Arthropleura

Article

January 18, 2022

Arthropleura (scientific name: Arthropleura, Japanese name: Kodaioyasude) is a genus of millipedes that inhabit the Carboniferous and Permian periods about 300 million years ago and are classified as Arthropleura. It is divided into three parts on the side and has a back plate with large and small humps on the surface. It is a famous paleontology as a giant arthropod, including species over 2 meters long, and is considered to be one of the largest arthropods in history, along with some Eurypterids. Fossils have been found in various parts of Europe and North America.

Name

The scientific name "Arthropleura" is derived from the Greek words "arthron" (joint) and "pleuron" (side plate, a term once used to refer to the left and right bulges of the genus tergum). There is "Kodaio Yasude" as a Japanese name.

Form

A wide back plate (tergite, exoskeleton on the back) is divided into three leaves, and it is an Arthropleuride millipede characterized by having large and small humps on the surface. Although it is a famous paleontology as a giant arthropod, some features, especially the anterior structure and the tergum, are rare because the well-arranged fossil specimens are rare and the anterior-posterior and abdominal structures are even less well aligned. It is still difficult to restore the correspondence between the legs and the legs. The known exoskeleton fossil specimens are unusually thin, 2 mm thick, despite their size, but this is a molting shell, and the original exoskeleton appears to be thicker and stronger, and the molting shell itself is also thinner. On the contrary, it is said to maintain a certain degree of hardness (see below).

Head and neck plate

Definitive head structures have been found in the other Arthropleuras, Microdickemplex (almost complete) and Eurypterid (mandible only), whereas the head of this genus is still almost complete. The structure, which was unknown and was once interpreted as the head, was later reconsidered as a misunderstanding of another ("jaw limb" is a fragment of the jaw base derived from the leg of Eurypterid, "round head" is the cervical plate, described later). Immediately before the first trilobal tergum is a slightly smaller, rounded exoskeleton. This exoskeleton has a pair of dents on the left and right, with large and small humps on the surface, and the trailing edge is slightly raised and crossed by a single groove. Before the 21st century, this exoskeleton was interpreted as a "round head", and it was speculated that the pair of left and right dents were originally visible. However, in re-examinations since the 21st century, this has come to be reconsidered as the neck plate (collum, the first back plate of the torso specialized immediately after the millipede's head) rather than the head. Like other millipedes, the (unknown) head was originally under this cervical plate, and is thought to be almost completely hidden in the cervical plate from above, like the microdickemplex. It is possible that the pair of dents on the left and right sides of the cervical plate corresponded to unidentified trumpet-like protrusions that traveled from the head, as seen in microdickenplexes, rather than the eyes. In Briggs & Almond 1994, a rounded structure was found in the indentation of the cervical plate of Arthropleura (which was still interpreted as the head at that time), and it is thought that this is a protrusion derived from the head as described above. Kraus & Brauckmann 2003 and Kraus 2005 described some fragmentary fossil specimens that may have originated from the head. According to these specimens, the head of Arthropleura has a folded structure similar to the modern millipede and the base of the antennae on both edges, the surface is densely populated with fine humps, and the vertices are smooth oval. The presence or absence of eyes and the morphology of the head appendages (antenna, mandible, maxilla / lip) are almost unknown. Antennae are completely unknown, but at least not filamentous (millipede antennae)

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