New decapod crustaceans (Thalassinidea, Galatheoidea, Brachyura) from the Middle Oligocene of Patagonia, Argentina

Abstract

A robust decapod fauna from middle Oligocene rocks near Bariloche, Argentina, has yielded several new forms. New genera include Baricarcinus and new species include CalHanopsis australis, Proterocarcinus corsolini, Trichopeltarion levis, Baricarcinus mariae, and Asthenognathus microspimis. Munida casadioi (Schweitzer and Feldmann, 2000a) is also reported. This is the first notice of CalHanopsis de Saint Laurent, 1973, in the southern hemisphere. The species of Trichopeltarion and Asthenognathus described herein are the oldest known representatives of their respective genera, and Asthenognathus is one of the oldest known genera within the Pinnotheridae de Haan, 1833. The fauna of the Foyel Formation is significantly different from that of the slightly younger Centinela Formation, exposed approximately 500 km to the south, suggesting that paleoecological conditions were conducive to specialization in the decapod fauna-of southern South America.

Oligocene and Miocene Decapoda (Crustacea: Axiidea, Anomura, Brachyura) from Southern Argentina

“…Neither the type specimens nor those discussed herein bear evidence of supraorbital spines that are characteristic for Munida. Specimens illustrated by Casadío et al (2004) have tiny supraorbital nodes or lack the features altogether suggesting that they do not represent the strong spines seen on confirmed specimens of Munida .…”

“…Munida casadioi (Schweitzer and Feldmann, 2000b). Garassino and De Angeli, 2003, p. 132; Casadío et al, 2004, p. 24.…”

“…5A). Archaeogeryon corsolini bears only three anterolateral spines on an anterolateral margin that is straight and nearly parallel to the midline (Casadío et al 2004: fig 5). The overall surface of Archaeogeryon lophos is more granular, although that may be a reflection of preservation (Feldmann et al 1995: fig.…”

“…The decapod crustacean fauna known from Cenozoic exposures in southern Patagonia, Argentina, has expanded both in terms of numbers of taxa and geographic localities. Field work by the authors and others has resulted in definition of new faunas from the region of Bariloche, Río Negro Province (Casadío et al 2004), Peninsula Valdes, Chubut Province (Casadío et al 2005), and Tierra del Fuego (Feldmann et al 2011). In addition, a few decapod species were described from the Estancia 25 de Mayo Formation (previously named the Centinela Formation), near Calafate, Santa Cruz Province (Schweitzer and Feldmann 2000a, b, c, 2001).…”

Fossil calibrations for molecular analyses and divergence time estimation for true crabs (Decapoda: Brachyura)

“…Besides Liocarcinus heintzi, there are several other occurrences of polybiid and polybiid-like genera and species in the Paleogene. Archaeogeryon corsolini (Casadío, De Angeli, Feldmann, Garassino, Hetler, Parras and Schweitzer, 2004, as Proterocarcinus), and A. lophos (Feldmann, Casadío, Chirino-Gálvez, and Aguirre-Urreta, 1995), are known from the middle Oligocene and Paleocene (Danian, 66.0-61.6 Ma) of Argentina, respectively (Feldmann et al, 1995;Casadío et al, 2004;Casadío et al, 2005;Feldmann et al, 2011b). The latter species, represented by the holotype and sole specimen, is moderately preserved and shows some dorsal and sternal features that suggest affinity with portunids in general, but the fronto-orbital margin and part of the anterolateral margins are eroded, precluding a detailed comparison with polybiids in general.…”