MARCH 2002
New Theropod Trackway with Two Gaits
A Nature article by Julia Day, David Norman et al describes an exciting new trackway by a three toed animal that is walking and then speeds up. It was found at the Ardley Quarry in Oxfordshire in the UK. and is dated to 163 MYA (Middle Jurassic). The two speed tracks indicate that they used different hindlimb postures for the two gaits. They are with prints from two sauropods and another theropod. Most of the theropod tracks are wide gauge with the toes slightly facing inwards. In this trackway, #13, they start out wide gauge and then shift into narrow gauge with the toes slightly facing outwards (for 115 feet). The action of placing the feet in line maximizes the stride length and reduces energy lost by the displacement of center of gravity. The slower wider gait was probably more stable for normal walking. They estimate the dino to be 1 to 2 metric tons. The estimate of speed is 4 mph at the walk and 18 mph at the run. The dinosaur may be a megalosaurus whose remains have been found in many nearby quarries
New "Parental Care" Theory of Bird Evolution
A German journal article by James Carey of UC Davis reports on a third theory of bird evolution. The current trees down or arboreal theory says that tree dwelling dinosaurs began to glide from tree to tree and to the ground and eventually developed feathers for powered flight. Carey argues that if this were the case, they would have developed membranes like bats have. The cursorial or ground up theory says that quadrupedal reptiles developed feathers from scales to help gain thrust and lift for flight from the ground. This theory requires that each step in the development of feathers have useful advantages and Carey is not convinced that can be shown. With his parental care theory he suggests that protection for the ground nest began the transition with feathers developing from scales for camouflage and insulation of the eggs. They began to feed their young in the nest that they moved into bushes and small trees to protect them from predation. The forelimbs became elongated and fully feathered to manipulate the eggs and to glide to the ground. Beaks evolved to pinpoint feeding the young instead of for lightening the animal for flight. Features of Archaeopteryx support this theory with clawed wings for tree climbing, primitive beak, the limited ability for flight, and feathers more advanced than other bird features. In many ways this just sounds like a modified trees-down theory. He also suggests that pterosaurs died out because of their lack of parenting skills rather than competition with birds. Interesting idea since they were around almost as long as the long lived dinosaurs!
Crinoid Decapitation and Death?
An article in the recent issue of Lethaia presents an interesting study on what happens to crinoids when the heads are removed by predation or by self-decapitation. It was thought that the stem would die without its crown. But in fact the stems can repair the damaged end and continue to survive (for more than a year in a lab) by absorbing nutrients through its ectoderm. Looking back at fossils of stems, many are found to have a cap on the end rather than a sharp break, indicating that there had been some repair done while the stem was still alive. The crown may have been lost by predation by cephalopods or other predators or by self-decapitation in a time of stress (the crown may have been able to grow a new stem elsewhere after a flood or other disaster, making this a survival mechanism). There is some question as to whether the capped end is really at the crown end or at the base end, where it might have been dislocated from its holdfast. And of course there is always a risk when one tries to relate activities of extant life with its fossil precursors. But the authors (Stephen Donovan and David Schmidt) feel that their evidence is quite strong. So you might want to take a look at your crinoid fossils to see if the headless stem ends are sharp or rounded (see photos in article posted on board).
New Book & Three New Dinos
Finally got my copy of Ken Carpenter’s new book "The Armored Dinosaurs" and it looks good. There are many chapters covering stegosaurs and ankylosaurs by many experts in the field. Three new genera are introduced in this book.
A new primitive stegosaur from the Morrison Formation of Wyoming is named Hesperosaurus mjosi (western reptile and Ron Mjosi the collector) and is known from a skull and most of the body. It is reported by Ken Carpenter et al and is one of the oldest known stegosaurs in North America.
A new primitive ankylosaur from the Lower Cretaceous of Utah is named Cedarpelta bilbeyhallorum (from Cedar Mountain Formation and for its finders Sue Ann Bilbey & Evan Hall) and is known from the skeletons of two animals found in the same quarry. The skull shows similarities to an Asian animal Shamosaurus strengthening the Asian exchange theory. The cranial armor of these animals is made up of individual elements that do not cross suture boundaries and is thus considered ornamentation rather than armor. Both of these animals are estimate to be about 26 feet long. This chapter is by Carpenter and Kirkland.
The third is actually a redescription of bones that were originally identified as a nodosaur Stegopelta. In the chapter by Ford and Kirkland it is called an ankylosaur because of its hollow dorsal armor, limb morphology and tooth form. Aletopelta coombsi (wandering shield and honor to Walter Coombs) is from the Upper Cretaceous of California. This is the first ankylosaurid from marine strata, although it is common for nodosaurids. It is also the southernmost ankylosaur found from North America.
An interesting chapter by Carpenter and Galton explains a problem with O. C. Marsh’s reconstruction of Stegosaurus in 1891. It was constructed with paired plates on its body, a single row on its tail and 4 pairs of tail spikes (which was considered diagnostic for Stegosaurus ungulatus). However, after research of quarry data and research notes, it looks like there were never more than two pairs of tail spikes found associated with the tail vertebrae. Early interpretations of Stegosaurus made it an aquatic animal built very like a turtle. Some even thought it was bipedal because the front legs were so much shorter than the rear ones. The number of tail spikes was thought to vary among different species with 4 pair being the maximum. However, now it is believed that all stegosaurs have only 4 tail spikes in pairs.
Another interesting chapter is by McWhinney, Rothschild et al and covers pathologies in Stegosaurus tail spikes. They found injuries in only 10 % of 51 tail spikes. In each case there was remodeled bone growth which indicates that all the animals survived the injury. The authors conclude that the tail spikes probably were used as defensive weapons, contrary to the belief that they were mainly for display.
New Dinos in 2001
If anyone tells you that there is nothing new in the dinosaur world, you can list the new genera reported during 2001. This list is from the Dinosaur Genera List of Dinogeorge in order reported during the year.
Jeholosaurus Nothronychus Ruehleia Aletopelta
Masiakasaurus Jinzhousaurus Citipati Cedarpelta
Draconyx Quilmesaurus Khaan Hesperosaurus
Eotyrannus Venenosaurus Liaoningosaurus Jiangshanosaurus
Paralititan Planicoxa Rapetosaurus Neimongosaurus
Losillasaurus Bienosaurus Eshanosaurus Pukyongpsaurus
There were also some others named that were not formally documented or reclassified.:
Saltrisaurus Aucasaurus Colossosaurus Yibinosaurus
Tanycolagreus Hanwulosaurus Heilongjiangosaurus Alashansaurus
Szechuanoraptor Deuterosaurus Wellnhoferia Spondylosoma
Patricosaurus Gobisaurus
500 MYA Jellyfish Found
A Geology article by James Hagdorn of the California Institute of Technology and Dan Damrow a fossil dealer report on thousands of impressions found at a Wisconsin quarry (in Mosinee about 200 miles northwest of Milwaukee) dated at 510 MYA. Rare soft body preservation shows that some of the jellyfish are about 3 feet in diameter. They were found in seven layers of sandstone in 12 vertical feet of rock spanning about one million years. The slabs show water ripple marks as well as impressions that are concave circular shapes where the pumping action of the jellyfish were as they tried to swim back out to deeper water. It is suggested that storms blew them onto the shores where they succumbed. The species has not yet been identified
Madagascar – The Field Museum – John Flynn
The February issue of Scientific American has an article by John Flynn and Andre Wyss describing their discoveries from Mesozoic Madagascar. Madagascar is indeed revealing very important information about past life. The two major discoveries so far are the two dinosaur jaws showing that dinosaurs evolved earlier (230 MYA) than previously thought and the early mammals that tell us that they may have evolved in the Southern rather than the Northern hemisphere as currently thought. This is exciting news on both fronts. The two new prosauropod dinosaurs have still not been named, but some of the mammals have. The fact that the dinos were discovered along with skulls of traversodontids and rhynchosaurs strengthens the dating of the jaws (there are no volcanic rocks nearby to help with the dating). The four-inch long mammal Ambondro mahabo is dated to the middle Jurassic at 167 MYA when the earliest mammal previously was dated to the Late Jurassic. It is characterized by its tribosphenic tooth structure that is the characteristic found in placentals and marsupials. There are some that argue that it doesn’t mean that they originated in the south but that it may instead be the precursor to a second line of tribosphenic mammals that led to monotremes. However, Flynn and Wyss do not believe that their features match. There is currently a debate going on about a northern or southern origin for the mammal groups so this is one more interesting piece in the puzzle. As usual more fossils are needed to help answer this question.
Karen Nordquist, ESCONI Paleontology Study Group
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