Leptaena

Classification
Phylum: Brachiopoda
Class: Strophomenata
Order: Strophomenida
Family: Rafinesquinidae
Genus: Leptaena Dalmon, 1828
Cincinnatian Species: Leptaena richmondensis

Taxonomic Details

Synonyms: Leptaenopoma Marek & Havlicek, 1967 and Turgenostrophia
Type species: Leptaena rugosa Dalman, 1828 (Jin et al., 1997)

Geologic Range
Ordovician (Llanvirn) – Devonian (Pragian, ? Emsian)

Common Paleoecology
Leptaena is an extinct genus of falcultatively mobile epifaunal suspension feeders.

Identification in Hand Sample:

  • Concentric wrinkling in the shell
  • Wrinkling is abruptly deflected anteriorly
  • Concentric lines on the shell sometimes appear almost rectangular
  • Semiquadrate to semielliptical
  • Concavo-convex
  • Finely striated
  • Muscle area of the ventral valve is subcircular, and the diductor muscle scars are fan-shaped (flabellate)
  • The Cardinal process is split into two parts (Bifid)
  • Hinge line is straight

Geographic Occurrences

Published Description

Treatise on Invertebrate Paleontology, Part H, Vol. 2 (2000):

  • Outline usually transverse, rounded anteriorly; profile concavo-convex with sharp anterior dorsal genticulation; ornament costellate to unequally parvicostellate; concentric rugae variably but usually well developed; small pseudodeltidium; large chilidium; short dental plates; ventral muscle field varies from subcircular to elongate with bounding ridges usually developed posterolaterally, sometimes curving round anteriorly; cardinal process lobes elongate, ventrally directed; socket ridges present but usually weak, sometimes with crenulations; dorsal muscle field variably impressed with median ridge often present; transmuscle ridges, diaphragm variably developed in dorsal valve. Lacking the distinctive two pairs of dorsal transmuscle ridges found in L. (Septomena)

Fossils of Ohio (1996):

  • A medium-sized to large, concavoconvex strophomenid brachiopod. Its semicircular outline is truncated by a straight hinge line. Leptaena is characteristically wider than long and has concentric ridges or rugae. It also has numerous fine ribs radiating across each valve from the umbones. Leptaena is recorded from the Cincinnatian Series and ranges into the Devonian of Ohio.

Arthur McFarlan (1931):

  • Concavo-convex, finely striated Strophomenids characterized by a conspicuous concentric wrinkling of the shell which is abruptly deflected anteriorly. Outline transversely subquadrate or semi-elliptical, hinge line forming greatest width. Muscle area of pedicle valve subcircular, with flabellate diductors. Cardinal process bifid. Interior of brachial valve prominently elevated at line of geniculation.

L. richmondensis