South American Ordovician phyllocarids (Crustacea Malacostraca)

Abstract

A detailed morphological analysis of exoskeleton remains of the South American Ordovician phyllocarid crustaceans leads to the recognition of a previously unexpected biodiversity from the Tremadocian up to the Katian. As a result, the genus Caryocaris, as up to now understood, clearly appears to be a comprehensive genus. Taxonomically significant characters are listed and discussed. Two new caryocaridid genera are described: Janviericaris gen. nov., and Ivocaris gen. nov. The diagnosis of the Family Caryocarididae is emended accordingly. In addition to the previous description of Caryocaris acuta Bulman, 1931 from Peru, C. bodenbenderi Aceñolaza & Esteban, 1996 and C. delicata Racheboeuf, Vannier & Ortega, 2000 from Argentina, seven phyllocarid species belonging to five genera are identified from the Tremadocian up to the Sandbian of Argentina and Bolivia. New caryocaridid representatives are Caryocaris acoitensis sp. nov., Ivocaris saltitensis sp. nov., Janviericaris formosa sp. nov. and J. jujuyensis sp. nov.; three other Sandbian and lower Katian forms are provisionally left in open nomenclature as Caryocaris sp. A to C. Ceratiocaridids are represented by the Upper Ordovician genus Pumilocaris Racheboeuf, Vannier & Ortega, 2000, with Pumilocaris granulosa Racheboeuf, Vannier & Ortega, 2000 and Pumilocaris acuta (Bulman, 1931). The familial assignment of the late Tremadocian-Floian genus Rolfecaris gen. nov., represented by Rolfecaris lethiersi sp. nov. and R. parchaensis sp. nov., to the Family Ceratiocarididae still remains uncertain. Caryocaridid phyllocarids have been revealed to be a significantly potential tool for both Ordovician biostratigraphy and palaeobiogeography.