Category Archives: Geology

The Mystery of Mass Extinctions Is No Longer Murky

If you are curious about Earth’s periodic mass extinction events such as the sudden demise of the dinosaurs 65 million years ago, you might consider crashing asteroids and sky-darkening super volcanoes as culprits. However, a new study, published June 15, 2008, in the journal Nature, suggests that it is the ocean, and in particular the epic ebbs and flows of sea level and sediment over the course of geologic time, that is the primary cause of the world’s periodic mass extinctions over the past 500 million years.

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The Boneyard – Edition #18

Welcome to the 18th edition of the Boneyard, the blog carnival devoted to all things palaeo, from dinosaurs to pollen to hominids and everywhere in between.

We begin this latest edition in the Middle Palaeolithic with Julien Riel-Salvatore of ‘A Very Remote Period Indeed’ who discusses the interpretation of a new isotopic study of Neanderthal diet, based on material from a Neanderthal tooth from the French Middle Paleolitihic site of Jonzac.

A little further back time, we find Tim Jones at ‘Remote Central‘ discussing Pre-Clovis Humans in the Oregon High Desert, whilst at the same blog Terry Toohill puts ‘Human Evolution on Trial – North to Alaska’.. Meanwhile, here at Archaeozoology, we examine the later evolution of Pleistocene Horses in the New World.

We move into the Tertiary period with Emile of ‘The World We Don’t Live In‘ who discusses The oreodonts: the tylopods successful venture. Meanwhile, Brian Switek at ‘Laelaps‘ describes the ‘Truly Terrifying Entelodonts’ of the Early Miocene and Oligocene. In the same blog we also find a tale of another fearsome predator, this time of the middle Eocene: the Bad Cat from Wyoming, the largest meat-eating mammal from what would become the Wind River Formation.

Travelling back into the Mesozoic, we have two blogs about the ever-popular topic of dinosaurs. Darren Naish of ‘Tetrapod Zoology‘ talks about the land ‘Where the scelidosaurs and iguanodontians roam’, whilst GrrlScientist at ‘Living the Scientific Life (Scientist, Interrupted)‘ reviews ‘What Bugged the Dinosaurs? Insects, Disease and Death in the Cretaceous’ by George Poinar, Jr., and Roberta Poinar.

David Hone of ‘Archosaur Musings‘ brings us a series of three posts on the Early Triassic pterosaur Raeticodactylus filisurensis: part one describes the pterosaur, part two introduces Rico Stecher, the man behind Raeticodactylus, and part three is an interview with Rico about his work. Also from the Triassic comes the story of enigmatic hellasaurs, some of the most important insect fossils in the world from the Madygen Formation of Kyrgyzstan, courtesy of ‘microecos‘.

Reaching the Permo-Triassic boundary we find Peter Ward discussing ‘Suspending Life’ in Seed magazine; If almost every species on Earth was killed some 250 million years ago, how did our ancient ancestors survive and evolve into us?

We take a look at ancient plant-life with Christopher Taylor of ‘Catalogue of Organisms‘ as he tells us about Prototaxites, one of the Giants of the Silurian.

Dinochick, meanwhile, brings us more proof that only money speaks in a discussion of the recent news about fossils for sale.

We finish on a lighter note with Zach of ‘When Pigs Fly Returns‘ and Spinodracus dysonii, the porcupine dragon.

Thanks go to everyone who contributed to this edition of the Boneyard. The next edition will be hosted by Familiarity Breeds Content on May 3rd.

Pleistocene Horses in the New World

The later evolution of horses can be problematic and this is perhaps best illustrated in the Americas, where more than 50 species of Pleistocene equids have been named, most of them during the 19th and early 20th centuries (Weinstock et al., 2005: 0001). Whilst it has been argued that this number should be drastically revised, no consensus has as yet been reached about the number of valid species or their phylogenetic relationships (Weinstock et al., 2005: 0001). It was to address this problem that a recent study by Weinstock et al., looked at a segment of between 349 and 716 base pairs of the mitochondrial control region of fossil equid remains from a number of different localities in North and South America and Eurasia ranging in date from c. 53,000 years ago to historical times (Weinstock et al., 2005: 0002).

Using maximum likelihood, phylogenetic analysis resolved Hippidion, New World ‘stilt-legged’ horses (NWSL) and caballines (including the domestic horse, Equus caballus, and the extant wild Przewalskii horse) as three genetically divergent species within a monophyletic group (Weinstock et al., 2005: 0002). African zebras and asses and Asian asses (onager and kiang) form a basal polytomy (Weinstock et al., 2005: 0002). However, the close phylogenetic relationship between Hippidion and caballine horses is in direct contrast to palaeontological models of hippidiform origins (Weinstock et al., 2005: 0002; Benton, 1997: 342).

It is suggested that the origin of Hippidion should not be seen as a descendent of Miocene pliohippines; instead, its origins appear to be more recent, probably during the last stages of the Pliocene (c. 3 Ma), which is close to the time of the first fossil occurrence of this genus (Weinstock et al., 2005: 0003). This is in opposition to views expressed by authors such as McFadden (1997) who claim that hippidiforms (genera Hippidion and Onohippidium) were present in North America as early as the late Miocene (c. 7 – 8 Ma).

The situation with the phylogenetic position of the NWSL is also apparently resolved with the molecular evidence, which places them as North American endemics tather than Eurasian migrants (Weinstock et al., 2005: 0003). Specimens from both north (Alaska/Yukon) and south (Wyoming/Nevada) of the Pleistocene ice sheets clearly belong to the same taxon. This apparent large geographic distribution raises the possibility that other Late Pleistocene NWSL currently described as different species (E. francisci, E. tau, E. quinni, E. cf. hemionus, E (Asinus) cf. kiang) may in fact represent the same taxon (Weinstock et al., 2005: 0003). Their origins probably lie south of the Pleistocene ice sheets, where Mid-Pleistocene remains (c. 0.5 Ma) with similar limb characteristics have been found (Weinstock et al., 2005: 0003). Frequencies of NWSL are much lower in the north and they appear to have a restricted temporal distribution. It would appear that, despite their presence in eastern Beringia (unglaciated Alaska/Yukon), they failed to disperse through the Bering land-bridge into western Beringia (north-east Siberia) (Weinstock et al., 2005: 0003).

All caballine horses from western Europe to eastern Beringia – including the domestic horse – would appear to be a single Holarctic species (Weinstock et al., 2005: 0003). This group can be split into two major clades. The first is broadly distributed from central Europe to North America north and south of the ice. The second clade appears to have been restricted to North America. If present in the Old World at all, it would appear to have disappeared before domestication of the horse took place, around 5,000 years BP, as all domestic horses cluster in the first clade (Weinstock et al., 2005: 0004).

Reference:

Benton, MJ. 1997.Vertebrate Palaeontology. Second Edition. London: Chapman and Hall.

McFadden, BJ. 1997. Pleistocene horses from Tarija, Bolivia, and the validity of the genus Onohippidium (Mammalia: Equidae). Journal of Vertebrate Palaeontology 17: 199-218

Weinstock, J, Willerslev, E, Sher, A, Tong, W, Ho, SYW, Rubenstein, D, Storer, J, Burns, J, Martin, L, Bravi, C, Prieto, A, Froese, D, Scott, E, Xulong, L, and Cooper, A. 2005. Evolution, systematics, and phylogeography of Pleistocene horses in the New World: a molecular perspective. PLoS Biology 3 (8): 0001-0007.

The Boneyard – Submissions Reminder

The next edition of the Boneyard blog carnival will be hosted here at Archaeozoology on April 19th so please get your palaeontology submissions in to me by the end of the week.  The email address to send things to is silverthorn AT bardicweb DOT com or you’re welcome to leave a link in the comments.

Blog Carnival – The Boneyard

The latest edition of the Boneyard, the blog carnival for all things palaeo (from dinosaurs to pollen to hominids and everywhere in between), is currently up at Greg Laden’s blog.

The next edition of the carnival will be hosted here at Archaeozoology on April 19th. Submissions can be made as per the guidelines. If you want to send things directly to me, the email address is silverthorn AT bardicweb DOT com or you’re welcome to leave a link in the comments.

The oldest lucky rabbit’s foot?

One day last spring, fossil hunter and anatomy professor Kenneth Rose, Ph.D. was displaying the bones of a jackrabbit’s foot as part of a seminar at the Johns Hopkins University School of Medicine when something about the shape of the bones looked oddly familiar.

That unanticipated eureka moment has led researchers at the school to the discovery of the oldest known record of rabbits. The fossil evidence in hand, found in west-central India, predates the oldest previously known rabbits by several million years and extends the record of the whole category of the animal on the Indian subcontinent by 35 million years.

Published online in the February Proceedings of the Royal Society, the investigators say previous fossil and molecular data suggested that rabbits and hares diverged about 35 million years ago from pikas, a mousy looking member of the family Ochotonidae in the order of lagomorphs, which also includes all of the family Leporidae encompassing rabbits and hares.

But the team led by Johns Hopkins’s Rose found that their rabbit bones were very similar in characteristics to previously unreported Chinese rabbit fossils that date to the Middle Eocene epoch, about 48 million years ago. The Indian fossils, dating from about 53 million years ago, appear to show advanced rabbit-like features, according to Rose.

“What we have suggests that diversification among the Lagamorpha group-all modern day hares, rabbits and pikas-may already have started by the Early Eocene,” says Rose, professor in the Center for Functional Anatomy and Evolution at the Johns Hopkins University School of Medicine.

Rose says the new discovery was delayed a few years because the researchers had not been looking specifically to determine the age of rabbits. “We found these bones on a dig in India a few years ago and didn’t know what animal they came from, so we held onto them and figured we’d look at them later,” he says. “It didn’t occur to us they would be rabbits because there were no known rabbits that early in time and the only known rabbits from that part of the world are from central Asia.”

But one day, while using the jackrabbit foot bones as a teaching tool for a class, the shape of the bones in the class struck him as something he’d seen before among his collection of unidentified bones.

Sure enough, the tiny bones about a quarter of an inch long from India looked remarkably similar to ankle and foot bones from modern day jackrabbits, which are 4 to 5 times bigger.

Rose and his team set out and measured every dimension of their Indian bones and compared them to eight living species of rabbits and hares. They also compared them to two species of the related pika-that mouse-like, mountain-dwelling critter that lives in the Rocky Mountains of North America, among other places.

Using a technique called character analysis, the team first recorded measurements of 20 anatomical features of the bones, which showed that the bones are definitely Lagomorph and closer to rabbits than pikas. The scientists then ran a series of statistical tests on the individual measurements to see how they compared with the Chinese fossils as well as living rabbits and pikas. They found that although the Indian fossils resemble pikas in some primitive features, they look more like rabbits in specialized bone features.

Asked how many years of good luck one gets with a 53 million-year-old rabbit foot bone, Rose quipped that he “already got lucky with the feet, but what we really would like are some teeth that tell how different these animals really were.”

Source: EurekAlert!

A fossilized giant rhino bone questions the isolation of Anatolia

Contrary to generally accepted belief, Anatolia was not geographically isolated 25 million years ago (during the Oligocene epoch): this has just been demonstrated by researchers from the Laboratoire des Mécanismes et Transferts en Géologie (LMTG) (CNRS/ University of Toulouse 3/IRD) and the Paléobiodiversité et paléoenvironnements laboratory (CNRS/Muséum national d’histoire naturelle/University of Paris 6). These results were obtained thanks to analyses of the first fossilized giant rhinocerotoid bone discovered in 2002 in an Anatolian deposit during a Franco-Turkish paleontology expedition funded by the ECLIPSE INSU-CNRS program. The presence of this bone in Anatolia, with the remains of associated fauna, are indicative of animal migrations between Europe and Asia. The results, published online in the March 2008 issue of the Zoological Journal of the Linnean Society, thus call into question the isolation of Anatolia, which until now was considered to have been an archipelago.

This is the first time that a fossilized giant rhinocerotoid bone dating from the Oligocene epoch (a period corresponding to intense tectonic movements around the Mediterranean Sea) has been found in Anatolia. Discovered in 2002 during a Franco-Turkish paleontology expedition in the region of ÇankiriÇorum (Central Anatolia, Turkey), the bone fragment from the forearm (radius) described by the scientists measures 1.20 meters long and probably belonged to a very large male (about 5 meters to the shoulder), attributed to the Paraceratherium genus. These herbivorous animals, also called baluchitheres or indricotheres, are considered to have been the largest terrestrial mammals that ever existed, equal in size to the largest mammoths (with a height to the shoulder estimated to be 5 meters or more, and a body weight of 15 to 20 tons).

As well as this specimen of Paraceratherium, known to have existed notably in Pakistan, China, Mongolia and Kazakhstan, the remains of ruminants and rodents were also found in the deposit. They enabled dating of the specimen to about 25 million years, and also exhibited close affinities with contemporary fauna in Asia and/or Europe. This observation is particularly surprising in that Anatolia was until now considered to have been an archipelago at that time, separated from both Europe and Asia by what is referred to as the Paratethys Sea; the Black, Caspian and Aral seas are today the only remaining vestiges of this body of water. The discovery thus proves the existence of terrestrial communication and close links at that period between Europe (including France) and Asia (China, Mongolia, Pakistan). Thus, during the Oligocene epoch, Anatolia was not isolated by the sea and was at least an isthmus: animals could therefore cross on dry land from continental Asiato Anatolia. On the other hand, this discovery also tends to confirm that there was indeed a separation from Africa, as to date no species of African affinity has been found in the Oligocene soils of Anatolia.

Source: EurekAlert!