INTRASPECIFIC VARIABILITY IN THE EARLY MIOCENE STRUTHIOLARIID GASTROPOD PERISSODONTA AMEGHINOI (IHERING, 1897) FROM TIERRA DEL FUEGO, ARGENTINA

LÓPEZ CABRERA, MARÍA; OLIVERO, EDUARDO

Publicación Electrónica de la Asociación Paleontológica Argentina

Asociacion Paleontologica Argentina

Lugar: CABA; Año: 2021 vol. 21 p. 24 - 52

The early Miocene marine deposits in Tierra del Fuego bear a group of struthiolariid gastropods that stand out for their highmorphological variability. since the end of the 19th century this variability was interpreted as reflecting (1) a highly diversified rapidly evolvinggroup of species or (2) a single, plastic species characterized by ample intraspecific variability. The morphological study of more than 100specimens of the Fuegian struthiolariid genus Perissodonta Martens collected in the Carmen silva, Viamonte, and Irigoyen formations indicatethat significant parameters, such as shell shape, spire length and number of spiral and axial sculptures (cords, threads, tubercles) varycontinuously within an ample range of values, favoring a single, plastic species. Topotype specimens of Perissodonta ameghinoi (Ihering), collectedfrom the early Miocene Monte León Formation in Patagonia, show similar plasticity of characters. Furthermore, recent topotype material ofPerissodonta georgiana strebel from Islas Georgias del sur, a species considered very close or junior synonym of the genotype species P. mirabilis(smith), indicates a similar degree of plasticity. Accordingly, the Fuegian struthiolariids previously assigned to Perissodonta ameghinoi; P. fueguina(Ihering); or P. densestriata (Ihering) are here referred to P. ameghinoi, a struthiolariid gastropod restricted to the early Miocene in Tierra delFuego and Patagonia