Effigia palate and occiput

Updated March 13, 2015 with a new palate figure based on the photo, not the original drawing in Effigia and Shuvosaurus was modified in turn.

We looked at the poposaur Effigia earlier here and here. Having never attempted a reconstruction of the palate I do so here.

effigia588

Figure 1. Effigia. is an odd derived poposaur with tiny hands and no teeth. In competition with dinosaurs, poplars did not fare as well. The dentary and predentary have been modified here from prior attempts to more closely match the mandible of Shuvosaurus (Fig. 3).

Effigia okeeffeae (Nesbitt and Norell 2006, Nesbitt 2007) Carnian, Late Triassic, ~210 mya, ~ 2 m in length, was originally considered an early theropod dinosaur by Colbert, who collected the specimen in the late 1940s but never removed it from its jacket. A recent reassessment by Nesbitt and Norell (2006) and Nesbitt (2007) nested Effigia among the poposauridis. It is an odd bipedal poposaur and perhaps the most derived member of a clade composed almost entirely of odd derived members. The reconstruction of the skull has been controversial. Perhaps only a direct tracing and shifting of the elements can solve this puzzle. All the pieces in the disarticulated fossil will come together precisely if they are correctly reassembled.

The palate 
It is possible that the palatine (Fig. 2). was misidentified originally as the right ectopterygoid. If so, then the palate resembles that of known sister taxa, like Shuvosaurus (Fig. 3)..

Figure 2. Effigia palate in situ (left) and reconstructed by reassembling colored elements (at right).

Figure 2. Effigia palate in situ (left) and reconstructed by reassembling colored elements (at right). Click to enlarge.

Due to the long premaxilla
and the short maxilla the Effigia palate shifts most of the palatal elements into a smaller space. Even so all maintain their original and typical connections to the other skull elements.

Figure 3. Shuvosaurus, a sister to Effigia, has a similar palate in this reconstruction, but it was not reconstructed like this originally.

Figure 3. Shuvosaurus, a sister to Effigia, has a similar palate in this reconstruction, but it was not reconstructed like this originally.

You really can’t talk about
the palate of Effigia without comparing it to its sister, Shuvosaurus (Fig. 3). Here the main triangular part of the pterygoid must be imagined, but the quadrate processes are present and quite robust. The palatines frame the internal nares posterior to the palatal processes of the maxilla and premaxilla.

effigia-occiput588

Figure 4, the occiput of Effigia colorized here to segregate elements. That’s the central supraoccipital in pink flanked by two opisthotics in lavender, all displace dorsally. Originally they were framed by the squamosals in gold. Quadrates in red and basisphenoid in purple.

Effigia occiput
The above image (Fig. 4, Nesbitt 2007) is a CT scan of the Effigia occiput colorized to aid identification of the elements. The occiput is so inclined it is almost continuous with the palate. Originally the supraoccipital + opisthotics were identified as the two parietals with no median element recognized. Neither the supraocipital or the opisthotic were identified otherwise.

Effigia References
Nesbitt SJ and Norell MA 2006. Extreme convergence in the body plans of an early suchian (Archosauria) and ornithomimid dinosaurs (Theropoda). Proceedings of the Royal Society B 273:1045–1048. online
Nesbitt S 2007. The anatomy of Effigia okeeffeae (Archosauria, Suchia), theropod-like convergence, and the distribution of related taxa. Bulletin of the American Museum of Natural History, 302: 84 pp. online pdf
AMNH Effigia webpage
wiki/Effigia

Shuvosaurus References
Alcober O, Parrish JM. 1997. A new poposaurid from the upper Triassic of Argentina. Journal of Vertebrate Paleontology 17:548–556
Brusatte SL, Benton MJ, Desojo JB and Langer MC 2010. The higher-level phylogeny of Archosauria (Tetrapoda: Diapsida), Journal of Systematic Palaeontology, 8:1, 3-47.
Chatterjee S 1991. An unusual toothless archosaur from the Triassic of Texas: the world’s oldest ostrich dinosaur? Abstract, Journal of Vertebrate Paleontology, 8(3): 11A.
Chatterjee S 1993. Shuvosaurus, a new theropod: an unusual theropod dinosaur from the Triassic of Texas. National Geographic Research and Exploration 9 (3): 274–285.
Rauhut OWM 1997. On the cranial anatomy of Shuvosaurus inexpectatus (Dinosauria: Theropoda). In: Sachs, S., Rauhut, O. W. M. & Weigert, A. (eds) 1. Treffen der deutschsprachigen Palaeoherpetologen, Düsseldorf, 21.-23.02.1997; Extended Abstracts. Terra Nostra 7/97, pp. 17-21.
Long R and Murry P 1995. Late Triassic (Carnian-Norian) Tetrapods from the Southwestern United States. New Mexico Museum of Natural History and Science Bulletin 4, Pp. 153-163.

wiki/Shuvosaurus

 

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2 thoughts on “Effigia palate and occiput

  1. Better than your first attempt, but look at figure 16 in Nesbitt (2007). That stipled portion of the pterygoid’s lateral process is the ectopterygoid articular surface, so it extends posteriorly to the tip of the lateral process but doesn’t go anteriorly past it. More problematic is that Nesbitt states “Both ectopterygoids are preserved in AMNH FR 30587 out of articulation”, so your using the right and left (as a palatine) line drawings as if they were bones in ventral view and the right one articulated doesn’t reflect reality. In particular, the right side of the lavender ‘ectopterygoid’ doesn’t exist as an actual element, and that section between the labeled ect and mx isn’t necessarily the ectopterygoid (e.g. could be a jugal fragment). If the left ectopterygoid is a palatine, then what’s the left palatine (as seen in side view)? Similarly, you just rearranged the ‘ectopterygoid’ and ‘palatine’ of Shuvosaurus as drawn by Lehane (2005) as the partial pterygoid and ectopterygoid, though there’s no guarantee they’re in ventral view once reidentified. Indeed, the ‘ectopterygoid’ is illustrated as a pterygoid in figure 18, and contra Lehane and your drawing, E/F make sense in lateral/medial view while A/B are in dorsal/ventral view. These are examples of what I critiqued back in 2013 about your methods, when I said “Bones aren’t just shapes that can be rearranged.”

    • Unfortunately I based the tracing on the line drawing, taking the easy way out, rather than the photo. So you were correct and I thank you for noting the ectopterygoid issue. With regard to the palatine/ectopterygoid issue, I may have made a mistake, but what Nesbitt identifies as the right ectopterygoid does not have the same shape as the left ectopterygoid, particularly so when the long process rimming the pterygoid on the left is removed. The left palatine is now identified, a mirror image of the new right one.

      With regard to Shuvosaurus I’m working from online Lehane drawings, but I think you are correct that the posterior quadrate process of the pterygoid is drawn in palatal view when it actually shows us the lateral or medial view and a change was made. Thank you for the Lehane reference. I have it now. It was lost here after a backup drive crash. I will review it shortly.

      You comment about bone shapes is a good one, but actually, in most cases, they can be traced to make accurate reconstructions, more accurate than freehand cartoons, which has become the norm. The problem here is what happened between the ears. Thank you and keep your specific comments coming. Remember, it’s not like I’m the only one in the world of paleo who is making mistakes, so no blackwashing is necessary. I do appreciate your efforts in helping me correct the problems.

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