A 'consensus cladogram' for artiodactyls

I can't discuss because I know not first thing about it, but undeterred by that I would like to ask you: do you have any suggestions about where the various extinct clades might fit in the diagram? e.g. the protoceratids?

I think the protoceratids would fall under Tylopoda, if I'm not mistaken

AN ANATOMICAL AND PHYLOGENETIC STUDY
OF THE OSTEOLOGY OF THE PETROSAL OF
EXTANT AND EXTINCT ARTIODACTYLANS
(MAMMALIA) AND RELATIVES
MAUREEN A. OâLEARY
Department of Anatomical Sciences, HSC T-8 (040)
Stony Brook University, Stony Brook, NY 11794-8081
(maureen.oleary@stonybrook.edu)
BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY
Number 335, 206 pp., 119 figures, 3 tables
Issued June

O'Leary's paper repeat Spaulding's cladogram showing Andrewsarchus nested in Cetancodonta, and out of Mesonychia; and Mesonychia closer to Perissodactyla than to Artiodactyla. It seems a bit surprising.

Basal position of Tylopoda implies: polyphyletism of Neoselenodontia; independent evolution of herbivory in Tylopoda and Pecora; omnivore ancestor for stem Tylopoda.

An interesting common trait in Whale-Hippo-Ruminant clade is headbutting. A nice name instead of Cetruminantia would be Frontipercurssoria "Head-butters".

"Whippomorpha"?!?

Who can say that with a straight face?

Didn't Paul Barrett call these "expertograms"?

Furthermore, the Spaulding et al. (2009) cladogram has, in the strict consensus:
* A clade of whippomorphs and archaeotheres + Andrewsarchus
* Ruminantia with tragulids, antilocaprids, and giraffids as successively closer outgroups to bovids + cervids
* A fairly classic Tylopoda (camelids, cainotheres, oreodonts)
* No resolution of the basal polytomy between the above clades, suiformes, and a few basal taxa.

The paper in question is Spaulding, M., M. A. O'Leary, and J. Gatesy. 2009. Relationships of Cetacea (Artiodactyla) among mammals increased taxon sampling alters interpretations of key fossils and character evolution. PLoS One 4:1â14.

And like so many phylogenetic studies fails to sample the great diversity of fossil artios.

So, secondary loss of herbivory and ruminating in suids and in whales (hippos do ruminate)?

Phylogenetic studies concentrate on one group: taxon sampling is unlikely to be adequate outside the focus. In the case of O'leary (I haven't looked at Spaulding): sampling of Cetartiodactyls dense enough to inspire confidence, but I have much less confidence in the placing of Mesonychids (and "condylarths" like, I think I remember, Phenacodus): the topology of that, basal, part of the tree might be an artifact due to inadequate sampling.

Which isn't a criticism: you CAN'T do everything, and you shouldn't expect the "periphery" to be as robust as the in-focus part of the picture.

----

Of the tree in Darren's slide: much of it seems to be getting to be well-established (so: selenodonty and rumination are convergent between Tylopoda and Pecora), but the branching pattern within Pecora still seems subject to change with each new study. I suspect the radiation of the Pecorans was so sudden (in paleontological terms) that phylogenetic analysis is difficult.

Shouldn't the camel be closer to the "conventional" artiodactyls, instead of down there at the bottom by its lonesome? Since all members of the group have 2 toes, I'd assume that would put them closer to deer and girraffes than the whippomorphs.

Same probably goes for the pigs, too.

Based on ear anatomy and other features, protoceratids are more similar to ruminants, and are unlikely to belong within Tylopoda (see Joeckel and Stavas, 1996) - their similarities to Tylopoda are likely to be convergent. Unfortunately selenodonty and toe reduction are pretty clearly convergent in several lineages.

To answer Darren's call: What's up with the moschids and tragulids?

Do entelodonts fall within Whippomorpha or Suiformes nowadays?

This post was thrown up on a whim, late on a Sunday, and I'm pleased to see it resulting in so much discussion.

Protoceratids: Prothero (1998) said "The debate over the affinities of protoceratids has been one of the longest and most confused in the mammalian literature". Most early authors regarded them as ruminants, but by the 1960s the idea of tylopod affinities had become popular and it could probably be said to be the 'mainstream' view by the 1980s. As noted in comment 13, this was contested by Joeckel & Stavas (1996). As for other extinct groups, I'll try to say as little as possible here or I'll end up spending hours on a single comment.

Andrewsarchus away from 'mesonychians' and forming part of a clade with entelodonts and anthracotheres is not new (we looked at it in one of the mesonychian articles), but the recovery of this clade as sister to Cetancodonta is novel to Spaulding et al.'s (2009) total evidence cladogram. Raoellids and dichobunids were closer to cetaceans than were entelodonts and anthracotheres, in keeping with Thewissen et al. (2007). The name Cetancodontamorpha was used for this (entelodont + anthracothere) + cetancodontan clade.

And we might consider giving up on Whippomorpha and using Cetancodonta, given that Spaulding et al. (2009) provided a node-based definition for it ('The least inclusive clade that includes Tursiops truncatus and Hippopotamus amphibious' [yikes, typo there is from their paper])

Moschids and tragulids: a lot could be said about their possible phylogenetic position. They could be ruminants outside of Pecora in the cladogram shown above; moschids are the sister-taxon to Cervidae in some studies, and (surprisingly) the sister-taxon to Bovidae in others.

Refs - -

Joeckel, R. M. & Stavas, J. M. 1996. Basicranial anatomy of Syndyoceras cooki (Artiodactyla, Protoceratidae) and the need for a reappraisal of tylopod relationships. Journal of Vertebrate Paleontology 16, 320-327.

Prothero, D. R. 1998. Protoceratidae. In Janis, C. M., Scott, K. M. & Jacobs, L. L. (eds) Evolution of Tertiary Mammals of North America. Volume 1: Terrestrial Carnivores, Ungulates, and Ungulatelike Mammals. Cambridge University Press, pp. 431-438.

Spaulding, M., OâLeary, M. A. & Gatesy, J. 2009. Relationships of Cetacea (Artiodactyla) among mammals: increased taxon sampling alters interpretations of key fossils and character evolution. PLoS ONE 4(9): e7062. doi: 10.1371/journal.pone.00070672

Thewissen, J. G. M., Cooper, L. N., Clementz, M. T., Bajpai, S. & Tiwari, B. N. 2007. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature 450, 1190â1195.

Tylopoda including camelids, protoceratids and oreodonts seems plausible because they were endemic Paleogene North American groups. Their evolution was parallel to Eurasian Ruminants. Entelodonts were Holarctic omnivores, while Suoids were initially nested in tropical latitudes (in fact, Suids remained mainly paleotropical animals, with the exception of Sus scrofa, and didnt reach America,unlike basal Tayassuids, that crossed Beringia). The craddle of Artiodactyla seems to be tropical Southeast Asia jungles, with successive waves of clades spreading to northern latitudes, and at least one (anthracotheres, probably including proto-hippos) going to pre-Miocene Africa.

If cainotheres, anoplotheres, xiphodontids and so on are tylopods, this group is far from exclusively American (but, maybe you're only talking about a hypothetical clade within Tylopoda).

If Cainotheres-Anoplotheres-Xiphodonts clusters in a "Eurotylopoda" clade, it would imply a common ancestor in Earliest Eocene Holarctica. If they don't, Basal Cetartiodactyla's topology is much more complicated.

One of key elements to understand Eocene mammalian clades is the temporal evolution of Europe and Western Asia paleogeography, there was a vast archipelag with a very complex puzzling pattern of isthmuses and straits, changing regularly in each epoch. For example, some of the West European endemic mammals didnt appear in Sparnacian, but in Middle Eocene, probably coming from some another Eurasian "island", maybe Italy, Greece, Turkey,etc.

If Whippomorpha is Hippos+Cetaceans...then what is Girrafids+Pronghorn ?

Giraffidae + Antilocapridae = Giraffoprongia.

Giraffidae + Antilocapridae = Prongiraffomorpha

Ruminantia+Whippomorpha = Rwhippomorpha
Rwhippomorpha + Suiformes = Surwhippomorpha
Surwhippomorpha + Tylopoda = Tsurhwippomorpha

Fascinating stuff..I will leave speculating on this to the experts, except to say, we need more material! Someone needs to convince a Silicon Valley 100-millionaire that funding expeditions to look for Andrewsarchus etc would provide a great bang for their buck (pun not intended). Hey, it worked for geobiology with the Agouron Institute, founded by biotech gazillionaire John Abelson: he was looking for a fledgling research area where funding could make an impact, and so geobiologists got to ride on chartered jets to field sites and stay in nice hotels, at least in the early days when John Abelson tagged along..

Let me get this straight with the newly revised Cetancodonta: they found it a clade define as {{Andrewsarchus + {Entelodontidae + Anthracotheriidae + {Hippopotamidae + {Dichobunoidea + CETACEA}}. While I heard the about that dichobunoids (especially Indohyus and Gervachoerus) are closer to whales and Andrewsarchus being consider as an arcahic member of this group in order to please both sides of an artiodactyl or mesonychia orgin, I have a few questions or statements on this:

1. What characteristics do entelodonts have with whales? Alot of studies have purposed that they are desendants of helohyids (unless the Helohyidae have also been classified as members of the whale-hippo clade). Not mention they have cloven hooves.

2. Some like Boisserie and Lihoreau have considered that hippos are in fact a direct surviving lineage of anthracothere. If so, unless hippos are part of the {Entelodontidae + Anthracotheriidae} and not sister to {Dichobunoidea + CETACEA}, might as well lump the whales and dichobunoids into Athracotheriidae as well.

3. Is Dichobunoidea monophyletic? Not everyone seems to agree so. Some please some members closer to whales, and other members at the base of the Cetartiodactyla order.

4. Also can anyone tell me how are the cetacean families (or at least the modern families) are related to one and another? Cause I hear some say sperm whales form a clade with river dolphins and beaked whales while others please sperm whales as a basal lineage of the tooth whales. Some even place sperm whales closer to baleen whales!

Note that hippos don't ruminate (have an enlarged forestomach different from the condition in ruminants and don't chew the cud). No need to postulate loss of herbivory (parsimony be damned) --- herbivory evolves convergently many times in mammals, and the earliest artiodactyls had bunodont cheek teeth indicative of omnivory). I still worry about basal camelids (and as we still don't know what "tylopods" really encompass the biogeography thing is sort of moot) -- not for the selenodonty but for the embryological similarity of stomach evolution (of course those data could be garbage, somebody should reexamine them).

Wow - Christine Janis on Tet Zoo :)

Riggy (comment 26): it would take several thousand words to answer your questions properly! Quick responses...

1. Which characters do entelodonts share with cetaceans? You're looking for cetacodontamorphan synapomorphies. Spaulding et al. (2009) provided a supplementary table, and therein the following two characters are provided for Cetacodontamorpha: P4 protocone relative to M1 paracone: greater than twice the height of M1 paracone, and M1 parastyle: absent.

2. There are competing views on the affinities between hippos and anthracotheres, but Merycopotamus at least was found to be part of Cetancodonta by Spaulding et al. (2009), and O'Leary & Gatesy (1998) found an anthracothere clade to be the sister-group to a hippo + raoellid + entelodont clade. Have you seen Pickford (2008)?

3. A lot of work is needed to sort out the 'dichobunoids' and it is (I think) agreed that they are not monophyletic, but rather grouped together for convenience. Prothero & Foss's The Evolution of Artiodactyls is an excellent source on these taxa (and others!).

4. Crown-cetaceans: if you use the search box over on the left for 'sperm whale', 'odotocete' etc., you might find some of the answers you're looking for.

Refs - -

O'Leary, M. & Gatesy, J. 2008. Impact of increased character sampling on the phylogeny of Cetartiodactyla (Mammalia): combined analysis including fossils. Cladistics 24, 397-442.

Pickford, M. 2008. The myth of the hippo-like anthracothere: the eternal problem of homology and convergence. Revista Española de PaleontologÃa 23, 31-90.

This just in with regards to fossil artios:

Orliac, M., J.-R. Boisserie, L. MacLatchy, and Fabrice Lihoreau. in press. Early Miocene hippopotamids (Cetartiodactyla) constrain the phylogenetic and spatiotemporal settings of hippopotamid origin. PNAS Published online before print June 14, 2010, doi: 10.1073/pnas.1001373107

Abstract

The affinities of the Hippopotamidae are at the core of the phylogeny of Cetartiodactyla (even-toed mammals: cetaceans, ruminants, camels, suoids, and hippos). Molecular phylogenies support Cetacea as sister group of the Hippopotamidae, implying a long ghost lineage between the earliest cetaceans (â¼53 Ma) and the earliest hippopotamids (â¼16 Ma). Morphological studies have proposed two different sister taxa for hippopotamids: suoids (notably palaeochoerids) or anthracotheriids. Evaluating these phylogenetic hypotheses requires substantiating the poorly known early history of the Hippopotamidae. Here, we undertake an original morphological phylogenetic analysis including several âsuiformâ families and previously unexamined early Miocene taxa to test previous conflicting hypotheses. According to our results, Morotochoerus ugandensis and Kulutherium rusingensis, until now regarded as the sole African palaeochoerid and the sole African bunodont anthracotheriid, respectively, are unambiguously included within the Hippopotamidae. They are the earliest known hippopotamids and set the family fossil record back to the early Miocene (â¼21 Ma). The analysis reveals that hippopotamids displayed an unsuspected taxonomic and body size diversity and remained restricted to Africa during most of their history, until the latest Miocene. Our results also confirm the deep nesting of Hippopotamidae within the paraphyletic Anthracotheriidae; this finding allows us to reconstruct the sequence of dental innovations that links advanced selenodont anthracotheriids to hippopotamids, previously a source of major disagreements on hippopotamid origins. The analysis demonstrates a close relationship between Eocene choeropotamids and anthracotheriids, a relationship that potentially fills the evolutionary gap between earliest hippopotamids and cetaceans implied by molecular analyses.

And we might consider giving up on Whippomorpha and using Cetancodonta, given that Spaulding et al. (2009) provided a node-based definition for it

That means we could give the corresponding total-group definition to Whippomorpha. MWA HA HA HA HAAAAAH...

Tom: the Orliac et al paper provides good arguments that those are basal-most hippos, but I don't buy the argument that they are necessarily anthracotheres, as the taxon sampling is, again, missing LOT of basal Eocene taxa.

Jessica: thanks for the info!

Well Darren (comment 28) my questions and statements were in fact based on Prothero & Foss's The Evolution of Artiodactyls (which BTW it's really good! The only thing I have a problem is that some families were missing, especially the whales. But all well). Pardon me for the helohyids, they indeed are part of the Cetacodontamorpha (as dichobunoids).

So entelodonts are now consider as distant kin to whales based on their teeth, huh? But what if the teeth is just the result convergent evolution? For all you know (just for argument sakes) entelodonts are really deer that evolved into the badass creatures we all know and love (while it sounds cool, entelodonts are no where near kin to deer and I rather see them as dead relatives of the Cetacodontamorpha than that of pigs. They look nothing like pigs at all, not even remotely).

And as for the whale phylogeny, I did a little work and found Nikaido et al. paper of the retroposon of the cetacean lineages. Appearantly, within odontocetes, they're two clades: Physeteroidea (Sperm Whales and kin, which we all know) and Platanistoidea (dolphins and beaked whales. It turns out that either A. river dolphins is polyphyletic or B. river dolphins is paraphyletic as it's define as {{Platanistidae + {Ziphiidae + {Lipotidae + Pontoporiidae + Iniidae + Delphinoidea}}).
If you haven't seen the paper the link is www.pnas.org/content/98/13/7384.full

1. Why not ressurrect Haeckel's OBESA for Cetancodonta? Haeckelian Obesa included and hippos and whales (and walruses)

2. Hippos probably have an African origin, maybe from some Late Eocene Cetancodontan stock.

Foremost, I am not a scientist, just an avid fan of the Tet Zoo blog and an admitted paleo-nerd since childhood, so my comment here will have nothing to do with anything previously discussed. I just thought it funny that when doing a Google image search for Syndyoceras, one of the images returned in the query was that of Darren Naish. So now we have to find which clade he belongs in!

Seriously, I want to thank Mr. (Professor?) Naish for all his hard work on Tet Zoo, as well as the thought provoking comments he receives from folks across so many schools of thought.

Carry on!