THE HYPOSTOME AND I
Excerpts from Fossil News , January, 2000
Not only do hypostomes rarely appear in fossil shows, they are not widely recognized. Often or in may cases totally lost in molting and death, hypostotmes were part of the feeding apparatus of these primitive arthropods, were lodged under the cephalon. Given the great variety of trilobites over the hundreds of millions of years of their existence, diets would have varied a great deal. Forms and textures would be subject to change according to orders, families, and even genera.
This limited selection, spanning time from an earliest Ordovician olenid to a middle Devonian lichid, gives a sampling of the notable differences that make for intriguing study. It is hard to believe that the illustrations of the Hoekaspis and the Asaphellus are both from asaphids. The fingerprint-like ridge marks on the Hoekaspis may have facilitated food ingestion. The main body of the cephalon was eroded disclosing this setting for its under-anatomy.
As often as not, hypostomes are found displaced from other parts of their anatomy. The large specimen of a Fenestraspis amauta was preserved through the ages in a concretion all to itself. The bulbous main body would have been on the underside of the glabella... Not surprisingly no head that size has been collected.
Devonian LichidAcanthopyge balliviani - Large
Ordovician AsaphidAsaphellus palquiensis - Large
Ordovician AsaphidAsaphelus riojanus - Large
Devonian CalmonidEldredgeia venustus - Large
Devonian DalmanitidFenestraspis amauta - Large
Devonian DalmanitidFrancovichia branisi - Large
Ordovician AsaphidHoekaspis yahuari - Large
Devonian CalmoniidMalvinocooperella pregiganteus - Large
Ordovician OlenidParabolina argentina - Large
Ordovician AsaphidJuvinile Asaphid - Large
Devonian PhacopidViaphacops salteri - Large , Closeup
Devonian CalmoniidVogesina lacunafera - Large
Devonian CalmoniidWolfartaspis cornutus - Large
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