New Evidence for a Therapsid/Ophiacodont Relationship in the Palate ??

The palates of Haptodus, Ophiacodon and Biarmosuchus.

Figure 1. The palates of Haptodus, Ophiacodon and Biarmosuchus. More traits are shared by the latter two to the exclusion of Haptodus. Okay, that’s wrong. I had a bad bit of data here for the Biarmosuchus skull. I went with a published image, then realized the mistakes I made here. Do-over in process.

Another short one. The picture tells the story (that was written Jun 17. And sometimes that story is wrong when the data is wrong. All the copy here in red was written the day after, the 18th. I’m trying to keep up a one-a-day blog schedule and fell into “well, isn’t that convenient” trap. Hopefully today we’ll put in a few fixes. Nuf sed. See next blog. Apologies. 

Addendum. Now I see that M. Mortimer has some comments as well. Looks like we have some house cleaning here. Let’s do it and see what comes of it. 

2 thoughts on “New Evidence for a Therapsid/Ophiacodont Relationship in the Palate ??

  1. Reisz et al. (1992) states Ophiacodon has vomerine teeth, which is also true in Laurin’s (1990) matrix. Just because Romer and Price (1940; which your figure is from) didn’t illustrate them doesn’t mean they were absent.

    Benson codes all three as having pterygoid transverse processes, and this is true in your figure and Laurin (1990 thesis- pg. 29 and figure 8) for Haptodus.

    Haptodus is more similar to therapsids than Ophiacodon in lacking the medial shelf on the quadrate ramus of the pterygoid. The shelf in Ophiacodon is visible on the right pterygoid in your figure, but you wrongly have it colored in light green so that it looks more ventral to the adjacent bone (note Romer and Price only showed the lateral groove on the left side and the medial shelf on the right side; this leads to a different morphology than you show). In any case, the shelf is figured clearly by Brinkman and Eberth (1986- figure 2B). This character isn’t in your matrix.

    Haptodus is more similar to therapsids than Ophiacodon in having teeth on its pterygoid transverse flange anterior to the main transverse posterior row. This character isn’t in your matrix.

    On the other hand, interpalatine contact, pterygoid-jugal contact length and ectopterygoid transverse width aren’t in Benson’s matrix. However, note that Romer and Price (1940- plate 3) say for Ophiacodon “The palatal elements were disarticulated and their margins somewhat imperfect, hence the sutures in broken lines are approximations only.” You correctly kept those dotted lines in there, but seem to have treated them as known boundaries. Since they are not, this makes all three of these characters uncertain for the genus and leaves you with no palatal characters to support this phylogeny for these three taxa. Benson has two palatal characters to support the standard topology though.

  2. And to follow up, you miscoded Edaphosaurus and Haptodus as lacking vomerine teeth, which must have just been a mistake on your part. You also coded the pterygoid flange (character 104, lateral edge with a sharp angle, right?) as correctly existing in Haptodus and only lacking in Edaphosaurus, which contrasts with your statement here. I couldn’t find interpalatine contact, pterygoid-jugal contact length or palatine-ectopterygoid contact length in your matrix. Are those just in your synapsid matrix?

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