Wednesday, May 20, 2009
Earliest Relative of Monkeys
Well, this was a cool article I found, it talks about a fossil found that may be one of the earliest direct links to the evolution of monkeys. Well, everyone by now should know how fascinated I am by primates, so this article really hits home with me. It caught my attention right away, anyway. My apologies to my readers for not being on here much, I'm planning something with my supervisor that should be very big in getting the word out for UMG Productions! So, I've had a busy week planning and plotting with her.
Skeleton Sheds Light on Primate Evolution
Malcolm Ritter, Associated Press
May 19, 2009 -- The nearly complete skeleton of a small 47 million-year-old creature found in Germany was displayed Tuesday by scientists who said it would help illuminate the early evolution of monkeys, apes and humans.
About the size of a small cat, the animal has four legs and a long tail. It's not a direct ancestor of monkeys and humans, but it provides a good indication of what such an ancestor may have looked like, researchers said at a news conference.
Because the skeleton is so remarkably complete, scientists believe it will provide a window into primate evolution. The animal was a juvenile female that scientists believe died at about 9 or 10 months.
"She tells so many stories. We have just started the research on this fabulous specimen," said Jorn Hurum, of the University of Oslo Natural History Museum, one of the scientists reporting the find.
The creature is nicknamed Ida after Hurum's 6-year-old daughter.
The unveiling, at New York's Museum of Natural History, was promoted by a press release for the cable TV show History, which called it a "revolutionary scientific find that will change everything."
Mayor Michael Bloomberg, among the speakers at the news conference, called it an "astonishing breakthrough."
The story of the fossil find will be shown on History, which is owned by A&E Television Networks. A book also will be published.
Hurum saw nothing wrong with the heavy publicity which preceded the research's publication Tuesday in the scientific journal PLOS (Public Library of Science) One.
"That's part of getting science out to the public, to get attention. I don't think that's so wrong," Hurum said.
Monday, May 11, 2009
Family of the Week: the Shrubucks
The Ungulascelididae is the first family to evolve off the elephant shrews in the Metazoic. They basically resemble giant versions of these animals, and they are every bit as flexible. They are basically quadrupedal animals, though they occasionally rear up on their hind legs to reach for any food items that are out of reach to quadrupeds. The nose is long and flexible, the ears are large and pointed. The eyes are large, some species even have tusks. They are slenderly built animals, the legs are long and the feet are soft, like those of camels, with blunt hooves. They are very agile animals, and leap and bound much like we see in modern deer and antelope. The tail is long and thick, and used to balance the animals as they rear up on their hind legs. There are 4 toes on each foot, and in the genus Scopulus, one of the toes on each forefoot is flexible, giving them an added advantage in grasping branches they want to feed on. These animals travel together in rather large herds, usually led by a dominant male.
The largest member of this family is Mananasus, which is a large forest-dwelling shrubuck that has a long, flexible nose like a modern elephant. They stand about 10 feet tall, and with the long proboscis, can reach leaves an extra 4 feet above their head. This species often will stand on their hind legs to attempt to reach higher leaves. This is the one species that is fully vegetarian, feeding only on leaves and fruits from high branches. Most other shrubucks are omnivores. Ungulascelides is known to scavenge kills from other animals, acting rather like modern jackals in the early Metazoic era. The smallest of the shrubucks is in the genus Varicares. These are rather small animals, and most shelter in burrows. In the early Metazoic, these animals take the place of warthogs. Though they are not quite as ugly. The legs are shorter in this genus than any other variety of shrubuck. This is also the only one of the shrubucks that made it out of Africa. One variety lives in the mountainous forests of southern Europe. This animal feeds on low growth vegetation, as well as insects, earthworms, slugs, grubs and carrion. They live in smaller family groups, much like wild boar today, and all members of the family roost in large burrows dug by the adults in the family.
These animals are like most others around during the Metazoic, they are diurnal. They prefer to roost at night, and do their hunting and traveling during the day. They live in a variety of habitats, but most species prefer drier areas. Though there are quite a few species in this family that are forest and even jungle dwellers. Females usually have more than one calf, and are quite protective of them. Males play very little in the way of family life. Though they too are defensive of their families.
Shrubucks have several enemies. Mostly large reptiles like crocodiles and pythons. Pythons normally take the young animals. Rarely, if ever, any adults. Carnivorous rats and squirrels will also take on these animals as well as wild dogs. Shrubucks defend themselves quite well by way of powerful kicks. The tail also acts as a defensive mechanism. The tail is long and thick, and excellent for slapping at an attacker. Though most predators find a way around this. These animals are the start of a line of animals that would later in the Metazoic become the Choerocaballids, the therapeds and even the deinognathids. But their most unique and unusual descendants will be the sinecrus, that take to the water.
The largest member of this family is Mananasus, which is a large forest-dwelling shrubuck that has a long, flexible nose like a modern elephant. They stand about 10 feet tall, and with the long proboscis, can reach leaves an extra 4 feet above their head. This species often will stand on their hind legs to attempt to reach higher leaves. This is the one species that is fully vegetarian, feeding only on leaves and fruits from high branches. Most other shrubucks are omnivores. Ungulascelides is known to scavenge kills from other animals, acting rather like modern jackals in the early Metazoic era. The smallest of the shrubucks is in the genus Varicares. These are rather small animals, and most shelter in burrows. In the early Metazoic, these animals take the place of warthogs. Though they are not quite as ugly. The legs are shorter in this genus than any other variety of shrubuck. This is also the only one of the shrubucks that made it out of Africa. One variety lives in the mountainous forests of southern Europe. This animal feeds on low growth vegetation, as well as insects, earthworms, slugs, grubs and carrion. They live in smaller family groups, much like wild boar today, and all members of the family roost in large burrows dug by the adults in the family.
These animals are like most others around during the Metazoic, they are diurnal. They prefer to roost at night, and do their hunting and traveling during the day. They live in a variety of habitats, but most species prefer drier areas. Though there are quite a few species in this family that are forest and even jungle dwellers. Females usually have more than one calf, and are quite protective of them. Males play very little in the way of family life. Though they too are defensive of their families.
Shrubucks have several enemies. Mostly large reptiles like crocodiles and pythons. Pythons normally take the young animals. Rarely, if ever, any adults. Carnivorous rats and squirrels will also take on these animals as well as wild dogs. Shrubucks defend themselves quite well by way of powerful kicks. The tail also acts as a defensive mechanism. The tail is long and thick, and excellent for slapping at an attacker. Though most predators find a way around this. These animals are the start of a line of animals that would later in the Metazoic become the Choerocaballids, the therapeds and even the deinognathids. But their most unique and unusual descendants will be the sinecrus, that take to the water.
Sunday, May 10, 2009
Attack of the Synapsids
Otherwise known as attack of your great, great, great, great, great grandparents, aunts, and uncles. Anyway, its here...Will Baird and Zach Miller (and also Scott Elyard, apparently) have posted some stuff on their project, appropriately titled the XenoPermian. Zach has his picture of the "Triassic" seaside coast both on Will's blog and on Art Evolved, and Will has posted an overview of the first chunk of the project on his blog, The Dragon's Tales.
The reason I put the "Triassic" of this timeline in quotes is, quite simply, because there isn't one in this time period. In the XenoPermian, the volcanic eruptions that caused the P-T extinction never happened, or were at least spread out over many millions of years. As a result of this, the Permian bleeds smoothly into the Triassic. Actually, the Triassic being consumed by the Permian would be a better word, since a lot of the fauna that characterize the Permian never goes extinct (gorgonopsids, for one) and a lot of the fauna that characterize the Triassic never evolves (nothosaurs, placodonts, for example).
So, here are the two links. Zach's picture can be found here (http://blogevolved.blogspot.com/2009/05/long-road-to-failure.html), and Will's post is located here (http://thedragonstales.blogspot.com/2009/05/welcome-to-xenopermian.html)
The reason I put the "Triassic" of this timeline in quotes is, quite simply, because there isn't one in this time period. In the XenoPermian, the volcanic eruptions that caused the P-T extinction never happened, or were at least spread out over many millions of years. As a result of this, the Permian bleeds smoothly into the Triassic. Actually, the Triassic being consumed by the Permian would be a better word, since a lot of the fauna that characterize the Permian never goes extinct (gorgonopsids, for one) and a lot of the fauna that characterize the Triassic never evolves (nothosaurs, placodonts, for example).
So, here are the two links. Zach's picture can be found here (http://blogevolved.blogspot.com/2009/05/long-road-to-failure.html), and Will's post is located here (http://thedragonstales.blogspot.com/2009/05/welcome-to-xenopermian.html)
Friday, May 8, 2009
Shuvosaurus and Protoavis: Two Enigmas From the Triassic of Texas
The Late Triassic of the American Southwest was home to a bewildering array of fascinating creatures, completely unlike anything we know of today. Patrolling the forests and riverbanks of the Triassic were fierce rauisuchians, and swift herrerasaurids and coelophysoids. Lounging in the lazy waters were huge crocodile-like phytosaurs and the archaic metoposaurs. Browsing from the thickets of vegetation were armored aetosaurs, the strange tusked dicynodonts, silesaurids, prosauropods, and even a couple of ornithischians. At the same time, all of this was being played out on a smaller scale on the forest floor and canopy, with dog-like crocodilians running around after proconlophids and trilophosaurs. However, the strange creatures of this alien world paled in comparison to two bizarre oddities, Shuvosaurus and Protavis. So yeah, once again I find myself blogging about the archosaurs of Texas.
Shuvosaurus was first described by Dr. Sankhar Chatterjee in 1993. When first discovered, Chatterjee thought that Shuvosaurus appeared to be a Triassic ornithomimosaur. This shocked and bewildered the paleontological community. Not only are ornithomimosaurs some of the most specialized theropods of all time, but they didn't even appear in the fossil record until the Cretaceous (even today, no ornithomimosaur is known from even the Jurassic). Because of the amount of paleontological upheaval Chatterjee's theory would have caused (not to mention the incompleteness of the Shuvosaurus skeleton), many paleontologists viewed Shuvosaurus with skepticism. Since then, there were numerous theories on what exactly was Shuvosaurus. Chatterjee, as far as I know, stood by his ornithomimosaur hypothesis. Dixon, in one of his dinosaur books, suggested that Shuvosaurus was a specialized coelophysoid theropod. Others suggested that Shuvosaurus was a chimera, a fossil "taxon" made of the body parts of more than one animal.
So, it appeared Shuvosaurus was doomed to remain a mystery, an unsolvable enigma of the Triassic. That is, until the discovery of Effigia in 2006. Discovered posing as a coelophysoid theropod in fossils the American Natural History Museum collected from Ghost Ranch, While at first glance Effigia appeared to be a dinosaur, the structure of the hip and ankle told scientists a different story; Effigia was a rauisuchian, distant cousins of modern crocodiles which . And so the pieces clicked together, and the mystery was solved. Shuvosaurus wasn't a dinosaur at all, but a species of beaked, bipedal, herbivorous rauisuchian, one which had evolved conveniently to the oviraptorosaurs and ornithomimosaurs of the Late Triassic. In fact, the discovery of Effigia showed that not only was Shuvosaurus a rauisuchian, but Chatterjea, another odd rauisuchian with suspicious similarities to Shuvosaurus, was actually the same species!
While Shuvosaurus was unusual, it paled in comparison to the controvery stirred up by Chatterjee's other discovery, Protoavis. Protoavis was described as a fossil Triassic bird by its discoverer, a creature about 35 centimeters tall. Even more unusual, several features that Chatterjee described in Protoavis would suggest that it is more advanced than the earliest definite known bird, Archaeopteryx, despite living 75 million years earlier. One of these features is that Protoavis has a very bird-like skull, with teeth even more reduced than in Archaeopteryx. Some scientists have called the validity of Protavis into serious question, but Chatterjee has stood by his claim.
Enter the drepanosaurids. Drepanosaurids, more informally known as monkey lizards, were a group of arboreal reptiles that have been found across the world during the Triassic period (for more info on drepanosaurs see the excellent post at the Hairy Museum of Natural History here http://www.hmnh.org/galleries/monkeylizards/index.html). Some species appear to have taken the place of squirrels or primates, others may have lived a life like the modern tamandua, and still others may have even been aquatic or flying squirrel-like animals. But most importantly, these animals had a very bird-like skull, to the point where one of their "other" names is avicephalans (bird heads). The best specimens of these animals have been found in the Eastern U.S. (Hyperonector) or Italy (Drepanosaurus and Megalancosaurus), but there is a species of drepanosaurid known from the American Southwest, Dolabrosaurus, found in the sediments of Petrified Forest National Park.
While Shuvosaurus was unusual, it paled in comparison to the controvery stirred up by Chatterjee's other discovery, Protoavis. Protoavis was described as a fossil Triassic bird by its discoverer, a creature about 35 centimeters tall. Even more unusual, several features that Chatterjee described in Protoavis would suggest that it is more advanced than the earliest definite known bird, Archaeopteryx, despite living 75 million years earlier. One of these features is that Protoavis has a very bird-like skull, with teeth even more reduced than in Archaeopteryx. Some scientists have called the validity of Protavis into serious question, but Chatterjee has stood by his claim.
Enter the drepanosaurids. Drepanosaurids, more informally known as monkey lizards, were a group of arboreal reptiles that have been found across the world during the Triassic period (for more info on drepanosaurs see the excellent post at the Hairy Museum of Natural History here http://www.hmnh.org/galleries/monkeylizards/index.html). Some species appear to have taken the place of squirrels or primates, others may have lived a life like the modern tamandua, and still others may have even been aquatic or flying squirrel-like animals. But most importantly, these animals had a very bird-like skull, to the point where one of their "other" names is avicephalans (bird heads). The best specimens of these animals have been found in the Eastern U.S. (Hyperonector) or Italy (Drepanosaurus and Megalancosaurus), but there is a species of drepanosaurid known from the American Southwest, Dolabrosaurus, found in the sediments of Petrified Forest National Park.
So it appears quite likely that Protoavis is a paleontological chimera, a fossil made up of the dislocated remains of a coelophysoid theropod and a drepanosaur. There are other features which seem to suggest this. The quarry where Protoavis was found suggests that it was the remnants of a group of flash flood victims, as the animals are all jumbled up and disassembled. In addition, several of the alleged Protoavis vertebrae appear to be rather similar to the vertebrae of the drepanosaur Megalancosaurus. And of course the bones of Protoavis are very badly preserved in the first place.
Well, there you have it...the two weirdest fossils from the New World of the Triassic (I won't say the entire Triassic, as Sharovipteryx and Longisquama may give these two a run for their money). Two Texas enigmas, one vindicated by further paleontological discoveries and has emerged as one of the most unique animals in the Triassic world, the other a chimera made of two parts juvenile coelophysoid, and one part drepanosaur (mix well). I hope you enjoyed this little presentation, and stay tuned to Metazoica!
References
Jacobs, L. 1995. Lone Star Dinosaurs. Texas A&M University Press, College Station, Texas
Fraser, N. 2006. Dawn of the Dinosaurs, Life in the Triassic. Indiana University Press
Oh No!
Ah great, just what we need. I was doing some digging on Protohadros and the Arlington Archosaur Site recently, and it turns out there is some bad news. The site itself is only going to be opened for five more months. Unfortunately, after that, the site will be bulldozed to make way for a housing complex. I have heard some rumors that the deadline will be extended, but I have not heard anything finalized yet. This is a sad turn of events, seeing as this one of the few sites of this time period in the U.S., and probably the only site that has post cranial material of Protohadros (if the creature found here is indeed Protohadros at all!).
Tuesday, May 5, 2009
Pleurocoelus No More
Until recently, most paleontology books would have one believe that sauropods all across the Northern Hemisphere (especially North America) went extinct in the Late Jurassic. The small-brained herbivores found themselves unable to adapt to a changing world and thus gave way to the (moderately) smarter ornithopods and ankylosaurs of the Cretaceous. In truth, sauropods are a much tougher breed than people give them credit for. While they did take a hit in diversity in the Cretaceous, the group as a whole survived and kept going on, surviving and adapting to the changing conditions of the Cretaceous. In fact, over the Cretaceous some titanosaurs were becoming more efficient and gracile, a topic which I may blog about someday.
Neither did sauropods just leave North America in the hands of the iguanodonts and nodosaurs. While the diplodocids did go extinct in North America after the Late Jurassic, the continent was still overrun by titanosaurs and their kin, the little buggers. There was Sauroposeidon, essentially an Early Cretaceous version of Brachiosaurus on steroids. There was also smaller titanosaurs, like Venenosaurus. But I would like to focus your attention to the dinosaurs oftentimes described as "Pleurocoelus"
The first fossil ever to be attributed the name Pleurocoelus were some fossils found about 1859 in the Arundel Formation of Maryland. However, it was not called Pleurocoelus at all, rather it was named Astrodon. Discovered by Christopher Johnson at this time, who coined the name, Astrodon really did not enter the paleontology lexicon until 1865, when Joseph Leidy described the species and attributed a species name to it, johnstoni, after its discoverer. So why Pleurocoelus then? Well, some years later, more sauropod specimens that looked exactly like Astrodon were brought to Othniel Marsh, who rather than follow the rules and refer them to Astrodon, created his own taxon for them, Pleurocoelus. This actually happened quite often between Cope and Marsh, neither would accept names coined by each other or other paleontologists, and so made up their own names. Over the years, numerous other taxa were attributed to the genus Pleurocoelus, from places as far away as Texas and Utah. Before long Pleurocoelus became a wastebasket taxon, a taxon to which numerous different remains are attributed.
For a long time, sauropod fossils found in Texas have been referred to as Pleurocoelus. These include the famous "sauropod vs. Acrocanthosaurus" footprints of Glen Rose. However, it soon became apparent that there were some differences between the supposed "Pleurocoelus" specimens of Texas and Maryland. For example, the Texas specimens apparently lacked a claw on one of their digits, making their feet rather distinct. These were not "Pleurocoelus", they were a species all their own. In 2007, the Texas fossils of "Pleurocoelus" were redescribed as a new genus, Paluxysaurus jonesi. Like Astrodon and other former members of "Pleurocoelus", Paluxysaurus is a basal titanosauriform, a group that was quite common across North America during the Early Cretaceous.
And what of Astrodon, the "original" specimen of Pleurocoelus? Well, in a study done by Kenneth Carpenter and Virginia Tidwell, they found that Astrodon was indeed a unique species, and that the name Astrodon should be kept, per ICZN legislation. In addition, the study found that there were differences between the supposed "Pleurocoelus" teeth from Texas differed from those of Astrodon.
So what does this mean for Early Cretaceous paleobiology? Well, rather than one sauropod as expected, it now seems that there were two sauropods running around in Early Cretaceous North America (in addition to the other sauropods, such as Sauroposeidon). First there was Astrodon, a somewhat smaller coastal-dwelling sauropod. Then there was the larger Paluxysaurus, who lived more to the west and inland of the East Coast dwelling Astrodon.
Ironically, there is a final twist to our story. While most of the Texas sauropod fossils known can probably be attributed to Paluxysaurus, one; a partial skeleton from Wise County, Texas, cannot. There has not been a study done yet comparing the Paluxysaurus holotype, but there appear to be some differences in the bone. But at the same time, it is difficult to tell these Pleurocoelus remains apart from those of Paluxysaurus.
References
Carpenter, K. and Tidwell, V. 2005. Reassessment of the Early Cretaceous sauropod Astrodon johnstoni Leidy 1865 (Titanosauriformes)
Rose, Peter J. (2007). "A new titanosauriform sauropod (Dinosauria: Saurischia) from the Early Cretaceous of central Texas and its phylogenetic relationships" (web pages). Palaeontologia Electronica 10 (2). http://palaeo-electronica.org/2007_2/00063/.
Jacobs, L. 1995. Lone Star Dinosaurs. Texas A&M University Press, College Station, Texas
Fraser, N. 2006. Dawn of the Dinosaurs, Life in the Triassic. Indiana University Press
Neither did sauropods just leave North America in the hands of the iguanodonts and nodosaurs. While the diplodocids did go extinct in North America after the Late Jurassic, the continent was still overrun by titanosaurs and their kin, the little buggers. There was Sauroposeidon, essentially an Early Cretaceous version of Brachiosaurus on steroids. There was also smaller titanosaurs, like Venenosaurus. But I would like to focus your attention to the dinosaurs oftentimes described as "Pleurocoelus"
The first fossil ever to be attributed the name Pleurocoelus were some fossils found about 1859 in the Arundel Formation of Maryland. However, it was not called Pleurocoelus at all, rather it was named Astrodon. Discovered by Christopher Johnson at this time, who coined the name, Astrodon really did not enter the paleontology lexicon until 1865, when Joseph Leidy described the species and attributed a species name to it, johnstoni, after its discoverer. So why Pleurocoelus then? Well, some years later, more sauropod specimens that looked exactly like Astrodon were brought to Othniel Marsh, who rather than follow the rules and refer them to Astrodon, created his own taxon for them, Pleurocoelus. This actually happened quite often between Cope and Marsh, neither would accept names coined by each other or other paleontologists, and so made up their own names. Over the years, numerous other taxa were attributed to the genus Pleurocoelus, from places as far away as Texas and Utah. Before long Pleurocoelus became a wastebasket taxon, a taxon to which numerous different remains are attributed.
For a long time, sauropod fossils found in Texas have been referred to as Pleurocoelus. These include the famous "sauropod vs. Acrocanthosaurus" footprints of Glen Rose. However, it soon became apparent that there were some differences between the supposed "Pleurocoelus" specimens of Texas and Maryland. For example, the Texas specimens apparently lacked a claw on one of their digits, making their feet rather distinct. These were not "Pleurocoelus", they were a species all their own. In 2007, the Texas fossils of "Pleurocoelus" were redescribed as a new genus, Paluxysaurus jonesi. Like Astrodon and other former members of "Pleurocoelus", Paluxysaurus is a basal titanosauriform, a group that was quite common across North America during the Early Cretaceous.
And what of Astrodon, the "original" specimen of Pleurocoelus? Well, in a study done by Kenneth Carpenter and Virginia Tidwell, they found that Astrodon was indeed a unique species, and that the name Astrodon should be kept, per ICZN legislation. In addition, the study found that there were differences between the supposed "Pleurocoelus" teeth from Texas differed from those of Astrodon.
So what does this mean for Early Cretaceous paleobiology? Well, rather than one sauropod as expected, it now seems that there were two sauropods running around in Early Cretaceous North America (in addition to the other sauropods, such as Sauroposeidon). First there was Astrodon, a somewhat smaller coastal-dwelling sauropod. Then there was the larger Paluxysaurus, who lived more to the west and inland of the East Coast dwelling Astrodon.
Ironically, there is a final twist to our story. While most of the Texas sauropod fossils known can probably be attributed to Paluxysaurus, one; a partial skeleton from Wise County, Texas, cannot. There has not been a study done yet comparing the Paluxysaurus holotype, but there appear to be some differences in the bone. But at the same time, it is difficult to tell these Pleurocoelus remains apart from those of Paluxysaurus.
References
Carpenter, K. and Tidwell, V. 2005. Reassessment of the Early Cretaceous sauropod Astrodon johnstoni Leidy 1865 (Titanosauriformes)
Rose, Peter J. (2007). "A new titanosauriform sauropod (Dinosauria: Saurischia) from the Early Cretaceous of central Texas and its phylogenetic relationships" (web pages). Palaeontologia Electronica 10 (2). http://palaeo-electronica.org/2007_2/00063/.
Jacobs, L. 1995. Lone Star Dinosaurs. Texas A&M University Press, College Station, Texas
Fraser, N. 2006. Dawn of the Dinosaurs, Life in the Triassic. Indiana University Press
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