Early Orthides (Brachiopoda) from the Tremadocian (Lower Ordovician) of Northwestern Argentina

VILLAS, E.; HERRERA, Z.A.; ORTEGA, G.

JOURNAL OF PALEONTOLOGY

PALEONTOLOGICAL SOC INC

Año: 2009 vol. 83 p. 604 - 613

0022-3360

Two brachiopod species of two of the earliest rhynchonelliformean families are described from one ofthe first studied Ordovician fossiliferous localities of northwestern Argentina. One is a new species of the familyEuorthisinidae (Orthida, Plectorthoidea), Notorthisina musculosa Villas and Herrera. It displays peculiar featuresnot observed in the family before, as well as a combination of internal and external features previously considereddiagnostic of different genera, leading to emendment of the familial and generic diagnoses. Its dorsal muscle field,best impressed in large specimens, resembles that of Kvania Havlı´cˇek (Nanorthidae) in having four scars arrangedradially. This feature reinforces the phylogenetic proximity of Kvania to the euorthisinids. The second studiedspecies, Nanorthis bifurcata Harrington, has not been revised since its superficial description in 1937–1938, its typehaving been lost. Its description herein, based on a new collection from its type locality, allows a better knowledge ofthe group and helps clarify its supra-familial assignment