In the southern part of the State of Puebla, central Mexico, the town of Tepexi de Rodriguez is a well-known fossiliferous area because of the beautiful and extraordinary Early Cretaceous vertebrates recovered from the Tlayua Quarry (Applegate, 1996; Espinosa-Arrubarrena and Applegate, 1996; Reynoso-Rosales, 1996a, 1996b, 1997, among others), and a Tertiary plant locality known as “Los Ahuehuetes” (Magallón-Puebla and Cevallos-Ferriz, 1994; Velasco de León and Cevallos-Ferriz, 1997; Ramírez-Garduño, 1998, among others). The Axamilpa river drains this area and along its banks a sequence of Late Cenozoic sands, silts, and gravels are exposed. In these sediments scattered fossil mammalian remains had been recovered (Torres-Martínez and Agenbroad, 1991; Montellano-Ballesteros and Castro-Azuara, 1996; Fig. 1).

Werdelin and Lewis (2000) recently described a new species of the saber-tooth genus Megantereon (Mammalia, Carnivora, Felidae) from Late Pliocene (∼3.5 Ma) deposits of the Nachukui Formation south of the Turkwel River in Turkana, northern Kenya (Ward et al., 1999). The new species, Megantereon ekidoit, is said to represent the earliest occurrence of this genus in Africa. It was described from a right mandibular ramus (KNM-St 23812) with i3–ml. As discussed below, the post-canine diastema is longer than the cheek-tooth row, since there does not appear to have been a third premolar (p3), and the coronoid process is relatively well developed, showing a hook-shaped morphology (Werdelin and Lewis, 2000: Fig. 1). The fourth premolar (p4) and the lower carnassial tooth (ml) show considerable wear.

Gasconsia Northrop, 1939, is a rare trimerellid that appears in the Upper Ordovician (Ashgill) and then reappears in the Upper Silurian (Wenlock/Ludlow) (Hanken and Harper, 1985; Popov and Holmer, 2000). This note is the first documented report of Gasconsia from the type Ludlow of the Welsh Borderland. Gasconsia transversus (Salter) occurs in the Lower Bringewood beds (upper part of Gorstian stage) in a small quarry on the north side of the Holloway to Upper Millichope road, directly opposite the entrance to Millichope Park (grid ref. SO 52748911). The material consists of internal and external molds of one brachial valve and one articulated individual (Fig. 1). This species was described as Obolus Davidsoni var. transversus [Salter MS] by Davidson (1866) from the Wenlock (Homerian stage) of the Dudley and Woolhope areas of the English Midlands and Welsh Borderland. Davidson and King (1874) subsequently referred to it as Dinobolus transversus (Salter), and Cocks (1978), in selecting a lectotype of transversus, retained its assignment to Dinobolus. However, illustrations of transversus in Davidson (1866, pl. 5, figs. 1-6) and Davidson and King (1874, pl. 18, fig. 12) clearly show that it belongs in Gasconsia rather than Dinobolus.

Many sandstones (89 of 127 tested) disaggregate in warm dimethyl sulfoxide (DMSO); no crushing is necessary and there is no known effect on minerals other than kaolinite. Fossils should be cleanly released from the sandstone matrix by gentle washing with water. Treatment is simple and relatively inexpensive. DMSO is not a serious chemical hazard or environmental problem (but see necessary precautions discussed later). Some sandstones disaggregate overnight; others require a month or so. It has been proven to work on some very hard, supposedly silica-cemented sandstones and on some carbonate-cemented concretions in sandstones. In general, disaggregation in DMSO appears to be associated with the presence of kaolinite (which is more abundant in non-marine depositional environments) and with the absence of deep burial or deformation. Even so, there is no way to predict the behavior of a given sandstone; susceptibility to disaggregation must be established by trial.

Permian conodonts were recovered for the first time from the Dingjiazhai Formation, a well-known diamictite-bearing stratigraphic unit in the Gondwana-derived Baoshan Block in West Yunnan, Southwest China. The conodont fauna occurs in limestone units within the upper part of the formation and consists of Sweetognathus bucaramangus (Rabe), S. whitei (Rhodes), Mesogondolella bisselli (Clark and Behnken), and an unidentified ramiform element. Based on the known stratigraphic distribution of 5. bucaramangus (Rabe), the fauna is referable to the upper Sweetognathus whitei-Mesogondolella bisselli Zone, and thus is dated as middle Artinskian according to the current definition of the stage. The Dingjiazhai Formation is overlain paraconformably by the Woniusi Formation, which is represented mostly by basalts and basaltic volcaniclastics related to rifting volcanism during the separation of the Baoshan Block from Gondwanaland. The present discovery of conodonts from the upper part of the Dingjiazhai Formation reveals that the glaciogene diamictites in the Dingjiazhai Formation are older than middle Artinskian, and the inception of rifting volcanism of the Baoshan Block is later than middle Artinskian.

Occurrence of an essentially warm water element, Sweetognathus bucaramangus (Rabe), in the Dingjiazhai conodont assemblage notwithstanding, the entire fossil faunas including brachiopods and fusulinoideans from the limestone units of the formation can be best interpreted as a middle latitudinal, non-tropical, and still substantially Gondwana-influenced assemblage developed at the northern margin of Gondwanaland just after deglaciation in the southern hemisphere during Early Permian time. This time could be regarded as the beginning of the Cimmerian Region, which had mixed or transitional paleobiogeographic characteristics between the Paleoequatorial Tethyan and cool/cold Gondwanan realms, and which became well developed during Middle Permian time.

Palmqvist (2002) has criticized our attribution of the mandibular ramus of Megantereon from South Turkwel, Turkana Basin, Kenya, to a new species, M. ekidoit (Werdelin and Lewis, 2000), suggesting instead that it “unequivocally” belongs to the African species M. whitei. We believe that this criticism stems from a misunderstanding of our statements and from an erroneous view of variability within Megantereon. In this reply we shall address Palmqvist's criticisms, showing that M. ekidoit is not synonymous with M. whitei, and also that the specific attribution of various Megantereon specimens is not as clear cut as Palmqvist (2002; Martinez Navarro and Palmqvist, 1995, 1996) believes.

The passing of Ronald Pearson Tripp marks the end of the career of a great trilobite taxonomist and one of the last great “gentleman geologists.” I had the pleasure of knowing him personally since 1973.

A collection of over 1,700 small theropod teeth from the Judith River Group (Campanian;˜79.5–74 Ma) allows our understanding of the diversity and variation of small theropods in this assemblage to be refined. In addition to the previously recognized taxa, a series of morphologically distinct groups are recognized that may represent distinct taxa in some cases. Teeth with the Paronychodon-like features of a flat surface with longitudinal ridges on one side are resolved into a few discrete morphotypes. Two of these are included in Paronychodon lacustris and two additional morphotypes are hypothesized to represent distinct taxa, here referred to as ?Dromaeosaurus morphotype A and Genus and species indet. A. The teeth of Paronychodon lacustris and ?Dromaeosaurus morphotype A share a distinctive wear pattern that suggests tooth functioning involved contact between the flat surfaces of opposing teeth. Two species of Richardoestesia, R. gilmorei and R. isosceles, are present in the assemblage. Additionally, bird teeth are identified in the assemblage and are described in this review.

Bivariate plots were used to document the variation in the theropod teeth, especially in the features that distinguish between Richardoestesia gilmorei, R. isosceles, Saurornitholestes, and Dromaeosaurus. Considerable overlap is present in all plots, so although the teeth are morphologically distinct, they are not easily distinguished by quantitative means.

The Pericyclidae are distinctive ancestral (middle Tournaisian-lower Viséan) Goniatitina characterized by prominent transverse sculpture. Ancestry of the group was in Goniocyclus Gordon, 1986 (type species, Goniatites blairi Miller and Gurley, 1896). These diminutive (generally less than 35 mm), coarsely ribbed pericyclids are distinguished by sharply angular ventral sinuses and sutures with primitive, incipiently bifid ventral lobes. Goniocyclus characterizes the late Kinderhookian (late middle Tournaisian) Siphonodella isosticha—Upper Siphonodella crenulata conodont Zone where it is represented by at least six distinctive species in the North American Cordillera and Midcontinent (Gordon, 1986). The earliest record, which extends the generic range back to the base of the traditional middle Tournaisian, is a widely discussed, but previously undescribed, species from the Hannibal Shale of Missouri (Work et al., 1988; Becker, 1993a, 1993b; Popov and Kusina, 1997) described herein as Goniocyclus hannibalensis new species.

The Polychaetes of the Mazon Creek biota have been documented previously (Dawson, 1881; Thompson and Johnson, 1977; Thompson, 1979; Fitzhugh et al., 1997). Owing mainly to their rarity, several genera of fossil polychaetes had been noted but not described. Active amateur collecting of Mazon Creek concretions has allowed a number of uncommon, undescribed, flabelligerid annelid specimens to be cataloged into private and museum collections. All flabelligerid individuals are considered to be of one species.

Siluriformes constitute an important monophyletic group of mainly freshwater fishes (Fink and Fink, 1996). Presently, there are about 35 families with over 2,000 species in all continents except Antarctica (Lundberg, 1993; Nelson, 1994); however, at least in the Eocene, they also inhabited Antarctica as well (Grande and Eastman, 1986). A small number of catfishes (most of the ariids and many of the plotosids) are marine and some species of other families can enter brackish waters (Nelson, 1994). Pre-Cenozoic catfishes are extremely rare outside of South America.