''Protosialis casca'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of alderfly in the

Sialidae Alderflies are megalopteran insects of the family Sialidae. They are closely related to the dobsonflies and fishflies as well as to the prehistoric Euchauliodidae. All living alderflies – about 66 species all together – are part of the subf ...

subfamily Sialinae. The species is solely known from the early

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

Burdigalian The Burdigalian is, in the geologic timescale, an age (geology), age or stage (stratigraphy), stage in the early Miocene. It spans the time between 20.43 ± 0.05 annum, Ma and 15.97 ± 0.05 Ma (million years ago). Preceded by the Aquitanian (sta ...

stage,

Dominican amber Dominican amber is amber from the Dominican Republic derived from resin of the extinct tree ''Hymenaea protera''. Dominican amber differentiates itself from Baltic amber by being nearly always transparent, and it has a higher number of fossil incl ...

deposits on the island of

Hispaniola Hispaniola (, also ; es, La Española; Latin and french: Hispaniola; ht, Ispayola; tnq, Ayiti or Quisqueya) is an island in the Caribbean that is part of the Greater Antilles. Hispaniola is the most populous island in the West Indies, and th ...

. ''Protosialis casca'' is one of only two known alderfly species present in the

West Indies The West Indies is a subregion of North America, surrounded by the North Atlantic Ocean and the Caribbean Sea that includes 13 independent island countries and 18 dependencies and other territories in three major archipelagos: the Greater A ...

, the only other species is the living '' Protosialis bifasciata'' native to Cuba.

History and classification

The species is known only from the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, number "Mact 2090", which is a single male specimen currently residing in the private collection owned by Ettore Morone of

Turin, Italy Turin ( , Piedmontese: ; it, Torino ) is a city and an important business and cultural centre in Northern Italy. It is the capital city of Piedmont and of the Metropolitan City of Turin, and was the first Italian capital from 1861 to 1865. T ...

, and was first studied by

Michael Engel Michael S. Engel, FLS, FRES (born September 24, 1971) is an American paleontologist and entomologist, notable for contributions to insect evolutionary biology and classification. In connection with his studies he has undertaken field expedit ...

and David Grimaldi. Engel and Grimaldi's 2007

type description A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have be ...

paper was published in the journal '' American Museum Novitates''. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

"''casca''" was derived by the authors from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

', which translates to "old" in reference to the age of the specimen. When first described ''P. casca'' was named ''Sialis (Protosialis) casca'' by Engel and Grimaldi. They used the alderfly classification system put forth by Dr. Michael Whiting in his 1994 paper on the

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

North American North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Ca ...

alderflies which treated '' Protosialis'' as a subgenus of ''

Sialis ''Sialis'' is a genus of alderfly belonging to the order Megaloptera family Sialidae. Description These alderflies are small and mainly brown with a relatively heavy body and forewings reaching a length of 10 to 20 millimeters. Females are us ...

''. Currently most taxonomists treat ''Protosialis'' as a separate genus from ''Sialis'' making this species ''Protosialis casca'' and ''Sialis (Protosialis) casca'' a

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

Description

The holotype of ''Protosialis casca'' is in length with a

forewing Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments (the mesothorax and metathorax), and the two pairs are often referred to as the forewings and hindwin ...

length of between . The forewing length cannot be determined more precisely due to the apical portions of the wings being missing. The orange and black coloration of the head and pronotum combined with the reduced number of crossveins in the costal region of the forewing are unique to the genus ''Protosialis''. The legs display black and white color patterning, with the area of the protibia and mesotibia white and the rest of the leg is black. The wing membranes are overall a dusky brownish gray, with veins a darker brow to black. The abdomen, light brown in color, is bent downwards near the midpoint and slightly distended.

References

{{Taxonbar, from=Q7252122 Megaloptera Fossil taxa described in 2007 Miocene insects Prehistoric insects of the Caribbean Fauna of Hispaniola