Murkworms

Murkworms are a lineage of secondarily aquatic binucleid worms closely related to Saucebacks. The two lineages together form a larger grouping known as Beastworms.

Today, Murkworms are only represented by a small subgroup, the Prickworms. All modern species are aquatic, but an extinct branch, the Rustworms, re-adapted for life on land.

Anatomy
Similar to their better-known cousins, the Saucebacks, Murkworms breathe air using microlungs and spiracles along their back. They lack eyes, depending on their senses of smell and hearing to find food and evade predators. They have a ring of scent pits around their faces, and an equal number of chitinous teeth in a ring inside their mouths. They have a horizontal fin at the end of the tail. Like in all beastworms, the brain, hip girdle, and most major organs of murkworms are all contained in one segment, the cephalic segment, and the "head" in front of its carapace is technically a proboscis.

Like most binucleid worms, Murkworms have red iron-based blood. They lay their eggs in water and have worm-like larvae.

Diet
Lacking any way to see their surroundings, the diet options of Murkworms are limited. Unable to actively hunt, most take to scavenging, filter-feeding, or consuming detritus.

Evolution
Murkworms first evolved in generation 19, actually predating the Saucebacks by millions of years. The first Mudworm appeared in Generation 25, and the first Filterworm in Generation 53.

The last common ancestor of all extant murkworms, the Cave Prickworm, evolved in generation 139.

Succeeded
These have living descendants, but the descendants do not resemble their ancestors.