Check the listing for details. NICE 15.25” Texas Cretaceous Fossil Ammonite, Eopachydiscus Marcianus! Sutures. Condition: New. Listed at 296.00 USD. This beautiful, heavily (naturally) sutured eopachydiscus marcianus ammonite was found right by TCU and the Fort Worth Zoo next to a University Drive construction site. The geological formation is the Duck Creek formation, an early Cretaceous zone in Tarrant County, TX.