Paradoxides

Paradoxides is a genus of large to very large trilobite found throughout the world during the Middle Cambrian period. One record-breaking specimen of Paradoxides davidis, described by John William Salter in 1863, is . The cephalon was semicircular with free cheeks ending in long, narrow, recurved spines. Eyes were crescent shaped providing an almost 360° view, but only in the horizontal plane. Its elongate thorax was composed of 19–21 segments and adorned with longish, recurved pleural spines. Its pygidium was comparatively small. Paradoxides is a characteristic Middle-Cambrian trilobite of the 'Atlantic' (Avalonian) fauna. Avalonian rocks were deposited near a small continent called Avalonia in the Paleozoic Iapetus Ocean. Avalonian beds are now in a narrow strip along the East Coast of North America, and in Europe.

== Description == The exoskeleton of Paradoxides is large to very large, relatively flat, and about one and a half times longer than wide, with greatest width across the genal spines. The cephalon is close to semicircular with long genal spines developed from the posterolateral corners of the cephalon. Depending on species the facial sutures are of variable length behind the palpebral lobes. The preocular sections of the facial suture follows a slight S-curve and intersect the anterior cephalic margin in front of the eye. Four pairs of glabellar furrows are usually present, the posterior two pairs (1p and 2p) are transglabellar. 3p and 4p furrows short with 4p commonly directed forwards and outwards to intersect axial furrows opposite maximum glabellar width. Palpebral lobes are short and of variable length. Hypostoma in some species is fused with the rostral plate, e.g. in Paradoxides davidis, a character that distinguishes the genus from all other trilobites, except in some Cambrian Corynexochida such as Oryctocephalus and Fieldaspis.