caiman, Lewisuchus and Rhea. They are not aware that the old definition of Archosauromorpha now includes synapsids when given the taxon list of the LRT.

Figure 10. Basal pterosaur and basal dinosaur pedes (feet) compared. While convergent in many respects, certain traits separate these two unrelated clades.

Pterosaurs are traditionally considered archosaurs, 
but that was shown to be invalid twenty years ago. Perhaps it would help if a basal archosaur dinosaur and a basal lepidosaur pterosaur were shown side-by-side (Fig. 10). We’ve already seen many instances of convergence in the tarsal evolution of archosauromorphs and lepidosauromorphs. This is just one more instance of the same. It is time for paleontologists to stop dragging their tails and get up to speed in this arena.

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References
Blanco MVF, Ezcurra MD and Bona P 2020. New embryological and palaeontological evidence sheds light on the evolution of the archosauromorph ankle. Nature Scientific Reports (2020)10:5150. https://doi.org/10.1038/s41598-020-62033-8
Peabody FE 1951. The origin of the astragalus of reptiles. Evolution 5(4):339–344.

Oculudentavis in more incredible detail! (thanks to Li et al. 2020)

Li et al. 2020 bring us
higher resolution scans of the putative tiny toothed ‘bird’ (according to Xing et al. 2020) Oculudentavis (Fig. 1). Following a trend started here a week ago, Li et al. support a generalized lepidosaur interpretation, but then tragically overlook/deny details readily observed in their own data (Fig.1).

FIgure 1. CT scan model from Li et al. 2020, who denied the presence of a quadratojugal and an antorbital fenestra, both of which are present. Colors applied here. The previously overlooked jugal-lacrimnal suture becomes apparent at this scale and presentation.

Li et al. deny the presence of a clearly visible antorbital fenestra.
They report, “One of the most bizarre characters is the absence of an antorbital fenestra. Xing et al. argued the antorbital fenestra fused with the orbit, but they reported the lacrimal is present at the anterior margin of the orbit. This contradicts the definition of the lacrimal in birds, where the lacrimal is the bone between the orbit and antorbital, fenestra. In addition, a separate antorbital fenestra is a stable character among archosaurs including non-avian dinosaurs and birds, and all the known Cretaceous birds do have a separate antorbital fenestra.”

Contra Li et al.
a standard, ordinary antorbital fenestra is present (Fig. 1 dark arrow) and the lacrimal is between the orbit and antorbital fenestra. This is also the description of the antorbital fenestra and fenestrasaurs, like Cosesaurus (Fig. 2), Sharovipteryx and pterosaurs (Peters 2000).

Li et al. report,
“The ventral margin of the orbit is formed by the jugal.”

Contra Li et al.
the lacrimal is ventral to half the orbit (Fig. 1). The jugal is the other half. The suture becomes visible at the new magnification.

Li et al. report,
“Another unambiguous squamate synapomorphy in Oculudentavis is the loss of the lower temporal bar.” 

Contra Li et al.
the lower temporal bar is created by the quadratojugal, as in Cosesaurus, Sharovipteryx and pterosaurs. In Oculudentavis the fragile and extremely tiny quadratojugal is broken into several pieces. DGS (coloring the bones) enables the identification of those pieces (Fig. 1).

Figure 2. Cosesaurus with colors applied. Compare to figure 1.

Li et al. conclude,
“Our new morphological discoveries suggest that lepidosaurs should be included in the phylogenetic analysis of Oculudentavis.” 

Contra Li et al.
these are all false ‘discoveries’.

Also note that Li et al. cannot discern
which sort of lepidosaurs should be tested in the next phylogenetic analysis of Oculudentavis. That’s because lepidosaur tritosaur fenestrasaurs, like Cosesaurus (Fig. 2), are not on their radar. That’s because pterosaur referees have worked to suppress the publication of new data on Cosesaurus and kin. And that’s what scientists get for not ‘playing it straight.’

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References
Li Z, Wang W, Hu H, Wang M, Y H and Lu J 2020. Is Oculudentavis a bird or even archosaur? bioRxiv (preprint) doi: https://doi.org/10.1101/2020.03.16.993949
Xing L, O’Connor JK,; Schmitz L, Chiappe LM, McKellar RC, Yi Q and Li G 2020. Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature. 579 (7798): 245–249.

wiki/Oculudentavis