The palates of poposaurs are poorly known Some have not been described or reconstructed (Fig.1). Others have been wrongly reconstructed or partially reconstructed (Fig. 4). Here (Fig. 1) are two poposaurs, Effigia and Shuvosaurus next to Daemonosaurus (Sues et al. 2011, also largely guessed at from broken pieces) and Thecodontosaurus, which provides more certitude. Most unfortunately, the palate of Lotosaurus has not been described or illustrated despite the presence of several specimens and museum casts. The little question is: On Daemonosaurus, which way do the ectopterygoids go? Long side against the pterygoid, as in rauisuchids? Or short side, as in Effigia and other dinosaurs?
Figure 2. Effigia palate in situ (left) and reconstructed by reassembling colored elements (at right).
On rauisuchians, as in ornithosuchians (Fig. 2), the ectopterygoid has a larger contact area with the lateral pterygoid and it produces a small “stem” to contact the jugal (as in Saurosuchus) or the maxilla (as in Riojasuchus). If you flip the ectopterygoid of Daemonosaurus, you get the rauisuchian type of ectopterygoid. Left as is (Fig. 1), however, you get the dinosaurian type, and that is the preferred reconstruction here based on phylogenetic bracketing.
Figure 2. Click to enlarge. Euparkeriid, ornithosuchian, rauisuchian, aetosaurian, and basal archosaur palates. Here are Euparkeria and Osmolskina, both euparkeriids. Ornithosuchus and Riojasuchus are ornithosuchids. Saurosuchus and Postosuchus are both rauisuchians. Stagonolepis is an aetosaur. Pseudhesperosuchus is close to the basal archosaur pattern with a much smaller ectopterygoid and smaller ectopterygoid/pterygoid contact. The original configuration is shown on the right side. A possible alternative is shown on the left. Not sure how it was preserved. I’d like to know if you have this data. If the left is correct in figure 2 (Pseudohesperosuchus), and Shuvosaurus is also correct in figure 1, these suggest that Daemonosaurus is correctly drawn in figure 1.
Figure 4. Silesaurus palate with missing elements restored on the right. Illustration (without color) from Dzik 2003 who illustrated missing elements on the left.
Silesaurus Palate The missing ectopterygoid and palatine were not illustrated for Silesaurus. Given the palates of related taxa (Fig.1), I have added the missing elements on the right here (Fig. 4) to match them. Thus these restorations are guesses that appear to make sense in context. When better data come along, we’ll make improvements.
This has been a first attempt at reconstructing the palates of several poposaurs at once based on similar morphologies in close kin. The palates should remain somewhat similar. If anyone has good data on the palates of other rauisuchians and basal dinosaurs, please forward them on.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
Figure 3 is absent from this post now. Apologies. I had it in my files for several years and thought it had been published by now. It had not.
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