Formation of sedimentary layers of white clay, Tamilnadu, India

Fossil site for wood fossils, Tamilnadu, India

Fossil site in Kerala, India

Fossil site in Kerala, India

Fossil wood park maintained by geological survey of India at Tamilnadu

Cretaceous fossil sites india

Fossils in rack:-Cyad

Fossils in rack:-echiniderms

Fossils in rack:-Rastellum sp

Pre-historic seabed, Cretaceous period

Iconic Australasian Trees Found as Fossils in South America

January 11th, 2014 Riffin

Today in Australia they call it Kauri, in Asia they call it Dammar, and in South America it does not exist at all unless planted there. But 52 million years ago the giant coniferous evergreen tree known to botanists as Agathis thrived in the Patagonian region of Argentina, according to an international team of paleobotanists, who have found numerous fossilized remains there.

“These spectacular fossils reveal that Agathis is old and had a huge range that no one knew about — from Australia to South America across Antarctica,” said Peter Wilf, professor of geoscience, Penn State.

Agathis trees currently grow thousands of miles from Argentina, ranging from Sumatra to New Zealand. They often prefer mountain rainforests, where it is wet and warm all year round. They can grow as tall as 200 feet, but are usually between 130 and 150 feet at maturity. Economically, they are prized and heavily cut for their soft, workable wood. In the past, the Agathis resin, known as manila copal, was exploited for linoleum and varnishes, but synthetics replaced most of that use.

Fossil of leafy Agathis tree branch. (Credit: Peter Wilf/Penn State)

Fossil of leafy Agathis tree branch. (Credit: Peter Wilf/Penn State)

The researchers report in the current issue of American Journal of Botany that “Agathis was a dominant, keystone element of the Patagonian Eocene floras, alongside numerous other plant taxa that still associate with it in Australasia and Southeast Asia.”

“There is a fossil record of Agathis in Australia and New Zealand, where it still lives,” said Wilf. “However, Agathis fossils have never been found anywhere else until now, and they have never been as complete as these.”

Wilf and his colleagues work at two sites in Patagonia, Argentina: Laguna del Hunco that dates to the early Eocene at about 52.2 million years ago, and Río Pichileufú dating to about 47.7 million years ago.

“These sites were discovered in the 1920s and 1930s, but the remoteness of the locations and the hardness of the rock are why they hadn’t been investigated in detail before we started in 1999,” said Wilf. “Now, with modern amenities — satellite phones for example — and especially the presence of our partner institution, the Egidio Feruglio Museum, in the same region as the dig sites, recovering these fossils becomes much easier.”

Agathis grew in Patagonia when South America was part of the remainder of the southern supercontinent of Gondwana, composed of South America, Antarctica and Australia. Much earlier, India, Madagascar, New Zealand and Africa separated and moved north, but around the time of these fossils, South America was just beginning to part from Antarctica, which was not ice covered at the time.

“Agathis probably existed in all three areas, Australia, Antarctica and South America, at that time,” said Wilf. “Climate change in Antarctica — the cold and ice — killed them there, and a change to seasonal dryness in southern South America put an end to them in Patagonia.”

Subsequently, the trees, which are wind dispersed, moved away from the cooling south, and some left northward-moving Australia for southeast Asia, where they thrive except for human interference, but they no longer grow in cold, often dry, Patagonia.

Wilf ‘s team recovered not only leaves, but also numerous branches, pollen cones, seed cones and even a winged seed still attached to the cone. The various species of Agathis are usually identified by their pollen cones, so this is the first time that a fossil Agathis could be directly compared to trees growing today.

“We also went to Borneo and studied the most similar living relative of the fossil Agathis, a threatened species there,” said Wilf. “We collected DNA samples to better understand the fossil-modern relationship.”

According to the researchers, the Argentinian fossil Agathis clearly belongs to the same natural group as those living today up to almost 10,000 miles away in the tropical West Pacific.

“Agathis is a very dramatic example of survival via huge range shifts, from the far south to the tropics, in response to climate change and land movement over millions of years,” said Wilf. “It is not clear that Agathis can adapt to the severely more rapid human-induced pressures it is experiencing now from deforestation, selective logging and climate change.”

Also working on this research are Ignacio H. Escapa and Rubén Cúneo, Consejo Nacional de Investigaciones Científicas y Técnicas and Museo Paleontológico Egidio Feruglio, Chubut, Argentina; Robert M. Kooyman, National Herbarium of New South Wales, Sydney; Kirk R. Johnson, Smithsonian Institution; and Ari Iglesias, Consejo Nacional de Investigaciones Científicas y Técnicas and División Palontología, Universidad Nacional del Comahue, Río Negro, Argentina.

The National Science Foundation, the David and Lucile Packard Foundation, National Geographic Society,University of Pennsylvania Research Foundation and the Andrew W. Mellon Foundation supported this work.

Amber Fossil Reveals Ancient Reproduction in Flowering Plants

January 7th, 2014 Riffin

A 100-million-year old piece of amber has been discovered which reveals the oldest evidence of sexual reproduction in a flowering plant — a cluster of 18 tiny flowers from the Cretaceous Period — with one of them in the process of making some new seeds for the next generation.

The perfectly-preserved scene, in a plant now extinct, is part of a portrait created in the mid-Cretaceous when flowering plants were changing the face of the Earth forever, adding beauty, biodiversity and food. It appears identical to the reproduction process that “angiosperms,” or flowering plants still use today.

Researchers from Oregon State University and Germany published their findings on the fossils in the Journal of the Botanical Institute of Texas.

The flowers themselves are in remarkable condition, as are many such plants and insects preserved for all time in amber. The flowing tree sap covered the specimens and then began the long process of turning into a fossilized, semi-precious gem. The flower cluster is one of the most complete ever found in amber and appeared at a time when many of the flowering plants were still quite small.

Even more remarkable is the microscopic image of pollen tubes growing out of two grains of pollen and penetrating the flower’s stigma, the receptive part of the female reproductive system. This sets the stage for fertilization of the egg and would begin the process of seed formation — had the reproductive act been completed.

“In Cretaceous flowers we’ve never before seen a fossil that shows the pollen tube actually entering the stigma,” said George Poinar, Jr., a professor emeritus in the Department of Integrative Biology at the OSU College of Science. “This is the beauty of amber fossils. They are preserved so rapidly after entering the resin that structures such as pollen grains and tubes can be detected with a microscope.”

Ancient flower. (Credit: Image courtesy of Oregon State University)

Ancient flower. (Credit: Image courtesy of Oregon State University)

The pollen of these flowers appeared to be sticky, Poinar said, suggesting it was carried by a pollinating insect, and adding further insights into the biodiversity and biology of life in this distant era. At that time much of the plant life was composed of conifers, ferns, mosses, and cycads. During the Cretaceous, new lineages of mammals and birds were beginning to appear, along with the flowering plants. But dinosaurs still dominated the Earth.

“The evolution of flowering plants caused an enormous change in the biodiversity of life on Earth, especially in the tropics and subtropics,” Poinar said.

“New associations between these small flowering plants and various types of insects and other animal life resulted in the successful distribution and evolution of these plants through most of the world today,” he said. “It’s interesting that the mechanisms for reproduction that are still with us today had already been established some 100 million years ago.”

The fossils were discovered from amber mines in the Hukawng Valley of Myanmar, previously known as Burma. The newly-described genus and species of flower was named Micropetasos burmensis.

‘Nedoceratops’: An Example of a Transitional Morphology

January 4th, 2014 Riffin

The holotype and only specimen of the chasmosaurine ceratopsid dinosaur ‘Nedoceratops hatcheri’ has been the source of considerable taxonomic debate since its initial description. At times it has been referred to its own genus while at others it has been considered synonymous with the contemporaneous chasmosaurine Triceratops. Most recently, the debate has focused on whether the specimen represents an intermediate ontogenetic stage between typical young adult Triceratops and the proposed mature morphology, which was previously considered to represent a distinct genus, ‘Torosaurus’.

Methodology/Principal Findings

The only specimen of ‘Nedoceratops hatcheri’ was examined and the proposed diagnostic features of this taxon were compared with other chasmosaurine ceratopsids. Every suggested autapomorphy of ‘Nedoceratops’ is found in specimens of Triceratops. In this study, Triceratops includes the adult ‘Torosaurus’ morphology. The small parietal fenestra and elongate squamosals of Nedoceratops are consistent with a transition from a short, solid parietal-squamosal frill to an expanded, fenestrated condition. Objections to this hypothesis regarding the number of epiossifications of the frill and alternations of bone surface texture were explored through a combination of comparative osteology and osteohistology. The synonymy of the three taxa was further supported by these investigations.

Conclusions/Significance

The Triceratops, ‘Torosaurus’, and ‘Nedoceratops’ morphologies represent ontogenetic variation within a single genus of chasmosaurine: Triceratops. This study highlights how interpretations of dinosaur paleobiology, biodiversity, and systematics may be affected by ascribing ontogenetic and other intraspecific variation a taxonomic significance.

Figure 1. USNM 2412, the holotype and only specimen of ‘Nedoceratops hatcheri’. show more A. Left lateral view. B. Right lateral view. Scale bars equal 10 cm. doi:10.1371/journal.pone.0028705.g001

Figure 1. USNM 2412, the holotype and only specimen of ‘Nedoceratops hatcheri’.A. Left lateral view. B. Right lateral view. Scale bars equal 10 cm.
doi:10.1371/journal.pone.0028705.g001 

Figure 2. Nasal horn variation in Triceratops. show more A. USNM 4720, originally named the holotype of Triceratops ‘obtusus.’ This specimen preserves a very low, blunt nasal horn. B. USNM 2412, the holotype of ‘Nedoceratops hatcheri.’ The nasal horn of this specimen (if present – see discussion) is a low, smooth boss. C. UCMP 128561, originally named the holotype of ‘Ugrosaurus olsoni.’ The nasal horn of this specimen is a low rugose boss. D. MOR 981 (previously ‘Torosaurus’). This specimen bears a low boss which is undifferentiated from the nasals. Scale bars equal 10 cm. doi:10.1371/journal.pone.0028705.g002

Figure 2. Nasal horn variation in Triceratops.
A. USNM 4720, originally named the holotype of Triceratops ‘obtusus.’ This specimen preserves a very low, blunt nasal horn. B. USNM 2412, the holotype of ‘Nedoceratops hatcheri.’ The nasal horn of this specimen (if present – see discussion) is a low, smooth boss. C. UCMP 128561, originally named the holotype of ‘Ugrosaurus olsoni.’ The nasal horn of this specimen is a low rugose boss. D. MOR 981 (previously ‘Torosaurus’). This specimen bears a low boss which is undifferentiated from the nasals. Scale bars equal 10 cm.
doi:10.1371/journal.pone.0028705.g002

 

Figure 3. Ventral view of the right half of the parietal of USNM 2412. show more A. When viewed with offset lighting, the rim of a shallow depression surrounding the small fenestra is apparent. B. Extent of the depression is outlined. The area within the outline is markedly thinner than the remainder of the parietal. The extent of the depression is partially obscured by the framework which supports the skull. Scale bars equal 10 cm. doi:10.1371/journal.pone.0028705.g003

Figure 3. Ventral view of the right half of the parietal of USNM 2412.
A. When viewed with offset lighting, the rim of a shallow depression surrounding the small fenestra is apparent. B. Extent of the depression is outlined. The area within the outline is markedly thinner than the remainder of the parietal. The extent of the depression is partially obscured by the framework which supports the skull. Scale bars equal 10 cm.
doi:10.1371/journal.pone.0028705.g003

Figure 4. Dorsal view of the parietal fenestra of USNM 2412. show more Although much of the parietal is obscured by reconstruction, a transition in surface texture from the posterior margin (white arrow) to the area immediately adjacent to and surrounding the fenestra (red arrows) is apparent. Scale bar equals 10 cm. doi:10.1371/journal.pone.0028705.g004

Figure 4. Dorsal view of the parietal fenestra of USNM 2412.
Although much of the parietal is obscured by reconstruction, a transition in surface texture from the posterior margin (white arrow) to the area immediately adjacent to and surrounding the fenestra (red arrows) is apparent. Scale bar equals 10 cm.
doi:10.1371/journal.pone.0028705.g004

Figure 5. Lateral views of USNM 1201 and USNM 2142. show more A. Left lateral view of USNM 1201, originally named the holotype of Triceratops ‘elatus.’ Note that the ventral extremity of the squamosal (denoted by upper horizontal line) is positioned well above the alveolar process of the maxilla (denoted by lower horizontal line). B. USNM 2412, right lateral view (reversed for direct comparison with USNM 1201 which only preserves the left side of the skull; the right squamosal of USNM 2412 is more elevated than the left). The alveolar process of the maxilla is positioned on the lower horizontal line, allowing for a direct comparison with USNM 1201. Note that the squamosal is not elevated to the extent found in USNM 1201. The position of the ventral extremity above the alveolar process of the maxilla can thus not be used to distinguish ‘Nedoceratops hatcheri’ from Triceratops. Scale bars equal 10 cm. doi:10.1371/journal.pone.0028705.g005

Figure 5. Lateral views of USNM 1201 and USNM 2142.
A. Left lateral view of USNM 1201, originally named the holotype of Triceratops ‘elatus.’ Note that the ventral extremity of the squamosal (denoted by upper horizontal line) is positioned well above the alveolar process of the maxilla (denoted by lower horizontal line). B. USNM 2412, right lateral view (reversed for direct comparison with USNM 1201 which only preserves the left side of the skull; the right squamosal of USNM 2412 is more elevated than the left). The alveolar process of the maxilla is positioned on the lower horizontal line, allowing for a direct comparison with USNM 1201. Note that the squamosal is not elevated to the extent found in USNM 1201. The position of the ventral extremity above the alveolar process of the maxilla can thus not be used to distinguish ‘Nedoceratops hatcheri’ from Triceratops. Scale bars equal 10 cm.
doi:10.1371/journal.pone.0028705.g005

 

Figure 6. Episquamosal of MOR 2975. show more The presence of two peaks is suggestive of midline erosion. Scale bar equals 5 cm. doi:10.1371/journal.pone.0028705.g006

Figure 6. Episquamosal of MOR 2975.
The presence of two peaks is suggestive of midline erosion. Scale bar equals 5 cm.
doi:10.1371/journal.pone.0028705.g006

Figure 7. Ventral view of the parietal of MOR 1122. show more A. The entire parietal with midline denoted by vertical line. Dashed rectangle indicates area of interest in B and C. B. Impressed vascular traces are found over the entire ventral surface of the parietal. Epiparietals are indicated by arrows. MOR 1122 does not appear to possess an epiparietal over the midline of the parietal. C. Major vascular traces are highlighted in red. Note that the most prominent vascular traces lead to the epiparietals (highlighted in blue). Two large vascular traces lead to the midline of the parietal (denoted by red arrow), suggesting that an epiparietal occupied this position but was lost taphonomically. Scale bars equal 10 cm. doi:10.1371/journal.pone.0028705.g007

Figure 7. Ventral view of the parietal of MOR 1122.
A. The entire parietal with midline denoted by vertical line. Dashed rectangle indicates area of interest in B and C. B. Impressed vascular traces are found over the entire ventral surface of the parietal. Epiparietals are indicated by arrows. MOR 1122 does not appear to possess an epiparietal over the midline of the parietal. C. Major vascular traces are highlighted in red. Note that the most prominent vascular traces lead to the epiparietals (highlighted in blue). Two large vascular traces lead to the midline of the parietal (denoted by red arrow), suggesting that an epiparietal occupied this position but was lost taphonomically. Scale bars equal 10 cm.
doi:10.1371/journal.pone.0028705.g007

Figure 8. Osteohistology of the postorbital horn core of MOR 981. show more The dense, multigenerational ‘Haversian’ tissue is indicative of a mature individual. doi:10.1371/journal.pone.0028705.g008

Figure 8. Osteohistology of the postorbital horn core of MOR 981.
The dense, multigenerational ‘Haversian’ tissue is indicative of a mature individual.
doi:10.1371/journal.pone.0028705.g008

 

Citation: Scannella JB, Horner JR (2011) ‘Nedoceratops’: An Example of a Transitional Morphology. PLoS ONE 6(12): e28705. doi:10.1371/journal.pone.0028705

Editor: Leon Claessens, College of the Holy Cross, United States of America

 

 

 

 

 

 

 

Earth’s Crust Was Unstable in Archean Eon; Dripped Down Into Mantle

January 1st, 2014 Riffin

Earth’s mantle temperatures during the Archean eon, which commenced some 4 billion years ago, were significantly higher than they are today. According to recent model calculations, the Archean crust that formed under these conditions was so dense that large portions of it were recycled back into the mantle. This is the conclusion reached by Dr. Tim Johnson who is currently studying the evolution of Earth’s crust as a member of the research team led by Professor Richard White of the Institute of Geosciences at Johannes Gutenberg University Mainz (JGU).

According to the calculations, this dense primary crust would have descended vertically in drip form. In contrast, the movements of today’s tectonic plates involve largely lateral movements with oceanic lithosphere recycled in subduction zones. The findings add to our understanding of how cratons and plate tectonics, and thus also Earth’s current continents, came into being.

computer simulation

computer simulation

Because mantle temperatures were higher during the Archean eon, Earth’s primary crust that formed at the time must have been very thick and also very rich in magnesium. However, as Johnson and his co-authors explain in their article recently published in Nature Geoscience, very little of this original crust is preserved, indicating that most must have been recycled into Earth’s mantle. Moreover, the Archean crust that has survived in some areas such as, for example, Northwest Scotland and Greenland, is largely made of tonalite-trondhjemite-granodiorite complexes and these are likely to have originated from a hydrated, low-magnesium basalt source. The conclusion is that these pieces of crust cannot be the direct products of an originally magnesium-rich primary crust. These TTG complexes are among the oldest features of our Earth’s crust. They are most commonly present in cratons, the oldest and most stable cores of the current continents.

With the help of thermodynamic calculations, Dr. Tim Johnson and his collaborators at the US-American universities of Maryland, Southern California, and Yale have established that the mineral assemblages that formed at the base of a 45-kilometer-thick magnesium-rich crust were denser than the underlying mantle layer. In order to better explore the physics of this process, Professor Boris Kaus of the Geophysics work group at Mainz University developed new computer models that simulate the conditions when Earth was still relatively young and take into account Johnson’s calculations.

These geodynamic computer models show that the base of a magmatically over-thickened and magnesium-rich crust would have been gravitationally unstable at mantle temperatures greater than 1,500 to 1,550 degrees Celsius and this would have caused it to sink in a process called ‘delamination’. The dense crust would have dripped down into the mantle, triggering a return flow of mantle material from the asthenosphere that would have melted to form new primary crust. Continued melting of over-thickened and dripping magnesium-rich crust, combined with fractionation of primary magmas, may have produced the hydrated magnesium-poor basalts necessary to provide a source of the tonalite-trondhjemite-granodiorite complexes. The dense residues of these processes, which would have a high content of mafic minerals, must now reside in the mantle.

 

 

Global Map Predicts Locations for Giant Earthquakes

December 31st, 2013 Riffin

A team of international researchers, led by Monash University’s Associate Professor Wouter Schellart, have developed a new global map of subduction zones, illustrating which ones are predicted to be capable of generating giant earthquakes and which ones are not.

The new research, published in the journal Physics of the Earth and Planetary Interiors, comes nine years after the giant earthquake and tsunami in Sumatra in December 2004, which devastated the region and many other areas surrounding the Indian Ocean, and killed more than 200,000 people.

Andaman Sea. "For the Australian region subduction zones of particular significance are the Sunda subduction zone, running from the Andaman Islands along Sumatra and Java to Sumba, and the Hikurangi subduction segment offshore the east coast of the North Island of New Zealand. Our research predicts that these zones are capable of producing giant earthquakes," Dr Schellart said. (Credit: © vichie81 / Fotolia)

Andaman Sea. “For the Australian region subduction zones of particular significance are the Sunda subduction zone, running from the Andaman Islands along Sumatra and Java to Sumba, and the Hikurangi subduction segment offshore the east coast of the North Island of New Zealand. Our research predicts that these zones are capable of producing giant earthquakes,” Dr Schellart said. (Credit: © vichie81 / Fotolia)

Since then two other giant earthquakes have occurred at subduction zones, one in Chile in February 2010 and one in Japan in March 2011, which both caused massive destruction, killed many thousands of people and resulted in billions of dollars of damage.

Most earthquakes occur at the boundaries between tectonic plates that cover the Earth’s surface. The largest earthquakes on Earth only occur at subduction zones, plate boundaries where one plate sinks (subducts) below the other into the Earth’s interior. So far, seismologists have recorded giant earthquakes for only a limited number of subduction zone segments. But accurate seismological records go back to only ~1900, and the recurrence time of giant earthquakes can be many hundreds of years.

“The main question is, are all subduction segments capable of generating giant earthquakes, or only some of them? And if only a limited number of them, then how can we identify these,” Dr Schellart said.

Dr Schellart, of the School of Geosciences, and Professor Nick Rawlinson from the University of Aberdeen in Scotland used earthquake data going back to 1900 and data from subduction zones to map the main characteristics of all active subduction zones on Earth. They investigated if those subduction segments that have experienced a giant earthquake share commonalities in their physical, geometrical and geological properties.

They found that the main indicators include the style of deformation in the plate overlying the subduction zone, the level of stress at the subduction zone, the dip angle of the subduction zone, as well as the curvature of the subduction zone plate boundary and the rate at which it moves.

Through these findings Dr Schellart has identified several subduction zone regions capable of generating giant earthquakes, including the Lesser Antilles, Mexico-Central America, Greece, the Makran, Sunda, North Sulawesi and Hikurangi.

“For the Australian region subduction zones of particular significance are the Sunda subduction zone, running from the Andaman Islands along Sumatra and Java to Sumba, and the Hikurangi subduction segment offshore the east coast of the North Island of New Zealand. Our research predicts that these zones are capable of producing giant earthquakes,” Dr Schellart said.

“Our work also predicts that several other subduction segments that surround eastern Australia (New Britain, San Cristobal, New Hebrides, Tonga, Puysegur), are not capable of producing giant earthquakes.”

Fossil Worm Burrows Reveal Very Early Terrestrial Animal Activity and Shed Light on Trophic Resources after the End-Cretaceous Mass Extinction

December 28th, 2013 Riffin

The widespread mass extinctions at the end of the Cretaceous caused world-wide disruption of ecosystems, and faunal responses to the one-two punch of severe environmental perturbation and ecosystem collapse are still unclear. Here we report the discovery of in situ terrestrial fossil burrows from just above the impact-defined Cretaceous-Paleogene (K/Pg) boundary in southwestern North Dakota. The crisscrossing networks of horizontal burrows occur at the interface of a lignitic coal and silty sandstone, and reveal intense faunal activity within centimeters of the boundary clay. Estimated rates of sedimentation and coal formation suggest that the burrows were made less than ten thousand years after the end-Cretaceous impact. The burrow characteristics are most consistent with burrows of extant earthworms. Moreover, the burrowing and detritivorous habits of these annelids fit models that predict the trophic and sheltering lifestyles of terrestrial animals that survived the K/Pg extinction event. In turn, such detritus-eaters would have played a critical role in supporting secondary consumers. Thus, some of the carnivorous vertebrates that radiated after the K/Pg extinction may owe their evolutionary success to thriving populations of earthworms.

Figure 1. Terrestrial K/Pg boundary site at Mud Buttes, North Dakota. show more (A) Stratigraphic section through K/Pg boundary interval; this section is located ~150 m southwest of the Mud Buttes burrow locality (adapted from Bercovici et al. 2009). (B) X marks location of Mud Buttes locality in southwestern North Dakota, USA. (C) View of K/Pg boundary in situ at Mud Buttes burrow locality. Note that burrow layer is ~6 cm above the orange-hued boundary clay at this site. Tic marks at left are in 1 cm increments. (D) Plan view of the undersides of burrows at lignite/silty sandstone interface (specimen KT4/UCM 98213). (E) Close-up of lignitic coal showing poorly-compacted plant debris. (F) Close-up of boundary clay showing abundant spherules ~40 µm in diameter. doi:10.1371/journal.pone.0070920.g001

Figure 1. Terrestrial K/Pg boundary site at Mud Buttes, North Dakota.
(A) Stratigraphic section through K/Pg boundary interval; this section is located ~150 m southwest of the Mud Buttes burrow locality (adapted from Bercovici et al. 2009). (B) X marks location of Mud Buttes locality in southwestern North Dakota, USA. (C) View of K/Pg boundary in situ at Mud Buttes burrow locality. Note that burrow layer is ~6 cm above the orange-hued boundary clay at this site. Tic marks at left are in 1 cm increments. (D) Plan view of the undersides of burrows at lignite/silty sandstone interface (specimen KT4/UCM 98213). (E) Close-up of lignitic coal showing poorly-compacted plant debris. (F) Close-up of boundary clay showing abundant spherules ~40 µm in diameter.
doi:10.1371/journal.pone.0070920.g001

 

Figure 2. Planolites isp. burrows from Mud Buttes. show more (A) Plan view showing undersides of closely packed horizontal burrows at coal/silty sandstone interface. Note coal still adherent to some burrows (specimen KT3/UCM 98212). (B) Discernible burrows colored and numbered to illustrate minimum burrow density within 8 cm2 (specimen KT4/UCM 98213). Portions of at least 23 burrows comprise roughly 30% of area of white box. Burrows are colored different shades of green to illustrate overlapping relationships. The burrowing activity likely took place within a short period of time, but burrows colored darker green were lower in the soil profile and appear to have been crossed in situ by other burrows (lighter shades of green). Burrows colored lightest green were the topmost burrows. Note that this specimen is the same as that in Figure 1D. (C) Close-up of burrow 19 in B (specimen KT4/UCM 98213). doi:10.1371/journal.pone.0070920.g002

Figure 2. Planolites isp. burrows from Mud Buttes.
(A) Plan view showing undersides of closely packed horizontal burrows at coal/silty sandstone interface. Note coal still adherent to some burrows (specimen KT3/UCM 98212). (B) Discernible burrows colored and numbered to illustrate minimum burrow density within 8 cm2 (specimen KT4/UCM 98213). Portions of at least 23 burrows comprise roughly 30% of area of white box. Burrows are colored different shades of green to illustrate overlapping relationships. The burrowing activity likely took place within a short period of time, but burrows colored darker green were lower in the soil profile and appear to have been crossed in situ by other burrows (lighter shades of green). Burrows colored lightest green were the topmost burrows. Note that this specimen is the same as that in Figure 1D. (C) Close-up of burrow 19 in B (specimen KT4/UCM 98213).
doi:10.1371/journal.pone.0070920.g002

 

3. Thin sections of bioturbated sediment (A, B) and a section of burrow fill (C, D). show more (A) Photomicrograph of thin section of epoxy-impregnated bioturbated layer (specimen KT3-T2b/UCM 98212). Bottom of photo is at the coal/silty sandstone interface, and top is several mm higher in section. The ~3 mm diameter circular structure labeled “b” in the center of the photograph appears to be a cross section of a burrow. A thin layer of fractured coal is evident below this (“c”). Numerous pelletoid blebs are visible, including one in the burrow cross-section, and several others massed together in the upper part of the photo (two are labeled “p”). (B) QEMSCAN (Quantitative Evaluation of Minerals by SCANning electron microscopy) image of portion of thin section in A showing distribution of clay minerals (brown), quartz (pink), and feldspars (turquoise) in the bioturbated sediment (note that organic matter was not detected at the kV setting used to analyze minerals). Concentrated blebs of clay are conspicuous. Same letter designations apply as in A. (C) Thin section of partial burrow fill from KT3-T3b/UCM 98212. This burrow was sandwiched between the underlying coal and a thin layer of coal on top, indicating burrowing within the Paleocene peat. Red box in lower left shows site of photomicrograph in D. (D) Close-up of area of red-box in C showing a pelletoid clay mass containing tiny (<25 µm) mineral clasts; this clay bleb appears to be a fecal pellet from a deposit-feeding invertebrate. (E) Color key of minerals in QEMSCAN image B and calculated QEMSCAN mass percentages of minerals in bioturbated sediment sample (portion of which shown in B, and in burrow fill shown in C. doi:10.1371/journal.pone.0070920.g003

3. Thin sections of bioturbated sediment (A, B) and a section of burrow fill (C, D).
(A) Photomicrograph of thin section of epoxy-impregnated bioturbated layer (specimen KT3-T2b/UCM 98212). Bottom of photo is at the coal/silty sandstone interface, and top is several mm higher in section. The ~3 mm diameter circular structure labeled “b” in the center of the photograph appears to be a cross section of a burrow. A thin layer of fractured coal is evident below this (“c”). Numerous pelletoid blebs are visible, including one in the burrow cross-section, and several others massed together in the upper part of the photo (two are labeled “p”). (B) QEMSCAN (Quantitative Evaluation of Minerals by SCANning electron microscopy) image of portion of thin section in A showing distribution of clay minerals (brown), quartz (pink), and feldspars (turquoise) in the bioturbated sediment (note that organic matter was not detected at the kV setting used to analyze minerals). Concentrated blebs of clay are conspicuous. Same letter designations apply as in A. (C) Thin section of partial burrow fill from KT3-T3b/UCM 98212. This burrow was sandwiched between the underlying coal and a thin layer of coal on top, indicating burrowing within the Paleocene peat. Red box in lower left shows site of photomicrograph in D. (D) Close-up of area of red-box in C showing a pelletoid clay mass containing tiny (doi:10.1371/journal.pone.0070920.g003

Citation: Chin K, Pearson D, Ekdale AA (2013) Fossil Worm Burrows Reveal Very Early Terrestrial Animal Activity and Shed Light on Trophic Resources after the End-Cretaceous Mass Extinction. PLoS ONE 8(8): e70920. doi:10.1371/journal.pone.0070920

Editor: Richard J. Butler, University of Birmingham, United Kingdom

 

 

 

Oldest big cat fossil found in Tibet

December 26th, 2013 Riffin

The oldest big cat fossils ever found – from a previously unknown species “similar to a snow leopard” – have been unearthed in the Himalayas.The skull fragments of the newly-named Panthera blytheae have been dated between 4.1 and 5.95 million years old. Their discovery in Tibet supports the theory that big cats evolved in central Asia – not Africa – and spread outward.The findings by US and Chinese palaeontologists are published in the Royal Society journal Proceedings B.They used both anatomical and DNA data to determine that the skulls belonged to an extinct big cat, whose territory appears to overlap many of the species we know today.

 “This cat is a sister of living snow leopards – it has a broad forehead and a short face. But it’s a little smaller – the size of clouded leopards,” said lead author Dr Jack Tseng of the University of Southern California.

“This ties up a lot of questions we had on how these animals evolved and spread throughout the world.

“Biologists had hypothesised that big cats originated in Asia. But there was a division between the DNA data and the fossil record.”

Surprising find The so-called “big cats” – the Pantherinae subfamily – includes lions, jaguars, tigers, leopards, snow leopards, and clouded leopards. DNA evidence suggests they diverged from their cousins the Felinae – which includes cougars, lynxes, and domestic cats – about 6.37 million years ago. But the earliest fossils previously found were just 3.6 million years old – tooth fragments uncovered at Laetoli in Tanzania, the famous hominin site excavated by Mary Leakey in the 1970s.

Fossil skull of Panthera blytheae

It is rare for such an ancient carnivore fossil to be so well preserved

The new fossils were dug up on an expedition in 2010 in the remote Zanda Basin in southwestern Tibet, by a team including Dr Tseng and his wife Juan Liu – a fellow palaeontologist. They found over 100 bones deposited by a river eroding out of a cliff, including the crushed – but largely complete – remains of a big cat skull.

“We were very surprised to find a cat fossil in that basin,” Dr Tseng told BBC News.

“Usually we find antelopes and rhinos, but this site was special. We found multiple carnivores – badgers, weasels and foxes.”

Among the bones were seven skull fragments, belonging to at least three individual cats, including one nearly complete skull. The fragments were dated using magnetostratigraphy – which relies on historical reversals in the Earth’s magnetic field recorded in layers of rock. They ranged between 4.10 and 5.95 million years old, the complete skull being around 4.4 million years of age.

“This is a very significant finding – it fills a very wide gap in the fossil record,” said Dr Manabu Sakamoto of the University of Bristol, an expert on Pantherinae evolution.

“The discovery presents strong support for the Asian origin hypothesis for the big cats.

“It gives us a great insight into what early big cats may have looked like and where they may have lived.”

However, Prof William Murphy of Texas A&M University, another expert on the evolutionary relationship of big cats, questioned whether the new species was really a sister of the snow leopard.

“The authors’ claim that this skull is similar to the snow leopard is very weakly supported based on morphological characters alone, and this morphology-based tree is inconsistent with the DNA-based tree of living cats,” he told BBC News.

“It remains equally probable that this fossil is ancestral to the living big cats. More complete skeletons would be beneficial to confirm their findings.”

Dr Tseng and his team plan to return to the fossil site in Tibet next summer to search for more specimens.

Source: Report by James Morgan Science reporter, BBC News

Mapping the Demise of the Dinosaurs

December 24th, 2013 Riffin

About 65 million years ago, an asteroid or comet crashed into a shallow sea near what is now the Yucatán Peninsula of Mexico. The resulting firestorm and global dust cloud caused the extinction of many land plants and large animals, including most of the dinosaurs. At this week’s meeting of the American Geophysical Union (AGU) in San Francisco, MBARI researchers will present evidence that remnants from this devastating impact are exposed along the Campeche Escarpment — an immense underwater cliff in the southern Gulf of Mexico.

The ancient meteorite impact created a huge crater, over 160 kilometers across. Unfortunately for geologists, this crater is almost invisible today, buried under hundreds of meters of debris and almost a kilometer of marine sediments. Although fallout from the impact has been found in rocks around the world, surprisingly little research has been done on the rocks close to the impact site, in part because they are so deeply buried. All existing samples of impact deposits close to the crater have come from deep boreholes drilled on the Yucatán Peninsula.

This close-up image of the Campeche Escarpment from the 2013 sonar survey shows a layer of resistent rock that researchers believe may contain rocks formed during an impact event 65 million years ago. (Credit: Copyright 2013 MBARI)

This close-up image of the Campeche Escarpment from the 2013 sonar survey shows a layer of resistent rock that researchers believe may contain rocks formed during an impact event 65 million years ago. (Credit: Copyright 2013 MBARI)

In March 2013, an international team of researchers led by Charlie Paull of the Monterey Bay Aquarium Research Institute (MBARI) created the first detailed map of the Campeche Escarpment. The team used multi-beam sonars on the research vessel Falkor, operated by the Schmidt Ocean Institute. The resulting maps have recently been incorporated in Google Maps and Google Earth for viewing by researchers and the general public.

Paull has long suspected that rocks associated with the impact might be exposed along the Campeche Escarpment, a 600-kilometer-long underwater cliff just northwest of the Yucatán Peninsula. Nearly 4,000 meters tall, the Campeche Escarpment is one of the steepest and tallest underwater features on Earth. It is comparable to one wall of the Grand Canyon — except that it lies thousands of meters beneath the sea.

As in the walls of the Grand Canyon, sedimentary rock layers exposed on the face of the Campeche Escarpment provide a sequential record of the events that have occurred over millions of years. Based on the new maps, Paull believes that rocks formed before, during, and after the impact are all exposed along different parts of this underwater cliff.

Just as a geologist can walk the Grand Canyon, mapping layers of rock and collecting rock samples, Paull hopes to one day perform geologic “fieldwork” and collect samples along the Campeche Escarpment. Only a couple of decades ago, the idea of performing large-scale geological surveys thousands of meters below the ocean surface would have seemed a distant fantasy. Over the last eight years, however, such mapping has become almost routine for MBARI geologists using underwater robots.

The newly created maps of the Campeche Escarpment could open a new chapter in research about one of the largest extinction events in Earth’s history. Already researchers from MBARI and other institutions are using these maps to plan additional studies in this little-known area. Detailed analysis of the bathymetric data and eventual fieldwork on the escarpment will reveal fascinating new clues about what happened during the massive impact event that ended the age of the dinosaurs — clues that have been hidden beneath the waves for 65 million years.

In addition to the Schmidt Ocean Institute, Paull’s collaborators in this research included Jaime Urrutia-Fucugauchi from the Universidad Nacional Autónoma de Mexico and Mario Rebolledo- Vieyra of the Centro de Investigación Científica de Yucatán. Paull also worked closely with MBARI researchers, including geophysicist and software engineer Dave Caress, an expert on processing of multibeam sonar data, and geologist Roberto Gwiazda, who served as project manager and will be describing this research at the AGU meeting.

Multivariate Analyses of Small Theropod Dinosaur Teeth and Implications for Paleoecological Turnover through Time

December 23rd, 2013 Riffin

Isolated small theropod teeth are abundant in vertebrate microfossil assemblages, and are frequently used in studies of species diversity in ancient ecosystems. However, determining the taxonomic affinities of these teeth is problematic due to an absence of associated diagnostic skeletal material. Species such as Dromaeosaurus albertensis, Richardoestesia gilmorei, and Saurornitholestes langstoni are known from skeletal remains that have been recovered exclusively from the Dinosaur Park Formation (Campanian). It is therefore likely that teeth from different formations widely disparate in age or geographic position are not referable to these species. Tooth taxa without any associated skeletal material, such as Paronychodon lacustris and Richardoestesia isosceles, have also been identified from multiple localities of disparate ages throughout the Late Cretaceous. To address this problem, a dataset of measurements of 1183 small theropod teeth (the most specimen-rich theropod tooth dataset ever constructed) from North America ranging in age from Santonian through Maastrichtian were analyzed using multivariate statistical methods: canonical variate analysis, pairwise discriminant function analysis, and multivariate analysis of variance. The results indicate that teeth referred to the same taxon from different formations are often quantitatively distinct. In contrast, isolated teeth found in time equivalent formations are not quantitatively distinguishable from each other. These results support the hypothesis that small theropod taxa, like other dinosaurs in the Late Cretaceous, tend to be exclusive to discrete host formations. The methods outlined have great potential for future studies of isolated teeth worldwide, and may be the most useful non-destructive technique known of extracting the most data possible from isolated and fragmentary specimens. The ability to accurately assess species diversity and turnover through time based on isolated teeth will help illuminate patterns of evolution and extinction in these groups and potentially others in greater detail than has previously been thought possible without more complete skeletal material.

Tooth measurements used in this study. show more ADM, anterior denticles per millimetre; BW, basal width; CH, crown height; FABL, fore-aft basal length; and PDM, posterior denticles per millimetre. doi:10.1371/journal.pone.0054329.g001

Tooth measurements used in this study.
ADM, anterior denticles per millimetre; BW, basal width; CH, crown height; FABL, fore-aft basal length; and PDM, posterior denticles per millimetre.
doi:10.1371/journal.pone.0054329.g001

Qualitative morphotypes used to construct a priori categories within formations and the qualitative characters that define them. show more A, Saurornitholestinae; B, Dromaeosaurinae; C, cf. Zapsalis; D, Dromaeosauridae; E, cf. Richardoestesia gilmorei; F, cf. Richardoestesia isosceles; G, cf. Pectinodon; and H, cf. Troodon. Qualitative characters: 1, posterior denticles apically oriented (that is, asymmetric denticles with a shorter apical side); 2, anterior denticles much smaller than posterior denticles; 3, posterior denticles rounded; 4, anterior denticles the same or slightly smaller than posterior denticles; 5, anterior denticles usually absent; 6, strong longitudinal ridges; 7, posterior denticles large and apically oriented; 8, posterior denticles are small and rounded; 9, anterior denticles are similar in size to posterior denticles or absent; 10, tall isosceles triangle shape; 11, posterior denticles very large and often rounded with apex of tooth frequently forming apical-most denticle; 12, posterior denticles are very large and apically hooked; and 13, anterior denticles are very large or absent. A, B, and H modified from Larson et al. 2010; C–F modified from Larson (2008); and G modified from Longrich (2008). Scale bars are 1 mm and correspond to images of crowns. doi:10.1371/journal.pone.0054329.g002

Qualitative morphotypes used to construct a priori categories within formations and the qualitative characters that define them.
A, Saurornitholestinae; B, Dromaeosaurinae; C, cf. Zapsalis; D, Dromaeosauridae; E, cf. Richardoestesia gilmorei; F, cf. Richardoestesia isosceles; G, cf. Pectinodon; and H, cf. Troodon. Qualitative characters: 1, posterior denticles apically oriented (that is, asymmetric denticles with a shorter apical side); 2, anterior denticles much smaller than posterior denticles; 3, posterior denticles rounded; 4, anterior denticles the same or slightly smaller than posterior denticles; 5, anterior denticles usually absent; 6, strong longitudinal ridges; 7, posterior denticles large and apically oriented; 8, posterior denticles are small and rounded; 9, anterior denticles are similar in size to posterior denticles or absent; 10, tall isosceles triangle shape; 11, posterior denticles very large and often rounded with apex of tooth frequently forming apical-most denticle; 12, posterior denticles are very large and apically hooked; and 13, anterior denticles are very large or absent. A, B, and H modified from Larson et al. 2010; C–F modified from Larson (2008); and G modified from Longrich (2008). Scale bars are 1 mm and correspond to images of crowns.
doi:10.1371/journal.pone.0054329.g002

Summary of quantitative morphotypes showing their stratigraphic ages. show more Each tooth icon likely represents a distinct taxon with the indicated known range based on formation as observed in this study. A, Lancian Saurornitholestinae gen. et sp., UCMP 187036 (reversed); B, Pectinodon bakkeri; C, Lancian cf. Richardoestesia gilmorei, UCMP 120255 (reversed); D, Lancian cf. Richardoestesia isosceles, UCMP 187175 (reversed); E, Atrociraptor marshalli, TMP 2000.045.0035; F, Horseshoe Canyon Dromaeosaurinae gen. et sp., TMP 1999.050.0116 (reversed); G, Horseshoe Canyon cf. Troodon sp., TMP 2000.045.0024 (reversed); H, Horseshoe Canyon cf. R. gilmorei, TMP 2003.015.0002; I, Saurornitholestes langstoni, TMP 1995.147.0026; J, Bambiraptor feinbergi, AMNH FR 30556; K, Dromaeosaurus albertensis, TMP 1986.130.0211; L, Zapsalis abradens, TMP 1987.050.0008; M, Troodon formosus, TMP 1995.147.0025; N, Dinosaur Park cf. Pectinodon sp., TMP 2000.021.0001; O, Richardoestesa gilmorei, TMP 2000.019.0004; P, Oldman cf. R. gilmorei, 1987.080.0035; Q, Richardoestesia isosceles, LSUMGS 489∶6238 (reversed); R, Milk River Saurornitholestinae gen. et sp., UALVP 50531 (reversed); S, Milk River Dromaeosauridae gen. et sp., UALVP 48365 (reversed); T, Milk River Dromaeosaurinae gen. et sp., UALVP 49571; U, Milk River cf. Zapsalis sp., UALVP 49582; V, Aquilan cf. Richardoestesia gilmorei, UALVP 48157 (reversed); and W, Aquilan cf. Richardoestesia isosceles, UALVP 48279 (reversed). B modified from Longrich (2008); H modified from Larson et al. (2010); J modified from Burnham (2004); P modified from Sankey et al. (2002); Q modified from Sankey (2001); R–W modified from Larson (2008). Teeth scaled to matching FABL. [full page width]. doi:10.1371/journal.pone.0054329.g006

Summary of quantitative morphotypes showing their stratigraphic ages.
Each tooth icon likely represents a distinct taxon with the indicated known range based on formation as observed in this study. A, Lancian Saurornitholestinae gen. et sp., UCMP 187036 (reversed); B, Pectinodon bakkeri; C, Lancian cf. Richardoestesia gilmorei, UCMP 120255 (reversed); D, Lancian cf. Richardoestesia isosceles, UCMP 187175 (reversed); E, Atrociraptor marshalli, TMP 2000.045.0035; F, Horseshoe Canyon Dromaeosaurinae gen. et sp., TMP 1999.050.0116 (reversed); G, Horseshoe Canyon cf. Troodon sp., TMP 2000.045.0024 (reversed); H, Horseshoe Canyon cf. R. gilmorei, TMP 2003.015.0002; I, Saurornitholestes langstoni, TMP 1995.147.0026; J, Bambiraptor feinbergi, AMNH FR 30556; K, Dromaeosaurus albertensis, TMP 1986.130.0211; L, Zapsalis abradens, TMP 1987.050.0008; M, Troodon formosus, TMP 1995.147.0025; N, Dinosaur Park cf. Pectinodon sp., TMP 2000.021.0001; O, Richardoestesa gilmorei, TMP 2000.019.0004; P, Oldman cf. R. gilmorei, 1987.080.0035; Q, Richardoestesia isosceles, LSUMGS 489∶6238 (reversed); R, Milk River Saurornitholestinae gen. et sp., UALVP 50531 (reversed); S, Milk River Dromaeosauridae gen. et sp., UALVP 48365 (reversed); T, Milk River Dromaeosaurinae gen. et sp., UALVP 49571; U, Milk River cf. Zapsalis sp., UALVP 49582; V, Aquilan cf. Richardoestesia gilmorei, UALVP 48157 (reversed); and W, Aquilan cf. Richardoestesia isosceles, UALVP 48279 (reversed). B modified from Longrich (2008); H modified from Larson et al. (2010); J modified from Burnham (2004); P modified from Sankey et al. (2002); Q modified from Sankey (2001); R–W modified from Larson (2008). Teeth scaled to matching FABL. [full page width].
doi:10.1371/journal.pone.0054329.g006

 

Citation: Larson DW, Currie PJ (2013) Multivariate Analyses of Small Theropod Dinosaur Teeth and Implications for Paleoecological Turnover through Time. PLoS ONE 8(1): e54329. doi:10.1371/journal.pone.0054329

Editor: Alistair Robert Evans, Monash University, Australia

 

 

 

Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans

December 22nd, 2013 Riffin

The Late Cretaceous (~95–66 million years ago) western North American landmass of Laramidia displayed heightened non-marine vertebrate diversity and intracontinental regionalism relative to other latest Cretaceous Laurasian ecosystems. Processes generating these patterns during this interval remain poorly understood despite their presumed role in the diversification of many clades. Tyrannosauridae, a clade of large-bodied theropod dinosaurs restricted to the Late Cretaceous of Laramidia and Asia, represents an ideal group for investigating Laramidian patterns of evolution. We use new tyrannosaurid discoveries from Utah—including a new taxon which represents the geologically oldest member of the clade—to investigate the evolution and biogeography of Tyrannosauridae. These data suggest a Laramidian origin for Tyrannosauridae, and implicate sea-level related controls in the isolation, diversification, and dispersal of this and many other Late Cretaceous vertebrate clades.

(A) Skeletal outlines showing recovered elements of Lythronax argestes (UMNH VP 20200) and (B) Teratophoneus curriei (UMNH VP 16690). Selected postcranial elements of Teratophoneus in left lateral view: (C) cervical vertebra 3; (D) cervical vertebra 9; (E–G) three caudal vertebrae; (H) right ilium (photoreversed with left illium in the background in grayscale); (I) pubis; (J) ischium; (K) right femur in lateral view; (L) right tibia in anterior view; and (M) right fibula in medial view. Elements of Lythronax figured include: (N) the left pubis in lateral view; (O), left tibia in anterior view (photoreversed); and (P) left fibula in medial view (photoreversed). Scale bar for a and b is 1 meter, c-g 5 cm and h-p 10 cm. Abbreviations: ac, acetabulum; af, astragalar facet; bf, brevis fossa; cc, cnemial crest; dp, diapophysis; ep, epipophysis; ff, fibular flange; ffa, fibular facet; ft, fourth trochanter; if, iliofibularis muscle scar; ip, ischial peduncle; lt, lesser trochanter; mff, fibular fossa; ns, neural spine; of, obturator flange; pa, parapophysis; pb, pubic boot; pc, pleurocoel; pp, pubic peduncle; poz, postzygapophysis; prz, prezygapophysis; sac, supraacetabular crest; sar, supraacetabular ridge; tp, transverse process. doi:10.1371/journal.pone.0079420.g001


(A) Skeletal outlines showing recovered elements of Lythronax argestes (UMNH VP 20200) and (B) Teratophoneus curriei (UMNH VP 16690). Selected postcranial elements of Teratophoneus in left lateral view: (C) cervical vertebra 3; (D) cervical vertebra 9; (E–G) three caudal vertebrae; (H) right ilium (photoreversed with left illium in the background in grayscale); (I) pubis; (J) ischium; (K) right femur in lateral view; (L) right tibia in anterior view; and (M) right fibula in medial view. Elements of Lythronax figured include: (N) the left pubis in lateral view; (O), left tibia in anterior view (photoreversed); and (P) left fibula in medial view (photoreversed). Scale bar for a and b is 1 meter, c-g 5 cm and h-p 10 cm. Abbreviations: ac, acetabulum; af, astragalar facet; bf, brevis fossa; cc, cnemial crest; dp, diapophysis; ep, epipophysis; ff, fibular flange; ffa, fibular facet; ft, fourth trochanter; if, iliofibularis muscle scar; ip, ischial peduncle; lt, lesser trochanter; mff, fibular fossa; ns, neural spine; of, obturator flange; pa, parapophysis; pb, pubic boot; pc, pleurocoel; pp, pubic peduncle; poz, postzygapophysis; prz, prezygapophysis; sac, supraacetabular crest; sar, supraacetabular ridge; tp, transverse process.
doi:10.1371/journal.pone.0079420.g001

 

Skull reconstructions and selected cranial elements of Lythronax argestes. show more These stippled reconstructions (A) are based on cranial elements recovered (B) for UMNH VP 20200. Selected elements of L. argestes holotype (UMNH VP 20200) including: (C) maxilla in lateral (photoreversed) and ventral views; (D) nasal in left lateral and dorsal view; (E) photoreversed frontal and laterosphenoid in lateral and dorsal view; (F) jugal in left lateral and dorsal view; (G) quadrate in left lateral and caudal view; (G) surangular in left lateral view; (I) prearticular in left lateral view; (J) dentary in lateral and ventral views. Abbreviations: a1-a11, alveoli 1–11; fpc, frontoparietal midsagittal crest; jf, jugal flange of the quadrate; jpr, jugal pneumatic recess; ljo, lateral jugal ornamentation; ls, laterosphenoid; mf, maxillary fenestra; na, naris; pf, palatine flange; pp, premaxillary process of nasal; qf, quadrate foramen; qjf, quadratojugal facet; sf, surangular foramen; sog, supraorbital groove; sop, suborbital process; vjo, ventral jugal ornamentation. Scale bars in A and C–J represent 10 cm and scale bar in B represents a total of 50 cm. doi:10.1371/journal.pone.0079420.g002

Skull reconstructions and selected cranial elements of Lythronax argestes.
These stippled reconstructions (A) are based on cranial elements recovered (B) for UMNH VP 20200. Selected elements of L. argestes holotype (UMNH VP 20200) including: (C) maxilla in lateral (photoreversed) and ventral views; (D) nasal in left lateral and dorsal view; (E) photoreversed frontal and laterosphenoid in lateral and dorsal view; (F) jugal in left lateral and dorsal view; (G) quadrate in left lateral and caudal view; (G) surangular in left lateral view; (I) prearticular in left lateral view; (J) dentary in lateral and ventral views. Abbreviations: a1-a11, alveoli 1–11; fpc, frontoparietal midsagittal crest; jf, jugal flange of the quadrate; jpr, jugal pneumatic recess; ljo, lateral jugal ornamentation; ls, laterosphenoid; mf, maxillary fenestra; na, naris; pf, palatine flange; pp, premaxillary process of nasal; qf, quadrate foramen; qjf, quadratojugal facet; sf, surangular foramen; sog, supraorbital groove; sop, suborbital process; vjo, ventral jugal ornamentation. Scale bars in A and C–J represent 10 cm and scale bar in B represents a total of 50 cm.
doi:10.1371/journal.pone.0079420.g002

Skull reconstructions and selected cranial elements of Teratophoneus curriei. show more These stippled reconstructions (A) are based on all available material. Some of the preserved elements of the referred specimen T. curriei (UMNH VP 16690) including: (B) left maxilla in lateral view, (C) both lacrimals superimposed and in lateral view; (D) photoreversed postorbital in lateral view; (E) frontals, parietals, and laterosphenoids in lateral and dorsal views; (F) braincase in caudal and lateral view; (G) squamosal in lateral and dorsal views; (H) quadratojugal in lateral view; (I) quadrate in lateral and caudal views; (J) left palatine in lateral view; (K) prearticular in left lateral view; (L) angular in left lateral view; (M) surangular in lateral view. Element recovery maps (N) of T. curriei (UMNH VP 16690) from which the reconstruction in A are derrived. Other Kaiparowits T. curriei specimens include two right jugals (UMNH VP 16691 & BYU 8120) and a left dentary from BYU 8120. Abbreviations: bpt, basipterygoid process; bt, basal tubera; bsr, basisphenoid recess; cb, cornual boss; fpc, frontoparietal midsagittal crest; jf, jugal flange of the quadrate; ls, laterosphenoid; lva, lacrimal vacuity; mf, maxillary fenestra; nc, nuchal crest; oc, occipital condyle; p, parietal; pop, paroccipital process; qc, quadrate cotylus; qf, quadrate foramen; sf, surangular foramen; so, supraoccipital; sof, suborbital flange; sog, supraorbital groove. All scale bars represent 10 cm except N which represents 50 cm. doi:10.1371/journal.pone.0079420.g003

Skull reconstructions and selected cranial elements of Teratophoneus curriei.
These stippled reconstructions (A) are based on all available material. Some of the preserved elements of the referred specimen T. curriei (UMNH VP 16690) including: (B) left maxilla in lateral view, (C) both lacrimals superimposed and in lateral view; (D) photoreversed postorbital in lateral view; (E) frontals, parietals, and laterosphenoids in lateral and dorsal views; (F) braincase in caudal and lateral view; (G) squamosal in lateral and dorsal views; (H) quadratojugal in lateral view; (I) quadrate in lateral and caudal views; (J) left palatine in lateral view; (K) prearticular in left lateral view; (L) angular in left lateral view; (M) surangular in lateral view. Element recovery maps (N) of T. curriei (UMNH VP 16690) from which the reconstruction in A are derrived. Other Kaiparowits T. curriei specimens include two right jugals (UMNH VP 16691 & BYU 8120) and a left dentary from BYU 8120. Abbreviations: bpt, basipterygoid process; bt, basal tubera; bsr, basisphenoid recess; cb, cornual boss; fpc, frontoparietal midsagittal crest; jf, jugal flange of the quadrate; ls, laterosphenoid; lva, lacrimal vacuity; mf, maxillary fenestra; nc, nuchal crest; oc, occipital condyle; p, parietal; pop, paroccipital process; qc, quadrate cotylus; qf, quadrate foramen; sf, surangular foramen; so, supraoccipital; sof, suborbital flange; sog, supraorbital groove. All scale bars represent 10 cm except N which represents 50 cm.
doi:10.1371/journal.pone.0079420.g003

Sea level change and the hypothesized evolutionary diversification of Tyrannosauroidea. show more Sea level indicators include: (A) Time-calibrated phylogenetic relationships and paleobiogeographic distribution of tyrannosaurids with biogeographic origin indicated by color (see Methods and File S1 for details of analyses and the stratigraphic and phylogenetic relationships of tyrannosauroids within theropod dinosaurs). (B) Late Cretaceous regional transgression-regression cycles on Laramidia (brown [31]); global sea-level fluctuations (blue [34], [35]); and areal extent of Laramidia at minimum (alluvial plain) and maximum (alluvial plain and coastal plain) sea levels (green [1]). doi:10.1371/journal.pone.0079420.g004

Sea level change and the hypothesized evolutionary diversification of Tyrannosauroidea.
Sea level indicators include: (A) Time-calibrated phylogenetic relationships and paleobiogeographic distribution of tyrannosaurids with biogeographic origin indicated by color (see Methods and File S1 for details of analyses and the stratigraphic and phylogenetic relationships of tyrannosauroids within theropod dinosaurs). (B) Late Cretaceous regional transgression-regression cycles on Laramidia (brown [31]); global sea-level fluctuations (blue [34], [35]); and areal extent of Laramidia at minimum (alluvial plain) and maximum (alluvial plain and coastal plain) sea levels (green [1]).
doi:10.1371/journal.pone.0079420.g004

Reconstruction of the skull of Lythranax (UMNH VP 20200). show more Elements were surface scanned and then digitally mirrored and expressed as a 3-D surface scan in lateral (A), rostral (B), dorsal (C) and ventral (D) views. The quadratojugal, shaded gray, is that of Teratophoneus scaled to fit the larger skull of Lythronax. The quadratojugal is conservative across Tyrannosauridae and was used to place the quadrate. doi:10.1371/journal.pone.0079420.g005

Reconstruction of the skull of Lythranax (UMNH VP 20200).
Elements were surface scanned and then digitally mirrored and expressed as a 3-D surface scan in lateral (A), rostral (B), dorsal (C) and ventral (D) views. The quadratojugal, shaded gray, is that of Teratophoneus scaled to fit the larger skull of Lythronax. The quadratojugal is conservative across Tyrannosauridae and was used to place the quadrate.
doi:10.1371/journal.pone.0079420.g005

 

Citation: Loewen MA, Irmis RB, Sertich JJW, Currie PJ, Sampson SD (2013) Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans. PLoS ONE 8(11): e79420. doi:10.1371/journal.pone.0079420

Editor: David C. Evans, Royal Ontario Museum, Canada

 

 

 

 

 

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