ZEACRINITES MAGNOLIAEFORMIS

This lovely specimen is Zeacrinites magnoliaeformis, an Upper Mississippian-Chesterian crinoid found by Keith Metts in the Glen Dean Formation, Grayson County, Kentucky, USA.

Crinoids are unusually beautiful and graceful members of the phylum Echinodermata. They resemble an underwater flower swaying in an ocean current. But make no mistake they are marine animals. Picture a flower with mouth on the top surface that is surrounded by feeding arms. Awkwardly, add an anus right beside that mouth. That's him!

Crinoids with root-like anchors are called Sea Lilies. They have graceful stalks that grip the ocean floor. Those in deeper water have longish stalks up to 3.3 ft or a meter in length.

Then there are other varieties with that are free-swimming with only vestigial stalks. They make up the majority of this group and are commonly known as feather stars or comatulids.

Unlike the sea lilies the feather stars can move about on tiny hook like structures called cirri. It is this same cirri that allows crinoids to latch to surfaces on the sea floor.

Like other echinoderms, crinoids have pentaradial symmetry. The aboral surface of the body is studded with plates of calcium carbonate, forming an endoskeleton similar to that in starfish and sea urchins.

These make the calyx somewhat cup-shaped, and there are few, if any, ossicles in the oral (upper) surface called a tegmen. It is divided into five ambulacral areas, including a deep groove from which the tube feet project, and five interambulacral areas between them. The anus, unusually for echinoderms, is found on the same surface as the mouth, at the edge of the tegmen.

Crinoids are alive and well today. They are also some of the oldest fossils on the planet. We have lovely fossil specimens dating back to the Ordovician.

CROCODILIAN UPSTARTS: THE CRUROTARSANS

Dinosaurs, long hailed as the rulers of the Triassic almost lost the title belt to a group of crocodilian upstarts, the crurotarsans. In a short-lived battle for survival, geologically speaking, the two groups ran head-to-head for about thirty million years.

The Crurotarsi or "cross-ankles" as they are affectionately known, are a group of archosaurs - formerly known as Pseudosuchians when paleontologist Paul Serono, the darling of National Geographic, renamed them for their node-based clade in 1991. Image: By Nobu Tamura (http://spinops.blogspot.com) - Own work, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=19459679

HEXACORALLIA

Hexacorallia is a subclass of Anthozoa comprising approximately 4,300 species of aquatic organisms formed of polyps, generally with six-fold symmetry. Their temporal range is from the Fortunian to the Holocene. The subclass includes all of the stony corals, most of which are colonial and reef-forming, as well as all sea anemones, and zoanthids, arranged within five extant orders.

The hexacorallia are distinguished from another subclass of Anthozoa, Octocorallia, in having six or fewer axes of symmetry in their body structure; the tentacles are simple and unbranched and normally number more than eight. These organisms are formed of individual soft polyps which in some species live in colonies and can secrete a calcite skeleton. As with all Cnidarians, these organisms have a complex life cycle including a motile planktonic phase and a later characteristic sessile phase. Hexacorallia also includes the significant extinct order of rugose corals.

AURELIA AURITA: MOON DANCERS

Moon Jelly Fish / Aurelia Aurita

Aurelia aurita (also called the common jellyfish, moon jellyfish, moon jelly or saucer jelly) is a widely studied species of the genus, Aurelia. All species in the genus are closely related, and it is difficult to identify Aurelia medusae without genetic sampling; most of what follows applies equally to all species of the genus.

The genus Aurelia is found throughout most of the world's oceans, from the tropics to as far north as latitude 70° north and as far south as 40° south. The species Aurelia aurita is found along the eastern Atlantic coast of Northern Europe and the western Atlantic coast of North America in New England and Eastern Canada. In general, Aurelia is an inshore genus that can be found in estuaries and harbours.

The genus Aurelia is found throughout most of the world's oceans, from the tropics to as far north as latitude 70° north and as far south as 40° south. The species Aurelia aurita is found along the eastern Atlantic coast of Northern Europe and the western Atlantic coast of North America in New England and Eastern Canada. In general, Aurelia is an inshore genus that can be found in estuaries and harbours.