PELYCOSAURIAN REPTILES FROM THE MIDDLE PENNSYLVANIAN OF NORTH AMERICA ROBERT REISZ^ TABLE OF CONTENTS Abstract Introduction 27 27 AcknowledynK'nts --30 Suborder Opliiaeodontia 30 FaniiK Ophiacodoutidae — 30 Archacothijris florensis gcu. ct sp. nov. 31 Echhicrpcton intcniicdiiini yen. ct sp. uox . 15 Other pel\c'()saurian material Iroiu Morence, No\a Scotia 50 Protoclcpstjdwps Impious -52 Interrelationships of primitive Pelycosauria 54 The origin of pelycosaurs 55 References ---— 60 earliest pelycosaurs indicates that the temporal opening developed in response to selection for more efficient use of the jaw musculature in forms of increasing body size. INTRODUCTION The Order Pelyeosauria represents the (>arHest stage in tlie e\'olution of mamnial-Hke reptiles. Early w^ork on forms from the Lower Permian redbeds of Texas and New Mexico by Cope ( 1877, 1878 ) , Case ( 1907 ) , Williston' (1911), and von Huene (1925) demonstrated the prominence of the group among primitive fossil reptiles. Our current understanding of the order is based primarily on the work of Romer and Price ( 1940 ) . This extensive study indicated that the Pelycosauria comprised a large order with at least three major lin-eages: 1) Suborder Opliiaeodontia — primi-Abstract. At least fi\e species of pelycosaurs ha\e been found in the Middle Pennsxbanian terres-trial deposit of Florence, Xo\ a Scotia. ArcJiacotluj-ris florensis is a primitive but typical ophiacodont, ^ \\'hih EchincrpeUm intermediuiu is an ophiiKodunt j.j^,g amphibious piscivores; 2) Suborder with some sphenacodont characteristics including Sphenacodontia— ad^'anced terrestrial car-elongate neural spines. Vertebral material trom f o \ <-i i t-j t, three other pelvcosaurs is also present. The occur-nivores; 3) Subordcr Edaphosauna— spe-rence of this rich fauna in the Middle Pennsyl-ciaHzcd swamp-dwellmg herbivores. Most vanian permits reconsideration of the ta.xonomic pelvcosaurs are known from the Lower interrelationships of primitive pelycosaurs. Al-p^^j-mian ( Autunian ) of North America and though ophiacodonts did not duerge as drasticali\-^ ' i • i i • from the ancestral romeriid pattern as sphenaco-Europe (see chart of geological honzons, donts or edaphosaurs, none of die known early Fig. 1). In the Pennsylvanian, fossil re-ophiacodonts could be ancestral to the other sub-j-,-^ains are limited both in varietv and num-orders. Even if pelycosaurs evolved from a single romeriid species, the separation of tlie major pelycosaurian lineages must have occurred earh-in the evolution of the order, probably at about the time of the foniiation of the Joggins deposits. Com-parison of romeriid captorhinomorphs and the ^ Redpath Museum. McGill University, Montreal. Bull. Mus. Comp. ZooL, 144(2 bers, but are sufficient to show that pelyco-saurs were already highly diversified. Upper Pennsylvanian (Stephanian) localities from which pelycosaurs are known are limited to: 1) The McLeansboro Fomiation near Dan-\dlle, Illinois: fragmentary skeletal elements 27-62. Jul}-, 1972 27
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