Abstract

HUITRON-VARGAS, Gilberto  and  TORRES-MARTINEZ, Miguel A.. New records of columnar ossicles of crinoids from the Permian (early Cisuralian) of Chiapas, Mexico. Bol. Soc. Geol. Mex [online]. 2023, vol.75, n.2, A120423.  Epub June 07, 2024. ISSN 1405-3322.  https://doi.org/10.18268/bsgm2023v75n2a120423.

We described a new association of 10 morphospecies of crinoid columnar ossicles from eight different morphogenera. The biota includes Cylindrocauliscus fiski, Cyclocaudex cf. plenus, Cyclocaudex costatus, Preptopremnum cf. rugosum, Preptopremnum leave, Heterostelechus jeffordsi, Cycloscapus laevis, Cyclocaudiculus regularis, Nothrosterigma merum, and Cyclogrupera minor. The specimens were located in rocks from the Grupera Formation of Asselian-Sakmarian age (lower Permian). The lithostratigraphic unit belongs to the Carboniferous-Permian succession that outcrops in the Chicomuselo region in southeastern Mexico. It is recorded the first occurrence of C. costatus, P. rugosum, C. laevis, and N. merum for the Cisuralian of North America. Likewise, it highlights the first record of N. merum in Mexico, which along with P. rugosum are reported for the first time in the Cisuralian of North America. Despite controversy over the usefulness of crinoid ossicles as index fossils, it was possible relating the rocks of the locality studied to an approximate Asselian-Sakmarian age (early Cisuralian), previously suggested for the formation. Furthermore, the find of ossicles associated with other filtering marine invertebrates such as bryozoans and brachiopods, as well as preservation and lithological features of the rocks, allowed establishing that the depositional paleoenvironment was related to shallow water facies of high energy, well-illuminated, and with an important terrigenous supply. Regarding paleobiogeography, the distribution of crinoids was associated with the region’s geologic history, which was influenced by oceanic and continental changes that occurred during the formation of the Pangea supercontinent in the Late Pennsylvanian. This favored the emergence of generic and specific provincialisms in North America.

Keywords : Crinoid ossicles; Asselian - Sakmarian; Grupera Formation; paleoenvironment; paleobiogeography.

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