Jonathan R. Hendricks

Exceptionally Preserved Jellyfishes from the Middle Cambrian

Cnidarians represent an early diverging animal group and thus insight into their origin and diversification is key to understanding metazoan evolution. Further, cnidarian jellyfish comprise an important component of modern marine planktonic ecosystems. Here we report on exceptionally preserved cnidarian jellyfish fossils from the Middle Cambrian (∼505 million years old) Marjum Formation of Utah. These are the first described Cambrian jellyfish fossils to display exquisite preservation of soft part anatomy including detailed features of structures interpreted as trailing tentacles and subumbrellar and exumbrellar surfaces. If the interpretation of these preserved characters is correct, their presence is diagnostic of modern jellyfish taxa. These new discoveries may provide insight into the scope of cnidarian diversity shortly after the Cambrian radiation, and would reinforce the notion that important taxonomic components of the modern planktonic realm were in place by the Cambrian period.

Middle Cambrian Arthropods from Utah

Abstract The Middle Cambrian Spence Shale Member (Langston Formation) and Wheeler and Marjum Formations of Utah are known to contain a diverse soft-bodied fauna, but important new paleontological material continues to be uncovered from these strata. New specimens of anomalocaridids include the largest and smallest near complete examples yet reported from Utah. New material of stem group arthropods includes two new genera and species of arachnomorphs: Nettapezoura basilika and Dicranocaris guntherorum. Other new arachnomorph material includes a new species of Leanchoilia comparable to L. protogonia Simonetta, 1970; Leanchoilia superlata? Walcott, 1912; Sidneyia Walcott, 1911a; and Mollisonia symmetrica Walcott, 1912. L. protogonia from the Burgess Shale is confirmed as a separate species and is not a composite fossil. The first example of the trilobite Elrathia kingii preserving traces of the appendages is described. In addition, new material of the bivalved arthropods Canadaspis Novozhilov in Orlov, 1960; Branchiocaris Briggs, 1976; Waptia Walcott, 1912; and Isoxys Walcott, 1890 is described.

W(h)ither Fossils? Studying Morphological Character Evolution in the Age of Molecular Sequences

Abstract A major challenge in the post-genomics era will be to integrate molecular sequence data from extant organisms with morphological data from fossil and extant taxa into a single, coherent picture of phylogenetic relationships; only then will these phylogenetic hypotheses be effectively applied to the study of morphological character evolution. At least two analytical approaches to solving this problem have been utilized: (1) simultaneous analysis of molecular sequence and morphological data with fossil taxa included as terminals in the analysis, and (2) the molecular scaffold approach, in which morphological data are analyzed over a molecular backbone (with constraints that force extant taxa into positions suggested by sequence data). The perceived obstacles to including fossil taxa directly in simultaneous analyses of morphological and molecular sequence data with extant taxa include: (1) that fossil taxa are missing the molecular sequence portion of the character data; (2) that morphological characters might be misleading due to convergence; and (3) character weighting, specifically how and whether to weight characters in the morphological partition relative to characters in the molecular sequence data partition. The molecular scaffold has been put forward as a potential solution to at least some of these problems. Using examples of simultaneous analyses from the literature, as well as new analyses of previously published morphological and molecular sequence data matrices for extant and fossil Chiroptera (bats), we argue that the simultaneous analysis approach is superior to the molecular scaffold approach, specifically addressing the problems to which the molecular scaffold has been suggested as a solution. Finally, the application of phylogenetic hypotheses including fossil taxa (whatever their derivation) to the study of morphological character evolution is discussed, with special emphasis on scenarios in which fossil taxa are likely to be most enlightening: (1) in determining the sequence of character evolution; (2) in determining the timing of character evolution; and (3) in making inferences about the presence or absence of characteristics in fossil taxa that may not be directly observable in the fossil record.

The Generification of the Fossil Record

Abstract Many modern paleobiological analyses are conducted at the generic level, a practice predicated on the validity of genera as meaningful proxies for species. Uncritical application of genera in such analyses, however, has led—perhaps inadvertently—to the unjustified reification of genera in an evolutionary context. While the utility of genera as proxies for species in evolutionary studies should be evaluated as an empirical issue, in practice it is increasingly assumed (rather than demonstrated) that genera are suitable proxies for species. This is problematic on both ontological and epistemological grounds. Genera are arbitrarily circumscribed, non-equivalent, often paraphyletic, and sometimes polyphyletic collections of species. They are useful tools for communication but have no theoretical or biological reality of their own and, whether monophyletic or not, cannot themselves operate in the evolutionary process. Attributes considered important for understanding macroevolution—e.g., geographic ranges, niche breadths, and taxon durations—are frequently variable among species within genera and will be inflated at the generic level, especially in species-rich genera. Consequently, the meaning(s) of results attained at the generic level may not “trickle down” in any obvious way that elucidates our understanding of evolution at the species level. Ideally, then, evolutionary studies that are actually about species should be pursued using species-level data rather than proxy data tabulated using genera. Where genera are used, greater critical attention should be focused on the degree to which attributes tabulated at the generic level reflect biological properties and processes at the species level.

New Phylogenetic Insights into the Cambrian Radiation of Arachnomorph Arthropods

Abstract The Cambrian fossil record of the Arachnomorpha is rich and diverse and includes trilobites, chelicerates, and many taxa known from various soft-bodied faunas including the Burgess Shale and the Chengjiang. Exceptionally well-preserved arthropod fossils are also known from Middle Cambrian strata in Utah. Recently, two new arachnomorphs (Dicranocaris Briggs, Lieberman, Hendricks, Halgedahl, and Jarrard, 2008 and Nettapezoura Briggs, Lieberman, Hendricks, Halgedahl, and Jarrard, 2008) were described from the Wheeler and Marjum formations of Utah. Cladistic analysis is undertaken to investigate arachnomorph relationships in light of these two new genera. The character matrix of Edgecombe and Ramsköld (1999) serves as the foundation for this study, augmented by new characters and taxa. The results of our cladistic analysis suggest that at least three distinct arachnomorph clades had diverged by the Middle Cambrian, and perhaps much earlier; the Utah genera can be referred to groups within one of these clades.

Glowing seashells: diversity of fossilized coloration patterns on coral reef-associated cone snail (Gastropoda: Conidae) shells from the Neogene of the Dominican Republic.

The biology of modern Conidae (cone snails)—which includes the hyperdiverse genus Conus—has been intensively studied, but the fossil record of the clade remains poorly understood, particularly within an evolutionary framework. Here, ultraviolet light is used to reveal and characterize the original shell coloration patterns of 28 species of cone snails from three Neogene coral reef-associated deposits from the Cibao Valley, northern Dominican Republic. These fossils come from the upper Miocene Cercado Fm. and lower Pliocene Gurabo Fm., and range in age from about 6.6-4.8 Ma. Comparison of the revealed coloration patterns with those of extant species allow the taxa to be assigned to three genera of cone snails (Profundiconus, Conasprella, and Conus) and at least nine subgenera. Thirteen members of these phylogenetically diverse reef faunas are described as new species. These include: Profundiconus? hennigi, Conasprella (Ximeniconus) ageri, Conus anningae, Conus lyelli, Conus (Atlanticonus?) franklinae, Conus (Stephanoconus) gouldi, Conus (Stephanoconus) bellacoensis, Conus (Ductoconus) cashi, Conus (Dauciconus) garrisoni, Conus (Dauciconus?) zambaensis, Conus (Spuriconus?) kaesleri, Conus (Spuriconus?) lombardii, and Conus (Lautoconus?) carlottae. Each of the three reef deposits contain a minimum of 14–16 cone snail species, levels of diversity that are similar to modern Indo-Pacific reef systems. Finally, most of the 28 species can be assigned to modern clades and thus have important implications for understanding the biogeographic and temporal histories of these clades in tropical America.

Chapter 4 Global distributional dynamics of Cambrian clades as revealed by Burgess Shale-type deposits

Abstract The Cambrian geographical and temporal distributions of many clades remain poorly understood, despite their importance for elucidating the palaeobiogeographical context of the Cambrian radiation. New species and genus level occurrence databases were developed to analyse temporal and geographical distributional patterns in taxa belonging to 14 clades from over 60 globally distributed early and Middle Cambrian Burgess Shale-type lagerstätten. Analyses demonstrate that clades with confirmed Precambrian origins were, on average, more widespread and temporally persistent than clades with first fossil occurrences in the Cambrian. Despite their dominance in diversity, arthropods were less widely distributed and temporally persistent than many other groups. Finally, a significant correlation between geographical range and temporal persistence is demonstrated, supporting the hypothesis that Cambrian taxa with wider geographical ranges were less likely to go extinct than those with narrower ranges. Supplementary material: Species and genus data tables are available at: http://www.geolsoc.org.uk/SUP18665

THE HIERARCHY OF TIME

At one time, phylogeny was almost the exclusive province of paleontology (e.g., Simpson, 1961; Scagel et al., 1966). The stratigraphic positions of fossil taxa, coupled with the intermediate morphologies represented by the same taxa, guided interpretations of the evolutionary transformations of lineages. No repeatable methodologies, however, guided the construction of phylogenetic hypotheses; rather, evolutionary trees were devised on the basis of suites of characters considered important on the basis of the accumulated knowledge of qualified experts. The advent of a cladistic framework (Hennig, 1950, 1966) and computational methodologies (e.g., Farris, 1970; Fitch, 1971; Felsenstein, 1981) allowed the construction of phylogenetic hypotheses that were explicit. In contrast to earlier approaches, characters were enumerated, the weight given to each was stated, and trees were constructed using specific algorithms. Although phylogenetic systematics still faces some philosophical and methodological challenges, the superiority of these methods for constructing explicit hypotheses of relationships among taxa has led to their widespread adoption by biologists and, to a lesser extent, paleontologists. A consequence of the adoption of phylogenetic systematics, however, was the subsequently diminished role of paleontology in studies of phylogeny. Today, many phylogenies are constructed using molecular sequence data, usually DNA sequences, extracted from extant organisms alone, with morphological evolution, if considered at all, often considered after the fact. Although the weaknesses of such an approach have been highlighted (e.g., Axsmith et al., 1998), at the present time it seems unlikely that paleontology will again play the central role in phylogeny reconstruction that it once did. Despite this, paleontological data are experiencing something of a renaissance among biologists because of increased recognition of and renewed interest in the two unique attributes that fossils can bring to phylogenetic studies: a record of extinct morphologies and a temporal framework. The latter attribute is the focus …

A method for constraining the age of origination of derived characters

Fossils are the physical records of the history of morphological character evolution on Earth and can provide valuable information concerning the sequence and timing of origination of derived characters. Knowledge of the timing of origination of synapomorphies makes it possible to estimate when unobserved character changes occurred in the geological past. Here we present a method for estimating the temporal interval during which synapomorphies evolved. The method requires either direct inclusion of fossil taxa (with or without extant taxa) in cladistic analyses based on morphological or combined data, or indirectly using the “molecular scaffold approach.” Second, characters of interest are mapped on a most parsimonious tree and “minimum age node mapping” is used to place minimum ages on the nodes of the tree. Finally, characters of interest are evaluated for younger and/or older temporal constraints on the time of their origination; application of the older bound assumes ancestry of fossil terminals included in the tree. A key is provided herein describing the method. Among other applications, this approach has the potential to provide a powerful test of purported evolutionary cause–effect relationships. For example, the method has the ability to discover that derived characters of suggested adaptational significance may considerably pre‐date the cause(s) that are hypothesized to have favored their establishment.

The Digital Atlas of Ancient Life: delivering information on paleontology and biogeography via the web

The fundamental data of paleontology consist of taxonomically identified specimens of known spatiotemporal provenance that are curated in museum collections. Analyses of these data can lead to insights into biostratigraphy, macroevolution, biogeography, phylogeny, and paleoecology. Although historical collections may contain specimens of vague or indeterminate geographic and stratigraphic position, most paleontologists have recorded these data with a high degree of precision for many years. One challenging problem with using paleontological collections for research, however, is making correct identifications of fossil material at lower taxonomic levels—in particular species, but also at the genus level. One aspect of the challenge is philosophical in nature, and involves the human activity of circumscribing species and higher taxa such that they best approximate biological reality (see Hendricks et al., 2014; Allmon, in press). This activity is the concern of the systematist, who makes such decisions based on expert knowledge of a given group. Another concern—which we focus on here—is practical in nature and has to do with identifying fossil specimens in hand sample and attaining information about the spatiotemporal occurrences of taxa from what may be far-flung museum collections. Short of having in-depth knowledge of a particular group, identifications of fossils at lower taxonomic levels still largely rely upon access to printed literature, such as regional guides (e.g., Linsley, 1994; Petuch, 1994; Feldmann and Hackathorn, 1996; Davis, 1998; Peterson and Peterson, 2008; Wilson, 2014) and systematic treatments (e.g., Hendricks, 2009, 2015; Rode and Lieberman, 2002; Stigall et al., 2014a; Wright and Stigall 2013, 2014), or major compendia such as the Treatise of Invertebrate Paleontology (see Selden, 2012). Such literature may be expensive, locked behind journal paywalls, out-of-print, and/or may also contain technical jargon that is inaccessible to nonprofessionals and students, especially those new to paleontology. An additional problem presented by older literature is that it may not reflect current