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.
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.
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).
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.
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.
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.
When Zangerl and Williams 1976 looked at the Pennsylvanian shark, Cobelodus aculeatusFMNH 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.
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.
Cobelodus nests as a derived shark close to megamouth sharks (Megachasma. Fig. 3) among living taxa, first discovered in 1976 and described in 1983.
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.
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 Franceand 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.
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.
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 SilurianLoganellia(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.
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.
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?
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.
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“).
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.
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.
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.
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.”
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.
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.
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).
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 ViséanSilvanerpeton, 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
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.
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).
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.
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.
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.
That’s a lot of clades. For starters, you can see Micropholis and two versions of Eoscopusillustrated here (Fig. 1). The yellow one is from Huttenlocker et al. 2007. Other definitions follow the citations below.
Digital Graphic Segregation (DGS) traced a different skull (Figs. 1, 2, 4) over the Late Carboniferous temnospondyl, Eoscopusthan 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).
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).
The Huttenlocker et al. 2007 nestingof 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).
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.
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.
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
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.”
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).
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.”
By contrast the LRT (Fig. 3) nests these two between Trimerorhachis + Dendrepeton and Perryella + Tersomimus far fromAmphibamus 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.
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.
Cervifurca nasuta (Zangerl 1997; Pennsylvanian; FMNH PF13228; Figs. 1, 2) was described by a partial, slightly disarticulated skeleton lacking a (probably short) anterior rostrum.
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.”
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.
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.
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
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.
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.
Finarelli and Coates do not mention Heteropetalus. They note, “Lund (1982) re-described key anatomical features of Chondrenchelys in his comparative description of the slightly younger holocephalan Harpagofututor volsellorhinus from the Bear Gulch fauna, placing both genera in the Family Chondrenchelyidae (Berg 1940), based on their anguilliform (eel-like) body plans, and general similarities in the morphologies of the pectoral fin and tooth plates.”
The abstract continues: “Here, we provide a comprehensive new description of this taxon using three new specimens, in which we observe many morphological features for the first time. Much of the cranial morphology is closer to that of living chimaeroid holocephalans than was previously appreciated.“
The phylogenetic splitting of chimaeroid holocephalians from these moray eel (= Gymnothorax) relatives is unique to the LRT due to traditional taxon exclusion elsewhere. Add pertinent taxa to your favorite claodgram to split these clades.
The abstract continues: “For this reason, we provide original figures illustrating the chondrocranium of a hatchling Callorhinchus milii demonstrating these similarities. In Chondrenchelys, although the jaw articulation is positioned at the posterior margin of the orbit, the high-walled lamina orbitonasalis and densely-mineralised antorbital crest provide evidence for forward rotation of the jaw adductor musculature. Preserved foramina for the efferent superficial ophthalmic nerves show that the sensory organs on the rostrum were enervated in a manner similar to modern sharks, with the ophthalmic nerves not enclosed in an ethmoid canal, as in modern holocephalans.”
The abstract continues: “The conjunction of numerous distinctly holocephalan features with those that are otherwise general to Chondrichthyes demonstrates a decoupling of several of the structural conditions that characterise the distinctive morphological complex of the extant holocephalan skull.
The superficial convergence is readily observable.
The abstract continues: “The anguiliform postcranium is more elongate than previously reconstructed, and it is now clear that the axial skeleton extended beyond the posterior extremity of the elongate dorsal fin. Morphological characters are reviewed with a view to further phylogenetic analyses.
The abstract continues: “We recommend using the appearance of Chondrenchelys at 336.5 Ma as a hard minimum age for the last common ancestor of elasmobranchs and chimaeroids, because of its secure association with other holocephalans, and current uncertainties concerning elasmobranch stem lineage membership.”
Or not. Finarelli and Coates report, “published phylogenies of fossil holocephalans show little agreement. Grogan et al.’s (2012) tree of chimaeriforms and their fossil relatives differs profoundly from Stahl (1999), and both conflict with the topology of the holocephalan taxa in Pradel et al. (2011).”
The authors continue: “Relating the morphological disparity of living chondrichthyans to the increasingly detailed range of Palaeozoic forms presents a growing challenge; hence the significance of the new Mumbie Quarry specimens, which offer a more detailed and effective comparison between ancient and modern holocephalans.”
The authors conclude: “We do not undertake a phylogenetic reconstruction here; a comprehensive analysis will be undertaken in a related study (currently in preparation) on undescribed specimens from Bearsden, Scotland.”
A Google search failed to find a more recent (2015–2021) paper on Holocephali from Bearsden, Scotland, home of Stethacanthus. However, the authors of Wikipedia consider stethacanthids “prehistoric holocephalians’.Akmonistion (Fig. 5) is considered a stethacanthid, but it does not nest within the clade Holocephali in the LRT (Fig. 4). The LRT indicates it is time to split up the traditional members of this clade.
This appears to be a novel hypothesis of interrelationships. If not, please provide a citation so I can promote it here.
Thoughtful readers will note the LRT now has more than 2000 taxa, still splitting and lumping virtually all of them using the same 238 multi-state characters. They said it could not be done, but that’s the current state of this online experiment. The LRT continues to be relegated by professors, students, paleoartists, underemployed PhDs and trolls worldwide, often because it contradicts textbooks. Corrections continue wherever warranted. The early tree topology from 2011 has remained essentially unchanged, but for the addition of 10x more taxa, including several hundred fish. Thank you for your comments and readership as the pool of untested taxa continues to dry up. Hopefully new/old taxa will keep showing up.
References Finarelli JA and Coates MI 2014.Chondrenchelys problematica (Traquair, 1888) redescribed: a Lower Carboniferous, eel-like holocephalan from Scotland. Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 105 , Issue 1 , March 2014 , pp. 35 – 59 DOI: https://doi.org/10.1017/S1755691014000139