Concordia cunninghami is the oldest known and most basal captorhinid so far and the only recognized species of the genus. It is known from two almost complete skulls coming from Upper Pennsylvanian rocks of the famous Hamilton Quarry in Greenwood County, Kansas.
C. cunninghami not surprisingly shows many features that are typical for basal eureptiles but are not present in more derived captorhinids. The premaxilla is small and seems not to have formed a down-curved "beak" as it is seen in almost all of the remainder of the captorhinids. The lacrimal is dorsoventrally expanded and forms the main portion of the lateral wall of the snout which is similar to the condition in Rhiodenticulatus. The skull table lacks the tabular bone, a feature considered as synapomorphy among captorhinids. The supratemporal is small as well and points, in dorsal view, anteromedially into the posterolateral corner of the parietal as seen in another basalmost captorhinid, Romeria, or in the "Protorothyridid" Protorothyris. The same applies for the posterior margin of the skull roof which is embayed bilaterally in contrast to the pattern present in more derived captorhinids where this margin posesses a single median embayment. Like in Romeria and Protocaptorhinus the parietal foramen is very large compared to the overall size of the skull.
Maxilla and dentary are lined with a single row of as much as 18 small, pointed teeth. The palatal bones and the basisphenoid (a ventral element of the braincase) are covered with numerous denticles. A unique feature of C. cunninghami is that the vomer not only exhibits medial rows of denticles but, in addition, has also lateral ones. An important captorhinid apomorphy, the reduction of the ectopterygoid and replacement of that bone by the adjacent ones, seems to be present in C. cunninghami where it is obviously replaced by the transverse process of the pterygoid. In Captorhinus, however, it is rather a medial process of the jugal that occupies the position of the ectopterygoid. A remarkable occipital feature is that the opisthotic seems not to have the lateral projection which usually contacts the cheek bones, known as paroccipital process. This process is a characteristic trait in all basal amniotes as well as in more modern reptiles, such as squamates.
The oldest known eureptile and one of the closest relatives of captorhinids is the "Protorothyridid" Hylonomus from the Upper Pennsylvanian of Nova Scotia. Thus, although still geologically younger, the discovery of C. cunninghami considerably shortens the ghost lineage of the captorhinids.
|†Concordia cunninghami Müller & Reisz 2005|
Stratigraphic Range: Upper Pennsylvanian (Late Carboniferous): Virgilian
MÜLLER, J. and REISZ, R.R. (2005): An early captorhinid reptile (Amniota: Eureptilia) from the Upper Carboniferous of Hamilton, Kansas. J. Vert. Paleontol., 25(3), pp. 561-568
An image of the C. cunninghami type specimen and some critical remarks (regardless whether legitimate or not) on the paper by Müller & Reisz (2005) are available at palaeos.com
--Zidane 09:22, 26 May 2008 (PDT)