Elviniid trilobites from the Elvinia Zone (late Cambrian, Furongian) of Mendoza, western Argentina

Abstract

In the 1950s, Carlos Rusconi reported the biostratigraphically important Furongian trilobites Elvinia Walcott and Irvingella Ulrich and Resser from an exotic limestone block (La Cruz Olistolith) of the San Isidro area, Precordillera of Mendoza, western Argentina. Although several local species were erected by Rusconi at that time, most of them were later listed as junior synonyms of E. roemeri (Shumard) or I. major Ulrich and Resser, and this was followed in subsequent studies. A systematic revision of all the available specimens of Elvinia and Irvingella from the Rusconi collection at the Museo de Ciencias Naturales y Antropológicas J.C. Moyano (Mendoza) is provided herein. The occurrence of E. roemeri is supported by the present study, while the associated Irvingella species include I. jorusconii Rusconi, I. platycephala Rusconi, and Irvingella sp. The latter represent “advanced” forms in terms of morphological development in the Irvingella lineage, and these, together with E. roemeri, are typical of the uppermost part of the Elvinia Zone (uppermost Steptoean). Irvingella jorusconii, I. platycephala, and Irvingella sp. appear to be endemic to the Argentinian Precordillera, but are related to species from central Texas and northwest Canada.

Trilobites from theCedaria prolificaZone (Cambrian, upper Guzhangian) of the Precordillera of Mendoza, western Argentina

“…3.12–3.17 (see for further synonymy).2000 Kormagnostus seclusus ; Stitt and Perfetta, p. 203, fig. 6.1–6.4.2011 Kormagnostus seclusus ; Tortello, p. 118, fig. 2C, D, G.

Figure 2.( 1, 2 ) Kormagnostus seclusus (Walcott, 1884): ( 1 ) mostly exfoliated cephalon, MCNAM 17795; ( 2 ) testate pygidium, MCNAM 17369, Kormagnostus cuchillensis Rusconi, 1954 paratype (not illustrated previously).

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“…In addition to North America, it was described from Sakhayan and Nganasanian horizons of Siberia (Rosova, 1964), the Kormagnostus simplex (= K . seclusus ) Zone of Kazakhstan (Ergaliev, 1980), and the Lejopyge laevigata Zone of the Precordillera of San Juan and the northern Precordillera of Mendoza, Argentina (Poulsen, 1960; Robison, 1988; Bordonaro and Liñán, 1994; Tortello, 2011).…”

“…Occurrence. —Widespread in the Guzhangian of the United States (e.g., Nevada, Utah, Texas, Missouri, Tennessee, South Dakota, Wyoming, Montana), northwest and eastern Canada, Greenland, western Argentina, Kazakhstan, and Siberia (e.g., Palmer, 1954a, b; Rosova, 1964; Ergaliev, 1980; Robison, 1988 and references therein; Pratt, 1992 and references therein; Tortello and Bordonaro, 1997 and references therein; Peng and Robison, 2000, p. 35; Stitt and Perfetta, 2000; Tortello, 2011).…”

“…It is now recognized that Cambrian trilobites from the Argentinian Precordillera have clear Laurentian affinities. Recent systematic revisions of the Rusconi collections provided updated information on several standard North American trilobite zones such as the Glossopleura walcotti , Ehmaniella , Lejopyge laevigata , Elvinia and Saukia zones (Tortello and Bordonaro, 1997; Bordonaro, 2003, 2014; Bordonaro and Fojo, 2011; Pratt and Bordonaro, 2014; Tortello, 2018, 2020, 2022).

Figure 1.Map of the San Isidro area, Mendoza Province, Argentina (after Bordonaro et al, 1993 and Tortello, 2022).

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Cambrian trilobites from the Glossopleura walcotti Zone (Miaolingian Series, Wuliuan Stage) of Mendoza, western Argentina

“…During the 1940s and 1950s, the Argentinian naturalist Carlos Rusconi discovered key Cambrian outcrops in the southern Precordillera of Mendoza, western Argentina, and described large numbers of invertebrates including trilobites, hyoliths, mollusks, brachiopods, and sponges (Rusconi, 1946(Rusconi, , 1954a(Rusconi, , 1955(Rusconi, , 1956Cerdeño, 2005). These pioneering investigations, together with additional contributions of Leanza (1947), V. Poulsen (1958), and C. Poulsen (1960), gave great impetus to the understanding of the paleontology of Mendoza, which was subsequently refined by up-to-date systematic revisions of Rusconi's collections at the Museo J.C. Moyano (e.g., Palmer, 1965;Robison, 1988;Tortello and Bordonaro, 1997;Bordonaro, 2014;Tortello, 2018Tortello, , 2020 and the study of additional trilobite faunas (e.g., Bordonaro and Liñán, 1994;Shergold et al, 1995;Bordonaro, 2003Bordonaro, , 2014Bordonaro and Fojo, 2011;among others). Most of these fossils come from early Miaolingian to late Furongian limestone allochthonous blocks (olistoliths) occurring within Middle and Upper Ordovician shales (Bordonaro et al, 1993;Keller, 1999).…”