Juliformia is a taxonomic

superorder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...

millipede Millipedes (originating from the Latin , "thousand", and , "foot") are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derive ...

s containing three living orders:

Julida Julida is an order of millipedes. Members are mostly small and cylindrical, typically ranging from in length. Eyes may be present or absent, and in mature males of many species, the first pair of legs is modified into hook-like structures. Addit ...

Spirobolida Spirobolida is an Order (biology), order of "round-backed" millipedes containing approximately 500 species in 12 family (biology), families. Its members are distinguished by the presence of a "pronounced Suture (anatomy), suture that runs "verti ...

, and

Spirostreptida Spirostreptida is an order of long, cylindrical millipedes. There are approximately 1000 described species, making Spirostreptida the third largest order of millipedes after Polydesmida and Chordeumatida. Description Spirostreptida are generall ...

, and the extinct group

Xyloiuloidea Xyloiuloidea is an extinct superfamily of millipedes that existed from the Lower Devonian through the Upper Pennsylvanian period in Europe and North America. Description Xyloiuloids are more or less cylindrical, with sternites, pleurites, an ...

known only from fossils.

Morphology

The species possess long cylindrical bodies with

sclerite A sclerite (Greek language, Greek , ', meaning "hardness, hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instea ...

s (skeletal plates consisting of ventral

sternite The sternum (: sterna) is the ventral portion of a segment of an arthropod thorax or abdomen. In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case the su ...

s, lateral pleurites, and dorsal

tergite A ''tergum'' (Latin for "the back"; : ''terga'', associated adjective tergal) is the Anatomical terms of location#Dorsal and ventral, dorsal ('upper') portion of an arthropod segment other than the head. The Anatomical terms of location#Anterior ...

s) fused into complete rings. Juliform millipedes possess defensive repugnatorial glands on all body segments except the last few, and are the only known millipedes to produce quinones in their defensive secretions. Juliform males have two pairs of

gonopod Gonopods are specialized appendages of various arthropods used in reproduction or egg-laying. In males, they facilitate the transfer of sperm from male to female during mating, and thus are a type of intromittent organ. In crustaceans and millipe ...

s consisting of the modified 8th and 9th pair of legs: in Julida and Spirobolida the posterior gonopods (9th leg pair) are primarily involved in sperm-transferring, while in Spirostreptida it is the anterior gonopods (8th leg pair). Juliformians also lack Tömösváry organs and have a large collum (first body segment) which overhangs the rear of the head.

Taxonomy

The

is an extinct superfamily of fossil millipedes of uncertain placement within the Juliformia. Known from the Lower Devonian to the Upper Pennsylvanian, Xyloiuloidea consists of four families and several genera. The group was formerly considered a suborder of Spirobolida, but newly discovered species in 2006 required a reconsideration of classification, and the order to which Xyloiuloidea belongs remains undetermined.

References

Millipede taxonomy Arthropod superorders {{Millipede-stub