Timothy S. Myers

Lone Star Pterosaurs

The state of Texas has one of the greatest records of pterosaurs in the world, sur- passing all other US states and most countries in the number of occurrences. Uniquely, this record extends over the entire 150! million history of the Pterosauria. A review of this pterosaur record confirms at least 30 pterosaurs known from 13 occurrences, including five valid species. The holo- types of two of these species have been described before and are diagnosed and erected here as the new species Radiodactylus langstoni, gen. et sp. nov., named in honour of Dr. Wann Langston Jr, the father of Texas pterosaurology, and Alamodactylus byrdi, gen. et sp. nov.. Phylogenetic analysis of all Texas pterosaurs that can be coded for more than one character confirms that these species are distinct from others and occupy phylogenetic positions close to their original classifications. Radio- dactylus langstoni is recovered as a non-azhdarchid azhdarchoid, Quetzalcoatlus northropi as an azhdarchid, Alamodactylus byrdi as a non-pteranodontoid pteranodontian, Aetodactylus as a ptera- nodontoid, and Coloborhynchus wadleighi as an ornithocheirid. The presence of eudimorphodontid, dsungaripterid, as well as other azhdarchid and pteranodontoid pterosaurs, is also confirmed in Texas.

Estimating soil pCO2 using paleosol carbonates: implications for the relationship between primary productivity and faunal richness in ancient terrestrial ecosystems

Abstract In this paper we present a method for estimating soil pCO2 in ancient environments using the measured carbon-isotope values of pedogenic carbonates and plant-derived organic matter. The validity of soil pCO2 estimates proves to be highly dependent on the organic δ13C values used in the calculations. Organic matter should be sourced from the same paleosol profiles as sampled carbonates to yield the most reliable estimates of soil pCO2. In order to demonstrate the potential use of soil pCO2 estimates in paleoecological and paleoenvironmental studies, we compare samples from three Upper Jurassic localities. Soil pCO2 estimates, interpreted as a qualitative indicator of primary paleoproductivity, are used to rank the Late Jurassic terrestrial environments represented by the Morrison Formation in western North America, the informally named Lourinhã formation in Western Europe, and the Stanleyville Group in Central Africa. Because modern terrestrial environments show a positive correlation between primary productivity and faunal richness, a similar relationship is expected in ancient ecosystems. When the relative paleoproductivity levels inferred for each study area are compared with estimates of dinosaur generic richness, a positive correlation emerges. Both the Morrison and Lourinhã formations have high inferred productivity levels and high estimated faunal richness. In contrast, the Stanleyville Group appears to have had low primary productivity and low faunal richness. Paleoclimatic data available for each study area indicate that both productivity and faunal richness are positively linked to water availability, as observed in modern terrestrial ecosystems.

Earliest Occurrence of the Pteranodontidae (Archosauria: Pterosauria) in North America: New Material from the Austin Group of Texas

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 Lagerstätten in North America may produce underestimates of true pterosaur richness during this interval, thereby obscuring a subsequent drop in diversity.

A NEW ORNITHOCHEIRID PTEROSAUR FROM THE UPPER CRETACEOUS (CENOMANIAN-TURONIAN) EAGLE FORD GROUP OF TEXAS

North American pterosaurs are edentulous with the exception of Coloborhynchus (Lee, 1994). In contrast, toothed pterosaurs be longing to the Ornithocheiridae are widely distributed and abun dant in other parts of the world at this time, with documented occurrences on every continent except Antarctica (Molnar and Thulborn, 1980; Lee, 1994; Mader and Kellner, 1999; Kellner and Tomida, 2000; Unwin, 2001; L? and Ji, 2005; Unwin and Mar till, 2007). The specimen described here, consisting of a nearly complete lower jaw, represents only the second documented oc currence of an ornithocheirid pterosaur in North America. Fur thermore, this specimen represents one of the youngest defini tive occurrences of the Ornithocheiridae. Discovered in the mid

Multiproxy approach reveals evidence of highly variable paleoprecipitation in the Upper Jurassic Morrison Formation (western United States)

Elemental analyses of paleosol B horizons in the Upper Jurassic Morrison Formation of the western United States provide estimates of mean annual precipitation (MAP) and allow determination of humidity regimes. Samples were collected from the lower Morrison Formation in New Mexico and the upper Morrison Formation in Wyoming and Montana. The chemical index of alteration minus potassium (CIA – K) and the calcium and magnesium weathering index (CALMAG) were used to estimate paleorainfall. CIA – K values calculated for paleosols without shrink-swell (vertic) features correspond to MAP estimates between 800 and 1100 mm yr –1 , with an average of 1000 mm yr –1 . CALMAG values, calculated for vertic paleosols, correspond to MAP estimates between 50 and 1200 mm yr –1 , with an average of 700 mm yr –1 . MAP estimates from the older New Mexico strata indicate that early Morrison environments were relatively arid. MAP estimates from the younger Wyoming and Montana deposits reflect wetter conditions in the northernmost part of the Morrison Formation, but the transition from arid interior environments was abrupt. Humidity provinces inferred from geochemical proxy-based estimates of evapotranspiration and energy influx from precipitation range from semiarid to superhumid, suggesting wetter conditions than the MAP estimates, but supporting the relative differences in moisture among the three study areas. Paleoprecipitation patterns within the Morrison depositional basin do not match the modern latitudinal distribution of rainfall that arises from zonal atmospheric circulation. Comparison with the Upper Jurassic Lourinha Formation in Portugal and the Vega Formation in Spain reveals that MAP in Late Jurassic Portuguese environments was similar to that in the wet northern part of the Morrison Formation, although more arid conditions prevailed in some areas of Portugal. Inferred humidity regimes for the Lourinha Formation, which range from semiarid to superhumid, also indicate small-scale geographic variability in climate, although less pronounced than that observed in the Morrison Formation. Paleoenvironments in northern Spain were similar to the drier Morrison environments in the continental interior. Given the abrupt climatic transitions inferred here for the Morrison Formation, paleoprecipitation estimates derived from a geographically restricted sample may reflect only local conditions and should not necessarily be extrapolated to larger areas.

First North American occurrence of the toothed pteranodontoid pterosaur Cimoliopterus

ABSTRACT A new pterosaur species, Cimoliopterus dunni, sp. nov., is described based on a partial rostrum from the upper Cenomanian Britton Formation in the Eagle Ford Group of north-central Texas. The holotype preserves alveoli for a minimum of 26 upper teeth and bears a thin premaxillary crest that begins above the fourth pair of alveoli. The rostrum, characterized by a slight lateral flare, lacks the pronounced lateral expansion found in ornithocheirids and anhanguerids. The tip of the snout is small and blunt, and the anterior face of the rostrum is oriented posteroventrally, forming an approximately 45° angle with the anterior portion of the palate. The anteroventrally oriented first pair of alveoli is directed more ventrally than anteriorly. Phylogenetic analysis suggests that Cimoliopterus dunni and Cimoliopterus cuvieri, from the Cenomanian Grey Chalk Subgroup in Kent, England, are basal pteranodontoids that are closely related to Aetodactylus halli from the middle Cenomanian Tarrant Formation of north Texas. Cimoliopterus dunni marks only the second known occurrence of Cimoliopterus, extending its geographic range from Europe to North America. In conjunction with Coloborhynchus wadleighi from the upper Albian Pawpaw Formation, Cimoliopterus dunni provides unambiguous evidence of biogeographic linkages between the pterosaur faunas of North America and Europe in the middle Cretaceous.