A preliminary review of the fossil species of Ranina Lamarck, 1801 (Decapoda, Brachyura, Raninidae), with systematic remarks

Abstract

-The systematics of the fossil representatives of Ranina Lamark, 1810, has been discussed by several authors in the last century, showing some problematics above all due to the lack of a close diagnosis of the type species (R. ranina) and to the scarce number of well-preserved type series of each fossil species. However, based upon a close comparison among the type series of each species, authors' original descriptions, and the main diagnostic characters of Ranina, this preliminary review finds that twelve species have to be considered as doubtful species within Ranina, as follows: ?Ranina americana Withers, 1924 Riassunto -Revisione preliminare delle specie fossili di Ranina Lamarck, 1801 (Decapoda, Brachyura, Raninidae), con osservazioni sistematiche.La sistematica dei rappresentanti fossili di Ranina Lamark, 1810 è stata discussa da numerosi autori nell'ultimo secolo, mettendo in evidenza alcuni problemi dovuti alla mancanza di una approfondita diagnosi della specie tipo (R. ranina) e alla scarsità e povera conservazione degli esemplari originali di ciascuna specie fossile. Tuttavia, grazie ad un confronto tra gli esemplari originali di ciascuna specie, le loro descrizioni originali e i principali caratteri diagnostici di Ranina, questa revisione preliminare ha permesso di stabilire che dodici specie sono da considerarsi specie dubbie di Ranina:

Checklist of fossil decapod crustaceans from tropical America. Part I: Anomura and Brachyura

“…Ranina berglundi † Squires and Demetrion, 1992 [middle Eocene and Ypresian, Baja California Sur] (Schweitzer et al, 2006b;Vega et al, 2008;Pasini and Garassino, 2017 (Vega and Feldmann, 1991;Vega et al, 1995a;2016).…”

Critical review of fossil record of Ranina Lamarck, 1801 (Decapoda, Brachyura, Raninidae), with description of Tethyranina n. gen.

“…The fossil specimens tentatively assigned to Ranina Lamarck, 1801, are still very scarce (Pasini & Garassino, 2017a), including mostly incomplete or badly preserved specimens, with the ambulatory legs and pleonal parts that are often scarcely preserved, and therefore, not useful in morphological comparisons. Moreover the absence of a clear definition for the diagnostic external morphologic characters [proxy characters sensu Schweitzer (2003)] of the type species (Ranina ranina) has resulted not clearly defined characters for fossil specimens (Guinot pers.…”

“…Tethyranina n. gen. seems to include fossil taxa only from the paleo-Mediterranean area. Indeed we cannot exclude that some of the European species (too poorly preserved for a certain assignment) and still considered doubtfully ?Ranina (see Pasini & Garassino, 2017a) could also represent different taxa within this genus (see: ?Ranina brevispina, ?R. haszlinskyi, and perhaps ?R.…”

“…Recently Pasini & Garassino (2017a) gave a preliminary review of the 23 fossil species previously referred to Ranina by Karasawa et al (2014). As result, three species were assigned to Lophoranina Fabiani, 1910, one species to Calappa Weber, 1795, one was considered a doubtful species within Decapoda, four specimens were considered as Ranina nomina dubia, and twelve were considered doubtful species within the genus.…”