Hamatolenus sp. new type

Family: Protolenidae Richter and Richter 1948; Sub-family: Myopsoleninae Hupe 1953;  Genus: Hamatolenus; Location: Tinjdad

According to Hupe the palpebral lobe is longer in Myopsolenus than in Hamatolenus and reaches the posterior border furrow of the cranidia, opposite of Geyer.  For Hupe the Hamatolenus palpebral lobe does not reach the posterior furrow of the cranidium just like Collyrolenus (Invertebrate Paleontology, Part O, Trilobita page O211).

Under Hupe staminops is characterized by the glabella being pointed in the front (anterior) of the glabella.  The glabella of Hamatolenus is tapered forward, just not as pointed anteriorly as staminops because the latter has a generally narrower glabella. The posterior part of the Hamatolenus glabella is thicker than the staminop's example I have diagnosed. The diagnosis to introduce a new type, however, has to do with the "shovel" like pygidium which is not known in any other genus or species that are connected with the family Protolenidae.

There are twelve thoracic rings on the thorax.  The palpebral lobes and eye ridge have a wider axis distally from the glabella and are sub-parallel to the anterior border like myopsolenus. This specimen also has a short pre-glabellar field.  The palpebral lobes (below) do not seem to reach the posterior border of the cranidium, confirming that this is cf. (like) Hamatolenus.  Collyrolenus also is characterized by similar palpebral lobes; however, I place this under Hamatolenus because the glabella is much wider than the Collyrolenus specimen that was previously diagnosed.  It is also not a moroccanus because of the lack of the "s" shaped palpebral lobes and general height and shape of the cranidium.

However, not at all typical, the "shovel-like" pygidium is the first time I have seen such a feature.  All the rest of the pygidiums of Hamatolenus and Myopsolenus have been very non-descript, button-like, and typically small, usually semi-circular or half moon-like in appearance.  The two photos below show a wedge-like or shovel-like pygidium. The specimen itself is real and natural and not tampered with as far as any restoration. 

The pygidium may have been used like a "rudder" for control of the body and may have been used in swimming.  It would have given the creature control over going up or down in the water column.  The bottom photo shows the relative convexity of the glabella in comparison to the other areas of the body.  A rudder-like pygidium would have given this trilobite an advantage over other trilobites with the usual button-like pygidium.

Kenjiro 2020.5.24.