Yeh Kuei-yu (2009) A Middle Jurassic radiolarian fauna from South Fork Member of Snowshoe Formation, east-central Oregon // Collection and Research. Vol.22. P.15-125
This study describes a highly diversified Middle Jurassic radiolarian fauna from one single micritic nodule from South Fork Member of Snowshoe Formation, east-central Oregon. Totally 158 species attributed to 52 genera were documented and illustrated; among them 1 new family (Telacapsularidae Yeh), 5 new genera (Antexitus Yeh, Laxuscingula Yeh, Minutusolla Yeh, Neoconocaryomma Yeh and Telacapsula Yeh) and 27 new species were described. In addition, 2 families (Praeconocaryommidae Pessagno and Orbiculiformidae Pessagno) and 2 genera (Orbiculiforma Pessagno, Leugeo Yang and Wang) were emended herein. According to North American radiolarian zonation proposed by Pessagno et al., the studied fauna is assignable to zone1F of Superzone 1. Ammonites or other age indicative megafossils have never been recovered from the same horizon of the studied fauna. However, it can be certain that the age of the studied fauna is not older than late Bajocian and not younger than late Bathonian on the basis of ammonite data obtained from the horizons above and below the sample locality. The results of this study provide many new occurrence records for revising the ranges of Jurassic forms including some marker taxa (e.g., Pantanellium foveatum and Perispyridium gujohachimanense ) of Jurassic zonal schemes. Significant differences also observed in the faunal composition between the studied fauna and an Alpine Tethys fauna assigned previously to Bathonian age. Further studies need to be done to figure out the causes of faunal difference.