Cyclopsia

## Range

Rimunian - Today (Oavyuian - Holocene) 537 - 0

From top left to bottom right: †Ikatutellus. †Lymkicyclops. †Marmeitankylus. †Iseraqcyclops. Banded Emerald Pener. Sapphire-Backed Excret Beetle.

## Families

* †Ceratocyclopsoidea
* †Cyclopsidae
* †Cyclopsisidae
* †Monoculidae
* †Pyskovoidea
* Ankylocyclopsia

Cyclopsians (Sy-klops-ians) are a class of Ecdysozoans. Cyclopsians are one of the earliest-known groups of Ecdysozoans. The first appearance of Cyclopsians was at the beginning of the Rimunian during the Oavyuian stage as the genus *Monoculus*. Cyclopsians are considered one of the most successful groups of animals existing to modern day. Because of most Cyclopsians' armor, they leave quite the extensive fossil record. They lived various lifestyles from benthic to nektonic and even terrestrial, Cyclopsians were also one of the first groups to take flight during the Carboniferous Period.

## Evolution

Cyclopsians belong to the Pancyclopsia group of Ecdysozoans, a group characterized by their soft bodies (though Cyclopsians eventually were covered in armor) as well as their eyes. Because of their non mineralized bodies, early Cyclopsians are extremely hard to find as they usually don't fossilize. The exact relationship of Pancyclopsians and other Ecdysozoans is uncertain, but they tend to share a similar body plan that likely originated from an unknown common ancestor, similar to Protobilateria.

### Fossil record of earliest cyclopsians

The earliest known cyclopsian is Monoculus, a soft bodied, poorly preserved animal. What can be seen on the fossil is the signature single eye that cyclopsians possess. Monoculus shows no mineralized outer armor or skin suggesting it was completely exposed to predators, perhaps suggesting that the threat of predators in its environment was extremely low. Because of its soft body, it is unclear whether it possessed antennae or legs like the later terrestrial cyclopsians.

### Divergence

The main theory behind the sudden diversification of cyclopsians is due to the threat of predators. Evolving a hard mineralized exoskeleton would protect the cyclopsian from most predators, thus leading to an arms race between predator and prey. Whatever the reason, the body plan of cyclopsians apparently worked and worked well to reach such numbers throughout history.

#### Pre-Rimunian

Though there is no fossil evidence of cyclopsians in the Ediacaran, the sudden diversification of cyclopsians could suggest that they may have originated in the Ediacaran but left no known fossil record.

#### Rimunian

Most groups of cyclopsians evolved during the Rimunian; including the Monoculids, Cyclopsids, Cyclopsisids, Ceratocyclopsoids, Pyskovoids, and Ankylocyclopsoids.

##### Notable Genera:

* Cyclops ("Stage 2")
* Monoculus (Oavyuian)
* Ceratocyclopsis (Liaopingian)
* Eoankylus (Ivagdian)
* Pyskovia (Fuyuanian)
* Zalinicyclops ("Stage 10")
* Trullaspis ("Stage 10")
* Paleolatescosus ("Stage 10")

#### Poonlaloocian

The Poonlaloocian saw some of the fully armored cyclopsians, however there were still plenty of partially armored ones. Certain cyclopsians like Somenoankylus evolved to be able to roll into an armored ball to protect themselves from predators whereas others like Safus evolved better eyesight to avoid predators.

##### Notable Genera:

* Marmeitankylus (Balwangian)
* Dawankylus (Tandaoian)
* Somenoankylus (Carnildian)
* Pedeenankylus (Cardobian)
* Meiweiankylus (Cardobian)
* Ptericyclops (Cardobian)
* Blaviatellus (Cohenian)
* Safus (Shaskvian)
* Chishduceratus (Shaskvian)
* Temlacyclops (Shaskvian)
* Titanoankylus (Shaskvian)

#### Pabuonian

The Pabuonian saw many extinctions of various marine cyclopsian families. However, by the end of the Pabuonian, some cyclopsians began venturing onto land.

##### Notable Genera:

* Tavirocephalus (Sibabinskian)
* Shiyangceratus (Ookengian)
* Agalaspis (Madangueian)
* Cewetoankylus (Eibendingian)
* Kagaceratus (Guangonian)
* Okunapodus (Guangonian)

#### Savian

The Savian saw more extinctions to various marine cyclopsians but just as much diversification in surviving families, including the terrestrial cyclopsians which were starting to evolve a more terrestrial body plan.

##### Notable Genera:

* Sunaia (Cazilian)
* Dakotacyclops (Aveicoian)
* Ococlovacyclops (Azizkian)
* Narsaqia (Ikasukian)
* Mekkeshcyclops (Frazanian)

#### Carboniferous

The Carboniferous saw the second most diversification in the history of the cyclopsian families. The diversification took place mainly in terrestrial families known as the diplects, where they began evolving body plans similar to modern genera. It was also during the Carboniferous were marine diversity of cyclopsian families reached an all-time low.

##### Notable Genera:

* Malvankylus (Velatinian)
* Elmdingichnus (Velatinian)
* Nabatashellus (Velatinian)
* Manvernankylus (Ganzuelian)
* Eswaypterus (Ganzuelian)
* Juguadamella (Pyatovian)
* Dibriselius (Gibbiensian)

#### Balnikian

##### Notable Genera:

* Gansaphobus (Nukuchuukian)

## Importance

Many cyclopsian species have helped understand the evolution of various body plans throughout Ratera's history. Likewise, such diversity in one group of animals has allowed geologists to be able to identify the age of certain rocks based on what cyclopsian fossil is found within it.

## Morphology

Marine cyclopsians tend to have a few main body plans that are all relatively similar (Exceptions are in the terrestrial cyclopsians in which case see this article: Diplecta). Cyclopsians range in size from less than 3 millimeters (0.12 in.) to over 30 centimeters (12 in.) with an average size around 10 - 15 centimeters (3.9 - 5.9 in.)

The exoskeleton is composed of calcite and calcium phosphate minerals in a lattice of chitin that covers the upper surface of the cyclopsian and curls around the lower edge to produce a small fringe, leaving the under surface exposed, possibly allowing legs, mandibles and antennae to be able to work. Otherwise, the chitin is divided into three main segments in most cyclopsians: the cephalon (head), thorax (body), and pygidium (tail).

#### Cephalon

A cyclopsians' cephalon, or head section, is highly variable, with some species having smoother cephalons and others have large or long spinal protrusions both horizontally and vertically. The cephalon can be divided into three main segments. The fixigena is the face or cranidium segment, which contains the eye and cannot grown any spines. The librigena are the 'cheek' segments which in some species grow outwards into a pair of spines. The glabella is the central part of the cephalon, in some species it can grow outwards into one or more spines. In early cyclopsians such as the ceratocyclopsoids the glabella was divided into two segments, the anterior glabella and posterior glabella. The posterior glabella is what evolved into the thorax of fully armored species of cyclopsians.

#### Various other structures

The ocular structures of Cyclopsians are somewhat similar to those of the triopsian and mollusc families, which possess multiple various photo-sensitive cells which evolved independently of eyes in fish and arthropods. Certain species of cyclopsians have a large eye, whereas others may have a small, if not absent eye. Some species like Safus evolved eye stalks to be able to see further around them in an almost 360-degree range.

#### Spines

Some species of cyclopsians evolved spines on various parts of their body independently of one another, suggesting that spines were a mutually beneficial way to keep away predators without regard to their body plans.

#### Volvation

Some cyclopsians were found fossilized rolled up into a ball, however, it is hypothesized that not all cyclopsians were capable of doing this. Some species of cyclopsians appear to be permanently rolled into a ball, possibly living a sessile life, or one where they roll along the sea floor carried by currents.

### Soft body parts

Very few specimens of cyclopsians are preserved with soft body parts. Early cyclopsians such as the Monoculids, Cyclopsids and Cyclopsisids had only part of their body covered in a mineral cephalon, suggesting that all cyclopsians had soft bodies below their outer exoskeleton.

#### Appendages

Along with a soft body, it is possible that most if not all cyclopsians possessed appendages such as legs and mandibles. This idea is supported in part because modern terrestrial cyclopsians possess legs and the extinct armored cyclopsians likely would need legs to be able to move, as ungulating their body would be impossible with their exoskeleton covering their whole upper body.

#### Antennae

It is entirely possible that marine cyclopsians had antennae due to terrestrial cyclopsians having them, though there is little fossil evidence of antennae in marine species.

#### Sensory Pits

In some fossils of cyclopsians, the cephalon possess a few holes in the exoskeleton, suggesting that these pores were used as sensory organs to perhaps detect motion, light, smell, or electricity in the water.