Orthocormus: a bony fish with an odd reversal: a shark face

Everyone agrees
that Orthocormus roeperi (Weitzel 1930; Arratia and Schultze 2013; Early Jurassic; 45cm; BSPG 1993 XVIII-VFKO B1) is a pachycormiform fish. In the large reptile tree (1781+ taxa) Orthocormus nests with a more derived, Late Jurassic pachycormiform with a longer snout, Aspidorhynchus (Figs. 3, 4), the famous Rhamphorhynchus nibbler.

For reasons unknown,
Aspidorhynchus (Figs. 3, 4) is not traditionally considered a pachycormiform fish.

Arratia and Schultze 2013 consider 
“The fish described here is the best-preserved pachycormiform from Bavaria, Germany, as well as from the Upper Jurassic worldwide.”

Figure 1. Orthocormus, a small, bony fish with a shark-like face.

Figure 1. Orthocormus, a small, bony fish with a shark-like face. Shown 1/3 actual size on a 72dpi screen.

According to Wikipedia
“Pachycormiformes were characterized by having serrated pectoral fins (though more recent studies demonstrated that fin shape diversity in this group was high, reduced pelvic fins and a bony rostrum.”

Figure 2. The shark-like skull of Orthocormus, a ray-fin bony fish.

Figure 2. The shark-like skull of Orthocormus, a ray-fin bony fish. The extended rostrum is a reversal from shark ancestors.

As you can see, this is less than accurate description.
The pelvic fins are not reduced in Orthocormus nor are the pectoral fins serrated. Pachycormus does not have a bony snout. Wikipedia lists several synapomorphies (“Pulling a Larry Martin“) and does not list Aspidorhynchus as a pachycormiform. Better to just run the analysis and find the last common ancestor to determine clade membership.

Rhamphorhynchus entangled with Aspidorhynchus

Figure 3. Rhamphorhynchus entangled with Aspidorhynchus. Both complete and articulated. Inside the belly of Rhamphorhynchus are several smaller fish. Inside its throat is another. Image from Frey and Tischlinger (2012).

Dentition according to Arratia and Schultze 2013:
“There are small conical teeth on the upper jaw, a large tooth on the posterior part of the premaxilla, and both large and small teeth on the maxilla; the lower jaw carries large teeth anteriorly and smaller ones posteriorly.”

Notochord
“The vertebral column is formed by a persistent notochord without chordacentra,”

The tail
“The scaly caudal apparatus, formed by large modified scales with a precise arrangement, is interpreted as an adaptation to fast swimming comparable to that of modern tunas.”

Spiral valve
Another apparent reversal is the presence of a soft tissue spiral intestine, as found in sharks and several other various taxa without apparent pattern, including sarcopterygians. This is the only time Arratia and Schultze 2013 mention the term, ‘shark’ in their text.

Figure 2. The face of the Wyoming Dinosaur Center CSG 255 specimen of Asphidorhynchus + Rhamphorhynchus with facial bones identified using DGS.

Figure 4. The face of the Wyoming Dinosaur Center CSG 255 specimen of Asphidorhynchus + Rhamphorhynchus with facial bones identified using DGS.

Wkipedia reports on Pachycormiformes,
“Their exact relations with other fish are unclear, but they are generally interpreted as stem-teleosts.”

By adding taxa, the LRT provides exact relations with other fish, in this case, within bony fish, close to the base, not in the stem. Again, a wider view provided by the LRT supplements and aids the more focused view of those describing the fossil firsthand. Reversals and convergent traits can be tricky. Let the unbiased software do the decision-making.


References
Arratia G and Schultze H-P 2013. Outstanding features of a new Late Jurassic pachycormiform fi sh from the Kimmeridgian of Brunn, Germany and comments on current understanding of pachycormiforms. Pp. 87–120 in Mesozoic Fishes 5 – Global Diversity and Evolution, Arratia G, Schultze H-P and Wilson MVH (eds.).
Weitzel K 1930. Drei Riesenfische aus den Solnhofener Schiefern von Langenaltheim. – Abh. Senckenberg. Naturforsch. Ges. 42 (2): 85-113.

wiki/Orthocormus
wiki/Pachycormiformes

The stargazer, Uranoscopus, is a frogfish-mimic

Preview
I am aware and working on a comprehensive comment for the Nature paper that just came out today positing a lagerpetid origin for pterosaurs using a chimaera of specimen bits and pieces while omitting competing complete and articulated candidates with soft tissue (= Cosesaurus and kin). So here is today’s entry as planned. Expect the report on the lagerpetid mish-mash authored by 18 misguided PhDs as soon as it gets done, surely in less than a day.

The marbled stargazer,
Uranoscopus bicinctus (Linneaus 1758), looks and acts like a frogfish/anglerfish. The giant jaws of these half buried ambush predators open dorsally. A small ‘lure’ wiggles over the jaws. Large pectoral fins spread laterally. Smaller ‘chin fins’ are present.

Figure 1. The marbled stargazer, Uranoscopus bicinctus, is an angler-frogfish-mimic, but nests in the LRT with other thread fins.

Figure 1. The marbled stargazer, Uranoscopus bicinctus, is an angler-frogfish-mimic, but nests in the LRT with other thread fins.

The chin fins are thread fins,
homologs to sea robin (Prionotus) fingers and the thread fins of Polydactylus. The pelvic fins of the stargazer are stumpy vestiges. Robust circumorbital bones are present. One is a a palatine/lacrimal. Frogfish and anglers don’t have circumorbital bones.

Figure 2. Skull of Uranoscopus with colors added. Purple elements are chin fins.

Figure 2. Skull of Uranoscopus with colors added. Purple elements are threadfins.

The two cleithrum spines
per side are venomous. Uranoscopus can also produce an electric shock, but does not have electroreceptors.


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/Uranoscopus

Kryptoglanis: a catfish mimic

Workers wondered, where did those big teeth come from?
Catfish don’t have such long, interlocking teeth. No wonder Vincent and Thomas 2011 called Kryptoglanis shajii (Figs. 1–3; 6cm) an ‘enigmatic’ subterranean catfish. No wonder Britz et al. erected a new clade of catfish to put it in.

Figure 1. The uncatfish-like teeth of Kryptoglanis in anterior view.

Figure 1. The uncatfish-like teeth of Kryptoglanis in anterior view.

According to Wikipedia
“[Kryptoglanis] has also been seen in dense vegetation in paddy fieldsThe species strongly avoids light and feeds on small invertebrates.”

“The morphology of K. shajii differs from all other known species of catfish and includes such features as the absence of dorsal fin; the presence of four pairs of barbels; an upwardly directed mouth, with a distinctly projecting lower jaw with 4 set[s] of teeth; subcutaneous eyes; anal fin completely confluent with the caudal fin; anal and caudal fins together carry 70–74 fin rays; and no spines in any of the fins.”

Figure 2. Kryptoglanis in 3 views. Note the catfish-like barbels.

Figure 2. Kryptoglanis in 3 views. Note the catfish-like barbels.

Figure 3. Skull of Kryptoglanis, a knife fish, not a catfish.

Figure 3. Skull of Kryptoglanis, a knife fish, not a catfish.

Here’s where we put on our lab coats and act like scientists.
Whenever a taxon is described as ‘differs from all other known species’, that’s the time to expand the taxon list. We’ve seen this so many times before. And every time the LRT has found less traditional and more parsimonious sister taxa simply by adding taxa.

Figure x. Gymnotus carapo in vivo.

Figure 4. Gymnotus carapo in vivo.

Figure 8. Skull of Gymnotus.

Figure 5. Skull of Gymnotus.

According to
the large reptile tree (LRT, 1750+ taxa) those catfish-like barbels on Kryptoglanis developed by convergence on an eel-like knife fish, nesting between the eel, Anguilla and two knifefish, Gymnotus and Electrophorus, the electric eel. This clade of fish DO have large interlocking teeth and a long list of other traits shared with Kryptoglanis. They just don’t have barbels. Seems like prior authors were caught “Pulling a Larry Martin” by focusing on the barbels to the exclusion of all the other traits.

Figure 1. Subset of the LRT focusing on the ray fin only clade of bony fish. Fundulus (yellow) is the new taxon. It attracted Anableps. Various convergent eel-like taxa are shown in baby blue.

Figure 1. Subset of the LRT focusing on the ray fin only clade of bony fish. Fundulus (yellow) is the new taxon. It attracted Anableps. Various convergent eel-like taxa are shown in baby blue.


References
Vincent M and Thomas J 2011. Kryptoglanis shajii, an enigmatic subterranean-spring catfish (Siluriformes, Incertae sedis) from Kerala, India. Ichthyological Research. 58 (2): 161–165. doi:10.1007/s10228-011-0206-6.
Britz R, Kakkassery F and Raghavan R 2014. Osteology of Kryptoglanis shajii, a stygobitic catfish (Teleostei: Siluriformes) from Peninsular India with a diagnosis of the new family Kryptoglanidae. Ichthyological Exploration of Freshwaters. 24 (3): 193–207.

wiki/Kryptoglanis_shajii

Flatfish origin no longer ‘uncertain’ ca. 2008

Revised February 18, 2020
when Polydactylus moved from flatfish to piranhas.

Revised again February 28, 2020
when Polydactylus moved from piranhas to sea robins.

Revised again April 28, 2021
when Polydactylus moved to gars and ratfish (Gadus and Coryphaenoides).

We took an earlier look
at flatfish origins here. Today, more taxa and a look at earlier hypotheses proposing a dual origin for flatfish.

Friedman 2008 wrote, “The evolutionary origins of flatfish asymmetry are uncertain because there are no transitional forms linking flatfishes with their symmetrical relatives. Here I show that Amphistium (Fig. 4) and the new genus Heteronectes (Fig. 3), both extinct spiny-finned fishes from the Eocene epoch of Europe, are the most primitive pleuronectiforms known. The orbital region of the skull in both taxa is strongly asymmetrical, as in living flatfishes, but these genera retain many primitive characters unknown in extant forms. Most remarkably, orbital migration was incomplete in Amphistium and Heteronectes, with eyes remaining on opposite sides of the head in post-metamorphic individuals.”

Friedman 2008 was a major discovery supported by the LRT in 2019.
But it did not go as deep as the LRT (Fig. 9, see below).

If you’re interested in seeing how flatfish operate in vivo,
here’s a video from YouTube:

Here
in the large reptile tree (LRT, 1579 taxa, subset Fig. 9) we can trace the origin of flatfish immediately to the tuna (Thunnus, Fig. 1) and then further back to jawless Silurian fish.

Figure 3. Thunnus, the tuna, skeleton and skin.

Figure 1. Thunnus, the tuna, skeleton and skin. More primitive than traditional cladograms recover it.

Thunnus thyrnnus (Linneaus 1758; 4.6m long; Fig. 1) is the extant Atlantic tuna. Traditionally it is considered a member of the perch family. Here it nests following the Late Carboniferous Coccocephalichthys wildi. The jugal is retained. The squamosal is absent. The maxilla appears to retain one tiny tooth. Note the lacrimal contacts the ventral jugal, creating an orbit not confluent with a lateral temporal fenestra. The tip of the premaxilla descends and carries tiny teeth.

Figure 3. Heteronectes is transitional between Polydactylus and flatfish.

Figure 3. Heteronectes is transitional between tuna and flatfish.

Heteronectes chaneti (Friedman 2008, 2012) is an Eocene fish with an assymetric face originally considered basal to extant flatfish. Note the retention of circumorbital bones. It is transitional between Thunnus (Fig. 2) and Amphistium (Fig. 4).

Figure 4. Amphistium is transitional between Heteronectes and flatfish.

Figure 4. Amphistium is transitional between Heteronectes and flatfish.

Amphistium paradoxum (Agassiz 1835) is an Eocene fish with an asymmetric face, transitional to extant flatfish. It also has the flatfish shape, so it probably swam broadside down.

Figure 6. Psettodes is the most primitive living flatfish. Note the dorsal position of the right eye.

Figure 6. Psettodes is the most primitive living flatfish. Note the dorsal position of the right eye.

 

FIgure 6. Cynoglosses is the extant tongue sole, a flatfish so derived that the pectorals are absent, the tail is continuous with the dorsal and anal fins, the mouth is no longer terminal and both eyes are in the ventral half of the left side of whatever remains of the skull.

FIgure 6. Cynoglosses is the extant tongue sole, a flatfish so derived that the pectorals are absent, the tail is continuous with the dorsal and anal fins, the mouth is no longer terminal and both eyes are in the ventral half of the left side of whatever remains of the skull.

Flatfish
are found over sand or mud flats and beaches, and among mangroves. They feed mostly on crustaceans, as well as chaetognaths, polychaetes, fishes, and some plant material. The common presence of small juveniles throughout the year suggests a prolonged spawning season. The reproduction of a few related species has been studied and they appear to be protandrous, sex changing from male to female with growth (Motomura 2004). I mean, with all the other changes… why not?

For awhile fish workers were thinking
“Flatfish can be divided into two groups: the three species of spiny turbot that make up the family Psettodidae, and the much larger suborder Pleuronectoidei.  Unsurprisingly, fish biologists long assumed that both groups of flatfish evolved from a single common ancestor; it is hard to imagine such a bizarre adaptation having evolved multiple times.”

“Recently however, this common-sense assumption has come under attack. Several studies have found support for the distinct flatfish adaptation having evolved on two separate occasions. Is the flatfish body-plan not as unique as it appears?” (Fig. 7).

Figure 1. Eight cladograms printed by Harrington et al. 2016, four of which recover a monophyletic clade of flatfish. Four others recover a diphyletic split. None of these duplicate the diphyletic results recovered in the LRT.

Figure 7. Eight previously published genomic cladograms printed by Harrington et al. 2016, four of which recover a monophyletic clade of flatfish. Four others recover a diphyletic split. None of these duplicate the diphyletic results recovered in the LRT. This becomes the question Harrington et al. wanted to answer.

 

Harrington et al. 2016 report,
“Here, we recovered significant support for flatfish monophyly and relationships among carangimorphs through analysis of over 1,000 UCE loci.”

Figure 2. Friedman et al. genomic study puts flatfish together (orange and yellow added).

Figure 8. Harrington et al. 2014 genomic study puts flatfish together (orange and yellow added). Again, this tree is not replicated by the LRT.  Scombroides is related to Thunnus.

Figure x. Subset of the LRT focusing on basal vertebrates (= fish).

Figure x. Subset of the LRT focusing on basal vertebrates (= fish).

The LRT employs fossil taxa
(Fig. 9) and, like Harrington 2014 (Fig. 8) does not find a dual origin for flatfish. So, finally a genomic study matches a phenomic study!


References
Bloch ME and Schneider JG 1801.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, Pls. 1-110.
Friedman M 2008.
The evolutionary origin of flatfish asymmetry. Nature 454:209–212.
Friedman M 2012. Osteology of †Heteronectes chaneti (Acanthomorpha, Pleuronectiformes), an Eocene stem flatfish, with a discussion of flatfish sister-group relationships. Journal of Vertebrate Paleontology (32) 4: 735-756; doi: 10.1080/02724634.2012.661352
Girard CF 1858. Notes upon various new genera and new species of fishes, in the museum of the Smithsonian Institution, and collected in connection with the United States and Mexican boundary survey: Major William Emory, Commissioner. Proceedings of the Academy of Natural Sciences of Philadelphia. 10: 167-171.
Harrington RC, et al. (6 co-authors) 2016. Phylogenomic analysis of carangimorph fishes reveals flatfish asymmetry arose in a blink of the evolutionary eye. BMC Evolutionary Biology 16 (224).
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
McCoy F 1855. A synopsis of the classification of the British Palaeozoic rocks, with a systematic description of the British Palaeozoic fossils. Fasciculus 3, Mollusca and Palaeozoic fishes. British Palaeozoic Fossils, Part II. Palaeontology 407-666.

Manta ray: curious reversals + head fins

Manta rays (= devil rays)
(genus: Manta; Figs. 1, 6; sometimes genus: Mobula) have an odd mixture of derived and primitive traits. We’ll review those today.

Figure 1. The largest manta ray to scale with humans.

Figure 1. The largest manta ray to scale with humans. Note the unique cephalic fins hanging down at lower left.

The manta is different from other rays

  1. Mantas have a unique third set of ‘fins’, the cephalic ‘fins’. These are not connected to the pectoral fins, but originate ventral to the eyes (Fig. 1).
  2. In skates, rays and guitarfish the anterior pectoral fin attaches in front of the orbit, on the prefrontal. In mantas + cownose rays (genus: Rhinoptera (Figs. 4, 5) the pectoral fins attaches further back, near the jaw articulation. This is a reversal going back to Rhincodon, the whale shark (Fig. 3) and Thelodus (Fig. 3), the jawless outgroup taxon of the clade Gnathostomata (jawed vertebrates) in the LRT.
  3. Most sharks, guitarfish, skates and rays have a long nasal bone that gives them a rostrum (which gets really long and toothy in saw fish). A similar elongate nasal is missing in cow nose rays and mantas. This is a reversal, too.
  4. Typical guitarfish, skates and rays have a ventral mouth adapted for bottom feeding (Fig. 2). By contrast, the manta ray mouth opens anteriorly, as in the whale shark, for open water feeding. This is a reversal.
  5. Typical guitarfish, skates and rays have electric prey sensing organs. Manta rays do not. This is also a reversal.
  6. Typical guitarfish, skates and rays cruise sandy sea floors seeking buried hard-shelled prey. Mantas do not. They cruise open waters seeking tiny planktonic and mid-sized oceanic prey they trap using internal gill bars prior to digestion. This is also a reversal going back to whale sharks.
  7. Because their mouths are buried in sediment, typical guitarfish, skates and rays ‘inhale’ through an alternate dorsal opening, the spiracle. The manta ray does not. It ‘inhales’ through its cavernous anterior mouth, like most fish, including the whale shark. This is also a reversal.

    Figure 4. Rhinobatus jaw mechanism animation. This is how skates and rays eat, distinct from the Thelodus/ whale shark/ manta ray method of ram feeding.

    Figure 2. Rhinobatus jaw mechanism animation. This is how skates and rays eat, distinct from the Thelodus/ whale shark/ manta ray method of ram feeding.

  8. Typical guitarfish, skates and rays have eyes essentially on the top of their flattened heads. The eyes of manta and cownose rays are placed laterally, as in the whale shark. This is also a reversal.

With so many reversals
I wondered if Manta might be the taxon that broke the ability of the LRT to lump and separate 1558 taxa based on a small (238) character list originally created to lump and separate reptiles. Fortunately, everything came out okay. We’ve seen reversals several times previously here and elsewhere [use keyword: “reversal” in the search box.]

The cephalic ‘fins’ in Manta 
are not used for propulsion. Instead, these lobes help funnel and gather food. They can curl into a spiral to cut drag while swimming rapidly. A series of flexible cartilage rods, like fins rays, fits inside each one (Fig. 6). The origin of these appendages baffled workers for decades.

Figure 1. Rhincodon typus, the extant whale shark, shares traits with jawless Thelodus, armored Entelognathus, and the walking catfish, Clarias.

Figure 3. Rhincodon typus, the extant whale shark, shares traits with jawless Thelodus, armored Entelognathus, a basal placoderm with bone that informs the identity of the cartilage in Manta. Even Thelodus is not far from Manta.

Swenson et al. 2018 shed new light on the origin of manta cephalic ‘fins’. 
They studied a series of embryo cownose rays (genus: Rhinoptera bonasus) because cownose rays are the closest relatives of the manta. Cownose rays also have movable cephalic lobes (Figs. 4, 5), similar to the cephalic fins of mantas, but completely attached to the head along the long axis, like a tailgate.

Figure 2. Cownose ray lobes open and close like flaps.

Figure 4. Cownose ray lobes open and close like flaps. These are homologous to the cephalic fins seen in Manta. See these in operation in figure 5.

Swenson et al. report, “In cownose rays, cephalic lobes do not develop from independent fin buds emanating from the head; rather, they develop as modifications to the anterior pectoral fins, closely resembling the hooks at the anterior of developing skate and ray pectoral fins (Babel, 1966; Luer et al., 2007; Maxwell et al., 2008). However, unlike the anterior pectoral fins of other batoids, cephalic lobes are distinguished from the rest of the pectoral fin by a small region of reduced tissue outgrowth we call the ‘notch.'” 

With their an ontogenetic series of cownose ray embryos
Swenson et al. documented the disconnection of the anteriormost portion of the pectoral fin from the face in younger embryos and the later fusion to the face prior to hatching. Mantas are similar, but skip this last stage and so retain more flexible anteriormost pectoral fins arising from the lower lateral face.

Figure 2. Cownose ray feeding by dropping their cephalic lobes to increase the suction on their oyster prey.

Figure 5. Cownose ray feeding by dropping their cephalic lobes to increase the suction on their oyster prey. See figure 4 to see these lobes closed like landing gear doors, streamlined prior to swimming.

The Swenson et al. results
showed that the devil ray’s horns are not a third set of fins after all – they’re simply the foremost bit of pectoral fin, modified for a new purpose and separated from the main portion of the pectoral fin. The cownose ray documents a modified transitional phase.

Figure 6. Three views of the skeleton of Manta, colors added. Green represents the maxilla. Note the terminal mouth, distinct from other rays, skates and guitarfish. The pectoral fins do not reach the orbit. The cephalic fins are highly modified maxillae, still gathering food. Note the attachment to the quadrate. The premaxilla extends across the mouth.

Figure 6. Three views of the skeleton of Manta, colors added. Note the near terminal mouth, distinct from other rays, skates and guitarfish. The pectoral fins do not reach the orbit. The cephalic fins are independently mobile extensions of the anterior pelvic fins.

Also added to
the large reptile tree (LRT, 1558 taxa) is one of the basal rays, the guitarfish, Rhinobatos, (Figs. 7, 8). Both taxa enter alongside Isurus, the mako shark. Manta (Figs. 1, 6) is, perhaps, the most derived ray (clade Batoidea). Rhinobatos is, perhaps, one of the most basal batoids, closer to sharks, in morphology. Very likely all the rest of the batoids will nest in the LRT between these two taxa. We’ll test that rather orthodox guess as time goes by.

Figure 2. Rhinobatos, the guitarfish, and Rhina the bowhead guitarfish, are transitional to skates and rays, but not mantas. Note the ventral mouth and pectoral fins extending anterior to the orbits.

Figure 7. Rhinobatos, the guitarfish, and Rhina the bowhead guitarfish, are transitional to skates and rays, but not mantas. Note the ventral mouth and pectoral fins extending anterior to the orbits.

Fun fact: brain size
According to Wikipedia, “The oceanic manta has one of the largest brains (ten times larger than a whale shark) and the largest brain-to-mass ratio of any cold blooded fish.”

Figure 5. Guitarfish (Rhinobatos) skull. Colors, eyeballs and spiracles added.

Figure 8. Guitarfish (Rhinobatos) skull. Colors, eyeballs and spiracles added.

Fun fact #2:
That anterior portion of the pectoral fin lateral to the eye of the guitarfish (Figs. 7, 8) is what evolves to become the flap-like cephalic lobes in cownose rays (Figs. 4, 5) and the anteriorly detached, ever-curling cephalic ‘fins’ in manta rays (Figs. 1, 6).


References
Bancroft EN 1829. On the Fish known in Jamaica as the Sea-Devil. The Zoological Journal. 4: 444–457.
Bloch MC and Schneider JG 1891. Systema anclystoma.
Fisher RA 2010, revised 2012. Life history, trophic ecology, & prey handling by cow nose ray, Rhinoptera bonasus, from Chesapeake Bay.
Garman S 1884. An Extraordinary Shark. Bulletin of the Essex Institute: 47–55.
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Smith A 1829. Descriptions of new, or imperfectly known objects of the animal kingdom, found in the south of Africa. South African Commercial Advertiser 3: 2.
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
Swenson JD et al. 2018. How the Devil Ray Got Its Horns: The Evolution and Development of Cephalic Lobes in Myliobatid Stingrays (Batoidea: Myliobatidae). Front. Ecol. Evol, published online November 13, 2018; doi: 10.3389/fevo.2018.00181
White WT et al. 2018. Phylogeny of the manta and devilrays (Chondrichthyes: mobulidae), with an updated taxonomic arrangement for the family. Zoological Journal of the Linnean Society, 2018, 182, 50–75.

wiki/Manta
wiki/Giant_oceanic_manta_ray
wiki/Whale_shark
sci-news.com/biology/manta-rays-cephalic-lobes.html

The deep-sea gulper eel (Eurypharynx) also arises from Gregorius

Updated April 22, 2020
with the addition of taxa Gymnothorax and Eurypharynx are both derived from Gregorius prior to the major dichotomy that splits bony fish in two (see updated cladogram

Earlier we resurrected an ‘extinct’ clade of rhizodont lobefin fish,
when the moray eel, Gymnothorax (Fig. 2) entered the large reptile tree (LRT, 1521 taxa) along with the the rhizodont, Barameda. Today the deep sea gulper eel, Eurypharynx (Figs. 1,2), nests with Gymnothorax. 

Update: Both are now derived from the pre-bony fish, Gregorius

Figure 1. The skull of Eurypharynx from Gregory 1936 with colors added. Compare to Gymnothorax in figure 2.

Figure 2. The skull of Eurypharynx from Gregory 1936 with colors added. Compare to Gymnothorax in figure 2.

Eurypharynx pelecanoides (= Gastrostomus Vailiant 1882; up to 75cm long) is the extant deep sea pelican eel or gulper eel. Like its sister, the moray eel (Gymnothorax, Fig. 2), the naris, antorbital fenestra, orbit and temporal fenestra are confluent. Pectoral fins are barely present. Distinctly the jaw joint is far behind the occiput and hyperelongated hyomandibular and quadrate. The stomach can stretch to accomodate large prey. The muscle segments are V-shaped, not W-shaped, as in most bony fish. The lateral line system projects from the body, rather than lying in a groove.

This appears to be a novel hypothesis of interrelationships.
If someone else has published on this earlier, please let me know so I can cite them properly.

The YouTube video (above)
shows the slender, oversized jaws can balloon with water AND the dorsal half above the skull does, too! This is done, evidently, as a threat display, to appear much larger than ordinary, and to feed — convergent with the blue whale (Balaenoptera) and other rorqual mysticetes.

Figure x. Subset of the LRT focusing on basal vertebrates. This represents the latest hypothesis of interrelationships and includes several changes from prior versions of this section.

Figure x. Subset of the LRT focusing on basal vertebrates. This represents the latest hypothesis of interrelationships and includes several changes from prior versions of this section.


References
Bloch ME 1795. Naturgeschichte der ausländischen Fische. Berlin. v. 9. i-ii + 1-192, Pls. 397-429.
Valliant LL 1882. Sur un poisson des grandes profondeurs de l’Atlantique, l’Eurypharynx pelecanoides. Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences, Série D, Sciences Naturelles 95: 1226-1228.

wiki/Gogonasus
wiki/Onychodus
wiki/moray eel
wiki/Barameda
wiki/Rhizodus
wiki/Eurypharynx

Restoring and re-nesting Murusraptor

Traditional megaraptorans,
like Megaraptor namunhuaiquii (Novas 1998, Fig. 1) and Murusraptor barrosaensis (Coria and Currie 2016; Rolando, Novas and Agnolin 2019; MCF-PVPH-411; Fig. 1), are currently only known from bits and pieces. Perhaps for these reasons Wikipedia reports, “the clade Megaraptora (Benson, Carrano and Brusatte 2010 ) has controversial relations to other theropods.”

According to Wikipedia
“Murusraptor is a megaraptoran, one of a group of large predatory dinosaurs whose exact classification remains disputed. Once believed to be dromaeosaurids, they have since been classified as either allosauroid carnosaurs or as tyrannosauroid coelurosaurs. While the discovery of Murusraptor does not clarify as of yet the placement of this group of theropods, the specimen does add further clarity to some aspects of megaraptoran anatomy and potentially, eventual classification of the Megaraptora within the theropod evolutionary tree.”

Definition
Megaraptora (Benson et al 2010) “The most inclusive clade comprising Megaraptor namunhuaiquii, but not Chilantaisaurus tashuikouensis.” 

Wikipedia reports,
“Megaraptorans were most diverse in the early Late Cretaceous of South America, particularly Patagonia. However, they had a widespread distribution. Fukuiraptor, the most basal (“primitive”) known member of the group, lived in Japan. Megaraptoran material is also common in Australia, and the largest known predatory dinosaur from the continent, Australovenator, was a megaraptoran.” 

Taxa traditionally included within Megaraptora:

  1. Megaraptor (known from a long maxilla and forelimb, Figs. 1, 2)
  2. Fukuiraptor (known from jaw fragments, coracoids, humeri, femur, acetabulum, two vertebrae
  3. Australovenator (known from a dentary, a few dorsal ribs, distal forelimbs and nearly complete hind limbs)
  4. Murusraptor (known from several skull elements and other bones Figs. 1, 2)

Of these, only two, Megaraptor and Murusraptor, are tested in the LRT.

Other megaraptoran traits according to Wikipedia

  1. “Their forelimbs were large and strongly built,
  2. The ulna bone had a unique shape (except Fukuiraptor).
  3. The first two fingers were elongated, with massive curved claws ,
  4. The third finger was small. 
  5. Megaraptoran skull material is very incomplete, but a juvenile Megaraptor described in 2014 preserved a portion of the snout, which was long and slender. 
  6. Leg bones referred to megaraptorans were also quite slender and similar to those of coelurosaurs adapted for running. 
  7. Although megaraptorans were thick-bodied theropods, their bones were heavily pneumatized, or filled with air pockets. The vertebrae, ribs, and the ilium bone of the hip were pneumatized to an extent which was very rare among theropods, only seen elsewhere in taxa such as Neovenator
  8. Other characteristic features include opisthocoelous neck vertebrae
  9. and compsognathid-like teeth.” 

Several of the above traits
are shared with other taxa. The LRT employes a suite of 231 shared, unique and often convergent traits to lump, split and ultimately nest all taxa. Surprisingly, even the poorly preserved, disarticulated and incomplete Megaraptor and Murusraptor found secure nodes.

Araciaga, Rolando, Novas and Agnolin 2019
bring us ‘new evidence about the phylogenetic relationships of Megaraptora.’ They report, “The current study lends further support to the hypothesis that megaraptorans are basal members of Coelurosauria (supported by 20 synapomophies), with strongest affilation with Tyrannosauroidea (supported by > 20 synapomorphies).”

From their abstract:
“Murusraptor is particularly similar to juvenile specimens of tyrannosaurids; both share: 1) lacrimal with a long anterior prosess; 2) corneal process and; 3) lateral pneumatic fenestra; 4) square and dorsoventrally low frontals; 5) parietals with well-developed sagittal and nuchal crests, among other features. The current study lends further support to the hypothesis that megaraptorans are basal members of Coelurosauria (supported by 20 synapomophies), with strongest affilation with Tyrannosauroidea (supported by > 20 synapomorphies).”

“Murusraptor is unique in having several diagnostic features that include anterodorsal process of lacrimal longer than height of preorbital process, and a thick, shelf-like thickening on the lateral surface of surangular ventral to the groove between the anterior surangular foramen and the insert for the uppermost intramandibular process of the dentary.

“Other characteristic features of Murusraptor barrosaensis n.gen. et n. sp. include a large mandibular fenestra, distal ends of caudal neural spines laterally thickened into lateral knob-like processes, short ischia distally flattened and slightly expanded  dorsoventrally. Murusraptor belongs to a Patagonian radiation of megaraptorids together with Aerosteon, Megaraptor and Orkoraptor.”

A little backstory with links for more details:
Aerostean is a giant (9m) Late Cretaceous theropod with no skull material known. Orkorpator is a large (6m) Latest Cretaceous theropod includes only a post-orbital and quadratojugal for skull material and bits and pieces otherwise.

Figure 1. Murusraptor compared with related taxa to scale.

Figure 1. Murusraptor compared with related taxa to scale. Ghosted rostrum of Guanlong added to missing rostrum of Mururaptor.

Phylogenetic analysis
In the large reptile tree (LRT, 1415 taxa; Fig. 4) Megaraptor (Fig. 1) nests with the basal theropod, Sinocalliopteryx. Murusraptor (Fig. 1) nests between long-snouted Dilong and the long-snouted Guanlong / Spinosaurus clade.

One problem comes from
the hypothesis of relationships published by Coria and Currie 2016 that nests long-snouted Xiongguanlong, Dilong, Proceratosaurus and Guanlong with robust-snouted Tyrannosaurus, rather than with long-snouted spinosaurs. Even so, Coria and Currie 
nest Murusraptor with Megaraptor. The closest theropod also tested in the LRT is the finback allosaurAcrocanthosaurus. So, the Coria and Currie cladogram is different in most respects from the LRT. Coria and Currie also nest the giant horned theropod, Ceratosaurus, as a basalmost/outgroup taxon. In the LRT (Fig. 4) Ceratosaurus has no descendants.

Figure 2. Megaraptor, Murusraptor and Sinocalliopteryx. See figure 1 for revised restoration of Murusraptor. Not to scale.

Figure 2. Megaraptor, Murusraptor and Sinocalliopteryx. See figure 1 for revised restoration of Murusraptor. Not to scale. The Rolando et al. restoration draws more on Megaraptor and Dilong.

In counterpoint to Coria and Currie 2016,
Novas et al. 2016 reported, “megaraptorids retained several of the manual features present in basal tetanurans, such as Allosaurus. In this regard, Megaraptor and Australovenator are devoid of several manual features that the basal tyrannosauroid Guanlong shares with more derived coelurosaurs (e.g., Deinonychus).” 

In the LRT,
(Fig. 4) Guanlong is closer to Allosaurus than to Tyrannosaurus.

Figure 4. Megaraptor also preserves a complete and distinct manus, here compared to Sinocalliopteryx, which also has a digit 4, and Suchomimus has a robust ungual 1.

Figure 3. Megaraptor also preserves a complete and distinct manus, here compared to Sinocalliopteryx, which also has a digit 4, and Suchomimus has a robust ungual 1. According to the LRT, Suchomimus is not related to Megaraptor, but is shown here to demonstrate the convergence.

According to the writers of Wikipedia,
the large compsognathid, Sinocallioteryx (Figs. 1-3) is not related to megaraptorids, despite the many similarities in the skull. Curiously, other long-snouted theropods with massive curved claws on their forelimbs, like Suchomimus (Fig. 3), are also not traditionally considered related to megaraptorids. I wish they were. Everyone wishes they were. However, I have to report results, no matter how controversial, as I have for the last eight years. That way, if I made mistakes, someone will tell me. If someone has forgotten certain taxa, perhaps next time they will add them.

Figure 4. Subset of the LRT focusing on basal theropods. Megaraptor and Murusraptor are highlighted.

Figure 4. Subset of the LRT focusing on basal theropods. Megaraptor and Murusraptor are highlighted.

In conclusion
Murusraptor barrosaensis
  (Coria and Currie 2016; Rolando, Novas and Agnolin 2019; Late Cretaceous) was originally considered a sister to Megaraptor and close to tyrannosaurs. Here (Fig. 4) Murusraptor nests between Dilong and Guanlong closer to spinosaurs. Megaraptor nests with Sinocalliopteryx, a basal theropod, not close to Murusraptor. Wherever other traditional megaraptorans (see list above) nest has not yet been tested in the LRT. We looked at the relationship of long-snouted theropods with spinosaurs, rather than tyrannosaurs earlier here.


References
Rolando AMA, Novas FE and Agnolin FL 2019. A reanalysis of Murusraptor barrosaensis Coria & Currie (2016) affords new evidence about the phylogenetical relationships of Megaraptora. Cretaceous Research. https://doi.org/10.1016/j.cretres.2019.02.021
Benson RBJ, Carrano MT and Brusatte SL 2010. A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic.
Naturwissenschaften 97(1): 71–78.
Coria RA and Currie PJ 2016. A New Megaraptoran Dinosaur (Dinosauria, Theropoda, Megaraptoridae) from the Late Cretaceous of Patagonia. PLoS ONE 11(7): e0157973. doi:10.1371/journal.pone.0157973
Novas FE 1998. Megaraptor namunhuaiquii, gen. et sp. nov., a large-clawed, Late Cretaceous theropod from Patagonia. Journal of Vertebrate Paleontology. 18: 4–9. doi:10.1080/02724634.1998.10011030
Novas FE, Rolando AMA and Agnolín FL 2016. Phylogenetic relationships of the Cretaceous Gondwanan theropods Megaraptor and Australovenator: the evidence afforded by their manual anatomy. Memoirs of Museum Victoria. 74: 49–61.
Porfiri JD, Novas FE, Calvo JO.; Agnolín FL.; Ezcurra MD and Cerda IA. 2014. Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation. Cretaceous Research. 51: 35–55.

wiki/Megaraptor
wiki/Murusraptor
wiki/Megaraptora

Allactaga and Pedetes enter the LRT

Those leaping rodents from Africa,
jerboas (genus: Allactaga) and jumping hares (genus: Pedetes, Fig. 1), are more closely related to chinchillas and guinea pigs (Cavia), than to the marsupial kangaroos (Macropus) they converge with.

Allactaga major (Cuvier 1836; Late Miocene to present; snout-vent length 5–15cm; Fig. 1) is the extant jerboa, a nocturnal bipedal rodent that burrows into sand during the day. The long hind limbs help it hop, like a kangaroo, zig-zagging over long distances, and avoid attacking owls. They can hurdle several feet in a single bounce. Some have short ears, others have giant ears for cooling. Closest relatives in the LRT include Pedetes and Chinchilla, not the traditional Mus.

Figure 1. Skeletons of Pedetes and Allactaga to scale.

Figure 1. Skeletons of Pedetes and Allactaga to scale. Not sure yet if the jerboa is a miniature spring hare, or if the spring hare is a giant jerboa.

Figure 3. The spring hare (Pedetes) nests with the jerboa (Allactaga) in the LRT.

Figure 2. The spring hare (Pedetes) nests with the jerboa (Allactaga) in the LRT.

Pedetes capensis (Illiger 1811; snout-vent length: 35-45cm; Figs. 1, 2) is the extant South African springhare, a diurnal burrower and a nocturnal hopper native to South Africa. Pedal digit 1 is absent. Young are born with fur and are active within days.


References
Cuvier F 1836. Proceedings of the Zoololgical Society of London 1836:141.
Illiger 1811. Prodromus systematis mammalium et avium additis terminis zoographicis utriusque classis, eorumque versione germanica. Sumptibus C. Salfeld, Berolini [Berlin]: [I]-XVIII, [1]-301.

wiki/Allactaga
wiki/Pedetes

Dactylopsila, the striped possum, enters the LRT

Dactylopsila trivirgata (Gray 1858) is the extant striped possum (Fig. 1), closely related to the sugar glider, Petaurus and the marsupial lion, Thylacoleo (below), according to the large reptile tree (LRT, 1412 taxa). Dactylopsila is an arboreal marsupial with a prehensile tail the size and proportions of a placental squirrel. The fourth finger is elongated and used to extract beetles and caterpillars from tree bark, analogous to the extant aye-aye, Daubentonia. Dactylopsila, also eats leaves, fruit and small vertebrates.

By convergence
Dactylopsila has similar teeth and overall proportions to the extinct arboreal placental Apatemys (Fig. 2).

Figure 1. Dactylopsila skull in 3 views, plus in vivo. Comparisons to the extinct arboreal placental Apatemys (figure 2) are intriguing, showing convergence.

Figure 1. Dactylopsila skull in 3 views, plus in vivo. Comparisons to the extinct arboreal placental Apatemys (figure 2) are intriguing, showing convergence.

For comparison, we recently looked at Apatemys
here as it relates to the extant shrew opossums Caenolestes and Rhyncholestes, now nesting as apatemyid placentals in the LRT, rather than as traditional didelphid marsupials. The convergence is powerful here. Despite the phylogenetic distance, only 12 extra steps are needed to nest caenolestids with basal didelphids.

Figure 3. Apatemys skull in situ and reconstructed shares several similar traits with the extant striped opossum, Dactylopsila, including a squirrel-like size, elongate fingers and similar teeth.

Figure 2. Apatemys skull in situ and reconstructed shares several similar traits with the extant striped opossum, Dactylopsila, including a squirrel-like size, elongate fingers and similar teeth.

The nesting of Dactylopsila
close to Petaurus (Fig. 3) is not controversial.

Figure 1. Subset of the LRT showing the nesting of Dactylopsila, the striped opossum.

Figure 3. Subset of the LRT showing the nesting of Dactylopsila, the striped opossum, with Petaurus the sugar glider and Thylacoleo, the marsupial lion.

The problem continues to be
the traditional nesting of the marsupial lion, Thylacoleo (Fig. 4), as a member of the wombats (Vombatiiformes), rather than the Phalangeriformes and Petauroidea, as recovered by the LRT (Fig. 3), which points to a bigger problem…

Nowhere in traditional taxon lists
will you find interatheres, toxodontids and creodonts. All these taxa need to be tested in traditional metathere trees because the LRT has tested them and they nest with metatheres. It’s a good time for a confirmation or a refutation. PhD students… are you looking for a good subject to write about for your dissertation?

Figure 2. Thylacoleo skeleton compared to Petaurus skeleton to scale.

Figure 4. Large Thylacoleo skeleton compared to small Petaurus skeleton to scale. Dactylopsila is similar in size to Petaurus.

Here, again,
is where tradition, opinion and bias have, so far, trumped testing. Taxon exclusion needs to be tested with taxon inclusion. The list of taxa needing testing is provided by the LRT.


References
Gray JE 1858. List of species of Mammalia sent from the Aru Islands by Mr A.R. Wallace to the British Museum. Proceedings of the Zoological Society of London. 26: 106–113.

wiki/Striped_possum – Dactylopsia trivirgata

Numbat genesis in the Early Jurassic

Coelocanth. Tuatara. Numbat.
Name three taxa that have not changed much in hundreds of millions of years.

Figure 1. Myrmecobius, the living numbat, has remained essentially unchanged for nearly 200 million years.

Figure 1. Myrmecobius, the living numbat, has remained essentially unchanged for nearly 200 million years based on the LRT. Note the loss of posterior molars and the simplification of the remaining anterior molars. Orange arrow point to palatal pits that receive the long lower canines.

Extant numbats
(genus: Myrmecobius, Fig. 1) nest in the large reptile tree (LRT, 1412 taxa; subset Fig. 2) basal to Early Cretaceous Anebodon, Middle Jurassic Docofossor and the extant marsupial mole (genus: Notoryctes). All arise from the extant Dasycercus (Fig. 3). So that provides an interesting cladogram with members that span from the Triassic to the present. That means some extant taxa had nearly identical ancestors that shared the planet with the first dinosaurs and pterosaurs.

Figure 2. Subset of the large reptile tree focusing on the basal phytometatheria, including extant numbats, basal to Middle Jurassic Docofossor.

Figure 2. Subset of the large reptile tree focusing on the basal phytometatheria, including extant numbats (Myrmecobius), basal to Middle Jurassic Docofossor.

Myrmecobius fasciatus (Waterhouse 1841) is the extant numbat. Here it nests between Dasycercus and Anebodon. Since an ancestral taxon, Docofossor, is known from the Middle Jurassic, a sister to Myrmecobius had its genesis in the Early Jurassic. The molars are narrow and simplified. This is a marsupial termite eater, convergent with placental termite- and ant-eaters. Over each orbit is the reappearance of an old bone, the postfrontal. The canine is smaller. The jugal is straighter.

Figure 5. Dasycercus, the extant mulgara, is the carnivorous phylogenetic ancestor to the clade that includes numbats, Docofossor and kin in the LRT.

Figure 3. Dasycercus, the extant mulgara, is the carnivorous phylogenetic ancestor to the clade that includes numbats, Docofossor and kin in the LRT.

What’s interesting are the molars in Myrmecobius.
Take a good look (Fig. 1). The molars are narrow and simplified because this taxon eats termites (or vice versa). A phylogenetic descendant, Docofossor (Fig. 5) was considered a docodont based on its simple tooth morphology. Another phylogenetic descendant, Anebodon, was considered a symmetrodont based on its tooth morphology.

The LRT results remind us
not to put so much emphasis on tooth morphology. The LRT makes mammal systematics so much simpler by nesting taxa according to all their tested traits, not just a few, rather plastic, dental traits.

Figure 4. Dasycercus in vivo. This is the extant mulgara, a carnivorous nocturnal basal marsupial.

Figure 4. Dasycercus in vivo. This is the extant mulgara, a carnivorous nocturnal basal phytomarsupial with origins in the Early Jurassic.

Dasycercus cristicauda (originally ‘Chaetocercus‘ Krefft 1867; Peters 1875; 22cm + 13 cm tail) is the extant mulgara, considered a dasyurid marsupial. Here carnivorous, nocturnal Dasycercus nests apart from Dasyurus between Anebodon and Myrmecobius at the base of the herbivorous clade of marsupials. The pouch is reduced to two lateral folds of skin.

Figure 1. Docofossor in situ with DGS tracings.

Figure 5. Docofossor in situ with DGS tracings. This Middle Jurassic taxon nests as a derived descendant of Dasycercus and Myrmecobius in the LRT.

Docofossor brachydactylus (Luo et al. 2015; Middle Jurassic, 160 mya; BMNH 131735; 9cm in precaudal length) was originally considered a member of the Docodontidae along with Docodon and Haldanodon outside of the Mammalia. Here it nests as a Jurassic sister to Anebodon and Notoryctes. Broad, short-fingered hands, larger than the feet, along with other traits mark Docofossor as a digging animal, similar to moles like Talpa and Chrysochloris.


References
Bi S-D, heng X-T, Meng J, Wang X-L, Robinson N and Davis B 2016. A new symmetrodont mammal (Trechnotheria: Zhangheotheriidae) from the Early Cretaceous of China and trechnotherian character evolution. Nature Scientific Reports 6:26668 DOI: 10.1038/srep26668
Gadow H 1892. On the systematic position of Notoryctes typhlops. Proc. Zool. Soc. London 1892, 361–370.
Luo Z-X, Meng QJ, Ji Q, Liu D, Zhang Y-G, Neande AI 2015.Evolutionary development in basal mammaliaforms as revealed by a docodontan. Science. 347 (6223): 760–764.
Peters WCH 1875. Sitzungsberichte der Gesellschaft Naturforschender Freunde zu Berlin 1875: 73.
Stirling EC 1888. Transactions of the Royal Society, South Australia 1888:21
Stirling EC 1891. Transactions of the Royal Society, South Australia 1891:154
Tate GHH 1951. The banded anteater, Myrmecobius Waterhouse (Marsupialia). American Museum Novitates 1521, 8 pp.
Waterhouse GR 1836. Myrmecobius fasciatus. Proc. Zool. Soc. London 4: 69–131.
Waterhouse GR 1841. Description of a new genus of mammiferous animals from Australia, belonging probably to the order Marsupialia. Trans. Zool. Soc., London2, aricle. 11, p 149.

wiki/Dasycercus
wiki/Myrmecobius