Undescribed Super Spiny Aglaspid Rarity from Utah

Description: This Aglaspid, is one of only two known. Both having been found in the Weeks Formation, House Range, Utah. The other is currently being studied and described as this offering is made. This fossil is a positive and negative. The impression is a stain. It would not be possible to prepare the specimen with air abrasion, as it has no “skin”. Please note the long thoratic spines coming off the (8?) segments. Though not preserved on this specimen, the aglaspid would have had a tail spine almost as long as the body. What’s more, the tail spine would have had short secondary spines. It is a singular and unique fossil offering, with current and on-going scientific significance.

The Aglaspida (Aglaspids) are an unranked (incertae sedis) clade of early arthropods that due to their resemblance to horseshoe crabs were once believed to ancestral horseshoe crabs, and were included with the chelicerata. Most recently, aglaspids are held to be distinct group, possibly closely related trilobites, The older idea that they link trilobites within Chelicerata is no longer predominant. Although aglaspid fossils are distributed worldwide, they are relatively rare in the fossil record. They are, in fact, one of the largest non-trilobite arthropod groups in the fossil record. Aglaspids had 8 to 12 pairs of appendages and a prominent telson. These morphological characteristics have caused considerable support for Aglaspids being the maker of Protichnites ichnofossils. Protichnites of the Upper Cambrian Mount Simon Sandstone in Wisconsin have been suggested as the first footprints on land in the fossil record, possibly marking the transition to terrestrial life that took tens of millions years more to complete.

Please excuse my poor photos. The specimen was sprayed with water to enhance the color and contrast.