Sentences with word «placoderm»

Daeschler and Olive's work focused largely on comparing the Red Hill site to Strud, noting many similarities between the two and using the size and shape of placoderm fossils from Red Hill, housed at the Academy of Natural Sciences, to establish the relative maturity of samples found in Strud.

But whether these modern - day species spawn or copulate, the equipment they use to get the job done derives from the same embryonic tissue under the direction of the same so - called hox genes that formed claspers in placoderms.

With three different types of placoderm fossils discovered at Strud — Grossilepis rikiki, Turrisaspis strudensis and Phyllolepis undulata — it opens a question for scientists like Daeschler.

The fossils Ahlberg found belong to early jawed fish called placoderms, which had tough sheets of body armour that covered their heads and parts of their bodies.

SEX AND BONES Although the discovery of internal fertilization in 375 - million - year - old fossils is as important as John A. Long makes it out to be in «Dawn of the Deed,» his article made the leap from placoderms to tetrapods without mention of lobe - finned fish.

An artist's depiction of what the Strud nursery ecosystem may have looked like, including the three different placoderm species discovered at the site.

Sculpture of placoderm Dunkleosteus; image courtesy of Esben Horn, 10tons; supervised by Martin Rücklin, John Long and Philippe Janvier The ancient ocean was a frightening place.

Before the extinction, fish were dominated by two groups: the armor - plated, predatory placoderms and the lobe - finned fish, whose fins are borne on a fleshy, scaly stalk extending from the body.

Although placoderms are long extinct, getting glimpses of their lives puts more pieces together in the evolutionary puzzle.

Dating back to the Devonian period, an era predating the dinosaurs by hundreds of millions of years, the site yielded smaller - sized fossils that show immature placoderms occupied the area.

«Adult placoderms may have used the nursery of Strud only to lay eggs and / or give live birth, and would have generally lived away from the nursery in deeper waters,» wrote the research team, which also included paleontologists Gaël Clément of the Museum national d'Histoire Naturelle in Paris, and Vincent Dupret, of Uppsala University in Sweden.

The top ocean predator of the time, its prey could have included early sharks, large nautiluslike mollusks, arthropods and other placoderms, Westneat says.

At the same time, larger placoderm fossils, indicating mature fish, were not found.

«We are quite sure that the juvenile - only placoderm assemblage is not the result of sorting of small material by water currents because there are larger skeletal elements of other kinds of fish.

«In the case of placoderms like these, we're looking at some of the earliest jawed vertebrates,» Olive said.

This backs up a 2013 study that showed that several traits thought to be unique to bony fish, such as the presence of large platelike bones, were in fact present in placoderms, an extinct group of jawed fish related to the ancestor of both cartilaginous and bony fish.

Some had well - known cousins on other continents, for example, the extinct armoured fish called placoderms, the massive sauropod dinosaurs and the armoured ankylosaurs.

Using fragments from three placoderm fossils, Ahlberg was able to piece together some of their musculature.

A quarry in Strud, Belgium, that was excavated between 2004 and 2015 yielded fossils of multiple species of placoderms, which are extinct, armored fish that represent some of the earliest jawed vertebrates on Earth.

If, as his article suggests, claspers are the progenitors of tetrapod limbs, then where do nearly amphibious lobe - finned fish such as Tiktaalik, of the same age as his placoderms, fit in this phylogeny?

The fossil fish Tiktaalik, discovered in 2006, dates back to the same period, and its skeleton bears many more similarities to tetrapods than to the placoderms described in Long's article — including homologous arm bones and shoulder, neck and ear features.

Placoderms were eliminated by the end - Devonian extinction, and most of the lobe - finned fish perished as well, though survivors live on today in the lungfish and the coelacanth.

Nobody knows why the placoderms had abdominal muscles like these.

These muscles may have made the placoderms fiercer predators, says Ahlberg.

The big surprise was in the placoderms» abdominal muscles.

As the placoderm swam, waving its tail from side to side, the back half of its body would have swung from side to side as well.

Ahlberg found that each placoderm also had two pairs of muscles reaching from its shoulder girdle to the top of its head.

But the placoderms had strips of transverse muscles, running at right angles to the other muscles, on their bellies.

Dunkleosteus grew up to 33 feet long and was the largest of a group of armor - plated predatory fish, the placoderms.

Correction (10/28/15): An earlier mention of placoderms has been removed to reflect the general consensus that this fish had likely gone extinct prior to the Permian period.

placoderm An extinct type of armored fish which lived from the Silurian to Devonian periods.

Fossils inlaid within the rocks in the Cliff area hint at previous inhabitants of the island, consisting of enormous trilobite lookalikes, gastropods, placoderm fish, and eurypterids as well.

An ichthyologist specializing in placoderms, or armored fish, Dean was also an enthusiastic collector of armor.