Maiopatagium: perhaps another case of taxon exclusion

Meng et al. 2017 bring us
a new gliding mammaliaform (pre-mammal) from the Jurassic (160 mya) of China, Maiopatagium furculiferum (BMNH 2940, Figs. 1,2).

Unfortunately
it does not look like any pre-mammals tested here.

Figure 1. Maiopatagium in situ in white and UV light. The X marks an area surrounded by fur lacking proptagial data. Is the propatagium wishful thinking?

Figure 1. Maiopatagium in situ in white and UV light. The X marks an area surrounded by fur lacking proptagial data. Is the propatagium wishful thinking?

Meng et al nest Maiopatagium
between Sinoconodon and Haldanodon, taxa more primitive than mammals. By contrast the large reptile tree (LRT, 1044 taxa) nests Maiopatagium between the interatheres, Interatherium + Paedotherium and the former enigma taxa Groeberia + Vintana, all  marsupials, not Haramyidae, contra Meng et al. 2017, who do not appear to have tested against all ;possible candidate taxa.

Figure 2. Maiopatagium imagery from Meng et al. 2017, plus reconstruction of the extended manus and pes and some bones colorized.

Figure 2. Maiopatagium imagery from Meng et al. 2017, plus reconstruction of the extended manus and pes and some bones colorized. The purported gliding membrane may instead simply be loose skin. Pink area between fingers perhaps falsely adds gliding membrane.

There is another newly described and similar taxon,
Vilevolodon that I need to look at before proceeding further. I’ll have more to say about both taxa later. 

References
Meng Q-J, Grossnickle DM, Liu D, Zhang Y-G, Neander AI, Ji Q and Luo Z-X 2017.
New gliding mammaliaforms from the Jurassic. Nature (advance online publication)
doi:10.1038/nature23476

wiki/Maiopatagium

 

Argyrolagus: a South American kangaroo!

Earlier we looked at giant South American wombats, like Toxodon and Pyrotherium. And, of course, the basal stem marsupial, Didelphis, still lives in North America. So don’t be too surprised to find kangaroos (Figs. 1-4)  and other unrecognized derived marsupials in South America. They were there!

First you find them in the ground,
then you find them in a large gamut cladogram where taxa nest themselves with a miniimum of traditional bias.

Simpson 1970 reported, “Argyrolagids are marsupials, but show no clear affinity with any others known. They probably arose from didelphids independently of other known families and are distinct at the superfamily level, at least.” Well, all marsupials and placentals arose from didelphids in the large reptile tree, but let’s save that cladogram (Fig. 4) for later.

Sanchez-Villagra and Kay 1997 reported, “The Argyrolagidae are one of the most enigmatic extinct groups of South American mammals.” Several workers have even questioned the marsupial affinities of this clade. What they needed was the LRT.

Argyrolagids look like little kangaroos.
They probably hopped like little kangaroos. So what set them apart from kangaroos? Turns out, not much…

Argyrolagus palmeri and Proargyrolagus bolivianus (Fig. 1; Ameghino 1904; Simpson 1970, Sanchez-Villagra and Kay 1997; Late Oligocene, Plio-Pleistocene)) was just added to the large reptile tree (LRT, 1031 taxa), and it nested with a big kangaroo, Macropus (Fig. 2).

So why was Argyrolagus
EVER considered an enigma? Is it because kangaroos don’t live in South America? Or is this yet another case of taxon exclusion?

Figure 1. The skull of Proargyrolagus and an illustration of Argyrolagus. The traits shown here align very closely with Macropus, the kangaroo, to no one's surprise... so why was this considered an enigma taxon?

Figure 1. The skull of Proargyrolagus and an illustration of Argyrolagus. The differences are subtle yet notable. In either case, the traits shown here align very closely with Macropus, the kangaroo (see figure 2). So why were these considered enigma taxa?

Perhaps so.
Online I don’t see many cladograms that include both taxa. In the large gamut  reptile tree Argyrolagus shares nearly all of its tested traits with Macropus, the kangaroo (Fig. 2) and it’s easy to see why. The small list of differences incude: smaller size, four premaxillary teeth, naris open ventrally, caudals 3x longer than tall, lack of a maxillary diastema.

Figure 2. The extant kangaroo, Macropus, nests as a sister to Proargyrolagus in the LRT.

Figure 2. The extant kangaroo, Macropus, nests as a sister to Proargyrolagus in the LRT. Even the pelvis in lateral view looks like the one n Argyrolagus.

Based on their similar small size
Argyrolagus has been compared to extant ricocheting rodents, like kangaroo rats. Surprisingly and apparently argyrolagids haven’t yet been compared to real kangaroos in a phylogenetic analyses.

Argyrolagids and toxodontids are found in South America.
Kangaroos and wombats come from Australia. 180–140 million years ago, during the Jurassic, Gondwana split these related taxa apart. So their genesis and radiation must have been earlier, perhaps in the early Jurassic.

If you know of a paper
that includes both Argyrolagus and Macropus as taxa, and they nest far from each other, let me know. I’d like to learn the details. This could be a grand case of homoplasy. But at present, we’re looking at overlooked homology and both giant wombats and tiny kangaroos in Bolivia.

On a similar note
Smithsonian online mentioned the roots of kangaroos and wombats in South America. The article referenced Nilsson et al. (Fig. 3) who studied the genomics of Australian and South American marsupials. They report, “The evolutionary relationships among the seven marsupial orders have, however, so far eluded resolution.  In particular, the relationships between the four Australasian and three South American marsupial orders have been intensively debated since the South American order Microbiotheria was taxonomically moved into the group Australidelphia.The four Australasian orders share a single origin with Microbiotheria as their closest sister group, supporting a clear divergence between South American and Australasian marsupials. Placing the retroposon insertion pattern in a paleobiogeographic context indicates a single marsupial migration from South America to Australia.” (Marsupials are resolved in the LRT).

Figure 3. Phylogenetic tree of marsupials derived from retroposon data from Nilsson et al. No extinct taxa are shown here.

Figure 3. Phylogenetic tree of marsupials derived from retroposon data from Nilsson et al. No extinct taxa are shown here.

Nilsson et al. 2010 further report,
Dromiciops is clearly only distantly related to Australian marsupials, supporting a single Gondwanan migration of marsupials from South America to Australia.” In the LRT Dromiciops, a South American opossum, is closely related to tested marsupials (Fig. 4) from Australia and South America.

Figure 4. Geographic distribution of basal Theria, focusing on marsupials.

Figure 4. Geographic distribution of basal Theria, focusing on marsupials. Patterns are just beginning to emerge with this number of taxa all radiating before the mid-Jurassic splitting of Gondwana.

The geographical radiation of basal therians
(Fig, 4) indicates a world-wide distribution with both marsupials and placentals (metatherians and eutherians) arising out of Asia before being restricted to North America (Didelphis), South America, Madagascar and Australia. At least that’s how it looks with this admittedly small sample set.

References
Ameghnino F 1904. Nuevas especies de mamíferos, cretáceos y terciarios de la República Argentina [New species of mammals, Cretaceous and Tertiary, from the Argentine Republic]. Anales de la Sociedad Cientifica Argentina 56–58:1-142.
Nilsson MA et al. (6 co-authors) 2010. Tracking marsupial evolution using archaic genomic retroposon insertions. https://doi.org/10.1371/journal.pbio.1000436
Sanchez-Villagra MR and Kay RF 1997. A skull of Proargyrolagus, the oldest argyrolagid (Late Oligocene Salla Beds, Bolivia), with brief comments concerning its paleobiology. Journal of Vertebrate Paleontology 17(4):717-724.
Simpson GG 1970. The Argyrolagidae, extinct South American marsupials. Bulletin of the Museum of Comparative Zoology 139, 1–86.

wiki/Argyrolagus

Eurygenium: another wombat close to Toxodon

This was a odd-looking cover taxon
in the Journal of Vertebrate Paleontology back in 1997 (Fig. 1).

Figure 1. Eurygenium is a smaller, less robust, longer legged version of Toxodon.

Figure 1. Eurygenium is a smaller, less robust, longer legged version of Toxodon. The original reconstruction appears to be trying to feed itself with its right hand, but this appears to be unlikely based on phylogenetic bracketing and that antebrachium does not appear to be able to pronate.

Eurygenium latirostris (Ameghino 1894. E. pacegnum Shokey 1997; late Oligocene, 25 mya; 76 cm in length) was described by Shockey as close to the origins of Toxodontidae. That is confirmed here in the large reptile tree (LRT (1028 taxa), but no prior authors nested these taxa with wombats and marsupials as they do here. Most authors considered both taxa notoungulates, a taxon that has been dispersed and essentially invalidated here in the LRT.

Figure 1. Toxodon was a notoungulate placental. Now it's a wombat marsupial.

Figure 2. Toxodon WAS a notoungulate placental. Now it’s a wombat marsupial. Now, just imagine tiny little toxodons or maybe just one tiny little toxodon in the marsupium of this beast. Wombats wear their pouches backwards, by the way. So if the baby wants to look outside the pouch, it sees a short thick tail wagging back and forth. Quite a sight, I’m sure, for baby and all outside observers.

Eurygenium is also close to Pyrotherium, and is from the same beds.

By the way…
Wombats wear their pouches backwards, so if the baby wants to look outside the pouch, it sees a short thick tail wagging back and forth. Quite a sight, I’m sure, for baby and all outside observers.

References
Shockey BJ 1997. Two new notoungulates (Family Notohippidae) from the Sall Beds of Bolivia (Deseadan: late Oligocene) : systematics and functional morphology. Journal of Vertebrate Paleontology 17(3):584-599.

Oops! What’s wrong with this picture?

So far you’ve learned so much about the skeletons of vertebrates. Now, can you tell what is wrong with the published image below? It will be obvious once you know what to look for. Scroll down for the solution.

Figure 1. Can you tell what is wrong with this picture of a museum mount of Ernanodon published in Vickers-Rich and Rich 1993?

Figure 1. Can you tell what is wrong with this picture of a museum mount of Ernanodon published in Vickers-Rich and Rich 1993?

Earlier we looked at and nested the basal marsupial, Ernanodon (Figs. 1, 2). The museum mount published in Vickers-Rich and Rich 1993, has one glaring error. Can you spot it?

Ernanodon anteilos (Ting [Ding] 1979; Paleocene; 50 cm in length) was originally considered placental mammal, perhaps a primitive anteater, then regarded as a primitive pangolin, like Manis. Here Ernanodon nests with Hyaenodon and Deltatheridum as a creodont marsupial, sharing large canines with both.

The skull was robust with a jaw joint nearly as far back as the occiput. The claws were broad and long, ideal for digging. The tail was long, but very slender.

Figure 2. Here is the same museum mount repaired in Photoshop. The pelvis was originally installed backwards. Here the pelvis is correctly mounted.

Figure 2. Here is the same museum mount repaired in Photoshop. The pelvis was originally installed backwards. Here the pelvis is correctly mounted.

Answer
The pelvis of the museum mount was installed backwards. Here (Fig. 2) the pelvis has been flipped in Photoshop to its correct position.

References
Ding SY 1979. A new edentate from the Paleocene of Guangdong. Vertebrata PalAsiatica 17:57–64. [Chinese 57–61; English 62–64].
Vickers-Rich P and Rich TH 1993. Wildlife of Gondwana. REED, Chatswood, Australia. 276 pp.

wiki/Ernanodon

Deltatheridium revisited

Deltatheridium
according to Wikipedia, is “an extinct species of metatherian. It lived in what is now Mongolia during the Upper Cretaceous, circa 80 million years ago. It was a basal metatherian, which places it near start of the lineage that led to the marsupials. It had a length of 15 cm (5.9 in). Its teeth indicate it was carnivorous.” 

The large reptile tree does not support that nesting, but nests Deltatheridium (Gregory and Simpson 1926, Rougier et al. 1998, Fig. 1) basal to Borhyaeana (Fig. 2), though much smaller. Ernanodon and Hyaenodon are outgroup taxa.

Figure 1. Deltatheridium skulls, PSS-MAE 132, 133 and AMNH 21706.

Figure 1. Deltatheridium skulls, PSS-MAE 132, 133 and AMNH 21706. The back of the skull in the 133 specimen is imagined twice. The elevated posterior rim matches sister taxa like Borhyaena. These skulls are almost twice life size based on a 72dpi monitor.

From the Rougier et al. 1998 abstract:
“We describe here two new specimens of the mammal Deltatheridium pretrituberculare from the Late Cretaceous period of Mongolia. These specimens provide information on tooth replacement in basal therian mammals and on lower jaw and basicranial morphology. Deltatheroidans, known previously from isolated teeth, partial rostra and jaws from the late Cretaceous of Asia and possibly North America have been identified variously as eutherians, as basal metatherians (the stem-based clade formed by marsupials and their extinct relatives) or as an outgroup to both eutherians and metatherians. Resolution of these conflicting hypotheses and 

Figure 2. Borhyaena compared to the smaller Deltatheridium.

Figure 2. Borhyaena compared to the smaller Deltatheridium.

understanding of the early evolution of the therian lineage have been hampered by a sparse fossil record for basal therians. The new evidence supports metatherian affinities for deltatheroidans and allows a comprehensive phylogenetic analysis of basal metatherians and marsupials. The presence of specialized marsupial patterns of tooth replacement and cranial vascularization in Deltatheridium and the basal phylogenetic position of this taxon indicate that these features are characteristic of Metatheria as a whole. Other morphological transformations recognized here secure the previously elusive diagnosis of Metatheria. The new specimens of Deltatheridium illustrate the effectiveness of fairly complete fossil specimens in determining the nature of early evolutionary events.”

Figure 1. The nesting of Deltatheridium according to Rougier et al. 1998. The LRT does not support this cladogram.

Figure 3. The nesting of Deltatheridium according to Rougier et al. 1998. The LRT does not support this cladogram. Pink highlights are taxa both cladograms share in common.

The large reptile tree 
subset (Fig. 3) includes a different set of taxa, none based on mandible only or tooth only taxa. Here Deltatheridium is a small ancestor to Didelphodon and Borhyaena and none of these taxa are basal metatherians, which more closely resemble Eomaia and Didelphis.

Figure 3. Subset of the LRT focusing on marsupials and Deltatheridium nesting with Borhyaena.

Figure 4. Subset of the LRT focusing on marsupials and Deltatheridium nesting with Borhyaena.

References
Rougier GW, Wible JR and Novacek JJ 1998. Implications of Deltatheridium specimens for early marsupial history. Nature 396, 459-463. doi:10.1038/24856
Gregory WK and Simpson GG 1926. Cretaceous mammal skulls from Mongolia. American Museum Novitates 225, 7-20.

wiki/Deltatheridium
wiki/Didelphodon
wiki/Borhyaena

Notoryctes the marsupial mole

Wikipedia reports, “Marsupial moles are a family (Notoryctidae) of cladotherian mammals of the order Notoryctemorphia. They are rare and poorly understood. Once classified as monotremes, they are now thought to be marsupials. Their precise classification was for long a matter for argument.”

Earlier we looked at other mammal moles.

  1. Eastern mole – Talpa  (Carnivora, Placentalia)
  2. Docofossor (basal Placentalia)
  3. Golden mole – Chrysochloris (Glires, Placentalia)

And some reptilian ‘moles’.

  1. Mexican mole lizard – Bipes (Scincomorpha, Squamata)
  2. Mermaid skink – Sirenoscincus mobydick (Scincomorpha, Squamata)
  3. Texas blind snake – Leptotyphlops dulcis (Serpentes, Squamata)

Today we’ll round out this topic
with the extant marsupial mole (Notoryctes; Stirling 1888, 1891;  Figs. 1-3; 12-16 cm long) which nests with Anebodon at the base of the Marsupialia in the large reptile tree. The two-teat pouch opens backwards to keep dirt out.

Figure 2. Notoryctes skeleton. The hind limbs were not included so the femur and tibia are added here.

Figure 1. Notoryctes skeleton. The hind limbs were not included so the femur and tibia are added here.

We see burrowing synapsids
all the way back to Thrinaxodon, but moles spend all their time underground.

FIgure 3. Notoryctes in vivo.

FIgure 2. Notoryctes in vivo.

Notoryctes typhlops (Stirling 1891; extant; up to 16 cm in length) is the marsupial mole.  This taxon is blind with eyes reduced to vestigial lenses and without external ears. Three molars are present. Several neck vertebrae are fused, as are the sacrals. The tail verts are quite robust, especially for a mole. Tiny epipubes are present. A cloaca is present, a trait otherwise seen in monotremes and tenrecs. The forelimb has transformed to support the two large digging claws.

Figure 1. Notoryctes skull from copyright Digimorph.org, used with permission.

Figure 3. Notoryctes skull from copyright Digimorph.org, used with permission. Colors added. Although the orbit portion of the confluent lateral temporal fenestra, the eyeball is small and blind.

The claws of the third and fourth digits
are enormous. The canine (orange, Fig. 1) is considered by some as a 4th upper and 3rd lower incisor.

Figure 2. Anebodon partial skull. This is the only known and tested sister to Notoryctes.

Figure 4. Anebodon partial skull. This is the only known and tested sister to Notoryctes.

 

 

References
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.
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/Notoryctes

Former ‘notoungulate’ Periphrangis is really a wombat

Periphrangis harmeri (Roth 1899; Fig. 1; Oligocene, 48-28 mya) has long been considered a notoungulate. Earlier the LRT nested two former notoungulates as wombats. Periphranigis also shares several wombat traits, including a jugal that contacts the jaw glenoid, procumbent incisors and a septomaxilla.

Figure 1. Periphrangis was considered a notoungulate, but it is clearly a wombat with four molars and a jugal that contacts the jaw glenoid, among several other identifying traits.

Figure 1. Periphrangis was considered a notoungulate, but it is clearly a wombat with four molars and a jugal that contacts the jaw glenoid, among several other identifying traits.

When we first looked at Haramiyavia
(Jenkins et al. 1997, Luo et al. 2005) here, this small Late Triassic mammal was considered a basal multituberculate. Now that several wombats have been added to the LRT Haramiyava could be another wombat. Wombats share procumbent incisors and a convex ventral mandible. Hard to tell with present data. In either case, both wombats and multituberculates are rather derived taxa for the Late Triassic.

Figure 1. Haramiyavia reconstructed and restored. Missing parts are ghosted. Three slightly different originals are used for the base here.

Figure 2. Haramiyavia reconstructed and restored. Missing parts are ghosted. Three slightly different originals are used for the base here.

Arctocyon
(Fig. 3; Blainville 1841, Gould and Rose 2014; YPM VP 021233; 60 mya) was long and widely considered (see Wikipedia page) a primitive plantigrade ungulate condylarth procreodi placental.  In the LRT Arctocyon nests with basal carnivorous/omnivorous marsupials. Essentially it is a giant opossum, like Didelphis, but with a few derived traits, more like Thylacinus, a taxon that reduces the epipubes and molar count, hence the earlier traditional confusion. Just look at these taxa side-by-side. It’s obvious, but it’s also in the matrix scores.

Figure 3. Arctocyon is no longer an ungulate placental, but a carnivorous marsupial, close to Thylacinus.

Figure 3. Arctocyon mumak is no longer an ungulate placental, but a carnivorous marsupial, close to Thylacinus.

Small brains and long jugals extending to the jaw glenoid
also give them away as metatherians. Not sure why even recent authors (Gould and Rose 2014) are not seeing this. They must be counting molars.

References
Blainville HM 1841. Osteographie et description iconographique des Mammiferes récentes et fossiles (Carnivores) 1, 2 Paris.
Gould FDH and Rose KD 2014. Gnathic and postcranial skeleton of the largest known arctocyonid ‘condylarth’ Arctocyon mumak (Mammalia, Procreodi) and ecomorphological diversity in Procreodi. Journal of Vertebrate Paleontology 34(5):1180-1202.
Jenkins FA, Jr, Gatesy SM, Shubin NH and Amaral WW 1997. Haramiyids and Triassic mammalian evolution. Nature 385(6618):715–718.
Luo Z-X, Gatesy SM, Jenkins FA, Jr, Amaralc WW and Shubin NH 2015. Mandibular and dental characteristics of Late Triassic mammaliaform Haramiyavia and their ramifications for basal mammal evolution. PNAS 112 (51) E7101–E7109.
Roth S 1899. Aviso preliminar sobre mamíferos mesozóicos encontrados en Patagonia [Preliminary notice on Mesozoic mammals found in Patagonia]. Revista del Museo de La Plata 9:381-388