We document the occurrence of Early Triassic (Olenekian) crinoid ossicles in exotic blocks contained within the black limestone unit of the Thaynes Formation, which overlies the Dinwoody Formation at the classic Crittenden Springs Smithian ammonoid locality. Crinoid ossicles include two species, i.e., Holocrinus sp. and Articulata ord., fam., gen. et sp. indet. Furthermore, two co-occurring, age diagnostic conodonts, i.e., Neospathodus pakistanensis and Ns. posterolongatus, constrain the age of the crinoids from the early Smithian to the earliest middle Smithian. This discovery represents the third report of Smithian Holocrinidae in the Panthalassan area and it provides important data for the study of crinoid recovery during the Early Triassic.

Ontogeny and variation of the three barroisiceratine ammonoids Yabeiceras orientale Tokunaga and Shimizu, Yabeiceras cf. manasoaense Collignon, and Forresteria (F.) yezoensis Matsumoto were studied by means of X-ray micro-computer tomography based on the well-preserved material from the probable upper Turonian Obisagawa Member of the Ashizawa Formation, Futaba Group in Fukushima Prefecture, northeast Japan. Specimens of Y. orientale, F. (F.) yezoensis, and F. (F.) muramotoi from the Coniacian of the Yezo Group in Mikasa City, central Hokkaido, northern Japan were also examined for comparison. As the shell of Y. orientale grows, the relative umbilical size (U/D) becomes rapidly larger at shell diameter (D) of 30–50 mm, and the relative whorl thickness (W/H) first increases to the stage of 30–50 mm in D and then decreases gradually. The growth rate of whorl width in costal section (W) is relatively constant up to a diameter of 30–50 mm and then decreases gradually, whereas that of whorl height (H) is relatively constant throughout ontogeny. The intraspecific variations in U/D and W/H in middle whorls are wider than those in early and late whorls, as evidenced by the data from the present and previous studies. As the shell of F. (F.) yezoensis grows, U/D is almost constant, and W/H decreases gradually after D exceeds 30–50 mm. Forresteria (F.) yezoensis shows relatively narrow intraspecific variations in relative umbilical size and whorl thickness, as evidenced by the measurement data from the present and previous studies.