New paper, old Chanaresuchus: traditional taxon exclusion issues

A new look at the holotype of Chanaresuchus
by Trotteyn and Ezcurra 2020 provides crisp color photos of the holotype material from several angles, in white light and after µCT scanning.

Unfortunately their small focused cladogram
is a little too small and a little too focused for their taxon list. It might seem large because it includes 115 active taxa from a list of 151 total taxa from (Ezcurra 2016), but, as before, it omits several taxa that would move the thalattosaur, Vancleavea, and the pterosaur, Dimorphodon, out of Archosauromorpha (along with other lepidosaurs like Macrocnemus and Tanystropheus.

Earlier we looked at the many problems in Ezcurra 2016. The largest problem: Ezcurra did not and still does not understand that traditional diapsid taxa are diphyletic and convergent, with some among the Lepidosauria and others starting with Petrolacosaurus and kin within the Archosauromorpha. The Viséan last common ancestor of all reptiles is their last common ancestor.

Earlier we looked at a similar taxon list by Nesbitt 2011 in a 7-part series and demonstrated dozens of scoring errors. After corrections the tree topology came to match the large reptile tree (LRT, 1698+ taxa).

Figure 1. Updated image of various proterosuchids and their kin. When you see them all together it is easier to appreciated the similarities and slight differences that are gradual accumulations of derived taxa.

From the Trotteyn and Ezcurra 2020 abstract:
“Proterochampsids are one of the several diapsid groups that originated, flourished and became extinct during the Triassic Period. Here we redescribe, figure and compare in detail the holotype of one of these rhadinosuchine species, Chanaresuchus bonapartei from the Chañares Formation. Our new cladistic analyses find stronger support than previous studies for the monophyly of Rhadinosuchinae and the clades that include Doswelliidae + Proterochampsidae and Tropidosuchus + Rhadinosuchinae. Doswelliids are recovered within Proterochampsidae, as the sister taxon to the genus Proterochampsa, in some analyses under implied weights.”

If you find any taxa
in figures 1 and 2 missing from the above list (hint: there are several), those are the taxa Trotteyn and Ezcurra need to add to their next look at proterochampsids.

Figure 2. Cladogram of basal archosauriforms. Note the putative basalmost archosauriform, Teyujagua (Pinheiro et al 2016) nests deep within the proterosuchids. The 6047 specimen that Ewer referred to Euparkeria nests as the basalmost euarchosauriform now.

References
Ezcurra MD 2016. The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ, 4, e1778. doi:10. 7717/peerj.1778
Trotteyn MJ and Ezcurra MD 2020. Redescription of the holotype of Chanaresuchus bonapartei Romer, 1971 (Archosauriformes: Proterochampsidae) from the Upper Triassic rocks of the Chañares Formation of north-western Argentina.
Journal of Systematic Palaeontology (advance online publication)
doi: https://doi.org/10.1080/14772019.2020.1768167
https://www.tandfonline.com/doi/full/10.1080/14772019.2020.1768167

https://pterosaurheresies.wordpress.com/2016/04/29/basal-archosauromorpha-paper-ezcurra-2016/

Rahonavis returns! (still without resolution due to taxon exclusion)

Forster et al. 2020
bring us up to date on Rahonavis (Fig. 1), a tiny theropod with long forelimbs that has been traditionally hard to nest. Forster et al. adds Rahonavis to two previously published analyses of bird-like theropods …still without resolution (due to taxon exclusion).

Figure 1. Rahonavis nests in the LRT as a tiny derived therizinosaur based on the few bones currently known.

From the abstract:
“Recent phylogenetic analyses place Rahonavis either within the non-avialan Unenlagi- inae, an early-diverging clade within Dromaeosauridae, or at the base of Avialae. Rahonavis is one of the best represented and preserved Gondwanan paravians, and remains a pivotal taxon for understanding the evolution and biogeography of paravians.”

So the most recent analyses by Forster et al.
have not nested Rahonavis with confidence. In one study (based on the phylogenetic analyses of Lefèvre et al. 2017) Rahonavis nests between Archaeopteryx and Balaur. In the other study (based on Brusatte et al. 2014) Rahonavis nests at the base of three troodontids, Buitreraptor, Austroraptor and Unenlagia. In that study Balaur nests with Velociraptor and kin and all are derived from a sister to Mahakala.

So Rahonavis is not the only theropod
to shift places between the two published studies.

By contrast
the large reptile tree (LRT, 1698+ taxa; subset Fig. 3) nests Rahonavis outside the taxon lists employed by Forster 2020. In the LRT Rahonavis nests with Jianchangosaurus, Falcarius, and Beiapiosaurus, three therizinosaurs not tested by Forster et al. We looked at this still heretical nesting of Rahonavis a few years earlier here. Prior to the addition of therizinosaurs (and a thousand other taxa), Rahonavis nested with Velociraptor in the LRT. So back then, with fewer taxa, the LRT also suffered from taxon exclusion.

Following Forster et al. 2020,
to move Rahonavis to the Berlin specimen of Archaeopteryx adds 18 steps. To move Rahonavis to Buitreraptor adds 14 steps in the LRT. Those smnall numbers are based on the relatively few bones, all post-cranial, preserved by Rahonavis.

Figure 2. Jianchangosaurus nests at the base of the Maniraptora in Cau 2018, but with therizinosaurs in the LRT. Note the large pedal ungual 2, as in Rahonavis.

Therizinosaurus
are typically larger than Rahonavis, and feathered. Thus phylogenetic bracketing indicates Rahonavis was likely feathered, too.

Rahonavis (orignally Rahona ostromi – Forster et al. 1998, Late Cretaceous, 70mya, UA 8656, 70 cm) was originally considered a bird-like theropod. The partial skeleton is much smaller than sister taxa among the Therizionsauria. The pubis was ventrally oriented and the radius + ulna were very long. The tail was comparatively short with few vertebrae.

Figure 3. Subset of the LRT focusing on theropods and basal birds. Colors added for large (greater than a meter), medium (about a meter), and small (less than a meter) in length.

By minimizing taxon exclusion,
the LRT manages to nest all included taxa with high confidence and high Bootstrap numbers. As demonstrated over and over again, it doesn’t matter how many characters you use (at least 200 multi-state characters). You just have to barely nest taxa with complete resolution. You can only do this by adding taxa. That minimizes taxon exclusion, the biggest single problem in paleontology right now, whether workers know it or not.

Solve your problems by adding taxa.
It works here all the time. It will work for you, too.

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References
Forster CA, Sampson SD, Chiappe LM, Krause DW 1998. The Theropod Ancestry of Birds: New Evidence from the Late Cretaceous of Madagascar. Science 279 (5358): 1915–1919.
Forster CA, O’Connor PM, Chiappe LM and Turner AH 2020. The osteology of the Late Cretaceous paravian Rahonavis ostromi from Madagascar. Palaeontologia Electronica, 23(2):a31. https://palaeo-electronica.org/content/pdfs/793.pdf

wiki/Rahonavis

New study on Thylacosmilus atrox: “not a marsupial saber-tooth predator”??

Janis et al. 2020
bring us some heretical views regarding Thylacosmilus, the famous saber-toothed marsupial (Fig. 1).

Figure 1. Thylacosmilus skull. Note the deep maxillae in dorsal contact containing giant canine roots. These are not present in Patagosmilus.

For those in a hurry:
The Janis et al. study includes a phylogenetic analysis of placental sabertooth cats that nests the saber-toothed marsupial, Thylacosmilus (Fig. 1), at the base of the clade (Fig. 2). In a way, that is true, but this is missing so many transitional taxa that we’re left with apples and oranges. So, that’s not going to work because Janis et al. are testing analogy and convergence, rather than homology. It’s better to test apples and apples, even when dealing with stress tests, etc.

Figure 2. Cladogram from Janis et al. 2020. Note the lack of marsupial taxa, other than Thylacosmilus at the base. Be wary whenever the taxon under review nests at the base of the cladogram.

Lacking here
is a phylogenetic analysis that includes the closest marsupial relatives of Thylacosmilus: 1. Schowalteria (Fig. 3), 2. Vincelestes + Conorytes, 3. Huerfanodon 4. Monodelphis + Chironectes. That’s how they line up in the large reptile tree (LRT, 1698+ taxa). You need related taxa to decipher the phylogenetic bracketing of Thylacosmilus based on homology, not analogy. The last two taxa are extant. One is an omnivore, the other an aquatic carnivore. Among the extinct taxa, Schowalteria, Vincelestes, Conoryctes and Huefanodon all appear to have been marsupial saber-toothed predators, contra the Janis et al. headline. Vincelestes goes back to the Early Cretaceous.

Figure 3. Showalteria. Not much there, but enough to nest it with Thylacosmilus. Is this a predator? According to Wikipeia,.. no.

Janis et all. 2020 wrote:
“While the superficial appearance of Thylacosmilus atrox resembles that of placental saber- tooths, its detailed anatomy makes this animal an ecomorphological puzzle, and the analyses performed here show it to be unlike other carnivores, saber-toothed or otherwise”

That’s because they omitted related taxa…where are the comparable marsupials?

“While we can demonstrate that T. atrox could not have been a predator in the mode proposed for the saber-toothed feliform carnivorans, it is challenging to propose an alternative mode of life.”

That’s because they omitted related taxa…where are the comparable marsupials?

“We note that, while there is often the temptation to shoehorn an extinct animal into the ecomorphological role of an extant one (see Figueirido, Martín-Serra & Janis, 2016)—or even, as in this case, the proposed ecomorphological role another extinct animal—T. atrox may well have had no analogs in the extant or extinct fauna.

That’s because they omitted related taxa…where are the comparable marsupials?

“We extend this discussion of extinct animals without living analogs in the conclusions. Here we present some ecomorphological hypotheses for T. atrox that align with the peculiarities of its anatomy.”

1. We note that the unusual subtriangular shape of these canines makes them appear more like a claw than a blade; and, like a claw, they appear well-adapted for pulling back.
2. Our biomechanical study shows that both the skull and the canines of T. atrox are better in resisting pull back stresses than those of S. fatalis.
3. The small infraorbital foramen of T. atrox supports the hypothesis that its canines were not used for killing prey, as it would not require such careful and precise positioning of the canines.
4. The postcanine teeth of T. atrox exhibit blunted tip wear, unlike the shearing wear on the teeth of carnivores that specialize on flesh
5. T. atrox was clearly not a bone-crusher: this type of diet is contraindicated by the DMTA analysis and the lack of cranial specializations (including evidence for powerful jaw adductors) seen in extant bone-crushers
6. T. atrox had less powerful jaw adductor and head depressor muscles than placental saber-tooths. The cervical and caudal cranial anatomy are not indicative of the ability for extreme head elevation and forceful head depression, as observed in the anatomy of placental saber-tooths, implicated in those carnivores for a predatory head strike.
7. The virtual absence of incisors (certainly the absence of a stout incisor battery) in T. atrox is challenging for the hypothesis of a cat-like mode of feeding, as it would have been unable to strip flesh from a carcass or transport its prey.

Janis et al. wonder:
“Could [soft internal organs] have been the preferred diet of the marsupial saber-tooth?”

Janis et al. propose:
“Incisor loss or reduction in mammals is correlated with the use of a protrusible tongue in feeding, as seen in myrmecophageous mammals.”

Janis et al. propose:
“T. atrox has been ‘‘shoehorned’’ (see Figueirido, Martín-Serra & Janis, 2016) into the saber-tooth ecological role: much less attention has been paid to the way in which this animal differs in its morphology from placental saber-toothed predators, making a similar type of predatory behavior unlikely.

“We advance the suggestion that it was not an active predator, but rather relied on the use of existing carcasses, deploying its large canines for carcass opening rather than for killing, a hypothesis supported by our biomechanical analyses that show superior performance in a ‘‘pull-back’’ scenario.”

“Thylcosmilus atrox was a very different type of carnivorous mammal than the placental saber-tooths: the oft-cited convergence with placentals such as Smilodon fatalis deserves a rethink, and the ‘‘marsupial saber-tooth’’ may have had an ecology unlike any other known carnivorous mammal.”

Figure 4. Maximum gape of Thylacosmilus. At upper left is the placental, Smilodon, for comparison.

Geology = Environment
Thylacosmilus was found in a vast Miocene tidal flat environment with a wide variety of terrestrial and shalllow aquatic taxa. So that doesn’t help much.

Saving the best for last: getting back to Late Cretaceaous Schowalteria
Wikipeda report, “It is notable for its large size, being among the largest of Mesozoic mammals,^[ as well as its specialization towards herbivory, which in some respects exceeds that of its later relatives.” This is based on tooth wear, with nearly all crowns gone (Fig. 3) in the only specimen known. Traditionally Schowalteria has been allied with styinodonts (Carnivora close to seals, but not to sea lions) and to taeinodonts (which the LRT found to be poylphyletic). Certainly, what little is known of Schowalteria is similar to these taxa. Others have omitted these LRT sisters in their analyses. Janis et al. omit the word ‘sister’ from their text.

Figure 5. Patagosmilus to scale alongside Hadrocodium. These sabetooth taxa are not directly related to Thylacosmilus in the LRT.

Patagosmilus has been called a sister to Thylacosmilus,
but the LRT nested Patagosmilus (Fig. 5) with the tiny basal therian, Hadrocodium (Fig. 5) as we learned earlier here. Taxon inclusion produces surprises like this.

At times like this it’s good to test.
Deletion of Thylacosmilus changes nothing in the LRT. Deletion of Schowalteria changes nothing in the LRT.

In my opinion
it was great that Janis et al. 2020 tested Thylacosmilus with its placental analogs, but they should also have tested Thylacosmilus with its marsupial homologs.

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References
Janis CM, Figueirido B, DeSantis L, Lautenschlager S. 2020. An eye for a tooth: Thylacosmilus was not a marsupial ‘‘saber-tooth predator’’. PeerJ 8:e9346 http://doi.org/10.7717/peerj.9346

https://en.wikipedia.org/wiki/Ituzaing%C3%B3_Formation

https://pterosaurheresies.wordpress.com/2018/12/20/marsupial-sabertooth-taxa-are-polyphyletic/

A juvenile Eusthenopteron enters the LRT

Fish expert, John Long 1995 (p. 209) wrote:
“The juvenile skull of a crossopterygian fish, Eusthenopteron (Figs. 1,3) has more features in common with that of an early amphibian Crassigyrinus (Fig. 4), that it’s adult skull would have had.”

Long goes on to explain about paedomorphosis and heterochrony during the transition from fish to tetrapod.

Euthenopteron was a good transitional taxon several years ago. Recently it was replaced in the LRT by a flatter taxon, Cabonnichthys.

Figure 1. Eusthenopteron juvenile in situ from Schultze 1984. Large plate ventral to the mandible overlaps a convex ventral margin. The quadratojugal is not labeled here. Several bones are re-labeled here.

Let’s put Long’s 1995 statement to the test
by adding Eusthenopteron ‘junior’ (Schultze 1984) to the large reptile tree (LRT, 1698+ taxa; subset Fig. 5).

Results: The juvenile nested with the adult Eusthenopteron in the LRT, falsifying Long’s statement.
Note: Several bones are relabeled here vs. Schultze’s original designations.

Worthy of note:
The juvenile Eusthenopteron shares several traits with another, often overlooked, small taxon with similar large eyes, Koilops, which nests at the base of a nearby derived node in the LRT (Fig. 5). Based on phylogenetic bracketing, Koilops is also a juvenile. All sister taxa are larger and without juvenile proportions.

Figure 2. Koilops is a flat-headed smaller sister to Elpistostege, but with larger teeth, larger orbits and a shorter snout. These traits indicate Koilops is a juvenile.

So Long’s point about paedomorphosis and heterochrony
was  not correct in this case. His ‘matching tetrapod’, Crassigyrinus (Fig. 4), nests several nodes apart from pre-tetrapods in the LRT (off the subset chart in Fig. 5).

Koilops post-crania remains unknown,
but it nests at the base of Elpistostege, Tiktaalik and Spathicepahlus on one branch, Panderichthys + Tetrapoda on the other. So Koilops likely had lobe fins and a straight tail. Perhaps Koilops was a juvenile elpistostegid ready to mature into something larger, with smaller eyes, more like Elpistostege.

Figure 3. Juvenile and adult Eusthenopteron compared from Schultze 1984. The cranium of the juvenile appears convex here, but was likely flatter based on figure 1.

From the Schultze 1984 abstract:
“A size series of thirty-five specimens of Eusthenopteron foordi Whiteaves, 1881 , shows isometric and allometric changes. As in Recent fishes, the main difference between small (juvenile) and large (adult) specimens is the relative size of the orbit and of the head. With the exception of the caudal prolongation, all fin positions remain isometric to standard length.”

Figure 4. Crassigyrinus has little to no neck.

Contra Long 1995 and all prior basal tetrapod workers, the LRT indicates the transition from fish to tetrapod occurred among flat-head taxa, like Trypanognathus.  Crassigyrinus Fig. 4) is a distinctly different stegocephalid with a taller skull, more like those of the more famous traditional transitional taxa, Ichthyostega and Acanthostega. The new fish-to-tetrapod transitional taxa were recovered by simply adding taxa overlooked by prior workers. Taxon exclusion continues to be the number one problem with vertebrate paleontology today, according to results recovered by the LRT. This free, online resource minimizes taxon exclusion.

Figure x. Subset of the LRT, focusing on fish for July 2020.

Not sure if fish expert John Long
would make the same statement today. Let’s hope things have changed in the last 25 years of vertebrate paleontology.

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References
Long JA 1995. The Rise of Fishes. The Johns Hopkins University Press, Baltimore and London 223 pp.
Schultze H-P 1984. Juvenile specimens of Eusthenopteron foordi Whiteaves, 1881 (Osteolepiform Rhipidistian, Pisces) from the Late Devonian of Miguasha, Quebec, Canada. Journal of Vertebrate Paleontology 4(1):1–16.

wiki/Eusthenopteron

What is Polymorphodon adorfi?

Sues et al. 2020 bring us a new Middle Triassic German diapsid,
Polymorphodon adorfi (Fig. 1; SMNS 91343, SMNS 91400) with a large toothy premaxilla and a hint of an antorbital fenestra.

Figure 1. Skull elements of Polymorphodon. Consider the possibility that the quadrate had an anterior lean, as in figure 2,, elongating the postorbital region of the skull.

At first glance Polymorphodon looks a lot like
Archosaurus (Fig. 2; Late Permian, eastern Europe), a taxon not yet tested in the LRT due to a paucity of material.

Figure 2. Archosaurus is not in the LRT, but shares several traits with Polymorphodon.

From the Sues et al. abstract
“Skeletal remains of a small reptile with a distinctive dentition from the Lower Keuper (Erfurt Formation; Middle Triassic, Ladinian) of the Schumann quarry near Eschenau, in the municipality of Vellberg in Baden-WÃrttemberg, Germany, represent a new taxon of non-archosaurian archosauriforms, Polymorphodon adorfi.”

That’s a wee bit general. Let’s see if the large reptile tree (LRT, 1698+ taxa; subset Fig. 5) can nest it more precisely.

The Sues et al. abstract continues:
“It is diagnosed by various craniodental autapomorphies, including mesial and distal carinae of labiolingually flattened maxillary and dentary tooth crowns with large, somewhat hook-shaped denticles aligned at distinct angle to apicobasal axis of tooth crown; premaxilla with long, leaf-shaped posterodorsal process that is slightly longer than body of element; presence of prominent lateral fossa on premaxilla anteroventral to external narial fenestra; premaxilla with five gently recurved, conical teeth; medial surface of maxilla with distinct ledge above the interdental plates; and maxilla and dentary with distinctly heterodont dentition”

The Sues et al. diagnosis is focusing on the dentition, plus the premaxilla and maxilla. Again, not much to work with, even though quite distinctive.

The Sues et al. abstract continues:
“Phylogenetic analysis recovered Polymorphodon adorfi in a position crownward of Erythrosuchus africanus but in an unresolved polytomy with derived non-archosaurian archosauriforms such as Proterochampsidae and Euparkeria capensis and with Archosauria.”

The first red flag: Proterochampsidae is not related to Euparkeria in the LRT. Simply add taxa to fix this.

The Sues et al. abstract continues:
“The maxillary and dentary teeth of Polymorphodon adorfi differ from those of other non-archosaurian archosauriforms and indicate a different, possibly omnivorous diet, suggesting that these reptiles were more diverse in terms of feeding habits than previously assumed.”

This abstract plus Wikipedia information plus results from the LRT indicate taxon exclusion is the issue here.

In the LRT (subset Fig. 5, not yet updated)
Polymorphodon nests at the base of the Pararchosauriformes, basal to all the many included proterosuchids, choristoderes, phytosaurs and proterochampsids in that order (Fig. 5). In the LRT the clade Pararchosauriformes is a sister to the clade Euarchosauriformes, which begins with two specimens of Euparkeria and ends with crocs, dinos and birds. All these are derived from the UC 1528 specimen of Youngoiides (Fig. 3), the most derived of the various non-archosauriform younginids.

Figure 3. Cladogram on the Polymorphodon Wikipedia page based on Ezcurra 2016. Note the lack of taxa preceding the taxon “Proterosuchidae”, which is where the LRT nests Polymorphodon.

So, yes, taxon exclusion is the problem
with the Sues et al. 2020 cladogram based on the Ezcurra 2016 cladogram, which suffered from taxon exclusion, as detailed here four years ago.

Polymorphodon is a late survivor
of a Late Permian radiation and is a key taxon with many pararchosauriform descendants. This hypothesis of relationships was overlooked by the original authors due to taxon exclusion.

Figure 4. Updated image of various proterosuchids and their kin within the LRT clade, Pararchosauriformes. When you see them all together it is easier to appreciate the similarities and slight differences that are gradual accumulations in derived taxa.

I still have not seen the Sues et al. 2020 PDF.
When it arrives (see below) we’ll see if it includes Youngoides, Archosaurus and many of the pertinent taxa in figure 4. Since they are using Ezcurra 2016 the odds are reduced. For now the nesting of Polymorphodon in the LRT is more certain and more stem-ward than originally proposed (Fig. 3).

Figure 5. Cladogram of basal archosauriforms from 2016. Polymorphodon nests basal to Proterosuchus BPI 1 4016, awaiting an update soon.

Adding taxa solves so many problems.
Not sure why academics are hesitating to do what needs to be done. Sure it’s hard work, but it only has to be done once.

Via email
Hans Sues indicated that a PDF of the paper will be ready within a week due to some publisher issues linking the supplemental information. We may explore this taxon again if that data provides information not available from present sources. For now, only a little data from a new taxon was enough to nest it with confidence, so long as taxon exclusion is minimized, as it is in the LRT. This helpful online resource is free for all to use.

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References
Sues H-D, Schoch RR, Sobral G and Irmis RB 2020. A new archosauriform reptile with distinctive teeth from the Middle Triassic (Ladinian) of Germany. Journal of Vertebrate Paleontology Article: e1764968 (advance online publication)
doi: https://doi.org/10.1080/02724634.2020.1764968
https://www.tandfonline.com/doi/abs/10.1080/02724634.2020.1764968Â

wiki/Polymorphodon

Tanyrhinichthys is an armored goblin shark

Revised December 24, 2020
with additional data moving Tanyrhyichthys closer to Mitsukurina, the goblin shark, a taxon omitted by prior authors.

Sallan et al. 2020 return again to
Tanyrhinichthys mcallisteri (Gottfried, 1987; Stack, Hodnett, Lucas and Sallan 2018; Figs. 1, 2; 15 cm length) and focus on its long rostrum, imagining a bottom-dweller, sturgeon-like lifestyle. Oddly they fail to phylogenetically connect it with the extant goblin shark, Mitsukurina (Figs. 3, 4) due to taxon exclusion and some misinterpretation of the skull and gill bars. In the large reptile tree (LRT, 1498+ taxa then, 1781 taxa now; subset Fig. 5).

Figure 1. Tanyrhinichthys in situ and traced.

Based on that phylogeny,
Tanyrhinichthys had a Silurian genesis. Consider it an armored goblin shark.

Figure 2. Skull of Tanyrhinichthys (above) with two bones relabeled. The premaxilla carries teeth. The nasal does not. The other fish, Saurichthys, is unrelated. Compare to figure 2b.

Figure 3. Tanyrhinichthys face after color tracing. Operculum in lavender. Crowded gill bars in several colors follow.

Figure 4. Mitsukurina, the goblin shark. Note the deep premaxilla, and gracile jugal + fused postorbital as in Tanyrhinichthys in figure 3.

Tanyrhinichthys had deep jaws and sharp, narrow, marginal teeth,
so it nests crownward of Chondrosteus (which had jaws, but no marginal teeth), apart from sturgeons (which lack jaws and marginal teeth). Both have underslung, shark-like jaws..

Stack et al. followed tradition
in assuming sturgeons are aberrant actinopterygian (ray-fin) fish. The LRT does not make assumptions, but tests all possibilities and included taxa. In the LRT (fish subset in Fig. 5) sturgeons have an extendible toothless oral cavity, the first step toward the jaws seen in Chondrosteus and all later taxa. They are not aberrant derived taxa.

From the abstract
“The earliest ray-finned fishes (Actinopterygii) with elongate rostra are poorly known, obscuring the earliest appearances of a now widespread feature in actinopterygians.”

This may be an exaggeration. The LRT tests several long rostra taxa. Several nest close to one another. Note the authors are already assuming Tanyrhinichthys is an actinopterygian just because it has ray-fins. Only a comprehensive cladogram can determine whether or not ray fin fish are monophyletic. They are not, according to the LRT, unless sharks are included, which is not the intent of the clade name or definition.

“We redescribe Tanyrhinichthys mcallisteri, a long-rostrumed actinopterygian from the Upper Pennsylvanian (Missourian) of the Kinney Brick Quarry, New Mexico. Tanyrhinichthys has a lengthened rostrum bearing a sensory canal, ventrally inserted paired fins, posteriorly placed median fins unequal in size and shape, and a heterocercal caudal fin. Tanyrhinichthys shares these features with sturgeons, but lacks chondrostean synapomorphies, indicating convergence on a bottom-feeding lifestyle.”

Note: The authors mention sturgeons, but oddly fail to mention goblins sharks.

“Elongate rostra evolved independently in two lineages of bottom-dwelling, freshwater actinopterygians in the Late Pennsylvanian of Euramerica, as well as in at least one North American chondrichthyan (Bandringa rayi).”

These taxa are not ‘evolved independently.’ Actually all are related to goblin sharks in the LRT. This is what tinkering does… it solves problems no one else ever thought was a problem.

“The near-simultaneous appearance of novel ecomorphologies among multiple, distantly related lineages of actinopterygians and chondrichthyans was common during the Carboniferous radiation of fishes.”

This statement assumes Tanyrhinichthys is an actinopterygian. In the LRT Tanyrhinichthys precedes sharks and bony fish, despite having ray fins. (Don’t make the mistake of ‘Pulling a Larry Martin.’)

Quotes from ScienceDaily.com, focusing on the new paper:
“Sturgeon are considered a ‘primitive’ species, but what we’re showing is that the sturgeon lifestyle is something that’s been selected for in certain conditions and has evolved over and over again,” says Sallan, senior author on the work.

Not so, according to the LRT where sturgeons and paddlefish are related with Chondrosteus and goblin sharks.

The Sallen et al. 2020 abstract,
continues to press the resemblance of Tanyrhinichys to sturgeons, while avoiding goblin sharks.

“Tanyrhinichthys mcallisteri, a member of the diverse and well-preserved fish fauna within the Upper Pennsylvanian (Missourian) Atrasado Formation of the Kinney Brick Quarry (KBQ), is a small (standard length ~15 cm), elongated actinopterygian with a lengthened rostrum. New material suggests that Tanyrhinichthys was a bottom feeder morphologically similar to the modern sturgeon (Acipenser). Like sturgeon, Tanyrhinichthys had a rostrum that extended past its lower jaw and a resultant small, subterminal mouth, as well as a number of other convergent features, including a long anal fin set forward of the dorsal, large lateral line scales, and an anteriorly-deepened body with ventral insertion of the paired fins. Two other long-rostrumed actinopterygians, an unnamed taxon from Indiana and Phanerorhynchus from the U.K., are known from similarly-aged, Pennsylvanian freshwater coal deposits. Various skeletal features indicate that these long-rostrumed fishes were not closely related.

In the LRT these ‘long-rostrumed fishes’ are all related. So where are comparisons to paddlefish and goblin sharks? They immediately follow:

“As supported by the existence of the paddlefish-like shark Bandringa in similarly aged deposits from Illinois, there was widespread convergence on a bottom-feeding freshwater morphotype amongst Pennsylvanian fishes.”

“Tanyrhinichthys falls into a group of fishes with short electro-sensory rostra with less skeletal support anteriorly, likely facilitating a bottom-roving feeding strategy. This group of fishes includes living taxa (sturgeon, paddlefish, and armored catfishes), along with fossil taxa such as Phanerorhynchus. Although there are some exceptions, it appears that long-rostrumed fishes are driven to evolve grossly similar structures in pursuit of distinctive life modes.”

Thus the authors make only the vaguest of connections between Tanyrhinichthys and paddlefish and no connection to goblin sharks.

re: Gottfried 1987 (below): the clade ‘Aeduelliform’ seems to have been used only by him and him alone. A Google search revealed no other attributions or usages.

Tanyrhinichthys seems to have had both
crowded gill slits and an operculum (Fig. 3).

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References
Gottfried MD 1987. A Pennsylvanian aeduelliform (Osteichthyes, Actinopterygii) from North America with comments on aeduelliform interrelationships.
7Paläontologische Zeitschrift 61(1):141-148.
Stack J, Hodnett JM, Lucas S and Sallan L 2018. Tanyrhinichthys, a long-rostrumed Carboniferous ray-finned fish (Actinopterygii), and the evolution of elogate snouts in fishes. Journal of Vertebrate Paleontology abstracts 2018.
Sallan L, Lucas SG, Hodnett J-P and Stack J 2020. Tanyrhinichthys mcallisteri, a long-rostrumed Pennsylvanian ray-finned fish (Actinopterygii) and the simultaneous appearance of novel ecomorphologies in Late Palaeozoic fishes. Zoological Journal of the Linnean Society, 2020; DOI: 10.1093/zoolinnean/zlaa044

Ancient “sturgeon” was not a sturgeon

https://www.sciencedaily.com/releases/2020/06/200622133022.htm

http://reptileevolution.com/polyodon.htm

Reversals produce whale teeth, part 2

Short one today.
You might remember over a year ago a presentation on the evolution of mammal molars from simple to complex and back to simple again in toothed whales (Odontoceti, Fig. 1).

Figure 1. Mammal tooth evolution alongside odontocete tooth evolution, reversing the earlier addition of cusps.

On the same note,
here’s a presentation of three skulls, Pachygenelus (pre-mammal cynodont), Megazostrodon (last common ancestor of all mammals in the large reptile tree (LRT, 1698+ taxa), and Maiacetus, a toothed pre-whale with limbs (Fig. 2).

Figure 2. The pre-mammal, Pachygenelus, the first mammal, Megazostrodon, and a transitional toothed whale, Maiacetus, with teeth highlighted to show the reversal in odontocete molars. This may be the first time Megazostrodon was compared to a pre-whale.

Just concentrate on the teeth today,
and note how the simple cones (Fig. 3) of basal therapsids, then the canine led simple triangles of basal cynodonts (Fig. 2) then multicusped teeth of basal mammals (Fig. 2), slowly reversed over time to become, once again, triangles, then simple cones in odontocete whales (Fig. 4).

Figure 3. Basal therapsids, including Cutleria, with simple cones for teeth, as in odontocete whales.

Figure 4. The killer whale (Orcinus orca) skeleton and skull with parts colorized. Simple conical teeth line the jaws as in pre-cynodont synapsids.

As long-time readers know, baleen whales had their own evolution
as mysticetes arose from mesonychids, hippos, anthracobunids and desmostylians in turn, according to results recovered from the large reptile tree, which minimizes taxon exclusion by testing a wide gamut of nearly 1700 taxa.

Still waiting for a competing analysis
that tests a similar gamut of taxa. Emails to whale experts have not earned replies.

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References

https://pterosaurheresies.wordpress.com/2019/01/02/mammal-tooth-evolution-toward-complexity-and-then-simplicity/

What happened to the postfrontal and postorbital in birds?

Fauth and Rauhut 2020 bring us
“A short overview of the evolution of the skull of birds.”

From the first paragraph (Google translated from German)
“There are a number of advantages to being able to fly, be it the possibility of rapid geographical expansion, the settlement of trees, the escape from predators or the development of new feed sources, including prey capture. However, it cannot be regarded as the sole factor for the success of birds.”

Thereafter
the authors discuss and show (Fig. 1) skull traits, but make a traditional mistake based on a lack of attention to detail. Foth and Rauhut provide only one figure (Fig. 1), in which the postorbital is identified (in orange) only in Allosaurus (B) Archaeopteryx (C) and the enanthiornine, Shenqiornis (D). The postorbital is deemed absent in the extant Crax (A) and the extinct Ichthyornis (E) despite its presence in their diagram.

Figure 1. Theropod and bird skulls from Foth and Rauhut 2020. Postorbital is highlighted in orange, but not the same vestigial postorbital is not highlighted in bird skulls. Note: ‘Archaeopteryx’ is a wastebasket taxon with variation among the 13 known specimens.

Unfortunately
Foth and Rauhut took the easy way out by using previously provided oversimplified diagrams that lack the data needed to create a valid figure. They also followed paleontological tradition, which, at times like this, fail to provide valid data in the details.

Here are the missing details
in an actual Crax skull (Fig. 2) colorized using DGS methods. It shows a descending postfrontal (orange) and a vestigial postorbital (yelllow splint, but see caption for one more option). The postfrontal is largely fused to the frontal, but that does not negate its presence. No unfused frontal descends beyond mid depth in any vertebrate skull. We should label and score with reason, not with invalid traditions.

Figure 2. Crax tuberosa skull in three views. Note the splint-like post0rbital (yellow). Alternate hypothesis: the splint is the postorbital process of the jugal (cyan, separate ossification from the base below the quadratojugal (olive). That would make the lumpy orange postfrontal the postfrontal + fused postorbital. Time to look at some embryos to see what is happening here: another great PhD dissertation.

The Eichstätt specimen of Archaeopteryx (= Jurapteryx)
shows the separation of the postfrontal (orange) from the frontal and the postorbital (in yellow) disarticulated and shifted slightly posteriorly in situ. This is the specimen basal to extant birds.

Figure 3. The Eichstätt specimen, Jurapteryx recurva, nests with the living ostrich, Struthio, presently in the LRT.

The tiny Early Cretaceous theropod, Scipionyx
(Fig. 4), demonstrates the separation of the frontal (blue), postfrontal (yellow-green) and postorbital (orange) in non-avian theropods. These elements tend to fuse with size. Phylogenetic miniaturization (= neotony) tends to separate the original elements. When dealing with shrinking taxa, like birds, try to keep this in mind.

Figure 4. Scipionyx skull and overall. The tail and feet are restored.

The enantiornithine, Shenqiornis,
will be considered in greater detail In future blogposts.

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References
Foth C and OWM Rauhut 2020. Eine kurze Betrachtung der Evolution des Vogelschädels [A short overview on the evolution of the skull of birds]. Jahresbericht 2019 und Mitteilungen 48. ISSN 0942-5845 ISBN 978-3-89937-253-3

Flatheaded Triassic Annaichthys enters the LRT

Earlier we looked at the holotype of Pholidophorus.

Figure 1. Annaichthys holotype in situ.

Almost finless Annaichthys is definitely a pholidophorid,
but it also nests with eel-like Tarrassius at the base of the Lepisosteus (the extant long nose gar) clade. Several transitional taxa separate these two distinct taxa.

Figure 2. Annaichthys skull in situ and reconstructed.

Annaichthys pontegiurinensis (Arratia 2013; MCSNB 11282a,b,c; Triassic) is known from one fossil in part and two counterparts. This taxon nests with Tarrasius. Small fins are visible on the fossil with ventral and lateral surfaces exposed. Pholidophorids are traditionally considered actinopterygii, but in the large reptile tree (LRT, 1675+ taxa) they nest near the base of a large clade of stem lobefins. That means, over deep time, tetrapods are also pholidophorids.

Figure x. Subset of the LRT, focusing on fish for July 2020.

Previously Tarrasius entered the LRT
despite a distinctive tadpole-like morphology (straight tail and lacking pelvic fins).

Pholidophorids are traditionally considered extinct,
but in the LRT the arowana, Osteoglossum, is an extant pholidophorid. So are tetrapods.

According to Arratia 2020,
“Pholidophoriformes Berg (1937) is a poorly known assemblage of Mesozoic actinopterygian fishes whose close association with teleosts and their closest relatives makes them an important group for the understanding of the modern radiation of fishes.”

“More recently, however, the monophyly of †Pholidophoriformes and the relationships of its constituent families have been cast into doubt. The rhombic ganoid scales with peg-and-socket articulation and the elongate or fusiform body shape shared by †pholidophoriforms are now recognized to have a broad distribution within primitive actinopterygians. As a result, the nature and phylogenetic affinities of the various taxa constituting †Pholidophoriformes (collectively referred to here as ‘pholidophoriforms’) are uncertain.”

In Arratia’s 2020 memoir,
Annaichthys was considered, but Tarrasius was not. “Pholidophorus and its somewhat vague original definition (Agassiz, 1832), which has led to it becoming a taxonomic wastebasket for fish possessing rhombic ganoid scales.”

Arratia disputed Berg 1937 when reporting,
“Feature 1, scales and bones built as in Lepidosteus (= Lepisosteus), is difficult to evaluate because it could refer to many different aspects of the scale (e.g., thickness, rnamentation).Even so, there are major differences in the scales and bones of taxa identified as pholidophoriforms by Berg (1937), so it is not clear how this feature unites the group.”

Berg listed 12 traits he thought were shared by Pholidophormes.
In doing so Berg ‘pulled a Larry Martin‘. There is only one way to define any clade and that is by phylogenetic analysis as it determines a last common ancestor. Of course, this may change as taxa are added, so start with a wide gamut analysis like the LRT.

Arratia’s 2020 figure 95 cladogram
nested two dissimilar taxa, Amia (the bowfin) and Lepisosteus (the long nose gar) as outgroup taxa to a clade Teleosteomorpha, which included Pachycormus in a basal clade. The LRT includes more outgroup taxa and does not support this topology.

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References
Arratia G 2020. Morphology, taxonomy, and phylogeny of Triassic pholidophorid fishes (Acinopterygii, Teleostei). Memoir Journal of Vertebrate Paleontology 33:sup1:1–138.

Pholidophoridae Woodward 1890

 

 

Origin of tetrapod herbivory, effects on local plant diversity

Brocklehurst, Kammerer and Benson 2020
discuss the origin of tetrapod herbivory and its effects on local plant diversity. Plant diversity will not be covered here, but we can discuss basal tetrapod herbivory.

According to the authors,
“Time-series regression analysis supports a negative relationship of plant richness with herbivore richness but a positive relationship of plant richness with minimum herbivore body size. This is consistent with studies of present-day ecosystems… Thus far, there has been little discussion on how the origin and early evolution of herbivory, either in arthropods or tetrapods, affected pat- terns of community richness in plants.”

Brocklehurst, Kammerer and Benson 2020 report,
“The earliest tetrapod herbivores appear in the fossil record in the Pennsylvanian, although the precise time of origin for this behaviour is uncertain due to the difficulty of assessing diet in extinct organisms. Potentially herbivorous taxa appear in the Bashkirian (earliest Pennsylvanian)-aged Joggins Formation: pantylid microsaurs with robust palatal dentition, a possible adaptation for grinding plant material or crushing the thick exoskeletons of arthropods (or both). More probable herbivores are known from the Kasimovian stage later in the Pennsylvanian: specimens of the diadectid Desmatodon from the Conemaugh Group of Pennsylvania.”

The authors make no distinction
between reptiles and pre-reptiles (= amniotes and anamniotes) in their paper. And that’s fine. Neither do they put their herbivores into a phylogenetic context. And that’s fine. They don’t take a stand whether diadectids were reptiles or not. They are just concerned about herbivory… and that’s fine.

Reptile herbivory
is a subject touched on in 2012, following a placodont herbivory paper (Diedrich 2011). That old cladogram needs to be revisited again based on the large number of added taxa since then. Even so, many of the hypotheses advanced eight years ago still hold up today.

From 2012:

“The separation between plant-eaters and insect-eaters formed the basal split in the large reptile tree. The emergence of Limnoscelis and its kin and Lanthanosuchus and its kin from this clade bear further scrutiny. I’m sure there’s a story brewing there. Turtles also emerged from this clade of herbivores.

“Among charted lepidosauromorphs we don’t see any other herbivores until Iguana and even it supplements with insects when young. Let me know if I’m missing any others.

“On the archosauromorph side, Edaphosaurus is the first herbivore with several therapsid clades not far behind. Thereafter we don’t see any until the Placodontia (if they were indeed herbivores and not shell crushers), the Aetosaurs and the Phytodinosauria.”

Getting back to the present day:
In the large reptile tree (LRT, 1698+ taxa) herbivory seems to appear on one branch only at the basal dichotomy of reptiles immediately following Silvanerpeton. Many, and potentially all of the basal taxa in the new Lepidosauromorpha are herbivores. Most are universally accepted herbivores: captorhinids, diadectids + bolosaurids + procolophonids, pareiasaurids and caseasaurids. The taxa surrounding and interweaving with these obvious herbivore clades could also be herbivores based on phylogenetic bracketing. These include: Milleretta, Concordia, Cephalerpeton (Fig. 1) and even Limnoscelis.

Figure 1. Opisthodontosaurus (above) with missing bones in color. Black lines represent the referred specimen, OMNH 77470 scaled to fit the holotype, OMNH
77469, here in ghosted lines. Colors represent missing bones.

No taxa in the basal Archosauromorpha
are obvious herbivores until the sailback synapsid, Edaphosaurus.and again in the therapsid clade Anomodontia. Insectivory seems to have evolved into carnivory most of the time.

Among microsaurs
Pantylus and Stegotretus seem to stand alone as likely herbivores among anamniotes (basal tetrapods) confirming Brocklehurst, Kammerer and Benson 2020.

According to Brocklehurst, Kammerer and Benon
(their figure 1) throughout most of the Carboniferous plants maintained their greatest diversity. That changed during the latest Carboniferous when plants experienced a large diversity reduction coeval with the arrival of tetrapod herbivores. The authors conclude, “We find that the early Permian diversification of herbivorous tetrapods constrained the α-diversity of plants for the rest of the Palaeozoic.”

A chronological tree of tetrapods
can be found here. As you’ll see, only a few, rare taxa are known before the Late Carboniferous. Thereafter, and especially in the Early Permian, fossils from a variety of clades are known, including herbivores. The question is: Did tetrapods suddenly flourish? Or did the world change and tetrapods suddenly find themselves in areas that tended to fossilize better?

In other words,
would figure 1 of Brocklehurst, Kammerer and Benson look about the same if just insectivores and carnivores were included? Perhaps their conclusions would have been stronger if insectivores and carnivores were also included, just to be sure it was indeed the herbivores responsible for a reduction in plant diversity and not the planet at the time.

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References
Brocklehurst N, Kammerer CF and Benson RJ 2020 The origin of tetrapod herbivory: effects on local plant diversity. Proceedings of the Royal Society B 287: 20200124. http://dx.doi.org/10.1098/rspb.2020.0124
Diedrich CG 2011. Fossil middle triassic “sea cows” – placodont reptiles as macroalgae feeders along the north-western tethys coastline with pangaea and in the germanic basin. Natural Science 3 (1) 9-27 (2011)

https://pterosaurheresies.wordpress.com/2019/10/16/you-heard-it-here-in-2011-diadectids-are-amniotes/
http://reptileevolution.com/reptile-tree2.htm