Freshwater Anableps finds a new home with deep sea Gigantura

Weeks of work on ray-fin fish
continue to produce fascinating results. Unfortunately only one or two taxonomic insights are appearing at a time, as readers have witnessed. Convergence is a frustrating problem. Hundreds of mistakes have been corrected with new data similar to today’s new data.

A problematic taxon, Anableps,
the fresh water four-eyed fish (Figs. 1, 3), finally finds a home with a taxon that shares a long list of previously overlooked traits, a deep-sea predator, Gigantura, the telescope fish (Figs. 2, 3). This match only came about because data on the dorsal view of the skull of Anableps became known. This skull architecture appears in only these two taxa. Perhaps, not surprisingly, but rather obviously, both Anableps and Gigantura have eyeballs that extend beyond the skull boundaries.

LCA
Trachinocephalus, a so-called lizard fish (Fig. 3) is a last common ancestor. It prefers shorelines. Lepidogalaxias, a so-called salamander fish (Fig. 3), is another relative one step removed, but has a similar elliptical caudal fin and prefers fresh water. So we’re getting new clues to the ancestry of these highly derived, yet basal bony fish, Anableps and Gigantura.

If Gigantura and Anableps have ever been nested together
in an academic publication, let me know so I can cite it. Otherwise this appears to be an overlooked hypothetical interrelationship.

Let’s look at these two together,
perhaps for the first time.

Figure 1. Dorsal and lateral views of the skull of Anableps from Perez et al. 2017. Colors added as tetrapod homologs.

Figure 1. Dorsal and lateral views of the skull of Anableps from Perez et al. 2017. Colors added as tetrapod homologs. Note the tiny postorbital here identified for the first time.

Figure 2. Gigantura skull in dorsal and lateral views assembled and colorized here from Konstantinidis and Johnson 2016.

Figure 2. Gigantura skull in dorsal and lateral views assembled and colorized here from Konstantinidis and Johnson 2016. Note their palatine is here a premaxilla. Their vomer is here a maxilla. Their maxilla is here a lacrimal. Their frontal is here divided with a parietal.

Dorsal views of the two skulls
(Figs 1, 2) show nearly identical architecture. In the large reptile tree (LRT, 1801+ taxa) no other taxon nests closer to Anableps than Gigantura and it’s even stranger relative, Stylephorus (Fig. 3). Given that semi-related Doliodus (Fig. 3) comes from the Early Devonian, all these taxa have had plenty of time to go their separate ways from a basal bony fish radiation.

Th interrelationship between Gigantura and Anableps
may have gone unnoticed thus far because lateral views of the skulls differ:

  1. In Gigantura the occiput is far anterior to the jaw joint
  2. In Anableps the occiput is far posterior to the jaw joint
  3. In Gigantura the maxilla is greatly reduced below the nasal
  4. In Anableps the maxilla is not reduced
  5. In Gigantura the nasals are greatly reduced
  6. In Anableps the nasals are larger than typical

Konstantidnidis and Johnson 2016 
discussed the homology of the tooth-bearing upper jaw elements. The authors considered the upper jaw composed of the palatine alone “based on topological evidence.” Anableps was not mentioned in their text. Based on comparative anatomy with Anableps, new identities are assigned to certain bones in the Gigantura skull.

  1. The ‘palatine’ (Fig. 2) is here a premaxilla.
  2. The ‘vomer’ is here a vestigial maxilla, still dorsal to the premaxilla.
  3. The leaf-like ‘maxilla’ is here a lacrimal, as in Anableps.
  4. The frontals include parietals, perhaps fused
Figure 1. Taxa from the LRT on one branch of the bony fish. Doliodus is one of these.

Figure 3. Taxa from the LRT on one branch of the bony fish. Doliodus is one of these.

Anableps tetrophthalmus
(originaly Cobitis anableps Linnaeus 1758, Scopolis 1777; 32 cm) is the extant four-eyed fish (aka: cuatro ojos), a surface predator of insects that fall into fresh waters or are preyed upon on shallow shores where Anableps beach themselves to eat. The short lower jaw enables this. Traditionally Anableps is a member of the pupfish (guppy, killifish, topminnow) family. Here Anableps nests with deepsea telescope fish like Gigantura. The naris is anterolateral. Traditionally the fossil record is unknown, but now see figure 3. Females are much larger than males. Internal fertilization (with a modified tubular anal fin) leads to live birth (viviparity) of up to 14 young. The vertebral number is higher than typical for most ray-fin fish.

Figure x. Rayfin fish cladogram

Figure x. Rayfin fish cladogram

Gigantura indica 
(Brauer A 1901Konstantinidis P and Johnson GD 2016; 20 cm standard length, not counting caudal fin) is the extant telescope fish. This small fish can swallow prey larger than itself.

Stylephorus chordatus 
(Shaw, 1791, Regan 1924) is the extant tube-eye or thread-tail. It was considered an oarfish relative, but here nests with Gigantura. Distinct from Gigantura, but convergent with seahorses and oarfish, the tube-eye feeds on tiny plankton sucked in as its tubular mouth enlarges the oral cavity by 40x.


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.
Michel KB, Aerts P, Gibb AC and Van Wassenberg S 2015. Functional morphology and kinematics of terrestrial feeding in the largescale foureyes (Anableps anableps). Journal of Experimental Biology (2015) 218, 2951-2960 doi:10.1242/jeb.124644
Perez et al. (9 co-authors) 2017. Eye development in the four-eyed fish Anableps anableps: cranial and retinal adaptations to simultaneous aerial and aquatic vision. Proc. R. Soc. B 284: 20170157.  http://dx.doi.org/10.1098/rspb.2017.0157
Scopoli GA 1777. Introductio ad historiam naturalem sistens genera lapidum, plantarum, et animalium. Wolfgang Gerle, Pragae 3-506.
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/Anableps
wiki/Telescopefish = Gigantura

wiki/Tube-eye = Stylephourus

Is the early evolution of bony fishes obscured?

Updated February 17, 2021
with the shifting of Anableps to the basal bony fish (Fig. 1).

For readers in a hurry,
the answer to the headline question is, ‘no.’

Romano 2021 reports:
“About half of all vertebrate species today are ray-finned fishes (Actinopterygii), and nearly all of them belong to the Neopterygii (modern ray-fins). The oldest unequivocal neopterygian fossils are known from the Early Triassic.”

Clade membership: According to Wikipedia“Neopterygii is a subclass of ray-finned fish (Actinopterygii). They could move more rapidly than their ancestors. Their scales and skeletons began to lighten during their evolution, and their jaws became more powerful and efficient.” Electroreception is a lost sense, even if it has later been re-evolved within Gymnotiformes and catfishes, which possess nonhomologous teleost ampullae. Better control of the movements of both dorsal and anal fins, resulting in an improvement in their swimming capabilities. 

According to the Wikipedia cladogram, Neopterygii include

  1. Lepisosteifomres (gars)
  2. Amiformes (bowfins)
  3. Teleosts (the rest of the ray-fin fish)

By contrast,
in the large reptile tree (LRT, 1801+ taxa) the earliest unequivocal ray fin fish is Doliodus (Fig. 1)  from the Early Devonian. Gars, bowfins, lobefins, placoderms and spiny sharks nest within the bony fish. Moray eels are among the most primitive taxa, and these are derived from hybodontid sharks. Counterintuititively, some of the more bizarre-looking bony fish, often deep sea forms, are among the most primitive bony fish.

Figure 1. Taxa from the LRT on one branch of the bony fish. Doliodus is one of these.

Figure 1. Taxa from the LRT on one branch of the bony fish. Doliodus is one of these.

Romano 2021 continues:
“In the Middle Triassic neopterygians were already species-rich and trophically diverse, and bony fish faunas were more regionally differentiated compared to the Early Triassic. Still little is known about the early evolution of neopterygians leading up to this first diversity peak. Here, I review the fossil record of Early and Middle Triassic marine bony fishes (Actinistia and Actinopterygii) at the substage-level in order to evaluate the impact of this hiatus on our understanding of their diversification after the largest mass extinction event of the past.”

Figure 1. Taxa from the LRT on the other branch of the bony fish, including spiny sharks, bony tongues, placoderms, catfish and lobefins.

Figure 2. Taxa from the LRT on the other branch of the bony fish, including spiny sharks, bony tongues, placoderms, catfish and lobefins derived from Gregorius.

Taxon inclusion in the LRT
permits the association of taxa that had traditionally not been associated before. Traditional memberships and traditional clades are not supported by the LRT where spines evolve to become fins and vice versa.


References
Romano C 2021. A hiatus obscures the early evolution of modern lineages of bony fishes. Frontiers. Earth Science 8:618853 doi: https://doi.org/10.3389/feart.2020.618853
https://www.frontiersin.org/articles/10.3389/feart.2020.618853/full

Tiny Santanichthys is a bonefish

Updated April 28, 2021
with a closer look at Santanichthys now nesting with bonefish like Albula and Opisthoproctus.

This was a paragraph from the earlier post:
Two very closely related taxa, one 20x times larger,
enter the LRT today. Santanichthys (Silva Santos 1995; Figs. 1, 5) is only 3m in length. Notelops (Woodward 1901; Figs. 2–4) reaches 60cm in length. Both are from the Santana Formation, Early Cretaceous.

Figure 1. Tiny Santanichthys is a phylogenetically miniaturized taxon at the base of the Ostariophysi clade.
Figure 1. Tiny Santanichthys is a phylogenetically miniaturized taxon at the base of the Ostariophysi clade.

Santanichthys diasii 
(Silva Santos 1958; Filleleul and Maisey 2004; Early Cretaceous; 3cm; DGM-DNPM 647P) was a tiny Santana Formation fish considered the oldest characiform and otophysan. Here Santanichthys nests with Albula the extant bonefish (Fig. 2). According to Filleleul and Maisey, this is the earliest appearance of a Weberian apparatus, a sound amplifier that connects the swim bladder to the auditory system.

Figure 2. The skull and diagram of tiny Santanichthys from Filleul and Maisey 2004, colors added.

These taxa are considered members of the Characiformes,
a clade that traditionally includes piranha. Likewise the large reptile tree (LRT, 1801 taxa then, 1839 taxa now; subset Fig. x) nests them together, derived from the piranha clade. Traditionally Characiformes also includes knife fish and catfish. These clades are not related to piranha in the LRT, nor are they related to bonefish.

Figure 1. Albula vulpes skull with highly derived facial bones reidentified here. Note the lateral premaxillary processes and 'floating' cheek bones. Green vertebrae are caudals.
Figure 3. Albula vulpes skull with highly derived facial bones reidentified here. Note the lateral premaxillary processes and ‘floating’ cheek bones. Green vertebrae are caudals.

Santanichthys and Albula
share a long list of traits. Tiny Opisthoproctus (Fig 4) has fewer vertebrae, like Santanitchthys.

Figure 3. Opisthoproctus nests with Santanichthys in the LRT.
Figure 4. Opisthoproctus nests with Santanichthys in the LRT.
Figure x. Rayfin fish cladogram

If your studies dive deep into fish science  
you’ll come across the traditional clade Ostariophysi, in which member taxa all have a Weberian apparatus (see above). The LRT indicates that some fish with this trait evolved it independently, while others later lost it by convergence. Be careful. Lumping taxa together using one trait or a dozen is called “Pulling a Larry Martin.” Try to always determine clades with a phylogenetic analysis that tests hundreds of traits and then determine your clades based on a last common ancestor and all of its descendants. Convergence is rampant.

Membership within the clade
Ostariophysi (Lord 1922) includes

Gonorynchiformes — milkfish, untested in the LRT

Cypriniformes — perch, a clade distally derived from Santanichthys in the LRT.

Characiformes — piranha, a clade that proximally precedes Santanicthys in the LRT

Siluriformes — catfish, a clade unrelated to Santanichthys in the LRT

Gymnotiformes — knife fish, a clade that distally precedes Santanichthys in the LRT


References
Filleul A and Maisey JG 2004. Redescription of Santanichthys diasii (Otophysi,
Characiformes) from the Albian of the Santana Formation and Comments on Its Implications for Otophysan Relationships. American Museum Novitates 3455:21pp.
Forey PL 1977. The osteology of Notelops Woodward, Rhacolepis Agassiz Pachyrhizodus Dixon (Pisces: Teleostei). Bulletin of the British Museum (Natural History) 28(2):123–204.
Silva Santos R 1995. Santanichthys, novo epiteto generico para Leptolepis diasii Silva Santos, 1958 (Pisces, Teleostei) da Formacao Santana (Aptiano), Bacia do Araripe, NE do Brasil. Anais da Academia Brasileira de Ciencias 67:249–258.
Woodward AS 1901. Catalogue of the Fossil Fishes in the British Museum (Natural History), 4. xxxviii + 636 pp., 19 pis, 22 figs. Brit. Mus. (Nat. Hist.), London.

wiki/Santanichthys
wiki/Notelops
wiki/Characiformes
wiki/Ostariophysi

Electric eel ancestors were cave dwellers

Here’s another series of taxa,
this time related to the infamous electric eel (Electrophorus, Figs. 1, 2) going back only as far as the Early Cretaceous bowfin, Calamopleurus (Figs. 1, 2).

Figure 1. Electric eel ancestors going back to the Early Cretaceous bowfin Calamopleurus.

Figure 1. Electric eel ancestors going back to the Early Cretaceous bowfin Calamopleurus.

We looked at
Kryptoglanis earlier here, and Electrophorus + cave fish earlier here. With fewer taxa and less understanding of shifting skull bones, I only guessed the conclusions proposed then and there… prior to adding Typhlichthys (Figs. 1, 2) to the large reptile tree (LRT, 1800+ taxa).

Figure 1. Skulls of electric eel ancestors going back to the Early Cretaceous bowfin Calamopleurus.

Figure 1. Skulls of electric eel ancestors going back to the Early Cretaceous bowfin Calamopleurus.

Typhlichthys subterraneus
(Girard 1859, 10cm) is the extant Southern cave fish and a killifish-mimic. This blind ambylopsid relative of Amia and the electric eel has a maxilla overlapping the premaxilla, a toothy palatine, two postfrontals, and three separate jugals. No pelvic fins are present. Scales are absent along with their pigment. Chemoreceptors dot the body. The vomer lacks teeth. The mandible is prognathus.

Kryptoglanis shajii 
(Vincent and Thomas 2011; 5.9cm long; extant) was originally considered an enigmatic subterranean catfish due to its barbels. Here it nests as an eel-knifefish with catfish-like barbels by convergence.

Figure x. Rayfin fish cladogram

Figure x. Rayfin fish cladogram

Gymnotus carapo
(Linneaus 1758; up to 100cm in length) is the extant banded knifefish, a nocturnal small prey predator with essentially no dorsal, caudal or pelvic fins. The anal fin undulates for slow propulsion. The electric signal is weak. A close relative is Electrophorus.

Electrophorus electricus
(Linneaus 1766, 2m in length) is the extant electric eel. Nearly blind, these appear to be derived from cave fish (above) let loose into fresh water rivers feeding into the Amazon. The electric organs, derived from muscles, form the majority of the body by volume.

References
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.
Girard C 1859. Ichthyological notes. Proceedings of the Academy of Natural Sciences, Philadelphia 11:56–68.
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
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)
Putnam FW, 1872. The blind fishes of the Mammoth Cave and their allies. American Naturalist v. 6 (no. 1): 6-30. Also published in: Packard, Jr. and Putnam 1872. Life in the Mammoth Cave, etc. chapter 3, pp. 29-54.
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.

wiki/Kryptoglanis_shajii
wiki/Electrophorus
wiki/ 
Spring_cavefish
wiki/Gymnotus
wiki/Amblyopsidae

The smartest bony fish: Mormyridae

They say
that members of the clade Morymyridae (Figs. 1, 2) are the smartest fish based on their encephalization quotient (= brain volume divided by total volume). Wikipedia nests mormyrids with Osteoglossiformes like Osteoglossum. Several are electro-sensitive and can produce a very mild electric field in order to sense their environment in muddy river waters. They use their distended mouth parts to feed on small buried invertebrates.

By contrast
the large reptile tree (LRT, 1799+ taxa) nests mormyrids with the Brycon, the plant-eating piranha (Figs. 1, 2), and Serrasalmus, the flesh-eating piranha. Here are sample taxa close to the ancestry of two mormyrids, Mormyrops and Gnathonemus (Figs. 1, 2). In the LRT, Osteoglossiformes are in the OTHER bony fish clade, the one that includes all the placoderms, catfish, spiny sharks and lobefins.

Figure 1. Mormyrid evolution as told by sample taxa from their ancestry.

Figure 1. Mormyrid evolution as told by sample taxa from their ancestry. Arrows point to the vestigial pelvic  fins.

Note the gradual migration
of the anterior dorsal fin to the posterior position in this hypothetical sequence of ancestors to Gnathonemus, along with the reduction of the pelvic fin to a spine.

Figure 2. Mormyrid skull evolution as told by sample taxa from their ancestry. Note the layering of the green supratemporal atop the yellow-green intertemporal begins with Brycon.

Figure 2. Mormyrid skull evolution as told by sample taxa from their ancestry. Note the layering of the green supratemporal atop the yellow-green intertemporal begins with Brycon.

Adding taxa, like Mormyrops and Brycon,
(Figs. 1, 2) the newest additions to the LRT helped resolve the issue of where to place the very weird, very different, Gnathonemus. I could not have done it without Mormyrops. Adding characters would not have helped, despite entreaties from PhDs.

Figure x. Rayfin fish cladogram

Figure x. Rayfin fish cladogram

Brycon dentex 
(Müller and Troschel 1844; 80cm) is the extant South American trout or Sabalo barracuda. Here it nests between Serrasalmus (below) and Mormyrops, all descending from Salmo, the salmon (a type of trout) This omnivore eats fruit and seeds that fall into the water, along with small fish and invertebrates. The naris entrance is confluent with the exit. The teeth are robust and continue down the maxilla.

Mormyrops deliciosus
(Leach 1818, originally Mormyrops anguilloides Linneaus 1758; up to 1.5m in length) is the extant Cornishjack, a weakly electric river fish from Sub-Saharan Africa. The maxilla lacks teeth. The skull is extended due to an enlarged braincase. The teeth are robust, as in the ancestral Brycon.

Gnathonemus curvirostris
(Gill 1863) is the extant elephantfish, a member of the clade Mormyridae, ranging in size from 5cm to 1.5m. Traditionally considered a sister to Osteoglossum, here it nests as a sister to Mormyrops (above) and the piranha-sister, Brycon. Note the matching dorsal and anal fins. The cerebullum is greatly enlarged. The supratemporal appears as a ‘scale’ over the intertemporal. This slow, brackish water micro-predator uses electrical impulses to find tiny prey in cloudy waters convergent with electric eels, which evolved from pitch-black cave waters.


References
Brünnich MT 1788. Om en ny fiskart, den draabeplettede pladefish, fanget ved Helsingör i Nordsöen 1786. K. Danske Selsk. Skrift. N. Saml. 3: 398-407.
Gill TN 1863. Notes on the labroids of the western coast of North America. Proc. Acad. Nat. Sci. Phila. v. 15: 221-224.
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.
Müller JP and Troschel FH 1844. Synopsis generum et specierum familiae Characinorum. (Prodromus descriptionis novorum generum et specierum). Archiv für Naturgeschichte 10(1): 81-99 (Zu pag. 99 foldout).

wiki/Mormyridae
wiki/Brycon
wiki/Cornish_jack
wiki/Mormyridae
wiki/Gnathonemus

 

Heers et al. 2021 discuss the origin of flight using hatchling birds

Short one today
as Heers et al. 2021 miss the one key trait in the evolution of flapping flight in bird origins: a locked-down elongate coracoid necessary for left-right simultaneous flapping. This morphology is derived from the primitive disc-like coracoid sliding on the sternal rim, originally used during quadrupedal locomotion to extend each stride (Fig. 1). Disc-like coracoids are retained in bipedal theropods like TyrannosaurusKhaan, and Haplocheirus.

The coracoids (in pink)

Figure 1. The coracoids (in pink) slide along the sternum behind the interclavicle.

By contrast
in Velociraptor, Archaeopteryx and living birds the coracoid is no longer mobile and disc-like, but narrows and becomes immobile. These are flapping bipeds. This fact was overlooked by Heers et al. who looked a baby birds.

Figure 3. The Eichstätt specimen, Jurapteryx recurva, nests with the living ostrich, Struthio, presently in the LRT.

Figure 2. The Eichstätt specimen, Jurapteryx recurva, nests with the living ostrich, Struthio, presently in the LRT.

From the Heers et al. abstract:
“Although extinct theropods are most often compared to adult birds, studies show that developing birds can uniquely address certain challenges and provide powerful insights into the evolution of avian flight: unlike adults, immature birds have rudimentary, somewhat “dinosaur-like” flight apparatuses and can reveal relationships between form, function, performance, and behavior during flightless to flight-capable transitions. Here, we focus on the musculoskeletal apparatus and use CT scans coupled with a three-dimensional musculoskeletal modeling approach to analyze how ontogenetic changes in skeletal anatomy influence muscle size, leverage, orientation, and corresponding function during the development of flight in a precocial ground bird (Alectoris chukar).”

Unfortunately, even baby birds have a locked-down elongate coracoid. So the transition to flapping must be found in the fossil record, not the ontogeny of chicks. Heers et al. needed an outgroup and a convergent set of taxa.

Figure 1. Cosesaurus flapping - fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

Figure 3. Click to enlarge and animate. Cosesaurus flapping – fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

Figure 2. Cosesaurus torso and forelimbs. The hot pink stem-like coracoids are found in pterosaurs. So are the strap-like scapula, distinct from the discs found in Macrocnemus. There is a close association of the clavicles, interclavicle and sternum. In pterosaurs this is known as a sternal complex.

Figure 4. Cosesaurus torso and forelimbs. The hot pink stem-like coracoids are found in pterosaurs. So are the strap-like scapula, distinct from the discs found in Macrocnemus. There is a close association of the clavicles, interclavicle and sternum. In pterosaurs this is known as a sternal complex.

Figure 1. Ptilcercus (above) and Icaronycteris (below), sister taxa in the origin of bats.

Figure 5. Ptilcercus (above) and Icaronycteris (below), sister taxa in the origin of bats.

Pterosaurs,
starting with Cosesaurus (Figs. 3, 4) had bird-like immobile coracoids.

Bats
(Fig. 5) don’t have coracoids. but elongate locked-down clavicles are analogous.


References
Heers AM, Varghese SL, Hatier LK and Cabrera JJ 2021. Multiple Functional Solutions During Flightless to Flight-Capable Transitions

Locked down coracoid discussion

New turtle clades: destined for revision due to taxon exclusion

Joyce et al. 2021 report,
“Over the last 25 years, researchers, mostly paleontologists, have developed a system of rank-free, phylogenetically defined names for the primary clades of turtles. As these names are not considered established by the PhyloCode, the newly created nomenclatural system that governs the naming of clades, we take the opportunity to convert the vast majority of previously defined clade names for extinct and extant turtles into this new nomenclatural framework.”

As long as Joyce et al. are working within a valid phylogenetic context, this sounds like a great idea!

“We are confident that we are establishing names that will remain accepted (valid in the terminology of the ICZN 1999) for years to come.

Well, let’s see if Joyce et al. followed a valid phylogenetic context.

Archelosauria Crawford et al., 2015,
“The smallest crown clade containing the archosaur Crocodylus (orig. Lacerta) niloticus (Laurenti, 1768) and the turtle Testudo graeca Linnaeus, 1758, but not the lepidosaur Lacerta agilis Linnaeus, 1758 (Fig. 1b).”

Not a good start. In the large reptile tree (LRT, 1796+ taxa; subset Fig. 1) the smallest clade that includes Crocodylus and Testudo is a junior synonym for Reptilia (= Amniota). Joyce et al. are not familiar with the basal dichotomy that split reptiles into Lepidosauromorpha (lepidosaurs + turtles) and archosauromorpha (mammals and archosaurs) in the Viséan with Silvanerpeton as the last common ancestor. What can be done when turtle experts don’t agree (see below) on the origin of turtles?

Figure 1. Carbonodraco enters the LRT alongside another recent addition, Kudnu, at the base of the pareiasaurs + turtles.

Figure 1. Carbonodraco enters the LRT alongside another recent addition, Kudnu, at the base of the pareiasaurs + turtles.Figure 1. Carbonodraco enters the LRT alongside another recent addition, Kudnu, at the base of the pareiasaurs + turtles.

Joyce et al. continue:
“Comments—The name Archelosauria was recently introduced by Crawford et al. (2015) for the clade that unites Testudines and Archosauria Cope, 1869b [Gauthier and Padian, 2020] exclusively.” 

That was a mistake due to taxon exclusion. Don’t accept mistakes that put you into an invalid phylogenetic context.

Ankylopoda Lyson et al., 2012,
“Definition—The smallest crown clade containing the lepidosaur Lacerta agilis Linnaeus, 1758 and the turtle Chrysemys (orig. Testudo) picta (Schneider, 1783), but not the archosaur Crocodylus (orig. Lacerta) niloticus (Laurenti, 1768)

In the LRT that clade is the Millerettidae (Watson 1957) with Milleretta as the last common ancestor.

Figure 4. Milleretta, a Late Permian descendant of the Late Pennsylvanian ancestor of turtles and Eunotosaurus.

Figure 2. Milleretta, a Late Permian descendant of the Late Pennsylvanian ancestor of turtles and Eunotosaurus.

Joyce et al. continue:
“Comments—A clade consisting of Testudines and Lepidosauria Haeckel, 1866 [de Queiroz and Gauthier, 2020] to the exclusion of Archosauria has been retrieved in a number of phylogenetic hypotheses (e.g., Rieppel and Reisz 1999; Rieppel 2000; Li et al. 2008), but was only named Ankylopoda relatively recently (Lyson et al. 2012).”

What can be done when turtle experts don’t agree (see above) on the origin of turtles?

Testudinata Klein, 1760
“Definition—“The clade for which a complete turtle shell, as inherited by Testudo graeca Linnaeus, 1758, is an apomorphy. A ‘complete turtle shell’ is herein defined as a composite structure consisting of a carapace with interlocking costals, neurals, peripherals, and a nuchal, together with the plastron comprising interlocking epi-, hyo-, meso- (lost in Testudo graeca), hypo-, xiphiplastra and an entoplastron that are articulated with one another along a bridge” (Joyce et al. 2020b: 1044).

In the LRT (subset Fig. 1) soft-shell turtles (Fig. 3) had a separate parallel origin alongside hard-shell turtles (Fig. 4). Their last common ancestor had no shell: the pareiasaur, Bunostegos (Fig. 4). Workers like Joyce et al. 2021 are working under an assumption that is not true. Turtles are not monophyletic. You can read that manuscript on ResearchGate.net here. Turtle workers did not let this get published.

Figure 3. Soft shell turtle evolution featuring Arganaceras, Sclerosaurus, Odontochelys and Trionyx.

Figure 3. Soft shell turtle evolution featuring Arganaceras, Sclerosaurus, Odontochelys and Trionyx.

Figure 2. Another gap is filled by nesting E. wuyongae between Bunostegos and Elginia at the base of hard shell turtles in the LRT.

Figure 4. Another gap is filled by nesting E. wuyongae between Bunostegos and Elginia at the base of hard shell turtles in the LRT.

The remainder of Joyce et al. 2021
lists and defines various clades of turtles. Without a clear understanding of parallel turtle origins, even some of these are subject to change when pertinent taxa are included. Most will likely remain the same as they distance themselves from turtle origins.


References
Joyce et al. (15 co-authors) 2021. A nomenclature for fossil and living turtles using phylogenetically defined clade names. Swiss Journal of Palaeontology 140:5 https://doi.org/10.1186/s13358-020-00211-x

 

 

 

https://en.wikipedia.org/wiki/Millerettidae.

Ray fin fish phylogeny, slowly coming into focus

Updated February 11, 2021
with new data some taxa are reordered.

Every day there are changes 
in the ray-fin fish subset of the large reptile tree (LRT, 1796+ taxa). This constant involvement, day-after-day has been as rewarding as frustrating. Earlier we looked at some of the more interesting and unexpected pairings. Here (Fig. 1) is the latest iteration:

Figure x. Rayfin fish cladogram

Figure x. Rayfin fish cladogram

This, then, is a step back to look at the clade in toto,
to see if any taxa or clades don’t belong together. I don’t profess that this cladogram is finished or perfect. Rather, it is presented to expose its frailties in order to repair them.

Some takeaways (at present):

  1. Basalmost taxa are derived from Gregorius and the moray eel clade
  2. Basalmost taxa retain teeth on the maxilla and the parietals are not separated medially
  3. Basalmost taxa are related to spiny sharks on the other bony fish clade, the one that leads to placoderms, catfish, lobefins and tetrapods
  4. Basalmost taxa skew toward a deep sea niche today, perhaps not in the past
  5. Basalmost taxa radiated in the Late Silurian to Early Devonian
  6. Xiphactinus represents the largest size attained by tested clade members
  7. Sea horses, like Hippocampus, are among the smallest and least similar to ancestral taxa
  8. The loosening of the maxilla occurred by convergence several times
  9. The appearance of the palatine as a cheek bone occurred several times
  10. Basalmost taxa are generally small and slow. Transitional taxa are speedy, open-sea predators. Derived taxa return to bottom-dwelling sit-and-wait predation
  11. Some basal taxa (e.g. Amia) can breathe air. Lepidogalaxias estivates.
  12. Only the mudskipper, Periophthlamus (Fig. 2), crawls out above the surface, keeping its gills bathed with cheekfulls of water. No other ray-fin taxa develop anything like a crawling, lobe-like fin.

Figure 4. The mudskipper, Periophthalmus, nests with the neon goby, Elacatinus, in the LRT.

Figure 2. The mudskipper, Periophthalmus, nests with the neon goby, Elacatinus, in the LRT.

Macrauchenia: the good and bad of genomic studies

From the Wesbury et al. 2021 abstract
“The unusual mix of morphological traits displayed by extinct South American native ungulates (SANUs) confounded both Charles Darwin, who first discovered them, and Richard Owen, who tried to resolve their relationships. Here we report an almost complete mitochondrial genome for the litoptern Macrauchenia (Fig. 1). Our dated phylogenetic tree (Fig. 2) places Macrauchenia as sister to Perissodactyla, but close to the radiation of major lineages within Laurasiatheria. This position is consistent with a divergence estimate of B66Ma.”

Note they don’t ask us to pay as much attention to the proximal outgroup for Macrauchenia: the clade Carnivora (Fig. 2).

Figure 1. Macrauchenia museum mount.

Figure 1. Macrauchenia museum mount.

According to Wikipedia
Laurasiatheria is a gene-based clade “that includes that includes hedgehogs, even-toed ungulates, whales, bats, odd-toed ungulates, pangolins, and carnivorans, among others.”

Isn’t that an odd assemblage? 
Think about it. According to Wesley et al. (Fig. 2), sabertooth cats are closer to horses, rhinos and Macrauchenia than other long-legged, placental herbivores. By the way, in gene studies elephants appear in an unrelated major clade, Afrotheria.

Figure 1. Gene-based cladogram from Westbury et al. 2021 (slightly compressed to fit). Note the close relationship between Carnivora and Macrauchenia here. That is not replicated in a trait-based study (Fig. 2).

Figure 2. Gene-based cladogram from Westbury et al. 2021 (slightly compressed to fit). Note the close relationship between Carnivora and Macrauchenia here. That is not replicated in a trait-based study (Fig. 2).

A more reasonable, trait-based, phylogenetic analysis
(the large reptile tree, LRT, 1794+ taxa, subset Fig. 3) also nests the Macrauchenia clade basal to tapirs, rhinos and horses. The outgroup is the hyrax + elephant + manatee clade, then the artiodactyls, then the mesonychids + hippos + desmostylians + mysticetes. Off this chart (Fig. 3), the clade Carnivora is the basalmost placental clade, not the proximal outgroup to Macrauchenia.

Figure 2. Subset of the LRT focusing on derived placentals. Yellow highlights the Macrauchenia clade.

Figure 3. Subset of the LRT focusing on derived placentals. Yellow highlights the Macrauchenia clade.

Perhaps taxon exclusion is at fault here.
On the other hand, gene studies too often produce such odd interrelationships (Carnivora nesting closer to Macrauchenia than other herbivore clades). Gene studies too often deliver false positives in deep time studies. That’s a fact, not a hypothesis.

If your professor is asking you to help out on a deep time genomic study,
run.


References
Westbury M et al. (21 co-authors) 2021. A mitogenomic timetree for Darwin’s enigmatic South American mammal Macrauchenia patachonica. Nature Communications | 8:15951 | DOI: 10.1038/ncomms15951 |www.nature.com/naturecommunications

https://en.wikipedia.org/wiki/Laurasiatheria
reptileevolution.com/macrauchenia.htm

The best ‘Sordes’ uropatagium… is another overlooked wing

This much talked about, but rarely seen ‘Sordes’ specimen
(Fig. 1), has been known for decades. It made a brief appearance some 30 years ago at an SVP talk by David Unwin where it caused quite a stir. I haven’t seen it again since. A scale bar is not shown and the museum number is unknown, but may be one of these three: PIN 104/73, PIN 2585/36, PIN 2585/37.

Today this rare ‘tail-less’ specimen made another brief appearance
in an online Palaeontological Assocation talk “Resolving the pterosaur bauplan using a quantitative taphonomic approach” by Rachel Belben (2012, video link), one of Unwin’s students. We looked at Belben’s nearly identical 2020 abstract here.

Figure 1. Image from Belben's December 2020 talk about the pterosaur bauplan.

Figure 1. Image from Belben’s December 2020 talk about the pterosaur bauplan. That’s Belben inset in red. Click to view video on YouTube.

Not one, but two similar Sordes specimens
were presented by Unwin at SVP decades ago. Both appeared to have a distinct uropatagium stretched bat-like between the sprawling hind limbs (Figs. 1, 2). Everyone wondered whether that membrane was 1) above or below the cloaca, 2) attached or not attached to the tail, and 3) what sort of precursor taxa would gradually develop such a membrane controlled by hyperflexed lateral toes. In bats, of course, the vaguely similar calcar arises from the ankle. The toes are not involved.

Sharov 1971
first described and figured the Sordes holotype (Fig. 2, upper right) with a small drawing that appeared to clearly show a uropatagium stretched between the hind limbs and controlled by those odd Tanystropheus-like elongated lateral toes.

Unwin and Bakhurina 1994
brought this odd bit of flight membrane to a wider audience with a short paper in Nature. Their drawing (Fig. 2 middle right) paid less attention to detail.

Peters 1995
disputed the uropatagium, considering it a displaced wing membrane. That critical hypothesis was presented again in Peters 2002 (Fig. 2, left and bottom).

Elgin, Hone and Frey 2012
sided with Sharov, Unwin and Bakhurina, also paying little attention to the specimen.

Figure 4. Sordes wing drift hypothesis from Peters (2002) which attempted to show that the wings and uropatagia of Sordes were more like those of other pterosaurs than the other way around. The very deep uropatagia are misinterpretations prior to the realization that the left brachiopatagium (main wing membrane) was displaced to the ankle area.

Figure 2. Sordes wing drift hypothesis from Peters (2002) which attempted to show that the wings and uropatagia of Sordes were more like those of other pterosaurs than the other way around. The very deep uropatagia are misinterpretations prior to the realization that the left brachiopatagium (main wing membrane) was displaced to the ankle area.

Back in 2011,
the uropatagium of the Sordes holotype showed up here with another tracing (Fig. 5) that showed the displaced radius + ulna and its displaced membrane.

Figure 6. The PIN 2585/3 specimen of Sordes showing displaced left radius and ulna dragging their membranes along with them. The right wing is articulated.

Figure 3. The PIN 2585/3 specimen of Sordes showing displaced left radius and ulna dragging their membranes along with them. The right wing is articulated and shows a short chord wing membrane. Uropatagia are in red.

A new tracing of the rare specimen
(Fig. 4) shows the purported uropatagium extending far beyond the hind limb. That indicates a problem! This is not a uropatagium. Maybe that’s why we haven’t seen this rare specimen for 30 years. A closer examination reveals a series of pterosaur arm bones beneath the hind limb elements. Arm bones or not, this ‘uropatagium’ is a brachiopatagium, a wing membrane, complete with aktinofibrils (Fig. 5).

Figure 4. Color tracing applied to the rare 'Sordes' specimen reveals another displaced wing (deep blue) along with overlooked wing elements. See figure 5 for a reconstruction.

Figure 4. Color tracing applied to the rare ‘Sordes’ specimen reveals another displaced wing (deep blue) along with overlooked wing elements. See figure 5 for a reconstruction.

Adding what little is known
to the large pterosaur tree (LPT, 256 taxa) nests the rare specimen not with Sordes, but with the tiny flightless anurognathid PIN 2585/4 specimen that shares the plate with the holotype of Sordes, PIN 2585/3 (Fig. 2). We looked at that rarely seen specimen earlier here.

Figure 5. Reconstruction of the specimen in figure 4.

Figure 5. Reconstruction of the specimen in figure 4.

Distinct from the flightless PIN 2585/4 anurognathid specimen,
this one has large, robust wings.

In summary
this rarely seen specimen

  1. is not Sordes
  2. does not present a uropatagium
  3. can now explain why a Sordes-like tail is absent here
  4. evidently has never been carefully examined before
  5. has fooled pterosaur experts for decades
  6. is one source of pterosaur mythology that many pterosaur workers and their minions continue to believe in fifty years after its original description.

Someone please tell Rachel Belben
so she can wash her hands of this decades-old error and start fresh.

The Sordes uropatagium is a misinterpretation.
We need to bury this mistake and forget it. Stop promoting and believing this myth. It has been exposed.


References
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeonntologica Polonica 56(1): 99-111.
Peters D 1995. Wing shape in pterosaurs. Nature 374, 315-316.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277–301.
Sharov AG 1971. New flying reptiles from the Mesozoic of Kazakhstan and Kirghizia. – Transactions of the Paleontological Institute, Akademia Nauk, USSR, Moscow, 130: 104–113 [in Russian].
Unwin DM and Bakhurina NN 1994. Sordes pilosus and the nature of the pterosaur flight apparatus. Nature 371: 62-64.

wiki/Sordes

https://pterosaurheresies.wordpress.com/2015/03/10/the-evolution-of-the-sordes-wing-and-uropatagia-1971-to-2011/

https://pterosaurheresies.wordpress.com/2015/03/09/how-one-sordes-evolved-into-dorygnathus-via-cacibupteryx/

https://pterosaurheresies.wordpress.com/2014/03/15/variation-in-three-sordes-specimens/

https://pterosaurheresies.wordpress.com/2012/07/17/what-is-happening-between-the-legs-of-sordes/

https://pterosaurheresies.wordpress.com/2020/10/21/svp-abstracts-3-belben-contributes-to-the-bat-wing-pterosaur-myth/