Jurodidae

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Jurodidae
Temporal occurrence
Middle Jurassic to recent
Systematics
Arthropod (arthropoda)
Insects (Insecta)
Beetle (Coleoptera)
Archostemata
Jurodidae
Scientific name
Jurodidae
Ponomarenko , 1985

The Jurodidae are a small family of beetles with only one recent species, Sikhotealinia zhiltzovae , of which only one specimen (the type specimen ) has been found so far . Four other fossil species are known, all of which are placed in the genus Jurodes . Jurodidae belong to the very original suborder Archostemata .

features

Jurodidae are small, about 4 to 6 millimeters long, somewhat flattened beetles with an approximately oval body shape. In general they resemble the Rhysodidae . The head is about as long as it is wide and narrowed towards the back; in addition to the large complex eyes protruding slightly from the head contour, it has three point eyes ( ocelli ) that sit on a slightly raised region of the forehead ( frons ). The front plate ( clypeus ) and the labrum are exposed. The eleven-jointed antennae are turned into the gena in front of the complex eyes or at the front edge of the frons , they are relatively short and never reach the base of the elytra when put back. The last antenna segment is egg-shaped and about twice as long as the penultimate one. The pronotum is small, about the same width, but shorter than the head and less long than wide, it is much narrower than the base of the elytra; its sides are rounded. The scutellum is small and rounded at the back. The elytres have rows of points, the row points are about their diameter apart.

The fossil species differ from the recent species by the somewhat longer antennae, the position of the antennae and the shape of the occiput (in the recent species with neck-shaped constriction and clear temples). In addition, the fossil species have more rows of dots on the wing covers and the veins of the hind wings differ somewhat. All other characteristics are very similar. Sikhotealinia zhiltzovae can therefore be classified as a living fossil with an unchanged morphology since the Mesozoic.

The shape of the abdomen of the trunk (thorax) is important for the systematic position of the family.

Locations and distribution

The recent species was discovered in the Sichote-Alin Mountains in the Primorye region in eastern Russia. The fossil species come from two deposits: They were first discovered in the Novospasskoe deposit near Unda in Transbaikalia, Russia . The calcareous sediments of a freshwater lake are exposed, the age is estimated at about 183 to 172 million years. The Chinese finds come from Daohugou in Ningcheng County in northeast Inner Mongolia , China. The Daohugou strata are an important fossil deposit made of fine-grain sandstone and claystone alternating with tuff. They were probably deposited in freshwater at the end of the Middle Jurassic or at the beginning of the Upper Jurassic, around 159 to 164 million years ago. Beetle fossils from more than 10 families are known from the deposit. The fossil finds and the recent site are strikingly relatively close together.

Systematics

There are five species described in two genera:

  • Genus Jurodes
    • Jurodes ignoramus Ponomarenko, 1985. Type species of the genus (and thus also of the family). Novospasskoe, Russia
    • Jurodes minor Ponomarenko, 1990. Novospasskoe, Russia
    • Jurodes daohugouensis Yan et al., 2014. Daohugou, China
    • Jurodes pygmaeus Yan et al., 2014. Daohugou, China
  • Genus Sikhotealinia
    • Sikhotealinia zhiltzovae Lafer, 1996. recent.

The classification of the family was initially problematic because some features indicated a closer relationship with the Adephaga , while others were regarded as typical of the Polyphaga . In the meantime, according to more recent phylogenetic studies, belonging to the Archostemata is quite well established. The internal phylogeny of the Archostemata is largely unexplained; a sister group of the family cannot therefore be specified.

swell

  • Evgeny V. Yan, Bo Wang, Alexander G. Ponomarenko, Haichun Zhang (2014): The most mysterious beetles: Jurassic Jurodidae (Insecta: Coleoptera) from China. Gondwana Research 25: 214-225. doi : 10.1016 / j.gr.2013.04.002
  • > Rolf G. Beutel, Si-qin Ge, Thomas Hörnschemeyer (2008): On the head morphology of Tetraphalerus, the phylogeny of Archostemata and the basal branching events in Coleoptera. Cladistics 24: 270-298. doi : 10.1111 / j.1096-0031.2007.00186.x
  • Thomas Hörschemeyer: Archostemata. in Rolf G. Beutel, Richard AB Leschen: Handbuch der Zoologie - Coleoptera, Beetles, Volume 1: Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim) . 1st edition. de Gruyter , 2005, ISBN 3-11-017130-9 (English). limited preview on Google Books

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