Misinformation from whale expert JGM ‘Hans’ Thewissen

Figure 1. Book cover for ‘The walking whales” by JGM Hans Thewissen author. April 2019 pub date.

A 2014 book
on the origin of whales (Fig. 1) by Dr. JGM ‘Hans’ Thewissen just had another burst of publicity from Discover Magazine online (see link below). Article headline: “How ancient deer lost their legs and became whales”

Ancient deer???

Dr. Thewissen is a professor
at Northeast Ohio Medical University.

According to the Discover article by Joshua Rapp Learn:
“Cetaceans include everything from dolphins to whales.”

By contrast,
in the large reptile tree (LRT, 1818+ taxa; subsets Figs. 5, 6) Cetacea is no longer a clade. That’s because traditional ‘whales’ are diphyletic with separate ancestries still not recognized by whale experts like Dr. Thewissen. Odontocetes (toothed whales, Figs. 2, 6) arise from tenrecs (which also echolocate). Mysticetes (baleen whales, Figs. 3–5) arise from mesonychids, hippos, anthracobunids and desmostylians.

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.

According to the Discover article:
“Indohyus belonged to the even-toed group of ungulates, which today includes giraffes, horses, pigs and cetaceans. Indohyus basically looked like a tiny little deer, a deer the size of a cat,” says Hans Thewissen, a professor at Northeast Ohio Medical University who has studied whale evolution for years and wrote the book The Walking Whales: From Land to Water in Eight Million Years. Today, a distant deer-like relative called the water chevrotain (or African mouse-deer) can be found from central to southern Africa. These deer eat flowers and fruits and live near rivers, which they use as escape routes to flee land-based predators or even eagles.

Ungulates have no relationship to whales in the LRT.
Think of it. Four, two or one-toed hooves to flippers? That’s untenable, but evidently that’s what taxon exclusion gives you. Simply adding taxa in the LRT (Figs. 2–4) shows that Thewissen’s study suffered from taxon exclusion prior to Pakicetus (Fig. 2), the most basal taxon common to both studies.

Figure 3 Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

Figure 4. Taxa in the lineage of right whales include Desmostylus, Caperea and Eubalaena. The tiny bit of jugal posterior to the orbit (in cyan) is found in all baleen whales tested so far. The frontals over the eyes are just roofing the eyeballs in Desmostylus, much wider in Caperea and much, much longer in Eubalaena.

According to the Discover article:
“Thewissen’s research examining stable isotopes in Indohyus fossils shows they ate land plants, but their dense bones suggest they spent a lot of time in the water. The hippopotamus — the closest living relative of whales that live outside the ocean — also has dense bones, which help weigh it down while walking along the bottom of lakes or rivers. The evolutionary descendant of Indohyus, called Pakicetus, began to adopt a more aquatic lifestyle as they abandoned a vegetarian diet, based on the way their teeth look, Thewissen says.”

So this explains why Thewissen did not answer my emails.
Two years earlier he had authored a book (Fig. 1) that promoted the myth of a single origin of all whales originating from hoofed ungulates. The news I sent him, that whales were not a single clade, was probably upsetting, considering the time, treasure and reputation Thewissen put into his career and his publications. You can’t fix print once it is printed.

Figure 5. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT

It should be up to professionals and PhDs
to build matrices and run analyses of fossil taxa. That’s what they are getting paid to do. They are the ones who know how to run the analyses. They are the ones who have access to fossils. They have professional colleagues, post-docs, PhD candidates, undergrads, volunteers and grants. Since the pros and PhDs have chosen to exclude so many pertinent taxa, amateurs are taking up the slack, hoping to contribute to this ancient science we call paleontology.

Figure 6. Subset of the LRT focusing on the odontocetes and their ancestors.

Taxon exclusion remains the number one problem
vexing paleontology and paleontologists. Adding taxa to minimize taxon exclusion is what the LRT is all about. It resolves problems like the origin of whales with taxa that document in detail the gradual accumulation of traits (Figs. 3, 4) we expect from microevolution over deep time, now back to Ediacaran nematodes.

Since this is science,
anyone can repeat this experiment simply by following the materials and methods. You don’t have to be a scientist. You don’t have to be an expert. That will come with time and study, the same way it comes with time and study for those who pay dearly for their education. Don’t trust me. Don’t trust others, even paid professionals with PhDs. Build your own matrix and run the analyses yourself to find out for yourself that deer, or any other ungulate, did not give rise to whales.

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References
Thewissen JGM et al. (4 co-authors) 2007. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature 450:1190–1194.

Nature Comment: “Adding taxa documents the origin of odontocetes from anagalids, leptictids and tenrecs (which echolocate) leading to Indohyus and Pakicetus apart from the origin of mysticetes from mesonychids, hippos, anthracobunids and desmostylians with Desmostylus closer to right whales and Behemotops closer to rorquals. Cladogram here: http://reptileevolution.com/reptile-tree.htm and manuscript here: https://www.researchgate.net/publication/328388746_The_triple_origin_of_whales”

Thewissen JGM 2019, 2014. The walking whales. From land to water in eight million years. University of California Press. 256pp.

ResearchGate.net manuscript on the triple origin of whales

Publicity:
article by Joshua Rapp Learn in Discover Magazine online: how-ancient-deer-lost-their-legs-and-became-whales

A giant Eocene whale from Ukraine

Davydenko et al. 2021
report the discovery of new giant basilosaurid from Ukraine.

From the abstract:
“The earliest fully aquatic cetaceans arose during the Middle Eocene; however, the earliest stage of their divergence is obscure. Here, we provide a detailed redescription of an unusual early cetacean, “Platyosphys einori”, from the Late Eocene of Ukraine (37.8–35.8 million years ago), with new data on its body size, skeletal microanatomy and suggestions on phylogenetic relationships.”

By contrast, in the large reptile tree (LRT, 1793+ taxa) the earliest stage of ‘their divergence’ (mysticetes and odontocetes) extends back to tiny tree shrews in the Jurassic. Contra public and professional opinion, whale divergence is not obscure. Taxon exclusion hampers the Davydenko et al. study.

Figure 1. Cladogram from Davydenko et al. 2021 showing how they nested Playosphys einori. See figure 2 for their proposed mysticetes (with teeth!)

Unfortunately the authors presented an outdated cladogram
that considered the former clade ‘Cetacea’ monophyletic. Their paper perpetuates an invalid hypothesis of interrelationships (Figs. 1,2) that omits the ancestors of mysticetes: desmostylians, anthracubunids, hippos, mesonychids and oreodonts. They also omit the ancestors of pakicetids: tenrecs and anagalids.

Figure 2. Portion of the cladogram from figure 1 enlarged and rotated. Llancetus and kin are not mysticete ancestors when more taxa, like Behemotops, are included in the analysis.

Sadly,
whale workers continue to perpetuate the myth that whales are monophyletic. That was invalidated several years ago here by simply adding taxa.

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References
Davydenko S, Shevchenko T, Ryabokon T. et al. 2021. A Giant Eocene Whale from Ukraine Uncovers Early Cetacean Adaptations to the Fully Aquatic Life. Evol Biol (2021). https://doi.org/10.1007/s11692-020-09524-8

researchgate.net/publication/328388746_The_triple_origin_of_whales

reptileevolution.com/reptile-tree.htm

Interested in whale carpals?

Gavazzi et al. 2020 bring us their views
on whale and pre-whale carpal elements. They used the invalidated artiodactyls, pig (Sus) and  (Diacodexis) as outgroup taxa. The latter is incompletely known, slender and appears to be not far from the more completely known Cainotherium.

By contrast
here  (Figs. 1–3, 5, 7, 8) competing whale and pre-whale carpal elements are presented along with tree shrew (Ptilocercus) carpals (Fig. 4) as an example of the plesiomorphic condition in placentals.

Bottom line:
Due to taxon exclusion, actual evolutionary patterns were overlooked by Gavazzi et al., but that didn’t matter much. About the same story can be told with the wrong outgroup taxa. Carpals don’t change much across these members of the placental clade.

Figure 1. Odontocete flipper and ancestral taxa manus. Homologous wrist elements are colored the same. Green is the pisiform, missing in the dolphin, Tursips.  Ambulocetus image from Gavazzi et al. 2020 and repaired here. Dorudon image from Cooper et al. 2007 and repaired here.

From the Gavazzi et al. 2020 abstract:
“During the land-to-water transition in the Eocene epoch, the cetacean skeleton underwent modifications to accommodate life in the seas. These changes are well-documented in the fossil record. The forelimb transformed from a weight-bearing limb with mobile joints to a flipper with an immobile carpus.”

Unfortunately Gavazzi et al. still consider ‘Cetacea’ a monophyletic clade. That hypothesis of interrelationships became invalid in 2017 with a blogpost here and an online paper here.

Figure 2. The manus of Eubaelana, an extant right whale (bottom) compared to two desmostylians. Note the similarities between the two unrelated clades. Missing parts are restored based on phylogenetic bracketing.

Mammal carpal homologs:

1. Distal carpal 1 = Trapezium – red
2. Distal carpal 2 = Trapezoid – cyan
3. Distal carpal 3 = Capitum – lavender
4. Distal carpal 4+5 = Hamatum – yellow green
5. Radiale = Scaphoideum – pink
6. Intermedium = Lunatum – yellow
7. Ulnare = Triquetrum – pale orange
8. Centrale = Centrale – indigo
9. Pisiform = Pisiform – green

Figure 3. Hippos manus. Pisiform in green.

Continuing from the Gavazzi et al. 2020 abstract:
“We used micro-CT imaging to assess evolutionary changes in carpal size, orientation, and articulation within Eocene cetacean taxa associated with the transition from a terrestrial to amphibious niche. We compared Ambulocetus natans (Fig. 1), a well-preserved amphibious archaeocete, with other archaeocetes, and with Eocene terrestrial artiodactyls, the sister group to Cetacea.”

Figure 4. Ptilocercus is a tree shrew closer to the plesiomorphic wrist condition. Compare to taxa in figures 1 and 2.

Figure 5. X-ray of Tursiops flipper showing no trace of a pisiform. But look at digit 5. Compare to figure 4.

Eocene terrestrial artiodactyls are not the sister group to Cetacea, which is not a monophyletic clade in the LRT. Adding overlooked taxa resolves this issue.

“A cylindrical carpus in terrestrial taxa evolved into a mediolaterally flattened, cambered carpus in the semi-aquatic and fully aquatic cetaceans.

Gavazzi et al. chose the wrong terrestrial taxa.  Tenrec carpals (Figs. 1, 7) are not as cylindrical as those of pigs and their ancestors, though the pisiform does orient itself ventroposteriorly. All flippers are flattened with a lateral pisiform, which turns out to be a reversal back to the tree shrew orientation (Fig. 4).

“Specifically, the pisiform bone shifted from a ventral [= posterior, Fig. 3] orientation in terrestrial taxa to a lateral orientation, in plane with the carpus, within semi-aquatic and fully aquatic taxa.”

A ventroposterior pisiform is also found in Tenrec (Fig. 1)  and Hippopotamus (Fig. 3) among the actual ancestors of odontocetes and mysticetes respectively.

“Flattening of the carpus, including lateral rotation of the pisiform, likely relates to functional shifts from weight-bearing terrestrial locomotion to aquatic locomotion. This laterally projecting pisiform morphology is retained in all extant cetaceans.”

Gavazzi et al. used the wrong outgroup taxa. In both Tenrec and Hippopotamus the carpus is less cylindrical than in the artiodactyls, Sus and Diacodexis.

By the way, the pisiform is absent in the dolphin Tursiops (Figs. 1, 5), but look at the lateral orientation of digit 5 in comparison to the lateral orientation of the pisiform in the plesiomorphic wrist of Ptilocercus (Fig. 4). One wonders if Gavazzi et al. mistook digit 5 in Tursiops for a pisiform, given their statement.

“Our results suggest this shift, along with other modifications to the carpus, predominantly occurred during the middle Eocene and facilitated an obligatorily aquatic lifestyle in late Eocene cetaceans.”

Without the real ancestors, the Gavazzi et al. paper and its conclusions would be a waste of time, except that carpals are largely interchangeable in quadrupedal placentals. So their conclusions remain largely valid. Thirteen years ago Cooper et al. 2007 also looked at whale carpals and compared them to predecessor taxa (see below).

Figure 6. Ambulocetus carpals from Gavazzi et al. (left) here restored to their original positions and colored.

Try to always restore scattered elements
to their original positions. Don’t leave the work half done. Colors help to make this process easier and aid in making confident comparisons between taxa.

Figure 7. Manus and wrist of the extant tenrec Hemicentetes (from Digimorph.org and used with permission). Colors added. Compare to related taxa in figures 1 and 6. Pisiform in bright green.

The traditionally overlooked overall resemblance of tenrecs
to Indohyus (Fig. 8) and later odontocete ancestors (Fig. 8) extends to the manus and carpus.

Whale workers who refereed the manuscript
‘The Triple Origin of Whales‘ declined to allow it to be published. In that light, one wonders why whale workers prefer to cherry-pick pigs and pig ancestors rather than adding valid taxa to their cladograms. Keeping their blinders on is a continuing problem in paleontology, which is why this blogpost exists. For those readers hoping someday to make discoveries in this field of science, beware. Many professors will attempt to suppress your work to  keep the discoveries for themselves.

Figure 8. Odontoceti (toothed whale) origin and evolution. Here Anagale, Andrewsarchus, Sinonyx, Hemicentetes, Tenrec Indohyus and Leptictidium precede Pakicetus. Maiacetus and Orcinus are aquatic odontocetes.

Figure 9. Taxa in the lineage of right whales include Desmostylus, Caperea and Eubalaena. The tiny bit of jugal posterior to the orbit (in cyan) is found in all baleen whales tested so far. The frontals over the eyes are just roofing the eyeballs in Desmostylus, much wider in Caperea and much, much longer in Eubalaena.

Cooper et al. 2007
dissected extant whale flippers and compared them to Ambulocetus (Fig. 1) and Dorudon (Fig. 1) without correcting for disarticulation problems in fossils. Cooper et al. report, “Most odontocetes also reduce the number of phalangeal elements in digit V, while mysticetes typically retain the plesiomorphic condition of three phalanges.” Perhaps Cooper et al. did not notice there are four phalanges on digit five in Eubaelana (Fig. 2). The unguals are tiny.

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References
Cooper LN, Berta A, Dawson SD and Reidenberg JS 2007. Evolution of hyperphalangy and digit reduction in the cetacean manus. The Anatomical Record Special Issue: Anatomical Adaptations of Aquatic Mammals 290(6): https://doi.org/10.1002/ar.20532
Gavazzi LM, Cooper LN, Fish FE, Hussain ST and Thewissen JGM 2020. Carpal Morphology and Function in the Earliest Cetaceans. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2020.1833019

https://www.researchgate.net/publication/328388746_The_triple_origin_of_whales

SVP abstracts 18: Palatal foramina and the origin of baleen in mysticetes

Peredo and Pyenson 2020 discuss
the origin of baleen in mysticetes by looking at palatal foramina.

“Baleen whales (mysticetes) filter-feed using specialized keratinous plates, called baleen, to sieve large quantities of prey laden water. Baleen represents a wholly novel integumentary structure, with no apparent homologous structure in any living animal. The origins of baleen, and filter-feeding in whales, have been the topic of much debate. In particular, the lack of osteological correlates for baleen makes it unclear which (if any) stem mysticetes first had keratinous structures for filter feeding.”

The origin of baleen in whales is found in traditionally overlooked nearly toothless desmostylians like Desmostylus (Fig. 2) and Behemotops (Fig. 3), taxa nesting basal to mysticetes in the large reptile tree (LRT, 1751+ taxa; subset Fig. 1).

Figure 1. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT

“One potential osteological correlate are palatal foramina and sulci: structures in the roof of the mouth that may vascularize the baleen plates.”

Peredo and Pyenson are “Pulling a Larry Martin” by looking for a few ‘key’ traits rather than running a phylogenetic analysis of all traits without excluding pertinent taxa, such as Desmostylus and Behemotops.

“Palatal foramina are present and well developed in extant and fossil crown mysticetes and are preserved in some stem mysticetes as well. Here, we report the presence of numerous and well-developed palatal foramina in non-filter-feeding cetaceans, including crown and stem odontocetes and in stem cetaceans (so-called archaeocetes).”

Peredo and Pyenson are excluding pertinent taxa.

“Additionally, we observe the presence of palatal foramina in 61 observed species of terrestrial artiodactyls.”

Peredo and Pyenson are excluding pertinent taxa. No artiodactyls are basal to any whales in the LRT. Hippos are not artiodactyls in the LRT. Toothed whales arise from tenrecs and anagalids.

Figure 2. Taxa in the lineage of right whales include Desmostylus, Caperea and Eubalaena. The tiny bit of jugal posterior to the orbit (in cyan) is found in all baleen whales tested so far. The frontals over the eyes are just roofing the eyeballs in Desmostylus, much wider in Caperea and much, much longer in Eubalaena.

The Peredo and Pyenson abstract continues:
“CT scanning demonstrates consistent internal morphology across all observed palatal foramina, suggesting that the palatal foramina observed in extant mysticetes are homologous to those of terrestrial artiodactyls.”

This sounds like cherry-picking taxa. Perhaps palatal foramina are typical of non-arboreal mammals? What do tenrec and desmostylian foramina look like?

Figure 3. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

The Peredo and Pyenson abstract continues:
“The presence of palatal foramina in non-filter-feeding whales (odontocetes and archaeocetes) and in terrestrial artiodactyls suggest that the structures are more probably associated with an elaborate gingiva or other oral tissue and are alone not reliable osteological correlates for the presence of baleen in fossils.”

Next time, just add pertinent taxa and run the analysis… then see what turns up. The origin of baleen in whales was answered here in 2016. ResearchGate.net has an unpublished paper to read on the triple origin of whales here.

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References
Peredo CM and Pyenson N 2020. Palatal foramina in stem whales and terrestrial artiodactyls obfuscate their potential for inferring baleen in stem mysticetes. SVP abstracts 2020.

wiki/Baleen_whale

From Berkeley: pterosaur origins and whale evograms

Professor Kevin Padian (U of California, Berkeley)
has been a champion for evolution over the past several decades. In the 1980s I became acquainted with him when he was the science expert for my first book, Giants.

The following one hour video on YouTube caught my eye.
Professor Padian brilliantly discusses how school districts dealt with invading Creationists. Padian has been leading the charge on many fronts regarding evolution. Unfortunately, he has stayed in his tent sipping tea regarding the origin of flight in pterosaurs (Padian 1985), and the origin of whales, as you’ll see below.

 

From the Berkeley.edu page on pterosaur flight:
“Pterosaurs are thought to be derived from a bipedal, cursorial (running) archosaur similar to Scleromochlus in the late Triassic period (about 225 million years ago). Other phylogenetic hypotheses have been proposed, but not in the context of flight origins. The early history of pterosaurs is not yet fully understood because of their poor fossil record in the Triassic period. We can infer that the origin of flight in pterosaurs fits the “ground up” evolutionary scenario, supported by the fact that pterosaurs had no evident arboreal adaptations. Some researchers have proposed that the first pterosaurs were bipedal or quadrupedal arboreal gliders, but these hypotheses do not incorporate a robust phylogenetic and functional basis. The issue is not yet closed.”

This comes 20 years after Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama (Fig. 1) were added to four previously published phylogenetic analyses and all nested closer to pterosaurs than any tested archosaur (Peters 2000). Aspects of this topic were reviewed here in 2011 and here in 2015.

Figure 2. Click to enlarge. The origin of the pterosaur wing from Huehuecuetzpalli (B) to Cosesaurus (C) to Sharovipteryx (D) to Longisquama (E) to the basal pterosaur, Bergamodactylus (F and G).

The same webpage notes:
“Pterosaurs also had a bone unique to their clade. It is called the pteroid bone, and it pointed from the pterosaur’s wrist towards the shoulder, supporting part of the wing membrane. Such a novel structure is rare among vertebrates, and noteworthy; new bones are unusual structures to evolve — evolution usually co-opts bones from old functions and structures to new functions and structures rather than “reinventing the wheel.”

This comes 11 years after Peters 2009 showed the pteroid was not unique, but a centralia that had migratred medially in Cosesaurus (like the panda’s ‘thumb’). Likewise, the not-so-unique pteroid was co-opted from old functions, contra the Berkeley evolution page.

The same webpage notes:
“Pterosaurs had other morphological adaptations for flight, such as a keeled sternum for the attachment of flight muscles, a short and stout humerus (the first arm bone), and hollow but strong limb and skull bones.”

We’ve known since Wild 1993 that what Padian 1985 called a keeled sternum is actually a sternal complex composed of a fused interclavicle + clavicle + single lepidosaur sternum (Fig. 3) after migration over the interclavicle.

Figure 3. Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex.

Backstory…
25 years ago, when I first met Kevin Padian and Chris Bennett, they both impressed upon me, at the same time and during a single conversation, the need for a proper phylogenetic context before making any sort of paleontological hypothesis. That’s when MacClade and PAUP were still ‘newish’. That’s why you might find it ironic that neither Padian nor Bennett have ever tested the addition of the four key taxa in figure 3 to prior published analyses that included pterosaurs, as I did in Peters 2000.

On the second topic of whale evolution:
Padian’s ‘evogram’ (evolution diagram) simply lacks a few key taxa. Odontocetes don’t arise from hippos. Only mysticetes do. Here (Fig. 4) a few missing transitional taxa are added to the existing evogram. Likewise the outgroup for Pakicetus and Indohyus now include overlooked tenrecs and leptictids. They look more like Indohyus than the hippo because microevolution becomes more apparent when pertinent taxa are added. Otherwise it’s a big morphological jump from hippos to Indohyus. Adding taxa makes ‘the jump’ much smaller as the LRT has demonstrated dozens of times. No one should be afraid to simply add taxa.

Figure 4. Whale evogram from Berkeley website and what happens when you add taxa based on the LRT. Two frames change every 5 seconds. It’s not good that the outgroup to the slender Indohyus is the massive Hippopotamus. Frame two repairs that inconsistency with a little microevolution.

As you can see,
the University of California at Berkeley no longer stands at the vanguard of paleontology. Rather it has been promoting traditional myths on its website for the last twenty years.

According to Padian’s online talk (above):
“Just because you have  a degree in science does not mean you’re a scientist. Scientists are people who do research, publish peer-reviewed research as a main part of their living.”

That’s good to know. Of course, it doesn’t help if one suffers from the curse of Cassandra. On that point, I’m not asking anyone to ‘believe the LRT’, but to simply add taxa to your own favorite cladograms, as Peters 2000 did to four different previously published studies that each had their own taxon and character lists. That’s what the large reptile tree has continued to do over the last 9 years. Others who have added taxa and recovered results confirming those recovered by the LRT are listed here. The pair of PhDs who decided those results should be erased are listed here.

Ingroup scientists who attempt to exclude outgroup scientists is a common thread in human history. Here’s a YouTube video trailer for an upcoming Marie Curie biography. I’m sure you all know the story of her pioneering work in radioactive elements.

References
Padian K 1985. The origins and aerodynamics of flight in extinct vertebrates. Palaeontology 28(3):413–433.
Peters D 1989. Giants of Land, Sea and Air — Past and Present. Alfred A. Knopf/Sierra Club Books
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-133.
Wild R 1993. A juvenile specimen of Eudimorphodon ranzii Zambelli (Reptilia, Pterosauria) from the upper Triassic (Norian) of Bergamo. Rivisita Museo Civico di Scienze Naturali “E. Caffi” Bergamo 16: 95–120.

https://pterosaurheresies.wordpress.com/2011/09/09/the-origin-of-the-pterosaur-sternal-complex/

https://www.researchgate.net/publication/328388746_The_triple_origin_of_whales

https://evolution.berkeley.edu/evolibrary/article/evograms_02

https://evolution.berkeley.edu/evolibrary/article/evograms_03

https://evolution.berkeley.edu/evolibrary/article/evograms_04

https://evolution.berkeley.edu/evolibrary/article/evograms_05

https://evolution.berkeley.edu/evolibrary/article/evograms_06

https://evolution.berkeley.edu/evolibrary/article/evograms_07

https://ucmp.berkeley.edu/vertebrates/flight/pter.html

https://en.wikipedia.org/wiki/Kevin_Padian

3x a tiny mammal tail evolved flukes

I found the following results
recovered from the large reptile tree (LRT, 1709+ taxa) to be particularly fascinating given the apparent illogic of developing a robust swimming tail with flukes from an tiny ancestral tail barely able to act as a ‘flap’.

You might remember
earlier we looked at the reversal of teeth in the lineage of odontocetes (toothed whales), reversing step-by-step to a simple cone from the typical complex, multi-cusped molar of a tree shrew.

Likewise in toothed whales, but not exactly correlated,
the tail also experienced a reversal, becoming longer and more robust after derivation from the tiny speck of a tail in tenrec ancestors.

With that introduction
here are the three times the tail has elongated and grown horizontal flukes in placental mammals:

1 – Manatee tail evolution
The terrestrial Moeritherium-like ancestors of today’s aquatic manatees and dugongs had a long torso and tiny tail, distinctly unlike the robust tail with flukes found in today’s Sirenia (Figs. 1–3). Prorastomus (Fig. 2) is a transitional taxon having a more robust tail. Procavia, the living hyrax, has an even smaller tail than these taxa and is more primitive.

Figure 1. Moeritherium skeleton. Note the tiny, slender tail.

 

Figure 2. Prorastomus is a pro-sirenian with legs. All four feet remain unknown.

The splitting in two of ancestrally longer caudal vertebrae (or the increase in caudal number while reducing each caudal vertebral length) appears to be the method employed by evolution to create a longer, more robust tail in manatees and their ancestors.

Figure 3. Dusisiren, a manatee sister has a robust tail and presumably, flukes.

2 – Mysticete tail evolution
Neoparadoxia (Fig. 4), a desmostylian ancestor of modern toothless (baleen) whales, likewise had a tiny tail, similar to that of its hippo-like ancestors, useless for propulsion.

Figure 4. GIF animation of the Neoparadoxia (original image from Barnes 2013). It seems illogical that the tiny tail of a desmostylian like this would ever become the giant tail of a mysticete, while the giant hind limbs disappear into the torso, but phylogenetic analysis recovers just such a scenario. Many long-jawed desmostylians are known from cranial material only and these are likely to be those that had large tails and smaller hind limbs.

The re-elongation of the tail in mysticete ancestors is not (yet) documented in transitional fossils, which is one factor in keeping this bit of evolution a secret, even from whale experts. Nevertheless, the rest of the anatomy is enough to nest these two former clades together into one clade. Here the number of tail vertebrae does not increase so much as the robust morphology of each one (Figs. 5–7).

Figure 5. Taxa in the lineage of right whales include Desmostylus, Caperea and Eubalaena. The tiny bit of jugal posterior to the orbit (in cyan) is found in all baleen whales tested so far. The frontals over the eyes are just roofing the eyeballs in Desmostylus, much wider in Caperea and much, much longer in Eubalaena.

The apparent length of the tail is enhanced by the disappearance of the hind limbs and the pelvis in mysticetes and other completely aquatic mammals.

Figure 6. Caperea, the pygmy right whale, is a much smaller sister to Eubalaena. Only the skeleton with the ribs angled back fits the stranded in vivo specimen and the skull is a better fit when it is slightly larger.

Behemotops and Miocaperera fossils (Fig. 7) do not presently preserve tail vertebrae. These transitional taxa are the ones most likely to transition to reduced legs and a robust tail. It is also apparent that these taxa are ancestral to rorquals, while Desmostylus (Fig. 5) is ancestral to right whales… which means 4x a tiny mammal tail evolved flukes.

Figure 7. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

3 – Odontocete tail evolution
The elongation of the torso and tail in the ancestors of odontocete (toothed) whales is better preserved in the fossil and extant record.

Figure 8 The short-tailed tenrec, Hemicentetes. Other than size and tail length, this taxon shares a long list of traits with the basal whale, Maiacetus in figure 1.

Here, starting with the tiny tail found in Hemicentetes (Fig. 8), the tail elongates in Indohyus and Leptictidium (Fig. 9) to become the swimming organ used in Pakicetus and fully aquatic toothed whales.

Figure 9. Odontoceti (toothed whale) origin and evolution. Here Anagale, Andrewsarchus, Sinonyx, Hemicentetes, Tenrec Indohyus and Leptictidium precede Pakicetus. Maiacetus and Orcinus are aquatic odontocetes.

Since a long, robust tail is already in the gene pool,
a placental mammal can redevelop a long, robust tail from not much of one.

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References
.researchgate.net/The_triple_origin_of_whales
wiki/Evolution_of_sirenians

Coombs et al. 2020 re-study odontocete skull asymmetry

Coombs et al. 2020 described odontocete (toothed whale) skull asymmetry
but did not trace it back to its origins in tenrecs (Fig. 1), as we did here two years ago. Without a valid phylogenetic context, the answers they sought evaded the Coombs team.

Nine years ago
whale skull asymmetry was studied by Fahlke et al. 2011, likewise without including tenrecs.

Figure 2. Hemicentetes an extant echolocating tenrec, also has a twisted skull, like its descendants, the odontocete whales.

From the Coombs et al. abstract:
“Unlike most mammals, toothed whale (Odontoceti) skulls lack symmetry in the nasal and facial (nasofacial) region. This asymmetry is hypothesised to relate to echolocation, which may have evolved in the earliest diverging odontocetes.”

Earlier. See figure 1.

“Early cetaceans (whales, dolphins, and porpoises) such as archaeocetes, namely the protocetids and basilosaurids, have asymmetric rostra, but it is unclear when nasofacial asymmetry evolved during the transition from archaeocetes to modern whales.”

Earlier. See figure 1.

“Early ancestors of living whales had little cranial asymmetry and likely were not able to echolocate.”

Incorrect conclusion. Add taxa. See figure 1. And see Gould 1965, who described echolocation in tenrecs.

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

Illustrations like these
(Fig 2) can be extremely helpful for ‘seeing’ evolution take place in a series of micro-evolutionary events. Typical of evolution, several lineages go extinct, while one or a few continue to the present day. Here we are lucky enough to have a few flesh and blood tenrecs at the genesis and several odontocetes to compare. This would make a great PhD project.

Coombs et al. 2020
are still not aware that the traditional clade ‘Cetacea’ is no longer valid because odontocete ‘whales’ arise apart from mysticete ‘whales’ in the large reptile tree. Click the links in this paragraph and in the citations below to get more backstory.

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References
Coombs EJ, Clavel J, Park T, Churchill M and Goswami A 2020. BMC Biology 18:86 https://doi.org/10.1186/s12915-020-00805-4
Fahlke JM,  Gingerich PD, Welsh RC and Wood AR. 2011. Cranial asymmetry in Eocene archaeocete whales and the evolution of directional hearing in water. PNAS 108 (35) 14545-14548; https://doi.org/10.1073/pnas.1108927108
Gould E 1965. Evidence for Echolocation in the Tenrecidae of Madagascar
Proceedings of the American Philosophical Society 109 (6): 352-360. online here.

https://www.researchgate.net/publication/328388746_The_triple_origin_of_whales

 

Reversals produce whale teeth, part 2

Short one today.
You might remember over a year ago a presentation on the evolution of mammal molars from simple to complex and back to simple again in toothed whales (Odontoceti, Fig. 1).

Figure 1. Mammal tooth evolution alongside odontocete tooth evolution, reversing the earlier addition of cusps.

On the same note,
here’s a presentation of three skulls, Pachygenelus (pre-mammal cynodont), Megazostrodon (last common ancestor of all mammals in the large reptile tree (LRT, 1698+ taxa), and Maiacetus, a toothed pre-whale with limbs (Fig. 2).

Figure 2. The pre-mammal, Pachygenelus, the first mammal, Megazostrodon, and a transitional toothed whale, Maiacetus, with teeth highlighted to show the reversal in odontocete molars. This may be the first time Megazostrodon was compared to a pre-whale.

Just concentrate on the teeth today,
and note how the simple cones (Fig. 3) of basal therapsids, then the canine led simple triangles of basal cynodonts (Fig. 2) then multicusped teeth of basal mammals (Fig. 2), slowly reversed over time to become, once again, triangles, then simple cones in odontocete whales (Fig. 4).

Figure 3. Basal therapsids, including Cutleria, with simple cones for teeth, as in odontocete whales.

Figure 4. The killer whale (Orcinus orca) skeleton and skull with parts colorized. Simple conical teeth line the jaws as in pre-cynodont synapsids.

As long-time readers know, baleen whales had their own evolution
as mysticetes arose from mesonychids, hippos, anthracobunids and desmostylians in turn, according to results recovered from the large reptile tree, which minimizes taxon exclusion by testing a wide gamut of nearly 1700 taxa.

Still waiting for a competing analysis
that tests a similar gamut of taxa. Emails to whale experts have not earned replies.

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References

https://pterosaurheresies.wordpress.com/2019/01/02/mammal-tooth-evolution-toward-complexity-and-then-simplicity/

Livyatan (originally Leviathan) enters the LRT

Lambert et al. 2010 made a ‘big splash’
when they introduced a giant ‘raptorial’ odontocete, Leviathan melvillei (Fig. 1). Distinct from a similarly-sized sperm whale (Physeter), Leviathan has a shorter rostrum and retained giant teeth on the maxilla. It also had a preoccupied name, so it was later renamed Livyatan.

Figure 1. Livyatan diagram from Lambert et al. 2010 and colored here.

Size:
The skull of Livyatan was fifty percent larger skull than the largest sauropterygians, similar in size to the skull of the largest ichthyosaurs, 3/4 the length of the skull of the largest odontocete, Physeter, but with much larger teeth.

Phylogeny
In the large reptile tree (LRT, 1666+ taxa), Livyatan is transitional between several extinct archaeocetes and all extant odontocetes of which Physeter and Tursiops  are the most primitive. The dolphin smile famously worn by Tursiops had its genesis in Livyatan (Fig.1) and was lost in long-jawed Physeter.

One question:
The lateral extent of the premaxilla in the Lambert et al. diagram (Fig. 1) is different in dorsal, lateral and palatal views.

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References
Lambert O et al. (6 co-authors) 2010. The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru. Nature 466:105–108.

wiki/Livyatan (Leviathan)
wiki/Physeter

One more trait linking hippos to mysticetes (baleen whales)

Vibrassae
are sensory organs found in hippos and baleen whales. Odontocete whales lack such vibrissae.

Figure 1. Mysticete (right whale) vibrissae compared to hippo vibrissae. Odontocete whales lack such structures.

Earlier the large reptile tree (LRT, 1644+ taxa) showed that odontocete members of the traditional clade Cetacea are not related to mysticetes, which arise from a clade of mesonychids, hippos and desmostylians. Odontocetes arise from tenrecs.