A Devonian lamprey, Priscomyzon

i-f8c33e4d4a3f687abcda3de1f433b764-priscomyzon_recon.jpg
Reconstruction of Priscomyzon in dorsal (top) and left lateral (bottom) views. b, Macropthalmia stage of Lampetra showing anterior location of orbit and smaller oral disc, both positioned in front of the branchial region. The total length of the specimen is 116 mm. Drawings in a and b are scaled to show equivalent head lengths: from anterior limit of the oral disc to rear of the branchial region. Horizontal bars indicate the anterior–posterior span of the oral disc in each species.

The life of a parasite must be a good one, and often successful; the creature at the top of the drawing above is a primitive lamprey from the Devonian, 360 million years ago, and the similarities with the modern lamprey (at the bottom) are amazing. It’s less eel-like and more tadpole-like than modern forms, but it has the same disc-shaped mouth specialized for latching on to the flank of its host, it has similar circumoral teeth for rasping through scales and skin for its blood meal, the same pharyngeal adaptations for a life spent clamped to a fish.

I’ve put a photo of the fossil and a cladogram below the fold.

[Read more…]

Mysterious marine whatsis

i-8b66a24aed4a6b448d2460b32e284063-mystery_blob.jpg

Strange things are found in the sea, like this mysterious gelatinous blob bobbing about in the Norwegian fjords.

On Oct. 1 Rudolf and his brother Erling were diving when he spotted the unusual object.

“It was 50-70 centimeters (19.5-27.5 inches) in diameter and looked like a huge beach ball. It was transparent but had a kind of thick, red cord in the middle. It was a bit science-fiction,” Svensen told newspaper Bergens Tidende’s web site.

It’s something cool: a large squid egg sac. Mmmmm…two-foot diameter ball of squid eggs.

Dissecting embryos from half a billion years ago

i-7fe823a8a3ad74c60cac67b5ec0a8689-fossil_embryos_tease.jpg

There is a treasure trove in China: the well-preserved phosphatized embryos of the Doushantuo formation, a sampling of the developmental events in ancient metazoans between 551 and 635 million years ago. These are splendid specimens that give us a peek at some awesomely fragile organisms, and modern technology helps by giving us new tools, like x-ray computed tomography (CT), scanning electron microscopy (SEM), thin-section petrography, synchrotron X-ray tomographic microscopy (SRXTM), and computer-aided visualization, that allow us to dig into the fine detail inside these delicate specimens and display and manipulate the data. A new paper in Science describes a survey of a large collection of these embryos, probed with these new techniques, and rendered for our viewing pleasure…that is, we’ve got pretty pictures!

[Read more…]

Gogonasus andrewsae

Here’s another tetrapodomorph fish to consternate the creationists. These Devonian/Carboniferous animals just keep popping up to fill in the gaps in the evolutionary history of the tetrapod transition to the land—the last one was Tiktaalik.

i-8b2442cac1020896a08aca4650293aa3-gogonasus_skull_lat.jpg
Skull in lateral view.

This lovely beastie is more fish than frog, as you can tell—it was a marine fish, 384-380 million years old, from Australia, and it was beautifully preserved. Gogonasus is not a new species, but the extraction and analysis of a new specimen has caused its position in the evolutionary tree to be reevaluated.

[Read more…]