FOSSILIZED SEA URCHIN: AM'DA'MA

This lovely little biscuit is a Holectypus sea urchin from 120 million-year-old deposits from the Lagniro Formation of Madagascar.

The specimen you see here is in the collections of my beautiful friend Ileana. She and I were blessed to meet in China many years ago and formed an unbreakable bond that happens so few times in one's life. 

Holectypus are a genus of extinct echinoids related to modern sea urchins and sand dollars. They were abundant from the Jurassic to the Cretaceous (between 200 million and 65.5 million years ago).

This specimen is typical of Holectypus with his delicate five-star pattern adorning a slightly rounded test and flattened bottom. The specimen has been polished and was harvested both for its scientific and aesthetic value. 

I have many wonderful memories of collecting their modern cousins that live on the north end of Vancouver Island and along the beaches of Balaklava Island. In the Kwak̓wala language of the Kwakiutl or Kwakwaka'wakw, speakers of Kwak'wala, of the Pacific Northwest, sea urchins are known as a̱m'da̱'ma and it is this name that I hear in my head when I think of them.

In echinoids, the skeleton is almost always made up of tightly interlocking plates that form a rigid structure or test — in contrast with the more flexible skeletal arrangements of starfish, brittle stars, and sea cucumbers. Test shapes range from nearly globular, as in some sea urchins, to highly flattened, as in sand dollars. 

Sea Urchin Detail

Living echinoids are covered with spines, which are movable and anchored in sockets in the test. These spines may be long and prominent, as in typical sea urchins and most have lovely raised patterns on their surface. 

In sand dollars and heart urchins, however, the spines are very short and form an almost felt-like covering. The mouth of most echinoids is provided with five hard teeth arranged in a circle, forming an apparatus known as Aristotle’s lantern.

Echinoids are classified by the symmetry of the test, the number and arrangement of plate rows making up the test, and the number and arrangement of respiratory pore rows called petals. Echinoids are divided into two subgroups: regular echinoids, with nearly perfect pentameral (five-part) symmetry; and irregular echinoids with altered symmetry.

Because most echinoids have rigid tests, their ability to fossilize is greater than that of more delicate echinoderms such as starfish, and they are common fossils in many deposits. The oldest echinoids belong to an extinct regular taxon called the Echinocystitoidea. 

They first appeared in the fossil record in the Late Ordovician. Cidaroids or pencil urchins appear in the Mississippian (Early Carboniferous) and were the only echinoids to survive the mass extinction at the Permo-Triassic boundary. Echinoids did not become particularly diverse until well after the Permo-Triassic mass extinction event, evolving the diverse forms we find them in today. 

True sea urchins first appear in the Late Triassic, cassiduloids in the Jurassic, and spatangoids or heart urchins in the Cretaceous. Sand dollars, a common and diverse group today, do not make an appearance in the fossil record until the Paleocene. They remain one of my favourite echinoderms and stand tall amongst the most pleasing of the invertebrates.

AMMONITE TRACE FOSSIL

This is a particularly fetching trace fossil of an ammonite.

Trace fossils or ichnofossils are burrows, footprints, tracks or even faeces left behind by plants and animals that lived long ago. 

Animals may have scurried across a muddy exposure or sea bottom, perhaps eaten a tasty meal then pooped it out — leaving behind clues to how they lived, what they ate and what the environment was like at the time. These are wonderfully informative clues to our ancient world.

OPABINIA REGALIS

Opabinia regalis is an extinct stem-group arthropod found in the Greater Phyllopod Bed, Middle Cambrian Burgess Shale Lagerstätte of British Columbia, Canada. 

These marine arthropods flourished from 505 million years ago to 487 million years ago.

Charles Doolittle Walcott found nine partially complete fossils of Opabinia regalis and a few of what he classified as Opabinia media, that he published in 1912. 

The bizarre arthropod's name is derived from the Opabin pass between Mount Hungabee and Mount Biddle, southeast of Lake O'Hara, British Columbia, Canada. 

In 1966–1967, Harry B. Whittington found a rather good specimen which he published in 1975. He provided a detailed description based on a very thorough dissection of some specimens and photographs of these specimens lit from a variety of angles. Harry was a very thorough fellow.

But he was still ridiculed. Opabinia looked so strange that the audience at the first presentation of Whittington's analysis laughed.

Earth's ancient seas teemed with new life 541 - 485 Million Years Ago. The Cambrian Explosion had arrived. Weird and wonderful life forms like Hallucigenia and Anomalocaris are found in the fossil record giving us a peek at ancient life half a billion years ago.

THE DUDLEY BUG: CALYMENE BLUMENBACHII

A lovely rolled trilobite, Calymene blumenbachii,  from outcrops in the UK. This wee beauty is in the collections of the deeply awesome Theresa Paul Spink Dunn — or perhaps in her daughter Layla's collections as she is quite the budding palaeontologist. This Silurian beauty is from the Homerian, Wenlock Series, Wrens Nest, Dudley, UK.

Calymene blumenbachii, sometimes erroneously spelled blumenbachi, is a species of trilobite found in the limestone quarries of the Wren's Nest in Dudley, England.

Nicknamed the Dudley Bug or Dudley Locust by an 18th-century quarryman, it became a symbol of the town and featured on the Dudley County Borough Council coat-of-arms. Calymene blumenbachii is commonly found in Silurian rocks (422.5-427.5 million years ago) and is thought to have lived in the shallow waters of the Silurian, in low energy reefs.

This particular species of Calymene — a fairly common genus in the Ordovician-Silurian — is unique to the Wenlock series in England and comes from the Wenlock Limestone Formation in Much Wenlock and the Wren's Nest in Dudley. These sites seem to yield trilobites more readily than any other areas on the Wenlock Edge, and the rock here is dark grey as opposed to yellowish or whitish as it appears on other parts of the Edge, just a few miles away, in Church Stretton and elsewhere. This suggests local changes in the environment in which the rock was deposited. The Wenlock Edge quarry is closed now to further collecting but may be open to future research projects. We shall have to see.