A New Genus of Kufengoceratinae from the Pipeline Shale Member, Brushy Canyon Formation (Upper Roadian Stage), Guadalupe Mountains, West Texas
A comparative study of ammonoids from the Pipeline Shale of the Brushy Canyon Formation in the Guadalupe Mountains, West Texas, and the Las Delicias Valley in Northern Mexico was conducted in order to determine the systematic assignment of an unusual cyclolobid from the Guadalupe Mountains. Suture lines and conch dimensions are compared quantitatively and qualitatively between study specimens and the literature. This study centers around the Pipeline Shale specimen, as it represents a transition between subfamilies Kufengoceratinae and Cyclolobinae. That specimen is classified as "Tongluceras" n. gen., n. sp., and is advanced enough to represent a transitional step from Tongluceras→Demarezites. The other two specimens are classified as cyclolobins. One specimen is determined to be Waagenoceras n. sp., because it satisfies conditions for an advanced Demarezites specimen to be considered Waagenoceras. Another specimen represents a juvenile Demarezites, classified as Demarezites cf. D. lidacensis. A previously undocumented mature modification is also described. This study finds the ammonoids of the Pipeline Shale in West Texas and the Waagenoceras Zone in Las Delicias to represent key transitions between the Roadian and Wordian stages.