Morgatia hupei (NION & HENRI 1967)

 

The specimen previously presented on this page has been reassignated to Phacopidina micheli TROMELIN 1877. I leave nevertheless the diagnosis for reference.

 

 

Diagnose :

 

Order

 

 

 

 

 

 

 

Phacopida

 

 

 

 

 

 

 

SALTER 1864

 

 

 

 

 

 

 

Occurrence: Lower Ordovician (Tremadoc) to Upper Devonian (Famennian).

  • Cephalon: Proparian (Phacopina and Cheirurina), gonatoparian (Calymenina) or opisthoparian (Calymenina),
  • Preglabellar field often very short or absent.
  • 4 or fewer pairs of glabellar furrows.
  • Eyes : when present, schizochroal (Phacopina) or holochroal (Cheirurina and Calymenina).
  • With rostral plates (Calymenina and Cheirurina) or without (some Phacopina).
  • Hypostome conterminant (all suborders) to impendent (some devonian Phacopina).
  • Exosqueletton generally granulous.
  • Thorax: 8 – 19 segments, sometimes distinctly furrowed.
  • Axis sometimes broad (e.g., Homalonotidae).
  • Pygidium : Typically micropygous (most Calymenina and Phacopina), but variable (e.g., subisopygous in Dalmanitoidea and Acastoidea).
  • May be lobed or spiny (e.g., Cheirurina, some Dalmanitoidea, Acastoidea), or smooth-margined, with round or subtriangular outline (e.g., Calymenina, Phacopoidea).

Sub-order

 

 

 

 

 

Phacopina

 

 

 

 

 

STRUVE 1959

 

 

 

 

 
  • Cephalon : Proparian sutures (sometimes fused).
  • Schizochroal eyes.
  • Glabella expands forwards.
  • Librigena typically yoked as single piece.
  • Hypostome conterminant to impendent, some with no rostral plate.
  • Some with genal spines.
  • Thorax: 10 to (typically) 11 segments.
  • Pleurae furrowed, articulating facets distinct.
  • Rounded, angular, or spinose tips.
  • Pygidium : Typically smaller than cephalon (but subisopygous in Dalmanitoidea and Acastoidea).
  • Smooth or spinose.

Superfamily

 

Phacopoidea

 

HAWLE & CORDA 1847

 
  • Cephalon : Auxiliary impressions short or lacking.
  • Dorsal furrows strongly diverging.
  • "anterior" lobe composite.
  • No genal spines.
  • Vincular furrow generally present.

Family

 

Phacopidæ

 

HAWLE & CORDA 1847

 
  • Cephalon : Glabella broadening markedly forward.
  • S2 and S3 lateral glabellar furrows obsolescent.
  • S1 generally transglabellar, thus forming a more or less distinct "intercalating ring".
  • Auxiliary impressions field ovale to circular.
  • Genal angles rounded, lobiform or angular.
  • No genal spines.
  • Hypostoma triangular to trapezoidal.
  • Thorax : Thoracic pleurae with rounded ends.
  • Pygidium : Well-rounded, semicircular or shorter.
  • Margin complete.
  • No spine.

Genus

Morgatia

HAMMANN 1972
  • Cephalon : Large eyes.
  • Eyes close to the posterior furrow.
  • Internal end of S1 forked.
  • S3 with double inflexion, orthogonal to the dorsal furrows.
  • Rounded genal angles, without genal spines.
  • Cephalic border with vincular furrow (coaptative structure).
  • Pygidium : Rounded.
  • 3 to 6 axial rings.
  • 3 to 5 pleural ribs.
  • No posterior border.

Species

hupei

(NION & HENRI 1967)

 
  • Cephalon : Glabella little convex, narrow, markedly broadening forward.
  • Eyes very large, reaching almost the cephalic posterior furrow.
  • External half of S3 bent forward.
  • Cephalic doublure with marginal furrow and lateral pits.
  • Pygidium : 6 to 7 axial rings.
  • 4 pleural ribs with anterior ribs more distinct.

 

Complementary pictures :

 

Synthetogram of Morgatia hupei (NION & HENRI 1967) (After P. Lebrun, 2002)

 

 

Differential diagnoses :

Morgatia primitiva

It is differenciated from M. hupei by a convex and less widening glabella, furrows S3 whose obliqueness is less marked, a reduced former cephalic edge, eyes of relatively smaller size and a well segmented pygidium.. One will retain also the absence of "fossettes latérales" on the connective sutures of the cephalic doublure (5 to 6 pairs for M. hupei).

In addition, in France, the two species are found in the formation of Postolonnec where M. hupei is more frequent, while in Spain M. primitiva is found in the synclinal of Navas de Estena and Puebla de Don Rodrigo while M. hupei is found in the synclinal de Puerto-Ilano-Almuradiel.

 

Species

primitiva

HAMMANN 1972

 
  • Cephalon : Glabella convex.
  • Eyes large.
  • Distance between the posterior border of the eyes and the posterior furrow equals to the 1/4th of the total occular length.
  • 27 or 28 dorso-ventral rows of 9 lenses max.
  • Pygidium : Rounded.
  • Rachis broad and hardly elevated.
  • 6 axial rings, very distinct on external molds.
  • 4 pleural ribs.
  • Interpleural furrows superficial.

 

Synthetogram of Morgatia primitiva HAMMANN 1972

(After P. Lebrun, 2002)

 

 

Morgatia zguidensis (DESTOMBES 1972)

Upper Llanvirn. Morocco. No diagnosis.

Species

zguidensis

(DESTOMBES 1972)

?

 

 

References :

HAMMANN W. 1972. Neue Propare Trilobiten aus dem Ordovizium Spaniens. [New Proparian Trilobites from the Ordovician of Spain]. Senckenb. Lethaea, 53 (5) : pp 371 - 381. hb,

HAMMANN W. 1974. Phacopina und Cheirurina (Trilobita) aus dem Ordovizium von Spanien. Senckenb. Lethaea, 55 (1/5) : pp 1 - 151.

LEBRUN P. 2002. Trilobites de France. Tome I. Généralités sur les trilobites, Massif Armoricain (bretagne, Normandie, Vendée). Minéraux et Fossiles. Hors série N°14.

RABANO I. 1989. Trilobites del Ordovícico Medio del sector meridional de la zona Centroibérica española. Bol. geol. min. n° 3, 4, 5, 6. Vol. 100.

 

Back to Home Page