Bears, bears and more bears

This post had its genesis
in a recent YouTube video all about bears by Moth Light Media. After phylogenetic analysis in the large reptile tree (LRT, 1834+ taxa, subset Fig. 1) ‘bears’ are no longer monophyletic. Instead the various extant ‘bears’ are better considered giant kinkajous, weasels, wolverines and bush dogs, all converging on similar ‘bear’-like morphologies.

Figure 1. Subset of the LRT focused on Carnivora, a placental mammal clade. Note the polyphyletic nesting of various 'bears' indicating that they are all just large kinkajous, weasels, wolverines and bush dogs converging on similar bear-like morphologies.

Figure 1. Subset of the LRT focused on Carnivora, a placental mammal clade. Note the polyphyletic nesting of various ‘bears’ indicating that they are all just large kinkajous, weasels, wolverines and bush dogs converging on similar bear-like morphologies. Note the separation of seals (dark yellow) from sea lions (peach).

Jiangzuo and Flynn 2020
discussed the earliest ursine bear and the origin of plant-dominated omnivory in Carnivora. Unfortunately they worked within an invalid phylogenetic context brought about by taxon exclusion. The wolf, Canis lupus, was their outgroup taxon. So their cladogram was upside-down compared to the LRT (Fig. 1). Basalmost members of Carnivora and their outgroups among basalmost Placentalia were all agile arboreal omnivores, not digitigrade cursors (runners), like Canis.

Jiangzuo and Flynn consider the spectacled bear,
Tremarctos, a member of the ursine bears. In the LRT Tremarctos arises from the bush dog, Speothos, far apart from ursines.

Jiangzuo and Flynn consider the wolverine,
Gulo, a member of the mustelids. In the LRT the short face bear, Arctodus, arises from the wolverine, Gulo, apart from ursines. 

Jiangzuo and Flynn consider the giant panda,
Airluropoda, a type of bear. In the LRT it arises from the herbivorous kinkajou (genus: Potos) before the appearance of the ancestor of the rest of the ‘bears’, Mustela, the weasel.

Jiangzuo and Flynn do not include
Speothos or Potos in their text. The authors separate Gulo in the clade Mustelida, apart from bears in their study. So taxon exclusion mars this otherwise detailed study of bear dentition and diet.

In like fashion,
McLellan and Reiner 1994 also excluded a long list of pertinent taxa in their review of bear evolution.

Sharp-eyed readers will note the addition of two taxa
to the Carnivora, the sea otter (Enhydra) and the basal walrus (Protodobenus).


References
Jiangzuo Q and Flynn JJ 2020. The earliest ursine bear and the origin of plant-dominated omnivory in Carnivora. iScience 23, 101235, June 26, 2020.
McLellan B and Reiner DC 1994. A review of bear evolution. Int. Conf. Bear Res. and Manage. 9(1):85-96

 

Purgatorius and Plesiadapis are still not primates contra Wilson et al. 2021

Short one today
on Purgatorius (Early Paleocene; Fig. 1), a mandible taxon considered by Wilson et al. 2021 to be a member of the Plesiadapiformes (Fig. x).

Figure 1. Purgatorius compared to other basal and often Paleocene mammals.

Figure 1. Purgatorius compared to other basal and often Paleocene mammals.

Wilson et all 2021 report
“Plesiadapiforms are crucial to understanding the evolutionary and ecological origins of primates and other euarchontans (treeshrews and colugos) as well as the traits that separate those groups from other mammals.”

No they are not.

Adding taxa
shifts plesiadapiformes deep into the clade Glires (Fig. x) where Plesiadapis joins Daubentonia as primate-like rodents close to Carpolestes and Ignacius.

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

Figure 2. Ignacius and Plesiadapis nest basal to Daubentonia in the LRT.

Wilson et al. also reported
similarities in Purgatorius to Palaechthon, which nested in 2017 with the demopteran, Cynocelphalus in the large reptile tree (LRT, 1807+ taxa). Wilson et al. considered Palaechthon a member of the Plesiadapiformes.

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

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

We looked at Purgatorius earlier
here in 2017.

Colleagues, expand your taxon lists.
If you don’t look in there, you won’t see what’s in there. So look. Add taxa. Sometimes traditions, professors and textbooks are not complete or incorrect. Find out for yourself.


References
Wilson MGP et al. , (9 co-aiuthors) 2021. Earliest Palaeocene purgatoriids and the initial radiation of stem primates Royal Society open science 8210050
http://doi.org/10.1098/rsos.210050

https://pterosaurheresies.wordpress.com/2019/03/07/tweaking-palaechthon-basal-volitantia/

The coatimundi (Nasua) enters the LRT basal to almost all placentals

Traditionally
the coatimundi (Nasua nasua (Figs. 1, 3, 4; originally Viverra nasua Linneaus 1766) is considered a close relative of the raccoon (Procyon), a member of the Carnivora. So it has not gotten the spotlight it deserves.

Figure 1. The coatimundi (Nasua) compared to the ring-tailed lemur (Lemur).

Figure 1. The coatimundi (Nasua) compared to the ring-tailed lemur (Lemur).

By contrast, 
here in the large reptile tree (LRT, 1804+ taxa, Fig. x) Nasua nests outside the Carnivora, alongside Protictis, a Middle Paleocene taxon, and former enigma.

This nesting in the LRT
means the resemblance between coatimumndis and primitive carnivores, like Procyon, primitive primates, like Lemur (Fig. 1), and primitive tree shrews like Tupaia and Ptilocercus, is not mere convergence, but homology.

Overlooked until now,
coatimundis are basal to virtually all placental mammals, including primates and humans. That’s why they look like lemurs. That’s why they look like big tree shrews. That’s why they look like the LRT ancestor of bats, Chriacus, already with those large claws and feet able to rotate 180º enabling head-down descent from trees.

And that’s not all.
Coatimundis also dig with those big claws. So it is no coincidence that Talpa, the mole, is only a few nodes deep in the base of the Carnivora.

It is also worthwhile to compare
Nasua to an outgroup taxon, Caluromys (Fig. 4), an arboreal marsupial close to the base of the Placentalia.

Figure x. Subset of the LRT focusing on Carnivora and basal Placentalia after the addition of Nasua.

Figure x. Subset of the LRT focusing on Carnivora and basal Placentalia after the addition of Nasua. This phenomic cladogram is very different from genomic cladograms you may have seen, some that employ tapirs for outgroups.

Distinct from all members of the Carnivora
in the LRT, Nasua retains three large molars and a vestigial fourth along with a long list of other more subtle traits. Members of the Carnivora have only two molars typically with a large carnassial tooth preceding the upper molars.

Figure 2. Skull of Nasua compared to mid-Paleocene Protictis. The two are a close match and nest together in the LRT.

Figure 2. Skull of Nasua compared to mid-Paleocene Protictis. The two are a close match and nest together in the LRT. Shown about three-fifths life size.

According to Wikipedia
“Adult coatis measure 33 to 69 cm (13 to 27 in) from head to the base of the tail, which can be as long as their bodies. Males can become almost twice as large as females and have large, sharp canine teeth.Coatis have non retractable claws for climbing and digging. They prefer to sleep or rest in elevated places and niches, like the rainforest canopy, in crudely built sleeping nests. Coatis are active day and night but are not nocturnal animals. In the wild, coatis live for about seven years, while in captivity they can live for up to 15 or 16 years. Coatis communicate their intentions or moods with chirping, snorting, or grunting sounds. The pregnant females separate from the group, build a nest on a tree or in a rocky niche and, after a gestation period of about 11 weeks, give birth to litters of three to seven kits. About six weeks after birth, the females and their young will rejoin the band. Females become sexually mature at two years of age, while males will acquire sexual maturity at three years of age.”

The tail is not prehensile, but is used for balance.
Coatis able to rotate their ankles beyond 180°; they are therefore able to descend trees head first.

Figure 3. Skeleton of the coatimundi (Nasua) along with images of the hands, feet, antebrachium and humerus.

Figure 3. Skeleton of the coatimundi (Nasua) along with images of the hands, feet, antebrachium and humerus.

Although Middle Paleocene Protictis
(Fig. 2). nests alongside Nasua, they both had their origin deep in the Jurassic based on Jurassic remains of more derived taxa among the multituberculates. So the coatimundi was a friend, a meal, or at least an observer, of dinosaurs. This genus is a previously overlooked living relative of human ancestors, much more than the agricultural pest some people think.

Figure 1. Mammals at the base of the Placentalia include the outgroup taxon: Caluromys, a basal placental: Genetta, a basal Carnivora: Eupleres, a basal Volitantia: Ptilocercus, a basal Primates: Microcebus, and basal Glires: Tupaia.

Figure 4. Mammals at the base of the Placentalia include the outgroup taxon: Caluromys, a basal placental: Genetta, a basal Carnivora: Eupleres, a basal Volitantia: Ptilocercus, a basal Primates: Microcebus, and basal Glires: Tupaia.

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


References
Linneaus C 1766. Systema naturae : per regna tria natura, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. 1 (12 ed.). Holmiae: L. Salvii.
wiki/Coati
wiki/South_American_coati

 

 

 

Variation within the genus Tupaia (tree shrew)

Another tree shrew post today.
Following yesterday’s post on a partial Oligocene tree shrew fossil.

Figure 1. Skulls of Tupaia to scale, plus a list from Wikipedia and others shown here not on that list.

Figure 1. Skulls of Tupaia to scale, plus a list from Wikipedia and others shown here not on that list.

Tree shrews
in the large reptile tree (LRT, 1787+ taxa) are basal to several basal placental clades.

Figure 3. Subset of the LRT focusing on the clade Scandentia (tree shrews) and the three arboreal clades that arise from it.

Figure 2. Subset of the LRT focusing on the clade Scandentia (tree shrews) and the three arboreal clades that arise from it.

I didn’t realize the species variation
in the extant genus Tupaia (Fig. 1) was so wide. And that is only the part I was able to find (red species). These species are all variations on a Jurassic radiation, so they had a long time to evolve, chiefly in equatorial arboreal jungle environs. Some of these may enter the LRT. Can you tell which ones?

Tupaia chinensis (skull) Tupaia tana (the large tree shrew, Raffles 1821) extant, was derived from a sister to Ptilocercus and was basal to Macroscelides and Chrysochloris. The tree shrew acts like a squirrel, but instead of eating nuts, it eats insects. Tupaia probably originated deep in the Mesozoic (Late Jurassic), but their fossils go back only 3 million years. Note the dorsal expansion of the ear bones, which continues in Macroscelides and Chrysochloris. The incisors and canines are similar. The dentary incisors extend anteriorly, as in shrews like Scutisorex.


References
Raffles TS 1821. Descriptive Catalogue of a Zoological Collection made on account of the Honourable East India Company, in the Island of Sumatra and its Vicinity, under the Direction of Sir Thomas Stamford Raffles, Lieutenant-Governor of Fort Marlborough; with additional Notices illustrative of the Natural History of those Countries. The Transactions of the Linnean Society of London (Linnean Society of London) XIII: 239–340.

wiki/Tupaia

Borophagus enters the LRT, but not with Canis

The apex predator of North America
for tens of millions of years, Borophagus (Cope 1892; Fig. 1; 80 cm in length), the bone-crushing traditional ‘dog’ of the Middle Miocene to the Late Pliocene entered the large reptile tree (LRT, 1742+ taxa; subset Fig. 2), but not with Canis, the wolf. Rather Borophagus nested at the base of the clade containing two South American members of Carnivora, Speothos, the South American bush dog, and Tremarctos, the South American spectacled bear.

So Borophagus is not a canid in the LRT (contra tradtion).

Figure 1. Borophagus skull with colors added.

Figure 1. Borophagus skull with colors added.

In Borophagus secudus
the premaxilla extends to mid-canine and contacts the frontals, as in other clade members.

Figure 2. Subset of the LRT focusing on the Carnivora.

Figure 2. Subset of the LRT focusing on the Carnivora.

According to Wikipedia
“Borophagus, like other borophagines, are loosely known as “bone-crushing” or “hyena-like” dogs.”

“Typical features of this genus are a bulging forehead and powerful jaws. 

“Borophagus has been considered to be probably a scavenger by paleontologists in the past.[Its crushing premolar teeth and strong jaw muscles would have been used to crack open bone, much like the hyena of the Old World. However, Borophagus fossils are so abundant and geographically widespread that some paleontologists now argue that Borophagus must have been both the dominant carnivore of its time, and thus an active predator because carrion feeding alone could not have sustained such a large population.”


References
Cope ED 1892. A hyena and other Carnivora from Texas. American Naturalist 26:1028–1029.

Asiatherium enters the LRT: mammal nomenclature issues follow

Everyone agrees
that Asiatherium (Figs, 1,2) nests close to Monodelphis, Caluromys and placentals. Trofimov and Szalay 1994 agreed. So did Denyer, Regnault and Hutchinson 2020. So did the large reptile tree (LRT, 1729+ taxa, subset Fig. 3).

Figure 1. Asiatherium in situ from Szalay and Trofimov 1996.

Figure 1. Asiatherium in situ from Szalay and Trofimov 1996.

Asiatherium reshetovi (Trofimov and Szalay 1994, Szalay and Trofimov 1996; PIN 3907; Late Cretaceous; 80mya; Figs. 1, 2) is a key Mongolian metathere ancestral to monodelphids and Caluromys, which is ancestral to placentals. It is derived from Triassic sisters to extant late survivors, DidelphisGilronia and Marmosops.

Figure 2. Asiatherium skull slightly modified from Szalay and Trofimov 1996. Colors added here.

Figure 2. Asiatherium skull slightly modified (longer lateral view premaxilla to match dorsal and ventral views) from Szalay and Trofimov 1996. Colors added here.

The problem is,
according to results recovered by the LRT, mammal clade nomenclature needs to go back to basics. Several modern mammalian clade names are found to be junior synonyms of traditional clades in the LRT.

Prototheria (Gill 1872) is a junior synonym
for Monotremata (Bonaparte 1837) in the LRT.

According to Wikipedia, “Prototheria is a paraphyletic subclass to which the orders MonotremataMorganucodontaDocodontaTriconodonta and Multituberculata have been assigned, although the validity of the subclass has been questioned.”

In the LRT Morganucodon is a a marsupial (see below). Docodon is a taxon within Monotremata. Triconodon is a taxon within Monotremata. Multituberculata is a clade within the placental clade Glires (Fig. 4). So, the clade Monotremata is monophyletic and has precedence.

Theria (Parker and Haswell 1897) is a junior synonym
of Marsupialia (Illiger 1811). Metatatheria (Thomas Henry Huxley 1880) is also a junior synonym of Marsupialia.

The late-surviving basalmost marsupial in the LRT (Fig. 4), Ukhaatherium (Fig. 3), has epipubic (marsupial) bones. That long rostrum indicates this taxon is close to monotremes.

Figure 3. Ukhaatherium in situ.

Figure 3. Ukhaatherium in situ.

Unlike the monophyletic clade Monotremata,
a series of nested marsupial clades are present. The last of these gives rise to Placentalia, only one of several that lose the pouch (Fig. 4). New names are proposed here where appropriate:

  1. Marsupialia = Ukhaatherium and kin + all descendants (including placentals)
  2. Paleometatheria = Morganucodon and kin + all descendants.
  3. Didelphimetatheria = Eomaia and kin + all descendants
  4. Phytometatheria = Marmosops and kin + all descendants
  5. Carnimetatheria = Asiatherium and kin + all descendants
  6. Transmetatheria = Caluromys and kin + all descendants
  7. Placentalia = Vulpavus and kin + all descendants

Figure 4. Subset of the LRT cladogram of basal Mammalia. Note the traditional clade Metatheria is a grade with new names proposed here.

Figure 4. Subset of the LRT cladogram of basal Mammalia. Note the new names proposed here.

Basal marsupial taxa are omnivores. 
Derived phytometatheres are herbivores. Derived carnimetatheres are carnivores to hyper-carnivores. Transmetatheres (Carluromys) and basal Placentalia remain omnivores.

In the LRT Eutheria (Gill 1872) is a junior synonym
of Placentalia (Owen 1837). Omnivorous civets like Nandinia are basal placentals. Carnivora is a basal placental clade following basal placental civets.

Competing cladograms
Denyer, Regnault and Hutchinson 2020 recently looked at the marsupial patella, or more specifically the widespread absence or reduction of the kneecap. The authors concluded, “metatherians independently ossified their patellae at least three times in their evolution.”

Unfortunately, Denyer et al. tested Caenolestes, the ‘shrew opossum’. Not surprisingly it nested close to placentals in their cladogram. Caenolestes was earlier nested in the LRT within the placental clade, Glires, closer to shrews than to opossums. It has no pouch, but converges with marsupials in several aspects. Inappropriate taxon inclusion, like Caenolestes, occurs due to taxon exclusion. Excluded taxa would have attracted and removed the inappropriate taxon. Taxon exclusion plagues Denyer et al.

Historically, you may remember,
Bi et al. 2018, while presenting Early Cretaceous Ambolestes, suffered from massive taxon exclusion and traditional bias in attempting to produce a cladogram of mammals. Bi et al. recovered Sinodelphys (Early Cretaceous) and Juramaia (Late Jurassic) as ‘eutherians’. In the LRT both are monotremes.

Other basal mammal cladograms
depend too much on tooth traits. Convergence in tooth traits creates problems, as documented earlier. We’ll look at this problem in more detail soon.

The above subset of the LRT appears to be a novel hypothesis
of interrelationships. If not, please provide a citation so I can promote it.


References
Bi S, Zheng X, Wang X, Cignetti NE, Yang S, Wible JR. 2018. An Early Cretaceous eutherian and the placental marsupial dichotomy. Nature 558(7710):390395 DOI 10.1038/s41586-018-0210-3.
Denyer AL, Regnault S and Hutchinson JR 2020. Evolution of the patella and patelloid in marsupial mammals. PeerJ 8:e9760 http://doi.org/10.7717/peerj.9760
Szalay FS and Trofimov BA 1996. The Mongolian Late Cretaceous Asiatherium, and the early phylogeny and paleogeography of Metatheria. Journal of Vertebrate Paleontology 16(3):474–509.
Trofimov BA and Szalay FS 1994. New Cretaceous marsupial from Mongolia and the early radiation of Metatheria. Proceedings of the National Academy of Sciences 91:12569-12573

Chimento and Agnolin 2020: Litopterna interrelations suffers from taxon exclusion

Chimento and Agnolin 2020
discuss interrelationships within and outside the clade Litopterna, famous for including Macrauchenia (Fig. 1), the odd South American ungulate. Strangely the chalicotheres were excluded. In the large reptile tree (LRT, 1721+ taxa, subset Fig. 2), litopterns and chalicotheres nest in the same clade. Phylogenetically, Macrauchenia IS a chalicothere in the LRT.

Figure 1. Macrauchenia museum mount.

Figure 1. Macrauchenia museum mount.

From the abstract
“The Litopterna is an extinct clade of endemic South American ungulates that range from Paleocene up to late Pleistocene times. Because of their unique anatomy, litopterns are of uncertain phylogenetic affinities”

Not so. The LRT (Fig. 2) nests litopterns with high Bootstrap scores between paenungulates and perissodactyls and following chalicotheres. Omitting chalicotheres may be the cause of prior problems.

Figure 1. Subset of the LRT focusing on hoofed mammals.

Figure 1. Subset of the LRT focusing on hoofed mammals.

From the abstract
“However, some nineteenth century authors, considered litopterns as related to perissodactyl ungulates, a hypothesis recently sustained by molecular data. The aim of the present contribution is to include litopterns and other South American related taxa in a comprehensive phylogenetic analysis together with several extant and extinct basal perissodactyl ungulates.”

The Chimento and Agnolin taxon list is far from comprehensive. Many extant taxa were excluded.

Figure 3. From Chimento and Agnolin 2020, colors added. Grayed out taxa are not tested in the LRT. Many of these are based on teeth only.

Figure 3. From Chimento and Agnolin 2020, colors added. Grayed out taxa are not tested in the LRT. Many of these are based on teeth only.

“The analysis resulted in the nesting of litopterns and kin as successive stem-clades of crown Perissodactyla. Further, litopterns are not phylogenetically grouped with any North American basal ungulate, in agreement with some previous proposals”

Notably the authors excluded chalicotheres (Fig. 2) from their taxon list. Some of these are known from North America. Europe, Africa and Asia and they nest with Macrauchenia in the LRT. Phylogenetically, Macrauchenia IS a chalicothere in the LRT. Theosodon is a taxon employed by both cladograms. Macrauchenia is not found in the Chimento and Agnolin cladogram.

Figure. 2. Chalicothere skulls to scale. Lophiodon is an outgroup closer to tapirs.

Figure. 4. Chalicothere skulls to scale. Lophiodon is an outgroup closer to tapirs.

“Presence of pan-perissodactyls in South America and India indicates that southern continents probably played an important role in the early evolution of hoofed mammals.”

Or not. These continents might have been more of a backwater or refuge for highly derived taxa with earlier, pre-continental-separation origins.


References
Chimento NR and Agnolin FL 2020. Phylogenetic tree of Litopterna and Perissodactyla indicates a complex early history of hoofed mammals. Nature.com/scientific reports.

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

Recalibrating clade origins, part 4

Earlier
we looked at the first part and second part and third part of Marjanovic’s 2019 chronological recalibration of vertebrate nodes. Today we continue in part 4 of 5.

Mammalia (Prototheria + Theria)
Based on the literature, Marjanovic 2019 considers morganucodontans and tiny Hadrocodium to be mammalomorphs, not mammals. He is unsure about haramiyidans. With regard to the first dichotomy of mammals, he reported, “I recommend a hard minimum age of 179 Ma for this calibration.”

By contrast the large reptile tree (LRT, 1630+ taxa) nests Morganucodon (Late Triassic, 205 mya), Hadrocodium (Early Jurassic) and Henosferus (Middle Jurassic) together in the most basal subclass within Theria, part of the first dichotomy within Mammalia. Marjanovic considered Henosferus one of the oldest uncontroversial mammals at 179 mya. Megazostrodon is a late surviving (early Jurassic) last common ancestor taxon of all mammals in the LRT. It must have appeared prior to Morganucodon in the Late Triassic.

Theria (Metatheria + Eutheria)
Marjanovic reports, “The oldest securely dated eutherian is Ambolestes at 126 Ma.” Then he reports, “Accepting that Juramaia is not from the Lanqi Fm, I propose 160 Ma as the soft maximum age of this calibration.”

By contrast, Morganucodon (Late Triassic, 210mya) nests as the oldest therian. Ambolestes nests with Didelphis, the opossum, within the Theria, not Eutheria.  Thereafter the traditional Metatheria splits in three clades in the LRT, a largely herbivorous branch with Glironia and Marmosops at its base, and a largely carnivorous branch with Monodelphis and Chironectes at the base of one branch and Caluromys + Placentalia at yet another. So, while Caluromys (Fig. 3) retains a pouch, it is also the last common ancestor of all placentals.

Figure 1. Pteropus and Caluromys compared in vivo and three views of their skulls. Caluromys is in the ancestry of bats and shows where they inherited their inverted posture.

Figure 1. Pteropus and Caluromys compared in vivo and three views of their skulls. Caluromys is in the ancestry of bats and shows where they inherited their inverted posture.

Marjanovic often errors by not including extant taxa that are more primitive than extinct taxa that are older. This comes back to bite him several times, especially so when he relies on a single fossil tooth rather than a living animal he can hold. The LRT tests both living and extinct taxa to minimize taxon exclusion.

Marjanovic discusses the possibility that Sinodelphys is the oldest known metatherian, but Sinodelphys nests as one of the most primitive prototherians in the LRT, as we learned earlier here.

Placentalia (Atlantogenata + Boreo(eu)theria)
In the world of gene studies, Atlantogenata include the highly derived elephants and anteaters. The Boreoeutheria include the highly derived whales, humans and hooved mammals. Genomic studies deliver false positives, and these are among the most blatant, so ignore these. They don’t deliver a gradual accumulation of derived traits.

By contrast, in the LRT the first dichotomy in the placentalia splits arboreal Vulpavus from arboreal Nandinia and thereafter arboreal Carnivora (mongooses and raccoons) from arboreal Volantia (bats and colugos) + arboreal Primates and the rest of the Placentalia. All of these civet-like and tree opossum-like taxa look like Caluromys (Fig. 1), as you can see. Elephants and anteaters come later. Adding living taxa to Marjanovic’s search for primitive placentals would have helped clarify his research and conclusions, preventing him form perpetuating old myths.

Carnivora (Feliformia + Caniformia)
Marjanovic errs by reporting the basal dichotomy within Carnivora splits cats from dogs.

By contrast in the LRT cats and dogs are closely related and derived taxa, not basal. As mentioned above, civets, mongooses and raccoons are basal Carnivora.

Euarchontoglires/Supraprimates (Gliriformes + Primatomorpha)
Marjanovic discusses several poorly preserved, sometimes one tooth only, fossil taxa from the early Paleocene (65mya). Some of these are anagalids, which nest at the base of yet another clade in the LRT, the one with tenrecs and odontocetes (toothed whales).

By contrast in the LRT lemur-like adapids appear at the base of the Primates. Tree-shrews appear at the base of the Glires.

Marsupialia (Didelphimorphia – Paucituberculata + Australidelphia)

  • Didelphimorphia = opossums from North America
  • Paucituberculata = South American marsupials, sans Dromiciops
  • Australidelphia = Australian and Asian marsupials, plus Dromiciops

Marjanovic reports, “I therefore propose 55 Ma as a probably overly strict hard minimum age for this calibration.” He later reports, “Rather than the beginning of the Maastrichtian, I propose the beginning of deposition of the Lance and Hell Creek formations, where Glasbius has been found, as the hard maximum age for this calibration, which I estimate as 68 Ma.”

See Figure 1 for a different three-part marsupial split from the LRT. Dromiciops is only one of many similar herbivorous marsupials. Middle Late Cretaceous Asioryctes is a basal member of the largely herbivorous clade. Early Cretaceous Vincelestes is a basal member of the largely carnivorous clade. So Middle to Late Jurassic (175mya) is a better estimate for the genesis of marsupial diversity. That means marsupials dispersed during the Pangean era without the need of an oceanic dispersal.

Marjanovic mistakenly reports, “Marsupials, other metatherians and indeed other therians are wholly absent from the Late Cretaceous mammaliform record of South America, which consists instead of gondwanatherian haramiyidans and a very wide variety of meridiolestidan stem-theriiforms.”

  • Meridiolestida = non-therian mammals (= Prototheria, Montremata) seems to be based on tooth traits. Cronopio and Necrolestes are among the only tested taxa also  found in the LRT. Cronopio is an omnivorous member of the pre-metatherian Theria in the LRT. Necrolestes is a basal member of the placental clade, Glires, derived from the treeshrew Tupaia in the LRT. So, again, we have a mismatch due to not testing all the mammals against all the mammals. That is what makes the LRT such a powerful tool that should be more widely used to avoid such old school mythology.

More tomorrow as we conclude part 5 of 5.


References
Marjanovic D 2019. Recalibrating the transcriptomic timetree of jawed vertebrates.
bioRxiv 2019.12.19.882829 (preprint)
doi: https://doi.org/10.1101/2019.12.19.882829
https://www.biorxiv.org/content/10.1101/2019.12.19.882829v1

SVP abstracts – Ambolestes and the origin of placentals

Bi S-D et al. 2019 discuss Early Cretaceous Ambolestes
(Figs. 1, 2) and the Early Mesozoic marsupial/placental split.

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

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

From the abstract:
“Extant placental and marsupial mammals are the dominant vertebrates in many ecosystems, which makes the placental-marsupial dichotomy a significant event in Earth’s history.”

The large reptile tree (LRT, 1592 taxa) splits placentals from marsupials as shown below (Figs. 3, 4). The Early Cretaceous marsupial Bishops splits from the placental outgroup taxon, the extant marsupial Caluromys (Fig. 6). More timely, derived placental multituberculates, like Megaconus (Fig. 5), have been found in Middle Jurassic strata. That means a long line of undiscovered small, arboreal, placentals extends back to the Late Triassic/Earliest Jurassic.

Figure 3. Ambolestes skull reconstructed. Jaw tips restored.

Figure 2. Ambolestes skull reconstructed. Jaw tips restored.

Bi et al. continue:
“Molecular estimates of the divergence of placentals and marsupials (and their broader clades Eutheria and Metatheria) fall primarily in the Jurassic.”

Since Early Jurassic Megazostrodon is the proximal outgroup for all mammals, and Early Triassic Morganucodon is a marsupial, and Middle Jurassic Megaconus the LRT supports a Late Triassic split for placentals and marsupials.

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

Figure 3. Select basal cynodonts and mammals set chronologically. The divergence times for placentals (Eutheria), marsupials (Metatheria) and monotremes (Mammalia) are estimated here. Note the large gaps of time in which fossils are not known.

Bi et al. continue:
“In support, the oldest purported eutherian, Juramaia, is reported to be from the early Late Jurassic (160 million-years ago) of Liaoning Province, northeastern China.”

In the LRT (subset Fig. 1) Juramaia nests as a basal prototherian, an egg laying basal mammal.

“The oldest purported metatherian, Sinodelphys, is 35 million-years younger from the
Early Cretaceous Jehol Biota also in Liaoning Province, northeastern China.”

In the LRT Sinodelphys is another monotreme.

“In 2018, we reported a new eutherian, Ambolestes zhoui, also from the Jehol Biota. The fossil, a nearly complete skeleton, preserves anatomical detail unknown from contemporaneous eutherians including the hyoid apparatus and ectotympanic. The complete hyoid is the first known for any Mesozoic mammaliaform, and the ectotympanic resembles that in some extant didelphid marsupials.”

In the LRT (Fig. 1) Ambolestes (Figs. 3, 4) is a metathere/marsupial close to the extant Virginia opossum, Didelphis.

Figure 1. Subset of the LRT focusing on the Kynodontia and Mammalia. Non-eutherian taxa in red were tested in the LRT but not included because they reduce resolution. Eutherian taxa in red include a basal pangolin and derived xenarthran, clades that extend beyond the bottom of this graphic. The pink clade proximal to mammals was considered mammalian by Lautenschlager et al. due to a convergent mammalian-type jaw joint.

Figure 4. Subset of the LRT focusing on the Kynodontia and Mammalia. Non-eutherian taxa in red were tested in the LRT but not included because they reduce resolution. Eutherian taxa in red include a basal pangolin and derived xenarthran, clades that extend beyond the bottom of this graphic. The pink clade proximal to mammals was considered mammalian by Lautenschlager et al. due to a convergent mammalian-type jaw joint.

Bi et al. continue:
“In our phylogenetic analysis concentrating on the eutherian-metatherian 
dichotomy, the closest relative of Ambolestes was Sinodelphys, and both fell within Eutheria.”

As shown above, the LRT does not confirm that hypothesis of interrelationships.

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

Figure 5. Subset of the LRT focusing on Glires and subclades within.

Bi et al. continue:
“With Sinodelphys as a eutherian, postcranial differences formerly thought to indicate different invasions of a scansorial niche by meta and eutherians in Jehol are only variations among the early members of the placental lineage. Additionally, the earliest known metatherians are approximately 15 million years younger than previously thought and their

fossils, isolated teeth and fragmentary jaws, are from North America. Our tree results in a 50 million-year ghost lineage for Metatheria, accepting the 160 million-years age for Juramaia. 

The LRT confirms a 210 mya origin for Metatheria, starting with Morganucodon, so no ghost is necessary.

Figure 8. Caluromys, the largest of the mouse opossums, to scale with its LRT sister, Vulpavus, a basal member of Carnivora.

Figure 6. Caluromys, the largest of the mouse opossums, to scale with its LRT sister, Vulpavus, a basal member of Carnivora and Placentalia.

Bi et al. continue:
“A possibility raised elsewhere is that the age of Juramaia is incorrect; rather than Late Jurassic, perhaps it is from the Early Cretaceous Jehol Biota. In our study, Juramaia is in a clade with Albian/Aptian Prokennalestes and Late Cretaceous eutherians by having a more molariform ultimate upper premolar. In contrast, Ambolestes, as in the outgroups, has a non-molariform ultimate upper premolar. Although resolution of this intriguing debate is not currently possible, our understanding of the issues has been furthered by the discovery of Ambolestes.”

As shown above, the LRT does not confirm the Bi et al. hypothesis of interrelationships.


References
Bi S-D et al. 2019. The Early Cretaceous eutherian Ambolestes and its implications for the Eutherian/Metatherian dichotomy. Journal of Vertebrate Paleontology abstracts.