Ricinulei Group represented: Neoricinuleids Forwarded cucullus hiding the chelicerae 2-segmented small chelicerae Carapace densely granulated Males’ 2° femur enlarged Double trochanter (3° & 4° pairs of walking legs) Complex dorsal lock between the prosoma & the narrowed 1° opisthosomal segment Trilobed opisthosoma with Lateral Lobe/Plate & Median Lobe/Plate Last 3 segments of the opisthosoma form a short postabdomen Pedipalps ending with a small pincer claw Males’ 3° legs modified for reproduction Tracheal openings hidden among the legs Pedipalp folded under the body & ending with a pincer claw

Phalangiotarbida Genus represented: Mesotarbus Small leg-like pedipalps Extremely small chelicerae, exact morphology unsure 6 eyes arranged in 3 pairs on a trifoliate tubercle First 6 segments of the opisthosoma are densely packed on the dorsal side Broad 3-segment end of opisthosoma (often fused) Dorsal anal opening Ogive-shaped main body Crab-like heavy walking legs 1 pair of spiracled linked to unknown respiratory organs reproductive’s morphology unknown Note: This group is still poorly known; further research could change several details radically.

Pseudoscorpiones Group represented: Cheliferoids Pedipalps turned into pincer claws (with venomous glands in iocheirates species) Small 2-segmented chelicerae with a small spinneret called “galea” on the moveable digit linked to a silk gland 0 to 4 simple eyes on the forward rims of prosoma Patella usually is longer than the femur Exoskeleton can be heavily ornamented with tubercles Opisthosoma ending by an anal cone, no telson 2 pairs of tracheae Large genital plate First opisthosomal segment non-visible on ventral side Endite (extension of the pedipalp’ coxae to process food)

Scorpiones Group represented: Orthosternians Pedipalps turned into pincer claws 2 median eyes in & little lateral pairs Legs telescoped backwards Legs’ coxae well-developed & forming a stomotheca (a pre-oral chamber before the mouth) Sternum Genital opening & Pectines (ventral sensory appendages close to the ground) closely grouped 4 pairs of book lungs Opisthosoma subdivided into a mesosoma of 7 segments & a metasoma (=”tail”) of 5 segments Telson turned into a venomous sting Acculeus (sting) Vesicle (contains the venom) Note: Scorpions changed a lot since the Silurian, many of the paleozoic species didn’t have stomotheca for example. This diagram is mostly representative of today’s species.

Orders of unclear affinities & scorpion-like figures: ricinulei, phalangiotarbida, pseudoscorpiones and scorpiones

#Cheliceratime #arachnid #ricinulei #phalangiotarbida #pseudoscorpion #scorpion
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This species from Ghana is the largest ricinuleid in the world, part of the “giant ricinuleids grade” found in Africa. Males have enlarged second leg’s width compared to females. Size: 1cm of body length Time period: Holocene (present day) Conservation status: Least concern/Near threatened The animal drawn is a ricinuleid, looking like a armored little spider withouth eyes or fangs

What time is it? It’s #Cheliceratime!
Today we're talking about ricinuleids, small tropical arachnids, with one of their most notorious member, Ricinoides atewa!

All the basic infos are here but if you want to learn more, there’s more below!⬇️

#ricinulei #arachnid #sciart #bugsky #invert

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Fixed the strobing. Another #Baltic #amber specimen - this time a couple of really neat, rare and highly detailed arachnids called Hooded Tick Spiders ( #Ricinulei ). They are unique among arachnids in that the fossil animal was found before the extant one (in the 1830s by William Buckland)