''Anderella'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of synziphosurine, a

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

group of fossil

chelicerate The subphylum Chelicerata (from Neo-Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. Chelicerates include the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks ...

arthropods Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

. ''Anderella'' was regarded as part of the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

Prosomapoda Prosomapoda is a clade of Chelicerata, euchelicerates including the groups Xiphosura (horseshoe crabs) and Planaterga (a group comprising Bunodidae, bunodids, Pseudoniscidae, pseudoniscids, Chasmataspidida, chasmataspidids, Eurypterida, eurypteri ...

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s of the single and

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, ''A. parva'', have been discovered in

deposits A deposit account is a bank account maintained by a financial institution in which a customer can deposit and withdraw money. Deposit accounts can be savings accounts, current accounts or any of several other types of accounts explained below. ...

of the

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

, in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. ''Anderella'' is the first and so far (as of 2020) the only Carboniferous synziphosurine being described, making it the youngest member of synziphosurines. ''Anderella'' is also one of the few synziphosurine genera with fossil showing evidence of appendages, but the details are obscure due to their poor preservation. The

prosoma The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...

of ''Anderella'' possess a suboval

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

slightly longer than the externally 10-segmented

opisthosoma The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma ( cephalothorax). It is a distinctive feature of the subphylum Chelicerata (arachnids, horseshoe crabs and others). Although it is similar in most respects ...

(excluding

telson The telson () is the hindmost division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment (biology), segment of the arthropod body, or an additional division that is not a true segm ...

). A row of axial nodes run through the opisthosomal

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. The last 3 opisthosomal segments (which forming the postabdomen) are longer and lacking pleurae (lateral extensions).

References

Synziphosurina Carboniferous first appearances Carboniferous arthropods Fossils of the United States Fossil taxa described in 2007 {{Chelicerata-stub