Shrew opossums (caenolestids) are supposed to be marsupials

According to Wikipedia,
“The family Caenolestidae contains the seven surviving species of shrew opossum: small, shrew-like marsupials that are confined to the Andes mountains of South America.”

Figure 1. Caenolestes skull and in vivo.

Figure 1. Caenolestes skull and in vivo. It sure looks more like a shrew than an opossum. Skull images from Digimorph.org and used with permission. Colors added.

The trouble is
tested caenolestids, Caenolestes (Fig. 1) and Rhyncholestes (Fig. 2), do not have a pouch. Nor do they nest with marsupials in the large reptile tree (LRT, 1412 taxa, subset Fig. 3). But female caenolestids do have a marsupial-like double vagina (see below).

On the traditional side,
Dr. Darren Naish reported online for Tetrapod Zoology/Scientific American in 2015, “Incidentally, the most frequently used name for the group – shrew-opossums – might not be a particularly good one, seeing as they don’t look much like shrews, don’t live like shrews, and don’t act like shrews. And they’re not technically opossums, either, but perhaps we can let that go.”

Contra Dr. Naish’s amusing musings,
shrew opossums nest with placental shrews alongside the otherwise extinct Apatamys (Fig. 3) + Trogosus (Fig. 4) in the Glires clade. All are derived from a tree shrew taxon close to Tupaia. It’s unfortunate that Dr. Naish did not test these taxa while they were on his mind in 2015. That’s how initial errors become perpetuated as long-standing traditions.

Figure 1. Skull of Rhyncholestes along with in vivo photo.

Figure 2. Skull of Rhyncholestes along with in vivo photo.

Rhyncholestes raphanurus (Osgood, 1924; long-nosed shrew-opossum, Chilean shrew opossum, extant; snout-vent length 20cm), nests in the large reptile tree between the shrew-mole, Uropsilus, and the tree shrew, Tupaia at the base of the Apatemys clade. all within the placental clade, Glires. Wikipedia and other sources consider this shrew-like South American mammal a marsupial, but Wiki also notes that Rhyncholestes lacks a marsupium (pouch).

Figure 2. Apatemys nests as a proximal sister to bats in the Halliday et al. tree. But it shares very few traits with bats. Note the very odd dentition.

Figure 3. Apatemys nests as a proximal sister to bats in the Halliday et al. tree. But it shares very few traits with bats. Note the shrew-opposum/rodent-like dentition.

Genetically
Wikipedia reports. “Genetic studies indicate that they are the second most basal order of marsupials, after the didelphimorphs” (Nilsson et al. 2010). That’s exactly where the LRT documents the splitting of eutherian mammals from the phytometatherians and carnimetatherians.  Even so, we’re talking about deep time here. Don’t trust genes. Test traits.

Figure 3. Subset of the LRT focusing on primates and basal glires, including the caenolestids, Caenolestes and Rhyncholestes.

Figure 4. Subset of the LRT focusing on primates and basal glires, including the caenolestids, Caenolestes and Rhyncholestes.

According to AnimalDiversity.org, “In general, members of family Caenolestidae can be distinguished from other marsupial groups by their unique dentition. Their lower middle incisors are large and have a forward slope; likewise, they have a reduced number of incisors. The dental formula for genus Caenolestes is: I 4/3, C 1/1, P 3/3, M 4/4, 46 teeth total. Shrew opossums have short robust limbs, each containing 5 digits; their middle 3 digits are shorter than the outside two. Their humeri are extremely heavy; in comparison, their femurs are relatively slender. Members of family Caenolestidae have unusual lip flaps, they may function as a method of preventing debris from interfering with their whiskers or they may help prevent ingestion of unwanted debris. Similar to other marsupials, Caenolestid females have 2 uteri and 2 vaginas. Members of genus Caenolestes lack a pouch but do have 4 mammae, 2 on either side of their abdomen.”

Unfortunately
the LRT tests only skeletal material, not for ‘number of uteri and vaginas’. While Larry Martin and Darren Naish might wave this trait about in support of a marsupial affinity, the LRT documents the emergence of placentals from marsupials. So the reappearance of a long-lost trait, like a long tail, a sixth digit, or double vaginas is well within the realm of possibilities in placentals.

As a matter of fact,
a double vagina sometimes occurs in humans.

Here, as elsewhere in paleontology,
maximum parsimony is the only yardstick. PAUP is free to nest taxa wherever 231 unbiased scores indicate it should. Moving the two caenolestids to the Metatheria adds 12 steps to the MPT.

The Apatamyidae is a clade that was long considered extinct.
Now it joins several other clades that are no longer extinct, thanks to the LRT.

Rhyncholestes raphanurus (Osgood, 1924; long-nosed shrew-opossum, Chilean shrew opossum, extant; snout-vent length 20cm), nests in the LRT between the shrew-mole, Uropsilus, and a large living shrew, Scutisorex, all within the placental clade, Glires. Wikipedia and other sources consider this shrew-like South American mammal a marsupial, but Wiki also notes that Rhyncholestes lacks a marsupium (pouch).

Caenolestes fuliginosus (originally Hyracodon fuliginosus Tomes 1863)

Apatemys chardini (Marsh 1872, Eocene, 50-33 mya) was a squirrel-lke arboreal herbivore with a massive skull. Here it nests with Trogosus and Tupaia, a tree shrew. It had long slender fingers, a long flexible lumbar region, and a long gracile tail.


References
Marsh OC 1872. Preliminary description of new Tertiary mammals. Part II. American Journal of Science 4(21):202-224.
Nilsson MA, et al. (6 co-authors) 2010. Tracking Marsupial Evolution Using Archaic Genomic Retroposon Insertions”. PLoS Biology. 8 (7): e1000436. doi:10.1371/journal.pbio.1000436
Osgood WH 1924. Field Mus. Nat. Hist. Publ., Zool. Ser. 14:170.

tetrapod-zoology/you-never-hear-much-about-shrew-opossums/
wiki/Shrew_opossum = Caenolestidae
animaldiversity.org/accounts/Caenolestes_fuliginosus/
wiki/Apatemyidae
wiki/Rhyncholestes
wiki/Caenolestes
wiki/Paucituberculata
wiki/Uterus_didelphys

Click here for Glires skulls compared.

Deinogalerix: not a giant extinct hedgehog, but close!

Rather,
Deinogalerix (Fig. 1, 2) is a giant moonrat, (Fig. 3) according to its nesting in the large reptile tree (LRT, 1399 taxa)

Figure 1. Skull of Deinogalerix with bones colored in DGS overlay.

Figure 1. Skull of Deinogalerix with bones colored in DGS overlay. Note the separation of the prefrontal and lacrimal along with the large size of the premolars relative to the small molars.

Deinogalerix koenigswaldi  (Freudenthal 1972; Villiera et al. 2013; Late Miocene 10-5mya; skull length 20cm, snout-vent length 60cm) is the extinct giant moon rat (not hedgehog), restricted to a Mediterranean island, now part of a peninsula. Giant premolars and tiny molars make the dentition unusual. Seven species have been identified.

Figure 2. Deinogalerix skeleton.

Figure 2. Deinogalerix skeleton. Snout to vent length = 60cm.

Echinosorex gymnura (Blainville 1838; length to vent up to 40cm, tail up to 30cm, Fig. 3) is the extant moonrat, or gymnure, an omnivore that looks like an opossum or rat. Here it nests with Pholidocercus, a Messel pit armadillo-mimic we looked at earlier here. Distinct from most Glires, the canines are large.

Figure 3. Echinosorex, the extant moonrat, looks like an opossum, but nests with Deinogalerix in the large reptile tree.

Figure 3. Echinosorex, the extant moonrat, looks like an opossum, but nests with Deinogalerix in the large reptile tree.

References
Freudenthal M 1972. Deinogalerix koenigswaldi nov. gen., nov. spec., a giant insectivore from the Neogene of Italy. Scripta Geologica. 14: 1–19.
Villiera B, Van Den Hoek Ostendeb L, De Vosb J and Paviaa M 2013. New discoveries on the giant hedgehog Deinogalerix from the Miocene of Gargano (Apulia, Italy). Geobios. 46 (1–2): 63–75.

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Pholidocercus: a long tailed armadillo-mimic hedgehog

Reversals in this taxon make it interesting.
Pholidocercus hassiacus (Fig. 1; von Koenigswald & Storch 1983; HLMD Me 7577; Middle Eocene) is a member of the rabbit/rodent/multituberculate clade Glires, but without the large anterior incisors that are found in most other members. This is a reversal hearkening back to basal placentals.

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).

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).

Three upper molars are present,
as in primates, and basal members of Glires, like Ptilocercus, the tree shrew. Other hedgehogs have only two upper molars.

Four upper premolars are present,
one more than in basal placentals and other hedgehogs.

Other hedgehogs have a stub for a tail.
Yet another reversal, Pholidocercus has a long, tail. It is bony and armored,  analogous to that of an armadillo (genus: Dasypus). Sister hedgehogs have just a stub for a tail. The curling of all hedgehogs for defense also recalls the spinal flexion of armadillos for defense. This is a trait basal therian mothers originally used to help guide their newborns from birth canal to teat.

Figure 2. Pholidocercus skull with DGS colors added. Distinct from most members of the Glires, the canine becomes more robust in the hedgehog clade. Note the posterior jaw joint, the opposite of mouse-like rodents.

Figure 2. Pholidocercus skull with DGS colors added. Distinct from most members of the Glires, the canine becomes more robust in the hedgehog clade. Note the posterior jaw joint, the opposite of mouse-like rodents. The short jugal is typical of this clade. No elongate dentary incisors here, yet another reversal to a basal placental condition.

Those sacral neural spines
(Fig. 1) are taller than in sister taxa. Armadillos also have tall sacral spines.

The clade Lipotyphyla, according to Wikipedia
“is a formerly used order of mammals, including the members of the order Eulipotyphla as well as two other families of the former order Insectivora, Chrysochloridae and Tenrecidae. However, molecular studies found the golden moles and tenrecs to be unrelated to the others.” 

The clade Eulipotyphyla, according to Wikipedia
“comprises the hedgehogs and gymnures (family Erinaceidae, formerly also the order Erinaceomorpha), solenodons (family Solenodontidae), the desmansmoles, and shrew-like moles (family Talpidae) and true shrews (family Soricidae).”

The clade Erinaceidae, according to Wikipedia
“Erinaceidae contains the well-known hedgehogs (subfamily Erinaceinae) of Eurasia and Africa and the gymnures or moonrats (subfamily Galericinae) of South-east Asia.”

The LRT largely confirms this clade,
but moles (genus: Talpa) nest separately in the clade Carnivora with the mongoose, Herpestes.

When you come across a taxon like Pholidocercus
first you eyeball it and declare it a… a… well, there are so many reversals here that it is best to avoid pulling a Larry Martin and just add it to a wide gamut phylogenetic analysis to let a large suite of traits decide for themselves based on maximum parsimony. Luckily the LRT had enough taxa to nest Pholidocercus with confidence with the hedgehogs, despite the several distinguishing traits and reversals.

Just added to the LRT:
Echinosorex, the extant moonrat. It also has a long tail and nests with Pholidocercus.

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/Hedgehogs
wiki/Erinaceus
wiki/Echinops
wiki/Pholidocercus

Another flawed aye-aye origin paper: Gunnell et al. 2018

Earlier we looked at µCT scans of the aye-aye (Figs. 1, 4), Daubentonia made by Morris, Cobb and Cox 2018 and comparisons to Lemur catta (Fig. 2), a taxon often considered a sister to Daubentonia.

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

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

 

Figure 2. Lemur catta in vivo and skeleton.

Figure 2a. Lemur catta in vivo and skeleton.

Figure 2. Lemur catta skull in 3 views.

Figure 2b. Lemur catta skull in 3 views. Compare this skull to Daubentonia in figure 4. Note the large canines missing in Daubentonia, replaced by giant incisors and no canines.

Gunnell et al. 2018
reidentified the fossil jaw bone of Propotto leaky (Simpson 1967, 20mya; Fig. 3). “In a study published August 21 in the journal Nature Communications, researchers have re-examined Propotto’s fossilized remains and suggest that the strange creature wasn’t a bat, but an ancient relative of the aye-aye, the bucktoothed nocturnal primate that represents one of the earliest branches of the lemur family tree.” 

Figure 1. Propotto and Plesiopithecus nest with Daubentonia in Gunnell et al. 2018, which does not test many rodents, despite the rodent-like teeth shown here.

Figure 3. Propotto and Plesiopithecus nest with Daubentonia in Gunnell et al. 2018, which does not test many rodents, despite the rodent-like teeth shown here.

Unfortunately
when I ran the Gunnell et al. matrix the clade of rodent-toothed taxa (Daubentonia, Propotto and Pleisopithecus) nested with the primate-toothed Lemur catta. All primates in the large reptile tree (LRT, 1372 taxa) have large canines and two small incisors (except humans and kin where the canines are not fangs). Rodents have the opposite, small to absent canines together with single giant incisors. Rodent-toothed Carpolestes and Plesiadapis (Fig. 6) were tested by Morris, Cobb and Cox 2018, but nested far from the Daubentonia clade. That is strange. No other rodents were tested to eliminate the possibility that rodent-toothed taxa might actually be closer to rodents than primates or that Carpolestes and Pleisadapis might be rodents themselves. In the LRT they are primate-like rodents, not rodent-like primates.

Strangely, but traditionally,
the outgroup taxa for primates in the Morris, Cobb and Cox 2018 study were Tupaia and Ptilocercus, two taxa that nest not with primates, but with Glires (shrews + rodents + multituberculates and kin) in the LRT, which includes more taxa.

A toothless diastema
occurs between the one to two premolars and the giant dentary incisors of Daubentonia, Plesiadapis, Ignacius and most rodents. I don’t see that morphology in figure 3 where three premolars fill the space between the molars and incisors of Propotto and Plesiopithecus. Such a mandible morphology is found in more basal members of Glires, like the hedgehog (Echinops), Apatemys and some shrews, like Scutisorex. None of these taxa were tested by the Gunnell team in their study of Propotto and Plesiopithecus.

The Gunnell et al. cladogram may have suffered from
too many dental traits and too few Glires taxa. It did not deliver the expected ‘gradual accumulation of traits’ that mark every good cladogram (because that’s how evolution works). Rather, like too many cladograms we’ve looked at over the years, sister taxa just don’t look like each other and the enigma taxon looks too much like something else in the cladogram.

Quote mining from the Duke U PR online article:
Propotto: “In 1967, paleontologist George Gaylord Simpson inspected the fragments and classified the specimen as a previously unknown member of the loris family, nocturnal primates with enormous eyes. But a colleague named Alan Walker took a look and thought otherwise, eventually convincing Simpson that the bones belonged to a bat.

For nearly half a century the creature’s identity appeared to have been settled, until 2016, when another paleontologist, the late Gregg Gunnell of Duke University, began taking a fresh look at the fossil. To Gunnell’s eye, the creature’s hind teeth were more reminiscent of a primate than a bat. He also noted the stump of a broken front tooth, just visible in cross section, which would have jutted out from its mouth like a dagger — a trait only known in aye-ayes, the only living primates with rodent-like teeth.

“Gregg wrote to us and said, ‘Tell me I’m crazy,’” Seiffert said.

The researchers found that Propotto shared a number of features with a similarly buck-toothed primate that lived 34 million years ago in Egypt called Plesiopithecus, and that both were ancient relatives of the aye-aye.

In the new study, Seiffert, Gunnell and colleagues propose that the ancestors of aye-ayes split from the rest of the lemur family tree roughly 40 million years ago, while still on the African continent, and the resulting two lineages didn’t make their separate ways to Madagascar until later.

The findings suggest they arrived around the same time as other mammals, such as rodents, Malagasy mongooses and hedgehog- and shrew-like animals called tenrecs. Frogs, snakes and lizards may have made the trip around the same time.”

In the LRT, all these taxa were already on Madagascar in the Mesozoic and did not have to raft over after the split from Africa. 

“Lemurs can’t swim, so some scientists hypothesize that the small-bodied creatures crossed the 250-mile-wide channel that lies between Africa and Madagascar after being swept out to sea in a storm, by holding on to tree limbs or floating mats of vegetation before finally washing ashore.

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

Figure 4. Skeleton of Daubentonia (aye-aye). Like other plesiadapids, it convergences with the lemuroid primates. Consider it a primate-like rodent, not a rodent-like primate. Compare this skull to figure 5.

“But if the arrival were more recent, they might have had a shorter distance to travel, thanks to lower sea levels when the Antarctic ice sheet was much larger. “It’s possible that lemurs weren’t in Madagascar at all until maybe the Miocene,” as recently as 23 million years ago, Boyer said. Some of the lowest sea levels were also during this time,” Heritage said.

Figure 4. Perodicticus potto, the extant potto, has a typical lemur dentition, lacking giant incisors.

Figure 5. Perodicticus potto, the extant potto, has a typical lemur dentition, lacking giant incisors. Compare this skull to figure 4. Note the large canines missing in Daubentonia. 

What about the extant potto, Perodicticus potto?
Perodicticus potto (Bosman 1704, Fig. 5) does not have large rodent-like lower incisors. Rather it has a skull somewhat midway between the lemurs and tarsioids (Fig. 3) with large canines.

Figure 1. Ignacius and Plesiadapis nest basal to Daubentonia in the LRT.

Figure 6.  Ignacius and Plesiadapis nest basal to Daubentonia in the LRT.

This brings up the unfortunate habit
of naming taxa that are not related to the taxa they are purportedly related to, like Propotto and Plesiopithecus (Fig. 3).

And yet another example of ‘Pulling a Larry Martin’:

Figure 7. How Gunnell et al. 'Pulled a Larry Martin'. They cherry-picked taxa. They focused on just a few traits in the mandible. They hope that four tiny incisors might evolve into two giant incisors.

Figure 7. How Gunnell et al. ‘Pulled a Larry Martin’. They cherry-picked taxa. They focused on just a few traits in the mandible. They hope that four tiny incisors might evolve into two giant incisors.

For those who don’t read captions.
How Gunnell et al. ‘Pulled a Larry Martin‘. (Fig. 7).

  1. They cherry-picked taxa, (= taxon exclusion, where is Lemur catta in figure 7?).
  2. They focused on just a few traits in the mandible.
  3. They hoped that four tiny incisors might evolve into two giant incisors.
  4. They did not recognize the convergence that the LRT recovered.

References
Gunnell GF et al. (9 co-authors) 2018. Fossil lemurs from Egypt and Kenya suggest an African origin for Madagascar’s aye-aye. Nature Communications. PDF
Simpson GG 1967. The tertiary lorisiform primates of Africa. Bull. Mus. Comp. Zool. 136, 39–62.

Ancestry of the aye-aye (Daubentonia) illustrated

Yesterday we looked at a paper that compared
the squirrel, Sciurus, to the squirrel-like aye-aye, Daubentonia (Fig. 1) using µCT scans. The authors considered this a case of convergence and nested Daubentonia (from Madagascar) with lemurs (from Madagascar) based on gene studies.

Figure 1. Ignacius and Plesiadapis nest basal to Daubentonia in the LRT.

Figure 1. Ignacius and Plesiadapis (Paleocene) nest basal to Daubentonia (extant) in the LRT. Note the short snout in Daubentonia, a sign of neotony. 50 million years separates Daubentonia from its ancestors.

As a follow-up
I’ll show the ancestry of Daubentonia based on the large reptile tree (LRT, 1370 taxa). The short list includes Ignacius and Plesiadapis, two other taxa also previously considered basal primates, but nest in the LRT with rodents. In the LRT Ignacius is sister to the Mus/Sciurus (= mouse/squirrel) clade.

Daubentonia has a postorbital bar,
convergent with that found in primates. Don’t be guilty of ‘Pulling a Larry Martin’. One character can appear on unrelated clades. Use an unbiased suite of traits and let the taxa nest wherever they want to. Compared to Plesiadapis, Daubentonia appears to be neotonous with a shorter rostrum and mandible, along with a smaller zygomatic arch and large braincase. The mandible has a similar morphology to multituberculates.

Basal taxa in the LRT
are what they are supposed to be: generalized forms ready to evolve into wild and exotic types. In that regard, wild and exotic Daubentonia (Fig. 4) is a poor candidate as a basal primate. In the LRT it nests as a highly derived wild and exotic rodent with no known descendants.

Figure 1. Notharctus, an Eocene adapid (lemur) and likely sister to Manis.

Figure 2. Notharctus, an Eocene adapid (lemur) and a basal primate. Compare to the convergent Plesiadapis in figure 3 and Daubentonia in figure 4.

Ignacius frugivorus (formerly Phenacolemur; Matthew and Granger 1921) was originally based on upper jaw with teeth. It was originally and is here considered a plesiadapiform, close to Plesiadapis.

Plesiadapis

Figure 3. Plesiadapis, formerly considered a basal primate, is here considered an aye-aye ancestor.

Plesiadapis tricuspidens (Gervais 1877) Paleocene ~55 mya. The Plesiadapiformes were widely thought to be the earliest representatives of the primate order, but here they nest wihthin Glires. Derived from a sister to IgnaciusPlesiadapis phylogenetic preceded the living aye-aye, Daubentonia. This clade nests between traditional rodents and multituberculates. Distinct from Ignacius, the skull of Plesiadapis had a deeper shorter rostrum and a higher orbit, but a smaller braincase. The jugal was more robust. The ear was raised. The mandible was more robust with deeper surfaces for muscle attachement and a more robust angular process and a longer coronoid process. The cervicals were shorter. The dorsals, ribs and lumbars were more robust along with the caudals. Chevrons developed at a likely sitting point. The limbs and girdles were more robust. The radius was anteriorly boewed and the ulna developed a large olecranon process (elbow). The unguals were large and deep. The feet were larger than the hands. The joints were nearly all transversely aligned indicating a simple extension/flexion motion for the fingers and toes.

Figure 7. Highlights of the aye-aye (Daubentonia) skeleton focusing on the small bones medial to the humerus (procoracoid + coracoid) and the lateral rotation of the ankle and pes where the astragalus still sits on top of the calcaneum, as the dorsal surface of the pes is now lateral.

Figure 4. Highlights of the aye-aye (Daubentonia) skeleton focusing on the small bones medial to the humerus (procoracoid + coracoid) and the lateral rotation of the ankle and pes where the astragalus still sits on top of the calcaneum, as the dorsal surface of the pes is now lateral.

Daubentonia madagascariensis (Gmelin 1788, Sciurus madagascariensis; Geoffrey Saint-Hilaire 1795; 40 cm snout-to-vent length) is the extant aye-aye. Originally considered a squirrel, then traditionally an odd sort of lemur-like primate with rodent-like teeth, here Daubentonia returns to Glires to nest with Plesiadapis, which has also been wrongly considered a basal primate. This nocturnal arboreal mammal has a long slender digits, particularly manual digit 3, which is used to probe for insects below tree bark. Note the hallux-like pedal digit 1. Like primates, a postorbital bar appears in this taxon, but the eyeballs are no more rotated or stereoscopic than ancestors.

An expert on mammals
(name omitted) replied to a recent query with the following note on Daubentonia“At the moment, your phylogenetic results in many ways resemble 19th century studies in which superficial similarities were interpreted as evidence of close relationship – for example, it’s striking that you find that Daubentonia is not a primate: this was debated during the early part of the 19th century, before researchers collectively reached a consensus that it is a primate, and this is overwhelmingly supported by molecular data too.”

I’m still looking for the phenomic cladogram
that includes the above taxa and others in the LRT. To my knowledge there is none as genomics has taken paleontologists to fantasyland. And, it’s not just superficial similarities… it’s a suite of 231 traits that overwhelms the few convergent traits with primates. 21st century phylogenetics should be accepted over 19th century debates. Let’s hope science and unbiased experimentation will someday triumph over tradition and ego.

References
Bloch JI, Fishe DC, Rose KD and Gingerich PD 2001. Stratocladistic analysis of Paleocene Carpolestidae (Mammalia, Plesiadapiformes) with description of a new late Tiffanian genus. Journal of Vertebrate Paleontology. 21 (1): 119–131.
Bloch JI and Boyer DM 2006. Grasping primate origins. Science 298:1606-1610.
Gervais P 1877. Enumeration de quelques ossements d’animaux vertebres recueillis aux environ de Reims par M. Lemoine. Journal de Zoologie (Paris) 6:74–79.
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).
Gingerich PD 1976. Cranial Anatomy and Evolution of Early Tertiary Plesiadapidae (Mammalia, Primates). Papers on Paleontology, Museum of Paleontology, The University of Michigan. 1-141. online pdf
Hahn G & Hahn R 2000. Multituberculates from the Guimarota mine, pp. 97-107 in Martin T & Krebs B (eds), Guimarota – A Jurassic Ecosystem, Verlag Dr Friedrich Pfeil, München.
Matthew WD and Grange W 1921. New genera of Paleocene mammals. American Museum Novitates 13:1-7
Owen R 1863. Monograph on the Aye-Aye ((Chiromys madagascariensis, Cuvier)
Picone B and Sineo L 2012. The phylogenetic position of Daubentonia madagascariensis (Gmelin, 1788; primates, Strepsirhini) as revealed by chromosomal analysis. Caryologia: International Journal of Cytology, Cytosystematics and Cytogenetics 65(3):223-228. online here.
Geoffroy Saint-Hilaire E 1795. La décade philosophique, litteraire, et politique. Memoires d’Histoire Naturelle 4(28):193– 206.
Sterling E. 1994. Taxonomy and distribution of Daubentonia: a historical perspective.Folia Primatologica 62:8-13.
Yoder AD, Vilgalys R and Ruvolo M 1996. Molecular Evolutionary Dynamics of Cytochrome b in Strepsirrhine Primates: The Phylogenetic Significance of Third-Position Transversions. Mol. Biol. Evol. 13(10):1339-1350.

wiki/Aye-aye
wiki/Plesiadapis
fossilworks/Ignacius

Heretical origin and evolution of moles and shrew-moles

The traditional clade Insectivora
is a now-abandoned clade because its former members have been shown to be polyphyletic. Both shrews and moles are traditional members.

Unfortunately,
a remnant order, Eulipotyphla, still includes both shrews and moles. The large reptile tree (LRT, 1360 taxa, subset Fig. 4) nests moles, like Talpa, within Carnivora, derived from the mongoose, Herpestes, and the traditional canid ancestor, Prohesperocyon. All these taxa (Fig. 1) have transverse premaxillae and long, sharp canines. Talpa and Prohesperocyon both have a bulbous occiput, gracile zygomatic arch and elongate rostrum.

Figure 1. Taxa in the origin and evolution of moles, Herpestes, Prohesperocyon and Talpa.

Figure 1. Taxa in the origin and evolution of moles, Herpestes, Prohesperocyon and Talpa.

Uropsilinae is the clade of shrew-moles
Wikipedia reports, “The shrew moles (Uropsilus) are shrew-like members of the mole family of mammals. They share a full zygomatic arch with all other moles, while this arch is completely absent in shrews.” Notice how this author just ‘pulled a Larry Martin‘? A complete arch is a plesiomorphic (basal) trait. That means it is plesiomorphic for shrews, too. Some shrews, like Rhyncholestes (Fig. 3), retain a complete arch.

Figure 2. The mole-shrew, Uropsilus, is not related to the mole, Talpa (Carnivora), but is related to the shrew (clade Glires).

Figure 2. The shrew-mole, Uropsilus, is not related to the mole, Talpa (Carnivora), but is related to the shrew (clade Glires). Note the long premaxilla, large incisors, tiny canine (orange), arched jugal arch. Image from Hoffmann 1984. Despite the overall similarity of this skull to that of Talpa, note the differences in the dentition and various skull bone proportions, all scored for the LRT.

Uropsilus (Milne-Edwards 1871)
is a shrew-mole (Fig. 2) was described by Hoffmann 1984: “These small insectivores are shrew-like in external appearance, but exhibit a mole0like skull and dentition. The tail is long and forefeet are not enlarged, while the zyogmatic arch is complete, and the tympanic bones form an auditory bulla. Thus, this “shrew-mole” lacks skeletal specializations for digging found in more derived moles, and the derived characters of skull and dentition found in shrews.” Not sure what Hoffman was smoking here, but Uropsilus has a shrew skull (Fig. 2) and readily nests with shrews, like the formerly traditional marsupial, Rhyncholestes, in the LRT, apart from moles.

Figure 1. Skull of Rhyncholestes along with in vivo photo.

Figure 3. Skull of Rhyncholestes along with in vivo photo. This is the long-nosed shrew-opossum and its skull. This taxon is a sister to Uropsilus, but has a longer snout and more incisors. It does not nest with marsupials in the LRT.

Backstories for today’s players:
Herpestes ichneumon (Linneaus 1758; extant; 48-60cm in length) is the Egyptian mongoose. 9-10 teeth (x4) line the jaws with large carnassials. Derived from a sister to ProtictisHerpestes is a lower, shorter-legged ancestor to Procyon (above) with a relatively shorter rostrum.

Prohesperocyon wilsoni (Wang 1994; Late Eocene, 36 mya) was considered the earliest canid, but here nests between Herpestes, the mongoose, and Talpa the mole. Note the long, pointed skull, expanded occipital and reduced jugal and squamosal. These traits are further emphasized in Talpa (below).

Talpa europaea (Linnaeus 1758, extant) is the extant mole, a small burrowing mammal derived from Herpestes and Prohesperocyon. The large hand, enlarged with a finger-like centralia that extends like a 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 and those are large canines.

Uropsilus scoricipes (Milne-Edwards 1871; Hoffmann 1984) is the extant shrew-mole, long considered the link between shrews and moles. Here Uropsilus nests with shrews, apart from moles. Note the tiny canines, deep premaxilla and arched jugal.

Rhyncholestes raphanurus (Osgood, 1924; long-nosed shrew-opossum, Chilean shrew opossum, extant; snout-vent length 20cm), nests in the LRT with another shrew with a complete zygomatic arch, Uropsilus. Wikipedia and other sources consider this shrew-like South American mammal a marsupial, but Wiki also notes that Rhyncholestes lacks a marsupium (pouch). Females have seven nipples. We looked at Rhyncholestes earlier here.

Figure 3. Subset of the LRT focusing on Carnivora, the basalmost eutherian clade. Talpa is the European mole. Shrews and shrew-moles nest within the clade Glires.

Figure 4. Subset of the LRT focusing on Carnivora, the basalmost eutherian clade. Talpa is the European mole. Shrews and shrew-moles nest within the clade Glires in the LRT.

Lots of “low hanging fruit” here…
Someone (= lots of biologists/paleontologists) left these mistakes for others (= yours truly) to repair. Should have been done ages ago. Taxon inclusion is once again the solution to traditional taxon exclusion problems.

References
Hoffmann RS 1984. A review of the shrew-moles (genus Uropsilus) of China and Burma. Journal of the Mammalian Society, Japan 10(2):69–80.
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.
Milne-Edwards  H 1871.
 Descriptions of new species, in footnotes, pp. 92-93 In David, A., Journal d’un voyage en Mongolia et en Chine fait en 1866-68. Nouv. Arch. Mus. d’Hist. Nat. Paris, 7 (Bull.): 75–100.
Osgood WH 1924. Field Mus. Nat. Hist. Publ., Zool. Ser. 14:170.
Wang X 1994. Phylogenetic systematics of the Hesperocyoninae. Bulletin of the American Museum of Natural History. 221: 1–207.

wiki/Uropsilus
wiki/Talpa
wiki/Herpestes
wiki/Prohesperocyon

Origin of rodents and lagomorphs paper omits key taxa

From the Wu et al. 2012 abstract:

“The timing of the origin and diversification of rodents remains controversial, due to conflicting results from molecular clocks and paleontological data. The fossil record tends to support an early Cenozoic origin of crown-group rodents. In contrast, most molecular studies place the origin and initial diversification of crown-Rodentia deep in the Cretaceous, although some molecular analyses have recovered estimated divergence times that are more compatible with the fossil record. Here we attempt to resolve this conflict by carrying out a molecular clock investigation based on a nine-gene sequence dataset and a novel set of seven fossil constraints, including two new rodent records (the earliest known representatives of Cardiocraniinae and Dipodinae). Our results indicate that rodents originated around 61.7–62.4 Ma, shortly after the Cretaceous/ Paleogene (K/Pg) boundary, and diversified at the intraordinal level around 57.7–58.9 Ma.”

The Wu et al. cladogram
correctly derives placentals from marsupials, but employs Monodelphis as the outgroup rather than the Caluromys, as recovered by the large reptile tree (LRT, 1360 taxa, subset Fig. 1). The Wu et al. cladogram incorrectly nests horses with carnivores in the invalid clade, Laurasiatheria. The next split produces the clade Primates + Glires, omitting the clade Volitantia. Within the clade Glires, only two extant lagomorphs are employed, omitting 16 tree shrews, false tenrecs and many fossil taxa that preceded them as recovered by the LRT. Within the clade Rodentia, the large extant clades within the Wu et al. study matched the LRT, but the Wu et al. study omitted all fossil taxa, including plesiadapiformes, multituberculates, carpolestids and the extant aye-aye (Daubentonia).

Contra Li et al. 1987 and Wu et al. 2012,
rodents and rabbits diversified in the Early Jurassic, as we learned earlier, because their ancestors, the multituberculates and Henkelotherium (related to living pikas, Fig. 1), appear in the Middle and Late Jurassic. DNA does not work in deep time studies.

Figure 4. Mesozoic euthrerians (placentals, in black). Later taxa in light gray. All taxa more primitive than Mesozoic taxa were likely also present in the Jurassic and Cretaceous. None appear after Onychodectes. Madagascar separated from Africa 165-135 mya, deep into the Cretaceous with a population of tenrecs attached. No rafting was necessary. 

Figure 4. Mesozoic euthrerians (placentals, in black). Later taxa in light gray. All taxa more primitive than Mesozoic taxa were likely also present in the Jurassic and Cretaceous. None appear after Onychodectes. Madagascar separated from Africa 165-135 mya, deep into the Cretaceous with a population of tenrecs attached. No rafting was necessary.

References
Li C-K., Wilson RW, Dawson MR, Krishtalka L 1987. The Origin of Rodents and Lagomorphs. In: Genoways H.H. (eds) Current Mammalogy. Springer, Boston, MA
Wu S et al. (8 co-authors) 2012. Molecular and Paleontological Evidence for a Post-Cretaceous Origin of Rodents. PLoS ONE 7(10): e46445. https://doi.org/10.1371/journal.pone.0046445

The extant pika has a Late Jurassic sister: Henkelotherium

We’ve known
since 2016 that the tiny Late Jurassic mammal, Henkelotherium is a basal rabbit (contra traditional studies that exclude rabbits). Today the extant pika (genus: Ochotona, Figs. 1, 2) enters the large reptile tree (LRT, 1348 taxa).

Figure 1. Pika skull (genus: Ochotona) in three views.

Figure 1. Pika skull (genus: Ochotona) in three views. It’s cuter with a coat of fur (Fig. 2).

Figure 2. Pika is a basal rabbit that prefers mountainous terrain. A sister, Henkelotherium, goes back to the Late Jurassic.

Figure 2. Pika is a basal rabbit that prefers mountainous terrain. A sister, Henkelotherium, goes back to the Late Jurassic.

Ochotona princeps (originally Lepus dauuricus Pallas, 1776; Link 1795; Richardson 1828) is the extant pika, a rock-dwelling herbivore nesting between Henkelotherium and rabbits. Pikas live in mountainous areas in Asia and North America. Distinct from Henkelotherium, Ochotona is larger, with a near complete loss of the tail. Both have spreading metatarsals and four upper molars. In pikas the second incisors are posteromedial to the first incisors, creating a larger cheek area. A medial pedal digit 1 is present in both.

Fossil pikas are known from the Miocene, 16mya, to the recent, but Henkelotherium goes back to the Late Jurassic.

Figure 2. Henkelotherium reconstructed from DGS tracings in figure 1. Note the tiny manus and large pes, traits that continue into extant rabbits.

Figure 3. Henkelotherium reconstructed from DGS tracings in figure 1. Note the tiny manus and large pes, traits that continue into extant rabbits. The image is 75% larger than life size.

Figure 4. Subset of the LRT featuring Ochotona and the rabbits.

Figure 4. Subset of the LRT featuring Ochotona and the rabbits.

Henkelotherium guimarotae (Krebs 1991; Late Jurassic 150 mya, Fig. 3) was traditionally considered eupantothere. Henkelotherium nests within the rabbit clade as a very early member of the tree shrew/ shrew/ rodent/ rabbit clade: Glires. Like its sisters, the manus was small and the pes had long digits with sharp claws. The lumbar region was long and flexible, ideal for hopping and galloping. Note the long robust tail.

This new nesting further confirms
the hypothesis that rodents (including multituberculates) and rabbits (including Henkeleotherium) had a deep Mesozoic origin (Fig. 5).

Figure 1. Select basal cynodonts and mammals set chronologically. The divergence times for placentals (Eutheria), marsupials (Metatheria) and monotremes (Mammalia) are estimated here.

Figure 5. Select basal cynodonts and mammals set chronologically. The divergence times for placentals (Eutheria), marsupials (Metatheria) and monotremes (Mammalia) are estimated here.

References
Link HF 1795.  Über die Lebenskräfte in naturhistorischer Rücksicht und die Classification der Säugthiere. – Beyträge zur Naturgeschichte (Rostock, Leipzig) 2: 1-41.
Kear BP, Cooke BN, Archer M and Flannery TF 2007. Implications of a new species of the Oligo-Miocene kangaroo (Marsupialia: Macropodoidea) Nambaroo, from the Riversleigh World Heritage Area, Queensland, Australia, in Journal of Paleontology 81:1147-1167.
Krebs B 1991. Skelett von Henkelotherium guimarotae gen. et sp. nov. (Eupantotheria, Mammalia) aus dem Oberen Jura von Portugal. Berl Geowiss Abh A.: 133:1–110.

wiki/Pika
wiki/Henkelotherium

 

SVP 2018: More complete material of Mixodectes

I know nothing about Mixodectes as I write this.
But based on the abstract description, I will put it into a phylogenetic perspective.

Sargis et al. 2018 report: 
“Mixodectids are eutherian mammals from the Paleocene of North America that have been considered close relatives of the extinct plagiomenids, microsyopid plesiadapiforms,and/or dermopterans, making them relevant to better understanding euarchontan relationships. We analyzed a new dentally associated skeleton of Mixodectes pungent (NMMNH P-54501). It is the most complete skeleton of a mixodectid known, preserving a partial skull with all teeth erupted and previously unknown elements of the axial skeleton, forelimbs, and hind limbs, all with epiphyses fused.”

The authors believe plesiadapiforms are basal to primates,
which is invalid based on the results in the large reptile tree (LRT, 1315 taxa). Plesiadapiforms are more closely related to carpolestids (including Daubentonia, the extant aye-aye) and multituberculates.

The NMMNH P-54501 mixodectid has

  1. Humeral traits indicating a mobile shoulder and elbow.
  2. The humerus has a large medial epicondyle and the proximal phalanges have
    pronounced flexor sheath ridges, both indicating powerful flexion of the digits.
  3. Pelvis traits as in arboreal euarchontans.
  4. The femur suggests a habitually flexed knee.
  5. The astragalus and calcaneum indicates mobility in the ankle joints and is often present in arboreal taxa capable of pedal inversion.
  6. The authors do not discuss the teeth…which are important: are they rodent-like (with large incisors as in Glires)?… or carnivore like (with canine fangs as in other primates)?

Sargis et al. conclude: “In summary, the postcranial morphology of Mixodectes is very similar to that of arboreal euarchontans, including plesiadapiforms, supporting inferences based on less complete material that mixodectids were both arboreal and members of Euarchonta.”

Euarchonta (Waddell et al. 1999) = Scandentia (tree shrews), Dermoptera (colugos), Plesiadapiformes (Plesiadapis) and Primates (lemurs to humans). Together these taxa are not monophyletic in the LRT (subset Fig. 1).

Figure 3. Subset of the LRT focusing on Glires, rodents and multituberculates.

Figure 1. Subset of the LRT focusing on Glires, rodents and multituberculates. Primates are the sister clade to the clade shown above.

References
Sargis EJ et al. (4 co-authors) 2018. Functional morphology of a remarkably complete skeleton of Mixodectes pnugens: evidence for arboreality in an enigmatic eutherian from the Early Paleocene. SVP abstracts.

Rugosodon (multituberculate) tarsals

Traditionally
multituberculates, like Late Jurassic Rugosodon (Figs. 1, 2), have been considered rodent-like mammals nesting near the origin of mammals.

In the pre-cladistic era Simpson 1945
nested multituberculates close to Prototheria.

In the cladistic era Novacek 1992 wrote:
“Neither molecular nor morphological probes have been successful in resolving major sectors of the mammalian tree. Both molecular and morphological results seem to converge on the idea that New World edentates (sloths, armadillos and anteaters) represent an early (perhaps even the earliest) branch in the placental mammal tree. Although this case is rather tenuous from an anatomical standpoint…” Certainly there are no marsupials or edentates that resemble one another.

By contrast
in the large reptile tree (LRT, 1305 taxa) multituberculates nest as derived rodent carpolestids, despite their Jurassic antiquity. Among extant taxa, they are most closely related to today’s aye-aye (Daubentonia). Aye-ayes are not rodent-like primates, but living rodent carpolestids in the LRT. Even their tarsals are similar (Fig. 2). Earlier here and here we looked at related multituberculate, rodent and carpolestid skulls and teeth.

Based on LRT results, Novacek 1992 wrongly nested:

  1. All marsupials as a separate clade
  2. Marsupial Creodonta with placental Carnivora.
  3. Multituberculata apart from Rodentia, close to Monotremata
  4. Pholidota apart from Chiroptera
  5. Scandentia with Primates and Dermoptera
  6. Insectivora apart from Rodentia
  7. Cetacea as a monophyletic clade
  8. Cetacea with Artiodactylia and Tubulidentata
  9. Hippos with Artiodactyla
  10. Tubulidentata apart from Edentata
  11. Embrithopoda with Proboscidea and Desmostylia
  12. Novacek 1992 also omitted several relevant taxa, like Tenrec and Caluromys

Novacek did correctly nest

  1. Condylarthra and all hooved placentals as derived taxa.
  2. Monotremata was correctly nested as a basal clade.
  3. Palaeoryctoids, then including Asioryctes, were correctly nested between Metatheria and Eutheria.
Figure 1. Rugosodon in situ with original tracing.

Figure 1. Rugosodon in situ with original tracing.

With that introduction
Luo et al. 2016 studied the ankle of the multituberculate, Rugosodon, “the earliest-known postcranial fossil of a multituberculate mammal. They report, “Multituberculates as a group can now be diagnosed by derived features of the astragalus, the navicular, and the entocuneiform.” Those are the light red, bright green and yellow bones in figure 2. “These features are correlated with the mobility of the upper ankle joint and pedal digit I, indicating that early multituberculates acquired new locomotor functions of the limb and foot. However, the standing pedal posture of the basal multituberculates is plantigrade, typical of primitive mammaliaforms. The digitigrade posture appeared later in derived multituberculates.” (Like Kryptobaatar, a taxon with a digitigrade pes we looked at earlier here.)

Figure 2. Pes of Rugosodon compared to related taxa in the LRT.

Figure 2. Pes of Rugosodon compared to related taxa in the LRT. Several calcanea of multituberculates in light cyan above.  Note the medial rotation of the astragalus in Carpolestes and Rugosodon, making the appearance of a pre-mammal via atavism or reversal. Note the ability of pedal digit 1 to adduct on the entocuneiform saddle.

Rugosodon has a large, plate-like parafibula
proximal to the fibula itself, but not co-osified. Luo et al. note most placentals do not have a parafibula, but Rattus and Daubentonia do. The parafibula is co-ossified to the fibula in prototherian mammals.

Figure 3. Subset of the LRT focusing on Glires, rodents and multituberculates.

Figure 3. Subset of the LRT focusing on Glires, rodents and multituberculates. The Middle and Late Jurassic appearance of the most derived taxa in this clade indicate earlier splits of more basal clades herein, but so far their fossil have not been found in Early Jurassic strata. This cladogram predicts their appearance.

Taxon exclusion
The Luo et al. paper does not include reference or comparisons to rodents, carpolestids or Daubentonia, yet another case of taxon exclusion revealed here. Clearly these taxa need to be added to multituberculate studies in the future. Paulchoffatia, mentioned in the Luo et al. title, nests basal to a sister clade to the multituberculates.

References
Luo Z-X, Meng Q-J, Liu D, Zhang Y-G and Yuan C-X 2016. Cruro-pedal structure of the paullchoffatiid Rugosodon eurasiaticus and evolution of the multituberculate ankle.Palaeontologia Polonica 67:149-169.
Novacek MJ 1992. Mammalian phylogeny: shaking the tree. Nature 356:121–135.
Simpson GG 1945. The principals of classification and a classification of mammals. Bulletin of the American Museum of Natural History 85:350pp.