Hollardops

Hollardops

Order:  PHACOPIDA  Salter, 1864

Suborder: PHACOPINA  Struve, 1959

Superfamily: ACASTOIDEA  Reijers, 1972

Family: ACASTIDAE  Delo, 1935

Subfamily: ASTEROPYGINAE  Delo, 1935

Genus HOLLARDOPS  Morzadec, 1997

 

Diagnosis

by Bignon and Crônier, 2014

Cephalon: Frontal lobe rounded; axial furrows curved between S2 and S3; L2 and L3 more elevated than L1; 6–11 lenses per dorsoventral file of visual surface; genal spine as long as glabella, anterior tip of palpebral lobe posterior to intersection of axial furrows and S3.

Thorax with 10 segments.

Pygidium: 10 to 16 pygidial axial rings; 5 pleural segments, rounded pleural bands; verywide pleural furrows; 5 pairs of pygidial spines developed from posterior and anterior pleural bands, shorter than pleural width (tr.); terminal medial spine shorter than adjacent pygidial spines, wider than axis.

 

Occurence

There are 6 species of Hollardops. 4 of them occur in Morocco in the Eifelian and upper Emsian. We will discuss them below. The other two species are Hollardops lemaitreae  Morzadec, 1997  from the upper Emsian in Algeria and Hollardops struvei  Morzadec, 1969  from the upper Emsian in France.

 

Recognizing Hollardops species

hollardops mesocristata (chatterton 2006) copyAdjusted from Chatterton et all (2006)


Hollardops mesocristata

Le Maître, 1952  (upper Emsian – Morocco)

Cephalon:
the eyes have 29 rows of max 9 (rarely 11) lenses

Pygidium:
The pygidial axis has 14 rings.
The pygidial spines are the same length, short and then curved inwards.

Hollardops aithassainorum copy

Adjusted from Chatterton et all (2006)

 

Hollardops aithassainorum

Chatterton et al., 2006 (Eifelian – Morocco)

Cephalon:
The eyes have 27 rows of max 9 lenses. There is no low ridge below the eye.

Pygidium:
The pygidial axis has 15-16 rings. The pygidial spines are short and rounded distally.

 

 

Hollardops boudibensis

Morzadec, 2001 (upper Emsian – Morocco)

Cephalon:
S2 does not reach the dorsal furrows. The eyes have 27 rows of max 6 (rarely 7) lenses.

Pygidium:
The pygidial axis has 12 rings. The pygidial spines are wide, short and rounded. The pygidium is rather rounded.

Picture adjusted from and used with permission of trilowelt.de

Hollardops burtandmimiae

Lieberman & Kloc, 1997 (upper Emsian and Eifelian – Morocco)

Cephalon:
The front of the cephalon is less rounded than H. mesocristata. The eyes have 27 rows of max 8 (rarely 11) lenses.

Pygidium:
The pygidial axis has 15-16 rings. Some pygidial spines are longer and sharper. The median spine is shorter.

 

References

Bignon, A., Crônier, C., 2014. The systematics and phylogeny of the Devonian subfamily Asteropyginae (Trilobita: Phacopida). Journal of Systematic Palaeontology 12, 637–668.

Chatterton, B., Fortey, R., Brett, K., Gibb, S., McKellar, R., Trilobites from the upper Lower to Middle Devonian Timrhanrhart Formation, Jbel Gara el Zguilma, southern Morocco. Paleontographica Canadiana 25.

Morzadec, P. 2001. Les Trilobites Asteropyginae du Dévonien de l’Anti-Atlas (Maroc). Palaeontographica, Abt A , 262, 53-85.