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Did Effigia have a postfrontal?
Applying color to the dorsal skull of Effigia appears to show unfused postfrontals (Fig. 1), a trait seen in archosaurs that are not crocs and not dinos (in other words: virtually all archosaurs). Very few basal crocs, like Gracilisuchus, retain an unfused postfrontal. Nesbitt (2007) did not identify a postfrontal but did identify an asymmetrical posterior nasal suture, which may not have been accurate.
Figure 1. Dorsal view of Effigia skull from Nesbitt 2007. At left postfrontals are identified. Bits of the broken nasals are also in that cranial area.
Earlier the poposaurs, including Effigia, shifted their position on the large reptile tree to nest with Turfanosuchus, a basal poposaur, which also has a postfrontal. A postfrontal has been reported on Lotosaurus (Parrish 1993), but I haven’t seen a good dorsal view of the skull. Poposaur skulls, and poposaur cranial regions are quite rare. This is one of the few examples.
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
Parrish JM 1993. Phylogeny of the Crocodylotarsi, with reference to archosaurian and crurotarsan monophyly. Journal of Vertebrate Paleontology 13:287–308
Zhang F-K 1975. A new thecodont Lotosaurus, from Middle Triassic of Hunan. Vertebrata PalAsiatica 13:144-147.
AMNH Effigia webpage
wiki/Effigia
Source: http://pterosaurheresies.wordpress.com/2014/05/05/did-effigia-have-a-postfrontal/
