INTRODUCTION

William James (American Philosopher) wrote that "A new idea is first condemned as ridiculous and then dismissed as trivial, until finally, it becomes what everybody knows." It would appear that the "new idea" of Paleocene dinosaurs is now somewhere between phases one and two of the above quotation. The nearly instantaneous response by Lucas et al. (2009) to my recent paper in Palaeontologia Electronica (Fassett, 2009) documenting the presence of in-place Paleocene dinosaur fossils was not unexpected because the belief that all dinosaurs became extinct at the end of the Cretaceous has become a matter of faith among vertebrate paleontologists, thus my heresy had to be quickly challenged. The rather strident words "No definitive evidence" in the title of the critique by these authors smacks of a clear attempt to challenge my paper primarily by use of a declarative title rather than by an even-handed evaluation of the data at hand.

Fassett (2009) presented new data that confirmed the Paleocene age of the dinosaur-bearing Ojo Alamo Sandstone throughout the San Juan Basin based on paleomagnetic and palynologic evidence. This paper amplified recent publications by Fassett and Lucas (2000), Fassett et al. (2000), and Fassett et al. (2002) that also concluded that Paleocene dinosaurs had been documented in the San Juan Basin. In addition, Fassett (2009) presented data attesting to the presence of dinosaur fossils in the Paleocene Animas Formation in the northern part of the San Juan Basin. And new geochemical data were presented that buttressed earlier findings that the many dinosaur-bone specimens present in the Ojo Alamo Sandstone could not have been reworked from underlying Cretaceous strata.

The Lucas et al. (2009) paper consists essentially of the same rhetorical arguments against the presence of Paleocene dinosaurs in the San Juan Basin presented in Sullivan et al. (2005). There is an ironic circularity to this process because Fassett (2009) addressed and refuted these same arguments, and again does so in this paper. The Lucas et al. (2009) critique addresses the lithostratigraphy, palynology, and magnetostratigraphy of the Ojo Alamo Sandstone and includes a discussion of the geochemistry of bone samples from the Ojo Alamo Sandstone vs. samples from underlying Cretaceous strata. These authors also discuss the value of vertebrate fossils as geochronologic tools generally throughout the Western Interior of North America and include a short discussion of the dinosaurs of the Animas Formation. The following remarks respond to the Lucas et al. (2009) paper by these major topics.