Andrewsiphius enters the LRT outside walking whales, with tenrecs

Updated August 29, 2021
with new data on Andrewsiphius: a photo of the skull (Fig. x), humerus and femur. Note the differences between the bones and the diagram (Fig. 1).

Figure x. Andrewsiphius skull

This is yet another case
of taxon exclusion and therefore… another excellent subject for a PhD dissertation!

According to Wikipedia,
“Andrewsiphius (Fig. 1) is an extinct remingtonocetid early whale known from the Eocene.” 

Figure 1. The reconstructed and restored skull of Andrewsiphius from Theiwissen 2009 and colorized using DGS methods here. Tenrec skull is to scale.

Not quite.
In the large reptile tree (LRT, 1695+ taxa, subset Fig. 2), which tests more taxa, Andrewsiphius nests as the proximal outgroup to Pakicetus (Fig. 3), the most primitive known walking whale. Prior studies omitted tenrecs and other basal taxa recovered by the LRT.

Andrewsiphius also nests as the proximal outgroup to extant tenrecs (Figs. 3, 5). So, if Andrewsiphius IS a walking whale, so are living tenrecs.

Andrewsiphius was derived from basal leptictids, like Leptictis.  One of these leptictids is extant, the long-nosed elephant shrew, Rhynchocyon (Fig. 6), ancestor to the misunderstood giant predator, Andrewsarchus.

Figure 2. Subset of the LRT focusing on Odontoceti and their ancestors. Here is the nesting of Eocene Andrewsiphius basal to extant tenrecs between leptictids and pakicetids.

Figure Y. Taxa added August 29, 2021 and the new data from the skull photo (Fig. x) change things slightly in this subset of the LRT.

Andrewsiphius sloani (originally Protocetus sp. Salni and Mishra 1972; Thewissen and Bajpal 2009; Eocene 50mya est. 3m) was originally considered an early whale with feet, but here nests basal to smaller tenrecs, in a clade between Leptictis and Pakicetus. The rostrum was long and narrow with molars simplified and premolarized. The orbital notch is quite small, as in other tenrecs. The narrow sagittal crest is distinct from the somewhat broader crania found in living tenrecs, but similar to extinct lepitictids including Andrewsarchus.

Figure 3. Skulls of transitional taxa between tenrecs and Odontoceti (toothed whales). These include Tenrec, Lepticitidium, Pakicetus, Rhodhocetus and Orcinus.

According to Wikipedia,
“Andrewsiphius and Kutchicetus (Fig. 4) share several characteristics not present in other remingtonocetids: an elongated snout that is higher than it is wide; foramina (small holes) on the tip of the snout suggesting the presence of whiskers; eyes located dorsally near the cranial midline, resulting in an appearance of a mammalian crocodile; and a very large sagittal crest overhanging the back of the skull. Other characteristics make them distinct: the second and third upper and lower premolars are double-rooted in Andrewsiphius but single-rooted in Kutchicetus; the large diastemata in the former are absent the latter; and the tail vertebrae are more robust in Andrewsiphius.”

Figure 4. Kutchicetus, a sister to Andrewsiphius.

Molars go through a massive reversal in odontocetes and their ancestors,
from multi-rooted, multi-cusped back to single-rooted, single-cusped, as in basal reptiles.

Figure 5. Tenrec museum mount. The long snout of archaeocete and odontocete whales is already evident here.

Tenrec ecaudatus (Lacépède 1799; extant; common or tailless tenrec; 26-39cm; Fig. 5) is a Madagascar predator that gives birth to as many as 32 young and is able to hibernate for up to 9 months. Gould 1965 found evidence for echolocation in tenrecs.

Figure 6. Rhynchocyon, a living elephant shrew, is a living leptictid.

Rhynchocyon chrysopygus (Peters 1847) is the extanct golden rumped elephant shrew that nests here with the tenrecs, unlike another ‘elephant shrew’, Macroscelides, which nests with tree shrews. In Rhynchocyon the cranium is not expanded, the rotrum is long and the orbit is set posteriorly on the skull. It can run fast on narrow limbs as it spends its day seeking invertebrates in leaf litter.

Previous clades of placentals
(Carnivora, Volitantia, Primates, Glires, Scandentia) are derived from arboreal tree shrews descending from Early Jurassic sisters to arboreal Caluromys. The tenrec-odontocete clade is the most primitive clade of placentals that is terrestrial, as are all that follow except derived members of the Xenarthran (small sloths and anteaters) which exceptionally return to the trees.

I hope this stirs more interest into the tenrec origin of Odontoceti
documented in the paper “Triple Origin of Whales” available online here. It was considered a ‘just so’ story and rejected when originally submitted because it explained everything the experts had missed. The nesting of Andrewsiphius as a large Eocene tenrec supports and cements the current hypothesis of interrelationships recovered by the LRT.

If you know of any earlier iteration of this hypothesis,
let me know so I can promote it.

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References
Gould E 1965. Evidence for Echolocation in the Tenrecidae of Madagascar
Proceedings of the American Philosophical Society 109 (6): 352-360. online here.
Sahni A and Mishr VP 1972. A new species of Protocetus (Cetacea) from the Middle Eocene of Kutch, western India. Palaentology 15(3):490–495.
Thewissen JGM and Bajpai S 2009. New skeletal material of Andrewsiphius and Kutchicetus, two Eocene cetaceans from India. Journal of Palaeontology 83(5):635–663.

tenrecs-and-echolocation/

wiki/Leptictis
wiki/Rhynchocyon
wiki/Hemicentetes
wiki/Tenrec
wiki/Andrewsiphius

Crayssac basal pterosaur tracks? …or tenrec tracks?

Earlier we looked at Mazin and Pouech 2020
who claimed they had discovered “the first non-pterodactyloid pterosaurian trackways.” At the time, only the abstract was available to discuss and criticize.

Nine years ago
Peters 2011 published anurognathid tracks, which makes them the first non-pterodactyloid pterosaurian trackways published. Notable by its exclusion, Mazin and Pouech 2020 did not cite, “A catalog of pterosaur pedes for trackmaker identification” (Peters 2011), confirming Dr. S. Christopher Bennett’s threat, “You will not be published. And if you are published, you will not be cited.”

Now that I have seen the paper and the tracks,
(Figs. 1, 2) let’s determine what sort of tetrapod made those tracks named, Rhamphichnus crayssacensis, because they don’t look like other pterosaur tracks, as workers (see below) acknowledge.

Diagnosis from Mazin and Pouech 2020:
“Quadrupedal trackway with tridactyl digitigrade manus-prints and pentadactyl plantigrade to digitigrade pes-prints. Subparallel manus digit-prints orientated anteriorly. Pentadactyl pes-prints with more or less divergent digit prints. Pedal digit V divergent and postero-laterally rejected. Manus trackway slightly to clearly wider than the pes trackway.”

Distinct from typical pterosaur manus tracks:

1. tridactyl digit prints are subparallel (rather than widely splayed)
2. digits are oriented anteriorly (rather than laterally to posteriorly)
3. digits sometimes include additional medial and lateral impressions (never seen in other pterosaur tracks)
4. no claw marks are present (that seems wrong based on Fig. 1)
5. the manus impression is just anterior to the pes impression (rather than laterally and posteriorly, as in other pterosaur tracks)

Figure 1. Images from Mazin and Pouech 2020. Some manus tracks have at least four digits.

There are many
basal and derived pterosaurs with pedal digit 2 (or 2 and 3) the longest, distinct from Triassic pterosaurs. These were all examined and rejected as potential trackmakers matching Rhamphichnus for various reasons.

I also looked at 1600+ non-pterosaur trackmakers
due to the many unexpected traits (see list above) present in the Rhamphichnus tracks.

First and foremost,
the pterosaur antebrachium (radius + ulna) could not be pronated to produce anteriorly-oriented Rhamphichnus tracks. Due to folding and flying issues, pterosaurs, like birds, do not have the ability to pronate and supinate the wing. That’s why all pterosaur manus tracks are oriented laterally with fingers at full extension, impressing into the substrate. That manus digit 3 is often rotated posteriorly is a clue to its lepidosaurian ancestry. These facts form the hypothesis of a secondarily quadrupedal configuration for some, but not all pterosaurs.

One overlooked trackmaker stood out as a good match
for Rhamphichnus: the tenrec, Tenrec (Fig. 2), a small digitigrade quadrupedal mammal currently restricted to Madagascar. The medial and lateral manual digits are shorter than 2-4, which are parallel in orientation.

Figure 2. Rhamphichnus tracks compared to a Tenrec trackmaker. The brevity of pedal digit 5 is a mismatch, but a related taxon, Leptictidium, likewise reduces pedal digit 5.

One of those Tenrec sisters,
Rhynchocyon, greatly reduces manual digits 1 and 5, but pedal digit 3 is the longest.

Another Tenrec sister,
Leptictidium (Fig. 3), has a pes with a reduced pedal digit 5, but a short digit 2, but the manus is also a good match for Rhamphichnus. So there is great variation in the pes of tenrec clade members. Still, a small tenrec-like mammal remains a more parsimonious trackmaker than any Late Jurassic pterosaur. They were able to pronate the manus!

Figure 3. Elements of Leptictidium from Storch and Lister 1985.

Due to taxon exclusion,
Mazin and Pouech 2020 did not consider alternative trackmakers for the pterosaur-beach Rhamphichnus tracks that don’t match other pterosaur tracks or extremities. Now we’re stuck with an inappropriate name for these Late Jurassic tenrec tracks.

A late Jurassic tenrec?
The large reptile tree (LRT, 1637 taxa) supports the probability that a sister to Tenrec was present in in the Late Jurassic based on the coeval presence of derived members of Glires (Multiturberculata). Placental mammal fossils remain extremely rare in the Mesozoic, but these impressions add to their chronology.

It is worth repeating, due to the subject matter,
the Crayssac pterosaur beach still includes the pes of the JME-SOS 4009 specimen attributed to Rhamphorhynchus, as mentioned earlier. Here it is again (Fig. 4).

Figure 4. Crayssac track different from all others. Inset: Pes of Rhamphorhynchus muensteri JME-SOS 4009, no. 62 in the Wellnhofer catalog

twitter.com/Mark Witton mistakenly reports:
“Turns out we’ve been over-thinking it (pedal digit 5): it just lays flat on the ground during walking, like a regular toe.”

“For one, the walking fingers face forward, not sideways, as in pterodactyloids. This seems weird, but it turns out that non-ptero wing fingers fold roughly perpendicular to the walking digits.”

These basic bungles by a PhD pterosaur worker
demonstrate the dominance of myth-making among purported experts due to accepting published results like a journalist, without testing them, like a scientist. Dr. Witton’s 2013 pterosaur book is full of similar mistakes reviewed here in a seven-part series.

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References
Mazin J-M and Pouech J 2020.The first non-pterodactyloid pterosaurian trackways and the terrestrial ability of non-pterodactyloid pterosaurs. Geobios 16 January 2020. PDF
Peters, D. 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification
Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605

https://pterosaurheresies.wordpress.com/2020/01/18/first-non-pterodactyloid-pterosaurian-trackways-ever-described-no/

 

SVP 2018: Where to nest and what is the Anagalidae?

López-Torres and Fostowicz-Frelik seek to understand
the phylogenetic position of the Anagalidae, “an enigmatic and poorly studied group of primitive members of Euarchontoglires known from the Palaeogene of China.” 

On the other hand
this clade is well understood in the large reptile tree (LRT, 1311 taxa, subset Fig. 3). The genus Anagale (Fig. 1) is basal to Andrewsarchus, tenrecs and odontocetes, taxa notably missing from traditional lists (see below). Taxon inclusion is the key to understanding this and all other tetrapod clades.

First of all, some traditional clade members:

1. Traditional Euarchontoglires = rodents, lagomorphs (rabbits) treeshrews, colugos and primates.
2. Traditional Anagalidae = elephant shrews, rodents and lagomorphs.
3. Traditional Anagaloidea = also includes Zalambdalestes (a Solenodon (clade = Glires) sister in the LRT).

None of these groupings
are recovered in the LRT (which is genus to specimen-based).

Figure 1. Anagale nests at the base of the tenrec – odontocete clade, not with rabbits, in the LRT.

All prior clade memberships suffer from taxon exclusion.
Anagale (Figs, 1, 2) itself nests at the base of the tenrec – odontocete clade (Fig. 2) a hypothesis first recovered in the LRT.

Where Anagale and kin nest in the LRT:

1. Anagalidae = Anagale (Fig. 2), some but not all elephant shrews, tenrecs, pakicetids, toothed whales and their kin. In other words, this is the tenrec-odontocete clade.

Figure 2. Odontoceti (toothed whale) origin and evolution. Here Anagale, Andrewsarchus, Sinonyx, Hemicentetes, Tenrec Indohyus and Leptictidium precede Pakicetus. Maiacetus and Orcinus are aquatic odontocetes.

López-Torres and Fostowicz-Frelik 2018 report:
“Anagalids were originally suggested to be closely related to modern treeshrews, lagomorphs, some primitive eutherian groups such as zalambdalestids and pseudictopids, and Macroscelidae (within the broader concept of ‘Anagalida’), but that idea was later rejected, especially with growing evidence of molecular relationships among major mammalian clades and the generally accepted monophyly of Glires. Our study presents a new, more comprehensive phylogenetic analysis based on 190 dental characters.”

Figure 5. Subset of the LRT focusing on the tenrec/odontocete clade with several whales added.

Dental characters only???
Yikes. The authors continue: “The resulting strict consensus tree (based on 76 equally-parsimonious trees) disagrees with the previous conception of anagalid monophyly. Instead, anagalids are heavily paraphyletic, appearing as several offshoots at the base of Glires, which suggests that anagalids could be considered stem Glires.” 

The LRT is nearly fully resolved and anagalids are not stem Glires.
They are the sisters to Glires. Add these relevant taxa (Fig. 2) and let us know if your tree recovers the same tree topology.

These authors need to expand their taxon and character lists.
Contra tradition, Anagale and kin have little to do with rodents or rabbits. Add taxa. Let the taxa nest where they want to. Don’t limit the taxon list. Soon this clade will be well understood, no longer an enigma.

References
López-Torres S and Fostowicz-Frelik L 2018. The phylogenetic position of the Anagalidae within Euarchontoglires and its implication for the evolution of Glires and Euarchonta. SVP abstract.

wiki/Euarchontoglires
wiki/Anagaloidea

Fleshing out Andrewsarchus, the giant elephant shrew, close to tenrecs

Updated July 15, 2022
with more taxa and corrections to scoring errors. Click here for the update.

All we know of Andrewsarchus
is its skull — without a mandible. A few days ago the dentary of a sister taxon, Sinonyx, was added to the skull of Andrewsarchus ((Osborn 1924; middle Eocene, 45 mya; AMNH 20135; 83cm skull length; also see Fig. 1) just to see if it would fit.

Before that…
everyone forever has always fleshed out Andrewsarchus like a giant bear/dog, moving the eyeballs to the top and giving it a bear/dog nose. Image googling “Andrewsarchus“ will give you an idea what a widespread and accepted tradition that has been. I even followed that tradition back in 1989 in the book Giants, which you can see here as subset 1 of a larger pdf of the entire book.

Unfortunately,
Andrewsarchus does not nest with bears, dogs or mesonychids. It nests with tenrecs and Rhynchocyon (Fig. 2.), one type of elephant shrew. (The other type of elephant shrew is unrelated, as we learned here, Fig. 2). Tenrecs have a long flexible nose.

So, here, without further adieu
is a first shot at adding tenrec soft tissue to the skull of Andrewsarchus (Fig. 1). Is it close to being correct? I hope so, given the present evidence.

Figure 1. Andrewsarchus restored as giant tenrec alongside, Canis, the wolf to scale. Note the small and low-set eyes on Andrewsarchus. The mandible comes from Sinonyx. Note the natural tilt of the canid skull permitting binocular vision. Andrewsarchus had low-set eyes, rather un-canid-like. We have to give up the bear-dog restoration of Andrewsarchus.

Now, just imagine the post-crania…
and the best clue we have is the living tenrec, Rhynchocyon (Fig. 2) with long legs, robust torso and short tail, only ten times bigger.

Figure 2. Rhynchocyon (above) and Macroscelides (below) the other type of elephant shrew compared. Though both are considered elephant shrews, they nest in separate major mammal clades in the LRT.

Maybe it’s time to 
give up the bear-dog restoration for Andrewsarchus and give it the giant  tenrec restoration it deserves based on phylogenetic bracketing and phylogenetic analysis.

Figure 3. The skull of Andrewsarchus mated to the body of Leptictis to make a chimaera.

References
Osborn HF 1924. Andrewsarchus, giant mesonychid of Mongolia. American Museum Noviattes 146: 1-5.

These two images of Paratriisodon added January 5, 2022.

Figure 4. Paratriisodon mandible and palate compared to Andrewsarchus.

Figure 5. Mandible of Paratriisodon is a good match for the skull of Andrewsarchus, and a good match for the mandible of Rhynchocyon, the elephant shrew.

An imaginary mandible for Andrewsarchus

Updated July 15, 2022
with more taxa and corrections to scoring errors. Click here for the update.

All I did
was take the mandible from sister Sinonyx and scale it to Andrewsarchus (Fig. 1; Osborn 1924). I also added a patch to extend the apparently broken and missing posterior nasals over the fontanelle between the frontals because that’s how far the nasal extends in Sinonyx.

See how sometimes
you don’t ‘see’ something until after you see it in a sister?

Figure 1. Andrewsarchus with Sinonyx mandible. The lower canine helps constrain the shape of the missing upper canine. Note the transparent extension of the posterior nasals to cover up the fontanelle between the frontals, as in Sinonyx.

BTW
it bothered me that Sinonyx and Andrewsarchus were so much larger than their sisters, especially their closest sister, a type of elephant shrew, Rhynchocyon. Moreover, several traits appear to be homologous. So I retested the relationship of Sinonyx and Andrewsarchus with mesonychids and I retested them with prejudice. Any traits that could relate Sinonyx and Andrewsarchus with mesonychids I scored that way.

In the end,
I was not able to nest Sinonyx and Andrewsarchus with mesonychids.

Furthermore
when I removed all tenrec and odontocete sisters from the tenrec clade (see Fig. 2), leaving only Sinonyx and Andrewsarchus alone they still did not nest with mesonychids, but kept their node unchanged between the Ptilocercus clade and Onychodectes.

Figure 2. Tenrec-Odontocete clade with Leptictis now nesting with the elephant shrew Rhynchcyon and the long-tailed tenrecs nesting with the short tailed tenrecs, basal to Pakicetus. This tree moves Sinonyx closer to Pakicetus. Indohyus has already been associated with pakicetids.

Testing like this
brought certain problems to the surface. The current tree has been improved over earlier versions.

Here’s how the tenrec clade now stands:
(Fig. 2) Leptictis and the elephant shrew Rhynchocyon now nest together. They are both similar in size and build.

Giant Andrewsarchus and smaller Sinonyx still nest together. Would still like to see some post-crania for  these two.

The two living short-tailed terrestrial tenrecs, Hemicentetes and Tenrec now nest with two extinct long-tailed aquatic tenrecs, Lepticitidium and Indohyus. The latter has already been associated with pakicetids in the literature  (Rao 1971, Thewissen et al. 2007.)

Likewise Sinonyx and Andrewsarchus have already been associated with the origin of whales in the literature. The new tree topology brings them closer to Pakicetus.

Early members of the tenrec clade
were insectivore speedsters with long slender legs, based on the habits of Rhynchocyon. More derived tenrecs like Tenrec, are not speedy and Hemicentetes is protected with spines. Leptictidium had much longer hind limbs than fore limbs and was likely bipedal. Indohyus had subequal limbs so likely remained a quadruped. Tradtionally Indohyus has been considered an artiodactyl, but given the opportunity to nest with artiodactyls in the LRT, it does not do so.

Perhaps the most convergent clade
By all the present evidence, some tenrecs converged with rabbits and elephant shrews, some with mesonychids, others with artiodactyls and still others with mysticete whales. It’s a pretty amazing and woefully under appreciated clade.

It is interesting to consider the possibility
that since both elephant shrews and tenrecs have a proboscis that extends beyond the jaw line, it is possible that early land whales, Andrewsarchus and Sinonyx, might have had a similar long nose. Some of these taxa might have used such a snorkel to breathe while underwater, just below the surface — or — the long nose was the first soft tissue to disappear during the transition, because whales have no such nose.

References
Osborn HF 1924. Andrewsarchus, giant mesonychid of Mongolia. American Museum Noviattes 146: 1-5.
Rao AR 1971. New mammals from Murree (Kalakot Zone) of the Himalayan foot hills near Kalakot, Jammu and Kashmir state, India. Journal of the Geological Society of India. 12 (2): 124–34.
Thewissen JGM, Cooper LN, Clementz MT, Bajpai S and Tiwari BN 2007. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature 450:1190-1195.

wiki/Leptictidium
wiki/Indohyus

Splitting up the Tenrecidae

Everyone agrees
that the current list of genera within the clade Tenrecidae are a diverse lot. Asher and Hofreiter 2006 report, “With the exception of a single genus of shrew (Suncus), insectivoran-grade mammals from Madagascar are members of the family Tenrecidae. This group of placental mammals consists of eight genera endemic to Madagascar and two from equatorial Africa and is remarkably diverse, occupying terrestrial, semi-arboreal, fossorial, and semiaquatic niches.” Finlay and Cooper 2015 sought to quantify that diversity. They report, “There are tenrecs which resemble shrews (Microgale tenrecs), moles (Oryzorictes tenrecs) and hedgehogs (Echinops and Setifer tenrecs). The small mammal species they resemble are absent from the island.”

Olson and Goodman 2003 report,
“Morphological studies have not support [genomic studies], however and the higher-level origins of both tenrecs and golden moles remain in dispute.” However, they limited their report to tenrecs, assuming a single origin.

According to Poux et al. 2008
Tenrecidae includes the following clades:

1. Potamogalinae includes the genera Potamogale and Micropotamogale
2. Tenrecinae includes the genera Tenrec, Echinops, Setifer and Hemicentetes;
3. Oryzorictinae includes the genera Oryzorictes, Limnogale and Microgale;
4. Geogalinae: includes Geogale. 

What makes a tenrec a tenrec?
Wikipedia provides no clue. And the academic literature has been similarly bereft. Instead all authors emphasize the diversity in this clade. The traditional and recent hypotheses of common ancestry are based on genomic studies that provide no clues to skeletal similarities and differences. As mentioned earlier, the anus and genitals revert to a single opening, as in golden moles and the scrotum reverts to an internal arrangement, distinct from many other mammals, but similar to odontocetes and hippos + mysticetes. The permanent dentition in tenrecs tends not to completely erupt until well after adult body size has been reached. Some tenrecids [which ones?] erupt their molars before shedding any deciduous teeth other than the third milk incisors.

Helping to define tenrecs, MacPhee 1987 reported,
“Shrew tenrecs are sometimes considered to be the most primitive members of Tenrecoidea. They outwardly resemble other unspecialized soricomorph insectivores (e.g., Crocidura) in possessing dense, rather velvety fur, abundant vibrissae, tiny eyes, short pentadactyl limbs slung under a long, fusiform body, and an elongated skull tapering into a narrow rostrum. Notably, like other tenrecs they retain ancient plesiomorphies that have been lost in virtually all other eutherian lineages (including true shrews), such as variable and rather low body temperature and cloacae in both sexes.”

Genomic analysis
by Asher and Hofreiter 2006 found Tenrecidae to be monophyletic. The proximal outgroup taxon was  Chrysospalax, a highly derived genus within the Chrysochloridae, or golden moles. In like fashion, Elephantulus, an elephant shrew, and Procavia, the hyrax, were successive outgroups as members of the Afrotheria, a diverse clade that only arises in genomic analyses and seems to provide a long list of oddly matched sister taxa.

Figure 1. Subset of the LRT highlighting tenrecs and former tenrecs

By contrast
The large reptile tree (LRT, Fiig. 1) found the members of the former Tenrecidae so diverse that they nested in three different clades, apart from one another.

1. Potamogale and Micropotamogale (both from Africa) nested with the shrew, Scutisorex within Glires.
2. Echinops, Limnogale and Microgale (all from Madagascar) nested with the hedgehog, Erinaceus, despite lacking spines and also within Glires,
3. Hemicentetes and Tenrec (both from Madagascar) nested with several fossil leptictids basal to odontocetes (toothed whales)  among extant taxa.

Those taxa nesting in Glires
have enlarged central incisors lacking in Hemicentetes and Tenrec, which have a longer, more pointed rostrum with relatively tiny incisors. Shifting aquatic Limnogale to nest with aquatic Potamogale adds 13 steps, so water habits are convergent.

Genomic sequencing lumps

1. Limnogale and Microgale, as in the LRT.
2. Micropotamogale and Potamogale, as in the LRT.
3. Hemicentetes and Tenrec, as in the LRT.

Dissimilarities in DNA and trait-based tree topologies arise
with greater phylogenetic distance. The LRT permits one to include fossil taxa and to observe changes in traits that genomic codes can not do.

In the LRT
Hemicentetes and Tenrec are surrounded by fossil lepitictids. Asher and Hofreiter do not list odontocetes in their analysis, but these nest with Hemicentetes and Tenrec among living taxa in the LRT. Rose 1999 ran an analysis of postcranial traits that included Leptictidae and Tenrecidae. It nested Tenrecidae between Solenodon and shrews and Leptictidae between Tupaia and Zalambdalestes, distinct from the LRT which includes more characters, more body parts and more taxa. In the LRT Lepticitis and Lepticitidium nest with Andrewsarchus and Tenrec between them.

See what happens when you include more taxa? Topologies change.

Body masses of tenrecs
Finlay and Cooper 2015 report, “Body masses of tenrecs span three orders of magnitude (2.5 to >2,000 g): a greater range than all other families, and most orders, of living mammals.” The new phylogenetic set will not include the tiniest shrew tenrecs, but it will include the sperm whale weighing in at 57,000 kg.

If anyone has access to 
skeletal images of Geogale and/or Oryzorictes, please send them my way in order to add them to the LRT.

When you use molecules

1. you don’t use traits. Therefore you lump and divide taxa based on combinations of DNA you can’t see or argue about.
2. you don’t use fossils. Therefore you can’t tell which fossil taxa gave rise to which other fossil and extant taxa.
3. you often recover very odd sister taxa that anti-evolutionists love to use in their PowerPoint lectures. That gives them power over audiences who want to see the evidence of evolution, which the LRT provides.

We have to own up to the shortcomings of DNA
while we still can. Great for criminals and baby daddies, bad for turtles and archosaurs. I think we need to get back to morph studies in mammal phylogeny. Molecules have given us very weird and unwieldy answers that don’t start small, extinct and simple and end large, extant and exotic, like the LRT does.

Authority
Granted if have not seen any specimens first hand, nor am I anywhere near a tenrec expert. Like Galileo, I am metaphorically tossing balls off the Tower of Pisa, coming to my own conclusions following repeatable observations. Because you can do that in Science. Others may argue methods and observations, but they will have to duplicate the list of taxa before they can do so with their own authority. This post provides an expanded taxon list and tentative insights for future studies.

References
Asher RJ and Hofreiter M 2006. Tenrec phylogeny and the noninvasive extraction of nuclear DNA. Systematic Biology 55(2):181-194. 
Asher RJ 2007. A web-database of mammalian morphology and a reanalysis of placental phylogeny. BMC Evol Biol. 7: 108-10 online
Asher  RJ and Helgen KM 2010. Nomenclature and placental mammal phylogeny. BMC Evolutionary Biology 10:102 online
Du Chaillu P 1860. Descriptions of mammals from equatorial Africa. Proceedings of the Boston Society of Natural History, 7, 358–369.
Eisenberg JF and Gould E 1970. The tenrecs: a study in mammalian behavior and evolution. Smithsonian Institution Press, Washington, DC. 138 pp. PDF online
Finlay S and Cooper N 2015. Morphological diversity in tenrecs (Afrosoricida, Tenrecidae): comparing tenrec skull diversity to their closest relatives. PeerJ 3:e927; DOI 10.7717/peerj.927
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
MacPhee RDE 1987. The shrew tenrecs of Madagascar: systematic revision and Holocene distribution of Microgale (Tenrecidae, Insectivora).
Martin WCL 1838. On a new genus of insectivorous mammalia. Proceedings of the Zoological Socieety, London, 6:17.
Mouchaty SK, Gullberg A, Janke A, Arnason U 2000. Phylogenetic position of the Tenrecs (Mammalia: Tenrecidae) of Madagascar based on analysis of the complete mitochondrial genome sequence of Echinops telfairi. Zoologica Scripta. 2000, 29 (4): 307-317. 10.1046/j.1463-6409.2000.00045.x.
Nicoll M 1985. The biology of the giant otter shrew *Potamogale velox*. National Geographic Society Research Reports, 21: 331-337.
O’Leary, MA et al. 2013. The placental mammal ancestor and the post-K-Pg radiation of  placentals. Science 339:662-667. abstract
Olson LR and Goodman SM 2003. Phylogeny and biogeography of tenrecs. Pp. 1235-1242 in Natural History of Madagascar, SM Goodman & JP Benstead (eds.), University of Chicago Press, Chicago.
Poux C, Madsen O, JGlos J, de Jong WW and Vences M 2008. Molecular phylogeny and divergence times of Malagasy tenrecs: Influence of data partitioning and taxon sampling on dating analyses. BMC Evolutionary Biology 8:102. Open Access
Rose KD 1999. Postcranial skeleton of Eocene Leptictidae (Mammalia), and its implications for behavior and relationships. Journal of Vertebrate Paleontology 19(2):355-372.
Suárez R, Villalón A, Künzle H and Mpodozis J 2009. Transposition and Intermingling of Gαi2 and Gαo Afferences into Single Vomeronasal Glomeruli in the Madagascan Lesser Tenrec Echinops telfairi. PLoS ONE 4(11): e8005. doi:10.1371/journal.pone.0008005

Tenrec bones website here (Microgale and Tenrec skulls and jaws)

The ‘hedgehog’ tenrecs: they nest with hedgehogs

This is a think piece.
You’re going to be faced with

1. a geographically inspired return of the cloaca (proposed heresy) or
2. MASSIVE convergence involving everything but the cloaca (current and traditional paradigm)

Arguments will be presented.
You decide which is more parsimonious. We may need to bring in the DNA guys here, and I would welcome them! I don’t think such a study involving a wide range of purported and actual tenrecs has been proposed or done yet. Let me know as I am unaware of published work on this subject.

The present problem had its genesis in whale phylogenetic studies.
Earlier, from skeletal data, the the large reptile tree (LRT) nested odontocete (toothed) whales with tenrecs and mysticete (baleen) whales with hippos and desmostylians.

However
current DNA studies do not support the tenrec – odontocete relationship — perhaps because workers used the lesser hedgehog tenrec (Echinops telfairi, Martin 1838, Figs. 2, 3) in their DNA studies. Echinops is traditionally considered a tenrec, but it may not be one based on bones (Fig. 3) and massive homology/convergence with the European hedgehog, Erinaceus (Figs. 1, 3).

Figure 1. European hedgehog, Erinaceus, a member of Glires.

It’s the single genital slit (similar to a monotreme cloaca) that seems to matter most
in tenrec studies. Plus the location: Madagascar.

Figure 2. Madagascar hedgehog tenrec, Echinops, perhaps not a tenrec, but another member of hedgehog family within Glires.

There are two extant hedgehog tenrecs (HHTs):
the greater HHT (Setifer = Ericulus setosus) and the lesser HHT (Echinops telfari). Their skulls are not that different from each other, except in size. They have similar skeletons and spines coats. So we’ll focus on the lesser HHT as other workers have done before.

The problem is
the large reptile tree (LRT) nests Echinops rather convincingly with hedgehogs, like Erinaceus, within Glires, not with tenrecs like Tenrec (Fig. 1). Shifting Echinops to the tenrecs adds 30 steps to the LRT. Shifting the entire tenrec clade (ncluding the odontocetes) to the hedgehogs adds only 12 steps.

We’ve seen something like this before
when the purported tenrec, Potamogale (Du Chaillu 1860, Nicoll 1985; extant), the giant otter shrew that was supposed to be a tenrec, instead nested rather convincingly with shrews, far from tenrecs. It, too, has a cloaca.

Maybe it’s because they’re all from Madagascar.
Not sure what it is about that island that takes a perfectly good set of genital and anal openings and reverts them back into a single primitive cloaca. But that appears to be happening here among unrelated taxa, by convergence.

Among mammals
monotremes have a cloaca and that is most likely the primitive condition, as a cloaca is found in all other reptiles. Most marsupials separate the anus and genitals, so no cloaca is present — except in the very derived marsupial moles. Marsupials are basal to placentals according to the LRT, so any appearance of a cloaca in placentals is a reversal. Thus the Madagascar hedgehogs, the African golden moles and giant otter shrews (Potamogale) that redevelop a cloaca are examples of phylogenetic reversals.

So you  have a choice in nesting these purported tenrecs:

1. Do you follow the bones and other soft (and prickly, Fig. 2) tissue with the exception of the cloaca?
2. Or do you follow the cloaca alone? Current taxonomy and experts for over a century favor this choice.

To my knowledge,
mtDNA studies have not been conducted yet to resolve interrelationships among tenrecs and other mammals. If Echinops is indeed a hedgehog, then tenrecs have not been genetically tested against odontocetes. In fact, tell me if I’m wrong, but this may be the first time such a study has been conducted on morphology alone. Asher and Hofreiter 2006 stated at the time: “Due in part to scarcity of material, no published study has yet cladistically addressed the systematics of living and fossil Tenrecidae (Mammalia, Afrotheria).”

Echinops was employed by Mouchaty et al. 2000. Echinops might have been used by Meredith 2011 and Song 2012 to nest tenrecs with golden moles (Chrysocloris) as Afrotheres, related to elephants (Elephas) and hyraxes (Procavia). I don’t see any other tenrecs being used in molecular studies.

Echinops was recently employed by
Suarez 2009 in a study of the vomernasal system (VNS). The distribution of both vomernasal pathways in Eutheria was found to be present in rodents and Echinops, but not in other tested eutherians, none of which included other tenrecs. Of course, hedgehogs nest with rodents in the LRT.

Figure 3. The skulls of Erinaceus (above), Echinops (middle) and Tenrec (below), compared. Note the large premaxillary teeth common to all members of the Glires to the exclusion of other clades, including Tenrecidae. The anterior maxillary tooth of Erinaceus might be a canine, but it is not at the anterior rim of the maxilla, where one expects a canine.

Let’s compare
a hedgehog, a tenrec and the lesser hedgehog tenrec and perhaps you’ll see that a mistake was made over 100 years ago that continues to adversely affect phylogenetic analyses today. Perhaps a member of Glires has been long considered a member of Tenrecidae by virtue of its location, Madagascar, and its cloaca.

The European hedgehog
Erinaceus europaeus (Linneaus 1758; 20-30cm; extant) this omnivore can roll itself into a ball, erecting its spines for defence. Unlike most Glires, the hedgehog does not have a diastema. The jugal is very tiny in this clade.

The lesser hedgehog tenrec
Echinops telfairi (Martin 1838; extant, 13-17 cm) the lesser or pygmy hedgehog tenrec is widely considered a tenrec, but here it nests with hedgehogs and other Glires including rodents. This omnivore is restricted to Madagascar, home of severalt tenrecs. Note the large canines, like tenrecs and unlike hedgehogs. Note the large premaxillary teeth, like hedgehogs and unlike tenrecs. Unlike tenrecs, the ears are prominent. Like tenrecs, the jugal is absent.

Given that the Madagascar mammals with a cloaca
all do some burrowing, I wonder if the genitals and anus retreated beneath the cover of a single opening in order to keep dirt out? If that’s not the answer, I wonder what the common thread is that these unrelated taxa have that caused that primitive trait to reappear? And I wonder if there are any analyses based on morphology that include several tenrecs and other eutherians for comparison? So far I have found none, so the LRT is shedding light where it may be needed.

If Echinops is indeed a hedgehog with a cloaca
then we have to go get some mtDNA from Tenrec to see if it is a good match for odontocete mtDNA. At present, Tenrec has not been tested for its mtDNA, that I know of, so the whale connection question remains open.

While we’re at it it
count the stomachs in Tenrec. Even odontocetes have subdivided stomachs. Let’s find out when that trait appeared.

References
Asher RJ 2007. A web-database of mammalian morphology and a reanalysis of placental phylogeny. BMC Evol Biol. 7: 108-10 online
Asher  RJ and Helgen KM 2010. Nomenclature and placental mammal phylogeny. BMC Evolutionary Biology 10:102 online
Du Chaillu P 1860. Descriptions of mammals from equatorial Africa. Proceedings of the Boston Society of Natural History, 7, 358–369.
Eisenberg JF and Gould E 1970. The tenrecs: a study in mammalian behavior and evolution. Smithsonian Institution Press, Washington, DC. 138 pp. PDF online
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Martin WCL 1838. On a new genus of insectivorous mammalia. Proceedings of the Zoological Socieety, London, 6:17.
Mouchaty SK, Gullberg A, Janke A, Arnason U 2000. Phylogenetic position of the Tenrecs (Mammalia: Tenrecidae) of Madagascar based on analysis of the complete mitochondrial genome sequence of Echinops telfairi. Zoologica Scripta. 2000, 29 (4): 307-317. 10.1046/j.1463-6409.2000.00045.x.
Nicoll M 1985. The biology of the giant otter shrew *Potamogale velox*. National Geographic Society Research Reports, 21: 331-337.
O’Leary, MA et al. 2013. The placental mammal ancestor and the post-K-Pg radiation of  placentals. Science 339:662-667. abstract
Suárez R, Villalón A, Künzle H and Mpodozis J 2009. Transposition and Intermingling of Gαi2 and Gαo Afferences into Single Vomeronasal Glomeruli in the Madagascan Lesser Tenrec Echinops telfairi. PLoS ONE 4(11): e8005. doi:10.1371/journal.pone.0008005

Zygorhiza mandible issues

Zygorhiza kochiii (Late Eocene, 36mya; 5.2m; Kellogg 1936) is a dorundontine odontocete, smaller than Zeuglodon (Basiliosaurus), but larger than Maiacetus. Like its tenrec ancestors, Zygorhiza had long, slender toothy jaws.

Figure 1. (above) Zygorhiza kochi from George Mason University website, likely captured from Kellogg 1936. To make the jaws fit and teeth occlude the mandible had to be reduced and the cranium had to tilted down posteriorly.

Today’s problem involves the jaws
which were presented, apparently, in a scale that did not permit the teeth to occlude properly when reattached to the skull. By reducing the mandible and lowering the rear of the skull all the parts mesh and match. Not sure what the fossil looks like, but this is what happens when you test the restoration and create a reconstruction.

Perhaps
the mandible and skull come from two different specimens. It’s also worth noting how this odontocete whale’s teeth appear to be evolving back to primitive shapes, that is, cusps aligned all in a row, rather than W -shaped in occlusal view. And, of course, extant odontocete teeth have no distinct cusps, but have all reverted to a complete arcade of canine-like pegs largely made up of former premolars.

References
Kellogg R 1936. A review of the Archaeoceti. Washington: Carnegie Institution of Washington. pp. 100–177.

wiki/Zygorhiza

All toothless whales are baleen whales

Updated November 20, 2016 based on input from Dr. RW Boessenecker who corrected a mistake I made reconstructing Tokarahia by noting the mandible was axially rotated in situ 180º. Correcting that error produces the bowed out Gothic arch set of mandibles, typical of mysticetes. 

Preamble
Several of the mistakes discussed below are based on the long-standing tradition that whales are monophyletic. That is, odontocetes (toothed whales) and mysticetes (baleen whales) were long thought to have a common ancestor with flukes and fins. That paradigm  was overturned by the large reptile tree (LRT) earlier here. Workers thought that common ancestor would be an archaeocete, but, so far, all tested archaeocetes nest basal to extant odontocetes and were derived from tenrecs in the LRT.

Almost fifty years ago whale monophyly was questioned
by Van Valen (1968), who listed a number of traits that distinguish Odontoceti from Mysticeti. Unfortunately this was before computer-assisted phylogenetic analysis and neither desmostylians nor tenrecs were offered as basal taxa with legs. This was also long before any whales with legs had been discovered. Gotta give Van Valen credit for his insight way back then.

Yesterday we looked at the desmostylian ancestors of today’s mysticete (baleen) whales. Less than 24 hours ago I encountered for the first time Aetiocetus (Emlong 1966; Figs. 1, 2). I learned it has long been considered a toothed basal mysticete. Evidently some of the back teeth are leaf-shaped and all of the teeth are small and widely spaced. Most whale workers are happy with this hypothesis or relationships, but the LRT finds otherwise based on an expanded taxon list.

Figure 1. Aetiocetus skull in several views. Most whale workers today consider this taxon close to the origin  of baleen whales. The transversely crested cranium is a trait found in living odontocetes, not mysticetes.

I added Aetiocetus
to the large reptile tree and, while given the opportunity to nest with mysticetes, Aetiocetus nested instead between Zygorhiza and Orcinus + Physeter, all members of the Odontoceti. As recently as 2015, Ekdale et al. (Fig. 2) were trying to use Aetiocetus to explain the origin of baleen in modern whales.

Figure 2. Palate and teeth of the odontocete Aetiocetus alongside palates of juvenile gray whale and embryo fin whale, members of the Mysticeti. Aetiocetus was long thought to be a basal mysticete.

18 hours ago I encountered another mysticete,
Tokarahia kauaeroa (Boessenecker and Fordyce 2015; Late Oligocene; OU 2235), which has no teeth. Their reconstruction (Fig. 2) is

Figure 3. Tokarahia, a toothless odontocete long thought to be a basal mysticete. Original interpretation of materials is presented alongside a new interpretation, closer to the bones in situ. See figure 4. The humerus is rotated so the ball joint fits into the ventral socket of the scapula.

Unfortunately
I thought Boessenecker and Fordyce changed the curve of the mandible in their reconstruction and did not follow the very narrow mandibles in restoring the largely missing or buried rostrum. They also moved the orbit anteriorly. I attempted a mistaken correction (Fig. 3) that was based on a narrow mandible interpretation. Dr Boessenecker reported the mandible was axially rotated in situ (Fig. 4). Those corrections was applied shortly thereafter. A good lesson in keeping an open mind.

Figure 4. Tokarahia in situ and as originally reconstructed (on right). Flipping the right mandible and reconstructing the skull anew (at left).

12 hours ago
I also learned about Isanacetus laticephalus (Kimura and Ozawa 2002; early Miocene, 18 mya; MFM 28501; Fig. 5, 6). This fossil whale is indeed a mysticete. In the LRT it nests between the desmostylian Behemotops (presumably with at least front legs) and extant baleen whales.

Figure 5. Isanacetus skull in several views. I also present skull tracings in DGS that differ in some respects from the published drawings. Isanacetus is a basal mysticete, derived from a sister to Behemotops.

Like all mysticetes and derived desmostylians
Isanacetus has a ventrally concave rostrum, a wide flat skull and other traits that distinguish mysticetes from odontocetes + tenrecs. Isanacetus is also one of the smallest known mysticetes, about twice the size of its current desmostylian sister, Behemotops (Fig. 6) and half again longer in the skull than the more completely known Desmostylus.

Figure 6. Isanacetus compared to sisters recovered in the LRT. Balaeonoptera is much reduced. The loss of teeth actually occurred when mysticetes had legs!

More backstory for those keenly interested
Below are some earlier and traditional reports on Aetiocetus and aetiocetids, which was considered by these authors to be related to mysticetes and cetotheres (extinct mysticetes).

Whitmore and Sanders 1976 report,
“The cheek teeth [of Aetiocetus] are leaf shaped, similar to those of Patriocetus, but smaller and with the roots coalesced. The triangular rostrum, reduced dentition, and the conformation of the posterior ends of the maxillae, premaxillae, and nasals (Ernlong, 1966:s) are characters that would be expected in the ancestor of the mysticetes. Thenius (1969:489) stated: “Even if Aetiocetus, because of its geologic age (upper Oligocene) cannot be a direct stem form of the cetotheres, yet this genus documents that a specific family (Aetiocetidae) must be classified as ancestor, the link between ancient and baleen whales.

“Among the few Cetacea known from deposits of middle Oligocene age are two occurrences of unmistakable Mysticeti. One of these, Mauicetus Benham, 1939, from New Zealafid, has long nasals embraced by premaxillae and maxillae which extend posteriorly to the level of the supraorbital process of the frontal, together with an anteriorly thrusting triangular supraoccipital. The Oligocene Mysticeti, had already evolved the elongated, edentulous rostrum, constituting 3/4 to 4/5 of total skull length, that typifies the modern baleen whales. The mandible of Oligocene Mysticeti was also edentulous and, like those of modem baleen whales, was long and slim.”

Berta and Demere 2005 reported,
“Aetiocetids are the most taxonomically and morphologically diverse clade of toothed mysticetes known from the late Oligocene of the eastern and western North Pacific. Aetiocetids can be distinguished from other toothed mysticetes by the following unequivocal synapomorphies: lobate or triangular parietal-frontal suture; zygomatic process of squamosal expanded near anterior end; “window” in the palate exposing vomer; short, broad extension of the palatine that overlaps the pterygoid; and exoccipital developed ventrally as an anteriorly directed posterior sinus.

The presence of palatal nutrient foramina associated with the upper teeth in all aetiocetids suggests that these toothed mysticetes had already evolved some type of baleen. The form and function of this rudimentary baleen is currently unknown, but the fact that these archaic mysticetes also possessed procumbent anterior teeth, broad diastemata, and posterior teeth with sharply pointed cusps, accessory denticles, and longitudinal enamel ridges suggests development of a specialized type of filter feeding differing from that of other toothed and edentulous mysticetes.”

Unfortunately
these authors had not expanded their taxon set to include desmostylians, which pull mysticetes away from odontocetes + tenrecs.

Eckland et al. 2015 report
“The origin of baleen in mysticetes heralded a major transition during cetacean evolution. Extant mysticetes are edentulous in adulthood, but rudimentary teeth develop in utero within open maxillary and mandibular alveolar grooves. The teeth are resorbed prenatally and the alveolar grooves close as baleen germ develops.”

That’s all well and good, but you really need a wide gamut taxon inclusion set that includes whales, tenrecs and desmostylians to find the diphyletic origins of extant whales and in desmostylians one should look for the origin of baleen, as discussed earlier here.

References
Berta A and Demere TA 2005. Phylogenetic relationships among the diverse toothed mysticete clade the aetiocetidae and reconsideration of the filter feeding niche. Evolution of  aquatic tetrapods. Fourth triennial convention abstracts May 16-20 2005, Akron, OH, USA.
Boessenecker RW and Fordyce RE 2015. A new genus and species of eomysticetid (Cetacea: Mysticeti) and a reinterpretation of ‘Mauicetus’ lophocephalus Marples, 1956: Transitional baleen whales from the upper Oligocene of New Zealand. Zoological Journal of the Linnean Society. in press. doi:10.1111/zoj.12297.
Demere TA 2005. Palate vascularization in an Oligocene toothed mysticete (Cetacea: Mysticeti): Aetiocetidae); implications for the evolution of baleen. Evolution of  aquatic tetrapods. Fourth triennial convention abstracts May 16-20 2005, Akron, OH, USA.
Ekdale EG, Demere TA and Berta A 2015. Vacularization of the gray whale palate (Cetacea, Mysticeti, Eschrichtius robustus): soft tissue evidence for an alveolar source of blood to baleen. The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 298(4) · February 2015.
Whitmore FC Jr and Sanders AE 1976. Review of the Oligocene Cetacea. US Geological Survey Staff — Published Research. Paper 237.
Van Valen L 1968. Monophyly or diphyly in the origin of whales”. Evolution. 22 (1):37–41.

wiki/Aetiocetus
wiki/Tokarahia
wiki/Isanacetus – not created yet

Adding Pakicetus and Indohyus to the LRT

Pakicetus inachus (Gingerich & Russell 1981; middle Eocene; Figs. 1, 2) was originally hailed as “one of the oldest whales known anywhere.” Despite its lack of fins and flukes, Pakicetus was considered a whale based largely on the large posterior process of the periodic (near the ear region) and the thick, dense auditory bulla characteristic of all cetaceans. These traits indicate a underwater hearing and habitat even though Pakicetus had slender running legs and no flukes (Fig. 1). The resemblance of Pakicetus to Tenrec is striking — and remember some tenrecs, like Limnogale (Fig. 4), retained a long tail and are aquatic with webbed feet.

Figure 1. Odontoceti (toothed whale) origin and evolution. Here Anagale, Andrewsarchus, Sinonyx, Hemicentetes, Tenrec Indohyus and Leptictidium precede Pakicetus. Maiacetus and Orcinus are aquatic odontocetes. Mysteceti (baleen whales) had a separate origin in Desmostylia.

The case for a tenrec ancestry for Odontoceti continues
Indohyus major (Fig. 1; Rao 1971, Thewissen et al. 2007; Eocene, 48 mya; 1m in length) was considered an artiodactyl, but nests in the large reptile tree (LRT with Leptictidium (Fig. 1) between tenrecs and odontocete whales. So the case for Leptictidium as a whale ancestor is strengthened with the addition of its sister Indohyus. The case for a traditional artiodactyl ancestor for whales is much diminished.

As we learned earlier, mysticete (baleen) whales are derived from desmostylians like Paleoparadoxia and Behemotops.

Figure 2. Skulls of transitional taxa between tenrecs and Odontoceti (toothed whales). These include Tenrec, Lepticitidium, Pakicetus, Rhodhocetus and Orcinus. The gradual accumulation of traits should be readily visible to the casual observer here.

One of the major problems with the artiodactyl-whale hypothesis
is this: artiodactyls are herbivores. Odontocetes are carnivores. Tenrecs eat a wide variety of animals.

Mystecete whales have no teeth, and did not evolve from carnivores. Although hippos, mesonychids and desmostylians all have big teeth, all are herbivores. Their largest teeth function more like tusks.

Figure 3. Indohyus skeletal elements nest between tenrecs and whales. While a sister to Leptictidium, the lines are more nearly equal in length here. We don’t know if Indohyus had claws or hooves. Leptictidium had long claws.

The mystery tenrec, Limnogale
No Limnogale skeletons are known to tenrec experts I contacted and little else is known of this extant, nocturnal, aquatic and long-tailed tenrec from Madagascar. It may hold a key place in the origin of whales. It appears to be plesiomorphic enough to do so, but it sure would be great to someday see a skeleton. The ears and eyes are small, the whiskers are bushy. Some tenrecs echolocate, but this taxon has been so little studied that I don’t know if it is an echolocator.

Figure 4. Is this the true ancestor of odontocete whales? The rare and rarely studied web-footed tenrec Limnogale mergulus, which has a long tail, is nocturnal and aquatic. Both images copyright PJ Stephenson and used with permission.

Thewissen et al. 2007 report,
Indohyus shares a similar auditory bulla with cetaceans, not present in artiodactyls. “Other significant derived similarities between Indohyus and cetaceans include the anteroposterior arrangement of incisors in the jaw, and the high crowns in the posterior premolars.”

Well, those traits,
as you can see (Fig. 2) are also found in Tenrec and its sisters, but Thewissen et al. did not test tenrecs and any of the sisters recovered in the LRT, other than Andrewsarchus and Sinonyx. Indohyus had thick bones (osteosclerosis) which provided ballast for underwater activities. That it nests with Leptictidium (Figs. 1, 2) adds credence to the aquatic hypothesis advanced earlier here.

Figure 5. Subset of the LRT, higher placental mammals with a focus on whales (yellow) and their ancestral clades, the Tenrecidae and Mesonychidae. Both are a fair distance from artiodactyls. Note the displacement of Janjucetus. Now it looks like it probably had legs. We’ll look at Behemotops soon.

Traditional paleontology
holds that “Mysticeti split from Odontoceti (toothed whales) 34 million years ago during the Eocene” and whales moved to the sea 50 mya (Rose 2001) having descended from hooved mammals. The present hypothesis (Fig. 5) holds that indeed Mysticeti were derived from hooved mesonychids/hippos/desmostylians. However, Odontoceti, the toothed carnivorous/piscivorous whales arise from clawed tenrecs, like Leptictidium (Figs, 1, 2). The hands and feet of the protowhale Artiocetus (Fig. 6) are well known and at least several of its unguals are claws — though much reduced and somewhat transformed due to their much reduced use on land and unknown extent of the webbing. At least one tenrec had webbed feet, Limnogale (Fig. 4). I know of no artiodactyls with webbed feet.

6. Artiocetus manus and pes had reduced claw-like unguals, not hooves. And Limnogale shows some tenrecs had webbed feet.

India/Pakistan and Madagascar
where odontocetes started and tenrecs now survive, were one continuous island that split apart some 88 million years ago… so there is no geographical barrier to the present hypothesis of tenrec and odontocete relations. But it does indicate the antiquity of the tenrec – odontocete split and relationship.

Australia and the Pacific rim
where mysticetes started and desmostylians were found is a much, much wider area. We find Desmostylia like Paleoparadoxia and Behemotops have only been found along the Pacific rim (Japan > Russia > Aleutian Islands > Pacific coast of North America  south to Baja California. A desmostylian sister, Anthracobune, is found in Eocene (40 mya) Pakistan. Janjucetus is found in younger 25 mya strata in Australia. A hippo and mesonychid sister, Ocepeia, dates to the Paleocene (60 mya) in Morocco, which is even further from Australia. So, the origin of the Mysticeti, appears to be somewhere along the Pacific rim.  More details tomorrow.

References
Gingerich PD and Russell DE 1981. Pakicetus inachus, A New Archaeocete (Mammalia, Cetacea) from the Early-Middle Eocene Kuldana Formation of Kohat (Pakistan). Contributions from the Museum of Paleontology, The Museum of Michigan. 25 (11): 235–246.
Rao AR 1971. New mammals from Murree (Kalakot Zone) of the Himalayan foot hills near Kalakot, Jammu and Kashmir state, India. Journal of the Geological Society of India. 12 (2): 124–34.
Thewissen JGM, Williams EM, Roe LJ and Hussain ST 2001. Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls. Nature 413:277-281.
Rose KD 2001. The Ancestry of Whales. Science. 293 (5538): 2216–2217. PDF
Thewissen JGM, Cooper LN, Clementz MT, Bajpai S and Tiwari BN 2007. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature 450:1190-1195.

wiki/Indohyus
wiki/Pakicetus