Proterogyrinus scheelei Romer, from the Upper Mississippian of Greer, West Virginia is one of the earliest known members of the amphibian infraorder Embolomeri. The primitive, eogyrinid-like skull conforms to Panchen's allometric plot of the British eogyrinids. The only distinct autapomorphy is a raised pineal foramen rim and an acuminate median ridge on the skull table posteriorly, flanked by deep bilateral pockets. The kinetic junction extends from the otic notch anteriorly to the posterodorsal corner of the orbit. The braincase, bearing no ossified roof, is composed of separate otic-occipital and sphenethmoid units, the latter being undivided. The vertebrae are similar to those of embolomeres, except that the pleurocentrum retains a dorsal suture in adults, and the intercentrum, unossified dorsally in adults, is a ventral crescent. The presacral count is 32. The atlas-axis is reptiliomorph. Zygapophysis structure indicates that the column must have undergone axial rotation during lateral flexion. The limbs and girdles are similar to those of Archeria, except that they are slightly stouter. Humerus structure is primitive. Range of limb movement, at least in the pectoral limb, is very restricted. An almost total lack of autapomorphies indicates that Proterogyrinus is a primitive member of the stem family (Proterogyrinidae) of the infraorder Embolomeri. Although most of the supposed autapomorphies of anthracosaurs that were formerly thought to preclude them from reptile ancestry are not considered to be valid, there are no identifiable synapomorphies with reptiles either, making it impossible to support close relationship between the two groups.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.68686 |
| Date | January 1982 |
| Creators | Holmes, Robert, 1950- |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000150978, proquestno: AAINK61098, Theses scanned by UMI/ProQuest. |
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