December 22 is Coelacanth Day!


Palaeoblog pointed out on December 22 that it was the anniversary of Marjorie Courtenay-Latimer’s discovery of an extant coelacanth. The fish was a member of the coelacanth family but not in the same species or even genus as all other coelacanth specimens, which were known only from fossils.

See also “Latimer didn’t ‘just happen’ on coelacanth.”

Advertisements

Devonian Times

The Devonian Times highlights the fossils, both plants and animals, of the Red Hill Devonian deposits in Pennsylvania, U.S.

Green dinosaur: Hydatellaceae


Hydatellaceae, an obscure family of dwarf, aquatic flowering plants. is a survivor from before the evolutionary split between dicot and monocot plants. (A monocot has one leaf in the seed, like grass, and a dicot has two, like a bean.)

Previously, the Hydatellaceae were thought to be in the Poales (the order of flowering plants including grasses, sedges, bromeliads, etc.). Instead, they are early angiosperm plant family that belongs near the very root of the evolutionary tree of flowering plants. (The flowering plants began to diversify at least 135 million years ago, in the age of the dinosaurs.)

Through DNA analysis and morphological investigations, the researchers found evidence that the Hydatellaceae are more closely related to the Nymphaeaceae, or water lilies.

The research team was led by scientists at the UBC Botanical Garden & Centre for Plant Research. The researchers, led by UBC Associate Professor Sean Graham and his graduate students Jeffery M. Saarela (now at the Canadian Museum of Nature) and Hardeep Rai.

The discovery was announced in the March 15, 2007 issue of Nature. As noted in the abstract to the article, this discovery rewrites our understanding of angiosperm structural and reproductive biology, physiology, ecology and taxonomy”.

Microscopic missing link: Stephanopogon

OK, this is silly. I keep (reading statements by Intelligent Design apologists blandly claiming that complex life appeared “suddenly” — that’s suddenly in geological time, mate! — and that scientists have no clue how it happened. Or that “we” have no clue, which is closer to the truth, because the writer never looked at the wealth of evidence.

Currently I’m reading a 20-year-old textbook about invertebrate life. I’m reading it because many years have passed since I took biology. Not only have I forgotten many of the details, but knowledge has grown manyfold since I was an undergrad. So I’m taking a private refresher. It’s an old book because new ones are expensive, while old ones are practically free: an old textbook costs pennies or a few dollars at a thrift store. And it’s working! I’m finding out new things, learning new details, and every few pages saying, “Aha! That’s more evidence for evolution.” Here’s just one of them from the chapter on protozoans: a transitional form between flagellates and ciliates. (The image is Stephanopogon paramesnili, from PlanktonNet.)

From the 1987 edition of Living Invertebrates, by Vicki Pearse et al.:

A diagnostic characteristic of all ciliates is the presence of two different kinds of nuclei [a micronucleus and a macronucleus]… (page 51)

Stephanopogon formerly was listed as a primitive and exceptional ciliate with only one kind of nucleus…. This benthic marine protozoan looks like a ciliate, but recent studies have shown that it lacks typical ciliate infraciliature and pellicle structure and that it divides like a flagellate It has been removed from the ciliates and placed among the flagellates as a separate flagellate order or phylum, Pseudociliata. (page 51, sidebar)

The main link is to the “recent” (1982) study, “Stephanopogon, a Phylogenetically Important “Ciliate,” Shown by Ultrastructural Studies to Be a Flagellate” by Diana L. Lipscomb and John O. Corliss.

That article was cited in a very interesting paper from 2003, “Bridging Morphological Transitions to the Metazoa,” in the journal of Integrative and Comparative Biology:

Our inability to answer many questions regarding the development of metazoan complexity may be due in part to the prevailing idea that most eukaryote “phyla” originated within a short period of geologic time from simple unicellular ancestors. This view, however, is contradicted by evidence that larger groups of eukaryotes share characters, suggesting that these assemblages inherited characters from a common ancestor. —Ruth Ann Dewell, et al.

Follow the “Morphological Transitions” link to read more about the researchers’ methods and conclusions. I hope to write more about it later.

Frilled Shark live

This video shows a recently captured frilled shark, Chlamydoselachus anguineus. They are rarely seen alive because they live in deep water, where they catch fish and squid. A fisherman reported finding this one. It’s alien to the upper waters and it looks like an alien!

Hat tip to P. Z. Myers at Pharyngula.

Wollemi pine


One of the nice things about not being a scientist is that I get to discover new things long after everyone else has heard of them—sort of like an isolated person getting their newspaper months late. But it’s still news to me.

Take the Wollemi pine, for instance. It’s not really a pine. It’s older than the dawn redwood, we knew only from fossils until someone recognized it growing in China some decades ago.

The Wollemi pine was knows from fossils dating back to the Cretaceous era, but not afterwards. It disappeared from the fossil record. Then, in 1994, climbers exploring a remote canyon in Wollemi National Park in Australia’s New South Wales found a stand of the trees. Of course, these trees have changed over the millenia, but their closest relatives were last seen 100 million years ago.

By appearance, it’s a missing link, between tree ferns and conifers.

Its trunk is a mass of buds rather than a sheet of bark. It has palm-like fronds with short leaflets from a central stalk. Gosh, they look like yew leaves on a giant scale. Is is possible that pine needles are descended from palm leaflets? At the end of those leaves are unmistakeable, delicate, pine cones with thin scales. Each tree bears both male cones (providing pollen) and female cones (setting seed).

There were only 38 adult trees. The location is a closely guarded secret to prevent “poaching.” At this time, seedlings are dying after a few years, and we don’t know why. Scientists are investigating. The canyon may have run out of nutrients; or the trees may be too inbred. All 38 trees are genetically identical and only 10% of the seed they set is viable. A few years ago, a couple of hundred cuttings grown from the trees were sold at auction in an attempt to raise money for more research and to spread the trees around the world so that they might survive elsewhere.

Family: Araucariaceae
Species: Wollemia nobilis

Simplest multicellular animal

photo of multicellular animal like a flat lichen
Intelligent Design apologists talking about the “irreducible complexity” never mention this little fellow. It is the simplest multicellular animal with the simplest DNA.

“…no head, no sense organs, no nervous system, no gut, just a collection of cells that hang together and slurp up algal slime. They are, however, multicellular, and their bodies contain at least four functionally distinct cell types, and the molecular evidence suggests affinities to other animal groups (they have a ProtoHox /ParaHox gene, for instance)… so they are definitely metazoans.”

See the link below for more about Trichoplax on Pharyngula, including pictures, such as the one I stole from Pharyngula. Also, check out Richard Howey’s article about finding and growing Trichplax and the research questions surrounding it.

%d bloggers like this: