Strabops is a genus of strabopid, an extinct group of arthropods. Strabops is known from a single specimen from the Late Cambrian (Furongian age) of the Potosi Dolomite, Missouri, collected by a former professor, Arthur Thacher. It is classified in the family Strabopidae of the monotypic order Strabopida, a group closely related to the aglaspidids with uncertain affinities. The generic name is composed by the Ancient Greek words στραβός, meaning "squinting", and ὄψῐς, meaning "face" (and therefore, "squinting face"). The history of Strabops has been turbulent and confusing since its original description by Charles Emerson Beecher, who classified it as a eurypterid. Many authors do not agree with this and have classified Strabops and its allies as part of the Aglaspidida order, while others classify them in their own order. Although the latter is the taxonomic position currently accepted, other paleontologists prefer to simply omit the strabopids from their analyzes due to the poor preservation of their fossils. In addition, it has been suggested that the closely related Paleomerus represents a synonym of Strabops, which are uniquely differentiated by the size of the telson (the posteriormost division of the body) and the position of the eyes.
Description
As the other strabopids, Strabops was a small-sized arthropod, measuring only 11 centimetres (4.3 inches) in length. However, it was the largest of the strabopids, surpassing Paleomerus (9.3 cm, 3.7 in) and Parapaleomerus (9.2 cm, 3.6 in). Like some other arthropod groups, the strabopids possessed segmented bodies and jointed appendages (limbs) covered in a cuticle composed of proteins and chitin. The arthropod body is divided into two tagmata (sections); the anterior prosoma (head) and posterior opisthosoma (abdomen). The appendages were attached to the prosoma, and although they are unknown in strabopids (except for one undescribed specimen of Parapaleomerus), it is most likely they owned several pairs of them. Although the chemical composition of the strabopid exoskeleton is unknown, it was probably mineralized (with inorganic substances), sturdy and calcareous (containing calcium). The head of the strabopids was very short, the back was rounded and lacked trilobation (being divided into three lobes), the abdomen was composed by 11 segments and was followed by a thick tail-like spine, the telson. In the genus Strabops, the prosoma was short and broad, with a rounded outline. The eyes were located in the middle of the front of the prosoma. These were medium-sized, ovate and narrow, and pointed obliquely inwards (hence the name Strabops). Two spots between the eyes indicate the presence of the ocelli (light-sensitive simple eyes). In its abdomen, there were eleven segments, being the third the widest. The ends of the segments were rounded on the sides. In the posterior part of the segments, a row of tiny crenulations was visible. The first six segments were uniform in size, the three following ones were somewhat shorter and the last two were the longest. The telson was a broad, flat spine, and it rose slightly in the middle. The appendages are unknown, although it has been suggested that they be less than seven pairs (what has been considered an overestimate). Strabops differed only from Paleomerus in the position of the eyes, which were closer together and farther from the margin than in Paleomerus, and the size of the telson, being longer and narrower than in the latter.
History of research
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