The origin of pterosaurs delayed…

In Peters 2000
pterosaurs were found to be indisputably derived from the fenestrasaurs, Longisquama, Sharovipteryx and Cosesaurus in order of increasing distance.

In Peters 2007
pterosaurs (and other fenestrasaurs) were found to be indisputably derived from a new clade of lepidosaurs, including Huehuecuetzpalli.

In Peters 2011–2018
more taxa (up to 1253 at last count) cemented those relationships. Other works, cited below, further cement those relationships.

Switek 2018 reported,
“We’ve cataloged plenty of species, with more named every year, but understanding how they [pterosaurs] fit into the Mesozoic world has eluded us.”

This, dear readers,
is called suppression. Perhaps Dr. SC Bennett (personal communication) said it best, “You won’t get published and if you do get published, you won’t be cited.” What other science is like this?

Dr. J. Ostrom, famous for his bird origin work, lamented the same problem. 
According to the Hartford Courant (2000), “In 1973, Ostrom broke from the scientific mainstream by reviving a Victorian-era hypothesis (see above) that his colleagues considered far-fetched: Birds, he said, evolved from dinosaurs. And he spent the rest of his career trying to prove it.” With the announcement of the first dinosaurs with feathers from China, Ostrom (then age 73) was in no mood to celebrate. He is quoted as saying, ““I’ve been saying the same damn thing since 1973, `I said, `Look at Archaeopteryx!’” Ostrom was the first scientist to collect physical evidence for the theory. Ostrom provoked a debate that raged for decades. “At first they said, `Oh John, you’re crazy,”’ Ostrom said in 1999.”

So, it’s not just me. It’s paleontology.
For readers thinking about getting into this field, here’s fair warning. And I’m going to call it out every time I see it, just like John Ostrom did.

References
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist 
Historical Biology 15: 277-301
Peters D. 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330
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
Peters D 2011–2018. ReptileEvolution.com and PterosaurHeresies.Wordpress.com
Switek B. 2018. https://blogs.scientificamerican.com/laelaps/digging-into-pterosaur-diets/

Hartford Courant (2000)

Think of aardvarks and sloths as naked and hairy glyptodonts respectively

Because
that’s what they really are… aardvarks are naked and sloths are hairy glyptodonts. And, yes, that comes as a surprise, it breaks a paradigm, it spins your head around, it’s heretical… and it’s exactly where the data takes us.

The Edentata is an odd clade
in which the basalmost taxa, like Barylambda, Glyptodon and Holmesina are very large. On the other hand, terminal extant and derived taxa, like Peltephilus and Cyclopesare much smaller, just the opposite of most mammal clades (in which smaller usually lead to larger, following Cope’s Rule.)

According to Wikipedia,
“Glyptodontinae (glyptodonts or glyptodontines) are an extinct subfamily of large, heavily armored armadillos which developed in South America and spread to North America.”

In the large reptile tree (LRT, 1252 taxa) the glyptodont, Glyptodon, nests between the massive Barylambda and giant sloths, followed by smaller tree sloths and small extinct horned armadillos, like Peltephilus. On another branch (Fig. 1) another large glyptodont, Holmesina, nests between the massive Barylambda and the much smaller aardvark, Orycteropus, the armadillo, Dasypus, and the anteaters, Tamandua and Cyclopes.

Such a big-to-small phylogenetic pattern,
is known as phylogenetic miniaturization or the Lilliput Effect and is often the product of neotony (adults retaining juvenile traits, including juvenile size).

Figure 2. Holmesina, the glyptodont ancestor to aardvarks, anteaters and armadillos.

Figure 2. Holmesina, the glyptodont ancestor to aardvarks, anteaters and armadillos. Those are aardvark hands (Fig. 3), glyptodont feet.

Holmesina (Fig. 2) is added to the LRT today.
Basically it is a longer-snouted glyptodont, basal to the longer snouted above-mentioned aardvarks, armadillos and anteaters.

Following a reader comment,
(suggesting ‘taxon exclusion’ was the issue that did not unite glyptodonts with armadillos) I was looking for a transitional taxon to more closely nest glyptodonts with armadillos, rather than sloths. I did so and the tree topology did not change when Holmesina was added. Armadillos are still one taxon removed from glyptodonts, but at least now we have a glyptodont on the long-nosed clade of aardvarks, etc.. As before, aardvarks nest between glyptodonts and armadillos. Looking at all the edentate taxa in detail and overall. I think this nesting and this tree topology seem very reasonable (= it produces a gradual accumulation of derived traits at all nodes and between all taxa).

Figure 3. Orycterpus, the extant aardvark, is a living sister to Barylambda from the Paleocene.

Figure 3. Orycterpus, the extant aardvark, is a living sister to Barylambda from the Paleocene. Aardvarks traditionally nest alone, but in the LRT they are edentates without armor… or hair.

Other workers, like Fernicola, Vizcaíno and Fariña 2008,
described the phylogeny of glyptodonts by putting taxa like Holmesina at the base while omitting Barylambda. Thus such studies do not present the full picture due to taxon exclusion. Everyone seems to omit Barylambda and all the other edentate outgroups back to Devonian tetrapods… but not the LRT.

Goodbye ‘Xenarthra’. Goodbye ‘Pilosa’. Goodbye ‘Cingulata’.
According to Wikipedia, “The order Pilosa is a group of placental mammals, extant today only in the Americas. It includes the anteaters and sloths, including the extinct ground sloths, which became extinct about 10,000 years ago.” According to Wikipedia, Cingulata, part of the superorder Xenarthra, is an order of armored New World placental mammals.” In the LRT ‘Xenarthra’ (Cope 1889) is a junior synonym for ‘Pilosa’ (Flower 1883) and that is a junior synonym for Edentata (Darwin 1859).

References
Darwin C 1859. On the origin of species.
Fernicola JC, Vizcaíno SF and Fariña RA 2008.
The evolution of armored xenarthrans and a phylogeny of the glyptodonts. Chapter 7 in: The Biology of the Xenarthra, Eds: Vizcaíno SF and Loughry WJ. University Press of Florida.
Gaudin TJ and Croft DA 2015. Paleogene Xenarthra and the evolution of South American mammals. Journal of Mammalogy 96 (4): 622–634. https://doi.org/10.1093/jmammal/gyv073

http://www.finedictionary.com/Edentata.html

 

 

 

 

Marmosa, Caluromys and Chironectes: the living, breathing origin of the Eutheria

These are the mouse, wooly and water opossums:
Marmosa (Fig. 1), Caluromys (Fig. 4) and Chironectes (Figs. 8, 9). As traditional didelphids, they’ve received too little attention. In a world in love with DNA phylogenetic analysis, they’ve received too little attention. In the large reptile tree (LRT, 1252 taxa, subset Fig. 3) these are the much sought after transitional taxa between Metatheria (marsupials) and Eutheria (placentals).

As simple and logical as this sounds
the present hypothesis of interrelationships (Fig. 3) is heretical. From Novacek 1989, 1992 to Tarver et al. 2016 other workers have placed armadillos, pangolins and elephants at the base of the Eutheria using gene analyses. As mentioned earlier, it is discouraging to see serious paleontologists (references below, including a certain science blogger) among the ‘believers’ as they embrace and put their faith in a method (gene analysis) that fails to deliver a gradual accumulation of derived traits at every node in large phylogenetic analyses, hoping for eventual redemption. They just accept the results without questioning. And that is surprising, because as a professor, you can’t really explain to students how these results gradually evolve. Rather these studies mix up and confuse the placental clades as others have mixed up the bird clades using DNA. We’ll take a look at these influential placental DNA papers and list their problems in detail in a few days. It’ll be horrible, untenable and illogical, so prepare yourself.

FIgure 1. Marmosa murina in vivo.

FIgure 1. Marmosa murina in vivo. Yes, this pouch less marsupial is carrying babies in front of its thigh. This is what basal placentals, like bats and flying lemurs do.

 

Marmosa murina
(Gray 1821, Voss and Jansa 2009) 
is one of 19 species of ‘mouse opossums’ native from Mexico to Argentina. In the large reptile tree (LRT, 1252 taxa, Fig. 3) Marmosa nests at the base of the last metatherian clade prior to the origin of eutherians (placentals), the clade that includes Monodelphis, and Chironectes (a swimmer). Like other mouse opossums (Fig. 5) Marmosa lacks a marsupium (= pouch) like its sisters (Fig. 5).

Marmosa waterhousi (Gray 1821) skull is shown below (Fig. 2).

Figure. 2. Marmosa waterhousi skull.

Figure. 2. Marmosa waterhousi skull.

 

Caluromys derbianus
(Allen 1904; Fonseca and Astúa 2018; Fig. 4) is the living ‘wooly opossum’, native to Central America. Sometimes it feeds inverted as seen in bats and hypothesized for pre-bats. It is an omnivore, like related placental carnivore, Nandinia.

Caluromys nests just inside of the first placental clade, Carnivora, alongside Vulpavus (Fig. 6), a taxon omitted from all prior papers on didelphids. Basal Carnivora are larger than other basal shrew- and mouse-sized placentals. In like fashion, Caluromys is the largest of these opossums, similar in size and shape to Vulpavus.

Figure 4. Subset of the LRT focusing on the Metatheria (=Marsupials). Here the diprotodont dentition evolved twice.

Figure 3. Subset of the LRT focusing on the Metatheria (=Marsupials). Here the diprotodont dentition evolved twice.

As we discussed earlier
here regarding Mondelphis (a genus including 22 species of short-tailed opossum) and the origin of bats and dermopterans, the transition from metatherians to eutherians was a gradual one that took place at this phylogenetic transition. So there is no great revelation here, just more evidence piling on.

Figure 1. Caluromys skull and mandible (sized to fit).

Figure 4 Caluromys skull and mandible (sized to fit).



Voss and Jansa found a ‘pouch’ in Caluromys,
but no pouch in the slightly more primitive and perhaps more plesiomorphic, Marmosa and Monodelphis. They report, “The marsupium of Caluromys philander uniquely consists of deep lateral skin folds that enclose the nursing young and open in the midline.” 

But wait!
In this regard the marsupium of Caluromys more closely resembles that of placental dermopterans and bats, taxa that expand these deep lateral skin folds to create newborn nurseries and ultimately, gliding membranes. Voss and Jansa do not mention the term ‘Eutheria’ and do not mention placentals as descendants of mouse opossums in their paper. This was an opportunity missed, but resolved here.

Didelphids
Take a look at the nesting of Didelphis in the LRT (subset in Fig. 3) and you’ll see that this is the primitive clade from which all other metatherians evolved. Most large carnivores and herbivores split off on a separate clade, leaving the mouse-sized didelphids (the Proeutherians) a more direct route to the Eutherian grade. This hypothesis of interrelationships has not been noticed or published before.

Pouch-less marsupials?
Why not just call them what they are? Transitional taxa. This is exactly how the Eutheria evolved from the Metatheria. Is this a heretical hypothesis? Or is it just another overlooked hypothesis that should have been proposed a century ago.

Figure 6. Mammary glands in pouchless marsupials. These taxa have not been tested in the LRT.

Figure 5. Mammary glands in pouch-less marsupials (mouse opossums). Pouch-less marsupials? Why not just call them what they are? Transitional taxa.

Other hypotheses
In the pre-cladistic era, Lillegraven et al. 1987 described the origin of Eutherian mammals “with high intensity food habits, small body masses and adaptations to very cold climates.” The authors focused on soft tissue traits the involve reproduction and metabolismn and put forth a hypotheses as to how nonspecific eutherians could have arisen from nonspecific metatherians… when they could have just studied mouse, wooly and water opossums and removed the guesswork. As mentioned above, modern authors delved far astray in their search for taxa at this transition.

In a very real sense
when you look at these images of mouse, wooly and water opossums you’re looking at an excellent example of the last common ancestors of all placental mammals, probably originating in the Early Jurassic (based on the first appearance of placental multituberculate Megaconus in the Middle Jurassic, in the LRT). These small didelphids are not terminal taxa. They are living breathing late-surviving representatives of an Early Jurassic split between pouch-less metatherians and pouch-less eutherians.

Figure 8. Caluromys, the largest of the mouse opossums, to scale with its LRT sister, Vulpavus, a basal member of Carnivora.

Figure 6. Caluromys, the wooly opossum, to scale with its LRT sister, Vulpavus, a basal member of Carnivora.

Here’s an unexpected finding:
Caluromys, the woolly opossum, nests as the basalmost member of the Carnivora (Fig. 3), but it retains a pouch. Time in the pouch is not particularly short. Size at birth is not particularly large. Sister taxa, including Vulpavus and Deltatherium, are both extinct, so we don’t know whether they had a pouch, but we know that on the main branch of carnivores, starting with Nandinia, the pouch was gone, convergent with mouse opossums (Fig. 5). Caluromys also has more molars than other carnivores and a longer nasal bone.

But remember,
in phylogeny it’s not the particular cherry-picked traits that determine what clade a taxon is a member of, its the nesting within a clade based on a suite of traits that is paramount.

So, similar to mammal-like reptiles,
amphibian-like reptiles, walking whales and dinosaur-like birds, Caluromys was a very basal metathere-like carnivore. And that’s how evolution really works in trait analysis.

Figure 8. Chironectes minimus skull.

Figure 8. Chironectes minimus, the water opossum, skull.

We didn’t spend much time with the water opossum, Chironectes.
It’s important to note that it, too, has a pouch. This sole aquatic marsupial has a water-proof pouch with a unique sphincter for access. And it nests in the LRT as the proximal outgroup taxa to the Eutheria, although the aquatic niche and webbed feet are autapomorphies not retained in descendant taxa among the placental mammals. These traits have had the entire Cretaceous and Cenozoic to develop after that phylogenetic split.

When you’re looking for transitional taxa,
keep looking for the little, plain, brown taxa and you will often find them.

Figure 9. Chironectes minimus, the water opossum, in vivo.

Figure 9. Chironectes minimus, the water opossum, in vivo. This sole aquatic marsupial has a water-proof pouch with a unique sphincter for access.

References
Allen JA 1904. Mammals from southern Mexico and Central and South America. Bulletin American Museum of Natural History 20(4): 29-80.
Burnett GT 1830. Illustrations of the Quadrupeda, or Quadrupeds, being the arrangement of the true four-footed Beasts indicated in outline. Quarterly Journal of Science, Literature and Art, July to December, 1829, 336–353.
Cifelli RL 1993. Theria of metatherian-eutherian grade and the origin of marsupials. In FS Szalay, MJ Novacek, and MC McKenna (editors), Mammal phylogeny: Mesozoic differentiation, multituberculates, monotremes, early therians, and marsupials, 205–215. New York: Springer.
Gray JE 1821. On the natural arrangement of vertebrose animals. London Medical Repository 15(1):296–310.
Hallstrom BM, Kullberg M, Nilsson MA and Janke A 2007. Phylogenomic data analyses provide evidence that Xenarthra and Afrotheria are sister groups. Molecular Biology and Evolution 24, 2059–2068.
Lillegraven JA, Thompson SD, McNab BK and Patton JL 1987. The origin of eutherian mammals. Biological Journal of the Linnean Society 32:281–336.
Murphy WJ, et al. 2001. Molecular phylogenetics and the origins of placental mammals. Nature 409, 614-618.
Naish D 2015. The Refined, Fine-Tuned Placental Mammal Family Tree. scientificamerican.com/tetrapod-zoology/
Novacek MJ 1989. Higher mammal phylogeny: the morphological-molecular synthesis. In Fernholm, B., Bremer. K. & Jornvall, H. (eds) The Hierarchy of Life. Elsevier, Amsterdam, pp. 421-435.
Novacek MJ 1992a. Fossils, topologies, missing data, and the higher level phylogeny of eutherian mammals. Systematic Biology 41, 58-73.
Novacek MJ 1992b. Mammalian phylogeny: shaking the tree. Nature 356, 121-125.
Pine RH, Flores DA and Bauer K 2013. The second known specimen of Monodelphs unistriata (Wagner) (Mammalia: Didelphimorphia), with redescription of the species and phylogenetic analysis. Zootaxa3640 (3):425-441.
Tarver JE et al. 2016. The Interrelationships of Placental Mammals and the Limits of Phylogenetic Inference. Genome Biol. Evol. 8(2):330–344. doi:10.1093/gbe/evv261
Voss RS and Jansa SA 2009. Phylogenetic relationships and classification of didelphid marsupials, an extant radiation of New World metatherian mammals. Bulletin of the American Museum of Natural History, no. 322. PDF
Wildman et al. 2007. Genomics, biogeography, and the diversification of placental mammals. Proceedings of the National Academy of Sciences of the United States of America 104, 14395-14400 PDF.

wiki/Monodelphis
wiki/Marmosa
wiki/Caluromys derbianus
https://animaldiversity.org/accounts/Chironectes_minimus/
wiki/Water_opossum

Origin of pterosaurs and origin of archosauriforms abstracts

Part 2 
The following manuscripts are independently published online without peer-review at the DavidPetersStudio.com website. http://www.davidpetersstudio.com/papers.htm

Better to put them out there this way
than to let these works remain suppressed. Hope this helps clarify issues.


Peters D 2018c.
Cosesaurus avicepsSharovipteryx mirabilis and Longisquama insignis reinterpreted
PDF of manuscript and figures

Currently the majority of pterosaur and archosaur workers maintain the traditional paradigms that pterosaurs appeared suddenly in the fossil record without obvious antecedent and that pterosaurs were most closely related to archosaurs because they shared an antorbital fenestra and a simple hinge ankle. Oddly, these hypotheses continue despite the widely accepted acknowledgement that no archosauriformes document a gradual accumulation of pterosaurian traits. The minority view provided four phylogenetic analyses that documented a gradual accumulation of pterosaurian traits in three fenestrasaurs, Cosesaurus aviceps, Sharovipteryx mirabilis, and Longisquama insignis and their ancestors. These three also had an antorbital fenestra and a simple hinge ankle by convergence. Unfortunately the minority view descriptions also included several misinterpretations. Those are corrected here. The revised descriptions add further support to the nesting of pterosaurs with fenestrasaurs, a clade that now nests within a new clade of lepidosaurs between Sphenodontia and Squamata. The new data sheds light on the genesis of active flapping fight in the nonvolant ancestors of pterosaurs.


Peters, D. 2018d
Youngoides romeri and the origin of the Archosauriformes

Prior workers reported that all specimens attributed to Youngopsis and Youngoides could not be distinguished from the holotype of Youngina capensis. Others considered all specimens attributed to ProterosuchusChasmatosaurus and Elaphrosuchus conspecific. In both cases distinct skull shapes were attributed to taphonomic variations due to distortion pressure or allometric growth. Here a large phylogenetic analysis of the Amniota (1248 taxa) tests those hypotheses. The resulting tree recovers a den of small Youngina specimens preceding the Protorosauria. Another specimen nests at the base of the Protorosauria. Six others nest between the Protorosauria and the Archosauriformes. The most derived of these bears a nascent antorbital fenestra. Two other putative Youngina specimens nest at unrelated nodes. In like fashion, the various specimens assigned to Proterosuchus are recovered in distinct clades. One leads to the Proterochampsidae, Parasuchia and Choristodera. The latter lost the antorbital fenestra. Another clade leads to all higher archosauriforms. The present analysis reveals an evolutionary sequence shedding new light on the origin and radiation of early archosauriforms. Taphonomic distortion pressure and allometry during ontogeny were less of a factor than previously assumed. The splitting of several specimens currently considered Youngina and Proterosuchus into distinct genera and species is supported here.


These manuscripts benefit from
ongoing studies at the large reptile tree (LRT, 1251 taxa) in which taxon exclusion possibilities are minimized and all included taxa can trace their ancestry back to Devonian tetrapods.

The diet of Thylacoleo, the giant sugar glider

The diet of Thylacoleo, the so-called ‘marsupial lion,’
has been a puzzle for decades. The jaws and teeth look dangerous and carnivorous, but Thylacoleo nests in the middle of an herbivorous clade of wombat-like marsupials.

That’s the problem.
Morphology and phylogeny provide the problem… and the answer to the diet of Thylacoleo. This answer could have been known decades earlier, but alas… the same taxon exclusion issue that pervades paleo was also present here.

Morphology
One look at the palate of Thylacoleo documents a very different sort of mammal palate:

  1. The jawline curves laterally near the premolars
  2. Several molars seem to have fused to become one giant tooth
  3. There is an asymmetry in the lineup of the posterior teeth
Figure 1. The palate of Thylacoleo is unusual in several respects. See text for details.

Figure 1. The palate of Thylacoleo is unusual in several respects. See text for details. Vertical arrows point to asymmetries. Horizontal arrow lines up with parasagittal plane.

 

Phylogeny
In the large reptile tree (LRT, 1250 taxa) the closest living sisters to Thylacoleo, the sugar gliders, like Petaurus, should provide some sort of natural guidance as to what the giant sugar glider ate. And they do.

Sugar glider diet
From the Wikipedia page on sugar gliders: Sugar gliders are seasonally adaptive omnivores with a wide variety of foods in their diet… In summer they are primarily insectivorous, and in the winter when insects (and other arthropods) are scarce, they are mostly exudativorous (feeding on acacia gum, eucalyptus sap, manna, honeydew or lerp). Sugar gliders have an enlarged caecum to assist in digestion of complex carbohydrates obtained from gum and sap.

To obtain sap and nectar from plants, sugar gliders will strip the bark off trees or open bore holes with their teeth to access stored liquid gum. Little time is spent foraging for insects, as it is an energetically expensive process, and sugar gliders will wait until insects fly into their habitat, or stop to feed on flowers. They are opportunistic feeders and can be carnivorous, preying mostly on lizards and small birds. They eat many other foods when available, such as nectar, acacia seeds, bird eggs, pollen, fungi and native fruits. Pollen can make up a large portion of their diet, therefore sugar gliders are likely to be important pollinators of Banksia species.”

Well, there you have it. 
Little sugar gliders can be carnivorous. They can also strip bark off trees to get at the gum inside. That’s a rare diet. As sister taxa, giant sugar gliders, like Thylacoleo, were therefore likely also carnivorous and/or stripped bark off trees to get at the gum. For the latter odd reason the odd skull of Thylacoleo was likely adapted, and predation, if you insist, but predators don’t have the odd palate and teeth that Thylacoleo has.

We don’t have to provide a narrow dietary answer for Thylacoleo
because the diet of living sugar gliders is diverse. AND sugar gliders provide the long-sought carnivorous exception to this herbivorous clade.

Petaurus breviceps (Waterhouse 1839; Early Miocene to present; up to 30cm) is the extant sugar glider, a nocturnal squirrel-like marsupial able to climb trees and glide with furry membranes between the fore and hind limbs. An opposable toe is present on each hind foot. Sharp claws tip every digit.

Thylacoleo carnifex (Owen 1859; Pliocene-Pleistocene; 1.14 m long) was a giant sugar glider like Petaurus. Thylacoleo had the strongest bite of any mammal with the largest, sharpest molars of any mammal. It had fewer but larger teeth than Petaurus. The manus included retractable claws. The pes had a very large heel bone (calcaneum). This supposedly carnivorous ‘marsupial lion’ nests with herbivores. Pedal digit 1 likely had a phalanx and claw, but it has not been shown. Sugar gliders strip bark off of trees and the very odd teeth of Thylacoleo could have done the same on a larger scale.

References
Owen R 1859. On the fossil mammals of Australia. Part II. Description of a mutilated skull of the large marsupial carnivore (Thylacoleo carnifex Owen), from a calcareous conglomerate stratum, eighty miles S. W. of Melbourne, Victoria. Philosophical Transactions of the Royal Society 149, 309-322.
Waterhouse GR 1838. Observations on certain modifications observed in the dentition of the Flying Opossums (the genus Petaurus of authors). Proceedings of the Zoological Society of London. 4: 149–153.

wiki/Petaurus
wiki/Thylacoleo
NOVA | Bone Diggers | Anatomy of Thylacoleo | PBS
https://en.wikipedia.org/wiki/Sugar_glider
https://www.wired.com/2009/06/thylacoleo-herbivore-or-carnivore/

Sinodelphys: not a marsupial in the LRT

2003 was just too early for this taxon to be properly nested.
Sinodelphys (Luo et al., 2003) was considered the oldest known metathere (= marsupial) and was compared with Didelphis, the extant Virginia opossum. Here in the large reptile tree (LRT, 1250 taxa, subset Fig. 1) Sinodelphys nests between Chaoyangodens and Brasilitherium + Kuehneotherium among the prototheres, basal egg-laying mammals. Sinodelphys may have been mistakenly nested because Chaoyangodens and Brasilitherium are newer taxa. Several of the other taxa are also more recently published.

Figure 2. Mesozoic prototherians + Megazostrodon, the last common ancestor of all mammals. Only two taxa (gray) are post-Cretaceous.

Figure 2. Mesozoic prototherians + Megazostrodon, the last common ancestor of all mammals. Only two taxa (gray) are post-Cretaceous.

The Luo et al. study nests Sinodelphys
just inside the Metatheria, very close to the Eutheria/Metatheria split. Among taxa both analyses have in common, very few have matching sister taxa. Many are not even in the same large clade (Eutheria/Metatheria/Prototheria). This may be due to an over reliance on dental traits in the Luo et all. study and an under reliance of dental traits in the LRT, which employs a wider gamut of taxa (vs. taxon exclusion in the Luo et al. study).

Figure 2. Sinodelphys skeleton in situ with select bones colored using DGS.

Figure 2. Sinodelphys skeleton in situ with select bones colored using DGS.

Clearly
Sinodelphys has a dorsal naris with short ascending processes on the premaxilla, not a terminal naris opening anteriorly. This trait alone nests Sinodelphys with the egg-laying mammals. Even so, a long list of traits support that nesting. Perhaps if Sinodelphys were described today, after so many other prototheres have been reported, it would have been identified as one of them.

Figure 3. Skull and forelimbs of Sinodelphys in situ. Arrow shows the displacement of the entire hand that otherwise appears to be lost beyond the matrix. How fortuitous!

Figure 3. Skull and forelimbs of Sinodelphys in situ. Arrow shows the displacement of the entire hand that otherwise appears to be lost beyond the matrix. How fortuitous!

With an inch-long skull
this is a tiny Early Cretaceous egg-layer, ancestral to today’s platypus and echidna.

Figure 4. Reconstruced skull of Sinodelphys based on DGS methods. This is very close to Brasilitherium.

Figure 4. Reconstruced skull of Sinodelphys based on DGS methods. This is very close to Brasilitherium, but with a larger set of canines. Like other prototheres, the nares are dorsal, not terminal.

The fingers on both hands are jumbled up (Fig. 3).
If Luo et al. are correct in their manus reconstruction, the only change I would make is to flip it left to right. Note their digit 5 is missing the proximal phalanx (Fig. 5). That is more likely the thumb because then digits 3 and 4 are the longest, as in sister taxa in the LRT.

Figure 4. Manus of Sinodelphys as originally reconstructed. Flipping the hand, as in the revised image, more closely matches sister taxa with digits 3 and 4 the longest.

Figure 5. Manus of Sinodelphys as originally reconstructed. Flipping the hand, as in the revised image, more closely matches sister taxa with digits 3 and 4 the longest.

References
Luo Z-X, Ji Q, Wible JR and Yuan C-X 2003. An Early Cretaceous tribosphenic mammal and metatherian evolution. Science 302:1934–1939.

A surprising ancestor for kangaroos: Interatherium

Traditionally the short-faced kangaroo,
(genus: Procoptodon; Owen 1870; Pleistocene; Figs. 1, 3) was considered an aberrant taxon with a weirdly shortened face, so unlike that of traditional kangaroos, like Macropus (Fig. 1). However, by adding taxa, like Procoptodon and Dendrolagus (Fig. 1), to the large reptile tree (LRT, 1248 taxa, subset Fig. 4) Interatherium (Figs. 1,2) shifts over to become an ancestral kangaroo, despite lacking hopping legs and diprotodont teeth. The skulls of Interatherium and Procoptodon are incredibly similar, even if the post-crania and dental formula of Procoptodon has evolved.

Figure 1. The skulls of Toxodon, Procoptodon and Interatherium resemble one another more than their post-crania might suggest. Now they nest together in the LRT (subset in figure 2).

Figure 1. The skulls of Toxodon, Procoptodon and Interatherium resemble one another more than their post-crania might suggest. Now they nest together in the LRT (subset in figure 2).

Interatherium (Mid-Miocene)
has not been linked to Procoptodon (Pleistocene) before.

And why should it?

  1. Balbaroo (Flannery, Archer and Plane, 1983; Black et al. 2014, Middle Miocene) was hailed as a kangaroo ancestor, but in the LRT it nests with the phalanger, Phalanger
  2. Cookeroo bulwidarri (Butler et al. 2016; Late Oligocene, Early Miocene, 23-18mya)was hailed as a non-hopping kangaroo ancestor. The LRT has not tested it yet, but it looks like Macropus (Fig. 1).
  3. Palaeopotorous priscus (den Boer and Kear 2018; middle Miocene) was hailed as a non-hopping kangaroo ancestor, based on teeth.
  4. Tradition considers Interatheriidae “an extinct family of notoungulate (placental) mammals from South America, known from the Eocene through the Miocene. These animals were principally small-sized, occupying a habitat like hares and marmots.The majority were very small, like rodents.”
  5. Interatherium has four fingers (Fig. 2), lacking a thumb (convergent, it turns out, with Protypotherium, a placental herbivore traditionally considered related). Kangaroos retain five fingers (but I’d like to see a good X-ray or something similar).
Figure 2. Interatherium is the surprising ancestor of kangaroos, with a special affinity to the short-face kangaroo.

Figure 2. Interatherium is the surprising ancestor of kangaroos, with a special affinity to the short-face kangaroo.

Current DNA studies
place a small wallaby, Lagostrophus, at the base of their kangaroo cladogram, but Lagostrophus already has diprodontid teeth. That’s too easy. We’re looking for an earlier, more primitive taxon, without obvious kangaroo traits.

Figure 4. Procoptodon is a basal kangaroo, close to Interatherium (Fig. 3).

Figure 3. Procoptodon is a basal kangaroo, close to Interatherium (Fig. 3). Here longer legs and longer feet differentiate this taxon from Interatherium.

Interatherium (Miocene) represents a late-surviving member
of a much earlier (Late Jurassic) kangaroo radiation, in which the interathere clade lost its thumb. Alternate scenario: perhaps the thumb was never collected in the matrix. The epipubes were likewise somehow overlooked, though I think I see them is an online image of an in situ fossil. More data needed here.

This Late Jurassic kangaroo genesis
is based on the Early Cretaceous appearance of Anebodon, a kangaroo cousin more closely related to the extant marsupial mole, Notoryctes. These burrowers, in turn, have more kangaroo-like sister taxa, today represented by the bandicoot Perameles and the biliby, Macrotis, which combine long hind limbs and digging front limbs.

Note, the front dentary teeth of Interatherium
(Fig. 1). The change to diprotodonty (two anterior fangs) has not happened yet in Interatherium, but the canines are on the way out and the squamosals are very tall.

Figure 4. Subset of the LRT focusing on the Metatheria (=Marsupials). Here the diprotodont dentition evolved twice.

Figure 4. Subset of the LRT focusing on the Metatheria (=Marsupials). Here the diprotodont dentition evolved twice.

Interatherium rodens (Ameghino 1887, 1894; Middle Miocene; 50cm in length) the Interatheridae and Interatherium were long considered members of the Notoungulata, a clade that has broken up in the LRT. Here (Fig. 4) Interatherium nests at the base of the kangaroos, derived from the more basal marsupials like Eomaia. Interatherium retains several small incisors, but apparently has lost its thumb, unlike kangaroos.

Note
that Interatherium, nesting at the base of the kangaroo clade (Fig. 4), is also the sister to the Toxodon + the wombat (genus: Vombatus) clade. There the diprotodont dental pattern appears by convergence because, like Interatherium, basal taxa (genus: Eurygenium, late Oligocene, and Toxodon) lack a diprotodont dental pattern.

Goodbye, Diprotodontia.
The clade Diprotodontia is no longer monophyletic (Fig. 4) and can no longer be exclusively defined by the diprotodont dental pattern, which now appears twice within the Metatheria. Please test this heresy and let me know what you get. Taxon exclusion is once again the problem here.

References
Ameghino F 1887. Observaciones generales sobre el orden de mamíferos estinguidos sud-americanos llamados toxodontes (Toxodontia) y sinopsis de los géneros y especies hasta ahora conocidos. Anales del Museo de La Plata 1:1-66.
Ameghino F 1894. Enumeration synoptique des especes de mammifères fossiles des formations éocènes de Patagonie. Boletin de la Academia Nacional de Ciencias en Cordoba (Republica Argentina) 13:259-452.
Black KH et al. 2014. A New Species of the Basal “Kangaroo” Balbaroo and a Re-Evaluation of Stem Macropodiform Interrelationships. PloseOne https://doi.org/10.1371/journal.pone.0112705
den Boer W and Kear BP 2018. Is the fossil rat-kangaroo Palaeopotorous priscus the most basally branching stem macropodiform? Journal of Vertebrate Paleontology; e1428196 DOI: 10.1080/02724634.2017.1428196
Butler K, Travouillon KJ,Price GJ, Archer M and Hand SJ 2016. Cookeroo, a new genus of fossil kangaroo (Marsupialia, Macropodidae) from the Oligo-Miocene of Riversleigh, northwestern Queensland, Australia. Journal of Vertebrate Paleontology. doi:10.1080/02724634.2016.1083029.
Cooke BN 2000. Cranial remains of a new species of balbarine kangaroo (Marsupalia: Macropodoidea) from the Oligo-Miocene freshwater limestone deposits of Riversleigh World Heritage Area, Northern Australia. Journal of Paleontology 74(2) 317-26.
Flannery TF, Archer M and Plane MD 1983. Middle Miocene kangaroos (Macropodoidea: Marsupialia) from three localities in northern Australia, with a description of two new subfamilies. Bureau of Mineral Resources, Journal of Australian Geology and Geophysics 7: 287–302.
Owen R 1873. Procoptodon goliah, Owen. Proceedings of the Royal Society of London 21, 387.

wiki/Interatherium
wiki/Lagostrophus
wiki/Procoptodon
http://www.abc.net.au/news/2016-02-19/extinct-non-hopping-species-may-be-ancestors-of-kangaroo/7185650
Palaeopotorous PR: https://www.sciencedaily.com/releases/2018/04/180411111019.htm

Dual origin of turtles and triple origin of whales abstracts

It used to be easier to get papers published.
The following are manuscripts independently published online without peer-review at the DavidPetersStudio.com website. http://www.davidpetersstudio.com/papers.htm

Better to put it out there this way
than to let this work remain suppressed. Hope this helps clarify issues.


Peters D 2018a. The Dual Origin of Turtles from Pareiasaurs
PDF of manuscript and figures

The origin of turtles (traditional clade: Testudines) has been a vexing problem in paleontology. New light was shed with the description of Odontochelys, a transitional specimen with a plastron and teeth, but no carapace. Recent studies nested Owenetta (Late Permian), Eunotosaurus (Middle Permian) and Pappochelys (Middle Triassic) as turtle ancestors with teeth, but without a carapace or plastron. A wider gamut phylogenetic analysis of tetrapods nests Owenetta, Eunotosaurus and Pappochelys far from turtles and far apart from each other. Here dual turtle clades arise from a clade of stem turtle pareiasaurs. Bunostegos (Late Permian) and Elginia (Late Permian) give rise to dome/hard-shell turtles with late-surviving Niolamia (Eocene) at that base, inheriting its Baroque horned skull from Elginia. In parallel, Sclerosaurus (Middle Triassic) and Arganaceras (Late Permian) give rise to flat/soft-shell turtles with Odontochelys (Late Triassic) at that base. In all prior phylogenetic analyses taxon exclusion obscured these relationships. The present study also exposes a long-standing error. The traditional squamosal in turtles is here identified as the supratemporal. The actual squamosal remains anterior to the quadrate in all turtles, whether fused to the quadratojugal or not.


Peters D 2018b. The Triple Origin of Whales
PDF of manuscript and figures

Workers presume the traditional whale clade, Cetacea, is monophyletic when they support a hypothesis of relationships for baleen whales (Mysticeti) rooted on stem members of the toothed whale clade (Odontoceti). Here a wider gamut phylogenetic analysis recovers Archaeoceti + Odontoceti far apart from Mysticeti and right whales apart from other mysticetes. The three whale clades had semi-aquatic ancestors with four limbs. The clade Odontoceti arises from a lineage that includes archaeocetids, pakicetids, tenrecs, elephant shrews and anagalids: all predators. The clade Mysticeti arises from a lineage that includes desmostylians, anthracobunids, cambaytheres, hippos and mesonychids: none predators. Right whales are derived from a sister to Desmostylus. Other mysticetes arise from a sister to the RBCM specimen attributed to Behemotops. Basal mysticetes include Caperea (for right whales) and Miocaperea (for all other mysticetes). Cetotheres are not related to aetiocetids. Whales and hippos are not related to artiodactyls. Rather the artiodactyl-type ankle found in basal archaeocetes is also found in the tenrec/odontocete clade. Former mesonychids, Sinonyx and Andrewsarchus, nest close to tenrecs. These are novel observations and hypotheses of mammal interrelationships based on morphology and a wide gamut taxon list that includes relevant taxa that prior studies ignored. Here some taxa are tested together for the first time, so they nest together for the first time.


Both of these manuscripts benefit from
ongoing studies at the large reptile tree (LRT, 1247 taxa) in which taxon exclusion possibilities are minimized and all included taxa can trace their ancestry back to Devonian tetrapods.

Metathere (aka: marsupial) issues

Metatherians
(aka marsupials) can be a difficult clade to understand phylogenetically. Taxon exclusion, as usual, causes problems, here and elsewhere. Case in point: recently adding taxa to the large reptile tree (LRT, 1247 taxa) shifted and clarified some prior interrelationships in which certain untenable dental patterns appeared. This was cause for concern and re-study. I’m pleased to report that the herbivorous metathere subset of the tree topology did change to a more logical and gradual pattern after adding several taxa. Now the dental atavisms no longer appear. But this new topology comes at the cost of recovering a dual and parallel origin for the diprotodont form of dentition (Fig. 1) in which the anteriormost dentary teeth are larger than typical canines and jut out anteriorly.

Figure 1. Marsupial mandibles. Traditional diprodonts have two large anterior dentary teeth. These arose twice in the LRT.

Figure 1. Marsupial mandibles. Traditional diprodonts have two large anterior dentary teeth. These arose twice in the LRT with the present list of taxa, once with kangaroos, and again with wombats. See figure 3.

First and second,
let’s take a look at two previously published metatherian tree topologies: Horovitz and Sánchez-Villagra 2003 (which covers many living and some extinct taxa) and Williamson, Brusatte and Wilson 2014 (in which taxa are all Cretaceous or earlier and most are known from isolated teeth). The LRT includes no tooth-only taxa… and that’s a good thing.

Horovitz and Sánchez-Villagra 2003 (Fig. 2) employed bones and soft tissue.
From their abstract: “We… assembl[ed] a morphological data matrix consisting of a new suite of 149 postcranial characters and incorporated a series of previously published data on the craniodental (76 characters) and soft tissue (5 characters) anatomy. Twenty-one marsupial terminal taxa representing all the major radiations of marsupials and 10 outgroups… were investigated. All currently accepted marsupial orders were recovered by the analysis.”

Figure 2. A cladogram of metatherian mammals based on skeletal and soft traits by Horovitz and Sánchez-Villagra 2003. This cladogram lacks a large number of carnivorous metatherians, a large number of basal prototheres and a large number of basal eutherians. On the other hand, the LRT is missing the uncolored taxa. Colors correspond to the metathere subset of the LRT (Fig. 3). Horovitz and Sánchez-Villagra 2003 recovered a monophyletic Diprotodontia in contrast to the LRT.

Figure 2. A cladogram of metatherian mammals based on skeletal and soft traits by Horovitz and Sánchez-Villagra 2003. This cladogram lacks a large number of carnivorous metatherians, a large number of basal prototheres and a large number of basal eutherians. On the other hand, the LRT is missing the uncolored taxa. Colors correspond to the metathere subset of the LRT (Fig. 3). Horovitz and Sánchez-Villagra 2003 recovered a monophyletic Diprotodontia in contrast to the LRT.

More recently,
Williams et al. 2014 reported, “Our understanding of this group has increased greatly over the past 20 years, with the discovery of new specimens and the application of new analytical tools. Here we provide a review of the phylogenetic relationships of metatherians with respect to other mammals, discuss the taxonomic definition and diagnosis of Metatheria, outline the Cretaceous history of major metatherian clades, describe the paleobiology, biogeography, and macroevolution of Cretaceous metatherians, and provide a physical and climatic background of Cretaceous metatherian faunas.” They built their study on Williams 2012, which focused on teeth. They report, “As in the previous analysis of Williamson et al. (2012), homoplasy is rampant.” Hmm. That’s a phrase I used to describe character distribution in the LRT!

Williams et al. 2014 reported, 
“The oldest confidently identified therian fossil is the eutherian Juramaia from the early Late Jurassic (ca. 160 million years old) of China (Luo et al. 2011).” The LRT nests Juramaia as a basalmost prototherian. They considered Sinodelphys (Early Cretaceous, 120 mya) to be the oldest known marsupial. In 2015 (a year after Williams et al.) Agilodocodon (Middle Jurassic, 170 mya) was announced as a docodont (but nests with Eomaia, Early Cretaceous, 125 mya) in the LRT.

Williams et al. 2014 reported, 
“Deltatheroidans were long regarded as eutherians (Gregory and Simpson 1926; Van Valen 1966) or stem boreosphenidan species (Fox 1974; Kielan-Jaworowska et al. 1979), but are now generally accepted as basal metatherians (Butler and Kielan-Jaworowska 1973; Kielan-Jaworowska and Nessov 1990; Rougier et al. 1998).” The LRT confirms a nesting within the Metatheria for Deltatheridium, not as a sister.

Williams et al. 2014 reported,
“The interrelationships of most major metatherian subclades are unresolved.” This is due to taxon exclusion and using too many tooth-only taxa. On the other hand, the metatherian taxa and clades within the LRT are fully resolved. The two studies share only 4 taxa in common so the Wiliams et al. cladogram will not be shown. Despite the availability of museum specimens, no extant taxa were used in Williams et al. 2014 study, which concentrated on Cretaceous taxa to the detriment of the study.

Maybe it would have been better
for Williams et al. 2014 to first establish relationships using extinct and extant skeletons of a wide gamut of mammals, as the LRT does, and then see where the tooth-only taxa fit in.

Figure 3. Subset of the LRT focusing on the Metatheria (= Marsupials). Here the diprotodont dentition evolved twice.

Figure 3. Subset of the LRT focusing on the Metatheria (= Marsupials). Here the diprotodont dentition evolved twice.

 

More on metatherians soon…

References
Horovitz I and Sánchez-Villagra MR 2003. A morphological analysis of marsupial mammal higher-level relationships. Cladistics 19(3):181 – 212.
DOI: 10.1111/j.1096-0031.2003.tb00363.x
Myers P, Espinosa R, Parr CS, Jones T, Hammond GS and Dewey TA 2018. The Animal Diversity Web (online). Accessed at https://animaldiversity.org.
info@tree-kangaroo.net
Williamson TE, Brusatte SL and Wilson GP 2014. The origin and early evolution of metatherian mammals: the Cretaceous record. ZooKeys 465:1–76.

doi: 10.3897/zookeys.465.8178
http://zookeys.pensoft.net

The biliby, the rabbit-bandicoot

Yesterday we took a peek at the bandicoot (genus: Perameles). Today we’ll look at its rabbit-eared sister, the biliby (genus: Macrotis, Fig. 1).

Figure 1. Macrotis skeleton and invivo.

Figure 1. Macrotis skeleton and invivo. No wonder they call the biliby the rabbit-bandicoot.

Macrotis and Perameles are basal marsupials with a skull similar to the Late Cretaceous Cronopio (South America) one of the most basal mammals and most basal prototheres.

Figure 1. Macrotis, the Australian biliby (rabbit-bandicoot) compared to the Late Cretaceous Cronopio (South Ametica).

Figure 2. Macrotis, the Australian biliby (rabbit-bandicoot) compared to the very much smaller Late Cretaceous Cronopio (South Ametica), a basal protothere and one of the most basal mammals.

That’s about it for today.
These taxa are part of the changes we’ll talk about soon in the lineage of marsupials.