Think of aardvarks and sloths as naked and hairy glyptodonts respectively

Because
that’s what they really are… aardvarks are naked and sloths are hairy glyptodonts. And, yes, that comes as a surprise, it breaks a paradigm, it spins your head around, it’s heretical… and it’s exactly where the data takes us.

The Edentata is an odd clade
in which the basalmost taxa, like Barylambda, Glyptodon and Holmesina are very large. On the other hand, terminal extant and derived taxa, like Peltephilus and Cyclopesare much smaller, just the opposite of most mammal clades (in which smaller usually lead to larger, following Cope’s Rule.)

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

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

According to Wikipedia,
“Glyptodontinae (glyptodonts or glyptodontines) are an extinct subfamily of large, heavily armored armadillos which developed in South America and spread to North America.”

In the large reptile tree (LRT, 1252, edentate subset Fig. 1) the glyptodont, Glyptodon, nests between the massive Barylambda and giant sloths, followed by smaller tree sloths and small extinct horned armadillos, like Peltephilus and Fruitafossor. On another branch (Fig. 1) another large glyptodont, Holmesina, nests between the massive Barylambda and the much smaller aardvark, Orycteropus, the armadillo, Dasypus, and the anteaters, Tamandua and Cyclopes.

Such a big-to-small phylogenetic pattern,
is known as phylogenetic miniaturization or the Lilliput Effect and is often the product of neotony (adults retaining juvenile traits, including juvenile size).

Figure 2. Holmesina, the glyptodont ancestor to aardvarks, anteaters and armadillos.

Figure 2. Holmesina, the glyptodont ancestor to aardvarks, anteaters and armadillos. Those are aardvark hands (Fig. 3), glyptodont feet.

Holmesina (Fig. 2) is added to the LRT today.
Basically it is a longer-snouted glyptodont, basal to the longer snouted above-mentioned aardvarks, armadillos and anteaters.

Following a reader comment,
(suggesting ‘taxon exclusion’ was the issue that did not unite glyptodonts with armadillos) I was looking for a transitional taxon to more closely nest glyptodonts with armadillos, rather than sloths. I did so and the tree topology did not change when Holmesina was added. Armadillos are still one taxon removed from glyptodonts, but at least now we have a glyptodont on the long-nosed clade of aardvarks, etc.. As before, aardvarks nest between glyptodonts and armadillos. Looking at all the edentate taxa in detail and overall. I think this nesting and this tree topology seem very reasonable (= it produces a gradual accumulation of derived traits at all nodes and between all taxa).

Figure 3. Orycterpus, the extant aardvark, is a living sister to Barylambda from the Paleocene.

Figure 3. Orycterpus, the extant aardvark, is a living sister to Barylambda from the Paleocene. Aardvarks traditionally nest alone, but in the LRT they are edentates without armor… or hair.

Other workers, like Fernicola, Vizcaíno and Fariña 2008,
described the phylogeny of glyptodonts by putting taxa like Holmesina at the base while omitting Barylambda. Thus such studies do not present the full picture due to taxon exclusion. Everyone seems to omit Barylambda and all the other edentate outgroups back to Devonian tetrapods… but not the LRT.

Goodbye ‘Xenarthra’. Goodbye ‘Pilosa’. Goodbye ‘Cingulata’.
According to Wikipedia, “The order Pilosa is a group of placental mammals, extant today only in the Americas. It includes the anteaters and sloths, including the extinct ground sloths, which became extinct about 10,000 years ago.” According to Wikipedia, Cingulata, part of the superorder Xenarthra, is an order of armored New World placental mammals.” In the LRT ‘Xenarthra’ (Cope 1889) is a junior synonym for ‘Pilosa’ (Flower 1883) and that is a junior synonym for Edentata (Darwin 1859).

References
Darwin C 1859. On the origin of species.
Fernicola JC, Vizcaíno SF and Fariña RA 2008.
The evolution of armored xenarthrans and a phylogeny of the glyptodonts. Chapter 7 in: The Biology of the Xenarthra, Eds: Vizcaíno SF and Loughry WJ. University Press of Florida.
Gaudin TJ and Croft DA 2015. Paleogene Xenarthra and the evolution of South American mammals. Journal of Mammalogy 96 (4): 622–634. https://doi.org/10.1093/jmammal/gyv073

http://www.finedictionary.com/Edentata.html

 

 

 

 

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‘The Dawn of Mammals’ YouTube video illuminates systematic problems

Part of this YouTube video (see below, click to view)
pits DNA paleontolgist, Dr. Olaf Bininda-Emonds (U. Oldenburg), against bone trait paleontologist, Dr. John Wible (Carnegie Museum of Natural History) in their common and contrasting search for basal placental mammals. Both realize that DNA cladograms do not replicate bone cladograms and DNA cannot be utilized with ancient fossils.

Dr. Bininda-Emonds, used molecular clocks
in living taxa to hypothetically split marsupials from placentals about 160 mya ago (Late Jurassic).

By contrast, Dr. Wible reports (28:53),
“Our study supported the traditional view that there were no fossils living during the Cretaceous [that] were members of the placental group itself. There were only ancestors of the placentals living.” (unscripted verbatim)

The impulse for this argument
came from the discovery of Maelestes (Wible et al. 2007a,b; 28:30 on the video) from the Late Cretaceous (75 mya). Dr. Wible’s paper nested Maelestes with the pre-placental, Asiorcytes, another tree-shrew-like mammal from the Late Cretaceous. By contrast, the LRT, nests Maelestes unequivocally at the base of the tenrec/odontocete clade, well within the placental clade (Fig. 2), as we learned earlier here.

The large reptile tree
 (subset in Fig. 2) nests the first known placental mammals at the 160 mya mark, matching the DNA predictions of Dr. Bininda-Emonds et al. A long list of taxa, including Maelestes, nest in the Jurassic and Cretaceous, contra Wible et al. Only more complete taxa are tested in the LRT and dental traits are not emphasized.

Figure 2. Mesozoic time line showing the first appearances of several fossil mammals and the clades they belong to.

Figure 2. Mesozoic time line showing the first appearances of several fossil mammals and the clades they belong to. Many, if not most of the listed taxa are late survivors of earlier radiations, sometimes much earlier radiations. Monodelphis and Didelphis are extant animals that originated in the Early Jurassic at the latest. Note also the large gaps over tens of millions of years, highlighting the rarity of fossil bearing locales.

In the video Dr. Wible says, “Many modern groups, according to the molecular clock analysis, actually are, they should be, present in the Cretaceous fossil record. We can’t find them.” Actually Dr. Wible already found them, but does not recognize them for what they are. That’s a common problem in paleontology, largely due to taxon exclusion, that we’ve seen before here, here, here and here. And in dozens of other mislabeled clades, like multituberculates.

The Bininda-Edmonds et al. paper reports,
“Here we construct, date and analyse a species-level phylogeny of nearly all extant Mammalia to bring a new perspective to this question. Our analyses of how extant lineages accumulated through time show that net per-lineage diversification rates barely changed across the Cretaceous/Tertiary boundary. Instead, these rates spiked significantly with the origins of the currently recognized placental superorders and orders approximately 93 million years ago, before falling and remaining low until accelerating again throughout the Eocene and Oligocene epochs. Our results show that the phylogenetic ‘fuses’ leading to the explosion of extant placental orders are not only very much longer than suspected previously, but also challenge the hypothesis that the end-Cretaceous mass extinction event had a major, direct influence on the diversification of today’s mammals.”

The LRT agrees with the timing indicated by the DNA analysis
Placentals are indeed found in the LRT Cretaceous and Jurassic fossil record (Fig. 2). They were not recognized by traditional workers using smaller taxon lists, for what they were. The LRT minimizes taxon exclusion and so solves many paleo problems with an unbiased and wide gamut approach currently unmatched in the paleo literature. Extant birds have a similar deep time record based on a few recent finds.

Perhaps overlooked
there are currently large gaps spanning tens of millions of years, highlighting the rarity of fossil bearing locales. All Mesozoic mammals are rare.

The DNA tree
of the Bininda-Emonds team correctly splits monotremes from therians, but incorrectly nests ‘Afrotherians‘ with Xenarthrans at the base of all mammals followed by moles + shrews, bats + carnivores + hoofed mammals + whales, followed by primates and rodents. As anyone can see, this is a very mixed up order, placing small arboreal taxa in derived positions and stiff-backed elephants and in in basal nodes. This DNA analysis is not validated by the LRT.

To its credit, basal mammals in the LRT
greatly resemble their marsupial ancestors. Then derived mammals become generally larger, with derived tooth patterns, stiffer dorsal/lumbar areas and longer pregnancies with more developed (precocious) young.

Given three cladograms of placental relationships,
none of them identical, how does one choose which one is more accurate? Here’s my suggestion: look at each sister at each node and see where you best find a gradual accumulation of derived traits, without exception. And look at outgroups leading to basal members of the in group.

Some readers are still having a hard time realizing
that someone without direct access to fossils and without a PhD is able to recover a more highly resolved cladogram that features gradual changes between every set of sister taxa than trees published over the last ten years in the academic literature. I agree. This should not be taking place. This is not what I expected to find when I started this 7-year project. One tends to trust authority. It’s been an eye-opening journey. In nearly all tested studies overlooking relevant taxa continues to be the number one shortcoming. The LRT minimizes that issue. The number two problem is blind faith in DNA results. The number three problem is an apparent refusal to examine phylogenetic results to weed out mismatched recovered sister taxa.

The video spends also some time with Zhangheotherium,
which we looked at earlier here and here. The interviewed workers talk about the ankle spur, but as a venom injector, as in the duckbill, Ornithorhynchus, not as a membrane frame, like a calcar bone, as in bats.

The video considers Repenomamus a large Early Cretaceous mammal
but the LRT nests Repenomamus as a late-surviving synapsid pre-mammal, derived from a sister to Pachygenelus, as we learned earlier here.

PS. As touched on earlier,
many basal arboreal mammals were experimenting with gliding (e.g. Volaticotherium and Maiopatagaium), but only one clade, bats, experimented with flapping. This was, perhaps not coincidentally, during the Middle to Late Jurassic (Oxordian, 160 mya). Remember, these gliding membranes were all extensions of the infant nursery membrane found in colugos and other volatantians, not far from the basalmost placental, Monodelphis.

References
Bininda-Emonds ORP, et al., (9 co-authors) 2007. The delayed rise of present-day mammals. Nature 446(7135):507-512.
Wible JR, Rougier GW, Novacel MJ and Asher RJ 2007a. The eutherian mammal Maelestes gobiensis from the Late Cretaceous of Mongolia and the phylogeny of Cretaceous Eutheria. Bulletin of the American Museum of Natural History 327:1–123.
Wible JR, Rougier GW, Novacek MJ and Asher RJ 2007b. Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary.” Nature, 447: 1003-1006.

 

Resurrecting the clade ‘Volitantia’ Illiger 1811.

Volitantia
was defined by Illiger 1811 as Chiroptera (bats) + Dermoptera (colugos). Wikipedia authors consider this clade obsolete and polphyletic. The large reptile tree (LRT, 1233 taxa) nests these two taxa together in a monophyletic clade that also includes the pangolins and their closest ancestors (e.g. Zhangheotherium). We looked at their traditionally overlooked relationships a few days earlier here.

Szalay and Lucas 1996 reported, “We find support for the Volitantia in the nature of the shared derived similarities (and phyletically significant differences as well) in the elbow complex, and in Leche’s (1886) suggestion of the synapomorphus and unique presence (in non aquatic mammals) of an interdigital membrane of the hand in bats and colugos. They studied Chriacus and Mixodectes (not yet tested), not pangolins.

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

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

Like another clade traditionally considered obsolete,
Enaliosauria, that was resurrected by the LRT, Volitantia is likewise resurrected as a monophyletic clade, but it now includes the Pholidota (pangolins) according to LRT results.

Goodbye ‘Ferae’
The putative clade ‘Ferae‘ (pangolins + carnivorans) is not supported by the LRT because pangolins nest within the Volitantia.

As long-time readers know,
many traditional relationships between placental clades are not supported by the LRT, which continues to document a gradual accumulation of derived traits at every node in nearly full resolution for a wide gamut of tetrapod taxa.

Many arboreal mammals were experimenting with gliding
(e.g. Volaticotherium and  Maiopatagaium), but only one clade, bats, experimented with flapping. This was, perhaps not coincidentally, during the Middle to Late Jurassic (Oxordian, 160 mya). Remember, these membranes were all extensions of the infant nursery found in colugos and other volatantians, not far from the basalmost placental, Monodelphis. It is possible that all basalmost mammals had these membrane extensions and most of their ancestors lost them.

References
Illiger C 1811. Prodromus systematis mammalium et nivium additis terminis zoograhicis utriudque classis. Berlin: C. Salfeld.
Szalay F and Lucas SG 1996. The postcranial morphology of Paleocene Chriacus and Mixodectes and the phylogenetic  relationships of archontan mammals. Bulletin of the New Mexico Museum of Natural History and Science 7: 47 pp.

wiki/Volitantia

 

Cifelliodon: new echidna ancestor from the Early Cretaceous of Utah

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

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

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

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

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

As usual the LRT recovered a different nesting.

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

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

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

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

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

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

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

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

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

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

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

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

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

 

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

wiki/Cifelliodon

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

Multituberculate origins: Two views

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

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

Or is that solution possible
only due to taxon exclusion?

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

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

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

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

Figure 2. Cladogram of multituberculate origins according to the LRT

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

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

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

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

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

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

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

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

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

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

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

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

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

Eutherian phylogeny and niches

Over the past two weeks
I’ve been attracted to poor Bootstrap scores in the large reptile tree (LRT, 1151 taxa, subset Fig. 1) reexamining data and re-scoring where necessary. The result is a tree with improved Bootstrap scores. Herewith, the eutherian (placental) mammal subset of the LRT.

Figure 1. Subset of the LRT focusing on eutherian mammals. Colors refer to niches.

Figure 1. Subset of the LRT focusing on eutherian mammals. Colors refer to niches.

Sharp-eyed readers
will find the one node that is not resolved in this tree. Hint: the specimens lacking resolution are known from damaged skulls and a few post-cranial bones, so they can be scored for a relatively few character traits.

Curious readers
seeking more information for any genera listed above need only use it for a keyword in the search feature of this blog post (above).

Even though
the present tree has been improved, there is still room for improvement, probably around the weaker Bootstrap scores.

 

Heuristic testing
of just the basal tetrapods and lepidosauromprhs (370 taxa, 1 tree) took less than 51 seconds for a completely resolved subset of the LRT. Testing of just the archosauromorphs (781 taxa, 2 trees) took 8:45 minutes of computing time. So, 410 more taxa and one more tree take more time.

Taking it to the final step: Testing of the entire LRT (1151 taxa, 14 trees) took 1 hour 50 minutes. You can see computing time rises exponentially with increasing taxa, even with the next best thing to complete resolution.

So where did those 12 extra trees come from?
Should be from no more than 3 unresolved nodes. Here’s where PAUP fails (or becomes exhausted) with high taxon numbers:

Basalmost Synapsida  (Ellioitsmithia, Apsissaurus, Aerosaurus, etc.), Lepidosauria/Sphenodotia/Marine Younginiformes/Diadectomorpha + Pareiasauria/ Caseasauria/Basal Lepidosauromorpha/ Basal Archosauromorpha/ Basal Diapsida/ 13 more little clades/15 single taxa and…Hypuronector/Vallesaurus/Megalancosaurus

So with all those problems
(way more than expected) I ran PAUP again, sans mammals and terrestrial younginiforms (including protorosaurs and archosauriforms): so…. basically all the primitive taxa were included. Result: 565 taxa, 2 trees) took 5:54 minutes with loss of resolution between (Megazostrodon + Hadrocodium) and (Brasilitherium + Kuehneotherium), three of which are skull-only taxa just outside of the deleted mammals. No other tree topology changes are recovered.

Just so you know…
it seems that PAUP does exhaust itself in large cladograms, even in a simple Heuristic search.

 

Basal mammals: Guess what they evolved to become.

Can you guess
(or do you know) which of these taxa evolved to become a human? a killer whale? a rabbit? a giraffe? a bat? a pangolin?

Figure 1. Can you guess which of these taxa evolved to become a human? a killer whale? a rabbit? a giraffe?

Figure 1. Can you guess which of these taxa evolved to become a human? a killer whale? a rabbit? a giraffe?

H. Onychodectes – basal to all large herbivorous mammals, including giraffes.

G. Maelestes – basal to tenrecs and toothed whales.

F. Tupaia – basal to the gnawing clade including rodents and rabbits.

E. Ptilocercus – basal to Primates, including humans (but note the loss of all premaxillary teeth in this extant taxon).

D. Palaechthon – basal to flying lemurs, bats and pangolins.

C. Monodelphis – basal to all placental mammals.

B. Asioryctes – basal to Monodelphis and all placental mammals.

A. Eomaia – basal to all therian mammals (placentals + marsupials).

These are the basalmost taxa
in various clades of Eutherian (placental) mammals. Not a lot of difference to start (which makes scoring difficult). So much potential at the end. Eomaia goes back to the Early Cretaceous, so it’s not difficult to imagine the radiation of these taxa throughout the Cretaceous.

This falls in line with
the splitting of the African golden mole (Chrysochloris) from its South American sister, Necrolestes, a diversification, migration and split that had to happen before Africa split from South American in the Early Cretaceous.

Sharp-eyed readers
will note the re-identification of bones and teeth in Palaechthon, Ptilocercus and Tupaia. It’s been a long weekend trying to figure out long-standing problems in this portion of the LRT. Some of these taxa were some of the first studied and my naiveté was the source of the earlier disinformation, now corrected. If you see any errors here, please advise and, if valid, repairs will be made.