Wilson et al. 2022 reported, “The relative scarcity of well-preserved fossils from the earliest history of stem lineages often limits our ability to establish robust, broad-based evolutionary patterns. This is certainly the case for the pan-radiation of archosaurs whose earliest stem taxa remain poorly understood relative to the crownward archosauriforms. Trilophosaurus buettneri is a North American Triassic stem archosaur that lies near the base of this expansive pan-radiation.”
Stop thinking Trilophosaurus is an archosauriform. It is a lepidosaur in the large reptile tree (LRT, 2207 taxa). It always has been. Adding taxa reveals this.
In addition, the earliest history of all stem lineages is well documented in the LRT, which documents ancestors back to the Cambrian. There’s no scarcity.
This trilophosaur = archosauriform myth is only the latest version of a myth first promoted by Benton 1985 (Fig 2). Yes, that’s the same vertebrate paleontology textbook author, Michael Benton, who holds huge sway in this field. He even convinced/cajoled his student, David Hone, to co-author two papers that undiscovered the ancestry of pterosaurs, which are also lepidosaurs.
Neither Benton 1985 nor other authors following him included enough taxa to recover the basal split following the last common ancestor of all reptiles in the LRT, Silvanerpeton. This embarrassing oversight due to taxon exclusion has clung to these authors and their followers like the myth of tail dragging in dinosaurs. Despite calls to fix this problem, there’s a curious lack of curiosity among paleoworkers. That lack should be a trait absent in a scientist, but in paleontology all evidence indicates it’s plesiomorphic.
Let’s add taxa to fix all decades-old problems, no matter what.
References Benton MJ 1985. Classification and phylogeny of the diapsid reptiles. Zoological Journal of the Linnean Society. 84 (2): 97–164. Wilson JD, Wisniewski A, Nesbitt S and Bever GS 2022. Comparative braincase morphology of Trilophosaurus buettneri and the early evolution of the pan-archosaurian neurocranium. Journal of Vertebrate Paleontology Article: e2123712
From the Beckett and Friedman 2015 abstract: “The monotypic scombrid fish Micrornatus is represented by a single skull from the early Eocene (Ypresian) London Clay Formation of southeastern England. Here we re-examine this specimen using computed microtomography. Scans reveal new details of the braincase, suspensorium and ventral hyoid arch. “
The huge (35cm) skull of Micrornatusis shown infigure 1.
It’s good to see workers coloring bones, but some standardization would be better. Here the authors’ colors are replaced with tetrapod homology colors used at ReptileEvolution.com (e.g. premaxilla = yellow, maxilla = green, etc). You might notice a few bones here (e.g. the nasals and frontals, the dentary and articular) are reidentified.
Micrornatus hopwoodi (Casier 1966, formerly Eocoelopoma hopwoodi, Beckett and Friedman 2015, early Eocene, BMNH 36136 = NHMUK PV OR 36136) was considered a mackerel close to Scomber, but in the large reptile tree (LRT, 2206 taxa) nests with Esox, the muskellunge (muskie, Fig 2) a type of pike. The premaxilla and its teeth on marine Micrornatus are much larger than on the freshwater pike, which has larger dentary teeth.
Micrornatus is more muskie (Esox) than mackerel (Scomber). This is what the LRT recovers (Fig 3). Micrornatus was likely a late survivor in the early Eocene.
TAt this point, eleven years into the project, the LRT (subset Fig 3) needs confirmation, refutation or modification by workers employing the same taxon list and a list of their own 200+ random characters.
References Beckett HT and Friedman M 2015. The one that got away from Smith Woodward: cranial anatomy of Micrornatus (Acanthomorpha: Scombridae) revealed using computed microtomography. In: Johanson Z Barrett PM, Richter M and Smith M (eds) Arthur Smith Woodward: His Life and Influence on Modern Vertebrate Palaeontology. Geological Society, London, Special Publications, 430, http://doi.org/10.1144/SP430.16 Pauca M 1929. Vorläufige Mitteilung über eine fossile Fischfauna aus den Oligozänschiefern von Suclânesti (Muscel). Acad. Roum. Sect. Sci. Bull. v. 12, p. 112-121.
Kligman et al 2023 announced the discovery of a tiny new stem caecilian, Funcusvermis gilmorei, known from a few broken and disarticulated parts (Fig 1). The new genus was found in the Late Triassic Chinle Formation of Petrified Forest National Park (PEFO), Arizona, USA.
Late Triassic Funcusvermis (Fig 1) is about the same size as the Early Jurassic crown caecilian, Eocaecilia(Fig 2), a derived member of the Microsauria in the large reptile tree (LRT, 2206 taxa, subset Fig 3).
Kligman et al considered Funcusvermis “the geologically oldest stem caecilian—a crown lissamphibian from the Late Triassic epoch of Arizona, USA—extending the caecilian record by around 35 million years.”
The LRT recovers a different tree topology (Fig 4) that separates caecilians from frogs + salamanders by simply adding taxa omitted by Kligman and his six co-authors.
Kligman et al followed a traditional myth still taught at the university level, that caecilians were closely related to frogs + salamanders. They did not test that old hypothesis by adding taxa. Kligman et al reported, “Living amphibians (Lissamphibia) include frogs and salamanders (Batrachia) and the limbless worm-like caecilians (Gymnophiona).”
Yes, there are only three living clades of ‘amphibians,’ but these three alone do not constitute a monophyletic group. Distinct from Kligman et al, the LRT (Fig 3) separates caecilians from frogs + salamanders with a long list of fossil taxa they and others traditionally omit. In the LRT caecilians are living microsaurs, apart from the clade Lissamphibia.
The stem caecilian question The Kligman et al hypothesis of interrelationships posited a rapid loss of large limbs from taxa like Celtedens (Fig 4) to Eocaecilia. Other caecilian-like taxa recovered by the LRT (Figs 2–5) were either omitted or recovered as convergent (some of these taxa are listed below).
I would be more interested in arguments for convergence if Kligman et al had included the microsaur taxa in the LRT (subset Fig 3) they omitted. With regard to time, the LRT recovers older stem caecilians than Late Triassic Funcusvermis (Fig 5).
Because Late Triassic Funcusvermis, is known from only a few mandibles (aka pseudodentaries) and a scattering of dissassociated other bones, the “funky worm,” Funcusvermis, will not be added to the LRT.
Kligman et al. wrote, “We tested the relationships of Funcusvermis gilmorei in a modified dataset of 63 terminal taxa including stem tetrapods, stem and crown amniotes, and temnospondyl amphibians including stereospondyls and lissamphibians.”
63 cherry-picked taxa is not enough, according to the LRT. Those 63 taxa gave the authors a distorted idea how tetrapods evolved from fish, which taxa were basal to reptiles, and which taxa were related to caecilians. Adding taxa resolves all issues. Omitting taxa does not.
In either hypothesis (Figs 2, 4) caecilians are the product of phylogenetic miniaturization and neotony. Perhaps those details are worth exploring sometime soon.
Publicity phys.org/news reported: “The smallest of newly found fossils can upend what paleontologists know about our history.”
Not true. Caecilians are not in the human lineage. Neither are frogs nor salamanders.
“A team of paleontologists from Virginia Tech and the U.S. Petrified Forest National Park, among others, have discovered the first “unmistakable” Triassic-era caecilian fossil—the oldest-known caecilian fossils—thus extending the record of this small, burrowing amphibian by roughly 35 million years. The find also fills a gap of at least 87 million years in the known historical fossil record of the amphibian-like creature.”
The time span between the Late Triassic of Funcusvermisand the Early Jurassic of Eocaecilia is actually somewhat less than 87 million years.
“The discovery of the oldest caecilian fossils highlights the crucial nature of new fossil evidence. Many of the biggest outstanding questions in paleontology and evolution cannot be resolved without fossils like this,’ said Kligman, ‘Seeing the first jaw under the microscope, with its distinctive double row of teeth, sent chills down my back,” Kligman said. “We immediately knew it was a caecilian, the oldest caecilian fossil ever found, and a once-in-a-lifetime discovery.”
That double row of teeth on such tiny jaws (Fig. 1) is a strong sign of caecilian affinity.
Crucial? Biggest? Outstanding? Chills down my back? Once-in-a-lifetime? I wonder if Romer, Colbert, Broom, Marsh and Cope ever got this excited about their discoveries? Or is this Kligman’s nature? Or just a sign of the modern age of Internet journalism?
Sounds like a Disney cartoon, but it’s the latest match made on the large reptile tree (LRT, 2206 taxa). Now Sphyraena, the barracuda, and Elops, the ladyfish (Figs 1 and 2) nest together between the cod (Gadus) and the cobia (Rachycentron). Let’s take a closer look.
Phylogenetic miniaturization and reversal evolved the ladyfish from the barracuda. In Elops, the ladyfish, the rostrum is shorter, the orbit is larger, the post-circumorbital bones are larger, the teeth are smaller (and so are its prey), the parietals contact each other medially, the pelvic fins are set further toward the tail, and the dorsal fin is above the pelvic fins, rather than above the anal fin (Figs 1, 2).
These newly evolved traits all make Elops look like a more primitive taxon. That’s what makes phylogenetic analysis a little tricky. That’s why it’s important to do a little ‘housekeeping‘ every so often. Take a look at a series of barracuda larvae shown below (Fig 4) for confirmation of this novel hypothesis on interrelationships.
These bauplan changes between Sphyraena and Elops are part of the reason why this interrelationship went unnoticed until now. Related taxa, like the cod and cobia, share more traits with the barracuda. Elops is the oddball, often, but not always, the morphological exception at its present nesting in the LRT. Even so, trust your software because it recovers a longer list of similar traits that nest Elops with Sphyraena rather than elsewhere. That’s called maximum parsimony, the guiding principle behind phylogenetic analysis. And that’s why “Pulling a Larry Martin” (relying on just one or only a few traits) should be avoided.
Matsuura and Suzuki 1997 provided a diagram of barracuda embryos and hatchlings (Fig 4) in which the rostrum is initially short and the orbit large relative to older barracuda. Note the dual dorsal fins at the last stage. Dual dorsal fins are found in related cod (Gadus). The anterior dorsal fin is retained by Elops, the ladyfish. The anterior dorsal fin is lost in adult Sphyraena, the barracuda. With these observations, larval development in Sphyraena, the barracuda, supports the recovery of Elops, the ladyfish as a close relative in the LRT largely due to phylogenetic miniaturization and reversal.
According to Wikipedia, Elops is a member of the Elopiformes, then the Actinopterygii. Traditional members of the elopiformes include the tarpon, Megalops. The LRT does not support that hypothesis of interrelationships. Wikipedia does not connect the barracuda and the ladyfish.
Rather than indicate broad, vague and nebulous interrelationships, like Wikipedia reports, the LRT documents the interrelationships and ancestries of every included taxon down to the level of genus back to the last common ancestor, a Cambrian or Ediacaran nematode worm close to Enoplus. As always, this novel hypothesis of interrelationships (Fig 3) now needs competing studies for confirmation, refutation or modification.
References Matsuura Y and Suzuki K 1997. Larval development of two species of barracuda, Sphyraena guachancho and S. tome (Teleostei: Sphyraenidae), from southeastern Brazil. Ichthyological Research 44:369–378.
By contrast in the large reptile tree (LRT, 2206 taxa, subset Fig 2) sailfish and swordfish are not in separate orders, but are only two nodes apart.
The sails (= tall dorsal fins) came first, before the swords. Swordless Late Cretaceous Pentanogmius(Fig 1) has a tall sail. So does swordless Alepissaurus (Figs 1, 2). According to these results (Fig 2) sailfish and swordfish diverged at 70mya, not 15mya and without a sword. So the sword is convergent.
If you’re wondering how Anguilla, the European eel, is related to Xiphias, the swordfish, we covered that earlier here. Baby swordfish look more like eels (Fig 3). Neotony gave us eels.
Pentanogmius evolutus (originally Anaogomius or Bananogmius evolutus Cope 1877; Taverne 2004; Late Cretaceous; 1.7m long) is traditionally considered a member of the Tselfatiiformes, thought to have gone extinct in the Late Cretaceous. Here it nests with Istiophorus, the extant sailfish.
Istiophorus platypterus (Shaw 1792 in Shaw and Nodder 1792; 3m) is the extant sailfish descending from Late Cretaceous Pentanogmius. The rostrum is extended, convergent with another fast, open ocean predator, the swordfish, Xiphias. The anterior dorsal fin is larger than the lateral area of the fish itself. Teeth are absent. The pectoral fins are long and slender. The anal fin is divided in two. The vertebral column is composed of relatively few, but large vertebrae.
Xiphias gladius (Linneaus 1758; Gregory and Conrad 1937; up to 4.5m in length) is the extant swordfish, nesting between Bavarichthys and Anguilla. 1cm long hatchlings more closely resembled little eels, then growing to little sailfish before reducing the long dorsal fin. The sword is not used to spear, but to slice and maim smaller fish traveling in schools. The pelvic fins and ribs are absent, as in eels. Larger females produce more eggs, up to 29 million.
…because multituberculates nest within Placentalia in the large reptile tree (LRT, 2206 taxa). That nesting happened in 2012.
Ten years later, Weaver et al 2022 reported, “Multituberculate bone histology closely resembles that of placentals, suggesting that they had similar life history strategies. A stem-therian clade exhibiting evidence of placental-like life histories supports the hypothesis that intense maternal-fetal contact characteristic of placentals is ancestral for therians. Alternatively, multituberculates and placentals may have independently evolved prolonged gestation and abbreviated lactation periods.”
Consider a third more parsimonious (= fewer steps) alternative: According to the LRT multituberculates were placental close to rodents and the aye-aye. Here’s an otherwise excellent paper on the histology of mammals undercut by taxon exclusion. This happens too often out there.
Publicity: According to the U of Washington online: “In a paper published July 18 in The American Naturalist, a team led by researchers at the University of Washington and its Burke Museum of Natural History and Culture present evidence that another group of mammals — the extinct multituberculates — likely reproduced in a placental-like manner. Since multituberculates split off from the rest of the mammalian lineage before placentals and marsupials evolved, these findings question the view that marsupials were “less advanced” than their placental cousins.”
By contrast, in the LRT multituberculates (Figs 1, 2) nest with aye-ayes and rodents as derived members of the clade Glires (gnawers) within Placentalia.
“This study challenges the prevalent idea that the placental reproductive strategy is ‘advanced’ relative to a more ‘primitive’ marsupial strategy,” said lead author Lucas Weaver, a postdoctoral researcher at the University of Michigan who conducted this study as a UW doctoral student. “Our findings suggest that placental-like reproduction either is the ancestral reproductive route for all mammals that give birth to live young, or that placental-like reproduction evolved independently in both multituberculates and placentals.”
No. Their traditional cladogram is wrong. Add taxa to figure this out for yourself.
“Weaver and his colleagues obtained cross sections of 18 fossilized femurs — the thigh bone — from multituberculates that lived approximately 66 million years ago in Montana. he researchers then examined femoral cross sections taken from 35 small-bodied mammalian species that are living today — 28 placentals and seven marsupials, all from Burke Museum collections. Nearly all of the placental femurs showed the same “sandwich” organization as the multituberculates. But all of the marsupial femurs consisted almost entirely of organized bone, with only a sliver of disorganized bone. “This is compelling evidence that multituberculates had a long gestation and a short lactation period similar to placental mammals, but very different from marsupials,” said Weaver.”
“Based on this correlation, the researchers estimate that multituberculates had a lactation period of approximately 30 days — similar to today’s rodents.”
The LRT recovered a close interrelationship between rodents and multis back in 2012 (time-stamped link below). That link has not wavered in the eleven years since.
The Weaver team wrote, “Multituberculata, an extinct mammalian clade that is phylogenetically stemward of Theria.”
That hypothesis is not supported here. The post-dentary bones that suggest a more stemward node are the result of neotony causing a reversal, likely due to the large propalinal movement of the jaws (Fig 1) interfering with the inner ear bones normal development. Members of Placentalia recapitulate their phylogeny during their development as embryos. Multis simple stopped developing inner ear bones in this hypothesis. Reversals, like odontocete molar shapes, also reverse to earlier morphologies.
Williams et al. 2023 argue “that an “African ape model” (referring largely to the postcranial anatomy and positional behaviors exhibited by extant African apes, Pan and Gorilla) for the origins of human bipedalism is a well-justified inference, the best-supported model given available evidence, and is currently and will remain testable against the fossil record. Given the long history of this debate, we have no illusion our conclusions about model building and testing will be universally accepted, but we argue that rejecting an African ape model requires significantly better evidence than currently exists.”
‘Significantly better evidence’ does exist (Fig 1) in a lineage of gibbons leading to humans. This line was recovered in a cladogram that minimizes taxon exclusion: the LRT.
Williams and other anthropologists follow a tradition that posits the African ape model. Often it includes Australopithecus (Fig 3), an African biped.
Williams et al. 2023 continue: “The ‘molecular revolution’ revealed a close relationship and recent (late Miocene, 5–7 Ma) divergence of humans and chimpanzees. Many morphologists remained skeptical of a hominine (Gorilla-Pan-Homo) clade or supported a Pan-Gorilla clade to the exclusion of hominins. Some morphological studies did successfully recover a Pan-Homo clade but arguably most came to this conclusion well after the molecular relationships were established.”
“At the same time, many paleoanthropologists continue to advance ideas that the LCA was not African ape-like in its body plan and positional behavioral repertoire despite the fact that such standpoints require increasingly more complex scenarios and greater instances of homoplasy to justify them.”
Unfortunately the ‘molecular revolution’ too often recovers untenable results based on continental areas (e.g. Afrotheria) rather than morphology. And fossils are off the table.
Taking another tack, Almécija et al 2021 wrote, “There is no consensus on the phylogenetic positions of the diverse and widely distributed Miocene apes. This has led some authors to exclude known Miocene apes from the modern hominoid radiation. Early hominins likely originated in Africa from a Miocene LCA that does not match any living ape (e.g., it might not have been adapted specifically for suspension or knuckle walking). Despite phylogenetic uncertainties, fossil apes remain essential to reconstruct the “starting point” from which humans and chimpanzees evolved. Bipedalism would have emerged because of the selection pressures created by the progressive fragmentation of forested habitats and the need for terrestrial travel from one feeding patch to the next.”
A fact apparently omitted from all prior bipedal studies: gibbons run bipedally (Fig 3).
“We need more fossils because we are likely missing vastly more than what we have.”
The LRT does not require more fossils. What the authors are missing is largely due to omission: taxon exclusion.
“Habitual bipedalism is reflected in several traits across the body (e.g., foramen magnum position and orientation; pelvic, lower-back, and lower-limb morphology), present (or inferred) in the earliest hominins Darwin linked the origin of bipedalism with an adaptive complex related to freeing the hands from locomotion to use and make tools (replacing large canines), leading to a reciprocal feedback loop involving brain size, cognition, culture, and, eventually, civilization.”
Ironically, gibbons depend even more on their hands for locomotion AND they are bipedal runners. Tall grass may have been the reason for bipedal locomotion in Australopithecus (Fig 3), but not in gibbons.
“Notably, Keith developed a scenario in which a “hylobatian” brachiating stage preceded an African ape-like creature: a knuckle-walking “troglodytian” phase immediately preceding bipedalism.”
Keith could have skipped the knuckle-walking African ape-like creature step. Keith did not report bipedalism in gibbons. That omission continues widespread to this day.
“Keith (1902, 1923) initially coined “orthograde” to describe the positional behavior of hylobatids: “The body is held, in all movements, upright to the plane of progression.”
Williams et al reported, “Focused on Keith’s “hylobatian” stage, Morton proposed that the “vertically suspended posture” of a small-bodied hylobatid-like ancestor caused the erect posture of human bipedalism. Gregory, another prominent “brachiationist,” supported similar views. Morton argued that knuckle walking did not represent an intermediate stage preceding bipedalism but rather a reversion toward quadrupedalism in large-bodied apes specialized for brachiation. At that time, “brachiation” was used for any locomotion in which the body was suspended by the hands. Now, it refers to the pendulum-like arm-swinging locomotion of hylobatids”.
Williams et al concluded, “Thus, in the absence of evidence to the contrary (which currently does not exist), our phylogenetic position within the African ape clade dictates that interpretation.”
The gibbon lineage hypothesis of the LRT now needs confirmation, refutation or modification with a taxon lists that include Oreopithecus, Homo floresiensis (Fig 3). Perhaps somedaysomeone will add taxa to the Mongle et al. cladogram (Fig 2) to see if it becomes a little more bushy.
Everyone agrees that knuckle-walking was not part of the evolution of bipedal humans, yet both the Mongle et al 2019 cladogram and the Williams et al 2023 foot series (Fig 1) indicate that three successive knuckle-walkers (Pongo, Pan and Gorilla) are in the lineage of humans, contra the LRT.
References Almécija S et al 2021. Fossil apes and human evolution. Science, 372, eabb4363. Morton DJ 1926. Evolution of man’s erect posture (preliminary report). J. Morphology 43: 147–179. 10.1002/jmor.1050430108 Gregory WK 1027. How near is the relationship of man to the chimpanzee-gorilla stock? Q. Rev. Biol. 2, 549–560. 10.1086/394289 Keith A 1902. The extent to which the posterior segments of the body have been transmuted and suppressed in the evolution of man and allied primates. Journal of Anatomy and Physiology, 37, 18–40. Keith A 1923. Man’s posture: Its evolution and disorders. British Medical Journal, 1, 451–454. Mongle CS, Strait DS and Grine FE 2019. Expanded character sampling underscores phylogenetic stability of Ardipithecus ramidus as a basal hominin. Journal of Human Evolution 131:28–39. Peters D 1991. From the Beginning – The Story of Human Evolution Wm. Morrow. Tuttle RH 1981. Evolution of hominid bipedalism and prehensile capabilities. Philosophical Transactions of the Royal Society of London B, 292, 89–94. Williams SA et al (4 co-authors) 2023. African apes and the evolutionary history of orthogrady and bipedalism. Am J Biol Anthropol. 2023;1–23.
Wonderful new fossil pterosaur. Only a few changes today. Balaenognathus (Martill et al 2023, NKMB P2011-633, Figs 1–3) is a beautifully preserved fossil pterosaur from Solnhofen (Late Jurassic) limestones. This mid-sized ctenochasmatid had a laterally expanded dentary tip and a full arcade of needle-like teeth with hook-ish tips. These traits, and those long legs, distinguish Balaenognathus from closely related taxa, like Ctenochasma elegans(SMNS 81803, Fig 3, known from skull-only data) and more basal ctenochasmatids.
It came as a pleasant surprise to see the authors applying colors to digitally segregate bones in their graphics (Fig 2).
Ctenochasmatid skull elements are well known from several specimens (Fig 3). The maxillae contact one another at mid-rostrum, covering the ascending process of the premaxilla and the nasals at that point.
When added to the large pterosaur tree (LPT, 266 taxa, subset Fig 4a) Balaenognathus nested with the skull-only SMNS 81803 specimen of Ctenochasma (Fig. 3), nearly identical, but for the expanded dentary tip and vertical teeth of the new genus.
Martill et al also nested Balaenognathus with ctenochasmatids. The authors employed far fewer taxa (Fig 4b) and their cladogram was far less resolved.
The nesting of Pterodactylus basal to the invalid clade, Pterodactyloidea is also troublesome. When more taxa are added Pterodactyloidea break up into four convergent clades, two are shown in figure 3 arising from various specimens attributed to Dorygnathus.
Both taxon exclusion traditions indicate the authors are cherry-picking rather than scientifically testing a wide gamut of taxa to determine outgroups and ingroups. The LRT and LPT minimize taxon exclusion by including 2206 and 266 taxa respectively.
Martill et al did not present a reconstruction. So a rough reconstruction is presented here (Fig 5) based on their DGS tracing (Fig 2).
Martill et al reported, “Despite both wrists being in an excellent state of preservation and articulation, both pteroids are missing. While it is possible that these elements are concealed underneath forearm elements, they are not visible on the X-ray. It appears plausible that they were unossified given the excellent general state of preservation. We know of no pterosaur in which the pteroids are absent.”
Both pteroids are present (Fig 6) The authors also mislabeled the coracoid and scapula.
Balaenognathus is a beautiful and unique specimen. Thankfully, the authors decided it was time to apply DGS colors to the bones. That served this study well. Next time let’s hope pterosaur authors will add two hundred more taxa to their pterosaur cladograms. Twenty years of taxon exclusion is long enough.
References Martill DM, Frey E, Tischlinger H, Mäuser M, Riversa-Sylva HE and Vidovic SU 2023. A new pterodactyloid pterosaur with a unique filter‑feeding apparatus from the Late Jurassic of Germany. PalZ https://doi.org/10.1007/s12542-022-00644-4
The question today is: which characters in the LRT mark this dichotomy?
LRT characters present in theropods + phytodinosaurs not in herrerasaurids: 2. Skull shorter than cervicals 7. Premaxilla loose 54. Prefrontal fused to postorbital 73. Quadrate vertical – not anterior lean 128. Mandible straight ventrally 129. Nine or more cervicals 135. Cervical rib orientation: slender, low angle 152. Anterior caudal spines about size of centra 195. Tibia / femur ratio not less than 1.0 211. Proximal metatarsals 1 and 5 reduced 223. Pedal digit 5 absent
LRT characters present in phytodinosaurs not in herrerasaurids and theropods: 8. Snout not constricted 74. Quadrate lateral coverage minimal 84. Postorbital extends to posterior parietal 108. Four or more premaxillary teeth 117. Surangular lateral shelf not present 119. Dentary tip straight 127. Retroarticular process straight
LRT characters present in phytodinosaurs not in Buriolestes: 13. Lateral rostral shape convex, smooth curve 14.. Pmx-mx notch < 45º 22. Narial opening lateral – not anterolateral 107. Palatal teeth present 112. Maxillary teeth no 2x deeper than wide 113. Most maxilla teeth not canines 114. Posterior maxilla teeth mid orbit – not anterior orbit
LRT characters present in theropods not in herrerasaurids and phytodinosaurs: 11. Dorsal nasal shape narrows toward naris 57. Frontal/nasal angle anteriorly oriented 60. Postfrontal contact with upper temporal fenestra 121. Coronoid process absent 140. Dorsal transverse processes shorter than centra 144. Three or four sacral vertebrae 147. Second caudal transverse process > centrum 157. Furculum 177, 178. Manual digit 4 poorly ossified
The LRT tests 236 multi-state characters and 2206 taxa from basal chordates to birds, humans, turtles and everything in between. Fossil taxa are included. Poorly preserved partial fossil taxa are included, but not often. The LRT is fully resolved except for one node at present. Academics said that was theoretically unlikely to impossible ten years ago when the the LRT included only 240 taxa. Their hypothesis was not confirmed. Corrections have been made and will continue to be made. New taxa continue to be added. The fact is: the LRT works. Even so, it’s a hypothesis that now requires confirmation, refutation or modification from a competing studies.
Calábková et al 2023 described “well-preserved isolated tracks, manus-pes couples, and a slab with trackways composed of approximately 20 tracks in at least four different directions belonging to early-diverging, or ‘pelycosaur-grade’, synapsids… assignable to the ichnotaxon Dimetropus.”
See figure 1.
Calábková et al 2023 concluded “It is impossible to assign the studied tracks beyond early-diverging, or ‘pelycosaur-grade’, Synapsida at present.”
No pelycosaur manus and pes graphics were presented and compared to the tracks by the authors, so let’s apply them here (Fig 1).
Calábková et al report, “From a general perspective, early-diverging, or ‘pelycosaur-grade’, synapsids are extremely rare in the Permo-Carboniferous basins of the Czech Republic, and all originate from Pennsylvanian (upper Carboniferous) coal seams.”
“Among these, the ophiacodontid Archaeothyris sp. from the Moscovian (Westphalian D) of Nýřany (Pilsen Basin, Kladno Formation), the stratigraphically oldest European sphenacodontid Macromerion schwarzenbergi and the historically oldest European edaphosaurid Bohemiclavulus mirabilis both from the Gzhelian (Stephanian B) of Kounov (Kladno-Rakovník Basin, Slaný Formation), and the largest known edaphosaurid, referred to as ‘Ramodendron obvispinosum’, from the Gzhelian (Stephanian C) of Oslavany (Boskovice Basin, Rosice-Oslavany Formation), likely represent the most significant specimens. In this contribution we provide the full description of the synapsid tracks and trackways, illustrate the material using three-dimensional modeling, and assess it especially with respect to the taxonomic affinities of their trackmakers.”
The manus and pes were not preserved in the above named taxa.
“The Dimetropus leisnerianus footprints are most commonly considered to belong to sphenacodontids, orearly-diverging sphenacodontians in general, which is associated especially with their typically elongated ulnare,a character that is reflected by proximodistally elongated palm impressions of D. leisnerianus. In ophiacodontids, caseids, varanopids, and edaphosaurids, the ulnare is typically relatively shorter.”
“Ophiacodontids are extremely rare in Europe.”
Basal synapsid fossils are extremely rare all over the planet.
Application of manus and pes graphics to the ichnites (Fig 1) were instructive enough to score the pes in phylogenetic analysis in the large reptile tree (LRT, 2206 taxa). Parallel interphalangeal lines (PILs, Peters 2000, Peters 2011) were applied.
Tested against Lepidosauromorphs the footprint nests with just two taxa. Eocaptorhinus had very short metacarpals, not longer than the phalanges, so they don’t match the tracks under study (Fig 1). Sphenodonappears too late and has a gracile pes.
Tested against Archosauromorphs the footprint nests in an unresolved array of nine taxa. Among those of the proper age, Gephyrostegus had digits that were too short medially and too long laterally. The rest were basal synapsids. The digit length and width disparity were likewise too great in Varanodon. Only digits 3 and 4 were too long in Varanops and Aerosaurus.
The best match, so far, (Fig 1) is with Ophiacodon, (Figs 2, 3) supplemented with two slightly longer metatarsals, 1 and 2. Ophiacodon was not selected by the LRT because metatarsals one, two and three align. By contrast, in the track under study (Fig 1), metatarsals 2 and 3 appear to align with pedal 1.1.
Colleagues, use Photoshop to apply fossil graphics to ichnites. Use PILs to understand and mark wherever phalanges flex in sets or do not.
The present hypothesis of trackmaker identity awaits confirmation, refutation or modification.
References Calábková G et al (3 co-authors) 2023. Synapsid tracks with skin impressions illuminate the terrestrial tetrapod diversity in the earliest Permian of equatorial Pangea. Nature scientific reports. (2023) 13:1130. Peters D 2000. Description and interpretation of interphalangeal iines in tetrapods Ichnos, 7:11-41. Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605