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.)

Figure 1. Subset of the LRT focusing on edentates and their outgroup, Barylambda. Here two glypotodonts nest at the bases of the two major clades.

Figure 1. Subset of the LRT focusing on edentates and their outgroup, Barylambda. Here two glypotodonts nest at the bases of the two major clades.

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, edentate subset Fig. 1) the glyptodont, Glyptodon, nests between the massive Barylambda and giant sloths, followed by smaller tree sloths and small extinct horned armadillos, like Peltephilus and Fruitafossor. 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

 

 

 

 

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Ukhaatherium: a late-surviving Morganucodon in the LRT

Ukhaatherium nessovi (Late Cretaceous, Novacek et al. 1997) has traditionally been nested with the proto-placental, Asioryctes. Here in the large reptile tree (LRT, 1243 taxa), Ukhaatherium nests as a basal therian in the large reptile tree. Morganucodon (Latest Triassic/Earliest Jurassic, Küehne 1949) nests with Ukhaatherium, with virtually identical scores and are similar in size.

Figure 1. Morganucodon skull in several views. Compare to Ukhaatherium in figure 2.

Figure 1. Morganucodon skull in several views. Compare to Ukhaatherium in figure 2.

When you see them together,
(Figs. 1,2) the similarities between Morganucodon and Ukhaatherium are strikingly obvious.

Figure 2. Skull and dentition of Ukhaatherium. Compare to Morganucodon in figure 1.

Figure 2. Skull and dentition of Ukhaatherium. Compare to Morganucodon in figure 1.

The long snout of prototheres
is retained in basal therians like Morganucodon and Ukhaatherium. The epipubic bones found in Ukhaatherium are no surprise in the LRT, where it nests in the middle of other taxa that share this trait.

Figure 3. Ukhaatherium in situ.

Figure 3. Ukhaatherium in situ.

Rowe 1988 defined Mammaliaformes
as Morganucondontidae + Mammalia. Here Morganucodontidae nest within the Mammalia, so Mammaliaformes is a junior synonym of Mammalia.

Figure 3. Subset of the LRT with the addition of Perameles and Morganucodon.

Figure 4. Subset of the LRT with the addition of Perameles and Morganucodon. Sharp-eyed readers with good memories will not subtle changes in this tree near protorotheres.

And, by the way,
Ukhaatherium + Morganucodon is still close to Asioryctes in the LRT. If we let a little time go by from the Latest Triassic to the Latest Cretaceous, then that’s enough time for the tiny posterior jaw bones in Morganucodon to evolve into the tiny ear bones of Ukhaatherium, convergent and parallel to those of other therian and prototherian mammals (which already show distinct patterns in this regard).

References
Kuehne WG 1949. On a triconodont tooth of a new pattern from a fissure-filling in South Glamorgan. Proceedings of the Zoological Society of London 119:345-350
Novacek MJ, Rogier GW, Wible JR, McKenna MC, Dashzev g D and Horovitz I 1997. Epipubic bones in eutherian mammals from the Late Cretaceous of Mongolia Nature 389: 483-486.
Rowe TS 1988. Definition, diagnosis and origin of Mammalia. Journal of Vertebrate Paleontology 8(3):241–264.

wiki/Ukhaatherium
wiki/Morganucodon

New(?) mammal at the Eutheria-Metatheria split

Bi et al. 2018 bring us a small Virginia opossum from the early Cretaceous
“Molecular estimates of the divergence of placental and marsupial mammals and their broader clades (Eutheria and Metatheria, respectively) fall primarily in the Jurassic period. Supporting these estimates, Juramaia, the oldest purported eutherian is from the early Late Jurassic (160 million years ago) of northeastern China. Sinodelphys, the oldest purported metatherianâis from the same geographic area but is 35 million years younger, from the Jehol biota. Here we report a new Jehol eutherian, Ambolestes zhoui, with a nearly complete skeleton that preserves anatomical details that are unknown from contemporaneous mammals, including the ectotympanic and hyoid apparatus. This new fossil demonstrates that Sinodelphys is a eutherian, and that postcranial differences between Sinodelphys and the Jehol eutherian Eomaia, previously thought to indicate separate invasions of a scansorial niche by eutherians and metatherians, are instead variations among the early members of the placental lineage. The oldest known metatherians are now not from eastern Asia but are 110 million years old from western North America, which produces a 50-million-year ghost lineage for Metatheria.”

Figure 1. Ambolestes tracing from Bi et al. 2018.

Figure 1. Ambolestes tracing from Bi et al. 2018. plate and counter plate. Note the scale bar. This taxon is one third the size of the extant opossum. Apparently and oddly no unguals were preserved.

In the large reptile tree (LRT, 1131 taxa) the new fossil at the Metatheria/ Eutheria split is phylogenetically identical to and therefore congeneric with Didelphis, the Virginia opossum. So, this is pre-marsupial in a clade at the base of the marsupial/placental split. There are also a series of pre-placentals, some of which are extant and retain a reduced pouch, like Monodelphis.

Figure 2. Ambolestes skull in situ with DGS applied.

Figure 2. Ambolestes skull in situ with DGS applied.

Ambolestes zhoui gen. & sp. nov. (Bi et al. 2016, 126 mya; 25cm in length) is is one third the size of the extant opossum, but otherwise nearly identical based on tested traits. In the LRT Didelphis nests with Ambolestes and they nest with Eomaia and Agilodocodon as the last common ancestors to Metatheria and Eutheria. Bi said in an interview, “Ambolestes zhoui is an early member of the placental lineage. It also carries mixed features both placentals and marsupials”. In the LRT, Ambolestes is exactly as much in the placental lineage (Fig. 4) as Didelphis is… and Didelphis has a pouch. Both have prepubic (epipubic) bones.

Since Ambulestes is congeneric with Didelphis,
you heard it hear first when the LRT nested Didelphis as the last common ancestor of Metatheria and Eutheria. Good to see confirmation.

Figure 3. Ambolestes skull reconstructed. Jaw tips restored.

Figure 3. Ambolestes skull reconstructed. Jaw tips restored. Lower last molar appears to be just erupting. No retroartcular process is apparent here, which sometimes happens with Didelphis (Mohamed 2018)

The Pittsburgh Post-Gazette reported,
“The well-preserved new mammal, an ancient furry creature most similar to a modern tree shrew, is named Ambolestes zhoui.” Actually Ambolestes was a little less exotic than that.

“John Wible, curator of mammals at the Carnegie Museum of Natural History, became involved in the project about two years ago.As soon as I saw the photographs of the fossil I was like, ‘Oh my God this is amazing,’ ” he said. “It was amazingly complete. Right off the bat I saw there were skeletal parts of the body that were not known of other animals of that time period.”

But if Dr. Wible happened upon a certain type of roadkill
or went out after midnight with a flashlight he would have seen a living version of the Early Cretaceous fossil. Rather than, “this is amazing” he could have said, “we could have predicted this.”

Figure 7. Subset of the LRT focusing on basal live-bearing mammals.

Figure 4. Subset of the LRT focusing on basal live-bearing mammals.

The Post-Gazette also reported, 
“The fossil was not allowed to leave China, said Mr. Wible, noting that this is the first paper he’s published where he’s been unable to actually hold the fossil, though he hopes to see it in person in the next few years. Instead, he relied on detailed photographs and scanned images.”

Figure 4. Didelphis, the extant opossum, a sister to the smaller Ambolestes

Figure 5. Didelphis, the extant opossum, a larger sister to the smaller and 126 million years older Ambolestes.

Now it’s important to remember 
that tooth traits can converge and reverse. Think about archaeocetes (pre-whales), which have three cusps all in a row, like cynodont. Consider odontocetes, which have simple cones, like basal reptiles. Thus, tooth only taxa must be treated separately from skeletal taxa and cladograms must be based on skeletal traits, not tooth traits, which can be dangerous based on the issues that arise from the Bi et al. cladgoram (Fig. 6).

Take another look at taxa listed in Bi et al. 2018
Maelestes, when tested with more taxa, nests at the base of the tenrec/odontoete clade. Necrolestes nests with the golden mole, Chrysochloris, a basal member of Glires. Zhangeotherium is a basal pangolin. They (Bi et al. and other basal mammal workers) are going to have to expand their taxon lists to include at least all the mammals that don’t have hooves, and that includes a few that do have quasi-hooves, like the descendants of Maelestes.

FIgure 8. Cladogram published in Bi et al. 2018 with colors added to show taxa appearing elsewhere in the LRT. As you can see, this is a mess, likely created by too much emphasis on teeth traits, which converge and reverse.

FIgure 6. Cladogram published in Bi et al. 2018 with colors added to show taxa appearing elsewhere in the LRT. As you can see, this is a mess, likely created by too much emphasis on teeth traits, which converge and reverse. Treeshrew-like Maelestes, when tested with more taxa, nests at the base of the tenrec/odontoete clade. Necrolestes nests with the golden mole, Chrysochloris, a basal member of Glires. Zhangeotherium is a basal pangolin.

References
Bi S-B, Zheng X-T, X, Wang X-L, Cignetti N-E, Yang SL and Wible JR 2018.
An Early Cretaceous eutherian and the placental/marsupial dichotomy. Nature (advance online publication) DOI: https://doi.org/10.1038/s41586-018-0210-3
https://www.nature.com/articles/s41586-018-0210-3
Mohamed R. 2018. Anatomical and radiographic study on the skull and mandible of the common opossum (Didelphis marsupialis Linneaus, 1758 (in the Caribbean). Veterinary Sciences 5(44) 10 pp. doi:10.3390/vetsci5020044

https://carnegiemnh.org/press/new-mammal-fossil-provides-insights-on-early-placental-mammal-evolution/

 

Cifelliodon: new echidna ancestor from the Early Cretaceous of Utah

This one seemed pretty obvious from the first impression,
but failed to make the same impression on the original authors (Huttenlocker et al., 2018).

Usually mammal teeth are found without a skull.
Huttenlocker et al., 2018 found a skull largely without teeth (most don’t erupt beyond the rim of the very few alveoli), certainly a derived trait for mammals. And this is one more way tetrapods became toothless. They named their new taxon, Cifelliodon wahkarmoosuch (Fig. 1).

Figure 1. Early Cretaceous Cifelliodon is ancestral to the living echidna, Tachyglossus according to the LRT. The lack of teeth here led to toothlessness in living echidnas. The skull of Tachyglossus is largely fused together, lacks teeth and retains only a tiny lateral temporal fenestra (because the jaws don't move much in this anteater. Compared to Cifelliodon the braincase is greatly expanded, the lateral arches are expanded and the two elements fuse, unlike most mammals.

Figure 1. Early Cretaceous Cifelliodon is ancestral to the living echidna, Tachyglossus according to the LRT. The reduced number and size of teeth here led to toothlessness in the living echidna. The skull of Tachyglossus retains only a tiny lateral temporal fenestra (because the jaws don’t move much in this anteater. Compared to Cifelliodon the braincase is greatly expanded, the lateral arches are expanded and the two elements fuse, unlike most mammals.

According to Wikipedia:
“Cifelliodon is an extinct genus of haramiyid mammal from the Lower Cretaceous of North America. It is a mammaliaform, and is one of the latest surviving haramiyids yet known, belonging to the family Hahnodontidae. Its discovery led to the proposal to remove hahnodontids from the larger well-known group, the multituberculates.”

As usual the LRT recovered a different nesting.

Figure 2. Cifelliodon skull in three views, plus DGS, plus the original drawing, which is not very accurate.

Figure 2. Cifelliodon skull in three views, plus DGS, plus the original drawing, which is not very accurate. A mandible is restored here.

Figure 3. Subset of the LRT focusing on Monotremes, now including Cifelliodon.

Figure 3. Subset of the LRT focusing on Monotremes, now including Cifelliodon.

Here
in the large reptile tree (LRT, 1233 taxa) Cifelliodon wahkarmoosuch from the Early Cretaceous of Utah nests strongly with Tachyglossus (Figs. 1, 4, 5), one of the extant egg-laying echidnas, currently restricted to Australia and surrounding islands. Tachyglossus was tested in the (Huttenlocker et al. analysis of basal mammal relationships, but the two taxa did not nest together.

Unfortunately Huttenlocker et al., 2018
experienced taxon exclusion problems that nested Cifelliodon with the distinctly different wombat Vintana and those two with the distinctly different multituberculates all more primitive than monotremes.

To their credit
Huttenlocker et al. linked this North American taxon with others from Gondwana which includes Australia, which broke off 99 mya, 40 million years after the appearance of Cifelliodon in Utah. In an interview for USC, Huttenlocker reported, “Most of the fossil record of early mammal relatives is based on teeth. Cifelliodon is unique in that it is one of the only near-complete skulls of a mammal relative from the basal Cretaceous of North America and is the only fossil of early mammal relatives from this time interval in Utah.”

“The fact that the skull looked so primitive compared to other known mammal groups from the Cretaceous made figuring out its relationships extremely difficult. It shows some unique dietary specializations that are seen in only a handful of groups that lived during the age of dinosaurs. Ultimately, the structure of the preserved molars showed clear similarities to some neglected fossil teeth from Northern Africa. So we think that Cifelliodon represents an archaic offshoot whose relatives may have dispersed into the southern continents and became fairly successful during the Cretaceous.”

Figure 3. Tachyglossus skeleton, manus and x-rays. Note the perforated pelvis.

Figure 4. Tachyglossus skeleton, manus and x-rays.

The skull of Tachyglossus
retains only a tiny lateral temporal fenestra (because the jaws don’t move much in this anteater. Compared to Cifelliodon the braincase is greatly expanded, the lateral arches are expanded and the two elements fuse, unlike most mammals.

Figure 1. The echidna (genus: Tachyglossus) in life. This slow-moving spine-covered anteater has digging claws.

Figure 5. The echidna (genus: Tachyglossus) in life. This slow-moving spine-covered anteater has digging claws. Many of the derived traits seen here developed during the last 100 million years since Cifelliodon.

 

References
Huttenlocker AD, Grossnickle DM, Kirkland JI, Schultz JA and Luo Z-X 2018. Late-surviving stem mammal links the lowermost Cretaceous of North America and Gondwana. Nature Letters  Link to Nature

wiki/Cifelliodon

https://news.usc.edu/143411/why-you-should-care-about-this-130-million-year-old-fossil/

Multituberculate origins: Two views

A recent paper by Csiki-Sava et al. 2018
described a new multituberculate, Litovoi. The authors also produced a cladogram of multituberculates (Fig. 1).

Long have I wondered
which taxa were considered outgroups for the multituberculates in modern paleo-thinking. Thanks to Csiki-Sava et al. now we know they nested Haramiyavia as the outgroup (Figs. 1, 2).

Or is that solution possible
only due to taxon exclusion?

Figure 1. Cladogram of multituberculate origins and interrelations by Csiki et al. 2018.

Figure 1. Cladogram of multituberculate origins and interrelations by Csiki-Sava et al. 2018.

By contrast
the large reptile tree (LRT, 1201 taxa) nested multis with rodents and plesiadapids (Fig. 2). Haramiyavia nested far distant, as a pre-mammal, not far from Pachygenelus. While the .nex files include all the details, the illustration of skulls (Fiji. 3) compares the two hypotheses of relationships.

Figure 2. Cladogram of multituberculate origins according to the LRT.

Figure 2. Cladogram of multituberculate origins according to the LRT

Taking the skulls from Figure 2
(Fig. 3) one can compare the traditional hypothesis of multituberculate origins with that recovered by the LRT, offering a sort of short hand of all the data scores. One should appear to demonstrate a gradual accumulation of traits. The other should appear to not do so well. Which outgroup lineage appears to have more multituberculate traits in your judgement?

Figure 3. Comparing multituberculate origins: Cziki-Sava et al. vs. LRT.

Figure 3. Comparing multituberculate origins: Cziki-Sava et al. vs. LRT. Gray background taxa are multituberculates. The morphological gap between Haramiyavia and multis is great, much greater than the gap between Paramys and multis.

The closest living relative of long extinct multituberculates,
according to the LRT is Daubentonia, the aye-aye (Figs. 4, 5), once considered a lemur-like primate, but here nesting with extinct Carpolestes and the multis. No other primate, living or extinct (Plesiadapis is also a rodent relative in the LRT), has such a suite of bony traits, including those very large, rodent-like (due to homology) incisors.

Figure 1. Daubentonia was considered a primate for over 150 years. Here it nests with Plesiadapis, rodents and rabbits.

Figure 4. Daubentonia was considered a primate for over 150 years. Here it nests with Plesiadapis, rodents and rabbits.

According to Wikipedia
“The multituberculates existed for about 166 or 183 million years, and are often considered the most successful, diversified, and long-lasting mammals in natural history. They first appeared in the Jurassic, or perhaps even the Triassic, survived the mass extinction in the Cretaceous, and became extinct in the early Oligocene epoch, some 35 million years ago. The oldest known species in the group is Indobaatar zofiae from the Jurassic of India, some 183 million years ago, and the youngest are two species, Ectypodus lovei and an unnamed possible neoplagiaulacid, from the late Eocene/Oligocene Medicine Pole Hills deposits of North Dakota. If gondwanatheres are multituberculates (all tested taxa are not in the LRT), then the clade might have survived even longer into the Colhuehuapian Miocene in South America, in the form of Patagonia peregrine.”

Figure 2. Skeleton of Daubentonia (aye-aye). Like other plesiadapids, it convergences with the lemuroid primates.

Figure 5. Skeleton of Daubentonia (aye-aye). Like other plesiadapids, it convergences with the lemuroid primates.

Employing taxon inclusion,
the LRT presents a heretical and more parsimonious hypothesis of multituberculate origins (Figs 2, 3) that tests Haramiyavia and over 1000 other possible candidates.

To test this hypothesis,
simply add the above suggested relevant taxa to your favorite wide gamut phylogenetic analysis and run. Let me know if your analysis then confirms the LRT—or do you find yet another origin/set of outgroups for the multituberculates? Haramiyavia has very few multi traits, far fewer than rodents and Daubentonia.

References
Csiki-Sava ZVremir MMeng JBrusatte SL and Norell MA 2018. Dome-headed, small-brained island mammal from the Late Cretaceous of Romania. 

https://en.wikipedia.org/wiki/Haramiyavia
https://en.wikipedia.org/wiki/Multituberculata

Maybe the best way to compare congeneric taxa

Online presentations
have certain advantages over published books and journals. What you’ll see today could be more widely presented in the future as biology, morphology and phylogeny move from books and journals to the Internet, complete with inexpensive animation, transparency and lap dissolves.

Figure 1. GIF movie of tiger and leopard skulls for comparison. See text for details.

Figure 1. GIF movie of tiger and leopard skulls for comparison. See text for details.

Obviously related to one another,
but isolated geographically to produce distinct species, the tiger (Panthera tigris) and the leopard (Panthera pardus, Fig. 1) are interesting to compare one skull with another. A GIF movie makes comparisons easy to see. A roll-over would be easier to handle, but roll-overs are not permitted on WordPress.com sites yet.

Helpless and able newborn mammals

I’m going to crowd source this one,
but I think I covered all the bases here. In this subset of the large reptile tree (LRT, 1165 taxa) I’ve divided placental mammals born helpless (blue) from mammals born able to walk, swim and see (pink). I’ll need your help if there are any exceptions, like pangolins, that I missed one way or the other. Fossils are colorized based on phylogenetic bracketing.

Figure 1. Newborn mammals are born either helpless, like humans, or able to keep up with their mother, like horses. I think I located the split correctly here. Let me know I missed a few.

Figure 1. Newborn mammals are born either helpless, like humans, or able to keep up with their mother, like horses. I think I located the split correctly here. Let me know I missed a few. Fossil taxa are colored based on phylogenetic bracketing. 

Marine taxa need to be ready to go from the first minute.
Apparently so do the large plant-eaters ( including ant and copepod eaters), beginning with long-legged former tree shrew, Onychodectes.

Dens and nests
are associated with basal mammals, like us. Not so much with the derived herbivores (and anteaters) of the plains and forests. All of them get milk from their mothers before they start to dine on meat, plants, ants and copepods. Some of them have to keep up with here. Some of them have to keep up with her underwater.

BTW
there also seems to be a behavioral node at Maelestes in which succeeding taxa are all leaving the trees for good. Of course, that also happens exceptionally with the various mole and aquatic clades in more basal mammals.