The Order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Microconchida is a group of small, spirally-coiled, encrusting fossil "worm" tubes found from the Upper Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 to the Middle Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 (Bathonian

Bathonian

In the geologic timescale the Bathonian is an age or stage of the Middle Jurassic. It lasted from approximately 167.7 Ma to around 164.7 Ma...

) around the world (Weedon, 1991; Vinn, 2006, 2010; Vinn and Mutvei, 2009; Zaton and Vinn, 2011). They have lamellar calcitic shells, usually with pseudopunctae or punctae and a bulb-like origin. Many were long misidentified as the polychaete

Polychaete

The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...

 annelid Spirorbis

Spirorbis

Spirorbis is a genus of very small polychaete worms, usually with a white coiled shell. Members of the genus live in the lower littoral and sublittoral zones of rocky shores. Spirorbis worms usually live attached to seaweeds, but some species live directly on rocks, shells or other hard substrates...

until studies of shell microstructure and formation showed significant differences (Taylor and Vinn, 2006). All pre-Cretaceous "Spirorbis" fossils are now known to be microconchids (Taylor and Vinn, 2006). Their classification at the phylum level is still debated. Most likely they are some form of lophophorate, a group which includes phoronid

Phoronid

Phoronids are a phylum of marine animals that filter-feed with a lophophore , and build upright tubes of chitin to support and protect their soft bodies. They live in all the oceans and seas including the Arctic Ocean but excluding the Antarctic Ocean, and between the intertidal zone and about...

s, bryozoa

Bryozoa

The Bryozoa, also known as Ectoprocta or commonly as moss animals, are a phylum of aquatic invertebrate animals. Typically about long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia...

ns and brachiopods (Vinn, 2010).