Schultze et al 2023 described, but did not phylogenetically analyze a tiny (3.5cm) Late Norian (Triassic) ray-fin fish they named Seinstedtia parva (Figs 1, 2). They placed their discovery within “Teleosteomorpha, family incertae sedis.”
According to Arratia 2001 “The large actinopterygian clade comprising the stem-groups of teleosts and the Teleostei (including fossil and extant members) and excluding the Halecomorphi (Amia and relatives) and the Ginglymodi (Lepisosteus and relatives) is formally named Teleosteomorpha.”
Prior workers have not yet recognized the multiple origin of ray-fin taxa by convergence with members of the Actinopterygii recovered by the thelarge reptile tree(LRT, 2266 taxa). The LRT minimizes taxon exclusion by testing a wider gamut of taxa.
According to Wikipedia, “Teleosts have a movable premaxilla and corresponding modifications in the jaw musculature which make it possible for them to protrude their jaws outwards from the mouth.”
The LRT does not confirm the traditional hypothesis of interrelationships based on a single shared trait. Rather the LRT bases interrelationships on the last common ancestor method, which permits traits to develop by convergence. In the LRT Seinstedtia nests with Australosomus at the base of the Palaeonisciformes.
Seinstedtia parva (schultze et al 2023, MLU Sei.2010.76, Norian, Triassic, 3.5cm long) is a tiny relative with an upturned jawline of Australosomus in the LRT. Both are basal to members of the Onychodectidae (Strunius and Onynchodus) and several palaeonisciformes, including Palaeoniscum.
Australosomus merlei (Priem 1924, Pivetau 1930; Early Triassic; 230 mya, 12cm long) is a traditional member of the Pholidopleuriformes and Chondrostei, but nests here as a basal paleoniscid basal to Strunius. Other workers document an upper temporal fenestra, but that represents the hole of a dislocated intertemporal.
This appears to be a novel hypothesis of interrelationships. If not, please provide a citation so I can promote it here.
References Arratia G 2001. The sister-group of Teleostei: Consensus and disagreements. Journal of Vertebrate Paleontology 21(4):767–773. Schultze H-P, Arratia G, Hauschke N and Wilde V 2023. Osteichthyan Fishes from the Uppermost Norian (Triassic) of the Fuchsberg near Seinstedt, Lower Saxony (Germany). Diversity 2022, 14, 901. https://doi.org/10.3390/d14110901
Wang and Zhou 2023 studied changes in limb sizes and proportions, but employed only one Solnhofen bird in their analysis (Fig 1), which does not match the large reptile tree (LRT, 2266 taxa, subset Fig 2), which uses nine Solnhofen birds.
Only a few of the Solnhofen birds nest with each other in the LRT (subset Fig 2). Most are basal to the variety of established Early Cretaceous bird clades. Only one of these is basal to extant birds.
Archaeopteryx should not be used as a wastebasket taxon. Start employing all the complete and articulated specimens (Figs 2, 3) to find this out for yourself and stop undercutting your valuable research.
Wang and Zhou reported, “Contrary to the traditional wisdom that an evolutionary innovation like flight would promote and accelerate evolvability, our results show a shift to low disparity and decelerated rate near the origin of avialans.”
The authors’ analysis and results were undercut due to taxon exclusion. The variety of Solnhofen birds indicates a >high< disparity near the origin of avialans (Fig 3).
Don’t omit data. If it’s available. Use it.
References Wang M and Zhou Z 2023. Low morphological disparity and decelerated rate of limb size evolution close to the origin of birds. Nature Ecology and Evolution 2023. https://doi.org/10.1038/s41559-023-02091-z
So, its not a big jump from one clade to the other. The two clades likely split in the Early Jurassic, giving bats, primates and Microcebus the entire Mesozoic to evolve unique traits. Alongside several other basal placentals Microcebus found a refugium in Madagascar prior to the geological splitting of that island from Africa and India.
Today social data supports the LRT nesting of Microcebus with bats.
Zimmermann 2010 wrote, “The Malagasy mouse lemurs (Microcebus ssp.) represent an excellent model group to gain insight into early evolutionary roots of primate affective communication, since mouse lemurs are suggested to reflect the most ancestral primate condition (Martin, 1972).”
That’s almost true according to the LRT, since bats are sisters to primates and Microcebus is the basal-most bat in the LRT.
Zimmermann 2010 wrote, “They [mouse lemurs] are nocturnal and small-bodied, about the size of a gerbil, but inhabit the fine branch niche of dense parts of forests. Their highly mobile, bat-like ears and their broad auditory sensitivity (Niaussat and Petter, 1980) are ideal prerequisites for vocal communication”.
“Mouse lemurs live in dispersed multi-male/multi-female societies, in which home ranges within and between sexes overlap (Radespiel, 2006).
Similar to bats.
“Individuals forage solitarily during the night, but related females form temporarily stable sleeping groups during the day (Lutermann et al., 2006). Groups occasionally change their sleeping sites, mainly tree holes and leaf nests; however, the composition of sleeping groups remains stable over time.”
Similar to bats.
“Group-specific calls are used by females for coordination of group movement and for guiding group reunion (Braune et al., 2005). Vocal activity in mates is enhanced during the breeding season when males actively search for estrous females (Zimmermann and Lerch, 1993; Craul et al., 2004).”
Perhaps basal bats vocalized to locate each other, prior to raising pitch which enabled them to locate insects and fly at night without light.
“Females give birth to one to four infants which may be nursed cooperatively by all females of the same sleeping group; however, females transport their own infants individually (Eberle and Kappeler, 2006).”
Similar to bats.
“Mouse lemurs evolved an infant-parking system (Ross, 2001), where mothers park their infants temporarily in nests of dense vegetation during foraging.”
Similar to bats. Supporting this observation Jones 2022 reports,“Simultaneous GPS tracking of mother bats and their young has revealed that mothers ‘park’ infants in trees close to their colony. As pups become more independent they return to the trees by themselves, suggesting that mothers help their offspring learn how to navigate.”
“Since mouse lemurs live in such a dispersed and individualized network of complex social relations, in which acoustic signals are ideally suited to coordinate social interactions, they represent a promising group to study the vocal expression of emotions.”
Bats are not known for primate emotions. Neither are basal primates, like lemurs.
References Jones G 2022. Animal behaviour: Mother bats teach their pups to help build independence. Current Biology 32(2):R74–R76 Zimmermann E 2010. 2. Mouse lemurs as a model group for primate affective communication in the acoustic domain. Handbook of Mammalian Vocalization in Handbook of Behavioural Neuroscience.
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.
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.
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.
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.
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.
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.”
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).
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.
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.
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.
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.
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.
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).
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.
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.
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.
Arratia 2022 described Marcopoloichthys (Tintori et al 2008, originally Pholidorphorusfaccii Gortani 1907, Fig 1) as a tiny (4cm) Middle Triassic suction feeder with highly mobile mouth parts, as seen in highly derived ray-fin fish taxa in the large reptile tree (LRT, 2264 taxa).
Specimens recovered in China were described by Tintori et al 2008. Tintori and Arratia described specimens from the Italian Alps. Hence the name ‘Marco Polo fish’.
From the Arratia 2022 abstract “Marcopoloichthys furreri sp. nov., a small scaleless fish from the Ladinian of Switzerland, is described based on ten well preserved specimens, which provide outstanding morphological information. The combination of primitive and advanced characters proved to be critical when M. furreri was added to a previous hypothesis of neopterygian relationships, because it provided unquestionable support for Marcopoloichthys as a stem teleost or teleosteomorph.”
By contrast, the LRT nests Marcopoloichthys among the most derived taxa close to Nematalosa (Fig 2), Clupea and Tarpon. This indicates the entire spectrum of ray-fin fish clades were present by this time. Nematalosa was not mentioned in prior papers.
From the Arratia 2022 abstract “Marcopoloichthyids were suction-feeding fishes, and the excellent preservation of the new species permits discussion of the anatomical modifications involved in the feeding and resting processes.”
The tiny size of Marcopoloichthys is significant. Related taxa are all larger to much larger. Related taxa have juveniles that resemble Marcopoloichthys, particularly the third stage (Fig 3). This would be a good study for a PhD candidate.
This appears to be a novel hypothesis of interrelationships. If not, please provide a citation so I can provide it here.
References Arratia G 2022. The outstanding suction-feeder Marcopoloichthys furreri new species (Actinopterygii) from the Middle Triassic Tethys Realm of Europe and its implications for early evolution of neopterygian fishes. Fossil Record 23(2):231–261. Gortani M 1907.Pholidophorus faccii nel Raibliano di Cazzaso in Carnia. Riv. It. Paleont., 13: 117-124, Perugia. Tintori A et al (6 co-authors) 2008. New specialized basal neopterygians (Actinopterygii) from Triassic of the Tethys realm. Geologica Insubrica 10:13-20
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).
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).
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
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).”
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.
So, paddlefish are not sturgeon sisters. This comes from standard phylogenetic analysis and taxon inclusion.
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 ), 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.”
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.