Leaf Stomata Tell Story of Altitude

Jenny McElwain, Paleobotanist from the Field Museum, has made the news again (Geology cover story). Previously she wrote about the stomata of leaves that told the story about CO2 levels during periods of extinction. Now she finds that they also tell the story of the growth of mountains. The crucial detail is that the number of pores on the fossil leaves tells the concentration of carbon dioxide in the atmosphere, the more pores the lower the level of the gas. There is less CO2 at higher levels. Jenny studied leaves from different locations all over California to establish the number of stomata at various altitudes. She then looked at fossil leaves at sea level to form a baseline and other leaves from the same formation to determine how high and when the mountains were. She may collaborate in the future with David Rowley at the University of Chicago who has tried to determine the growth and time of the growth of the Himalayas by measuring carbon and oxygen isotopes in rocks. The leaf study may help solve this mystery also.

              Spanish 13 MY Early Ape Fossil – Pierolapithecus

This exciting new 13 MY old fairly complete fossil appears to be closely related to the earliest ape family, the large bodied long lived intelligent family including humans. This is the most ancient ape to show an upright posture, muzzleless face and other characters that link it to great apes and people. This individual was found in a village in Catalonia named Els Hostalets de Pierola leading to its name – Pierolapithecus catalaunicus. They find a combination of monkeylike and apelike traits. The 30 kg male fossil has a reduced muzzle like apes. The rib cage and vertebrae indicate upright posture like great apes, but it was a tree dwelling fruit and vegetation eater. It has flexible wrists like swinging apes but small hands and straight fingers like monkeys. This combo indicates they first climbed vertically through trees and later developed adaptations for tree swinging behavior like great apes. This may mean that chimps and orangs evolved the behavior separately. Because there are so few fossils they are unsure where this fossil fits on the tree. (Moya-Sola et al in Science V.306/Nov. 19)

               Humans Geared for Endurance

Humans have usually been considered slow and inefficient in running because we do not do well in sprints compared to quadrupeds. Other animals can maintain maximum speeds for longer in sprints, use less energy to do it and have more maneuverable bodies. However, this new study shows that endurance running (ER or long distance aerobic running) may have evolved 2 MY ago with the evolution of Homo from its relatives. ER is unique to humans among primates and seen only in social carnivores and migratory ungulates. Many of the reasons for our success in running are found in traces on the skeleton. There are four demands to be considered – energetics, strength, stabilization and thermoregulation. The Achilles tendon, the arch of the foot and stride length are factors for energetics. One problem is that traces of the Achilles tendon are not found in the early fossils. Enlarged joint surfaces on the lower limbs help dissipate the stress of running. Expanded areas of the sacrum and an enlarged gluteus maximus help stabilize the body when it leans forward during running. Cooling during running is aided by less hair, sweating, narrow elongate body form, and mouth breathing. Most of the features needed appear in H. erectus, but some are found in H. habilis. Why Homo evolved the capability for ER is still unknown. Was it helpful in its search for food - hunting or scavenging? Did they run their prey to exhaustion (weapons came later)? Or were they trying to compete with other scavengers? There are still many questions. (Bramble & Lieberman in Nature V. 432/Nov. 18)

Growth Study on Small Dinos and Pterosaurs by Horner/Padian

In the wake of the two reports on bone studies on tyrannosaurids by Erickson and Horner, here is another Horner/Padian study on smaller dinos and pterosaurs. The studies indicate that the large animals grew more like mammals and birds rather than like reptiles. Now bone studies of smaller animals like Scutellosaurus (a bipedal ornithiscian of the Early Jurassic) indicate slower growth rate than the big guys. Others including Oreodromeus, some basal birds grow more like young rapidly growing crocs. Also small basal pterosaurs (like Eudimorphodon and Rhamphorhynchus) show similar growth patterns. They believe that the larger size was possible by using rapid growth strategies seen in highy vascularized bone tissues in the cortex. The Nile Monitor ages like Maiasaura and Psittacosaurus, and mid-sized crocs are like sauropod Janenschia. Deinosuchus seems to extend the curve but merely reflects its larger adult size.
(Padian, Horner et al in JVP V.24/Sept.)

New Brazilian Early Dino - Unaysaurus

A new early dinosaur dated to 225 MYA has been found in Brazil. It shows close relationships to European dinosaur (Plateosaurus) reconfirming the super-continent theory of plate tectonics. It has been named Unaysaurus tolentinoi for its site meaning black water with the species name honoring the fossil finder. It is the first prosauropod ever found in Brazil and is relatively small at 8.2 feet long. The skeleton is semi-articulated with an almost complete skull. (Leal et al in Zootaxa 690/p. 1)

New 300 MY Old Amphibian Found

A freshman geology student found a rock in a road cut near the Pittsburgh airport that is turning into a very important specimen. It had teeth and the outline of a skull which Carnegie Museum paleontologists say is new to science. It is a trematopid amphibian that was about 3 to 4 feet long and terrestrial. There are only two other skulls from this family known, one from New Mexico. It is like a giant salamander but has some croc characteristics. Its early predecessors would probably have lived son 5 to 10 MY earlier. The skull is boxy with long rows of spikey teeth with 3 sets of “tusks” along the roof of the mouth. It has not been written up or named yet but the name of the finder is Adam Striegeli. (Chicago Tribune 11/10)
 

           Karen Nordquist, ESCONI Paleontology Study Group