Tully Monster From the Gzhelian Carboniferous is a Vertebrate

The Tully Monster, an oddly configured sea creature with teeth at the end of a narrow, trunk-like extension of its head and eyes that perch on either side of a long, rigid bar, has finally been identified.

A Yale-led team of paleontologists has determined that the 300-million-year-old animal—which grew to only a foot long—was a vertebrate, with gills and a stiffened rod (or notochord) that supported its body. It is part of the same lineage as the modern lamprey."I was first intrigued by the mystery of the Tully Monster. With all of the exceptional fossils, we had a very clear picture of what it looked like, but no clear picture of what it was," said Victoria McCoy, lead author of a new study in the journal Nature. McCoy conducted her research as a Yale graduate student and is now at the University of Leicester.

For decades, the Tully Monster has been one of the great fossil enigmas: It was discovered in 1958, first described scientifically in 1966, yet never definitively identified even to the level of phylum (that is, to one of the major groups of animals). Officially known as Tullimonstrum gregarium, it is named after Francis Tully, the amateur fossil hunter who came across it in coal mining pits in northeastern Illinois.

link.

paper link.

More at the Catalog of Organisms.

The Albian/Maastrichtian Cretaceous Vertebrate Fauna of India's Cauvery Basin

Cretaceous vertebrate fauna of the Cauvery Basin, southern India: Palaeodiversity and palaeobiogeographic implications

Author:

Verma

Abstract:

The vertebrate fauna from the late Albian to Maastrichtian succession of the Cauvery Basin, south India has been known since 1845, but it received only scant attention as compared to the vertebrates already known from the Deccan volcanic province of peninsular India. Recent fossil discoveries appear to support the emergence of significantly diverse marine and non-marine vertebrates comprising fishes, frogs, reptiles (ichthyosaurs, plesiosaurs, turtles, crocodiles and dinosaurs) and a mammal from the Cauvery Basin have revived the interest in the fauna of the basin as it has significant implications for understanding the palaeobiogeography of India. The latest Albian to Turonian marine vertebrates such as sharks, ichthyosaurs and plesiosaurs show a wide geographic distribution and marine territory, while sharks are typically cooler water fauna of high palaeolatitudes. The latest Maastrichtian non-marine vertebrates especially turtles, crocodiles, dinosaurs and a mammal are considered to show mixed Gondwanan and Laurasian affinities thus providing new lines of evidence in favour of a latest Cretaceous biotic links between India and the neighbouring continents. An overview of the vertebrate faunal diversity of the Cretaceous sequences of the Cauvery Basin and its palaeobiogeographic considerations are presented.

Jawless Fish (Ostracoderms) Went Extinct due to Environmental Factors, Range Restriction, not Competition With Jawed Fish

Discriminating signal from noise in the fossil record of early vertebrates reveals cryptic evolutionary history

Authors:

Sansom et al

Abstract:

The fossil record of early vertebrates has been influential in elucidating the evolutionary assembly of the gnathostome bodyplan. Understanding of the timing and tempo of vertebrate innovations remains, however, mired in a literal reading of the fossil record. Early jawless vertebrates (ostracoderms) exhibit restriction to shallow-water environments. The distribution of their stratigraphic occurrences therefore reflects not only flux in diversity, but also secular variation in facies representation of the rock record. Using stratigraphic, phylogenetic and palaeoenvironmental data, we assessed the veracity of the fossil records of the jawless relatives of jawed vertebrates (Osteostraci, Galeaspida, Thelodonti, Heterostraci). Non-random models of fossil recovery potential using Palaeozoic sea-level changes were used to calculate confidence intervals of clade origins. These intervals extend the timescale for possible origins into the Upper Ordovician; these estimates ameliorate the long ghost lineages inferred for Osteostraci, Galeaspida and Heterostraci, given their known stratigraphic occurrences and stem–gnathostome phylogeny. Diversity changes through the Silurian and Devonian were found to lie within the expected limits predicted from estimates of fossil record quality indicating that it is geological, rather than biological factors, that are responsible for shifts in diversity. Environmental restriction also appears to belie ostracoderm extinction and demise rather than competition with jawed vertebrates.

Nesonektris aldridgei Shows Cambrian Vetulicolians Were Vertebrate Cousins

A new vetulicolian from Australia and its bearing on the chordate affinities of an enigmatic Cambrian group

Authors:

García-Bellido et al

Abstract:

Background

Vetulicolians are one of the most problematic and controversial Cambrian fossil groups, having been considered as arthropods, chordates, kinorhynchs, or their own phylum. Mounting evidence suggests that vetulicolians are deuterostomes, but affinities to crown-group phyla are unresolved.
Results

A new vetulicolian from the Emu Bay Shale Konservat-Lagerstätte, South Australia, Nesonektris aldridgei gen. et sp. nov., preserves an axial, rod-like structure in the posterior body region that resembles a notochord in its morphology and taphonomy, with notable similarity to early decay stages of the notochord of extant cephalochordates and vertebrates. Some of its features are also consistent with other structures, such as a gut or a coelomic cavity.
Conclusions

Phylogenetic analyses resolve a monophyletic Vetulicolia as sister-group to tunicates (Urochordata) within crown Chordata, and this holds even if they are scored as unknown for all notochord characters. The hypothesis that the free-swimming vetulicolians are the nearest relatives of tunicates suggests that a perpetual free-living life cycle was primitive for tunicates. Characters of the common ancestor of Vetulicolia + Tunicata include distinct anterior and posterior body regions – the former being non-fusiform and used for filter feeding and the latter originally segmented – plus a terminal mouth, absence of pharyngeal bars, the notochord restricted to the posterior body region, and the gut extending to the end of the tail.

Vertebrate Fauna of the Anisian Triassic Otter Sandstone River

The ‘Otter Sandstone River’ of the mid-Triassic and its vertebrate fauna

Author:

Hart

Abstract:

The Triassic succession of the East Devon coastline is a key component of the Jurassic Coast World Heritage Site. Within these strata are the sediments deposited by two major river systems: the Budleigh Salterton Pebble Beds and the Otter Sandstone Formation. The latter are significant as both a reservoir for the Dorset oilfields near Wareham and as a source of significant numbers of vertebrate fossils. The Otter Sandstone Formation, of Anisian (Middle Triassic) age, has a lower part formed of aeolian sands but these pass upwards into a series of river channel deposits. These river channels, which are best seen between the mouth of the River Otter and Ladram Bay, contain a series of classic features such as erosive channel bases, channel lag deposits, de-watering structures, calcified root systems (rhizoliths), reworked calcretes and (rare) overbank mudstones. The rivers that formed the various braided channel deposits flowed northwards or north-eastwards and there are at least 4 or 5 separate channel units within the Ladram Bay area. The Otter Sandstone Formation has yielded a great many rhynchosaur fragments and at least one partial skeleton. This juvenile individual appears to have fallen into one of the channels, resulting in the loss of its head (skull), as this was not recovered when the specimen was found by the author in 1990. This important specimen of Fodonyx spenceri (Benton, 1990) is housed in the Royal Albert Memorial Museum in Exeter.

The Early Evolution of Vertebrates

Early vertebrate evolution

Authors:

Donoghue et al

Abstract:

Debate over the origin and evolution of vertebrates has occupied biologists and palaeontologists alike for centuries. This debate has been refined by molecular phylogenetics, which has resolved the place of vertebrates among their invertebrate chordate relatives, and that of chordates among their deuterostome relatives. The origin of vertebrates is characterized by wide-ranging genomic, embryologic and phenotypic evolutionary change. Analyses based on living lineages suggest dramatic shifts in the tempo of evolutionary change at the origin of vertebrates and gnathostomes, coincident with whole-genome duplication events. However, the enriched perspective provided by the fossil record demonstrates that these apparent bursts of anatomical evolution and taxic richness are an artefact of the extinction of phylogenetic intermediates whose fossil remains evidence the gradual assembly of crown gnathostome characters in particular. A more refined understanding of the timing, tempo and mode of early vertebrate evolution rests with: (1) better genome assemblies for living cyclostomes; (2) a better understanding of the anatomical characteristics of key fossil groups, especially the anaspids, thelodonts, galeaspids and pituriaspids; (3) tests of the monophyly of traditional groups; and (4) the application of divergence time methods that integrate not just molecular data from living species, but also morphological data and extinct species. The resulting framework will provide for rigorous tests of rates of character evolution and diversification, and of hypotheses of long-term trends in ecological evolution that themselves suffer for lack of quantitative functional tests. The fossil record has been silent on the nature of the transition from jawless vertebrates to the jawed vertebrates that have dominated communities since the middle Palaeozoic. Elucidation of this most formative of episodes likely rests with the overhaul of early vertebrate systematics that we propose, but perhaps more fundamentally with fossil grades that await discovery.

Neogene Marine Vertebrate Paleodiversity in Temperature Pacific South America

Rise and fall in diversity of Neogene marine vertebrates on the temperate Pacific coast of South America

Authors:

Villafaña et al

Abstract:

Even though Neogene outcrops along the temperate Pacific coast of South America harbor a rich marine vertebrate fossil record, no studies have examined the diversification patterns of these taxa. Here, we analyze diversification trends based on the stratigraphic ranges of 86 genera of marine vertebrates, including sharks, rays, chimaeras, marine mammals, and seabirds. The richness of genera shows a hump-shaped trend, with maximum values around the late Miocene, driven by a large pulse of origination during mid-Miocene and higher extinction rates during the Pliocene. Trends varied markedly among taxa and departed largely from expectations based on global diversification patterns. Moreover, these trends cannot be explained solely as a sampling artifact derived from sampling intensity (i.e., number of occurrences) or sedimentary rock availably (i.e., number of geologic maps). A large fraction of genera (42%) went globally extinct by the late Pliocene–Pleistocene, and the extinction was highly selective according to different ecological and life-history traits. An analysis using “randomForest” showed that taxonomic structure and the geographic midpoint of distribution could explain up to 83% of extinction of genera. The extinction was taxonomically clumped (i.e., disproportionally high in Cetacea and very low in Carcharhiniformes) and concentrated in the northern area of the temperate Pacific coast of South America. Our results suggest that the particular paleogeographic, paleoclimatic, and paleoceanographic events that took place during the Neogene along the temperate Pacific coast of South America had a significant effect on the structure of marine biodiversity.

A Primitive Fish Fossil From the Cambrian of North America

A primitive fish from the Cambrian of North America

Authors:

Conway Morris et al

Abstract:

Knowledge of the early evolution of fish largely depends on soft-bodied material from the Lower (Series 2) Cambrian period of South China. Owing to the rarity of some of these forms and a general lack of comparative material from other deposits, interpretations of various features remain controversial, as do their wider relationships amongst post-Cambrian early un-skeletonized jawless vertebrates. Here we redescribe Metaspriggina on the basis of new material from the Burgess Shale and exceptionally preserved material collected near Marble Canyon, British Columbia and three other Cambrian Burgess Shale-type deposits from Laurentia. This primitive fish displays unambiguous vertebrate features: a notochord, a pair of prominent camera-type eyes, paired nasal sacs, possible cranium and arcualia, W-shaped myomeres, and a post-anal tail. A striking feature is the branchial area with an array of bipartite bars. Apart from the anterior-most bar, which appears to be slightly thicker, each is associated with externally located gills, possibly housed in pouches. Phylogenetic analysis places Metaspriggina as a basal vertebrate, apparently close to the Chengjiang taxa Haikouichthys and Myllokunmingia , demonstrating also that this primitive group of fish was cosmopolitan during Lower–Middle Cambrian times (Series 2–3). However, the arrangement of the branchial region in Metaspriggina has wider implications for reconstructing the morphology of the primitive vertebrate. Each bipartite bar is identified as being respectively equivalent to an epibranchial and ceratobranchial. This configuration suggests that a bipartite arrangement is primitive and reinforces the view that the branchial basket of lampreys is probably derived. Other features of Metaspriggina, including the external position of the gills and possible absence of a gill opposite the more robust anterior-most bar, are characteristic of gnathostomes and so may be primitive within vertebrates.

Vertebrates from the Late Triassic Thecodontosaurus-bearing Strata

Vertebrates from the Late Triassic Thecodontosaurus-bearing rocks of Durdham Down, Clifton (Bristol, UK)

Authors:

Foffa et al

Abstract:

Since the discovery of the basal sauropodomorph dinosaur Thecodontosaurus in the 1830s, the associated fauna from the Triassic fissures at Durdham Down (Bristol, UK) has not been investigated, largely because the quarries are built over. Other fissure sites around the Bristol Channel show that dinosaurs represented a minor part of the fauna of the Late Triassic archipelago. Here we present data on microvertebrates from the original Durdham Down fissure rocks, which considerably expand the taxonomic diversity of the island fauna, revealing that it was dominated by the sphenodontian Diphydontosaurus, and that archosauromorphs, including sphenosuchian crocodylomorphs, coelophysoid theropods, and the basal sauropodomorph Thecodontosaurus, were diverse. Importantly, a few fish teeth provide new information about the debated age of the fissure deposit, which is identified as lower Rhaetian. Thecodontosaurus had been assigned an age range over 20–25 Myr of the Late Triassic, so this narrower age determination (209.5–204 Myr) is important for studies of early dinosaurian evolution.

Mollusc vs Vertebrate War: Battle in the Monterey Bay

nice pop sci write up at the Running Ponies about the squid.

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.

A Phylogeny of the Spiny-Rayed Fish

Phylogeny and tempo of diversification in the superradiation of spiny-rayed fishes

Authors:

1. Thomas J. Neara,1,
2. Alex Dornburga,
3. Ron I. Eytana,
4. Benjamin P. Keckb,
5. W. Leo Smithc,
6. Kristen L. Kuhna,
7. Jon A. Moored,
8. Samantha A. Pricee,
9. Frank T. Burbrinkf,
10. Matt Friedmang, and
11. Peter C. Wainwrighte

Affiliations:

a. Department of Ecology and Evolutionary Biology and Peabody Museum of Natural History, Yale University, New Haven, CT 06520;

b. Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996;

c. Division of Fishes, The Field Museum, Chicago, IL 60605;

d. Wilkes Honors College and Harbor Branch Oceanographic Institution, Florida Atlantic University, Jupiter, FL 33458;

e. Department of Evolution and Ecology, University of California, Davis, CA 95616;

f. Biology Department, College of Staten Island/City University of New York, Staten Island, NY 10314; and

g. Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, United Kingdom

Abstract:

Spiny-rayed fishes, or acanthomorphs, comprise nearly one-third of all living vertebrates. Despite their dominant role in aquatic ecosystems, the evolutionary history and tempo of acanthomorph diversification is poorly understood. We investigate the pattern of lineage diversification in acanthomorphs by using a well-resolved time-calibrated phylogeny inferred from a nuclear gene supermatrix that includes 520 acanthomorph species and 37 fossil age constraints. This phylogeny provides resolution for what has been classically referred to as the “bush at the top” of the teleost tree, and indicates acanthomorphs originated in the Early Cretaceous. Paleontological evidence suggests acanthomorphs exhibit a pulse of morphological diversification following the end Cretaceous mass extinction; however, the role of this event on the accumulation of living acanthomorph diversity remains unclear. Lineage diversification rates through time exhibit no shifts associated with the end Cretaceous mass extinction, but there is a global decrease in lineage diversification rates 50 Ma that occurs during a period when morphological disparity among fossil acanthomorphs increases sharply. Analysis of clade-specific shifts in diversification rates reveal that the hyperdiversity of living acanthomorphs is highlighted by several rapidly radiating lineages including tunas, gobies, blennies, snailfishes, and Afro-American cichlids. These lineages with high diversification rates are not associated with a single habitat type, such as coral reefs, indicating there is no single explanation for the success of acanthomorphs, as exceptional bouts of diversification have occurred across a wide array of marine and freshwater habitats.

Vertebrates Can Deal With a Change of 1 Degree C Per Million Years

Many vertebrate species would have to evolve about 10,000 times faster than they have in the past to adapt to the rapid climate change expected in the next 100 years, a study led by a University of Arizona ecologist has found.

Scientists analyzed how quickly species adapted to different climates in the past, using data from 540 living species from all major groups of terrestrial vertebrates, including amphibians, reptiles, birds and mammals. They then compared their rates of evolution to rates of climate change projected for the end of this century. This is the first study to compare past rates of adaption to future rates of climate change.

The results, published online in the journal Ecology Letters, show that terrestrial vertebrate species appear to evolve too slowly to be able to adapt to the dramatically warmer climate expected by 2100. The researchers suggested that many species may face extinction if they are unable to move or acclimate.

"Every species has a climatic niche which is the set of temperature and precipitation conditions in the area where it lives and where it can survive," explained John J. Wiens, a professor in UA's department of ecology and evolutionary biology in the College of Science. "For example, some species are found only in tropical areas, some only in cooler temperate areas, some live high in the mountains, and some live in the deserts."

Wiens conducted the research together with Ignacio Quintero, a postgraduate research assistant at Yale University.

"We found that on average, species usually adapt to different climatic conditions at a rate of only by about 1 degree Celsius per million years," Wiens explained. "But if global temperatures are going to rise by about 4 degrees over the next hundred years as predicted by the Intergovernmental Panel of Climate Change, that is where you get a huge difference in rates. What that suggests overall is that simply evolving to match these conditions may not be an option for many species."

For their analysis, Quintero and Wiens studied phylogenies – essentially evolutionary family trees showing how species are related to each other – based on genetic data. These trees reveal how long ago species split from each other. The sampling covered 17 families representing the major living groups of terrestrial vertebrates, including frogs, salamanders, lizards, snakes, crocodilians, birds and mammals.

They then combined these evolutionary trees with data on the climatic niche of each species to estimate how quickly climatic niches evolve among species, using climatic data such as annual mean temperature and annual precipitation as well as high and low extremes.

"Basically, we figured out how much species changed in their climatic niche on a given branch, and if we know how old a species is, we can estimate how quickly the climatic niche changes over time," Wiens explained. "For most sister species, we found that they evolved to live in habitats with an average temperature difference of only about 1 or 2 degrees Celsius over the course of one to a few million years."

"We then compared the rates of change over time in the past to projections for what climatic conditions are going to be like in 2100 and looked at how different these rates are. If the rates were similar, it would suggest there is a potential for species to evolve quickly enough to be able to survive, but in most cases, we found those rates to be different by about 10,000-fold or more," he said.

"According to our data, almost all groups have at least some species that are potentially endangered, particularly tropical species."

Species can respond to climate change by acclimating without evolutionary change or by moving over space to track their preferred climate. For example, some species might be able to move to higher latitudes or higher elevation to remain in suitable conditions as the climate warms. In addition, many species could lose many populations due to climate change but might still be able to persist as a species if some of their populations survive. Barring any these options, extinction is the most likely outcome.

I have nontrivial doubts about this.  The Pleistocene ought to have been a case of massive die offs all the time with the .  It wasn't until the end.  Even then it had more to do with a new predator...

Helicoprion: The Spiral Toothed Shark Explained

Jaws for a spiral-tooth whorl: CT images reveal novel adaptation and phylogeny in fossil Helicoprion

Authors:

1. Leif Tapanila (a,b)
2. Jesse Pruitt (b,c)
3. Alan Pradel (d)
4. Cheryl D. Wilga (e)
5. Jason B. Ramsay (e)
6. Robert Schlader (c)
7. Dominique A. Didier (f)

Affiliations:

a. Department of Geosciences, Idaho State University, Pocatello, ID 83209, USA

b. Division of Earth Sciences, Idaho Museum of Natural History, Pocatello, ID 83209, USA

c. Idaho Virtualization Lab, Idaho Museum of Natural History, Pocatello, ID 83209, USA

d. Department of Vertebrate Paleontology, American Museum of Natural History, New York, NY 10024, USA

e. Department of Biological Sciences, University of Rhode Island, Kingston, RI 02881, USA

f. Department of Biology, Millersville University, Millersville, PA 17551, USA

Abstract:

New CT scans of the spiral-tooth fossil, Helicoprion, resolve a longstanding mystery concerning the form and phylogeny of this ancient cartilaginous fish. We present the first three-dimensional images that show the tooth whorl occupying the entire mandibular arch, and which is supported along the midline of the lower jaw. Several characters of the upper jaw show that it articulated with the neurocranium in two places and that the hyomandibula was not part of the jaw suspension. These features identify Helicoprion as a member of the stem holocephalan group Euchondrocephali. Our reconstruction illustrates novel adaptations, such as lateral cartilage to buttress the tooth whorl, which accommodated the unusual trait of continuous addition and retention of teeth in a predatory chondrichthyan. Helicoprion exemplifies the climax of stem holocephalan diversification and body size in Late Palaeozoic seas, a role dominated today by sharks and rays.

Pop sci write up.

Diversity of Tetrapod Herbivores From the Late Carboniferous to the Mid Triassic

Reconstructing the diversity of early terrestrial herbivorous tetrapods

Authors:

1. Marianne R. Pearson (a.*)
2. Roger B.J. Benson (a, b)
3. Paul Upchurch (a)
6. Jörg Fröbisch (c)
5. Christian F. Kammerer (c)

Affiliations:

a. University College London, Department of Earth Sciences

b. University of Cambridge, Department of Earth Sciences

c. Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung an der Humboldt-Universität zu Berlin

*.  Author With Whom Communication Is Intended: Email:marianne.pearson@ucl.ac.uk

Abstract:

Terrestrial herbivorous tetrapods first appear in the fossil record during the Late Carboniferous (306.5 Ma). The diversification of herbivores is a key aspect of the transition to the modern trophic structure of terrestrial vertebrate ecosystems, because it allowed tetrapods to exploit terrestrial (i.e. non-aquatic) primary productivity. However, the palaeodiversity dynamics of the earliest terrestrial vertebrate herbivores have received relatively little attention, apart from a few studies that focus on specific clades. A new data set containing 287 species occurrences of herbivorous tetrapods including the major Palaeozoic and Early Triassic clades Anomodontia, Archosauromorpha, Bolosauridae, Captorhinidae, Caseidae, Cynodontia, Dinocephalia, Diadectomorpha, Edaphosauridae, Pareiasauria, Poposauroidea, Procolophonoidea, Rhynchosauria, Silesauridae and Therocephalia is used to analyse palaeodiversity from the Late Carboniferous to the Middle Triassic (~ 306.5 – ~ 236 Ma), taking into account the effects of potential sampling biases by using the number of tetrapod-bearing formations as a proxy. The results support a gradual increase in taxic diversity from the Late Carboniferous to the Wordian, followed by a dip in diversity during the Guadalupian (Middle Permian), and an increase to a peak in the Late Permian at the Wuchiapingian/Changhsingian boundary. Herbivorous tetrapods were strongly affected by the end-Permian mass extinction with both the herbivorous Pareiasauria and Captorhinidae becoming extinct and the observed number of anomodont species decreasing by up to 80%. The drop in observed diversity at the end Permian is dampened slightly because of the radiation of new herbivorous forms during the Early Triassic. A strong biological signal is apparent even after correcting for sampling.

They use the "Land Vertebrate Faunachrons", which I thought were considered flawed.

Sooo...not sure what the accuracy of this is. I Am Not a Triassic (or any really) Paleontologist though.

Devonian GeoSys-BioEvo Interaction Bun Fight

There's an interesting bun fight that has started. It has to do with whether or not there is a correlation between the rapid rise in oxygen during the Devonian and the evolution of large bodied predatory fish. Oxygen levels did, in fact, rise significantly during the Devonian. Large bodied fish that filled the predator niche also arose then.

This has been playing out in PNAS. The original paper raised the suggestion that there was a direct correlation. A researcher wrote an objection. The original researchers responded.

There is a long ongoing argument about how much the environment and the geophysical systems influence evolution. Some feel that it has overwhelming evidence in support of this. The idea that the environment is the driver of evolution is very common. Sometimes a change in climate would be a driver in evolution: the general cooling and drying at the end of the Eocene and into the Oligocene, for example. Others, as above, have suggested that the oxygen levels have been another driver. Desertification, temperature rise, etc have all been pitched as important drivers.

Others have some strong objections to this. Butterfield is a good example above. Another noted individual that you may recognize is John Hawks. He frequently objects to the idea that the environment was the driver behind human evolution.

I have to wonder. There are times when I object too when it seems like the authors are overstretching. That seems to happen alot in this realm. The grand handwave seems to be pretty common, nevermind those details. On the other hand, it seems hard to deny that the environment isn't one of the greatest, if not the greatest driver of evolution. It can and does wipe out populations of various species. It has wiped out whole ecosystems before, thereby terminating their participation in following evolutionary tales.

Sometimes the objections seem silly. Sometimes the handwavium is near violating causality. Either way, I caution that people ought to look at the details before objecting or accepting a theory.

Holocene Mass Extinction Disaster Taxon IDed

Jellyfish moved into the oceans off the coast of southwest Africa when the sardine population crashed. Now another small fish is living in the oxygen-depleted zone part-time and turning the once ecologically dead-end jellyfish into dinner, according to an international team of scientists.

"Originally there were sardines in the area but over fishing caused the sardine population to collapse in the 1960s and 1970s," said Victoria A. Braithwaite, professor of fisheries and biology, Penn State. "The sardines never recovered and jellyfish became a huge and serious problem, eating what the sardines had eaten."

Jellyfish are considered a dead end food source because, while they eat lots of small fish and other sea creatures, they have few predators. However, the research team found that the bearded goby, Sufflogobius bibarbatus, a 4-to-6-inch long, 1.5 inch-wide fish, eats jellyfish. Larger fish like hake and mackerel, sea mammals like sea lions and porpoises, and sea birds, like gannets and gulls, eat gobies, putting jellyfish back into the food cycle.

"We don't know if they are eating dead jellyfish from the bottom, or if they are coming up to oxygen-filled layers to eat jellyfish, but they are eating jellyfish," said Braithwaite.

Even stranger than a jellyfish diet is the gobies' use of the dead zone in the area. One reason there were so many sardines and now so many jellyfish is a large area of up-welling water off the southwest coast of Africa from Namibia to South Africa. This deep cold water brings with it large amounts of nutrients. When plankton voraciously eat the nutrients, their populations increase massively. Excess nutrients and dead plankton then fall to the ocean floor.

"A horrible toxic sludge forms, and very few things can live in it except for some bacteria and nematodes," said Braithwaite. "Somehow the gobies can withstand the toxic environment, but we don't know exactly how they are doing it."

Remarkably, the gobies cope without oxygen for hours at a time while they rest on the muddy seabed but remain alert.

"When we touch them with a rod, they show rapid escape responses," said Braithwaite.

Gobies can stay in the anoxic or oxygen-depleted area for at least 10 to 12 hours at a time. The researchers suggest they may be able to remain there even longer. The mud is not just lacking oxygen, but the bacteria that live there use sulfur for energy and produce high levels of hydrogen sulfide, a toxic gas. The researchers report the results of their study in today's (July) 16 issue of Science.

"Normally, other animals cope with anoxia by anaerobic respiration, which causes a build up in lactate," said Braithwaite. "But something else is going on in these gobies as the lactate build up declines after an hour or so without oxygen. Our next step is to look to see what they are doing to cope with anoxia."

hmmm.

Fedexia striegeli: A New, Exquisitely Preserved 300 MYA Trematopid

A team of researchers from Carnegie Museum of Natural History has described a new genus and species of carnivorous amphibian from western Pennsylvania. The fossil skull, found in 2004 near Pittsburgh International Airport, was recovered from rocks deposited approximately 300 million years ago during the Late Pennsylvanian Period. Named Fedexia striegeli, it is one of only a very few relatively large amphibian fossils to display evidence of a predominantly terrestrial (land-based) life history so early in geologic time. The rocks where Fedexia was found are nearly 20 million years older than the localities of its fossil relatives, suggesting that the expansion and diversification of this group occurred much earlier than had been recognized previously. The full paper will be released today in Annals of Carnegie Museum, Volume 78, Number 4, 15 March 2010.

Fedexia was described on the basis of a remarkably well-preserved fossil skull. Unlike similar discoveries, the five-inch-long (11.5 cm) fossil skull remained three-dimensional over time because it was never crushed by rocks that were deposited above it. Fedexia striegeli was named for FedEx, the corporation that owns the land on which the fossil was found, and for amateur discoverer Mr. Adam Striegel, who originally found the specimen on a geology field trip while a senior at the University of Pittsburgh.

Fedexia represents an extinct group of amphibians called Trematopidae that lived about 70 million years before the first dinosaurs appeared. Unlike almost all other Pennsylvanian Period amphibians, which did not often venture out of the water, this rare, diverse group lived mostly on land, returning to the water perhaps only to mate or lay eggs. The trematopids also provide evidence of the earliest vertebrate life in North America adapted to a mostly terrestrial existence. Their success may have been a result of a long-term, global trend toward drier, warmer conditions that reached its climax near the end of the Pennsylvanian Period.

Soooo...does this one count as a reptilomorph or not? Is there a good, modern text on Carboniferous-Permian nonamniote vertebrate evolution out there?

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.

Early Tetrapods' Evolution Was Convoluted

Both extinct species, known as Ichthyostega and Acanthostega, lived an estimated 360-370 million years ago in what is now Greenland. Acanthostega was thought to have been the most primitive tetrapod, that is, the first vertebrate animal to possess limbs with digits rather than fish fins.

But the latest evidence from a Duke graduate student's research indicates that Ichthyostega may have been closer to the first tetrapod. In fact, Acanthostega may have had a terrestrial ancestor and then returned full time to the water, said Viviane Callier, who is the first author of a report on the findings to be published in today's issue of the journal Science.

"If there is one take-home message, it is that the evolutionary relationship between these early tetrapods is not well resolved," Callier said.

Co-author Jennifer Clack of the University Museum of Zoology in Cambridge, England -- where she supervised Callier's work for a master's degree -- found the fossils embedded in rocks collected from East Greenland.

Rather than trying to remove them -- an action that would have destroyed much of the evidence -- the researchers studied the fossils inside the stone with computed tomography (CT) scanning. Callier "reconstructed" the animals using imaging software (Amira and Mimics) to analyze the CT scans, focusing on the shapes of the two species' upper arm bones, or humeri.

The CT slices revealed that Clack had found the first juvenile forms of Ichthyostega. Previously known fossils of Ichthyostega had come from adults.

Anatomies can morph as animals move towards adulthood, Callier said. And such shifts can help scientists deduce when in development the animal acquired the terrestrial habit. The fossils suggest that Ichthyostega juveniles were aquatically adapted, and that the terrestrial habit was acquired relatively late in development. The fossils bore evidence that the muscle arrangement in adults was better suited to weight-bearing, terrestrial locomotion than the juvenile morphology. It is possible that Ichthyostega came out of the water only as a fully mature adult.

In contrast, in Acanthostega "there is less change from the juvenile to the adult. Although Acanthostega appears to be aquatically adapted throughout the recorded developmental span, its humerus exhibits subtle traits that make it more similar to the later, fully terrestrial tetrapods," Callier said

Because the shapes of its adult limbs seemed the most fin-like, scientists had previously concluded that Acanthostega was "more primitive," Callier said. "But now, if we look at the details of the humeri, Ichthyostega's are actually more similar to earlier fishes."

Ironically, the shape of Acanthostegas limb's, in both adult and the newly-discovered juvenile forms, is more "paddle-like" than Ichthyostega's, Callier said. "They would have been really good swimmers. So, although Acanthostega had limbs with digits, we don't think it was really terrestrial. We think even the adults were aquatic."

"If Ichthyostega is actually more primitive than Acanthostega, then maybe animals evolved towards a terrestrial existence a lot earlier than originally believed," she said. "Maybe Acanthostega was actually derived from a terrestrial ancestor, and then, went back to an aquatic lifestyle."

I saw this over the weekend, but didn't have time for posting. Paleoblog has a link to the paper. Also a link to the Eureka Alert.