''Vidria vespa'' is a proetid

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

belonging to the family

Phillipsiidae Phillipsiidae is a family of proetid trilobites, the various genera of which comprise some of the last of the trilobites, with a range that extended from the Kinderhookian epoch of the Lower Mississippian, to the end of Changhsingian age at P ...

. The fossils are found in Middle

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

-aged marine strata of Western

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

. It is unique among Permian-aged trilobites in having a posterior spine emanating from the pygidium of the adult (two such posterior spines are present in immature individuals).

References

* Proetida fact shee

Permian trilobites Trilobites of North America Phillipsiidae Proetida genera Guadalupian genera {{proetida-stub