''Strudiella devonica'' is a species of extinct arthropod from the

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

.Garrouste, Romain; Clément, Gaël; Nel, Patricia; Engel, Michael S.; Grandcolas, Philippe; D’Haese, Cyrille; Lagebro, Linda; Denayer, Julien; Gueriau, Pierre; Lafaite, Patrick; Olive, Sébastien; Prestianni, Cyrille; Nel, André (2012). "A complete insect from the Late Devonian period". Nature. 488 (7409): 82–85. , It was recovered in the Strud (

Gesves Gesves (; ) is a municipality of Wallonia located in the province of Namur, Belgium. The municipality consists of the following districts: Faulx-les-Tombes, Gesves, Haltinne, Mozet, and Sorée. It also includes the hamlets of Gramptinne, Go ...

, Belgium) environment from the Bois des Mouches Formation, Upper

Famennian The Famennian is the later of two faunal stages in the Late Devonian epoch. The most recent estimate for its duration is that it lasted from around 371.1 to 359.3 million years ago. An earlier 2012 estimate, still used by the International Commis ...

. It was originally described as the first complete Late Devonian terrestrial insect, but due to its poor state of preservation, its affinity is discussed.

Description

''Strudiella'' is known from a single specimen. It is a small arthropod with length about . Structures like antennae and a number of pairs of legs can be seen. Due to the poorly preserved nature of this fossil, its interpretation and classification depend on the authors.

Garrouste et al. (2012)

In the first description by Garrouste ''et al.'' (2012), it was described as the first complete Devonian insect. The median abdominal structures are filled with guts, which excludes the possibility that is a molting shell. It is interpreted to have 3 pairs of legs from the

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

, the tibiae and femora are long and thin. The antennae are uniramous, the scape and pedicel are wider than the 10-segmented flagellum. The triangular

mandibles In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

have a continuous series of sharp, small irregular molar and incisor cusps. Its small head had large eyes. The large thorax had a rounded structure covering its head, corresponding to an expanded pronotum. The

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

had 10 segments (while a drawing in the paper shows 11 segments), and the authors considered that it lacked any lateral leglets,

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...

s or other appendicular structures. There is a rounded apical structure on the tip of the abdomen. The lack of wings and small size would indicate that it is a

nymph A nymph (; ; sometimes spelled nymphe) is a minor female nature deity in ancient Greek folklore. Distinct from other Greek goddesses, nymphs are generally regarded as personifications of nature; they are typically tied to a specific place, land ...

. It is interpreted to be a

terrestrial Terrestrial refers to things related to land or the planet Earth, as opposed to extraterrestrial. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on o ...

insect, and the mandible morphology suggests its diet would be

fungivore Fungivory or mycophagy is the process of organisms consuming fungi. Many different organisms have been recorded to gain their energy from consuming fungi, including birds, mammals, insects, plants, amoebas, gastropods, nematodes, bacteria and othe ...

and/or

saprophagy Saprophages are organisms that obtain nutrients by consuming decomposing dead plant or animal biomass. They are distinguished from detritivores in that saprophages are sessile consumers while detritivores are mobile. Typical saprophagic animals i ...

Hörnschemeyer et al. (2013)

However, Hörnschemeyer ''et al.'' (2013) questioned its interpretation as an insect. The mandible and its teeth cannot be confirmed, the mandibular teeth would be caused by the idiosyncratic way the rock parted. The eyes are vague, the indication of eye rims by Garrouste ''et al.'' is considered as arbitrary. The scape, pedicel and flagellum on its antennae cannot be confirmed, and the whole antennae is wider than the legs which is highly unusual for insects. The alleged subdivision of the trunk into thorax and abdomen is also questionable. Importantly, over 3 pairs of legs can be observed. This poor state of preservation allows numbers of alternate interpretations like a decayed crustacean.

Garrouste et al. (2013)

In the same volume of ''

Nature Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...

'', Garrouste ''et al.'' replied to Hörnschemeyer ''et al.'' (2013). They supported mandibular teeth structure again. They argued that visible maxillary palps are abnormal under the crustacean hypothesis. They considered that scape, pedicel and flagellum can be confirmed from width of antennae, and antennae being wider than legs would not deny insect affinity. For the extra legs that Hörnschemeyer ''et al.'' confirmed, they considered as internal organs extruded during compression and decay.

Other studies

Multiple later studies about Strud fossils call ''Strudiella'' as "putative insect". Haug and Haug (2017) listed presumed Devonian insect fossils, and commented that "Its very incomplete preservation makes its interpretation problematic".

Importance of discovery

The discovery of ''Strudiella'' as a Devonian insect reduces a previous gap of 45 million years in the evolutionary history of insects, part of the arthropod gap (the 'gap' still occurs in the early Carboniferous, coinciding and extending past the Romer's gap for tetrapods, which may have been caused by low oxygen levels in the atmosphere).Ward, P.; Labandeira, C.; Laurin, M.; Berner, R. A. (2006). "Confirmation of Romer's Gap as a low oxygen interval constraining the timing of initial arthropod and vertebrate terrestrialization". Proceedings of the National Academy of Sciences. 103 (45): 16818–22. Bibcode:2006PNAS..10316818W. PMC 1636538 Freely accessible. . However, Hörnschemeyer ''et al.'' (2013) which denied its interpretation as insect commented that it is crucial to prevent this fossil from entering

entomology Entomology (from Ancient Greek ἔντομον (''éntomon''), meaning "insect", and -logy from λόγος (''lógos''), meaning "study") is the branch of zoology that focuses on insects. Those who study entomology are known as entomologists. In ...

textbooks. Most of fossil records of Devonian insects like '' Rhyniognatha'' or ''

Leverhulmia ''Leverhulmia'' is an extinct genus of probable hexapod, known from a single partial specimen with preserved gut contents, found in the Windyfield (Rhynie) chert. Description ''Leverhulmia'' is an arthropod roughly long, with at least f ...

'' are questionable, and the early fossil records of insects still remains scarce and problematic.

References

External links

* * {{Taxonbar, from1=Q12072575, from2=Q119983774 Fossil taxa described in 2012 Late Devonian animals Famennian life Fossils of Belgium Evolution of insects Taxa named by Michael S. Engel Controversial taxa Devonian arthropods of Europe History of Namur Gesves