Human Origins: The Fossil Record

3rd ed. By Clark Spencer Larsen, Robert H. Matter, and Daniel L. Gebo. Prospect Heights, IL: Waveland Press. 1998. 225 pp. ISBN 1-57766-002-1. $18.95 (paper).     

The Fossil Record of Long-Proboscid Nectarivorous Insects

Entomological Review - The paper overviews the fossil record of insects with long mouthparts and rostra adapted to feeding on floral nectar and pollination drops of extinct gymnosperms. The...     

The Fossil Record of Feather Evolution in the Mesozoic

The oldest known feathers from the Late Jurassic are alreadymodern in form and microscopic detail. Because these oldestexamples are assignable to an extinct branch (Sauriurae) ofthe basal avian dichotomy, their features must have been establishedat a significantly earlier date. The skin of a wide varietyof dinosaurs is now known and is unlikely to represent a predecessorto a feather bearing integument. Examples of feathered dinosaursresult from erroneous identification of internal structuresas part of the skin covering, and from the confusion of flightlessbirds from the Early Cretaceous of China with dinosaurs.     

The Fossil Record of Vertebrate Tracks in Mexico

The fossil record of vertebrate tracks in Mexico is taxonomically rich and geographically diverse, and ranges in age from Middle Jurassic to Pleistocene and possibly Holocene. Middle Jurassic saurischian dinosaur tracks from Oaxaca represent the oldest record of vertebrate tracks in Mexico. Tracks attributed to Late Jurassic theropods and ornithopods are known from Michoacán. Theropod tracks of supposed Jurassic age are known from Durango. Lower Cretaceous Saurischian and ornithopod tracks are known from southern Puebla. Central Mexico has yielded Late Cretaceous hadrosaurid and sauropod tracks (Puebla), and tracks belonging to Theropoda and Ornithopoda (El Aguaje, Michoacan). In Coahuila several tracksites occur within the Cerro del Pueblo Formation and include tracks of mesoreptiles, pterosaurs, small to large theropods, bipedal and quadrupedal ornithopods, birds and possibly a mammal. A tracksite in the Olmos Formation includes tracks of turtles, crocodilians, medium-sized theropods, small ornithopods, and birds. Bird tracks of supposed Eocene age are known from Sinaloa. Two important Pleistocene ichnofaunas occur in the states of Puebla (Tepexi de Rodríguez) and Jalisco (San Juan de los Lagos), and include tracks of camelids, artiodactyls, small ungulates, elephants, large felids and birds. Pleistocene human tracks occur in Coahuila and Jalisco. Mexico's track record provides important insights into vertebrate diversity, paleoecology, and paleoenvironments. Given the rate of new discoveries since 1998, there is no doubt that new sites await to be found.     

The Fossil Record of Shell Boring by Snails

The predatory boring habit common to many recent snails probablyarose first in the Polinicinae (Naticacea) during Upper Cretaceous(Cenomanian) times (100 million years B.P.) . In the fossilrecord the frequency of bored shells increasesgreatly in rocksof latest Cretaceous age and becomes more widespread duringearly Tertiary times coincident with the major diversificationof the primary groups of boring snails. The borings in these Cretaceous and Tertiary shells show thesame characteristics of preference of penetration in one pelecypodvalve rather than the other or in position of the boring siteon the shell that are found in recent shell assemblages. Borings in Paleozoic brachiopod shells (230–550 millionyears old) that have previously been attributed to gastropodpredation are herein attributed to other but unknown boringorganisms. In part these borings are not accepted as evidence of Paleozoicgastropod predation because it necessitates: (1) Postulationof the separate development of a boring habit ith its concomitantdevelopment of an accessory boring organ in a groupwhose descendantsare all herbivores, and (2) The development of such a habithundreds of millions of years before the appearance of any relativesof present day borers.     

Global Completeness of the Bat Fossil Record

Bats are unique among mammals in their use of powered flight and their widespread capacity for laryngeal echolocation. Understanding how and when these and other abilities evolved could be improved by examining the bat fossil record. However, the fossil record of bats is commonly believed to be very poor. Quantitative analyses of this record have rarely been attempted, so it has been difficult to gauge just how depauperate the bat fossil record really is. A crucial step in analyzing the quality of the fossil record is to be able to accurately estimate completeness. Measures of completeness of the fossil record have important consequences for our understanding of evolutionary rates and patterns among bats. In this study, we applied previously developed statistical methods of analyzing completeness to the bat fossil record. The main utility of these methods over others used to study completeness is their independence from phylogeny. This phylogenetic-independence is desirable, given the recent state of flux in the higher-level phylogenetic relationships of bats. All known fossil bat genera were tabulated at the geologic stage or sub-epoch level. This binning strategy allowed an estimate of the extinction rate for each bat genus per bin. Extinction rate—together with per-genus estimates of preservation probability and original temporal distributions—was used to calculate completeness. At the genus level, the bat fossil record is estimated to be 12% complete. Within the order, Pteropodidae is missing most of its fossil history, while Rhinolophoidea and Vespertilionoidea are missing the least. These results suggest that 88% of bats that existed never left a fossil record, and that the fossil record of bats is indeed poor. Much of the taxonomic and evolutionary history of bats has yet to be uncovered.     

Fossil Record and Age of the Asteridae

The Asteridae is a group of some 80,000 species of flowering plants characterized by their fused corollas and iridoid compounds. Recent phylogenetic analyses have helped delimit the group and have identified four main clades within it; Cornales, Ericales, Lamiids and Campanulids, with the last two collectively known as the Euasteridae. A search for the oldest fossils representing asterids yielded a total of 261 records. Each of these fossils was evaluated as to the reliability of its identification. The oldest accepted fossils for each clade were used to estimate minimum ages for the whole of the Asteridae. The results suggest that the Asteridae dates back to at least the Turonian, Late Cretaceous (89.3 mya) and that by the Late Santonian-Early Campanian (83.5 mya) its four main clades were already represented in the fossil record.     

Spatial Bias in the Marine Fossil Record

Inference of past and present global biodiversity requires enough global data to distinguish biological pattern from sampling artifact. Pertinently, many studies have exposed correlated relationships between richness and sampling in the fossil record, and methods to circumvent these biases have been proposed. Yet, these studies often ignore paleobiogeography, which is undeniably a critical component of ancient global diversity. Alarmingly, our global analysis of 481,613 marine fossils spread throughout the Phanerozoic reveals that where localities are and how intensively they have been sampled almost completely determines empirical spatial patterns of richness, suggesting no separation of biological pattern from sampling pattern. To overcome this, we analyze diversity using occurrence records drawn from two discrete paleolatitudinal bands which cover the bulk of the fossil data. After correcting the data for sampling bias, we find that these two bands have similar patterns of richness despite markedly different spatial coverage. Our findings suggest that i) long-term diversity trends result from large-scale tectonic evolution of the planet, ii) short-term diversity trends are region-specific, and iii) paleodiversity studies must constrain their analyses to well-sampled regions to uncover patterns not driven by sampling.     

Evolutionary Transitions in the Fossil Record of Terrestrial Hoofed Mammals

In the past few decades, many new discoveries have provided numerous transitional fossils that show the evolution of hoofed mammals from their primitive ancestors. We can now document the origin of the odd-toed perissodactyls, their early evolution when horses, brontotheres, rhinoceroses, and tapirs can barely be distinguished, and the subsequent evolution and radiation of these groups into distinctive lineages with many different species and interesting evolutionary transformations through time. Similarly, we can document the evolution of the even-toed artiodactyls from their earliest roots and their great radiation into pigs, peccaries, hippos, camels, and ruminants. We can trace the complex family histories in the camels and giraffes, whose earliest ancestors did not have humps or long necks and looked nothing like the modern descendants. Even the Proboscidea and Sirenia show many transitional fossils linking them to ancient ancestors that look nothing like modern elephants or manatees. All these facts show that creationist attacks on the fossil record of horses and other hoofed mammals are completely erroneous and deceptive. Their critiques of the evidence of hoofed mammal evolution are based entirely on reading trade books and quoting them out of context, not on any firsthand knowledge or training in paleontology or looking at the actual fossils.     

Biology of the Epacridaceae

No abstract     

The First Record of Fossil Wood of Winteraceae from the Upper Cretaceous of Antarctica

Fossil wood of the Winteraceae from the Upper Cretaceous sedimentsof James Ross Island, Antarctic Peninsula, is described herefor the first time. The specimen is characterized by the absenceof vessels, rays of two distinct sizes and tracheids with one–threerows of circular bordered pits, mainly on the radial walls,grading to horizontally elongate and scalariform. Despite anatomicalconformity to the family Winteraceae, the fossil wood is notidentical to any one extant genus and therefore has been assignedto the fossil organ genus Winteroxylon Gottwald with which thefossil shows greatest similarity. Copyright 2000 Annals of BotanyCompany Antarctica, Cretaceous, angiosperm, wood, anatomy, Winteraceae, Winteroxylon, fossil, palaeoclimate