Lutrinsidus

Lutrinsidus fluvius

Genus: Lutrinsidus
Common name: Ambush otter
Evolved from Celernantida

Ambush otters actually evolved from a land decendant of Celernantids, but have returned to water environments and are all semiaquatic, aquatic or marine.
These are medium to large animals that gave up external plates in favor of leathery skin and bony endoskeleton.
They have long, slim bodies with 4 limbs, which evolved from the second and fourth pair. These mostly are longer compared to Earth otters, but also posses webbed feet used to swim. The first and third pair of limbs evolved to resemble fins that aid in maneuvering through water.
The most striking anatomical feature is the broad tail used to propel the animal forward. Swimming is achieved by up and down motion of the body and the tail with limbs resembling breaststroke.
One of the proboscises turned into a mouth like structure being much shorter and wider, still possessing bony projections (teeth). Biting is possible thanks to a set of strong round muscles around the mouth opening.
Two remaining proboscises lack any kind of teeth, but evolved very sensitive somatosensors as well as slime glands. The slime can be used to discourage unwanted attention from other organisms, but is a great way to ensure safety of eggs since the slime contains chemicals that are disgusting to most organisms.
They possess a keen sense of smell, which is enhanced by small muscles, which evolved in the land decendant of Celernantids to suck air (or water) in, hold, and let out.
Large compund eyes split into two pairs. One allows vision in regular spectrum of colors, while the smaller pair can see infrared radiation.
Spiracles were reduced to only three and moved up onto the back based on the "new" lifestle of ambush otters, so they can more easily breathe when close to water surface. An individual can last without a breath from a few minutes to over an hour depending on the species.
Ambush otters are carnivores that hunt mostly underwater, but occasionally can take down an animal from the bank. The hunting technique depends on the species, but most use ambush from below.
There is almost none sexual dimorphism, males tend to be a little larger.
Fertilization happens inside a females reproductive organ. She then lays eggs inside a "lodge" or the rim of an ice floe (L. hiems), and covers them in a layer of slime. Temperature doesn't affect the gender of the offspring, which hatches looking like a miniature of an adult. The eggs have a leathery shell.
The mother then take care of the litter for a few months.
Sexual maturity occurs between the ages of 10 to 15 months for both males and females. Ambush otters have a lifespan of about 25 years, larger species can live up to 35 years.
Most ambush otters are solitary.

Species:
Lutrinsidus palus - the smallest of ambush otters, length without proboscis around 1 m, slightly smaller eyes, lacks some webbing on the hind limbs, slimmer tail, lives in bogs and swamps
Lutrinsidus fluvius - length without proboscis around 2 m, lives in big rivers
Lutrinsidus hiems - length without proboscis around 5 m, wider head and tail, lives in cold and polar regions of the planet, the slime has antifreezing properties (up to -15 °C), but mostly laying eggs in warmer seasons.