News Article | March 16, 2016
About 68 million years ago, a pregnant Tyrannosaurus rex died in ancient Montana. Her remains might provide clues about how to identify male and female theropods, or bipedal meat-eating dinosaurs, a new study finds. The finding is an exciting one — researchers verified that the T. rex was pregnant by looking at the organic components in the dinosaur's bone structure, elements that had survived for tens of millions of years since the predator's death, said study lead researcher Mary Schweitzer, an evolutionary biologist at North Carolina State University. "We need to quit selling fossils short," Schweitzer told Live Science. "They have a lot more information in them than we would think of [finding in] 65-million-year-old bone." [Image Gallery: The Life of T. Rex] A paleontologist discovered the T. rex in Hell Creek Formation in 2000. Bob Harmon, of the Museum of the Rockies in Montana, sat down in dinosaur territory one day, and unexpectedly felt a fossil behind his back, Schweitzer said. Harmon shared the good news with his colleagues, and they spent the next three years excavating the enormous specimen. Afterward, the paleontologists gave the femur, a leg bone, to Schweitzer, who, along with her colleagues, examined the microscopic features of the fossil. In 2005, the team published a study in the journal Science announcing that the fossil contained medullary bone, which is a type of bone with extra calcium deposits that help female egg-laying creatures, such as birds, lay eggs. Medullary bone is present only just before or during the egg-laying process, so its occurrence suggested the T. rex was pregnant, Schweitzer said. But recently, Schweitzer found herself wondering whether the finding was accurate. New technologies and information had come to light in the intervening years. Schweitzer wondered if she did the experiment again, whether she would still get the same results and find that the dinosaur was pregnant, she said. "I think good scientists should always be second-guessing themselves," Schweitzer said. So, she decided to check the chemistry of the T. rex's femur. Such a test would show whether the fossil had medullary bone, or whether it actually had osteopetrosis, a condition that makes bones unusually dense. Under the microscope, medullary bone and bone with osteopetrosis look remarkably similar, Schweitzer said. However, the two are chemically different. Medullary bone contains the organic compound keratan sulfate, and bone with osteopetrosis does not. Schweitzer and her colleagues tested for the compound using different chemicals, including monoclonal antibodies (immune cells that bind only to a specific agent — in this case, keratan sulfate). The researchers found that the ancient bone still contained some keratan sulfate. The researchers also used the antibodies to analyze medullary bone from an ostrich and chicken. The results confirmed those from the 2005 study, that the T. rex had medullary bone and was likely pregnant when she died, Schweitzer said. "This analysis allows us to determine the gender of this fossil, and gives us a window into the evolution of egg laying in modern birds," Schweitzer said in a statement. Because medullary bone is present only in females during egg-laying periods, it's relatively rare in fossils. Even when present, it can be difficult to identify without cutting off a sample of dinosaur bone and examining it under a microscope or with a chemical test. But the researchers found that doing an initial computed tomography (CT) scan of dinosaur bone can help determine whether a fossil is worth investigating, Schweitzer said. [Gallery: Photos of Tiny Dinosaur Embryos] This technique could help researchers find more medullary bone, said study co-author Lindsay Zanno, a paleontologist at North Carolina State University. Moreover, once the presence of medullary bone confirms that a dinosaur is a female, researchers can look for other clues that might help determine whether it's a boy or a girl dinosaur. "It's a dirty secret, but we know next to nothing about sex-linked traits in extinct dinosaurs. Dinosaurs weren't shy about sexual signaling, all those bells and whistles, horns, crests, and frills, and yet we just haven't had a reliable way to tell males from females," Zanno said in the statement. "Just being able to identify a dinosaur definitively as a female opens up a whole new world of possibilities. Now that we can show pregnant dinosaurs have a chemical fingerprint, we need a concerted effort to find more [medullary bone]."
Wings O.,Niedersachsisches Landesmuseum Hanover |
Tutken T.,University Mainz |
Fowler D.W.,Museum of the Rockies |
Martin T.,University of Bonn |
And 3 more authors.
Palaontologische Zeitschrift | Year: 2014
The Middle and early Late Jurassic Qigu and Shishugou Formations of the southern and central Junggar Basin yielded teeth of theropods (Theropoda indet.), sauropods (Eusauropoda indet.), and stegosaurs. The dinosaur assemblage of the southern Junggar Basin is less diverse and is represented by smaller forms than in the central part of the basin. The microwear of the teeth of Eusauropoda indet. resembles that observed in Camarasaurus and may have formed as a result of biting through resistant woody materials. Carbon and oxygen isotope data of the sauropod and theropod teeth indicate feeding within a C3-plant ecosystem in a continental setting. Differences in enamel δ13C and δ18O values between Eusauropoda indet. and the theropod teeth are comparable to those observed in other herbivorous and carnivorous vertebrates, and suggest at least partial preservation of original dietary signals. © 2014 Springer-Verlag Berlin Heidelberg.
Woodward H.N.,Museum of the Rockies |
Woodward H.N.,Oklahoma State University |
Freedman Fowler E.A.,Montana State University |
Farlow J.O.,Indiana University |
Horner J.R.,Montana State University
Paleobiology | Year: 2015
Fossil bone microanalyses reveal the ontogenetic histories of extinct tetrapods, but incomplete fossil records often result in small sample sets lacking statistical strength. In contrast, a histological sample of 50 tibiae of the hadrosaurid dinosaur Maiasaura peeblesorum allows predictions of annual growth and ecological interpretations based on more histologic data than any previous large sample study. Tibia length correlates well (R2>0.9) with diaphyseal circumference, cortical area, and bone wall thickness, thereby allowing longitudinal predictions of annual body size increases based on growth mark circumference measurements. With an avian level apposition rate of 86.4 μm/day, Maiasaura achieved over half of asymptotic tibia diaphyseal circumference within its first year. Mortality rate for the first year was 89.9% but a seven year period of peak performance followed, when survivorship (mean mortality rate=12.7%) was highest. During the third year of life, Maiasaura attained 36% (x=1260 kg) of asymptotic body mass, growth rate was decelerating (18.2 μm/day), cortical vascular orientation changed, and mortality rate briefly increased. These transitions may indicate onset of sexual maturity and corresponding reallocation of resources to reproduction. Skeletal maturity and senescence occurred after 8 years, at which point the mean mortality rate increased to 44.4%. Compared with Alligator, an extant relative, Maiasaura exhibits rapid cortical increase early in ontogeny, while Alligator cortical growth is much lower and protracted throughout ontogeny. Our life history synthesis of Maiasaura utilizes the largest histological sample size for any extinct tetrapod species thus far, demonstrating how large sample microanalyses strengthen paleobiological interpretations. © 2015 The Paleontological Society. All rights reserved.
Gates T.A.,Utah Museum of Natural History |
Horner J.R.,Museum of the Rockies |
Hanna R.R.,Terra Paleo Research |
Nelson C.R.,Brigham Young University
Journal of Vertebrate Paleontology | Year: 2011
A new hadrosaurid dinosaur, Acristavus gagslarsoni, is here named on the basis of several autapomorphic characteristics of the frontal, postorbital, and dentary. Acristavus is a member of the newly erected clade Brachylophosaurini, which along with its other members, Brachylophosaurus and Maiasaura, constitutes the earliest hadrosaurine hadrosaurid clade. The new taxon occurred approximately 79 million years ago and has been recovered from the Two Medicine Formation of western Montana and nearly simultaneously in the Wahweap Formation of southern Utah. Corresponding with its age and relationship to the other members of the Brachylophosaurini, it is not surprising that Acristavus possesses traits seen in both Brachylophosaurus and Maiasaura, but not necessarily shared between them. One of the most interesting morphological features of Acristavus is the lack of cranial osteological ornamentation, which is in stark contrast to every other hadrosaurid dinosaur except Edmontosaurus. Combining stratigraphic and phylogenetic data from Acristavus yields support for the hypothesis that the hadrosaurid ancestor did not possess cranial ornamentation, and that the subfamilies Hadrosaurinae and Lambeosaurinae each independently developed display structures. © 2011 by the Society of Vertebrate Paleontology.
Prieto-Marquez A.,American Museum of Natural History |
Bolortsetseg M.,Institute for the Study of Mongolian Dinosaurs |
Horner J.R.,Museum of the Rockies
Alcheringa | Year: 2012
We describe a new specimen of small maniraptoran theropod from the Early Cretaceous Öösh locality, Övörkhangai province, central Mongolia. This exemplar ISMD-VP09 preserves a maxillary fragment, two teeth and partial appendicular elements. The strict consensus of a parsimony analysis of 68 coelurosaur taxa places this theropod within Deinonychosauria with an unresolved relationship with the other members of the clade. Support for this clade was based on two unambiguous synapomorphies: maxillary dentition with at least some teeth lacking denticles anteriorly, and ungual and penultimate pedal phalanx II highly modified for hyperextension, with ungual II being more strongly curved and substantially larger than that of digit III. The finding of a new small theropod specimen in the Öösh Formation adds to the deinonychosaur fossil record from the same beds, until now restricted to the dromaeosaurid Shanag ashile. © 2012 Copyright Taylor and Francis Group, LLC.
Wings O.,University of Tübingen |
Daniela S.-W.,Humboldt University of Berlin |
Fowler D.W.,Museum of the Rockies
Neues Jahrbuch fur Geologie und Palaontologie - Abhandlungen | Year: 2011
In April 2006, three new dinosaur localities were discovered in the upper part of the Middle to Late Jurassic Shishugou Formation within "Dinosaur Valley", a classic Junggar Basin locality for Jurassic vertebrates. Recovered bones comprise cervical vertebrae of an adult and a juvenile sauropod and several sauropod forelimb elements. The vertebrae show several affinities to Mamenchisaurus, but a generic assignment cannot be undertaken considering the fragmentary nature of the material and the uncertain status of taxa assigned to the genus Mamenchisaurus. Comparisons make it likely that they are more closely related to Mamenchisaurus and Omeisaurus than to other eusauropods and Euhelopus. All vertebrae expose an accessory lamina at the vertebral centrum, which might also be present but remained undescribed in species of Mamenchisaurus. Indications in the forelimb elements, such as humerus, ulna, and pollex claw, do not allow a determination of the taxa, although there are no distinct differences to Mamenchisaurus. The remains are important because of their extreme size, including potentially the first recognized juvenile remains of a Mamenchisaurus relative, and demonstrate further evidence for the occurrence of non-neosauropod eusauropods in the Junggar Basin. © 2011 E. Schweizerbart'sche Verlagsbuchhandlung Stuttgart Germany.
Woodruff D.C.,Museum of the Rockies |
Woodruff D.C.,Montana State University
Journal of Morphology | Year: 2014
Vertebral neural spine bifurcation is considered to be restricted to sauropodomorph dinosaurs, supposedly an adaptation in response to the increasing weight from the horizontally extended cervical column. In this issue of the Journal of Morphology, Cary Woodruff (pp. 1053-106510.1002/jmor.20283) reports about his studies on the soft tissue surrounding neural spine bifurcation in a terrestrial quadruped model species, Ankole-Watusi cattle. With horns weighing up to a combined 90 kg, the Ankole-Watusi is unlike any other breed of cattle in terms of cranial weight and presence of neural spine bifurcation. The cover image shows the world record holding Ankole-Watusi steer "Lurch". The circumference of Lurch's horns are 95.25 cm, and from tip-to-tip the horns are nearly 243 cm in breadth. © 2014 Wiley Periodicals, Inc.
News Article | November 12, 2015
The fossil of a new species of duckbilled dinosaur, which paleontologists have dubbed "Superduck," sheds light on how such dinosaurs evolved and got their distinctive skull crest, researchers say. The flashy head crest of Probrachylophosaurus bergei, found in Montana, may represent a missing link between other already well-known dinosaur species, they point out. Paleontologists say they have linked the new species to an earlier dinosaur relative that had no crest and to another later species that sported a large, distinctive crest. P. bergei falls somewhere in the middle between non-crested Acristavus and Brachylophosaurus with its large crest, says Elizabeth Freedman Fowler of the Museum of the Rockies and Montana State University. The crest of the "Superduck" dinosaur "would have only poked up a little bit on the top of the head, above the eyes," she explained. "It is a perfect example of evolution within a single lineage of dinosaurs over millions of years," she said. Dubbed "Superduck" because of its size, P. bergei could grow to about 30 feet in length and be as heavy as 5 tons. It lumbered over terrain about 79 million years ago, the researchers report in the journal PLOS ONE. An examination of the fossil leg bones found in the Judith River Formation in north-central Montana shows this "Superduck" was 14 years old when it died, not quite fully grown. Duckbilled dinosaurs, named for beaks that resemble a duck's bill, were common on Earth in the later parts of the Cretaceous Period. The crests of duckbilled species would have been either too small or too large and fragile to be used as a weapon during fights, the researchers suggest. Rather, it is likely the head crests — possessed by both males and females — allowed individuals to recognize others of their species and would have been a sign that an animal was sexually mature, the researchers say. "On a crowded floodplain, you want to make sure you stay with the right (dinosaur) herd," Freedman Fowler says. "The crests may have also helped them attract mates." Most of the skull, pelvis, hind legs, vertebrae and ribs of the "Superduck" have been excavated, which gives a good impression of the overall configuration of the creature and of its evolving crest. "Because the fossil record is very spotty and we only get glimpses of evolutionary trends, it is always exciting to find evidence of transitional species," said Freeman Fowler's MSU colleague Jack Horner.
News Article | November 11, 2015
Undated handout illustration courtesy of paleoartist John Conway shows the Probrachylophosaurus bergei dinosaur. REUTERS/Courtesy of John Conway/Handout via Reuters More WASHINGTON (Reuters) - In a warm, lush environment near a meandering river 79.5 million years ago in Montana, a dinosaur nicknamed "Superduck" munched on leaves and kept a lookout for predators related to Tyrannosaurus rex that might threaten its herd. Scientists on Wednesday announced the discovery of fossils of the dinosaur they named Probrachylophosaurus bergei that was about 30 feet (9 meters) long, weighed more than 5 tons and donned a small, triangular bony crest atop its skull. It was a member of a plant-eating group called duck-billed dinosaurs, known for beaks resembling a duck's bill, common during the latter part of the Cretaceous Period. Many duck-billed dinosaurs boasted head crests of various shapes and sizes. Probrachylophosaurus, one of the earliest with a prominent crest, offers insight into the evolution of these features, the researchers said. Its skull bones are very similar to those of Acristavus, a duck-billed dinosaur from about 81 million years ago thought to be its ancestor, and Brachylophosaurus, which lived about 78 million years ago and is thought to be its descendant. "Acristavus does not have a crest. The top of its skull is flat. Brachylophosaurus has a large, flat, paddle-shaped crest that completely covers the back of the top of its skull," said Elizabeth Freedman Fowler, curator of paleontology at the Great Plains Dinosaur Museum in Malta, Montana. "It is a perfect example of evolution within a single lineage of dinosaurs over millions of years." Paleontologist Jack Horner of Montana State University and the Museum of the Rockies added, "Because the fossil record is very spotty and we only get glimpses of evolutionary trends, it is always exciting to find evidence of transitional species." Freedman Fowler said she gave Probrachylophosaurus (pronounced pro-BRAH-KEE-loh-foh-saw-rus) the nickname "Superduck" because it was pretty big for a duck-billed dinosaur, although not the largest. Growth rings in its leg bones, akin to annual growth rings in trees, showed it was 14 years old, still not fully grown. "We think that the crests of dinosaurs were visual signals so that they could recognize members of their own species, and also tell whether the animal was mature or not," Freedman Fowler said. The scientists unearthed most of its skull, its pelvis, hind legs, vertebrae and ribs near the north-central Montana town of Rudyard. They unearthed less-complete remains of a second Probrachylophosaurus, more of an adolescent in age. The research was published in the journal PLOS ONE.