Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina)

MEROI ARCERITO, F., ; WAISFELD, B.G.; BALSEIRO, D.

GEODIVERSITAS

PUBLICATIONS SCIENTIFIQUES DU MUSEUM

Lugar: Paris; Año: 2015 vol. 37 p. 131 - 150

1280-9659

p { margin-bottom: 0.25cm; line-height: 120%; }AsaphellusCallaway, 1877is the earliest widespread genus of the familyAsaphidae Burmeister, 1843, and although its systematics bearsseveral problematic issues, an input to overcome these difficultieshas been attempted. Our main focus is a group of strongly effacedAsaphellus species from the Cordil-lera Oriental (NW Argentina),including new material from the Santa Rosita Formation(Furongian-Tremadocian), mainly belonging to Alfarcito and Rupascamembers (Quebrada del Arenal, Perchel, Jujuy Province). Asaphellusis reconsidered herein in order to restrict some features anddiscuss others not taken in account before. Moreover, severalproblematic Argentinean species are revised. The poorly known, butextensively cited, A. catamarcensis Kobayashi, 1935 is assessedhere upon the type series in order to clarify its taxonomy andprevious assignments. A reappraisal of A. stenorhachis (Harrington,1938), another enduring problematic taxon, is proposed. Besides, A.isabelae n. sp., a unique species within the genus mainly due toits extreme effacement is defined herein. Other species left in opennomenclature are also described. Regarding local random occurrencesin the Furongian, the genus radiated locally from the earlyTremadocian (Tr1) onwards, however, taxonomic diversification wasnot mirrored by the abundance of Asaphellus in local communities.From the middle Tremadocian (Tr2) this diversification is associatedwith an increase in abundance, and even dominance of the taxon innumerous assemblages, further expanding its environmental range intoshallower settings. The increase of Asaphellus diversity (Tr1-early Tr2) is decoupled from the records of local increase inAsaphidae diversity since the late Tremadocian (Tr3) and Floian,underscoring the complex pattern of diversification at differenttaxonomic levels