Evidence Pareiasaurs had a Lifestyle Very Different From Modern Megafauna

Bone microstructure of pareiasaurs (Parareptilia) from the Karoo Basin, South Africa: implications for growth strategies and lifestyle habits

Authors:

Canoville et al

Abstract:

Numerous morphological studies have been carried out on pareiasaurs; yet their taxonomy and biology remain incompletely understood. Earlier works have suggested that these herbivorous parareptiles had a short juvenile period as compared to the duration of adulthood. Several studies further suggested an (semi-) aquatic lifestyle for these animals, but more recent investigations have proposed a rather terrestrial habitat.

Bone paleohistology is regarded as a powerful tool to assess aspects of tetrapod paleobiology, but few studies have been conducted on pareiasaurs. The present study assesses intra and inter-specific histovariability of pareiasaurs and provides fresh insights into their paleobiology, thereby permitting a re-evaluation of earlier hypotheses. Our sample comprises various skeletal elements and several specimens covering most of the taxonomic and stratigraphic spectrum of South African pareiasaurs, including large and basal forms from the Middle Permian, as well as smaller and more derived forms from the Late Permian.

Our results concerning size of elements and histological tissues show that for pareiasaurs, element size is not a good indicator of ontogenetic age, and furthermore, suggest that the specific diversity of the Middle Permian pareiasaurs may have been underestimated. The bone histology of these animals shows that they experienced a relatively rapid growth early in ontogeny. The periosteal growth later slowed down, but seems to have been protracted for several years during adulthood. Pareiasaur bone microanatomy is unusual for continental tetrapods, in having spongious stylopod diaphyses and thin compact cortices. Rigorous paleoecological interpretations are thus limited since no modern analogue exists for these animals.

The Trouble With Turtles...and Their Phylogenic Placement

Traditional paleontological research has been upended over the past few decades, as less traditional fields, such as genomics and developmental biology, have weighed in on vertebrate evolution. Researchers have examined the lingering color elements in dinosaur feathers, the genetics of woolly mammoths, purported proteins and blood from dinosaurs, and other ancient fossil signatures using modern tools. But the question of turtle evolution has remained resistant to both traditional and novel methods.

More than 300 species of turtles exist today, but where they came from isn’t entirely clear. Turtles are the last big living vertebrate group to be placed firmly on the tree of life, and the arguments are getting messy. Three fields in particular — paleontology, developmental biology and microbiology/genomics — disagree about how, and from what, turtles may have evolved.

Traditional paleontologists have placed turtles, which are indisputably reptiles, in relation to a group of mostly extinct reptilian animals called anapsids, which don’t have holes in their skulls; however, analyses in the 1990s put turtles in the diapsid camp, which originally had two holes in their skulls, and closer to modern reptiles like snakes. Morphology places them near the group made up of lizards and birds and crocodiles.

Within that group, genomicists have found molecular data that places turtles closer to birds and crocodiles, rather than lizards and snakes. But even within genomics, there is debate.

Meanwhile, developmental biologists have figured out that turtles have very special shells, giving them unusual characteristics that might be found in the fossil record, though what that might look like remains to be seen.

All this disagreement thus leads back to paleontology. Find more fossils and you find more answers. But until that happens, what else can be done to solve the mystery of turtle evolution?

link.

Parareptiles Not Hit as Badly by Permian Extinction?

The end-Permian extinction, by far the most dramatic biological crisis to affect life on Earth, may not have been as catastrophic for some creatures as previously thought, according to a new study led by the University of Bristol.

An international team of researchers studied the parareptiles, a diverse group of bizarre-looking terrestrial vertebrates which varied in shape and size. Some were small, slender, agile and lizard-like creatures, while others attained the size of rhinos; many had knobbly ornaments, fringes, and bony spikes on their skulls.

The researchers found that, surprisingly, parareptiles were not hit much harder by the end-Permian extinction than at any other point in their 90 million-year history. Furthermore, the group as a whole declined and diversified time and time again throughout its history, and it was not until about 50 million years after the end-Permian crisis that the parareptiles finally disappeared.

During the end-Permian extinction, some 250 million years ago, entire groups of animals and plants either vanished altogether or decreased significantly in numbers, and the recovery of the survivors was at times slow and prolonged before new radiations took place.

By studying the fossil record, palaeontologists can examine how individual groups of organisms responded to the end-Permian event and assess just how dramatic it was. However, as the quality and completeness of the fossil record varies considerably, both geographically and stratigraphically, palaeontologists need to find a way to ‘join the dots’ and piece together the fragments of a complex mosaic to give a more satisfactory and better picture of ancient life’s diversity.

Paper here.

Old: Rainforest Collapse Drove Reptile Evolution

Global warming devastated tropical rainforests 300 million years ago. Now scientists report the unexpected discovery that this event triggered an evolutionary burst among reptiles -- and inadvertently paved the way for the rise of dinosaurs, 100 million years later.

This event happened during the Carboniferous Period. At that time, Europe and North America lay on the equator and were covered by steamy tropical rainforests. But when the Earth's climate became hotter and drier, rainforests collapsed, triggering reptile evolution.

Dr Howard Falcon-Lang of Royal Holloway, University of London, UK explained: "Climate change caused rainforests to fragment into small 'islands' of forest. This isolated populations of reptiles and each community evolved in separate directions, leading to an increase in diversity."

Professor Mike Benton of the University of Bristol, UK added: "This is a classic ecological response to habitat fragmentation. You see the same process happening today whenever a group of animals becomes isolated from its parent population. It's been studied on traffic islands between major road systems or, as Charles Darwin famously observed in the Galapagos, on oceanic islands."

Ms Sarda Sahney, also of the University of Bristol, UK said: "It is fascinating that even in the face of devastating ecosystem-collapse, animals may continue to diversify through the creation of endemic populations." However, she warned that: "Life may not be so lucky again in the future, should the Amazon rainforest collapse."

To reach their conclusions, the scientists studied the fossil record of reptiles before and after rainforest collapse. They showed that reptiles became more diverse and even changed their diet as they struggled to adapt to rapidly changing climate and environment.

The paper is here. However, I lack a copy of it. That's why I haven't written about it before. If someone would be so kind, I'd appreciate it. It's also available here.

Turtles: Back to Parareptilia You Go!

The position of turtles based on molecular (1: e.g. Hugall et al. 2007) and morphological datasets (2: e.g. deBraga & Rieppel 1997; 3: Gauthier et al. 1988). The addition of key fossils eliminates the apparent disagreement among morphological datasets in support of turtles outside Diapsida (3). The Permian ‘parareptile’ Eunotosaurus shares uniquely derived features with turtles that help fill important gaps in the evolutionary origin of the turtle shell. Bootstrap (top) and Bremer (bottom) support values are provided for the Eunotosaurus-turtle clade. Star indicates complete shell.

Transitional fossils and the origin of turtles

1. Tyler R. Lyson (a,*)
2. Gabe S. Bever (a)
3. Bhart-Anjan S. Bhullar (b)
4. Walter G. Joyce (c)
5. Jacques A. Gauthier (a)

a. Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA

b. Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA

c. Institut für Geowissenschaften, University of Tübingen, 72076 Tübingen, Germany

* Author for correspondence (tyler.lyson@yale.edu).

Abstract:

The origin of turtles is one of the most contentious issues in systematics with three currently viable hypotheses: turtles as the extant sister to (i) the crocodile–bird clade, (ii) the lizard–tuatara clade, or (iii) Diapsida (a clade composed of (i) and (ii)). We reanalysed a recent dataset that allied turtles with the lizard–tuatara clade and found that the inclusion of the stem turtle Proganochelys quenstedti and the ‘parareptile’ Eunotosaurus africanus results in a single overriding morphological signal, with turtles outside Diapsida. This result reflects the importance of transitional fossils when long branches separate crown clades, and highlights unexplored issues such as the role of topological congruence when using fossils to calibrate molecular clocks.

The tug of war continues over the turtles! Once anapsida then parareptilia, then diapsida and back once more into parareptilia! Oy!

That said, I am beginning to think that the molecular clock isn't nearly as regular as is often assumed. I get the distinct feeling that there are bursty times of rapid mutation and other quieter moments of stasis and little change. Perhaps the molecular clock just needs more fiber in its diet, eh?

Accute Hearing in Parareptiles and an Interesting Buried Comment

Impedance-Matching Hearing in Paleozoic Reptiles: Evidence of Advanced Sensory Perception at an Early Stage of Amniote Evolution

1. Johannes Müller*,

2. Linda A. Tsuji

Humboldt-Universität zu Berlin, Museum für Naturkunde, Berlin, Germany


Abstract:

Background

Insights into the onset of evolutionary novelties are key to the understanding of amniote origins and diversification. The possession of an impedance-matching tympanic middle ear is characteristic of all terrestrial vertebrates with a sophisticated hearing sense and an adaptively important feature of many modern terrestrial vertebrates. Whereas tympanic ears seem to have evolved multiple times within tetrapods, especially among crown-group members such as frogs, mammals, squamates, turtles, crocodiles, and birds, the presence of true tympanic ears has never been recorded in a Paleozoic amniote, suggesting they evolved fairly recently in amniote history.

Methodology/Principal Findings

In the present study, we performed a morphological examination and a phylogenetic analysis of poorly known parareptiles from the Middle Permian of the Mezen River Basin in Russia. We recovered a well-supported clade that is characterized by a unique cheek morphology indicative of a tympanum stretching across large parts of the temporal region to an extent not seen in other amniotes, fossil or extant, and a braincase specialized in showing modifications clearly related to an increase in auditory function, unlike the braincase of any other Paleozoic tetrapod. In addition, we estimated the ratio of the tympanum area relative to the stapedial footplate for the basalmost taxon of the clade, which, at 23:1, is in close correspondence to that of modern amniotes capable of efficient impedance-matching hearing.


Conclusions/Significance

Using modern amniotes as analogues, the possession of an impedance-matching middle ear in these parareptiles suggests unique ecological adaptations potentially related to living in dim-light environments. More importantly, our results demonstrate that already at an early stage of amniote diversification, and prior to the Permo-Triassic extinction event, the complexity of terrestrial vertebrate ecosystems had reached a level that proved advanced sensory perception to be of notable adaptive significance.

Paper link above. Think gecko or aye-aye parareptile here.

The interesting comment?

If so, then adaptations to dim-light environments might have been the driving force not only in the diversification of the herein investigated taxa, but even more so in the procolophonoids, and were possibly an important factor in their survival of the Permo-Triassic extinction event. This interpretation can also be applied to Archosauriformes, another amniote clade that was not significantly affected by the Permio-Triassic extinction, and for which there is molecular data indicating that the clade Archosauria, which is nested within Archosauriformes, was ancestrally nocturnal [33]. In addition, the fact that Early Triassic synapsids living immediately after the extinction apparently had specific burrowing life habits [34] also suggests that adaptations to dim-light environments were potentially an important factor in the survival of the Permo-Triassic transition.

Cuz the UV blasted the diurnal species? Perhaps the PT was more selective after all?

Query: Were Mesosaurs Parareptiles or Basal Amniotes?

I'm a little bit confused. I've been reading a few different papers on parareptiles and I am getting a conflicting picture from various group's cladistic analyzes. Some place mesosaurs as parareptiles. Others have been placing them as basal amniotes. So, my appeal to the professional paleo types that read my blog at least occasionally:

What are they?

Thanx.

TYPE SPECIES! Well, New Paleo Artist, at least.

Link in the title, like always.

Cretaceous Turtle Has Eggs in CT Scan

Michael Knell carried a 75-million-year-old turtle into Bozeman Deaconess hospital recently, then laid it carefully on the bed that slides into the CT scanner.

Hardly an ordinary patient, the turtle fossil was only the second in the world found with eggs inside it, said Knell, a Montana State University graduate student in earth sciences. His turtle (from the genus Adocus) came from the Grand Staircase-Escalante National Monument in Kanab, Utah. The previously described turtle, which was found in Alberta, is also an Adocus and lived about the same time. Knell wanted his fossil scanned to see if he could find a skull and more eggs and learn whether or not the eggs contained embryos.

"It allows us to peer inside without digging into it," Knell said. "It gives us a hands-off look without having to break anything."

"It's very cool," added Frankie Jackson, an MSU paleontologist who specializes in eggs.

The CT machine looks like a giant doughnut with a narrow bed attached. Patients normally lay on the bed, then ride through the scanner while it takes images of a particular area. In this case, Knell wanted to scan the entire turtle. Although the edges of its shell were missing, the fossil measured about one foot across and weighed 40 to 50 pounds.

[...]

Spence operated the scanner from an adjoining room while Knell and Jackson looked over her shoulders. As the CT scanner took cross-sections of the fossil, white images appeared -- slice by slice -- on Spence's computer screen.

"It's very, very dense," Spence said of the shell. "You can lose some detail when that happens. You have to penetrate enough to see, but you can sometime lose detail that way."

Jackson said CT scans generally work better on fossils than X-rays and MRIs do.

"Usually embryo bone doesn't show up too well on a CT scan, so we might no be able to see embryos very well, but it could clue you in that you need to look at the eggs a little closer," Jackson added.

As time went by, the scientists realized that the eggs weren't showing up as clearly as they'd expected and they'd need to examine the images more closely. As a result, Spence saved her images to a disc and gave it to Knell. He and Jackson said they would contact the Museum of the Rockies, which has special software for looking at CT images from a variety of angles. The researchers expect to present their findings during the fourth international Symposium on Dinosaur Eggs and Babies. Knell's adviser, David Varricchio, and Jackson are organizing the event, which will be held Aug. 8-10 at MSU.

sweet! Anyone have pix?

Mexican Cretaceous Sea Turtle Fossil Found

Paleontologists on Thursday unveiled the oldest fossil remains of a sea turtle that lived 72 million years ago in northern Mexico, the National Institute of Anthropology and History (INAH) said.

"It is the oldest sea turtle of its kind and it belongs to the chelonia family. The oldest specimen of this species up to now was 65 million years old and was found in New Jersey, United States," the INAH said in a statement.

The fossils of seven sea turtles were found at different sites in Coahuila, the state that Mexican scientists call "the paradise of paleontology."

I presume that this is a oldest modern sea turtle...

Odontochelys Rendition

To Osteoderm or Not Osteoderm?

With hard bony shells to shelter and protect them, turtles are unique and have long posed a mystery to scientists who wonder how such an elegant body structure came to be.

Since the age of dinosaurs, turtles have looked pretty much as they do now with their shells intact, and scientists lacked conclusive evidence to support competing evolutionary theories. Now with the discovery in China of the oldest known turtle fossil, estimated at 220- million-years-old, scientists have a clearer picture of how the turtle got its shell.

Working with colleagues in China and Canada, Olivier Rieppel, PhD, chairman of The Field Museum's department of geology, has analyzed the Chinese turtle fossil, finding evidence to support the notion that turtle shells are bony extensions of their backbones and ribs that expanded and grew together to form a hard protective covering.

The fossilized turtle ancestor, dubbed Odontochelys semitestacea (translation: half-shelled turtle with teeth), likely lived in the water rather than on land.

A report from Chun Li of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences in Beijing, and Xiao-Chun Wu of the Canadian Museum of Nature in Ottawa, along with Field's Rieppel, will appear in the journal Nature. Other co-authors include Li-Ting Wang of the Geological Survey of Guizhou Province in Guiyang, China, where the fossil was discovered and Li-Jun Zhao of the Zhejiang Museum of Nature History in Hangzhou, China.

Prior to discovery of Odontochelys, the oldest known turtle specimen was Proganochelys, which was found in Germany. Because Proganochelys has a fully-formed shell, it provides little information about how shells were formed. Odontochelys is older than Proganochelys and is helpful because it has only a partial shell, Rieppel said.

"This is the first turtle with an incomplete shell," Rieppel said. "The shell is an evolutionary innovation. It's difficult to explain how it evolved without an intermediate example."

Some contemporary reptiles such as crocodiles have skin with bony plates and this was also seen in ancient creatures such as dinosaurs. Some researchers theorized that turtle shells started as bony skin plates, called osteoderms, which eventually fused to form a hard shell.

There are problems with this idea, including studies of how shells form in turtle embryos as they develop within eggs, Rieppel said. Embryo studies show that the turtle backbones expand outward and the ribs broaden to meet and form a shell, he said.

While paleontologists take such studies into account, they aren't sufficient to prove how anatomy evolved over time, and evidence can be read in different ways. The limbs of Proganochelys, for example, show signs of bony plates in the skin.

But Odontochelys has no osteoderms and it has a partial shell extending from its backbone, Rieppel said. It also shows a widening of ribs. Although Odontochelys has only a partial shell protecting its back, it does have a fully formed plastron – complete protection of its underside – just as turtles do today.

This strongly suggests Odontochelys was a water dweller whose swimming exposed its underside to predators, Rieppel said. "Reptiles living on the land have their bellies close to the ground with little exposure to danger," he said.

Other arguments favor the notion that turtle shells evolved as extensions of the reptile's backbones and ribs, Rieppel said, but the partial shell of Odontochelys speaks very clearly.

"This animal tells people to forget about turtle ancestors covered with osteoderms," he said.

That's interesting because Bill Parker blogged about a recent fossil that indicated that osteoderms were the likely ancestral form of the turtle shell. Y'know, I have to wonder if turtles are actually paraphyletic. Could we be seeing multiple linages with convergence? Just a thought.

Eileanchelys waldmani: Transitional Turtle

(image credit: BBC)

Fossils of the earliest known swimming turtles have been uncovered on an island in northwest Britain, scientists reported today.

The fossils of the previously unknown species suggest turtles first took to water during the Middle Jurassic period (180 to 160 million years ago).

Four crushed but intact skeletons had been found along with the remains of two other specimens, in a single slab of rock in 2004 on Scotland's Isle of Skye. Since then, researchers have painstakingly freed the fossils.

The fossils belonged to a pond turtle, Eileanchelys waldmani, which bridges the evolutionary gap between primitive land turtles and modern aquatic turtles.

Turtles first appeared in the Triassic period some 210 million years ago. They were exclusively land creatures, said study team member Jérémy Anquetin, a French Ph.D. student at the Natural History Museum in London.

These earliest turtles were heavy, lumbering creatures armed with thick shells and protective spikes, he said.

But the new fossil turtle had a domed, tortoise-like shell measuring up to 11.8 inches (30 centimeters) long and it was much more delicately built.

"It's light framed, just like an aquatic turtle," Anquetin said.

"Until the discovery of Eileanchelys, we thought that adaptation to aquatic habitat might have appeared among primitive turtles, but we had no fossil evidence of that," he added.

"Now we know for sure that there were aquatic turtles around 164 million years ago," Anquetin said.

Kewl! Callovian anapsida fossils! Woot! BBC also has a very nice science article on the subject. Whew. I was worried I'd only get HPC related posts out today.

Skulls

I found this while googling for something else. I was under the impression that anapsids were no longer considered basal most due to some dna testing found that turtles are derived diapsids. What that does to the other anapsids place in the world, IDK. In fact, many books/papers I have read have brought that up making it sound as though there are exceedingly few Permian anapsid specialists. Anyone really know?

NatGeo Adds a Little More to the Triassic Burrows

Anthony Martin is a paleontologist at Emory University in Atlanta who was not involved with the study.

"Burrows give a major survival advantage to whoever is living in them," Martin said.

"So there were good reasons for why Mesozoic animals were burrowing to avoid freezing temperatures outside the burrow, all while getting away from predators or safely raising their young."

Except I don't think cold was much of a problem in the early Triassic. Somehow I don't think the Olenekian was terribly cold. The NatGeo article never mentions the procs and only talks about Thrinaxodon.

Early Triassic Burrow Found in Antarctica

For the first time paleontologists have found fossilized burrows of tetrapods – any land vertebrates with four legs or leglike appendages – in Antarctica dating from the Early Triassic epoch, about 245 million years ago.

The fossils were created when fine sand from an overflowing river poured into the animals' burrows and hardened into casts of the open spaces. The largest preserved piece is about 14 inches long, 6 inches wide and 3 inches deep. No animal remains were found inside the burrow casts, but the hardened sediment in each burrow preserved a track made as the animals entered and exited.

In addition, scratch marks from the animals' initial excavation were apparent in some places, said Christian Sidor, a University of Washington assistant professor of biology and curator of vertebrate paleontology at the Burke Museum of Natural History and Culture at the UW.

"We've got good evidence that these burrows were made by land-dwelling animals rather than crayfish," said Sidor, who is lead author of a paper describing the find, which is being published in the June edition of The Journal of Vertebrate Paleontology.

Co-authors are Molly Miller, a geology professor at Vanderbilt University, and John Isbell, a geosciences professor at the University of Wisconsin-Milwaukee. The work was funded by the National Science Foundation.

Fossils of tetrapod bones from later in the Triassic period have been found in a section of Antarctica called Victoria Land, but the fossil burrows predate those bone fossils by at least 15 million years, Sidor said.

The fossilized burrows were collected in 2003 and 2005-06 from the Fremouw Formation at Wahl Glacier and from the Lashly Formation at Allan Hills, both toward the outer edges of Antarctica.

Despite the absence of fossil bones, the burrows' relatively small size prompted Sidor to speculate that their owners might have been small lizardlike reptiles called Procolophonids or an early mammal relative called Thrinaxodon.

At least they didn't call Thrinaxodon at "mammal-like reptile" this time. The New Scientist all but commits this sin: be careful, the NS draws some conclusions that may - or may not - be true. However, some explanations are in order here.

Traditionally, there are three big groups of amniotes that people talk about, the anapsids, synapsids, and diapsids. These were all based on the number of holes in the skull of an amniote. Anapsids had none. Synapsids have one. Diapsids have two. Of the anapsids, it has been argued, only the turtles remain (and even some contest this!) The rest went extinct between the Permian extinction and some time in the Triassic by and large. The synapsids have also undergone a great winnowing of their numbers. Once there were a great number of different types. Between the Permian Extinction to, possibly, the Paleocene all but one lineage of this amazing group died out. Who is that one remaing lineage? The mammals. You and I and even your cat, though your cat would never admit any kinship. The diapsids actually are probably more diverse than the rest of us: they're the other traditional reptiles (lizards, snakes, etc) and...birds. The two candidate critters according to the article that might have made the burrows are the procolophonids and Thrinaxodon. The Procolophonids were anapsids. Thrinaxodon is a synapsid. Initially, the procs, as I'll call them for now, were largely insectivorous. They filled a role not all that different from modern lizards, but would also become herbivorous not unlike how some lizards do. Thrinaxodon was definitely a carnivore and it definitely known that this, erm, puppy was a burrower.

One of the interesting bits about this is where they were found. If you take a look at where Antarctic was at the time, it was very, very far south. If you take into account the climate, if these burrows were made by procs, then it helps verify that the climate was very warm: the procs were never warmed blooded. Thrinaxodon, otoh, very well may have been warm blooded and, in fact, probably was: the cynodonts, which Thrinaxodon was a member of, were what mammals evolved out of as far as we can tell and based on other information we have from other pre-Thrinaxodon therapsids (a kind of synapsid), endothermy arose during the Permian among this lineage. Other therapsids, for what its worth, that I have written about are the dicynodonts and the gorgonopsids. At some point, hopefully before the end of the year, I am going to write about the therocephalians as well. And the Permian terrestrial ecology. And the No Permian Extinction evolution.

Oy.

Rockets first though.