Finally the large reptile tree (LRT, 1840+ taxa) nests a new taxon pretty close to where original authors said it should nest. The LRT cladogram includes a wider gamut of turtles in general with ancestors going back to Ediacaran worms. By contrast the Joyce et al. 2021 cladogram has more closely related pelomedusid turtles from the Late Cretaceous of Madagascar and India.
Figure 1. Sahonachelys skull from Joyce et al. 2021, colorized here based on pareiasaur homologs. The frontas are fused with the parietals, based in basal taxa, like Macrochelys, the alligator snapping turtles. The prefrontals are fused to the nasals.
Joyce et al. wrote: “A functional assessment suggests that Sahonachelys was a specialized suction feeder that preyed upon small-bodied invertebrates and vertebrates. This is a unique feeding strategy among crown pelomedusoids that is convergent upon that documented in numerous other clades of turtles.”
In the LRT Sahonachelys is not unique, but nests between Pelomedusa (Fig. 3) and two other, long-necked suction feeding turtles, Early Cretaceous Araripemys (Fig. 2) and extant Chelus. Ancestors include the ancestors of box turtles (Terrapene), snapping turtles (Macrochelys).
Figure 2. Araripemys overall in dorsal and ventral views, plus manus and pes from Meylan 1996.
So, first these turtles snapped, then they sucked and snapped. Flat-headed Sahonachelys is the transitional taxon in the LRT.
References Joyce WG et al. 2021. A new pelomedusoid turtle, Sahonachelys mailakavava, from the Late Cretaceous of Madagascar provides evidence for convergent evolution of specialized suction feeding among pleurodires. Royal Society. Open Scence. 8: 210098. https://doi.org/10.1098/rsos.210098
Choiniere et al. 2021 bring us new inner ear data on Shuvuuia (Figs. 1, 4), a tiny alvarezsaurid theropod dinosaur we earlier considered as a Cretaceous tickbird (Fig. 2). Instead of perching on rhinos, Shuvuuia would have picked insects off larger, sometimes feathered dinosaurs (Fig. 1). Other workers, including Choiniere et al. follow tradition in considering Shuvuuia a digger. Presumably that would be difficult given the tiny forelimb proportions (Fig. 4).
Figure 1. Giant Deinocheirus, a contemporary of Mononykus and Shuvuuia, might have served as the host and dining room for a series of ever smaller and more specialized parasite eaters.
From the Choiniere et al. abstract: “Owls and nightbirds are nocturnal hunters of active prey that combine visual and hearing adaptations to overcome limits on sensory performance in low light. Such sensory innovations are unknown in nonavialan theropod dinosaurs and are poorly characterized on the line that leads to birds. We investigate morphofunctional proxies of vision and hearing in living and extinct theropods and demonstrate deep evolutionary divergences of sensory modalities. Nocturnal predation evolved early in the nonavialan lineage Alvarezsauroidea, signaled by extreme low-light vision and increases in hearing sensitivity. The Late Cretaceous alvarezsauroid Shuvuuia deserti had even further specialized hearing acuity, rivaling that of today’s barn owl. This combination of sensory adaptations evolved independently in dinosaurs long before the modern bird radiation and provides a notable example of convergence between dinosaurs and mammals”.
Not sure why the authors are being so coy in their abstract. They could have gotten right to the point, as they did for the publicity in the science website Phys.org. The authors reported Shuvuuia had “a fragile, bird-like skull, brawny, weightlifter arms with a single claw on each hand, and long, roadrunner-like legs. This odd combination of features has baffled scientists since its discovery in the 1990s. The eyes of Shuvuuia were also of note, as they had some of the proportionally largest pupils yet measured in birds or dinosaurs, suggesting that they could likely see very well at night. The extremely large lagena of this species is almost identical in relative size to today’s barn owl, suggesting that Shuvuuia could have hunted in complete darkness.”
Learn more about the lagena below.
Figure 2. Tickbirds sitting atop a pair of rhinos, perhaps a modern analog for mononykids.
These traits could have had a different explanation. Other than owls, most birds bed down for the night. The authors reported to Phys.org that “Many carnivorous theropods such as Tyrannosaurus and Dromaeosaurus had vision optimized for the daytime,” so these theropods also slept at night on stable ground or tree limbs. On the other hand, if you are a Cretaceous tickbird, the substrate on which you live and sleep is itself alive and moving about, like a rocking ship in a storm. In this scenario Shuvuuia needed a better-than-average balancing organ and clinging forelimbs, which is what they say it had!
When is the best time to jump on a giant dinosaur? Probably at night, when it is sleeping. Perhaps that is why larger, but still relatively tiny, ancestral Haplocheirus (Fig. 1) had larger eyes… all the better to seek out dinosaur hosts by moonlight.
Figure 3. The ear of a bird with the cochlea and lagena highlighted. The cochlea is the hearing organ. The lagena has other duties in birds.
So, what is the lagena? “The lagena in birds can be related to their navigation abilities (birds are supposed to be capable of orienting within the magnetic field of the Earth due to the magnetic properties of the lagenar otoconia; this structure can also provide detection of movements along the vertical axis.”
According to Wildlife-sound.org, “The function of the lagena is uncertain, but it is considered that it is more likely to be concerned with balance rather than hearing.”
“There is a conspicuous difference between the hearing organ or cochlea of the mammal and the bird. That of the mammal is a thin, coiled tube while the bird’s cochlea is relatively short, broad and has only a slight curve; both organs are filled with fluid. With the bird, as with the mammal, a basilar membrane traverses the cochlea; it carries sensitive hair cells with nerve fibres running to the auditory nerve and hence to the brain. The hair cells are covered by a tectorial membrane and have a far greater concentration per unit area of membrane than those of the mammalian cochlea.”
Funny thing… in the Choiniere et al. text, there is no mention of the lagena, which they emphasize in the publicity. Rather the authors discuss the elongation of the cochlear duct, the part devoted to sound reception and conversion to nerve impulses.
Figure 4. Shuvuuia and Mononykus to scale in various poses. The odd digit 1 forelimb claws appear to be retained for clasping medial cylinders, like tree trunks. The forelimb is very strong. Perhaps these taxa rest vertically and run horizontally.
Choiniere was quoted in Phys.org “Nocturnal activity, digging ability, and long hind limbs are all features of animals that live in deserts today, but it’s surprising to see them all combined in a single dinosaur species that lived more than 65 million years ago.”
Figure 5. Sharovipteryx reconstructed. Compare proportions to Shuvuuia in figure 4.
The digging ability of Shuvuuia has always been suspect, given its Sharovipteryx-like proportions (Fig. 6), with arms barely deeper than the chest and long, gracile legs better suited to leaping and running.
With regard to the ‘large’ eyes of Shuvuuia — size matters. I’s a tiny taxon with much larger ancestors (Fig. 1). In archosaurs juveniles have proportionately larger eyes than adults. Shuvuuia was phylogenetically miniaturized as an adult, retaining juvenile traits. There’s nothing more to it than that. Surprised this wasn’t brought up among the 13 co-authors. Apparenlty no one was given the assignment to be the Tenth Man.
Headline grabbing? Choinierre et al. wrote: “sensory evolution in birds and their theropod stem lineage is poorly understood [but see, e.g., (6–9)]. This is a substantial shortcoming in our understanding of dinosaurian biology and of the structure of Mesozoic ecosystems.” Did Choinerre shed light on this problem, if it is indeed a problem? Or did they just add to the myth? The words ‘balance’, ‘neotony’ and ‘paedomorphism’ are not mentioned in the text. Sometimes workers get lost in the details and lose the overall perspective, blinding themselves to alternate possibilities.
Artists! Start showing alvarezsaurids riding bareback, clinging to Late Cretaceous Mongolian dinosaur quills and feathers.
PS added 48 hours later: Birds with a similar wide diameter maximum iris diameter, like Apus, the swift, and Struthio, the ostrich, are apparently active day and night. In these taxa the iris itself must be highly variable to adapt to changes in lighting. That puts a whole new spin on dinosaurs. These facts were not highlighted on the authors’ chart, nor were their stories told. Like them, maybe Shuvuuia stayed awake night and day (not scratch digging!) clinging to mothership dinosaurs loaded with insect prey.
References Choiniere JN et al. (+12 co-authors) 2021. Evolution of vision and hearing modalities in theropod dinosaurs Science 372 (6542): 610-613 DOI: 10.1126/science.abe7941
I misunderstood Tristychius earlier, and so did other workers who considered this odd shark a hybodontid. Those large dorsal spines (Fig. 2) turn out to be not so important phylogenetically. They are not a ‘key’ trait. After analysis (Fig. 6), Tristychius dorsal spines turn out to be only convergent with those of hybodontid and other ‘spiny’ sharks.
Figure 1. Tristychius skull from Coates et al. 2019 with new identities assigned based on tetrapod homolog colors. Note what appears to be the orbit does not tightly enclose the eyeball. Rather phylogenetic bracketing indicates the eyeball was on a long optic nerve, as in the whale shark, Rhincodon (Fig. 3).
For too long Tristychius was a bad fit in the LRT. In the LRT bad fit = bad scores. When I finally put the skull of Tristychius together with that of Rhincodon, the whale shark (Fig. 3), I understood things that had escaped me previously. For instance, prior to this weekend I had no idea a small eyeball could lie far outside what looked like the orbit, supported by long optic muscles and a long optic nerve (Fig. 3).
Figure 2. Tristychius, a basal shark from the Early Carboniferous. Despite the large dorsal spines, this taxon nests closer to Rhincodon, the whale shark, in the LRT. Note the mistaken underslung jaws of this reconstruction.
In 1978 JRF Dick described Tristychius (Fig. 2), a shark known from Early Carboniferous iron nodule concretions.
From the Dick 1978 abstract: “Tristychius arcuatus sensu stricto is a medium-sized hybodont shark with a short gape, a functionally heterocercal tail and narrow-based, tribasal pectoral fins. Its most unusual feature is a well developed opercular gill cover composed of long hyoid rays. Evidence suggests that this character was present in several Palaeozoic sharks, although it is absent in all Recent elasmobranchs. It is not clear whether it was primitively present in chondrichthyans or evolved separately in several lineages.”
Coates et al. 2019 disagreed with Dick 1978 about those opercular gill covers. Coates et al. 2019, wrote, “The hyoid rays are well preserved but, in contrast with previous reconstructions (Dick 1978), are much too short to form an opercular flap.”Sister taxa in the LRT do not have opercular gill covers composed of long hyoid rays… BUT only one node apart, ancestral taxa also with jaws lacking teeth (Chondrosteus and Stronglyosteus) and sturgeons do have opercular gill covers. We talked about gill covers and sharks earlier here.
In 1978 Dick was unable to use software to perform a phylogenetic analysis. So he did what everyone did back then, he made a judgement call based on a few traits (= “Pulling a Larry Martin“).
From the Dick 1978 abstract (continued): “Hybodonts and ctenacanths are recognised as separate, specialised shark radiations, neither of which can be directly ancestral to Recent sharks. Of the two, hybodonts appear to be more closely related to Recent forms, although the presence of typical hybodont finspines in Tristychius arcuatus indicates that they had diverged from ancestral euselachians before the beginning of the Carboniferous.”
In the LRT hybodonts are basal to bony fish (= recent forms). Tristychius is close to extant whale sharks.
More recently,Coates et al. 2019 considering Tristychius a suction feeder 50 million years before the bony fish equivalent. The authors also report, “The labial cartilages are large and comparable to examples known in Mesozoic hybodontids and modern suction feeding elasmobranchs such as nurse sharks (genus Ginglymostoma).”(see short video above).
The question of suction feeding depends on two things: 1) how fast the mouth opens and closes, and 2) whether or not the mouth cavity is capable of expanding rapidly to produce the inrush of water. Nurse sharks have perfected this technique (see video above). Whale sharks are more primitive. They simply open their mouths and engulf without a rapid inrush. So which type of feeding to Tristychius employ? Phylogenetic bracketing should tell us. Coates et al. did not mention either Rhincodon or Loganeillia, but did mention Ginglystoma, the nurse shark.
Figure 3. Comparative anatomy: Rhincodon on left and Ginglymostoma on right. Compare both to Tristiychius in figure 1, which has larger labial cartilages, a smaller lacrimal and jaws similar in length, like the whale shark.
In the LRT Tristychius is more closely related to whale sharks than nurse sharks (Fig. 5), so we are free to consider Tristychius as more passive, open-mouth feeder than a quick suction feeder. Coates should have included more comparative taxa after a valid phylogenetic analysis, and not just cherry-pick a favorite or two.
Figure 4. The whale shark, Rhincodon, slowly opens its gaping mouth, the opposite of the nurse shark, Ginglymostoma, the vacuum cleaner in the video above.
Tristychius arcuatus (Agassiz 1837; Dick 1978; Coates et al. 2019; Early Carboniferous; 24 cm est based on the skull in figure 1, 60cm max est.) was considered a Hybodus relative, but here nests with the whale shark, Rhincodon (Figs. 3, 4). Tristychius has a shorter torso, large pectoral and pelvic fins and large dorsal spines. Like the whale shark and similar basal sharks (like the nurse shark, the manta, etc.) the nares point anteriorly, slightly ventrally. Teeth are nearly absent with only a few, no longer than a millimeter, present. The postfrontal is strongly developed here, as in the whale shark. Note the large anterior gill bars (= labial cartilages in red) that restrict jaw depression and create lateral walls for the open jaws. The hyomandibular is tall and slender in Tristychius and the parietal is split medially, traits distinct from Rhincodon. The ceratohyal has less of a lateral exposure here than in the whale shark or nurse shark.
Figure 5. New tracing of Longanellia. This is a Rhincodon and Tristychius ancestor from the Early Silurian. The transition from micro scales to micro teeth around the jaw margins had its genesis with this taxon.
Coates et al. 2019 reported, “The jaws of Tristychius (Fig. 2, A to C, G, and I) differ in numerous respects from the standard jaw morphology found in most Paleozoic chondrichthyans.” That’s the sort of clue that should have made Coates et al. expand their taxon list.
Examination indicated by phylogenetic bracketing reveals that Early Silurian Loganellia (Fig. 5) is the basalmost taxon with labial cartilages, reducing the gape of its jaws while providing shark cheeks. If Loganellia were suction feeding in the Early Silurian, then Chondrosteus-types (Fig. 7) were suction-feeding in the Ordovician. So that sets the clock back on the shark-sucking hypothesis of Coates et al. (regarding Early Carboniferous Tristychius) another 180 million years.
Figure 6. Newly revised subset of the LRT focusing on basal vertebrates. Here Tristychius nests with Rhincodon as t basal position on the shark family tree, nowhere near Hybodus.
Coates et al. estimated the oral volume changes of Tristychius through the bite cycle, but did not make comparisons to the voluminous oral cavity of Rhincodon. Coates et al. did not provide a phylogenetic analysis because their paper focused on functional morphology. Even so, an analysis is always called for. Otherwise you’ll be comparing whale sharks to hybodontids.
Figure 7. Chondrosteus is a late survivor of an earlier radiation that also fed by suction, extending the jaws while depressing the ceratohyal (gray shape) to expand the oral cavity. This, in turn, improves on the similar method of feeding in sturgeons.
Given the nature of sister taxa, Tristychius was more likely a planktonic filter feeder with a slow-moving jaw opening mechanism. Fast opening and biting jaws first appeared in the vertebrate recored n the very next clade in the LRT (Fig. 6), currently occupied by the nurse shark, Ginglymostoma (Fig. 3), a traditional relative of whale sharks, which it greatly resembles.
References Agassiz L 1837. Recherches Sur Les Poissons Fossiles. Tome III (livr. 8-9). Imprimérie de Petitpierre, Neuchatel viii-72. Coates MI, Tietjen K, Olsen AM and Finarelli JA 2019. High-performance suction feeding in an early elasmobranch. Science Advances 5 (9): eaax2742 Dick JRF 1978. On the carboniferous shark Tristychius arcuatus Agassiz from Scotland. Earth and Environmental Sciences Transactions of the Royal Society, Edinburgh. 70: 63–108.
This is becoming a repeating pattern. Taxon exclusion mars an otherwise wonderful detailed study of Triassic dinosaur interrelations.
From the Novas et al. 2021 abstract: “Triassic beds from Argentina and Brazil provide the most relevant fossil record of early dinosauriforms in terms of numerical abundance and taxonomic diversity.”
Correction: When more taxa are added, as in the large reptile tree (LRT, 1839+ taxa) Crocodylomorpha is the outgroup for the Dinosauria (Fig. 1). These two clades combine to create the clade Archosauria. Therefore there will never be such thing as a dinosauriform, except herrerasaurids, which are outside the Passer + Triceratops definition.
“This record currently represents the best source to understand the origin and early evolutionary radiation of dinosaurs.”
That’s true. And by the way, some of the best basal bipedal crocodylomorphs (e.g. Pseudhesperosuchus, Fig. 1) are also from South America. They were omitted from Novas et al. 2021… AND their last common ancestor, the phylogenetically miniaturized PVL 4597 specimen (Fig. 1) wrongly attributed to Gracilisuchus(Fig. 1), is also from South America.
Figure 1. The origin of dinosaurs in the LRT to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor. Note the phylogenetic miniaturization at the origin of Archosauria (Crocs + Dinos).
The abstract continues: “In the present paper we offer an updated review focused on the available evidence of Carnian dinosaurs from this continent, but we also discuss the record of Triassic dinosaur precursors and the evolution of Triassic dinosaurs in other continents.”
Unfortunately Novas et al. delete the valid proximal Triassic dinosaur precursors. By putting herbivorous silesaurids basal to dinosaurs, herbivorous ornithischians were attracted to the base of the Dinosauria. Now we have a problem. An herbivorous clade precedes carnivorous basal dinosaurs (= herrerasaurids). In the LRT once some dinosaurs became herbivorous, they stayed herbivorous while carnivorous basal dinos arose from carnivorous bipedal crocs.
“It is clear that, aside the agreed taxonomic composition of some particular dinosaurian subclades (e.g., Herrerasauridae, Neotheropoda), there is no consensus about early dinosaur phylogeny, and our paper is not the exception.”
Why is there no consensus? Because all prior workers also omitted basal bipedal crocs.
“Recent years witnessed the discovery of several new early dinosaurian taxa, as well as reviews of the taxonomic allocation of several renowned forms such as Lagerpeton, Lewisuchus, Pisanosaurus, and Eorpator. New analyses demonstrate that evidence supporting the taxonomic referrals of pre-Norian dinosaurs to Theropoda, Sauropodomorpha and Ornithischia are tenuous, at best.”
Why tenuous at best? Because all prior workers also omitted basal bipedal crocs.
“Here we present new anatomical observations and comparisons for each of these South American early dinosauriforms with the aim to test previous phylogenetic interpretations.”
Their testing was flawed by taxon exclusion as Novas et al. omit basal bipedal crocs.
Figure 2. Cladogram from Novas et al. 2021 omits members of Crocodylomorpha, the outgroup for the Dinosauria in the LRT. Instead Novas et al. nest herbivorous Silesauridae outside the Dinosaria, which mistakenly attracts herbivorous dinosaurs to the base of the clade.
The abstract continues: “Evidence from South America allows reviewing the phylogenetic relationships of taxa from other continents, including Tawa, Chindesaurus, and Daemonosaurus, which are here suggested to nest within Herrerasauria.”
“Here suggested”??? Let’s do better than that. In the LRTTawa (Fig. 1) is THE basal theropod. Daemonosaurus is a basal member of the Ornithischia, a clade within Phytodinosauria (= Ornithischia + Sauropodomorpha and their ancestors, includng Eoraptor, Fig. 1). Novas et al. fail to find these relationships due to including Silesauridae (herviorous derived members of the dinosaur mimic clade, Poposauridae) as the dinosaur outgroup due to excluding carnivorous basal bipedal crocs. Two basal members of the Poposauridae, the dinosaur mimics Turfanosuchus and Poposaurus, were also omitted from Novas et al.
“Evidence at hand indicates that herrerasaurs were a successful clade of archaic predatory saurischians that inhabited both South and North America, and probably also India and Europe.”
This is true. So, why do workers continue to omit basal bipedal crocodylomrophs, the most similar taxa to Herrerasaurus (Fig. 1) and basal bipedal dinosaurs? I wonder, too.
Don’t waste your time and your readers’ time with detailed studies of any clade or taxon without first setting the stage within a valid phylogenetic context. It never hurts to add taxa. It always hurts to omit taxa. And once you have it, you can use it forever with authority, updating it whenever you please. Cherry-picking taxa is something you can say you did when you were young and foolish.
References Novas FE, Agnolin FL, Ezucrra MD, Müller RT, Martinelli A and Langer M 2021. Review of the fossil record of early dinosaurs from South America, and its phylogenetic implications. Journal of South American Earth Sciences xxx (xxxx) 103341.
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.
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.
Summary for those in a hurry: Three PhDs cherry-pick taxa, “Pull a Larry Martin” by cherry-picking a convergent neck trait, omit dozens of taxa that separate protorosaurs (pre-archosaurs) from tanystropheids (lepidosaurs), and omit several small tanystropheids that learned how to flap, then fly because the authors thought the details too confusing to deal with.
Spiekman SNF, Fraser NC and Scheyer TM 2021 propose a “new phylogenetic hypothesis of Tanystropheidae”. It’s not new. So, others call this headline-grabbing.
From the abstract: “The historical clade “Protorosauria” represents an important group of archosauromorph reptiles that had a wide geographic distribution between the Late Permian and Late Triassic.”
Simply adding taxa, as in the large reptile tree (LRT, 1839+ taxa) separates members of the Protorosauria that do indeed nest within the new Archosauromorpha (e.g. Protorosaurus, Prolacerta, Ozmik) from convergent tanystropheids that nest within the new Lepidosauromorpha. This was presented in Peters 2007, uncited in the Spiekman et al. paper.
“Protorosaurs” are characterized by their long necks, which are epitomized in the genus Tanystropheus and in Dinocephalosaurus orientalis. “
Three PhDs are here caught “Pulling a Larry Martin”. Dr. Martin would have had a good chuckle at this short-sighted blunder. As we learned many times earlier, never-ever cherry-pick a trait like this. You don’t know if it is convergent (as it is in this case) with unrelated taxa without the benefit of a phylogenetic analysis.
“Recent phylogenetic analyses have indicated that “Protorosauria” is a polyphyletic clade, but the exact relationships of the various “protorosaur” taxa within the archosauromorph lineage is currently uncertain.”
That’s a clue that their taxon list is incomplete.
“Several taxa, although represented by relatively complete material, have previously not been assessed phylogenetically.”
If so… good! However, not only did these three authors add unrelated taxa, they omitted ingroup taxa. So ignore this Spiekman et al. paper and wait for a valid phylogenetic analysis that includes all ingroup taxa and no outgroup taxa.
“We present a new phylogenetic hypothesis that comprises a wide range of archosauromorphs, including the most exhaustive sample of “protorosaurs” to date and several “protorosaur” taxa from the eastern Tethys margin that have not been included in any previous analysis.”
This is false. The LRT represents the most exhaustive sample of protorosaurs and tanystropheids to date. The authors do not realize that tanystropheids are lepidosaurs when appropriate taxa are added. Both analyses, you should note, were published online.
“The polyphyly of “Protorosauria” is confirmed and therefore we suggest the usage of this term should be abandoned.”
By contrast, in the LRT the Protorosauria is a monophyletic clade (Fig. 1). Tanystropheidae is also monophyletic, but nests elsewhere (Fig. 2). These PhDs did not do enough work to see that their cherry-picked taxa had convergent traits. Let a wide-gamut family tree, like the LRT, choose your taxon list. Do not cherry-pick taxa that ‘look like they belong. Do not let textbooks tell you cretain taxa belong together. Find out for yourself. Don’t be lazy.
Figure 1. Two unrelated clades from the LRT. Compare to figure 2 from the Spiekman et al. paper.
From the abstract (continued): “Tanystropheidae is recovered as a monophyletic group and the Chinese taxa Dinocephalosaurus orientalis and Pectodens zhenyuensis form a new archosauromorph clade, Dinocephalosauridae, which is closely related to Tanystropheidae.”
Figure 2. Cladogram from Spiekman et al. 2021(above). Colors added to show how many clades were mixed together during the cherry-picking process.
From the abstract (continued): “The well-known crocopod and former “protorosaur” Prolacerta broomi is considerably less closely related to Archosauriformes than was previously considered.”
In the LRT,Prolacerta is a basal protorosaur. Just add taxa. Don’t cherry-pick to your own biases. And that concludes the abstract.
Unfortunately these authors omitted so many pertinent taxa that they nested tanystropheids within Archosauromorpha, rather than Lepidosauromorpha (Peters 2007). They also omitted the tanystropheids, Cosesaurus, Sharovipteryx, Longisquama and the clade Pterosauria (Fig. 3). Their motivation: keep the academic status quo.
Historically a jumbled roadkill specimen of Tanystropheus was first named Tribelesodon because the long neck bones were originally considered wing phalanges and the pedal morphology and trident teeth were nearly identical to those of basal pterosaurs. That’s a clue!
At least Spiekman et al. cited Peters 2000 and 2005. Other peer-reviewed academic publications on this subject by Peters were omitted (see below). What Spiekman et al. said about the small bipedal taxa featured in those pubs (Fig. 3) sheds light on this subject (see below).
Figure 3. Squamates, tritosaurs and fenestrasaurs in the phylogenetic lineage preceding the origin of the Pterosauria.
From Spiekman et al. 2021: “Cosesaurus aviceps is known from a single specimen, which represents an impression of a complete skeleton. As such, the outline of the specimen is well-preserved, but the detailed morphology of the taxon is very poorly known.”
This is false. I encourage readers to click this Cosesaurus page link to see the wealth of detail captured in this holotype fossil. Better to ‘show’ than ‘tell’.
“Due to the lack of morphological information, the phylogenetic affinities of Cosesaurus aviceps are unclear.”
This is an excuse not to visit the fossil or to cite online data.
“Previous analyses by Peters (2000), which has been widely criticized (e.g., Hone & Benton, 2007), it was concluded that Pterosauria are a derived lineage within “Prolacertiformes”.
Spiekman et al. apparently never read Hone & Benton 2007, 2009, in which Hone and Benton mis-scored data and upon learning that Cosesaurus was igoing to appear as a pterosaur ancestor in their supertree (as opposed to professor Benton’s personal favorite, the crocodilomorph with tiny fingers, Scleromochlus, Hone and Benton 2009 dropped all reference to Peters 2000 and gave credit to Bennett for the Peters 2000 hypothesis. Not sure why others haven’t jumped on this scandal (see below for link) other than to preserve the academic status quo and keep the origin of pterosaurs ‘an enigma’.
“This was largely based on several morphological characters observed in Cosesaurus aviceps, as well as the poorly known, gracile reptiles Sharovipteryx mirabilis and Longisquama insignis (Peters, 2000).”
This is false. Those two taxa are so well preserved that soft tissue is readily apparent, as everyone knows. Link to Sharovipteryxhere. Link to Longisquamahere. Link to a ResearchGate.net manuscript on these taxa here.
“Although Cosesaurus aviceps might represent a “protorosaur”, the lack of morphological information does not allow this taxon to be reliably incorporated in phylogenetic analyses, and recent phylogenetic investigations into archosauromorph or “protorosaurian” affinities did not consider this taxon.”
This is how academics avoid a subject. No one wants to do the work or be accused of helping an amateur who somehow got this ‘discovery’ published.
“Peters (2000) used the matrices of Evans (1988), Jalil (1997), and Bennett (1996) and reran each of them after adding a number of characters and rescoring some characters for certain taxa, for a total taxon sample that included 11 “protorosaurs”, other non-archosauriform archosauromorphs, the pterosaur Eudimorphodon, and two enigmatic and possibly gliding diapsids, Longisquama insignis (Sharov, 1970) and Sharovipteryx mirabilis (Cowen, 1981; Sharov, 1971).”
This is true. This hopefully shows that Peters 2000 followed the scientific method by personally examining the specimens, employing previously published cladograms and simply adding taxa. But keep reading. That’s not going to be good enough.
“Sharovipteryx is an enigmatic gliding reptile with a membrane stretched between the hindlimbs, which represents an entirely unique morphology among gliding reptiles.”
Gliding is a traditional assumption. Probably a mistake. What Spiekman et al. fail to note is Sharovipteryx was an obligate biped with a longer tibia than femur, indicating cursorial abilities. Again, don’t you think these three PhDs should have examined the specimens firsthand, instead of parroting traditional literature?
“Its phylogenetic position is highly uncertain due to its highly specialized, yet very poorly known morphology.
This is false, as noted above. Even though it was tested three times by Peters 2000, Sharovipteryx still does not enter the Spiekman et al. cladogram. Trying to avoid a trip to Moscow, the authors considered ‘these grapes are probably sour.”
“Peters (2000) found “protorosaurs”, and Longisquama and Sharovipteryx, to be very closely associated with Eudimorphodon, from which a “protorosaurian” ancestry for pterosaurs was concluded. However, the exact topologies varied strongly between the different analyses, and this hypothesis of pterosaur ancestry has widely been rejected by other phylogenetic studies on pterosaurs and early archosaurs (e.g., Ezcurra, 2016; Ezcurra et al., 2020; Hone & Benton, 2007; Nesbitt, 2011; Padian, 1997).”
Wait a minute! Padian 1997 can’t reject Peters 2000! The other authors listed in the paragraph above also cited Hone and Benton 2007, 2009 (it was a two-part study) and that’s why they reject Peters 2000. Not because they looked at the specimens and added them to their analyses. They didn’t want to do the decade of work shown in the LRT and visit the specimens firsthand.
“The datasets of Benton & Allen (1997), Dilkes (1998), and Jalil (1997) were combined into one larger character list of 239 characters by Rieppel, Fraser & Nosotti (2003), which was used specifically to address “protorosaur” phylogeny, and in particular the question of “protorosaur” monophyly, which had now been put in doubt (Dilkes, 1998). This approach included seven “protorosaur” taxa (Protorosaurus, Drepanosaurus, Megalancosaurus, Prolacerta, Macrocnemus, Langobardisaurus, and Tanystropheus longobardicus), and four outgroup taxa (Petrolacosaurus, Youngina, Rhynchosaurus, and Trilophosaurus).”
Readers… now do you recognize when PhDs cherry-pick taxa to their own biases? And note: Rieppel, Fraser and Nosotti (2003) omitted adding the taxa published in Peters 2000? Why not just add them to test them? (Note: co-author Fraser is also a co-author of the present work under discussion, Spiekman et al. 2021.)
“Additional analyses were performed after subsequently including Euparkeria and Proterosuchus, and the lesser known “protorosaurs” Boreopricea and Jesairosaurus. Although the first analysis found a monophyletic “Protorosauria”, the other two resulted in paraphyly for the group. Although Rieppel, Fraser & Nosotti (2003) concluded that the monophyly of “Protorosauria” as previously regarded (e.g., Benton & Allen, 1997; Jalil, 1997) could not be maintained, they argued the need for an extensive phylogenetic investigation into “protorosaurs”.
That has been provided for all to see, test, confirm or refute in the LRT.
“Senter (2004) investigated the phylogenetic position of drepanosaurids in an analysis that comprised “protorosaurs” (Prolacerta, Macrocnemus, and Langobardisaurus), Longisquama, non-archosaurian Archosauriformes, birds, a non-avian dinosaur, and a number of early diapsids. This study found drepanosaurids to form a clade with Longisquama and Coelurosauravus, which was termed “Avicephala”, as the sister group to Neodiapsida, which in his analysis encompassed Youngina, the rhynchocephalian Gephyrosaurus, and several archosauromorphs. The included “protorosaurs” formed a monophyletic clade within Archosauromorpha.”
To be fair, Senter 2004 was publishing his PhD dissertation in 2004. It suffered from cursory examination of the specimens (or photos of the specimens) in which Senter could only pick out a few elements and many of those were misidentified.
“However, an analysis using the same character list by Renesto & Binelli (2006) could not reproduce the same topology.”
To be fair, you need the same taxon list to reproduce the same topology. Cladograms lump and separate taxa, not characters.
“Renesto et al. (2010) reaffirmed the position of drepanosaurids among “protorosaurs”, whereas Pritchard & Nesbitt (2017) recovered Drepanosauromorpha as a separate clade of non-saurian diapsids.”
These workers did not employ enough taxa to know that the diapsid skull morphology is convergent, with one clade appearing in the Archosauromorpha and another in the Lepidosauromorpha. Spiekman et al. are also in the dark with regard to diapsid monophyly.
“Müller (2004) included four different “protorosaur” taxa in his broad-scale analysis of diapsid relationships, which consisted of 184 characters compiled mainly from Rieppel, Mazin & Tchernov (1999) and DeBraga & Rieppel (1997). This study also inferred a polyphyletic “Protorosauria”, with Tanystropheus, Macrocnemus, and Prolacerta being successive sister taxa to rhynchosaurs and Trilophosaurus, whereas drepanosaurids were only quite distantly related to these taxa.”
Taxon exclusion is once again the problem here.
In summary, don’t cherry-pick taxa, like these PhDs did. Let your wide-gamut cladogram choose your clades for you. Don’t trust anyone, even me. Test everything for yourself. I hope everyone was able to pick up a few clues as to how to avoid ‘believing’ certain cherry-picked citations. See how they accumulate? If you know Spiekman, Fraser or Scheyer, send them this link. They should know that what they produced was unprofessional and misleading.
References Peters D 2000. A reexamination of four Prolacertiformes with implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106:293–336 DOI 10.13130/2039-4942/6148. Peters D 2005. Suction feeding in a Triassic protorosaur? Science 308(5725):1112c–1113c DOI 10.1126/science.308.5725.1112c. Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27. Spiekman SNF, Fraser NC and Scheyer TM 2021. A new phylogenetic hypothesis of Tanystropheidae (Diapsida, Archosauromorpha) and other “protorosaurs”, and its implications for the early evolution of stem archosaurs. PeerJ 9:e11143 DOI 10.7717/peerj.11143
Daliatias licha (Bonnaterre 1788, Rafinesque 1810; 1 to 1.8ml Fig. 1) is the extant kite fin shark. This slow-moving sea floor skimmer is the largest luminous vertebrate.
Here, in the large reptile tree (1839+ taxa, subset Fig. 3), this solitary predator nests with the cookie cutter shark, Isistius(Fig. 2), another deep sea luminous vertebrate.
The jaws of the kitefin shark do not extend to produce suction as in the cookie-cutter shark. In the kitefin shark the gill openings extend both above and below the pectoral fin (Fig. 1). The large labial cartilages restrict jaw depression and create lateral walls for the open jaws.
Figure 1. Daliatias overall and in detail.
Given the phylogenetic nesting of Isistius and Daliatias, (Fig. 4) these taxa are surprisingly close to the lineages of sharks that gave rise to bony fish and thereafter to tetrapods and ultimately humans. Since those actual bony fish ancestors would have lived during the Silurian, we can safely assume that Silurian ancestors of Isistius and Daliatias were more plesiomorphic in appearance with smaller teeth and less specialized jaws.
Figure 2. Isistius brasiliensis in several views.
Isistius brasiliensis (Quoy and Gaimard 1824; Fig. 2) is the extant cookiecutter shark, a living sister to Daliastias (Fig. 1). This deep-water shark has light-emiting photophores covering its underside. It migrates to the surface every day to take a circular bite out of larger vertebrates, like whales and sharks. In this way it can be seen as a sort of lamprey-mimic. Isistius also consumes smaller free-swimming prey, like squid. Note the anterior nostrils and larger dentary teeth.
Figure 3. The mako shark, Isurus, had little to no labial cartilages. It nests basal to the kitefin and cookie cutter sharks in the LRT, skipping the long rostrum taxa of sawfish, guitarfish, etc.
The mako shark, Isurus (Fig. 3), is ancestral to the kitefin and cookie cutter sharks. The teeth are smaller, the rostrum is longer, the fins are all larger in this open sea fast predator, distinct from its more plesiomorphic and currently unknown Silurian ancestors resembling the nurse shark, Ginglymostoma, which is among the most basal vertebrates with marginal teeth.
Figure 4. Subset of the LRT focusing on cartilaginous fish. There are several changes here from prior tree topologies, but sharks still arise from sturgeons and give rise to bony fish. So this is a grade, not a monophyletic clade.
The present subset of the LRT (Fig. 4) represents changes made over the weekend after a continuing review of sharks and other basal chordates. Readers are watching this experiment in real time, with changes appearing whenever new light is shed on hypothetical interrelationships. Thank you for your patience and understanding. I’m learning as I go.
References Bonaterre PJ 1788. Tableau encyclopédique et méthodique des trois regnes de la nature. Quoy JRC and Gaimard JP 1824–1825. des Poissons. Chapter IX”. In de Freycinet, L (ed.). Voyage autour du Monde…exécuté sur les corvettes de L. M. “L’Uranie” et “La Physicienne, pendant les années 1817, 1818, 1819 et 1820. Paris 192–401. Rafinesque CS 1810. Caratteri di alcuni nuovi generi e nuove specie di animali e piante della sicilia, con varie osservazioni sopra i medisimi. Per le stampe di Sanfilippo: Palermo, Italy. pp. 105, 20 fold. Pl., online
One of the wierdest fish ever, EVER, EVER, was Drepanolepis (Figs. 1, 2). Wikipedia says very little about this taxon, other than to say it is “a thelodont.”
Figure 1. Drepanolepis, traced from Wilson and Caldwell 1998, has a ventral oral cavity and nests with Birkenia in the LRT.
By contrast, in the large reptile tree (LRT, 1839+ taxa; subset Fig. 3) Drepanolepis is not related to Early SilurianThelodus (a sturgeon ancestor), but to Jaymoytius, Birkenia and Euphanerops(Fig. 2). So, Drepanolepis is not a thelodont, despite having similar distinctive scales.
Turns out this taxon is best studied by direct examination AND by comparative anatomy. Until now, outgroup taxa were either not known or mistaken.
We first looked at the fork-tailed fish, Drepanolepis, and re-interpreted the location of the circular lancelet-like oral cavity (not quite a mouth) a year ago here. At that time Drepanolepis nested only withBirkenia (Fig. 2). Now two other taxa join this clade (Fig. 3).
Jamoytius – Early Silurian Birkenia – Middle Silurian Euphanerops – Late Devonian (late survivor from an earlier radiation) Drepanolepis – Early Devonian
Figure 2. Two drepanolepiids and ancestors back to Jamoytius, shown to scale and actual size if viewed on a 72 dpi monitor.
One key to understanding this clade is to remember that the lancelet-like oral cavity opened ventrally, rather than anteriorly as first imagined by Wilson and Caldwell (1993, 1998). That makes them all bottom feeders on microscopic prey.
Another key to understanding this clade is to remember that drepanolepid ancestors had a hypocercal tail with fringes on top (Fig. 1). The top-most fringe of a taxon like Euphanerops (Fig. 1) continued to grow (phylogenetically) until it matched the lower fleshy portion of the tail in Furcacauda (Fig. 2), the portion that always and forever included a notochord.
Figure 3. Subset of the LRT focusing on basal chordates including Drepanolepis (above) and a thelodont, below. The former is tall and narrow. The latter is low and flat and basal to later vertebrate taxa. All these taxa precede the Gnathostomata (Chondrosteus is the last common ancestor).
All these taxa have a sharp little rostrum, a pair of eyeballs, a precursor anal fin, patches that will someday become skull bones and a ventral gill basket with a series of tiny circular gill openings.
All these taxa lack paired nares, paired pectoral fins, paired pelvic fins, dorsal fins, teeth and jaws.
Drepanolepis maerssae (Wilson and Caldwell 1993, 1998; Early Devonian; 2cm in length) is a traditional thelodont and a member of the Furcacaudiformes (forked tails). Drepanolepis is derived from Jamoytius, Birkenia and Euphanerops (Fig. 2), but with a smaller, taller, shorter, angelfish-like body. These taxa have a ventral ‘mouth’ and a hypocercal tail, somewhat elaborated in Euphanerops and more so in Drepanolepis. The gill atrium remains quite large and the nasal extends from the orbit down to the oral cavity.
References Traquair RH 1898. Report on fossils fishes. Summary of Progress of the Geological Survey of the United Kingdom for 1897: 72-76. Wilson MVH and Caldwell MW 1993. New Silurian and Devonian fork-tailed ‘thelodonts’ are jawless vertebrates with stomachs and deep bodies. Nature. 361 (6411): 442–444. Wilson MVH and Caldwell MW 1998. The Furcacaudiformes, a new order of jawless vertebrates with thelodont scales, based on articulated Silurian and Devonian fossils from northern Canada. Journal of Vertebrate Paleontology 18 (1): 10-29.
From the Roston and Roth 2021 abstract: “Anatomical and functional differences between the two cetacean sub-orders, echolocating whales (odontocetes) and baleen whales (mysticetes), suggest that NP reorientation may be the result of convergent or parallel evolution rather than homology. Our findings add evidence suggesting that NP reorientation evolved twice within Cetacea and lay a foundation for future syntheses of data from fossils and other species.”
You heard it herefirst in 2016: ‘Whales’ are diphyletic with separate ancestries for odontocetes and mysticetes among terrestrial taxa (Figs. 1, 2). A more recent post about whales (with comments) can be found here.
Phys.org/news (link below) wrote: “The two major types of cetaceans appear to have evolved their characteristic blowholes through different anatomical transformations, according to a study being presented at the American Association for Anatomy annual meeting during the Experimental Biology (EB) 2021 meeting, held virtually April 27-30.“
“The main difference we observed is in how the nostrils reach this position during prenatal development—there does not seem to be one way to do it,” said Rachel Roston, Ph.D., a postdoctoral fellow at the University of Washington and the study’s lead author. “The dolphin species and other toothed whales showed backwards bending of the skull, whereas the fin whale and other baleen whales showed changes in the occipital bone at the back of the skull.”
“Researchers have previously studied other differences in the nasal passages of the two types of cetaceans; for instance, toothed whales have a single nostril whereas baleen whales have two. By focusing on the part of the skull that connects the nasal passage and the rest of the body, the new study examines previously unexplored territory at the intersection of nasal passage orientation and head-body alignment.”
Simply add pertinent taxa to your favorite cladogram that includes mysticetes and odontocetes and you will recover a diphyletic cetacea, too!
Figure 1. Subset of the LRT focusing on the odontocetes and their ancestors.
Figure 2. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT
Traditionally the flying gurnard, Dactylopterus (Fig. 1), nests with sea horses and pipefish, even though, with those giant pectoral fins and free ‘fingers’ it looks more like the sea robin, Prionotus. This was one of those difficult-to-understand taxa, until it suddenly made sense.
Figure 1. Dactylopterus skull with colors added to match tetrapod taxa.
At last and finally, toothless Dactylopterus nests with a very toothy basal ray fin fish, Calamopterus (Figs. 2-4).
Figure 2. Skull of Calamopleurus updated with new colors.
Figure 3. Calamopleurus skull from a different view.
Dactylopterus volitans (Linneaus 1758; 50 cm; Fig. 1) is the extant flying gurnard, a bottom-feeder living in warm shallow seas. Typically Dactylopterus is allied with long-snouted pipefish and seahorses. Here it nests much earlier, with Calamopterus (Figs. 2-4). Note the remnant of the heterocercal tail (Fig. 5), a primitive trait. Like its tooth sister, Calamopterus, the skull of Dactylopterus has a wide and slightly concave box shape in cross section. The mouth is horizontal. The nares are vertical on the anterior corners of the skull created by robust prefrontals. Distinct from its sister, the teeth of Dactylopterus are tiny to absent.
Figure 4. Calamopleurus overall. The pectoral fin is not a wing yet, as in Dactylopterus, figure 1.
When startled the butterfly-like pectoral fins spread wide as the undulating tail pushes the fish away from danger. The tabulars are quite large and extend like a dorsal shield. The pelvic fins are below the giant pectoral fins, convergent with more derived fish. The anterior pectoral fin spines are separate from the large fan and are more mobile, like sea robin (Prionotus) ‘fingers’, but webbed.
Figure 3. The heterocercal tail bones of Dactylopterus reflect their ancient ancestry. This was predicted, sought and found online yesterday.
Calamopleurus cylindricus (Agassiz 1841, Early Cretaceous; 25cm) is a relative of Amia, the bowfin and basal to the cave and electric eels. Many fossil specimens are known of this genus.
Once you get these two taxa together, the resemblance is obvious, both overall and in detail. Getting these two together took the addition of another similar fossil taxon, Sauropsis longimanus (Fig. 4), Solnhofen (Late Jurassic fish traditionally allied with Pachycormiformes. Yes, the species name does mean ‘long hand’, setting the stage for the flying gurnard of the modern era.
Figure 4. Sauropsis longimanus from the Late Jurassic also nests with Calamopleurus and Dactylopterus.
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. Agassiz L 1833-43. Recherches sur les poissons fossiles. Imprimerie de Petitpierre et Prince, Neuchâtel. wiki/Calamopleurus wiki/Flying_gurnard
