The salamanderfish and the lizardfish enter the LRT together

Earlier we looked at a new extant deep sea sister for the Devonian basal ray fin fish, Cheirolepis (Fig. 1). Today, we add two more overlooked extant cousins (Figs. 2,3) to the Cheirolepis branch of the the LRT.

Figure 1a. Cheirolepis fossils.

Figure 1a. Cheirolepis fossils from Devonian strata. Note the upper one leans toward acanthodians (spiny sharks).

An overlooked extant saltwater shoreline taxon
Trachinocephalus myops (Fig. 2), the blunt-nosed lizardfish, nests with Cheirolepis in the large reptile tree (LRT, 1527 taxa). A variety of living lizardfish are known. Some are deep sea denizens.

Figure 1. The lizardfish, Trachinocephalus with colors added. Diagram from Gregory 1936. This taxon nests with Devonian Cheirolepis, a basal ray-fin fish.

Figure 2. The lizardfish, Trachinocephalus with colors added. Diagram from Gregory 1936. This taxon nests with Devonian Cheirolepis, a basal ray-fin fish.

Trachinocephalus myops (originally Salmo myops and Saurus myops Forster 1801; 40 cm) is the extant blunt-nosed lizardfish. Traditionally it nests in the clade Synodontidae.

Figure 4. Lepidogalaxias, the salamander fish is not yet tested in the LRT, but the resemblance of this freshwater version of the saltwater lizardfish is apparent.

Figure 3. Lepidogalaxias, the salamander fish is not yet tested in the LRT, but the resemblance of this freshwater version of the saltwater lizardfish is apparent. The bending neck is shown at upper right.

The salamander fish
Lepidogalaxias salamandroides (Mees 1961, 7cm in length) is the extant salamanderfish, the only fish with a neck capable of turning the head nearly at right angles to the torso. Like lungfish, the freshwater salamanderfish is capable of surviving dry seasons by burrowing into the sand.

Molecular studies
consistently recover Lepidogalaxias close to the base of the Telostei where Cheirolepis also nests (when fossils and traits are tested), but the connection has never been made until now (let me know if there is a prior citation I missed).

It is so important to use extant and extinct taxa.
For that reason alone, avoid genetic tests. The second reason is: genetic tests don’t match trait tests over deep time in this and other major clades. The third reason: lots of extant taxa go way, way back phylogenetically.

Figure 3. Subset of the LRT focusing on bony ray fin fish and kin. Here Devonian Cheirolepis nests with extant deep sea Malacosteus.

Figure 4. Subset of the LRT focusing on bony ray fin fish and kin. Here Devonian Cheirolepis nests with extant deep sea Malacosteus. Alongside are Lepidogalaxias and Trachinocephalus.

According to tolweb.org
“Fink (1984) referred to Lepidogalaxias as a ‘potpouri of contradictory and reductive characters’ and placed it in an unresolved trichotomy with the Salmonidae as the sister group of the Neoteleostei. The phylogenetic affinity of this bizarre little fish has been enigmatic since Mees (1961) described it as a galaxiid.”

With about 390 million years between them
it is no wonder that the lizardfish and salamander fish developed traits not seen in Cheirolepis… so did all the other fish that are derived from Cheirolepis! The wonder is, why so few traits evolved to distinguish the extant taxa from the overlooked Devonian sister?


References
Forster JR 1801. in Bloch, ME and Schneider JG editors, Systema Ichthyologiae Iconibus cx Ilustratum. Post obitum auctoris opus inchoatum absolvit, correxit, interpolavit Jo. Gottlob Schneider, Saxo. Berolini. Sumtibus Auctoris Impressum et Bibliopolio Sanderiano Commissum. i-lx + 1-584.
Mees GF 1961. Description of a new fish of the family Galaxiidae from Western Australia. J. Roy. Soc. West. Aust. 44: 33-38.

wiki/Cheirolepis
wiki/Trachinocephalus
wiki/Lepidogalaxias

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The primitive arowana (Osteoglossum) enters the LRT

Osteoglossum formosum (Cuvier 1829; up to 2m in length; Figs. 1, 2) is the extant arowana or bonytongue. A facultive air breather, the slow-moving, heavily-scaled arowana feeds on prey just above the water. Fossils extend back to the Late Jurassic. The pelvic fins are reduced to strands. In the large reptile tree (LRT, 1516 taxa, Fig. 3), Osteoglossum nests with Early Jurassic Dapedium.

Figure 1. The arowana, an Amazon River predator, nests with Late Jurassic Dapedium in the LRT.

Figure 1. The arowana, an Amazon River predator, nests with Late Jurassic Dapedium in the LRT. The pink dot indicates the position of the pelvic fins, absent in the skeleton below, present in the specimen above.

I hope the DGS colors added to these fish skulls
make them more accessible for learning. Consider this a starting point on your own academic journey and learn as much as you can on your own.

FIgure 2. Osteoglossum skull with colors added to identify bones.

FIgure 2. Osteoglossum skull with colors added to identify bones.

And if you ever wanted to swim with a Jurassic fish,
you don’t have to start with a drop of blood from a mosquito. Just jump into the Amazon, the Nile or any of the rivers of Borneo and Western Australia. Prior to the split of these exclusively freshwater fish, all these areas were united at Pangaea and Gondwana.

For that matter
the walking catfish (Clarias) will take you back to the Silurian (430 mya), and it will get out of the water to walk with you! Or the headless lancelet (Amphioxous) will take you back to the Cambrian (550mya), about as far back as swimming chordates go.


References
Cuvier GCLD 1829. Le Règne Animal distribué d’apres son organisation, pour servir de base a l’histoire naturelle des animaux et d’introduction a l’anatomie comparée. Avec figures dessinées d’après nature. Nouvelle édition, revue et augmentée. Tome V. Suite et fin des Insectes. Par M. Latreille. Déterville & Crochard, Paris, i-xxiv + 556pp.

The reason the freshwater fish arowana live across the sea

wiki/Dapedium
wiki/Osteoglossum
wiki/Arowana

Triassic Pholidophorus nests with Devonian Strunius

This is another overlooked relationship
assisted by a relabeling of fish skull bones using tetrapod names (Fig. 1).

Figure 1. Pholidophorus in situ + two skull drawings relabeled with tetrapod names.

Figure 1. Pholidophorus in situ + two skull drawings relabeled with tetrapod names.

Pholidophorus sp. (Agassiz 1832; Middle-Late Triassic; 40cm long) was a herring-like fish with primitive ganoid scales and poorly ossified spine. Traditionally considered an early teleost, with large eyes, here it nests with Late Devonian Strunius, but lacks the central process of the tail. Here the skull bones are re-identified with tetrapod labels. The pectoral and pelvic fins were similar in size.

Figure 2. Strunius skull enlarged to show detail. Inset shows the second origin of the dual external naris as the original apparently splits by the addition of a skin bridge creating two openings. Compare to figure 1.

Figure 2. Strunius skull enlarged to show detail. Inset shows the second origin of the dual external naris as the original apparently splits by the addition of a skin bridge creating two openings. Compare to figure 1.

Strunius rolandi (Jessen 1966; originally Glyptomus rolandi Gross 1956; 10 cm in length; Late Devonian) was considered a lobe-fin fish with ray fins. Here it nests with Cheirolepis, a traditional and transitional ray fin fish. The origin of the double naris in this lineage appears here as a split dividing the original single in two. The palate and possible choana are not known.

Figure 4. Subset of the LRT focusing on fish. Note the traditional members of the Holostei do not nest together here largely because they don't look alike, but more like other, more attractive taxa.

Figure 3. Subset of the LRT focusing on fish. Note the traditional members of the Holostei do not nest together here largely because they don’t look alike, but more like other, more attractive taxa.


References
Agassiz L 1832. Untersuchungen über die fossilen Fische der Lias-Formation. Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefaktenkunde, 3, 139–149.
Agassiz JLR 1835. Recherches sur les Poissons fossiles, 5 volumes. Imprimerie de Petitpierre et Prince, Neuchaatel, 1420 pp.
Agassiz JLR 1835. On the fossil fishes of Scotland. Report of the British Association for the Advancement of Science, British Association for the Advancement of Science, Edinburgh.

wiki/Strunius
wiki/Pholidophorus

Mola mola enters the LRT

Unbelievable and unforgettable.
The ocean sunfish (Mola mola; Linneaus 1758; 4.3m tall and 3m long; Fig. 1) nests traditionally and in the large reptile tree (LRT, 1512 taxa) with the pufferfish. Both are traditional members of the order Tetraodontiformes.

Figure 4. Mola mola is a relative of Diodon in the LRT. It has no circumorbital bones, but as a hatchling has pufferfish proportions and spines.

Figure 4. Mola mola is a relative of Diodon in the LRT. It has no circumorbital bones, but as a hatchling has pufferfish proportions and spines.

This slow-moving surface predator
eats small fish, fish larvae, squid and floating crustaceans. The dorsal and anal fins provide propulsion, as in the pufferfish, Diodon.

According to Wikipedia,
“The fish develop their truncated, bullet-like shape because the back fin, with which they are born, never grows. Instead, it folds into itself as the creature matures, creating a rounded rudder called a clavus.” (Fig. 1)

“Their teeth are fused into a beak-like structure, and they are unable to fully close their relatively small mouths.”

“Females of the species can produce more eggs than any other known vertebrate,[3] up to 300,000,000 at a time.”


References
Linnaeus C von 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

wiki/Diodon
wiki/Tetraodontidae
wiki/Ocean_sunfish
wiki/Mola_(fish)

 

Diodon, the pufferfish, enters the LRT

Diodon the pufferfish
(Fig. 1) offers a vexing problem for phylogenetic scoring. Are those facial spines transformed from circumorbital bones? Ore are they novel dermal ossifications?

Figure 1. Diodon the pufferfish offers a problem. Are those facial spines circumorbital bones? Ore are they novel dermal ossifications?

Figure 1. Diodon the pufferfish offers a problem. Are those facial spines circumorbital bones? Ore are they novel dermal ossifications?

The two cheek spines
are placed like the lacrimal and jugal in the bowfin Amia (Fig. 2).

FIgure 3. The bowfin, Amia calva, is basal to both the electric eel and halibut in the LRT.

FIgure 3. The bowfin, Amia calva, is basal to both the electric eel and halibut in the LRT.

On the other hand,
a traditional sister taxon, Mola mola (Fig. 4), does not have circumorbital bones. As a hatchling Mola has pufferfish proportions and spines. So in the large reptile tree (LRT, 1514 taxa, Fig. 5) the spines of the pufferfish were not scored as circumorbital bones. And the ocean sunfish is an overgrown puffer!

Figure 4. Mola mola is a relative of Diodon in the LRT. It has no circumorbital bones, but as a hatchling has pufferfish proportions and spines.

Figure 4. Mola mola is a relative of Diodon in the LRT. It has no circumorbital bones, but as a hatchling (upper left) has pufferfish proportions and spines.

Pufferfish are traditional members of the Tetraodontiformes
which traditionally nest with Perciformes using genomic scores. That nesting is confirmed by the LRT.  Hughes et al. 2018 nested highly derived Tetraodontiformes with highly derived Lophiformes (angler fish). In the LRT, these clades are also related, though other taxa are closer.

Diodon sp. (Linneaus 1758) is the extant porcupinefish. The teeth are extremely tiny, lining or (perhaps due to tooth fusion), creating beak-like jaws. The spines are distributed all over the body and skull. Pelvic fins are absent. The tail is reduced. The pectoral fins provide thrust distinct from Mola. I do not see dorsal ribs inside the spines (Fig. 1). If present, they would presumably restrict the pufferfish’s ability to expand to a balloon like shape as it fills with water or air when threatened.

FIgure 4. Teleost (bony fish) cladogram. Diodon nests with Mola here.

FIgure 5. Teleost (bony fish) cladogram. Diodon nests with Mola here. Gymnothorax is the moray eel.


References
Linnaeus C von 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

wiki/Amia
wiki/Diodon
wiki/Tetraodontidae
wiki/Mola

The tarpon (Megalops): closer to piranhas than to eels in the LRT

…Well, at least it is not related
to the two tested eels in the LRT, the moray eel (Gymnothorax) and the European eel (Anguilla), which we looked at earlier here and here. The former is closer to lobe finned rhizodontids from the Devonian and Carboniferous. The latter is closer to barracuda. Are there other eels out there the tarpon might be closely related to? I’ll find out as I add taxa, I suppose.

Figure 1. Tarpon (Megalops) skeleton.

Figure 1. Tarpon (Megalops) skeleton. Not very eel-like. Closer to the piranha.

Traditionally
the tarpon (Megalops atlanticus) has been considered an eel relative. Perhaps this is based on its life cycle, which includes elongated larvae born at sea. According to the Tennesee Aquarium, hatchling piranhas are also born tiny and slender.

Figure 2. Tarpon (Megalops) skull with tetrapod skull colors added.

Figure 2. Tarpon (Megalops) skull with tetrapod skull colors added. Note the large plate like postorbital and jugal here. Compare to Figure 3.

After testing
in the large reptile tree (LRT, 1511 taxa) Megalops (Figs. 1,2) nested with the piranha, Serrasalmus (Fig. 3). The former has hundreds of the tiniest teeth lining its jaws. The latter has a few large triangular teeth.

Megalops atlanticus (Cuvier and Valenciennes 1847; up to 2.5m) is the extant Atlantic tarpon. Fast-swimming Megalops has large eyes and large fins. This open-seas predator sometimes uses its swim bladder as a lung by gulping air.

Figure 2. GIF movie, 2 frames, identifying bones by color, the same as in tetrapods. The jugal is missing here. The quadrate is hidden beneath. The parietal forms a sagittal crest. The nostrils are large. Skeleton from ©Steve Huskey and used with permission.

Figure 3. GIF movie, 2 frames, identifying bones by color, the same as in tetrapods. The jugal is missing here. The quadrate is hidden beneath. The parietal forms a sagittal crest. The nostrils are large. Skeleton from ©Steve Huskey and used with permission.

Figure x. Subset of the LRT focusing on fish/basal vertebrates.

Figure x. Subset of the LRT focusing on fish/basal vertebrates.


References
Cuvier G and Valenciennes A 1847. Histoire naturelle des poissons. Tome dix-neuvième. Suite du livre dix-neuvième. Brochets ou Lucioïdes. Livre vingtième. De quelques familles de Malacoptérygiens, intermédiaires entre les Brochets et les Clupes. 19: i-xix + 1-544 + 6 pp. Pls. 554-590.

wiki/Piranha
wiki/Serrasalmus
wiki/Tarpon

 

The giant oarfish (Regalecus) is a kind of seahorse!

The giant oarfish
(Regalecus glesne, Ascanius 1772; Figs. 1, 2) can be one of the longest bony fish in the sea, with the record holder measuring 11 meters. More commonly 3m is a typical length.

Until a closer sister taxon is added
to the large reptile tree (LRT, 1512 taxa) the giant oarfish nests with the seahorse (Hippocampus, Fig. 3). The oarfish can undulate its entire tail, like most fish. It can also undulate just the dorsal fin while the body itself remains essentially straight and motionless, much like a seahorse. The skin of is scaleless, but covered with tubercles (like sticklebacks and seahorses). The oarfish has been seen swimming vertically, tail down, like a seahorse. The short pectoral fins are vestiges. The long pelvic fins with oar-like tips are not used for locomotion, but trail behind.

Traditional cladograms
nest seahorses within the clade Percomorpha (perches, pufferfish, anglerfish, tunas, cichlids, etc.) distinct from the the clade Lampriformes (opahs, oarfish, etc.).

At present
the clade Percomorpha (Perca at its base) is confirmed, within the LRT (subset Fig. 4).

The clade Lampriformes is not confirmed as monophyletic.
Opah nests with flounders. Oarfish nest with seahorses.

Figure 1. The giant oarfish, Regalecus glesne, to scale with a couple of swimmers. Sometimes it swims vertically, often at great depths.

Figure 1. The giant oarfish, Regalecus glesne, to scale with a couple of swimmers. Sometimes it swims vertically, often at great depths.

The skull is strange
and hard to score (Fig. 2). It is best understood like a seahorse with a short, bulldog-like rostrum, distinct from most long rostrum pipefish and sea horses.

Figure 2. Skull of the giant oarfish, Regalecus glesne. Note the mouth opens like a drawbridge with a dorsal premaxilla. The pectoral and pelvic girdles are merged. The elaborate postparietals anchor the cranial frill. Not sure about the 'second quadrate'. I could find no homolog for that bone.

Figure 2. Skull of the giant oarfish, Regalecus glesne. Note the mouth opens like a drawbridge with a dorsal premaxilla. The pectoral and pelvic girdles are merged. The elaborate postparietals anchor the cranial frill. Not sure about the ‘second quadrate’. I could find no homolog for that bone.

Let’s start with the fact
that the mouth is vertical and the premaxilla is dorsal, distinct from most vertebrates, except seahorses. The pectoral girdle is fused to the pelvic girdle. So the giant oarfish is nearly all tail.

Figure 2. Most of the bones of the tetrapod skull are also found in sea horses with some odd changes, like the placement of the quadrate well anterior to the orbit. Hippocampus illustration from Franz-Odendaal and Adriaens 2014. Not the parasphenoid passing midway through the orbit, while in tetrapods the orbit is typically raised above this anteriorly-directed splint-like bone arising from the basicranium. Everything below it is mouth cavity.

Figure 3. The vertically rotated mouth found in the giant oarfish (Figs. 1, 2) is shared by the pipefish and seahorse clade shown here. Without these guides, the skull of Regalecus would be very difficult to figure out.

The eggs are 2.5mm in diameter.
Diet includes krill, small fish and squid, when large enough to prey on those items.

Other common names for the giant oarfish include:
Pacific oarfish, king of herrings, ribbonfish, and streamer fish.

Figure x. Subset of the LRT focusing on fish/basal vertebrates.

Figure 4. Subset of the LRT focusing on fish/basal vertebrates.


References
Ascanius P 1772. Philine quadripartita, et förut obekant sjö-kräk, aftecknadt och beskrifvet. Kongliga Vetenskaps Academiens Handlingar 33 (10-12): 329-331, pl. 10.,

https://www.dailymail.co.uk/news/article
wiki/Giant_oarfish