Brocklehurst and Field 2021 report, “The origin of crown bird edentulism has been discussed in terms of a broad-scale selective pressure or trend toward toothlessness, although this has never been quantitatively tested. Here[Fig. 1], we find no evidence for models whereby iterative acquisitions of toothlessness among Mesozoic Avialae were driven by an overarching selective trend. Instead, our results support modularity among jaw regions underlying heterogeneous tooth loss patterns, and indicate a substantially later transition to complete crown bird edentulism than previously hypothesized (∼ 90 MYA). We show that patterns of avialan tooth loss adhere to Dollo’s law and suggest that the exclusive survival of toothless birds to the present represents lineage-specific selective pressures, irreversibility of tooth loss, and the filter of the K–Pg mass extinction.”
Never? Not true and more quantitively than in Brocklehurst and Field. According to the LRT a clade of Cretaceous toothed birds arose from a series of toothless taxa, including Megapodius (Figs. 2, 3). Brocklehurst and Field could have found this, too, but their taxon list is too small. Taxon exclusion is the #2 problem in paleontology.
Figure 1. Cladogram from Brocklehurst and Field 2021. Colors added to clades. Note the paucity of cherry-picked taxa compared to the LRT. Entire clades of extinct birds are missing here due to taxon exclusion.
When you minimize taxon exclusion,
as in the LRT (subset Fig. 2) the actual patterns of evolution start to emerge. When you cherry-pick taxa (Fig. 1), you risk missing the important nodes and steps that Brocklehurst and Field missed.
Figure 4. Subset of the LRT focusing on birds. The amber box are the toothed Cretaceous birds, descendants of toothless taxa like Megapodius.
The Brocklehurst and Field 2021 study depends on a valid phylogenetic context, but suffers from taxon exclusion. Only one ‘Archaeopteryx‘ taxon was used. A competing online cladogram (the LRT, subset Fig. 2) finds that nine of thirteen Solnhofen birds are needed to flesh out the origins of various succeeding bird clades, each with a few Solnhofen birds at their base.
Figure 1. Click to enlarge. Toothed birds of the Cretaceous to scale.
Several toothless extant birds
that phylogenetically precede the Eogranivora to Ichthyornis and Yanornis clade (Figs. 2, 3) were excluded from this analysis. Missing taxa include Apteryx, Megapodius, and all members of the Palaeognathae, both living and extinct. Brocklehurst and Field missed a great opportunity due to taxon exclusion.
References Brocklehurst N and Field DJ 2021. Macroevolutionary dynamics of dentition in Mesozoic birds reveal no long-term selection towards tooth loss, ISCIENCE (2021), doi: https://doi.org/10.1016/j.isci.2021.102243.
Here’s a YouTube video featuring Dr. Karma Nanglu (Smithsonian National Museum of Natural History) showing and discussing Cambrian taxa from the Burgess Shale ancestral to living hemichordates, pterobranchs (= graptolites and kin) and enteropneusts = acorn worms).
Nanglu reports, “This talk will guide you through a series of recent studies using Burgess Shale fossils that shine a light on hemichordate origins, one of the most mysterious parts of the animal tree of life. These exceptional fossils reveal unanticipated combinations of morphological and ecological characteristics early in the history of this animal group, including surprising combinations of those found in their modern relatives.”
Unfortunately, when it came time to present last common ancestors at an hour into the presentation, Nanglu left much of the work undone. His graphic showed question marks at the ancestral nodes (Fig. 1).
Figure 1. Frame from Nanglu talk on YouTube (see above) showing stars and question marks on his cladogram of chordate/hemichordate origins.
By contrast and thirty years ago Peters 1991 found hemicordates arose from basal chordates (Fig. 3) like the lancelet, Branchiostoma(Fig. 2), itself derived from nearly featureless roundworms (Fig. 3). You might recall that adult lancelets are sessile feeders, anchoring themselves tail first into sandy and muddy substrates, distinct from their free-swimming tiny hatchlings that more greatly resemble tiny fish in their activity. All this occurred during the Cambrian.
Distinct from chordates,
sessile (= essentially immobile) pterobranchs emphasize and enlarge the suspension feeding cirri made sticky with mucous strands (Fig. 3).
Distinct from chordates,
worm-like enteropneusts emphasize the rostrum (= proboscis, Fig. 3).
Both hemichordates
gave up the chevron-shaped swimming muscles and internal gill basket found in lancelets and fish. However, enteropneust hatchlings present a vestigial post-anal tail that is resorbed or transformed in adults.
Figure 2. Extant lancelet (genus: Amphioxus) in cross section and lateral view. The gill basket nearly fills an atrium, which intakes water + food, sends the food into the intestine and expels the rest of the water.
Nanglu 2021 confirms this 30-year-old hypothesis of interrelationships (Fig. 3) as he nests chordates basal to hemichordates and echinoderms.
Nanglu also presents
a tube-building, vermiform last common ancestor between pterobranchs and enteropneusts, with post-anal attachment and possible tube building. In Peters 1991 pterobranchs are basal to crinoids, blastoids and other echinoderms, taxa that further emphasize and enlarge the gracile cirri that encircles the mouth of lancelets until the cirri comprise the entire anatomy of the starfish. So starfish are walking on their greatly enlarged and elaborate mouth parts, having given up or absorbed the rest of the ancestral lancelet anatomy.
Figure 3. Chordate evolution, changes to Romer 1971 from Peters 1991. Here echinoderms have lost the tail and gills of the free-swimming tunicate larva.
We looked at chordate origins
in more detail earlier here (summarized in Fig. 3).
References Peters D 1991. From the Beginning – The story of human evolution. Wm Morrow. Romer AS 1971. The Vertebrate Body – Shorter Version 4th ed. WB Saunders.
Figure 1. Illustration of Charnia showing growth stages. Each segment is a planula colony or family.
Summary for those in a hurry: Charnia (Figs. 1, 2) can be nothing else than a family of interconnected planulae (Fig. 4). There were no other choices back in the Ediacaran. Taxonomically, it’s that simple.
Enigmatic Charnia
(Figs. 1, 2) is a frond-like animal near the base of all macroscopic animals. It lived in the Ediacaran Period prior to the Cambrian Period. The Cambrian lasted for 55 million years (so, no explosion). That’s when a wide variety of animal taxa appeared for the first time and many disappeared. By contrast, the Ediacaran was much less diverse and has a reputation for being more mysterious.
The extant planula
is a tiny blastula full of cells without a mouth or anus (Fig. 4). Several more derived animals go through a planula stage during their development (Figs. 5, 6). Others, develop more directly from an invaginated blastula.
Taxonomically
a planula also nests at the base of all macroscopic animals. Hmmm. Happy coincidence?
Given no other taxonomic choices, Charnia can only be a family of interconnected tiny planula, convergent with the extant demosponge Callyspongia (Fig. 3), but without the central invagination (Fig. 5).
Dunn, Liu and Donoghue 2017 reported, “Extant members of Porifera do not show a serially repetitive body plan in the same way as certain cnidarians, and do not display the same level of colonial integration (i.e. the division of labour). However, certain sponges (e.g. the demosponge Callyspongia vaginalis) are constructed of serially repeated units.”
Figure 2. Charnia in situ with holdfast.
Dunn et al. 2018 presented
a wide-ranging study of Charnia (Fig. 1), a frond-like sessile animal known from tiny 1.7cm juvenile specimens to 2m tall adults all confined to the Ediacaran era.
From the abstract: “The Ediacaran macrofossil Charnia masoni Ford is perhaps the most iconic member of the Rangeomorpha: a group of seemingly sessile, frondose organisms that dominates late Ediacaran benthic, deep-marine fossil assemblages. We evaluate specimens from the UK, Canada and Russia, representing the largest morphological study of this taxon to date. “
Figure 3. Callyspongia is an extant sponge that grows in a manner similar to Charnia according to Dunn, Liu and Donoghue 2017.
Earlier Antcliffe and Brasier 2008
reviewed the history of this taxon. They reported, “We show that Charnia cannot be related to the modern cnidarian group, the sea pens, with which it has for so long been compared, because they have opposite growth polarities.”
“Next to sponges, Cnidaria comprise the most primitive animal phylum and their presence in Precambrian strata before the emergence of the other animal phyla is a reasonable expectation.”
Figure 4. Planula evolution from a microscopic blastula. It simply fills with cells that have to be nourished from external cells. This is the level of animal development at the time of Charnia. Illustration from Peters 1991.
The term ‘planula’
is not found in these works. Seems the planula was forgotten or overlooked.
Figure 5. Planula can develop into sponges, hydras, medusas or flatworms (see figure 6) simply by invaginating, something Charnia parts never did. Illustration from Peters 1991. In Charnia the planula does not invaginate.
Figure 6. When a planula evolves a ventral opening the internal cells can spill out to cover prey items, the retreat again to continue digestion. This is also a stage that Charnia never reached. No mouth/anus is found on any Charnia frond.
Given the time (the Ediacaran)
and the primitive development of animal tissues at the time, Charnia can be nothing else than a collection of planulae, none with an invagination, mouth or anus. Reproductive divisions did not separate siblings and that’s how the colony grew serially. The shape and size was variable (Fig. 7).
Figure 7. Ediacaran biota. Many of these are all variations on a single note, the planula. The mobile ones are more derived segmented flatworms. All we had in the Ediacaran were planulae, sponges, hydras, medusae and flat worms.
Evidently defenseless sessile planula families
did not repeat this temporarily very successful experiment when the Cambrian became a thing. By then predaceous relatives, like hungry flatworms developed. Some large, swimming flatworms became hyper-predators in the Cambrian as discussed earlier here.
What about the other Ediacaran taxa?
Same answer for many of them. Planula colonies experimented with several immobile shapes that ultimately fell prey to the one mobile shape that preyed upon them, the flatworm, which, in turn, gave rise to a wide variety of swimming, crawling and burrowing taxa… ultimately humans. All we had in the Ediacaran were planulae, sponges, hydras, medusae and flatworms to work with. Everything else arose in the Cambrian from these basal animals at the genesis of all animals.
References Antcliffe JB and Brasier MD 2008. Charnia at 50: Developmental models for Ediacaran fronds. Palaentology https://doi.org/10.1111/j.1475-4983.2007.00738.x Dunn FS, Liu AG and Donoghue PCJ 2017. Eidacaran developmental biology. Biological Reviews doi: 10.1111/brv.12379 Dunn FS et al. (6 co-authors) 2018. Anatomy of the Ediacaran rangeomorph Charnia masoni. Papers in Palaeontology 2018:1–20. Ford TD 1958. Pre-Cambrian fossils from Charnwood Forest. Proceedings of the Yorkshire Geological & Polytechnic Society, 31, 211–217. Ford TD 1962. The oldest fossils. New Scientist, 15, 191–194. Laflamme M, Narbonne GM, Greetree C and Anderson MM 2006. Morphology and taphonomy of an Ediacaran frond: Charnia from the Avalon Peninsula of Newfoundland. Geological Society London Special Publications 286(1):237-257. Peters D 1991. From the Beginning – The story of human evolution. Wm Morrow.
Short one today
on Purgatorius (Early Paleocene; Fig. 1), a mandible taxon considered by Wilson et al. 2021 to be a member of the Plesiadapiformes (Fig. x).
Figure 1. Purgatorius compared to other basal and often Paleocene mammals.
Wilson et all 2021 report “Plesiadapiforms are crucial to understanding the evolutionary and ecological origins of primates and other euarchontans (treeshrews and colugos) as well as the traits that separate those groups from other mammals.”
Figure 2. Ignacius and Plesiadapis nest basal to Daubentonia in the LRT.
Wilson et al. also reported
similarities in Purgatorius to Palaechthon, which nested in 2017 with the demopteran, Cynocelphalusin the large reptile tree (LRT, 1807+ taxa). Wilson et al. considered Palaechthon a member of the Plesiadapiformes.
Figure x. Subset of the LRT focusing on basal placentals, including multituberculates.
Colleagues, expand your taxon lists.
If you don’t look in there, you won’t see what’s in there. So look. Add taxa. Sometimes traditions, professors and textbooks are not complete or incorrect. Find out for yourself.
References Wilson MGP et al. , (9 co-aiuthors) 2021. Earliest Palaeocene purgatoriids and the initial radiation of stem primates Royal Society open science 8210050 http://doi.org/10.1098/rsos.210050
Notothenia (Figs. 1, 3), the extant Antarctic yellow belly rock cod, nests with Coryphaena, the mahi-mahi (Figs. 2, 4), in the large reptile tree (LRT, 1806+ taxa). The two taxa look alike overall… except for the broad-shape of the fins in the former, vs the narrow fins of the latter. And the lack of color and sexual dimorphism in the former. Plus several other relatively, or presently, inconsequential differences you are free to note.
Figure 1. Notothenia is a deep sea mahi-mahi in the LRT.
Figure 2. This is where the high forehead of the male mahi-mahi (Corphaena) comes from, one of the very few fish with a frontal crest.
Figure 3. Notothenia is a Coryphaena sister of the deepest oceans. Here it converges with the wolf eel, Anarhichas.
Figure 4. Mahi-mahi (Coryphaena) mounted as if in vivo.
Notothenia coriiceps (Richardson 1844; 50cm) is the extant Antarctic yellowbelly rockcod. It lacks a swim bladder and the bones are dense, accounting for its reduced buoyancy. The body is adapted to sub freezing temperatures. Here it nests with the mahi-mahi, Corphaena (above), not with traditional perch.
Coryphaena hippurus (Linneaus 1758; 1.5m length) is the extant open seas predator mahi-mahi or dolphinfish, here related to the similar, but deeper Notothenia. The dorsal fin starts at the skull. The caudal fin is deeply forked. The teeth are needle-like. Males have a tall fleshy forehead supported by a bony crest. A smaller-crested female is also shown above.
Figure x. Rayfin fish cladogram. This one represents the latest subset of the LRT.
The yellow belly rock cod nests with the mahi-mahi and THEY nest close to the Atlantic cod, Gadus (Fig. 5), a taxon added to the LRT earlier here. I guess yellow-belly rock cod sounds better than yellow-belly mahi-mahi.
Figure 5. Atlantic cod, Gadus morhua, in lateral view.
“The task is…not so much to see what no one has yet seen; but to think what nobody has yet thought, about that which everybody sees.” ~ Erwin Schrödinger
References Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Richardson J 1844. Ichthyology of the voyage of H.M.S. Erebus & Terror. In: Reptiles, fishes, Crustacea, insects, Mollusca, Longman, Brown,London.: 1-16.
Another series of taxa pulled from the LRT
focusing on phylogenetic miniaturization (PM) in the lineage of sea horses (Fig. 1). PM starts with 60cm-long Early Cretaceous Notelops and similar extant Scomberoides, the queenfish (Fig. 1), which is also (quite obviously) basal to mackerel and tuna.
Figure 1. Seahorse evolution back to Notelops (Early Cretaceous).
Less obviously,
in the large reptile tree (LRT, 1806+ taxa) another descendant of Scomberoides is the 10x smaller zebra fish (Danio, Fig. 1).
Here’s where it gets interesting…
The sagittal crest present in Scomberoides (Fig. 1) is absent in Danio and the parietals return to meet each other medially, as in basal bony fish like Amia and Prohalecites. This phylogenetic reversal makes creating a cladogram more difficult, due to convergence, but all the more challenging. Danio descendants remains tiny and crestless. I have no data if Scomberoides hatchlings have crests or not. If so that would be a case of neotony leading to Danio.
Relative to Notelops,
larger eyes are first seen, not in tiny Danio, but in big Scomberoides (Fig. 1), prior to PM. That increase in orbit size comes at the cost of a reduction in cheek plates that never comes back in descendant taxa. In Scomberoides the circumorbital ring actually overlaps the preopercular (light yellow) and hyomandibular (dark green). That’s a rare trait that makes it a bit difficult to score.
The jugal (cyan color) in Danio (Fig. 1) is still large, though disconnected from the circumorbital ring where Gregory 1933 labels it the symplectic. According to Wikipedia, the symplectic is “an additional bone linking the jaw to the rest of the cranium.” That also makes that bone difficult to score. Seeing this bone in a variety of taxa led to the conclusion that it was homologous to the jugal. Starks 1901 listed several synonymies used by various authors for bones of the fish skeleton. None synonymized the jugal and symplectic. That may have changed in the 120 years since. Let me know, if so.
Stickleback stickles
readily seen in Gasterosteus, are first seen in Scomberoides (Fig. 1), though lost in Danio.
Jaw joint migration from behind the orbit
to way out in front of the orbit in this series of taxa starts with Scomberoides, documents a mid-point in Danio, and reaches a conclusion in Gasterosteus (Fig.1).
Figure x. Rayfin fish cladogram. This one represents the latest subset of the LRT.
That’s the utility of the LRT
and the ready-at-your-fingertips online data with all bones colorized using DGS.
References Starks EC 1901. Synonymy of the fish skeleton. Proceedings of the Washington Academy of Sciences 3:507-539. PDF here.
Sometimes more common and more ordinary fish,
like the Atlantic cod, Gadus (Figs. 1, 2), also enter the large reptile tree (1806+ taxa).
Figure 1. Atlantic cod, Gadus morhua, in lateral view.
Actually
it’s only ordinary on the outside. The skull is unique, but like al vertebrates shares a long list of traits with related taxa.
Figure 2. Skull of the Atlantic cod, Gadus. Note the posterior process of the hyomandibular (dark green).
Gadus morhua (Linneaus 1758) is the Atlantic cod, nesting between two open ocean predators, Coryphaena and Rachycentron. Instead of one long dorsal fin, it is split in three. The anal fin is split in two. The chin has a barbel. The postparietal forms a long crest that divides the parietal. The naris is a long opening from snout tip nearly to the orbit. Note the elongate postfrontal (orange) and hyomandibular (dark green) with accessory processes.
Figure x. Rayfin fish cladogram. This one represents the latest subset of the LRT.
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.
Cawley et al. 2020
brought us an overview of a clade of Mesozoic fish, the Pycnodontiformes (Fig. 1).
From the abstract “Two other neopterygian clades possessing similar ecological adaptations in both body morphology (†Dapediiformes) and dentition (Ginglymodi) also occurred in Mesozoic seas.”
Short note: Dapediformes includes Dapedium and kin (taxa related to gars, like Lepisosteus in the LRT). Ginglymodi includes Semionotiformes (Semionnotus) and Lepidotidae (Lepidotes and Lepisosteus (= gars)). These taxa nest basal to catfish + placoderms in the LRT. They are Silurian in origin, not related to Pycnodus (Fig. 2) and Albula (Figs. 1, 3) in the LRT.
From the introduction: “The overarching goal of this study is to evaluate the success but also final demise of pycnodontiform fishes, which represented the major marine actinopterygian elements from the Late Triassic to Palaeogene.”
Figure 1. Color image from Cawley et al. 2020. Albula added. Taxa below the gray line are Semionotiformes unrelated to pycnodontiformes.
Unfortunately Cawley et al. fails to mention the extant pycnodontiform, the bonefish, Albula, which nests with the pycnodontiforms, Flagellipinna and Pycnodus (Agassiz 1835), in the large reptile tree (LRT, 1804+ taxa).
Also unfortunately,
Cawley et al. inappropriately includes several members of the Dapediidae and Semionotiformes (Fig. 1). Due to taxon exclusion the authors don’t realize these taxa nest in the other major clade of bony fish, apart from most ray fins, closer to spiny sharks, placoderms and lobefins, far from Pycnodus and Albula.
Cawley et al. reports, “Pycnodontiforms represent a well-defined monophyletic group…”
then admits, “but the intrarelationships of various taxa and groups remain debated.” The LRT tests virtually all other fish clades.
Figure 2. Pycnodus with bones colorized according to tetrapod homologies. Third frame shows maxilla and lacrimal returned to in vivo positions.
Wikipedia reports, “Pycnodontiformes is an extinct order of bony fish. The group evolved during the Late Triassic and disappeared during the Eocene. The group has been found in rock formations in Africa, Asia, Europe, North and South America. The pycnodontiforms were small to middle-sized fish, with laterally-compressed body and almost circular outline. Pycnodontiform fishes lived mostly in shallow-water seas. They had special jaws with round and flattened teeth, well adapted to crush food items. One study links the dentine tubules in pycnodont teeth to comparable structures in the dermal denticles of early Paleozoic fish. Some species lived in rivers and possibly fed on molluscs and crustaceans.”
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.
Pycnodus according to Wikipedia “The known whole fossils of Pycnodus are around 12 centimetres (5 in) long, and have a superficial resemblance to angelfish or butterflyfish. The animals, as typical of all other pycnodontids, had many knob-like teeth, forming pavements in the jaws with which to break and crush hard food substances, probably mollusks and echinoderms. These teeth are the most common form of fossil.”
According to Wikipedia Bonefishes live in inshore tropical waters and moves onto shallow mudflats or sand flats to feed with the incoming tide. The bonefish feeds on benthic worms, fry, crustaceans, and mollusks. Ledges, drop-offs, and clean, healthy seagrass beds yield abundant small prey such as crabs and shrimp. It may follow stingrays to catch the small animals they root from the substrate.”
Apparently no one has reported
that pycnodontiformes is an extinct clade within the extant clade Albulidae. Likewise no one has reported that Semionotifomes are not related to Pycnodontiformes. If so, please send the citation so I can promote it here.
References Agassiz JLR 1835.Recherches sur les Poissons fossiles, 5 volumes. Imprimerie de Petitpierre et Prince, Neuchaatel, 1420 pp. Bleeker P 1859. xx
Cawley JJ et al. (5 co-authors) 2020. Rise and fall of Pycnodontiformes: Diversity, competition and extinction of a successful fish clade. Ecology and evolution DOI: 10.1002/ece3.7168
According to Wikipedia “Galeaspida lived in shallow, fresh water and marine environments during the Silurian and Devonian times (430 to 370 million years ago) in what is now Southern China, Tibet and Vietnam. Superficially, their morphology appears more similar to that of Heterostraci than Osteostraci, there being currently no evidence that the galeaspids had paired fins. However, Galeaspida are in fact regarded as being more closely related to Osteostraci, based on the closer similarity of the morphology of the braincase.”
Figure 1. Galeaspids from Halstead 1985.
“The defining characteristic of all galeaspids was a large opening on the dorsal surface of the head shield, which was connected to the pharynx and gill chamber, and a scalloped pattern of the sensory-lines. The opening appears to have served both the olfaction and the intake of the respiratory water similar to the nasopharyngealduct of hagfishes.”
Figure 2. Skull of Dunyu with tetrapod homolog colors applied here. Note the elongated dorsal opening. In other galeaspids the opining is more oval. On a 72 dpi monitor this image is only slightly smaller than life size.
Dunyu longiforus (Fig. 2) from the Late Silurian was described by Zhu et al. 2012.
Figure 3. Subset of the LRT focusing on basal chordates, including Dunyu.
Here
(Fig. 3) in the large reptile tree (LRT, 1803+ taxa) Dunyu nests between the thelodont, Thelodus, and the osteostracan, Hemicyclaspis (Fig. 3). The resemblance between the three is readily observed. Phylogenetic bracketing (Fig. 3) provides galeaspids with pectoral fins. Closest living relatives are hagfish and sturgeons.
References Halstead LB 1985. The vertebrate invasion of fresh water. Philosophical Transactions of the Royal Society London B 309:243–258. Janvier P 1984. The relationships of the Osteostraci and Galeaspia. Journal of Vertebrate Paleontology 4(3):344–358. Liu YH 1965. New Devonian aganathans from Yunnan. Vertebrata PalAsiatica 9(2):125–134. Zhu M and Gai Z-K 2006. Phylogenetic relationships of Galeaspids (Agnatha). Vertebrate PalAsiatica 44:1–27. Zhu M, Liu Y-H, Jia L-T and Gai Z-K 2012. A new genus of eugaleaspidiforms (Agnatha: Galeaspida) from the Ludlow, Silurian of Qujing, Yunnan, Southwestern China. Vertebrata PalAsiatica. 50 (1): 1–7.
Here are the taxa
(Fig. 1) in the large reptile tree (LRT, 1803+ taxa; subset Fig. 2) in the lineage of Xiphactinus (Fig. 1) a large Late Cretaceous predator from the Niobrara formation, starting with Calamopleurus, the Early Cretaceous bowfin with long, wicked teeth. Calamopleurus likely had a Late Silurian ancestry based on an Early Devonian relative, Doliodus.
Figure 1. Taxa in the lineage of Xiphactinus going back to Salmo, the salmon.
As mentioned earlier,
wrestling with data on these 90 or so ray-fin bony fish over the last 2-3 months has been a full-time task. Many, many corrections were made. The present subset of the LRT still needs some polishing, but it is settling into a logical model for evolutionary processes distinct from traditional cladograms that do not recognize the origin of bony fish from hybodontid sharks and Gregorius.
Figure x. Rayfin fish cladogram. This one represents the latest subset of the LRT.
The white notch
that includes mormyrids and piranha (Fig. 2) was covered earlier here.
