This newly discovered (Britz et al. 2016) swamp eel, Monopterus, is also blind.
Figure 1. Monopterus in vivo. Color faded from deep magenta. Note the single ventral gill opening.
As in the related swamp eel, Synbrachus (Fig. 3), Monopterus has no pectoral fins and no pelvic fins. More derived yet, Monopterus also lacks dorsal, anal and caudal fins. Essentially Monopterus has reverted back to resembling a basal chordate, like the lancelet Amphioxus (= Branchostoma, Fig. 4), including the single ventral gill opening.
Figure 2. From Britz et al. 2016. Colors added here. The upper images lack the premaxilla and maxilla, highlighted in yellow and green below.
Monopterus luticolus (Britz et al. 2016; 20 cm in length) is an extant species of swamp eel close to Symbranchus and the first from Africa. Others are from Asia. Note the tiny blind eyes and single ventral gill opening. No fins are present on the adult. In life the color is deep magenta, not the washed out peach-color that results after immersion in preservative.
Britz et al. report, “Several species are known for their burrowing, amphibious life-style and their ability to survive outside of water due to the possession of highly vascularized secondary air-breathing organs accompanied by substantial changes to their vasculatory systems.”
“There is no clear discontinuity in structure between abdominal and caudal vertebrae in synbranchids.”
In other words, lowly Monopterus represents yet another attempt by fish to leave water and adopt a more terrestrial existence, this time without fins or limbs, like a worm. Pretty amazing.
Figure 3. Synbranchus, another swamp eel with a caudal fin operating eyeballs. Note the short premaxilla.
Distinct from Synbranchus (Fig. 3), with its short, transverse premaxilla, in Monopterus (Fig. 2) the premaxilla is quite long and ventral to and separate from the maxilla. This trait is convergent with several related and unrelated fish.
Figure 4. Extant lancelet (genus: Amphioxus) in cross section and lateral view. The gill basket nearly fills an atrium, which intakes water + food, sends the food into the intestine and expels the rest of the water. This taxon also has a single ventral gill opening.
References Britz et al. (4 co-authors) 2016. Monopterus luticolus, a new species of swamp eel from Cameroon (Teleostei: Synbranchidae )Ichthyol. Explor. Freshwaters, Vol. 27, No. 4, pp. 309-323.
No surprises here. Bos taurus (cow + bull = cattle, Linneaus 1758; Figs. 1, 2) nests between Micromeryx (a deer)+ Ovis (a sheep) and Giraffa (a giraffe) in the large reptile tree (LRT, 2045 taxa). All are artiodactyls. All put their weight on the paired unguals (hooves) of digits 3 and 4. None are related to whales.
Figure 1. Bos taurus skeleton in lateral view.
So, phylogenetically speaking, a deer is a type of camel, a sheep is a type of deer, a cow or bull is a type of sheep and a giraffe is a very tall type of cattle. The other artiodactyls, pigs and entelodonts, diverge earlier than camels. Hippos are not artiodactyls.
Figure 2. Skull of Bos taurus. Colors added here. The cranium is robust. The dentary rises anteriorly. The premolars are molarized.
Today’s taxon was suggested by a reader. Thank you!
References Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
First described by Cope 1873, Achaenodon (Fig. 1) is traditionally considered an Eocene artiodactyl. That is incorrect.
Figure 1. Achaenodon skull data.
According to Wikipedia, “The affinities of Achaenodon are unclear: for a long time this animal has been classified among the entelodontids, the so-called “terror pigs” typical of the Oligocene and Miocene; this classification was mainly due to the large size of Achaenodon and the similarities in the particularly massive teeth. In fact, the similarities between Achaenodon and entelodonts were mainly due to evolutionary convergence and the development of characteristics due to the large size.”
Taxon exclusion is once again the problem here. Expand your taxon list to find out where enigma taxa nest. They will nest somewhere. When the gamut is wide enough your taxon will nest more and more and more precisely.
Figure 2. Subset of the LRT focusing on oreodonts through mystcietes. Achaenodon nests in the cyan (bright blue) clade.
After testing in the large reptile tree (LRT, 2044 taxa, subset Fig. 2) Achaenodon nests between hippos and Cambaytherium(Fig. 3), yet another semi-aquatic herbivore in the lineage of mysticetes. Members of this entire clade, from oreodonts, to mesonychids, to hippos to desmostylians to mysticetes have been historically misunderstood and rarely associated with one another. Here (Fig. 2), at last, they lump together and apart from artiodactyls.
When taxa that have never been tested together are at last tested together, they are free to find their most similar sister in wide gamut taxon list without bias or restriction. And sometimes they do. Case in point: all the taxa in figure 2.
Achaenodon robustus is from North America. The cheek bones (jugals) were extremely wide (Fig. 1). Strong jaw muscles filled the large space around the narrow cranium and narrow crests.
Figure 3. Cambaytherium with a an alternate rostrum reversing taphonomic shifts.
Cambaytherium thewissi (Rose et al. 2014; Eocene, 55 mya; 45-75 lbs; Fig. 3) was originally considered a basal perissodactyl, but nests here between Hippopotamus (prior to the addition of Achaenodon) and Janjucetus. The canines and incisors are missing, perhaps absent. The posterior mandible had a long retroarticular process as in Anthracobune. Cambaytherium was found on the marine coastline of island India, close to where pakicetid walking whales and archaeocete swimming whales were convergently evolving from terrestrial tenrec ancestors, as we looked at a few days ago here.
References Cope ED 1873. Fourth notice of extinct Vertebrata from the Bridger and the Green River Tertiaries. Paleontological Bulletin 17:1–4. Rose, KD et al. (8 other authors) 2014. Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India. Nature Communications 5 (5570). doi:10.1038/ncomms6570. Rose KD et al, 2020. Anatomy, Relationships, and Paleobiology of Cambaytherium (Mammalia, Perissodactylamorpha, Anthracobunia) from the lower Eocene of western India, Journal of Vertebrate Paleontology (2020). DOI: 10.1080/02724634.2020.1761370
You would never think that paleontologists would stoop so low as to consider Euparkeria (Fig. 1) in the origin of birds, especially when they had excellent specimens in hand of the feathered theropod, Archaeopteryx, since the 1860s.
But they did.
Figure 1. The phytosaur, Parasuchus, surrounded by putative sisters according to Nesbitt 2011. Euparkeria was more primitive. Eudimorphodon and Ornithosuchus were more derived. Does anyone else see a problem here?? Why was this nesting not widely criticized?
According to Chiappe and Dyke 2006, “The notion that the ancestry of birds is to be found among primitive archosauromorphs can be traced to the discovery of Euparkeria from the Early Triassic of South Africa (Broom, 1913). Nonetheless, it was Heilmann (1926) in his influential book The Origin of Birds, who championed this idea. Central to his argument was the apparent loss of clavicles in theropods.”
At least there was ‘an argument’ in the clavicle-loss hypothesis. Even though that was committing the sin of “Pulling a Larry Martin“, that was at least something workers could use in their arguments.
Nowadays, thankfully, no one uses Euparkeria in bird origin studies. That’s because we know better now. And no one wants to look foolish in the eyes of their peers.
On a similar note…
You would never think that paleontologists would stoop so low as to consider armored Euparkeria (Fig. 1) in the origin of pterosaurs, especially with excellent specimens in hand of the flapping fenestrasaurs, Cosesaurus, Longisquama and Sharovipteryx (Fig. 2). These taxa have prepubes, sternal complexes, antorbital fenestrae, hollow bones, pterosaurian lateral toes, simple hinge ankles, elongated ilia, more than three sacrals, attenuated tails, strap-like scapulae, stem-like and locked down coracoids (for flapping), long manual digit 4s (for flappiing while bipedal) and various extradermal membranes including uropatagia (Peters 2000).
Figure 2. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx.
Nevertheless, many pterosaur workers since 2003 used and continue to use Euparkeria as an outgroup taxon in analytical studies (e.g. Vidovic and Martill 2017). They don’t feel the need to provide an argument to support their choice. They choose to use Euparkeria and refuse to consider competing candidate taxa. That’s a problem perpetuated in university textbooks. Many perosaur workers appear reluctant to leave Euparkeria in the dust. Apparently they prefer that comfort rather than the submit to the peer group discomfort of using (or even testing) fenestrasaur ancestors of pterosaurs (Fig. 2), even though they know that’s their job: to test competing hypotheses.
A recent exception: Ezcurra et al. 2020 created a chimaera from lagerpetid and protorosaur bits and pieces, then called it a pterosaur precursor close to dinosaurs. Euparkeria was not mentioned in the text and no reason was given for its omission.
This example only shows things are getting worse, not better. Workers are still cherry-picking outgroup taxa for dinosaurs and pterosaurs. They are not letting software choose outgroups for pterosaurs and dinosaurs from a wide gamut of candidate taxa. They are purposefully omitting fenestrasaurs even though fenestrasaurs are in the literature. Taxon exclusion continues to be the number one problem in paleontology. And it is self-inflicted.
References Chiappe LM and Dyke GJ 2006. The early evolutionary history of birds. Journal of the Paleontological Society of Korea 22(1):133-–151. Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336. Peters D unpublished.Cosesaurus aviceps, Sharovipteryx mirabilis and Longisquama insignis Reinterpreted. ResearchGate.org PDF Vidovic SU and Martill DM 2017. The taxonomy and phylogeny of Diopecephalus kochi (Wagner, 1837) and ‘Germanodactylus rhamphastinus’ (Wagner, 1851). From: Hone DWE., Witton MP and Martill DM (eds) New Perspectives on Pterosaur Palaeobiology. Geological Society, London, Special Publications, 455, https://doi.org/10.1144/SP455.12
Before the genesis of the LRT whale workers correctly took whale ancestry back to the newly discovered ‘walking whales’, Pakicetus andIndohyus (Figs. 1, 2).
Then, naturally enough, whale workers wanted to know which taxa gave rise to ‘walking whales’. After Gingerich et al. 1994 and 2001 reported that Artiocetus and Rhodhocetus had artiodactyl-like ankles, Thewissen et al. 2007, O’Leary and Gatesy 2008 and Spaulding et al. 2009 added extant artiodactyls (Fig. 2) to their cladograms.
While adding taxa is usually a good idea all three teams cherry-picked irrelevant taxa (Fig. 2) and omitted relevant taxa (Figs. 1, 4). As the LRT documents, sometimes it is better to simply add as many taxa as possible and let the software tell you which taxa are relevant.
Figure 1. Pakicetus and ancestors going back to the elephant shrew, Rhynchocyon and the living tenrecs, Tenrec and Hemicentetes.
By adding previously omitted taxa the large reptile tree (LRT, 2041+ taxa) recovered walking whale ancestors that look much more like pakicetids (Fig. 1). Previously omitted tenrecs and elephant shrews look much more like pakicetids than cattle, pigs or deer do. And these non-artiodactyls have artiodactyl-like ankles.
The LRT also recovered several taxa between Mesonyx and mysticetes (Fig. 4) and… big surprise… they were totally unrelated to pakicetids and odontocetes.
The splitting of the traditional clade ‘Cetacea’ happened here several years ago (October, 2016).
Decades earlier Van Valen 1968 discussed this possibility based on a long list of physical differences. It turns out Van Valen was correct. Myticetes and odontocetes are not related to one another in the LRT. Whale workers still haven’t figured that out. According to university textbooks, and recent manuscript reviews (see below), academics are still attached to dissimilar artiodactyls, none of which show any affinity to swimming or water as a niche environment for finding their food.
Figure 2. From Spaulding et al. 2009 showing three cladograms that mistakenly included artiodactyls as whale ancestors.
Simply adding more taxa moves artiodactyls away from Pakicetus and Indohyus and moves previously omitted tenrecs and elephant shrews closer to these ‘walking whales’. The extant elephant shrew, Rhynchocyon (Fig. 1) also has artiodactyl-like ankles, but no one noticed that until the LRT shed light on this taxon. Taxon exclusion is an easy sin to commit because it’s a sin of omission. You can’t understand and incorporate what you ignore or are not aware of.
Some of the taxarelated to Pakicetus recovered by the LRT (e.g. Rhynchocyon, Hemicentetes, Tenrec, Fig. 1) are still alive today and therefore should garner more attention in odontocete origin studies. For instance Tenrec finds prey by echolocation (Gould 1965), lacks a scrotum and travels in pods.
Unfortunately whale workers and university textbook writers still prefer their whales to stay monophyletic and for all whales to evolve from unspecified artiodactyls. Now, even though we know better, we shouldn’t expect any changes in textbooks for another several decades. Paleontology accepts discoveries much more slowly than any other science, as Yale professor John Ostrom lamented before his passing.
Also in the LRT mix: giant Andrewsarchus was also recovered close to the elephant shrew, Rhynchocyon (Fig. 1). Spaulding et al. 2009 (Fig. 2) included Andrewsarchus in whale origin studies, but did not understand ‘the big picture’ recovered by the LRT. They mistakenly considered Andrewsarchus another artiodactyl due to taxon exclusion.
Figure 3. The elephant shrew, Rhynchocyon, is also basal to another giant: Andrewsarchus. You discover this by simply adding taxa to your analysis.
Mysticete (baleen whale) ancestors are an entirely distinct lineage (Fig. 3), as we learned earlier here. Now we understand the various gradual stages of mysticete evolution very well. And by ‘we’ I mean Pterosaur Heresies readers. Whale workers at the university level are still several years behind on this subject (Fig. 2).
Figure 4. Mysticete ancestors according to the LRT going back to desmostylians, hippos, mesonychids, oreodonts and phenacodonts.
Whale workers mistakenly put their focus on artiodactyls, following Gingerich et al. 1994 and 2001. They should have expanded their taxon lists to include desmostylians, tenrecs and elephant shrews. Their misplaced results (Fig. 2) failed to document the gradual accumulation of traits recovered in the LRT for odontocete ancestors (Fig. 1) and mysticete ancestors (Fig. 4). It is disappointing that none of the academics recognized the folly of their hypotheses. Each team was guilty of “Pulling a Larry Martin” by putting all their faith in one cherry-picked trait, the ankle shape, rather than letting software consider the sum of every trait for a wider gamut of included taxa.
Sadly, when walking whale expert Phil Gingerich refereed the manuscript for “The Triple Origin of Whales“, he chose to reject it, calling it a “Just So Story”. Given that Gingerich became famous for discovering walking whales and associating them with artiodactyls, perhaps he didn’t want that fame tarnished by admitting his team and his colleagues made a mistake exposed by an amateur armed with nothing more than a wider gamut taxon list. That sin is all too common at the university level and it’s a sin of commission. We’ve seen this ‘rather not know‘ attitude from professors dozens of times in paleontology. That’s never good for science. If a hypothesis is wrong, show why it is wrong. Don’t ignore it, suppress it or call the author a crank or pseudoscientist.
Happily, if you’re interested in whale origins, you can join hundreds of researchers who have already downloaded and read the illustrated manuscript for “The Triple Origin of Whales” online here at ResearchGate.org. If you’re interested in odontocete and mysticete ancestors back to Ediacaran worms, visit the large reptile tree.
References Gingerich PD, et al. 1994. New whale from the Eocene of Pakistan and the origin of cetacean swimming. Nature 368 (6474): 844–847. Gingerich, PD et al. 2001. Origin of whales from early artiodactyls: hands and feet of Eocene Protocetidae from Pakistan. Science 293 (5538): 2239–2242. Gould E 1965. Evidence for Echolocation in the Tenrecidae of Madagascar Proceedings of the American Philosophical Society 109 (6): 352-360. online here. Huggenberger S, Leidenbere S and Oelschläger HHA 2018. Asymmetry of the nasofacial skull in toothed whales (Odontoceti). Journal of Zoology DOI: 10.1111/jzo.12425 O’Leary MA and Gatesy J. 2008. Impact of increased character sampling on the phylogeny of Cetartiodactyla (Mammalia): Combined analysis including fossils. Cladistics 24:397–442. Peters D unpublished. The triple origin of whales. PDF Spaulding M, O’Leary MA and Gatesy J 2009. “Relationships of Cetacea (Artiodactyla) among mammals: increased taxon sampling alters interpretations of key fossils and character evolution”. PLOS ONE. 4 (9): e7062. doi:10.1371/journal.pone.0007062 Thewissen JGM, Cooper LN, Clementz MT, Bajpai S and Tiwari BN 2007. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature 450:1190–1195. Van Valen L 1968. Monophyly or diphyly in the origin of whales. Evolution. 22 (1):37–41.
Or do they? Current data leans one way, but is sometimes equivocal when it comes to scoring.
If you study fish morphology, don’t start with these two. The lungfish Protopterus (Figs. 1, 2) and Neoceratodus(Fig. 3) are the most recent additions to the large reptile tree (LRT, 2041 taxa). Reisz and Smith 2001 report, “Lungfish… are unique in that adults lack marginal teeth and have to rely on palatal dental plates for crushing food.” Not only do they lack marginal teeth, they also lack the marginal bones that carry those teeth.
This can be confusing for PAUP because vertebrate taxa without tooth-bearing bones go back to Chondrosteus and sturgeons. Extant lungfish have a long lineage documented by Early Devonian lungfish. Bichirs join lungfish in the LRT, distinct from all prior studies that separated them before testing.
Figure 1. The traditional lungfish, Protopterus, here taking a breath of fresh air.
Adult Neoceratodus and Protopterus also lack a palatine and ectopalatine. Instead a large pterygoid and prearticular develop crushing tooth plates. External bony buttresses, unlike those in other vertebrates, develop to strengthen these jaw bones (Fig. 2).
Figure 2. Skull of Protopterus from Digimorph.org and used with permission here. Colors added here. Frame three restores missing bones, perhaps cartilaginous. This skull is different from sister taxa due to 40 million years of separation, but not closer to any other tested taxon in the LRT.
Protopterus dolloi (Boulenger 1900, Criswell 2015) is the spotted or slender lungfish from the Congo River in Africa. This obligate air-breather has an eel-like body with slender fins.
Criswell 2015 µCT scanned several lungfish skulls. So did Digimorph.org (Fig. 2). Adding to the difficulty in scoring these taxa, the Criswell µCT scans did not include circumorbital bones, a trait common to all other lungfish taxa, as documented in more complete specimens of Neoceratodus (Fig. 3), Howidpterus (Fig. 4) andPolypterus (Fig. 5). The last taxon, the bichir, also has lungs, can walk on land and nests with lungfish in the LRT, distinct from other analyses that excluded bichirs from testing with lobe-fin taxa.
The premaxilla, maxillla and circumorbital bones, are tentatively restored in Protopterus here in this Digimorph.org image (Fig. 2). The presence or absence of circumorbital bones in fish sometimes is not recorded in published data. Given the close relationship of Neoceratodus to Protopterus, the absence of circumorbital bones in both taxa presented in the Criswell 2015 study contrasts with their presence in another photo of Neoceratodus (Fig. 3). This discrepancy admits the possibility that Protopterus also had circumorbital bones, overlooked or removed by Criswell 2015. Whether or not, restored bones in Protopterus are not scored in the LRT.
Figure 3. Neoceratodus skull with dermal bones colored here. Note the circumorbital bones, the premaxilla and maxilla, all missing from the smaller Criswell 2015 skull. Note the lateral excavation of the nasals.
Neceratodus forsteri (Kreft = Krefft 1870; 150cm) is the extant Australian lungfish. Here (Fig. 3) the smaller skull from Criswell 2015) includes no premaxilla, maxilla, quadrate and circumorbital bones. But note, the larger skull (Fig. 3) includes all these bones, sometimes to a lesser extent than seen in other fish.
Figure 4. The Middle Devonian lungfish, Howidipterus, with subdivided skull bones colorized here to match tetrapod homologs. Lungfish have greatly subdivided dermal skulls, distinct from the skull of Protopterus.
Howidipterus donnae (Long 1992; NMV P181884; Middle Devonian) is a primitive lungfish with large medial fins. The pectoral and pelvic fins are not known. Howidipterus nests with Polypterus in the LRT. Note the many subdivided bones of the skull, typical of lungfish. The lateral teeth are absent. The pterygoid and prearticular develop a tooth plate during maturation. The splenial, angular and surangular take the place of the dentary. The squamosal is tiny.
Figure 5. Polypterus nests with lungfish. Note the fusion of the preoperucular with the squamosal along with the retention (or return) of marginal teeth and tooth-beaing marginal bones.
Criswell 2015 wrote: “Lepidosirenidae is a clade of freshwater lungfishes that include the extant South American Lepidosiren paradoxa Fitzinger, 1837 and African species of the genus Protopterus. These genera have been geographically separated since the break-up of Gondwana in the Early Cretaceous, but they display similar biology and morphology.”
Lungfish are ancient with basal representatives, like Powichthys (here updated in Fig. 6), Uranolophus and tiny Janusiscus radiating in the Early Devonian.
Figure 6. Early Devonian Powichthys, dorsal and palatal views. Colors added here. This image updates prior attempts at deciphering the myriad of subdivided skull bones.
Figure 7. Strunius is basal to Powichthys and lungfish in the LRT.
Criswell 2015 wrote: “The ancestry of the lepidosirenids remains poorly understood.”
In the LRTPowichthys (Fig. 6) and Strunius (Fig. 7) are proximal ancestral taxa. Deeper ancestors (Fig. 8) extend to coelacanths, spiny sharks, sharks, jawless fish and basal chordates.
Figure 8. Subset of the LRT focusing on the lobe-fin half of the bony fish. Lungfish are in green. Powicthys, the basalmost and earliest lungfish, is Early Devonian. So are Janusiscus and Uranolophus. Others are either recent of Middle Devonian.
References Boulenger GA 1900. A list of the batrachians and reptiles of the Gaboon (French Congo), with descriptions of new genera and species. Proceedings of the Zoological Society of London 1900: 433–456. Criswell KE 2015. The comparative osteology and phylogenetic relationships of African and South American lungfishes (Sarcopterygii: Dipnoi). Zoological Journal of the Linnean Society, 174, 801-858. Long JA 1992. Cranial anatomy of two new Late Devonian lungfishes (Pisces: Dipnoi) from Mount Howitt, Victoria. Records of the Australian Museum 44:299-318. Reisz R and Smith MM 2001. Lungfish dental pattern conserved for 360 Myr. Nature 411: 548.
Paul Ellenberger 1974, 1978, 1993 described Middle Triassic Cosesaurus as a pre-bird. Other paleontologists understood birds arose from small feathered theropod dinosaurs by the Late Jurassic. So Ellenberger’s hypothesis was not accepted.
Twenty+ years later, Dr. Ellenberger and I spent the day together at his home in Montpellier, a day after I examined his Cosesaurus in Barcelona. When I told him he actually discovered the long sought ancestor of pterosaurs (the one clade he did not test in his comparative anatomy studies), he dismissed the idea and refused any further discussion. He didn’t want to know, or even think about it. Perhaps Ellenberger kept his pet hypothesis to the grave. Don’t be like Dr. Ellenberger. Keep an open mind.
References Ellenberger P and de Villalta JF 1974. Sur la presence d’un ancêtre probable des oiseaux dans le Muschelkalk supérieure de Catalogne (Espagne). Note preliminaire. Acta Geologica Hispanica 9, 162-168. Ellenberger P 1978. L’Origine des Oiseaux. Historique et méthodes nouvelles. Les problémes des Archaeornithes. La venue au jour de Cosesaurus aviceps (Muschelkalk supérieur) in Aspects Modernes des Recherches sur l’Evolution. In Bons, J. (ed.) Compt Ren. Coll. Montpellier 12-16 Sept. 1977. Vol. 1. Montpellier, Mém. Trav. Ecole Prat. Hautes Etudes, De l’Institut de Montpellier 4: 89-117. Ellenberger P 1993.Cosesaurus aviceps. Vertébré aviforme du Trias Moyen de Catalogne. Étude descriptive et comparative. Mémoire Avec le concours de l’École Pratique des Hautes Etudes. Laboratorie de Paléontologie des Vertébrés. Univ. Sci. Tech. Languedoc, Montpellier (France). Pp. 1-664. Peters D 2000. A redescription of four prolacertiform genera and implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Dr. Michael Benton
Mike Benton 1999 reported pterosaurs and tiny Scleromochlus, were closely related — and he wasn’t the first. A year later Peters 2000 introduced a phylogenetic series of four previously overlooked pterosaur ancestors and explained that Scleromochlus was a basal bipedal crocodylomorph with tiny hands, tiny fingers and no fifth toe.
A few years later, Benton and his student, David Hone (2007-2008) undiscovered the origin of pterosaurs. After announcing a test of Peters 2000 in part one (2007) of their two-part study, Benton and Hone omitted Peters 2000 in part two (2009). Without the omitted data Benton and Hone were unable to recover one tenable pterosaur ancestor, let alone a phylogenetic series of ancestors. Using the supertree method, neither author had to examine any specimens. Their job was to cherry-pick previously published cladograms. For his part, Hone was awarded a PhD. For his part, Benton’s university textbook (2005, 2014), continues teaching students that Scleromochlus was a pterosaur and dinosaur ancestor.
More recently Benton (see video on YouTube) closely examined pterosaur integumentary structures (= pycnofibers) and called them feathers… because they look like feathers. Don’t fall for this shortcut. We call this convergence. We call this “Pulling a Larry Martin.” Instead: be a good scientist. Run an analysis with a wider gamut of taxa. Find out if your subjects are indeed related to one another using hundreds of traits, not just one, two or a dozen. When you nurture and coddle an invalid pet hypothesis, you run the risk of having others shed light on your folly. Like Dr. Benton, any reputation you manage to build up over the decades will be undercut by your taxon omissions.
References Benton MJ 1999.Scleromochlus taylori and the origin of dinosaurs and pterosaurs. Philosophical Transactions of the Royal Society London, Series B 354 1423-1446. Online pdf Benton MJ 2005. Vertebrate Paleontology 3rd Edition PDF online Wiley-Blackwell 455 pp. Benton MJ 2014. Vertebrate Paleontology 4th Edition Wiley-Blackwell 480 pp. Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469. Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60. Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Dr. Kevin Padian
Kevin Padian 1985 and his friend Jacques Gauthier placed pterosaurs within the clade Ornithosuchidae along with Lagosuchus and the Dinosauria. These two young PhDs were riding a new wave of computer software in the earliest days of phylogenetic analysis. Back then (1985) they did not realize they were omitting pertinent taxa that would invalidate their hypothesis of interrelationships.
Thirty-five years later Padian (2020) was still so attached to the similarities between pterosaurs and dinosaurs he wrote in support of Ezcurra et al. (2020), “Ezcurra et al. realized that, although lagerpetids didn’t fly, they share specific features with pterosaurs, such as … Their elongated hand (palm) bones (hyperelongated in pterosaurs, along with the fourth finger) suggest a good starting point for animals to evolve flight.”By contrast, Ezcurra et al. wrote, ” …lagerpetids, as with other archosauromorphs, _lack_ the enlargement of both the deltopectoral crest of the humerus and the fourth manual digit that characterizes pterosaur wings.”
Today Kevin Padian is a highly regarded professor at a major university (UC Berkeley) and a champion of evolution. So it comes as a disappointment when he clings to a pet hypothesis that was invalidated by Peters 2000. Padian’s example shows this can happen to anybody at any level of education. Since this mistake was published in Nature this will be a stain on Padian’s curriculum vitae forever. Remember Kevin Padian when you have to make a similar decision against the evidence.
References Gauthier JA and Padian K 1985. Phylogenetic, functional, and aerodynamic analyses of the origin of birds and their flight. In M. K. Hecht, J. H. Ostrom, G. Viohl, and P. Wellnhofer (eds.), The Beginnings of Birds: Proceedings of the International Archaeopteryx. Padian K 2020. Closest relatives found for pterosaurs, the first flying vertebrates. Nature News and Views (2020). https://www.nature.com/articles/d41586-020-03420-z Ezcurra MD et al. (17 co-authors) 2020. Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria. Nature (2020). https://doi.org/10.1038/s41586-020-3011-4
Consider these three academic examples as cautionary tales. If you’re a scientist, don’t be caught supporting or promoting invalid hypotheses. If there is a competing hypothesis out there, test it and see if your pet hypothesis lives or dies. Don’t think about your status and reputation. Don’t think about the money. Don’t think about the potential for embarrassment. Do what is right, do what you profess, do science.
If you do discover something in paleontology, like the origin of pterosaurs, expect crickets. In the 22 years since Peters 2000 no one has reached out to discuss their thoughts and arguments. Workers don’t want to know or even think about competing hypotheses. No one has improved on it, which is something I would welcome. Just don’t put your blinders on. Test all competing hypotheses. Figure this out for yourself.
Originally (Sanz et al. 1997) considered a nestling, and then (Cambra-Moo et al. 2006) a subadult, the still unnamed el Montsec bird is basal to two clades of named enantiornithine birds, some of them smaller.
FIgure 1. Plate and counterplate of the el Montsec bird from Sanz et al. 1995 shown 1.2x life size. The sternum here is green.
el Montsec bird LP4450-IE (Sanz et al. 1995; Cambra-Moo et al. 2006; Early Cretaceous; Fig. 1) was considered similar toArchaeopteryx(but which one?) in the skull. Here the el Montsec bird nests at the base of the Sulcavis(Fig. 3) clade far from any Archaeopteryx specimens (Fig. 2). The el Montsec bird clade nests basal to several tiny birds Fortunguavis, Cratoavis and Iberomesornis.
Figure 3. Subset of the LRT focusing on basal birds. Blue taxa are all Solnhofen birds (= traditional Archaeopteryx). Sulcavis and the el Montsec bird are highlighted in yellow.
Though small and originally considered a nestling, this specimen also nests basal to other small Cretaceous birds, then large Cretaceous birds leading to modern birds. Sinornis and Iberomesornis are smaller. So, let’s give this bird a name!
Figure 3. Sulcavis and the el Montsec bird to scale with Archaeornithura, Iberomesornis, Fortunguavis and Cratoavis.
References Cambra-Moo O, et al. (5 co-authors) 2006. Estimating the ontogenetic status of an enantiornithine bird from the Lower Barremian of El Montsec, Central Pyrenees, Spain. Estudios Geologicos 62(1):241-248. Sanz JL et al. (9 co-authors) 1997. A nestling bird from the Lower Cretaceous of Spain: Implications for avian skull and neck evolution. Science 276:1543–1546.
Seems like several newly added birds have taken this position lately, one after the other. I saw the name of this genus in a cladogram and wondered what it looked like. Meet Schizooura lii.
Figure 1. Schizooura lii from Zhou, Zhou and O’Connor 2012, here shown 0.75x full size.
Despite excellent preservation and preparation, Schizooura was inadequately identified, especially in the skull. Here (Fig. 2) the postorbital (amber), postfrontal (orange) and palatine (deep blue) are identified. Some bones were mislabeled originally, corrected here.
Figure 2. Skull of Schizooura lii from Zhou, Zhou and O’Connor 2012. Colors added here. Presented here 3x life size.
According to Zhou et al. 2012: “Phylogenetic analysis indicates that it is more derived than Jianchangornis and Archaeorhynchus, but more basal than all other known Jehol ornithurines.”
By contrast, in the large reptile tree (LRT, 2036+ taxa) that order is upside down, probably due to taxon exclusion.
Figure 3. Subset of the LRT focusing on basal birds. Blue taxa are all Solnhofen birds (= traditional Archaeopteryx). Schizooura and taxa mentioned by Zhou et al. 2012 are highlighted in yellow.
Schizooura lii (Zhou, Zhou and O’Conor 2012; Early Cretaceous) nests between the enantiornithine Rapaxavis and the Euornithes. The excellent preservation permits an accurate reconstruction and scoring. An extremely thin nasal process separates the naris from the antorbital fenestra. The postorbital is large enough to touch the jugal. Distinctly the quadrate curls posterodorsally and the postorbital contacts the squamosal. A short tail without a pygostyle is present. Toe 3 is the longest, as in most birds and theropods, but distinct from closely related taxa.
References Zhou S, Zhou Z-H and O’Conor JK 2012. A new basal beaked ornithurine bird from the lower Ctetaceous of Western Liaoning, China. Vertebrata Palasiatica 50(1):9–24.
Foth et al. 2021 bring us a smaller specimen correctly attributed to Archaeorhynchus (Fig. 1; LNTU-WLMP-18), an Early Cretaceous (Aptian, 120 mya) bird considered a member of the Euornithes by Foth et al.
That is confirmed by the large reptile tree (LRT, 2036 taxa, subset Fig. 4) which nests both specimens of Archaeorhynchus (Fig. 1) as basalmost crown birds (= basal to Palaeognatha on one branch and Neognatha on the other).
Foth et al. report: “Although juvenile characters have the potential to impedeaccurate identification of the specimen, morphological comparisons and cladistic analysis identify LNTU-WLMP-18 as most likely referable to the basal euornithine Archaeorhynchus, which would make the specimen the first juvenile bird from the Jehol Group that could be assigned to a specific taxon. Based on its size and the incomplete ossification of the bone surface, LNTU-WLMP-18 represents the smallest and therefore youngest known individual of this genus.”
There is reason to question the conspecific status of the smaller LNTU specimen. It has a distinctly different skull morphology, and a smaller skull relative to the cervical series. If younger and conspecific, the skull should have been relatively larger and with a larger orbit following typical archosaur growth patterns. So, let’s look for another adult that is a closer match.
Figure 1. Archaeorhynchus and the smaller LNTU specimen to scale. Note the skull shape and coracoid differences. Note the larger wings and shorter neck in the larger specimen.
Foth et al. report: “The jaws are edentulous, the coracoid bears a procoracoid process, and the ischium lacks a proximodorsal process. The pedal unguals are short and barely curved, indicating a ground-dwelling lifestyle. Feathers, including long primaries, are present as carbonized traces. Several characters indicate that LNTU-WLMP-18 is a juvenile: the bone surface has a coarsely striated texture and no fusion is evident between the carpals and metacarpals, between the tibia and the astragalus and calcaneum, or among the metatarsals.”
The LNTU specimen is a likely juvenile, but it does not appear to be a juvenile of Archaeorhynchus spathula. It is distinct from the holotype, yet not distinct enough to nest with any other tested taxon.
Figure 2. The LNTU specimen of Archaeorhynchus in situ. Colors and reconstructions added here. The u-shaped furcula is green. The sternum is covered by the right remiges (rre). The right manus is hidden beneath the right remiges.
Foth et al. report: “As a small-bodied, ground-dwelling, seed-eating bird with a precocial ontogeny, Archaeorhynchus filled an ecological niche that later allowed early crown birds to survive the K-Pg mass extinction.”
Foth et al. do not recover the same basalmost crown bird position for Archaeorhynchus, perhaps due to taxon exclusion. They nest Archaeorhynchus basal to Gansus and Archaeornithura. That’s upside-down relative to the LRT (subset Fig. 4).
Foth et al. also nest Gallus, the chicken, with Anas, the duck and with the Creteaceous toothed bird, Ichthyornis. None of these three taxa resemble one another. Many pertinent bird taxa were not included in Foth et al., among them, the basal crown birds: Megapodius and Rhynochetos (Fig. 3).
If you don’t include pertinent taxa, they will never nest together. So include more taxa to find out how each new taxon is related to every other. You might waste some time, but you might also recover a few traditionally overlooked interrelationships.
Figure 3. The extant kagu, Rhynochetos, compared to scale and to size with the LNTU specimen. These two are separated by one node in the LRT and 120 million years of evolution.
Foth et al. report: “Despite the general completeness of the specimen, some bones are hidden or missing, including various skull bones and the furcula, sternum (or anlagen for sternal ossification, see Zheng et al., 2012), sternal ribs, gastralia, right coracoid, right manus, and right metatarsus. Due to the loss of the counter slab, it is uncertain whether these bones were originally present or not.”
I found the furcula. The sternum would have been the same shape as the right remiges. The missing manus would have folded beneath the right remiges/sternum in life.
“The bone histology of Archaeorhynchus reveals relatively slow growth, with more than three years needed to reach skeletal maturity. This is different from the growth patterns found in other Early Cretaceous euornithines, like Iteravis and Yanornis, and from the growth of extant birds, but similar to Enantiornithes.”
Surprising to hear this, given the close relationship of Archaeorhynchus withIteravis in the LRT.
“The morphology of the humerus reveals that the deltopectoral crest was weakly developed in early juveniles, but grew more prominent during ontogeny.”
The difference between the two deltopectoral crests appears minimal (Fig. 1) and could be due simply to overall size.
Given so many other phylogenetic differences, let’s find the adult of the smaller specimen first before making such statements. Adding taxa sheds light on hypothetical interrelationships.
Figure 4. Subset of the LRT focusing on basal birds. Blue taxa are all Solnhofen birds (= traditional Archaeopteryx). Archaeorhynchus appears in light red at the bottom of this cladogram.
References Foth C et al. (4 co-authors) 2021. A juvenile specimen of Archaeorhynchus sheds new light on the ontogeny of basal Euornithes. Frontiers in Earth Science 9 604520:1–19.
The Pterosaur Heresies 