Psychopyge

Order:  PHACOPIDA  Salter, 1864

Suborder: PHACOPINA  Struve, 1959

Superfamily: ACASTOIDEA  Reijers, 1972

Family: ACASTIDAE  Delo, 1935

Subfamily: ASTEROPYGINAE  Delo, 1935

Genus PSYCHOPYGE  G. & H. Termier, 1950

 

Diagnosis

adjusted from Bignon and Crônier, 2014

Cephalon
Psychopyge has a rounded frontal lobe. In front of the cepahlon, it has a long sword shaped projection. It’s eyes have 9 to 10 lenses maximum per row. The genal spine is longer than the glabella and there is a long spine on the occipital ring. There are no metafixigenal spines (spines between the genal spines and the glabella).

Pygidium
The pygidial axis has 18 to 21 rings with median long spines; 5–6 pleural segments with length (tr.) increasing posteriorly, rounded pleural bands, interpleural furrows clearly incised; vertical spines on the distal part of each posterior band; 5 pairs of pygidial spines only developed from posterior pleural bands, longer than pleural width (tr.).

 

Occurence

Psychopyge mostly occurs in the upper emsian of Morocco and Germany.

 

Recognizing Psychopyge species

There are 6 species of Psychopyge. Pychopyge psyche (Basse, 2003) occurs in Germany, but not in Morocco. The others will be described below.


Psychopyge angeles and elegans

Psychopyge elegans

Termier & Termier, 1950 (Emsian)

This species is a bit tricky. It was described only on an incomplete pygidium. And that causes a lot of confusion it seems. Many Psychopyge are named as P. elegans, but are actually P. angeles.

The picture (Basse & Müller 2016, used with permission) clearly shows the differences. P. angeles is the upper picture. P. elegans is the picture below.

P. elegans does not have the pygidial pleural spines that are present in P. angeles (see black arrows). Another difference is that the width of the pleural field posterior to the posteriormost rib is wider and segmented in P. angeles. In P. elegans this width is smaller and the field is not segmented (see white markings).


Psychopyge angeles

Basse & Müller, 2016 (Emsian)

Cephalon:
P. angeles has a Y-shaped projection in front of the glabella. It is only a little bit longer as the thorax. The base is much wider. The glabella is granuated relatively evenly. The eyes have 32 rows of maximum 7-8 lenses.

Thorax:
The thorax has 11 segments. The thoraxal axis carries evenly short thorns.

Pygidium:
The pygidial axis has 17-18 well defined rings. They have evenly short thorns. There are 5 pairs of lateral spines. The fifth pair is clearly converging backwards.

Picture:
Basse & Müller, 2016


Psychopyge hammerorum

Psychopyge hammerorum

Chatterton et al., 2016 (Emsian)

Cephalon:
In front of the cephalon there is a long cephalic spine. It is wide at the base and ends in a point, what makes it look like a stretched triangular. It is covered with granulation.

Thorax:
The thoracic axis only has a median spine on the 4th and 8th rib.

Pygidium:
P. hammerorum has axial spines on the 2th, 6th, 10th and 14th rib. The lateral spines increase in length until the 4th pair. The 5th pair is one third in lenght of the 4th.


 

Psychopyge praestans

Psychopyge praestans

Morzadec, 2001 (Emsian)

Cephalon:
P. praestans is characterized by a median point that is narrow at the at the base, in front of the cephalon. It also has a reduced cephalic limb. The eyes have 35 rows of maximum 11 lenses.

Thorax:
The thoracic axis only has a median spine on the 4th and 8th rib.

Pygidium:
The pygidial axis counts 18 ribs of which only the 1th, 5th, 9th, 13th and 17th carry a median spine or tubercle. The length of the pygidial laterial spines triples between the 1th and the 4th pair. The 5th is 3 times shorter than the 4th.

Picture:
Adjusted from Morzadec, 2001


Psychopyge termierorum

Morzadec, 2001 (Emsian)

Cephalon:
P. termierorum is characterized by a very long median point in front of the cephalon (longer and smaller at the base than P. angeles). The eyes have 32 rows of maximum 10 lenses.

Pygidium:
There are 21 axial ribs in the pygidium, each with a median tubercle. It has only 6 pleural ribs. The 5 pairs of lateral spines are fine and their length increases towards the rear. The median spine is twice as short as the lateral ones.


References

Basse, M., Müller, P., 2016. Trilobiten aus dem Ober-Emsium und frühen Eifelium der südlichen Lahnmulde (Rupbach-Schiefer, Leun-Schiefer und Ballersbach-Kalk). Abhandlungen der Senckenberg Gesellschaft für Naturforschung.

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. D. E., Fortey, R. A., Brett, K., Gibb, S., and McKellar, R. 2006. Trilobites from the upper Lower to Middle Devonian Timrhanrhart Formation, Jbel Gara el Zguilma, southern Morocco. Palaeontographica Canadiana, 24:1177

Morzadec, P., 1988. Le genre Psychopyge (Trilobita) dans le Dévonien inférieur du Nord de l’Afrique et l’Ouest de l’Europe. Palaeontographica Abt. A 262: 53–58.

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