Turtles are Diapsids Follow up

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That's Settled: New Triassic Fossils Show Turtles Were had Diapsid, not Parareptilian Ancestry

The diapsid origin of turtles

Authors:

Schoch et al

Abstract:

The origin of turtles has been a persistent unresolved problem involving unsettled questions in embryology, morphology, and paleontology. New fossil taxa from the early Late Triassic of China (Odontochelys) and the Late Middle Triassic of Germany (Pappochelys) now add to the understanding of (i) the evolutionary origin of the turtle shell, (ii) the ancestral structural pattern of the turtle skull, and (iii) the phylogenetic position of Testudines. As has long been postulated on the basis of molecular data, turtles evolved from diapsid reptiles and are more closely related to extant diapsids than to parareptiles, which had been suggested as stem group by some paleontologists. The turtle cranium with its secondarily closed temporal region represents a derived rather than a primitive condition and the plastron partially evolved through the fusion of gastralia.

Multiple Tooth-rowed Captorhinids from the Early Permian Oklahoma

Multiple tooth-rowed captorhinids from the Early Permian fissure fills of the Bally Mountain Locality of Oklahoma

Authors:

Leblanc et al

Abstract:

Captorhinids were Paleozoic eureptiles that originated in the Late Pennsylvanian in Laurasia and dispersed across the major landmasses of Pangaea by the Late Permian. Their evolutionary success as omnivorous and herbivorous members of Permian terrestrial communities has been attributed to the evolution of multiple marginal tooth rows. Multiple tooth rows evolved at least twice within Captorhinidae: once in the omnivorous Captorhinus aguti and again in the diverse subfamily of herbivorous moradisaurines. The earliest known moradisaurines co-occured with C. aguti in Lower Permian strata of Texas; however C. aguti is also known from much older fissure fills in the famous Dolese Brothers quarry near Richards Spur, Oklahoma, suggesting that C. aguti preceded any other multiple-rowed captorhinid. Here we report on new material of multiple-rowed captorhinids from the Lower Permian fissure fills of the Bally Mountain locality in Oklahoma, only 35 miles from Richards Spur. Some of this material is referrable to Captorhinikos valensis, which was previously only known from younger strata in Texas, making this species the geologically and phylogenetically oldest moradisaurine. Furthermore, we determined that Ca. valensis co-existed with C. aguti at Bally Mountain and we explore the potential for niche partitioning in these early captorhinids. Lastly, we assess the potential temporal and environmental differences between Bally Mountain and Richards Spur, in order to explain the abundance of herbivorous moradisaurines at Bally Mountain and the complete lack of moradisaurines at the neighbouring Richards Spur locality.

Tetrapodophis amplectus: That Controversial Four Legged Snake From Aptian Cretaceous Brazil

A four-legged snake from the Early Cretaceous of Gondwana

Authors:

Martill et al

Abstract:

Snakes are a remarkably diverse and successful group today, but their evolutionary origins are obscure. The discovery of snakes with two legs has shed light on the transition from lizards to snakes, but no snake has been described with four limbs, and the ecology of early snakes is poorly known. We describe a four-limbed snake from the Early Cretaceous (Aptian) Crato Formation of Brazil. The snake has a serpentiform body plan with an elongate trunk, short tail, and large ventral scales suggesting characteristic serpentine locomotion, yet retains small prehensile limbs. Skull and body proportions as well as reduced neural spines indicate fossorial adaptation, suggesting that snakes evolved from burrowing rather than marine ancestors. Hooked teeth, an intramandibular joint, a flexible spine capable of constricting prey, and the presence of vertebrate remains in the guts indicate that this species preyed on vertebrates and that snakes made the transition to carnivory early in their history. The structure of the limbs suggests that they were adapted for grasping, either to seize prey or as claspers during mating. Together with a diverse fauna of basal snakes from the Cretaceous of South America, Africa, and India, this snake suggests that crown Serpentes originated in Gondwana.

Was Kungurian Permian captorhinid Eureptile Captorhinikos valensis a Herbivore?

The captorhinid reptile Captorhinikos valensis from the lower Permian Vale Formation of Texas, and the evolution of herbivory in eureptiles

Authors:

Modesto et al

Abstract:

Captorhinikos valensis is a poorly known, multiple-tooth-rowed captorhinid reptile from the Lower Permian Vale Formation of Texas. Our reappraisal of C. valensis reveals it to be a small moradisaurine, exhibiting a maximum of five rows of bullet-shaped teeth in the multiple-rowed region of both the maxilla and the dentary. The slightly radiating organization of the tooth rows distinguishes C. valensis from the parallel arrangement of the tooth rows exhibited by all other moradisaurines. Captorhinikos valensis is also distinguishable from the coeval moradisaurine Labidosaurikos meachami by a more conspicuously denticulated, broader, ‘U’-shaped transverse flange of the pterygoid, a plesiomorphic morphology shared with the large, single-rowed captorhinid Labidosaurus hamatus. Postcranial information is limited to two short series of presacral vertebrae not associated with the cranial materials; open neurocentral sutures are present in one specimen, indicating immaturity at death. We investigated the relationships of C. valensis to other captorhinids by adding it to the data matrix of a previously published analysis that included several moradisaurine captorhinids. A branch-and-bound PAUP analysis discovered a single optimal tree. Whereas a previous analysis of captorhinid interrelationships found the (undifferentiated) genus Captorhinikos to fall outside of a clade composed of L. hamatus and the large moradisaurines, our analysis recovered C. valensis in a clade with the genera Labidosaurikos, Gansurhinus, Moradisaurus, and Rothianiscus (i.e., Moradisaurinae sensu stricto), and Captorhinikos chozaensis as the sister species of a clade that includes L. hamatus and Moradisaurinae s.s.; Captorhinikos chozaensis is no longer classifiable as a moradisaurine (according to our phylogenetic definition for the group), and should be assigned to a new genus. Stratigraphic calibration of our captorhinid phylogeny indicates that moradisaurines evolved by the middle Kungurian (middle Leonardian).

Monitor Lizards in Miocene Neogene Spain

Early Miocene dispersal of the lizard Varanus into Europe: Reassessment of vertebral material from Spain

Authors:

Delfino et al

Abstract:

Iberovaranus Hoffstetter, 1969 was erected as a monotypic genus of varanine varanid lizard on the basis of a single trunk vertebra from the Miocene of Spain. Thanks to the study of the holotype, as well as of a still undescribed cervical vertebra from the same locality, we show that the vertebral morphology of Iberovaranus is contained within the known variability of Varanus. Therefore, Iberovaranus Hoffstetter, 1969 is considered a subjective junior synonym of Varanus Merrem, 1820, and the species Iberovaranus catalaunicus Hoffstetter, 1969 should be considered a nomen dubium.

Turtles: The Phylogenic Hockey Puck of Modern Zoology/Paleontology

Using Genes as Characters and a Parsimony Analysis to Explore the Phylogenetic Position of Turtles

Authors:

Lu et al

Abstract:

The phylogenetic position of turtles within the vertebrate tree of life remains controversial. Conflicting conclusions from different studies are likely a consequence of systematic error in the tree construction process, rather than random error from small amounts of data. Using genomic data, we evaluate the phylogenetic position of turtles with both conventional concatenated data analysis and a “genes as characters” approach. Two datasets were constructed, one with seven species (human, opossum, zebra finch, chicken, green anole, Chinese pond turtle, and western clawed frog) and 4584 orthologous genes, and the second with four additional species (soft-shelled turtle, Nile crocodile, royal python, and tuatara) but only 1638 genes. Our concatenated data analysis strongly supported turtle as the sister-group to archosaurs (the archosaur hypothesis), similar to several recent genomic data based studies using similar methods. When using genes as characters and gene trees as character-state trees with equal weighting for each gene, however, our parsimony analysis suggested that turtles are possibly sister-group to diapsids, archosaurs, or lepidosaurs. None of these resolutions were strongly supported by bootstraps. Furthermore, our incongruence analysis clearly demonstrated that there is a large amount of inconsistency among genes and most of the conflict relates to the placement of turtles. We conclude that the uncertain placement of turtles is a reflection of the true state of nature. Concatenated data analysis of large and heterogeneous datasets likely suffers from systematic error and over-estimates of confidence as a consequence of a large number of characters. Using genes as characters offers an alternative for phylogenomic analysis. It has potential to reduce systematic error, such as data heterogeneity and long-branch attraction, and it can also avoid problems associated with computation time and model selection. Finally, treating genes as characters provides a convenient method for examining gene and genome evolution.

and...

Turtle origins: insights from phylogenetic retrofitting and molecular scaffolds

Author:

M. S. Y. Lee

Abstract:

Adding new taxa to morphological phylogenetic analyses without substantially revising the set of included characters is a common practice, with drawbacks (undersampling of relevant characters) and potential benefits (character selection is not biased by preconceptions over the affinities of the ‘retrofitted’ taxon). Retrofitting turtles (Testudines) and other taxa to recent reptile phylogenies consistently places turtles with anapsid-grade parareptiles (especially Eunotosaurus and/or pareiasauromorphs), under both Bayesian and parsimony analyses. This morphological evidence for turtle–parareptile affinities appears to contradict the robust genomic evidence that extant (living) turtles are nested within diapsids as sister to extant archosaurs (birds and crocodilians). However, the morphological data are almost equally consistent with a turtle–archosaur clade: enforcing this molecular scaffold onto the morphological data does not greatly increase tree length (parsimony) or reduce likelihood (Bayesian inference). Moreover, under certain analytic conditions, Eunotosaurus groups with turtles and thus also falls within the turtle–archosaur clade. This result raises the possibility that turtles could simultaneously be most closely related to a taxon traditionally considered a parareptile (Eunotosaurus) and still have archosaurs as their closest extant sister group.

Do Reptile Embryos Have the Capacity to Thermoregulate?

Can Reptile Embryos Influence Their Own Rates of Heating and Cooling?

Authors:

1. Wei-Guo Du (a,b)

2. Ming-Chung Tu (a,c)

3. Rajkumar S. Radder (a)

4. Richard Shine (a)

Affiliations:

a. School of Biological Sciences, University of Sydney, Sydney, New South Wales, Australia

b. Key Lab of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, People’s Republic of China

c. Department of Life Science, National Taiwan Normal University, Taipei, Taiwan

Abstract:

Previous investigations have assumed that embryos lack the capacity of physiological thermoregulation until they are large enough for their own metabolic heat production to influence nest temperatures. Contrary to intuition, reptile embryos may be capable of physiological thermoregulation. In our experiments, egg-sized objects (dead or infertile eggs, water-filled balloons, glass jars) cooled down more rapidly than they heated up, whereas live snake eggs heated more rapidly than they cooled. In a nest with diel thermal fluctuations, that hysteresis could increase the embryo’s effective incubation temperature. The mechanisms for controlling rates of thermal exchange are unclear, but may involve facultative adjustment of blood flow. Heart rates of snake embryos were higher during cooling than during heating, the opposite pattern to that seen in adult reptiles. Our data challenge the view of reptile eggs as thermally passive, and suggest that embryos of reptile species with large eggs can influence their own rates of heating and cooling.

Eocene Lizard Fossil Skin Put Through Synchotron...And Teeth Found!

Synchrotron-based imaging techniques of a 50 million-year-old lizard skin have identified the presence of teeth which are invisible to visible light, demonstrating for the first time that this fossil animal was more than just a skin moult.

Researchers used Synchrotron Rapid Screening X-ray Fluorescence at the Stanford Synchrotron Radiation Lightsource in California to map the chemical make up of a rare fossil lizard skin - powerful x-rays enabled the team to map the presence of phosphorus from teeth in this ancient reptile.

The relative position of the phosphorous in the skin fossil helped the scientists identify the type of lizard. They believe that the more elongated snout in conjunction with the general jaw shape bears a strong resemblance to a shinisaurid lizard (Bahndwivici ammoskius). The presence of phosphorous also demonstrates for the first time that the fossil skin is more than just a moult, as no lizards can shed their teeth along with their skin!

Dr. Phil Manning from the Palaeontology Research group at the University of Manchester said, "Finding the presence of teeth changes almost everything we thought we knew about this fossil. We can identify the type of lizard for the first time, based upon the geometry of the teeth. Our findings also raise some fascinating questions about what happened to the animal after its death. What wiped out its bones but preserved the skin and the ghost of its teeth?

"The technique permits us to tease-out chemical information from fossils, information that you simply cannot see with the naked eye. Such chemical maps can help us see 'ghosts' of original biological structures that only remain in very dilute concentrations in the fossil."

83% of All Squamates Were Wiped Out by Chicxulub Impact (and the president gets his own fossil lizard)

The asteroid collision widely thought to have killed the dinosaurs also led to extreme devastation among snake and lizard species, according to new research — including the extinction of a newly identified lizard species Yale and Harvard scientists have named Obamadon gracilis.

"The asteroid event is typically thought of as affecting the dinosaurs primarily," said Nicholas R. Longrich, a postdoctoral associate with Yale's Department of Geology and Geophysics and lead author of the study. "But it basically cut this broad swath across the entire ecosystem, taking out everything. Snakes and lizards were hit extremely hard."

The study was scheduled for online publication the week of Dec. 10 in the Proceedings of the National Academy of Sciences.

Earlier studies have suggested that some snake and lizard species (as well as many mammals, birds, insects and plants) became extinct after the asteroid struck the earth 65.5 million years ago, on the edge of the Yucatan Peninsula. But the new research argues that the collision's consequences were far more serious for snakes and lizards than previously understood. As many as 83 percent of all snake and lizard species died off, the researchers said — and the bigger the creature, the more likely it was to become extinct, with no species larger than one pound surviving.

The results are based on a detailed examination of previously collected snake and lizard fossils covering a territory in western North America stretching from New Mexico in the southwestern United States to Alberta, Canada. The authors examined 21 previously known species and also identified nine new lizards and snakes.

They found that a remarkable range of reptile species lived in the last days of the dinosaurs. Some were tiny lizards. One snake was the size of a boa constrictor, large enough to take the eggs and young of many dinosaur species. Iguana-like plant-eating lizards inhabited the southwest, while carnivorous lizards hunted through the swamps and flood plains of what is now Montana, some of them up to six feet long.

"Lizards and snakes rivaled the dinosaurs in terms of diversity, making it just as much an 'Age of Lizards' as an 'Age of Dinosaurs,'" Longrich said.

The scientists then conducted a detailed analysis of the relationships of these reptiles, showing that many represented archaic lizard and snake families that disappeared at the end of the Cretaceous, following the asteroid strike.

One of the most diverse lizard branches wiped out was the Polyglyphanodontia. This broad category of lizards included up to 40 percent of all lizards then living in North America, according to the researchers. In reassessing previously collected fossils, they came across an unnamed species and called it Obamadon gracilis. In Latin, odon means "tooth" and gracilis means "slender."

"It is a small polyglyphanodontian distinguished by tall, slender teeth with large central cusps separated from small accessory cusps by lingual grooves," the researchers write of Obamadon, which is known primarily from the jaw bones of two specimens. Longrich said the creature likely measured less than one foot long and probably ate insects.

Paper link.