Random Assets from a Junior Ranger book I helped out with

Broad-nosed Weevil (Phyllobius arborator), family Curculionidae, Slovenia

photograph by Jaka Robnik

The first Palaeozoic spider (Arachnida: Araneae) from Germany

Published 16th July 2023

The first Palaeozoic spider from Germany is described as Arthrolycosa wolterbeeki, represented by a very well preserved and relatively complete fosill from the late Carboniferous strata of Piesberg.

Arthrolycosa wolterbeeki fossil and fossil illustration

Artist reconstruction of Arthrolycosa wolterbeeki

Source:

Phylum #15: Arthropoda!

In the Cambrian seas, strange, many-legged creatures were swimming and crawling. With signs of a segmented cuticle and of branched gills raised atop their legs, Opabinia and Anomalocaris were close relatives of true arthropods. The latter would develop this further into a fully articulated exoskeleton, with trilobites emerging during this same period.

Crustaceans are the first large group of arthropods, mainly occupying aquatic niches - from tiny one-eyed copepods to decapods like crabs or lobsters. Not all aquatic arthropods are crustaceans, with sea spiders and horseshoe crabs being more closely related to arachnids.

Arthropods radiated four times on land. Arachnids (spiders, scorpions and relatives) developed book lungs - tightly folded sheets maximizing surface area for respiration -, and fused the head and thorax in one structure. Myriapods followed the opposite path, elongating in tens of repeated articulated segments. Then two groups of highly derived crustaceans: isopods, and, the most successful of all, hexapods (insects, springtails and relatives). Both isopods and springtails are today ubiquitous in soils, playing essential roles as decomposers.

The hexapod radiation on land was followed by one in the skies. The only non-chordates to have achieved flight, insects quickly dispersed and diversified in hundreds of niches, dominating the skies for a full hundred million years. Even today, their success is hard to understate: half of the two million described animal species are insects, with possibly ten million more awaiting to be found.

Some arthropods depart radically from the usual, segmented and armored body plan. Tongue worms, enigmatic parasites bearing five hooks around their head, were only recently recognized to be highly derived crustaceans. In the same way, parasitic barnacles like Dendrogaster or rhizostomids have lost virtually all arthropod characteristics, reshaping their anatomy to fit their new role.