Hamatolenus (Hamatolenus) vincenti   Geyer and Landing 2004

Characterized by a long second macropleural spine, otherwise same characteristics (diagnosis) as other common Hamatolenus sub-genus Hamatolenus. This macropleural spine looks like it originates on the third thoracic spine in a number of specimens, but after closer examination it precipitates from the second thoracic ring.  What looks like the first thoracic ring is made up of the occipital ring and this ring is nearly identical to the thoracic segment complete with thoracic furrows. The occipital ring is part of the cranidium not the thorax.  Hamatolenus (Hamatolenus) includes a long palpebral lobe (above the eye lobe and coterminous with it) that reaches the posterior furrow of the cephalon or cranidium (except for maroccanus).  A parafrontal band connecting the palpebral lobes that in well preserved specimens can be traced in front of the glabella. The genus is in the Protoleninae sub-family under the family Protolenidae under the Ellipsocephalidae.  

The specimen above has a preserved genal spine on the left side that has broken off and rests lower than its life position.  Notice how well the occipital ring looks like the first thoracic segment, complete with furrows.  Also this one has a clear but narrow pre-glabellar field and an anterior border.

The right genal spine is preserved here but is somewhat disarticulated.  This specimen above also shows the occipital ring and the connected posterior furrow of the cranidium that looks like a thoracic segment. 


The specimen above disarticulated in the middle of the thorax shows the cranidium, and like the other two, the occipital ring and the posterior border (of the cranidium) that looks like a thoracic segment.  The free cheek flipped over lies to the left of the specimen.

 

This example above has a tightly connected free cheek and genal spine on the left side, but on the right side it looks like the free cheek broke off, and was preserved on top of the cranidium overlapping it.

This specimen above shows the Hamatolenus (Hamatolenus) characteristics of the palpebral lobe as it extends to the posterior border of the cranidium.  The posterior border forms the unusual cranidial spine that is connected to the occipital ring which is clearly visible here.  Notice the free cheek and genal spine at the bottom left of the trilobite.

The vincenti above showing rare preservation of the pygidium reflecting the Hamatolenus genus.

Kenjiro 2009.5.2 (Edited 2015.6.18)