Short fish, long fish… Sometimes fish interrelationships seem like a Dr Seuss book. You might remember earlier we looked at long fish that evolved to become short fish. Later we looked at short fish that became long fish here.
Today, another overlooked short > long pairing as short (13cm) extantPantodon now nests basal to long (1.5m) Late Jurassic Pseudoasthenocormus (Fig 1) in the large reptile tree (LRT, 2265 taxa, subset Fig 2).
Figure 1. Large Late Jurassic Pseudoasthenocormus nests with the little extant butterfly fish, Pantodon, in the LRT. When you put the two together, the resemblance becomes obvious.
Pantodon buchholzi (Peters 1876-7; 13cm) is the extant freshwater butterflyfish. Traditionally considered close to Osteoglossum, here little Pantodon nests between mono-fanged Eocene Clupeopis(Fig 1) and Late Jurassic Pseudoasthenocormus. Large pectoral fins and pelvic fins provide a bit of a glide for this fish after leaping from the water. This is an air-breather that stays close to the surface. Males have a copulatory organ.
Figure 2. The subset of the LRT focusing on one branch of basal ray-fin fish, including Pantodon and Pseudoasthenocormus. See figure 1.
Pseudoasthenocormus retrodorsalis (Eastman 1914; Late Jurassic; BSPG 1956 I 361, 1.5m) was originally considered a pachycormiform. Here Pseudoasthenocormus nests basal to fanged extinct predators, like Xipactinus, and extant Hydrolycus, the dogtooth characin, from the Amazon.
References Eastman CR 1914. Catalog of the fossil fishes in the Carnegie Museum. Part IV. Descriptive catalog of fossil fishes from the Lithographic Stone of Solenhofen, Bavaria. – Mem. Carnegie Mus. 6 (7): 389-423. Peters WKH 1876-7. Über eine merkwürdige von Hrn. Professor Dr. Buchholz entdeckte neue Gattung von Süsswasserfischen, Pantodon buchholzi, welche zugleich eine neue, den Malacopterygii abdominales angehörige Gruppe von Fischen, Pantodontes, repräsentirt. Monatsberichte der Akademie der Wissenschaft zu Berlin 1876: 195-200.
But note: the coatimundi (Nasua, Figs1,7) is basal to the grizzly bear (Ursus arctos) in the LRT (subset Fig 6), so Eoarctos is a ‘dawn bear’, too. Eoarctos is also a dawn seal, dawn cat and dawn dog.
Wang et al 2023 described an “exquisitely preserved male skeleton of an early arctoid, Eoarctos vorax” (Figs 1—3).
This is an excellent paper, unfortunately undercut by genomics and taxon exclusion.
‘Arctoids’ are the red genomic taxa in figure 4 (below), every carnivore except the genomic cat and wolf relatives. The trait-based LRT does not support this clade.
Figure 1. Above: Eoarctos as originally reconstructed by Wang et al 2023. Middle: Same with tail raised. Below: Nasua, the extant coatimundi, an ancestor to Ursus arctos, the grizzly bear in the LRT.
From the abstract “Eoarctos vorax [a] new genus and species, provides a unique window into the origin and early divergence of Carnivora. Recovered from the Fitterer Ranch locality in the early Oligocene (Orellan to Whitneyan North American Land Mammal ages) Brule Formation of southwestern North Dakota (∼32 Ma), the new arctoid offers an opportunity to evaluate the fundamental relationships of the caniform (dog-like) carnivorans.”
This is where this paper strays from excellence. Caniformia is a genomic clade, distinct from Feliformia. As we learned many times previously genomic cladograms too often recover untenable interrelationships. In this case cursorial digitigrade taxa nest basal to arboreal plantigrade taxa in the genomic studies of Flynn et al 2005 and 2010. In Wang et al none of the co-authors, editors or referees seemed to notice this logic problem. That’s why it takes an outsider (or the tenth man rule) to point out problems others ignore.
The large reptile tree (LRT, 2265 taxa) is based on trait analysis. The LRT does not split the clade Carnivora into these two genomic clades. Rather taxa like Eoarctos (Figs 1–3) nest at the base of the Carnivora with plantigrade raccoons, skunks, meerkats, coatimundis and civets. In the LRT (Fig 6) digitigrade wolves and cats nest as derived members of the Carnivora.
Figure 2. Eoarctos skull, manus and pes from Wang et al 2023. Colors added here.
From the abstract – continued: “Eoarctos vorax possesses a suite of plesiomorphic characters inherited from its miacid ancestors, making it an ideal model for ancestral arctoids. We present a comprehensive treatment of E. vorax, combining traditional description with photographic documentation, microCT, laser scans, and photogrammetry. Showing its plesiomorphic morphology, Eoarctos vorax is scansorial, somewhat like a modern raccoon, retaining the ability to climb trees and lacking cursorial adaptations present in the early canid Hesperocyon.”
In the LRT Hesperocyon is a derived, long-legged extinct civet.
Figure 3. Illustration by Mark Halett showing Eoarctos cracking a snail shell. By contrast, closely related Nasua, the coatimundi, and Nandinia, the palm civet, are both omnivores. See figure 7.
From the abstract – continued: “However, E. vorax shows clear signs of durophagous cranio-dental morphology, presumably for an obligatory diet of mollusks, with frequent damage to shell-crushing premolars, plus associated dental infections.”
Figure 4 Cladogram from Wang et al 2023, based on Flynn et al 2010 showing a cladogram of the Carnivora based on genomics graphically split to fit this blogpost vertical format. Essentially this topology is upside down compared to the LRT, which nests plantigrade, arboreal taxa at the base, digitigrade cursorial taxa as derived. Note the lack of a basal placental or transitional marsupial outgroup taxon. See the LRT for a list of outgroup taxa.
Figure 5. Cladogram from Wang et al 2023. Colors added here to match figure 6. Many of these taxa are fragments of dentaries with teeth, not complete fossils, hence the lack of resolution. Only a few extant taxa are included here. In the LRT Miacis and Vulpavus are not members of the Carnivora. Nasua is not listed here. In the LRT more complete and more extant taxa are tested.
From the abstract – continued: “We review several other key North American early arctoids and present total-evidence (nuclear DNA and discrete morphological characters) Bayesian and parsimony analyses of Caniformia phylogeny, including extinct stem taxa plus a living member of all modern families.”
When paleontologists prefer DNA (genomic, molecule) evidence they undercut their results with untenable, illogical interrelationships influenced by ancient viral infections. Nobody seems to notice this. DNA cannot be used with fossils. Better to stick with traits (Fig 3) to avoid the basic problems Flynn et al and Wang et al embraced (Figs 4, 5).
Figure 6. Subset of the LRT focusing on the clade Carnivora. Colors indicate basal dichotomy.
From the abstract – continued: “We recognize an endemic North American ursoid clade, Subparictidae, which includes Eoarctos vorax. We demonstrate the importance of North America as an early cradle of evolution for caniform carnivorans, including early precursors of Canidae, Amphicyonidae, Ursidae, and Pinnipedia.”
In the LRT (Fig 6) Eoarctos is indeed ancestral to one branch of the clade Carnivora, the branch that produced coatimundis (Nasua), cats, dogs, seals, weasels, sabertooths, badgers and several clades of bears. The other branch produced mongooses, civets and skunks.
Figure 7. Extant relatives of Eoacrtos (Fig 1) include Lemur, Nasua and Nandinia. These are all basal placentals in the LRT deived from arboreal marsupials lacking a complete pouch, like Monodelphis.
In the LRT Eoarctos is an Early Olgocene late survivor of a more ancient (Jurassic) radiation of omnivorous placentals resembling Nandinia and Nasua, both related to the basal primate,Lemur (Fig 7). Wang et al mention Nasua only once, in regad to the flexible ankle joint.
According to trait analyses, like the LRT molecular phylogenies do not model evoutionary events. In Flynn et al 2005, Flynn et al 2010 and Wang et al 2023 molecules invert the tree topology of the clade Carnivora.
“It doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are. If it doesn’t agree with experiment, it’s wrong.” –– Richard P. Feynman
References Flynn JJ, Finarelli JA, Zehr S, Hsu J, Nedbal MA 2005.Molecular phylogeny of the Carnivora (Mammalia): Assessing the impact of increased sampling on resolving enigmatic relationships”. Systematic Biology. 54 (2): 317–37. doi:10.1080/10635150590923326 Flynn JJ, Finarelli JA and Spaulding M 2010. Phylogeny of the Carnivora and Carnivoramorpha, and the use of the fossil record to enhance understanding of evolutionary transformations; pp. 25–63 in A. Goswami and A. Friscia (eds.), Carnivoran Evolution: New Views on Phylogeny, Form and Function. Cambridge University Press, Cambridge. Flynn, J. J., N. A. Neff, and R. Wang X et al (5 co-authors) 2023. An exquisitely preserved skeleton of Eoarctos vorax (nov. gen. et sp.) from Fitterer Ranch, North Dakota (early Oligocene) and systematics and phylogeny of North American early arctoids (Carnivora, Caniformia). Journal of Vertebrate Paleontology, 42:sup1, 1-123, DOI: 10.1080/02724634.2022.2145900
Here’s a photo of a pterosaur fossil (Figs 1, 2) that has no name, no museum number, no scale bar and no publication citation.
If you know this fossil’s provenance / backstory / ID,let us know. The two photos (Figs 1, 2) showed up as orphans on social media.
Figure 1. Pterosaur image from Facebook. Colors added here. What is the name? Museum number? Scale bar? Citation? At lower right the brown tibiae do not match in length and the hand elements likewise do not match.
My guess is no one knows what this pterosaur is (phylogenetically), so no one wants to publish on it. Or, perhaps workers believe the specimen was cobbled together (for a better, more remunerative sale to the museum) because it doesn’t neatly fit into any established clade, as is. In other words, this pterosaur represents something new.
That’s never a problem for the large pterosaur tree (LPT, 268 taxa, subset Fig 3). It tests more pterosaurs than ANY prior cladogram and so resolves some traditional issues pterosaur professors don’t want to touch and some those same professors created.
Figure 2. Skull of the ChinaX pterosaur flipped and reconstructed. DGS colors added here.
As is the ChinaX specimen nests alone in the LPT (Fig 3) between Eudimorphodon + Campylognathoides and all higher pterosaurs, from Changchengopterus+ Sordeson up. That would make this a Late Triassic- to Early Jurassic-grade pterosaur. Perhaps it was a late survivor from that earlier radiation – if the rumors are true that this specimen comes from Early Cretaceous strata. To anyone without an LPT, that would have also made this long-tailed specimen somewhat unexpected and disconcerting.
Figure 3. Subset of the LPT (large pterosaur tree) with the addition of the ChinaX pterosaur basal to most other pterosaurs.
If these online photos (Figs 1, 2) are the result of a ‘lab leak,’ direct your comments toward the unknown leaker.
References when I have citations, I’ll add them here. Looking forward to your input.
By adding traditionally omitted taxa the large reptile tree (LRT, 2264 taxa, subset Fig 2) often recovers overlooked interrelationships.
Today we’ll look at the traditional interrelationship of paddlefish (Polyodon, Fig 3) with sturgeons (Acipenser, Fig 2).
The 2011 Hilton et al cladogram rests on the hypothesis that sturgeon ‘jaws’ are degenerate. Adult sturgeons lose their teeth. So do paddlefish.
Both sturgeons and paddlefish employ external fertilizaton. By contrast, basking sharks fertilize internally. Phylogenetically miniaturized transitional taxa, like the palm-sized paddlefish, Bandringa (Fig 3) likely re-introduced external fertilization. The resemblance of this elasmobranch to paddlefish is not convergence, but homology.
As mentioned earlier, paddlefish sperm have fertilized sturgeon eggs with viable hybrids that either looked like sturgeons or paddlefish after one year (Kalday et al 2020). No one expected this. They intended the sperm to simply kickstart the sturgeon eggs (= gynogenesis) without the actual contribution of the sperm DNA.
Kaldy et al 2020 reported, “Besides the large phylogenetic distance (i.e., they diverged 184.4 Mya), representatives of Polyodontidae and Acipenseridae differ in their gross morphology (e.g., presence of scutes, the structure of mouth, rostrum, filter apparatus) as well as feeding behavior, preferred habitat, etc.”
The LRT pushes that split back to the earliest Cambrian, 530mya and agrees that the gross morphology of paddlefish and sturgeons are different.
On a side note, if you ever wondered, how naked, blood-sucking, worm-like lampreys (Pteromyzon, Fig 2) AND armored, filter-feeding, finless arandaspids (Arandaspis) could BOTH be basal fish you’ll find the LRT (Fig 2) sheds new light on these disparate morphologies.
Gymnopisces (‘naked fish’) would make a good name for the lamprey > sturgeon clade, even though a armored taxa are members.
Placopisces (‘plate fish’) would make a good name for the arandaspids > placoderm clade, even though unarmored taxa, including tetrapods and humans, are members.
Figure 1. Sturgeon and paddlefish interrelationships according to Hilton, Bemis and Grande 2011. Nine prior studies did not provide outgroup taxa, so kudos to Hilton et al for trying, even by cherry-picking.
In traditional cladograms (e.g. Hilton et all 2011, Fig 1) sturgeons (e.g. Acipenser) and paddlefish (e.g. Polydon) nest together derived from Peiapiaosteus (Figs 1, 3), Chondrosteus (Fig 3), Birgeria(Fig 1) and Boreosomus (Fig 1). These outgroup taxa appear to be cherry-picked because they don’t resemble one another, and when tested in the LRT, do not nest together.
Rather than cherry-picking outgroup taxa, let your own wide gamut LRT tell you which taxa are interrelated (Fig 2) going back several clades.
According to Wikipedia, “Acipenseriformes are assumed to have evolved from a “palaeonisciform” ancestor. Their closest relatives within the paleonisciformes are uncertain and contested. Eochondrosteus from the Early Triassic of China has been suggested by some authors to be the oldest acipenseriform. The oldest unambiguous members of the order are the Chondrosteidae, a group of large fish found in marine deposits from the Early Jurassic of Europe, which already have reduced ossification of the skeleton. The Peipiaosteidae are known from Middle Jurassic-Early Cretaceous freshwater deposits in Asia. The oldest known paddlefish is Protopsephurus from the Early Cretaceous of China, while the earliest known sturgeons appear in the Late Cretaceous in North America and Asia.”
By adding taxa the LRT recovers a different hypothesis of interrelationships (Fig 2) in which paddlefish (Bandringa to Polyodon, Fig 3) arose from basking sharks (Cetorhinus). Meanwhile sturgeons arose from Lasanius (Fig 2), and Hemicyclaspis (Fig 2).
Figure 2. Subset of the LRT focusing on basal chordates including sturgeons (Acipenseridae). Note the retention of armor from Hemicyclaspis to Acipenser. Paddlefish nest with Chondroteus and Peipiaopsteus in the clade Chondrichthyes. Note the origin of ray fins in Acipenser, derived from Lasanius. Note the changes in the tail shape from hypocercal to heterocercal to diphycercal.
Testing the LRT results 1. Removing all Chondrichthyes and Osteichthyes shifts the paddlefish clade to the sturgeon clade. Chondrosteus is the transitional taxon. This is similar to the Hilton et al topology. 2. Replacing all taxa except Chondrichthyes shifts the paddlefish clade to the Palaeonisciformes, close to Moythomasia. So the paddlefish clade shifts. 3. Replacing all taxa except derived Chondrichthyes shifts the paddlefish clade to the basal Chondrichyes (Rhincodon – Manta clade). Again, the paddlefish clade shifts.
Shifting the paddlefish clade to the sturgeon clade in the LRT adds 34 extra steps. PAUP only needs 2:29 minutes to fully resolve the current total of 468 fish taxa.
Figure 3. The basking shark (Cetorhinus) compared to the paddlefish (Polyodon). Note the disappearnace of the anterior dorsal fin and transformation of the gill slits to an operculum between the two palm-sized Bandringa specimens. Again, phylogenetic miniaturization attends the origin of new structures and new veretebrate clades. Ratfish also develope an operculum.
The second origin of jaws, feeble though they may be, occurs with Acipenser larvae and continues through Gonorhynchus (Fig 4) with even more feeble in Gonorhynchus.
Convergent tooth loss Bemis et al 1999 reported, “Figure 20 shows the oral region of a Polyodon larva, with two rows of conical teeth erupting in the upper jaw and a single row in the lower jaw. In large adult Polyodon, however, (>25 kg) teeth are not visible from the surface of the bone, and sections show that they are completely embedded in the jaw. The pattern of ontogenetic tooth loss is different in sturgeons: larvae have teeth, but the teeth and their attachment bones are absent in adults, and are generally considered to be shed during growth. (The biting surfaces of adult sturgeons are composed of thick collagenous pads, Nelson 1969.) Thus, this character is more complicated than usually stated, and available data for †Peipiaosteus and †Chondrosteus are inconclusive concerning the mode of ontogenetic tooth loss.”
In short, not homologous.
Phylogenetically sturgeon larval teeth are not far from the hydroxylapatite (phosphatic) oral elements of conodonts (e.g. Promissum, Fig 2). So the short-lived teeth of baby sturgeons are not homologous with the dentine + enamel teeth of gnathostomes that arise with derived placoderms (as bumps on the jaw skin, then evolve in basal sharks, spiny sharks and bony fish.
The conodont connection also explains the extensible tube-like mouth parts of sturgeons ALSO convergent with those of derived bony fish, sharks and rays.
Ray fins Lasanius (Fig 2) has ray fins, convergent with those found in Osteichthyes. Acipenser inherits those ray fins. See figure 2 for the convergent evolution of diphycercal tail fins from every other shape of tail fin.
Figure 4. Acipenser (sturgeon) larvae compared (not to scale) with an adult Gonorhynchus. This is the second origin of jaws, feeble though they may be and more feeble in derived taxa, but note the great increase in the size of the articular (purple) and pterygoid (brick red) in Gonorhynchus.
The traditional matching of paddlefish and sturgeon is here revealed by the LRT to be a matter of convergence. By simply adding taxa the LRT minimizes the traditional problem of taxon exclusion that once matched paddlefish with sturgeons.
This appears to be a novel hypothesis of interrelationships. If not please provide a citation and cladogram with a similar wide gamut taxon list so I can promote it here. This LRT hypothesis now required confirmation, refutation or modification.
I want to thank a PH reader ‘Sech’ for bringing this issue to my attention and making a long list of good arguments for keeping paddlefish and sturgeons together. Taxon exclusion was at the core of all prior hypotheses. You can read our correspondence here.
References Bemis WE, Findeis EK and Grande L 1997. An overview of Acipenseriformes. Environmental Biology of Fishes 48: 25–71, 1997. Egerton PDMG 1858.On Chondrosteus, an extinct genus of the Sturionidae, found in the Lias formation at Lyme Regis. Philosophical Transactions of the Royal Society of London 148:871-885. Grande L and Bemis WE 1991. Osteology and phylogenetic relationships of fossil and Recent paddlefishes (Polyodontidae) with comments on the interrelationships of Acipenseriformes. Society of Vertebrate Paleontology Memoir 1. Journal of Vertebrate Paleontology 11, Supplement to Number 1. 121pp. Grande L, Jin F, Yabumoto Y, Bemis WE 2002.Protopsephurus liui, a well-preserved primitive paddlefish (Acipenseriformes: Polyodontidae) from the Lower Cretaceous of China. Journal of Vertebrate Paleontology. 22 (2): 209–237. Gunnerus JE 1765. Brugden (Squalus maximus), Beskrvenen ved J. E. Gunnerus. Det Trondhiemske Selskabs Skrifter, 3: 33–49, pl. 2. Hennig E 1925.Chondrosteus Hindenburgi Pomp.—Ein «Stör» des württembergischen Ölschiefers (Lias\epsilon). Palaeontographica (1846-1933), 115-134. Hilton EJ 2005. Observations on the skulls of sturgeons (Acipenseridae): shared similarities of Pseudoscaphirhynchus kaufmanni and juvenile specimens of Acipenser stellatus. Environmental Biology of Fishes 72:135–144. Hilton EJ, Grande L and Bemis WE 2011. Skeletal Anatomy of the shortnose sturgeon, Acipenser brevirostrum Lesueur, 1818, and the systematics of sturgeons (Acipenseriformes, Acipenseridae). Fieldiana 1560:168 pp. Le Sueur CA 1818. Description of several species of chondropterygious fishes of North America, with their varieties. Trans. Amer. Phil. Soc. 1: 383–394. Linneaus C von 1766. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio duodecima, reformata. pp. 1–532. Holmiæ. (Salvius). Liu HT and Zhou JJ 1965. A new sturgeon from the Upper Jurassic of Liaoning, North China. Vertebrata PalAsiatica, 9, 3, 237-247. In Chinese with English abstract. Lu L-W 1994. A new paddlefish from the Upper Jurassic of China. Vertebrata PalAsiatica 32(2): 132–142. Muir WD, McCabe GT Jr, Parsley MJ and Hinton SA 2000. Diet of first-feeding larval and young-of-the-year white sturgeon in the Lower Columbia River. Northwest Science 74(1):25–33. Nikolskii AM 1900. Pseudoscaphirhynchus rossikowi, n. gen, et spec. Ann. Mus. Imp. Sci. St. Petersburg 4, 257–260 (text in Russian). Sewertzoff AN 1928. The head skeleton and muscles of Acipenser ruthensus. Acta Zoologica 13:193–320. Zarri LJ and Palkovacs EP 2018. Temperature, discharge and development shape the larval diets of threatened green sturgeon in a highly managed section of the Sacramento River. Ecology of freshwater fish 28(2): https://doi.org/10.1111/eff.12450 Zhou Z 1992. Review on Peipiaosteus based on new material of P. pani. Vertebrata PalAsiatica. 30: 85–101. Zhu Y-A et al (10 co-authors) 2022. The oldest complete jawed vertebrates from the early Silurian of China. Nature 609:954–958. online.
This sister toChondrosteus (Fig 2) gives us a dorsal view of the skull (Fig 1) not visible in the Chondrosteus diagram. It also has a soft, displaced rostrum with narial openings not presented in the Chondrosteus diagram.
Soft tissue is well preserved in several specimens (Fig 1).
Figure 1. Peipiaopsteus pani in situ. Colors and reconstruction added here. Scale bar absent. The round brick-colored bones are pterygoids, as in Chodrosteus (Fig 2). Note the displaced nasals and postparietal.
Peipiaopsteusis a traditional members of the Acipenseriformes (= sturgeons), but Acipenserand the other sturgeons nest far apart from these shark taxa in the large reptile tree (LRT, 2264 taxa).
Figure 2. Chondrosteus nests with Peipiaosteus in the LRT. The nose tends to fall off on these taxa.
Peipiaosteus pani (Liu and Zhou 1965, Zhou 1992, Aptian, Early Cretaceous) Three opercula appear in this taxon. Five to seven gill slits are found in ancestors and relatives. So is a single operculum (Fig 2).
References Egerton PDMG 1858. On Chondrosteus, an extinct genus of the Sturionidae, found in the Lias formation at Lyme Regis. Philosophical Transactions of the Royal Society of London 148:871-885. Hennig E 1925.Chondrosteus Hindenburgi Pomp.—Ein «Stör» des württembergischen Ölschiefers (Lias\epsilon). Palaeontographica (1846-1933), 115-134. Li X and Chen Y 2021. The Mesozoic Acipenseriformes in northeast China and adjacent areas. Sino-Russian ASRTU Forum “Ecology and Environmental Sciences” IOP Conf. Series: Earth and Environmental Science 864 (2021) 012005 IOP Publishing doi:10.1088/1755-1315/864/1/012005 Liu HT and Zhou JJ 1965. A new sturgeon from the Upper Jurassic of Liaoning, North China. Vertebrata PalAsiatica, 9, 3, 237-247. In Chinese with English abstract. Zhou Z 1992. Review on Peipiaosteus based on new material of P. pani. Vertebrata PalAsiatica. 30: 85–101. Zhu Y-A et al (10 co-authors) 2022. The oldest complete jawed vertebrates from the early Silurian of China. Nature 609:954–958. online
Updated December 6, 2023 with new skull bone identities and a new nesting of Protopsephurus, a traditional paddlefish, with Yanosteus, an extinct sturgeon.
Figure x. Updated 12.6.23 comparing Early Cretaceous Protopsephorus to coeval Yanosteus, a sturgeon.
Wikipedia reports, “Paddlefish (family Polyodontidae) are a family of ray-finned fish belonging to order Acipenseriformes, and one of two living groups of the order alongside sturgeons (Acipenseridae).”
Figure 1. Protopsephurus skull IVPP V10669 from Grande et al 2002. [misidentified] Tetrapod homology colors added here. Compare to extant taxa in figures 2 and 3.
Protopsephurus liui (Lu 1994, Grande et al 2002, Late Jurassic/Early Cretaceous China, 20cm length, Fig 1) is a shorter rostrum sister to Polyodon,the paddlefish (Fig 2). Teeth are absent. Skull bones are unfused. Some labels here are relabeled (colors added here) with tetrapod homologies.
Figure 2. Skull of Polyodon from a diagram published in Gregory 1938, plus a dorsal view and lateral photo.
So, paddlefish are not sturgeon sisters. This comes from standard phylogenetic analysis and taxon inclusion.
Figure 3. The basking shark (Cetorhinus) compared to the paddlefish (Polyodon).
The earliest known paddlefish are tiny (smaller than a human hand) specimens from Carboniferous. Hatchling paddlefish (Fig 3) lack a paddle and retain a basking shark-like morphology. Paddlefish grow fast, so yearlings have a large paddle.
The subject of paddlefish brings up the sturddlefish (= sturgeon + paddlefish hybrid) documented by Kaldy et al 2020.
Kaldy et al 2020 reported: “Although hybridization among acipenserid species is common, there are no reports of successful hybridization of acipenserids and polyodontids. Previous hybridization experiments on shovelnose sturgeon (Scaphirhynchus platorynchus) × American paddlefish or American paddlefish × Amur sturgeon (Acipenser schrenckii) have failed to result in viable offspring.”
“Besides the large phylogenetic distance (i.e., they diverged 184.4 Mya [15]), representatives of Polyodontidae and Acipenseridae differ in their gross morphology (e.g., presence of scutes, the structure of mouth, rostrum, filter apparatus) as well as feeding behavior, preferred habitat, etc.
“This suggests an inability to hybridize.”
“During an experiment to produce gynogenic Russian sturgeon progeny, a negative control was initiated using non-irradiated American paddlefish sperm and eggs from the Russian sturgeon. Unexpectedly, the control cross resulted in viable hybrids.”
Definition: “Gynogenesis: a form of parthenogenesis, is a system of asexual reproduction that requires the presence of sperm without the actual contribution of its DNA.”
Figure 5. Specimens in the sturddlefish hybrid experiment. This happened. No one expected this to happen, but it happened. No one has argued that Polyodon and Acipenser were conspecific, congeneric or even in the same family. And yet, these viable hybrids (at least to the yearling stage) resulted. A query to the lead author asked where these hybirds fertile? Haven’t heard back yet. Note how the sturgeon hybirds look like some of the allometric growth stages in Acipenser sturgeons. The paddlefish hybrid yearling has no sturgeon traits.
The take-away here is: “large phylogenetic distance.” So experts don’t argue for a close interrelationship.
In the LRT other taxa, both extinct and extant, are closer to paddlefish (Fig 3) and others are closer to sturgeons than they are to each other. With that in mind, a follow-up experiment should attempt to hybridize basking sharks and paddlefish. Another experiment should attempt to hybridize lampreys and sturgeon.
References Grande L and Bemis WE 1991. Osteology and phylogenetic relationships of fossil and Recent paddlefishes (Polyodontidae) with comments on the interrelationships of Acipenseriformes. Society of Vertebrate Paleontology Memoir 1. Journal of Vertebrate Paleontology 11, Supplement to Number 1. 121pp. Grande L, Jin F, Yabumoto Y, Bemis WE 2002.Protopsephurus liui, a well-preserved primitive paddlefish (Acipenseriformes: Polyodontidae) from the Lower Cretaceous of China. Journal of Vertebrate Paleontology. 22 (2): 209–237. Kaldy J et al. (12 co-authors) 2020. Hybridization of Russian Sturgeon (Acipenser gueldenstaedtii, Brandt and Ratzeberg, 1833) and American Paddlefish (Polyodon spathula, Walbaum 1792) and Evaluation of Their Progeny. Genes 2020, 11, 753. https://www.mdpi.com/2073-4425/11/7/753 Lu L-W 1994. A new paddlefish from the Upper Jurassic of China. Vertebrata PalAsiatica 32(2): 132–142.
According to Wikipedia, “The Palaeonisciformes (Palaeoniscida) are an extinct order of early ray-finned fishes (Actinopterygii). Palaeonisciformes sensu lato first appeared in the fossilrecord in the Late Silurian and last appeared in the Late Cretaceous.”
Adding taxa upsets this hypothesis. Now both hypotheses need to be tested.
Figure 1. Subset of the LRT focusing on Palaeonisciformes, including extant taxa like Malacosteus, Engraulis and Coilia. The uncolored taxa are traditional palaeonisciforms.
Recent housekeeping to the fish portion of the large reptile tree (LRT, 2262 taxa, Fig 1) recovered three extant taxa that arose directly from the Palaeonisciformes. These three (Malacosteus, Engraulis, and Coilia (Figs 2, 3) shifted out of the Actionopterygia (ray-fin fish) when facial bones in two taxa, Birgeria and Kalops (Figs 2, 3), were correctly identified based on tetrapod homologies.
Another traditional ray-fin fish, Late Triassic Birgeria (Figs 2, 3), now nests between the traditional Carboniferous palaeonisciform, Kalops (Fig 2) and the three newly identified Palaeonisciformes. That makes extinct Birgeria and Kalops pertinent parts of this previously untold story of macroevolution by way of microevolution.
Earlier three members of the extinct Onychodontiformes (Selenodus, Onychodus and Strunius) moved into the Palaeonisciformes (Fig 1). They don’t have lobe fins. Their two-part skull roof turns out to be convergent with Sarcopterygii. Let the software sort your taxon list into clades and let us know what you recover.
Figure 2. Extant palaeonisciformes in the LRT include Engraulis, Malacosteus and Coilia. All three share the trait of a large lateral orbit close to the short rostral tip extending even slightly beyond the jaws, convergent with sharks.
When Kalops was first described (Poplln and Lund 2002;) the authors reported, “It was decided not to perform a cladistic analysis herein to search for the interrelationships of Kalops. Moreover there is not yet any established classification of lower actinopterygians resulting from an inclusive, uncontested general phylogenetic analysis. We believe such an analysis would have been based on too limited a suite of species; it seems somewhat derisory to try narrow cladistic efforts each time a few or single new genus or species is described. Thus we have taken a more global approach to discuss the systematic status of this new genus. As in previous articles (e.g., Poplin and Lund, 2000), we use the term “Palaeoniscimorpha” (Lund et al., 1995) as a strict synonym of “Basal Actinopteri” sensu Patterson, 1982.”
We might have to wait awhile for ‘uncontested‘. The LRT provided the required ‘inclusive‘.
Figure 3. Once considered ray-fin fish, these four taxa, Birgeria, Malacosteus, Engraulis and Coilia, now nest as descendants of Kalops within the monophyloetic Palaeonisciformes in the LRT. See figure 1. Note the slender, angled operculum (lavender) and the nasals (pink) extending beyond the premaxilla (yellow).
Convergence. Add more taxa so you won’t be fooled by convergence.
Convergence is rampant in the Chordata. So don’t cherry-pick a short list of taxa while omitting others based on one, two or a dozen traits. Textbooks can be out-of-date. Always test several hundred traits in your own LRT and let the software tell you which taxa from a wide gamut list belong to novel or established clades.
Taxon exclusion remains the number one problem in paleontology. Let’s fix that.
The use of standard DGS colors (Fig 3) helps to establish and understand tetrapod homologies in all tested taxa. Labels and arrows become superfluous. Keep your graphics simple.
If you’re not part of this revolution in chordate phylogeny stop sitting on your hands and start building your own LRT with DGS methods. The LRT started with just 240 taxa. As in any and every scientific endeavor, replicating this experiment is essential because the current LRT hypothesis requires confirmation, refutation or modification from independent studies employing a similar taxon listand your own set of 200+ multi-state characters.
This appears to be a novel hypothesis of interrelationships. If not please provide a citation so I can promote it here.
References Ayres WO 1848. pp. 64–73. In: Proceedings of the Boston Society of Natural History, Vol. 3. Proceedings of the Boston Society of Natural History, Boston. Ayres WO 1849. Description of a new genus of fishes, Malacosteus. Boston Journal of Natural History 6:53–64. Figueroa RT et al (6 co-authors) 2023. Exceptional fossil preservation and evolution of the ray-finned fish brain. Nature https://doi.org/10.1038/s41586-022-05666-1 Gray JE 1830. : Illustrations of Indian Zoology 1, (pl. 85). Kenaley CP 2007. Revision of the Stoplight Loosejaw Genus Malacosteus (Teleostei: Stomiidae: Malacosteinae), with Description of a New Species from the Temperate Southern Hemisphere and Indian Ocean. Copeia. 2007 (4): 886–900. doi:10.1643/0045-8511(2007)7[886: Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Poplin CM and Lund R 2002. Two Carboniferous fine-eyed palaeoniscoids (Pisces, Actinopterygii) from Bear Gulch (USA). Journal of Paleontology 76(6):1014–1028. Romano C and Brinkman W 2009. Reappraisal of the lower actinopterygian Birgeria stensioei ALDINGER, 1931 (Osteichthyes; Birgeriidae) from the Middle Triassic of Monte San Giorgio (Switzerland) and Besano (Italy). Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen. 252: 17–31. Xu G-H, Ma X-Y and Zhao L-J 2018. A large peltopleurid fish (Actinopterygii: Peltopleuriformes) from the Middle Triassic of Yunnan and Guizhou, China. Vertebrata PalAsiatica 56(4):106–120.
From the Henkemeir, Jäger and Sander 2023 abstract “The description of the holotype of the non-pterodactyloid pterosaur Scaphognathus crassirostris from the Upper Jurassic Solnhofen Formation by the German palaeontologist Georg August Goldfuß in 1831 was the basis for the first published scientific life reconstruction of a pterosaur.
Ironically since then, Scaphognathus (Figs 1, 2) has been the subject of only a few works of art. It is the archetypal ‘plain brown sparrow‘ of pterosaurs. To its credit, in the large pterosaur tree (LPT, 267 taxa) Scaphognathus was basal to two clades of ‘pterodactyloid’-grade pterosaurs. Transitional taxa (Fig 3) first went through a strong phase of phylogenetic miniaturization.
Figure 1. Images from Henkemeier, Jáger and Sander 2023. Colors added here. The stains are not as interesting here as the textures.
From the Henkemeir, Jäger and Sander 2023 abstract “In this study, reflectance transformation imaging (RTI) was used to investigate fine surface details of the S. crassirostris type specimen. The observations of Goldfuß concerning the existence of different preservational patterns of the hair-like integumentary structures (pycnofibres) in this specimen were confirmed.”
As the authors explain, their focus was on tiny hairs identified 190 years ago. Apparently less attention was paid to the gular sac, wing membranes and other interesting hard and soft parts. Those are highlighted here (Figs 1, 2) by digitally putting the counterplate back on top of the plate, then registering them, decreasing color saturation and increasing contrast. No RTI was used, only Adobe PhotoShop.
Figure 2. Scaphognathus holotype plate and counterplate. Note the curved stripe impressions over the right femur and pelvis. These impressions could be parasagittal dorsal frills, as in Longisquama and Jeholopterus. Note the curve behind the knee, representing the slender uropatagium.
Phylogenetic analysis in the LRT nests pterosaurs with Longisquama, a flightless taxon famous for its dorsal and cranial frlls, also seen in Jeholopterus (Fig 4).
Fig. 3. The descendants of Scaphognathus. Note the size reduction followed by a size increase.
Like all pterosaurs. the Scaphognathus wing membrane (Fig 1) had a narrow chord and stretched between the elbow and wing tip, enabling complete disappearance during wing folding, as in birds. As often happens, the membrane on Scaphognathus is torn away from the wing finger during burial.
Figure 4. Reconstruction of Jeholopterus. This owl-like bloodslurper was covered with super soft pycnofibers to make it a silent flyer.
References Goldfuss GA 1830. Pterodactylus crassirostris. Isis von Oken, Jena pp. 552–553. Goldfuß GA 1831. Beiträge zur Kenntnis verschiedener Reptilien der Vorwelt. Nova Acta Physico-Medica Academiae Caesareae Leopoldino-Carolinae Naturae Curiosorum, 15:61- 128. Henkemeier N, Jáger KRK and Sander PM 2023. Redescription of soft tissue preservation in the holotype of Scaphognathus crassirostris (Goldfuß, 1831) using reflectance transformation imaging. Palaeontologia Electronica26(2):a16. https://doi.org/10.26879/1070 Wellnhofer P 1975a. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33. 1975b. Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. 1975c. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.
Some fish change shape as they grow up. The skull of a moray eel hatchling (Fig 1, genus: Gymnothorax) becomes longer, lower, and with shorter teeth as it transforms into an adult (Fig 2).
Figure 1. Gymnothorax (moray eel) hatchling compared to a similarly toothy Middle Triassic ancestor, Ctenognathichthys. See figure 4 for an enlargement of the skull.
A look-alike Middle Triassic fish, Ctenognathichthys bellottii (Fig 1, 3–5), essentially has the skull of a moray eel hatchling (Fig 1). This extinct ‘comb-jaw-fish’ entered the large reptile tree (LRT, 2261 taxa) alongside coeval Feroxicthys (Fig 6) just prior to the bony-fish split that produced ray-fins on one branch and lobe-fins on the other.
Moray eels are basal ray-fins in the LRT.
Figure 3. Gymnothorax (aka Lycodontis) funebris, a type of moray eel. Compare to the larva in figure 1.
Superficially the comb-jaw-fish is an example of convergencewith moray eels. However, since Ctenognathichthys (Figs 1, 3–5) nests in the ancestry of Gymnothorax, instead this may be an example of reversal as moray eel ontogeny recapitulates this stage of phylogeny.
Figure 3. Ctenognathichthys bellottii in situ.
Xu 2021 wrote, “During feeding, it used its long and sharp teeth to grasp and tear the prey from the substrate or to bite a piece from a larger prey item. Louwoichthys (a relative of Ctenognathichthys) might have fed on marine organism debris (e.g. dead fish and other animals). Other potential prey could have included fish eggs, arthropod larvae or small crustaceans (e.g. mysidaceans or isopods).”
Oddly, Xu 2021 did not mention Feroxichthys (Fig 6), which he had described a year earlier.
Figure 4. Skull of Ctenognathichthys bellottii in situ.
A related species, Ctenognathichthys revista (Fig 5), had a relatively smaller face and a deeper body with tiny, barely visible fins. This lack of large lateral fins is interesting because the moray eel totally lacks lateral fins. Even so, transitional taxa between these taxa had larger fins and more fusiform shapes.
Figure 5. Ctenognathichthys revista is a deeper bodiied congeneric relative. Not a fast-swimmer.
Xu 2021 held tight to the traditional view of fish systematics, writing, “Neopterygii is a taxonomically diverse group of ray-finned fishes, including Teleostei, Holostei and their closely related fossil taxa.”
With more taxa the LRT does not recognize a monophyletic Holostei or Neopterygii (= the remainder of Actinopterygii sans Holostei).
Figure 6. Feroxicthys (lower right) added to skull diagrams of taxa related to Ctenognathichthys from Mickle 2012. Colors and Feroxichthys (a Xu 2020 taxon) added here.
On a tangential note, Mickle’s 2012 PhD dissertation urged the adoption of a standard nomenclature for fish facial bones. She wrote, “Currently, there is no standardized nomenclatural scheme for identifying and naming the bones of the snout in lower actinopterygian fishes. This creates a situation where the same bone names are used to identify very different bones. This is problematic because it makes comparing taxa described by different scientists difficult and presents potential pitfalls for building character matrices for phylogenetic analyses. Because of the problems the absence of a standardized nomenclature scheme presents, a new set of rules for the identification of the bones of the snout of lower actinopterygians is proposed here.”
I agree. Mickle’s proposal is needed, but did not go far enough. Here (Figs 1–6) all facial bones are colored with tetrapod homologies, enabling the common ‘nomenclature’ necessary to score traits and build the LRT. The use of standard colors dispenses with the need to label individual fish face bones, which tend to split and fuse.
References De Alessandri G 1910. Studii sui pesci triassici della I-ombardia. Mem. S!oc. 1t Sc. Nat., 3(1): 1-145, Milano. Mickle K 2012. Unraveling the Systematics of Palaeoniscoid Fishes–Lower Actinopterygians in Need of a Complete Phylogenetic Revision. Mickle_ku_0099D_12123_DATA_1.pdf (9.926Mb) Tintori A 1998. Ctenognathichthys bellottii (de Alessandri, 1910): Nomenclature problems and stratigraphical importance of this Middle Triassic actinoopterygian fish. Rivista Italiana di Paleontologia e Stratigrafia 104(3)417–422. Xu G-H. 2020.Feroxichthys yunnanensis gen. et sp. nov. (Colobodontidae, Neopterygii), a large durophagous predator from the Middle Triassic (Anisian) Luoping Biota, eastern Yunnan, China. PeerJ 8:e10229 DOI 10.7717/peerj.10229 Xu G-H 2021. A new stem-neopterygian fish from the Middle Triassic (Anisian) of Yunnan, China, with a reassessment of the relationships of early neopterygian clades. Zoological Journal of the Linnean Society 191, 375–394.
Alopias vulpinus (Rafinesque 1810, up to 6m, Figs 1, 2) is the extant common thresher shark, known for its extra-long caudal fin.
Figure 1. The thresher shark, Alopias, in vivo.
Other than that tail… The orbit is longer than the rostrum or temple. The prefrontal contacts the maxilla. The premaxilla angles down (Fig 2) and the anal fin of Alopias is a mere vestige.
Figure 2. Alopias skull in two views from Simon De Marchi of Elasmo-Morph. Colors added here.
Here in the large reptile tree (LRT, 2260 taxa) Alopias nests with Isurus, the mako shark, which has a longer skull, larger teeth and, obviously, a shorter caudal fin.
References Rafinesque CS 1810. Caratteri di alcuni nuovi generi e nuove specie di animali e piante della sicilia, con varie osservazioni sopra i medisimi. Per le stampe di Sanfilippo: Palermo, Italy. pp. 105, 20 fold. Pl., online
The Pterosaur Heresies 