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 1. Prototheres (egg-laying mammals) including Sinodelphys.

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.

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!

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, 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 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.

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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. Skulls of kangaroo ancestors and sisters, including Procoptodon (short-faced kangaroo) alongside Interatherium (ancestral kangaroo) and Dendrolagus (basal kangaroo). Interatherium does not have diprotodont dentition. Nambaroo nests within Glires, not Metatheria.

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.

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 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.

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.

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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.

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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.

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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 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.

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.

 

 

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. 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 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.

 

Let’s look at bandicoots!

Although bandicoots
(genus: Perameles, Fig. 1) are omnivores, they are basal taxa in the herbivorous metatherian clade in the large reptile tree (LRT, 1242 taxa, Fig. 4). They are closest to digging and burrowing marsupials, like the golden mole, Notoryctes, yet still close to the ancestry of the fast, leaping kangaroos, like Macropus. And they are derived from a sister to Arctocyon, the large carnivore.

Figure 1. Perameles nasuta, the long-nosed bandicoot, nests as basal member of the herbivorous marsupials. Look at those huge lumbar vertebrae! Scale bar = 1cm.

Perameles nasuta (Geoffroy 1804, extant, 40 cm long) is the long nosed bandicoot. This basal marsupial is a nocturnal omnivore, like its ancestor Didelphis (Fig. 2). It has a rear-facing pouch, three long digging fingers, two short ones and a pes dominated by pedal digit 4. Digits 2 and 3 were reduced to grooming claws, as in kangaroos. Gestation lasts a mere 12.5 days, then the young spend another 8 weeks in the marsupium. The long nose of bandicoots is a basal trait retained by Ukhaatherium and prototheres like Cronopio and Juramaia.

YouTube videos
of bandicoots show they have a high metabolism and can scoot away rapidly, like rats or rabbits, distinct from their slower moving opossum ancestors. Of course, Perameles was ancestral to kangaroos, like Macropus (Fig. 3), so their leaping ability is nascent here and their odd feet are nearly identical. Kangaroo hands are still primitive with five sub-equal fingers, not evolved for digging, like odd hand of Perameles (Fig. 1).

According to Wikipedia
“The position of the Peramelemorphia within the marsupial family tree has long been puzzling and controversial. There are two morphological features in the order that appear to show a clear evolutionary link with another marsupial group: the type of foot, and the teeth. Unfortunately, these clear signposts point in opposite directions.” The LRT solves this problem by nesting omnivorous Perameles at the base of the herbivores and allowing for convergence between the large kangaroo and wombat anterior dentaries.

Adding taxa
is helping to clarify phylogenetic relationships among the marsupials. We’ll look at these soon.

References
Geoffroy E. 1804. Mémoire sur un nouveau genre de mammifères á bourse, nommé Perameles. Annales de la Musee National d’ Histoire Naturelle de Paris 4: 56–64.

The budgie has a pseudo-jugal!

Figure 1. The number 3 pet in the world (after cats and dogs) is the Budgerigar (genus: Melopsittacus).

Everyone loves the budgerigar!
(genus: Melopsittacus undulates), but few people know it has an unusually large/long lacrimal (tan) that curls under the orbit to contact the postfrontal (Fig. 2), as in it’s larger relative, Ara, the macaw. It looks like a typically jugal on other reptiles. The actual very birdy jugal appears beneath it (cyan).

Figure 2. The skull of Melopsittacus in three views. Note the tan lacrimal creating a false-jugal on top of the real jugal (in cyan). There’s a hinge between the nasal and frontal that lifts the premaxilla.

And where is the maxilla?
Hidden inside the premaxilla and overlapping nasal. The last of it is contacting the anterior jugal.

Figure 3. Melopsittacus skeleton. This is the budgie cut to the bone.

Melopsittacus undulatus (Linneaus 1758; extant ) is the extant budgerigar, a tiny parrot. Here the nasal wraps around the ventral naris. The lacrimal forms a send jugal below the orbit and contacts the postorbital and squamosal.

References
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.