Triopticus primus: a Triassic Archosauromorph Convergent With Pachycephalosaur Dinosaurs

A Dome-Headed Stem Archosaur Exemplifies Convergence among Dinosaurs and Their Distant Relatives

Authors:

Stocker et al

Abstract:

Similarities in body plan evolution, such as wings in pterosaurs, birds, and bats or limblessness in snakes and amphisbaenians, can be recognized as classical examples of convergence among animals [1, 2, 3]. We introduce a new Triassic stem archosaur that is unexpectedly and remarkably convergent with the “dome-headed” pachycephalosaur dinosaurs that lived over 100 million years later. Surprisingly, numerous additional taxa in the same assemblage (the Otis Chalk assemblage from the Dockum Group of Texas) demonstrate the early acquisition of morphological novelties that were later convergently evolved by post-Triassic dinosaurs. As one of the most successful clades of terrestrial vertebrates, dinosaurs came to occupy an extensive morphospace throughout their diversification in the Mesozoic Era [4, 5], but their distant relatives were first to evolve many of those “dinosaurian” body plans in the Triassic Period [6, 7, 8]. Our analysis of convergence between archosauromorphs from the Triassic Period and post-Triassic archosaurs demonstrates the early and extensive exploration of morphospace captured in a single Late Triassic assemblage, and we hypothesize that many of the “novel” morphotypes interpreted to occur among archosaurs later in the Mesozoic already were in place during the initial Triassic archosauromorph, largely non-dinosaurian, radiation and only later convergently evolved in diverse dinosaurian lineages.

link.

Gualicho shinyae: a Neovenatorid Carcharodontosaurian Theropod With a Tyrannosaur-like Hand From Cenomanian Cretaceous Argentina

An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina

Authors:

Apesteguía et al

Abstract:

Background

Late Cretaceous terrestrial strata of the Neuquén Basin, northern Patagonia, Argentina have yielded a rich fauna of dinosaurs and other vertebrates. The diversity of saurischian dinosaurs is particularly high, especially in the late Cenomanian-early Turonian Huincul Formation, which has yielded specimens of rebacchisaurid and titanosaurian sauropods, and abelisaurid and carcharodontosaurid theropods. Continued sampling is adding to the known vertebrate diversity of this unit.

Methodology/ Principal Findings

A new, partially articulated mid-sized theropod was found in rocks from the Huincul Formation. It exhibits a unique combination of traits that distinguish it from other known theropods justifying erection of a new taxon, Gualicho shinyae gen. et sp. nov. Gualicho possesses a didactyl manus with the third digit reduced to a metacarpal splint reminiscent of tyrannosaurids, but both phylogenetic and multivariate analyses indicate that didactyly is convergent in these groups. Derived characters of the scapula, femur, and fibula supports the new theropod as the sister taxon of the nearly coeval African theropod Deltadromeus and as a neovenatorid carcharodontosaurian. A number of these features are independently present in ceratosaurs, and Gualicho exhibits an unusual mosaic of ceratosaurian and tetanuran synapomorphies distributed throughout the skeleton.

Conclusions/ Significance

Gualicho shinyae gen. et sp. nov. increases the known theropod diversity of the Huincul Formation and also represents the first likely neovenatorid from this unit. It is the most basal tetatanuran to exhibit common patterns of digit III reduction that evolved independently in a number of other tetanuran lineages. A close relationship with Deltadromaeus from the Kem Kem beds of Niger adds to the already considerable biogeographic similarity between the Huincul Formation and coeval rock units in North Africa.

pop sci write up.

Thai Cavefish Cryptotora thamicola Climbs, Walks Like a Salamander

Tetrapod-like pelvic girdle in a walking cavefish

Authors:

Flammang et al

Abstract:

Fishes have adapted a number of different behaviors to move out of the water, but none have been described as being able to walk on land with a tetrapod-like gait. Here we show that the blind cavefish Cryptotora thamicola walks and climbs waterfalls with a salamander-like diagonal-couplets lateral sequence gait and has evolved a robust pelvic girdle that shares morphological features associated with terrestrial vertebrates. In all other fishes, the pelvic bones are suspended in a muscular sling or loosely attached to the pectoral girdle anteriorly. In contrast, the pelvic girdle of Cryptotora is a large, broad puboischiadic plate that is joined to the iliac process of a hypertrophied sacral rib; fusion of these bones in tetrapods creates an acetabulum. The vertebral column in the sacral area has large anterior and posterior zygapophyses, transverse processes, and broad neural spines, all of which are associated with terrestrial organisms. The diagonal-couplet lateral sequence gait was accomplished by rotation of the pectoral and pelvic girdles creating a standing wave of the axial body. These findings are significant because they represent the first example of behavioural and morphological adaptation in an extant fish that converges on the tetrapodal walking behaviour and morphology.

pop sci link.

Rusingoryx atopocranion: The Pleistocene Quaternary Wildebeest-like Bovine With a Duck-bill Dinosaur Nasal Dome

By poring over the fossilized skulls of ancient wildebeest-like animals (Rusingoryx atopocranion) unearthed on Kenya's Rusinga Island, researchers have discovered that the little-known hoofed mammals had a very unusual, trumpet-like nasal passage similar only to the nasal crests of lambeosaurine hadrosaur dinosaurs. The findings reported in the Cell Press journal Current Biology on February 4 offer "a spectacular example" of convergent evolution between two very distantly related taxa and across tens of millions of years, the researchers say.

"The nasal dome is a completely new structure for mammals-- it doesn't look like anything you could see in an animal that's alive today," says Haley O'Brien of Ohio University, Athens. "The closest example would be hadrosaur dinosaurs with half-circle shaped crests that enclose the nasal passages themselves."

This evolutionary convergence may be explained by similarities in the way Rusingoryx and hadrosaurs lived. In fact, hadrosaurs are sometimes referred to as the "cows of the Cretaceous."

link.

scientific paper.

Dryolestidan Cladotherian Paurodon valens was a Tithonian Jurassic Golden Mole Parallel

Ontogeny and taxonomy of Paurodon valens (Mammalia, Cladotheria) from the Upper Jurassic Morrison Formation of USA. (pdf)

Authors:

Averianov et al

Abstract:

Several basal cladotherian taxa previously referred to the “Paurodontidae” (Dryolestida) from the Upper Jurassic Morrison Formation of Wyoming, U.S.A. represent ontogenetic and individual variation of one single taxon, Paurodon valens Marsh, 1887 (=Archaeotrigon brevimaxillus Simpson, 1927, syn. n.; = Pelicopsis dubius Simpson, 1927, syn. n.; = Archaeotrigon distagmus Simpson, 1929, syn. n.; = Araeodon intermissus Simpson, 1937, syn. n.; = Foxraptor atrox Bakker et Carpenter, 1990, syn. n.). P. valens is characterized by prolonged dental replacement, including late eruption of m4 (and m5 as individual variation) and a time gap between shedding of dp2 and eruption of p2, which can be lost in aged individuals. By a shortened dentary and mandibular symphysis, two-three simple premolariform teeth, and four molariform teeth with tall trigonid and small talonid, P. valens is strinkingly similar to the modern golden moles (Chrysochloridae), particularly to Amblysomus hottentotus. This similarity suggests that P. valens was specialized on consuming earth worms in contrast to a more insectivorous diet characteristic for other dryolestidans.

Regaliceratops peterhewsi: A Maastrichtian Cretaceous Chasmosaurine Ceratopsid Nicknamed 'Hellboy'

A New Horned Dinosaur Reveals Convergent Evolution in Cranial Ornamentation in Ceratopsidae

Authors:

Brown et al

Abstract:

Ceratopsid (horned) dinosaurs are an iconic group of large-bodied, quadrupedal, herbivorous dinosaurs that evolved in the Late Cretaceous and were largely restricted to western North America. Ceratopsids are easily recognized by their cranial ornamentation in the form of nasal and postorbital horns and frill (capped by epiossifications); these structures show high morphological disparity and also represent the largest cranial display structures known to have evolved. Despite their restricted occurrence in time and space, this group has one of the best fossil records within Dinosauria, showing a rapid diversification in horn and frill morphology. Here a new genus and species of chasmosaurine ceratopsid is described based on a nearly complete and three-dimensionally preserved cranium recovered from the uppermost St. Mary River Formation (Maastrichtian) of southwestern Alberta. Regaliceratops peterhewsi gen. et sp. nov. exhibits many unique characters of the frill and is characterized by a large nasal horncore, small postorbital horncores, and massive parietal epiossifications. Cranial morphology, particularly the epiossifications, suggests close affinity with the late Campanian/early Maastrichian taxon Anchiceratops, as well as with the late Maastrichtian taxon Triceratops. A median epiparietal necessitates a reassessment of epiossification homology and results in a more resolved phylogeny. Most surprisingly, Regaliceratops exhibits a suite of cranial ornamentations that are superficially similar to Campanian centrosaurines, indicating both exploration of novel display morphospace in Chasmosaurinae, especially Maastrichtian forms, and convergent evolution in horn morphology with the recently extinct Centrosaurinae. This marks the first time that evolutionary convergence in horn-like display structures has been demonstrated between dinosaur clades, similar to those seen in fossil and extant mammals.

Academic Bun Fight Over Sulfur Cycling bacteria: Serial Convergence or 1.8 Billion Year Evolutionary Stasis?

Putative extremely long evolutionary stasis in bacteria might be explained by serial convergence

Authors:

Dvorak et al

Abstract:

In a recent paper, Schopf et al. (1) analyzed 1.8-Ga-old fossil sulfur bacteria and found an intriguing morphological similarity between fossil and modern species. Moreover, the authors showed that the deep-water sulfur cycling environment, where these bacteria reside, has not significantly changed throughout time. Thus, the authors hypothesize that this phenomenon is a result of an extreme evolutionary stasis in these bacteria. Such a static evolution is termed hypobradytelic and it has also been described in some cyanobacteria (2), where an evolutionary stasis is expected to be more than 2 Ga. However, these conclusions rely only on geological and morphological evidence.

Counterattack!

Reply to Dvořák et al.: Apparent evolutionary stasis of ancient subseafloor sulfur cycling biocoenoses

Authors:

Schopf et al

Abstract:

We thank Dvořák et al. for their comment (1) on our paper (2), in which we compare sulfur-cycling ∼1.8- and ∼2.3-Ga fossil communities with their modern counterparts and report that the community fabric of the fossil and modern microbes, as well as their organismal and cellular morphology, their interlinked energy-production via anaerobic sulfate-reduction and sulfur species oxidation, and their use of sulfate and nitrate to fuel this sulfur cycle appear to have remained unchanged over a segment of geological time equivalent to half the age of the Earth.

Evidence of Parallel Evolution in Synapsids From Caseid Casea broilii

New Postcranial Material of the Early Caseid Casea broilii Williston, 1910 (Synapsida: Caseidae) with a Review of the Evolution of the Sacrum in Paleozoic Non-Mammalian Synapsids

Authors:

LeBlanc et al

Abstract:

Here we use the description of a new specimen of the small caseid synapsid Casea broilii that preserves the sacral, pelvic and hind limb regions in great detail and in three dimensions, as a unique opportunity to reevaluate the early stages in the evolution of the sacrum in the lineage that led to mammals. We place this new material in the context of sacral evolution in early caseid synapsids and conclude that the transition from two to three sacral vertebrae occurred in small-bodied species, suggesting that it was not an adaptation to heavy weight bearing. Furthermore, we compare descriptions of sacral anatomy among known early synapsids, including caseids, ophiacodontids, edaphosaurids, varanopids, and sphenacodontians and review sacral evolution in early synapsids. Based on the descriptions of new species of caseids, edaphosaurids, and varanopids over the past several decades, it is clear that a sacrum consisting of three vertebrae evolved independently at least four times in synapsids during the Late Carboniferous and Early Permian. Furthermore, similarities in the morphologies of the sacral vertebrae and ribs of these early synapsids lead us to conclude that an anterior caudal vertebra had been incorporated into the sacral series convergently in these groups. Given the repeated acquisition of a three-vertebra sacrum in early synapsids and no apparent link to body size, we argue that this sacral anatomy was related to more efficient terrestrial locomotion than to increased weight bearing.

The Tussle Over the Croc-like Spinosaurus Goes on

link.

Spinosaurus was Really a Croc, erm, Parallel Evolution to a Croc

Semiaquatic adaptations in a giant predatory dinosaur

Authors:

Ibrahim et al

Abstract:

We describe adaptations for a semiaquatic lifestyle in the dinosaur Spinosaurus aegyptiacus. These adaptations include retraction of the fleshy nostrils to a position near the mid-region of the skull and an elongate neck and trunk that shift the center of body mass anterior to the knee joint. Unlike terrestrial theropods, the pelvic girdle is downsized, the hind limbs are short, and all of the limb bones are solid without an open medullary cavity, for buoyancy control in water. The short, robust femur with hypertrophied flexor attachment and the low, flat-bottomed pedal claws are consistent with aquatic foot-propelled locomotion. Surface striations and bone microstructure suggest that the dorsal “sail” may have been enveloped in skin that functioned primarily for display on land and in water.

Zombies ate Japan in the 1980s/90s. Now Marching on China?

America’s global dominance is fading—and a rising superpower in the East is poised to take its place. Renowned for their formidable work ethic, savings habit, discipline and math skills, its workers are already putting Westerners out of jobs. It’s the world’s second-biggest economy, and the question isn’t whether it will oust the US from its perch, but when.

Nope—we’re not talking about China, but 1980s Japan.

Anxiety around China’s rise today is a déjà vu of how the world’s leading economies once felt around Japan. But that rise could become a replay of Japan’s subsequent decline and stagnation, says Patrick Chovanec of Silvercrest Asset Management, an expert on the Chinese economy

“There are striking similarities between China and Japan in the 1980s and ’90s, and they’re not superficial,” he says. “They’re two very different countries but they ended up with a banking system that basically produces the same result—the outcome being a rapid deceleration of (hitherto high) growth, as well as zombie banks and corporations.”

Chovanec is referring to what happens when, during economic slowdowns, banks or the government refuse to let unprofitable companies die, keeping them alive on a steady drip of new credit. Japan’s decade of the living dead began after its export-led boom abruptly ended, leaving the country hooked on credit before it had developed market mechanisms to keep that borrowing bonanza in check.

China too has gone on a credit-fueled investment bender as its export-led boom has faded. The prevailing assumptions about what happens next are that China will either suffer a US-style banking crisis that forces unprofitable corporations to the wall, or implement reforms that keep it growing at a healthy clip.

But it’s actually likely to suffer a fate more like Japan’s: a “zombie infection” in which large companies feed off credit while the economy stagnates. To understand why, though, it’s important to understand what China’s rise has in common with Japan’s—and how it’s already exhibiting the same symptoms.

link.

An Anisian Triassic Silesaurid was Very Large

A large-bodied silesaurid from the Lifua Member of the Manda beds (Middle Triassic) of Tanzania and its implications for body-size evolution in Dinosauromorpha

Authors:

Barrett et al

Abstract:

Many dinosaur lineages were characterised by wide ranges of body-size, ranging from taxa that were < 1 m in length to the largest of all terrestrial vertebrates. On the other hand, the closest relatives of dinosaurs, the non-dinosaurian dinosauromorphs, such as Marasuchus and lagerpetids, were small-bodied animals with little variation in body-size. Here, we describe a partial femur of an unexpectedly large-bodied silesaurid (non-dinosaurian dinosauriform) from the Lifua Member of the Manda beds (?late Anisian) from southwestern Tanzania. This specimen (NHMUK R16303) is estimated to have had a femoral length of approximately 345 mm, which exceeds that of many Triassic and Lower Jurassic dinosaurs, and is either a large individual of the contemporary Asilisaurus kongwe or represents a new and otherwise unknown silesaurid taxon. In either case, it shows that body-size increases were more prevalent among early dinosauromorphs than realised previously. Moreover, silesaurid size increase occurred in parallel with that in early dinosaurs, alongside the convergent acquisition of other features related to locomotion and herbivory. However, Late Triassic faunas including large-bodied sauropodomorph and theropod dinosaurs lack similarly-sized non-dinosaurian dinosauromorphs, whereas the Lifua Member fauna includes both a large silesaurid and the early ?dinosaur Nyasasaurus, which overlapped in size.

Conodont Teeth, Vertebrate Skeleton Are Examples of Parallel Evolution

A comparison between the growth of the ‘teeth’ of the paraconodont

For decades, it was thought that our skeleton and all its characteristic bony tissues originated in the predators, known as 'conodonts'. However new research, led by the University of Bristol and published today in Nature, shows that they were evolutionary copy-cats who evolved tooth-like structures and tissues independently of other vertebrates. The origin of our skeleton is to be found in the armour of our mud-slurping ancestors who evolved bony armour to protect themselves from such predators.

Palaeontologists from Bristol, Peking University and the US Geological Survey collaborated with physicists from Switzerland to study the tooth-like skeleton of conodonts using high energy X-rays at the Swiss Light Source at the Paul Scherrer Institut in Switzerland. They showed that the tooth-like structures found in the mouths of conodonts evolved within their own evolutionary lineage, rather than in an ancestor shared with other vertebrates.

Lead author, Duncan Murdock of the University of Bristol said: "We were able to visualise every tissue, cell and growth line within the bony teeth, allowing us to study their development. We compared the tooth-like skeleton of conodonts to that of their 'paraconodont' ancestors and to teeth in living vertebrates, demonstrating that the tooth-like structure of conodonts was assembled through evolutionary time independently of other vertebrates."

Co-author, Professor Philip Donoghue of the University of Bristol's School of Earth Sciences said: "This removes a key piece of evidence from the hypothesis that teeth evolved before the skeletal armour, and suggests that the common ancestors of conodonts and other vertebrates likely lacked a mineralized skeleton. Rather, it seems that teeth evolved from the armour of our meek filter-feeding ancestors."

link.

Biomechanically Comparing Therian Sabretooths

Comparative Biomechanical Modeling of Metatherian and Placental Saber-Tooths: A Different Kind of Bite for an Extreme Pouched Predator

Authors:

1. Stephen Wroe (a,b)
2. Uphar Chamoli (b,c)
3. William C. H. Parr (b)
4. Philip Clausen (a)
5. Ryan Ridgely (d)
6. Lawrence Witmer (d)

Affiliations:

a. School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia

b. School of Engineering, University of Newcastle, Callaghan, NSW, Australia

c. St. George Clinical School, University of New South Wales, Sydney, NSW, Australia

d. Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, United States of America

Abstract:

Questions surrounding the dramatic morphology of saber-tooths, and the presumably deadly purpose to which it was put, have long excited scholarly and popular attention. Among saber-toothed species, the iconic North American placental, Smilodon fatalis, and the bizarre South American sparassodont, Thylacosmilus atrox, represent extreme forms commonly forwarded as examples of convergent evolution. For S. fatalis, some consensus has been reached on the question of killing behaviour, with most researchers accepting the canine-shear bite hypothesis, wherein both head-depressing and jaw closing musculatures played a role in delivery of the fatal bite. However, whether, or to what degree, T. atrox may have applied a similar approach remains an open question. Here we apply a three-dimensional computational approach to examine convergence in mechanical performance between the two species. We find that, in many respects, the placental S. fatalis (a true felid) was more similar to the metatherian T. atrox than to a conical-toothed cat. In modeling of both saber-tooths we found that jaw-adductor-driven bite forces were low, but that simulations invoking neck musculature revealed less cranio-mandibular stress than in a conical-toothed cat. However, our study also revealed differences between the two saber-tooths likely reflected in the modus operandi of the kill. Jaw-adductor-driven bite forces were extremely weak in T. atrox, and its skull was even better-adapted to resist stress induced by head-depressors. Considered together with the fact that the center of the arc described by the canines was closer to the jaw-joint in Smilodon, our results are consistent with both jaw-closing and neck musculature playing a role in prey dispatch for the placental, as has been previously suggested. However, for T. atrox, we conclude that the jaw-adductors probably played no major part in the killing bite. We propose that the metatherian presents a more complete commitment to the already extreme saber-tooth ‘lifestyle’.