A new species of Roadian (Lower Middle Permian) ammonoid from West Texas




Jordan, Janet L.

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A comparative study of Roadian Stage ammonoids from time-equivalent strata of the Delaware Basin of West Texas was conducted to determine if they were a completely new species of the genus Peritrochia, or a variation of the type species Peritrochia erebus. Both a quantitative and qualitative analysis of the suture and conch characteristics was performed through reproduction of the suture lines, and measurements taken of the basic conch parameters of seven specimens. These suture lines and measurements were compared to the characters of published species as well as to one another. Additionally, the familial association of Peritrochia was investigated through a literature review, and assessment of the characters of related genera to determine the validity of the recent change in familial assignment. Of the three previously unclassified Peritrochia sp. specimens it was determined that two of them are indeed immature representatives of a single new species of genus Peritrochia, while the third was evaluated as belonging to an entirely different genus, Pseudovidrioceras. The question of the validity of the change in familial association of Peritrochia was found to be lacking in evidence, and a recommendation was put forth to reassign the genus to the Family Marathonitidae.


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Ammonoid, Marathonitidae, Peritrochia, Permian, Roadian, Vidrioceratidae