Repairing a µCT scan of the deep sea slickhead, Narcetes

The fragile facial bones of ray-fin fish
are important when it comes to scoring them in the large reptile tree (LRT, 2223 taxa). So when they get jumbled, as in this cadaver (Figs 1, 2), it’s a good idea to use Photoshop to put the bones back to their original order and in vivo positions. Then score the traits.

To do this it with confidence takes a little experience to recognize previous errors and a good model, a Bauplan from a related taxon, to guide your changes.

Figure 1. µCT scan of the skull of the extant slickhead, Narcetes from Fujiwara et al 2021. Colors and facial bone shifts added here.

In this case the model for the 140cm long extant slickhead, Narcetes
(Fig 1) is a tiny 4cm long Middle Triassic basal bony ray-fin fish, Prohalecites (Fig 3). These two nest together in the LRT.

Figure 2. Narcetes from Fujiwara et al 2021. Compare to Prohalecites in figure 3.

Narcetes shonanmaruae
(Alcock 1890; Fujiwara et al. 2021; 140cm, typically 75cm) is the extant slickhead, a deep-sea relative of tiny Prohalecites. Anal fin entirely behind the dorsal fin, multiserial teeth on jaws, more scale rows than congeners, precaudal vertebrae less than 30, multiserial teeth on jaws, more scale rows than congeners, precaudal vertebrae less than 30, seven branchiostegal rays, two epurals, and head smaller than those of relatives. Most slickheads are benthopelagic or mesopelagic feeders of gelatinous zooplankton, but behavioural observations and dietary analyses indicate that the new species is piscivorous.

Figure 3. Tiny Middle Triassic Prohalecites nests with 1.4m long Narcetes in the LRT. Diagram from Tintori 1990.

Prohalecites porroi
Bellott 1857, Tintori 1990, MCSNIO P 348, Middle Triassic; 4cm) is a late surviving basal bony ray-fin fish (Actinopterygia, Osteichthyes). No trace of scales is preserved in any specimen (as in slickhead heads, Figs 1, 2). No neurocranial material is preserved. Tintori left Prohalecites as a Neopterygian incertae sedis, “because its characters do not perfectly fit in any of these cited groups.” Hemichordacentra are present. The preopercular is so slender it is rodlike.

Changes like this
(Fig 1) are only one reason why housekeeping on the ray-fin subset of the LRT is taking so long (moving from months to seasons).

This appears to be a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here.

References
Alcock AW 1890. Natural history notes from H. M. Indian marine survey steamer ‘Investigator’, Commander R. F. Hoskyn, R. N., commanding. No. 18. On the bathybial fishes of the Arabian Sea, obtained during the season 1889-1890. [Unspecified Publisher] Vol. 6: 295-311.
Arratia G and Tintori A 1999. The caudal skeleton of the Triassic actinopterygian †Prohalecites and its phylogenetic position, p. 121–142. In: Mesozoic Fishes 2—Systematics and Fossil Record. G. Arratia and H.-P. Schultze (eds.). Verlag Dr. F. Pfeil, München.
Arratia G 2015. Complexities of early Teleostei and the evolution of particular morphological structures through time. Copeia 103(4):999–1025.
Bellotti C 1857. Descizione di alcune nuove specie di pesci fossili di Perledo e di altre localtta lombarde. 419–432. In Sopani A (ed) Studi geologici sulla Lomabardia. Editore Turati, Milano.
Fujiwara Y et al. 2021. Discovery of a colossal slickhead (Alepocephaliformes: Alepocephalidae): an active-swimming top predator in the deep waters of Suruga Bay,
Japan. Nature Scientific Reports 11:2490
Tintori A 1990. The actinopterygian fish Prohalecites from the Triassic of northern Italy. Palaeontology 33:155–174.

wiki/Prohalecites
wiki/Narcetes

A tiny, ancient, African river fish, Cromeria, is another odd sturgeon

Updated March 31, 2023
with new labels for certain bones in Cromeria (Fig 1), which allies it with Acipenser the sturgeon, and especially with its larvae (neotony at play, Fig 3). Recently a larger marine fish, Gonorynchus (Fig 3), also nested with sturgeons.

Cromeria nilotica
(Boulenger 1901; 4.5cm; Figs 1-3) is an extant tiny African naked shellear previously not associated with Gonorynchus and sturgeons. Note the subterminal mouth. The scaleless body lacks a lateral line. The caudal fin extends anteriorly both dorsally and ventrally.

Figure 2. From Gregory 1933, diagram of Cromeria. Colors added here. Note the odd caudal fin extending anteriorly to the dorsal and anal fins.

Figure 3. Two species of Cromeria, the African naked shellear shown several times life size.

Figure 2. Acipenser (sturgeon) larvae compared (not to scale) with an adult Gonorhynchus.

This appears to be a novel hypothesis of interrelationships.
lf not, please provide a citation so I can promote it here.

References
Boulenger GA 1901. Diagnoses of new fishes discovered by Mr. W. L. S. Loat in the Nile. Annals and Magazine of Natural History, Including Zoology, Botany and Geology, Being a Continuation of the ‘Magazine of Botany and Zoology’, and of Louden and Charlesworth’s ‘Magazine of Natural History’, Series 7 8: 444-446.

wiki/Shortnose_sturgeon_Acipenser
wiki/Gonorhynchus – wiki/Gonorynchus_gonorynchus
wiki/Cromeria

With novel scoring Gonorynchus now nests with sturgeons in the LRT

Evolution, convergence, tradition and textbooks
made extant Gonorynchus (aka Gonorhynchus, Figs 1, 2) a difficult taxon to nest. Neotony (Fig 2) opened the door to possibilities. The large reptile tree (LRT, 2223 taxa) did the rest.

Evolution: No other fish have an underslung mouth, an operculum and a diphycercal tail.
Convergence: If this is not what the LRT indicates, then it’s more than superficially similar.
Tradition and textbooks: nest this taxon with dissimilar extant ‘relatives’.

Extant Gonorynchus gonorynchus
(originally Cyprinus gonorynchus Linneaus 1766; 60 cm, Figs 1, 2) goes by several common names including beaked salmon, ratfish, mousefish, sand eel, sand fish and shark whiting. The circumorbital bones are absent. The small, ventral jaw elements lack teeth. This nocturnal fish eats zooplankton and buried invertebrates, then buries itself during the day.

But what is it most closely related to? That’s the question.

Figure 1. Gonorhynchus nests by itself in most cladograms. New insights now nest it with sturgeons, based chiefly on skull traits illustrated by Gregory 1933. Colors added here. Note the label changes.

Gregory 1933 reported,
“It has an elongate cylindrical body and a sturgeon-like head with a pointed snout, a small inferiorly-placed mouth and a rostral barbel. The body and head are covered with small spiny scales.“

Here several bones labeled in Gregory 1933 are relabeled
according to sturgeon homologies. Adult sturgeons likewise have no tooth-bearing mouth parts. The rostrum + barbels extend anterior to the ventral oral cavity. The mouth parts are protactile. A notochord pierces the well-ossified abdominal vertebrae. The torso is squarish in cross-section. The pectoral fins are essentially immobile, all as in sturgeons.

Figure 2. Acipenser (sturgeon) larvae compared (not to scale) with an adult Gonorhynchus. Adult Acipenser lose the premaxilla, dentary and their ‘teeth’. Those calcium apatite ‘teeth’ are inherited from lamprey, hagfish and conodont ancestors. Enamel teeth appear later among placoderms. Not sure yet how those oral elements move.

As in sturgeon larvae,
(Fig 2) a premaxilla and preopercular are present. A postorbital is absent. The prefrontal is separated from the postfrontal.

Figure 3. Acipenser brevirostrum, 1m typical length. Records up to 1.47m.

Distinct from an adult sturgeon
(genus: Acipenser, Fig 3), a jugal is absent in Gonorynchus (Fig 1). The tail is diphycercal. Armor plates are absent. The prefrontal is separate from the postfrontal.

Sturgeon ancestors
in the LRT go back to the Early Cambrian. The armor plates are vestiges of ancestral full body armor, as seen in Osteostraci like Hemicyclaspis. Extant sturgeons are a diverse lot with some taxa having a longer preorbital than postorbital skull, as in Gonorynchus.

Are those tiny toothless oral elements in Gonorynchus original equipment handed down with few changes from sturgeon ancestors? Or are those vestigial jaws that once had enamel teeth in some other ancestors? That’s the other question.

This appears to be a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here. This hypothesis now requires confirmation, refutation or modification from other workers. Earlier (May 2022) the LRT nested Gonorynchus with bonefish, but noted the many surgeon traits. Corrections are part of the process of science.

PS
I recently became aware of the more intrusive, larger and more numerous advertising that has invaded this blogpost. Apologies. Apologies. Apologies.

References
Gregory WK 1933. Fish skulls. A study of the evolution of natural mechanisms. American Philosophical Society 23(2). Republished by Eric Lundberg, Laurel, Florida 1959.
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)

wiki/Gonorynchus
wiki/Gonorynchus_gonorynchus

Gonorhynchus, a bonefish with sturgeon traits, enters the LRT

Cheating anatomy to promote the ‘deer-like ancestry of whales’ hypothesis

Philip Perry, writing for BigThink.com
referenced a five-year-old paper by Vermeij and Motani 2018 regarding land-to-sea transitions in vertebrates. Perry’s online article was promoted with a photo of a model of Indohyus and the caption “Note it’s deer-like feet.” Unfortunately, the fossil of Indohyus does not have deer-like feet (Fig 1). As you can see, the feet of Indohyus are actually quite broad with spreading toes, like those of Pakicetus (Fig 2). Cheating anatomy is not good for science.

Figure 1. Model of Indohyus from the BigThink.com article compared to fossil material of Indohyus.

Promoting the deer-like hypothesis, the authors of Wikipedia wrote:
“Indohyus is an extinct genus of digitigrade even-toed ungulates known from Eocene fossils in Asia. This small chevrotain-like animal found in the Himalayas is one of the earliest known non-cetacean ancestors of whales.”

That hypothesis of interrelationships was shown to be false in 2016 due to taxon exclusion. It also does not make sense – but is widely embraced at the university level. According to the large reptile tree (LRT, 2223 taxa) Indohyus nests with an extant taxon, Tenrec (Fig 2), not with ungulates.

Figure 2. Skeleton of Tenrec alongside restored skeleton model of Pakicetus. Note: neither has deer-like feet. Neither are herbivores.

This all goes back to Gingerich et al 2001 and Thewissen et al 2007,
who wrote about “aquatic artiodactyls”. See figure 3.

Figure 3. Image from BigThink.com substituting Elomeryx instead of Indohyus basal to whales in general. This is a false narrative promoted by university professors and the press.

This whale origin problem could have been corrected several years ago,
but workers refereeing a manuscript submission rejected it. The manuscript points to ‘taxon exclusion’ as the only reason prior workers missed the mark. That might have been embarrassing to the academics like Gingerich and Thewiessen who mistakenly promoted the ‘early artiodactyl‘ and ‘aquatic artiodactyl’ hypothesis.

This instance of rejection was not an isolated incident, but is a common practice in paleontology. That’s why it took over a century for paleontologists to embrace the ‘birds are dinosaurs’ hypothesis and why other workers continue to embrace the ‘bat-wing bird’ hypothesis, among a slew of other bogus hypotheses presented to tuition-paying students.

You can read that rejected manuscript by Googling “Triple origin of whales”, at ResearchGate.net.

Special thanks to paleontologist, Don Prothero,
who linked the BigThink.com article to his Facebook page.

References
Gingerich, PD, Haq M, Zalmout IS, Khan IH, and Malkani MS 2001. Origin of whales from early artiodactyls: hands and feet of Eocene Protocetidae from Pakistan. Science, 293:2239-2242.
Perry P 2023. Ancient deer-like creatures returned to the ocean to become whales. But why? BigThink.com
Thewissen JGM, Cooper LN, Clementz MT, Bajpai S and Tiwari BN 2007. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature 450:1190-1195.
Vermeij GJ and Motani R 2018. Land to sea transitions in vertebrates: the dynamics of colonization. Paleobiology 44(2):237–250. online here

wiki/Indohyus

Tiny, toothless Stylephorus now nests with another blenny: toothy Gigantura

Untested traits include
those cylindrical eyeballs and that elongate lower caudal fin.

Figure 1. Gigantura compared to Stylephorus to a reduced scale.

Gigantura indica
(Brauer A 1901, Konstantinidis and Johnson 2016; 20 cm standard length, not counting the caudal fin, Figs 1–3) is the extant telescope fish. Comparisons with sister taxa indicate the indicated ‘palatine’ with teeth is actually the premaxilla in figure 2 from Gregory 1933. The toothless maxilla (green) is located at the posterior mandible. The postorbital (=circumorbital ring) is reduced to two vestiges. This small fish can swallow prey larger than itself.

Figure 2. Skull of Gigantura from Gregory 1933. Colors and new labels added here.

Figure 3. Gigantura magnified to show facial details including the cylindrical eyeballs.

Stylephorus chordatus
(Shaw, 1791, Regan 1924, Figs 4, 5) is the extant tube-eye or thread-tail. It was considered an oarfish relative (Fig 6), but here nests with Gigantura (Figs 1–3). Note the large eyes and flexible neck. Convergent with seahorses and oarfish, the tube-eye also feeds on tiny plankton sucked in as its tubular mouth enlarges the oral cavity by 40x (Figs 4, 5).

Figure 4. Stylephorus skull animated. Colors added here. Compare to Gigantura in figure 1. The maxilla (mx) labeled here is actually the anterior portion of the postorbital. And now you know why ray-fin fish can be difficult to score.

Figure 5. Stylephorus ontogeny. Feeding animated. Much enlarged. Note the eye-cylinders.

Both of these odd deep-sea fish
find a last common ancestor in the large reptile tree (LRT, 2223 taxa) close to Acanthemblemaria, the tube blenny (Fig 7). So all three are blennies.

Figure 7. Traditional fish cladogram nesting Stylephorus with opahs and oarfish.

Acanthemblemaria aceroi
(genus: Metzelaar 1919; species: Hastings, Eytan and Summers 2020) is a newly described tube blenny described with a µCT scan skeleton. Note the vestige maxilla (green) detached from the lacrimal (tan). Here it nests with Neoclinus, the sarcastic fringhead blenny.

Figure 7. Acanthemblemaria, the tube blenny is presently the last common ancestor of Gigantura and Stylephorus in the LRT. Note the emphasis on the eye sockets and the diminution of the maxilla (green) with a large vestige posteriorly, as in Gigantura (Fig 1).

Housekeeping the ray-fin fish clade continues unabated,
testing taxa together that rarely get tested together in trait analysis.

References
Brauer A 1901. Über einige von der Valdivia-Expedition gesammelte Tiefseefische und ihre Augen. Sitzungsberichte der Gesellschaft zur Beförderung der Gesamten Naturwissenschaften zu Marburg 8: 115–130.
Konstantinidis P and Johnson GD 2016. Osteology of the telescope fishes of the genus Gigantura (Brauer, 1901), Teleostei: Aulopiformes. Zoological Journal of the Linnean Society 179(2):338–353.
Regan CT 1924. The morphology of the rare oceanic fish, Stylophorus chordatus, Shaw; based on specimens collected in the Atlantic by the “Dana” expeditions, 1920–1922. Proceedings of the Royal Society B 96(674): PDF
Shaw G 1791. Description of the Stylephorus chordatus, a new fish. Transactions of the Linnean Society of London, 2d Ser: Zoology 1:90–92.

wiki/Stylephorus
wiki/Sarcastic Fringehead
wiki/Acanthemblemaria
wiki/Gigantura

Opah relatives in the LRT

Recent housekeeping
on the ray-fin fish portion of the large reptile tree (LRT, 2223 taxa) is finally coming to a conclusion (let’s hope!). Today’s graphic (Fig 1) presents the large, disc-shaped opah (genus: Lampris) and a menagerie of equally odd close relatives. These include the surface sprinter, Exocoetus, the deep-sea flashlight fish, Anomalops, and the elephant-nosed Gnathonemus (Fig 1). The sole fossil taxon, Massamorichthys, is from the Paleocene.

Figure 1. Lampris, the opah, shown in two views, plus its many smaller relatives to scale. Presently the last common ancestor of Lampris and Seriola rivoliana is the tiny stickleback, Gasterosteus, the outgroup taxon, which in turn is basal to pipefish, oarfish and seahorses.

A 3rd and 4th spine > ray fin transition

According to results recovered
by the sometimes growing and often changing large reptile tree (LRT, 2222 taxa), two more spiny sharks were basal to ray fin fish clades (Figs 1, 2). The Middle Silurian spiny shark, Nerepisacanthus, nests basal to the Middle Triassic ray-fin, Boreosomus (Figs 1, 2) and that fish alone, given the present taxon list.

By contrast,
the Middle Devonian spiny shark, Cheiracanthus (Fig 1), nests basal to the Sarcopterygii, including the lobe-fin coelocanths + fukanichthiids, and ultimately the tetrapods, PLUS Kalops (Fig 1) and the ray-fin Actinopterygii (Fig 1).

Figure 1. A third and fourth clade arising from spiny sharks (Acantodii) are shown here. Boreosomus is the only tested taxon that arises from Nerepisacanthus. The rest of the taxa leading to lobefin fish and tetrapods arise from Cheiracanthus.

We looked at three other spiny-shark to ray-fin transitions
earlier here and here and several years earlier here.

According to Wikipedia,
“They [acanthodians] are currently considered to represent a paraphyletic grade of various fish lineages basal to extant Chondrichthyes, which includes living sharks, rays, and chimaeras. Acanthodians possess a mosaic of features shared with both osteichthyans (bony fish) and chondrichthyans (cartilaginous fish).

In the LRT, acnathodians are not basal to sharks and kins, but to bony fish.

Figure 2. Overlooked until now, the Middle Triassic ray-fin Boreosomus nests with the Middle Silurian spine-fin Nerepisacanthus. The LRT recovers overlooked interrelationships, like this, by testing taxa together that have never been tested together before, minimizing the common problem of taxon exclusion.

This appears to be a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here. The LRT presents a hypothesis of interrelationships that requires confirmation, refutation or modification from independent research using a similar taxon list. In house modification continues at present.

References
Friedman M and Brazeau MD 2010. A reappraisal of the origin and basal radiation of
the Osteichthyes. Journal of Vertebrate Paleontology, 30:1, 36-56, DOI:
10.1080/02724630903409071
Schaeffer B 1968. The origin and basic radiation of the Osteichthyes; pp. 207–222 in T. Ørvig (ed.), Current Problems of Lower Vertebrate Phylogeny. Almqvist & Wiksell, Stockholm.

wiki/Acanthodii

A 2nd spine > ray fin transition

The transition(s) from spine fins to ray fins
apparently has not been documented until a few days ago, and again today as a second transition is recovered, this one leaving no living descendants.

Adding taxa minimizes traditional omissions. The large reptile tree (LRT, 2222 taxa) recovers overlooked interrelationships by testing taxa together than have never been tested together before. That’s the driver behind this twelve-year-old experiment in phylogenetic analysis, still a work in progress.

Figure 1. Taxa at a second spine to ray fin transition include Harpacanthus and Nerepisacanthus with spine fins, and Feroxichthys and Perleidus with gracile bundled spines, otherwise known as rays without webbing between the rays. Also note the co-ossification of the preopercular from more than a dozen discrete elements in Cheiracanthus.

The transition from spiny Middle Silurian Nerepisacanthus
to bundled-ray apparently without webbing Middle Triassic Feroxichthys is also told in the facial traits (Fig 2). Their shared premaxillary dentition is not seen in other tested taxa.

Figure 2. Above: Middle Silurian Nerepisacanthus. Below: Middle Triassic Feroxichthys to size and to scale.

Nerepisacanthus denisoni
(Burrow 2011; Middle Silurian, 13cm long) is the oldest near-complete acanthodian. Long tabulars (red) readily identify this genus.

Feroxichthys yunnanensis
(Xu 2020; Middle Triassic; 29cm length; IVPP V 25692) is a possible durophagus (eating hard-shelled prey or corals) fish with robust premaxillary teeth. Like other colobodontids this fish has small blunt button-like crushing teeth on the posterior jaws. Colobodontidae does not traditionally extend to Middle Silurian spiny sharks.

This appears to be a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here.

References
Burrow C 2011. A partial articulated acanthodian from the Silurian of New Brunswick, Canada. Canadian Journal of Earth Sciences. 48 (9): 1329–1341.
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

wiki/Cheiracanthus
wiki/Nerepisacanthus
wiki/Peltopleurus
wiki/Feroxichthys – not yet listed
wiki/Colobodontidae

Sea robin evolution

Once again,
graphics (Figs 1, 2) tell the evolutionary story documented by the LRT, a work in progress.

Figure 1. The evolution of sea robins, including Prohalecites, Albertonia, Thoracopterus, Potanichthys, Dactylopterus, Prionotus and Satyrichthys.

Here the origin of sea robins,
extant benthic undersea gliding ray-fin fish, is documented back to Prohalecites (Figs 1, 2), a small Triassic fish considered “the oldest known teleosteomorph”. Transitional taxa include Thoracopterus and Potanichthys (Figs 1, 2). These two are traditionally considered to be Triassic flying fish, unrelated to, but convergent with Exocoetus, the extant flying fish.

Figure 2. The evolution of sea robins, including Prohalecites, Albertonia, Thoracopterus, Potanichthys, Dactylopterus, Prionotus and Satyrichthys documented by their skulls in dorsal and lateral views. Not to scale. The preoperculum (light yellow) is distinct in this clade. Note the reduction of the jugal (cyan).

Sea robins do not approach the surface,
nor do they glide in the air like flying fish do. These two clades of fish with large pectoral fins are not related to one another. They developed large pectoral fins convergently and for different purposes. Sea robins seem to use the oversize pectorals for display and a bit of gliding over the sea floor (Fig 1). There is a third clade of ray-fins that also develop oversize pectoral fins.

Figure 3. Pterois volitans, the extant lionfish, is a member of the Scorpaeniformes, a clade sharing several traits with sea robins, but are not related in the LRT.

Traditionally
sea robins (= gurnards) are considered members of the Scorpaeniformes, like the lionfish (Pterois volitans, Fig 3), which have a similar skull and similar large pectoral fins. In the LRT lionfish nest apart from sea robins. Again, similar derived traits developed by convergence.

This appears to be a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here. Work on the LRT continues.

References
wiki/Triglidae
hwiki/Scorpaeniformes

Harpacanthus and Menaspis might both be related to Raja, the thorned skate

Two odd fossil vertebrates
could be related to each other and both to Raja, the extant thorned skate (Fig 1). Menaspis (Fig 1) is from the Permian. Harpacanthus (Fig 1) is from the Early Carboniferous.

This is a guess based on shared paired structures with no homology in any other known vertebrates. Plus recent re-scoriing in the large reptile tree (LRT, 2222 taxa, see below).

Figure 1. Raja, the thorned skate, compared to Permian Menaspis in ventral exposure and Early Carboniferous Harpacanthus in dorsal expoure. The three paired elements not found in other vertebrates appear to be similar. Not much else to go on here.

Menaspsis appears to be exposed in ventral view
(Fig 1) and is missing at least the rostrum and perhaps the skull. No mouth parts are known, unless certain anterior spines are identified as mouth parts (Patterson 1968). This fossil needs to be µCT scanned to see if part of a dorsal skull is inside the matrix. Too little is known of this taxon to add it to the LRT. Historically Menaspis has been considered a strange catfish, a spiny shark and a skate (Fig 1). This taxon is where wise men fear to tread.

By contrast Harpacanthus is exposed in dorsal view
(Fig 1) and presents the rostrum, scleral rings and braincase. An anterior extension of the rostrum may be hidden in the matrix below the three pairs of elongate ‘toothed’ elements. Again, this fossils needs to be µCT scanned to see if skate-like ventral mouth parts are preserved in the matrix.

Rescored in the LRT
with a possible skate-like Bauplan in mind (= bias) Harpacanthus nests with Raja and Leucoraja. Previously Harpacanthus was allied with Harpagofututor (Lund and Grogran 2004), in which males had jointed rostral appendages, and with extant bristlemouths (Gonostoma), a wide-ranging deep-sea fish with slender skull elements. Patterson 1968 did not include Raja in his tree topology.

If this hypothesis has any merit or problem
reply with a pertinent comment so corrections can be initiated. These taxa have been hair-pullers. Nothing is settled yet.

References
Bendix-Almgreen SE 1971. The anatomy of Menaspis armada and the phylogenetic affinities of the menaspid bradyodonts. Lethaia 4(1):21–49.
Ewald J 1848. Über Menaspis, eine neue fossile Fischgattung. Berichte Über die zur Bekanntmachung Geeigneten Verhandlungen der Königlich-Preussischen Akademie der Wissenschaften zur Berlin 1848:33-35.
Girard CF 1858. Fishes. In: General report upon zoology of the several Pacific railroad routes, 1857 (, ed.), Beverley Tucker, Washington, D.C. No. U.S. Senate Document No. 78: i-xiv, 1-400, pls. 1-21.
Goode GB and Bean TH 1883. Reports on the results of dredging under the supervision of Alexander Agassiz, on the east coast of the United States, during the summer of 1880, by the U. S. coast survey steamer “Blake,” Commander J. R. Bartlett, U. S. N., commanding. Bulletin of the Museum of Comparative Zoology.10(5): 183-226.
Günther 1878. Preliminary notices of deep-sea fishes collected during the voyage of H. M. S. `Challenger. Annals and Magazine of Natural History (Series 5). 2(7/8/9)17-28, 179-187, 248-251.
Jäckel O 1890. Über Menaspis, nebst allgemeinen Bemerkungen über die systematische Stellung der Elasmobranchii. Sitzungsb. Ges. nature. Freunde, Berlin 1891: 115–131.
Lund R 1977. New information on the evolution of the Bradyodont Chondrichthyes. Fieldiana Geol. 33:521–539.
Lund R and Grogan E 2004. Five new euchondrocephalan Chondrichthyes from the Bear Gulch Limestone (Serpukhovian, Namurian E2b) of Montana, USA. In G. Arratia, M. Wilson, R. Cloutier (eds.), Recent Advances in the Origin and Early Radiation of Vertebrates 505-531.
Morris and Roberts 1862. Quart. J. Geol. Soc., 18.
Ortlam D 1986. Neue Aspekte zur Deutung von Menaspis armata Ewald (Kupferschiefer, Zechstein 1, Deutschland) mit Hilfe der stereoskopischen Röntgentechnik. Geologisches Jahrbuch Reihe A, Band A 81.
Patterson C 1965. The phylogeny of the chimaeroids. Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences, 249(757): 101–219.
Patterson C 1968. Menaspis and the bradyodonts. In: T. Ørvig, Current Problems of Lower Vertebrate Phylogeny. (Hrsg.): Nobel Symposium. Band 4. Almquist and Wiksell, Stockholm 1968, S. 171–205.
Rafineque CS 1810. Indice d’ittiologia siciliana ossia catalogo metodico dei nomi latini, italiani, e siciliani dei pesci, che si rinvengono in Sicilia disposti secondo un metodo naturale eseguito da un appendice che contiene la descrizione di alcuni nuovi pesci siciliani. Opuscolo del signore C.S. Rafinesque Schmaltz. Messina. 70 pp. + 2 plates.
Schaumberg G 1992. Neue Informationen zu Menaspis armata Ewald. Paläontologische Zeitschrift 66:311.
Traquair RH 1886. On Harpacanthus, a new genus of Carboniferous Selachian Spines. Journal of Natural History. Series 5. 18(108): 493–496.

wiki/Sarcastic Fringehead
wiki/Harpacanthus
wiki/Gonostomatidae
wiki/Gonostoma
wiki/Cyclothone
wiki/Homalacanthus
wiki/Acanthodes
wiki/Menaspis
German wiki/Menaspis