''Rosamygale'' is a genus of extinct

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

spider Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species d ...

s, with a single described species, ''Rosamygale grauvogeli''. It is the oldest known member of the

Mygalomorphae The Mygalomorphae, or mygalomorphs, are an infraorder of spiders, and comprise one of three major groups of living spiders with over 3000 species, found on all continents except Antarctica. Many members are known as trapdoor spiders due to t ...

, one of the three main divisions of spiders, which includes well known forms such as

tarantulas Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,040 species have been identified, with 156 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although ...

and Australian funnel-web spiders. It was described by Selden and Gall in 1992, from specimens found in the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma ...

(

Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Trias ...

~ 247-242 million years ago) aged

Gres a Meules The Gres a Meules is a geologic formation in France. It preserves fossils dating back to the Triassic period. See also * List of fossiliferous stratigraphic units in France See also * Lists of fossiliferous stratigraphic units in Europe ...

and

Grès à Voltzia The Grès à Voltzia is a geologic formation in France. It preserves fossils dating back to the Triassic period. See also * List of fossiliferous stratigraphic units in France See also * Lists of fossiliferous stratigraphic units in Euro ...

geological formations A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan ar ...

. It is also considered to be the oldest known member of the

Avicularioidea Avicularioidea is a clade of mygalomorph spiders, one of the two main clades into which mygalomorphs are divided (the other being the Atypoidea). It has been treated at the rank of superfamily. Taxonomy The division of the Mygalomorphae into t ...

, one of the two main divisions of Mygalomorphae.

Description

''Rosamygale'' is known from

compression fossils A compression fossil is a fossil preserved in sedimentary rock that has undergone physical compression. While it is uncommon to find animals preserved as good compression fossils, it is very common to find plants preserved this way. The reason fo ...

consisting of brown-coloured organic cuticle remains of several juvenile and adult individuals, up to 6 mm in length.

Phylogeny

In the original description, ''Rosamygale'' was placed in the

Hexathelidae Hexathelidae is a family of mygalomorph The Mygalomorphae, or mygalomorphs, are an infraorder of spiders, and comprise one of three major groups of living spiders with over 3000 species, found on all continents except Antarctica. Many membe ...

, with reservations. However, later studies noted that it was placed in the family based on characters that are

plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, an ...

(ancestral) for many groups of mygalomorphs. It can be securely placed in

, one of the two major groupings of mygalomorph spiders based on the absence of an abdominal

scutum The ''scutum'' (; plural ''scuta'') was a type of shield used among Italic peoples in antiquity, most notably by the army of ancient Rome starting about the fourth century BC. The Romans adopted it when they switched from the military formatio ...

(a hard plate located on the underside of the body) and well-separated

posterior Posterior may refer to: * Posterior (anatomy), the end of an organism opposite to its head ** Buttocks, as a euphemism * Posterior horn (disambiguation) * Posterior probability, the conditional probability that is assigned when the relevant evidenc ...

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction * Lateral cricoarytenoid muscle * Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral co ...

spinnerets A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and are ...

(silk-spinning organs).

Palaeoenvironment

The sediments where the spiders were discovered represents a

deltaic A river delta is a landform shaped like a triangle, created by deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rare ...

environment, with the fossil found in what likely was a stagnant

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

pond that filled during the rainy season, surrounded by sparse vegetation. Associated terrestrial fauna includes

scorpions Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always end ...

myriapods Myriapods () are the members of subphylum Myriapoda, containing arthropods such as millipedes and centipedes. The group contains about 13,000 species, all of them terrestrial. The fossil record of myriapods reaches back into the late Silurian, ...

and

insects Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...

. With an associated aquatic fauna containing the

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, ...

Lingula Lingula is Latin for "little tongue". It can stand for: * ''Lingula'' (brachiopod), a brachiopod genus of the family Lingulidae, which is among the few brachiopods surviving today but also known from fossils over 500 million years old * Lingala la ...

,'' clam shrimps, and fish. The authors speculated, due to the nature of the locality, that ''Rosamygale'' burrowed into or near the banks of water courses. Primitive avicularioids such as ''Rosamygale'' are thought to have hunted using funnel and sheet webs.

References

Fossils of France Mesozoic arachnids Hexathelidae Triassic arthropods Monotypic Mygalomorphae genera Mygalomorphae genera {{Mygalomorphae-stub