Homoplasy or homology: Palaeosinopa

Traditional paleontology
considers Palaeosinopa (Matthew 1901, Paleocene, Fig. 1) a semi-aquatic pantolestid, one of several [purported] non-placental eutherian mammals. By contrast, the large reptile tree (LRT) nests Palaeosinopa between the raccoon, Procyon, and the seal, Phoca, both placental eutherian mammals.

Dunn and Rose 2015 report,
“Pantolestidae is a Paleogene Holarctic family of semi-aquatic mammals of uncertain phylogenetic affinity.”

Figure 1. Palaeosinopa, complete and largely articulated. Body length about 50 cm. Tail adds 35 cm. From Rose and Koenigswald 2005.

Figure 1. Palaeosinopa, complete and largely articulated. Body length about 50 cm. Tail adds 35 cm. From Rose and Koenigswald 2005.

So is this homology? Or homoplasy?
Do unrelated aquatic mammals converge on so many traits that they are difficult to phylogentically separate from one another? Or are workers putting too much emphasis on the teeth of mammals while overlooking the ‘big picture’? In other words, can a Carnivoran lose its carnasial tooth and still be considered a Carnivoran? At this point, Palaeosinopa has the opportunity to nest with non-placental eutherians in the LRT, but it does not do so. It nests within the Carnivora — but very few molar traits are employed. AND I’ve got nothing more primitive than non-placental Eutheria that looks anything like Palaeosinopa…yet. [Remember, Monodelphis does NOT have a pouch].

Figure 2. Palaeosinopa sans the tail with several bones colorized and extremities reconstructed.

Figure 2. Palaeosinopa sans the tail with several bones colorized and extremities reconstructed. From Rose and Koenigswald 2005.

 

The other big question is
why are pantolestids nesting within Carnivora? Wikipedia reports, “Carnivorans all share the same arrangement of teeth in which the last upper premolar (named P4) and the first lower molar (named m1) have blade-like enamel crowns that work together as carnassial teeth to shear meat.” Pantolestids don’t have such teeth. In fact, the molars tend to flatten with wear. And we all know fish-eaters tend to have different tooth shapes than their more terrestrial kin.

Wikipedia also reports, “Traditionally, the extinct family Viverravidae (viverravids, including Nandinia) had been thought to be the earliest carnivorans, with fossil records first appearing in the Paleocene of North America about 60 mya, but recently described evidence from cranial morphology now places them outside the order Carnivora.” 

Traditional paleontology sees
the origin of the clade Carnivora only after 65 mya. The large reptile tree pushes that origin back more than 60 million years with the appearance of Vincelestes. As we’ve seen with other taxa, it’s more important where the taxon nests than whether it has traits specified by paradigm for a certain clade. And this is especially true for basal members.

It gets pretty hairy.
Unlike seals AND unlike non-placental eutherians, Palaeosinopa has a long, robust tail. Like seals, the medial manual and pedal digits, especially digit 2 are longer than the others. The femur is short and robust. The scapulae are similar in shape.

Other pantolestids include
Buxolestes (Middle Eocene). If these are long-tailed pre-seals, they didn’t last long. I’ll add a sea otter within the week to see if it settles things down or mixes things up.

References
Dunn RH and Rose KD 2015. Evolution of early Eocene Palaeosinopa (Mammalia, Pantolestidae) in the Willwood Formation of the Bighorn Basin, Wyoming. Journal of Paleontology. DOI: 10.1017/jpa.2015.31
Gingerich PD 1980. A New Species of Palaeosinopa (Insectivora: Pantolestidae) from the Late Paleocene of Western North America. Journal of Mammalogy 61 (3): 449.
Linnaeus C von 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Matthew WD 1901. Additional observations on the Creodonta: Bulletin of the
American Museum of Natural History, v. 14, p. 1–38.
Rose KD and von Koenigswald W 2005. An exceptionally complete skeleton of Palaeosinopa (Mammalia, Cimolesta, Pantolestidae) from the Green River Formation, and other postcranial elements of the Pantolestidae from the Eocene of Wyoming (USA): Palaeontographica Abteilung A 273: 55–96.

wiki/Procyon
wiki/Palaeosinopa
wiki/Phoca

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13 thoughts on “Homoplasy or homology: Palaeosinopa

  1. Now that you’ve recovered multiple results that any mammal worker would laugh off as ridiculous (paraphyletic marsupials, non-therians as carnivorans, primates and rodents, paraphyletic artiodactyls, polyphyletic xenarthrans, etc.), is there any result you could recover that would make you reject your analysis as being useful for uncovering mammalian phylogeny?

  2. The data speaks for itself. Sisters all look alike and one can trace a gradual accumulation of traits among all derived taxa. So, where among the pre-eutherians is there a better match for multituberculates? If you can’t answer that with another taxon, then you’re giving me Creationist-style arguments, ala: “it is written!!!” Come on, Mickey, you’re better than this.

    • You can’t actually “trace a gradual accumulation of traits among all derived taxa” since you’re ignoring almost all the traits prior authors have plotted, as your tree was designed for non-synapsid amniotes. “Where among the pre-eutherians is there a better match for multituberculates”? Where they go in the consensus (e.g. “sister” to Shenshou in your terminology- Bi et al., 2014), based on more characters and taxa than you use.

      If I were you, I’d conclude since the results are so different from everyone else’s conclusions and not strengthened via an independent result, they’re probably wrong. But you go with the conclusion only you in the history of a field you entered this year are correct. If you’re right, the world’s thousands of amniote researchers should just plug taxa into your file and they’d find the correct answers. Doesn’t that sound unrealistic for anyone to claim?

  3. Once a hater, always a hater. And after all the success I’ve had through 766 taxa. To your view, I’m working on Haramiyavia now. Let’s see where that takes us. Could it be that multituberculates are showing a little reversal in their dental traits? After all they do lose their big primitive canines. I’m glad Galileo, Wegener and others did not take your POV.

    • You actually haven’t had objective success with your 766 taxa. Most zoologists familiar with your work think that you’re wrong. That _you_ think you’re successful means nothing to reality. So I repeat- “is there any result you could recover that would make you reject your analysis as being useful for uncovering mammalian phylogeny?”

      Also, are you seriously comparing yourself to Galileo and Wegener? You realize that all the crackpots do that? I’m NOT saying you’re a crackpot, but it really looks bad to claim you are the lone person ala perpetual motion machine pundits to find the Truth.

  4. Blackwashing is not helpful, Mickey. Again… just tell us what two taxa should not nest together and where should the wrong one nest? I understand you’re having trouble with this new paradigm. That’s normal.

  5. David, Mickey’s question is perfectly appropriate. The first question a scientist must ask is “What would demonstrate that my hypothesis is *incorrect*?” If you cannot describe a result that would make you reject your analysis, you are not being scientific.

  6. First of all it’s not one hypothesis, but a multitude of hypothetical relationships that all knit together.
    But to your point…

    If two taxa don’t look alike — then they should not nest together. If they don’t share more traits than any other pairing, then they should not nest together. If you can’t recover a model with complete resolution to echo Nature’s own family tree, then you have problems. I’ve said this before. Your personal paradigms are not letting this sink in. It’s time that anyone critical of the pairings here find the two that do not belong together. Blackwashing is how Creationists argue. Evolutionary scientist should be able to talk about specific problems, with specific taxa, which I do constantly. So, the ball is back in your court. Just find two strange bedfellows. If you cannot find a single problem with my analysis, YOU are not being scientific.

    • Countless professionals have described countless problems with your analysis. You refuse to hear them and then pretend that nobody has voiced them. In this very comment thread, Mickey has pointed out numerous “strange bedfellows”, but you just dismiss them because your analysis is “the data” and then you say that your analysis is correct because “the data” match it. Circular reasoning at its finest.

      I knew I was wasting my time by commenting. Maybe this time my resolve to disengage will last.

  7. re: Shenshou. Wikipedia reports: “The presence of a three-boned middle ear suggests these animals were mammals.”

    “The remains of Shenshou were discovered along with fossils of two other extinct squirrel-like animals, Xianshou songae and Xianshou linglong, in strata dating back 160 million years. The animals were found to belong to a group referred to as haramiyids, now identifiable as early mammals. They lived alongside another group of small rodent-like animals, the multituberculates, which were already accepted as mammals. This discovery has pushed the date of the origin of mammals back to the Late Triassic, the period in which the haramiyid-multituberculate clade, Allotheria, originated, about 220 million to 200 million years ago. Until this was established, mammals were thought to have originated in the Middle Jurassic, which lasted from 174 million to 164 million years ago.”

    Well, nice to get confirmation.

  8. “A hypothesis is accepted, but only tentatively, when it has withstood the most severe tests available, and when it has done better in that regard than any competing hypothesis.” From Kluge (1997)

    No effort is ever presented on this blog to show how the proposed tree is supported. I would be interested to see what bootstrap, jackknife, or Bremer supports look like for the LRT. I would also be interested to know whether the resolved tree reflects a less than strict consensus, a single MPT, or a strict consensus.

    Without needing to actually calculate it, it’s clear that the LRT is a worse tree as far as biogeography or stratigraphic congruence are concerned.

    Further, a tree based on a dataset which does not include the underlying data (i.e. the characters) used to support alternative nodes (read: the generally agreed upon consensus of relationships of taxa being presented here) cannot be treated as having falsified those alternative nodes (read: the generally agreed upon consensus of relationships of taxa being presented here).

    • You’re right. Everything is provisional.

      And you’re wrong. Following the rules of the phylogenetic ‘game’ I present the recovered tree here: http://www.reptileevolution.com/reptile-tree.htm with links there that provide all the characters and taxa on one simple to use MacClade file, yours free on request. This changes with every added taxon. You’ll also find the Bootstrap support figures there, where they have been posted for the last five years. You must be new here. Bootstrap figures are often, but not always, also shown on blog trees as subsets of the LRT. Check prior dates for those of interest to you. The tree currently reflects a single MPT, now with 775 taxa on the reptile tree, about 60 on another for synapsid skulls and 228, I think, on the pterosaur tree.

      Re: biogeography and strategic congruence: What makes you say it is worse? I would say don’t worry about biogeography. Based on the paucity of specimens through time, we’re going to have to live with extant taxa mixing with Triassic taxa, etc. etc.

      Re: generally agreed upon consensus of relationships: This is Science. Everyone and anyone is encouraged to test the results of every experiment themselves. And I encourage you to do so. If I can do it… you can do it. Let me know what you find.

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