Description

Chimerarachne is a genus of extinct arachnids comprising a single species, Chimerarachne yingi. Fossils of Chimerarachne were found in Burmese amber from Myanmar, dating back to the mid-Cretaceous, approximately 100 million years ago. It's believed to share a close relation with spiders, yet it doesn't fit within any existing spider group. The earliest spider fossils date back to the Carboniferous period, indicating the presence of a ghost lineage spanning at least 170 million years without any fossil records.

The name "Chimerarachne" is derived from the mythological chimera, a creature composed of various animal parts, representing the amalgamation of both primitive and advanced traits in this organism. The term "arachne" originates from the Greek word for "spider." The species name, "yingi," is in honor of Yanling Ying, a collector of one of the specimens.

Characteristics

This creature is quite diminutive, with a body length of only 2.5 millimeters and a tail extending about 3 millimeters. It exhibits two essential spider characteristics: spinnerets for silk production and a modified male reproductive organ on the pedipalp for sperm transfer. Additionally, it retains a whip-like tail, akin to that of whip scorpions and uraraneids. Chimerarachne is not the ancestor of spiders, as it appeared long after the oldest known spiders from the Carboniferous. Rather, it seems to be a late survivor of an extinct group closely related to spider origins. This suggests the existence of spider-like creatures with tails coexisting with true spiders for over 200 million years.

Chimerarachne exhibits spider-like characteristics in its legs and body, including chelicerae (mouthparts) similar to Mesothelae or mygalomorph spiders. The fang lacks the characteristic hairs seen in typical spiders, making it uncertain whether these animals were venomous. The male pedipalp has a palpal organ consisting of the tarsus, divided into two long lobes at the tip, and a relatively simple palpal bulb, akin to some mygalomorph spiders but seemingly less intricate than mesotheles.

The abdomen shows segmentation, resembling that of mesothele spiders.