Trilobites (Introduction)
by David Turell 
, Tuesday, March 04, 2014, 14:38 (3917 days ago)
Everywhere. They are everywhere, so evolved, so complex. Just for dhw, because he has one:-http://www.nytimes.com/2014/03/04/science/when-trilobites-ruled-the-world.html?nl=todaysheadlines&emc=edit_th_20140304
Trilobites: molting fossil
by David Turell , Tuesday, September 29, 2015, 01:04 (3344 days ago) @ David Turell
Just like arthropods do now:-http://www.uncommondescent.com/evolution/trilobite-caught-in-act-of-molting/
Trilobites: molting fossil
by David Turell , Thursday, March 02, 2017, 02:02 (2824 days ago) @ David Turell
It is now found that Trilobites were egg layers just like their relatives, the horseshoe crabs, do now:
http://www.evolutionnews.org/2017/02/roe-roe-roe-never-before-seen-check-out-fossilized...
Comment: There are no known relatives preceding Trilobites. They simply appear in the fossil record, like all of the Cambrian Explosion animals. Great evidence for God.
Trilobites: gills on legs
by David Turell , Wednesday, March 31, 2021, 20:35 (1333 days ago) @ David Turell
A new finding:
https://phys.org/news/2021-03-million-year-old-sea-creatures-leg.html
"A new study has found the first evidence of sophisticated breathing organs in 450-million-year-old sea creatures. Contrary to previous thought, trilobites were leg breathers, with structures resembling gills hanging off their thighs.
***
"A CT scanner was able to read the differences in density between the pyrite and the surrounding rock and helped create three-dimensional models of these rarely seen gill structures.
"'It allowed us to see the fossil without having to do a lot of drilling and grinding away at the rock covering the specimen," said paleontologist Melanie Hopkins, a research team member at the American Museum of Natural History.
"'This way we could get a view that would even be hard to see under a microscope—really small trilobite anatomical structures on the order of 10 to 30 microns wide," she said. For comparison, a human hair is roughly 100 microns thick.
***
"The researchers could see how blood would have filtered through chambers in these delicate structures, picking up oxygen along its way as it moved. They appear much the same as gills in modern marine arthropods like crabs and lobsters.
"Comparing the specimens in pyrite to another trilobite species gave the team additional detail about how the filaments were arranged relative to one another, and to the legs.
"Most trilobites scavenged the ocean floor, using spikes on their lower legs to catch and grind prey. Above those parts, on the upper branch of the limbs, were these additional structures that some believed were meant to help with swimming or digging."
Comment: Amazing finding. They required oxy gen and had to breathe somehow.
Trilobites: spears to fight
by David Turell , Monday, January 16, 2023, 20:42 (677 days ago) @ David Turell
Present but purpose unclear to me:
https://www.newscientist.com/article/2354846-trilobites-used-trident-like-horns-to-figh...
'Trident-like horns on the heads of some trilobites were probably used in fights over mates. This hypothesised behaviour is the oldest example of sexual combat that has been identified in the fossil record.
“'Extraordinary structures in organisms cry out for functional explanations,” says Alan Gishlick at Bloomsburg University in Pennsylvania.
"Previously, palaeontologists had suggested that the tines on Walliserops, a trilobite that lived around 400 million years ago, could have been used as a defence against ancient nautilus that were hungry for these marine invertebrates. The prongs could grow to more than 25 millimetres long, nearly the size of the rest of the animal.
"But Gishlick and his colleague Richard Fortey at the Natural History Museum in London have come to a different conclusion, after studying an unusual specimen of Walliserops with four tines instead of three.
"The four-pronged trilobite stuck out to Gishlick because it was comparable in size to other adult Walliserops, indicating that it had the expected lifespan for its species. This appeared to be evidence against the trident being a defensive weapon, as such an abnormality in a defensive structure might have made the trilobite more vulnerable.
***
"While the sex of the fossil trilobites is difficult to discern, the similarities between Walliserops and the rhinoceros beetles led Gishlick and Fortey to suspect the trident-bearing Walliserops were males.
“'It is amazing to see that such complex behaviours appeared very early in the course of evolution and have endured to the present day,” says Jean Vannier at the University of Lyon, France, who wasn’t involved in the study.
“'Anything that enables us to better understand past life and test our hypotheses as rigorously as possible is crucial to understand evolution of form and function,” says Gishlick."
Comment: Trilobites are always astounding. The horns could be defensive tools as well as sexual helpers to fight off other suiters.
Trilobites: latest complete fossils
by David Turell , Friday, June 28, 2024, 16:27 (148 days ago) @ David Turell
edited by David Turell, Friday, June 28, 2024, 16:37
Volcanic ash entombment:
https://www.sciencemagazinedigital.org/sciencemagazine/library/item/28_june_2024/420430...
"Knowledge of Cambrian animal anatomy is limited by preservational processes that result in compaction, size bias, and incompleteness. We documented pristine three-dimensional (3D) anatomy of trilobites fossilized through rapid ash burial from a pyroclastic flow entering a shallow marine environment. Cambrian ellipsocephaloid trilobites from Morocco are articulated and undistorted, revealing exquisite details of the appendages and digestive system. Previously unknown anatomy includes a soft-tissue labrum attached to the hypostome, a slit-like mouth, and distinctive cephalic feeding appendages. Our findings resolve controversy over whether the trilobite hypostome is the labrum or incorporates it and establish crown-group euarthropod homologies in trilobites. This occurrence of moldic fossils with 3D soft parts highlights volcanic ash deposits in marine settings as an underexplored source for exceptionally preserved organisms.
"Trilobites are arguably the most familiar of fossil invertebrates, known from over 22,000 species and millions of specimens spanning the Paleozoic. Their calcite exoskeleton confers high fossilization potential, providing a tool for early Paleozoic biostratigraphy and informing on their ontogeny and developmental evolution (2-4); and through their calcified eye lenses, it has been possible to gain insights into the vision of early arthropods. (my bold)
***
"In this study, we were able to establish that the labrum is distinct from the hypostome, the labrum being attached to the dorsal doublure at the posterior end of the hypostome, with the same relationship that the labrum has to the epistome in chelicerates. Similar to the robustly sclerotized epistome in Xiphosura, the trilobite hypostome is biomineralized—with the labrum being relatively soft in both clades—and the hypostome accommodates the antennal insertion, just as the xiphosuran epistome accommodates the chelicerae. Furthermore, we were able to identify the mouth opening in front of the dorsal platform of the labrum, which is consistent with the position of the start of the esophagus, demonstrating that the hypostome covered the mouth.
***
"Although the soft-bodied anatomy of trilobites has been known for over 100 years, the Tatelt specimens reveal critical details at a level not previously observed, despite the long stratigraphic range and abundance of this iconic group of Paleozoic fossils. The extraordinary preservation of fine anatomical detail in the ash deposit of a pyroclastic event is unexpected but points to the great potential of ashdeposits inmarine settings to yield further discoveries."
Comment: hopefully the website address will allow a look at the amazing illustrations. I would remind the reader this large population has no predecessors. They represent the Cambrian Gap. This article has the illustrations:
https://www.sciencealert.com/never-before-seen-trilobite-anatomy-preserved-by-pompeii-l...
"'Although the soft-bodied anatomy of trilobites has been known for over 100 years, the Tatelt specimens reveal critical details at a level not previously observed, despite the long stratigraphic range and abundance of this iconic group of Paleozoic fossils," the researchers write.
"The extraordinary preservation of fine anatomical detail in the ash deposit of a pyroclastic event is unexpected but points to the great potential of ash deposits in marine settings to yield further discoveries.'"
Trilobites: latest complete fossils
by David Turell , Tuesday, August 13, 2024, 15:46 (102 days ago) @ David Turell
Preservation detailed:
https://www.sciencenews.org/article/stunning-trilobite-fossils-soft-tissues
"To uncover how these trilobites and their tissues became so well preserved, Paterson and his team enlisted Robert Gaines, a geologist at Pomona College in Claremont, Calif., and an expert in how the soft parts of animals become fossils.
"It happened like this: First a volcano exploded, and superheated ash flowed from the eruption into nearby coastal waters. The ash dissolved and then remineralized out of the water, covering the exposed trilobites and entombing them in a matter of hours to days.
"The key step in this process, Gaines says, is that the ash hit water before hardening around the trilobites; without the cooling effects of ocean water, the hot ash would have burned the trilobites away.
"Gaines studies similar fossil preservation in other, older fossils, such as an arthropod called Aegirocassis, an alien-like animal with what appears to be a strange baleen-style feeding apparatus. “I recognized the similarities immediately,” Gaines says. “They pointed to the same process operating more than 20 million years earlier.”
"Besides being ready for a museum showcase, the fossils open new windows onto trilobite biology and evolutionary history.
“'The clarity of the preservation is astonishing and is of fundamental importance,” says Nigel Hughes, a paleontologist at the University of California, Riverside who was not involved in the new work. “It provides a level of preservation detail that unequivocally confirms a number of conjectures made based on less well-preserved material, which demonstrates the power and importance of exceptional preservation.”
"The fossils confirm, for instance, that trilobites ate using the many pairs of legs stretching from their head to their torso. They chewed food along a central groove while passing food particles toward a tiny mouth.
“'Food processing took place along the entire length of the animal,” Hughes says.
"This differs from other arthropods, such as crustaceans, which have more specialized limbs along their body lengths, used for tasks from self-defense to swimming.
***
"Volcanos, including ones near coasts, erupted relatively often over the vast stretches of geologic time, Paterson says. That means this kind of pristine preservation may be more common than scientists think.
“'Geology and paleontology students at universities are often told that fossils are found only in sedimentary rocks,” Paterson says. “But our new study completely contradicts that notion. I hope that our work will encourage others to reprogram their search image in the hunt for amazing fossils.'”
Comment: this opens up large areas to search for more Trilobite fossils. It does not answer the missing fossil theory since it is only helping to explain an existing fossilized species.