Lonchodomas

Lonchodomas is a genus of trilobites, that lived during the Ordovician. It was eyeless, like all raphiophorids, and had a long straight sword-like frontal spine, that gradually transforms into the relatively long glabella. Both the glabellar spine and the backward directed genal spines are subquadrate in section. Lonchodomas has five thorax segments and the pleural area of the pygidium has two narrow furrows. Lonchodomas occurred in what are today Argentina, Canada, Estonia, Latvia, Norway, Sweden, the Russian Federation and the United States.

Distribution

L. carinatus is found in the Upper Ordovician of the United States
L. clavulus is present in the Middle Ordovician of Newfoundland, Canada.
L. mcgeheei is present in the Upper Ordovician of Oklahoma, United States.
L. retrolatus was collected from the Ordovician of Nevada )
L. rostratus is known from the Upper Ordovician of Estonia and Latvia.
L. suriensis was excavated from the Middle Ordovician of Argentina
L. volborthi occurs in the Lower Ordovician of the Russian Federation. It was originally described as Ampyx volborthi but assigned to Lonchodomas in 1952 by Steinar Skjeseth.
Description

Like all raphiophorids, Lonchodomas is eyeless. The headshield and tailshield are subtriangular in outline. Lonchodomas looks a lot like Ampyx but the glabella is diamond-shaped in outline, and it has a ridge along the midline. The glabella gradually transforms into the spine, which makes it difficult to determine where the spine begins. The long median glabellar spine is subquadrate in section and is directed horizontally forward, from the frontal tip of the glabella. The glabella has 2 pairs of muscle scars. The genal spines are also subquadrate in section. The thorax has 5 segments. The pleural regions of pygidium have 2 pairs of narrow pleural furrows.

Lonchodomas

Distribution

Description