Ceratarges sp. n°1

 

Here is one of the breathtaking specimen of my collection. This beauty is due to Meredith Aaronson of Sahara Overland, whom Lab made a real high quality preparation work, where each of the spines could be set up free. The result is worth the price. Sadly, as I do lack a reference paper on Moroccan Lichids, I can't precisely ID this Ceratarges.

You can compare it to the second specimen I do present on the site. Some of the main differences here are the lack of secondary spines on the pygidial marginal spines, in contrast of median pairs of occipital spines and of a median pygidial spine. The occipital ring is more protruded, as the pygidial axis.

 

Description du spécimen

  • Trilobite standing prone on matrix.
  • Almost complete except for some tip of pleural spines.
  • Exceptionnal preparation work.
  • Total size : 70 mm.
  • Devonian.
  • Zerg, Morocco.

Dorsal view.
Up : frontal view. Down : Lateral view.

 

Diagnosis :

 

Order

Lichida

MOORE 1959

Typically spiny trilobites with densely granulate or tuberculate exoskeletons.

Occurrence: Cambrian to Devonian (Frasnian)

  • Cephalon : Opisthoparian sutures.
  • Glabella broad, large, extending to anterior border.
  • Glabellar lobation simple (Dameselloidea & Odontopleuroidea) to complex with fused lateral and glabellar lobes (Lichoidea).
  • Eyes typically present, holochroal, usually not large.
  • Conterminant hypostome.
  • Thorax : Variable morphology.
  • 8-13 segments usually spine-tipped, sometimes with distinctive spines (e.g., Odontopleuroidea).
  • Pygidium : Typically isopygous to macropygous, but sometimes short (e.g., Odontopleuroidea).
  • Often longer than wide.
  • Often with 3 pairs of furrowed pleurae, typically ending in spinose tips.

Superfamily

Lichoidea

(sensu FORTEY 1991)

Medium to large trilobites. Typically, surface sculpturing involves two size classes of granules or tubercles.

  • Cephalon : Opisthoparian sutures.
  • Glabella widening close to the occipital ring, extending to anterior border, with unique complex structure (lateral glabellar and occipital lobes often fused with each other and with cranidium).
  • L1a, L1b (subdivision of the preoccipital lobes) and bullar lobes flanking the median glabellar lobe.
  • Thorax: 10 - 11 segments.
  • Pleurae initially horizontal, bend retrograde at fulcrum.
  • Pleurae ending in free points.
  • Pygidium: Large, usually flattened.
  • Often with 3 pleural pairs of leaflike or spinose structures.

Family

Lichidæ

 HAWLE & CORDA 1847
  • Cephalon : L1a, L2a and bullar lobes distinct, but sometimes partially or totally fused with each other or with the adjacent part of the fixigenae.
  • Lack of preglabellar furrow in front of bullar lobe.
  • Anterior branches of the facial sutures parallel or slightly convergent anteriorly.
  • No eye ridges.
Subfamily Ceratarginæ TRIPP 1957
  • Cephalon : Bicomposite lateral glabellar lobes bounded at back by posterior lateral furrows (except in some species of Hemiarges).
  • Axial furrows usually obsolete behind bicomposite lobes.
  • Occipital lobes fused with basal lateral glabellar lobes (except in Trochurus and Dicranogmus).
  • Hypostoma with posterior margin not markedly indented. Middle body circumscribed, with small posterior lateral lobes.
  • Pygidium : Axis extended to posterior border or margin by narrow ridge.
  • Posterior bands of 1st and 2nd pleuræ narrower and more swollen than anterior bands.
  • Posterior pair of pleuræ unfurrowed.
Genus Ceratarges GÜRICH 1901
  • Cephalon : Glabellar furrows faintly impressed.
  • Librigenal spines long and slender, forwardly placed.
  • Long spines curving upward and backward on frontal lobe of glabella and pygidium.
  • Pygidium : Marginal spines.
Species sp.   to determine. (lack of references)

 

Complementary pictures :

 

Frontal view of the cephalon Right postero lateral view of the specimen

 

Right postero lateral view of the cephalon Dorsal view of the cephalon

 

Marginal spines of the cephalon, with an alternance in size. Dorsal view of the thorax

 

Median and adaxial pygidial spines.
Left lateral view of the specimen.

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