Eochonetes clarksvillensis

Phylum: Brachiopoda
Class: Strophomenata
Order: Strophomenida
Family: Sowerbyellidae
Genus: Eochonetes
Species: Eochonetes clarksvillensis (Foerste, 1912)

eclarksvillensis strat
[accordions title=”” disabled=”false” active=”1″ autoheight=”false” collapsible=”true”] [accordion title=”Taxonomic Details”]Formerly: Plectambonites rugosa-clarksvillensis, Sowerbyella clarksvillensis, Thaerodonta clarksvillensis, and Eoplectodonta clarksvillensis[/accordion] [/accordions]

Stratigraphic Occurrences

e.clarksvillensis strat

Geographic Occurrences

Map point data provided by iDigBio.
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Sequence (Formation)

  • C5 Sequence (Liberty, Waynesville)

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Identification in Hand Sample

  • Semicircular outline
  • Unequally costellate
  • Small apical pseudodeltidium
  • Dorsal denticles with ventral fossettes
  • Lateral ridges in dorsal muscle field
  • Pseudopunctae on interior

Eochonetes clarksvillensis from Waynesville formation of Greene County, Ohio (OUIP 1706)


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Jin & Zhan (2001):

  • General Description: Shell small; traversely semielliptical; 4.2-5.5 mm long and 8.0-10.7 mm wide with average length/width ratio about 0.53; concavo-convex; deepest in central part of shell; hinge line straight, being widest part of the shell; cardinal extremities subrectangular or slightly pointed; both ventral and dorsal interareas low (<0.5mm in height), apsacline and analine respectively; delthyrium and notothyrium open; entire shell covered by sharply differentiated parvicostellae, averaging 5-7 fine costellate (papillae) between two adjacent coarser costellate
  • Ventral Interior:Teeth small but relatively robust; dental plates low, extending anteriorly to become lateral bounding ridges of muscle field; 5 or 6 small hinge fossettes present in medial portion (between apex and cardinal extremity) on each side of hingeline; muscle field bilobate, well defined, occupying 35% of shell width and 64% of shell length; pair of diductor muscle scars diverging from each other at about 45 degrees with relatively large, wide, medial notch occupying approximately half of muscle-field length; adductor muscle scars small, oval-shaped, slightly deeper then diductor scars, extending posteriorly into round cavity underneath delthyrial platform, divided by median septum; median septum beginning immediately anterior of delthyrial platform, becoming stronger abruptly at anterior end of adductor scars, attaining greatest height at its anterior end, and then bifurcating into pair of low ridges as antero-medial bounding ridges of diductor scars; vascular markings saccate, with vascular media originating from anterior ends of diductor scars
  • Dorsal Interior: Cardinal process undercut, bearing trifid myophore with median lobe being highest, laterally continuous with socket ridges; socket ridges straight, short, thick, and divergent from each other antero-laterally at about 120 degrees; 5 or 6 denticles present in medial portion on each side of hingeline, corresponding to ventral dental fossettes; diductor muscle field suboval to subcircular in outline, attaining about 40% of shell width and 65% of shell length; pair of central side septa relatively long, high, and thin, originating immediately anterior of socket ridges, diverging from each other anteriorly at about 15-20 degrees, extending anteriorly for slightly over three-fourths of valve length, and attaining greatest height near anterior margin of muscle field; pair of lateral side septa (transmuscle ridges) variably developed but generally weak, separting each adductor muscle scar into inner and outer parts

Davis (1998)

  • Articulate brachiopod. Differs from Sowerbyella rugosa in having hinge line denticulations and a normally smooth exterior and in being somewhat less wide, relative to length. Waynesville and Liberty

Jin, Caldwell, & Norford (1997):

  • External Morphology: Relatively small size; prominently transverse; semicircular outline; unequal parvicostellae with strongly accentuated major costellate; dorsal valve:later side-transmuscle septa that are poorly developed; partial etchings of several specimens shows denticles on the hingelines of dorsal valves, thus confirming their identity as Thaerodonta; accentuated costellate: generally strong and closely spaced, increase anteriorly by intercalation, in some specimens, the parvicostellae are poorly differentiated; distance between adjacent major costellate varies (about 1mm before intercalation, narrowing to 0.5 mm after intercalation), with 3 to 6 minor, finer costellate; growth lines are poorly developed or poorly preserved; some specimens have weak, irregular, interrupted rugae, especially in posterolateral portions of the shell
  • Ventral Muscle Field: (typical of the genus) divergent lateral bounding ridges and a median ridge that bifurcates in the anterior part of the muscle field
  • Dorsal Interior: Cardinal process is unseen; a pair of strong central side septa are present; lateral side septa are short, low, or absent in relatively small forms; absent median septum (this septal pattern is similar to the weak or poorly developed, lateral side septa illustrated by Foerste 1912)

Howe (1988):

  • Thaerodonta clarksvillensis shows a wide variation in size and strength of hinge line denticulation which makes the character doubtful for species differentiation
  • T. clarksvillensis displays more divergent brachiophores than T. recedens
  • In large samples there is a complete gradation to less divergent brachiophores, for these reasons the Ohio Valley form, T. clarksvillensis is considered to be conspecific with T. recedens

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