EARLIEST OCCURRENCE OF THE PTERANODONTIDAE (ARCHOSAURIA: PTEROSAURIA) IN NORTH AMERICA: NEW MATERIAL FROM THE AUSTIN GROUP OF TEXAS TIMOTHY S. MYERS Roy M. Huffington Department of Earth Sciences, Southern Methodist University, Dallas, Texas 75275, USA, ,smyers@smu.edu. ABSTRACT—Remains of a pteranodontid pterosaur are recorded in the basal Austin Group of North Texas. The specimen described here comprises a partial left wing and strongly resembles Pteranodon although diagnostic features of that genus are lacking. With an estimated early Coniacian age, this specimen represents the earliest occurrence of the Pteranodontidae in North America and the second earliest occurrence worldwide, predated only by Ornithostoma from the Cambridge Greensand of England. Pterosaur material recovered from the Eagle Ford and Austin groups of Texas records an early Late Cretaceous change in the composition of North American pterosaur communities between the late Cenomanian and the early Coniacian. This faunal transition appears to be primarily a decrease in morphological disparity rather than a significant reduction in taxonomic diversity. However, the lack of Early Cretaceous Lagersta ¨tten in North America may produce underestimates of true pterosaur richness during this interval, thereby obscuring a subsequent drop in diversity. INTRODUCTION P TERANODONTID PTEROSAURS are highly abundant in the Late Cretaceous record of North America with a large number of Pteranodon specimens preserved in the Upper Cretaceous Niobrara Formation (Bennett, 2001). Indetermi- nate material attributed to the Pteranodontidae has been reported from other parts of the world (e.g., Obata et al., 1972), but outside of North America, pteranodontids are represented by only the single genus Ornithostoma. Definitive remains of the other member of the Pteranodontidae, Pteranodon, are known only from North America (Bennett, 2001). Pteranodon first appears in the upper Coniacian Smoky Hills Member of the Niobrara Formation and ranges into the early Campanian with the youngest known specimens reported from the Sharon Springs Member of the Pierre Formation (Bennett, 2001). Further pterosaur material collected from the Campanian of Delaware (Baird and Galton, 1981) and the Late Cretaceous of the Gulf Coast (Bennett and Long, 1991) is consistent with Pteranodon but lacks diagnostic features of the genus (Bennett, 2001). The specimen described here (SMU 76476), consisting of portions of a left wing recovered from the Upper Cretaceous Austin Group in the Dallas area, appears similar to Pteranodon, but its taxonomic affinities are not resolvable with certainty beyond inclusion within the Pteranodontidae. However, if SMU 76476 does represent Pteranodon, it constitutes the earliest occurrence of this genus. Deposition of the Austin Group coincided with the end of an early Late Cretaceous worldwide reduction in pterosaur diversity (Unwin, 1987, 1988, 2003; Butler et al., 2009). Although the Early Cretaceous pterosaur record in North America is poor, material recovered from the Eagle Ford and Austin groups of Texas corroborates a major transition in pterosaur community composition at the beginning of the Late Cretaceous. Institutional abbreviations used here include: SMU, Shuler Museum of Paleontology, Southern Methodist University, Dallas, Texas; TMM, Texas Memorial Museum, University of Texas at Austin; USNM, U.S. National Museum of Natural History, Washington, D.C. AGE AND GEOLOGICAL CONTEXT SMU 76476, comprising several elements of the left wing and associated small, unidentifiable bone fragments, was donated to the Shuler Museum without detailed information regarding provenance. The specimen was collected northwest of Dallas, from southwestern Collin County, southeastern Denton County, or northern Dallas County. The bones were encased in several blocks of light gray, muddy limestone with faint laminations. The bones were closely associated, but the specimen was completely disarticulated prior to burial. Inoceramid bivalves and fragmentary fish bones were scat- tered throughout the surrounding matrix. The palynological assemblage recovered from the matrix surrounding SMU 76476 contains two taxa (Tanyosphaeridium salpinx and Catastomocystis spinosa) that have last occurrences in the Turonian and two taxa (Dinogymnium acuminatum and Dinogymnium euclaense) that have first occurrences in the Coniacian. Pre-Coniacian reports (Londeix et al., 1996; Zippi, personal commun., 2009) of both D. acuminatum and D. euclaense initially suggested a likely Turonian age for SMU 76476, but the fissile, dark gray shales of the Turonian Eagle Ford Group north of Dallas are inconsistent with the matrix lithology. The limestone matrix surrounding SMU 76476 is consistent with the chalk deposits of the lower part of the Austin Group (Fig. 1), so T. salpinx and C. spinosa are interpreted as reworked from the underlying Eagle Ford Group. Given the presence of reworked Turonian taxa in the matrix, SMU 76476 must be derived from the basal Atco Formation within the Austin Group. In Dallas County, the Austin Group consists of approxi- mately 185 m of interbedded chalky limestones and calcareous shales (Dallas Petroleum Geologists, 1941). Pessagno (1969), using the stratigraphic terminology proposed by Durham (1957) for the Austin Group in central Texas, applied the names Atco, Bruceville, and Hutchins to the three divisions of the Austin Group recognized near Dallas. The lower contact of the Austin Group with the Eagle Ford Group is clearly disconformable, with much of the upper Turonian missing (Hancock and Walaszczyk, 2004), but the nature of the upper contact with the Taylor Group is the subject of considerable Journal of Paleontology, 84(6), 2010, p. 1071–1081 Copyright ’ 2010, The Paleontological Society 0022-3360/10/0084-1071$03.00 1071