New Scientific American cover story: Pterosaurs were monsters of the Mesozoic skies

Cover of Scientific American featuring article by Michael Habib.

Cover of Scientific American featuring article by Michael Habib. There are many things wrong with this image and Habib’s article.

Dr. Michael Habib reports,
online for Scientific American, “Fossils and mathematical modeling are helping to answer long-standing questions about these bizarre animals.”

Conspicuously absent from that subhead:
phylogenetic analysis, perhaps because that’s not Habib’s strong suit.

Figure 1. Chase Stone illustration from pterosaur article demonstrating how helium-filled giant azhdarchids on a smaller planet took flight.

Figure 1. Chase Stone illustration from pterosaur article demonstrating how helium-filled giant azhdarchids on a smaller planet took flight. Note now long it takes to perform the first downstroke. Figure 8 shows what would really happen in such a quad launch.

Habib begins with the widely agreed upon basics.
He reports, “Many possessed heads larger than their bodies, making them, in essence, flying jaws of death. No animal in the Mesozoic would have been safe from their gaze.” So, no exaggeration or hyperbole here. Just fulfilling the cover story headline. 

“All that paleontologists know about pterosaurs comes from the fossil record. And that record has been frustratingly fragmentary, leaving us with just a glimmer of their former glory and a host of questions about their bizarre anatomy and ill fate.” Again, another wild statement without the glimmer of reality. We have a rather complete cladogram of pterosaurs with no gaping holes in the fossil record.

“One of the enduring mysteries of pterosaurs is how the largest members of this group became airborne.” Simple answer: they were flightless. Get used to it.

Habib confessess, “After all, it seems unfathomable that birds of such sizes could fly (although this would be puzzling given their many anatomical adaptations for flight).” Simple answer: Their smaller ancestors with relatively longer wings flew.

Figure 2. Pterosaur artwork from SciAm Habib article. Frames 2 and 3 show accurate skeletons. Compare wing proportions of Quetz sp. with ornithocheirid.

Figure 2. Pterosaur artwork from SciAm Habib article. Frames 2 and 3 show accurate skeletons. Note the clipped wings of Quetz. sp. comparee to wing proportions of similarly-sized ornithocheirid. The wings of the big Quez look large enough to fly. but not when compared to other pterosaurs.

Habib reports, “Membrane wings, such as those of pterosaurs and bats, produce more lift per unit speed and area than the feathered wings of birds. This additional lift improves slow-speed maneuvering capability, which for small animals helps with making tighter turns and for big animals facilitates takeoff and landing.”

Habib continues, “Flying animals do not flap their way into the air or use gravity to take off from an elevated location such as a cliff.” Judge this statement after remembering all the flapping birds and bats you’ve ever seen taking off. The first thing they both do is open up their wings (Fig. 3).

Successful heretical bird-style Pteranodon wing launch

Figure 3. Click to play. Successful heretical bird-style Pteranodon wing launch in which the hind limbs produce far less initial thrust because the first downstroke of the already upraised wing provides the necessary thrust for takeoff in the manner of birds. This assumes a standing start and not a running start in the manner of lizards. Note three wing beats take place in the same space and time that only one wing beat takes place in the Habib/Molnar model.

Then Habib goes around the bend, “Many birds can manage impressive leaps. They are constrained by their heritage as theropod dinosaurs, however: like their theropod ancestors, all birds are bipedal, meaning they have only their hind limbs to use for jumping. Pterosaurs, in contrast, were quadrupedal on the ground. Their wings folded up and served as walking, and therefore jumping, limbs.” Therefore? How many animals leap with their folded wings or forelimbs? I have only seen a tiny grounded vampire bat (at 1.2 ounces) do this. But bats push large pulses of air down with their umbrella-like wings when they fly. Action = reaction, not high-pressure below vs. low pressure above, as in soaring birds and pterosaurs.

Anhanguera taking off

Figure 4. Anhanguera taking off in a plantigrade bipedal configuration according to Chatterjee and Templin 2003.Ridiculous.

It’s always fun to pull out
a bad study when trying to prove your point. Habib does this by recalling Chatterjee and Templin 2003 (Fig. 4)  in which “the animal could not weigh more than 165 pounds and had to run downhill into a headwind.”

Habib reports, “What really confuses scientists and enthusiasts alike is not the wings of pterosaurs but the heads. The skull on a rather typical Cretaceous pterosaur might be two or even three times the body length (usually taken as the distance between the shoulder and hip). Some had skulls surpassing four times the length of their bodies. In some species the neck is triple the length of the torso, with the head size triple again, such that the head and neck could make up more than 75 percent of the total length of the pterosaur. Why would any animal be so ridiculously proportioned? And how could such a body plan possibly work for a flying creature?” 

Habib argues against flight in giant azhdarchids when he confesses, “…it is the disproportionate effect that the skull weight has on the animal’s center of gravity. A huge head, especially if mounted on a huge neck, moves the center of gravity quite far forward.” (Fig. 2). “For a typical walking animal, this creates a serious problem with gait: the forelimbs have to move into an awkward forward position for the animal to be balanced.” Not so. We see the same thing in living storks (Fig. 5). They stand upright with their center of balance always beneath the wing root.

Figure 1. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

Figure 5. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

Habib reports, “Imagine using crutches to walk while minimizing the weight on both legs—you would advance both crutches simultaneously and let them bear all your weight, then swing your legs forward between them, touch down and repeat.” Now imagine using all your power to use your arms and crutches to leap 10 feet into the air to unfold your giant wings. Try as you might, you can’t do it. Neither could pterosaurs, even if they maintained balance over their wing roots (Figs. 6, 7).

Figure 2. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

Figure 6. The large azhdarchid pterosaur, Zhejiangopterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

 

Pterodactylus walk matched to tracks according to Peters

Figure 7. Click to animate. Plantigrade and quadrupedal Pterodactylus walk matched to tracks

Habib reports, “During takeoff, incidentally, the legs would have pushed first, followed by the arms, for a perfect one-two push-off.”

Not often. Perhaps never. And in the real world would have been awkward and dangerous (Fig. 8).

Habib reports, “This arrangement would not have made for the most efficient walking gait, but it was doable. And anyway, pterosaurs traveled primarily by flying.” Don’t you hate it when scientists lump every sort of pterosaur into the same bad habits and niches? Clearly ctenochasmatids and azhdarchids had different habits than anurognathids. BTW, Habib never introduces us to the three known types of flightless pterosaur, including the plover-sized SoS 2428 in the azhdarchid lineage.

Unsuccessul Pteranodon wing launch based on Habib (2008).

8. Unsuccessul Pteranodon wing launch based on Habib (2008) in which the initial propulsion was not enough to permit wing unfolding and the first downstroke.

Then Habib pulls his most famous ‘rabbit out of the hat’
by failing to show what happens the moment after the pterosaur quad launch (Fig. 9) while cheating contact between the fourth metacarpal and the substrate AND moving metacarpals 1-3 to the top of the metacarpal 4, instead of in front (medially) as in all other tetrapods and pterosaurs (Fig. 9).

Figure 9. Quad launch hypothesis from Habib's SciAm article. He cheats the position of metacarpals 1-3 and does not show what happens after the leap.

Figure 9. Quad launch hypothesis from Habib’s SciAm article. He cheats the position of metacarpals 1-3 to the dorsal surface of metacarpal 4 and does not show what happens after the leap. Think how high this pterosaur has to jump to open up that ventrally oriented giant wing finger. Example in figure 8 above.

If you’re at all interested,
here (Fig. 10) is the real folding mechanism on the same genus of pterosaur manus. Note the placement of fingers and metacarpals 1-3. Habib’s hypothesis depends on a snapping of the wing, like a grasshopper’s leg, produced through contact between the wing finger tendon and the substrate, which is impossible given pterosaur anatomy and hand prints which only show fingers 1-3 making an impression with digit 3 often pointing posteriorly beneath the wing finger (Fig. 10).

Figure 10. Above in color: Earlier image with shorter free fingers from Habib. Below: Tracing from bone photos for comparison.

Figure 10. Above in color: Earlier image with shorter free fingers from Habib. Below: Tracing from bone photos for comparison.

Habib discusses the solution to the center-of-gravity (balance) issue
in giant azhdarchids by angling the wings somewhat forward to match it. Of course, this is not necessary if the giant azhdarchid is forever flightless. The continuing problem with Habib’s hypothesis that he keep ignoring is the FACT that the distal phalanges of giant azhdarchids are reduced to vestiges, effectively clipping the wings. He also cheats the anatomy (Figs. 9, 10) and never acknowledges that issue.

Habib concludes with the widely held hypothesis
that only large pterosaurs existed 65 million years ago, too large to survive the impact extinction. He does not compare Late Cretaceous pterosaurs to Late Jurassic tiny Solnhofen pterosaurs that survived that extinction event.


References

https://www.scientificamerican.com/article/pterosaurs-were-monsters-of-the-mesozoic-skies/

New PBS Eons video: How pterosaurs got their wings

The good folks at PBS Eons
added a new video on the origin of pterosaurs. The following repeats (with added images) my comments on the PBS Eons video on YouTube.

This video is SO WRONG
so many times. The origin of pterosaurs is not ‘foggy.’

The Scleromochlus (Fig. 1) hypothesis for pterosaur origins was invalidated by Peters 2000 who tested it and all other candidates for pterosaur origins in four separate phylogenetic analyses by adding taxa to prior studies. Macrocnemus, Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama (Fig. 2) were recovered closer to pterosaurs.
Figure 3. Short-legged Gracilisuchus, along with sisters, long-legged bipedal Pseudhesperosuchus and Scleromochlus.

Figure 1. Short-legged Gracilisuchus, along with sisters, long-legged bipedal Pseudhesperosuchus and Scleromochlus.

Scleromochlus nested with basal bipedal crocodylomorphs,
(Fig. 1) close to the origin of dinosaurs. Note the tiny hands on Scleromochlus. Note the lack of pedal digit 5 on Scleromochlus. By contrast, pterosaurs had large hands and a specialized pedal digit 5 that had two large phalanges that folded together such that the distal phalanx was dorsal side down, making an impression behind pedal digits 1–4 (Figs. 10, 11). More on this below.
Figure 3. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx.

Figure 2. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx. Click to enlarge.

Pterosaurs didn’t fossilize very well?
False. Look at all the excellent pterosaur fossils we know of, some with soft tissue.
Pterosaurs are not archosaurs.
Peters 2000 introduced the clade Fenestrasauria for pterosaurs + their above named ancestors. These in turn were part of a new clade of lepidosaurs, named Tritosauria, nesting between Rhynchocephalians and Protosquamates published in Peters 2007.
Cosesaurus and Longisquama have extra-large fingers,
dominated by digit 4. See: http://reptileevolution.com/pterosaur-wings.htm
Ornithodirans are a junior synonym
for Reptilia (=Amniota, see cladogram link below). Not wise to bring up this invalidated clade name.
Figure 1. Scaphognathians to scale. Click to enlarge.

Figure 3. Scaphognathians to scale. Click to enlarge.

The pterodactyloid grade of pterosaur
was attained four times by convergence (two from the genus Dorygnathus, two more from the genus Scaphognathus, Fig. 3). Transitional taxa were all tiny Solnhofen forms (Fig. 3). As in many other clades, phylogenetic miniaturization attended the genesis of derived pterosaurs.
As in giant birds,
Quetzalcoatlus (Fig. 4) grew so large because it was flightless. All azhdarchids over six-feet-tall had clipped wings (vestigial distal wing phalanges) good for flapping and walking on, not for flying.
Figure 1. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

Figure 4. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

No pterosaur fossils had wing membranes extending ‘the length of their legs’.
All soft tissue shows the short chord wing membrane was stretched between the elbow and wing tip.  See: http://reptileevolution.com/pterosaur-wings.htm
Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex.

Figure 5. Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex.

How did pterosaurs get their wings? 
Convergent with theropods ancestral to birds, Cosesaurus reorganized its pectoral girdle to flap (Fig. 5). The scapula became immobile and strap-like. The coracoid became immobile and stalk-like. The clavicles, interclavicle and single sternum migrated together, then fused together. The forelimbs of Cosesaurus were too short for flight, but fully capable of flapping, probably as a mating ritual. Likewise the pectoral girdles of Sharovipteryx and Longisquama were similarly built. Of the three, Longisquama had the largest hands, but still could not fly. Bergamodactylus was the basalmost pterosaur and it could fly. See links below.
Why guess how a hypothetical ancestor learned to fly
when we have excellent samples of every stage? (see links below)
The arboreal leaping model
does not require flapping — and gliders do not evolve into flappers (e.g. colugos, squirrels, sugar gliders, etc.)
The arboreal parachute model
worked for bats, but they were seeking prey beneath their perches as fingers 3-5 then 2-5 elongated. Pterosaurs only elongated one digit: #4. It made a better wing than bug-in-the-leaf-litter trap.
The terrestrial model
is Lamarckian, growing bigger wings to catch insects just out of reach for most is not good science.
Figure 5. Cosesaurus forelimb with pro to-aktinofibrils trailing the ulna.

Figure 6. Cosesaurus forelimb with pro to-aktinofibrils trailing the ulna.

Sexy
The valid hypothesis for bird and pterosaur wing evolution is competitive attractiveness during mate selection (think birds-of-paradise) with cosesaur-like creatures flapping and displaying. BTW, both Cosesaurus and Longisquama are preserved with membranes trailing finger 4, (Fig. 6) which folds in the plane of the wing in Longisquama (Fig. 7).

Figure 7. Click to enlarge. The origin of the pterosaur wing and the migration of the pteroid and preaxial carpal. A. Sphenodon. B. Huehuecuetzpalli. C. Cosesaurus. D. Sharovipteryx. E. Longisquama. F-H. The Milan specimen MPUM 6009, a basal pterosaur.

Not to be outdone,
Sharovipteryx (Fig. 8) had membranes (uropatagia) trailing each hind limb. These are reduced in pterosaurs, which continue to use their hind limbs as horizontal stabilizers, their feet as twin rudders, as the flapping forelimbs, closer to the center of gravity, become ever larger, better for display, then for short flapping hops, then for flight.
Figure 3. Sharovipteryx reconstructed. Note the flattened torso.

Figure 8. Sharovipteryx reconstructed. Note the flattened torso.

Another false statement corrected here:
The scapula of Scleromochlus (Fig. 1) was tiny. It only had to support a tiny forelimb with vestigial fingers.
Scleromochlus had a ‘square pelvis’
because it, too was a biped. But that was nothing compared to the larger pelvis of Cosesaurus (Fig. 9), which also had a prepubis, a pterosaurian trait not found on Scleromochlus. The pelvis of Sharovipteryx was larger still.
Figure 1. Cosesaurus flapping - fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

Figure 9. Cosesaurus flapping. Tere should be some bounce in the tail and neck, but that would involve more effort and physics.

Scleromochlus had a long muscular tail.
As in crocs and dinos, and most reptiles, the caudofemoral muscles were pulling the femur. Compare that with the attenuated tail of pterosaurs, Cosesaurus and Sharovipteryx. Only pelvic muscles were pulling the femur.
Back legs longer than front legs in Scleromochlus?
That’s what we also see in Cosesaurus, Sharovipteryx and Longisquama.
Cosesaurus and Rotodactylus, a perfect match.

Figure 10. Cosesaurus and Rotodactylus, a perfect match. Elevate the proximal phalanges along with the metatarsus, bend back digit 5 and Cosesaurus (left) fits perfectly into Rotodactylus (right).

Walking on its toes?
We have Rotodactylus ichnites (hand and footprints, Figs. 10, 11) that match Middle Triassic Cosesaurus in the Early Triassic. These include the impression of pedal digit 5 behind toes 1-4. Nothing else like them in the fossil record.
True!
Scleromochlus was like the modern jerboa, with its tiny vestigial hands, totally inappropriate as a pterosaur ancestor.
False!
Not all pterosaur tracks are quadrupedal. Only derived pterosaurs, those that frequented beaches were. We have bipedal pterosaur tracks (Fig. 12). See references below.
Cosesaurus foot in lateral view matches Rotodactylus tracks.

Figure 11. Cosesaurus foot in lateral view matches Rotodactylus tracks.

Quadrupedality in pterosaurs is secondary.
Note the backward pointing manual digit 3 in quad tracks. Note the fusion of four to thirteen sacrals into a sacrum and the elongation of the ilium to anchor large femoral muscles and anchor the increasingly larger sacrum in all pterosaurs. In order to flap, you have to be a biped.
Figure 1. Pteraichnus nipponensis, a pterosaur manus and pes trackway, matched to n23, ?Pterodactylus kochi (the holotype), a basal Germanodactylus.

Figure 12. Pteraichnus nipponensis, a pterosaur manus and pes trackway, matched to n23, ?Pterodactylus kochi (the holotype), a basal Germanodactylus.

All quad pterosaurs can be attributed to pterodactyloid-grade pterosaurs,
those that underwent phylogenetic miniaturization during the Jurassic. At that time, the fly-size hatchlings of the hummingbird-sized adults (Fig. 13) could not leave the moist leaf litter or risk desiccation until growing to a sufficient size. So they walked around on all fours until attaining flight size.
A hypothetical hatchling No. 6

Figure 2. A hypothetical hatchling No. 6 alongside a fly, a flea and the world’s smallest insect, a fairy fly (fairy wasp). The fairy wasp is shown enlarged here (scaled in red) and in figure 1.

True!
The extinction of pterosaurs can be attributed to their great size at the end of the Cretaceous. They had no tiny representatives, like they did at the end of the Jurassic, to weather the rapid climate changes and/or seek shelter.

References

For a cladogram that documents the family tree of pterosaurs see: http://ReptileEvolution.com/MPUM6009-3.htm
For a cladogram that documents pterosaur and dinosaur ancestors back to Silurian jawless fish see: http://ReptileEvolution.com/reptile-tree.htm
For fossils and reconstructions of pterosaur ancestors, see:
And here are all the peer-reviewed academic publications
that some pterosaur experts don’t want to talk about:
Peters D 2000a. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2000b. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
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 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141.

Revisiting the horn sharks Heterodontus and Belantsea

The last four days
have been spent reviewing the data on fish in the large reptile tree (LRT, 1578 taxa). Still not finished. Many changes and greater understanding happening now that there seems to be a critical mass of taxa and data present.

Meanwhile, here’s something you might find interesting…

FIgure 1. Ratfish (chimaera) and Heterodontus to scale.

FIgure 1. Ratfish (chimaera) and Heterodontus to scale.

Wikipedia reports, “The horn shark [genus: Heterodontus, Fig. 1] is a sporadic swimmer that prefers to use its flexible, muscular pectoral fins to push itself along the bottom.”

The LRT nests Heterodontus
with the odd chimaerid Belantsea (Fig. 2) at the base of the chimaerids, a sister clade to sharks and their kin. This taxon retains several gill slits, like its sister Heterodontus, distinct from most chimaerids. In prior studies workers counted the gill slits and considered horn sharks to be sharks. Readers know to beware of relying on one or a dozen traits. That is ‘pulling a Larry Martin‘. The LRT uses the ‘last common ancestor’ method for determining interrelationships.

Figure 2. Belantsea has several gill slits, like its sister, Heterodontus.

Figure 2. Belantsea has several gill slits, like its sister, Heterodontus. Compare to figure 3.

Wikipedia also reports, “The bullhead sharks are a small order (Heterodontiformes) of modern sharks (Neoselachii). The nine living species are placed in a single genus, Heterodontus, in the family Heterodontidae. All are relatively small, with the largest species reaching just 1.65 metres (5.5 ft) in maximum length. They are bottom feeders in tropical and subtropical waters.

Figure 3. Heterodontus skull.

Figure 3. Heterodontus skull from Digimorph.org and used with permission. Colors added. Compare to figure 2.

The Heterodontiforms appear in the fossil record in the Early Jurassic, well before any of the other Galeomorphii, a group that includes all modern sharks except the dogfish and its relatives. However, they have never been common, and their origin probably lies even further back.

The bullhead sharks are morphologically rather distinctive. The mouth is located entirely anterior to the orbits. Labial cartilages are found in the most anterior part of the mouth. Nasoral grooves are present, connecting the external nares to the mouth. The nasal capsules are trumpet-shaped and well-separated from orbits. Circumnarial skin folds are present, but the rostral process of the neurocranium (braincase) is absent, although a precerebral fossa is present. Finally, the braincase bears a supraorbital crest.

The eyes lack a nictitating membrane. A spiracle is present, but small. The dorsal ends of the fourth and fifth branchial arches are attached, but not fused into a “pickaxe” as in lamniform sharks. Heterodontiforms have two dorsal fins, with fin spines, as well as an anal fin. The dorsal and anal fins also contain basal cartilages, not just fin rays.”

The horn sharks
are basal to chimaerids in the LRT. Belantsea is a horn shark in the LRT. Let me know if these contributions to paleontology were published earlier and I will provide the citation.


References

wiki/Bullhead_shark
wiki/Horn_shark
wiki/Belantsea

https://pterosaurheresies.wordpress.com/2019/06/08/belantsea-an-odd-early-carboniferous-ratfish/

https://pterosaurheresies.wordpress.com/2019/08/05/heterodontus-more-ratfish-than-shark/

 

Hongshanxi: just barely NOT a squamate

Updated July 7, 2020
the LRT moves Meyasaurus, Indrasaurus and Hoyalacerta to the base of the Yabeinosaurus + Sakurasaurus clade within the Scleroglossa and Squamata.

Dong, Wang, Mou, Zhang and Evans 2019 bring us
Hongshanxi xidi, a tiny, new and rare, complete, articulated and flattened Oxfordian (earliest late) Jurassic lepidosaur the authors had difficulty nesting with both traits and molecules.

In happy contrast,
the large reptile tree (LRT 1578 taxa) recovers Hongshanxi as the proximal outgroup to the clade Squamata, between Liushusaurus (Evans and Wang 2010) Early Cretaceous, ~10 cm) and IguanaEuposaurus cirinensis (Lortet 1892, MHNL 15681, Late Jurassic, Kimmeridgian, 155 mya, 3.5cm snout vent length) without firsthand observations.

Figure 1. Hongshanxi in situ with DGS colors added to pectoral region.

Figure 1. Hongshanxi in situ with DGS colors added to pectoral region.

From the abstract
It [Hongshanxi] is distinguished from other Jurassic-Cretaceous lizards by a unique combination of derived characters, notably a long frontal with posterior processes that clasp the short parietal; cranial osteoderms limited to the lower temporal and supraocular regions; and an elongated manus and pes. Phylogenetic analysis using morphological data alone places the new taxon on the stem of a traditional ‘Scleroglossa’, but when the same data is run with a backbone constraint tree based on molecular data, the new taxon is placed on the stem of Squamata as a whole. Thus its position, and that of other Jurassic and Early Cretaceous taxa, seem to be influenced primarily by the position of Gekkota.”

Figure 2. Hongshanxi skull with DGS colors added.

Figure 2. Hongshanxi skull with DGS colors added.

Unfortunately
Dong et al. were using an outdated and incomplete taxon list, that of Gauthier 2012 (610 characters, 192 taxa) with maybe a dozen additional Early Cretaceous taxa described since then. The authors report, “However, as with many other Jurassic and early Cretaceous taxa (e.g. Scandensia, Yabeinosaurus, Hoyalacerta, Liushusaurus), the phylogenetic position of Hongshanxi n. gen. cannot be clearly resolved.”

That may be because the authors do not understand that a series of lepidosaurs preceded the Squamata. These predecessors include the pterosaur clade, Tritosauria. In the LRT the Lepidosauria is completely resolved with high Bootstrap values at nearly all nodes with the addition of Hongshanxi, which looks quite a lot like its nearly coeval sister taxa and is similar in size and location.

Figure 3. Hongshanxi pelvic region in situ with DGS colors added

Figure 3. Hongshanxi pelvic region in situ with DGS colors added

The authors also do not realize
they cannot rely on molecular studies to clarify relationships in deep time. The solution to these problems is online, the LRT, ready for anyone to use. If workers want to continue ‘spinning their wheels’ recovering no clear solutions, that’s to the detriment of our science.

Oddly
the hands and feet of Hongshanxi are elongate, like their arboreal sisters, but the penultimate phalanges are shorter than the more proximal phalanges, distinct from their arboreal sisters. The torso is short relative to the femur length. The authors correctly note the very odd lack of a straight frontal-parietal suture. Also very odd is the open acetabulum (hip joint), which was overlooked by the authors.


References
Dong L, Wang Y, Mou L, Zhang G and Evans SW 2019. A new Jurassic lizard from China in Steyer J.-S., Augé M. L. & Métais G. (eds), Memorial Jean-Claude Rage: A life of paleo-herpetologist. Geodiversitas 41 (16): 623-641. https://doi.org/10.5252/geodiversitas2019v41a16.

http://geodiversitas.com/41/16

 

New PBS Eons video on “When Bats Took Flight”

Well, they got the ‘when” kind of right.
Unfortunately, the PBS team had no idea how, who, or why bats took flight.

The following is my summary comment
buried deeper on the PBS YouTube page with each passing hour and day:

“With phylogenetic analysis based on traits we know the ancestors of bats back to jawless fish. Currently Zhangheotherium, a basal pangolin, and Chriacus are proximal outgroups to bats. (see link below). DNA fails too often in deep time experiments (e.g. Laurasiatheria: camels, whales, etc.)

“The best way to understand the genesis of bat flght is to compare it to the colugo, which leaps from its perch and glides for distance using membranes stretched between long limbs. These membranes were coopted from an extended marsupium, a place to keep newborns safe in these very basal placentals not far from their marsupial ancestors. Colugos, like many primitive placentals, also hang upside down, but with four very long limbs and small fingers.

“By contrast bats are inverted bipeds with membranes stretched between elongate fingers and short hind limbs. They don’t fly like birds and pterosaurs do. Instead they push pulses of air down with their huge parachute-like wings and huge pectoral muscles. When pre-bats hung inverted from low branches, they were able to survey the leaf litter below, ready to pounce on insects and worms rustling in the leaves on the ground. The distance could have started at 10cm, then extended to a meter, then 10 meters. So that is where hyper-acute hearing first developed.

“Instead of leaping from tree to tree, pre-bats dropped straight down onto their prey. To slow their fall, they flapped their large parachute-type hands. These became larger over time. Embryo bats with big hands recapitulate the evolution of bats. Leaf litter provided a soft landing for the tiny parachuting pre-bats, but over time flapping before crashing slowly turned into hovering for accuracy inches above the leaf litter before pouncing. Some bats still do this today. Over still more time, improved hovering became flight.

“After flight, returning to their inverted roost was so much safer, due to no more tree trunk climbing.”

More details, images and links here: https://pterosaurheresies.wordpress.com/2018/06/18/the-origin-and-evolution-of-bats-part-4-distance-vs-accuracy/

The origin of bats is by far the most popular topic
here at PterosaurHeresies. Use keyword [bats] in the box above to find out more.

Cryodrakon boreas: new Canadian azhdarchid: pt. 2

Hone, Habib and Therrien 2019
bring us news of several bones from several individuals of various sizes of a new mid-sized Canadian azhdarchid, Cryodrakon boreas (Fig. 1). Earlier today we looked at the promotional materials for this paper. Now, praise and criticism for the authors.

The name is excellent.
“Cryodrakon derived from the Ancient Greek for ‘cold’ and ‘dragon,’ boreas from the Greek god of the north wind. This is therefore the ‘cold dragon of the north winds.’”

The authors uncritically cite Wellnhofer 1970 who,
“suggested that the cervical vertebrae of azhdarchids elongate during ontogeny (i.e., show positive allometry). If correct, this can make identification of positions of individual vertebrae, and comparisons between specimens and taxa, difficult when specimens are small.” 

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

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

Unfortunately,
this reliance on citation shows the authors’ lack of understanding about pterosaur isometric (lepidosaur-like) growth patterns, proven by the several growth series demonstrated in the azhdarchid, Zhejiangopterus (which they cite, Fig. 1), Rhamphorhynchus (the subject of a rejected paper), and Pterodaustro (not to mention the several pterosaur embryos known).

The authors discuss a very large cervical mid-shaft,
TMP 1980.16.1367, but do not show it. Dang.

The most complete specimen of Cryodrakon
TMP 1992.83 includes several disarticulated bones (Fig. 2) here reduced to x.70 to match tibias to scale with Quetzalcoatlus sp.

Figure 2. The most complete Cryodrakon compared to the most complete Q. sp. Most elements are identical in size when scaled x.70 to match tibia lengths, but the cervical, metatarsal and humerus are relatively smaller in Cryodrakon.

Figure 2. The most complete Cryodrakon compared to the most complete Q. sp. Most elements are identical in size when scaled x.70 to match tibia lengths, but the cervical, metatarsal and humerus are relatively smaller in Cryodrakon.

Bone thickness
The authors report, “A break in the humerus of Quetzalcoatlus sp. (TMM 47180) reveals that cortical bone thickness [1.07mm] is near identical to that of Cryodrakon [1.1-1.3mm] (for which cortical bone thickness data were obtained by computed tomography [CT] imaging).” Note that the cortical thickness ratio (x 0.82) nearly matches the scale difference x 0.70). Fact: Large flightless azhdarchids are not evolving more solid bones, distinct from giant flightless birds.

Back to the humerus
The authors report, “Overall, the humeri of Cryodrakon and Quetzalcoatlus are quite similar, varying in most proportions within the range that would be expected for intraspecific comparisons.” The images of both (Fig. 2) do not support that statement. The authors conclude, “The greatest difference in overall shape is the slightly exaggerated flaring of the humerus distally in Quetzalcoatlus.” 

You decide what the differences are.
The authors should have showed the two humeri side-by-side.

Flight
The authors report, “These similarities confirm that Cryodrakon and Quetzalcoatlus were likely of very similar size and build, and the two species likely shared similar flight performance characteristics and flight muscle fractions.” This assumes that azhdarchids of this size could fly, regardless of the vestigial distal wing phalanges (= clipped wings) that argue against that hypothesis in Q. sp. (Fig. 2; wingtip unknown in Cryodrakon).

Weight
The authors report, “Combined with the somewhat greater length of the humerus in Cryodrakon, it is likely that Cryodrakon was slightly heavier than Quetzalcoatlus but that their overall mass was likely similar.” Yes! True? But not so fast. Scaled to a similar tibia, pteroid and metacarpal length, the feet, neck and humerus were all smaller (Fig. 2). Then remember: to achieve that scale Cryodrakon was reduced to x 0.70 from its original size. So Cryodrakon had big legs, big hands, small feet (used as twin rudders in smaller taxa), a slender humerus… not really the traits you’re looking for in a volant pterosaur (by comparison, see Jidapterus below). Finally, weight is never the issue if you have plenty of thrust and lift. But those two factors are reduced in large azhdarchids, all of which had clipped wings (vestigial distal phalanges).

Cervical comparisons and bauplan
The authors report, “The cervical vertebrae of Cryodrakon are absolutely more robust than those of Quetzalcoatlus.” No. They are relatively smaller (Fig. 2). See for yourself.

It really does help to follow the scale bars,
placing the bones upon a good Bauplan (blueprint) to see how incompletely known taxa compare to more completely known taxa. This last graphic step is something the authors did not provide or experiment with. If they had done so, they would not come to such conclusions. The referees (Drs. Martill, Naish and Bever) could also have raised these issues or suggested graphic experiments (Fig. 2).

Cladistic analysis
The authors report, “The fragmentary nature of the material available, and possible ontogenetic trajectories, prevents us from conducting a cladistic analysis to determine the phylogenetic relationships of Cryodrakon boreas. Nevetheless, certain characteristics permit a preliminary assessment of the phylogenetic position of the taxon within Azhdarchidae. For example, it does lack distinct cervical zygapophyses for the middle cervicals, a trait that suggests that it does not lie within basal-most Azhdarchidae, but instead within the Jidapterus-Quetzalcoatlus clade.”

Figure 1. Jidapterus compared to the new Lower Cretaceous pterosaur tracks. It's a pretty close match.

Figure 3. Jidapterus compared to the new Lower Cretaceous pterosaur tracks. It’s a pretty close match.

Since the authors brought up Jidapterus
it is worth our while to see for ourselves the relative size of its humerus and wing in this small azhdarchid (Figs. 3,4). Note the relatively larger humerus in Jidapterus. Only wing phalanx 4.4 is shorter here, with a folded wing that extends higher than the shoulder girdle, distinct from the much larger flightless azhdarchids.

Azhdarchids and Obama

Figure 4. Click to enlarge. Here’s the 6 foot 1 inch President of the USA alongside several azhdarchids and their predecessors. Most were knee high. The earliest examples were cuff high. The tallest was twice as tall as our President. This image replaces an earlier one in which a smaller specimen of Zhejiangopterus was used.

Jidapterus and Chaoyangopterus represent the transitional ‘end of the road’
for flying in azhdarchids. What follows (Fig. 4) are shorter distal wings and much larger flightless taxa.

Let’s put an end to the myth
that large azhdarchids were the largest flying animals of all time, a myth promoted by pterosaur paleontologists who should know better, but have staked their professional reputations on showmanship (rather than science).  We still have long-winged pteranodontids and ornithocheirids to compete with long-winged Pelagoris, among the largest bird aviators. That’s the Bauplan nature insists on if you’re a big flyer.


References
Hone DWE, Habib MB and Therrien F 2019. Cryodrakon boreas, gen. et sp. nov., a Late Cretaceous Canadian azhdarchid pterosaur. Journal of Vertebrate Paleontology Article: e1649681 DOI: 10.1080/02724634.2019.1649681

www.nationalgeographic.com
www.newsweek.com

Cryodrakon boreas: new Canadian azhdarchid

Hone, Habib and Therrien 2019
bring us news of several bones from several individuals of various sizes of a new Canadian azhdarchid, Cryodrakon boreas (Fig. 1).

From the NatGeo webpage:
“For a long time [30+ years] paleontologists had instead assumed that the fossils belonged to a pterosaur called Quetzalcoatlus northropi [Figs. 1, 2], says study coauthor Dave Hone, a paleontologist at Queen Mary University of London.”

Figure 1. Cryodrakon humerus compared to Q sp. specimen (the small one). Yes, they are different. Zhejiangopterus also has a straight humerus shaft.

Figure 1. Cryodrakon humerus compared to Q sp. specimen (the small one). Yes, they are different. Zhejiangopterus also has a straight humerus shaft.

Here it took less than 2 minutes
to compare the humerus of Cryodrakon to that of Quetzalcoatlus (Fig. 1). Yes, they are different. Zhejiangopterus (Fig. 3) also has a straight humerus, like that of Cryodrakon.

Figure 1. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

Figure 2. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

From the Royal Tyrrell Museum webpage:
“The partial skeleton represents a young animal with a wingspan of about five metres, but one isolated giant neck bone from another specimen suggests that Cryodrakon could have reached a wingspan of around 10 metres when fully grown.”

Partial skeleton =
part of the wings, legs, neck and a rib. So, not a lot, but enough.

Figure 2. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

Figure 3. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.) On second look, perhaps less elbow and knee bend here.

Looking forward to learning more
about Cryodrakon after reading the paper. All the above comes from online promotional materials.


References
Hone DWE, Habib MB and Therrien F 2019. Cryodrakon boreas, gen. et sp. nov., a Late Cretaceous Canadian azhdarchid pterosaur. Journal of Vertebrate Paleontology Article: e1649681 DOI: 10.1080/02724634.2019.1649681

www.nationalgeographic.com
www.newsweek.com

A revised origin of flatfish in the LRT

Revised February 02, 2021
when the bluefish, Pomatomus, entered the LRT basal to flatfish. Click here to view.

Friedman 2008 described an asymmetric Eocene fish,
Heteronectes, which he described as “the most primitive pleuronectiforms known” due to the incomplete migration of the lower orbit. Heteronectes will be added to the LRT soon.

Symmetrical hatchlings
are planktonic, swimming closer to the surface. They require sunlight to swim upright, so at night hatchlings swim erratically.

According to a BMC blog by Christopher Foote
flatfish experts, “Friedman and Schreiber think that the flatfish’s anatomical makeover followed a change in its behavior. When threatened, some modern fish are known to lie flat on their side on the seafloor and briefly bury themselves in the sand. Others tip over to play possum, only to leap up and snatch unsuspecting prey. Perhaps the flatfish’s predecessor was a bilateral open water fish particularly adept at this kind of stealth.”


References
Friedman M 2008. The evolutionary origin of flatfish asymmetry. Nature 454:209–212.
Friedman M 2012. Osteology of †Heteronectes chaneti (Acanthomorpha, Pleuronectiformes), an Eocene stem flatfish, with a discussion of flatfish sister-group relationships. Journal of Vertebrate Paleontology (32) 4: 735-756; doi: 10.1080/02724634.2012.661352
Harrington RC, et al. (6 co-authors) 2016. Phylogenomic analysis of carangimorph fishes reveals flatfish asymmetry arose in a blink of the evolutionary eye. BMC Evolutionary Biology 16 (224).

wiki/Spiny_turbot
wiki/Flatfish

News articles:
sci-news.com/paleontology/article00431.html
bmcevolbiol.biomedcentral.com/articles/10.1186/s12862-016-0786-x
pbs.org/wgbh/nova/article/flatfish-evolution/

Coccocephalichthys enters the LRT

Updated September 1, 2021
with the shifting of taxa based on new skull identities, plus the addition of several more closely related taxa. See the large reptile tree for the latest updates, not always repaired here.

Coccocephalichthys wildi (originally Coccocephalus wildi Watson 1925; Whitley 1940; Poplin and Véran 1996; Late Carboniferous; Fig. 2) was originally considered a palaeoniscid, like Cheirolepis.

Figure 2. Coccocephalichthys (formerly Coccocephalus) is a Late Carboniferous transitional taxon between Devonian Strunius and Cretaceous Saurichthys.

Figure 2. Coccocephalichthys (formerly Coccocephalus) is a Late Carboniferous transitional taxon

In the large reptile tree (LRT, 1569 taxa) Late Carboniferous Coccocephalichthys among the paleoniscids. Several bones are re-identified above based on tetrapod homologs.

Most of the time,
this is how the LRT grows, by adding new transitional taxon between two presently tested taxa. In this case, the transitional taxon neatly helps illustrate the evolution that occurred between the two extremes. Using tetrapod labels (Fig. 2) has proven to help us understand the identity of facial bones in these fish.

Using colors to identify bones
is something I started doing in the vampire pterosaur, Jeholopterus (see header above, far right) in 2003. I was wondering if someone could send me an earlier example of this graphic technique? Today it seems to be growing in popularity, especially so since there are no additional color charges for papers published online.


References
Poplin C and Véran M 1996. A revision of the actinopterygian fish Coccocephalus wildifrom the Upper Carboniferous of Lancashire. In Milner, A. R. (ed.) Studies on Carboniferous and Permian vertebrates. Special Papers in Palaeontology 52: 7-29.
Watson DMS 1925. The structure of certain palæoniscids and the relationships of that group with other bony fish. Proceedings of the Zoological Society of London, 54: 815–870.
Whitley GP 1940. The Nomenclator Zoologicus and some new fish names. Australian Naturalist, 10:241–243.

wiki/Strunius
wiki/Thunnus
wiki/Cheirodus
wiki/Mimipiscis
wiki/Coccocephalichthys

Saturnalia skull parts!

Bronzati, Müller and Langer 2019 bring us
additional skull data for the basal sauropodomorph, Saturnalia tupiniquim (Fig. 1).

FIgure 1. GIF movie of Saturnalia skull as originally restored and using phylogenetic bracketing to restore a longer rostrum and teeth only anterior to the orbit.

FIgure 1. GIF movie of Saturnalia skull as originally restored and using phylogenetic bracketing to restore a longer rostrum and teeth only anterior to the orbit.

Saturnalia tupiniquim (Langer et al. 1999) Carnian, Late Triassic period, ~225 mya, 1.5 m in length, was one of the oldest true dinosaurs yet found. It was basal to the clade Prosauropoda, 

Figure 1. Grallator illustration from Li et al. 2019 with two basal phytodinosaur possible sisters to the track maker, Pampadromaeus and Saturnalia.

Figure 2. Grallator illustration from Li et al. 2019 with two basal phytodinosaur possible sisters to the track maker, Pampadromaeus and Saturnalia.

The skull was recently described (Bronzati, Müller and Langer 2019). It had a large orbit, like Pantydraco. More cervicals were present and each one was elongated, creating a much longer neck. The scapula was narrow in the middle. The forelimbs were more robust with a large deltopectoral crest on the humerus. The hind limbs were more robust. The calcaneum did not have such a large tuber.

Figure 2. Subset of the LRT focusing on the Phytodinosauria.

Figure 3. Subset of the LRT focusing on the Phytodinosauria.

Adding scores to Saturnalia
provided an opportunity to review scores for other phytodinosaurs in the large reptile tree (LRT, 1568 taxa). These changes resulted in small modifications to the tree topography and higher Bootstrap scores (Fig. 2). Basal phytodinosaurs still give rise to the clades Sauropodomorpha and Ornithischia.


References
Bronzati M, Müller RT, Langer MC 2019. Skull remains of the dinosaur Saturnalia tupiniquim (Late Triassic, Brazil): With comments on the early evolution of sauropodomorph feeding behaviour. PLoS ONE 14(9): e0221387. https://doi.org/ 10.1371/journal.pone.0221387
Langer MC, Abdala F, Richter M, and Benton M. 1999. A sauropodomorph dinosaur from the Upper Triassic (Carnian) of southern Brazil. Comptes Rendus de l’Académie des Sciences, 329: 511-517.
Langer MC 2003. The pelvic and hind limb anatomy of the stem-sauropodomorph Saturnalia tupiniquim (Late Triassic, Brazil). PaleoBios, 23(2): 1-30.

wiki/Saturnalia