You heard it here first: Small Tanystropheus specimens were adults, too.

Spiekman et al. 2020
used bone histology and µCT scans to determine that small Tanystropheus specimens (Fig. 1) were also adults. Six years ago, the large reptile tree (LRT, 1722+ taxa) determined the same thing using phylogenetic bracketing. That’s because…

Tanystropheids are tritosaur lepidosaurs, not archosauromorphs. 
In this clade, from Huehuecuetzpalli to Zhejiangopterus, hatchlings and juveniles are identical to adults, except for size. In other words tritosaur lepidosaurs grow isometrically (Peters 2018). Thus: differences indicate distinct genera. Spiekman et al. did not discuss this aspect of tanystropheids.

Figure 1. Tanystropheus and kin going back to Huehuecuetzpalli.

Spiekman et al. note:
“The configuration of the temporal region of Tanystropheus differs strongly from that of other early archosauromorphs.” 

Stuck in their traditional groove,
Spiekman et al. did not realize that tanystropheids are lepidosaurs (Peters 2007, 2011, 2018). They perpetuated the myth that tanystropheids and the similar, but unrelated Dinocephalosaurus were archosauromorphs (Fig. 2). The authors cited Pritchard et al. 2015, whose study included data from Nesbitt 2011, which was shown to be so poorly scored that Nesbitt’s cladogram changed radically after corrections were made earlier in a nine-part series ending here. Nesbitt’s repaired cladogram matched the LRT.

Spiekman et al. provided a cladogram
of interrelations (Fig. 2) that suffers from massive taxon exclusion and poor scores when compared to the LRT (Fig. 3). Spiekman et al. mix archosauromorphs with lepidosauromorphs, separates Protorosaurus from Prolacerta, separates some rib gliders from other rib gliders and matches little gliding Icarosaurus with big non-gliding Trilophosaurus among other red flags.

Figure 2. Cladogram from Spiekman et al. 2020. Colors added here to show mixing of archosauromorphs and lepidosauromorphs from the LRT. Gold taxa (at right) are tritosaurs in the LRT.

Trimming the LRT to match the taxon list in Spiekman et al. 2020
(Fig. 3) results in a topology that cleanly separates lepidosauromorphs and archosauromorphs… and the tritosaur lepidosaurs, including Huehuecuetzpalli, nest together.

Figure 3. LRT reduced to Spiekman et al. taxon list. Archosauromorpha – blue. Lepidosauromorpha – yellow. Tritosauria in amber.

Spiekman et al. report,
“A quadratojugal is identified confidently for the first time in Tanystropheus.” Actually that misidentified right-angle splint of bone is an ectopterygoid (Fig. 4). What Spiekman et al. identified as an ectopterygoid is instead a crushed anterior cervical (Fig. 4).

Figure 4. Identifying the quadratojugal as an ectopterygoid, and the ectopterygoid as a short anterior cervical.

A real quadratojugal 
was confidently identified in another specimen of Tanystropheus back in 2003 (Fig. 5). As in related taxa, including pterosaurs, the tritosaur quadratojugal is a small sharp extension of the posterior process of the jugal.

Figure 5. Skull of specimen Q of Tanystropheus. Only an arrow was added to show the location of the quadratojugal first identified in 2003.

To distinguish the large and small tanystropheids,
the team named the bigger one T. hydroides, after the hydra in Greek mythology. Its smaller cousin kept the original species name of T. longobardicus. If they were going to do this, they should have done it right and split the several large specimens apart, as done here in 2014 (Fig. 6).

Figure 6. Tanystropheus with skull reconstructions based on two specimens, exemplar i and exemplar m.

Bone growth rings
revealed to Spiekman et al. the smaller Tanystropheus were indeed adults, making it fairly clear that what the researchers had on their hands were two separate species, confirming results from six years ago.

Breathing
“The reptile’s skull has its nostrils perched on top, much like a crocodile’s snout – just the thing for an ambush predator to keep a lung full of air while waiting for a meal to pass by.”

This is not news. We’ve known large tanystropheids had such nostrils since at least Wild 1973. The breathing regime would have taken place as described earlier for the unrelated, but overall similar Dinocephalosaurus (Peters, Demes and Krause 2005, not cited in Spiekman et al. 2020).

Configuration
“We can now almost imagine the animal’s squat, croc-like body lying against the floor of a shallow coastline some 242 million years ago, its head rising high up to the surface so its nostrils can siphon down air, its bristling mouth slightly agape in anticipation of a stray squid to stumble by.”

This is not news either. As shown earlier with Dinocephalosaurus, the air bubble in the throat would have a difficult time moving down toward the deeper lungs while submerged without assuming a horizontal configuration, whether at the surface or sea floor, for at least that portion of the respiratory cycle. Exhaling would have been no problem in a vertical configuration. Consider the possibility of an exhaled bubble net, giving the long trachea another use: for stale air storage.

Cervicals
“Part of its oddness is the shape of the neck bones. Unlike those in a snake or lizard, the cervical vertebrae in Tanystropheus fossils are stretched out like a giraffe’s.

This is not news either. Spiekman et al. noted a diet of squid, but overlooked tanystropheids lived in crinoid forests. So, tanystropheids could have been crinoid stem mimics as shown earlier in 2012 (Fig. 7). Spiekman et al. did not discuss this possibility. Nor did he discuss why two anterior chevrons on Tanystropheus were exceptionally large. Standing as a biped these chevrons would have created a tripodal set-up for Tanystropheus.

Figure 7. Tanystropheus in a vertical strike elevating the neck and raising its blood pressure in order to keep circulation around its brain and another system to keep blood from pooling in its hind limb and tail.

Pterosaur homologies
“In fact, when its remains were first uncovered in 1852, the scattered bones were assumed to be the elongated wing bones of a flying pterosaur.”

Tanystropheids also have feet identical to basal fenestrasaurs and pterosaurs with a short metacarpal 5 and elongate p5.1 (Fig. 8). Only the tanystropheid cervicals were thought to be pterosaur wing bones in 1852. Not sure why no one other than Peters (2000a, b) included pterosaurs in tanystropheid studies and vice versa.

Figure 8. The best matches to Prorotodactylus and Rotodactylus. In this case, something between a small Tanystropheus and an even smaller Cosesaurus provides the best matches in all regards. These taxa were not even mentioned by Niedwiedcki et al. (2013) and skeletal fossils are known from geographically and chronologically similar sediments.

A valid phylogenetic context is key to understanding 
what a taxon is. Spiekman et al. lacked this understanding and context despite having seven co-authors, many with PhDs. Adding taxa and correcting scores clarifies all issues. Borrowing analyses perpetuates myths. Citing competing hypotheses might have helped this paper. Their µCT scans did not prevent them from including two mis-identifications, (noted above).

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References
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
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, Demes B and Krause DW 2005. Suction feeding in Triassic Protorosaur? Science, 308: 1112-1113.
Pritchard AC, Turner AH, Nesbitt SJ, Irmis RB and Smith ND 2015. Late Triassic tanystropheids (Reptilia, Archosauromorpha) from Northern New Mexico (Petrified Forest Member, Chinle Formation) and the biogeography, functional morphology, and evolution of Tanystropheidae. Journal of Vertebrrate Paleontology 35, e911186.
Spiekman SNF et al. (6 co-authors) 2020. Current Biology 30:1–7. https://doi.org/10.1016/j.cub.2020.07.025
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus (Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-162 plus plates.

https://pterosaurheresies.wordpress.com/2019/11/28/new-tanystropheid-paper-promotes-archosauromorph-myth/

https://pterosaurheresies.wordpress.com/2019/12/19/spiekman-and-scheyer-2019-discuss-variation-in-tanystropheus/

https://pterosaurheresies.wordpress.com/2014/10/17/the-many-faces-of-tanystropheus/

https://www.sciencealert.com/half-of-this-ancient-reptile-s-body-is-made-of-neck-and-we-now-know-how-it-used-it

From October 2018:
researchgate.net/publication_A_new_lepidosaur_clade_the_Tritosauria

From September 2011:
https://pterosaurheresies.wordpress.com/2011/09/22/the-tritosauria-an-overlooked-third-clade-of-lizards/

Mid-sized Changyuraptor nests between big Ornitholestes and small Microraptor in the LRT

Han et al. 2014 brought us a new feathered theropod,
Changyuraptor yangi (Aptian, Early Cretaceous, HG B016). In the large reptile tree (LRT, 1720+ taxa) Changyuraptor nests between a bigger Ornitholestes and a smaller Microraptor… in that order (from big to medium to small).

By contrast
Han et al. nested Changyuraptor in unresolved nodes with Microraptor and others (see below), all close to dromaeosaurids and several nodes apart from Ornitholestes.

Figure 1. Changyuraptor reconstructed.

Changyuraptor is not so much a giant microraptorine
as a small ornitholestid. At least that’s the phylogenetic order.

Flapping?
Stem-like locked-down coracoids (= narrower, not taller) are traits that indicate flapping in Changyuraptor. Maybe it was a little too big to fly. That would have to wait for Microraptor and Sinornithosaurus. Even so, that extra thrust might have added speed to running. The display function would have given it a good bluff or a seductive show.

Figure 2. Changyuraptor to scale with Ornitholestes, Scriurumimus and Microraptor.

From the abstract:
“Microraptorines are a group of predatory dromaeosaurid theropod dinosaurs with aerodynamic capacity.”

By contrast the LRT nests microraptorines as bird mimics, closer to Ornitholestes than to dromaeosaurids and troodontids. Elongate coracoids were overlooked by Han et al. So this clade was flapping long flight feathers symmetrically, as birds, pterosaurs and bats do, not just carrying them around for show.

“These close relatives of birds are essential for testing hypotheses explaining the origin and early evolution of avian flight.”

By contrast, in the LRT microraptors are phylogenetically bird mimics, unrelated to the avian lineage.

“Here we describe a new ‘four-winged’ microraptorine, Changyuraptor yangi, from the Early Cretaceous Jehol Biota of China. With tail feathers that are nearly 30 cm long, roughly 30% the length of the skeleton, the new fossil possesses the longest known feathers for any non-avian dinosaur. Furthermore, it is the largest theropod with long, pennaceous feathers attached to the lower hind limbs (that is, ‘hindwings’).”

In the LRT Changyuraptor is transitional both in size and morphology between Ornitholestes and microraptorines. Earlier, without Changyuraptor, Ornitholestes and microraptorines nested together in the LRT.

“The lengthy feathered tail of the new fossil provides insight into the flight performance of microraptorines and how they may have maintained aerial competency at larger body sizes. We demonstrate how the low-aspect-ratio tail of the new fossil would have acted as a pitch control structure reducing descent speed and thus playing a key role in landing.”

On this topic, the coracoids of Changyuraptor and microraptorines are relatively small (smaller than in the chicken, Gallus) and Changyuraptor is relatively large. Plus Han et al. also overlooked the large sternum on Changyuraptor, but it lacks a ventral keel (distinct from Gallus). These traits indicate relatively small pectoral muscles, just barely suitable for weak flapping, but inadequate for flight on this mid-sized theropod. So Changyuraptor would have been a runner, not a flyer. Thus the feathered tail would not have needed pitch control if it stayed on ‘the runway.’ Perhaps, along with raised feathered elbows, raised tail feathers might have served as secondary sexual traits or bluffs designed to increased apparent size to marauding predators.

“Diagnosis. A microraptorine dromaeosaurid theropod characterized by having the unique combination of traits: furcula more robust than that of Sinornithosaurus millenii and much larger than that of Tianyuraptor ostromi;

The LRT nests Tianyuraptor basal to tyrannosaurids along with Zhenyuanlong. Clavicles are separate and small elements in Ornitholestes, so the larger clavicles in Changyuraptor support the elongate coracoids.

“forelimb proportionally much longer when compared with hindlimb than in other microraptorines;

Figure 3. Changyuraptor limbs to scale. Distinct from sister taxa, this taxon has a long forelimb.

True. Both Ornitholestes and Microraptor have relatively shorter fore limbs relative to the hind limbs.

“humerus much longer (>20% longer) than ulna as opposed to Microraptor zhaoianus, in which these bones are more comparable in length;”

The humerus of Changyuraptor is not >1.2x the ulna (Fig. 3), but the humerus of Ornitholestes (Fig. 4) is in that ratio range.

“metacarpal I proportionally shorter than in Sinornithosaurus millenii (1/4–1/5 versus 1/3);”

Metacarpal 1 is also shorter in Ornitholestes (Figs. 4, 5).

Figure 4. Ornitholestes nests as a sister to Sciurumimus, between Compsognathus and Microraptor.

Large, procumbent teeth
on a short skull can be seen even in ventral view on Changyuraptor.

Figure 5. Ornitholestes with a short metacarpal 1.

“well-developed semi-lunate carpal covering all of proximal ends of metacarpals I and II as opposed to the small semi-lunate carpal that covers about half of the base of metacarpals I and II in most other microraptorines;”

Not illustrated in Ornitholestes.

“manual ungual phalanx of digit II is the largest, followed by that of digits I andt III, as opposed to Graciliraptor lujiatunensis in which the ungual of manual digit I is very small, and Sinornithosaurus millenii and Microraptor zhaoianus in which the unguals of manual digits I and II are comparable in size;”

See Ornitholestes (Figs. 4, 5) for available comparisons.

“ischium shorter than in Microraptor zhaoianus;

Ischium length is difficult to assess due to overlying elements.

“midshaft of metatarsal IV significantly broader than that of metatarsal III or metatarsal II, as opposed to G. lujiatunensis in which metatarsal IV is the narrowest;”

Comparables are difficult to assess in Ornitholestes due to lost metatarsals.

“mid-caudals roughly twice the length of dorsals as in Sinornithosaurus millenii as opposed to long caudal vertebrae in Microraptor zhaoianus;”

In Changyuraptor the midcaudals are 1.5x the dorsals length, and Sinornithosaurus is comparable. Note that Ornitholestes has a similarly hyper elongate tail.

“fewer caudal vertebrae (22 vertebrae) than Microraptor zhaoianus (25–26 vertebrae) and Tianyuraptor ostromi (28 vertebrae);”

Ornitholestes has many more than 20 caudal vertebrae.

“rectories significantly longer than in other microraptorines.”

Rectories not preserved in Ornitholestes.

This clade of microraptorine bird mimics evolved
by phylogenetic miniaturization. The coracoids became elongate (= narrower, not taller) and locked down for minimal flapping, much less than in extant fowl.

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References
Han G, Chiapped LM, Ji S-A, Habib M, Turner AH, Chinsamy A, Liu X and Han L 2014. A new raptorial dinosaur with exceptionally long feathering provides insights into dromaeosaurid flight performance. Nature Communications DOI: 10.1038/ncomms5382

wiki/Changyurapator

 

Early Silurian Sinacanthus compared to Early Cretaceous Bonnerichthys

Zhu 1998 brought us a peek at Early Silurian vertebrates
represented by distinctive Sinacanthus fin-spines (Fig. 1). These were variously considered acanthodian-like and shark-like.

Zhu argues
“Sinacanths are one of the oldest known chondrichthyans (sharks + ratfish) rather than acanthodians, and their spines are the oldest known shark fin spines.”

Figure 1. Sinacanthus fin spine. Scale unknown.

No comparable fin spines are currently
documented among the sharks and their kin at ReptileEvolution.com. So I looked at other taxa. After seeing a comparable fin spine that belonged to the Late Cretaceous bony fish, Bonnerichthys (Figs. 2, 3), I wondered if Sinacanthus was similar enough? This time I’ll let you decide because…

Figure 2. Bonnerichthys pectoral fin for comparison.

…there is no way
the large reptile tree (LRT, 1720+ taxa) can nest this fin alone given its present set of characters, none of which lump and split fin details.

According to (P’an 1959, 1964)
Sinacanthus wuchangensis (MG.V103a) and its relatives have fins with 15 to 50 ridges per side. Acanthodians have fewer ridges generally, which is why Zhu et al. preferred allying those fins with elasmobranchs rather than acanthodians.

Zhu et al. present a diagnosis
“Sinacanths with long and slender fin spines; spine gradually tapering, recurved posteriorly and dagger-shaped.” 

Zhu documented the histology of sinacanths.
Given today’s observations, perhaps the histology of Bonnerichthys will be worth looking into and comparing it to Sinacanthus. There’s another project for a grad student!

Zhu goes on to say in their Remarks:
“Since the phylogeny of early elasmobranchs remains obscure, the diagnosis given above is more descriptive than phylogenetic.”

Actually the phylogeny of early elasmobranchs is clear in the LRT. Nevertheless, nothing quite like this fin spine has shown up yet in tested elasmobranchs,

Chronology
in the LRT Late Cretaceous Bonnerichthys phylogenetically precedes some derived Late Silurian taxa (e.g. Entelognathus, Qilinyu, Romundina and Guiyu). So maybe this chronology jump is another opportunity to explore for that grad student.

Figure 3. Late Cretaceous Bonnerichthys parts from Friedman et al. 2010 and colorized here.

Apparently the earliest radiation of fish clades
occurred during the Ordovician. Unfortunately only a few ‘armored lancelet’ fossils, like Arandaspis, have been found in Ordovician strata so far. The LRT indicates there are more fish and more derived fish waiting to be found in that early stratum.

Figure x. Subset of the LRT focusing on fish. Spiny sharks are related to osteoglossiformes here.

A little housekeeping note…
the skull of Pachycormus (Figs. 4, 5) has been reviewed, overhauled and this taxon is now happier in its new home (Fig. x) with Bonnerichthys, the extant arowana, Osteoglossum (Fig. 6) and two extinct pseudo-swordfish, Protosphyraena and Aspidorhynchus.

Figure 4. Pachycormus fossil. Vestigial pelvic fins seem to appear near the vestigial anal fin. See figure 2 for closeup of the skull. Note the extra set of spines medial to the spiny pectoral fins.

Still wondering if
those slender curved spines medial to the pectoral fins are pelvic fins or new structures? Normal pelvic fins are absent, but a long set of dorsal ribs suggests the anus is still just anterior to the anal fin, as in all related taxa. Osteoglossum (Fig. 6) seems to have posterior pelvic fins, but the skeleton does not show them. So the situation is confusing at present.

Figure 5. Pachycormus macropterus has a new skull tracing and reconstruction. Originally I did this without template or guidance. Tinkering. Now osteoglossiformes provide a good blueprint.

These osteoglossiformes/pachcormiformes
arise from spiny sharks, a novel hypothesis of phylogenetic relationships recovered by the LRT earlier.

Figure 6. The arowana (Osteoglossum) an Amazon River predator has posterior pelvic fins and no mid pectoral fins in life, but the skeleton does not show that. Confusing.

This fish phylogeny recovered by the LRT,
including certain taxa not traditionally included with certain other taxa (Fig. x), is a novel hypothesis of interrelationships awaiting confirmation from an independent study with another character list, but a similar taxon list.

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References
P’an K 1959. [Devonian fish fossils of China and their stratigraphic and geographic distributions.] Monographic summary of basic data on Chinese geology 1:1–13 [in Chinese].
Zhu M 1998. Early Silurian sinacanths (Chondrichthyes) from China. Palaeontology 41(1):157–171.

Tuatara genes provide false-positive links to mammals

Preamble:
Genomic (gene) studies think they are unlocking secret doors
to understanding vertebrate interrelationships. Sometimes they do the opposite. Wide gamut phenomic (trait) studies show that gene studies over deep time introduce invalid hypotheses of interrelationships. So, worse than useless, gene studies (like today’s example) confuse readers and workers with false positives, false hopes that claim to be true, but are not valid when put to the test.

So why are they published?
Because gene studies work great over shallow time. Ask any prosecutor or Ancestry.com.

Figure 1. The dorsal spines of Tuatara (Sphenodon).

Gemmell and Rutherford et al. 2020 report:
“The tuatara (Sphenodon punctatus)… [is] A key link to the now-extinct stem reptiles (from which dinosaurs, modern reptiles, birds and mammals evolved), the tuatara provides key insights into the ancestral amniotes.”

In a competing phenomic study (the large reptile tree, LRT, 1717+ taxa; Fig. 2) the lepidosaur, Sphenodon (Fig. 1), is simply the last living proximal outgroup taxon to living squamates. On the other hand, tuataras and mammals share a last common ancestor all the way back in the Viséan, at the last common ancestor of all reptiles, Silvanerpeton.

Figure 2. Gemmell and Rutherford cladogram compared to LRT (with taxon list greatly reduced to match Gemmell and Rutherford).

Gemmell and Rutherford et al. continue:
“Here we analyse the genome of the tuatara, which—at approximately 5 Gb—is among the largest of the vertebrate genomes yet assembled. Our analyses of this genome, along with comparisons with other vertebrate genomes, reinforce the uniqueness of the tuatara. Phylogenetic analyses indicate that the tuatara lineage diverged from that of snakes and lizards around 250 million years ago [Earliest Triassic].”

This timing is confirmed by the LRT, but fossils generally represent periods of wide radiations, not moments of origin.

“This lineage also shows moderate rates of molecular evolution, with instances of punctuated evolution. Our genome sequence analysis identifies expansions of proteins, non-protein-coding RNA families and repeat elements, the latter of which show an amalgam of reptilian and mammalian features.”

Phenomic studies do not support a mammal connection other than at the very base of the Reptilia (see the LRT).

“The sequencing of the tuatara genome provides a valuable resource for deep comparative analyses of tetrapods, as well as for tuatara biology and conservation.”

False positives are not valuable resources. They steer readers and workers wrong. Gene studies too often deliver false p;positives compared to trait-based studies over deep time.

From an online story from phys.org with quotes from the authors.
“The tuatara genome contained about 4% jumping genes that are common in reptiles, about 10% common in monotremes (platypus and echidna) and less than 1% common in placental mammals such as humans,” said Professor Adelson.

“This was a highly unusual observation and indicated that the tuatara genome is an odd combination of both mammalian and reptilian components.”

“The unusual sharing of both monotreme and reptile-like repetitive elements is a clear indication of shared ancestry albeit a long time ago,” said Dr. Bertozzi.”

Or… this is a false positive. Not sure why false positives keep creeping in to gene studies, but they do.

Colleagues: Don’t publish genomic studies unless they are confirmed by phenomic studies.

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References
Gemmell NJ, Rutherford K., Prost, S. et al. 2020. The tuatara genome reveals ancient features of amniote evolution. Nature (2020). https://doi.org/10.1038/s41586-020-2561-9 DOI: 10.1038/s41586-020-2561-9 , www.nature.com/articles/s41586-020-2561-9

https://phys.org/news/2020-08-dinosaur-relative-genome-linked-mammals.html?fbclid=IwAR1VjTxtCI8Yd9VrUIAbuwxDmEhOM1q27WFueBbt1KIo062qKi2UqNnvzX0

https://www.researchgate.net/publication/342666056_Bird_phylogeny_false_positives_detected_in_a_gene_sequencing_study

Turtle body plans 2020: still not diapsids

Lyson and Bever 2020 once again propose
a diapsid origin for turtles that is not supported by the large reptile tree (LRT, 1719+ taxa, subset Fig. 1) where hardshell and soft-shell turtles arise in parallel from small horned pareiasaurus without temporal fenestrae — and all competing candidates for turtle ancestry are tested.

From the Lyson and Bever abstract:
“The origin of turtles and their uniquely shelled body plan is one of the longest standing problems in vertebrate biology.”

In the LRT this problem has been resolved for several years. Click here for an online paper on the dual origin of turtles from pareiasaurs. Click here for the dual origin of turtles to scale blogpost. Click here for the latest LRT cladogram.

“The unfulfilled need for a hypothesis that both explains the derived nature of turtle anatomy and resolves their unclear phylogenetic position among reptiles largely reflects the absence of a transitional fossil record.”

Not so. In the LRT several overlooked taxa well document a good transitional fossil record. Lyson and Bever omit, ignore and overlook these taxa in favor of several unrelated turtle mimics.

“Recent discoveries have dramatically improved this situation, providing an integrated, time-calibrated model of the morphological, developmental, and ecological transformations responsible for the modern turtle body plan. This evolutionary trajectory was initiated in the Permian (>260 million years ago) when a turtle ancestor with a diapsid skull evolved a novel mechanism for lung ventilation. This key innovation permitted the torso to become apomorphically stiff, most likely as an adaption for digging and a fossorial ecology. The construction of the modern turtle body plan then proceeded over the next 100 million years following a largely stepwise model of osteological innovation.”

Not so. Overlooked taxa known for decades (Elginia (Fig. 2), Sclerosaurus) have been traditionally excluded from turtle origin studies. Some recent discoveries (Eorhynochelys, Pappochelys) nest elsewhere, apart from turtles, as turtle mimics. The LRT tests all known candidates. Lyson and Bever do not. They are still excluding pertinent taxa. Adding more taxa shows that turtles and their ancestors have never been diapsids.

Figure 1. Carbonodraco enters the LRT alongside another recent addition, Kudnu, at the base of the pareiasaurs + turtles.

The most primitive hardshell turtles 
are not the oldest known hardshell turtles. Horned turtle skulls are widely and traditionally considered derived, not primitive. Elginia and Meiolania (Fig. 2) have never been tested together in analysis, and not by Lyson and Bever, despite their obvious similarities and homologies.

Turtle respiration was a big issue for Lyson and Bever.
Earlier we looked at pre-softshell turtle respiration in Sclerosaurus here.

Figure 2. Another gap is filled by nesting E. wuyongae between Bunostegos and Elginia at the base of hard shell turtles in the LRT.

Turtle mimics are out there.
Evidently only a wide gamut phylogenetic analysis, like the LRT, can lump and separate turtle ancestors from turtle mimics without bias and without traditional influences. Lyson and Bever mistakenly accepted several turtle mimics as turtle ancestors, then built a diapsid story around their cherry-picked taxa. Referees and editors also accepted this invalid scenario.

Add taxa
to find and separate real turtle ancestors from turtle mimics.

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References
Lyson TR and Bever GS 2020. Origin and Evolution of the Turtle Body Plan Annual Review of Ecology, Evolution, and Systematics 51:- (Volume publication date November 2020) Review in Advance first posted online on July 31, 2020. (Changes may still occur before final publication.) https://doi.org/10.1146/annurev-ecolsys-110218-024746

researchgate.net/_The_dual_origin_of_turtles_from_pareiasaurs

Chordate origins: Progress since Romer 1971

Added a few days after posting:
There was a spirited discussion in the comments section (below) regarding the origin of the mouth and anus in the proposed ancestor of chordates: a round worm (Fig. 2). The most recent progress on this subject can be found in the following citations:

https://en.wikipedia.org/wiki/Embryological_origins_of_the_mouth_and_anus
It includes a third possibility, ‘amphistomy” which is a new word for me, and the pertinent comment: “An alternative way to develop two openings from the blastopore during gastrulation, called amphistomy, appears to exist in some animals, such as nematodes.”

And here is a citation for a 2019 paper that seems to sum things up to date: https://onlinelibrary.wiley.com/doi/abs/10.1002/9780470015902.a0027481

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When the great paleontologist of the ’30s to early ’70s,
Alfred S. Romer, wrote his widely disseminated abridged textbook, The Vertebrate Body – Shorter Version (1971) he proposed the following scenario (Fig. 1) for the origin of chordates (animals with a notochord).

Figure 1. From Romer 1971 the origin of chordates. Note the impossibly complex basal taxon, the sessile arm-feeder at bottom. Here wriggling is highly derived. Compare to figure 2.

Unfortunately
Romer 1971 started with a notoriously complex stalked ‘sessile arm feeder’ (Fig. 1), way more derived than the simple and tiny flat worms, ribbon worms and round worms that were the most evolved animals at the time. Since these worms were soft-bodied they left few to no fossils in pre-Cambrian and pre-Ediacaran strata.

Figure 2. Chordate evolution, changes to Romer 1971 from Peters 1991. Here echinoderms have lost the tail and gills of the free-swimming tunicate larva.

Things changed with Peters 1991
who traced the human lineage from molecules to cells to worms and vertebrates. The round worm, a deuterostomate (mouth arising anew opposite the existing anus, Fig. 4), was put forth in that lineage as a placeholder taxon arising from more primitive flatworms and microscopic organisms. Then this wriggling “intestine wrapped in a layer of skin” (Fig. 2), developed a mesoderm and a notochord to restrict telescoping and so became a primitive chordate. This served as the first step toward swimming in the laterally undulating manner of lancelets and fish.

Added the day of publication when reader CB and Wikipedia both note nematodes are protostomates, not deuterostomates: That’s important to document and perhaps the reason why extant nematodes (roundworms) were never considered before. Given that only chordates, hemichordates and echinoderms are currently considered deuterostomes, we have to ask, which roundworm-like and ribbonworm-like taxa preceded these three derived clades? None, according to current thinking. None. That can’t be possible based on the need to get from a flatworm (mouth and anus are the same) to a lancelet. At this stage the roundworm (mouth on one end, anus on the other) serves as a model ancestor for all higher taxa. The solution to this problem: Either deuterostomate roundworm-types all became extinct, or one kind of protostomate roundworm became a deuterostomate, or deuterostomate roundworms are still around, but remain untested regarding their embryology. Thanks for bringing this fact to the surface. Here’s a problem that needs a better solution than we have now.

By contrast,
in Romer’s chart (Fig. 1), wriggling comes last.

In Peters 1991
sessile and free-floating forms, including those without an undulating tail, evolved far and away from simple notochord worm and lancelet bauplans. Some emphasized developing the cilia and mouth parts (echinoderms), while others emphasized developing the atrium (tunicates). These retained a primitive mobile wriggling bauplan as juveniles (betraying their ancestry, not their future), then metamorphosed into sessile adults.

Figure 3. Chordated evolution from Rychel et al. 2005.

Back to Academia… Rychel et al. 2005
likewise started with a benthic worm “with gill slits and acellular gill cartilages” (see Fig. 2 from Peters 1991), but were less clear in showing how complex and distinct starfish, tunicates, etc. evolved directly from that simple form. More to their focus, Rychel et al. 2005 write: “Chordates evolved a unique body plan within deuterostomes and are considered to share five morphological characters,

1. a muscular postanal tail,
2. a notochord,
3. a dorsal neural tube,
4. an endostyle,
5. and pharyngeal gill slits.

“No extant echinoderms share any of the chordate features, so presumably they have lost these structures evolutionarily. Hemichordates and cephalochordates, or lancelets, show strong similarities in their gill bars, suggesting that an acellular cartilage may have preceded cellular cartilage in deuterostomes. Our evidence suggests that the deuterostome ancestor was a benthic worm with gill slits and acellular gill cartilages.”

Figure 4. From Peters 1991 a diagram splitting deuterostomates from protostomates.

More recently, Satoh et al, 2014 write:
“Although the origin and evolution of chordates has been studied for more than a century, few authors have intimately discussed taxonomic ranking of the three chordate groups themselves.

“Accumulating evidence shows that echinoderms and hemichordates form a clade (the Ambulacraria), and that within the Chordata, cephalochordates diverged first, with tunicates and vertebrates forming a sister group. Chordates share tadpole-type larvae containing a notochord and hollow nerve cord, whereas ambulacrarians have dipleurula-type larvae containing a hydrocoel.

“We propose that an evolutionary occurrence of tadpole-type larvae is fundamental to understanding mechanisms of chordate origin.”

Satoh et al, 2014 discuss the four hypotheses then circulating. 

(1) “The paedomorphosis scenario: was the ancestor sessile or free-living?”

(2) “The auricular hypothesis – According to this view, the pterobranch-like, sessile animals with dipleurula (auricularia-like) larvae led to the primitive ascidians (as the latest common ancestor of chordates) through morphological changes both in larvae and adults.”

(3) “The inversion hypothesis – Recent debates on the origin of chordate body plans have focused most attention on inversion of the dorsal–ventral (D-V) axis of the chordate body, compared with protostomes”

(4) The aboral-dorsalization hypothesis – “Embryological comparison of cephalochordates with nonchordate deuterostomes suggests that, because of limited space on the oral side of the ancestral embryo, morphogenesis to form the neural tube and notochord occurred on the aboral side of the embryo (the side furthest from the mouth).“Namely, the dorsalization of the aboral side of the ancestral embryo may have been a key developmental event that led to the formation of the basic chordate body plan.”

Some of these recent hypotheses are still stuck in Romer’s world
of 50 years ago, replicating ‘primitive sessile arm feeders’ at the expense of ignoring wriggling round worms.

So, round worm exclusion has been going on for at least that long.
Is it because textbooks rule? New ideas are too expensive to bring to the classroom? Nobody questions the professor? No one else is thinking about this issue?

Funny that no competing hypotheses
consider the extremely simple, primitive, wriggling, telescoping, round worm as a suitable starting point in chordate origins. Evidently in 1991 this was heretical and remains so today. I thought, at the time, it was just being logical.

Next time, in Academia,
let’s start with a simple round worm, then discuss how a mesoderm and notochord developed incrementally over deep time as some roundworms evolved to become chordates and their kin back in the Cambrian or earlier.

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References
Peters D 1991. From the Beginning. The story of human evolution. Wm Morrow, Morrow Jr Books, New York. FromTheBeginning book.pdf
Romer AS 1971. The Vertebrate Body – Shorter Version 4th ed. WB Saunders.
Rychel AL, Smith SE, Shimamoto HT and Swalla BJ 2005. Evolution and development of the chordates: collagen and pharyngeal cartilage. Molecular Biology and Evolution 23(3): 541–549. https://academic.oup.com/mbe/article/23/3/541/1110188
Satoh N 2008. An aboral-dorsalization hypothesis for chordate origin. Genesis 46(11):614-22
Satoh N, Rokhsar D and Nishikawa T 2014. Chordate evolution and the three-phylum system. Proceedings of the Royal Society B Biological Sciences. https://doi.org/10.1098/rspb.2014.1729

Origin of chordates webpage

Somites = bilaterally paired blocks of paraxial mesoderm along the head-to-tail axis in segmented animals.

 

A little piranha sister, Hoplerythrinus, enters the LRT

And like its deep-bodied, big-toothed sister,
the aimara, trahira, gold wolf fish, etc. (genus: Hoplerythrinus unitaeniatus (hop-ler-rie-thry-nus) originally Erythrinus) also swims in South American rivers.

Figure 1. The araimaia, Hopolerythrinus, enters the LRT with the piranha, Serrasalmus.

The aimara is longer and leaner than the piranha,
more like their giant Cretaceous Niobrara cousins (Fig. 5), Portheus and Xiphactinus.

Figure 2. Araimaia (Hoplerythrinus) skull.

The Gregory 1938 diagram of the skull
(Fig. 2) clarifies and corrects several elements of the skull in the piranha (Serrasalmus), and the Niobrara taxa, Portheus and Xiphactinus.

Figure 3. Skeleton of the red eye piranha, Serrasalmus rhombeus, in lateral view. Distinct from its bottom foraging predecessor, Alma, the skull and torso of this more agile swimmer are deeper and narrower.

Hoplerythrinus unitaeniatus (originally Erythrinus unitaeniatus Spix and Agassiz 1829) is the extant gold wolf fish or aimara, found in South American rivers. Here this smaller, more primitive, less toothy taxon nests with the highly derived piranha. Like Amia, this taxon does well with stagnant, oxygen-poor water by gulping air.

Figure 4. Piranha (Serrasalmus) skull. Some skull bones re-identified here.

Figure 5. Xiphactinus fossil. The famous fish-within-a-fish.

Figure 4. Subset of the LRT focusing on basal ray fin fish. The clear resemblance to Amia hints at a series of similar transitional taxa leafing to inteventing clades.

The clear resemblance of Hoplerythrinus to the bowfin, Amia
(Fig. 5), hints at a series of similar transitional taxa leafing to inteventing clades.

Figure 5. Skull of the extant bowfin (Amia). Compare to figure 2.

The atypical contact between
the premaxillary ascending processes and the frontals (splitting the nasals, Fig. 2) in Hoplerythrinus recalls a similar morphology in Amia (Fig. 5), several nodes away (Fig. 4). This similarity hints at a transitional series of taxa that look more like Amia and Hoplerythrinus basal to the intervening clades including Elops, Megalops, Salmo and Hydrolycus .

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References
Spix JB von and Agassiz L 1829. Selecta genera et species piscium quos in itinere per Brasiliam annis MDCCCXVII-MDCCCXX jussu et auspiciis Maximiliani Josephi I…. colleget et pingendso curavit Dr J. B. de Spix…. Monachii.

 

AMNH pterosaur video: due for an Oculudentavis-type retraction

Recently (March 2020 to July 2020)
Xing et al. 2020 agreed to retract their paper on Oculudentavis because they said it was a bird and it turned out to be a lepidosaur.

Figure 1. Oculudentavis in amber much enlarged. See figure 2 for actual size.

Also recently (July 31, 2020)
the American Museum of Natural History posted a YouTube that reported pterosaurs were archosaurs (= birds, dinosaurs and crocs) and pterosaurs turn out to be lepidosaurs. whenever tested with typically excluded taxa. Should the AMNH be held to the same rigorous standards demonstrated by Nature magazine and Xing et al. 2020? Here’s the evidence:

Full set of comments on the AMNH pterosaur video (above)
are copied below.

Lots of misinformation here. Traditional myths are hard to kill.

No pterosaur wing membrane ever extends to the knee or thigh and no single uropatagium stretched between the lateral pedal digits. http://reptileevolution.com/pterosaur-wings.htm

No pterosaurs had their eyeballs in the front half of their skulls. http://reptileevolution.com/anurognathus-SMNS.htm 1:16

Size actually goes down to hummingbird-sized 1:41

German fossils also preserve wing membranes nicely. Not just in China. 2:18

No need to show old engravings that portray pterosaurs with bat-like ears. 2:34

Basal pterosaurs, like Dimorphodon, were bipeds with giant tree-trunk gripping foreclaws. Pedal digit 5 was not used to frame each uropatagium. Toe 5s are often preserved strongly flexed, used to help support a bipedal configuration, preserved in footprints (Rotodactylus) of pre-pterosaurs. When folded wing membranes nearly completely disappeared due to being stretched only between the elbow and wingtip. 2:54

When you test more taxa, pterosaurs leave dinosaurs and join fenestrasaur, tritosaur, lepidosaurs. These share a long finger 4, a long toe 5, a single sternum, sprawling hind limbs, a pteroid, a prepubis and many other traits not shared with dinosaurs. Sadly we’ve known this for 20 years and Alex Kellner was the peer-reviewer who approved the paper. 3:17

Not all pterosaurs walked on four limbs. We have bipedal track fossils. Only small-clawed beachcombers with flat feet left quadrupedal tracks. 4:09

When tested (ReptileEvolution.com) Archosauria includes only crocs + dinos. Pterosaurs nest with Fenestrasaurus (Cosesaurus), Tritosaurs (Huehuecuetzpalli) and Lepidosaurs. 5:30

Basal bipedal crocs were not dinosaur mimics. The both evolved from a last common ancestor that was bipedal. 5:40

The basal croc at 5:46 is not one at all, but from another family of archosauriformes. The ankle bone arrangement of pterosaurs and dinosaurs is by convergence. It happens often enough when reptiles become bipedal. Sharovipteryx for example. When scientists pull this trick, it’s called “Pulling a Larry Martin” to honor the Kansas professor who delighted in calling young know-it-alls out. 5:54

Actually dinosaurs (archosauromorphs) and pterosaurs (lepidosauromorphs) separated from one another some 335 million years ago, when the first amniotes (=reptiles), like Silvanerpeton, appeared. 5:50

The hole in the hip socket separates dinos from crocs. Like lizards and turtles and humans, pterosaurs have no hip socket hole. Same goes for the long humeral (deltopctoral) crest. No plesiomorphic reptile has ever been put forth as the last common ancestor of pterosaurs and dinosaurs, except the aforementioned Silvanerpeton. 6:02

No pterosaurs flew with hind legs trailing behind. As lepidosaurs pterosaurs had sprawling hind limbs that extended laterally, like horizontal stabilizers on modern aircraft. All preserved wing membranes show they stretched only between the wingtip and elbow, with a short fuselage fillet to mid thigh. Long narrow wings reduced drag. 11:33

No pterosaur took off by doing a dangerous jumping push-up. Better to start flapping with wings out while leaping, as birds do, instead of opening the wings later from a closed and ventral start. 11:56

The largest pterosaurs got to be that size, just as giant birds do today, because they gave up flying, as shown by their clipped wings (vestigial distal wing finger bones). They could still use their wings for thrust while running, like the earlier video images of the running swan. 12:06

If it’s tough enough for flapping swans, what the animators show at 12:40 (giant azhdarchid quad leap takeoff) is impossible, especially with ‘clipped’ wings. By the way, the elbows rose above the leading edge, creating camber. Also by the way, when Paul MacCready made his third-size flying model of Quetzalcoatlus, he added wingspan to make it work. https://pterosaurheresies.wordpress.com/2020/04/12/can-volant-fossil-vertebrates-inspire-mechanical-design/

Pterosaur wing membranes have less of an airplane-like camber and more of an ornithopter appearance, with a thick leading edge, but the rest is a thin membrane that folds to near invisibility. Forcing the air down and back, as in ornithopters, has the opposite and equal reaction of forcing the ornithopter/pterosaur up and forward. Unfortunately the animators for the AMNH used flat wings in flight, not dorsally bowed wings. 13:15

Many small pterosaurs flapped as often as small birds do (creating what should have been a blur in the animation). 14:30

Why did pterosaur ancestors learn to fly? Impressing females, rivals and predators (the video skips that step). That story is told by flapping, nonvolant Cosesaurus. Link here: http://reptileevolution.com/cosesaurus.htm

We have more than 150 pterosaur species right now. Those professors are not counting the small Solnhofen adults and multiple species within a single genus. 17:40

A cladogram that tests 250 different pterosaurs can be found here: http://reptileevolution.com/MPUM6009-3.htm

Short summary:
Just about everything the AMNH included in their pterosaur video was outdated and wrong with no evidence backing their traditional claims. So, should the AMNH retract this video? I mean, children are watching… and the AMNH should care about their public outreach.

Part 2 
If Oculudentavis (Figs. 1, 2) is a lepidosaur based on the Cau blogpost 2020 and Li et al. 2020 trait list (see below), how does the basalmost pterosaur in the LRT, Bergamodactylus (Fig. 2), match that list?

Figure 2. Skulls of Oculudentavis and Bergamodactylus compared. Not to scale. Note the dark blue palatine in Oculudentavis shows through the antorbital fenestra.

Here’s the Cau TheropodaBlogpost.com list:

1. “Absence of anti-orbital window.” AOF present in both (Fig. 2, note palatine (deep blue) is visible through AOF in Oculudentavis).
2. “Quadrate with large lateral concavity. This character is not typical of dinosaurs, but of lepidosaurs.” Not discernibly concave in crushed Bergamodactylus.
3. “The maxillary and posterior teeth of the maxilla extend widely below the orbit.” Last maxillary tooth below orbit in both.
4. “Dentition with pleurodont or acrodont implant.” Thecodont implantation in Bergamodactylus.
5. “Very large post-temporal fenestra.” As in Bergamodactylus.
6. “Spoon-shaped sclerotic plates is typical of many scaled lepidosaurs.” Plates much smaller in Bergamodactylus.
7. “Coronoid process that describes a posterodorsal concavity of the jaw reminds more of a lepidosaur than a maniraptor.” As in Bergamodactylus.
8. “Very small size comparable to those of the skulls of many small squamata found in Burmese amber.”  Much smaller skull than Bergamodactylus.

Here’s the Ling et al. 2020 list:

1. “absence of an antorbital fenestra” AOF present in both
2. “The ventral margin of the orbit is formed by the jugal.” Actually, the lacrimal, jugal and postorbital. It’s a big orbit, as in Bergamodactylus.
3. “Another unambiguous squamate synapomorphy in Oculudentavis is the loss of the lower temporal bar.” Actually the lower bar is formed by the tiny loose quadratojugal, lateral to the quadrate in both taxa.

FIgure 3. 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.

Only a few of the above are LRT traits.
The LRT compares 1717 taxa with 230 other characters and nests Early Cretaceous Oculudentavis with Middle Triassic Cosesaurus, a few nodes away from Late Triassic Bergamodactylus.

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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

Bonus video on becoming a PhD. You’re doing research on what you set for 3-4 years, sort of like creating and supervising the LRT for the last 9 years.

Enigmatic Jamoytius enters the LRT

Sansom et al. 2010 studied and discussed
Jamoytius kerwoodi (White 1946; Early Silurian; Fig. 1) an early eel-like taxon originally considered to be the most primitive known vertebrate, then a sister to lampreys, then a sister to Euphanerops (the subject of yesterday’s post). Turns out, it is none of these.

Sansom et al write:
“The study of the anatomy of problematic organisms can be aided by the use of a methodology designed to separate topological and morphological reconstruction from anatomical interpretation and to gather as much information as possible about the preserved features through taphonomic analyses.”

Unfortunately the authors did not trace the skull bones (Fig. 1) and those of several related taxa (Figs. 3, 4) and so missed the ability to score Jamoytius more completely and accurately.

“Interpretations of paired fins remain equivocal. Analyses of the phylogenetic affinity of Jamoytius identify a sister taxon relationship with Euphanerops. This clade, the Jamoytiiformes, is a primitive group of stem-gnathostomes and does not form a clade with the Anaspida.”

By contrast, the large reptile tree (LRT, 1718+ taxa, subset Fig. 2) nests Jamoytius not with lampreys, nor with Euphanerops, but between Birkenia (Fig. 3) and Thelodus (Fig. 4), taxa ignored by Sansom et al.

Figure 1. Jamoytius photo and diagram from Sansom et al. 2020. Colors and new labels added here. Note the lack of skull bone tracings on the diagram. It looks like each gill opening has a little opercular flap. Note the new identification for the left eye. The ‘notochord’ is here a dorsal ridge, a precursor to dorsal armor.

Jamotius kerwoodi (White 1946, Sansom et al. 2010; Early Silurian; 10+cm in length) shares a tiny circular mouth and naris at the tip of its short snout with closely related taxa along with a similar set of skull bones, plus a dorsal ridge!

Figure 2. Subset of the LRT focusing on basal chordates and Jamoytius.

 With a small circular oral cavity,
Jamoytius and its sisters could not have been open sea predators, or blood suckers, but likely scoured sea muds and lake sands for tiny buried prey, like young lancelets and This extant sturgeons. Sturgeons (Fig. 4) feed on a spectrum of small benthic prey. Larger  sturgeons are known to suck in larger prey, like salmon, into their toothless, nearly jawless oral cavity.

BTW,
these taxa are all buried deep in the human lineage. So, say ‘hello’ to your ancestors.

Figure 3. Birkenia skull for comparison to Jamoytius.

Paleontologists of all stripes are fond of saying,
‘first-hand examination of the fossil is essential’. Sansom et al. had several fossils to look at firsthand and did not trace skull bones (Fig. 1). As I’ve been saying for nine years, the computer monitor and a digitally scanned photo can be superior to a binocular microscope because the monitor can trace elements in color, thereby reducing the apparent chaos into discrete segregated units. That opens up a whole new world of data that can be used to confidently nest enigmatic taxa, like Jamoytius (Fig. 2).

Figure 4. Top to bottom: Thelodus a soft jawless fish with a ventral oral opening and gill slits, perhaps a hint of diamond-shaped armor laterally. Hemicyclaspis, adds extensive armor. Euphaneropsps, a late survivor of an Ordovician radiation basal to sturgeons. Acipenser, a sturgeon with a protrusible tube for a mouth and reduced armor. Chondrosteus, a fish with jaws, but no marginal teeth.

Taxon exclusion, once again. 
Sansom et al. did not mention, trace and test either Birkenia (Fig. 3) or Thelodus (Fig. 4). So taxon exclusion is also an issue resolved here by the LRT using character traits originally designed for reptiles and still working in basal chordates. It’s that simple. Just add taxa and enigmas get confidently nested.

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References
Sansom RS, Freedman K, Gabbott SE, Aldridge RJ and Purnell MA 2010. Taphonomy and affinity of an enigmatic Silurian vertebrate, Jamoytius kerwoodi White. Palaentology 53(6):1393–1409.
White EI 1946. Jamoytius kerwoodi, a new chordatefrom the Silurian of Lanarkshire. Geological Magazine, 83, 89–97.

wiki/Jamoytius

Euphanerops: basal to sturgeons with tiny new pelvic fins

Janvier and Arsenault 2007 took another look at
Euphanerops longaevus (Woodward 1900; Late Devonian, Figs. 1, 2) comparing it uncertainly to living lampreys and extinct jawless, finless fish. They report, “The anatomy of Euphanerops longaevus is reconstructed here on the basis of 17 specimens, 14 of which were hitherto undescribed. Practically all the mineralized elements that can be observed in the largest individuals of E. longevous display the same structure, which strikingly recalls that of lamprey cartilage, despite the uncertainty as to the origin of its mineralization.”

Elongated and confluent paired fins
“The new material of E. longaevus described here provides strong support for the presence of ventrolateral, ribbon-shaped, paired fins armed with numerous parallel radials. These fins extend from the anus to the anterior part of the branchial apparatus anteriorly, and are the first instance of paired fins with radials, whose anteroposterior extension largely overlaps that of the branchial apparatus in a vertebrate.”

Mostly true, but let’s not forget in manta rays and guitarfish, skates and rays, paired pectoral fins indeed do overlap the branchial apparatus (= gill basket), IF that is happening in Euphanerops (see below).

From the abstract
“Owing to the uncertainty as to the biogenic or diagenetic nature of the anatomical features described in E. longevous, no character analysis is proposed. Only a few possible homologies are uniquely shared by euphaneropids and either lampreys or anaspids, or both.”

Phylogenetically, the authors note:
“Euphanerops longaevus has been referred to as an anaspid, chiefly because of its distinctive hypocercal tail and anal fin. However, since it apparently has no mineralized dermal skeleton, E. longaevus lacks evidence for the tri-radiate postbranchial spine, which Forey (1984) proposed as the defining character of the Anaspida. Consequently, it is now often treated in recent phylogenetic analyses as a separate terminal taxon, alongside other scale-less (or “naked”) jawless vertebrate taxa also once regarded as anaspids, namely Endeiolepis and Jamoytius.”

Figure 1. Several basal chordates: Branchiostoma, Euphanerops, Jamoytius and Birkenia. The middle image of Euphanerops is the tracing. The others are freehand interpretations from Janvier and Arsenault 2007.

Here 
(Fig. 2) individual skull bones and tiny overlooked pectoral and pelvic fins are identified. Adding a missing (unossified?) rostrum (= nasal) restores the original profile. In the large reptile tree (LRT, 1717+ taxa) Euphanerops nests basal to sturgeons, like Pseudoscaphirhynchus (FIg. 3), a clade not mentioned by Janvier and Arsenault 2007. A previously enigmatic element in front of the mouth is here identified as a pair of barbels, as in sturgeons. The tiny dorsal spines of Euphanerops are also found as larger dorsal armor in Birkenia, osteostracans and sturgeons.

Figure 2. Euphanerops skull region showing tetrapod homolog bones and displace fin. See Birkenia for closer homologs. Image from Janvier and Arsenault 2007. Colors added here.

According to Wikipedia
Euphaneropidae have, “greatly elongated branchial apparatus which covers most of the length of the body.”

Here that area is identified as a typical subdivided and flattened ventral surface, as in Birkenia, sturgeons and osteostracans.

Figure 3. Skull of Pseudoscaphorhynchus. Note the mouth is created by the lacrimal and surangular, not the maxilla and dentary, which are tooth-bearing bones in more derived fish.

The hypocercal tail of Euphanerops
has heterocercal elements and this taxon nests between taxa with a heterocercal tail. With an Ordovician genesis, Late Devonian Euphanerops likely developed a dipping tail and larger propulsive dorsal fin secondarily, as a reversal. An ancestor, Birkenia, has a similar dipping tail.

Figure 4. Euphanerops caudal fin with elements re-identified.

Small enigmatic squares of rod-like elements near the cloaca
are here identified as primitive pelvic fins or vestiges of the same. More primitive taxa do not have pelvic fins. More derived taxa do.

Figure 5. Euphanerops with elements here identified as tiny pectoral fins just anterior to the cloaca and posterior to the ventral armor. Images from Janvier and Arsenault 2007.

Primitive pectoral fins
are known in ancestral and descendant taxa, so Euphanerops should have them, too. Here (Fig. 6) they are identified as vestiges.

Figure 6. Euphanerops plate and counter plate with colors added identifying elements.

Traditionally sturgeons have not been tested with osteostracans
(Fig. 7) and other jawless fish. The LRT tests a wide gamut of competing candidates and nests sturgeons prior to the advent of jaws and teeth in vertebrates, close to osteostracans and Euphanerops. Do not let one or two traits, like a dipping (hypocercal) tail, steer you off course in your wide-gamut analysis.

Figure 7. Top to bottom: Thelodus a soft jawless fish with a ventral oral opening and gill slits, perhaps a hint of diamond-shaped armor laterally. Hemicyclaspis, adds extensive armor. Euphaneropsps, a late survivor of an Ordovician radiation basal to sturgeons. Acipenser, a sturgeon with a protrusible tube for a mouth and reduced armor. Chondrosteus, a fish with jaws, but no marginal teeth.

The ‘paired fin ridges’ observed by Janvier and Arsenault
may be ray-like ossifications that gathered to produce the ventrolateral armor on sturgeons (Fig. 7) or were vestiges thereof. Additionally, that’s where basal chordate gonads are located.

A set of lamprey-like gill openings appear near the skull
of Euphanerops. This appears to be a retention of or reversal back to similar multiple openings seen in Birkenia (Fig. 1). Again, don’t judge a taxon by one or two traits. Test them all against a wide gamut of taxa, like the LRT. We may be seeing what happens a the transition from multiple gill openings to a sturgeon-like operculum here.

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References
Janvier P, Desbiens S, Willett JA and Arsenault 2006. Lamprey-like gills in a gnathostome related Devonian jawless vertebrate. Nature 440:1183–1185.
Janvier P and Arsenault M 2007. The anatomy of Euphanerops longaevus Woodward, 1900, an anaspid-like jawless vertebrate from the Upper Devonian of Miguasha, Quebec, Canada. Geodiversitas 29 (1) : 143-216.
Woodward AS 1900. On a new ostracoderm fish (Euphanerops longaevus) from the Upper Devonian of Scaumenac Bay, Quebec, Canada. Magazine of Natural History ser. 7, 5: 416-419.

wiki/Euphaneropidae