Turtle history (Introduction)
by David Turell 
, Monday, November 19, 2012, 20:28 (4189 days ago)
Note there is no 'before' in this history. That is because turtles appear out of thin air in the evolutionary record!-http://blogs.scientificamerican.com/tetrapod-zoology/2012/11/17/quick-history-of-turtles/?WT_mc_id=SA_DD_20121119
Turtle history:genetics
by David Turell , Monday, April 29, 2013, 15:49 (4028 days ago) @ David Turell
DNA studies now show that turtles are related to a branch of crocdilians and birds coming from dinosaurs during the period of the Permian extinction 240 million years ago.:-http://phys.org/news/2013-04-turtle-genome-analysis-evolution-turtle-specific.html-One wonders why evolution would invent such a strange vertibrate?
Turtle history:origin of shell
by David Turell , Tuesday, July 09, 2013, 15:42 (3957 days ago) @ David Turell
Turtles appear out of nowhere in the fossil record. The appearance of such a disadventageous form turns natural selection on its head. This article tries to explain the origin:-http://phys.org/news/2013-07-turtle-shell-mystery.html
Turtle history: neck retraction
by David Turell , Monday, March 06, 2017, 18:22 (2621 days ago) @ David Turell
Neck retraction evolved in turtles. They started out not able to do that:
https://phys.org/news/2017-03-evolution-turtle-neck-retraction.html
"One of the unique and most iconic features of many modern turtles is that they can withdraw their neck and head to hide and protect them within their shells. The group name of species which do this, Cryptodira, even means 'hidden-necked turtles' to reflect this unusual adaptation.
"Turtles and their ancestors have been around for more than 200 million years now, and are a remarkable evolutionary success story. We know that by studying their fossils, the earliest turtle ancestors had rigid necks though, and were unable to retract them as modern species do.
"New research from Jérémy Anquetin and colleagues has provided insight now into the reason this bizarre act evolved in turtles, showing that actually it occurred twice in their long history.
"The team investigated a fossil turtle known as Platychelys from the Late Jurassic, around 150 million years ago, of Europe. Europe at this time was completely different to now – it was more like an island archipelago, with warm shallow seas inhabited by a range of unusual and now extinct turtle species.
"Intriguingly, the neck morphology of Platychelys was remarkably similar to its modern cryptodire relatives, indicating that it was at least partially capable of retracting its neck. It is able to do this by folding the neck muscles vertically, causing the neck to move inwards towards the torso, but apparently not quite enough to actually be of any use for protection.
"Although the muscles of Platychelys are not preserved, the researchers were able to infer this based on the broad shape of the neck, or cervical, vertebrae, and the wide spacing between the parts of the bones that the muscles attached to. Cryptodires also have a double articulation on their neck vertebrae, a feature worth pointing out here only because the condition has the awesome name of 'ginglymoidy'.
"As well as partially retracting its neck, it also seems that Platychelys was able to shoot it back out again. This is a method to ambush and capture its prey underwater, like some modern turtles are capable of doing, and especially useful to catch rapidly darting fish. This means that neck retraction for protection might even have evolved as a sort of additional, non-intentional function driven by the evolution of this mode of feeding in Platychelys.
"As we see this sort of behaviour in modern turtles that are distantly related to Platychelys and separated by around 150 million years, this is an example of what is known as 'convergent evolution'. This is where different species have similar adaptations to their environment or ecology that are acquired independently but for the same purposes. In this case, neck retraction seems to have evolved multiple times to make capturing prey even easier, and originally had absolutely nothing to do with protection, as is commonly thought.
"This adds an additional layer of complexity to our understanding of the early evolution of turtles, and the team will investigate this in more detail in the future by examining more fossils and trying to work out their feeding habits."
Comment: Turtles remain as mysterious as ever. They appeared without specific precursors 200 myo. The neck adaptation is a logical adaptation considering their shells. One might ask, why turtles at all? My pat answer is balance of nature.
Turtle history: no shell fossil
by David Turell , Thursday, August 23, 2018, 18:40 (2086 days ago) @ David Turell
A two-meter long specimen without a shell but with other characteristics of turtle evolution. Origin is stsill unknown:
https://www.nature.com/articles/d41586-018-06012-0?utm_source=briefing-dy&utm_mediu...
"A fossilized turtle discovered in southwestern China fills an evolutionary hole in how the reptiles developed features such as a beak and shell, researchers report1 on 22 August in Nature. Although the specimen can help scientists to pin down when modern turtles developed such characteristics, it’s also muddied the waters when it comes to illuminating the group’s origins.
"The roughly 2-metre-long animal, dubbed Eorhynchochelys sinensis, lived about 230 million years ago. Its skull is similar to those of modern turtles, whereas the rest of the animal’s skeleton is more like that of a predecessor that lived 10 million years before.
***
"Turtles haven’t changed much over the past 210 million years. They all have a top shell formed from the fusion of their spine and ribs, a bottom shell that protects their belly, a sharp beak and a mouth without any teeth. But the group lacks a feature common to most modern reptiles — two pairs of holes in their skull, behind their eyes, where jaw muscles attached.
"The absence of those holes has contributed to a decades-long debate on the exact position of turtles on the reptile family tree. And this has compounded researchers’ struggle to work out when and how turtle characteristics first evolved.
"A specimen discovered in 2008, called Odontochelys semitestacea, offered the first clues2. The roughly 220-million-year-old animal possessed teeth and a bottom shell, and its wide ribs hinted at the beginnings of a top shell. But it lacked a beak and the pairs of holes in its skull.
"Then, in 2015, scientists found Pappochelys rosinae, a 240-million-year-old specimen that was missing a top shell, but showed the first signs of a bottom shell3. Unlike modern turtles, P. rosinae had two pairs of openings in its skull, indicating for the first time that turtles were closely related to other modern reptiles.
"Now, the discovery of Eorhynchochelys fills in the gap between these two species. The fossil turtle possesses a single pair of holes behind its eyes, suggesting a gradual transition from Pappochelys to modern turtles.
***
"Most genetic studies over the past 20 years have positioned crocodilians, dinosaurs and modern birds as the turtles’ closest evolutionary relatives. But some studies looking at DNA or RNA, as well as analyses of turtle anatomy, have pointed to lizards and snakes as the group’s closest relatives.
"After including Eorhynchochelys’s physical characteristics in an analysis with those of other fossilized reptiles, however, Wu and his colleagues say that turtles aren’t as closely related to any of those groups as other research suggests. They’re more of an offshoot from earlier ancestors, Wu says.
"Schoch is sceptical of this claim, however, saying that researchers don’t know enough about the anatomy of early reptilian ancestors to know for sure where turtles fall."
Comment: As usual evolutionists want to use phenotype when DNA genetics is a better guide.
Turtle history: no shell fossil
QUOTE: "A fossilized turtle discovered in southwestern China fills an evolutionary hole in how the reptiles developed features such as a beak and shell, researchers report on 22 August in Nature. Although the specimen can help scientists to pin down when modern turtles developed such characteristics, it’s also muddied the waters when it comes to illuminating the group’s origins.
"The roughly 2-metre-long animal, dubbed Eorhynchochelys sinensis, lived about 230 million years ago. Its skull is similar to those of modern turtles, whereas the rest of the animal’s skeleton is more like that of a predecessor that lived 10 million years before.
We should be surprised that any remains are found from 230 million years ago, but when they are found, they provide yet more evidence of links between earlier and later life forms, i.e. of common descent.
Turtle history: no shell fossil
by David Turell , Friday, August 24, 2018, 23:01 (2085 days ago) @ dhw
from David article: QUOTE: "A fossilized turtle discovered in southwestern China fills an evolutionary hole in how the reptiles developed features such as a beak and shell, researchers report on 22 August in Nature. Although the specimen can help scientists to pin down when modern turtles developed such characteristics, it’s also muddied the waters when it comes to illuminating the group’s origins.
"The roughly 2-metre-long animal, dubbed Eorhynchochelys sinensis, lived about 230 million years ago. Its skull is similar to those of modern turtles, whereas the rest of the animal’s skeleton is more like that of a predecessor that lived 10 million years before.
dhw: We should be surprised that any remains are found from 230 million years ago, but when they are found, they provide yet more evidence of links between earlier and later life forms, i.e. of common descent.
Turtles have no known fossil sequence, so they are still out of no where. Doesn't prove anything, but they are so unusual in phenotype they are somewhat like whales to create wonder why they bothered to devlop
Turtle history: no shell fossil
QUOTE: "A fossilized turtle discovered in southwestern China fills an evolutionary hole in how the reptiles developed features such as a beak and shell, researchers report on 22 August in Nature. Although the specimen can help scientists to pin down when modern turtles developed such characteristics, it’s also muddied the waters when it comes to illuminating the group’s origins.
"The roughly 2-metre-long animal, dubbed Eorhynchochelys sinensis, lived about 230 million years ago. Its skull is similar to those of modern turtles, whereas the rest of the animal’s skeleton is more like that of a predecessor that lived 10 million years before."
dhw: We should be surprised that any remains are found from 230 million years ago, but when they are found, they provide yet more evidence of links between earlier and later life forms, i.e. of common descent.
DAVID: Turtles have no known fossil sequence, so they are still out of no where. Doesn't prove anything, but they are so unusual in phenotype they are somewhat like whales to create wonder why they bothered to develop.
This article provides a link in the chain of common descent, which you profess to believe in. There are of course loads and loads of missing links. Fossils are rarities. Just this one from 230 million years ago. I’m surprised that you are starting to believe in organisms that come from nowhere, as opposed to coming from other organisms. This would certainly go against everything you learned during your medical training! And I’m delighted to see you wondering why they bothered to develop, which is a clear indication of autonomy. I’d have expected you to wonder why your God bothered to preprogramme them 3.8 billion years ago or to personally dabble them!
Turtle history: no shell fossil
by David Turell , Saturday, August 25, 2018, 18:15 (2084 days ago) @ dhw
QUOTE: "A fossilized turtle discovered in southwestern China fills an evolutionary hole in how the reptiles developed features such as a beak and shell, researchers report on 22 August in Nature. Although the specimen can help scientists to pin down when modern turtles developed such characteristics, it’s also muddied the waters when it comes to illuminating the group’s origins.
"The roughly 2-metre-long animal, dubbed Eorhynchochelys sinensis, lived about 230 million years ago. Its skull is similar to those of modern turtles, whereas the rest of the animal’s skeleton is more like that of a predecessor that lived 10 million years before."dhw: We should be surprised that any remains are found from 230 million years ago, but when they are found, they provide yet more evidence of links between earlier and later life forms, i.e. of common descent.
DAVID: Turtles have no known fossil sequence, so they are still out of no where. Doesn't prove anything, but they are so unusual in phenotype they are somewhat like whales to create wonder why they bothered to develop.
dhw: This article provides a link in the chain of common descent, which you profess to believe in. There are of course loads and loads of missing links. Fossils are rarities. Just this one from 230 million years ago. I’m surprised that you are starting to believe in organisms that come from nowhere, as opposed to coming from other organisms. This would certainly go against everything you learned during your medical training! And I’m delighted to see you wondering why they bothered to develop, which is a clear indication of autonomy. I’d have expected you to wonder why your God bothered to preprogramme them 3.8 billion years ago or to personally dabble them!
You always point on any statement that suggests I left out God. I feel God developed turtles as part of the balance of nature. Whatever forebear they came from, the changes required were much less than for whales, but turtles lead a problematic land life due to their armored phenotype. Sea turtles seem to handle it better. Either way it is a cumbersome body style.
Turtle history: no shell fossil
DAVID: Turtles have no known fossil sequence, so they are still out of no where. Doesn't prove anything, but they are so unusual in phenotype they are somewhat like whales to create wonder why they bothered to develop.
dhw: This article provides a link in the chain of common descent, which you profess to believe in. There are of course loads and loads of missing links. Fossils are rarities. Just this one from 230 million years ago. I’m surprised that you are starting to believe in organisms that come from nowhere, as opposed to coming from other organisms. This would certainly go against everything you learned during your medical training! And I’m delighted to see you wondering why they bothered to develop, which is a clear indication of autonomy. I’d have expected you to wonder why your God bothered to preprogramme them 3.8 billion years ago or to personally dabble them!
DAVID: You always point on any statement that suggests I left out God. I feel God developed turtles as part of the balance of nature. Whatever forebear they came from, the changes required were much less than for whales, but turtles lead a problematic land life due to their armored phenotype. Sea turtles seem to handle it better. Either way it is a cumbersome body style.
No problem. Thank you for dropping your statement that they are “out of nowhere” and for correcting your wondering "why they bothered to develop" to wondering why God bothered to develop them. You could ask the same about pointy eggs and weaverbird nests etc. etc. The rest of your comment is fine with me but has nothing to do with what I wrote.
Turtle history: no shell fossil
by David Turell , Sunday, August 26, 2018, 15:39 (2083 days ago) @ dhw
DAVID: You always point on any statement that suggests I left out God. I feel God developed turtles as part of the balance of nature. Whatever forebear they came from, the changes required were much less than for whales, but turtles lead a problematic land life due to their armored phenotype. Sea turtles seem to handle it better. Either way it is a cumbersome body style.
dhw: No problem. Thank you for dropping your statement that they are “out of nowhere” and for correcting your wondering "why they bothered to develop" to wondering why God bothered to develop them. You could ask the same about pointy eggs and weaverbird nests etc. etc. The rest of your comment is fine with me but has nothing to do with what I wrote.
Out of nowhere implies the lack of an evolutionary trail. There might not be one, if God chose to invent without evolving.
Turtle history: a review of aquatic species
by David Turell , Thursday, March 14, 2024, 17:31 (56 days ago) @ David Turell
They play a major role in our oceans:
https://www.discovermagazine.com/planet-earth/everything-to-know-about-the-secret-world...
"In the serene yet treacherous waters of our planet's oceans, sea turtles have thrived for ages, silently helping maintain the equilibrium of aquatic life. These marine reptiles, which are emblematic of both endurance and tranquility, play vital roles in oceanic ecosystems. However, their existence is increasingly threatened by a host of serious challenges.
"Sea turtles are marine reptiles that have been navigating the world's oceans virtually unchanged for some 110 million years. They belong to the order Testudines and are known for their large shells, which offer protection from predators. Unlike many other turtles and tortoises, sea turtles cannot retract their heads and limbs into their shells, and they have adapted flippers for swimming in the ocean.
"Sea turtles play key roles in marine ecosystems, contributing to the health of seagrass beds and coral reefs, which in turn support a wide array of other marine life.
***
"There are seven distinct species of sea turtles, each with its own unique set of characteristics, habitats, nesting habits, and dietary preferences. These species include:
"Green; Hawksbill; Leatherback; Loggerhead; Olive Ridley; Kemp's Ridley; and Flatback.
"Each species occupies a different niche in the marine environment, from shallow coastal waters to the open sea, and from tropical regions to more temperate zones.
***
"The size of sea turtles varies dramatically across species.
"The leatherback is the largest of all sea turtles, growing up to 6 feet in length and weighing up to 1,500 pounds. Other species, like the Hawksbill and the Green sea turtle, are smaller, though they can still reach impressive sizes, with adults typically ranging from 2.5 to 4 feet in length and weighing several hundred pounds.
"On the other end of the spectrum, a Kemp’s Ridley is the smallest sea turtle, averaging under 2 feet in length and typically weighing just shy of 100 pounds.
***
"The migratory behavior of sea turtles is equally impressive, with some species undertaking thousands of miles of travel between their feeding grounds and nesting beaches. Notably, female sea turtles exhibit a strong homing instinct, often returning to the exact beach where they were born to lay their own eggs.
"The diet of sea turtles varies significantly by species. While some species are omnivorous, most adult sea turtles are specialized feeders.
"For instance, green sea turtles are the only sea turtles that are herbivores, primarily feeding on seagrasses and algae, which gives them green-colored fat. Meanwhile, Hawksbills like to feed on sponges found in coral reefs. And leatherbacks and loggerheads, the giants of the turtle family, consume large quantities of open-ocean invertebrates like jellyfish, helping control jellyfish populations.
***
"Sea turtles are known for their impressive longevity. They can live for several decades, with many species reaching 50 to 100 years in age. But this long lifespan contributes to their late maturity, where some species don’t breed until they are 20 to 30 years old.
"A sea turtle’s journey to maturity is also fraught with peril. From the moment they hatch, sea turtles face countless predators and challenges, which is why only about one in 1,000 to one in 10,000 hatchlings survive until adulthood.
"Sea turtles play crucial roles in marine ecosystems, from maintaining healthy seagrass beds and coral reefs to controlling jellyfish populations. However, their survival hangs in the balance, largely due to human activities.
***
"Sea turtles cannot breathe underwater; they are air-breathing reptiles. However, they can hold their breath for several hours at a time. Depending on activity level, sea turtles can stay submerged for 4 to 7 hours. This allows them to undertake long dives while foraging for food or resting on the ocean floor.
***
"Sea turtles are known for their remarkable nesting behaviors, often returning to the same beaches where they were born to lay their eggs. A female sea turtle can lay hundreds of eggs during a single nesting season, burying them in the sand to incubate.
"However, the survival rate of these hatchlings is extremely low, with only a few per thousand making it to adulthood.
"Sea turtles have unique sleeping habits. They can sleep at the water’s surface or underwater, surfacing for air periodically. Some species find underwater resting spots nestled in coral or mud, where they can remain undisturbed, while others simply float at the surface."
Comment: they play important roles in ecosystems across all the warm to temperate oceans
Turtle history: leatherback migrations
by David Turell , Saturday, March 16, 2024, 18:23 (54 days ago) @ David Turell
A new study:
https://www.sciencedaily.com/releases/2024/03/240315160342.htm
"The waters off Cape Cod and Nantucket promote a high abundance of jellyfish in the late summer and early fall, which the leatherbacks appear to be taking advantage of. The scientists observed some of the leatherbacks tagged along Nantucket Shoals, stayed in the area for weeks to months after tagging before migrating back south.
"In the Mid-Atlantic Bight, the team inferred that there is food availability, given the high number of leatherbacks that displayed feeding-like behavior year after year. However, the team noted the lack of research on prey distributions in this area, and further observations for leatherbacks would benefit by returning to the site to deploy camera tags to determine what the leatherbacks are feeding on.
"The South Atlantic Bight appears to support several stages of the migration cycle: nesting, post-nesting foraging, and overwintering. Not as many leatherbacks frequented this area, but the ones that were tracked displayed feeding-like behavior especially along the continental shelf ridge. Previous research in the area indicates that blooms of cannonball jellyfish occur nearshore in the South Atlantic Bight primarily during the spring, which coincides with leatherbacks overwintering and nesting stages of their migration cycle.
"Our study revealed a significantly higher utilization of the U.S. coastline by leatherbacks, particularly along regions of the Mid-Atlantic Bight, South Atlantic Bight, and Southern New England. These areas emerged as possible major foraging grounds for leatherbacks migrating along the United States coastline, with notable activity observed off the coast of North Carolina.
"'A key finding was further defining the Mid-Atlantic Bight as a critical foraging ground for leatherbacks from past studies, identified through sophisticated behavioral analysis," said Rider. "By incorporating diving metrics such as dive frequency and duration, the study provides a comprehensive understanding of leatherback behaviors that distinguishes between their migration and foraging activities."
"Furthermore, the study highlighted the vulnerability of leatherbacks to incidental capture by fisheries and vessel strikes, underscoring the urgent need for conservation efforts to mitigate these risks. With impending developments, particularly the construction of offshore wind farms in the Mid-Atlantic Bight and Southern New England regions, the findings serve as a relevant guide for conservation managers to minimize impacts on this endangered species."
Comment: Along the Texas coast large numbers of eggs are left to incubate and must be protected, as elsewhere along the coast.