Paleomerus instance of taxon
Description
As the other strabopids, Paleomerus was a small-sized arthropod. The bigger species was P. hamiltoni at 9.3 centimetres (3.7 inches), while the smaller P. makowskii reached only 7.3 cm (2.9 in). Other Cambrian arthropods reached much greater lengths, such as the gigantic anomalocarid genus Anomalocaris that surpassed 1 m (3 ft 3 in). Within Strabopida, the closely related Strabops thacheri exceeded the length of Paleomerus with 11 cm (4.3 in), while Parapaleomerus sinensis reached a total length of 9.2 cm (3.6 in).Like some other arthropod clades, 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 frontal 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 in three lobes), the abdomen was composed by eleven segments and succeeded by a thick tail-like spine, the telson. In Paleomerus, the prosoma was parabolic (approximately U-shaped), and the opisthosoma can increase or decrease in width slightly or strongly. It was very flexible, possibly being able to flex laterally and roll up itself. The telson was trapezoidal, broad and tapering. Paleomerus may be the best model of a primitive arachnomorph.Paleomerus differs from Strabops only in the position of the eyes, which are farther from each other and closer to the margin than in Strabops, and the size of the telson, being shorter and broader than in the latter.
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