Updated August 17, 2016 with corrections to some of the nomenclature and graphics .Thanks to M. Mortimer for some valuable suggestions.
Now that several dozen mammal
and stem-mammal taxa have been added to the large reptile tree, and it recovered a distinct topology (Fig. 1), it is not only appropriate but a duty to propose new names for novel clades. Of course, we’ll retain all still-valid clade names.
Introducing new clade names also happened earlier
with the introduction of the clade name, Tritosauria, here online, and in a peer-reviewed academic publication (Peters 2000), when I introduced the Fenestrasauria for Cosesaurus through Pterosauria, long with other clade names for fenestrasaur outgroups, all recovered in phylogenetic analysis.
The new mammal tree topology
(Fig. 1) flips and mixes up the current paradigm (Kriegs et al. 2006) in which (untenably) carnivores are sisters to ungulates and ungulates are sisters to bats and elephants nest between marsupials and primates. None of that makes sense. Where are the gradual accumulations of derived traits? Evidently that was not important to Kriegs et al. As a remedy we now have this cladogram:
Here a gradual accumulation of derived traits can be demonstrated.
All basal taxa are tiny furry arboreal forms that look like each other and later evolve in various ways. Both the major (red) and minor (black) clades are discussed below.
The Red List (Fig. 1)
Each of these major monophyletic clades extend to the ungulates.
B. Cynodontia – Owen 1861 named Cynodontia, which he assigned to Anomodontia as a family. That is not valid, but the name is retained and in common use. Here, confirming Ruta et al. 2013, the clade is defined as: Procynosuchus, Hippopotamus their last common ancestor and all escendants.
C. Probainognathia – confirming Ruta et al. 2013, the clade includes Probainognatbus and the chiniquodontids and is defined as Probainognathus, Hippopotamus their last common ancestor and all descendants.
F. Theria – named by Parker and Haswell 1897, include all live-bearing mammals (sans Prototheria); Juramaia has been reported (Luo et al. 2010) as the earliest known therian, but it is not possible to know if it laid eggs or not. Provisionally this clade is defined as Juramaia, Hippopotamus, their last common ancestor and all descendants.
G. Panmetatheria – includes Metatheria (Huxley 1880, taxa more closely related to marsupials than to placentals) + Eutheria. Among tested taxa, Didelphis and the marsupials are also basal therians, traditionally known as metatherians.
H. Eutheria – include all placental mammals (sans Metatheria). The putative marsupial, Monodelphis, lacks a pouch. Eomaia has been reported (Ji et al. 2002) as the earliest known eutherian. Provisionally this clade is redefined as Monodelphis, Hippopotamus, their last common ancestor and all descendants. Basal taxa appear to have been small and arboreal.
I. Pancarnivora – Here the basalmost placental split is between the clade Carnivora and Eomaia. Provisionally this clade is defined as Vincelestes, Hippopotamus, their last common ancestor and all descendants.
J. Panprimates – The next split produced Ptilocercus, Primates, Demoptera, Chiroptera and Pholiodota. Provisionally this clade is defined as Ptilocercus, Hippopotamus, their last common ancestor and all descendants.
K. Panglires – The next split produced rabbit and rodent-like taxa with reduced canines and often enlarged incisors. Provisonally this clade is defined as Asioryctes, Hippopotamus, their last common ancestor and all descendants.
L. Pantenreccetacea – The next split produced long-snouted tenrecs and their sisters the Cetacea (whales). Provisionally this clade is defined as Leptictis, Hippopotamus, their last common ancestor and all descendants.
M. Pancondylarthra – The next split produced the larger basal herbivores, all lacking claws. Provisionally this clade is defined as Onychodectes, Hippopotamus, their last common ancestor and all descendants.
P. Ungulata – This is a traditional clade (Linneaus 1766), but now includes only odd-toed and even-toed ungulates, not aardvarks, hyraxes, sirenians, elephants and/or whales. Provisionally this clade is defined as Tapir, Hippopotamus, their last common ancestor and all descendants.
Q. Phenacodonta – The final split produced Uintatherium and Arsinoitherium on one branch, Hippopotamus and Mesonyx on the other branch. Provisionally this clade is defined as Phenacodus, Hippopotamus, their last common ancestor and all descendants.
The Black List (Fig. 1)
These are the smaller monophyletic clades that branch off sequentially from the main line of descent that ultimately leads to ungulates. Single node taxa are not listed here.
- Chiniquodontidae – is represented here by Chiniquodon, Probainognathus and Castorocauda.
- Tritheledontidae. – includes Pachygenelus, Repenomamus and the Tritylodontidae
- Monotremata – includes Sinoconodon and Ornithorhynchus.
- Morganucondonta – includes Megazostrodon and tiny Hadrocodium.
- Metatheria – includes the marsupials, of course, but not the traditional marsupials, Didelphis or Monodelphis.
- Carnivora – includes the larger meat-eating placentals with a carnassial tooth, like Canis and Phoca.
- Ptilocercia – includes the smaller omnivorous fanged placentals, like Pteropus and Proconsul, but also the termite-eater, Manis. This is a new clade composed of primates, bats, flying lemurs and pangolins.
- Asioryctitheria – named by Novacek et al. 1997, but here includes the smaller omnivorous fangless placentals, like Rattus and Plesiadapis.
- Tenreccetacea – includes the long-snouted omnivorous fangless placentals, like Leptictis and now whales, with stem-whale Maiacetus retaining limbs.
- Condylarthra – includes large herbivores, like
- Xenarthra – a traditional clade includes the anteaters, sloths (Bradypus), armadillos (Dasypus) and now aardvarks (Orycteropus), but not pangolins.
- Paenungulata – a traditional clade with Elephas, Dusisiren and Procavia, but no longer Paleoparadoxia and Arsinoitherium, which nest as basal ungulates.
- Perissodactylia – a tradional clade of odd-toed ungulates, including Tapirus and Chalicotherium.
- Artiodactylia – a traditional clade of even-toed ungulates, including Giraffa and Micromeryx.
- Phenacodontidae – Cope 1881 named this clade here expanded to include Uintatherium and Arsinoitherium.
- Mesonychidae – Cope 1880 named this clade, but here is redefined by Mesonyx, Hippopotamus, their last common ancestor and all descendants.
Of course this means
that the following traditional and molecule-based clades (Kriegs et al. 2006) have lost their utility due to paraphyly. See if these clades make sense to you. They were not recovered in the LRT.
- Atlantogenata – Afrotheria + Xenarthra
- Afrotheria – (from Africa): golden moles, elephant shrews, tenrecs, aardvarks, hyraxes, elephants, and extinct forms (not from Africa) sea cows (sirenians)
- Boreoeutheria – ungulates, carnivores, primates, rodents, rabbits, tree shrews, flying lemurs
- Euarchontoglires – primates, rodents, rabbits, tree shrews, flying lemurs
- Laurasiatheria – shrews, pangolins, bats, whales, carnivorans, odd- and even-toed ungulates.
- Scrotifera – same as Laurasiatheria sans shrews.
- Cetartiodactyla – whales and even-toed ungulates
- Ferae – carnivores and pangolins
Earlier studies by McKenna and Bell 1997
listed Xenarthra as the basalmost placental taxon, but they seem a little too derived to show up so early (but then, so are extant monotremes).
re-nested Haldanodon (Kühne and Krusat 1972) between Probainognathus and Liaoconodon (Fig. 1). These taxa are basal to Pachygenelus and the Tritylodontia and cannot be considered mammaliaforms, unless Pachygenelus and the Tritylodontia are also considered mammaliaforms. Read more about Haldanodon and the Docodonta here.
I realize that online publication without peer-review
is not going to be accepted, but this hypothesis of interrelationships has to start somewhere. Then again, even with peer-review, after 16 years, Peters 2000 is still not accepted, tested or debated, except for this one totally botched and biased attempt that landed its junior author a PhD.
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