Flying squirrels and aye-ayes: convergent with multituberculates

For those in a hurry, a two-part summary:
1. By convergence, basal multituberculates in the Jurassic (Figs. 1, 4), had a distinct  flying squirrel (Glaucomys, Figs. 2, 3)-like patagial (= gliding membrane) morphology.
2. Also by convergence, multituberculates in the Jurassic had a short post-dentary skull length with a sliding jaw joint and a nearly absent angular process as seen in the extant aye-aye (Daubentonia, Figs. 5, 6).

Figure 2. The paratype specimen of Arboroharamiya HG-M018, in situ. DGS color tracing added. The skull is in poor shape.

Figure 1. The paratype specimen of Arboroharamiya HG-M018, in situ. DGS color tracing added. The skull is in poor shape.

Today’s blogpost had its genesis
when I finally noticed several basal multituberculates that preserved soft tissue had flying-squirrel-like patagia preserved in the sediment (Fig. 1)… and squirrels nested more or less close to the origin of multituberculates. So, I added a flying squirrel, Glaucomys (Fig. 1) to the large reptile tree (LRT, 1810+ taxa) to see what would happen.

It should come as no surprise
that Glaucomys nested with the extant red squirrel Sciurus, NOT any closer to multituberculates. Thus, the ability to glide in the manner of a flying squirrel turned out to be by convergence in basal multituberculates of the Jurassic.

Figure 2. Glaucomys gliding.

Figure 2. Glaucomys gliding.

Figure 2. Multituberculates to scale. Carpolestes is the proximal outgroup taxon.

Figure 3. Multituberculates to scale. Carpolestes is the proximal outgroup taxon.

Based on the phylogenetic position
of squirrels and other rodents as sisters to multituberculates, either flying squirrels were also gliding from tree-to-tree during the Mesozoic, or they took their time and only appeared after the Mesozoic. That is the current paradigm based on present evidence.

End of part 1. Scroll down for part 2.

Figure 1. Subset of the LRT focusing on basal placentals, including multituberculates.

Figure 4. Subset of the LRT focusing on basal placentals, including multituberculates.

Part 2.
By convergence, the aye-aye, Daubentonia

(Fig. 5) has a multituberculate-like mandible lacking an angular process along with a large circumference, sliding jaw joint and reduced post-dentary skull.

Figure 1. Taxa in the lineage of Daubentonia and multituberculates.

Figure 5. Taxa in the lineage of Daubentonia and multituberculates. Note the loss of the angular process and the sliding jaw joint.

By convergence, Carpolestes
has an enlarged posterior lower premolar, as in multituberculates. So, lots of convergence surrounds the multituberculates.

The aye-aye is a traditional basal primate,
based on gene studies (Dene et al1980; Rurnpler et al 1988; Del Pero et al 1995; Porter et al 1995).

By contrast
the large reptile tree (LRT, 1810+ taxa; subset Fig. 4) nests the aye-aye (Daubentonia) with rodents, plesiadapiformes, carpolestids and multituberculates. We’ve seen how genomic studies produce false positives. Add Daubentonia to that list of flubs. Note that both lemurs and aye-ayes are both from Madagascar, lending more evidence to the hypothesis that geography and geology (e.g. Afrotheria, Laurasiatheria) affect genomics to a greater degree than professionally realized over deep time.

Like rodents:
The aye-aye does not have mammary glands on the chest, as in primates, but along the groin, as in non-primates. The aye-aye has a large diastema between the incisors and molars, as in plesiadapiformes and rodents, distinct from primates.

Like primates:
The aye-aye has a postorbital bar, stereoscopic vision and an opposable hallux. Owen 1863 considered such traits ‘must be ordained’ in arguments for God and against Darwin’s then novel hypothesis of natural selection and evolution.

Like rodents,
Perry et al. 2014 report: “the single pair of incisors consists of continuously growing, elongate, open-rooted chisels, both upper and lower incisors.”

Based on the LRT
mutltuberculates are netonous rodents, growing to adulthood without ontogenetically incorporating post-dentary bones into the tympanic and periotic (inner ear enclosing bones), as we learned earlier here.

Figure 6. The aye-aye, Daubentonia in vivo. This is the closest living relative of multituberculates and is itself a plesiadapiform member of Glires, close to rodents, not primates.

Figure 6. The aye-aye, Daubentonia in vivo. This is the closest living relative of multituberculates and is itself a plesiadapiform member of Glires, close to rodents, not primates.

By convergence
the aye-aye (Daubentonia. Fig. 6) likewise reduces the tympanic and periotic along with the angular process of the dentary, producing a sliding joint that would have interfered with the ear bones if allowed to develop as in most placentals.

Carter 2009 notes
(while mistakenly assuming a lemur affinity for Daubentonia), “The overall dimensions of the D. madagascariensis auditory ossicles are large and they have a unique morphology.” Carter also reports on the elongate manubrium of the malleus (the former articular). This is in accord with similar structures in the neotonous (not primitive!) multituberculate auditory bone chain you can see here.

What does the angular process of the plancental dentary do?
According to Meng et al. 2003, a huge angular process was present in Rhombomylus, an extinct gerbil. Meng et al. mapped insertions for the deep masseter and superficial masseter externally. Then they mapped insertions for the medial pterygoid and superficial masseter internally. The Rhomboylus glenoid has a small diameter and rotates. It does not slide.

Meng et al. write: “As the major muscle to move the mandible forward, the superficial masseter must be long enough so that it can work to bring the jaw forward at least the minimum working distance. In general, the action line of the anterior deep masseter is nearly perpendicular to the moment arm of the mandible, while the posterior one has an acute angle to the moment arm and, therefore, less mechanical advantage. the deep masseter must have been sizable and supplies the main force for mastication as in rodents.”

The point of which is: multituberculates and the aye-aye reduce and eliminate the angular process. So we can imagine the muscles listed by Meng et al. either migrate or are lost in multituberculates and the aye-aye.

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 7. Maiopatagium in situ in white and UV light. The X marks an area surrounded by fur lacking proptagial data. Is the propatagium wishful thinking? Yes. Those are long guard hairs, precursors to porcupine quills. There is no patagium here.

We can’t leave Jurassic flying squirrels
without a quick review of Maiopatagium (Early Jurassic, Fig. 7, Meng et al. 2017), which was hailed ever since as a gliding mammal or mammaliaform.

Contra Meng et al. 2017
phylogenetic analysis nested Maiopatagium with the extant porcupine (Coendou), not with gliding multituberculates, like Vilevolodon. Maiopatagium has long straight hairs and lacks any trace of a patagium. Those long straight hairs are the precursors to porcupine quills according to the LRT.

Phyogenetic analysis puts rodents and all their precursors
(Tupaia, Henkelotherium, Nasua) squarely and clearly in the earlier part of the Early Jurassic, though not yet recovered in fossils.

The myth about the patagium surrounding Maiopatagium
seems to have had its genesis in the fact that Vilevolodon was described at the same time,  by the same authors, in the same publication. Vilevolodon (Fig. 1) has a no-doubt, flying sqirrel-like patagium. Maiopatagium (Fig. 7) was described with a misidentified patagium and a misidentified bat-like calcar. No patagium is present, but long straight hairs are. As noted above, these are precursors to porcupine quills. Getting taxa into a proper phylogenetic context is the key to understanding soft tissue and taxonomy.


References
Carter Y 2009. Monkey Hear: A morphometric analysis of the primate auditory ossicles. Master of Arts thesis, The U of Manitoba.
Del Pero M et al (4 co-authors) 1995. Phylogenetic relationships among Malagasy lemuls as revealed by mitochrondrial DNA sequence analysis. Primates 36: 43I-440.
Dene H, Goodman M and Prychodlco V 1980. Immunodiffusion systematics of the primates. Mamalia 44:27-31.
Luo Z-X, (6-co-authors) 2017. New evidence for mammaliaform ear evolution and feeding adaptation in a Jurassic ecosystem. Nature. in press (7667): 326–329. doi:10.1038/nature23483
Meng et al. 2003. The osteology of Rhombomylus (Mammalia, Glires): Implications for phylogeny and evolution of Glires. Bulletin of the American Museum of Natural History 275: 1–247.
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
Owen R 1863. On the characters of the aye-aye as a test of the Lamarckian and Darwmian hypothesis of the transmutation and origin of the species. Rep Br Assoc Adv Sci 1863: 114-116.
Perry JM et al. (4 co-authors) 2014. Anatomy and adaptations of the chewing muscles in Daubentonia (Lermuriformes). The Anatomical Record 297:308–316.
Porter CA et al (5 co-authors) 1995. Evidence on primate phylogeny from e-globin gene sequences and flanking regions. Journal of Molecular Evolution 40: 30-55.
Rurnpler Y et al (4 co-authors) 1988. Chromosomal evolution of the Malagasy lemurs. Folio Primatologica 50 124-129.
Sterling EJ 1994. Taxonomy and distribution of Daubentonia madagascariensis: a historical perspective. Folio Primatologica 62: 8-I3.

wiki/Maiopatagium
wiki/Coendou
wiki/Multituberculata

https://pterosaurheresies.wordpress.com/2019/01/06/a-post-dentary-reversal-between-rodents-and-multituberculates/

The multituberculate, Barbatodon, enters the LRT with iron in its incisors

Yes, the element iron
is incorporated into the teeth of the multituberculate, Barpatodon (Fig. 1, Rãdulescu and Samson 1986; Smith and Codrea 2015), and other members of the gnawing clade, Glires to make them even stronger than ordinary enamel. That’s what gives those teeth that rusty appearance.

Figure 1. Barpatodon diagram from Smith and Codrea 2015 colorized here.

Figure 1. Barpatodon diagram from Smith and Codrea 2015 colorized here.

Barbatodon transylvanicus (Rãdulescu and Samson 1986; Late Cretaceous) is a small multituberculate preserving iron in its incisors as in several living rodents. Originally considered close to Taeniolabis, here it nests with Catopsbaatar. The premolars have been molarized. The ‘sliding jaw joint’ does not slide much.

Figure 4. Catopsbaatar greatly enlarged.

Figure 2. Catopsbaatar greatly enlarged.


References
Rãdulescu R and Samson P 1986. Précisions sur les affinités des Multituberculés du Crétacé supérieur de Roumaine. C R Acad Sci II: Mec-Phys, Chim, Sci Terre, Sci Univ 303p, p. 1825-1830.
Smith T and Codrea V 2015. Red Iron-Pigmented Tooth Enamel in a Multituberculate Mammal from the Late Cretaceous Transylvanian “Hateg Island”. PLoS ONE 10(7): e0132550. https://doi.org/10.1371/journal.pone.0132550

wiki/Barbatodon

The tiny multituberculate, Filikomys, enters the LRT

Figure 1. Ptilodus, Filikomys and Catopsbaatar to scale (at 72 dpi screen resolution).

Figure 1. Ptilodus, Filikomys and Catopsbaatar to scale (at 72 dpi screen resolution).

Filikomys primaevus 
(Weaver et al. 2020; NMC 1890; Late Cretaceous; Figs. 1, 2) is a cimolodont multituberculate found with others of its kind in a multi-season burrow/nest. Filikomys was originally nested close to Ptilodus (Figs. 1, 3), but here is more closely related to the even smaller Catopsbaatar (Fig. 1).

From the Weaver et al. abstract:
“Taphonomic and geologic evidence indicates that F. primaevus engaged in multigenerational, group-nesting and burrowing behaviour, representing the first example of social behaviour in a Mesozoic mammal. That F. primaevus was a digger is further supported by functional morphological and morphometric analyses of its postcranium.”

Figure 1. Filikomys from Weaver et al. 2020 and colorized here.

Figure 1. Filikomys from Weaver et al. 2020 and colorized here.

The Weaver et al. abstract continues:
“The social behaviour of F. primaevus suggests that the capacity for mammals to form social groups extends back to the Mesozoic and is not restricted to therians.”

By contrast, in the large reptile tree (LRT, 1754+ taxa) Filikomys is a multituberculate and they nest within the clade Glires, not far from the aye-aye (Daubentonia), rat (Rattus) and mouse (Mus), all within the clade Placentalia. Weaver’s cladogram is typical of analyses that include multituberculates where members of the clade Glires are not employed.

Figure 3. Ptilodus, an arboreal multituberculate.

Figure 3. Ptilodus, an arboreal multituberculate.

Traditional taxon exclusion problems, like this,
are minimized in the LRT, which includes a wide gamut of taxa. Colleagues, do the work you are paid to do. Don’t rest on old myths and traditions, even if they are in current textbooks and lectures.

Figure 4. Catopsbaatar greatly enlarged.

Figure 4. Catopsbaatar greatly enlarged.

The Weaver et al. paper concentrates on the subject
of sociality, first seen in basal tetrapods in the Carboniferous. Burrows go back at least to therapsids in the Permian. Filikomys was found in Late Cretaceous deposits.

Weaver et al. report,
“The material described herein includes the first associated multituberculate skeletons from the Mesozoic of North America and represents the oldest-known case of burrowing capabilities in a Mesozoic multituberculate.”

“Multiple lines of evidence thus indicate that F. primaevus was a terrestrial, scratch-digging mammal, functionally analogous to the Least Chipmunk, Neotamias minims.”

 

The above episode of “Old News”
(love that name!) features Christian Kammerer talking about multituberculates with a focus on tiny Filikomys. Click to play.


References
Weaver LN et al. 2020. Early mammalian social behaviour revealed by
multituberculates from a dinosaur nesting site. Nature ecology & evolution. https://doi.org/10.1038/s41559-020-01325-8

wiki/Kryptobaatar
wiki/Ptilodus
wiki/Catopsbaatar
wki/Filikomys
wiki/Ptilodontoidea

Mao et al. 2020 “Pull a Larry Martin” with the multituberculate, Sinobaatar

Mao et al. 2020 report on a
crushed and articulated Early Cretaceous multituberculate specimen of Sinobaatar (Fig. 1). Presently several species are known. This one was µCT scanned.

From the abstract
“We report a new Cretaceous multituberculate mammal with 3D auditory bones preserved. Along with other fossil and extant mammals, the unequivocal auditory bones display features potentially representing ancestral phenotypes of the mammalian middle ear.”

The authors made several basic mistakes with Sinobaatar.

  1. By concentrating on one set of traits (the middle ear), rather than the entire skeleton, the authors ‘Pulled a Larry Mrartin“.
  2. By not including derived members of Glires (gnawing placentals) in their phylogenetic analysis, their cladogram (Fig. 2) suffers from taxon exclusion and inappropriate taxon inclusion (e.g. Liaoconodon and Origolestes are mammal-mimics living in the Early Cretaceous alongside real mammals).
  3. The authors did not consider the possibility of convergence brought about by a reversal. When members of Glires are added to analysis (Fig. 3), the reversal becomes obvious (Fig. 4).

The takeaway:
Not matter what the configuration of the middle ear in Sinobaatar, if the rest of the skeleton nests it in Glires, maximum parsimony says: Sinobaatar and all multituberculates nest in Glires.

Figure 1. Sinobaatar skull in two views. DGS colors added.

Figure 1. Sinobaatar skull in two views. DGS colors added. The skull was crushed from side to side.

The authors report in the SuppData:
“Given several recent efforts of higher-level phylogenies of mammaliaforms [1-3] and the relatively stable position of multituberculates (Sinobaatar in particular) within mammals in all these studies, we consider it redundant to run another phylogenetic analysis.”

Redundant, yes, if using the same taxon list. But adding members of Glires to that taxon list changes everything.

Figure 2. Cladogram from Mao et al. 2020 with the wrong phylogenetic order, repaired on frame 2.

Figure 2. Cladogram from Mao et al. 2020 with the wrong phylogenetic order, repaired on frame 2 in which Origolestes and Liaoconodon are late-surviving mammal mimics, not mammals.

The wide gamut of the taxon list
in the large reptile tree (LRT, 1729+ taxa; subset Fig. 3) minimizes taxon exclusion. When taxa that have never been tested together before get tested together, sometimes they nest together. You just have to let the software do what it does best and keep shoveling in more taxa.

Figure 1. Subset of the LRT focusing on basal placentals, including multituberculates.

Figure 3. Subset of the LRT focusing on basal placentals, including multituberculates.

The authors report,
“While the auditory bones already detached from the dentary in the three phenotypes, the transitional middle ear of Liaoconodon is most primitive in that the malleus and ectotympanic have long anterior processes that are still in contact with the ossified Meckel’s cartilage; thus, hearing and chewing functions were not completely separated. Origolestes is more derived in having lost the bony contact of the auditory bones to the ossified Meckel’s cartilage so that hearing and chewing functions were decoupled.” 

Without a valid cladogram the authors assume the order of evolution without really knowing. In the LRT Origolestes is not a mammal and the more primitive of the two, hinting at an earlier stage in a reversal. The LRT lumps and separates taxa to reveal such reversals.

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

Figure 4. Comparing multituberculate origins: Cziki-Sava et al. vs. LRT.

The authors report, 
“With the assumption that the DMME evolved independently in monotremes, therians, and multituberculates, there should be no common ancestral phenotype of the middle ear for these clades.”

That is incorrect. The LRT nests multituberculates within the gnawing clade, Glires (Fig. 3). The LRT indicates the primitive nature of the middle ear of multituberculates is a reversal likely caused by the great propalinal movement of the gnawing jaw interfering with and preventing normal maturation of the placental middle ear and leaving it at a more primitive state. You can have more confidence in this hypothesis because more taxa are tested, ‘leaving no stone unturned.’

Every description you’ll ever see
of multituberculates, plesiadapiformes, carpolestids and the aye-aye, Daubentonia, includes the phrase, “rodent-like” for a very good reason. That’s because they are closely related, something Mao et al. 2020 and other multituberculate experts do not yet realize. Adding taxa always resolves problems. Just do it. Don’t “Pull a Larry Martin.”


References
Mao F-G, Liu C, Chase MH, Smith AK, Meng J 2020.
 Exploring ancestral phenotypes and evolutionary development of the mammalian middle ear based on Early Cretaceous Jehol mammals. Research Article Earth Sciences. National Science Review, nwaa188, https://doi.org/10.1093/nsr/nwaa188

wiki/Multituberculata
wiki/Sinobaatar

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

Labidolemur kayi
(Matthew and Granger 1921; Eocene, 55mya; Fig. 1) was re-described by Silcox et al. 2010 with µCT scans that provided cranial cavity and other never-before-seen details. The several skeletons analyzed in the publication were recovered from freshwater limestone in the Bighorn Basin by co-author Peter Houde of New Mexico State University.

Figure 1. Co-author Jonathan Block holding up the rather complete and articulated skeleton of Labidolemur still encased in a bit of reddish matrix.

Figure 1. Co-author Jonathan Block holding up the rather complete and articulated skeleton of Labidolemur still encased in a bit of reddish matrix.

According to a publicity release
(link below) “Researchers said the new information will aide future studies to better understand the origin of primates. Scientists have disputed the relationships of Apatemyidae, the family that includes L. kayi, for more than a century because of their unusual physical characteristics. With can opener-shaped upper front teeth and two unusually long fingers, apatemyids have been compared to a variety of animals, from opossums to woodpeckers.”

When added to
the large reptile tree (LRT, 1698+ taxa) Labidolemur unsurprisingly nests with Apatemys, within Glires (gnawing placentals). Labidolemur and Apatemys are virtually identical according to the LRT scores, but proportional differences can still be discerned when the two skulls are side-by-side.

So Labidolemur will not help us,
“better understand the origin of primates.”

Silcox et al. 2010 wrote:
“To test all of the hypotheses that have been suggested, it is necessary to include a very broad range of eutherians, including other apatemyids, eulipotyphlans, ‘proteutherians’ (leptictids and palaeoryctids), primates and other euarchontans, and any other groups that might be relevant for accurately reconstructing basal states for larger clades that include those taxa (e.g. carnivorans and gliroids). To this end we have assembled a matrix of 33 in-group taxa and one out-group (Ukhaatherium nessovi) that were assessed for 240 morphological characters (68 postcranial, 45 cranial, and 127 dental.”

Figure 2. Cladoram from and Bloch 2020 lacking many pertinent taxa.

Figure 2. Cladoram from Silcox et sl. 2020 lacking many pertinent taxa. See text for list.

A broad range, indeed, but not broad enough
according to the LRT. Missing taxa include:

  1. All three shrew opossums, which surround Microsyops and Trogosus. Labidolemur correctly nests with Apatemys.
  2. Any metatherians (marsupials), including Caluromys, the proximal outgroup to the Eutheria (placentals) of which Carnivora is the basalmost clade.
  3. Leptictidae are not basalmost placentals, but basal to tenrecs + odontocetes when more taxa are added
  4. Vulpavus and other arboreal, wooly opossum-like Carnivora nest at the base of the Eutheria apart from Erinaceus (hedgehog) and Sorex (shrew) both members of Glires. Missing basal shrew: Uropsilus.
  5. Tupaia is basal to Glires in the LRT. Missing relatives include Macroscelides, Chrysochloris and Necrolestes.
  6. All the rodents and multituberculates are missing. They attract carpolestids and plesiadiformes away from Primates in the LRT.
  7. Altanius requires study, but is represented by teeth and jaw fragments described as plesiadapiform-like.
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 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, largely matched to Labidolemur.

John Wible, is curator of mammals
at the Carnegie Museum of Natural History. After reviewing the Silcox et al. 2010b study, he reported, “It is now clear that any assessment of the origins of primates in the future will have to include apatemyids. Apatemyids are not some freakish dead-end, but significant members of our own history.”

Figure 1. Subset of the LRT focusing on Glires and subclades within.

Figure 3. Subset of the LRT focusing on Glires and subclades within. Slightly out of date, Ptilocercus now nests basal to colugos, but the nesting of Apatemys has not changed.

The LRT invalidates Wible’s statement.
Instead, apatemyids are indeed ‘some freakish-dead taxa’, nesting in Glires, far from Primates. The myth of a plesiadapid-primate interrelationship (that includes the aye-aye, Daubentonia) is not supported when more taxa are added. In the LRT plesiadapiformes, like Daubentonia, are primate-mimics nesting within Glires close to multituberculates and carpolestids. Simply adding taxa recovers this topology. That’s all it takes.


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

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

Microsyops enters the LRT between three overlooked shrew opossums

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

More taxa
solve this problem.

Figure 1. Micrsyops skull from Silcox et al. 2020. The third tooth is the canine.

Figure 1. Micrsyops skull from Silcox et al. 2020. The third tooth is the canine.

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

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

Figure 1. Not a marsupial, and not a shrew opossum, Palaeothentes nests in the LRT at the base of the Apatemys + Trogosus clade nest to the clade of living shrew opossums within Glires.

Figure 2. Not a marsupial, and not a shrew opossum, Palaeothentes nests in the LRT at the base of the Apatemys + Trogosus clade nest to the clade of living shrew opossums within Glires.

By contrast
in the large reptile tree (LRT, 1698+ taxa) using fewer traits and more taxa, Microsyops nests as a near basal member of Glires (gnawing mammals) between three traditional pouchless ‘marsupials’, the two extant shrew ‘opossums’, Rhyncholestes (Fig. 3) + Caenolestes and Palaeothentes (Miocene. Fig. 2). These nest at the base of Trogosus (Eocene) + the Apatemyidae (Eocene). None of these taxa, other than Apatemys, were included in the Silcox et al. cladograms.

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

Figure 3. Skull of Rhyncholestes along with in vivo photo.

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

Again, adding taxa
(more rodents, rabbits and shrew opossums ) solves this problem. Don’t assume pouchless shrew opossums are marsupials. In the LRT they are gnawing placentals, derived from tree shrews, as we learned earlier here. Call them marsupial-mimics.


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

wiki/Microsyops

Middle Jurassic moonrat: Asfaltomylos patagonicus

Ever since the LRT nested multiberculates within Glires,
we’ve been looking for non-multituberculate members of Glires (rats, rabbits, tree shrews, etc.) from the Jurassic to support that novel hypothesis. Here’s one.

Martin and Rauhut 2005
redescribed the mandible and teeth belonging to Asfaltomylos (Rauhut et al. 2002; Fig. 1) famous for being the first Jurassic mammal from South America and for apparently lacking a canine and incisors.

The question:
Is this an egg-laying monotreme (clade: Prototheria)? That’s what both Rauhut et al. 2002 and Martin and Rauhut 2005 thought based on tooth shape and a post-dentary groove in the medial dentary. They also excluded taxa listed below (and shown in figure 1). Such bias is a too common fault in traditional paleontology, as long time readers are well aware.

Figure 1. Asfaltomylos (MPEF-PV 1671) is a tiny mandible with teeth from in Jurassic strata in South America. Note the shape of the posterior premolar and how it relates to the giant posterior premolar in Carpolestes. The canine is tall. Not sure if Asfaltomylos had large incisors. Either way it does not matter, based on comparisons to Echinosorex and Erinaceus, the living moonrat and hedgehog.

Figure 1. Asfaltomylos (MPEF-PV 1671) is a tiny mandible with teeth from in Jurassic strata in South America. Note the shape of the posterior premolar and how it relates to the giant posterior premolar in Carpolestes. The canine is tall. Not sure if Asfaltomylos had large incisors. Either way it does not matter, based on comparisons to Echinosorex and Erinaceus, the living moonrat and hedgehog. Only the posterior molar in Erinaceus looks like the two molars in Asfaltomylos, separated in time by 166 million years.

Based primarily on tooth morphology,
Rauhut et al. 2002 considered Asfaltomylos a member of the Australosphenida, a clade of southern Jurassic mammals that is said to convergently evolve tribosphenic molars with northern mammals and probably gave rise to monotremes. Their taxon restricted cladogram nested Asfaltomylos between Shuotherium (Fig. 2) and several untested taxa leading to several platypus-like  taxa (including genus: Ornithorhynchus; Fig. 3.)

Question for you, dear readers:
Do the mandibles of Asfaltomylos (Fig. 1) and Shuotherium (Fig. 2) resemble one another? They should, given their proximity in the Rauhut et al. and Martin and Rauhut cladograms. If you think they don’t look similar, perhaps we need to expand the taxon list.

Figure 2. Medial view of Shuotherium. The last premolar is similar to the first molar, the coronoid process is tiny and the retroarticular process is absent, all distinct from Asfaltomylos (Fig. 1).

Figure 2. Medial view of Shuotherium. The last premolar is similar to the first molar, the coronoid process is tiny and the retroarticular process is absent, all distinct from Asfaltomylos (Fig. 1).

As a test, let’s add all the mammals in the LRT.
When we do, and based on very few mandible characters, Asfaltomylos foregoes the Prototheria and nests with derived members of Glires, derived from moonrats, the only members of Glires that sometimes do not have large gnawing incisors (yet another reversal).

Only the posterior molar
in the hedgehog, Erinaceus (Fig. 1), looks like the two molars in Asfaltomylos, separated in time by 166 million years. The premolar is nearly identical.

Moonrats
(Fig. 4) have an appropriately primitive appearance, and are different from other members of Glires in being chiefly carnivorous.

Rougier et al. 2007
considered Henosferus another member of the clade ‘Australosphenida’. With its  complete dental formula on a low profile mandible, Henosferous (Fig. x) nests with other basalmost therians, like Morganucodon (Fig. 3) in the LRT, not close to Asfaltomylos. So members of the invalidated clade ‘Australosphenida’ are polyphyletic in the LRT.

Figure 1. Henosferus mandible restored by Rougier et al. 2005 from several broken specimens.

Figure x. Henosferus mandible restored by Rougier et al. 2005 from several broken specimens.

Phylogenetic miniaturization and neotony
answer the problems posed by the low number of molars and the retention of the postdentary trough in Asfaltomylos. As you may recall, mammals recapitulate their phylogeny during ontogeny and Asfaltomylos matured at an earlier stage of development due to its small size.

Tooth morphology is something else to be ware of in phylogenetic analyses.
As an example, whale teeth devolved from multi-cusped in a square in their four-limbed terrestrial ancestors, to multi-cusped in a row in archaeocetes with flukes, to simple cones and toothlessness in derived odontocetes.

Figure 1. Brasilodon compared to Kuehneotherium, Akidolestes and Ornithorhynchus, the living platypus.

Figure 3. Brasilodon compared to Kuehneotherium, Akidolestes and Ornithorhynchus, the living platypus, and Monodelphis, a living tree opossum.

The problem is,
the high coronoid process and retroarticular (angular) process of Asfaltomylos are not found in Ornithorhynchus (Fig. 3) nor in other Prototheres in the large reptile tree (LRT, 1631+ taxa, Fig. 2). Prototheria are notable for their long rostra, lots of teeth and low coronoid process, traits that don’t match the  Asfaltomylos mandible. The medial surface of Asfaltomylos does include a dentary trough in which tiny posterior jaws bones would soon evolve to become ear bones… except that happens by convergence in highly derived arboreal mammals, like multituberculates, that experience that reversal in the auditory region, to the chagrin of Jurassic mammal workers worldwide.

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

Figure 4. Echinosorex, the extant moonrat, looks like an opossum, but nests with Deinogalerix in the large reptile tree.

In the LRT
Asfaltomylos nests with the moonrat Echinosorex, not far from Carpolestes (Fig. 1), a plesiadapiform in the LRT. 

Here’s a thought:
Take a look at that tall, narrow, posterior premolar in Asfaltomylos. That’s what turns into a similar posterior premolar in moonrats and hedgehogs. That’s what turns into a large cutting premolar in Carpolestes and multituberculates. 

Figure 1. Subset of the LRT focusing on Glires and subclades within.

Figure 5. Subset of the LRT focusing on Glires and subclades within. Moonrats and hedgehogs are not too far from Carpolestes and arboreal taxa like aye-aye.

Once again, the LRT shows why it is so important
to test all enigma taxa against a wide gamut of taxa, like the LRT. The LRT minimizes bias in the choice of the inclusion set of taxa. The number of characters for the mandible in the LRT comes down to less than dozen. Tooth cusp characters are largely omitted. So character count is, once again, shown to be not nearly as important, contra the opinions of workers who ask for more characters to no advantage.


References
Martin T and Rauhut OWM 2005. Mandible and dentition of Asfaltomylos patagonicus (Australosphenida, Mammalia) and the evolution of tribosphenic teeth. Journal of Vertebrate Paleontology 25(2):414–425.
Rauhut OWM, Martin T Ortiz-Jaureguizar E and Puerta P 2002. A Jurassic mammal from South America. Nature 416:165–168.
Rougier, GW, Martinelli AG, Forasiepi AM and Novacek M J 2007. New Jurassic mammals from Patagonia, Argentina : a reappraisal of australosphenidan morphology and interrelationships. American Museum novitates, no. 3566. online here.

wiki/Asfaltomylos

https://pterosaurheresies.wordpress.com-henosferus/

Heterohyus enters the LRT

Figure 1. Two of several Heterohyus specimens from the Messel Pit of Germany.

Figure 1. Two of several Heterohyus specimens from the Messel Pit of Germany.

Heterohyus nanus (Gervais 1848, late Eocene) from the Messel Pit in Germany nests with Apatemys in the large reptile tree (LRT, 1563 taxa). Relatively few traits differentiate the two. The lumbar region is shorter. The skull is larger. The naris is smaller and higher on the rostrum.

According to Wikipedia members of the Apatemyidae were
“small and presumably insectivorous. Size ranged from that of a dormouse to a large rat. The toes were slender and well clawed, and the family were probably mainly arboreal.[2] The skull was fairly massive compared to the otherwise slender skeleton, and the front teeth were long and hooked, resembling those of the modern aye-aye and marsupial Dactylopsila, both whom make their living by gnawing off bark with their front teeth to get at grubs and maggots beneath.”

The LRT nests apatemyids
as basal members of Glires, not related to other so-called cimolestids, a polyphyletic assembly of placental taxa. according to the LRT. Rather apatemyids are a clade of gnawing tree shrews, now extinct.


References
Gervais P 1848–52. Primates, Microchoeridae? Zoologie et Paléontologie Françaises. Paris, Arthrus Bertrand, text, 2 vols; atlas, 80 pls.

wiki/Heterohyus
wiki/Apatemyidae

 

New ‘rodents and rabbits’ cladogram

Asher et al. 2019
bring us a new phylogenetic + genomic cladogram of rabbits + rodents (clade = Glires) that fails to include taxa recovered by the large reptile tree (LRT, 1552 taxa, subset Fig. 1).

From their abstract:
“Our results support the widely held but poorly tested intuition that fossils resemble the common ancestors shared by living species, and that fossilizable hard tissues (i.e. bones and teeth) help to reconstruct the evolutionary tree of life.”

From their results:
“Our analysis supports Glires and three major clades within crown Rodentia: Sciuromorpha (squirrels and kin), Myomorpha ((beavers + gophers) + mice and kin), and Ctenohystrica (porcupines, chinchillas and kin).”

Figure 1. Subset of the LRT focusing on Glires and subclades within.

Figure 1. Subset of the LRT focusing on Glires and subclades within. This is an older image not updated yet with the dormouse, Eliomys.

The LRT
also supports these divisions. It also supports the basal nesting of ‘Tupaiidae’ relative to Glires. It does not support the inclusion of Primates within Glires, but the two are sister clades within a single clade. The LRT supports the basal nesting of Didelphis relative to Metatheria and Eutheria.

Some oddities in the results of Asher et al. 2019.

  1. Papio, the baboon, nests between Dermoptera (flying lemurs/colugos) and Plesiadapis + lemurs. That’s way too primitive for such a derived monkey.
  2. Rodent-toothed Pleisadapis nests with baboons and lemurs. This is a traditional nesting not recovered by the wider gamut LRT where Plesiadapis nests closer to multituberculates and the aye-aye, Daubentonia.

Asher et al. 2019 included dormice
(Eliomys and kin; Fig. 2), and found them to be rather primitive, closer to squirrels. So Eliomys was added to the LRT and it nested with Mus, the mouse.

Figure 2. Eliomys, the dormouse.

Figure 2. Eliomys, the dormouse.

How to tell a mouse from a dormouse.
The skulls are similar, but different. The dormouse tail is furry, not scaly. Dormice are more arboreal. The dormouse hibernates rather than seeking warm spots. Fossil dormice are found in the Eocene, but their genesis must go back to the Early Jurassic, where multituberculates are found, according to the LRT.


References
Asher RJ, Smith MR, Rankin A and Emry RJ 2019. Congruence, fossil and the evolutionary tree of rodents and lagomorphs. Royal Society Open Science 6:190387. http://dx.doi.org/10.1098/rsos.190387

Allactaga and Pedetes enter the LRT

Those leaping rodents from Africa,
jerboas (genus: Allactaga) and jumping hares (genus: Pedetes, Fig. 1), are more closely related to chinchillas and guinea pigs (Cavia), than to the marsupial kangaroos (Macropus) they converge with.

Allactaga major (Cuvier 1836; Late Miocene to present; snout-vent length 5–15cm; Fig. 1) is the extant jerboa, a nocturnal bipedal rodent that burrows into sand during the day. The long hind limbs help it hop, like a kangaroo, zig-zagging over long distances, and avoid attacking owls. They can hurdle several feet in a single bounce. Some have short ears, others have giant ears for cooling. Closest relatives in the LRT include Pedetes and Chinchilla, not the traditional Mus.

Figure 1. Skeletons of Pedetes and Allactaga to scale.

Figure 1. Skeletons of Pedetes and Allactaga to scale. Not sure yet if the jerboa is a miniature spring hare, or if the spring hare is a giant jerboa.

Figure 3. The spring hare (Pedetes) nests with the jerboa (Allactaga) in the LRT.

Figure 2. The spring hare (Pedetes) nests with the jerboa (Allactaga) in the LRT.

Pedetes capensis (Illiger 1811; snout-vent length: 35-45cm; Figs. 1, 2) is the extant South African springhare, a diurnal burrower and a nocturnal hopper native to South Africa. Pedal digit 1 is absent. Young are born with fur and are active within days.


References
Cuvier F 1836. Proceedings of the Zoololgical Society of London 1836:141.
Illiger 1811. Prodromus systematis mammalium et avium additis terminis zoographicis utriusque classis, eorumque versione germanica. Sumptibus C. Salfeld, Berolini [Berlin]: [I]-XVIII, [1]-301.

wiki/Allactaga
wiki/Pedetes