Cambaytherium 2020: Still not a primitive perissodactyl

We looked at this genus earlier
when Rose et al. 2014 first described Cambaytherium from some bits and pieces of this sheep-sized mammal from the Early Eocene (Fig. 1). Back in 2017 the large reptile tree (LRT; subset Fig. 5) nested Cambaytherium within the oreodont + mesonychid + hippo (Fig. 6) + anthracobunid (Fig. 2) + desmostylian (Figs. 3, 6) + mysticete (Fig. 3) clade. In the LRT that clade is far from Perissodactyla (= tapirs + horses + rhinos). 

Figure 2. Cambaytherium with a an alternate rostrum reversing taphonomic shifts.

Figure 1. Cambaytherium with a an alternate rostrum reversing taphonomic shifts.

Rose et al. 2020 update their discoveries
with new data (= more bones from more specimens) of Cambaytherium, which they still insist is a perissodactyl (rhino + horse) ancestor) ancestor.

Unfortunately,
taxon exclusion was the problem then and remains the problem now. The authors do not include  enough taxa that nest closer to Cambaytherium in LRT (subset Fig. 5), other than adding Anthracobune (Fig. 2) and Behemotops (Fig. 3).

Figure 3. Anthracobune reconstructed with a larger skull to match the teeth on the mandible.

Figure 2. Anthracobune reconstructed with a larger skull to match the teeth on the mandible.

Rose et al. 2020 employed 72 taxa.
That is twenty more than in Rose et al. 2014. Their more recent strict consensus resulted in 408 shortest trees. If that many shortest trees happened in the LRT using only 72 taxa, I would dive back in and fix what was wrong. In this case, taxon exclusion is still the problem with Rose et al. 2020.

Figure 1. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

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

Rose et al. 2020 explain their 20 taxon additions:
“The Eocene desmostylian Behemotops proteus was included for two reasons. First, there are interesting similarities between the teeth of this taxon and those of cambaytheres and anthracobunids (Ray et al., 1994). Second, the analysis of Cooper et al. (2014) placed Desmostylia in a polytomy that included most perissodactyls and anthracobunids (but not cambaytheres). Historically, paleontologists have considered Desmostylia (like anthracobunids) to be closely related to tethytheres (Domning et al., 1986; Ray et al., 1994).”

Rose et al. 2020 cherry-picked some of the right taxa, but not enough of the right taxa, according to the LRT. They are “Pulling a Larry Martin” (= putting too much attention on a few ‘key’ traits). These mammal experts still have no idea what the actual outgroups and relatives of Cambaytherium are because they don’t include enough pertinent taxa (see Fig. 5).

In the LRT, force-shifting Cambaytherium
to the base of the Perissodactylia added 18 steps to the LRT. That’s not a large number considering the phylogenetic distance, so convergence is an issue here. Convergence is something the LRT handles pretty well due to its wide gamut of taxa.

Another fault:
Rose et al. 2014 put their faith in genomic results with unclear and mixed results. Never put your faith in genomic results in deep time studies (especially fossil taxa). Also, don’t trust the work of others. Don’t borrow cladograms. Do your own phenomic analysis with a wide gamut of taxa, as in the LRT. Then you’ll have a good model for actual evolutionary events.

From the Rose et al. 2020 abstract:
“The anatomy of Cambaytherium, a primitive, perissodactyl-like mammal from the lower Eocene Cambay Shale Formation of Gujarat, India, is described in detail on the basis of more than 350 specimens that represent almost the entire dentition and the skeleton.”

Many of the specimens are small disarticulated and broken pieces of bone. At least one skull is pretty well fossilized in 3D (Fig. 1).

“Cambaytherium combines plesiomorphic traits typical of archaic ungulates such as phenacodontids with derived traits characteristic of early perissodactyls.”

The authors cannot be more specific due to taxon exclusion.

“Cambaytherium was a subcursorial animal better adapted for running than phenacodontids but less specialized than early perissodactyls. The cheek teeth are bunodont with large upper molar conules, not lophodont as in early perissodactyls; like perissodactyls, however, the lower molars have twinned metaconids and m3 has an extended hypoconulid lobe. A steep wear gradient with heavy wear in the middle of the tooth row suggests an abrasive herbivorous diet.

Homologous desmostylian and hippo teeth also show heavy wear.

“Three species of Cambaytherium are recognized: C. thewissi (∼23 kg), C. gracilis (∼10 kg), and C. marinus (∼99 kg). Body masses were estimated from tooth size and long bone dimensions. Biostratigraphic and isotopic evidence indicates an age of ca. 54.5 Ma for the Cambay Shale vertebrate fauna, the oldest Cenozoic continental vertebrate assemblage from India, near or prior to the initial collision with Asia.

“Cambaytheriidae (also including Nakusia and Perissobune (Fig. 4) and Anthracobunidae are sister taxa, constituting the clade Anthracobunia, which is sister to Perissodactyla.

You heard it here first: The LRT nested Cambaytherium with Anthracobune (Fig. 3), but far from Perissodactyla due to taxon exclusion.

Perissobune (Fig. 4) has not been tested in the LRT, but closely resembles the basal perissodactyl, Protapirus (Fig. 4), with a taller coronoid process and only two lower molars. Compare to the distinctly different mandible of Cambaytherium (Fig. 1).

“We unite them in a new higher taxon, Perissodactylamorpha.

This is invalid, inappropriate, premature and based on cherry-picked taxa.

Figure 3. Perissobune mandible compared to diagram of a primitive perissodactyl, Protapirus. Compare to figure 1.

Figure 4. Perissobune mandible compared to diagram of a primitive perissodactyl, Protapirus. Compare to figure 1.

Continuing from the Rose et al. 2020 abstract:
“The antiquity and occurrence of Cambaytherium—the most primitive known perissodactylamorph—in India near or before its collision with Asia suggest that Perissodactyla evolved during the Paleocene on the Indian Plate or in peripheral areas of southern or southwestern Asia.”

Figure 3. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT

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

Figure 1. Merycopotamus, Hippopotamus, and Paleoparadoxia compared to scale.

Figure 6. Merycopotamus, Hippopotamus, and Paleoparadoxia compared to scale.

Back in 2017 readers learned the following
from Rose et al. 2014, “Cambaytherium was found on the marine coastline of island India.”

Then I added, “close to where odontocete whales were also evolving from Tenrec relatives like Pakicetus. Based on its relationships and geography, Cambaytherium was likely much more aquatic than is typical for perissodactyls.”

Figure 1. Simbakubwa from Broths and Stevens 2019, colors added, and compared to a lion mandible. Note the two medial views of the mandible with different shapes. Dorsal view of indented mandible and palate is similar to hippos.

Figure 7. Simbakubwa from Broths and Stevens 2019, colors added, and compared to a lion mandible. Note the two medial views of the mandible with different shapes. Dorsal view of indented mandible and palate is similar to hippos.

For some reason no one wants to test enigma taxa with hippos 
and mesonychids. We looked at this same problem earlier with the putative carnivore, Simbakumba, which also turned out to be a hippo relative.


References
Rose, KD et al. (8 other authors) 2014. Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India. Nature Communications. 5 (5570). doi:10.1038/ncomms6570.
Rose KD et al, 2020. Anatomy, Relationships, and Paleobiology of Cambaytherium (Mammalia, Perissodactylamorpha, Anthracobunia) from the lower Eocene of western India, Journal of Vertebrate Paleontology (2020). DOI: 10.1080/02724634.2020.1761370

wiki/Cambaytherium
phys.org/news/2020-11-indian-fossils-hypothesis-hoofed-mammals.

From Phys.org
“New research published today in the Journal of Vertebrate Paleontology describes a fossil family that illuminates the origin of perissodactyls—the group of mammals that includes horses, rhinos and tapirs. It provides insights on the controversial question of where these hoofed animals evolved, concluding that they arose in or near present day India.”

Phylogeny of Desmostylia: Matsui and Tsuihiji 2019

Matsui and Tsuihiji 2019 bring us their views
on the phylogeny of taxa within their Desmostylia, an order of large aquatic (Pacific rim) mammals, best known from the early Oligocene (31mya) to the late Miocene (7.25mya). Traditionally there are relatively few taxa in the clade Desmostylia (Neoparadoxia (Fig. 2), Paleoparadoxia, Behemotops (Fig. 2), Desmostylus (Fig. 3) and a few others not as well represented in the fossil record.

Unfortunately the authors’ views
are too restricted with too few taxa under consideration. Desmostylians are not the extinct taxa Matsui and Tsuihiji think they are when more taxa are included (Fig. 1).

From their abstract:
“Background.
Desmostylia is a clade of extinct aquatic mammals with no living members.”

False. Although this is traditional thinking in the large reptile tree (LRT, 1638+ taxa; subset Fig. 1) living desmostylians include mysticete (baleen) whales. Their ancestors include oreodonts, mesonychids, hippos, cambaytheres and anthracobunids.

Figure 3. the Merycoidodon cladogram includes hippos, whales and a number of extinct taxa.

Figure 1. The Merycoidodon cladogram includes hippos, whales and a number of extinct taxa. Traditional desmostylians are in medium blue here.

 

The abstract continues:
“Today, this clade is considered belonging to either Afrotheria or Perissodactyla.”

Their figure 1 shows desmosytlians arising from either: (a) Equus, the horse, in the Perissodactyla hypothesis; (b) Elephas, the elephant, in the Afrotheria hypothesis, or (c) Procavia, the hyrax, in their Paenungulatomorpha hypothesis. In other words, the authors have no idea. Genomic studies deliver false positives like Afrotheria. and you can’t used genomic studies of deep time fossils. In the LRT, which uses traits, desmostylians arise from mesonychids, hippos and anthracobunids as we learned earlier here.

“In the currently-accepted taxonomic scheme, Desmostylia includes two families, 10
to 12 genera, and 1314 species. There have been relatively few phylogenetic analyses
published on desmostylian interrelationship compared to other vertebrate taxa, and
two main, alternative phylogenetic hypotheses have been proposed in previous studies.
One major problem with those previous studies is that the numbers of characters and
OTUs were small.”

So Matsui and Tsuihiji, are studying the details without understanding the big picture… which could affect the details. Better to have a firm foundation built, then afterwards add whatever decorations to your structure.

Figure 1. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

Figure 2. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

The abstract continues:
“Methods.

In this study, we analyzed the phylogenetic interrelationship of Desmostylia

based on a new data matrix that includes larger numbers of characters and taxa than in
any previous studies. The new data matrix was compiled mainly based on data matrices
of previous studies and included three outgroups and 13 desmostylian ingroup taxa.
Analyses were carried out using five kinds of parsimonious methods.”

Their three outgroups were: [1] Anthracobune, [2] Pezosiren + Moeritherium and [3] all three. Again, they are playing ‘pin the tail on the donkey‘ when the actual outgroups are available online (Fig. 1). No blind guesswork is necessary.

Figure 1. 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.

Figure 3. 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 abstract continues:
“Results.

Strict consensus trees of the most parsimonious topologies obtained in all

analyses supported the monophyly of Desmostylidae and paraphyly of traditional
Paleoparadoxiidae. Based on these results, we propose phylogenetic definitions of the
clades Desmostylidae and Paleoparadoxiidae based on common ancestry.”

That’s fine, but incomplete. This is another classic case of knowing so much about a few taxa, while knowing nothing about their ancestors, sisters and descendants, all based on taxon exclusion. That’s why the LRT is here. The LRT is the first instrument to report that the clade Cetacea was diphyletic. Members of the Odontoceti (toothed whales) are not related to members of the Mysticeti (baleen whales), contra traditional studies that exclude pertinent taxa.

Some workers insist
that I add characters to the LRT, but as you can see, adding more traits to the LRT would not reveal the ancestors, sisters or descendants of the Desmostylia. Only more taxa solve this problem. More taxa create greater resolution and nest all enigmas. More characters do not and cannot do that, so enough with that lame request.

If you want to add more or different traits
to your more focused studies, by all means, do so! But keep that taxon list complete. Let the LRT be your guide.


References
Matsui and Tsuihiji 2019. The phylogeny of desmostylians revisited: proposal of new clades based on robust phylogenetic hypotheses. PeerJ:e7430 http://doi.org/10.7717/peerj.7430

Simbakubwa: Not a giant carnivore. More like a hippo.

Borths and Stevens 2019 might have been confused by the giant canines
and giant molars of Simbakubwa (Fig. 1). The authors thought they were dealing with a giant carnivore related to hyaenodonts and creodonts (hence the title of their paper).

The large reptile tree (LRT, 1546 taxa) makes no assumptions. The LRT minimizes confusion by testing a wider gamut of taxa, including mesonychids (Fig. 2) and hippos. It turns out the great size of Simbakubwa is actually no big deal because it’s closer to hippos than lions. Most hippos are much bigger than most carnivores.

Figure 1. Simbakubwa from Broths and Stevens 2019, colors added, and compared to a lion mandible. Note the two medial views of the mandible with different shapes. Dorsal view of indented mandible and palate is similar to hippos.

Figure 1. Simbakubwa from Broths and Stevens 2019, colors added, and compared to a lion mandible. Note the two medial views of the mandible with different shapes. Dorsal view of indented mandible and palate is similar to hippos.

Simbakubwa kutokaafrika (Borths and Stevens 2019; Miocene, 23mya; size; Fig. 1) was originally considered a gigantic carnivore, a member of the Hyaeondonta and Creodonta. Here it nests with Ocepeia (Fig. 3) as an offshoot of basal hippos with anteriorly placed eyes, convergent with carnivores, derived from mesonychids (Fig. 2).

Strangely
in dorsal view the mandible (dentary) was originally presented with an unnatural lateral kink/bend, creating a large open space where the teeth do not occlude. The authors report, (dentary is reconstructed with the distal portion medially oriented out of natural position) and “the coronoid should be interpreted cautiously because it is reconstructed.”

Not sure why they published that mandible without fixing it. 
The authors note: “the tooth crowns are unworn”. Relative to the skull size, all the teeth were enormous and they extended far back in the skull. I note the shearing canines of extant hippos are already present here. It is also worthwhile to compare the only dentary premolar of Simbakubwa (Fig. 1) with the identical tooth found in the earlier mesonychid, Harpagolestes (Fig. 4). In any case, the suite to traits preserved nest Simbakubwa with mesonychid hippos, rather than hyaenodont creodonts (which are marsupials, not carnivores).

Hippos are not related to artiodactyls
in the LRT, contra the traditional myth. Hippo ancestors are basal to taxa leading to baleen whales. 

Figure 1. Mesonyx, the first known mesonychid was a sister to Hippopotamus in the large reptile tree. So maybe it was a plant eater.

Figure 2. Mesonyx, the first known mesonychid was a sister to Hippopotamus in the large reptile tree. So maybe it was a plant eater, even though, like Simbakubwa, it looks like a predator with large lower canines.

Wikipedia reports,
Simbakubwa, like other hyainailourids, probably was a specialist hunter and scavenger that preyed on creatures such as rhinoceroses and early proboscideans. It may have been somewhat less specialized in crushing bone than its later relatives such as Hyainailouros. However, like HyainailourosSimbakubwa possessed lingually rotating carnassial blades, ensuring a constant shearing edge throughout its life.” Hippos are also killers, but usually only for defense. They and all their sister taxa prefer plants.

Figure 1. Ocepeia: before and after. The original reconstruction is here compared to a tracing of CT scan, duplicated left to right.

Figure 3. Ocepeia: before and after. The original reconstruction is here compared to a tracing of CT scan, duplicated left to right.

Ocepeia daouiensis (Gheerbrant et al 2001, 2014; Paleocene, 60 mya; 9 cm skull length; Fig. 3) is a Hippopotamus ancestor derived from a sister to Merycoidodon. The original reconstruction was not an accurate representation of the fossil CT scan. The pneumatized skull contains many air spaces. The larger skulls have larger canines and so are considered male. The jugal deepens below the orbit, hiding the posterior molars in lateral view. The premaxilla is transverse. The upper canine rubs against the lower large incsior creating a facet, as in hippos and Harpagolestes (Fig. 4). Ocepeia was found with aquatic taxa and was probably amphibious.

Figure 5. Robust Harpagolestes nests between the hippos and Mesonyx.

Figure 4. Robust Harpagolestes nests between the hippos and Mesonyx. Note the identical lower premolar as in Simbakubwa (Fig. 1).

Several news organizations picked up on the sensational aspects
of this ‘gigantic carnivore’ discovery. Unfortunately, this may become embarrassing for the authors when confirmed.

The good news is:
we have more hippo and mysticete ancestors to study!


References
Borths MR and Stevens NJ 2019. Simbakubwa ￿kutokaafrika, gen. et sp. nov. (Hyainailourinae, Hyaenodonta, ‘Creodonta,’ Mammalia), a gigantic carnivore from the earliest Miocene of Kenya. Journal of Vertebrate Paleontology e1570222 (20 pages) https://doi.org/10.1080/02724634.2019.1570222

wiki/Simbakubwa

https://www.ranker.com/list/killer-hippos-are-dangerous/mariel-loveland

https://www.washingtonpost.com/news/senegals-killer-hippo-problem/

http://blogs.discovermagazine.com/deadthings/2019/04/18/simbakubwa/#.XTX-IRTT63A

https://www.cbsnews.com/news/giant-lion-fossil-found-inside-drawer-at-kenyan-museum-2019-04-19/

Two pre-hippo, pre-desmostylian, pre-mysticete taxa join the LRT

Figure 1. Agriochoerus is a late-surviving oreodont with a diastema and a sister to Merycoidodon.

Figure 1. Agriochoerus is a late-surviving oreodont with a diastema. It is a sister to Merycoidodon. A postorbital bar appears in the other tested oreodont, Merycoidodon, but is reconstructed here based on what appears to be broken bone.

An oreodont with a diastema
Agriochoerus antiquus (Leidy 1850; Late Eocene to Oligocene; 38–16mya) was similar to Merycoidodon, but had a diastema with the loss of the anterior premolars and the addition of one molar. The dentary canines were larger. Oreodonts nest at the base of the hippo-mysticete clade in the large reptile tree (LRT, 1381 taxa) and between the Phenacodus clade and the Homalodotherium + artiodactyl clades.

Figure 1. Merycopotamus, Hippopotamus, and Paleoparadoxia compared to scale.

Figure 2. Merycopotamus, Hippopotamus, and the desmostylian, Paleoparadoxia, compared to scale. The resemblance between taxa here are coming into clearer focus in the LRT, but overlooked elsewhere.

Not an anthracothere. Not even an artiodactyl.
Merycopotamus dissimilis (Falconer & Cautley 1847; Middle Miocene to Late Pliocene; Fig. 2) was considered an Asian anthracothere (pig-like artiodactyl), but here nests between Ocepeia and Hippopotamus (Fig. 2) apart from the artiodactyls, closer to oreodonts and mesonychids. Note the migration of the orbit posteriorly, the re-appearance of the postfrontal and prefrontal, the massive dentary with massive retroarticular process and the larger dentary canine, as in hippos.

Figure 3. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT

Figure 3. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT. These taxa were not nested together  in smaller studies that omitted various taxa.

Few mammals
enlarge the dentary to a size that competes with the skull. Hippos do that. Few mammals enlarge the retro process of the dentary to such a large size. Hippos do that. The retro process anchors the jaw-closing masseter muscle complex.

Figure 4. Merycopotamus skull and mandible with colors identifying the reappearances of the prefrontal and postfrontal.

Figure 4. Merycopotamus skull and mandible with colors identifying the reappearances of the prefrontal and postfrontal.

I looked at none of these taxa firsthand.
Rather, the data came from photos and these taxa were added to the LRT. For doing this and continuing to do this for the last seven years I have incurred the disdain of paleontologists and would-be paleontologists world-wide. Judge for yourself whether or not the LRT has provided scientific value or pseudoscientific propaganda, as others assert without testing.

References
Falconer H and Cautley PT 1847. Fauna antiqua sivalensis, Atlas. Smith, Elder and Co., London, 136 pp.
Leidy J 1850. [Abstract of remarks made before a meeting of the Academy of Natural Sciences of Philadelphia, December 17th, 1850]. Proceedings of the Academy of Natural Sciences of Philadelphia 5(1):121-122.
Thorpe MR 1921. Two new forms of Agriochoerus. American Journal of Science (8): 111–126.

wiki/Agriochoerus

 

Enigmatic oreodont, Merycoidodon, joins the LRT

Something of an enigma.
Wikipedia reports, “Merycoidodon is an extinct genus of terrestrial herbivore.” That’s rather vague for a common sheep-sized fossil from the USA.

Figure 1. Merycoidodon reconstruction traced by an unknown artist from an AMNH mount photo.

Figure 1. Merycoidodon reconstruction traced by an unknown artist from an AMNH mount photo.

In Late Eocene
to Late Oligocene (38–16mya) deposits, Merycoidodon (Leidy 1848) lived in large herds, principally in South Dakota. but also found from Alberta to Florida, typically preferring well-watered areas. Leidy considered it a member of the ruminantoid Pachydermata‘.

Figure 2. Merycoidodon skull. Colors added.

Figure 2. Merycoidodon skull. Colors added.

Merycoidodontoidea
Wikipedia reports, “Merycoidodontoidea, sometimes called “oreodonts,” or “ruminating hogs”, is an extinct superfamily of prehistoric cud-chewing artiodactyls with short faces and fang-like canine teeth. As their name implies, some of the better known forms were generally hog-like, and the group has traditionally been placed within the Suina (pigs, peccaries and their ancestors), though some recent work suggests they may have been more closely related to camels.” Evidently the phylogenetic nesting of Merycoidodon is not clear to the Wikipedia writers. That may be due to its generalize appearance.

Spaulding et al. 2009
nested Merycoidodon ancestral to Camelus + Lama, derived from Hyracotherium and Cainotherium, among tested taxa. The Spaulding et al. cladogram separated hippos from mesonychids, nesting hippos with Diacodexis (largely incomplete) and Indohyus, an omitted tenrec in the LRT.

Figure 3. the Merycoidodon cladogram includes hippos, whales and a number of extinct taxa.

Figure 3. the Merycoidodon cladogram includes hippos, whales and a number of extinct taxa.

In the large reptile tree
(LRT, 1376 taxa) Merycoidodon nests firmly as the proximal outgroup at the base of the Mesonyx to mysticete (baleen whale) clade (subset Fig. 3). Merycoidodon also nests between the Phenacodus clade and the Homalodotherium clade + artiodactyl clades.

It is worth noting again
that hippos do not nest with artiodactyls in the LRT, breaking a traditional paradigm.

Figure 1. Mesonyx, the first known mesonychid was a sister to Hippopotamus in the large reptile tree. So maybe it was a plant eater.

Figure 5 Mesonyx nests between oredonts, like Merycoidodon, and hippos, like Hippopotamus.

I’ve been curious about oreodonts for decades.
What were they? Happy to finally test it and nest it where it belongs, basal to hippos, and transitional to modern hoofed ruminants. The generalized appearance of Merycoidodon is appropriate to its basal and transitional nesting. Based on its nesting basal to Ocepeia (middle Paleocene), the genesis of Merycoidodon must extend to the early Paleocene, if not before.

Figure 3. Hippopotamus. This stout, wide-faced, fanged mammal does not nest with deer.

Figure 6. Hippopotamus. This stout, wide-faced, fanged mammal does not nest with deer,but with Mesonyx.

References
Leidy 1848. On a new fossil genus and species of ruminantoid Pachydermata: Merycoidodon culbertsonii. Proceedings of the Academy of Natural Sciences of Philedelphia Vol IV, 47-51.

Merycoidodontidae (Thorpe 1923)
Mesonychidae (Cope 1880)

wiki/Merycoidodontoidea
wiki/Merycoidodon

Resurrecting extinct taxa: Creodonta, Mesonychidae, Desmostylia and Gephyrostegidae

Taxonomy
“the branch of science concerned with classification, especially of organisms; systematics.”  Taxon: a taxonomic group of any rank, such as a species, family, or class.

The large reptile tree
(LRT, 1366 taxa) has resurrected several taxa (in this case, clades) long thought to be extinct.

Figure 1. Adding Sinopa to the LRT nests it here, between the extant quoll (Dasyurus) and the extant Tasmanian devil (Sarcophilus).

Figure 1. Members of the traditionally extinct Creodonta include the extant quoll (Dasyurus) and the extant Tasmanian devil (Sarcophilus).

Creodonta
According to Wikipedia: “Creodonta” was coined by Edward Drinker Cope in 1875. Cope included the oxyaenids and the viverravid Didymictis but omitted the hyaenodontids. In 1880. he expanded the term to include MiacidaeArctocyonidaeLeptictidae (now Pseudorhyncocyonidae), OxyaenidaeAmbloctonidae and Mesonychidae. Cope originally placed creodonts within the Insectivora. In 1884, however, he regarded them as a basal group from which both carnivorans and insectivorans arose. Hyaenodontidae was not included among the creodonts until 1909. Over time, various groups were removed, and by 1969 it contained, as it does today, only the oxyaenids and the hyaenodontids.

In the LRT, Oxyaena and Hyaenodon are members of an extinct clade. However, Sinopa is considered a hyaenodontid, and it nests between the extant quoll (genus: Dasyurus) and the extant Tasmanian devil (genus: Sarcophilus). Sarkastodon is considered an oxyaenid and it nests as a sister to Sarcophilus. So… either the quoll and Tasmanian devil are living members of the Creodonta, or we’ll have to redefine the Creodonta.

Figure 1. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

Figure 1. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

Desmostylia
According to Wikipedia: “Desmostylians are the only known extinct order of marine mammals. The Desmostylia, together with Sirenia and Proboscidea (and possibly Embrithopoda), have traditionally been assigned to the afrotherian clade Tethytheria, a group named after the paleoocean Tethys around which they originally evolved. The assignment of Desmostylia to Afrotheria has always been problematic from a biogeographic standpoint, given that Africa was the locus of the early evolution of the Afrotheria while the Desmostylia have only been found along the Pacific Rim. That assignment has been seriously undermined by a 2014 cladistic analysis that places anthracobunids and desmostylians, two major groups of putative non-African afrotheres, close to each other within the laurasiatherian order Perissodactyla.”

In the LRT, desmostylians are indeed derived from anthracobunids, which, in turn, are derived from hippos and mesonychids. Mysticeti, the clade of baleen whales are derived from desmostylians. So… baleen whales are extant desmostylians.

Figure 3. Four mesonychids to scale. Here Mesonyx, Anthracobune, Paleoparadoxia and Hippopotamus are compared.

Figure 3. Four mesonychids to scale. Here Mesonyx, Anthracobune, Paleoparadoxia and Hippopotamus are compared.

Mesonychidae
According to Wikipedia, “Mesonychidae is an extinct family of small to large-sized omnivorouscarnivorous mammals closely related to cetartiodactyls (even-toed ungulates & cetaceans) which were endemic to North America and Eurasia during the Early Paleocene to the Early Oligocene. The mesonychids were an unusual group of condylarths with a specialized dentition featuring tri-cuspid upper molars and high-crowned lower molars with shearing surfaces. They were once viewed as primitive carnivores, like the Paleocene family Arctocyonidae, and their diet probably included meat and fish. In contrast to this other family of early mammals, the mesonychids had only four digits furnished with hooves supported by narrow fissured end phalanges.”

In the LRT, mesonychids include hippos and baleen whales. So, they are extant mesonychids. On the other hand, Arctocyonidae includes Arctocyon, which nests in the unrelated marsupial clade, Creodonta (see above). Certain other traditional mesonychids, like Sinonyx and Andrewsarchus, are not mesonyhids, but nest with the elephant shrew, Rhychocyon, close to tenrecs.

Figure 1. Silvanerpeton and Gephyrostegus to the same scale. Each of the two frames takes five seconds. Novel traits are listed. This transition occurred in the early Viséan, over 340 mya. Gephyrostgeus is more robust and athletic with a larger capacity to carry and lay eggs.

Figure 1. Silvanerpeton and Gephyrostegus to the same scale. Each of the two frames takes five seconds. Novel traits are listed. This transition occurred in the early Viséan, over 340 mya. Gephyrostgeus is more robust and athletic with a larger capacity to carry and lay eggs.

Gephyrostegidae
According to Wikipedia, “Gephyrostegidae is an extinct family of reptiliomorph tetrapods from the Late Carboniferous including the genera GephyrostegusBruktererpeton, and Eusauropleura.”

In the LRT, Gephyrostegus is the last common ancestor of the Amniota (= Reptilia). So… gephyrostegids include all living mammals, archosaurs (crocs + birds) and lepidosaurs.

References

wiki/Gephyrostegidae
wiki/Mesonychidae
wiki/Desmostylia

SVP 2018: New Mammalodon relative with marine worm bores

Shipps, Peredo and Pyenson 2018 report
on a Late Oligocene mammalodontid, the first from the Northern Hemisphere. “The skull and teeth of this specimen bear boreholes from bone-eating Osedax worms, providing valuable information on the taphonomy of the specimen. Critically, this specimen preserves intact ear bones and several teeth.”

Osedax is marine worm.
According to Wikipedia, “The worms bore into the bones of whale carcasses to reach enclosed lipids, on which they rely for sustenance.”

Figue 1. Mammalodon nests within the clade Anthracobune basal to desmostylians and mysticetes.

Figue 1. Mammalodon nests within the clade Anthracobune basal to desmostylians and mysticetes.

Mammalodon (Fig. 1) is indeed in the lineage of mysticete whales, but several nodes distant (Fig. 2) in the large reptile tree. It is related to Janjucetus and Anthracobune, basal to desmostylians, not far from hippos. Desmostylians are also found along the Pacific rim, so this appearance of an ancestor in Washington state is expected. All are mesonychids, not ungulates.

Figure 2. Subset of the LRT focusing on mysticetes, including Sitsqwayk, and their predecessors.

Figure 2. Subset of the LRT focusing on mysticetes, including Sitsqwayk, and their predecessors.

References
Shipps BK, Peredo CM and Pyenson ND 2018. An unexpected Northerner with burrowed bones: a new mammalodontid (Mysticeti) from the Pacific Northwest with Osedax bores provides insight into Oligocene marine taphonomy and mysticete evolution. SVP abstracts.

wiki/Osedax
wiki/Janjucetus
wiki/Mammalodon
wiki/Anthracobune

 

Cornwallius: not a desmostylian, an ancestor to desmostylians

These taxa
are part of the a recent review of mysticete (baleen whale) ancestors you can read about here, here and here.

Cornwallius sookensis (originally Desmostylus sookensis, Hay 1923, Cornwall 1922; Beatty 2006a, b; Early Oligocene, 25 mya; Fig. 1) was originally and traditionally considered a desmostylian (Fig. 3). Here it nests with Cambaytherium (Fig. 2), both basal to anthracobunids like Janjucetus. These taxa have a narrow skull and a deep jugal beneath the squamosal. The nares are anterior, rather than dorsal in location.

Figure 1. Adult Cornwallius look more like desmostylians. Juveniles look more like anthracobunids. Both are descendant taxa.

Figure 1. Adult Cornwallius look more like desmostylians. Juveniles look more like anthracobunids. Both are descendant taxa.

Note the resemblance
(lack of a downturned snout) on the juvenile to Cambaytherium (above). Apparently, neotony produces a straights-snout anthracobunid. Otherwise it evolves to the tusky, droop-snout, desmostylian grade.

Figure 2. Cambaytherium with a an alternate rostrum reversing taphonomic shifts.

Figure 2. Cambaytherium with a an alternate rostrum reversing apparent taphonomic shifts.

Beatty 2006
produced the following cladogram (Fig. 3) in which desmostylians are derived from the Moeritherium/Elephas clade. In the large reptile tree (LRT, 1163 taxa) cambaytheres and desmostylians arise from mesonychids and hippos.

Figure 2. From Beatty 2006b, a phylogeny of desmostylians derived from moeritherium, an aquatic relative of elephants and sirenians (manatees). Actually desmostylians arise from cambaytheres and anthracobunids, arising from hippos and mesonychids. 

Figure 3. From Beatty 2006b, a phylogeny of desmostylians derived from moeritherium, an aquatic relative of elephants and sirenians (manatees). Actually desmostylians arise from cambaytheres and anthracobunids, arising from hippos and mesonychids.

References
Beatty, BL 2006a. Rediscovered specimens of Cornwallius (Mammalia, Desmostylia) from Vancouver Island, British Columbia, Canada. Vertebrate Palaeontology. 1(1):1–6.
Beatty, BL 2006b. Specimens of Cornwallius sookensis (Desmostylia, Mammalia) from Unalaska Island, Alaska. Journal of Vertebrate Paleontology. 26(3):785–87.
Cooper LN, Seiffert ER, Clementz M, Madar SI, Bajpai S, Hussain ST, Thewissen JGM 2014. Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls. PLoS ONE. 9 (10): e109232. doi:10.1371/journal.pone.0109232. PMID 25295875.
Cornwall IE 1922. Notes on the Sooke Formation, Vancouver Island, B.C. Canadian Field Naturalist. 36:121–23.
Hay OP 1923. Characteristics of sundry fossil vertebrates. Pan-American Geologist. 39:101–120.
Kumar K 1991. Anthracobune aijiensis nov. sp. (Mammalia: Proboscidea) from the Subathu Formation, Eocene from NW Himalaya, India”. Geobios. 24 (2): 221–39. doi:10.1016/s0016-6995(91)80010-w. OCLC 4656806310.
Rose, KD et al. (8 other authors) 2014. Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India. Nature Communications. 5 (5570). doi:10.1038/ncomms6570.

wiki/Cambaytherium
wiki/Cornwallius

Harpagolestes uintensis is a mesonychid. Harpagolestes macrocephalus is not.

Welcome to the wonderful world of convergence!
Harpagolestes uintensis (Fig. 2) and H. macrocephalus (Fig. 1) look similar enough to be considered similar, but they are not congeneric in the LRT. One of them needs a new generic name.

Of the several heresies
recovered by the large reptile tree (LRT, 1120 taxa) the latest is the separation of some former mesonychids (Fig. 1, Andrewsarchus, Sinonyx, Hapalodectes) from current and traditional mesonychids (Fig. 2, Mesonyx and Harpagolestes uintensis). The clade of former mesonychids now nests as giant tenrecs. This clade produced odontocete whales and transitional taxa. The latter group of true mesonychids gave rise to mysticete (baleen) whales and the following transitional taxa: hippos, anthrobunids and desmostylians.

Figure 1. Harpagolestes macrocephalus compared to sisters Sinonyx and Andrewsarchus to scale.

Figure 1. Harpagolestes macrocephalus compared to sisters Sinonyx and Andrewsarchus to scale.

Today the addition of Harpagolestes macrocephalus
(Fig. 1) to the LRT nests it not congenerically with Harpagolestes uintensis (Fig. 2), but between Andrewsarchus and Sinonyx. So the two are not congeneric.

Figure 1. Andrewsarchus, Sinonyx, Mesonyx and Harpagolestes to scale for direct comparison of these two tenrecs with these two mesonychids.

Figure 1. Andrewsarchus, Sinonyx, Mesonyx and Harpagolestes to scale for direct comparison of these two tenrecs with these two mesonychids.

We’ve seen convergence many times
in the LRT. This is just one more example of convergence that has been traditionally overlooked.

Deleting nine tenrecs
on either side of Sinonyx + Andrewsarchus + H. macrocephalus changes nothing in the LRT. The above taxa still nest with odontocetes far from mesonychids through mysticetes, though some loss of resolution occurs in the mammal subset of the LRT.

Deleting hippos and anthracobunids
from the mesonychid clade changes nothing.

References
O’Leary MA and Rose KD 1995. Postcranial skeleton of the early Eocene mesonychid Pachyaena (Mammalia: Mesonychia). Journal of Vertebrate Paleontology 15(2):401-430.

Related mammals that nest at the bases of several hoofed clades

The value
of the large reptile tree (LRT, 1013 taxa) and the reconstructions gathered together at ReptileEvolution.com lie in their ability to put faces on names (Figs, 1) sometimes to scale (Fig. 2) to help one recognize patterns that may have gone unrecognized while just looking at names and scores.

These are the mammals that nest with one another
as sisters after deletion of more derived taxa in each of their several clades (listed at right, Fig. 1). Thus they, more or less, represent the basal radiation of hoofed mammals prior to each clade radiation. And to no one’s surprise, they look like each other, despite wide variations in size.

Frankly,
I’m reexamining the traits of these taxa because the LRT had trouble resolving them. There were mistakes in there. Now, after some score corrections, the resolution is complete again, but some Bootstrap scores have risen to just above 50. Not great, but better than below 50. Remember, I don’t have access to these specimens and sometimes work from published drawings.

Figure 1. Skulls of taxa nesting at the bases of several mammal clades starting with mesonychids.

Figure 1. Skulls of taxa nesting at the bases of several mammal clades starting with mesonychids. The differences are harder to see than in derived taxa in each clade (column at right). See figure 2 for skeletons to scale.

Some of these basal taxa
gave rise to baleen whales. Others were ancestral to giraffes, elephants, horses and everything in between. None of these taxa are nearly so famous or interesting to the general public, but it is from these generalized (plesiomorphic) taxa that the few and subtle evolutionary changes that are key to each clade first make an appearance.

Figure 2. Skeletons of taxa basal to various clades derived from basal mesonychids, all to scale.

Figure 2. Skeletons of taxa basal to various clades derived from basal mesonychids, all to scale. Note the presence of phylogenetic miniaturization at the base of the Artiodactyla. Consider this scenario: mesonychids radiated widely, including to create larger and smaller taxa. The larger homalotheres did not radiate greatly, as far as we know. On the other hand, the smaller taxa radiated to become a long list of extinct and exact hoofed taxa. And, of course, the mesonychid clade radiated to include today’s hippos and baleen whales. 

Sometimes a ‘show and tell’ drives a point home
better than just a ‘tell’. Even so, these are not the precise individuals in the direct lineage of known derived taxa, but the close relatives of those perhaps eternally unknown and hypothetical individuals. The suite of traits that lump and separate these taxa can be gleaned from the present MacClade file, continually added to and updated, and available here., which is where you can also see the cladogram from which the above taxa were pulled.