Hominid Ichnotaxonomy: An Exploration of a Neglected Discipline

Although more than 60 ancient hominid track sites ranging in age from 3.7 million to less than 500 B. P. are recorded from all continents except Antarctica, no ichnotaxonomic names have ever been formally proposed for hominid tracks. There is no prohibition to the naming of fossil footprints of species that created tracks and trackways similar to those of living species. On the contrary, there is precedent for the naming of ichnotaxa corresponding to the dominant extant vertebrates classes: mammals = Mammalipedia and birds = Avipeda. The hominid track site sample includes only about a dozen sites where footprint preservation is good enough to show details of diagnostic foot morphology and typical trackway morphology. We infer that the Acahualinca Footprint Museum site in Nicaragua represents the most important ancient hominid track site that combines accessibility, a large sample of well-preserved trackways and reliable dating. For this reason, we select the Nicaraguan tracks as the type sample for the new ichnotaxon Hominipes modernus ichnogen., and ichnsp. et ichnosp. nov., which we infer to represent fully modern Homo sapiens. Our preliminary investigations of other track sites suggest that the majority also yield H. modernus. However, at many sites preservation is insufficient to make an ichnotaxonomic designation at the species level or to infer that the trackmaker was H. sapiens. Thus, at many sites including the famous Laetoli site, we apply the more general label of Hominipes isp. indet.     

Review of Japanese Dinosaur Track Localities: Implications for Ichnotaxonomy,Paleogeography and Stratigraphic Correlation

Nine dinosaur ichnospecies from the Lower Jurassic to Upper Cretaceous of Japan, including two that are new, are described herein. The new ichnotaxa are Asianopodus pulvinicalx ichnogen. et ichnosp. nov. and Schizograllator otariensis ichnosp. nov. The Japanese ichnotaxa are allied to Lower Jurassic ichnospecies in South China, North America, Western Europe and South Africa, and Upper Jurassic to Lower Cretaceous ichnospecies from Southeast and East Asia. This suggests they were part of a global ichnofauna before continental drift began in the Middle Jurassic, leading to the development of a more endemic dinosaur fauna in the Cretaceous. At least two assemblages, an ornithopod-gracile-toed theropod-dominated community, in northeastern Asia, and a robust theropod- and sauropod-dominated community in the southern part of the continent, existed in the Cretaceous. This parallels North American dinosaur distribution patterns in the Cretaceous and seems to be a reflection of paleolatitudinal controls.     

The Mississippian Tetrapod Footprint Ichnogenus Palaeosauropus: Extramorphological Variation and Ichnotaxonomy

Palaeosauropus primaevus is a tetrapod footprint ichnotaxon first described from the Upper Mississippian (Visean) Mauch Chunk Formation near Pottsville, Pennsylvania, United States. Our relocation of the type locality and stratigraphic horizon of P. primaevus, a long-available but unstudied collection of tetrapod footprints from these strata, and our new collections allow a much fuller characterization of this ichnotaxon and the range of extramorphological variation encompassed by it. P. primaevus is characterized as the footprints of a quadruped with a pentadactyl pes and a tetradactyl manus, in which the pes frequently oversteps the manus and with which tail drags are common. In the manus, all digits are relatively broad and have rounded tips, digit III is longest, and digit IV is more widely separated from digit III than the other digits are from each other. The pes has five digits that are also wide and blunt-tipped, digit IV is longest, and digit V projects nearly laterally. P. primaevus is the track of a relatively large temnospondyl (～400 mm gleno-acetabular length) and documents the Mississippian presence of such large amphibians long before their body fossil record. Palaeosauropus also occurs in Mississippian strata in Indiana and is distinguished from the geologically younger but similar temnospondyl footprint ichnogenus Limnopus by its relatively narrower manus and pes that lack broad and rounded sole impressions.     

Function and the Evolution of Phenotypic Stability: Connecting Pattern to Process

Phenotypes manifest a balance between the inherited tendencyto remain the same (phenotypic stability) and the tendency tochange in response to current environmental conditions (adaptation).This paper explores the role of functional integration and functionaltrade-offs in generating phenotypic stability by limiting theresponses of individual characters to environmental selection.Evolutionarily stable configurations (ESCs) are systems of functionallyinteracting characters within which characters are "judged"by their contribution to system-level functionality. This "internal"component of selection differs from traditional "external" selectionin that it travels with the organism wherever it goes and ismaintained across a wide range of environments. External selection,in contrast, is by definition environment-dependent. The temporaland geographic constancy of internal selection therefore actsto maintain phenotypic stability even as environments change.Functional trade-offs occur when one character participatesin more than one function, but can only be optimized for one.Participation of certain ("keystone") characters in a trade-offpotentially causes stabilization of an entire system owing toa cascade of functional dependencies on that character. Phylogeneticcharacter analysis is an essential part of elucidating theseprocesses, but patterns cannot be used as prima facie evidenceof particular processes.     

The Pattern of Helping in the Bell Miner Revisited: A Reply to Jamieson and Craig

Jamieson & Craig (1987) have argued that the feeding of nestlings by nonparental birds may simply be an unselected consequence of delayed dispersal in cooperatively breeding birds in which philopatric individuals are responding to the stimulus of begging young in their vicinity (see also Jamieson 1986, 1989). Jamieson & Craig (1990) recently criticized my attempt to examine what they describe as this “unselected” hypothesis of Williams (1966) and several selectionist (or adaptive) hypotheses for the current utility of helping behaviour in the bell miner (Manorina melanophrys) (Clarke 1989). In this paper I address specific issues raised by Jamieson & Craig (1990), especially whether the unselected hypothesis is an adequate explanation of the pattern of helping in the bell miner. I will also attempt to highlight the difficulty of formulating specific predictions from the unselected hypothesis and the apparent ease with which it can be modified to accommodate departures from its general predictions.     

Crocodylomorph Trackways from the Jurassic to Early Cretaceous of North America and Europe: Implications for Ichnotaxonomy

Trackways described as Batrachopus (Batrachopodidae Lull, 1904 Lull, R. S. 1904. Fossil footprints of the Jura-Trias of North America. Memoirs of the Boston Society of Natural History, 5: 461–557.  [Google Scholar]) from the Lower Jurassic of Europe are rare and in some cases different from the type trackways from North America. Differences may be in part attributable to preservation, but current evidence suggests that there is inherent variability in Batrachopodidae morphotypes, beyond that attributable to differential preservation. Type Batrachopus is a stout-toed form, with minimal digit divarication (i.e., a long foot), whereas Antipus describes slender-toed forms with a wider foot and wider digit divarications.

Antipus is also similar to Crocodylopodus (ichnofamily Crocodylopodidae: Fuentes Vidarte and Meijide Calvo, 1999 Fuentes Vidarte, C. and Meijide Calvo, M. 1999. Primeras Huellas de Cocodrilo en el Weald de Cameros (Sria, Espana) Nueva Familia Crocodilopodidae: Nuevo icnogenero: Crocodylopodus Nueva icnoespecie: C. meijidei. Actas de las jornadas internacionales sobre paleontologia de dinosairios y su entorno. Sala de los infantes (Burgos, Espana). Collectivo Arqueologico-Paleontologico de Salas, : 329–338.  [Google Scholar]) from near the Jurassic-Cretaceous boundary in Spain. Crocodylopodus has a relatively large manus, and a less outwardly rotated trackway, but is not sufficiently different from Batrachopodidae to warrant its own ichnofamily. Manus-pes size (area) ratios (heteropody) may also be important in differentiating different crocodylomorph ichnotaxa, as is the case with other archosaurian ichnotaxa. However, heteropody may change with size, and be less pronounced in large individuals. Manus and pes rotation patterns, and trackway width are variable and may be of use for differentiation of ichnotaxa but may also be a function of speed.     

Higher taxa: Reply to cartmill

Ian Tattersall is a curator emeritus at the American Museum of Natural History. He has worked on lemur systematics and ecology as well as paleoanthropology, where his special interest is in hominid diversity and cognitive evolution.     

Allozyme Diversity in Non-social Spiders: Pattern, Process and Conservation Implications

In this article we summarize estimates of genetic variation based on allozymes for 30 non-social spider species. Overall, these species show moderate levels of genetic variability (mean H_o = 6.8%) compared to other invertebrate species surveyed for allozymes, although a number of spiders possess only minimal variation. Fossorial spiders, especially those which are coastal dune dwellers, typically display less variation than other non-social arachnids. In general, differences in heterozygosity estimates between groups of non-social spiders in this article are not confounded by the varying mix of proteins that have been assayed by individual investigators. There is a significant positive relationship between genetic variability and gene flow (Nm), indicating that non-social spider populations which exhibit reduced variability are likely to be genetically isolated. Population bottlenecks, directional selection and environmental homogeneity have all been cited to account for reduced variability in particular non-social spiders. In addition, an analysis using the genus Lutica suggests that low genetic variation may be accompanied by decreased population fitness. Since the potential for evolutionary change is dependent on the existence of genetic variability, our findings indicate that a number of non-social spiders may be at risk in terms of long-term population viability. This conclusion should be verified/extended via a combination of more genetic surveys; genetic and ecological monitoring of populations and their fitnesses in the wild; and experimental studies of the mechanisms underlying fitness differences.