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Trilobites (/ ˈ t r aɪ l ə ˌ b aɪ t s, ... In Olenoides, the partially articulated junction with the body is distinct from the exopods of Chelicerata or ...
Chelicerata split from Mandibulata by the mid-Cambrian, as evidenced by stem-group chelicerates like Habeliida and Mollisonia present by this time. [2] The surviving marine species include the four species of xiphosurans (horseshoe crabs), and possibly the 1,300 species of pycnogonids (sea spiders), if the latter are indeed chelicerates. On the ...
2025 in arthropod paleontology is a list of new arthropod fossil taxa, including arachnids, crustaceans, trilobites, and other arthropods (except insects, which have their own list) that were announced or described, as well as other significant arthropod paleontological discoveries and events which occurred in 2025.
Trilobites were arthropods, like modern insects, spiders, millipedes and crustaceans, and they evolved into a wide range of shapes and sizes before going extinct around 252 million years ago. Most ...
The Artiopoda is a grouping of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 [5] to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomorpha.
The trilobites are thus, in their view, not stem-group chelicerates, a commonly held view, but rather, stem-group mandibulates. The status of the labrum is not resolved by this theory, but they argue that it the evidence for it being appendiculate is not compelling; thus it does not have to correspond to a well-developed appendage of any ...
Some studies recover Megacheira as closely related to chelicerates, while others recover them as outside the group containing Chelicerate and Mandibulata as stem-group euarthropods. [127] The placement of the Artiopoda (which contains the extinct trilobites and similar forms) is also a frequent subject of dispute. [128]
Horseshoe crabs are chelicerates, meaning their bodies are composed of two main parts : the cephalothorax and the opisthosoma. The first tagma, the cephalothorax or prosoma, is a fusion of the head and thorax. [25]: 555 This tagma is also covered by a large, semicircular, carapace that acts like a shield around the animal's body. It is shaped ...