Updated May 15, 2023 –originally August 2019– with more taxa and better scoring in the large reptile tree (LRT, 1556 taxa then, 2251 taxa today) the king mackerel, Scomberomorus (Fig 1) now nests basal to the Remora clade (Figs 1–3). This extant taxon replaces the strongly convergent cobia, Rachycentron (Fig 4), now nesting basal to barracuda in the Fundulus clade.
These examples of strong convergence are what made ray-fin fish such a difficult clade to score and understand over the past six months of focused study.
Figure 1. Remora evolution. Here Scomberomorous gives rise to tiny Opisthomyzon and the remora clade.
As reported atNationalGeographic.com “The remora is so ridiculous that no one would try to make it up. The top of its head is a giant, flat suction cup. It uses the cup to lock onto the bodies of bigger animals, such as sharks, sea turtles, and whales. As the big animal swims for miles in search of a meal, the remora hangs on for the ride. When its host finds a victim, the remora detaches and feasts on the remains.”
According to Williams et al 2003, those ‘remains’ include host feces. NatGeo was using a euphemism.
Figure 2. The head of a remora showing in three views of the adhesion disc that make this fish the one and only ‘shark-sucker.’ Suction is created by raising the Venetian blind-like strips shown here once the seal is made with the rim of the disc.
Figure 3. Skull of Remora with a large adhesion disc (postparietal) extending forward to the premaxilla. Colors added here represent tetrapod homologies. Note how the postorbital (amber) extends far forward ventral to the elongate naris. Not the protruding mandbile vs the mistmatched short premaxilla and maxilla.
As reported atNationalGeographic.com “Their closest relatives include Mahi-Mahiandamberjacks, neither of which has anything on their head that even faintly resembles the remora’s sucker.”
The LRT does not confirm those hypothetical interrelationships. Other taxa nest closer. For that list, see figure 1.
Figure 4. The cobia (Rachycentron). Note the superficial resemblance to Remora. Lacking an adhesion disc, six-to-nine tiny spine-hooks appear where an anterior dorsal fin appears on other fish. It was thought those little dorsal fin hooks led to more hooks, wider plates, then suction as the adhesion disc evolved. But the LRT indicates this was by convergence perhaps because both have the same niche: following sharks.
According to the Friedman et al 2013, the closest relatives of remoras include the barracuda (Sphyraena), the cobia (Rachycentron, Fig 4) and early Oligocene Opisthomyzon (Figs 1,5,6).
The LRT confirms only the association of Opisthomyzon. Friedman et al did not mention or test Scomberomorus (Fig 1). In the LRT Rachycentron (Fig 4) is basal to Ductor + Sphyraena (barracuda) in the strongly convergent Fundulus clade.
Figure 5. The tiny early Oligocene pre-remora, Opisthomyzon, with a small adhesion disc at the back of the flat skull replacing the postpariedal crest. Note the smaller dorsal fin and elevated pectoral fins. Shown full scale on 72dpi monitors.
Figure 6. The skull of Opisthomyzon in situ and reconstructed, slightly reconstructed. Note the small adhesion disk at the back of the skull: a modified postparietal crest. The splitting of the frontals follows patterns seen as ridges in Scomberomorus (Fig 6b). This image reflects revised skull bone identifies.
Figure 6b. Scomberomorus skull to scale with Remora and Opisthomyzon. Colors reflect homologies.
As reported atNationalGeographic.com “Britz and Johnson’s research indicates that the remora suction disk started out, improbably enough, as a dorsal fin.” (See Fig 7).
By contrast, phylogenetic bracketing in the LRT indicatesthe adhesion disc started out as a subdivided post-parietal (Fig 7) that expanded laterally and anteriorly during phylogeny. This is recapitulated during ontogeny as paired spines associated with the back of the skull – not associated with a single median dorsal fin associated with the spinal column.
Figure 7. From Britz and Johnson 2012 showing a hatchling remora, focusing on the tiny spines in the cervical region that ultimately become the adhesion disc. Compare to Rachycentron (Fig. 3). Like a very primitive form of Velcro, such backward pointing spines dig in deeper whenever the host is accelerating relative to the hitchhiker and dislodged whenever the reverse is initiated.
Figure 8. A remora attached to a much larger shark with an adhesion disc atop its head. Inverted swimming is no problem with this fish lacking a swim bladder.
Remoras lack a swim bladder. Thus they are able to attach themselves in an inverted or angled position on their host (Fig 8).
Figure 9. Cobia and remora surrounding a whale shark. Free-swimming cobia have to work harder to keep up. Shark-sucking remora rather easily hitch a ride instead.
Opisthomyzon glaronensis(Friedman et al. 2013; early Oligocene) is a small prehistoric remora with only a small ‘sucker’ arising from the postparietal. This specimen (Figs 5, 6) indicates that the adhesion disc originated as a subdivided postparietal, which arises from a median crest in Scomberomorus (Fig 6b).
Remora remora(Rafinesque 1810; 75cm) is the extant remora or shark-sucker. A flexible Venetian blind-like membrane rises due to blood flow atop the skull to produce suction (Flammang BE and Kenaley 2017). Hatchlings are less than a centimeter in length. At 3cm juvenile Remora has a fully formed 2mm sucking disc. By convergence with barracuda,the remora skull roof is flat and the lower jaw juts out beyond the upper one. Other traits in the LRT separate these convergent taxa.
Friedman et al report “We demonstrate that the “interneural rays” of echeneids are homologous with the proximal‐middle radials of Morone and other teleosts and that the “intercalary bones” of sharksuckers are homologous with the distal radials of Morone and other teleosts.”
Morone is the white perch, a discoidal fresh water fish, not related to remoras in the LRT. Echeneids are members of the remora clade.
“The “intercalary bones” or distal radials develop a pair of large wing‐like lateral extensions in echeneids, not present in this form in any other teleost.”
According to the LRT the postparietal of ray-fin fish develops phylogenetically from a series of post parietal bones that first appear in placoderms. Hiodon tergisus(Fig 10) is a more distant remora ancestor and it documents postparietal extensions and elaborations not seen in other ray-fin fish. So some strange things happen to the postparietal in this clade.
“Finally the “pectinated lamellae” are homologous with the fin spines of Morone and other acanthomorphs.”
According to Wikipedia,“A key anatomical innovation in acanthomorphs is hollow and unsegmented spines at the anterior edge of the dorsal and anal fins”. Acanthormorpha is a clade not recognized by the LRT, so this spine trait can be convergent among several clades.
Be careful of‘key anatomical innovations’ like this, which can be convergent. Focusing on one trait is what we call “Pulling a Larry Martin.” Always nest taxa using 200+ traits from head to tail, no matter what ‘key traits’ a taxon seems to display.
“The main part of each pectinated lamella is formed by bilateral extensions of the base of the fin spine just above its proximal tip, each of which develops a row of spinous projections, or spinules, along its posterior margin. The number of rows and the number of spinules increase with size, and they become autogenous from the body of the lamellae.”
Since there is phylogenetic disagreement here due to taxon exclusion, let’s try to figure out the phylogeny first by adding taxa wherever needed. Then we can determine homology, convergence and the origin of the adhesion disc with more consensus and authority.
Figure 10. Hiodon tergisus, the extant mooneye, is a ancient phylogenetic ancestor to the mackerel and remora clade. Note the extended postparietal (tan).
Finally let’s return to the Devonian to Carboniferous and the chimaera-like extinct clade, Iniopterygidae (Fig 11). These share with remoras the trait of large elevated pectoral fins – by convergence.
Figure 11. Imagine these Iniopterygidae (Iniopteryx, Promexyele, Iniopera and Sibyrhynchus) attaching their prickly fins to larger hosts. Remoras also have elevated pectoral fins, but without the tiny hooks.
Distinct from remoras, members of the Iniopterygidae (= Iniopterygiformes, 15-46cm in length) have pectoral fins with tiny hooks. Does anyone else wonder if these elevated pectoral fins and their tiny hooks enabled iniopterygids to hitch rides on larger hosts, convergent with remoras?
This appears to be a novel hypothesis of interrelationships. If not please provide a citation so I can promote it here.
References Britz R and Johnson GD 2012. Ontogeny and homology of the skeletal elements that form the sucking disc of remoras (Teleostei, Echeneoidei, Echeneidae). Journal of Morphology https://doi.org/10.1002/jmor.20105 online here. Flammang BE and Kenaley 2017. Remora cranial vein morphology and its functional implications for attachment. Scientific Reports 7(5914). https://www.nature.com/articles/s41598-017-06429-z Friedman M, et al. 2013. An early fossil remora (Echeneoidea) reveals the evolutionary assembly of the adhesion disc. Proc. R. Soc. B 280.1766 (2013): 20131200. Williams EH, et al. (6 co-authors) 2003. Echeneid-sirenian associations, with information on sharksucker diet. Journal of Fish Biology. 63 (5): 1176.
It’s tiny and probably a hatchling because sister taxa are much larger. Mengshanosaurus minimus (Yuan et al. 2021; Early Cretaceous, China; skull length 3.5cm) nests between Ikechosaurus and Champsosaurus in the LRT (subset Fig. 3). Note the indented remnants of the antorbital fenestra in the hatchling model (Fig. 1). Apparently the post-frontal fontanelle is not a pineal opening. Sister taxa do not have a pineal opening.
Figure 1. Full scale model of CT-scanned Mengshanosaurus skull.
Traditional skull misinterpretations continue in Yuan et al. Yuan et al did not properly label several fused bones (corrected Fig. 2 right) because they don’t know which taxa are choristodere outgroups and last common ancestors. That remains a traditional academic enigma that no one else seems to want to resolve, confirm or refute (Fig. 3) by simply adding taxa to find out.
Figure 2. Holotype of Mengshanosaurus.
Similarly, the authors had no idea where to nest choristoderes as reptiles. In the large reptile tree (LRT, 1879+ taxa; subset from 2013 in Fig. 3) choristoderes nest as derived proterosuchids. Tiny transitional taxa, like the BPI 2871 specimen, lose the antorbital fenestra. Sister clades within the Pararchosauriformes include the Parasuchia and Proterochampsia. Euarchosauriformes derived from Euparkeria evolve to Archosauria, Rauisuchia, Erythrosuchia, etc.
Figure 3. Subset of the large reptile tree from 2013 focusing on the pararchosauriformes and the Choristodera. This has not changed much, but for the addition of taxa, like Mengshanosaurus between Ikechosaurus and Champsosaurus.
If you don’t know where your clade resides, keep adding taxa until it becomes apparent and all candidate sister taxa are considered. Or just sneak a peek at the LRT. Don’t overlook tiny taxa. Often tiny taxa bridge gaps, forming transitions at the genesis of major clades in a process known as phylogenetic miniaturization. This time a tiny taxon just turned out to be a hatchling.
Figure 4. The choristodere, Champsosaurus laramiensis (USNM PL 544147) has a vestige antorbital fenestra in the usual place, anterior to the orbit. Here the frontal fontanelle is also present, as in Mengshanosaurus.
PS Sometimes adult choristoderes also retain a vestige of the antorbital fenestra (Fig. 4).
References Yuan M, Li D-Q, Ksepka DT and Yi H-Y 2021.A juvenile skull of the longirostrine choristodere (Diapsida: Choristodera), Mengshanosaurus minimus gen. et sp. nov., with comments on neochoristodere ontogeny. Vertebrata PalAsiatic in press DOI: 10.19615/ j.cnki.2096-9899.210607
Summary for those in a hurry:
Becoming a paleontologist who can support a family is difficult and rare. Up-and-comers end up supporting powerful professors. Outsiders and insiders with new ideas are sometimes ridiculed and/or ignored to silence debate and prevent upsetting the status quo.
PS (added 24 hours later). If you’re serious about paleontology,see Dr. Chris Brochu’s well-considered and insightful comments (below). Dr. Brochu agrees, disagrees and adds more data to many of the points made here.
Once you get your PhD in paleontology…
sure it’s a happy day of celebration, a great achievement invested with time and treasure. But then reality sets in as you realize you are not automatically a ‘made man‘ as in the gangster movie, “Goodfellas.”
You still need to get that first good paying job in paleontology,
and those are hard to come by. Black 2010 reports, “it is extremely difficult for researchers to find jobs and secure funding for their research. Prior to the beginning of the 20th century most paleontologists were self-funded enthusiasts who either used their family fortunes (O.C. Marsh and E.D. Cope, for example) or sold fossils (the Sternberg family, for example) to underwrite their work. For most paleontologists most of the time, research funding comes in the form of grants.”
Through the grapevine
I hear that anywhere from 40 to 80% of grant money goes to the university or museum that provides office space for the paleontologist. (Is that correct?).
It comes as a disappointment to many PhDs
that they end up as preparators, docents, research assistants, artists and librarians, rather than highly-paid professors making decisions, doing field work in the summer and buzzing around the world doing book tours. That jarring dose of reality comes at a time when young, former students are starting from scratch, trying to buy a house, start a family, pay off loans and hoping to make a name for themselves by publishing discovery after discovery.
Evidently it is worse for female students and scientists…
Harassment and bullying were chronicled in a recent (April 14, 2021) PBS NOVA documentary you can access here. Some notes follow:
PAULA JOHNSON,M.PH., M.D. (President, Wellesley College):“The best estimates are about 50 percent of women faculty and staff experience sexual harassment. And those numbers have not really shifted over time. If you think about science, right now, we have a system that is built on dependence, really, singular dependence of trainees—whether they are medical students, whether they are undergraduates, or if they’re graduate students—on faculty, for their funding, for their futures. And that really sets up a dynamic that is highly problematic. It really creates an environment in which harassment can occur.”
KATHRYN CLANCY, PH.D. (Biological Anthropologist):“Generally speaking, sexual forms of sexual harassment, like come-ons, unwanted sexual advances, those are actually the rarest forms of sexual harassment. They actually don’t happen very much; mostly you see putdowns.”
One woman noted, “an invitation to have a beer with someone important interested in your poster sometimes has little or nothing to do with your poster.” It is noteworthy that the dropout rate in STEM studies is higher in women, who suffer from unequal treatment according to this documentary.
Fossils are hard to come by.
If post-grads don’t find their own fossils in the field, the fossils that come in the door are going to be distributed by the professor as they please, like a mother bird feeding hungry nestlings. (BTW, I’m talking about paleontologists who like bones. Others in the petroleum industry with a Master’s Degree make better money than a PhD in dinosaur studies because they are in greater demand.)
In the typical bell-curve of success after a doctorate, every year or so, some few do come to international attention for their discoveries and publications. Most do not. Many struggle just to keep up an association with a university, quite aware of the fact that year after year another clade of young, eager, intelligent, well-connected future paleontologists with scholarships are coming into the professors’ view with the exact same dream and goal.
When grad students and post-docs are trying to establish themselves, they tend to maintain relationships with universities and ally themselves with groups that huddle around and support established professors. It’s the only game in town. These 20- and 30-somethings are known to professors as ‘cheap labor’ due to an over supply of young, eager and bright hopeful students.
Older, established professors decide
who of their underlings gets funding and who goes hungry. Well-known professors bring a lot of money into universities, so universities undervalue underlings based on this value system.
New hypotheses that upset those in textbooks are not welcome.
If those ideas come from outside the tribe, someone is sent out to dismiss and dismantle that radical. Discoveries and hypotheses are welcome only if the professor is made a co-author and it doesn’t depart from the paradigm (i.e. supporting invalid clades like ‘Ornithodira‘, ‘Avemetatarsalia’, ‘Afrotheria‘, ‘Laurasiatheria’ and ‘Cetacea‘).
Peer review was not always part of the publication process, but it is now. Dinerstein 2017 wrote, “The controversies that have plagued peer review from its earliest days, censorship, conflict of interest, the tension between early reporting and veracity, the need to fill space, the desire for prestige and income remain with us today. They may have assumed different forms, but at their core are flaws in a system designed by flawed humans. It may not be the best system, but it is the one we use.”
According to Kampourakis et al. 2015, “The peer review process can be one of the most subjective endeavors in the scholarly world. It should not be, and it does not have to be subjective, but it can be. Each reviewer has his/her own conceptualizations, views, experiences, and biases, which can collectively impact the stance taken toward a manuscript.”
Established authors,
who are often established professors, who are well-known to established editors, have an advantage over independent researchers. Reviewers (= referees) are typically other professors hoping to get their work favorably reviewed when their time comes. If papers support the general narrative found in textbooks, they are more likely to be published. Departures that show textbooks are in error are at a disadvantage. No one wants to weaken the power of established professors, least of all other professors who understand how to play the game.
More on manuscripts from Kampourakis et al. “Most manuscripts are not appropriate for publication when we initially receive them. They always have limitations, which authors themselves are unable to identify—we know this from our own publication experiences. Therefore, if the editors only relied on reviewers for a decision, this would most likely be a “reject” one in the first place. Reviewers are always experts in their domains, and when their review is constructive, it provides crucial feedback to authors.”
Actually reviewers/ professors are not experts in their domain if they are teaching untenable traditions as facts. You wouldn’t think that happens, but it does.
Actually reviewers/ professors can not be experts if the subject of the manuscript is a discovery, something new, something not seen or understood before by anyone.
The issue is: will reviewers and editors recognize ‘the new order’ or will they defend ‘the old order’, the one they teach, the one that creates their monthly paycheck coming from lectures and textbooks.
Discoveries should be a cause for celebration, if followed by confirmation after testing using methods and materials.
Instead
discoveries by outsiders encourage young PhDs (e.g Naish, Cau,Witton) to start name-calling (e.g. ‘pseudoscientist‘, ‘crank)‘. Be aware that this sort of behavior has a long history in humankind, going back at least as far as the Romans, who called non-citizens ‘barbarians’. So, if you make a discovery don’t hold your breath waiting for accolades and citations (see John Ostrom link below).
Name-calling by teachers/ professors/ colleagues is inappropriate.
Better to help colleagues with suggestions or data if genuine errors are found.
Errors are everywhere.
I just spent the weekend correcting errors in the LRT. Finding new insightful data is its own reward.
The LRT is online day and night, world-wide,
available to anyone looking for taxon list suggestions and citations. In like manner, ReptileEvolution.com is a source for data. It would be great if someone else were to create a parallel study to confirm, refute and compare discoveries found here. In the last ten years, no one has yet ventured forth to do this, or threatened to do this. That may be because they are stuck in the present academic world and all of its restrictions.
You should do science
because you love science.
There are only so many discoveries to be made, and fewer every year.
No PhD wants to simply confirm what someone else has already discovered. That’s not why they spent their time and treasure getting their PhDs. They want their own discoveries. When someone else makes a discovery, that’s one less out there waiting to be discovered. That’s the sort of frustration that has led to name-calling when it should have led to unemotional scientific confirmation or refutation following scientific methods and materials.
And speaking of vague insults,
the latest I’ve heard is “Your methods are flawed.” Really? No more specific instruction? No actual testing of the methods? I keep hearing, “your character list needs to be expanded.”Daily testing shows this is a myth. Experts are not always correct, as you will sooner or later find out for yourself.
Once you’ve shown and labeled
all your taxonomic data, let the software recover a cladogram in which all sister taxa actually look alike. This simple method has led to several satisfying discoveries, like ancestors for pterosaurs, snakes, whales, and turtles back to Ediacaran worms. Make all your .nex files available to strangers. Have the balls to tell PhDs that genetic analyses deliver false positives in deep time studies, if that’s what your studies reveal.
IMHO
“Your methods are flawed” comes off as a vague and baseless claim coming from an immature and insecure worker who has turned to projecting their own faults on others. Pressed for details, something real scientists are usually eager to fill an hour with, disgruntled post-grads usually retreat to social media. Funny that the ones who say, “your methods are flawed” do not repeat the same insult to their fellow PhDs when they make the same discoveries years later.
By design, the manuscript review process
usually takes months. It might take years. This is also a professional ‘brake’ on new ideas that keep the established professors behind their lecterns for as long as possible. Why would a professor return a favorable review on a paper that upsets his own hypotheses, lectures and textbooks? Professors rely on lectures and books for their salaries, royalties and status. Any manuscript that upsets the status quo is going to sit at the bottom of their growing IN pile for as long as possible, then begrudgingly returned with a ‘NO’. Cogent reasons are not required by editors.
In an ideal world
arguments should be published immediately, while the subject is still fresh in the public’s mind and before inaccurate myths get out there and spread into the world of general knowledge. Colleagues should treat each other more like co-pilots rather than saints vs. sinners.
Even if you become a tenured professor, you are not always free to do what you want to do. “One way of getting rid of tenured professor, that’s known, is you ask the person to report on their research and you load them up with teaching and you give them a lousy office. And then eventually they’ll just quit.” Eric Weinstein on Joe Rogan #1626 3:15 https://www.youtube.com/watch?v=l1jTUhwWJYA
Even tenured professors are steered.
The red pill and blue pill.
This is a common meme from a scene in the 1999 film The Matrix. It refers to a choice between the willingness to learn a potentially unsettling or life-changing truth, by taking the red pill, or remaining in contented ignorance with the blue pill. Over the last ten years of building the LRT I’ve come to realize when a PhD has taken the blue pill. Keep working and soon you will, too.
That’s why this blogpost exists.
Blogposts sponsored by major publications like Scientific American, are less about science and more about journalism, reporting the untested results of published papers.
Textbooks are too often used as unchangeable bibles, instead of jumping off points for the next set of discoveries.
American physicist,Richard Feynmanonce said, “As a matter of fact, I can also define science another way: Science is the belief in the ignorance of experts.”
Historically
it has taken an outsider, someone not beholding to one professor or to the rest of the professors, to clean house. Yale paleontologist John Ostrom was an insider with an outsider idea and even he had a frustrating story to tell about how long his ideas took to come to consensus.
The video above
at 33:40 discusses the tiny (5%) number of those who train for jobs in academia actually get jobs in academia. It also discusses the large percentage (50%) of grant money that goes directly to the university. Under this system the university hires students, often foreign students, to do the teaching for low wages leaving the successful grant writers to keep writing expensive grant applications.
The Dean Lomax video above
documents the education and career of this science communicator and paleontologist. Skipping a bachelor degree, Lomax went straight to his Masters and PhD, describing ichthyosaurs. He reports the job outlook for paleontologists is ‘super competitive.’
ResearchGate.net
reports readership for my papers and manuscripts on their site has surpassed 5000 with some papers exceeding 600 reads. That’s good to hear. Just getting the information out is why anyone writes a manuscript. Nowadays everything is downloaded. If you’re not a card-carrying student or faculty member at many universities, you’re not going to be allowed in their libraries to browse the increasingly old-fashioned book shelves.
Finally, it’s up to others to approve or dismiss,
and that’s out of our control no matter if we publish fact or fancy, online or in the literature. Good luck in your career. Don’t let anything restrict your studies.
Dr. Phil Hastings, Scripps professor and curator of the SIO Marine Vertebrate Collection delivers an online lecture and slide show sponsored by the University of California Television (UCTV). It runs for about an hour.
This is a traditional view of fishes lacking any mention of fossil taxa.
Unfortunately
Hastings follows molecular data. Hastings mentions that we humans are indeed members of the Osteichthys. Ichthyologist Neil Shubin and artist Ray Troll are also mentioned.
By contrast,
the large reptile tree (LRT, 1836+ taxa) presents a distinctly different view of fish systematics because it includes fossils and minimizes taxon exclusion.
Aeoliscus strigatus (Günther 1861, aka Centriscus strigatus, Amphisle strigata; 15cm) is the extant razorfish or shrimpfish. In the large reptile tree (LRT, 1834+ taxa) the shrimpfish nests with the sea horse, Hippocampus (Fig. 2). Thus Aeoliscus can be thought of as an upside-down sea horse despite many morphological difference (= no other tested vertebrate is closer). The dorsal fins have migrated to the caudal area. The caudal fin migrates to the anal area, bending the vertebral column to do so (Fig. 2). The tiny mouth, perhaps the smallest among vertebrates, is used like an eye-dropper to suck up minute brine shrimp. The preoperculum and operculum are large to produce suction for the tube mouth.
The preoperculum extends anteriorly beyond the orbit, merging with the quadrate (Fig. 2, at least in Gregory’s 1933 drawing). The lacrimal is absent (at least in Gregory’s 1933 drawing). As in the sea horse the naris is close to the orbit. The orbit is confluent with the antorbital fenestra. The supratemporal is absent or fused.
The shape of Aeoliscus was for hiding among sea grasses and other vertical sea floor environmental elements. The counter-shading of the body increases the illusion of slender background elements.
Aeoliscus lives in shallow sunlit waters protected from predators by the poisonous spines of nearby brainless sea urchins. Fertilized eggs and hatchlings drift without parental care. Males and females are nearly identical.
References Gregory WK 1933. Fish skulls. A study of the evolution of natural mechanisms. American Philosophical Society 23(2) 1–481. Günther A 1861. Catalog of Fishes in the British Museum 3: 586pp. British Museum, London.
This post had its genesis in a recent YouTube video all about bears by Moth Light Media. After phylogenetic analysis in the large reptile tree (LRT, 1834+ taxa, subset Fig. 1) ‘bears’ are no longer monophyletic. Instead the various extant ‘bears’ are better considered giant kinkajous, weasels, wolverines and bush dogs, all converging on similar ‘bear’-like morphologies.
Figure 1. Subset of the LRT focused on Carnivora, a placental mammal clade. Note the polyphyletic nesting of various ‘bears’ indicating that they are all just large kinkajous, weasels, wolverines and bush dogs converging on similar bear-like morphologies. Note the separation of seals (dark yellow) from sea lions (peach).
Jiangzuo and Flynn 2020 discussed the earliest ursine bear and the origin of plant-dominated omnivory in Carnivora. Unfortunately they worked within an invalid phylogenetic context brought about by taxon exclusion. The wolf, Canis lupus, was their outgroup taxon. So their cladogram was upside-down compared to the LRT (Fig. 1). Basalmost members of Carnivora and their outgroups among basalmost Placentalia were all agile arboreal omnivores, not digitigrade cursors (runners), like Canis.
Jiangzuo and Flynn consider the spectacled bear, Tremarctos, a member of the ursine bears. In the LRT Tremarctos arises from the bush dog, Speothos, far apart from ursines.
Jiangzuo and Flynn consider the wolverine, Gulo, a member of the mustelids. In the LRT the short face bear, Arctodus, arises from the wolverine, Gulo, apart from ursines.
Jiangzuo and Flynn consider the giant panda, Airluropoda, a type of bear. In the LRT it arises from the herbivorous kinkajou (genus: Potos) before the appearance of the ancestor of the rest of the ‘bears’, Mustela, the weasel.
Jiangzuo and Flynn do not include Speothos or Potos in their text. The authors separate Gulo in the clade Mustelida, apart from bears in their study. So taxon exclusion mars this otherwise detailed study of bear dentition and diet.
In like fashion, McLellan and Reiner 1994 also excluded a long list of pertinent taxa in their review of bear evolution.
Sharp-eyed readers will note the addition of two taxa to the Carnivora, the sea otter (Enhydra) and the basal walrus (Protodobenus).
References Jiangzuo Q and Flynn JJ 2020. The earliest ursine bear and the origin of plant-dominated omnivory in Carnivora. iScience 23, 101235, June 26, 2020. McLellan B and Reiner DC 1994. A review of bear evolution. Int. Conf. Bear Res. and Manage. 9(1):85-96
As the headlines reported, (see below) these two late-surviving pre-mammals lived under the feet of Early Cretaceous dinosaurs and probably only came out after dark.
From the Mao et al. 2021 abstract: “Mammaliamorpha comprises the last common ancestor of Tritylodontidae and Mammalia plus all its descendants. Tritylodontids are nonmammaliaform herbivorous cynodonts that originated in the Late Triassic epoch, diversified in the Jurassic period and survived into the Early Cretaceous epoch. Eutriconodontans have generally been considered to be an extinct mammalian group, although different views exist.”
“Here we report a newly discovered tritylodontid and eutriconodontan from the Early Cretaceous Jehol Biota of China. Eutriconodontans are common in this biota, but it was not previously known to contain tritylodontids.”
Figure 1. Fossiomanus in situ in two ventral views, plus manus, pes and pelvis reconstructed. Teeth colored. Taphonomically shifted pectoral girdle repaired on right. The current view of the skull material prevents a reconstruction at this time.
Figure 2. Skull of Jueconodon based on data from Mao et al. 2021.
Mao et al. continue: “These fossils shed light on the evolutionary development of the axial skeleton in mammaliamorphs, which has been the focus of numerous studies in vertebrate evolution and developmental biology. The phenotypes recorded by these fossils indicate that developmental plasticity in somitogenesis and HOX gene expression in the axial skeleton—similar to that observed in extant mammals—was already in place in stem mammaliamorphs. The interaction of these developmental mechanisms with natural selection may have underpinned the diverse phenotypes of body plan that evolved independently in various clades of mammaliamorph.”
Figure 3. Cladogram from Mao et al. 2021, color overlays added here to show how LRT divides these clades. Compare to figure 4.
Usually, ‘No hypotheses like this can proceed without first establishing a valid phylogeny.’ Parts of Mao et al. match the LRT. Unfortunately, Mao et al. follow invalid academic tradtion as they also include and therefore nest multituberculates with pre-mammals, rather than with rodents and plesiadapiformes in the gnawing clade, Glires. Just add pertinent taxa to resolve this problem. So far PhDs have been reluctant to do this and so the myth continues untested except here.
Mao et al. nestJueconodon between Liaoconodon and Chaoyangodens (Fig. 3). In the LRT (Fig. 4) Jueconodon also nests with Liaoconodon, but Chaoyangodens nests as a monotreme mammal, basal to the echidna and platypus (Tachyglossus and Ornithorhynchus).
Mao et al. nestFossiomanus with Kayentatherium, basal to four other tritylodontids including Tritylodonand Oligokyphus among mutually tested taxa. In the LRT (Fig. 4) Fossiomanus nests similarly.
Figure 4. Subset of the LRT focusing on pre-mammals with the addition of Fossiomanus and Jueconodon. Compare to original cladogram in figure 3 and to the LRT for a look at related taxa.
Mao et al. mention Liaoconodon often:
“The triangular shape of the skull may have been exaggerated by the crush of the specimen, but compared to those that have the similar preservation, such as Jeholodens, Liaoconodon, and Chaoyangodens, the triangular shape of Jueconodon is distinctive.
The morphology of the mandible is similar to those of other eutriconodontans, such as Liaoconodon (Meng et al., 2011). Given that Liaoconodon was interpreted as a semiaquatic animal (Chen and Wilson, 2015), the similar mandible in both species indicate that the lower jaw and teeth of Jueconodon were not specialized for digging.
The ossified Meckel’s cartilage on each side is preserved but displaced from its anatomical position. This suggests that the transitional mammalian middle ear, as best shown in Liaoconodon (Meng et al., 2011), was present in the fossorial eutriconodontans.“
Figure 5. Skull of Liaoconodon.
Figure 6. Liaoconodon in situ.
Mao et al. report, “the Manda cynodont and mammaliaforms that are considered terrestrial. Compared to extant mammals, Fossiomanus sinesis is superficially similar in body size and shape tothe Cape dune mole-rat Bathyergus suillus, the largest subterranean scratch-digger species ofthe African mole-rats (Montoya-Sanhueza et al., 2019). However, they differ fundamentallyin the axial skeleton in that mole-rat has the rodent body plan with the ancestral PV count ofmammals.”
Revised April 28, 2021 with a slight shift of Massamorichthys closer to Danio, the tiny zebra fish, derived from mackerels.
Massamorichthys wilsoni (Murray 1996; up to 20cm; Paleocene) is a small extinct transitional taxa linking Scomberoides to more derived taxa, including Danio. It does not appear to be related to PercopsisMassamorichthys lacks a crest, a trait present in basal taxa. This fish is related to tuna (Thunnus) and mackerel (Scomber).
Does this mean Massarmorichthys is chronologically correctly nested? In other words, are all the phylogenetic descendents younger than Massamorichthys? The answer is….No. Sphenocelphalus is a Late Cretaceous perch. Plectocretacicus is an early Late Cretaceous oarfish ancestor.
Figure 1 Updated May 17, 2023 from May 17, 2023: Massamorichthys, Eurypholis and their LRT relatives to scale.
PS Massarmorichthys looks like your standard, plesiomorphic fish. It is. Don’t omit such taxa from your cladograms just because they are not weird, scary or gigantic. Here and elsewhere the plain and small taxa are important, too.
References Murray AM 1996. A new Paleocene genus and species of percopsid, †Massamorichthys wilsoni (Paracanthopterygii) from Joffre Bridge, Alberta, Canada. Journal of Vertebrate Paleontology 16(4):642–652.
Losing its maxilla
(Fig. 1) did not stop this taxon from sporting a lot of other teeth in the palatine, ectopterygoid and maybe the vomer, even though only the premaxillary teeth line up with dentary teeth.
Figure 1. Skull of Proteus the white olm. Colors added. Note the lack of a lacrimal and maxilla.
Proteusthe white olm
(Figs. 1, 2), is a blind cave salamander with a long torso, tiny limbs and external gills (Fig. 2).
Figure 2. Skeleton of Proteus, the white olm.
Proteus anguinus (Laurenti 1768) nests with Necturus, the mudpuppy. The lacrimal and maxilla are absent. The postorbital and postfrontal are stretched out. External gills enable Proteus to remain underwater. Apparently the dorsal portion of the vertebral column is very short (about 5 vertebrae), with the majority comprised of lumbar vertebrae (without dorsal ribs).
References Laurenti JN 1768. Synopsin Reptilium. J.T. de Trattnern, Viennae, pp. 35–36.
While reviewing the terrestrial descendants of tree shrews yesterday, the Late Jurassic Fruitafossor (Figs. 1, 2) stuck out as a chronological misfit as it nested in the otherwise Tertiary edentates (= Xenarthrans).
Here is the problem,
and the solution.
A Jurassic edentate? No. Fruitafossor windscheffeli (Luo and Wible 2005) used to nest in the LRT with digging edentates, like the armadillo-mimic, Peltephilus (Miocene), and for good reason…
Wikipedia reports, “The teeth of Fruitafossor bear a striking resemblance to modern armadillos and aardvarks. Its vertebral column is also very similar to armadillos, sloths, and anteaters (order Xenarthra). It had extra points of contact among similar to the xenarthrous process that are only known in these modern forms.”
By contrast, Wikipedia concludes, “Its shoulder-girdle is similar to a platypus or reptile, but many other features are more similar to most other modern mammals.”
What would Larry Martinsay?
Run a complete analysis. Don’t rely on one, two or a dozen traits. And the Late Jurassic is so early in mammal evolution that it becomes important, too. There were fewer mammal clades back then. Edentates had not yet arrived.
Figure 1. Several drawings from Zhou and Wible that one must trust for accuracy. The verification data is too fuzzy to validate.
So is Fruitafossor a Late Jurassic edentate? Or an edentate-mimic in the Late Jurassic?
With current scoring in the LRT, shifting Fruitafossor from the edentates to the base of the Monotremata adds 23 steps. Shifting to Early Cretaceous Lactodens within the Monotremata adds just 17 steps, the lowest number I could find. Lactodens has typical differentiated teeth and five fingers with small, sharp claws, traits not shared with Fruitafossor + edentates. Lactodens nests with the echidnas, Tachyglossus (extant, Figs. 3–5) and Cifelliodon (Early Cretaceous; Fig. 3). The latter has simple blunt teeth and the former is a known digger.
Figure 2. Fruitafossor in situ from Digimorph.org and used with permission and here colorized to an uncertain extent.
So let’s reexamine scored traits… and solve this conundrum. Has the LRT met its match? Very few skull traits are known from Fruitafossor. Even so, earlier I overlooked or mis-scored the following that gain importance in hindsight:
Fruitafossor:
orbit contacts the maxilla
4 rather than 5 sacrals,
coracoid present
I could not score hind limb length without a pes and estimates won’t do
proximal sesamoid of fibula present
fibula diameter greater than half of tibia
dorsal osteoderms absent (I misinterpreted scattered elements at Digimorph.org)
Tachyglossus:
retroarticular process present as in Fruitafossor
metacarpal 1 and 2 are the longest as in Fruitafossor
longest manual digit 3 as in Fruitafossor
manual digit 4 narrower than 3 as in Fruitafossor
Cifelliodon:
three molars, as in Fruitafossor
Figure 3. Early Cretaceous Cifelliodon is ancestral to the living echidna, Tachyglossus according to the LRT. The lack of teeth here led to toothlessness in living echidnas. The skull of Tachyglossus is largely fused together, lacks teeth and retains only a tiny lateral temporal fenestra (because the jaws don’t move much in this anteater. Compared to Cifelliodon the braincase is greatly expanded, the lateral arches are expanded and the two elements fuse, unlike most mammals.
Figure 4. Tachyglossus skeleton, manus and x-rays. Note the perforated pelvis.
Figure 5. The echidna (genus: Tachyglossus) in life. This slow-moving spine-covered anteater has digging claws.
Results (as you might imagine, given these changes): Fruitafossor is an edentate-mimic nesting basal to Cifellidon and Tachyglossus as a Late Jurassic echidna and monotreme in the LRT. Glad to get rid of that problem!
In their original description of Fruitafossor,
Luo and Wible 2005 nested their discovery between a monotreme clade and a clade with the mammal-mimic, Gobiconodon at its base, then a clade with another egg-laying mammal, Tinodon at its base, then a pangolin ancestor, Zhangheotherium, then a rabbit ancestor Henkelotherium, then two other monotremes, Dryolestes, Amphitherium and the carnivorous marsupial, Vincelestes. Luo and Wible tested Tachyglossus, but not Cifelliodon, which was published in 2018. Note the simple, blunt teeth in Cifelliodon, nearly matching those in Fruitafossor. Given that the only fossil of Fruitafossor is a bit jumbled, it is possible that it, too, had five fingers in vivo, like other monotremes. With only four fingers (Fig. 1) Fruitafossor had a good excuse for pretending to be an edentate.
So, yes, the LRT was up to the challenge.
But it took insight, lacking until now, to provide the correct matrix scoring. I’m happy to announce that the twenty or so corrections made yesterday were added to the 120,000 or so corrections made over the past ten years. With these corrections the LRT gets better and stronger every week. Minimizing taxon exclusion maximizes the opportunity to correctly nest new and enigma taxa with old and established taxa, even if the new and old specimens are incomplete or scattered about.
The earlier August 2017 blogpost for Fruitafossor
was updated yesterday to erase old errors and enter the corrections.
References Huttenlocker AD, Grossnickle DM, Kirkland JI, Schultz JA and Luo Z-X 2018. Late-surviving stem mammal links the lowermost Cretaceous of North America and Gondwana. Nature Letters Link to Nature Luo Z-X and Wible JR 2005. A late Jurassic digging mammal and early mammal diversification. Science 308:103–107. Shaw G 1792. Musei Leveriani explicatio, anglica et latina.
The Pterosaur Heresies 