Little Ligulalepis grabbed headlines in 2018 (due to taxon exclusion)

Academic and publicity headlines:
“The most primitive osteichthyan braincase?”
“Neurocranial anatomy of an enigmatic Early Devonian fish shed light on early osteichthyan evolution.”

No. Far from it. Living moray eels (genus: Gymnothorax) have a much more primitive osteichthyan braincase than Ligulalepis (Fig. 1). A proper phylogenetic context (Fig. 2) is essential, but was not present in prior studies of this tiny fish due to taxon exclusion.

Figure 1. Ligulalepis shown at full scale and enlarged t show details. Colors and restoration added here. Blue arrows point in to incurrent naris and out excurrent naris (= choana).

More publicity headlines:
“The ancestor of all bony fish has a surprising link to humans.”
“400-Million Year-Old Fish Discovered Is Ancestor of Dinosaurs, Humans”

In the LRT Ligulalepis was a fish with no descendants (Fig. 2). A long list of omitted fossil taxa, along with extant moray eels, lungfish and coelocanths were ancestral to dinosaurs and humans (Fig. 2), but that story was overlooked. Once again, taxon exclusion creates a phylogenetic misstep and a journalistic headline grab.

Figure 2. Subset of the LRT focusing on the lobefin half of the bony fish (Osteichichthys). This is heretically different from traditional cladograms due to taxon inclusion. Doliodus is usually lumped in with sharks. With more taxa it nests with deep-sea dragonfish, which are bony ray-fin fish.

From the Wikipedia page:
“Ligulalepis was first described from isolated scales found in the Taemas-Wee jasper limestones of New South Wales (Early Devonian age) by Dr Hans-Peter Schultze (1968) and further material described by Burrow (1994). A nearly complete skull found in the same general location was described in Nature by Basden et al. (2000) claiming the genus was closely related to basal ray-finned fishes (Actinopterygii). In 2015 Flinders University student Benedict King found a more complete new skull of this genus which was formally described by Clement et al. (2018), showing the fish to be on the stem of all osteichthyans.”

Figure 3. Kenichthys at full size and enlarged to show detail. Note the migration of the excurrent naris to the jawline, convergent with tetrapodomorphs like lungfish.

Ligulalepis toombsi
(Schultze 1968; Basden et al. 2000; Clement et al. 2018; Late Silurian; Fig. 1) is a tiny partial skull considered basal to ray-fin fish. In the large reptile tree (LRT, 2006 taxa; subset Fig. 2) tiny Ligulalepis nests with slightly larger Early Devonian Kenichthys (FIg. 3), one of several tiny taxa related to larger Youngolepis and these are related to bottom-dwelling porolepiformes like the rounder Porolepis and the flatter Tungesnia, Guiyu and Stensioella (Fig. 4).

Contra tradition
in the LRT (subset Fig. 2) lobe-finned porolepiformes (e.g. Porolepis) and the coelocanths (e.g. Latimeria) are NOT closely related to tetrapods or tetrapodomorphs. So don’t “Pull a Larry Martin” and focus on those lobed fins alone. Test all the traits. In the LRT lobed fins convergently appear several times in the ‘lobe fin’ clade — and lobes disappear to become ray fins, also by convergence with ray fin taxa. Traditionally omitted herring (Engraulis) and bichirs (Polypterus) are closer to tetrapods in the LRT.

Despite its antiquity
Ligulalepis is not close to the origin of bony fish in the LRT (FIg. 2). Rather it is one more highly derived Late Silurian taxon that documents a great radiation in the Silurian that has not been discovered in fossil strata yet.

Earlier studies with fewer taxa
found a basal split between lobe-fins and ray-fins. It’s more complicated than that. In the LRT porolepiformes converge with unrelated lungfish sharing similar external and internal nares. These taxa also converge with lobe-finned coelocanths in their lobe fins. Many of these taxa are low, slow, flat and small fish. Others are low, slow, fat and large fish. Many are known from fused skull bones that often don’t preserve the wide cheek bones (e.g. jugal, postorbital, squamosal, quadratojugal). Stensioella (Fig. 4) is a rare exception that preserves virtually the whole specimen, at least on one side.

Figure 4. Stensioella from nose to tail. Note the large paddle-like pectoral fins, as in Guiyu (Fig. 5).

What does the small size of Ligulalepis tell us?
Phylogenetic miniaturization usually retains juvenile traits (e.g. short rostrum, large eyes, small size) into adulthood. These changes can lead to novel clades. Presently no new clades arise from Ligulalepis. That can change. Presently Ligulalepis is tiny without descendants, just the opposite of what the headlines said back in 2018.

References
Basden AM et al. 2000. The most primitive osteichthyan braincase? Nature 403(6766): 185–188.
Burrow CJ 1994. “Form and function in scales of Ligulalepis toombsi Schultze, a palaeoniscoid from the Early Devonian of Australia”. Records of the South Australian Museum. 27 (2):175–185.
Chang M-M and Yu X-B 1981. A new crossopterygian Youngolepis praecursor gen. et sp. nove.form Lower Devonianof E. Yunna, China. Scientia Sinica 24:89–97.
Chang M and Zhu M 1993. A new Middle Devonian osteolepidid from Qujing, Yunnan. Mem. Assoc. Australas. Palaeontol. 15 183-198.
Clement AM et al. 2018. Neurocranial anatomy of an enigmatic Early Devonian fish shed light on early osteichthyan evolution. eLife 7. doi:10.7554/eLife.34349
Schultze H-P 1968. Palæoniscoidea-Schuppen aus dem Unterdevon Australiens und Kanadas und aus dem Mitteldevon Spitzbergens. Bulletin of the British Museum. 16: 343–368.
Zhu M and Ahlberg P 2004. The origin of the internal nostril of tetrapods. Nature 432:94-97.

wiki/Kenichthys
wiki/Youngolepis
wiki/Ligulalepis

Publicity

theconversation.com/its-less-than-2cm-long-but-this-400-million-year-old-fossil-fish-changes-our-view-of-vertebrate-evolution-96419

labonline.com.au/content/life-scientist/news/the-ancestor-of-all-bony-fish-has-a-surprising-link-to-humans-433759295

An awkward Dorygnathus model from a museum in Karlsruhe, Germany

Middle Jurassic Germany was home
to quite a few Dorygnathus specimens (Fig. 1), among them the Donau specimen (Fig. 2), a basal dorygnathid in the Large Pterosaur Tree (LPT, 261 taxa) with shorter fingers and gracile wings.

Figure 8. Click to enlarge. The descendants of Sordes in the Dorygnathus clade and their two clades of pterodactyloid-grade descendants.

Figure 2. The Donau specimen of Dorygnathus is very close to Sordes. Note how slender this specimen is compared to the specimen in figure 4.

So it comes with equal parts surprise and disappointment
that the Dorygnathus model on display at the Natural History Museum, Karlsruhe, Germany (Paläozoologe Staatliches Museum für Naturkunde Karlsruhe) is so awkwardly posed (Fig. 3). Apparently this reflects the current mythology of a wing-launch in pterosaurs. It cheats pterosaur morphology in a similar fashion.

Figure 3. Dorygnathus model from the Natural History Museum in Karlsruhe, Germany. Arrows point to errors in the reconstruction described in the text.

The Karlsruhe Dorygnathus model manus
(Fig. 2) relocates the three free fingers to the top of the wing finger, raising the fingers off the substrate and impressing the wing finger into the substrate. This is just the opposite of all pterosaur manus impressions in which fingers 1–3 impress and wing finger 4 does not. No pterosaur specimens preserve this orientation. Rather this relocation comes from the imagination of pterosaur workers beginning with Michael Habib. and supported by Naish, Witton and Martin-Silverston 2021.

Figure 4. Pterodactylus walking to match tracks on top of wire frame model posed in figure 5. Here fingers 1-3 make an impression with the wing finger ‘knuckle’ elevated, as in all pterosaur manus tracks.

Figure 5. Walking pterosaur according to Bennett and the Karlsruhe Dorygnathus model. Note the forelimbs are angled so far anteriorly that only digit 3 has a chance of making an impression contra pterosaur manus ichnites. The wing finger might make an impression contra pterosaur manus ichnites.

The Karlsruhe Dorygnathus model pes
(Fig. 2) is plantigrade and extends pedal digit 5 laterally with nothing to do. We’ve known for twenty one years (since Peters 2000a, 2000b; Fig. 6) that pedal digit 5 bent beneath itself helping to support a digitigrade pes in basal pterosaurs like Dorygnathus (FIg. 7). This is documented in Rotodactylus tracks that match the pes of pterosaur precursor, Cosesaurus, with a similar metapodial lateral toe. Plantigrade pterosaur feet with a tiny lateral toe evolved later (Fig. 3).

Figuure 6. Cosesaurus matched to Rotodactylus from Peters 2000.

Pterosaurs have been traditionally depicted as awkward on land.
This myth goes back a century or two. Now that we know how pterosaurs walked (FIgs. 2, 4, 7), the old awkward model (Figs. 3, 5) supported only by errors has to go by the wayside, into the trash heap along with tail-dragging dinosaurs.

Figure 7. Dorygnathus model (based on a different specimen with more robust bones and larger fingers, in a more upright pose with fingers aligned as in all other tetrapods and lateral toe bent beneath itself.

Pterosaur expert,
NHM Karlsruhe professor Eberhard ‘Dino’ Frey, is probably responsible for the pose and errors in the Karlsuhe model Dorygnathus. Frey was also a co-author on a paper (Elgin, Hone and Frey 2011) that imagined bat-wing pterosaur membranes extending to the ankle (Fig. 8 top) where no such membranes exist. Note the dorsal placement of metacarpals 1–3 in the Elgin, Hone and Frey graphic. These errors are not just a difference of opinion. You might remember that Elgin, Hone and Frey 2011 explained away the factual appearance of Pterodactylus and Rhamphorhynchus narrow chord wings as ‘shrinkage.’ These are examples of professors cheating fossil data to support pet hypotheses and the sale of their textbooks and lectures.

Figure 8. Click to enlarge. Problems with the Elgin, Hone and Frey (2011) pterosaur wing model with corrections proposed by Peters (2002).

In the Peters 2002 model,
Fig. 5) the three metacarpals are aligned as they are in all tetrapods, flexor surface down. Only metacarpal 4 is rotated axially in order for digit 4 to flex (fold) and extend (fly) in the plane of the wing.

References
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica 56 (1), 2011: 99-111. doi: 10.4202/app.2009.0145
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 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.

http://reptileevolution.com/pterosaur-wings.htm
http://reptileevolution.com/pterosaur-wings2.htm

Cobelodus enters the LRT, but not at the base of all sharks and ratfish

When Zangerl and Williams 1976 looked at
the Pennsylvanian shark, Cobelodus aculeatus FMNH PF7347 (Fig. 1), they concluded, “These anacanthous [= spineless] sharks represent the most primitive gnathostome [= jaws] condition presently known.”

It is easy to imagine how this could be true. Unfortunately, this is not true when placed in a phylogenetic context (and relabeled, Fig. 1). Remember, we should not categorize taxa based on a short or long list of traits that can converge. Rather we should classify taxa based on their nesting in a wide gamut cladogram in which a last common ancestor can be determined and taxon exclusion has been minimized.

Figure 1. Cobelodus from Zangrel and Case 1976. Colors added here. Note the extremely tiny tooth (circled). That’s why Cobelodus is drawn in this diagram as if it had no teeth.

The LRT gives credit for the genesis of jaws
to toothless Chondrosteus (Fig. 2), following jawless sturgeons and preceding all sharks sometime in the Silurian.

Figure 2. Top to bottom: Thelodus a soft jawless fish with a ventral oral opening and gill slits, perhaps a hint of diamond-shaped armor laterally. Hemicyclaspis, adds extensive armor. Acipenser brevirostrum, a short-listed sturgeon with a protrusible tube for a mouth and reduced armor. Pseudoscaphorhynchus, a derived sturgeon. Chondrosteus, a fish with jaws, but no marginal teeth.

Cobelodus nests as a derived shark
close to megamouth sharks (Megachasma. Fig. 3) among living taxa, first discovered in 1976 and described in 1983.

Figure 3. Megachasma, the megamouth shark, is the closest living relateive of Cobelodus in the LRT.

According to Wikipedia,|
“Cobelodus is an extinct genus of holocephalid that lived in the Middle to Late Carboniferous period in what is today Illinois and Iowa“.

Here in the large reptile tree (LRT, 2006+ taxa, Fig. 5) Cobelodus nests with Falcatus (FIg. 4). These taxa nest far from extant and extinct holocephalids (ratfish, chimaeras).

“Cobelodus was a 2 metres (6.6 ft) long predator. Although it was related to chimaeras, Cobelodus had a number of differences from modern forms.”

Not related to chimaeras, so it’s no surprise
Cobelodus “had a number of differences from modern forms.”

“It had a bulbous head, large eyes, a high-arched back, and a dorsal fin placed far to the rear, above the pelvic fins. Because of its large eyes, it is thought to have lived in the deeper, darker parts of the sea, hunting crustaceans and squid. Another unusual physical feature of Cobelodus are the 30 centimetres (12 in) long, flexible cartilagenous ‘tentacles’ sprouting from its pectoral fins. Their purpose is unknown.”

See those pectoral ‘tentacles’ in figure 1.

Figure 4. Falcatus nests as a close relative of Cobelodus in the LRT.

Carroll 1988 reported,
“the simple skull surrounded by enlarged gill elements apparently evolving to become jaws, hyoids and the hyomandibular arch.”

It would seem so, but toothless jaws appeared on another taxon, Chondrosteus, phylogenetically much earlier than in Cobelodus.”

According to Wikipedia
“Symmoriiformes is an extinct order of holocephalians. Originally named Symmoriida by Zangerl (1981), it has subsequently been known by several other names. Lund (1986) synonymized the group with Cladodontida, while Maisey (2008) corrected the name to Symmoriiformes in order to prevent it from being mistaken for a family. The symmoriiform fossils record appear at the beginning of the Carboniferous. Most of them died out at the start of the Permian, but Dwykaselachus is known from the Artinskian–Kungurian of South Africa. However, teeth described from the Valanginian of France and Austria^[ indicates that members of the family Falcatidae might have survived until the Early Cretaceous.”

Adding taxa moves Falcatus and Cobelodus away from holocephalians in the LRT.

Figure 5. Subset of the LRT focusing on basal vertebrates. Note the clade Holocephali nests apart from Falcatus and kin. Cobelodus now nests with Falcatus, but this cladogram precedes that nesting.

Cobelodus aculeatus (Zangerl and Case 1976, originally Styptobasis aculeata Cope 1891; FMNH UF576; Pennsylvanian, Middle to Late Carboniferous; 2m) is a large, shark-like taxon originally considered a holocephalian. Here it nests with Falcatus as ‘the best known Paleozoic elasmobranch’ (ca 1976). Zangerl and Case note, “In the differentiation of the neurocranium and the visceral skeleton, Cobelodus presents a morphological condition not previously documented in any chondrichthyan, or, for that matter, any other fish.” The hyoid arch is not connected by ligaments in any with the mandibular arch. The authors considered this pirmitive, but reported, “Not everyone, nowadays, would agree that the aphetohyoidian condition in Cobelodus and its allies is primitive.” Large eyes suggest a deep sea niche. The pectoral fins have a 30cm trailing feeler supported by flexible cartilage. No anal fin is present. The pelvic fins are elongate.

References
Coates M, Gess R, Finarelli J, Criswell K and Tietjen K 2016. A symmoriiform chondrichthyan braincase and the origin of chimaeroid fishes. Nature. 541: 208–211.
Zangerl R 1981. Chondrichthyes I – Paleozoic Elasmobranchii. Handbook of Paleoichthyology. Stuttgart: Gustav Fischer Verlag. pp. i–iii, 1–115.
Zangerl R and Case GR 1976. Cobelodus aculeatus (Cope), an anacanthous shark from Pennsylvanian black shales of North America.
Zangerl R and Williams ME 1975. New evidence on the nature of the jaw suspension in Palaeozoic anacanthous sharks. Palaeontology, 18(2), 333–341.

Anacanthous = without a spine.
wiki/Cobelodus
wiki/Symmoriiformes

Middle Devonian Gladbachus enters the LRT alongside the previously omitted whale shark, Rhincodon

Gladbachus adentatus (Heidtke & Krätschmer 2001; Burrow and Turner 2013; Coates et al. 2018; Middle Devonian, est. 54cm; Figs. 1, 2) was originally considered an ‘unfamiliar’ basal chondrichthyan close to acanthodians (spiny sharks) and placoderms.

By contrast
in the large reptile tree (LRT, 2005 taxa) Gladbachus (Figs. 1, 2) nests with the whale shark, Rhincodon (Figs. 3, 4), derived from Early Silurian Loganellia (Fig. 5). Gladobachus was a toothless taxon with a low, wide gape, filtering small, nektonic (= free swimming) prey with enormous gill bars, yet has never been compared to the quite similar whale shark.

Figure 1. Gladbachus in situ. Skull and gill bars at left. Pelvic girdle at right. Estimated length = 54cm

Burrow and Turner 2013 reported,
“Gladbachus adentatus is a putative chondrichthyan, known only from the holotype specimen, which comprises an articulated endoskeleton complete from head to pelvic region with the squamation also preserved. The scales superficially resemble those of placoderms more than sharks, in having a similar gross morphology, lamellar cellular bone forming the base and upright dentinous tubercles comprising the crown. The odontocytic mesodentine in the tubercles is comparable to that in the Osteostraci and in some acanthodian taxa, known only from isolated scales, and is probably the plesiomorphic form of dentine for Gnathostomata.”

Notice how they are cherry-picking traits? Don’t do that. We call that “Pulling a Larry Martin.” Instead, use a cladogram and the last common ancestor method. That always works and avoids the problem of convergence. Osteostraci are armored, jawless fish nesting prior to jawless sturgeons (Fig. 6) in the LRT. The most primitive gnathostome, toothless Chondrosteus (Fig. 6), nests between sturgeons and Loganellia in the LRT.

Figure 2. Diagram and µCT scan from Coates et al. 2018, colored here to match tetrapod homologs. Note: the diagram has a short hyomandbiular and other differences from the µCT scan. Restoration of anterior elements added Oct 30, 2022.

Coates et al. 2018 reported,
“Although relationships among the major groups of living gnathostomes are well established, the relatedness of early jawed vertebrates to modern clades is intensely debated.

After you read this critique, ask yourself if relationships are indeed well-established, or are Coates et al. relying on out-dated textbooks and traditions based on taxon exclusion?

Figure 3. The whale shark, Rhincodon, has an enormous gill chamber for capturing planktonic prey.

Coates et al. 2018 continue:
Here, we provide a new description of Gladbachus, a Middle Devonian (Givetian approx. 385-million-year-old) stem chondrichthyan from Germany, and one of the very few early chondrichthyans in which substantial portions of the endoskeleton are preserved. Tomographic and histological techniques reveal new details of the gill skeleton, hyoid arch and jaws, neurocranium, cartilage, scales and teeth. Despite many features resembling placoderm or osteichthyan conditions, phylogenetic analysis confirms Gladbachus as a stem chondrichthyan and corroborates hypotheses that all acanthodians are stem chondrichthyans.

This is incorrect. Gladbachus is a crown condrichthyan, a sister to Rhincodon. No acanthodians are stem chondrichthyans in the LRT. Add more taxa to let taxa sort themselves out. Cherry-picking taxa often results in false statements and myths.

Figure 4. Skull of Rhincodon colored as in figure 1. A postfrontal present here is absent in Gladbachus.

Coates et al. 2018 continue:
The unfamiliar character combination displayed by Gladbachus, alongside conditions observed in acanthodians, implies that pre-Devonian stem chondrichthyans are severely under-sampled and strongly supports indications from isolated scales that the gnathostome crown group originated at the latest by the early Silurian (approx. 440 Ma).

Agreed. Evidence of this comes from Early Silurian Loganellia (Fig. 5),
also omitted by prior authors.

Moreover, phylogenetic results highlight the likely convergent evolution of conventional chondrichthyan conditions among earliest members of this primary gnathostome division, while skeletal morphology points towards the likely suspension feeding habits of Gladbachus, suggesting a functional origin of the gill slit condition characteristic of the vast majority of living and fossil chondrichthyans.”

Gills slits are a reversal in sharks. Ancestral sturgeons and Chondrosteus have/had an operculum. Don’t get caught assuming any trait (= “Pulling a Larry Martin“).

Figure 5. Early Silurian Loganellia (16cm length), ancestral to whale sharks and all other vertebrates with jaws, including tetrapods and humans.

Public comments in Chicago.edu reporting on Coates et al. 2018:
“The evolutionary descendants of Gladbachus died out, but new analysis of the fossil is helping build out the rest of the shark family tree.”

Taxon exclusion is the problem with all prior studies of Gladbachus.
Extant whale sharks are evolutionary descendants of Gladbachus.

“Sharks aren’t as primitive as generally assumed,” said Michael Coates, a paleontologist at the University of Chicago who led the new study of Gladbachus. “It’s a bit of a textbook cliché that the sharks you see swimming around today look much like their earliest ancestors. But that’s partly because people are uncertain of what our last common ancestors looked like.”

So ironic. Coates et al. never considered whale sharks,
which are nearly identical to Gladbachus.

GIF animation 1. µCT scan of Gladbachus skull rotating.

Rob Margetta reporting on NSF online
“Sharks have a reputation as ravenous hunters and apex predators, but new analysis of fossil records shows that some of the earliest sharks might have been filter feeders, taking in water through their mouths and catching food particles — think less great white and more anchovy, another filter feeder.”

Anchovy=?? Why not Rhincodon? It was completely omitted.
Cetorhinus, the basking shark, is mentioned briefly.

“instead having a stubby snout and large, forward-facing eyes. Its body would have been fairly flat, like a combination of a shark and a catfish. And, significantly, its head would have made up about a third of its body length, with big gills. “That long gill basket is a clue that it was likely a filter feeder,” Coates said.

That pretty much describes a whale shark (Figs. 3, 4).

“Instead of lurking on the seafloor and ambushing prey, as many of its contemporaries did, Gladbachus may have been one of the first vertebrates to live in the water column — the space between the ocean’s surface and bottom — where anchovies, sardines and herring make their home today.”

That pretty much describes a whale shark (Figs. 3, 4).

“This fish has been confusing,” Coates said. “We’ve only ever thought it to be a shark, but [it] didn’t evolve the way we thought sharks did. It’s almost like a facsimile or a copy of a shark, with some substitutions made.”

In the LRT, whale sharks are the blueprints from which all other sharks evolved. So strange that it was never mentioned by Coates et al and prior authors.

“Its scales were like the scales of placoderms, extinct fish that were often covered in thick, heavy armored plating.”

Adding taxa would have solved all these issues as the LRT documents. Whale shark scales were never considered by Coates et al.

“Sharks developed as an evolutionary offshoot from bony fish — non-armored species with skeletons made of bone, like modern fish. But rather than a complete split into a new family tree, Coates said, Gladbachus and its contemporaries were more like the tips of emerging shrubbery, with a whole range of body types — probably including some that resembled placoderms.”

Just the opposite. Bony fish developed from sharks, and placoderms are bony fish when more taxa are added, as the LRT documents.

“The earliest sharks might well have been armored,” Coates said. “We just don’t know how to recognize them yet.”

This is a bad guess. The LRT does not support this guess.

“the new findings indicate that the Silurian could hold new treasures for biologists, if they can find evidence of the organisms that were living there. Another thing this area of research shows,” Coates said, “is how poor the Silurian fossil record is.”

This is a good idea. The LRT supports this hypothesis.

Figure 6. Fish evolution from Hybodus to Amia documenting the shark to bony fish transition.

References
Burrow C and Turner S 2013. Scale structure of putative chondrichthyan Gladbachus adentatus Heidtke & Krätschmer, 2001 from the Middle Devonian Rheinisches Schiefergebirge, Germany. Historical Biology 25(3):385–390.
Coates et al. (7 co-authors) 2018. An early chondrichthyan and the evolutionary assembly of a shark body plan. Proc. R. Soc. B 285:20172418. http://dx.doi.org/10.1098/rspb.2017.2418
Heidtke UHJ and Krätschmer K 2001. Gladbachus adentatus nov. gen. et sp., ein primitiver Hai aus dem Oberen Givetium (Oberes Mitteldevon) der Bergisch Gladbach – Paffrath-Mulde (Rheinisches Schiefergebirge). Mainzer geowiss. Mitt. 30, 105–122.

Publicity from 2018:
https://www.livescience.com/61315-humans-sharks-common-ancestor.html

https://news.uchicago.edu/story/study-ancient-fossil-complicates-shark-family-tree

https://www.marinetechnologynews.com/news/ancient-sharks-likely-diverse-556106 “This research, supported by the National Science Foundation (NSF), pushes the date for the last common ancestor between sharks and other types of jawed vertebrates back to 440 million years ago – more than 17 million years older than the previous estimate – and raises new questions about what life was like during a prehistoric period long shrouded in secrecy.”

wiki/Gladbachus

Gephyrostegus moves one node to the base of the Archosauromorpha

Gephyrostegus bohemicus (Figs. 1, 2) was one of the first taxa added to the large reptile tree (LRT, 2003+ taxa) almost eleven years ago when this online experiment had its genesis at 200 or so taxa. Distinct from traditional studies, Gephyrostegus nested at or near the base of the Reptilia (= Amniota), occasionally trading places with Silvanerpeton (Figs. 1, 2) from the Viséan (Early Carboniferous). Thereafter reptiles split into two clades in the LRT: Lepidosauromorpha and Archosauromorpha (Fig. 1). This also breaks from textbooks and university traditions based on taxon exclusion. These vertebrate paleontology institutions are now ten years out of date.

Academic workers do not nest amphibian-like Gephyrostegus
within the Reptilia. Similarly, academic workers do not nest amphibian-like Limnoscelis and Diadectes within the Reptilia. This is unfortunate because Gephyrostegus is in the lineage of synapsids, mammals and humans in the LRT. It’s morphology teaches something about how one branch of reptiles laid larger eggs and crawled further from the water.

Figure 1. Click to enlarge. Gephyrostegus moves to the base of the Archosauromorpha with its long-legged, hump-backed relatives.

We’ve known about this basal dichotomy
for the last ten years. Add taxa to your own cladogram to confirm or refute this novel hypothesis because current workers are reticent to do so.

Figure 2. Eusauropleura to scale with ancestral and descendant taxa including Eucritta, Utegenia, Silvanerpeton and Gephyrostegus, the last common ancestor of all reptiles.

The robust torso and robust long legs of Gephyrostegus
(Fig. 1) seemed to link it to similar basal archosauromorphs, like Eldeceeon (Fig. 1) and Diplovertebron (= Gephyrostegus watsoni, Fig. 1). This is distinct from basal lepidosauromorphs with shorter legs, and more like their last common ancestor, Silvanerpeton (Fig. 2).

Figure 3. Revised skull of Gephyrostegus based on DGS tracing over photo published in Klembara et al 2014.

A review of ten-year-old scores for taxa
now surrounded by ten years of taxon inclusion revealed several dozen scoring errors that were corrected based on a photo of the skull published by Klembara et al. 2014 (Fig. 2) rather than tracings and freehand reconstructions by Carroll 1970. The many subtle changes found in the skull shifted Gephyrostegus to the base of the Archosauromorpha joining other taxa sharing a robust torso and larger limbs. Notably, there is no score for ‘large hind limbs’ or ‘humpback torso’ in the LRT MacClade matrix, which has enough characters, so long as they are correctly scored.

The number of corrections in the LRT
continues to rise, erasing former mistakes. Even so, the early LRT did a pretty good job, errors and all. Taxon inclusion continues to trump character inclusion. That’s because the LRT lumps and separates taxa, not characters.

Gephyrostegus bohemicus
(Jaeckel 1902) Upper Carboniferous (~310 mya)~22 cm snout-vent length, is the basalmost archosauromorph, derived from Viséan Silvanerpeton, the basalmost reptile. Gephyrostegus is 30 million years younger. Gephyrostregus phylogenetically preceded the basal archosauromorph, Eldeceeon, also from the Viséan.

Distinct from Silvanerpeton, the presacral vertebral count was reduced to 24. All four limbs were larger and robust. Manual digits IV and V were longer. The girdles were more robust. The intermedium is fused to create the astragalus.

Gephyrostegus bohemicus has no traditional amniote characters, but nests within the Reptilia. Gephyrostegus had more terrestrial, longer legs, fewer dorsal ribs, a fused astragalus, and a deeper pelvis. Phylogenetic bracketing indicates Gephyrostegus laid amniotic eggs, the key trait of the Amniota = Reptilia.

While most early tetrapods lived their lives in water, Gephyrostegus was among the few that preferred land (= moss covered swampy coal forest logs). Tiny circular scales covered the body except ventrally where large V-shaped scales were present.

Whenever the LRT seems to stumble or stall,
better data revealed by DGS tracings (Fig. 2) correct errant scores making possible the lumping and splitting that the LRT is built to do and generally does well based on minimizing taxon exclusion.

References
Brough MC and Brough J 1967. The Genus Gephyrostegus. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 252 (776): 147–165. doi:10.1098/rstb.1967.0006
Carroll RL 1970. The Ancestry of Reptiles. Philosophical Transactions of the Royal Society London B 257:267–308. online pdf
Gauthier JA 1986. Saurischian monophyly and the origin of birds. Memoirs of the California Academy of Science. 8: 1–55.
Jaeckel O 1902. Über Gephyrostegus bohemicus n.g. n.sp. Zeitschrift der Deutschen Geologischen Gesellschaft 54:127–132.
Klembara J, Clack J, Milner AR and Ruta M 2014. Cranial anatomy, ontogeny, and relationships of the Late Carboniferous tetrapod Gephyrostegus bohemicus Jaekel, 1902. Journal of Vertebrate Paleontology 34:774–792.
Moodie RL 1916. Journal of The coal measures Amphibia of North America. Carnegie Institution of Washington #238. 222 pp.
Ruta M, Jeffery JE and Coates MI 2003. A supertree of early tetrapods. Proceedings of teh Royal Society, London B (2003) 270, 2507–2516 DOI 10.1098/rspb.2003.2524 online pdf

wiki/Gephyrostegus

Milleretta and its unpopular and miscatergorized proximal descendants

Today’s topic covers a traditionally unrecognized clade of reptiles
recovered (so far) only by the LRT. Many members (Figs. 1–4) are traditionally considered uninteresting. Others are considered members of unrelated clades. Many of their names are not known by the next crop of paleontologists, let alone the general public. Worse yet, some (see below) are not even considered reptiles by university professors and textbook authors.

Here
in the large reptile tree (LRT, 2003+ taxa; subset Fig. 2) plain and unremarkable Milleretta (Figs. 1–4) gives rise to all later lepidosauromorphs: diadectids (including procolophonids and bolosaurids), nyteroleterids (including owenettids and lepidosauriformes), and stephanospondylids (including pareiasaurs and turtles). Most, if not all of these taxa were herbivores.

Figure 1. Milleretta and its descendants include diadectids, stephanospondylids (including pareiasaurs and turtles) and nycterleterids (including lepidosauriforms).

Not sure why
these relationships have gone unnoticed until the LRT recovered them in 2011. These taxa all look more or less alike. Some were bigger, others smaller. Some had flaring cheeks, other lost their cheeks to develop lateral temporal fenestra. Some had procumbent premaxillary teeth, others lost all teeth. Some had long tails, others did not. Some were armored, others were not. Later descendants learned to glide, fly, run bipedally, swim, slither, burrow and kill… but today we’re looking at only the proximal descendants of Milleretta (Figs. 1–4).

Figure 2. Subset of the LRT from 2018 focusing on turtle origins and unrelated eunotosaurs, all descendants of Milleretta. Several taxa (e.g. Kudnu, Carbonodraco) have been added to this subset since 2018.

Traditionally
diadectids (Fig. 1) have been known as reptilomorphs, in other words: not even reptiles. This myth arises from taxon exclusion and cherry-picking taught at the university level. This is especially odd because all the surrounding taxa are universally accepted as reptiles. Here in the LRT (subset Fig. 2) diadectids nested within lepidosauromorph reptiles in 2011. Diadectids look nothing like any known reptilomorphs.

Figure 3. Milleretta, caseasaurs and kin. The LRT nests these taxa together apart from the Synapsida, with which they share a lateral temporal fenestra.

The basal taxon, Milleretta,
(Figs. 1–4) is still considered a ‘parareptile’ in textbooks and Wikipedia. Due to taxon exclusion ‘Parareptilia‘ has been shown to be an invalid wastebasket of unrelated reptiles.

In the LRT
(subset Fig. 2) all taxa are equally important no matter how ‘uninteresting’ they appear to others. All taxa in the LRT are important because they keep solving phylogenetic problems better than the more spectacular taxa. That’s something you, too, will find out when you add these taxa to your cladogram.

Figure 4. The Feeserpeton-Eunotosaurus clade arising from Milleretta. Here the skulls of Feeserpeton, Australothyris, Delorhynchus, Microleter, Acleistorhinus, Eunotosaurus and Eorhynchochelys are shown to scale. Note the resemblance of the Milleretta to Eorhynchochelys, showing not much change including the broad ribs, other than size separates the first and last of these taxa. Eunotosaurus has fewer ribs.

Saved for last,
the first clade to arise from Milleretta includes the synapsid-mimic Caseasauria clade (Figs. 2–4) plus the Feeserpeton clade that includes the more famous turtle-mimics Eunotosaurus and Eorhynchochelys. These last two taxa have been mistakenly associated with turtles in academic circles, but this is only due to excluding the taxa listed and illustrated above, seen together for the first time today.

Happy Thanksgiving to my American readers.

References
wiki/Diadectomorpha
wiki/Millerettidae
wiki/Millerosauria

https://pterosaurheresies.wordpress.com/2013/05/19/diadectes-is-not-an-amphibian-and-procolophon-is-a-diadectid/

https://pterosaurheresies.wordpress.com/2011/09/27/moving-diadectomorphs-into-the-reptilia/

What is Eoscopus?

According to Wikipedia
“Eoscopus is an extinct genus of dissorophoidean euskelian temnospondyl in the family Micropholidae. It is known from Hamilton Quarry, a Late Carboniferous lagerstätte near Hamilton, Kansas.”

That’s a lot of clades.
For starters, you can see Micropholis and two versions of Eoscopus illustrated here (Fig. 1). The yellow one is from Huttenlocker et al. 2007. Other definitions follow the citations below.

Figure 1. Freehand skull figures from Huttenlocker et al. 2007 compared to three tracings from other authors and one DGS reconstruction based in tracing in figure 2. Occasionally freehand drawings are not as accurate as one would wish, but they are nice to look at.

Digital Graphic Segregation
(DGS) traced a different skull (Figs. 1, 2, 4) over the Late Carboniferous temnospondyl, Eoscopus than traditional methods using freehand drawing (Fig. 1). So much so that it nests in the large reptile tree (LRT, 2003+ taxa; subset Fig. 3) apart from taxa recovered by Huttenlocker et al. 2007 (Fig. 1).

Figure 2. Eoscopus traced using DGS methods. At left is the reconstruction of the skull based on the DGS tracings. A reconstruction of the overall skeleton appears in figure 2.

The LRT
nests small Late Carboniferous Eoscopus far from a traditional tiny sister, Micropholis (Fig. 1) and close to the small Early Permian temnospondyl, Zatrachys (Fig. 3). These two nest basal to two larger Permian taxa, Eryops and Edops (Fig. 5).

Figure 3. Subset of the LRT focusing on basal vertebrates. Pertinent taxa are highlighted.

The Huttenlocker et al. 2007 nesting of Eoscopus
with Micropholis (Fig. 1) corresponds to their freehand drawing of the Eoscopus skull (Fig. 1).

By contrast
DGS traced elements moved back to their in vivo positions reveal a large dorsal fontanelle and spiky quadratojugal in Eoscopus (Fig. 4), as in Zatrachys (Fig. 5).

Figure 4. Eoscopus reconstructed from DGS tracings in figure 1.

Eoscopus lockardi
(Daly 1994; Late Carboniferous) was originally considered a sister to Micropholis (Fig. 1), but here nests with Zatrachys (Fig. 4). Both share a large medial fontanelle and small nares located far from the snout tip. The posterior skull includes several quadratojugal and tabular spines. The skull is enormous relative to the body.

Figure 5. Two Zatrachys skulls. Compared to Eoscopus in figures 1 and 2.

Zatrachys serratus
(Cope 1878; Early Permian; Fig. 5) is related to Eryops and Edops (Fig. 6) in the LRT (Fig. 3), and now Eoscopus (Figs. 1, 2, 4). Adults had elaborate bony spikes on the skull. Note the large medial fontanelle between the nares. It may have housed an inflatable sac.

Figure 5. Edops in dorsal and palatal views.

Sometimes the less aesthetic, but more accurate tracing
is the one you should use for scoring character traits. Imagination should not be substituted for data. Imagination can lead others (e.g. Schoch 2018) astray.

References
Cope ED 1878. Description of extinct Batrachia and Reptilia from the Permian formation of Texas. Proceedings of the American Philosophical Society 17: 505–530.
Daly E 1994. The Amphibamidae (Amphibia: Temnospondyli), with a description of a new genus from the Upper Pennsylvanian of Kansas. University of Kansas Museum of Natural History Miscellaneous Publication 85.
Huttenlocker AK, Pardo JS and Small BJ 2007. Plemmyradytes shintoni, gen. et. sp. nov., an Early Permian Amphibamid (Temnospondyli: Dissorophoidea) from the Eskridge Formation, Nebraska”. Journal of Vertebrate Paleontology. 27 (2): 316–328.
Shoch R 2018. The putative lissamphibian stem-group: phylogeny and evolution of the dissorophoid temnospondyls. Journal of Paleontology 20pp. DOI: 10.1017/jpa.2018.67

Dissorphophus is a genus of armored, terrestrial, basal vertebrate close to Cacops.

Euskelia = all temnospondyls closer to terrestrial Eryops than to aquatic Parotosuchus.

Temnospondyls (from Wikipedia) = “Experts disagree over whether temnospondyls were ancestral to modern amphibians (frogs, salamanders, and caecilians), or whether the whole group died out without leaving any descendants. Different hypotheses have placed modern amphibians as the descendants of temnospondyls, another group of early tetrapods called lepospondyls, or even as descendants of both groups (with caecilians evolving from lepospondyls and frogs and salamanders evolving from temnospondyls). Recent studies place a family of temnospondyls called the amphibamids as the closest relatives of modern amphibians.”

wiki/Eryops
wiki/Edops
wiki/Zatrachys
wiki/Eoscopus
wiki/Euskelia
wiki/Temnospondyli

Pasawioops, Plemmyradytes and Micropholis enter the LRT together as human, frog and dinosaur ancestors

Fröbisch and Reisz 2014
brought us “a new dissoropoid amphibian”, Pasawioops, represented by an excellent small skull (Fig. 1) and a 2x larger partial skull (not shown).

Figure 1. Pasawioops skull in four views from Fröbisch and Reisz 2014. Colors added here.

From the abstract:
“A phylogenetic analysis of 17 ingroup taxa and 62 cranial and postcranial characters yielded a single most-parsimonious tree with the new taxon in a monophyletic Amphibamidae as the sister taxon to the Lower Triassic Micropholis (Fig. 2) from South Africa.”

Figure 2. Micropholis preserves the skull and post-crania.

In agreement with this nesting,
the large reptile tree (2003+ taxa; subset Fig. 3) nests Pasawioops (Fig. 1) with Plemmyradytes (Fig. 4) and Micropholis (Fig. 2).

Figure 3. Subset of the LRT focusing on Pasawioops and kin. Here Pasawioops is not related to Amphibamus and Trimerorhachis was not included in Fröbish and Reisz 2014.

By contrast
the LRT (Fig. 3) nests these two between Trimerorhachis + Dendrepeton and Perryella + Tersomimus far from Amphibamus which nests in the Reptilomorpha in the LRT. They phylogenetically precede Tulerpeton which lived in the latest Devonian, so that’s when these taxa radiated, despite a lack of similar fossils found so far in Late Devonian strata.

From the abstract
“In addition, the new analysis supports a basal split of Amphibamidae into two distinct clades, one containing the new taxon, Micropholis, along with Tersomius, and the other comprising Amphibamus, Gerobatrachus, Doleserpeton, Platyrhinops, Plemmyradytes, Eoscopus, and Georgenthalia. The data retrieved from this new taxon provides insights into the evolution and diversity of the Amphibamidae.”

Maybe 17 ingroup taxa is too few.
In the LRT some taxa employed by Fröbisch and Reisz 2014 nest with Micropholis and Pasawioops, but some taxa do not.

Plemmyradytes shintoni
(Huttenlocker et al. 2007; Early Permian) is known from a tiny partial skull. Here as elsewhere this taxon nests with Micropholis. These are traditionally considered members of the Amphibamidae, but neither nests close to Amphibamus.

Figure 4. Plemmyradytes shintoni as originally reconstructed in freehand by Huttenlocker et al. 2007(right) compared to DGS tracing of published photos and tracings (left).

Pasawioops mayi
(Fröbisch and Reisz 2008; Early Permian) was considered an amphibamiform, but does not nest with Amphibamus in the LRT. Here this small specimen nests between Dendrerpeton and Perryella.

Micropholis stowi
(Huxley 1859; Early Triassic) is known for nearly the entire skeleton. Here an alternate manus with a two-phalanx thumb is provided. Here the lateral view of the skull does not always match the dorsal view. Many specimens are known.

These taxa are in the lineage leading to Reptilomorpha and Anura.
Therefore these taxa are late survivors in the lineage of both Homo sapiens and frogs (e.g. Rana), if that matters to you.

References
Fröbisch NB and Reisz RR 2008. A New Lower Permian Amphibamid (Dissorophoidea, Temnospondyli) from the Fissure Fill Deposits Near Richards Spur, Oklahoma. Journal of Vertebrate Paleontology 28(4):1015–1030.
Huttenlocker AK, Pardo JS and Small BJ 2007. Plemmyradytes shintoni, gen. et. sp. nov., an Early Permian Amphibamid (Temnospondyli: Dissorophoidea) from the Eskridge Formation, Nebraska”. Journal of Vertebrate Paleontology. 27 (2): 316–328.
Huxley TH 1859. On some Amphibian and Reptilian Remains from South Africa and Australia. Quarterly Journal of the Geological Society. 15 (1–2): 642–658.

wiki/Dendrerpeton
wiki/Pasawioops
wiki/Micropholis

Cervifurca: the most remora-like of the odd Pennsylvanian iniopterygians

Cervifurca nasuta
(Zangerl 1997; Pennsylvanian; FMNH PF13228; Figs. 1, 2) was described by a partial, slightly disarticulated skeleton lacking a (probably short) anterior rostrum.

Figure 1. Cervifurca overall in lateral view from Zangerl 1997. Notes added here.

From the Zangerl abstract:
“This taxon is remarkable for its dorsoventrally flattened body habitus and probably (functionally) correlated enormous size of the pterygopodia, and for orbits that face dorsolaterad. The neurocranium is provided with very prominent nasal capsules, and the pelvic fins consist of a few very short and stout radials. Cervifurca nasuta was probably a member of the mobile benthos.”

Figure 2. Skull of Cervifurca in several views from Zangerl 1997. Colors added here using tetrapod homologs. Arrows show how Zangerl’s lateral view does not match the dorsal view with regard to the circumorbital ring. Note the unique break-up of the maxilla into discrete tooth-bearing units attached to the lacrimal. The palatoquadrate (pq) is relabeled here in white type.

The sharp teeth of Cervifurca,
and the large laterally extended nasals are reversals to a more shark-like morphology. Note, the dorsal orbits and complete circumorbital ring.

Figure 3. A remora attached to a much larger shark with an adhesion disc atop its head. Gone are the 6 to 9 dorsal spines. Note the position of the pectoral fins helping to wrap around the host’s larger body. The point is: remoras can attach themselves either way. The caudal fin is not used while hitching a ride.

Ecologically
Cervifurca was the most remora-like (Fig. 3) of all iniopterygians, using the tiny hooks of its huge pectoral fins to hold on to larger, faster, wider ranging hosts, rightside-up or upside-down.

Here
in the large reptile tree (LRT, 2003+ taxa) Cervifurca nests with Helodus within the ratfish clade.

Figure 4. Rainer ichthys from Grogan and Lund 2009. Colors added here.

A second iniopterygian,
Rainerichthys with a narrower skull featuring an intercranial joint (convergent with rhipidistians), was also added to the LRT.

References
Grogan ED and Lund R 2009. Two new iniopterygians (Chondrichthyes) from the
Mississippian (Serpukhovian) Bear Gulch Limestone of Montana with evidence of a new form of chondrichthyan neurocranium. Acta Zoologica (Stockholm) 90 (Suppl. 1): 134–151.
Zangerl R 1997. Cervifurca nasuta n. gen. et sp. : an interesting member of the Iniopterygidae (Subterbranchialia, Chondrichthyes) from the Pennsylvanian of Indiana, USA. Fieldiana, Geoloy new ser. no 35. Pub 1483. 24pp. PDF

wiki/Cervifurca – not yet posted
wiki/Rainerichthys– not yet posted

A Late Cretaceous fish with a predentary: Prosaurodon enters the LRT

In 1999 Stewart re-described Saurodon pygmaeus
(Loomis 1900) as a new genus: Prosaurodon pygmaeus (Fig. 1).

Today Prosaurodon enters
the large reptile tree (2002+ taxa) alongside the extant wolf herring, Chirocentrus (Figs. 2–4).

FIgure 1. Prosaurodon. Note the predentary ‘sword’. The maxilla (max) is divided here (color), distinct from the diagram (line tracing).

Traditionally
Prosaurodon is a member of the Saurodontinae, a clade within Icthyodectidae (Ichthyodectiformes), which includes the giant Late Cretaceous Xiphactinus (Fig. 4). The wolf herring, Chirocentrus (Figs. 2, 4), is an extant bastard taxon not recognized by paleontologists and ichthyologists as a long lost relative to these morphologically similar Late Cretaceous taxa.

Figure 2. The wolf herring (Chirocentrus) is a living fossil of the xiphactinid clade that includes Prosaurodon.

Figure 3. The large Saurodon with a longer predentary.

Figure 4. Taxa in the lineage of Xiphactinus going back to Salmo, the salmon.

Prosaurodon pygmaeus (Stewart 1999; Late Cretaceous) is a sister to the extant wolf herring in the LRT. Note the predentary ‘sword’.

Saurodon elongatus (Hays 1830; Late Cretaceous; 2.5m) is a larger genus discovered earlier.

References
Stewart JD 1999. A new genus of Saurodontidae (Teleostei, †Ichthyodectiformes) from Upper Cretaceous rocks of the Western Interior of North America. Mesozoic Fishes 2—Systematics and Fossil Record 335-360.

http://oceansofkansas.com/saurodon.html