The last four decades have witnessed a revolution in the study of dinosaurs. Scientists no longer examine just the structure of the skeletons and the relationships of these fascinating animals, but have started probing issues of their biology. How did dinosaurs move? How did they feed? What was their circulatory system like? How did they…
The middle ear of mammals contains a chain of three tiny bones (auditory ossicles), the hammer (malleus), anvil (incus), and stirrup (stapes). This chain transmits and amplifies sound vibrations from the eardrum to the inner ear. The eardrum (tympanic membrane) itself is stretched across an additional bone, the ectotympanic. In all other land vertebrates, a…
In recent decades paleontologists have been able to document in ever-greater detail the evolution of birds from small predatory dinosaurs. After establishing the broader outlines of this transition, researchers are now focusing on specific adaptations. It is widely believed that birds have no or at most a poorly developed sense of smell. A new study…
The giant extinct invertebrate Arthropleura resembled some modern millipedes, but could grow to be more than one-and-a-half feet wide, and may sometimes have been more than six feet long. Reconstruction of the giant millipede Arthropleura from the Pennsylvanian and earliest Permian of North America and Europe. The head capsule (marked by an asterisk) is shown…
A new study of venomous reptile fossils sheds light on the evolution of snake fangs. By Hans-Dieter Sues Venom is a highly effective means to subdue and kill prey before eating it, as well as a great defense against predators. Furthermore, studies have shown that some snake toxins can also help in breaking down proteins…
By Hans-Dieter Sues Charles Darwin noted that the oldest fossils known in his day already represented quite complex life forms such as trilobites, an immensely diverse group of extinct marine arthropods most closely related to horseshoe crabs, spiders, and their relatives. We now date these remains as middle Early Cambrian in age. Because Darwin assumed…
By Hans-Dieter Sues The oldest known birds, classified in the genus Archaeopteryx, lived near the end of the Jurassic Period (145.5 to 150.8 million years ago). Although Archaeopteryx has a fully developed plumage its skeleton still retains many features of its dinosaurian precursors, one of which is jaws with teeth. With the exception of some…
Ancestors of dinosaurs and other animals from the Haţeg Basin in Transylvania may have arrived from what was once a continent of Asiamerica by “island hopping,” suggests a fossil discovery published today. By Hans-Dieter Sues Islands are wonderful natural laboratories for the study of evolutionary change and for that reason have long attracted the attention…
By Hans-Dieter Sues About 60 million years ago, a group of extinct ground-dwelling birds of often spectacular size and with proportionately enormous heads, the Phorusrhacidae, first appeared in South America, an island continent until about three million years ago. They are informally and memorably known as “terror birds.” One species, Titanis walleri, crossed into North…
A remarkable new discovery redates the evolutionary split between the Old World monkeys and the ape-human lineage. By Hans-Dieter Sues The higher primates of the Old World (Catarrhini) are divided into two major lineages, one comprising the living monkeys of Africa, Asia, and Europe and their fossil relatives (Cercopithecoidea), and the other, humans, great apes,…
By Hans-Dieter Sues A lively debate continues regarding the cause(s) of the extinction of dinosaurs (other than their descendants, birds), along with many other organisms, at the end of the Cretaceous Period some 65 million years ago. While this subject has tremendous appeal, the biologically interesting issue of the origin and early evolution of these…
By Hans-Dieter Sues Among the great mammalian predators from the Pleistocene Epoch (1.8 million to 10,000 years ago) of North America, an enormous cat stands out. Only the giant bear Arctodus simus (discussed in a previous blog) exceeded it in size. No, I am not talking about the famous saber-toothed cat, Smilodon fatalis. Renowned American…
By Hans-Dieter Sues In the movie The Lost World (1997), the eccentric chaos theoretician Dr. Ian Malcolm (Jeff Goldblum) remarked on the all-too-soon apparent instability of the “Jurassic Park” world: “Life will find a way.” It always does. Some animals and plants make a living in almost unimaginably weird ways. For an evolutionary biologist like…
By Hans-Dieter Sues Shortly after World War II, an Australian geologist named Reginald Sprigg discovered peculiar impressions on slabs of ancient quartzite in the Ediacara (pronounced “Ee-dee-acra”) Hills of South Australia. These finds came from a level well below the rocks containing the oldest Cambrian fossils in the region. They did not fit the traditional…
By Hans-Dieter Sues In recent years, discoveries of a spectacular array of Jurassic and Early Cretaceous “missing links,” mostly from China, have allowed scientists to map the evolutionary transition from small predatory dinosaurs to birds in astonishing detail. The ancient lake deposits of the Yixian Formation in the northeastern corner of China have yielded a…