Ceratarges sp. n°2 et n°3

 

Another excellent specimen of Ceratarges sp. that can be compared to the first specimen I presented (Ceratarges sp n°1). The same remarks are valid, that is to say that I can't ID this bug do to the lack of references :)

The main differences with the other specimen are the presence of secondary spines on the pygidial marginal spines and the lack of occipital and pygidial median and adaxial spines.

 

Specimen description

  • 95 % complete trilobite (except for a few thoracic pleural tips).
  • Slightly arched on the matrix.
  • Secondary spines on the pygidial marginal spines.
  • Total size : 60 mm
  • Devonian.
  • Alnif, Mrocco.
First look : a classic specimen ?
lateral wiew : secondary spines on the pygidial marginal spines.

 

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

 

Remark : better quality pictures to come soon.

 

Postero-lateral view.

Oblic view to better show the secondary spines.

 

Frontal view of the cephalon.

 

Complementary specimen :

This a 3rd specimen of Ceratarges sp. Even if I couldn't make this preparation work, the overall quality is far below the specimen shown above. I think they are both the same species, though, due to the fact that one can see remnants of the secondary spines, highlightened with circles on the following pictures :

 

Dorsal view Very small tubercles, remnants of the secondary spines ?

 

Frontal view of the cephalon and its border.

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