Neither bear nor dog, the bear-dog Amphicyon major now nests with the puppy-like Hyopsodus, far from Carnivora and Perissodactyla

Updated August 4, 2022,
with both of these taxa joining the extant water opossum, Chironectes.

Once again
the overlooked Leptictis – Tenrec clade is attracting more taxa to the base of the Placentalia as ‘housekeeping’ continues to shed light on novel hypothetical interrelationships.

Figure 1. Hyopsodus and Amphicyon major nest together now in the LRT.

This time
the tiny, Eocene, short-legged, ‘basal perissodactyl’ Hyopsodus (Figs 1, 2) nests as an Eocene ancestor to the massive Miocene ‘bear dog’ Amphicyon major (Figs 1, 3, 4) at the base of the Placentalia in the large reptile tree (LRT, 2122 taxa, Fig 5). Basal placentals have three incisors, three premolars and four molars. Members of the Carnivora tend to lose molars.

Figure 2. Hyopsodus in situ. Colors added here.

This isn’t the first time
leptictid clade members were identified as ungulates. Basal odontocetes were also identified as artiodactyls by whale experts.

Figure 3. Amphicyon skull. Colors added here. Gracile cheek arch reconstructed from elements crushed beneath the mandible. Pink arrow points to in situ cheek arch posterior.

Hyopsodus lepticus
(H. paulus type, Leidy 1870; Late Eocene, 56-45 mya; ~20 cm in length; AMNH 143783, Fig 1, 2) was originally considered a condylarth or a perissodactyl, an odd-toed ungulate, despite having a five-clawed manus and a four-clawed pes. Here it nests as a sister to Miacis and Amphicyon major (Figs 1, 3). Four molars are present.

Amphicyon major
(Lartet 1836, Bergounious and Crouzel 1973, Argot 2010, Miocene) This bear dog is neither a bear nor a dog. It nests with tiny, Late Eocene Hyopsodus in the LRT, as if the two were adult and pup. Note the gracile cheek arch.

References
Argot C 2010. Morphofunctional analysis of the postcranium of Amphicyon major (Mammalia, Carnivora, Amphicyonidae) from the Miocene of Sansan (Gers, France) compared to three extant carnivores: Ursus arctos, Panthera leo, and Canis lupus. Geodiversitas 32 (1): 65-106.
Bergounious FM and Crouzel FC 1973. Amphicyon major Blainville du Miocene moyen de Sansan (Gers). Ann. Paleont., t. 59, fas. 1, pp. 3-76,47 fig. Paris.
Cope ED 1872. Third account of new vertebrata from the Bridger Eocene of Wyoming Territory. Proceedings of the American Philosophical Society 12(86): 469-472.
Heinrich RE, Strait SG and Houde P 2008. Earliest Eocene Miacidae (Mammalia: Carnivora) from northwestern Wyoming. Journal of Paleontology. 82 (1): 154–162.
Illiger C 1811. Prodromus systematis mammalium et avium additis terminis zoographicis utriusque classis, eorumque versione germanica. Sumptibus C. Salfeld, Berolini [Berlin]: [I]-XVIII, [1]-301, Errata et Omissa.
Lartet E 1836. Nomenclature des mammiféres et des coquilles qu’il a trouvés dans un terrain d’eau douce prés de Simorre et de Sansan (Gers). Bulletin de la Société Géologique de France 7: 217–220.
Leidy J 1870. Remarks on a collection of fossils from the western territories. Proceedings of the Academy of Natural Sciences of Philadelphia 22: 109–110.
Matthew WD and Granger W 1925. New mammals from the Irdin Manha Eocene of Mongolia. American Museum Novitates 198:1-10.
Orliac MJ, Argot C and Gilissen E 2012. Digital Cranial Endocast of Hyopsodus (Mammalia, “Condylarthra”): A Case of Paleogene Terrestrial Echolocation? PlosOne v.7(2); 2012PMC3277592
Wesley-Hunt GD and Flynn JJ 2005. Phylogeny of the Carnivora: Basal Relationships Among the Carnivoramorphans, and Assessment of the Position of ‘Miacoidea’ Relative to Carnivora. Journal of Systematic Paleontology, 3: 1-28.

wiki/Hyopsodus
wiki/Amphicyon

Moles and elephant shrews go back… way back to the Jurassic

Hiding from dinosaurs up in the trees,
and now beneath leaf litter and ultimately underground, is how the earliest placentals survived in the Jurassic, according to the latest changes in the large reptile tree (LRT, 2122 taxa, Fig 1).

Figure 1. Recent changes to the LRT move moles to the elephant shrews (sengis) very close to the origin of placental mammals. Obviously extant moles have come a long way since the Early Jurassic, but they have new roots there, avoiding predatory dinosaurs by hiding and digging.

Today
elephant shrews (Rhynchocyon and Macroscelides, Fig 2) and moles (like Talpa, Figs 1, 3) move to the Leptictis to Tenrec to Pakicetus to Orcinus clade in the LRT (Fig 1).

Figure 2. Rhynchocyon (above) and Macroscelides (below) compared. Both elephant shrews have an extended proboscis, like the one in extant moles and make their living in leaf litter. See figure 3.

These most recent changes are a result
of several weeks of ‘housekeeping’ the placental subset of the LRT, based on trait analysis, not genes. Likewise, a few days ago, spiny, semi-armored Eocene Pholidocercus also moved to the base of the Leptictis branch of early Placentalia (Fig 1). It was also a late survivor of that Jurassic placental radiation.

Figure 3. Turns out that extended proboscis in the European mole, Talpa, was inherited from elephant shrew relatives and ancestors.

Previously the LRT nested moles with mongooses,
primitive members of the Carnivora (Fig 1). Further examination (after a decade of adding taxa) moved Talpa, the European mole, over one clade, to nest with elephant shrews, tenrecs and ultimately (no one ever would have guessed this) odontocete whales.

Talpa europaea
(Linnaeus 1758, Figs 1, 3) is the extant mole, a small burrowing mammal derived from speedy leaf-litter dwelling elephant shrews, like Rhynchocyon and Macroscelides (Fig 2). The robust hand, further enlarged with a finger-like centralia that extends like a reverse pteroid along the medial axis, is anchored by huge muscles that arise from the anteriorly displaced scapula. The pelvic girdle is fused to an elongate sacrum. The premaxilla is transverse in Talpa (extended in other moles) and large canines are present. Tiny postfrontal and postorbital bones produce a circumorbital ring.

Figure 4. What little that is known of Plesioryctopus. In the LRT this is a small ground sloth, not a tenrec or a pseudo-aardvark. The restoration is guesswork.

As an unexpected consequence,
recently extinct Plesiorycteropus madagascariensis (Fihol 1895, MacPhee 1994, Fig 4) from Madagascar moves over to nest with Megatherium, the giant ground sloth of the Americas. Previously Plesiorycteropus was professionally considered a ‘pseudo aardvark’ and also nested with mongooses in the LRT. According to Wikipedia, “recent molecular evidence instead suggests that it is most closely related to the tenrecs (a group extant on the island)” [of Madagascar].

See what I mean about genes limited to geographic ‘islands’ producing false positives? Always work with traits. Never trust genes in deep time studies. Also according to Wikipedia, “Plesiorycteropus was probably a digging animal that fed on insects such as termites and ants. It also shows adaptations for climbing and sitting.” So there you go. It’s a sloth from Madagascar.

Also according to Wikipedia,
“However, phylogenetic analysis revealed that elephant shrews are not classified with true shrews, but are in fact more closely related to elephants than shrews.”

In fact?? That was based on gene studies. The LRT does not support the linking of elephant shrews with elephants.

Recent email conversations with an AMNH academic
indicate strict reliance and trust on genes over traits and fossils. Everyone can see genes can result in untenable results, like nesting bats with horses, ducks with chickens and elephant shrews with elephants. The problem is, workers seem to be wearing blinders. How can we turn this gene fad back around so paleontologists go back to using good old fossils and traits in phylogenetic analysis?

This appears to be a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here.

References
Filhol H. 1894. Observations concernant quelques mammiferes fossiles nouveaux de
Quercy. Ann. Sci. Nat., Zool. Paleontol. (7e ser.) 16: 129-150.
Linnaeus C von 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
MacPhee RDE 1994. Morphology, Adaptations, and Relationships of Plesiorycteropus, and a Diagnosis of a New Order of Eutherian Mammals.” Bulletin of the American Museum of Natural History, 220 (1994): 1-214.

wiki/Plesiorycteropus
wiki/Elephant_shrew
wiki/Talpa

Labidolemur skull reconstructed

Two years ago,
Late Paleocene Labidolemur (Fig 1) entered the large reptile tree (LRT, 2122 taxa) alongside Apatemys, a basal member of the gnawing clade, Glires. This is at odds with then current publicity that stated, ““Researchers said the new information will aide future studies to better understand the origin of primates.“

Taxon exclusion is the overall problem. Unfortunately the academic workers did not understand where apatemyids nested.

Here
(Fig 1) the skull is reconstructed for the first time from published images in Silcox et al. 2010, all part of the current housekeeping, cleaning up scores in the LRT.

Figure 1. From Silcox et al. 2010, colors added here. C and D are flipped right side images.

Labidolemur kayi
(Matthew and Granger 1921; Silcox et al. 2010, Late Paleocene, 55mya) is a close relative of Apatemys in the LRT.

Figure 1. Apatemys, only complete fossil skeleton of an apatemyid, turns out to be a basal member of the gnawing clade, Glires. Not a primate relative.

References
Matthew WD and Granger W 1921. New genera of Paleocene mammals. American Museum Novitates 13:1-7
Silcox MT, Bloch JI, Boyer DM and Houde P 2010. Cranial anatomy of Paleocene and Eocene Labidolemur kayi (Mammalia: Apatotheria), and the relationships of the Apatemyidae to other mammals. Zoological Journal of the Linnean Society160: 773–825.

https://www.floridamuseum.ufl.edu/science/labidolemur-kayi-bizarre-extinct-mammal/https://www.eurekalert.org/pub_releases/2010-10/w-uof101110.php

Labidolemur enters the LRT as a ‘freakish dead-end’ taxon

Selection of basal placental skulls to scale

Here
(Fig 1) are some of the skulls of taxa drifting toward the base of the Placentalia. The tiny marsupial without a pouch, Monodelphis is the outgroup taxon.

Figure 1. Several basal placental skulls to scale. Plesiomorphic tooth counts and shape patterns mark these taxa. as basal. Work continues on fine tuning the LRT.

Housekeeping continues.

Scaly, spiny, Eocene Pholidocercus is a leptictid, basal to tenrecs and odontocetes

According to Wikipedia,
“Pholidocercus is an extinct monotypic genus of mammal from the Messel pit related to and resembling the modern-day hedgehog with a single species, Pholidocercus hassiacus. Like the hedgehog, it was covered in thin spines. Unlike hedgehogs, it had scales on its head in a helmet-like formation, and had a long, thick, scaled tail.”

Here
in the large reptile tree (LRT, 2122 taxa) Pholidocercus (von Koenigswald & Storch 1983, Figs 1, 2) nests with Leptictis (Figs 3, 4), a basal Oligocene placental in the lineage of (some) elephant shrews (=sengis), tenrecs and odontocetes.

Figure 1. Only one of the several Messel Pit Pholidocercus specimens. This one has a truncated tail and a halo of soft tissue (pre-spines).

Pholidocercus hassiacus
(von Koenigswald & Storch 1983; HLMD Me 7577; Middle Eocene) is an extinct sister to Leptictis. Known from several fossils, Pholidocercus has a long thick tail provided with tall neural spines and deep chevrons. The rostrum is short. Soft tissue is preserved as scales on the head in a helmet-like formation and scales on the tail, a pattern convergent with armadillos.

Figure 3. Leptictis skull. Note the change in premolar identity.

Leptictis acutidens
(Leidy 1868, Rose 2006, early Oligocene) is an extinct elephant shrew nesting between the coatimundi, Nasua, and Rhynchocyon. Anagale is a close relative. All are basal placentals with four molars and three premolars. The tail was probably longer than preserved. The tiny manus appears to have only three digits. Note the large calcaneal heel, a trait usually found in digitigrade running mammals, like Rhynchocyon. This clade is basal to odontocete whales like Orcinus.

Figure 4. Extant Nasua, the extant coatimundi, is basal to Pholidocercus, Leptictis and extant Rhynchocyon, the elephant shrew.

This appears to be a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here… and the ‘housekeeping‘ of placentals continues.

References
von Koenigswald W and Storch Gh 1983. Pholidocercus hassiacus, ein Amphilermuride aus dem Eozan der “Grube Messel” bei Darmstadt (Mammalia: Lipotyphla). Senchenberg Lethaia 64:447–459.

wiki/Leptictis
wiki/Rhynchocyon
wiki/Pholidocercus

The Miocene mole, Necrolestes, is a marsupial close to Docofossor, the Middle Jurassic mole

Updated August 2, 2122
with a new nesting between the marsupial moles, Anebodon and Notoryctes + Docofossor.

Necrolestes patagonensis (Ameghino 1891; early Miocene, 16mya; Fig. 1; YPM PU 15065, 15384, and 15699) has been argued about for over a hundred years. Originally it was described as the only known extinct placental “insectivore” from South America and allied to Chrysochloris, the extant golden mole from Africa.

Figure 1. Necrolests, the Miocene mole, now nests with Marmosa, (figures 2, 3) in the LRT. Five incisor per premaxilla is a clue to marsupial affinities.Note the large antorbial fossa.

Unfortunately, as time went on…
Saban 1954 considered Necrolestes a palaeanodont (Ernanodon was previously considered one).

Patterson 1958 considered Necrolestes a borhyaenoid metatherian.

Asher et al. 2007 looked at several candidates and could not make a firm conclusion. They thought Cronopio, a partial skull from the Late Cretaceous.

Ladevèze et al. 2008 supported metatherian affinities.

Goin et al. 2008 also could not be specific with regard to a closest known sister taxon.

Figure 2. Anebodon from the Early Cretaceous is a marsupial mole.

The latest paper on the subject,
Rougier et al. 2012, reported, “earlier studies leaned toward placental affinities and more recent ones endorsed either therian or specifically metatherian relationships.” Ultimately they nested Necrolestes with Cronopio, which they considered a non-therian mammal. The authors considered an earlier Van Valen 1988 statement inspired, “…the enigmatic Miocene genus Necrolestes, usually thought to be a marsupial, is [conceivably] a late surviving Gondwantherian pantothere.” That is incorrect.

Figure 3. Notoryctes skull.

Taxon exclusion appears to be the issue here.
In the large reptile tree (LRT, 2123 taxa) Necrolestes nests with small marsupial moles from the Middle Jurassic to extant taxa.

Figure 4. Docofossor is a Middle Jurassic marsupial mole.

This appears to be a novel hypothesis of interrelationships.
If not, please send a citation so I can promote it here. The rescoring of this taxon and removal from its previous nesting in Placentalia, is part of the now several weeks long ‘housekeeping’ that is not yet near an end.

References
Ameghino F 1891. Nuevos restos de mamíferos fósiles descubiertos por Carlos Ameghino en el Eoceno inferior de la Patagonia austral. Especies nuevas, adiciones y correciones [New remains of fossil mammals discovered by Carlos Ameghino in the lower Eocene of southern Patagonia. New species, additions and corrections]. Rev Arg Hist Nat 1:289–328. Spanish.
Bi S-D, heng X-T, Meng J, Wang X-L, Robinson N and Davis B 2016. A new symmetrodont mammal (Trechnotheria: Zhangheotheriidae) from the Early Cretaceous of China and trechnotherian character evolution. Nature Scientific Reports 6:26668 DOI: 10.1038/srep26668
Gadow H 1892. On the systematic position of Notoryctes typhlops. Proc. Zool. Soc. London 1892, 361–370.
Luo Z-X, Meng QJ, Ji Q, Liu D, Zhang Y-G, Neande AI 2015. Evolutionary development in basal mammaliaforms as revealed by a docodontan. Science. 347 (6223): 760–764.
Stirling EC 1888. Transactions of the Royal Society, South Australia 1888:21
Stirling EC 1891. Transactions of the Royal Society, South Australia 1891:154

wiki/Docofossor
wiki/Notoryctes
wiki/Anebodon
wiki/Necrolestes

Microsyops revisited: now the basalmost member of the gnawing Glires clade

Silcox, Gunnell and Bloch 2020
described the cranium of Microsyops annectens (Leidy 1872, Marsh 1872, Fig. 1), but were not able to correctly nest it phylogenetically due to taxon exclusion. The authors mistakenly called it a plesidapiform and mistakenly considered plesiadapiforms ‘plausible stem primates.’

More taxa solve this problem.

Figure 1. Middle Eocene Microsyops from Silcox, Boyer and Houd 2010. Colors and restoration of a possible postorbital bar added here.

From their abstract:
“While results from phylogenetic analyses support euarchontan affinities, specific relationships of microsyopids to other plesiadapiforms (plausible stem primates), Euprimates (crown primates), Scandentia (treeshrews), and Dermoptera (colugos) are unresolved.”

From their discussion and conclusions:
“The basicranial anatomy of microsyopids does not provide evidence in support of a clear link to any of the extant euarchontans, and suggests that the primitive morphology of this region in Euarchonta was little differentiated from that observed in the primitive placental mammals.”

Figure 2. Palaechthon is a sister to Microsyops in the LRT.

By contrast
in the large reptile tree (LRT, 2122 taxa) using fewer traits and more taxa, Microsyops nests as a basal member of Glires (gnawing mammals) close to Palaechthon (Fig 2) and the IVPP V5235 specimen attributed to Hapalodectes (Fig 3). All are similar in size and post-cranial material is largely unknown. Together they help inform the identity of the teeth and certain likely sutures in the diagrams. A bit of guesswork here looking for confirmation, refutation or correction.

Figure 3. Hamster-sized Hapalodectes specimen IVPP V5235 at full scale and enlarged. Microsyops helps identify the teeth in this diagram.

Ten years earlier
Silcox, Bloch, Boyer and Houde (2010) wrote: “Microsyopids are the most similar to apatemyids in the basic form of the basicranium of any ‘plesiadapiform’.

In the LRT, apatemyids are also tree shrews within the Glires, not close to primates or plesiadapiforms.

This new nesting for Microsyops
is part of the ongoing housekeeping at the root of all the placental clades. This appears to be a novel hypothesis of interrelationships. If not, please provide a citation so I can promote it here.

---

References
Leidy J 1872. Remarks on fossils from Wyoming: Proceedings of the Academy of Natural Sciences, Philadelphia 1872: 19–21.
Marsh OC 1872. Preliminary description of new Tertiary Mammals. Parts I– IV: American Journal of Science 4: 122–128, 202–224.
Silcox MT, Bloch JI, Boyer DM and Houde P 2010. Cranial anatomy of Paleocene and Eocene Labidolemur kayi (Mammalia: Apatotheria), and the relationships of the Apatemyidae to other mammals. Zoological Journal of the Linnean Society160: 773–825.
Silcox MT, Gunnelll GF and Bloch JI 2020. Cranial anatomy of Microsyops annectens (Microsyopidae, Euarchonta, Mammalia) from the middle Eocene of Northwestern Wyoming. Journal of Paleontology, 28pp. 0022-3360/20/1937-2337
doi: 10.1017/jpa.2020.24

wiki/Microsyops

https://pterosaurheresies.wordpress.com/2020/06/15/microsyops-enters-the-lrt-between-three-overlooked-shrew-opossums/

Correction: Flying lemurs ARE lemurs close to indris

According to Wikipedia,
(and university textbooks), “Although they called “flying lemurs”, the colugos are not lemurs and do not fly.”

Recent housekeeping in the large reptile tree (LRT, 2122 taxa, subset Fig 1) now disputes the first half of the Wiki statement based on morphology. The second half is still true.

Figure 1. Subset of the LRT focusing on tree shrews, primates, bats and the gnawing clade, Glires. Cynocephalus (yellow) now nests with Indri here.

The colugo tested by the LRT
is Cynocephalus (Figs 2, 3). Although it has deep claws, rather than flat nails, Cynocephalus from SE Asia now nests most closely with Indri, the indri (a large lemur from Madagascar).

Figure 2. Cynocephalus, the colugo, compared to Indri, the lemur, Not to scale. Colugos have large claws, not nails. Other lemurs have a long tail. See figure 3 for skull comparisons.

Now separated by time and geography,
the last common ancestor of the colugo and lemur was similar to the lemur-like adapid, Notharctus, from North America, now nesting at the base of the Primates. That means adapids and lemurs once had a world-wide distribution and a Jurassic origin. This hypothesis is based on the presence of derived members of Glires in the Late Jurassic and Early Cretaceous, as well as the close relationship of coatimundis (= Nasua) to lemurs in the LRT.

The reappearance of large, deep claws on dermopterans is an apparent reversal.

Figure 3. Comparing the skulls of Cynocephalus, the colugo, with Indri, the lemur. Note the lack of canine teeth and the expanded retroarticular process on both. The ectopterygoids and palatines are similar in both.

Indri indri
(Gmelin 1788; extant; 70 cm long) is the largest living lemur. Note the extremely reduced tail. No claws are present. This is the basal-most lemur in the LRT, despite lacking a long tail.

Cynocephalus volans
(Linnaeus 1758, body length:33–38 cm + tail length: 17–27 cm) is the extant and nocturnal Philippine flying lemur. It is considered a member of the order Dermoptera, a clade with only two genera. The other (as yet untested) genus, Galeopterus, has longer, thinner arms. Extradermal membranes stretching from the chin to the thumb, between the fingers, to the toes, between the toes and to the tail tip surround Cynocephalus. These membranes extend glides up to 100m between trees.

This appears to be a novel hypothesis of interrelationships.
If not please send a citation so I can promote it here. Recent genomic and decades of phenomic work have often recovered a close relationship of demopterans to primates, but not with indris specifically.

References
Gmelin JF 1788. Caroli a Linné systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima tertia, aucta, reformata. – pp. [1-12], 1-500. Lipsiae. (Beer).
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

wiki/Indri
|wiki/Cynocephalus
youtube.com/Cynocephalushttps://en.wikipedia.org/wiki/Colugo
youtube.com indri lemurs
sciencenews.org/colugo-genome-reveals-gliders-primate-cousins

Ectoconus and Pantolambda also move very close to the base of the Placentalia

Yesterday the LRT nested
the large herbivore with giant fangs, Thomashuxleya, close to the base of the Placentalia. That node is marked by the tiny South American marsupial without a pouch, Monodelphis (Figs 1, 2).

Figure 1. The skulls of Alcidedorbygna and Monodelphis to scale and about 1.6x life size. These two have never been tested or shown together. This is how evolution works. Proportions change with size and extended ontogenetic age.

Today three more traditional condylarth pantodonts,
also nest close to Monodelphis (Figs 1, 2). These include rat-sized Alcidedorbignya (Figs 1. 3), and lamb-sized Pantolambda (Fig 4) and Ectoconus (Fig 5).

Figure 2. Monodelphis mother with her growing brood of young clinging to her fur and nipples.

Again,
the reason why these three taxa don’t look like other mammals (e.g. carnivores, ungulates, rodents, primates) is because they are derived from tiny monodelophids (Figs 1, 2), extant survivors of the original radiation of placentals.

Other workers excluded
Monodelphis from their phylogenetic studies. By contrast, the large reptile tree (LRT, 2122 taxa) keeps adding taxa.

Sometimes taxa nest together that have never been tested together.
This is one of those instances.

Figure 3. From Muizon et al. 2015, Alcidedorbygna posed as an arboreal mammal shown at full scale on a 72dpi monitor screen.

Alcidedorbignya inopinata
(Muizon and Marshall 1992 Muizon et al 2015; MHNC 8372, Early Paleocene, 64 mya; scale bar is 2cm) was originally considered a basal pantodont (Condylartha) close to Pantolambda. Here both taxa are basal placentals derived from Monodelphis. The rostrum is curved with a smaller naris. Claws are hooves on a semiplantigrade manus.

Figure 4. Pantolambda is now a transitional marsupial close to or convergent with the Placentalia.

Pantolambda bathmodon
(Cope 1882, Middle Paleocene, 66-63 mya, sheep-sized; AMNH 3956) is traditionally another basal condylarth and a pantodont. Here Pantolambda is a marsupial derived from Monodelphis and the taxa on this page, including Ectoconus. Pantolambda had a shorter skull, shorter lumbar region and shorter limbs. The cervical series appears gracile here, but that may be due to fossil erosion.

Figure 5. Another lamb-sized transitional marsupial – placental is Ectoconus.

Ectoconus ditrigonus
(Cope 1884 Early Paleocene, 66-63mya, sheep-sized) is tradiitionally considered a basal condylarth known from a rare complete skeleton. Here Ectoconus is derived from the marsupials, Alcidedorbignya and Monodelphis. It is a sister to Pantolambda. Though canines were present, Ectoconus was an herbivore with five digits on all four limbs. Shown here digitigrade, this taxon was likely plantigrade. Another species, Ectoconus majusculus, is shown here.

This appears to be a novel hypothesis of interrelationships.
If not please provide a citation so I can promote it here.

More to follow.

References
Cope ED 1882. On the condylarthra. Academy of Natural Sciences of Philadelphia Proceedings 1882:95-97.
Cope ED 1882. Synopsis of the Vertebrata of the Puerco Eocene epoch. Proceedings of the American Philosophical Society 20
Cope ED 1884. The Amblypoda. The American Naturalist 18 (112):6=461-471.
Simons EL 1960. The Paleocene Pantodonta. Transactions of the American Philosophical Society, New Series 50(6):1-8.
de Muizon C de & Marshall LG 1992. Alcidedorbignya inopinata (Mammalia: Pantodonta) from the early Paleocene of Bolivia: phylogenetic and paleobiogeographic implications. Journal of Paleontology 66 (3): 499-520.
deMuizon C, Billet G, Argot C, Ladeveze S and Goussard F 2015. Alcidedorbignya inopinata, a basal pantodont (Placentalia, Mammalia) from the early Palaeocene
of Bolivia: anatomy, phylogeny and palaeobiology. Geodiversitas 87(4):397-634.

wiki/Alcidedorbignya
wiki/Ectoconus
wiki/Pantolambda

Thomashuxleya moves close to marsupial interatheres in the LRT

Updated September 1, 2022
with new tracings of Thomashuxleya (Fig 1) and corrected scores moving it to the marsupial interatheres.

Apparently, the reason why
Thomashuxleya externa (Fig 1) doesn’t look like other large herbivorous mammals is because it doesn’t nest with other large herbivorous mammals. In the large reptile tree (LRT, 2135 taxa) 1.3m long Thomashuxleya now nests between Interatherium and Hegetotherium, all from Eocene South America.

Figure 1. Thomashuxleya is supposed to be a notoungulate, but was never tested with Interatherium and Hegetotherium. Now it nests with these taxa in the LRT.

A recent paper
(Carillo and Asher 2017) described “an exceptionally well-preserved skeleton of Thomashuxleya” as “one of the oldest notoungulate skeletons with associated craniodental and postcranial elements.” Unfortunately, the used Simpson’s 1936 reconstruction (Fig 2).

The traditional clade Notoungulata has been split apart by the LRT, but is still taught in university textbooks. Some ‘notoungulates’ are derived placentals. Others are derived marsupials. Carillo and Asher did not test Hegetotherium and Interatherium. So no matter how many characters were employed, not enough taxa were employed.

Figure 3. Thomashuxleya illustration from a freehand reconstruction (Simpson 1936).

The authors reported,
“The new material supports the placement of Thomashuxleya as an early, divergent member of Toxodontia.”

In the LRT Toxodon (Fig 2) is a derived interathere marsupial herbivore from South America distantly related to Thomashuxleya.

Figure 4 Toxodon and the much smaller Eurygenium to scale. These taxa are related to Thomashuxleya (Figs 1, 3).

Thomashuxleya externa
(Ameghino 1901; Carrillo and Asher 2017; Eocene, 48-40 mya; 0.33m skull length, 1.3 m overall length, Middle Eocene) was named for the famous 19th century paleontologist. Thomashuxleya had four fingers and four toes. Considered a notoungulate, this taxon nests here between Interatherium and Hegetotherium in the LRT. This bulky herbivore had flat teeth with premolars molarized.

Figure 4. Subset of the LRT focusing on Thomashuxleya and kin among the interatheres.

This appears to be a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here.

References
Ameghino F 1901. Notices préliminaires sur des ongulés nouveaux des terrains crétacés de Patagonie [Preliminary notes on new ungulates from the Cretaceous terrains of Patagonia]. Boletin de la Academia Nacional de Ciencias de Córdoba 16:349-429.
Carrillo JD and Asher RJ 2017. An exceptionally well-preserved skeleton of Thomashuxleya externa (Mammalia, Notoungulata) from the Eocene of Patagonia, Argentina. Palaentologia Electronica 20.2.34A online PDF

wiki/Oodectes
wiki/Thomashuxleya