A Three-Dimensional Skeletal Reconstruction of Diadectid Amniote Orobates pabsti

A Three-Dimensional Skeletal Reconstruction of the Stem Amniote Orobates pabsti (Diadectidae): Analyses of Body Mass, Centre of Mass Position, and Joint Mobility

Authors:

Nyakatura et al

Abstract:

Orobates pabsti, a basal diadectid from the lower Permian, is a key fossil for the understanding of early amniote evolution. Quantitative analysis of anatomical information suffers from fragmentation of fossil bones, plastic deformation due to diagenetic processes and fragile preservation within surrounding rock matrix, preventing further biomechanical investigation. Here we describe the steps taken to digitally reconstruct MNG 10181, the holotype specimen of Orobates pabsti, and subsequently use the digital reconstruction to assess body mass, position of the centre of mass in individual segments as well as the whole animal, and study joint mobility in the shoulder and hip joints. The shape of most fossil bone fragments could be recovered from micro-focus computed tomography scans. This also revealed structures that were hitherto hidden within the rock matrix. However, parts of the axial skeleton had to be modelled using relevant isolated bones from the same locality as templates. Based on the digital fossil, mass of MNG 10181 was estimated using a model of body shape that was varied within a plausible range to account for uncertainties of the dimension. In the mean estimate model the specimen had an estimated mass of circa 4 kg. Varying of the mass distribution amongst body segments further revealed that Orobates carried most of its weight on the hind limbs. Mostly unrestricted joint morphology further suggested that MNG 10181 was able to effectively generate propulsion with the pelvic limbs. The digital reconstruction is made available for future biomechanical studies.

High Extinction Rates Trigger Diversification in Amniotes

Elevated Extinction Rates as a Trigger for Diversification Rate Shifts: Early Amniotes as a Case Study

Authors:

Brocklehurst et al

Abstract:

Tree shape analyses are frequently used to infer the location of shifts in diversification rate within the Tree of Life. Many studies have supported a causal relationship between shifts and temporally coincident events such as the evolution of “key innovations”. However, the evidence for such relationships is circumstantial. We investigated patterns of diversification during the early evolution of Amniota from the Carboniferous to the Triassic, subjecting a new supertree to analyses of tree balance in order to infer the timing and location of diversification shifts. We investigated how uneven origination and extinction rates drive diversification shifts, and use two case studies (herbivory and an aquatic lifestyle) to examine whether shifts tend to be contemporaneous with evolutionary novelties. Shifts within amniotes tend to occur during periods of elevated extinction, with mass extinctions coinciding with numerous and larger shifts. Diversification shifts occurring in clades that possess evolutionary innovations do not coincide temporally with the appearance of those innovations, but are instead deferred to periods of high extinction rate. We suggest such innovations did not cause increases in the rate of cladogenesis, but allowed clades to survive extinction events. We highlight the importance of examining general patterns of diversification before interpreting specific shifts.

Were Amniote Lungs Basally Complex?

Lungs of the first amniotes: why simple if they can be complex?

Authors:

Lambertz et al

Abstract:

We show—in contrast to the traditional textbook contention—that the first amniote lungs were complex, multichambered organs and that the single-chambered lungs of lizards and snakes represent a secondarily simplified rather than the plesiomorphic condition. We combine comparative anatomical and embryological data and show that shared structural principles of multichamberedness are recognizable in amniotes including all lepidosaurian taxa. Sequential intrapulmonary branching observed during early organogenesis becomes obscured during subsequent growth, resulting in a secondarily simplified, functionally single-chambered lung in lepidosaurian adults. Simplification of pulmonary structure maximized the size of the smallest air spaces and eliminated biophysically compelling surface tension problems that were associated with miniaturization evident among stem lepidosaurmorphs. The remaining amniotes, however, retained the multichambered lungs, which allowed both large surface area and high pulmonary compliance, thus initially providing a strong selective advantage for efficient respiration in terrestrial environments. Branched, multichambered lungs instead of simple, sac-like organs were part and parcel of the respiratory apparatus of the first amniotes and pivotal for their success on dry land, with the sky literally as the limit.

Erpetonyx arsenaultorum: a new and Oldest Known Parareptile From Gzhelian Pennsylvannian Carboniferous Prince Edward Island

The oldest parareptile and the early diversification of reptiles

Authors:

Modesto et al

Abstract:

Amniotes, tetrapods that evolved the cleidoic egg and thus independence from aquatic larval stages, appeared ca 314 Ma during the Coal Age. The rapid diversification of amniotes and other tetrapods over the course of the Late Carboniferous period was recently attributed to the fragmentation of coal-swamp rainforests ca 307 Ma. However, the amniote fossil record during the Carboniferous is relatively sparse, with ca 33% of the diversity represented by single specimens for each species. We describe here a new species of reptilian amniote that was collected from uppermost Carboniferous rocks of Prince Edward Island, Canada. Erpetonyx arsenaultorum gen. et sp. nov. is a new parareptile distinguished by 29 presacral vertebrae and autapomorphies of the carpus. Phylogenetic analyses of parareptiles reveal E. arsenaultorum as the closest relative of bolosaurids. Stratigraphic calibration of our results indicates that parareptiles began their evolutionary radiation before the close of the Carboniferous Period, and that the diversity of end-Carboniferous reptiles is 80% greater than suggested by previous work. Latest Carboniferous reptiles were still half as diverse as synapsid amniotes, a disparity that may be attributable to preservational biases, to collecting biases, to the origin of herbivory in tetrapods or any combination of these factors.

Deltavjatia rossicus: a Lopingian Permian Pareiasaur From Russia Redescribed

Anatomy, cranial ontogeny and phylogenetic relationships of the pareiasaur Deltavjatia rossicus from the Late Permian of central Russia

Authors:

Linda A. Tsuji

Abstract:

New material of the pareiasaur Deltavjatia rossicus from the Kotel'nich locality, Kirov Province, Russia, is described in detail. The taxon is characterised by a distinctive pattern of dermal sculpture and the exaggerated embayment of the posterior skull roof, resulting in the dorsal exposure of the braincase. Postcranially, Deltavjatia shares some aspects of its morphology with basal pareiasaurs, including the osteoderm pattern. Features such as the forward-slanting and pointed iliac blade are shared with stratigraphically younger, more derived forms. Well-preserved material of the taxon spans a wide size-range, allowing an assessment of ontogenetic trends. A geometric morphometric analysis of the skull roof of Deltavjatia reveals an allometric increase in snout length and postorbital area, a result that can serve as a basis for examining morphological trends within pareiasaurs. A reassessment of pareiasauromorph relationships, using both parsimony and Bayesian methods of phylogenetic inference, recovers similar topologies in both cases. Four Bayesian analyses were completed, with and without a gamma-shaped parameter and with and without the inclusion of autapomorphies. Despite differing taxon and outgroup selection, the recovered topologies are similar to previous phylogenies of pareiasaurian relationships, with Deltavjatia appearing as a relatively basal taxon.

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.

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?

Salties Use Ocean Currents for Oceanic Travel

How did the world's largest living reptile, the saltwater crocodile, reach so many South Pacific islands separated by huge stretches of water despite being a poor swimmer?

Apparently, like a surfer catching a wave, these goliaths can ride currents on the ocean surface to cross large areas of open sea, researchers now reveal.

[...]

There were already many anecdotal accounts of large crocodiles sighted far out at sea, but nothing confirmed. Now, for the first time, using sonar transmitters and satellite tracking, scientists now find that saltwater crocodiles actually do ride surface ocean currents for long-distance travel, enabling them to voyage from one oceanic island to another.

"Because these crocodiles are poor swimmers, it is unlikely that they swim across vast tracts of ocean," said researcher Hamish Campbell, a behavioral ecologist from University of Queensland in Australia. "But they can survive for long periods in saltwater without eating or drinking, so by only traveling when surface currents are favorable, they would be able to move long distances by sea."

[...]

Working at the remote Kennedy River in northeastern Australia, the team of scientists - which included the late Steve Irwin, "The Crocodile Hunter" - tagged 27 adult seawater crocodiles with sonar transmitters, employing 20 underwater receivers deployed along a 39-mile-long stretch of the river (63 km) to track the reptiles' every move for more than 12 months. They found both male and female adult crocodiles undertook long-distance journeys, regularly traveling more than 30 miles (48 km) from their home area to the river mouth and beyond into open sea.

The scientists also discovered the "salties" always began long-distance travel within an hour of the tide changing, allowing them to go with the flow. They halted their journeys by hauling out onto the river bank or diving to the river bottom when the currents turned against them.

[...]

After they made their discovery on the river, Campbell and his colleagues re-analyzed archival data from the few crocodiles that have been satellite tracked while undertaking ocean travel. By overlaying the reptiles' movements with surface current estimates, they found the strategy of ocean-swimming crocodiles was similar to what they employed with rivers.

One satellite-tagged crocodile, 12.6-foot-long male (3.8 meters) - left the Kennedy River and travelled 366 miles (590 km) over 25 days, timing its journey to coincide with a seasonal current system that develops in the Gulf of Carpentaria.

Another croc - a 15.8-foot-long male (4.8 meters) - traveled more than 255 miles (411 km) in only 20 days through the Torres Straits, which are notorious for strong water currents. When the reptile arrived at the straits, the currents were moving opposite to his direction of travel - he then waited in a sheltered bay for four days and only passed through the straits when the currents switched to favor his journey.

These findings could explain why this crocodile species did not split into many other species despite occupying islands across such a large range, where in principle populations could have been isolated and diverged from their relatives over time.

"Regular mixing between the island populations probably occurs," Campbell said. "Crocodilians have crossed major marine barriers during their evolutionary past."

awesome.

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.

Permian Basal Synapsid Cladistics

Eothyris and Oedaleops: Do These Early Permian Synapsids from Texas and New Mexico form a Clade?

1. Robert R. Reisz (A,*)
2. Stephen J. Godfrey (A,B)
3. Diane Scott (A)

A. Department of Biology, University of Toronto at Mississauga, 3359 Mississauga Road, Mississauga, Ontario, L5L 1C6, Canada, robert.reisz@utoronto.ca;

B. Present Address: Department of Paleontology, Calvert Marine Museum, P.O. Box 97, Solomons, Maryland, 20688, U.S.A., Godfresj@co.cal.md.us

* Corresponding author.

Abstract:

The monospecific genera Eothyris (Petrolia Formation, Leonardian, Archer County, Texas) and Oedaleops (Abo/Cutler Formation, Wolfcampian, Rio Arriba County, New Mexico), known solely from cranial remains, are confidently assigned to the monophyletic Caseasauria based on cranial and dental characters. In addition, Eothyris and Oedaleops comprise the monophyletic Eothyrididae based on nine cranial and dental characters. In contrast to the medium to large sized herbivorous caseids, the small eothyridids exhibit dental features that indicate that they were faunivores. The presence of well-developed caniniform teeth suggests that they were predators. Both Eothyris parkeyi Romer and Oedaleops campi Langsten exhibit a suite of plesiomorphic cranial characters that identify them as basal synapsids. Thus, the eothyridids are better representatives of the primitive synapsid cranial morphotype than the oftenused ophiacodontids. Although they appear relatively late in synapsid evolution, both eothyridids are significantly older than all other caseasaurs, forcing the establishment of a long unrecorded lineage for caseids.

No time to comment. Link to paper in title.

Introducing Anoiapithecus from Miocene Spain

A unique Middle Miocene European hominoid and the origins of the great ape and human clade

1. Salvador Moyà-Solàa,1,
2. David M. Albab,c,
3. Sergio Almécijac,
4. Isaac Casanovas-Vilarc,
5. Meike Köhlera,
6. Soledad De Esteban-Trivignoc,
7. Josep M. Roblesc,d,
8. Jordi Galindoc and
9. Josep Fortunyc

-Author Affiliations

1.
aInstitució Catalana de Recerca i Estudis Avançats at Institut Català de Paleontologia (ICP) and Unitat d'Antropologia Biològica (Dipartimento de Biologia Animal, Biologia Vegetal, i Ecologia), Universitat Autònoma de Barcelona, Edifici ICP, Campus de Bellaterra s/n, 08193 Cerdanyola del Vallès, Barcelona, Spain;
2.
bDipartimento di Scienze della Terra, Università degli Studi di Firenze, Via G. La Pira 4, 50121 Florence, Italy;
3.
cInstitut Català de Paleontologia, Universitat Autònoma de Barcelona, Edifici ICP, Campus de Bellaterra s/n, 08193 Cerdanyola del Vallès, Barcelona, Spain; and
4.
dFOSSILIA Serveis Paleontològics i Geològics, S.L. c/ Jaume I núm 87, 1er 5a, 08470 Sant Celoni, Barcelona, Spain



Abstract

The great ape and human clade (Primates: Hominidae) currently includes orangutans, gorillas, chimpanzees, bonobos, and humans. When, where, and from which taxon hominids evolved are among the most exciting questions yet to be resolved. Within the Afropithecidae, the Kenyapithecinae (Kenyapithecini + Equatorini) have been proposed as the sister taxon of hominids, but thus far the fragmentary and scarce Middle Miocene fossil record has hampered testing this hypothesis. Here we describe a male partial face with mandible of a previously undescribed fossil hominid, Anoiapithecus brevirostris gen. et sp. nov., from the Middle Miocene (11.9 Ma) of Spain, which enables testing this hypothesis. Morphological and geometric morphometrics analyses of this material show a unique facial pattern for hominoids. This taxon combines autapomorphic features—such as a strongly reduced facial prognathism—with kenyapithecine (more specifically, kenyapithecin) and hominid synapomorphies. This combination supports a sister-group relationship between kenyapithecins (Griphopithecus + Kenyapithecus) and hominids. The presence of both groups in Eurasia during the Middle Miocene and the retention in kenyapithecins of a primitive hominoid postcranial body plan support a Eurasian origin of the Hominidae. Alternatively, the two extant hominid clades (Homininae and Ponginae) might have independently evolved in Africa and Eurasia from an ancestral, Middle Miocene stock, so that the supposed crown-hominid synapomorphies might be homoplastic.

I've sat on this for a couple days, so Brian posted a far, far better version of a write up than I could. Go read it.

Link to the paper at the top.

Sauropods WERE the Mesozoic Giraffes

Read about Darren, Matt and Mike's blog posts about their paper comparing sauropod vertebrae to real live animals, etc. Long story short. Sauropods really DID hold their heads up. Read about it here and here.

UPDATE: Paper is here. (warning, pdf)

Thylocoleo? Is That You?

Link at the top. Seriously, read it.

5 Million Year Old Ground Sloth Found

The nearly intact fossil of an ancient sloth that lived 5 million years ago has been unearthed in Peru, a find about 4 million years older than similar ones discovered in the Americas, researchers said.

The sloth was found beneath the cement floor of a house in the Andean region of Espinar in southern Peru when workers were installing a water system. Parts of a giant armadillo that has also been dated to 5 million years ago were also found nearby.

The sloth, about 10 feet long, was an herbivore and lived during the Mio-Pliocene era, said paleontologist Rodolfo Salas of Peru's Natural History Museum and one of the scientists on the dig sponsored by the French government.

"This skeleton of the sloth is especially important as it is the first complete skeleton of its kind that is 5 million years old in the Americas," he told Reuters. "Previously, discoveries have been made of partial skeletons of similar animals, but from the Pleistocene era, meaning from the last million years."

The sloth was found at 13,000 feet above sea level.

No time for commentary. Just to clarify though this is probably a Pliocene critter, but it does come close to being Miocene. The comment of Mio-Pliocene might have been a slip or a self correction that the reporter repeated verbatim.

I really wish more of Xenarthra had made it into modern times in the New World. Or to be more specific more of Pilosa.

Chimps Working Hard for Their Honey

Via Nat Geo.

Basal Theropods Had Bird Hands

Two handprints pressed into the mud of an ancient lakeshore 198 million years ago has given paleontologists new insights into the anatomy and evolution of early carnivorous dinosaurs. The theropod who crouched down had a bird-like forelimb structure with palms that always faced inwards, says lead researcher Andrew Milner, which indicates that they stopped using their forelimbs for walking early in their evolutionary history.

The handprints discovered in Utah are part of a larger track that clearly show the hind feet and, occasionally, the dragging tail. But at one point, Milner said, the theropod apparently stopped and crouched to rest. At that point, between the footprints, is the clear circular impression of the ischium or pelvis, “basically a butt print,” Milner said. And to each side of the tracks are the handprints, which are mirror images of each other. They clearly show the third digit pressed into the ground and traces of the second digit, with the claw curling inward. The hands were positioned as they would be for “holding on to a basketball rather than dribbling it,” [Los Angeles Times], comments paleontologist Tom Holtz, who wasn’t involved in the research.

The new study, published in the journal PLoS ONE, indicates that the unidentified species of theropod couldn’t turn the palms of its hands face down or face up like a human, but could bend them back against the arm similar to how a bird folds its wings. Jerry Harris, who coauthored the paper, said being able to fold the hands against the arms evolved before feathery wings — and at a time earlier than the period normally associated with theropods.

Sarah at Gombessa Girl has two posts on the subject. She knows the people involved and helped out to some extent it seems. Some interesting evolutionary implications here. I wonder how the "birds are not dinosaurs!!!" crowd are going to react? heh.

Paleo What-if

So what-if stegosaurs converged with sauropods more to produce a loooooong necked variety. Could we have seen vast stegosaur herds like we presume were the case with the sauropods? Or would they have been simply outcompeted as it seems was the case in OTL?